CN118603236A - A detection system and method for tracking and controlling the level of molten metal by eddy current induction - Google Patents

Abstract

The invention belongs to the technical field of tracking control of molten metal liquid level, and discloses a detection system and a detection method for tracking and controlling the molten metal liquid level by using eddy current induction, wherein the detection system mainly comprises a modulation and regulation main board, a temperature difference compensation control board and an eddy current induction head; according to the detection method of the detection system, firstly, an electric vortex induction head is used for obtaining an analog excitation impedance signal and a thermocouple temperature analog signal, then a modulation and demodulation main board is used for modulating and demodulating the excitation impedance signal which is simulated by the electric vortex induction head, then a temperature difference compensation module of a temperature difference compensation control board is used for carrying out temperature difference compensation operation on the excitation impedance signal which is simulated by the electric vortex induction head and the thermocouple temperature analog signal, and finally linkage control of a same-linear actuator, a potentiometer, a heat-resistant cover cylinder, the electric vortex induction head and a stopper rod is realized. The beneficial effects of the invention are as follows: the turn-to-turn capacitance and interlayer capacitance of the electromagnetic coil are greatly reduced, and the detection accuracy of the eddy current sensor is improved.

Description

A detection system and method for tracking and controlling the level of molten metal by eddy current induction

Technical Field

The invention belongs to the technical field of tracking and controlling the level of molten metal, and in particular relates to a detection system and method for tracking and controlling the level of molten metal by eddy current induction.

Background Art

The crystallizer is a very important part of the continuous casting machine. It is a bottomless ingot mold with forced water cooling. The crystallizer is a trough-shaped container equipped with a cooling device. By pulling the stopper rod from the bottom of the furnace, the molten metal enters the crystallizer from the upper part of the crystallizer and is cooled into a solid or soft condensed state. Then, the solid or soft condensed metal is pulled out of the bottom of the crystallizer by the ingot head for continuous casting. During the working process of the crystallizer (continuous casting), if the liquid level of the crystallizer is too high, it may overflow and cause an accident; if it is too low, the discharge may be discontinuous, forming a "leakage" (leakage: the discharge cannot block the bottom of the crystallizer, and the product is disconnected); when the liquid level is low, the material entering the crystallizer stays in the crystallizer for too short a time, which may cause insufficient solidification of this section of material and poor consistency of the quality of the ingot product. It can be seen that in the continuous casting production process, the fluctuation of the liquid level of the molten metal in the crystallizer must be kept within a certain process range, otherwise it will directly affect the quality of the billet and cause leakage accidents. By adopting automatic liquid level control, the liquid level of the molten metal in the crystallizer can be tracked and controlled within a certain range, which greatly improves the quality of billet drawing and avoids the occurrence of leakage.

The patent application number is 201210202732.X, and the patent name is a method for real-time monitoring of the interface of molten aluminum in an aluminum electrolytic cell. The above patent discloses that "an eddy current sensor is installed 200 to 1200 mm above the molten metal in the aluminum electrolytic cell, and the eddy current sensor is connected to the liquid level controller, which is connected to the computer control system; the frequency of the high-frequency oscillating current in the preamplifier of the liquid level controller is 1.25Hz-6GHz, and the high-frequency oscillating current is led to the eddy current sensor probe in the tank through an extension cable, generating an alternating magnetic field in the coil at the head of the probe; when the measured liquid approaches this magnetic field, an induced current is generated on the surface of the liquid, and at the same time, the eddy current field also generates an alternating magnetic field in the opposite direction of the head coil, causing the amplitude and phase of the high-frequency current of the probe head coil to change, and the change is processed by the liquid level controller and converted into an analog/digital signal and sent to the upper computer control system for processing, or directly forwarded by the liquid level controller to the tank control machine or other intelligent devices for real-time operation of the electrolytic cell."

The application number is 201811103688.0, and the name of the invention is Eddy Current Sensor. It specifically discloses that "the working steps of the eddy current sensor are divided into a first thread, a second thread and a third thread, and the characteristic is that the first thread uses the CPU to generate a dual-channel drive pulse, differentially drives the eddy current probe, passes through the low-noise amplifier, enters the AD differential sampling, and enters the CPU to wait for the comprehensive compensation of the other two measurement values."

Both of the above patents disclose the use of eddy current sensors to measure or detect the distance from a metal conductor (molten metal liquid surface). In the prior art, for eddy current sensors, since the eddy current sensors are in a high-temperature process environment for a long time when detecting the molten metal liquid surface (the surface temperature of the molten metal liquid surface reaches more than 600 degrees), the temperature of the electromagnetic coil is increased through heat radiation conduction. At the same time, the electromagnetic coil inside the eddy current sensor consumes a certain amount of electrical energy and generates weak heat during operation. The longer the current passes through the electromagnetic coil, the temperature of the electromagnetic coil will gradually increase. If the electromagnetic coil is in a high-temperature environment for a long time, the temperature drift of the electromagnetic coil will occur, which will cause the resistance and capacitance parameters of the electromagnetic coil to change, increase the temperature deviation of the electromagnetic coil, and further affect the stability of the detection (measurement) performance of the eddy current sensor. At the same time, there is a certain complementary relationship between the inter-turn distributed capacitance and the inter-layer distributed capacitance of the electromagnetic coil. The larger the inter-turn distributed capacitance and the inter-layer distributed capacitance of the electromagnetic coil, the greater the resistance error of the electromagnetic coil, which leads to a decrease in the detection accuracy of the eddy current sensor. Therefore, the main technical problems of the eddy current sensor used in the prior art when detecting the molten metal liquid level are: 1. Due to the serious temperature drift of the electromagnetic coil and the insufficient linearity, the detection stability and detection accuracy are reduced when the eddy current sensor is used to sense and track the molten metal liquid level; 2. The inter-turn distributed capacitance and inter-layer distributed capacitance of the electromagnetic coil are large, resulting in a large resistance error of the electromagnetic coil, which reduces the detection accuracy of the eddy current sensor. Based on the technical problems of the eddy current sensor in the prior art, the inventor has developed a detection system and method for eddy current induction tracking and control of the molten metal liquid level, which can well solve the above technical problems in the prior art.

Summary of the invention

In order to solve the above-mentioned technical problems, the present invention provides a detection system and method for eddy current induction tracking and controlling the molten metal liquid level. The present invention can solve the technical problems of severe temperature drift and insufficient linearity of the electromagnetic coil of the eddy current sensor, and also solves the technical problem of large resistance error of the electromagnetic coil due to large inter-turn distributed capacitance and inter-layer distributed capacitance of the electromagnetic coil.

The technical solution adopted by the present invention is: an eddy current induction tracking and control system for detecting the liquid level of molten metal, comprising a mounting fixture 1, a mounting slot 2, and a control box 3, wherein the mounting fixture 1 is fixedly mounted in the middle position of the mounting slot 2, the mounting fixture 1 is fixedly connected to one side of the crossbeam at the upper part of the crystallizer, the control box 3 is fixed at the front side of the mounting slot 2, the control box 3 is a hollow 7-shaped structure, and the box panel 4 is installed at the front side of the control box 3; an eddy current cooler 5 is fixedly arranged at the upper part of the control box 3 near the left side, the eddy current cooler 5 penetrates into the interior of the control box 3, and is used for air-cooling the inner wall of the control box 3; a main air inlet 6 is opened in the eddy current cooler 5 The rear side position of the three-way air valve 7 is fixedly arranged at the right side position of the vortex cooler 5, and the three-way air valve 7 extends to the interior of the control box 3; the wiring harness pipe 8 is fixedly arranged at the upper middle position of the control box 3, and the wiring harness pipe 8 is connected to the interior of the control box 3; the three-way branch pipe 9 is fixedly arranged at the bottom position of the three-way air valve 7, and the three-way branch pipe 9 is located at the upper left position of the control box 3; the modem main board 10 is fixedly arranged at the bottom position of the three-way branch pipe 9, and the rear side surface of the modem main board 10 is fixedly connected to the rear inner wall of the control box 3; the coaxial cable connector 11 is fixedly arranged at the middle position on the right side of the modem main board 10; the heat sink 12 is fixedly arranged on the modem main board 1 0, the rear side of the heat sink 12 is fixedly connected to the rear inner wall of the control box 3; the temperature difference compensation control board 13 is fixedly arranged on the outer surface of the heat sink 12; the main fixed card slot 14 is fixedly arranged at the lower right position of the inner wall of the control box 3, and the main fixed card slot 14 is used to install and fix the linear actuator 16; the secondary fixed card slot 15 is fixedly arranged at the lower right position of the main fixed card slot 14, and the secondary fixed card slot 15 is used to install and fix the potentiometer 17; the linear actuator 16 is installed and fixed in the main fixed card slot 14, and the telescopic rod of the linear actuator 16 is fixedly connected to the upper part of the square fixed body 21; the upper part of the potentiometer 17 is installed and fixed in the secondary fixed card slot 15, and the lower end of the potentiometer 17 is connected to the square The upper part of the fixed body 21 is fixedly connected; the sliding groove 18 is fixedly arranged on the partition at the lower right part of the control box body 3; the sliding box body 19 is fixedly arranged on the sliding groove 18, and the sliding box body 19 is telescopically pushed up and down by the linear actuator 16, and the lower part of the sliding box body 19 is fixedly connected to the surrounding sides of the square fixed body 21; the heat-resistant cover tube 20 is fixedly arranged at the bottom of the square fixed body 21, and the heat-resistant cover tube 20 is fixedly connected to the heat-resistant cover tube 20 by using a U-shaped fixing card 22 to pass through the heat-resistant cover tube 20 to form a whole; the eddy current induction head 23 is fixedly arranged at the inner center position between the square fixed body 21 and the heat-resistant cover tube 20, and the eddy current induction head 23 is used to track and induction control the height of the molten metal liquid level in the crystallizer.

A partition plate for installing the sliding groove 18 is fixedly provided at the lower right position inside the control box 3 .

The side end of the three-way valve 7 is fixedly connected to the main air inlet 6 of the vortex cooler 5 through an air pipe.

The power lines and signal transmission lines of the modem mainboard 10 and the temperature difference compensation control board 13 are neatly placed in the harness tube 8 and connected to the PLC terminal in the factory central control system; the modem mainboard 10 includes an FPGA chip module, a digital-to-analog conversion module 1, a digital-to-analog conversion module 2, a gain-adjustable operational amplifier 1, a gain-adjustable operational amplifier 2, a gain-adjustable operational amplifier 3, a phase-shifting transformer, a digital-to-analog conversion module 3, a DA conversion module, an analog signal output terminal and a power supply terminal; the power supply terminal of the modem mainboard 10 is fixedly connected to the power supply output terminal of the temperature difference compensation control board 13, and the temperature difference compensation control The board 13 provides power to the modem main board 10; the temperature difference compensation control board 13 includes an analog signal receiving module, a normalization processing module, a gain operational amplifier, an analog addition operation module, a thermocouple signal receiving module, a K-type temperature amplifier, a temperature difference compensation module, a potentiometer, a half-proportional adjustment module, a linear actuator maximum and minimum limit module, a linear actuator motor, and a linear actuator extension control module; the temperature difference compensation control board 13 is fixedly connected to the linear actuator motor and the potentiometer motor through the power output terminal, and the temperature difference compensation control board 13 provides driving power to the linear actuator motor and the potentiometer motor.

The heat sink 12 includes a heat sink body 121, which is fixed to the rear inner wall of the control box 3, an air inlet 122 is opened in the upper middle position of the heat sink body 121, and an exhaust hole 123 is opened in the right middle position of the heat sink body 121; the air inlet 122 is fixedly connected to the left end of the three-way branch pipe 9 through an air pipe, and the exhaust hole 123 extends to the outside of the control box 3 through the air pipe.

The sliding groove 18 includes a sliding groove body 181, which is fixedly arranged at the right side position of the internal partition on which the sliding groove 18 is installed. The sliding groove body 181 is U-shaped, and the strip groove 182 is opened in the middle position of the sliding groove body 181. The upper position of the strip groove 182 is closed, and the lower position of the strip groove 182 is open; the left side plate of the sliding box body 19 is mounted in the strip groove 182, so that the sliding box body 19 can slide up and down along the strip groove 182.

The sliding box body 19 includes a box body 191, which is a hollow square body. Four fixing holes 192 are symmetrically arranged on the front and rear sides of the bottom of the box body 191; the fixing holes 192 arranged on the bottom of the box body 191 correspond to the lateral fixing holes 215 of the square fixing body 21 body front and back, and the box body 191 and the square fixing body 21 body are fixed together by screws.

The heat-resistant cover tube 20 comprises a cover tube body 201 , and the cover tube body 201 is a structure with a convex ring 202 at the upper part and a hollow cylindrical structure at the lower part.

The square fixed body 21 includes an actuator telescopic rod fixing hole 211, which is opened at the upper part of the square fixed body 21 near the rear side, a cable hole 212 is opened at the left front side of the actuator telescopic rod fixing hole 211, a cooling hole 213 is opened at the front side of the cable hole 212, and a potentiometer fixing hole 214 is opened at the right rear side of the cooling hole 213; the actuator telescopic rod fixing hole 211, the cable hole 212 and the cooling hole 213 pass through the square fixed body 21 from top to bottom, the lateral fixing hole 215 is opened on the front and rear sides of the upper part of the square fixed body 21, and four lateral fixing holes 215 are symmetrically arranged front and back; the wire hole 216 is symmetrically opened front and back on the square fixed body 21 In the middle of the fixed body 21, near the left side, the clamping block 217 is integrally formed at the four corners of the middle bottom of the square fixed body 21, and the inner side of the clamping block 217 is an arc surface 218; the convex cylinder 219 is fixedly set at the bottom center position in the middle of the square fixed body 21, and the bottom of the convex cylinder 219 is symmetrically provided with tightening holes 2110 front and back; the exhaust grooves 2111 are symmetrically opened on the left and right sides of the middle bottom position of the square fixed body 21, and the inner side of the exhaust groove 2111 extends to the outer edge of the convex cylinder 219; the through hole 2112 is opened in the middle of the square fixed body 21, and the through hole 2112 is cross-connected with the actuator telescopic rod fixing hole 211, the cable hole 212 and the cooling hole 213.

The linear actuator 16 and the telescopic rod pass through the rear side of the box body 191, and the telescopic rod of the linear actuator 16 is fixedly connected to the actuator telescopic rod fixing hole 211; the telescopic rod of the potentiometer 17 passes through the box body 191 and is fixedly connected to the potentiometer fixing hole 214; the right end of the three-way branch pipe 9 is fixedly connected to the cooling hole 213 through the air pipe.

The outer side surface of the clamping block 217 is flush with the outer side surface of the middle part of the main body of the square fixing body 21, and the inner arc surfaces 218 of the four clamping blocks 217 form a circular space for installing the convex ring 202 of the heat-resistant cover tube 20, and a square opening is formed between the four clamping blocks 217; the exhaust groove 2111 is opened in the middle upper position of the square openings on the front and rear sides of the main body of the square fixing body 21.

The U-shaped fixing card 22 is sleeved on the outer side of the square fixing body 21, and is tightened and fixed by screws passing through the front and rear sides of the U-shaped fixing card 22 near the left side and the thread hole 216. A through hole larger than the diameter of the cover tube body 201 is opened in the center of the U-shaped fixing card 22; the U-shaped fixing card 22 is used to fix and clamp the cover tube body 201 and the convex ring 202.

The upper convex ring 202 of the cover tube body 201 is installed in a circular space formed by the inner arc surfaces 218 of the four clamping blocks 217, and the cover tube body 201 and the convex ring 202 are fixed and clamped by using a U-shaped fixing clamp 22.

The eddy current induction head 23 includes a protective shell 231, which is an upper hollow protrusion and a lower hollow cylindrical structure integrally formed of heat-resistant resin; the hollow protrusion on the upper part of the protective shell 231 is installed inside the convex cylinder 219, and the protective shell 231 and the convex cylinder 219 are tightened and fixed by screws passing through the tightening holes 2110 of the convex cylinder 219; the heat dissipation exhaust holes 232 are evenly arranged at the bottom center of the protective shell 231, and the heat dissipation exhaust holes 232 are used to discharge the heat in the protective shell 231; the annular fixing frame 233 and the protective shell 231 are an integrally formed structure, and the annular fixing frame 233 is located on the upper inner wall of the protective shell 231; the upper surface of the annular fixing frame 233 is symmetrically provided with thermocouple mounting holes 234, and the coil fixing body 235 is symmetrically arranged on the left and right sides. The coil fixing body 235 is formed integrally on the inner arc surface of the annular fixing frame 233, and a matching mounting hole 236 for fixing the positive terminal 2310 and the negative terminal 2311 of the double-layer coil 239 is opened on the inner end surface; the thermocouple 238 is fixedly installed on the thermocouple mounting hole 234, and the double-layer coil 239 is a spiral double-layer structure wound by a conductive material, and the positive terminal 2310 and the negative terminal 2311 of the conductive material pass upward through the matching mounting holes of the coil fixing body 235, the positive terminal 2310 is fixedly connected to the left end of the three-way coaxial cable connector 237, and the negative terminal 2311 is fixedly connected to the right end of the three-way coaxial cable connector 237; the upper middle connecting end of the three-way coaxial cable connector 237 is fixedly connected to the coaxial cable connector 11 of the modem mainboard 10 through a coaxial cable.

The eddy current induction head 23 is located at the center of the cover tube body 201, and the diameter and height of the eddy current induction head 23 are smaller than the diameter and height of the cover tube body 201 and the convex ring 202; the coaxial cable connecting the double-layer coil 239 passes through the cable hole 212 and is fixedly connected to the coaxial cable connector 11 of the three-way coaxial cable connector 237 at the lower end, and the upper end of the coaxial cable is fixedly connected to the coaxial cable connector 11 of the modem main board 10; the connecting wire connecting the thermocouple 238 passes through the cable hole 212, and its upper end is fixedly connected to the temperature difference compensation control board 13, and its lower end is fixedly connected to the two thermocouples 238 respectively.

The induction tracking control method of the eddy current induction tracking control molten metal liquid level detection system:

Step 1: Acquisition of excitation impedance signal simulated by eddy current induction head and temperature simulation signal of thermocouple: When the heat-resistant cover tube 20 and the eddy current induction head 23 are in the calibrated initial position, as the opening of the stopper rod (used to block the port for injecting metal liquid into the crystallizer) increases, the molten metal liquid in the crystallizer increases continuously, so that the molten metal liquid level in the crystallizer also increases continuously, and the eddy current induction head 23 and the heat-resistant cover tube 20 are linked with the linear actuator 16 and the potentiometer 17 (the extension of the linear actuator 16 is When the retracting rod is extended and retracted, the telescopic rod of the potentiometer 17 is also extended and retracted by the same distance). The eddy current induction head 23 and the heat-resistant cover tube 20 sense and track the position of the molten metal liquid level in the crystallizer in real time. At this time, the double-layer coil 239 in the eddy current induction head 23 obtains the simulated excitation impedance signal due to the change in the distance between the eddy current induction head 23 and the heat-resistant cover tube 20 and the molten metal liquid level. At the same time, the thermocouple 238 obtains the simulated temperature signal of the temperature change around the double-layer coil 239.

Step 2, modulation and demodulation processing of the excitation impedance signal simulated by the eddy current induction head: the simulated excitation impedance signal (AC) is transmitted to the modulation and demodulation main board 10 through the coaxial cable connected to the three-way coaxial cable connector 237 through the coaxial cable connector 11 on the modulation and demodulation main board 10; the FPGA chip module on the modulation and demodulation main board 10 generates a DDS frequency and phase adjustable signal through the FFT algorithm, and provides a simulated two-terminal sinusoidal excitation impedance signal to the digital-to-analog conversion module 1 and the digital-to-analog conversion module 2. This signal is converted into a digital two-terminal sinusoidal excitation impedance signal through the digital-to-analog conversion module 1 and the digital-to-analog conversion module 2, and is transmitted to the gain adjustable operational amplifier 1 and the gain adjustable operational amplifier 2. The gain adjustable operational amplifier 1 and the gain adjustable operational amplifier 2 convert the digital two-terminal sinusoidal excitation impedance signal into a digital single-ended sinusoidal excitation impedance signal, and amplify the digital single-ended sinusoidal excitation impedance signal. The driving energy of the excitation impedance signal; the digital single-ended sinusoidal excitation impedance signal processed by the gain-adjustable operational amplifier 1 and the gain-adjustable operational amplifier 2 is combined with the excitation impedance signal simulated by the eddy current induction head, and the phase of the combined digital single-ended sinusoidal excitation impedance signal and the excitation impedance signal simulated by the eddy current induction head is made consistent through the comparison operation of the gain-adjustable operational amplifier 3, and the driving energy of this signal is increased, and at the same time converted into a double-ended (differential) digital and analog excitation impedance signal; then the phase of the above signal is processed by a phase-shifting transformer, and the above signal is uniformly converted into a digital excitation impedance signal through a digital-to-analog conversion module 3, and finally processed by the FFT algorithm of the FPGA chip module, and converted into an analog excitation impedance signal (expressed as a distance signal between the eddy current induction head and the molten metal liquid surface) through the DA conversion module, and then transmitted to the analog signal receiving module of the temperature difference compensation control board 13 through the analog signal output end;

Step 3: Temperature difference compensation operation of the excitation impedance signal simulated by the eddy current induction head and the thermocouple temperature simulation signal: In the above step 2, after the analog signal receiving module of the temperature difference compensation control board 13 receives the signal, it is normalized by the normalization processing module of the temperature difference compensation control board 13, and then the simulated excitation impedance signal gain is amplified by the gain operational amplifier to enhance the signal strength and maintain the transmission linearity; at the same time, the thermocouple signal receiving module of the temperature difference compensation control board 13 receives the received thermocouple temperature simulation signal through a K-type temperature amplifier to convert the simulated temperature The signal is amplified and transmitted to the temperature difference compensation module. The temperature difference compensation module adds the temperature drift caused by the temperature increase of the double-layer coil 239, and the distance value between the eddy current induction head and the molten metal surface before the temperature of the double-layer coil 239 is detected and the distance value between the eddy current induction head and the molten metal surface after the temperature of the double-layer coil 239 is increased to make them consistent; then the analog signal of the thermocouple 238 processed by the temperature difference compensation module is amplified by the gain operational amplifier; at the same time, the linear actuator 16 and the potentiometer 17 are connected. Under the dynamic coordination action, the potentiometer 17 obtains the analog position signal of the telescopic action of the linear actuator 16 through the linear actuator maximum and minimum limit module of the temperature difference compensation control board 13, and the analog position signal of the telescopic action of the linear actuator 16 is halved through the half-proportional adjustment circuit of the half-proportional adjustment module to reduce the position error of the analog position signal of the telescopic action of the linear actuator 16 by half; finally, the excitation impedance signal simulated by the eddy current induction head 23, the temperature analog signal of the thermocouple 238 and the analog position signal of the telescopic action of the linear actuator 16 are added and calculated through the analog addition operation module to calculate the precise telescopic action control analog signal of the linear actuator 16, and the precise telescopic action control analog signal of the linear actuator 16 is transmitted to the central control room PLC module in the factory. The central control room PLC module accurately controls the motor of the linear actuator 16 through the linear actuator telescopic control module to achieve precise control of the telescopic action of the linear actuator 16, thereby achieving real-time induction tracking control detection of the rising molten metal liquid level in the crystallizer by the heat-resistant hood 20 and the eddy current induction head 23;

Step 4: After the temperature difference compensation operation of the excitation impedance signal simulated by the eddy current induction head and the temperature simulation signal of the thermocouple, the linear actuator, potentiometer, heat-resistant hood, eddy current induction head and stopper rod are controlled in linkage: when the stopper rod opening is at the maximum opening and lasts for a period of time, when the molten metal liquid in the crystallizer reaches the maximum liquid level position set by the process, the eddy current induction head 23 obtains the simulated excitation impedance signal when the molten metal liquid level is at the maximum liquid level set by the process, the thermocouple 238 obtains the real-time simulated temperature signal, and the potentiometer 17 obtains the real-time simulated position signal of the linear actuator 16, and then the excitation impedance signal simulated by the eddy current induction head in step 2 is The modulation and demodulation processing and the temperature difference compensation operation of the excitation impedance signal simulated by the eddy current induction head and the thermocouple temperature simulation signal in step three are used to accurately calculate the retraction stroke of the linear actuator 16, and the motor of the linear actuator 16 sends a control retraction stroke signal through the PLC module of the central control room. At this time, the eddy current induction head 23 and the heat-resistant hood tube 20 are at the process maximum liquid level position of the molten metal liquid surface driven by the retraction action of the linear actuator 16; at the same time, the PLC in the central control room sends a control signal of the corresponding closing opening to the control module of the stopper rod, and the stopper rod reduces the opening until the molten metal liquid level in the crystallizer is at the equilibrium liquid level height required by the process.

The beneficial effects of the present invention are as follows: 1. By means of real-time temperature measurement of the double-layer coil through the modulation and demodulation main board, the temperature difference compensation control board, and the thermocouple, the heat-resistant cover tube is cooled, and the double-layer coil is cooled, the problems of severe temperature drift and insufficient linearity of the electromagnetic coil are solved, and the detection stability and detection accuracy are improved when the eddy current induction head senses and tracks the molten metal liquid level; 2. By setting the double-layer coil, due to the staggered double-layer winding structure of the double-layer coil, the inter-turn distributed capacitance and inter-layer distributed capacitance of the electromagnetic coil are greatly reduced, the resistance error of the electromagnetic coil is reduced, and the detection accuracy of the eddy current induction head is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram of the structure of the present invention;

FIG2 is a rear view of FIG1 of the present invention;

Fig. 3 is a cross-sectional view of the present invention;

FIG4 is a schematic structural diagram of a linear actuator, a potentiometer, a sliding groove, a sliding box, a heat-resistant cover cylinder and a square fixed body according to the present invention;

FIG5 is an exploded view of the linear actuator, potentiometer, sliding slot, heat-resistant cover cylinder and square fixed body of the present invention;

FIG6 is a schematic structural diagram of a square fixed body of the present invention;

FIG7 is a cross-sectional view of a square fixing body of the present invention;

FIG8 is an exploded view of the square fixed body, the heat-resistant cover tube, and the eddy current induction head of the present invention;

FIG9 is a cross-sectional view of an eddy current induction head of the present invention;

FIG10 is a control block diagram of the present invention;

Markings in the figure: 1. Mounting body, 2. Mounting slot, 3. Control box, 4. Box panel, 5. Eddy current cooler, 6. Main air inlet, 7. Three-way air valve, 8. Harness tube, 9. Three-way branch pipe, 10. Modem main board, 11. Coaxial cable connector, 12. Heat sink, 121. Heat sink body, 122. Air inlet, 123. Exhaust hole, 13. Temperature difference compensation control board, 14. Main fixing slot, 15. Secondary fixing slot, 16. Linear actuator, 17. Potentiometer, 18. Sliding slot, 181. Sliding slot body, 182. Strip slot, 19. Sliding box, 191. Box body, 192. Fixing hole, 20. Heat-resistant cover, 201. Cover body, 202. Convex ring, 2 1. Square fixing body, 211. Actuator telescopic rod fixing hole, 212. Cable hole, 213. Cooling hole, 214. Potentiometer fixing hole, 215. Lateral fixing hole, 216. Thread hole, 217. Clamping block, 218. Arc surface, 219. Convex cylinder, 2110. Tightening hole, 2111. Exhaust groove, 2112. Through hole, 22. U-shaped fixing card, 23. Eddy current induction head, 231. Protective shell cylinder, 232. Heat dissipation exhaust hole, 233. Ring fixing frame, 234. Thermocouple mounting hole, 235. Coil fixing body, 236. Matching mounting hole, 237. Three-way coaxial cable connector, 238. Thermocouple, 239. Double-layer coil, 2310. Positive terminal, 2311. Negative terminal.

DETAILED DESCRIPTION

The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

The present invention provides a detection system and method for eddy current induction tracking and controlling the level of molten metal:

As shown in FIG. 1 or FIG. 2 , the mounting fixture 1 is fixedly mounted in the middle position of the mounting slot 2, the mounting fixture 1 is fixedly connected to one side of the crossbeam at the top of the crystallizer, the control box 3 is fixed at the front side of the mounting slot 2, the control box 3 is a hollow 7-shaped structure, and the box panel 4 is mounted at the front side of the control box 3. Through the above-mentioned arrangement of the mounting fixture 1 and the mounting slot 2, on the one hand, the control box 3 can be stably fixed at the upper position of the crystallizer, making it convenient to make the eddy current induction head perpendicular to the molten metal liquid level in the crystallizer. On the other hand, with the cooperation of the mounting slot 2, the disassembly of the mounting fixture 1 is convenient.

The above-mentioned setting of the control box 3, on the one hand, provides protection for the modem main board 10 and the temperature difference compensation control board 13, and on the other hand, provides a fixed installation carrier for the eddy current cooler 5, the three-way air valve 7, the three-way branch pipe 9, the heat sink 12, the linear actuator 16, the potentiometer 17, the sliding box 19, the heat-resistant cover tube 20, the square fixed body 21 and the eddy current sensor head 23, thereby realizing the up and down tracking induction control of the molten metal liquid level in the crystallizer by using the heat-resistant cover tube 20 and the eddy current sensor head 23.

As shown in Fig. 1-3, the vortex cooler 5 is fixedly arranged at the upper part of the control box 3 near the left side, and the vortex cooler 5 penetrates into the interior of the control box 3 to cool the inner wall of the control box 3 by air cooling; the main air inlet 6 is opened at the rear side of the vortex cooler 5; the three-way air valve 7 is fixedly arranged at the right side of the vortex cooler 5, and the three-way air valve 7 extends to the interior of the control box 3; the side end of the three-way air valve 7 is fixedly connected with the main air inlet 6 of the vortex cooler 5 through an air pipe. Through the above-mentioned setting of the vortex cooler 5, the three-way air valve 7 is used to transport high-pressure air to the main air inlet 6 of the vortex cooler 5, and the vortex cooler 5 blows the generated cooling gas to the inner wall of the control box 3, thereby cooling the inner wall of the control box 3.

As shown in Figs. 3 and 5, the three-way branch pipe 9 is fixedly arranged at the bottom of the three-way air valve 7, and the three-way branch pipe 9 is located at the upper left side of the control box 3; the air inlet 122 of the heat sink 12 is fixedly connected to the left end of the three-way branch pipe 9 through an air pipe, and the air outlet 123 extends to the outside of the control box 3 through the air pipe; the right end of the three-way branch pipe 9 is fixedly connected to the cooling hole 213 through the air pipe. The above-mentioned three-way branch pipe 9 is arranged to divide the cooling gas into two paths, one of which is fixedly connected to the air inlet 122 of the heat sink 12, and the other is fixedly connected to the cooling hole 213 on the upper part of the square fixed body 21. Under the connection and cooperation of the through hole 2112, the cooling gas is finally transported to the inside of the protective shell 231 in the eddy current induction head 23, so as to cool the double-layer coil 239.

As shown in Figure 3, the modem main board 10 is fixedly set at the bottom position of the three-way branch pipe 9, and the rear side surface of the modem main board 10 is fixedly connected to the rear inner wall of the control box 3; the coaxial cable connector 11 is fixedly set at the middle position on the right side of the modem main board 10.

As shown in FIG3 , the heat sink 12 is fixedly arranged at the lower part of the modem mainboard 10, and the rear side of the heat sink 12 is fixedly connected to the rear inner wall of the control box 3; the temperature difference compensation control board 13 is fixedly arranged on the outer surface of the heat sink 12. The heat sink 12 can cool and dissipate the temperature difference compensation control board 13 on the one hand, and can prevent the high temperature heat source of the molten metal surface in the crystallizer from being radiated and conducted to the temperature difference compensation control board 13 through the control box 3 on the other hand.

As shown in Fig. 3, the power lines and signal transmission lines of the modem main board 10 and the temperature difference compensation control board 13 are neatly placed in the harness tube 8 and connected to the PLC terminal in the factory central control system. The above central control system can monitor and control the opening of the injection port plug rod for injecting molten metal solution into the crystallizer in real time.

As shown in Figures 3, 4 and 5, the main fixed slot 14 is fixedly arranged at the lower right side of the inner wall of the control box body 3, and the main fixed slot 14 is used to install and fix the linear actuator 16; the secondary fixed slot 15 is fixedly arranged at the lower right side of the main fixed slot 14, and the secondary fixed slot 15 is used to install and fix the potentiometer 17; the linear actuator 16 is installed and fixed in the main fixed slot 14, and the telescopic rod of the linear actuator 16 is fixedly connected to the upper part of the square fixed body 21; the upper part of the potentiometer 17 is installed and fixed in the secondary fixed slot 15, and the lower end telescopic rod of the potentiometer 17 is fixedly connected to the upper part of the square fixed body 21.

As shown in Figures 4 and 5, the sliding groove 18 is fixedly arranged on the partition at the lower right side of the control box 3; the sliding box 19 is fixedly arranged on the sliding groove 18, and the sliding box 19 is telescopically pushed up and down by the linear actuator 16, and the lower part of the sliding box 19 is fixedly connected to the surrounding sides of the square fixed body 21; the sliding groove 18 includes a sliding groove body 181, and the sliding groove body 181 is fixedly arranged on the right side of the internal partition on which the sliding groove 18 is installed. The sliding groove body 181 is U-shaped, and the strip groove 182 is opened in the middle position of the sliding groove body 181, the upper position of the strip groove 182 is closed, and the lower position of the strip groove 182 is open; the left side plate of the sliding box 19 is sleeved in the strip groove 182, so that the sliding box 19 can slide up and down along the strip groove 182.

The arrangement of the strip groove 182 of the sliding groove 18 provides, on the one hand, a track for the sliding box 19 to slide up and down under the telescopic action of the linear actuator 16. On the other hand, it guides the sliding box 19 to slide up and down, thereby reducing the radial deviation of the sliding box 19 when it slides up and down.

As shown in Fig. 4 and Fig. 5, the lower part of the sliding box 19 is fixedly connected to the sides of the square fixed body 21. The sliding box 19 includes a box body 191. The box body 191 is a hollow square body. Four fixing holes 192 are symmetrically arranged on the front and rear sides of the bottom of the box body 191. The fixing holes 192 arranged at the bottom of the box body 191 correspond to the lateral fixing holes 215 of the square fixed body 21, and the box body 191 and the square fixed body 21 are fixed together by screws. The main purpose of the above arrangement is: under the condition that the sliding box 19 and the square fixed body 21 are fixedly connected as a whole, the telescopic action of the linear actuator 16 can be used to realize the sliding box 19 moving up and down along the strip groove 182 of the sliding groove 18, thereby driving the heat-resistant hood 20 and the eddy current induction head 23 to track and sense the molten metal liquid level at the upper part of the crystallizer. On the one hand, it plays the role of fixing the square fixed body 21, the heat-resistant cover tube 20 and the eddy current induction head 23; on the other hand, it enables the sliding box 19, the square fixed body 21, the heat-resistant cover tube 20 and the eddy current induction head 23 to follow the extension and retraction movement of the linear actuator 16 to achieve tracking and sensing control of the molten metal liquid level.

As shown in Figs. 3, 4 and 5, the heat-resistant cover barrel 20 is fixedly arranged at the bottom of the square fixed body 21, and the heat-resistant cover barrel 20 is fixedly connected to form a whole by passing through the heat-resistant cover barrel 20 with a U-shaped fixing clamp 22; the heat-resistant cover barrel 20 comprises a cover barrel body 201, and the cover barrel body 201 is a hollow cylindrical structure with a convex ring 202 arranged on the upper part and a hollow cylindrical structure at the lower part; the convex ring 202 on the upper part of the cover barrel body 201 is installed in a circular space formed by the inner arc surface 218 of the four clamping blocks 217, and the cover barrel body 201 and the convex ring 202 are fixed and clamped by the U-shaped fixing clamp 22. The above-mentioned U-shaped fixing clamp 22 is fixed in the thread hole 216 of the square fixed body 21 by screws passing through its body, so that the cover barrel body 201 and the convex ring 202 are fixed and clamped by the U-shaped fixing clamp 22.

The circular space formed by the inner arc surfaces 218 of the above-mentioned four clamping blocks 217, on the one hand, provides a space for convenient installation of the upper convex ring 202 of the cover tube body 201; on the other hand, when the upper convex ring 202 of the cover tube body 201 is tightly attached, with the cooperation of the exhaust groove 2111 of the square fixed body 21, the high-temperature gas in the heat-resistant cover tube 20 can be discharged by using cooling gas, thereby playing a role in cooling down the heat-resistant cover tube 20.

As shown in Figs. 3, 4, 5, 6, 7 and 8, the square fixed body 21 includes an actuator telescopic rod fixing hole 211, which is located at the upper part of the square fixed body 21 near the rear side, a cable hole 212 is located at the left front side of the actuator telescopic rod fixing hole 211, a cooling hole 213 is located at the front side of the cable hole 212, and a potentiometer fixing hole 214 is located at the right rear side of the cooling hole 213; the actuator telescopic rod fixing hole 211, the cable hole 212 and the cooling hole 213 penetrate the square fixed body 21 from top to bottom, the lateral fixing hole 215 is located on the front and rear sides of the upper part of the square fixed body 21, and four lateral fixing holes 215 are symmetrically arranged front and back; the wire hole 216 is located front and rear It is symmetrically opened in the middle of the square fixed body 21 near the left side, and the clamping block 217 is integrally formed at the four corners of the middle bottom of the square fixed body 21, and the inner side of the clamping block 217 is an arc surface 218; the convex cylinder 219 is fixedly set at the bottom center position in the middle of the square fixed body 21, and the bottom of the convex cylinder 219 is symmetrically opened with tightening holes 2110 front and back; the exhaust groove 2111 is symmetrically opened on the left and right sides of the middle bottom position of the square fixed body 21, and the inner side of the exhaust groove 2111 extends to the outer edge of the convex cylinder 219; the through hole 2112 is opened in the middle of the square fixed body 21, and the through hole 2112 is cross-connected with the actuator telescopic rod fixing hole 211, the cable hole 212 and the cooling hole 213.

The above-mentioned arrangement of the actuator telescopic rod fixing hole 211 and the potentiometer fixing hole 214, on the one hand, provides a fixed installation space for the telescopic rod of the linear actuator 16 and the telescopic rod of the potentiometer 17 (telescopic potentiometer); on the other hand, the linear actuator 16 and the potentiometer 17 can be fixedly connected with the square fixing body 21 as a whole, thereby further fixing the sliding box 19, the square fixing body 21, the heat-resistant cover tube 20 and the eddy current sensor head 23 as an integrated structure, and then, under the impetus of the telescopic action of the linear actuator 16, the heat-resistant cover tube 20 and the eddy current sensor head 23 can achieve the tracking, detection and control function of the molten metal liquid level.

By setting the fixing hole 211, cable hole 212, cooling hole 213 and through hole 2112 of the actuator telescopic rod, a cavity for collecting and evenly cooling gas is formed by utilizing the connecting function of the through hole 2112. When the cooling gas enters the interior of the square fixed body 21 from the cooling hole 213, a part of the gas enters the heat-resistant cover tube 20 through the lower end of the cooling hole 213 to cool the heat-resistant cover tube 20; the other part of the gas enters the protective shell tube 231 of the eddy current induction head 23 through the through hole 2112, thereby cooling the double-layer coil 239. After being cooled in the protective shell tube 231, the gas enters the heat-resistant cover tube 20 through the heat dissipation exhaust hole 232; finally, the gas entering the heat-resistant cover tube 20 from the cooling hole 213 and the gas entering the heat-resistant cover tube 20 from the heat dissipation exhaust hole 232 merge and are all discharged through the exhaust groove 2111. The main purpose of doing so is: on the one hand, the heat-resistant cover tube 20 can be cooled down, and on the other hand, the thermocouple 238 and the double-layer coil 239 can be cooled down at the same time. Finally, by cooling down the heat-resistant cover tube 20 and the protective shell tube 231, the temperature around the double-layer coil 239 reaches 75°C or less, and the eddy current induction head 23 can work normally.

The four clamping blocks 217 and the inner arc surface 218 of the clamping blocks 217 form a circular space for convenient installation and removal of the upper convex ring 202 of the cover tube body 201.

The above-mentioned arrangement of the convex cylinder 219 and the tightening hole 2110 provides a space for installing and fixing the protective shell 231 of the eddy current induction head 23. On the one hand, the protective shell 231 is fixedly connected to the square fixed body 21 as an integral structure, and on the other hand, the concentricity of the protective shell 231 and the heat-resistant cover cylinder 20 is maintained.

As shown in Figures 3, 8 and 9, the eddy current induction head 23 is fixedly arranged at the inner center position between the square fixed body 21 and the heat-resistant cover tube 20, and the eddy current induction head 23 is used to track and induction control the height of the molten metal liquid level in the crystallizer; the eddy current induction head 23 includes a protective shell tube 231, and the protective shell tube 231 is an upper hollow protrusion and a lower hollow cylindrical structure integrally formed of heat-resistant resin; the hollow protrusion on the upper part of the protective shell tube 231 is installed inside the convex cylinder 219, and the protective shell tube 231 and the convex cylinder 219 are tightened and fixed by screws passing through the tightening holes 2110 of the convex cylinder 219; the heat dissipation exhaust holes 232 are evenly arranged at the bottom center position of the protective shell tube 231, and the heat dissipation exhaust holes 232 are used to discharge the heat in the protective shell tube 231; the annular fixing frame 233 and the protective shell tube 231 are an integrally formed structure, and the annular fixing frame 233 is located on the upper inner wall of the protective shell tube 231; the annular fixing frame 233 is an integrally formed structure with the protective shell tube 231, and the annular fixing frame 233 is located on the upper inner wall of the protective shell tube 231; The upper surface of the fixed frame 233 is symmetrically provided with thermocouple mounting holes 234, the coil fixing body 235 is symmetrically and integrally formed on the inner arc surface of the annular fixing frame 233, and the inner end surface of the coil fixing body 235 is provided with matching mounting holes 236 for fixing the positive terminal 2310 and the negative terminal 2311 of the double-layer coil 239; the thermocouple 238 is fixedly installed on the thermocouple mounting hole 234, the double-layer coil 239 is a spiral double-layer structure wound with a conductive material, the positive terminal 2310 and the negative terminal 2311 of the conductive material pass upward through the matching mounting holes of the coil fixing body 235, the positive terminal 2310 is fixedly connected to the left end of the three-way coaxial cable connector 237, and the negative terminal 2311 is fixedly connected to the right end of the three-way coaxial cable connector 237; the upper middle connecting end of the three-way coaxial cable connector 237 is fixedly connected to the coaxial cable connector 11 of the modem mainboard 10 through a coaxial cable.

The material of the above-mentioned protective shell tube 231 and the annular fixing frame 233 is heat-resistant resin material, and the protective shell tube 231 and the annular fixing frame 233 are an integral structure of plastic forming; by utilizing the annular fixing frame 233 and the coil fixing body 235, on the one hand, the insulation performance of the protective shell tube 231 and the annular fixing frame 233 is improved; on the other hand, a stable mounting carrier is provided for the thermocouple 238 and the double-layer coil 239.

The above-mentioned setting of the thermocouple 238, on the one hand, plays the role of real-time monitoring of the temperature around the double-layer coil 239, and provides a detection basis for the long-term normal temperature control of the double-layer coil; on the other hand, the real-time temperature analog signal detected by the thermocouple 238 is used to provide real-time variable parameters for the temperature difference compensation and proportional addition operation of the distance position analog signal of the eddy current sensing head 23 and the heat-resistant cover tube 20 fed back by the modulation and demodulation main board 10, thereby improving the accuracy of the distance position analog signal of the eddy current sensing head 23 and the heat-resistant cover tube 20.

The above-mentioned setting of the double-layer coil 239, on the one hand, improves the smoothness of the electromagnetic induction magnetic field of the double-layer coil 239 in a high-temperature environment, so that the magnetic field generated by the double-layer coil 239 can be smoothly transmitted to the surface of the molten metal liquid in the crystallizer; on the other hand, it reduces the inter-turn distributed capacitance and the inter-layer distributed capacitance, because the double-layer winding structure of the double-layer coil 239 reduces the inter-turn spacing of the coil, and at the same time reduces the inter-layer spacing of the coil, thereby reducing the resistance error of the double-layer coil 239 and improving the detection accuracy of the eddy current induction head 23.

As shown in Figures 8 and 9, the eddy current induction head 23 is located at the center of the cover tube body 201, and the diameter and height of the eddy current induction head 23 are smaller than the diameter and height of the cover tube body 201 and the convex ring 202; the coaxial cable connecting the double-layer coil 239 passes through the cable hole 212 and is fixedly connected to the coaxial cable connector 11 of the three-way coaxial cable connector 237 at the lower end, and the upper end of the coaxial cable is fixedly connected to the coaxial cable connector 11 of the modem main board 10; the connecting wire connecting the thermocouple 238 passes through the cable hole 212, and its upper end is fixedly connected to the temperature difference compensation control board 13, and the lower end is fixedly connected to the two thermocouples 238 respectively.

The above-mentioned eddy current induction head 23 is located at the center of the cover barrel body 201, and the diameter and height of the eddy current induction head 23 are smaller than the diameter and height of the cover barrel body 201 and the convex ring 202. The main purpose of such arrangement is: on the one hand, the eddy current induction head 23 can be installed in the center of the cover barrel body 201 and the convex ring 202, and the cover barrel body 201 and the convex ring 202 play a role in protecting the eddy current induction head 23 from high temperature; on the other hand, the eddy current induction head 23 is located at the center of the heat-resistant cover barrel 20, and when the eddy current induction head 23 is electromagnetically induced with the molten metal liquid surface, the electromagnetic induction line can smoothly sense the surface of the molten metal liquid surface.

As shown in Figure 1-10, the induction tracking control method of the eddy current induction tracking control molten metal liquid level detection system is as follows:

Step 1: Acquisition of excitation impedance signal simulated by eddy current induction head and temperature simulation signal of thermocouple: When the heat-resistant cover tube 20 and the eddy current induction head 23 are in the calibrated initial position, as the opening of the stopper rod (used to block the port for injecting metal liquid into the crystallizer) increases, the molten metal liquid in the crystallizer increases continuously, so that the molten metal liquid level in the crystallizer also increases continuously, and the eddy current induction head 23 and the heat-resistant cover tube 20 are linked with the linear actuator 16 and the potentiometer 17 (the extension of the linear actuator 16 is When the retracting rod is extended and retracted, the telescopic rod of the potentiometer 17 is also extended and retracted by the same distance). The eddy current induction head 23 and the heat-resistant cover tube 20 sense and track the position of the molten metal liquid level in the crystallizer in real time. At this time, the double-layer coil 239 in the eddy current induction head 23 obtains the simulated excitation impedance signal due to the change in the distance between the eddy current induction head 23 and the heat-resistant cover tube 20 and the molten metal liquid level. At the same time, the thermocouple 238 obtains the simulated temperature signal of the temperature change around the double-layer coil 239.

Step 2, modulation and demodulation processing of the excitation impedance signal simulated by the eddy current induction head: the simulated excitation impedance signal (AC) is transmitted to the modulation and demodulation main board 10 through the coaxial cable connected to the three-way coaxial cable connector 237 through the coaxial cable connector 11 on the modulation and demodulation main board 10; the FPGA chip module on the modulation and demodulation main board 10 generates a DDS frequency and phase adjustable signal through the FFT algorithm, and provides a simulated two-terminal sinusoidal excitation impedance signal to the digital-to-analog conversion module 1 and the digital-to-analog conversion module 2. The signal is converted into a digital two-terminal sinusoidal excitation impedance signal through the digital-to-analog conversion module 1 and the digital-to-analog conversion module 2, and is transmitted to the gain adjustable operational amplifier 1 and the gain adjustable operational amplifier 2. The gain adjustable operational amplifier 1 and the gain adjustable operational amplifier 2 convert the digital two-terminal sinusoidal excitation impedance signal into a digital single-ended sinusoidal excitation impedance signal, and amplify the digital single-ended sinusoidal excitation impedance signal. The driving energy of the excitation impedance signal; the digital single-ended sinusoidal excitation impedance signal processed by the gain-adjustable operational amplifier 1 and the gain-adjustable operational amplifier 2 and the excitation impedance signal simulated by the eddy current induction head are merged, and the phase of the merged digital single-ended sinusoidal excitation impedance signal and the excitation impedance signal simulated by the eddy current induction head are made consistent through the comparison operation of the gain-adjustable operational amplifier 3, and the driving energy of this signal is increased, and at the same time converted into a double-ended (differential) digital and analog excitation impedance signal; then the phase of the above signal is phase-shifted by a phase-shifting transformer, and the above signal is uniformly converted into a digital excitation impedance signal through a digital-to-analog conversion module 3, and finally processed by the FFT algorithm of the FPGA chip module, and converted into an analog excitation impedance signal (expressed as a distance signal between the eddy current induction head and the molten metal liquid surface) through the DA conversion module, and then transmitted to the analog signal receiving module of the temperature difference compensation control board 13 through the analog signal output end;

Step 3: Temperature difference compensation operation of the excitation impedance signal simulated by the eddy current induction head and the thermocouple temperature simulation signal: In the above step 2, after the analog signal receiving module of the temperature difference compensation control board 13 receives the signal, it is normalized by the normalization processing module of the temperature difference compensation control board 13, and then the simulated excitation impedance signal gain is amplified by the gain operational amplifier to enhance the signal strength and maintain the transmission linearity; at the same time, the thermocouple signal receiving module of the temperature difference compensation control board 13 receives the received thermocouple temperature simulation signal through a K-type temperature amplifier to convert the simulated temperature The signal is amplified and transmitted to the temperature difference compensation module. The temperature difference compensation module adds the temperature drift caused by the temperature increase of the double-layer coil 239, and the distance value between the eddy current induction head and the molten metal surface before the temperature of the double-layer coil 239 is detected, and the distance value between the eddy current induction head and the molten metal surface after the temperature of the double-layer coil 239 is increased to make them consistent; then the analog signal of the thermocouple 238 processed by the temperature difference compensation module is amplified by the gain operational amplifier; at the same time, the linear actuator 16 and the potentiometer 17 are linked In the coordinated action, the potentiometer 17 obtains the analog position signal of the telescopic action of the linear actuator 16 through the linear actuator maximum and minimum limit module of the temperature difference compensation control board 13, and reduces the position error of the analog position signal of the telescopic action of the linear actuator 16 by half through the half-proportional adjustment circuit of the half-proportional adjustment module; finally, the excitation impedance signal simulated by the eddy current induction head 23, the temperature analog signal of the thermocouple 238 and the analog position signal of the telescopic action of the linear actuator 16 are added and calculated through the analog addition operation module to calculate the precise telescopic action control analog signal of the linear actuator 16, and the precise telescopic action control analog signal of the linear actuator 16 is transmitted to the central control room PLC module in the factory. The central control room PLC module accurately controls the motor of the linear actuator 16 through the linear actuator telescopic control module to achieve precise control of the telescopic action of the linear actuator 16, thereby achieving real-time induction tracking control detection of the rising molten metal liquid level in the crystallizer by the heat-resistant hood 20 and the eddy current induction head 23;

Step 4: After the temperature difference compensation operation of the excitation impedance signal simulated by the eddy current induction head and the temperature simulation signal of the thermocouple, the linear actuator, potentiometer, heat-resistant hood, eddy current induction head and stopper rod are controlled in linkage: when the stopper rod opening is at the maximum opening and lasts for a period of time, when the molten metal liquid in the crystallizer reaches the maximum liquid level position set by the process, the eddy current induction head 23 obtains the simulated excitation impedance signal when the molten metal liquid level is at the maximum liquid level set by the process, the thermocouple 238 obtains the real-time simulated temperature signal, and the potentiometer 17 obtains the real-time simulated position signal of the linear actuator 16, and then the excitation impedance signal simulated by the eddy current induction head in step 2 is The modulation and demodulation processing and the temperature difference compensation operation of the excitation impedance signal simulated by the eddy current induction head and the thermocouple temperature simulation signal in step three are used to accurately calculate the retraction stroke of the linear actuator 16, and the motor of the linear actuator 16 sends a control retraction stroke signal through the PLC module of the central control room. At this time, the eddy current induction head 23 and the heat-resistant hood tube 20 are at the process maximum liquid level position of the molten metal liquid surface driven by the retraction action of the linear actuator 16; at the same time, the PLC in the central control room sends a control signal of the corresponding closing opening to the control module of the stopper rod, and the stopper rod reduces the opening until the molten metal liquid level in the crystallizer is at the equilibrium liquid level height required by the process.

As shown in FIG. 10 , in step 2, the simulated excitation impedance signal (AC) is transmitted to the modem mainboard 10 through the coaxial cable connected to the three-way coaxial cable connector 237 and the coaxial cable connector 11 on the modem mainboard 10; the FPGA chip module on the modem mainboard 10 produces a two-terminal sinusoidal excitation impedance signal with adjustable DDS frequency and phase through the FFT algorithm, and provides the simulated two-terminal sinusoidal excitation impedance signal to the digital-to-analog conversion module 1 and the digital-to-analog conversion module 2, and the digital-to-analog conversion module 1 and the digital-to-analog conversion module 2 convert the simulated two-terminal sinusoidal excitation impedance signal into a digital two-terminal sinusoidal excitation impedance signal, and transmits the signal to the gain adjustable operational amplifier 1 and the gain adjustable operational amplifier 2, and the gain adjustable operational amplifier 1 and the gain adjustable operational amplifier 2 convert the digital two-terminal sinusoidal excitation impedance signal into a digital single-ended sinusoidal excitation impedance signal, and increase the driving energy of the digital single-ended sinusoidal excitation impedance signal. The main purpose of doing the above is: on the one hand, to produce a DDS frequency and phase adjustable analog two-terminal sinusoidal excitation impedance signal through the FFT algorithm in the FPGA chip module on the modulation and demodulation main board 10; on the other hand, to convert the frequency and phase adjustable analog two-terminal sinusoidal excitation impedance signal into a digital two-terminal sinusoidal excitation impedance signal through the analog conversion module 1 and the digital-to-analog conversion module 2, and at the same time, with the cooperation of the gain adjustable operational amplifier 1 and the gain adjustable operational amplifier 2, to convert the analog two-terminal sinusoidal excitation impedance signal into a digital single-ended sinusoidal excitation impedance signal, and to increase the driving energy of the digital single-ended sinusoidal excitation impedance signal.

Among them, in step 2, the digital single-ended sinusoidal excitation impedance signal processed by the gain-adjustable operational amplifier 1 and the gain-adjustable operational amplifier 2 and the excitation impedance signal simulated by the eddy current induction head are merged, and the phase of the merged digital single-ended sinusoidal excitation impedance signal and the excitation impedance signal simulated by the eddy current induction head are made consistent through the comparison operation of the gain-adjustable operational amplifier 3, and the driving energy of this signal is increased, and at the same time converted into a double-ended (differential) digital and analog excitation impedance signal; then the phase of the above signal is processed by a phase-shifting transformer, and the above signal is uniformly converted into a digital excitation impedance signal through a digital-to-analog conversion module 3, and finally processed by the FFT algorithm of the FPGA chip module, converted into an analog excitation impedance signal (expressed as a distance signal between the eddy current induction head and the molten metal liquid surface) through the DA conversion module, and then transmitted to the analog signal receiving module of the temperature difference compensation control board 13 through the analog signal output end. The main purpose of doing the above is: since the driving energy of the digital single-ended sinusoidal excitation impedance signal processed by the gain-adjustable operational amplifier 1 and the gain-adjustable operational amplifier 2 is large enough to merge the excitation impedance signal simulated by the eddy current induction head, thereby increasing the driving energy of the signal itself.

As shown in Figure 10, in step three, the thermocouple signal receiving module of the temperature difference compensation control board 13 amplifies the received thermocouple temperature simulation signal through a K-type temperature amplifier and transmits the simulated temperature signal to the temperature difference compensation module. The temperature difference compensation module adds the temperature drift caused by the increase in the temperature of the double-layer coil 239 through an addition operation, and adds the distance value between the eddy current induction head and the molten metal liquid surface before the temperature of the double-layer coil 239 is detected to be consistent with the distance value between the eddy current induction head and the molten metal liquid surface after the temperature of the double-layer coil 239 is increased. For example, before the temperature of the double-layer coil 239 does not rise, the detection distance between the eddy current induction head and the molten metal liquid surface is 15 mm, but as the temperature of the double-layer coil 239 rises, the temperature of the double-layer coil 239 begins to drift, resulting in a decrease in the detection accuracy of the eddy current induction head, thereby making the detection distance between the eddy current induction head and the molten metal liquid surface 16 mm; at this time, the system will think that the original detection distance between the eddy current induction head and the molten metal liquid surface is 15 mm, which is consistent with the detection distance between the eddy current induction head and the molten metal liquid surface of 16 mm caused by the increase in the temperature of the double-layer coil 239; at this time, through the addition operation of the temperature difference compensation module of the temperature difference compensation control board 13, the detection distance between the eddy current induction head and the molten metal liquid surface caused by the increase in the temperature of the double-layer coil 239 is forced to be reduced from 16 mm to the position where the distance between the eddy current induction head and the molten metal liquid surface is 15 mm before the temperature of the double-layer coil 239 does not rise.

Various modifications of the embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A detection system for tracking and controlling the level of molten metal by eddy current induction, comprising a mounting fixture, a mounting slot, and a control box, wherein the mounting fixture is fixedly mounted in the middle position of the mounting slot, the mounting fixture is fixedly connected to one side of the crossbeam on the upper part of the crystallizer, the control box is fixed in the front position of the mounting slot, the control box is a hollow font structure, and the box panel is mounted in the front position of the control box; characterized in that: an eddy current cooler is fixedly arranged at the upper part of the control box near the left side, the eddy current cooler penetrates into the interior of the control box, and is used for air-cooling the inner wall of the control box for heat dissipation; The main air inlet is opened at the rear side of the vortex cooler; the three-way air valve is fixedly arranged at the right side of the vortex cooler, and the three-way air valve extends to the inside of the control box; the wiring harness pipe is fixedly arranged at the upper middle position of the control box, and the wiring harness pipe is connected with the inside of the control box; the three-way branch pipe is fixedly arranged at the bottom of the three-way air valve, and the three-way branch pipe is located at the upper left side of the control box; The modem mainboard is fixedly arranged at the bottom of the three-way branch pipe, and the rear side of the modem mainboard is fixedly connected to the rear inner wall of the control box; the coaxial cable connector is fixedly arranged at the middle position on the right side of the modem mainboard; the heat sink is fixedly arranged at the lower part of the modem mainboard, and the rear side of the heat sink is fixedly connected to the rear inner wall of the control box; The temperature difference compensation control board is fixedly arranged on the outer surface of the heat sink; the main fixed card slot is fixedly arranged at the lower right position of the inner wall of the control box body, and the main fixed card slot is used to install and fix the linear actuator; the secondary fixed card slot is fixedly arranged at the lower right position of the main fixed card slot, and the secondary fixed card slot is used to install and fix the potentiometer; the linear actuator is installed and fixed in the main fixed card slot, and the telescopic rod of the linear actuator is fixedly connected to the upper part of the square fixed body; the upper part of the potentiometer is installed and fixed in the secondary fixed card slot, and the lower end of the potentiometer is fixedly connected to the upper part of the square fixed body; the sliding groove is fixedly arranged on the partition at the lower right part of the control box body; the sliding box body is fixedly arranged on the sliding groove, and the sliding box body is telescopically pushed up and down by the telescopic push of the linear actuator, and the lower part of the sliding box body is fixedly connected to the surrounding sides of the square fixed body; The heat-resistant cover tube is fixedly arranged at the bottom of the square fixed body, and the heat-resistant cover tube is fixedly connected into a whole by passing a U-shaped fixing card through the heat-resistant cover tube; the eddy current induction head is fixedly arranged at the inner center position between the square fixed body and the heat-resistant cover tube, and the eddy current induction head is used to track and induction control the height of the molten metal liquid level in the crystallizer. 2. According to claim 1, an eddy current induction tracking and control system for detecting the liquid level of molten metal, characterized in that: the heat sink includes a heat sink body, the heat sink body is fixed to the rear inner wall of the control box, the air inlet is opened in the upper middle position of the heat sink body, and the exhaust hole is opened in the right middle position of the heat sink body; the air inlet is fixedly connected to the left end of the three-way branch pipe through an air pipe, and the exhaust hole extends to the outside of the control box through the air pipe. 3. According to claim 1, an eddy current induction tracking and control system for detecting the liquid level of molten metal is characterized in that: the sliding groove includes a sliding groove body, the sliding groove body is fixedly arranged on the right side of the internal partition where the sliding groove is installed, the sliding groove body is U-shaped, the strip groove is opened in the middle position of the sliding groove body, the upper position of the strip groove is closed, and the lower position of the strip groove is open; the left side plate of the sliding box body is installed in the strip groove, so that the sliding box body can slide up and down along the strip groove. 4. According to claim 1, an eddy current induction tracking and control system for detecting the liquid level of molten metal is characterized in that: the sliding box body includes a box body, the box body is a hollow square body, and four fixing holes are symmetrically arranged on the front and rear sides of the bottom of the box body; the fixing holes arranged at the bottom of the box body correspond to the lateral fixing holes of the square fixed body front and back, and the box body and the square fixed body are fixed together by screws. 5. According to claim 1, an eddy current induction tracking and control system for detecting the molten metal liquid level is characterized in that the heat-resistant hood includes a hood body, which is a structure with a convex ring on the upper part and a hollow cylindrical structure on the lower part. 6. According to claim 1, an eddy current induction tracking and control system for detecting the liquid level of molten metal, characterized in that: the square fixed body includes an actuator telescopic rod fixing hole, the actuator telescopic rod fixing hole is opened at the upper part of the square fixed body body near the rear side, the cable hole is opened at the left front side of the actuator telescopic rod fixing hole, the cooling hole is opened at the front side of the cable hole, and the potentiometer fixing hole is opened at the right rear side of the cooling hole; the actuator telescopic rod fixing hole, the cable hole and the cooling hole pass through the square fixed body up and down, and the lateral fixing holes are opened on the front and rear sides of the upper part of the square fixed body body, and are front and rear. Four lateral fixing holes are symmetrically arranged; the thread holes are symmetrically opened in the middle of the square fixing body near the left side, the clamping blocks are integrally formed at the four corners of the middle bottom of the square fixing body, and the inner side of the clamping blocks is an arc-shaped surface; the convex cylinder is fixedly arranged at the bottom center position in the middle of the square fixing body, and the bottom of the convex cylinder is symmetrically opened with tightening holes in the front and back; the exhaust grooves are symmetrically opened on the left and right sides of the middle bottom position of the square fixing body, and the inner side of the exhaust groove extends to the outer edge of the convex cylinder; the through hole is opened in the middle of the square fixing body, and the through hole is cross-connected with the actuator telescopic rod fixing hole, cable hole and cooling hole. 7. According to claim 1, an eddy current induction tracking and control system for detecting the liquid level of molten metal is characterized in that: the linear actuator and the telescopic rod pass through the rear side of the box body, the telescopic rod of the linear actuator is fixedly connected to the actuator telescopic rod fixing hole; the telescopic rod of the potentiometer passes through the box body and is fixedly connected to the potentiometer fixing hole; the right end of the three-way branch pipe is fixedly connected to the cooling hole through the air pipe. 8. According to claim 6, an eddy current induction tracking and control system for detecting the liquid level of molten metal is characterized in that: the outer side surface of the clamping block is flush with the outer side surface of the middle part of the square fixed body, the inner arc surfaces of the four clamping blocks form a circular space for installing the heat-resistant cover tube convex ring, and a square opening is formed between the four clamping blocks; the exhaust groove is opened in the middle upper position of the square openings on the front and rear sides of the square fixed body. 9. A detection system for tracking and controlling the liquid level of molten metal according to claim 1, characterized in that: the eddy current sensing head includes a protective shell tube, the protective shell tube is an upper hollow protrusion and a lower hollow cylindrical structure integrally formed of heat-resistant resin; the hollow protrusion on the upper part of the protective shell tube is installed inside the convex tube, and the protective shell tube and the convex tube are tightened and fixed by screws passing through the tightening holes of the convex tube; heat dissipation exhaust holes are evenly arranged at the bottom center of the protective shell tube, and the heat dissipation exhaust holes are used to discharge the heat in the protective shell tube; the annular fixing frame and the protective shell tube are an integrally formed structure, and the annular fixing frame is located on the upper inner wall of the protective shell tube; the upper surface of the annular fixing frame is on the left A thermocouple mounting hole is symmetrically opened on the right, the coil fixing body is symmetrical on the left and right and is integrally formed on the inner arc surface of the annular fixing frame, and a matching mounting hole for fixing the positive terminal and the negative terminal of the double-layer coil is opened on the inner end surface of the coil fixing body; the thermocouple is fixedly installed on the thermocouple mounting hole, and the double-layer coil is a spiral double-layer structure wound by a conductive material, and the positive terminal and the negative terminal of the conductive material pass upward through the matching mounting hole of the coil fixing body, the positive terminal is fixedly connected to the left end of the three-way coaxial cable connector, and the negative terminal is fixedly connected to the right end of the three-way coaxial cable connector; the upper middle connecting end of the three-way coaxial cable connector is fixedly connected to the coaxial cable connector of the modem mainboard through a coaxial cable. 10. A detection method for a molten metal level detection system using eddy current induction tracking control according to any one of claims 1 to 9, characterized in that: Step 1, obtaining the excitation impedance signal simulated by the eddy current induction head and the temperature simulation signal of the thermocouple: when the heat-resistant hood and the eddy current induction head are in the calibrated initial position, as the stopper opening increases, the molten metal liquid in the crystallizer continues to increase, so that the molten metal liquid level in the crystallizer continues to rise, and the eddy current induction head and the heat-resistant hood are linked with the linear actuator and the potentiometer. The eddy current induction head and the heat-resistant hood control the position of the molten metal liquid level in the crystallizer in real time. At this time, the double-layer coil eddy current induction in the eddy current induction head obtains the simulated excitation impedance signal due to the change in the distance between the eddy current induction head and the heat-resistant hood and the molten metal liquid level, and at the same time, the thermocouple obtains the simulated temperature signal of the temperature change around the double-layer coil; Step 2, modulation and demodulation processing of the excitation impedance signal simulated by the eddy current induction head: the simulated excitation impedance signal is transmitted to the modulation and demodulation main board through the coaxial cable connected to the three-way coaxial cable connector through the coaxial cable connector on the modulation and demodulation main board; the FPGA chip module on the modulation and demodulation main board generates a DDS frequency and phase adjustable signal through the FFT algorithm, and provides a simulated two-terminal sinusoidal excitation impedance signal to the digital-to-analog conversion module 1 and the digital-to-analog conversion module 2. This signal is converted into a digital two-terminal sinusoidal excitation impedance signal through the digital-to-analog conversion module 1 and the digital-to-analog conversion module 2, and is transmitted to the gain adjustable operational amplifier 1 and the gain adjustable operational amplifier 2. The gain adjustable operational amplifier 1 and the gain adjustable operational amplifier 2 convert the digital two-terminal sinusoidal excitation impedance signal into a digital single-ended sinusoidal excitation impedance signal, and Increase the driving energy of the digital single-ended sinusoidal excitation impedance signal; merge the digital single-ended sinusoidal excitation impedance signal processed by the gain-adjustable operational amplifier 1 and the gain-adjustable operational amplifier 2 with the excitation impedance signal simulated by the eddy current induction head, and make the merged digital single-ended sinusoidal excitation impedance signal and the excitation impedance signal simulated by the eddy current induction head consistent in phase through the comparison operation of the gain-adjustable operational amplifier 3, increase the driving energy of this signal, and convert it into a double-ended digital and analog excitation impedance signal at the same time; then the phase of the above signal is shifted by a phase-shifting transformer, and the above signal is uniformly converted into a digital excitation impedance signal by a digital-to-analog conversion module 3, and finally processed by the FFT algorithm of the FPGA chip module, converted into an analog excitation impedance signal by the DA conversion module, and transmitted to the analog signal receiving module of the temperature difference compensation control board through the analog signal output end; Step 3, temperature difference compensation operation of the excitation impedance signal simulated by the eddy current induction head and the thermocouple temperature simulation signal: In the above step 2, after the analog signal receiving module of the temperature difference compensation control board receives the signal, it is normalized by the normalization processing module of the temperature difference compensation control board, and then the simulated excitation impedance signal gain is amplified by the gain operational amplifier to enhance the signal strength and maintain the transmission linearity; at the same time, the thermocouple signal receiving module of the temperature difference compensation control board amplifies the received thermocouple temperature simulation signal through a K-type temperature amplifier, and transmits it to the temperature difference compensation module. The temperature difference compensation module adds the temperature drift caused by the increase in the temperature of the double-layer coil through addition operation, and adds the distance value between the eddy current induction head and the molten metal liquid surface before the temperature of the double-layer coil is detected to be consistent with the distance value between the eddy current induction head and the molten metal liquid surface after the temperature of the double-layer coil is increased; then the thermocouple simulation signal processed by the temperature difference compensation module is amplified by the gain operational amplifier; at the same time, the linear actuator and the potentiometer are Under the linkage and coordinated action of the meter, the potentiometer obtains the analog position signal of the telescopic action of the linear actuator through the linear actuator maximum and minimum limit module of the temperature difference compensation control board, and reduces the position error of the analog position signal of the telescopic action of the linear actuator by half through the half-proportional adjustment circuit of the half-proportional adjustment module; finally, the excitation impedance signal simulated by the eddy current induction head, the thermocouple temperature simulation signal and the analog position signal of the telescopic action of the linear actuator are added and calculated through the analog addition operation module to obtain the precise telescopic action control analog signal of the linear actuator, and the precise telescopic action control analog signal of the linear actuator is transmitted to the central control room PLC module in the factory. The central control room PLC module accurately controls the motor of the linear actuator through the linear actuator telescopic control module to achieve precise control of the telescopic action of the linear actuator, thereby achieving real-time induction tracking control detection of the rising molten metal liquid level in the crystallizer by the heat-resistant hood and the eddy current induction head; Step 4: After temperature difference compensation calculation of the excitation impedance signal simulated by the eddy current induction head and the temperature simulation signal of the thermocouple, the linear actuator, potentiometer, heat-resistant hood, eddy current induction head and stopper are controlled in linkage: when the stopper opening is at the maximum opening and lasts for a period of time, when the molten metal liquid in the crystallizer reaches the maximum liquid level position set by the process, the eddy current induction head obtains the simulated excitation impedance signal when the molten metal liquid level is at the maximum liquid level set by the process, the thermocouple obtains the real-time simulated temperature signal, and the potentiometer obtains the real-time simulated position signal of the linear actuator, and then the excitation impedance signal simulated by the eddy current induction head in step 2 is obtained. The modulation and demodulation processing and the temperature difference compensation operation of the excitation impedance signal simulated by the eddy current sensing head and the temperature simulation signal of the thermocouple in step three are used to accurately calculate the retraction stroke of the linear actuator, and the motor of the linear actuator is sent to control the retraction stroke signal through the PLC module in the central control room. At this time, the eddy current sensing head and the heat-resistant hood are at the maximum liquid level position of the molten metal liquid under the drive of the retraction action of the linear actuator; at the same time, the PLC in the central control room sends a control signal of the corresponding closing opening to the control module of the stopper rod, and the stopper rod reduces the opening until the molten metal liquid level in the crystallizer is at the equilibrium liquid level required by the process.