CN105915139A - Vector control permanent magnet synchronous servo motor initial magnetic pole position search method - Google Patents

Abstract

The invention discloses a vector control permanent magnet synchronous servo motor initial magnetic pole position search method. Firstly position rough measurement is performed through a Hall position sensor, then a magnetic pole position is accurately searched by adopting the dichotomy, and an appropriate excitation signal is selected to excite a servo motor so that a rotor is enabled to slightly move; the increment of micro movement is measured by an incremental encoder; and the absolute position relationship of the rotor relative to a stator is acquired. Compared with the method in the prior art that initial magnetic pole control of the rotor is realized through the incremental encoder, the innovation resides in that firstly position rough measurement is performed through the Hall position sensor and a current electric angle interval is determined, and then the magnetic pole position is accurately searched by adopting the dichotomy through the incremental encoder so that searching of the magnetic pole position of the rotor can be greatly accelerated.

Description

A Search Method for Initial Magnetic Pole Position of Vector Control Permanent Magnet Synchronous Servo Motor

technical field

The invention relates to a permanent magnet synchronous motor, in particular to a search method for an initial magnetic pole position of a vector control permanent magnet synchronous servo motor.

Background technique

Servo motors are widely used in robot control. CNC machine tools and other fields that require high performance of the speed control system, servo motors used in high-performance CNC machine tools, robots and other fields almost all need to be equipped with position feedback components such as photoelectric encoders, and the control method is mostly vector control. Through the vector control method, the AC servo motor can be modeled as a DC motor in which the excitation winding and the armature winding rotate synchronously with the rotor, so that the theory of the DC speed control system is applied to the control of the permanent magnet synchronous servo motor to obtain high performance. Control effect.

In the vector control of the permanent magnet synchronous motor, the spatial position relationship between the rotor magnetic pole and the stator has an important influence on the stable operation of the motor. Because in the starting process of the motor, only the accurate spatial position relationship between the rotor and the stator can be obtained, so that the correct voltage phasor can be obtained, and thus the appropriate rotational torque can be obtained. If the motor and the drive power supply are powered on, the position of the rotor relative to the stator winding is arbitrary. According to the torque formula of the motor, since the angle of the rotor magnetic field relative to the angle θ _init of the stator winding cannot be determined when the power is turned on, normal position and speed control cannot usually be achieved. If the magnetic field angle θ is randomly selected as the initial value for control, the torque of the motor may be very small or zero, and the motor may rotate in the opposite direction, which may lead to serious consequences in some cases. At present, the detection methods for the motor rotor position of the permanent magnet synchronous servo drive system mainly include: resolver method, photoelectric encoder disc method (incremental and absolute), motor built-in position sensor method, position sensorless position detection method, these Except for the resolver method and the absolute photoelectric encoder disc, which contain the initial position information of the motor rotor and can be used for the initial positioning of the motor when it is powered on, other methods cannot perform initial positioning of the permanent magnet synchronous motor, and some methods require multiple The positioning of the servo system can only be completed after a second positioning correction. In practical applications, for the motor built-in position sensor method, this method has high requirements for the design of the motor. It is necessary to embed the detection winding while embedding the stator winding of the motor, which is not universal. The sensorless position detection method is a hot research issue at present, but when the permanent magnet synchronous motor is at rest or the motor is just powered on, there is no signal on the stator winding of the motor that can reflect the position information of the motor rotor, and these methods cannot For the initial positioning of the permanent magnet synchronous motor rotor.

Contents of the invention

The purpose of the present invention is to improve the prior art and propose a vector control permanent magnet synchronous servo motor initial magnetic pole position search method.

A vector control permanent magnet synchronous servo motor initial magnetic pole position search method of the present invention comprises the following steps:

(1) Determine the interval [θ _l , θ _h ] of the rotor pole of the servo motor through the sensor, and obtain the initial position of the rotor pole of the servo motor φ(0)=θ ₀ =(θ _l +θ _h )/2 , wherein θ _l is the upper limit value of the six electrical angle intervals of the servo motor rotor determined by the Hall sensor, and θ _h is the lower limit value of the six electrical angle intervals of the servo motor rotor determined by the Hall sensor, θ _h -θ _l = 60°, θ ₀ is the initial position of the rotor, the same below;

(2) adopt dichotomy method to carry out accurate search to described servomotor rotor magnetic pole position:

a. Select an excitation signal to excite the servo motor, so that the rotor of the servo motor generates micro-motion;

b. Use an incremental encoder to measure the increment Δθ _k of the micro-motion described in step a, which is the difference between the rotation angle of the motor in the two sampling periods, the same below;

c. Obtain the absolute position relationship of the rotor of the servo motor relative to the stator, that is, the initial magnetic pole position, according to the increment Δθ _k of the micro-motion in step b.

The sensor in step (1) is a Hall position sensor.

The micro-movement in step (2) means that the rotor of the servo motor rotates by 1° to 2°.

The excitation signal in step a is selected according to the initial position θ ₀ of the rotor pole of the servo motor described in step (1), and the excitation signal is a current signal or a voltage signal.

The method of obtaining the absolute position relationship of the servo motor rotor relative to the stator according to the increment Δθ _k of the micro-motion described in step b described in step c is as follows:

According to the increment Δθ _k of the micro-motion, it is judged that under the action of the current excitation signal, the state of the rotation of the servo motor is clockwise rotation, counterclockwise rotation or stop;

A. When the micro-motion increment Δθ _k is greater than 0, the state of the servo motor rotation is clockwise, and the current position θ of the servo motor rotor is between [θ ₀ , θ _h ]. At this time, the The stator magnetic field of the servo motor rotates counterclockwise (θ ₀ -θ _h )/2, return to step a;

B. When the micro-motion increment Δθ _k is less than 0, the servo motor rotates counterclockwise, and the current position θ of the servo motor rotor is between [θ _l , θ ₀ ]. At this time, the The stator magnetic field of the servo motor rotates clockwise (θ ₀ -θ _l )/2, return to step a;

C. When the increment Δθ _k of the micro-motion is equal to 0, the servo motor stops rotating, the direction of the magnetic field of the stator of the servo motor coincides with the center line of the rotor magnetic pole position, and the search process ends.

According to the measured rotor position information, the invention changes the direction of the stator magnetic field by correcting the stator excitation current, and finally locates the position of the stator magnetic field in the direction of the rotor magnetic field. This process obtains enough information about the rotor magnetic pole position. During the positioning process, the stator magnetic field may frequently swing left and right, and the swing amplitude is getting smaller and smaller. When the left and right swing range is smaller than the preset threshold, it can be considered that the initial rotor pole position search is basically over. First, the Hall position sensor is used to roughly measure the position; then the dichotomy method is used to search the magnetic pole position accurately, and the appropriate current vector is selected to excite the motor to make the rotor produce micro-motion; the incremental encoder is used to measure the increment of the micro-motion; The absolute positional relationship of the rotor relative to the stator. The method in the prior art mainly realizes the initial magnetic pole control of the rotor through an incremental encoder. Compared with the method in the prior art, the innovation of the present invention lies in that the position is roughly measured by the Hall position sensor to determine the current electrical angle interval. Then, through the incremental encoder, the dichotomy method is used to accurately search the magnetic pole position, which can greatly speed up the search for the rotor magnetic pole position.

Description of drawings

Fig. 1 is a flow chart of the method of the present invention;

Figure 2 shows the rotor flux and stator excitation current at initial power-on;

Figure 3 shows the relationship between rotor flux and stator position when the rotor does not rotate;

Figure 4 shows the relationship between the rotor clockwise corresponding to the rotor flux and the position of the stator;

Figure 5 shows the relationship between rotor counterclockwise corresponding to rotor flux and stator position.

detailed description

In conjunction with Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 describe a kind of vector control permanent magnet synchronous servo motor initial magnetic pole position search method of the present invention, comprise the following steps:

1. Roughly measure the position through the Hall position sensor;

In the vector control, the initial electrical angle is concerned, and an interval of every 60° electrical angle is determined according to the arrangement of the Hall sensor output signals HU, HW, and HV. In specific use, three signals are read in at a time through the IO port, and the current electrical angle interval can be determined according to their arrangement.

2. Use the dichotomy method to search the magnetic pole position precisely.

(1) Select the appropriate current vector to excite the motor to make the rotor produce micro-motion;

(2) Use an incremental encoder to measure the increment of the micro-motion;

(3) Obtain the absolute positional relationship of the rotor relative to the stator. The specific steps are:

Step 1: The interval of the rotor magnetic pole determined by the Hall position sensor is [θ _l ,θ _h ];

In the vector control, the initial electrical angle is concerned, and an interval of every 60° electrical angle is determined according to the arrangement of the Hall sensor output signals HU, HW, and HV. In specific use, read 3 signals at a time through the IO port, and determine the interval of the current electrical angle according to their arrangement;

Step 2: Record the initial position of the current rotor pole φ(0)=θ ₀ =(θ _l +θ _h )/2;

Step 3: According to θ ₀ , give a current command vector I _d = I _se , I _q = 0 (where I _se is the stator current vector, I _d and I _q are the values of I _se on the d-axis and q-axis of the two-phase coordinate system respectively component, the same below); (the excitation signal can also use a voltage command vector, the voltage command vector is obtained from the current command vector through vector transformation).

Step 4: Measure the rotation angle θ _k of the motor in the next sampling period, and calculate the difference with the previous θ _k-1 : Δθ _k = θ _k - θ _k-1 ;

Step 5: Determine whether the motor is rotating clockwise, counterclockwise or stalled under the action of the current current vector I _q (k) according to the judgment Δθ _k ;

a. When Δθ _k is greater than 0, the state of motor rotation is clockwise, indicating that the stator magnetic field generated by the current I _d of the motor pulls the rotor to rotate clockwise, indicating that θ is between [θ ₀ , θ _h ], at this time Rotate the stator magnetic field counterclockwise (θ ₀ -θ _h )/2, convert it again to obtain the current loop command, and perform current loop control. Measure the rotation angle θ _k of the motor in the next sampling cycle, and pass the judgment as in the previous step The rotation state of the motor determines the steering angle of the stator magnetic field, and repeats according to similar rules until the degree of subdivision meets the requirements, or the magnetic field angle determination process is ended after the motor stops;

b. When Δθ _k is less than 0, the state of motor rotation is counterclockwise, indicating that the stator magnetic field generated by the current I _d of the motor pulls the rotor to rotate counterclockwise, indicating that θ is between [θ _l , θ ₀ ], at this time Rotate the stator magnetic field clockwise (θ ₀ -θ _l )/2, convert it again to obtain the current loop command, and perform current loop control. Measure the rotation angle θ _k of the motor in the next sampling cycle, and pass the judgment as in the previous step The rotation state of the motor determines the steering angle of the stator magnetic field, and repeats according to similar rules until the degree of subdivision meets the requirements, or the magnetic field angle determination process is ended after the motor stops;

c. When Δθ _k is equal to 0, the motor stops rotating, indicating that the current stator magnetic field direction coincides with the center line of the rotor magnetic pole position, and the search process ends.

Step 6: After repeated testing, the initial angle of the rotor is obtained;

Step 7: The initial orientation is over and the motor starts to run normally.

Among them, I _s is the stator current vector, I _d and I _q are the components of I _s on the d-axis and q-axis of the two-phase coordinate system respectively, φ _m is the magnetic flux of the rotor pole, and the angle between φ _m and the axis of phase A is the rotor The spatial angle θ _init of the magnetic pole, HU, HW, HV are the three-phase output signals of the Hall sensor, θ is the current rotor position, θ ₀ is the initial position of the rotor, θ _l and θ _h are the six electrical angles determined by the Hall sensor A certain upper limit and lower limit of the interval, θ _h -θ _l = 60°, θ _k is the angle of rotation of the motor measured in the next sampling cycle, and θ _k-1 is the rotation of the motor measured in the previous sampling cycle Δθ _k is the difference between the motor rotation angles in two sampling periods.

Claims (5)

1. a vector control permanent magnet synchronous servo motor initial magnetic pole position search method is characterized in that comprising the steps: (1) Determine the interval [θ _l , θ _h ] of the rotor pole of the servo motor through the sensor, and obtain the initial position of the rotor pole of the servo motor φ(0)=θ ₀ =(θ _l +θ _h )/2 , wherein θ _l is the upper limit value of the six electrical angle intervals of the servo motor rotor determined by the Hall sensor, and θ _h is the lower limit value of the six electrical angle intervals of the servo motor rotor determined by the Hall sensor, θ _h -θ _l = 60°, θ ₀ is the initial position of the rotor, the same below; (2) adopt dichotomy method to carry out accurate search to described servomotor rotor magnetic pole position: a. Select an excitation signal to excite the servo motor, so that the rotor of the servo motor generates micro-motion; b. Use an incremental encoder to measure the increment Δθ _k of the micro-motion described in step a, which is the difference between the rotation angle of the motor in the two sampling periods, the same below; c. Obtain the absolute position relationship of the rotor of the servo motor relative to the stator, that is, the initial magnetic pole position, according to the increment Δθ _k of the micro-motion in step b. 2. The method for searching the initial magnetic pole position of a vector control permanent magnet synchronous servo motor according to claim 1, wherein the sensor in step (1) adopts a Hall position sensor. 3. The method for searching the initial magnetic pole position of the vector control permanent magnet synchronous servo motor according to claim 1, characterized in that the micro-movement in step (2) means that the rotor of the servo motor rotates by 1° to 2°. 4. vector control permanent magnet synchronous servo motor initial magnetic pole position search method according to claim 1, is characterized in that the described excitation signal of step a is to choose according to the initial position _θ of described servo motor rotor magnetic pole of step (1) , the excitation signal is a current signal or a voltage signal. 5. The vector control permanent magnet synchronous servo motor initial magnetic pole position search method according to claim 1, characterized in that the increment Δθ _k of the micro-motion described in step b according to step b obtains the relative position of the servo motor rotor The method of the absolute position relation of the stator is as follows: According to the increment Δθ _k of the micro-motion, it is judged that under the action of the current excitation signal, the state of the rotation of the servo motor is clockwise rotation, counterclockwise rotation or stop; A. When the micro-motion increment Δθ _k is greater than 0, the state of the servo motor rotation is clockwise, and the current position θ of the servo motor rotor is between [θ ₀ , θ _h ]. At this time, the The stator magnetic field of the servo motor rotates counterclockwise (θ ₀ -θ _h )/2, return to step a; B. When the micro-motion increment Δθ _k is less than 0, the servo motor rotates counterclockwise, and the current position θ of the servo motor rotor is between [θ _l , θ ₀ ]. At this time, the The stator magnetic field of the servo motor rotates clockwise (θ ₀ -θ _l )/2, return to step a; C. When the increment Δθ _k of the micro-motion is equal to 0, the servo motor stops rotating, the direction of the magnetic field of the stator of the servo motor coincides with the center line of the rotor magnetic pole position, and the search process ends.