WO1999011999A1

WO1999011999A1 - Method and apparatus for measuring rotation motion

Info

Publication number: WO1999011999A1
Application number: PCT/FI1997/000519
Authority: WO
Inventors: Harri Saario
Original assignee: Harri Saario
Priority date: 1996-03-05
Filing date: 1997-09-04
Publication date: 1999-03-11

Abstract

A method and an equipment to gauge rotary motion in which the device sampling the rotation of the part to be gauged includes a part (4) that generates a magnetic field, and a part (19) placed in the magnetic field mentioned which has at least the first (1) and the second (2) sensor gauging the field strength with the result that the parts (4 and 19) are rotating in relation to each other when the part to be gauged is rotating. The information on the magnetic field strength emitted by the first sensor is processed by voltage information in the unit of measurement. The maximum value of this information is registered to mark a certain angle position of the rotation. The information on the magnetic field strength emitted by the second sensor is processed by amplified voltage information in the unit of measurement. When the voltage information of the first sensor passes the maximum voltage point (Ux) and when the amplified voltage information of the second sensor exceeds (Ux), the unit of measurement inverts the voltage figure of the first sensor 180° round the voltage axis (Ux) to produce an ascending voltage signal per a full revolution in the first direction.

Description

METHOD AND APPARATUS FOR MEASURING ROTATION MOTION

The invention is concerned with the method that conforms to the introduction of the patent claim 1 and with the equipment that conforms to the introduction of the patent claim 8 to gauge rotary motion.

In the US patent 5,130,650 we already know the identification of the angle position in rotating axle where plenty of magnetic poles are placed on the axle circle as segments so that half of the poles are positive and half are negative, and together they form a bipolar ring. Two sensors identifying the magnetic field strength are placed outside the ring at an angle of 90^Q in relation to each other. Both sensors give a piece of continuously changing information on the magnetic field strength while the axle is rotating. The signals are simple sinusoidal. By using two sensors the signals are of form S1 =fcosα and S2=fsin . The signals can be processed by using a well-known electronic system whereupon the angle value is numeric.

A disadvantage of this solution is generating a magnetic field. Separate magnets ought to have the same strength and they ought to be in a segmental form filling the circumference of the circle. Besides, the gauging instrument must work out arithmetical operations to find out the angle value. The solution is not adapted for example for a quick regulating of the angle position of the axle where the axle must be stopped in a predetermined angle position, go immediately to a new position etc.

In the US patent 5,241 ,267 we know an identification of rotary motion to reach a high degree of accuracy. The identifier has a rotating axle with a wheel or a corresponding element on which circumference there are poles with positive and negative magnets alternately in large numbers. While the axle is rotating, the magnets are passing the three Hall sensors placed one after another in the direction of rotation. Each sensor gives a variable signal output. By combining the sensor outputs it is possible to double the output frequency and to improve the accuracy. The Hall sensors can be advantageously manufactured as one component.

A disadvantage of the US patent 5,241 ,267 is a need of a multipolar magnetic wheel or ring as well as the fact that the invention is only adapted for gauging slow rotation. With the solution it is possible to gauge the rotation of 360° when we know the number of the magnetic poles on the circumference of the wheel and when we sum up the course of the poles past the sensors. The gauging system will make rather complex.

The meaning of the invention in question is to solve these problems by using only one simple bipolar magnetic field and two sensors that identify the field while the field and the sensors are rotating in relation to each other. To a rotating or swinging axle, of which motion is gauged, is attached either a magnet or sensors. Characteristic of the method and the equipment that conform to the invention is what is presented in the patent claims.

By the method and the equipment that conform to the invention, with a simple magnet and a sensor position, by viewing outputs of two sensors, it is possible to generate an output signal of the rotary motion of the axle to be gauged which is continuously ascending or descending between 0° and 360°. A single output signal unambiguously correspond with each angle value. The axle can rotate in either direction. In continuous rotation there is used a revolution counter to count full revolutions.

The invention is represented below by referring to the enclosed drawings in which

Figure 1 shows a permanent magnet and the Hall sensors in its field Figure 2 shows voltage signals coming from the Hall sensors by functions of the rotational position Figure 3 shows the voltage signal of the sensor 1 by an ascending output Figure 4 shows the block diagram of the gauging system Figure 4a shows an ascending transmitting signal Figure 5 shows the placing of the magnetic field and the sensors by the gauging instrument.

Figure 1 shows a permanent magnet 4 that has the poles N and S, and that generates a magnetic field round itself. The magnetic field flux is represented by the lines of force 3. In the magnetic field there are two Hall sensors 1 and 2. The sensor 2 is in out-of-phase of approximately 90° in relation to the sensor 1. The phase displacement can be selected between 80° and 160° in this method.

The sensor arrangement shown in the figure 1 is viewed so that the sensors 1 and 2 are in their positions and the magnet 4 is rotating parallel with the figure. The magnet 4 is attached for example to a rotating axle. In the position shown in the figure 1 the Hall sensor 1 is in the strongest field and gives a maximum output. The field by the sensor 2 is lower.

Figure 2 graphically shows the voltage signals 5 and 6 emitted by the sensors 1 and 2 by a function of the swing angle of the magnet 4. The voltage signals are generated in a way that conforms to the invention by using normal Hall sensors to indicate the magnetic field strength. This way to carry out the gauging process includes a calibration circuit of the sensor 1 in which the voltage signal of the sensor 1 is calibrated between Uz and Ux volt. In an advantageous form of performance Uz is 1 V and Ux is 2,5 V. In the position shown in the figure 1 , as the pole N of the magnet 4 is in the strongest field by the sensor 1 , the voltage signal 5 is calibrated into value Ux. The magnet

4 being swung 180° and the pole S being by the sensor 1 , the voltage signal

5 is calibrated into the voltage value Uz. After that, while the magnet 4 is rotating in either direction, the signal curve 5 shown in the figure 2 is generated. The voltage signal 6 emitted by the sensor 2 is calibrated to the voltage value Ux in that angle position of the magnet 4 where the signal of the sensor 1 has its maximum value Ux, and in that angle position where the voltage signal of the sensor 1 has the value Uz. The former angle position is 180° and the latter one is 360°. This is possible as the voltage signal of the sensor 2 is amplified by its maximum value higher than Ux. For the value Uy is regulated just the best approximately 1 ,2 Ux. The curve 6 then intersects the voltage level Ux by the angle values 180^s, 360°, 540° etc. So, the gauging equipment indicates the processed voltage signals 5 and 6 coming from the sensors 1 and 2 as shown in the figure 2 while the magnet 4 is rotating.

Figure 3 shows the inverting of the voltage signal 5 of the sensor 1 conforming to the invention. This way to carry out the gauging process discovers the voltage signal 5 of the sensor 1 while the magnet 4 is rotating and the voltage of the signal is passing the maximum voltage value Ux. By help of the calibration circuit it is found out if the amplified voltage 6 of the sensor 2 exceeds the value Ux. If so, the magnet 4 rotates towards a higher angle value as the figure 2 shows, that is, in the figure 1 the magnet 4 rotates clockwise from the initial position.

The situation being this, the inverter inverts the curve 5 in this respect 180^s round the voltage axis Ux to a curve 5'. The inverting is carried out in the whole angular area 180^s - 360^s irrespective of which direction of rotation the area is reached from. When the frequency selected is just fast enough, for example 0 - 20 kHz, it is possible to get an accurate signal curve according to the figure 3 also of the quick rotation.

Thus, in the angular area 180^s - 360^s there appears on each revolution an inverted curve 5', and in the area of full revolution there appears an ascending voltage signal. Analogously, the signal in the area of full revolution can also be a descending one, like in the situation in which the magnet 4 is rotating in another direction. Inverting of the curve 5 stops by the angle values 0^s, 360^s, 720^s etc while the magnet is rotating clockwise because Uy is lower than Ux. However, the inverting begins by these angle values when the magnet 4 begins to rotate anti-clockwise, for Uy is then higher than Ux. Analogously, the inverting stops in anti-clockwise rotation by the angle values like 540^s and 180^s.

Inverting of the curve 5 (comparison Uy higher than Ux) is viewed while passing the maximum point of the curve 5 in either direction. The corresponding angle values in the figure 2 are for example 180^s, 540^s etc.

inverting of the curve 5 is viewed while passing the Uz point of the curve 5 from either direction, too. The corresponding angle values in the figure 2 are for example 0^s, 360^s, 720^s etc.

By means of this way to carry out the gauging process we get an unambiguous ascending or descending voltage figure 5, 5' from the rotation of the magnet 4 per each full revolution. The voltage curve can also be linearized into a graph 7 simply by using well-known methods. Transforming the voltage signal further for example into a numeric angle value is well- known technology in itself.

Figure 4 shows a way to carry out the gauging process in the form of a block diagram. It includes a part 4 that generates a magnetic field and a part 19 that gauges the magnetic field strength and consists of the Hall sensors 1 and 2. The part 4 is attached to the part to be gauged like to an axle, and it rotates with the axle in the first or second direction. For the sensor 1 there is calibration in the block 8 into a maximum value Ux. For the sensor 2 there is calibration in the block 11 into the values Ux by the angle values 180^s and 360^s.

In the block 14 there is an analog switch by which is selected, controlled by the comparator, if the signal inverted by the inverter 10 or the uninverted signal before the inverter is taken to be processed. The inverted signal is selected by the switch 14, if the voltage condition from the comparator 13 Uy is higher than Ux is met. To the comparator 13 comes a voltage from the sensor 2 and a voltage reference from the block 12 (comparison Ux/Uy).

The signal of the sensor 1 comes via an amplifier 9 into the block 14, and the inverter 10 inverts the signal. The inverted or uninverted signal selected by the switch 14 is transferred via a buffer 15 to a convertor from where a signal concerning a full revolution can move on after being modified and linearized, too, if required, by an ascending or descending voltage signal or, as represented in the figure 4a, by an ascending current signal for example l=24 - 40 mV (corresponding 0^s - 360^s).

A revolution counter, a frequency counter or a rotational speed counter is added to the block diagram if the part to be gauged rotates more than 360° or if it is for example a rotating axle.

Figure 5 shows an application attached to the gauging instrument. In the application there are a magnetic field generator 4 according to the invention, and a part 19 with the sensors 1 and 2 gauging the strength of the field. The part 19 is placed round the magnet 4. The sensors 1 and 2 indicate the rotation of the axle of the analog gauge 20, and the corresponding signals are transmitted through a cable 18 to the gauging equipment that conforms to the invention. The part 19 was made into a ring to protect the sensors 1 and 2. The ring is easily to be attached round the generating instruments of the magnetic field.

The invention can be modified in many ways within the inventive idea specified in the patent claims. The method and the equipment can be adapted to indicate and gauge slow or quick rotation, as well as to slow or quick swinging motions. This can be done by a graphic curve for example according to the figure 3, or by an angle value, and the number and speed of the revolutions can be indicated by the rotary motion.

Claims

PATENT CLAIMS

1. A method to indicate or gauge a swing angle or rotation in the first or second direction. The device sampling the rotation of the part to be gauged consists of a part (4) that generates a magnetic field, and a part (19) placed in the magnetic field mentioned which includes the first sensor (1 ) gauging the magnetic field (3) strength, and the second sensor (2) which is out-of- phase with the first sensor. Then the parts (4) and (19) are rotating in relation to each other while the part to be gauged is rotating, and from the sensors mentioned in the method are transmitted the intensity signals of the magnetic field (3) to the unit of measurement which processes the signals and by help of them indicates swing or rotary motion of the part to be gauged, is k n o w n for the property that

- the information of the magnetic field (3) strength emitted by the first sensor (1 ) is processed in the unit of measurement by a piece of voltage information (5), of which maximum value (Ux) and minimum value (Uz) are registered to mark certain angle positions of the rotation,

- the information of the magnetic field (3) strength emitted by the second sensor (2) is processed in the unit of measurement by a piece of amplified voltage information (6) compared to the previous one, of which voltage of the maximum value (Uy) is defined essentially higher than (Ux),

- while the voltage information of the first sensor (1) is passing the maximum voltage point (Ux) or the minimum voltage point (Uz), the amplified voltage information (6) of the second sensor (2) is discovered. When the value of the amplified voltage information is higher than (Ux), the unit of measurement inverts the voltage figure of the first sensor (1 ) 180^s round the voltage axis (Ux) to create an ascending or descending voltage signal per a full revolution in the first direction.

2. The method in accordance with the patent claim 1 is k n o w n for the property that by passing the maximum voltage value (Ux) of the first sensor (1 ) the value of the amplified voltage information of the second sensor (2) being lower than (Ux) indicates that the direction of rotation of the part to be gauged is opposite in relation to the first direction.

3. The method in accordance with the patent claims 1 and 2 is k n o w n for the property that the first (1 ) and the second (2) sensors are out-of-phase between 80^s and 160^s, just best between 90^s and 110^s, and the amplified voltage information of the second sensor is calibrated into the value (Ux) when the first sensor emits the maximum value (Ux) and the minimum value (Uz).

4. The method in accordance with some of the previous patent claims 1 - 3 is k n o w n for the property that the signals of the sensors (1 ) and (2) are indicated by positive voltage values between (Uz - Ux) and (Uz - Uy).

5. The method in accordance with some of the previous patent claims 1 - 4 is k n o w n for the property that the minimum value (Uz) of the voltage (5) corresponds with the angle position 0^s and the maximum value (Ux) corresponds with the angle position 180^s.

6. The method in accordance with some of the previous patent claims 1 - 5 is k n o w n for the property that the voltage signal (6) of the second sensor (2) is amplified 15 - 30% higher by its maximum value than the signal (Ux) of the first sensor.

7. The method in accordance with some of the previous patent claims 1 - 4 is k n o w n for the property that the unit of measurement generates a voltage signal per revolution of the part to be gauged, possibly linearizes the signal (7) and the number of full revolutions is discovered by help of the revolution counter attached to the unit of measurement.

8. An equipment to gauge or indicate rotary motion or the swing angle in the first or second direction whereupon the device sampling the rotation of the part to be gauged includes a part (4) that generates a magnetic field and a part (19) placed in the magnetic field mentioned. The part (19) consists of at least the first sensor (1 ) that gauges the magnetic field (3) strength, and the second sensor (2) that is out-of-phase with the first sensor, whereupon the parts (4) and (19) are rotating in relation to each other while the part to be gauged is rotating and whereupon the strength signals of the magnetic field (3) are transmitted to the unit of measurement which processes the signals, and by help of them indicates the rotary and swinging motion of the part to be gauged, is k n o w n for the property that the equipment includes

- an amplifier (9) that amplifies the voltage information (6) on the same magnetic field (3) strength emitted by the second sensor (2) essentially higher than the voltage information of the first sensor,

- an inverter (10) that inverts the voltage information of the first sensor (1 ) in relation to the voltage axis (Ux) (fig. 3) while the voltage information of the sensor (1 ) is passing the maximum value (Ux) or the minimum value (Uz) if the voltage information (6) of the second sensor (2) is higher than (Ux),

- a convertor (16) to indicate the rotational position of the part to be gauged in the area of full revolution by an ascending or descending voltage value (5,5') or (7), or by an ascending or descending current value (17).

9. The equipment in accordance with the patent claim 8 is k n o w n for the property that the minimum voltage information (Uz) of the first sensor (1 ) is regulated to correspond with the rotational angle value 0^s, 360^s etc and the maximum voltage information (Ux) is regulated to correspond with the angle value 180^s, 540^s etc.

10. The equipment in accordance with the patent claim 8 and 9 is k n o w n for the property that the sensors (1 and 2) are placed in a ring-shaped part (19), and the part is attached round the axle to be gauged or a corresponding element at the point where the generating instruments (4) of the magnetic field are situated.