JP2017161391A - Rotary encoder and method for correcting angle of rotary encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the highly accurate detection data of a rotational position by negating harmonics superimposed on the fundamental wave of a detection signal from a sensor that constitutes a portion of a rotary encoder.SOLUTION: When a magnetoresistive element 50 (first magnetoresistive element) detects the angle position of a rotary magnetic 30 (first rotary magnet) and a magnetoresistive element 60 (second magnetoresistive element) cancels harmonics of a prescribed order (e.g., seventh order) or below by a harmonics cancellation pattern 61 and detects the angle position of a rotary magnetic 40 (second rotary magnet), a data processing unit 10 corrects the detection data of the magnetoresistive element 60 (second magnetoresistive element) by correction data (e.g., electric angle correction angle) that negates harmonics exceeding a prescribed order (e.g., seventh order). Thus, harmonics of a prescribed order or below are canceled by the magnetoresistive element 60 (second magnetoresistive element), and harmonics exceeding a prescribed order are negated by the data processing unit 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rotary encoder suitable for correcting an angle error due to a harmonic component superimposed on a fundamental wave of a detection signal from a sensor constituting a part of a rotary encoder, and an angle correction method for the rotary encoder.

  The rotary encoder detects, for example, the rotational position of the motor shaft of the servo motor and feeds it back to the control system as detection data. Then, the control system compares the detection data from the rotary encoder with the control command value, and outputs a voltage command for controlling the detection data to approach the control value.

  As such a rotary encoder, for example, in Patent Document 1, a first magnet having a magnetized surface in which N poles and S poles are magnetized one by one in the circumferential direction, and the outer side of the first magnet are arranged in the circumferential direction. And a second magnet having an annular magnetized surface in which a plurality of N poles and S poles are alternately magnetized, and the rotational position on the first magnet side is detected by the first magnetoresistive element and the Hall element. A rotary encoder that detects the rotational position of the magnet side with a second magnetoresistive element is proposed.

Japanese Patent No. 5666886

  In the rotary encoder described above, from the detection data of the rotational position on the first magnet side detected by the first magnetoresistive element and the Hall element, and the detection data of the rotational position on the second magnet side detected by the second magnetoresistive element, A rotational position with high resolution can be detected.

  By the way, in such a rotary encoder, a sine wave signal having a constant repetition period is output from the second magnetoresistive element on the second magnet side having a large number of magnetic poles. Further, as is well known, this sine wave signal is a signal in which a harmonic component is superimposed on a fundamental wave component (output of one period with one magnet pole) and a fundamental wave component. In addition, harmonics are generated in prime orders such as the third, fifth, seventh, eleventh, thirteenth, etc., and the smaller the order, the larger the amplitude. That is, if the harmonic amplitude is large, the fundamental wave is distorted. This harmonic appears as an angular error of (order + 1) period.

  In this way, when the rotational position of the motor shaft of the servo motor, for example, is detected based on the sine wave signal on which the harmonics are superimposed, the detected rotational position has an angular error, so the accuracy is high. There was a problem that the detection data of the rotational position could not be obtained.

  The present invention has been made in view of such a situation, and cancels harmonics superimposed on a fundamental wave of a detection signal from a sensor that constitutes a part of a rotary encoder so that a highly accurate rotational position can be obtained. It is an object of the present invention to provide a rotary encoder capable of obtaining detection data and an angle correction method for the rotary encoder.

The rotary encoder of the present invention is a second rotary magnet in which N poles and S poles are magnetized one by one in the circumferential direction, and a plurality of N poles and S poles are alternately magnetized in the circumferential direction. A rotary encoder having a rotary magnet section including a first magnetoresistive element that detects an angular position of the first rotary magnet, and a first encoder that is disposed in proximity to the first magnetoresistive element. A first Hall element, a second Hall element disposed at a position shifted by 90 ° in the mechanical angle in the circumferential direction with respect to the first Hall element, and a second position detecting the angular position of the second rotating magnet. And the angle of the rotating magnet portion by data processing based on detection data of the first magnetoresistive element, the first hall element, the second hall element, and the second magnetoresistive element. And a data processing unit for determining the position. The second magnetoresistive element is provided with a harmonic cancellation pattern for canceling harmonics of a predetermined order or less, and the data processing unit uses the correction data for canceling harmonics exceeding a predetermined order to generate the second magnetoresistive element. The detection data of the magnetoresistive element is corrected.
In this configuration, the first magnetoresistive element detects the angular position of the first rotating magnet, and the second magnetoresistive element cancels the harmonics of a predetermined order or less by the harmonic canceling pattern and performs the second rotation. When the angular position of the magnet is detected, the data processing unit corrects the detection data of the second magnetoresistive element with correction data that cancels harmonics exceeding a predetermined order. As a result, harmonics of a predetermined order or less are canceled by the second magnetoresistive element, and harmonics exceeding the predetermined order are canceled by the data processing unit, so that a detection signal from a sensor constituting a part of the rotary encoder is detected. The harmonics superimposed on the fundamental wave can be canceled out.

The correction data is electrical angle correction data for canceling a cyclic angle error shared by the respective poles of the second rotating magnet, and the data processing unit includes the electrical angle correction data. , An electrical angle correction unit that corrects an angle error of detection data of the second magnetoresistive element using the electrical angle correction data, the first magnetoresistive element, and the first hole And an angular position determination unit that determines an angular position of the rotating magnet unit based on detection data of the element, the second Hall element, and detection data corrected by the electrical angle correction unit. And
In this configuration, the electrical angle correction unit uses the electrical angle correction data stored in the memory to cancel the cyclic angle error that each pole of the second rotating magnet has in common, and the angular position determination unit The angular position of the rotating magnet unit is determined based on the detection data of the first magnetoresistive element, the first Hall element, the second Hall element, and the detection data corrected by the electrical angle correction unit. It is possible to cancel the cyclic angle error that the respective poles of the rotating magnet have in common.

The electrical angle correction data includes data that cancels out harmonics of a predetermined order or less that remain without being canceled by the harmonic cancellation pattern.
In this configuration, the electrical angle correction unit can cancel harmonics of a predetermined order or less, which remain without being canceled by the harmonic cancellation pattern, using the electrical angle correction data.

The memory stores mechanical angle correction data for canceling an angular error periodically generated with the rotation of the first rotating magnet and the second rotating magnet, and the data processing unit It has a mechanical angle correction unit that corrects the angular position data determined by the angular position determination unit using mechanical angle correction data.
In this configuration, since the mechanical angle correction unit corrects the angular position data determined by the angular position determination unit using the mechanical angle correction data stored in the memory, the first magnetoresistive element, the first rotating magnet, Angle errors caused by mechanical factors such as the center misalignment and the center misalignment between the second magnetoresistive element and the second rotating magnet can be canceled out.

The electrical angle correction data has a value obtained by averaging errors due to all harmonics exceeding the predetermined order.
In this configuration, since the electrical angle correction data has a value obtained by averaging errors due to all harmonics exceeding a predetermined order, the storage capacity of the memory can be reduced, and a predetermined amount by the electrical angle correction unit can be reduced. It is possible to shorten the procedure of correction processing for canceling harmonics exceeding the order.

Further, the electrical angle correction data includes a value obtained by averaging errors caused by all the harmonics of the predetermined order or less remaining without being canceled by the harmonic cancellation pattern.
In this configuration, since the electrical angle correction data includes a value obtained by averaging errors due to all harmonics of a predetermined order or less that are not canceled by the harmonic cancellation pattern, the harmonic cancellation pattern It is possible to cancel harmonics of a predetermined order or less that remain without being canceled by.

Further, the electrical angle correction data has a value averaged for each specific order of harmonics exceeding the predetermined order.
In this configuration, since the electrical angle correction data has an average value for each specific order of harmonics exceeding a predetermined order, the electrical angle correction unit detects harmonics exceeding a predetermined order for each specific order. It is possible to cancel out, and it is possible to further reduce the periodic angular error that each pole of the second rotating magnet has in common.

Further, the electrical angle correction data includes a value averaged for each specific order of the harmonics equal to or lower than the predetermined order that remains without being canceled by the harmonic cancellation pattern.
In this configuration, since the electrical angle correction data includes an average value for each specific order of harmonics of a predetermined order or less, which remains without being canceled by the harmonic cancellation pattern, the electrical angle correction unit performs harmonics. Periodic angles that can be canceled for each specific order of harmonics that are not canceled by the wave cancel pattern and that are less than or equal to a predetermined order, and that each pole of the second rotating magnet has in common The error can be further reduced.

Further, the predetermined order is 7th order.
In this configuration, the second magnetoresistive element can cancel the seventh and lower harmonics by the harmonic cancellation pattern.

The angle correction method for a rotary encoder according to the present invention includes a first rotating magnet in which N poles and S poles are magnetized one by one in the circumferential direction, and a plurality of N poles and S poles alternately magnetized in the circumferential direction. A method of correcting an angle of a rotary encoder having a rotating magnet portion including a second rotating magnet, wherein the angular position of the first rotating magnet is detected by a first magnetoresistive element; A first Hall element disposed close to the first magnetoresistive element, a second Hall element disposed at a position shifted by 90 ° in the circumferential direction relative to the first Hall element, and a second The step of detecting the angular position of the second rotating magnet by a magnetoresistive element, and the data processing unit, the first magnetoresistive element, the first Hall element, the second Hall element, the second Based on the detection data of the magnetoresistive element Obtaining an angular position of the rotating magnet portion by a data processing, and the second magnetoresistive element is provided with a harmonic cancellation pattern for canceling a harmonic of a predetermined order or less, and the data processing The unit corrects the detection data of the second magnetoresistive element with correction data that cancels harmonics exceeding a predetermined order.
In this configuration, the first magnetoresistive element detects the angular position of the first rotating magnet, and the second magnetoresistive element cancels the harmonics of a predetermined order or less by the harmonic canceling pattern and performs the second rotation. When the angular position of the magnet is detected, the data processing unit corrects the detection data of the second magnetoresistive element with correction data that cancels harmonics exceeding a predetermined order. As a result, harmonics of a predetermined order or less are canceled by the second magnetoresistive element, and harmonics exceeding the predetermined order are canceled by the data processing unit, so that a detection signal from a sensor constituting a part of the rotary encoder is detected. The harmonics superimposed on the fundamental wave can be canceled out.

The correction data is electrical angle correction data for canceling a cyclic angle error shared by the poles of the second rotating magnet, and is stored in a memory by an electrical angle correction unit. The step of correcting the angle error of the detection data of the second magnetoresistive element using the electrical angle correction data, and the angular position determining unit, the first magnetoresistive element, the first Hall element, the first And a step of determining an angular position of the rotating magnet unit based on the detection data of the Hall element 2 and the detection data corrected by the electrical angle correction unit.
In this configuration, the electrical angle correction unit uses the electrical angle correction data stored in the memory to cancel the cyclic angle error that each pole of the second rotating magnet has in common, and the angular position determination unit The angular position of the rotating magnet unit is determined based on the detection data of the first magnetoresistive element, the first Hall element, the second Hall element, and the detection data corrected by the electrical angle correction unit. It is possible to cancel the cyclic angle error that the respective poles of the rotating magnet have in common.

The electrical angle correction data includes data that cancels out harmonics of a predetermined order or less that remain without being canceled by the harmonic cancellation pattern.
In this configuration, the electrical angle correction unit can cancel harmonics of a predetermined order or less, which remain without being canceled by the harmonic cancellation pattern, using the electrical angle correction data.

Further, the memory stores mechanical angle correction data for canceling an angular error periodically generated with the rotation of the first rotating magnet and the second rotating magnet. The method includes a step of correcting the angular position data determined by the angular position determination unit using mechanical angle correction data.
In this configuration, since the mechanical angle correction unit corrects the angular position data determined by the angular position determination unit using the mechanical angle correction data stored in the memory, the first magnetoresistive element, the first rotating magnet, Angle errors caused by mechanical factors such as the center misalignment and the center misalignment between the second magnetoresistive element and the second rotating magnet can be canceled out.

The electrical angle correction data has a value obtained by averaging errors due to all harmonics exceeding the predetermined order.
In this configuration, since the electrical angle correction data has a value obtained by averaging errors due to all harmonics exceeding a predetermined order, the storage capacity of the memory can be reduced, and a predetermined amount by the electrical angle correction unit can be reduced. It is possible to shorten the procedure of correction processing for canceling harmonics exceeding the order.

Further, the electrical angle correction data includes a value obtained by averaging errors caused by all the harmonics of the predetermined order or less remaining without being canceled by the harmonic cancellation pattern.
In this configuration, since the electrical angle correction data includes a value obtained by averaging errors due to all harmonics of a predetermined order or less that are not canceled by the harmonic cancellation pattern, the harmonic cancellation pattern It is possible to cancel harmonics of a predetermined order or less that remain without being canceled by.

Further, the electrical angle correction data has a value averaged for each specific order of harmonics exceeding the predetermined order.
In this configuration, since the electrical angle correction data has an average value for each specific order of harmonics exceeding a predetermined order, the electrical angle correction unit detects harmonics exceeding a predetermined order for each specific order. It is possible to cancel out, and it is possible to further reduce the periodic angular error that each pole of the second rotating magnet has in common.

Further, the electrical angle correction data includes a value averaged for each specific order of the harmonics equal to or lower than the predetermined order that remains without being canceled by the harmonic cancellation pattern.
In this configuration, since the electrical angle correction data includes an average value for each specific order of harmonics of a predetermined order or less, which remains without being canceled by the harmonic cancellation pattern, the electrical angle correction unit performs harmonics. Periodic angles that can be canceled for each specific order of harmonics that are not canceled by the wave cancel pattern and that are less than or equal to a predetermined order, and that each pole of the second rotating magnet has in common The error can be further reduced.

Further, the predetermined order is 7th order.
In this configuration, the second magnetoresistive element can cancel the seventh and lower harmonics by the harmonic cancellation pattern.

  According to the rotary encoder and the angle correction method of the rotary encoder of the present invention, the second magnetoresistive element cancels harmonics below a predetermined order, and the data processing unit cancels harmonics exceeding the predetermined order by the correction data. Therefore, the harmonics superimposed on the fundamental wave of the detection signal from the sensor that constitutes a part of the rotary encoder can be canceled, and highly accurate detection data of the rotational position can be obtained.

It is a figure which shows one Embodiment of the rotary encoder of this invention. FIG. 2 is a diagram for explaining the basic principle of angular position detection in the case where the harmonics of the rotating magnet portion in FIG. 1 are not included, and FIG. 2 (a) shows the waveforms of detection signals of the magnetoresistive element and Hall element; FIG. 2B is a diagram showing the angular position (electrical angle) of the rotating magnet portion. FIG. 3 shows a method for determining the angular position of the rotating magnet portion of FIG. 1, and FIG. 3A shows the angular position θ obtained from the detection signal (sin, cos) of the magnetoresistive element on the rotating magnet as 1; FIG. 3B shows the angular position θ obtained from the detection signals (sin, cos) of the magnetoresistive element on the rotating magnet, and FIG. 3C shows FIG. 3A. FIG. 4 is a diagram showing a case where the absolute angle data shown in FIG. 3 is combined with the incremental angle data shown in FIG. FIG. 4 shows a cyclic angle error or the like that each pole of the rotating magnet having a plurality of magnetized surfaces in FIG. 1 has in common, and FIG. 4A shows the N pole of the rotating magnet in FIG. The angle error before correction for 128 poles, which is the number of pairs with the S pole, is shown in an overlapped manner, and FIG. 4B is a diagram for 128 poles, which is the number of pairs of N poles and S poles of the rotating magnet in FIG. It is a figure which shows the angle error after correction | amendment overlaid. It is a figure which shows the angle error after correction | amendment for 4 poles among 128 poles of FIG.4 (b). It is a flowchart for demonstrating the angle correction method of the rotating magnet part of FIG.

  Hereinafter, an embodiment of a rotary encoder according to the present invention will be described with reference to FIGS.

  First, a configuration example of a rotary encoder will be described with reference to FIG. The rotary encoder 100 includes a data processing unit 10, a rotating magnet unit 20, a magnetoresistive element 50, Hall elements 51 and 52, a magnetoresistive element 60, amplifiers 70 to 72, and A / D conversion units 73 to 75. The rotary encoder 100 according to the present embodiment is characterized in that, for example, the angle error due to the harmonic component superimposed on the fundamental wave of the detection signal from the magnetoresistive element 60 is corrected. Details will be described later. . Details of the configuration of each unit will also be described in order. In addition, a magnetoresistive element 50, Hall elements 51 and 52 on the rotating magnet 30, which will be described later, and a magnetoresistive element 60 on the rotating magnet 40 are attached to a substrate (not shown) on a fixed plate. The magnetoresistive element 50, the hall elements 51 and 52, and the magnetoresistive element 60, which will be described later, are sensors that output detection signals along with the rotation of the rotating magnet unit 20 described later.

  The data processing unit 10 includes angle calculation units 11 and 12, a memory 13, an electrical angle correction unit 14, an angle position determination unit 15, and a mechanical angle correction unit 16.

  The angle calculation unit 11 performs an arithmetic process on the detection data after A / D conversion from the magnetoresistive element 50 and the Hall elements 51 and 52 to obtain an angular position. Further, the angle calculation unit 11 outputs the obtained angular position as angular position data. The angle calculation unit 12 performs an arithmetic process on the detection data after A / D conversion from the magnetoresistive element 60 to obtain an angular position. In addition, the angle calculation unit 12 outputs the obtained angular position as angular position data. In addition, how to obtain the angle position by the angle calculation units 11 and 12 will be described later.

  The memory 13 stores electrical angle correction data and mechanical angle correction data. Here, the electrical angle correction data is data for correcting a cyclic angle error that the poles of the rotating magnet 40 having a large number of magnetic poles of the rotating magnet unit 20 described later have in common. This periodic angle error is caused by harmonics superimposed on detection signals (sin, cos) of a magnetoresistive element 60 described later. In addition, the harmonic is a wave having a frequency that is an integral multiple of the fundamental wave (one period of output with one magnet), like the third, fifth, seventh, eleventh, thirteenth, etc. It occurs in the prime order.

  In this embodiment, as will be described later, the magnetoresistive element 60 is provided with a harmonic cancel pattern 61 that cancels, for example, the seventh and lower harmonics. For this reason, the electrical angle correction data is error correction data for canceling harmonics exceeding the seventh order. The electrical angle correction data is error correction data that cancels a cyclic angle error that the poles of the rotating magnet 40 have in common. Here, the electrical angle correction data may have a value obtained by averaging errors due to all harmonics exceeding the seventh order in order to cancel the angle error, or specifying the harmonics exceeding the seventh order. It is good also as a value averaged for every order. In addition, the electrical angle correction data may include error correction data that can cancel, for example, the seventh and lower harmonics that are not canceled by the harmonic cancellation pattern 61. In this case, it is possible to cancel, for example, the seventh and lower harmonics remaining without being canceled by the harmonic cancellation pattern 61.

  When the electrical angle correction data has a value obtained by averaging the errors caused by all the harmonics exceeding the 7th order in order to cancel the angle error, the storage capacity of the memory 13 can be reduced, and the electrical angle correction unit 14 can be shortened. On the other hand, when the electrical angle correction data has an average value for each specific order of harmonics exceeding the 7th order in order to cancel the angle error, the storage capacity of the memory 13 increases, and the electrical angle correction unit 14 Although the number of correction processing steps increases, the correction processing can be performed for each specific order by the electrical angle correction unit 14, so that the cyclic angle error shared by each pole of the rotating magnet 40 can be further reduced. .

  The mechanical angle correction data is error correction data for canceling an angular error due to mechanical factors. Incidentally, such angular errors due to mechanical factors are caused by variations in magnetization, misalignment of assembly, and the like. Typical positional deviations for assembly include a center deviation between the magnetoresistive element 50 and the rotating magnet 30, a center deviation between the magnetoresistive element 60 and the rotating magnet 40, and the like. Further, such an angle error is periodically generated as the rotating magnet 40 rotates. That is, such an angular error occurs at a fixed angular position.

  The electrical angle correction data and the mechanical angle correction data described above are error correction data obtained with reference to a master encoder (not shown). Further, these error correction data are obtained in advance by using a measuring device (not shown) as a reference with the master encoder as a reference. In the memory 13, the error correction value obtained by averaging the cyclic angle errors that the respective poles of the rotating magnet 40 have in common is used as electrical angle correction data to cancel the angle error due to mechanical factors. Error correction values are stored as mechanical angle correction data.

  Further, when the electrical angle correction data and the mechanical angle correction data are obtained by the measurement device, a method of calculating an intrinsic error component by Fourier-transforming an error of one rotation of the rotating magnet unit 20 with respect to the master encoder can be used. . As described above, since the electrical angle correction data and the mechanical angle correction data are obtained for each rotating magnet unit 20, appropriate error correction data can be determined for each rotating magnet unit 20. In addition, the measurement device measures, for example, the 7th or lower harmonics remaining without being canceled by the harmonic cancellation pattern 61 with the master encoder as a reference, and the measurement result is used as error correction data to obtain electrical angle correction data. May be included.

  The electrical angle correction unit 14 uses the electrical angle correction data stored in the memory 13 with respect to the angular position data obtained by the angle calculation unit 12, so that each pole of the rotating magnet 40 has a common period. Cancel the angular error. The angular position determination unit 15 determines the angular position of the rotary magnet unit 20 from the angular position data from the angle calculation unit 11 and the corrected angular position data from the electrical angle correction unit 14. The mechanical angle correction unit 16 corrects the angular position data determined by the angular position determination unit 15 using the mechanical angle correction data stored in the memory 13. As a result, it is possible to cancel an angular error caused by mechanical factors such as a center shift between the magnetoresistive element 50 and the rotating magnet 30 and a center shift between the magnetoresistive element 60 and the rotating magnet 40.

  The rotating magnet unit 20 includes rotating magnets 30 and 40. These rotating magnets 30 and 40 are attached to a rotating body (not shown) connected to a motor shaft of a servo motor, for example, and rotate around the rotation axis L in synchronization with the rotation of the motor shaft.

  The rotating magnet 30 has magnetized surfaces 31 and 32 in which N poles and S poles are magnetized one by one in the circumferential direction. These magnetized surfaces 31 and 32 are directed to the magnetoresistive element 50 and the Hall elements 51 and 52 disposed on the rotating magnet 30.

  On the other hand, the rotating magnet 40 has an annular magnetized surface 41 in which a plurality of N poles and S poles are alternately magnetized in the circumferential direction. A plurality of annular magnetized surfaces 41 are arranged in parallel in the radial direction. In this embodiment, two rows are formed in the radial direction, and the positions of the N pole and the S pole are shifted in the circumferential direction between the two rows. That is, the N pole and the S pole are shifted by one pole in the circumferential direction between the two rows. Further, the number of pairs of N poles and S poles is arbitrary, but in the present embodiment, it is set to 128, for example. The annular magnetized surface 41 is directed to the magnetoresistive element 60 disposed on the rotating magnet 40.

  The magnetoresistive element 50 on the rotating magnet 30 has an A phase (SIN) pattern and a B phase (COS) pattern having a phase difference of 90 ° with respect to the phase of the rotating magnet 30. The A-phase (SIN) pattern includes a + a-phase (SIN +) magnetoresistive pattern 50 c and a −a-phase (SIN-) magnetoresistive pattern 50 a that detect movement of the rotating magnet 30 with a phase difference of 180 °. . The B-phase (COS) pattern includes a + b-phase (COS +) magnetoresistive pattern 50d and a -b-phase (COS-) magnetoresistive pattern 50b that detect movement of the rotating magnet 30 with a phase difference of 180 °. . Here, the magnetoresistive patterns 50a to 50c constitute a bridge circuit. The Hall elements 51 and 52 are arranged so as to be shifted by 90 ° (mechanical angle) in the rotation direction around the rotation axis L.

  The magnetoresistive element 60 on the rotating magnet 40 has an A phase (SIN) pattern and a B phase (COS) pattern having a phase difference of 90 ° with respect to the phase of the rotating magnet 40. The A-phase (SIN) pattern includes a + a-phase (SIN +) magnetoresistive pattern 60d and a -a-phase (SIN-) magnetoresistive pattern 60b that detect movement of the rotating magnet 40 with a phase difference of 180 °. . The B phase (COS) pattern has a + b phase (COS +) magnetoresistive pattern 60c and a -b phase (COS-) magnetoresistive pattern 60a that detect the movement of the rotating magnet 40 with a phase difference of 180 °. . Here, the magnetoresistive patterns 60a to 60d constitute a bridge circuit.

  In addition, the magnetoresistive element 60 has a harmonic cancellation pattern 61 that cancels harmonics. Here, a sine wave signal having a constant repetition period is output from the magnetoresistive element 60 on the rotating magnet 40 having a large number of magnetic poles. As described above, this sine wave signal is a signal in which a harmonic component is superimposed on a fundamental wave component (output of one period with one magnet pole) and a fundamental wave component. In addition, harmonics are generated in prime orders such as third order, fifth order, seventh order, eleventh order, thirteenth order, etc., and the smaller the order, the larger the amplitude. This harmonic appears as an angular error of (order + 1) period.

  Therefore, it is theoretically possible to eliminate the angular error by providing the magnetoresistive element 60 with the harmonic cancellation pattern 61 that can cancel all the harmonics of the orders. However, the harmonic cancellation pattern 61 capable of canceling harmonics of all orders has a large number of pattern repetitions and increases in size. Further, the size of the magnetoresistive element 60 is limited due to the balance of the pitch between the magnetic poles of the rotating magnet 40. For this reason, in this embodiment, the magnetoresistive element 60 is provided with a harmonic cancel pattern 61 that can cancel, for example, the seventh and lower harmonics. The harmonic cancellation pattern 61 is not limited to the seventh order or lower. For example, it may be 11th order or less, or 6th order or less.

  The amplifier 70 is provided on the output side of the Hall elements 51 and 52 on the rotating magnet 30 and amplifies the detection signals of the Hall elements 51 and 52. The amplifier 71 is provided on the output side of the magnetoresistive element 50 on the rotating magnet 30 and amplifies the detection signal of the magnetoresistive element 50. The amplifier 72 is provided on the output side of the magnetoresistive element 60 on the rotating magnet 40 and amplifies the detection signal of the magnetoresistive element 60.

  The AC / DC converter 73 is provided on the output side of the amplifier 70 and converts the detection signal amplified by the amplifier 70 into detection data. The AC / DC converter 74 is provided on the output side of the amplifier 71 and converts the detection signal amplified by the amplifier 71 into detection data. The AC / DC converter 75 is provided on the output side of the amplifier 72 and converts the detection signal amplified by the amplifier 72 into detection data.

  Next, the basic principle of detection of the angular position of the rotating magnet unit 20 when harmonics are not included will be described with reference to FIGS. 2 and 3. 2A shows the waveforms of the detection signals of the magnetoresistive element 50 and the Hall elements 51 and 52 on the rotating magnet 30, and FIG. 2B shows the angular position (electrical angle) of the rotating magnet unit 20. Show. FIG. 3 shows a method for determining the angular position of the rotating magnet unit 20. FIG. 3A shows the angular position θ obtained from the detection signals (sin, cos) of the magnetoresistive element 50 on the rotating magnet 30 for one cycle. FIG. 3B shows the angular position θ obtained from the detection signals (sin, cos) of the magnetoresistive element 60 on the rotating magnet 40 for one cycle. FIG. 3C shows a case where the absolute angle data shown in FIG. 3A and the incremental angle data shown in FIG. 3B are combined.

  First, when the rotating magnets 30 and 40 are rotated, the detection signals of the magnetoresistive element 50 and the Hall elements 51 and 52 on the rotating magnet 30 are amplified by the amplifiers 70 and 71, and are detected by the A / D conversion units 73 and 74. It is converted and given to the data processing unit 10. The detection signal of the magnetoresistive element 60 on the rotating magnet 40 is amplified by the amplifier 72, converted into detection data by the A / D conversion unit 75, and given to the data processing unit 10. The data processing unit 10 obtains the absolute angular position of the rotating magnet unit 20 based on the detection data of the magnetoresistive element 50 and the Hall elements 51 and 52 and the detection data of the magnetoresistive element 60. The absolute angular position of the rotating magnet unit 20 is relative to an arbitrary reference position. The arbitrary reference position may be a position with respect to a fixed plate (not shown) to which the magnetoresistive element 50, the hall element 51 and the hall element 52 on the rotating magnet 30 and the magnetoresistive element 60 on the rotating magnet 40 are attached.

Here, when the rotating magnet 30 makes one rotation, the magnetic fluxes of the magnetized surfaces 31 and 32 of the rotating magnet 30 change as shown in FIG. Further, when the rotating magnet 30 makes one rotation, the A-phase (SIN) pattern and the B-phase (COS) pattern of the magnetoresistive element 50 having a phase difference of 90 ° from each other, as shown in (b) of FIG. In addition, sine wave signals sin and cos are output for two periods. Then, as shown in FIG. 2B, the data processing unit 10 obtains θ = tan ⁻¹ (sin / cos) from the sine wave signals sin and cos, so that the angular position θ of the rotating magnet unit 20 can be obtained. . This calculation process is performed by the angle calculation unit 11.

  Further, the Hall elements 51 and 52 on the rotating magnet 30 are arranged at positions shifted by 90 ° when viewed from the center of the rotating magnet 30. For this reason, when the rotating magnet 30 makes one rotation, the outputs of the Hall elements 51 and 52 change from (H, L) → (H, H) → (L, H) → (L, L). That is, by confirming that the output of the Hall elements 51 and 52 is any one of the four outputs, it can be determined in which section from 0 ° to 360 °. In addition, by monitoring the output states of the Hall elements 51 and 52, the angular position can be determined even when there are two combinations of the sin output and the cos output of the magnetoresistive element 50 as shown in FIG. Therefore, the rotational position and the angular position θ of the rotating magnet 30 are known from the output of the magnetoresistive element 50 and the outputs of the Hall elements 51 and 52.

Further, the magnetoresistive element 60 on the rotating magnet 40 outputs sine wave signals sin and cos corresponding to the number of pairs of the N pole and the S pole of the annular magnetized surface 41. In this case, with respect to the sine wave signals sin and cos output from the magnetoresistive element 60, as shown in FIG. 2B, if θ = tan ⁻¹ (sin / cos) is obtained, the angular position of the rotating magnet 40 is obtained. θ is known. This calculation process is performed by the angle calculation unit 12.

  Here, as shown in FIG. 3A, absolute angle data for one rotation and one cycle based on the detection data after A / D conversion of the magnetoresistive element 50 and the Hall elements 51 and 52 on the rotating magnet 30 Change. Further, the incremental angle data of one rotation N period based on the detection data after A / D conversion from the magnetoresistive element 60 on the rotating magnet 40 changes as shown in FIG. Therefore, the absolute angle data shown in FIG. 3C can be obtained by combining the absolute angle data shown in FIG. 3A and the incremental angle data shown in FIG. That is, FIG. 3C is absolute angle data obtained by complementing the absolute angle data shown in FIG. 3A with the angle data for 128 poles of the rotating magnet 40.

  Next, with reference to FIG. 4 and FIG. 5, a description will be given of the periodic angular error that each pole of the rotating magnet 40 has in common and the angular error after correction by the electrical angle correction unit 14.

  First, FIG. 4A shows the number of 128 poles, which is the number of pairs of N poles and S poles, of the rotating magnet 40 in an overlapping manner. FIG. 4A shows an angle error before correction due to a specific order (for example, 11th order) harmonics. The horizontal axis indicates the angle of one rotation, and the vertical axis indicates the angle error level when the resolution is 20 bits, for example.

  As can be seen from FIG. 4A, when a harmonic of a specific order (for example, 11th order) is superimposed on the fundamental wave (output of one period with one magnet pole), the maximum level is 20 and −22. The angle error is caused.

  FIG. 4B shows, in the same manner as FIG. 4A, the 128 poles that are the number of pairs of the N pole and the S pole of the rotating magnet 40 in an overlapping manner. FIG. 4B shows the corrected angle when the harmonic of a specific order (for example, 11th order) is canceled based on the electrical angle correction data obtained by averaging the harmonics of a specific order (for example, 11th order). Indicates an error. As can be seen from FIG. 4B, there is an angular error with the maximum level being 20 or -15. However, as can be seen from FIG. 4B, it can be seen that the repeated angular error where the maximum level is 20 and −22 is cancelled.

  FIG. 5 shows the angle error after correction for four poles out of 128 poles in FIG. As can be seen from FIG. 5, since the 11th-order harmonic is corrected, it can be seen that the angular error component of 12 cycles per rotation is reduced.

  Next, a method for correcting the angle of the rotating magnet unit 20 will be described with reference to FIG. In the following description, the detection signal from the magnetoresistive element 60 on the rotating magnet 40 will be described as a case where the harmonics of the 7th order and lower are canceled by the harmonic cancellation pattern 61.

(Step S101)
First, when the rotating magnet unit 20 rotates, the amplifiers 70 to 72 amplify the detection signal. That is, the amplifiers 70 and 71 amplify the detection signals of the magnetoresistive element 50 and the Hall elements 51 and 52 on the rotating magnet 30. The amplifier 72 amplifies the detection signal of the magnetoresistive element 60 on the rotating magnet 40.

(Step S102)
The detection signal is A / D converted. That is, the A / D conversion unit 73 A / D converts the detection signals of the Hall elements 51 and 52 on the rotating magnet 30. In addition, the A / D converter 74 A / D converts the detection signal of the magnetoresistive element 50 on the rotating magnet 30. Further, the A / D converter 75 A / D converts the detection signal of the magnetoresistive element 60 on the rotating magnet 40.

(Step S103)
Find the angular position. That is, the angle calculation unit 11 performs the calculation process of θ = tan ⁻¹ (sin / cos) on the detection data after A / D conversion from the A / D conversion units 73 and 74 to obtain the angle position. Further, the angle calculation unit 12 performs a calculation process of θ = tan ⁻¹ (sin / cos) on the detection data after A / D conversion from the A / D conversion unit 75 to obtain an angle position. In addition, in the detection data after A / D conversion from the A / D conversion unit 75, the harmonics of the 7th order or less are canceled by the harmonic cancellation pattern 61, and therefore the harmonic data exceeding the 7th order is included. include.

(Step S104)
Correct the electrical angle. That is, the electrical angle correction unit 14 cancels harmonics included in the angular position data obtained by the angle calculation unit 12 based on the electrical angle correction data stored in the memory 13. Here, as described above, the electrical angle correction data is, for example, a value obtained by averaging errors due to all harmonics exceeding the seventh order. The electrical angle correction data is a value that cancels a periodic angle error that the poles of the rotating magnet 40 have in common. Therefore, the electrical angle correction unit 14 corrects the angular position data obtained by the angle calculation unit 12 based on the electrical angle correction data, so that the cyclic angle error that the poles of the rotating magnet 40 have in common can be reduced. It is corrected. When the electrical angle correction unit 14 includes error correction data that can be canceled by the harmonic cancellation pattern 61, for example, the harmonics of the 7th order or lower can be canceled. Simultaneously with harmonics exceeding the 7th order, harmonics remaining for example without being canceled by the harmonic cancellation pattern 61 are canceled, for example, harmonics of the 7th order or less.

(Step S105)
Determine the angular position. That is, the angular position determination unit 15 determines the angular position of the rotating magnet unit 20 from the angular position data from the angle calculation unit 11 and the corrected angular position data from the electrical angle correction unit 14.

(Step S106)
Correct the mechanical angle. That is, the mechanical angle correction unit 16 cancels the mechanical angle component with respect to the angular position data determined by the angular position determination unit 15 based on the mechanical angle correction data stored in the memory 13. Here, the mechanical angle correction data is a value that cancels out an angular error caused by a mechanical factor such as a center shift between the magnetoresistive element 50 and the rotating magnet 30 or a center shift between the magnetoresistive element 60 and the rotating magnet 40. . Note that the angular error that any one of the poles of the rotating magnet 40 has is periodically generated as the rotating magnet 40 rotates. Further, such an angular error occurs at a fixed angular position. Therefore, the mechanical angle correction unit 16 corrects the angular position data determined by the angular position determination unit 15, thereby correcting the angular error that periodically occurs as the rotating magnet 40 rotates.

  Thus, in this embodiment, the magnetoresistive element 50 (first magnetoresistive element) detects the angular position of the rotating magnet 30 (first rotating magnet), and the magnetoresistive element 60 (second magnetoresistive element). ) Cancels harmonics of a predetermined order (for example, the 7th order) or less by the harmonic cancellation pattern 61 and detects the angular position of the rotating magnet 40 (second rotating magnet), the data processing unit 10 determines the predetermined order ( For example, the detection data of the magnetoresistive element 60 (second magnetoresistive element) is corrected by correction data (for example, electrical angle correction data) that cancels harmonics exceeding the seventh order. As a result, harmonics of a predetermined order (for example, the 7th order) or less are canceled by the magnetoresistive element 60 (second magnetoresistive element), and harmonics exceeding the predetermined order (for example, the 7th order) are canceled by the data processing unit 10. Since the cancellation is performed, the harmonics superimposed on the fundamental wave of the detection signal from the sensor (the magnetoresistive element 60) constituting a part of the rotary encoder 100 can be canceled, and the detection data of the rotational position with high accuracy can be obtained. Can do.

  Further, the electrical angle correction unit 14 uses the electrical angle correction data stored in the memory 13 to cancel the periodic angle error that each pole of the rotating magnet 40 (second rotating magnet) has in common, The angular position determining unit 15 detects the detection data of the magnetoresistive element 50 (first magnetoresistive element), the hall element 51 (first hall element), the hall element 52 (second hall element), and the electrical angle correction unit 14. Since the angular position of the rotary magnet unit 20 is determined based on the corrected detection data, the cyclic angle error common to each pole of the rotary magnet 40 (second rotary magnet) can be canceled out. it can.

  In addition, when the electrical angle correction data includes data that cancels out the harmonics of a predetermined order or less without being canceled by the harmonic cancellation pattern 61, the electrical angle correction unit 14 cancels the cancellation by the harmonic cancellation pattern 61. It is possible to cancel the harmonics of a predetermined order or less that remain without being processed.

  Further, since the mechanical angle correction unit 16 corrects the angular position data determined by the angular position determination unit 15 using the mechanical angle correction data stored in the memory 13, the magnetoresistive element 50 (first magnetoresistive element). Due to a mechanical misalignment between the center of the magnet and the rotating magnet 30 (first rotating magnet) and a center misalignment between the magnetoresistive element 60 (second magnetoresistive element) and the rotating magnet 40 (second rotating magnet). The generated angle error can be canceled out.

  Further, since the electrical angle correction data has a value obtained by averaging errors due to all harmonics exceeding a predetermined order, the storage capacity of the memory 13 can be reduced, and a predetermined amount by the electrical angle correction unit 14 can be reduced. It is possible to shorten the procedure of correction processing for canceling harmonics exceeding the order.

  Further, when the electrical angle correction data includes a value obtained by averaging the errors due to all the harmonics of a predetermined order or less that remain without being canceled by the harmonic cancellation pattern 61, the harmonic cancellation pattern 61 It is possible to cancel harmonics of a predetermined order or less that remain without being canceled by.

  When the electrical angle correction data has an average value for each specific order of harmonics exceeding a predetermined order, the electrical angle correction unit 14 cancels harmonics exceeding the predetermined order for each specific order. In addition, it is possible to further reduce the periodic angular error that the poles of the rotating magnet 40 (second rotating magnet) have in common.

  Further, when the electrical angle correction data includes a value averaged for each specific order of harmonics of a predetermined order or less, which remains without being canceled by the harmonic cancellation pattern, the electrical angle correction unit 14 performs harmonics. Harmonics below a predetermined order remaining without being canceled by the cancel pattern 61 can be canceled for each specific order, and each pole of the rotating magnet 40 (second rotating magnet) has in common. The periodic angular error can be further reduced.

  Further, by setting the order of the harmonic cancellation pattern 61 of the magnetoresistive element 60 (second magnetoresistive element) to 7th order or less, the magnetoresistive element 60 (second magnetoresistive element) is The 7th and lower harmonics can be canceled.

DESCRIPTION OF SYMBOLS 10 Data processing part 11, 12 Angle calculating part 13 Memory 14 Electrical angle correction | amendment part 15 Angular position determination part 16 Mechanical angle correction | amendment part 20 Rotary magnet part 30, 40 Rotary magnet 31, 32, 41 Magnetized surface 50, 60 Magnetoresistive element 50a to 50d, 60a to 60d Magnetoresistive pattern 51, 52 Hall element 61 Harmonic cancellation pattern 70 to 72 Amplifier 73 to 75 A / D converter 100 Rotary encoder

Claims (18)

Rotation including a first rotating magnet in which N and S poles are magnetized one by one in the circumferential direction, and a second rotating magnet in which a plurality of N and S poles are alternately magnetized in the circumferential direction A rotary encoder having a magnet part,
A first magnetoresistive element that detects an angular position of the first rotating magnet;
A first Hall element disposed proximate to the first magnetoresistive element;
A second Hall element disposed at a position shifted by 90 ° in the mechanical angle in the circumferential direction with respect to the first Hall element;
A second magnetoresistive element for detecting an angular position of the second rotating magnet;
A data processing unit for obtaining an angular position of the rotating magnet unit by data processing based on detection data of the first magnetoresistive element, the first Hall element, the second Hall element, and the second magnetoresistive element And
The second magnetoresistive element is provided with a harmonic cancellation pattern for canceling harmonics of a predetermined order or less,
The rotary encoder according to claim 1, wherein the data processing unit corrects detection data of the second magnetoresistive element with correction data that cancels harmonics exceeding a predetermined order. The correction data is electrical angle correction data for canceling a periodic angle error that each pole of the second rotating magnet has in common.
The data processing unit
A memory in which the electrical angle correction data is stored;
An electrical angle correction unit that corrects an angle error of detection data of the second magnetoresistive element using the electrical angle correction data;
An angular position of the rotating magnet unit is determined based on detection data of the first magnetoresistive element, the first Hall element, and the second Hall element and detection data corrected by the electrical angle correction unit. The rotary encoder according to claim 1, further comprising an angular position determination unit.   3. The rotary encoder according to claim 2, wherein the electrical angle correction data includes data that cancels out harmonics of a predetermined order or less that remain without being canceled by the harmonic cancellation pattern. . The memory stores mechanical angle correction data for canceling an angular error periodically generated with the rotation of the first rotating magnet and the second rotating magnet,
The rotary encoder according to claim 2, wherein the data processing unit includes a mechanical angle correction unit that corrects the angular position data determined by the angular position determination unit using the mechanical angle correction data.   The rotary encoder according to claim 2, wherein the electrical angle correction data has a value obtained by averaging errors due to all harmonics exceeding the predetermined order.   6. The electrical angle correction data includes a value obtained by averaging errors due to all harmonics of the predetermined order or less that remain without being canceled by the harmonic cancellation pattern. The rotary encoder described in 1.   The rotary encoder according to claim 2, wherein the electrical angle correction data has a value averaged for each specific order of the harmonics exceeding the predetermined order.   8. The electrical angle correction data includes a value averaged for each specific order of the harmonics of the predetermined order or less, which remains without being canceled by the harmonic cancellation pattern. Rotary encoder.   The rotary encoder according to claim 1, wherein the predetermined order is a seventh order. Rotation including a first rotating magnet in which N and S poles are magnetized one by one in the circumferential direction, and a second rotating magnet in which a plurality of N and S poles are alternately magnetized in the circumferential direction An angle correction method for a rotary encoder having a magnet part,
Detecting an angular position of the first rotating magnet by a first magnetoresistive element;
A first Hall element disposed proximate to the first magnetoresistive element;
A second Hall element disposed at a position shifted by 90 ° in the mechanical angle in the circumferential direction with respect to the first Hall element;
Detecting an angular position of the second rotating magnet by a second magnetoresistive element;
An angular position of the rotating magnet unit is obtained by data processing based on detection data of the first magnetoresistive element, the first hall element, the second hall element, and the second magnetoresistive element by a data processing unit. And a process for obtaining
The second magnetoresistive element is provided with a harmonic cancellation pattern for canceling harmonics of a predetermined order or less,
The angle correction method for the rotary encoder, wherein the data processing unit corrects the detection data of the second magnetoresistive element with correction data for canceling harmonics exceeding a predetermined order. The correction data is electrical angle correction data for canceling a periodic angle error that each pole of the second rotating magnet has in common.
A step of correcting an angle error of detection data of the second magnetoresistive element using the electrical angle correction data stored in a memory by an electrical angle correction unit;
Based on the detection data of the first magnetoresistive element, the first Hall element, and the second Hall element and the detection data corrected by the electrical angle correction unit by the angular position determination unit, the rotating magnet unit The method for determining the angle position of the rotary encoder according to claim 10, further comprising: determining an angular position of the rotary encoder.   12. The rotary encoder according to claim 11, wherein the electrical angle correction data includes data that cancels out harmonics of a predetermined order or less that remain without being canceled by the harmonic cancellation pattern. Angle correction method. The memory stores mechanical angle correction data for canceling an angular error periodically generated with the rotation of the first rotating magnet and the second rotating magnet,
The angle correction method for a rotary encoder according to claim 11 or 12, further comprising a step of correcting the angular position data determined by the angular position determination unit by using the mechanical angle correction data by a mechanical angle correction unit. .   12. The angle correction method for a rotary encoder according to claim 11, wherein the electrical angle correction data has a value obtained by averaging errors caused by all harmonics exceeding the predetermined order.   15. The electrical angle correction data includes a value obtained by averaging errors due to all harmonics of the predetermined order or less remaining without being canceled by the harmonic cancellation pattern. The angle correction method of the rotary encoder as described in 2.   12. The angle correction method for a rotary encoder according to claim 11, wherein the electrical angle correction data has a value averaged for each specific order of harmonics exceeding the predetermined order.   The electrical angle correction data includes a value averaged for each specific order of the harmonics of the predetermined order or less, which remains without being canceled by the harmonic cancellation pattern. Angle correction method for rotary encoders   The angle correction method for a rotary encoder according to claim 10, wherein the predetermined order is a seventh order.

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