Rotation angle detection device, motor control device, electric actuator product, electric power steering device, and rotation angle detection method

Abstract

To suppress the impact of a magnetic field on detection accuracy due to a power current or a polyphase current of a power converter when a magnetic sensor detects a rotation angle of a rotation shaft of a polyphase AC motor.SOLUTION: A rotation angle detection device comprises: a magnetic sensor 19 which detects a direction of a magnet magnetic field generated from a magnet 24 fixed to a rotation shaft of a polyphase AC motor 20; a rotation angle calculation unit 31 which calculates a rotation angle of the rotation shaft on the basis of a detection signal of the magnetic sensor 19; a current magnetic field calculation unit which calculates a current magnetic field generated in a location of the magnetic sensor due to at least one of a power current and a polyphase current of a power converter which outputs a polyphase current to the polyphase AC motor 20; an angle correction amount calculation unit which calculates an angle correction amount on the basis of a ratio of a current magnetic field to a magnitude of a magnet magnetic field, and an angle difference which is a difference between a direction of the magnet magnetic field and a direction of a current magnetic field; and a rotation angle correction unit 32 which corrects the rotation angle on the basis of the angle correction amount.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a rotation angle detection device, a motor control device, an electric actuator product, an electric power steering device, and a rotation angle detection method. [Background technology]

[0002] In recent years, magnetic sensors have been used to detect the rotation angle of a motor's shaft. The magnetic sensor is placed close to a magnet fixed to the motor's shaft and detects the rotation angle by detecting the change in the direction of the magnetic field generated by the magnet as the shaft rotates. Such magnetic sensors have the characteristic of being easily affected by the magnetic field caused by a current. For this reason, the following Patent Document 1 proposes a technique for canceling out the magnetic field generated by currents by passing currents of equal magnitude and direction around the magnetic sensor in positions symmetrical with respect to the center of the magnetic sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Unexamined Japanese Patent Publication No. 2012-39737 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it is not always possible to make the positional relationship of the currents flowing around the magnetic sensor symmetrical with respect to the center of the magnetic sensor. The present invention has been made in consideration of the above circumstances, and aims to suppress the influence on detection accuracy of the power supply current or the magnetic field caused by the polyphase current of a power converter that outputs polyphase current to a polyphase AC motor when the rotation angle of the rotating shaft of the polyphase AC motor is detected by a magnetic sensor. [Means for solving the problem]

[0005] In order to achieve the above-mentioned object, a rotation angle detection device according to one embodiment of the present invention includes a magnet fixed to a rotating shaft of a polyphase AC motor, a magnetic sensor that detects the direction of a magnetic field generated by the magnet, a rotation angle calculation unit that calculates the rotation angle of the rotating shaft based on the detection signal of the magnetic sensor, a current magnetic field calculation unit that calculates a current magnetic field generated at the position of the magnetic sensor by at least one of a power supply current and a polyphase current of a power converter that outputs polyphase current to the polyphase AC motor, an angle correction amount calculation unit that calculates an angle correction amount based on the ratio of the magnitude of the current magnetic field to the magnitude of the magnetic field and an angle difference that is the difference between the orientation of the magnetic field and the orientation of the current magnetic field, and a rotation angle correction unit that corrects the rotation angle based on the angle correction amount.

[0006] A motor control device according to another aspect of the present invention includes the above rotation angle detection device and a drive unit that drives a polyphase AC motor based on the rotation angle corrected by the rotation angle correction unit. An electric actuator product according to yet another aspect of the present invention includes a motor control device and a polyphase AC motor controlled by the motor control device. An electric power steering device according to yet another aspect of the present invention includes a motor control device and a polyphase AC motor controlled by the motor control device, and applies a steering assist force to a steering system of a vehicle by the polyphase AC motor.

[0007] According to yet another aspect of the present invention, there is provided a rotation angle detection method for detecting the rotation angle of a rotating shaft of a polyphase AC motor by detecting the direction of a magnetic field generated from a magnet fixed to the rotating shaft with a magnetic sensor. The rotation angle detection method calculates a rotation angle based on a detection signal from the magnetic sensor, calculates a current magnetic field generated at the position of the magnetic sensor by at least one of a power supply current and a polyphase current of a power converter that outputs a polyphase current to the polyphase AC motor, calculates an angle correction amount based on a ratio of the magnitude of the current magnetic field to the magnitude of the magnetic magnetic field and an angle difference that is the difference between the orientation of the magnetic magnetic field and the orientation of the current magnetic field, and corrects the rotation angle based on the angle correction amount. Effect of the Invention

[0008] According to the present invention, when the rotation angle of the rotating shaft of a polyphase AC motor is detected by a magnetic sensor, the influence on the detection accuracy of the power supply current or the magnetic field caused by the polyphase current of a power converter that outputs polyphase current to the polyphase AC motor can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] 1 is a configuration diagram showing an overview of an example of an electric power steering device according to an embodiment; [Diagram 2] FIG. 2 is a configuration diagram showing an outline of the configuration of the control device shown in FIG. [Diagram 3] FIG. 2 is an explanatory diagram of a magnet and a magnetic sensor fixed to a rotating shaft of a motor. [Figure 4] 2 is a block diagram illustrating an example of a functional configuration of a control device in FIG. 1. [Diagram 5] 5 is a block diagram showing an example of a functional configuration of a detection signal correction unit in FIG. 4. [Figure 6] 5(a) to 5(c) are diagrams illustrating offset errors, amplitude errors, and phase errors of a sine signal and a cosine signal, respectively. [Figure 7] 2 is a schematic diagram showing an example of a layout of magnetic sensors, power supply terminals, and motor output terminals on the power board of FIG. 1. [Figure 8] 3 is an explanatory diagram of a magnet magnetic field, a multi-phase current magnetic field, and a composite magnetic field thereof. FIG. [Figure 9] 5 is a flowchart illustrating an example of a process performed by a rotation angle correction unit in FIG. 4. [Figure 10] (a) and (b) are explanatory diagrams of a first example of simulation results of the direction and strength of the current magnetic field, (c) is a diagram showing the angle error due to the current magnetic field before and after correction by the rotation angle correction unit, and (d) is an enlarged diagram of the angle error after correction. [Figure 11] (a) and (b) are explanatory diagrams of a second example of simulation results of the direction and strength of the current magnetic field, (c) is a diagram showing the angle error due to the current magnetic field before and after correction by the rotation angle correction unit, and (d) is an enlarged diagram of the angle error after correction. [Figure 12]13(a) and (b) are explanatory diagrams of a third example of simulation results of the direction and strength of the current magnetic field, (c) is a diagram showing the angle error due to the current magnetic field before and after correction by the rotation angle correction unit, and (d) is an enlarged diagram of the angle error after correction. [Figure 13] 13(a) and (b) are explanatory diagrams of a fourth example of simulation results of the direction and strength of the current magnetic field, (c) is a diagram showing the angle error due to the current magnetic field before and after correction by the rotation angle correction unit, and (d) is an enlarged diagram of the angle error after correction. [Figure 14] 5 is a block diagram illustrating an example of a functional configuration of a motor control unit in FIG. 4. [Figure 15] 5 is a block diagram illustrating an example of a functional configuration of a correction amount setting unit in FIG. 4. [Figure 16] 11 is a flowchart of an example of a process performed by a correction amount setting unit. [Figure 17] 11A and 11B are diagrams illustrating simulation results of amplitudes of a sensor signal before and after correction after passing through a low-pass filter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. The embodiments of the present invention described below are merely examples of devices and methods for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not limit the configuration, arrangement, etc. of the components to those described below. The technical idea of ​​the present invention can be modified in various ways within the technical scope defined by the claims.

[0011] In the following explanation, an example of a rotation angle detection device that detects the rotation angle of a rotating shaft of a three-phase AC motor that provides a steering assist force to an electric power steering device will be described. However, the present invention is not limited to application to electric power steering devices, and can be widely applied to rotation angle detection devices that detect the rotation angle of the rotating shaft of a polyphase AC motor used for various purposes, motor control devices for polyphase AC motors, and electric actuator products equipped with a polyphase AC motor.

[0012] (composition) 1 is a schematic diagram showing an example of an electric power steering device according to an embodiment. A column shaft (steering shaft) 2 of a steering wheel (steering handle) 1 is connected to steered wheels 8L, 8R via a reduction gear (worm gear) 3 constituting a reduction mechanism, universal joints 4a and 4b, a pinion rack mechanism 5, and tie rods 6a and 6b, and further via hub units 7a and 7b.

[0013] The pinion rack mechanism 5 has a pinion 5a connected to a pinion shaft to which steering force is transmitted from the universal joint 4b, and a rack 5b that meshes with this pinion 5a. The rotational motion transmitted to the pinion 5a is converted into linear motion in the vehicle width direction by the rack 5b. A torque sensor 9 is provided on the steering shaft 2 to detect the steering torque Th applied to the steering wheel 1, and a motor 20 is connected to the column shaft 2 via a reduction gear 3 to assist the steering force of the steering wheel 1 in response to the steering torque Th. For example, a polyphase AC motor may be used as the motor 20. In this embodiment, an example will be described in which the motor 20 is a three-phase AC motor having A phase, B phase, and C phase.

[0014] The control device 10 is an electronic control unit (ECU) that controls the driving of a motor 20. Power is supplied to the control device 10 from a battery 11 that is a power source, and an ignition key signal IGN is input from an ignition key 12. The control device 10 calculates a steering assist command value of an assist command using an assist map or the like based on the steering torque Th detected by the torque sensor 9, and supplies a drive current to the motor 20 based on the calculated steering assist command value.

[0015] Fig. 2 is a configuration diagram showing an outline of the configuration of the control device 10 in Fig. 1. The control device 10 includes a control board 13 that processes signals of a control system, a power board 14 on which a drive circuit such as an inverter circuit for driving the motor 20 is formed, and a temperature sensor 15. Note that the control board 13 and the power board 14 may be formed as a single board. The control board 13 has a control circuit formed thereon, which includes a processor 13a, such as a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit), and peripheral components such as a storage device 13b.

[0016] The storage device 13b may include a semiconductor storage device such as a register, a cache memory, a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory) used as a main storage device, a magnetic storage device, an optical storage device, or the like. The signal processing of the control device 10 described below is realized, for example, by the processor 13a executing a computer program stored in the storage device 13b. The control board 13 may be equipped with dedicated hardware (for example, a programmable logic device such as an FPGA (Field-Programmable Gate Array)) for executing each information processing described below.

[0017] The power board 14 is equipped with a drive circuit 16, current sensors 17 and 18, and a magnetic sensor 19. The drive circuit 16 includes an inverter circuit for driving a motor 20, and generates three-phase currents Ia, Ib, and Ic of phases A, B, and C from a DC power source supplied from the battery 11 in accordance with a PWM (Pulse Width Modulation) signal output from the control board 13, and supplies the three-phase currents Ia, Ib, and Ic to the motor 20 as drive currents. The current sensor 17 detects the DC power supply current Ibat supplied from the battery 11 to the drive circuit 16 , and outputs a detection signal to the control board 13 .

[0018] The current sensor 18 detects three-phase currents Ia, Ib, and Ic supplied from the drive circuit 16 to the motor 20, and outputs a detection signal to the control board 13. The magnetic sensor 19 detects the direction of the magnetic field Bm generated by a magnet fixed to the rotating shaft of the motor 20, and outputs a sensor signal including a sine signal SIN0 and a cosine signal COS0 corresponding to the rotation angle of the rotating shaft to the control board 13.

[0019] 3 is an explanatory diagram of a magnet and a magnetic sensor 19 fixed to a rotating shaft of a motor 20. The magnet 24 is fixed, for example, to an end 23 opposite to an output end 22 of a rotating shaft 21 of the motor 20, and has different magnetic poles (south pole and north pole) arranged along the circumferential direction of the rotating shaft 21. The magnetic sensor 19 may be, for example, an MR (Magnetic Resistance) sensor whose electrical resistance changes depending on a magnetic field. The magnetic sensor 19 is disposed close to and facing the magnet 24, and detects the magnetic flux generated from the magnet 24 to generate a sine signal SIN0=A×sinθ and a cosine signal COS0=A×cosθ corresponding to the electrical angle θ of the motor 20.

[0020] 2, the temperature sensor 15 is disposed in the vicinity of the magnet 24 to measure the temperature Tp in the vicinity of the magnet 24 and outputs a measurement signal to the control board 13. 4 is a block diagram of an example of a functional configuration of the control device 10. The control device 10 includes a detection signal correction unit 30, a rotation angle calculation unit 31, a rotation angle correction unit 32, a linearity correction unit 33, an origin correction unit 34, a motor control unit 35, and a correction amount setting unit 36.

[0021] The detection signal correction unit 30 corrects the sine signal SIN0 and cosine signal COS0 output from the magnetic sensor 19 and converted into digital signals by an analog-to-digital converter (not shown) based on the correction amount data G1, Cs, Cc, and G2 calculated in the correction amount setting unit 36. The correction amount data G1, Cs, Cc, and G2 are a first gain for correcting an amplitude error in the cosine signal COS0, a sine offset correction value for correcting an offset error in the sine signal SIN0, a cosine offset correction value for correcting an offset error in the cosine signal COS0, and a second gain for correcting a phase error between the sine signal SIN0 and the cosine signal COS0, respectively. The method of setting the first gain G1, the sine offset correction value Cs, the cosine offset correction value Cc, and the second gain G2 by the correction amount setting unit 36 ​​will be described later.

[0022] 5 is a block diagram of an example of a functional configuration of the detection signal correction unit 30. The detection signal correction unit 30 includes a SIN offset correction unit 40, a COS offset correction unit 41, a COS gain correction unit 42, an adder 43, a subtractor 44, and a phase error correction unit 45. The SIN offset correction unit 40 calculates a sine signal SIN1 by removing the offset error (see FIG. 6(a)) from the sine signal SIN0 by subtracting the sine offset correction value Cs from the sine signal SIN0.

[0023] The COS offset correction unit 41 removes the offset error from the cosine signal COS0 by subtracting a cosine offset correction value Cc from the cosine signal COS0. The COS gain correction unit 42 multiplies the cosine signal COS from which the offset error has been removed by a first gain G1 to obtain a product as the cosine signal COS1, thereby equalizing the amplitudes of the sine signal SIN1 and the cosine signal COS1. This corrects the amplitude error (see FIG. 6(b)) between the sine signal SIN0 and the cosine signal COS0.

[0024] The adder 43 calculates the sum of the sine signal SIN1 and the cosine signal COS1 as a sum signal SA=(COS1+SIN1). The adder 43 outputs the sum signal SA=(COS1+SIN1) to the rotation angle calculation unit 31 and the correction amount setting unit . The subtractor 44 calculates the difference (COS1-SIN1) between the sine signal SIN1 and the cosine signal COS1. The subtractor 44 outputs the difference (COS1-SIN1) to the correction amount setting unit . The phase error correction unit 45 multiplies the difference (COS1-SIN1) by the second gain G2 to calculate the product as the difference signal SD=G2×(COS1-SIN1). This removes the influence of the phase error (see FIG. 6(c)) between the sine signal SIN1 and the cosine signal COS1 from the sum signal SA and the difference signal SD. The phase error correction unit 45 outputs the difference signal SD to the rotation angle calculation unit 31.

[0025] 4, the rotation angle calculation unit 31 calculates a measured angle θ0 of the electrical angle of the motor 20 based on the sum signal SA and the difference signal SD. The rotation angle correction unit 32 corrects an angle error that occurs in the measured angle θ0 calculated by the rotation angle calculation unit 31 due to a magnetic field generated at the position of the magnetic sensor 19 by the three-phase currents Ia, Ib, Ic and the power supply current Ibat. The rotation angle correction unit 32 is an example of a "current magnetic field calculation unit", an "angle correction amount calculation unit" and a "rotation angle correction unit".

[0026] Hereinafter, the magnetic field generated by the three-phase currents Ia, Ib, and Ic at the position of the magnetic sensor 19 will be referred to as the "multiphase current magnetic field Bi," and the magnetic field generated by the power supply current Ibat at the position of the magnetic sensor 19 will be referred to as the "power supply current magnetic field Bp." Furthermore, the multiphase current magnetic field Bi and the power supply current magnetic field Bp may be collectively referred to as the "current magnetic field." In the following explanation, an example is shown in which the rotation angle correction unit 32 corrects both the angle error caused by the multi-phase current magnetic field Bi and the angle error caused by the power supply current magnetic field Bp, but the rotation angle correction unit 32 may correct only one of the angle error caused by the multi-phase current magnetic field Bi and the angle error caused by the power supply current magnetic field Bp.

[0027] 7 is a schematic diagram of an example of the layout of the magnetic sensor 19 on the power board 14, the power supply terminal to which the power supply current Ibat is input, and the motor output terminals to which the three-phase currents Ia, Ib, and Ic are output. In FIG. 7, the X direction and the Y direction are parallel to the power board 14 and perpendicular to each other. The Z direction is perpendicular to the power board 14 and parallel to the rotating shaft 21 of the motor 20. The directions of the X direction and the Y direction may be set arbitrarily. In this specification, an example will be described in which the direction of the magnetic field Bm of the magnet 24 is set to the positive X direction when the electrical angle of the motor 20 is 0 [deg].

[0028] In this specification, the motor 20 is described as a double-winding motor having a winding pair consisting of a first system of motor windings and a second system of motor windings. The rotation angle correction unit 32 receives input of two systems of three-phase currents Ia, Ib, and Ic and two systems of power supply currents Ibat. Reference symbols 50a, 50b, and 50c denote motor output terminals that output three-phase currents (A-phase current Ia, B-phase current Ib, and C-phase current Ic) of a first system, respectively, and reference symbols 51a, 51b, and 51c denote motor output terminals that output three-phase currents of a second system. The motor output terminals 50a to 50c and 51a to 51c are arranged to extend in the Z direction so as to vertically penetrate the power board 14. Hereinafter, the A-phase, B-phase, and C-phase motor output terminals may be referred to as "A-phase terminals," "B-phase terminals," and "C-phase terminals," respectively.

[0029] In addition, reference symbols 52p and 52m are power supply terminals to which the first system power supply current Ibat is input, reference symbol 53 is a coil for removing noise contained in the first system power supply current Ibat, and reference symbols 53in and 53out are the input terminal and output terminal of coil 53. Reference symbols 54p and 54m are power supply terminals to which the power supply current of the second system is input, reference symbol 55 is a coil for removing noise contained in the power supply current of the second system, and reference symbols 55in and 55out are the input terminal and output terminal of coil 55.

[0030] The power supply terminals 52p, 52m, 54p, and 54m, the input terminals 53in and 55in, and the output terminals 53out and 55out are also arranged to extend in the Z direction so as to vertically penetrate the power board 14. In the case of power running, it is defined that the power supply current flows from the front to the back of the page in the positive power supply terminals 52p and 54p and the output terminals 53out and 55out, and that the power supply current flows from the back to the front of the page in the negative power supply terminals 52m and 54m and the input terminals 53in and 55in. During regeneration, the direction of the power supply current is reversed. In addition, the signs of the three-phase currents Ia, Ib, and Ic of the two systems are defined as positive when the current flows from the front to the back of the paper. The definitions of the directions and signs of the power supply current and three-phase current can be changed according to the mounting conditions on the board. The formulas described below will be changed according to the definitions of the directions and signs.

[0031] The A-phase terminal 50a of the first system and the A-phase terminal 51a of the second system are arranged in a point-symmetrical position with respect to the center point Pc of the magnetic sensor 19. The same is true for the B-phase terminal 50b and the B-phase terminal 51b, the C-phase terminal 50c and the C-phase terminal 51c, the positive power supply terminal 52p and the power supply terminal 54p, the negative power supply terminal 52m and the power supply terminal 54m, the input terminal 53in and the input terminal 55in, and the output terminal 53out and the output terminal 55out.

[0032] Therefore, when the magnitudes and directions of the three-phase currents of the first and second systems are equal, and the magnitudes and directions of the power supply currents of the first and second systems are equal, the current magnetic field generated at the center point Pc of the magnetic sensor 19 by the three-phase current and power supply current of the first system is offset by the current magnetic field generated by the three-phase current and power supply current of the second system. Therefore, no angle error occurs in the measured angle θ0 due to the three-phase current and power supply current. In this case, there is no need for the rotation angle correction unit 32 to correct the angle error. However, if only one of the first and second systems is driven, or if the load distribution between the first and second systems is different, the current magnetic field generated by the first system and the current magnetic field generated by the second system will not cancel each other out. For this reason, the rotation angle correction unit 32 corrects the angle error that occurs in the measured angle θ0 due to the three-phase currents and the power supply current in these cases.

[0033] Below, we will explain the correction of the angle error caused by the three-phase currents Ia, Ib, Ic and the power supply current Ibat of the first system, but the angle error can be corrected in the same way for the second system. When both the first and second systems are driven with different load distributions (i.e., when the currents of the first and second systems are different), the current magnetic field is calculated for each of the first and second systems, and the amount of correction for the angle error can be calculated based on the composite current magnetic field of the current magnetic field of the first system and the current magnetic field of the second system.

[0034] First, a method for calculating the first angle correction amount θi for correcting the angle error due to the multi-phase current magnetic field Bi will be described. The distances from the center point Pc to the A-phase terminal 50a, the B-phase terminal 50b, and the C-phase terminal 50c are respectively distances ra, rb, and rc, and the angles between the X-axis and the directions from the center point Pc toward the A-phase terminal 50a, the B-phase terminal 50b, and the C-phase terminal 50c are respectively angles θa, θb, and θc.

[0035] In the example of the layout shown in Fig. 7, the A-phase terminal 50a, the B-phase terminal 50b, and the C-phase terminal 50c are arranged along the Y direction perpendicular to the X direction, the distance ra and the distance rb are equal (ra = rb), the C-phase terminal 50c is on the X axis with the center point Pc as the origin (θc = 0), and the angles θa and θb are equal in magnitude and opposite in direction (θb = -θa). That is, the C-phase terminal 50c is at the midpoint of the line connecting the A-phase terminal 50a and the B-phase terminal 50b, and the distance d1 between the A-phase terminal 50a and the C-phase terminal 50c is equal to the distance d2 between the B-phase terminal 50b and the C-phase terminal 50c. Note that the following description will be given assuming that the counterclockwise angle is positive with respect to the positive X axis.

[0036] The rotation angle correction unit 32 calculates the multi-phase current magnetic field Bi according to the following equation (1).

number

[0037] The rotation angle correction unit 32 calculates the mechanical angle θm of the rotating shaft of the motor 20 based on the measured angle θ0 calculated by the rotation angle calculation unit 31. Furthermore, the rotation angle correction unit 32 calculates the absolute value Bt of the magnetic field Bm generated by the magnet 24 at the position of the center point Pc of the magnetic sensor 19, based on the temperature Tp in the vicinity of the magnet 24 detected by the temperature sensor 15. For example, the rotation angle correction unit 32 may calculate the absolute value Bt according to the following formula (2) based on the results of a prior magnetic field strength analysis. Bt=B20-K(Tp-20) … (2) In the above equation (2), B20 is the magnetic field when the temperature Tp in the vicinity of the magnet 24 is 20° C., and K is the temperature coefficient of the magnet 24. Although a method of detecting the temperature using the temperature sensor 15 has been described, a temperature estimation unit that estimates the temperature near the magnet 24 may be provided instead. For example, the characteristic that the magnitudes of the sine signal SIN0 and cosine signal COS0 generated by the magnetic sensor 19 change proportionally to the temperature is utilized. The temperature may be estimated from the ratio between the amplitudes (square root of the sum of squares) of the sine signal SIN0 and cosine signal COS0 at the reference temperature and the amplitudes of the sine signal SIN0 and cosine signal COS0 when measured. The change in the amplitude of one of the signals may also be used. Various temperature estimation methods may also be used.

[0038] The rotation angle correction unit 32 calculates the magnet magnetic field Bm according to the following equation (3).

number

[0039] 8 shows the magnet magnetic field Bm, the multi-phase current magnetic field Bi, and the composite magnetic field Bmi. The sine signal SIN0 and the cosine signal COS0 generated by the magnetic sensor 19 are signals indicating the vector direction of the composite magnetic field Bmi. Therefore, the rotation angle correction unit 32 calculates a first angle correction amount θi for correcting the vector direction of the composite magnetic field Bmi to the vector direction of the magnet magnetic field Bm. The calculation formula for deriving the first angle correction amount θi is given by the following formula (4).

[0040]

number

[0041] Since the multi-phase current magnetic field Bi is much smaller than the magnet magnetic field Bm (|Bi|<<|Bm|), the denominator of the fraction in the above equation (4) is approximated by |Bm|, and tan -1 Approximation of x(xx 3 / 3+x 5 / 5-x 7 / 7...), an approximation equation (5) of the first angle correction amount θi is obtained.

number

[0042] Next, a method for calculating the second angle correction amount θp for correcting the angle error due to the power supply current magnetic field Bp will be described with reference to Fig. 7. The distances from the center point Pc to the negative power supply terminal 52m and the positive power supply terminal 52p are distances rd and re, respectively, and the angles between the Y-axis and the directions from the center point Pc toward the power supply terminals 52m and 52p are angles θd and θe, respectively. The distances from the center point Pc to the input terminal 53in and the output terminal 53out of the coil 53 are distances rf and rg, respectively, and the angles between the direction from the center point Pc toward the input terminal 53in and the output terminal 53out and the Y-axis are angles θf and θg, respectively.

[0043] 7, the power terminals 52m and 52p are arranged along the X direction, and the midpoint of the line connecting the power terminals 52m and 52p is on the Y axis with the center point Pc as the origin (rd=re, θd=-θe). Therefore, the distances d3 and d4 between the Y axis and the power terminals 52m and 52p are equal (d3=d4). The input terminal 53in and the output terminal 53out are arranged along the Y direction, the distances from the X axis to the input terminal 53in and the output terminal 53out are df and dg, respectively, and the distance from the Y axis to the input terminal 53in and the output terminal 53out is d5. Therefore, rf=(df 2 +d5 2 ) -2 , rg = (dg 2 +d5 2 ) -2 θf=tan -1 (d5 / df), θg=tan -1 (d5 / dg). Note that the counterclockwise angle is positive with respect to the positive Y-axis.

[0044] The rotation angle correction unit 32 calculates the power supply current magnetic field Bp according to the following equation (6).

number

[0045] The rotation angle correction unit 32 calculates the second angle correction amount θp based on the approximation formula (7) which is similar to the approximation formula (5) of the first angle correction amount θi.

number

number

[0046] FIG. 9 is a flowchart illustrating an example of processing by the rotation angle correction unit 32. In step S1, the rotation angle calculation unit 31 calculates a measured angle θ0 of the electrical angle of the motor 20. In step S2, the temperature sensor 15 measures the temperature Tp in the vicinity of the magnet 24. In step S3, the rotation angle correction unit 32 calculates the magnetic field Bm that the magnet 24 generates at the position of the center point Pc of the magnetic sensor 19. In step S 4 , the rotation angle correction unit 32 calculates a multi-phase current magnetic field Bi generated by the three-phase currents Ia, Ib, and Ic at the position of the center point Pc of the magnetic sensor 19 .

[0047] In step S 5 , the rotation angle correction unit 32 calculates the power supply current magnetic field Bp that is generated at the position of the center point Pc of the magnetic sensor 19 by the power supply current Ibat. In step S6, the rotation angle correction unit 32 calculates a third angle correction amount θip for correcting an angle error caused by a composite magnetic field of the multiphase current magnetic field Bi and the power supply current magnetic field Bp. In step S7, the rotation angle correction unit 32 corrects the measured angle θ0 by the third angle correction amount θip to calculate the corrected rotation angle θc0=θ0+θip, and then the process ends.

[0048] Simulation results of the effect of correction by the rotation angle correction unit 32 are shown in Figures 10(a) to 10(d), 11(a) to 11(d), 12(a) to 12(d), and 13(a) to 13(d). The motor has six pole pairs. In these simulations, only one system was driven. 10(a) to 10(d) show the simulation results when the d-axis current and the power supply current Ibat are 70 [A] and 52.5 [A], respectively.

[0049] 11(a) to 11(d) show the simulation results when the q-axis current and the power supply current Ibat are 70 [A] and 52.5 [A], respectively. 12(a) to 12(d) show the simulation results when the d-axis current, the q-axis current, and the power supply current Ibat are 18.12 [A], 67.61, and 52.5 [A], respectively. 13(a) to 13(d) show the simulation results when the d-axis current, the q-axis current, and the power supply current Ibat are 35 [A], 60.62, and 52.5 [A], respectively.

[0050] In each figure, the horizontal axis represents the mechanical angle [deg] of motor 20. Figures 10(a) to 13(a) and 10(b) to 13(b) show the direction of the current magnetic field and the ratio of the magnitude of the current magnetic field to the magnitude of the magnet magnetic field at each mechanical angle, the dashed lines in Figures 10(c) to 13(c) represent the magnitude of the angle error included in the measured angle θ0 before correction by rotation angle correction unit 32, the solid lines represent the magnitude of the angle error included in the corrected rotation angle θc0, and Figures 10(d) to 13(d) are enlarged views of the angle error included in the corrected rotation angle θc0. From these simulation results, it can be seen that the angle error included in the corrected rotation angle θc0 can be made much smaller than the angle error included in the measured angle θ0 before correction.

[0051] Please refer to Fig. 4. The linearity correction unit 33 corrects the linearity of the corrected rotation angle θc0 based on linearity correction data created and stored in advance, and outputs the corrected rotation angle θc1. The linearity correction data may be, for example, correction map data that associates the value of the corrected rotation angle θc0 output from the rotation angle correction unit 32 with the value of the corrected rotation angle θc1 having good linearity. The origin correction unit 34 corrects the phase shift between the corrected rotation angle θc1 and the rotating shaft 21 of the motor 20 based on linearity correction data created and stored in advance, and outputs the corrected rotation angle θc2. As the linearity correction data, for example, the amount of phase shift between the corrected rotation angle θc1 and the rotating shaft 21 may be measured and used. The origin correction unit 34 outputs the corrected rotation angle θc2 to the motor control unit 35. In this embodiment, the origin correction unit is provided after the linearity correction unit 33. However, instead of this, the linearity correction unit 33 may be provided after the origin correction unit .

[0052] The motor control unit 35 receives as input the corrected rotation angle θc2 calculated by the origin correction unit 34, the detection value of the steering torque Th detected by the torque sensor 9, and the detection values ​​of the three-phase currents Ia, Ib, and Ic detected by the current sensor 18. The motor control unit 35 generates a PWM signal, which is a control signal for driving the motor 20 via the drive circuit 16, based on the corrected rotation angle θc2, the steering torque Th, and the three-phase currents Ia, Ib, and Ic. The motor control unit 35 drives the first and second systems, but the following description will be given for only one system. A similar configuration can be adopted for the second system.

[0053] 14 is a block diagram of an example of a functional configuration of the motor control unit 35. The motor control unit 35 includes a differentiator 60, a current command value calculation unit 61, a three-phase / two-phase conversion unit 62, subtractors 63 and 64, PI (proportional-integral) control units 65 and 66, a two-phase / three-phase conversion unit 67, and a PWM control unit 68. The differentiator 60 calculates the rotation speed ω of the motor 20 (that is, the rotation angular speed ω of the rotating shaft 21) by differentiating the corrected rotation angle θc2.

[0054] The current command value calculation unit 61 calculates a d-axis current command value Idref and a q-axis current command value Iqref using the steering torque Th and the rotation speed ω. The three-phase / two-phase converter 62 converts the three-phase currents Ia, Ib, and Ic into a d-axis motor current Idm and a q-axis motor current Iqm, which are two-phase currents, using the corrected rotation angle θc2. A subtractor 63 calculates a deviation Id (=Idref-Idm) between the d-axis current command value Idref and the fed-back d-axis motor current value Idm. A subtractor 64 calculates a deviation Iq (=Iqref-Iqm) between the q-axis current command value Iqref and the fed-back q-axis motor current value Iqm.

[0055] The PI control unit 65 calculates a d-axis voltage command value Vdref based on the deviation Id. Similarly, the PI control unit 66 calculates a q-axis voltage command value Vqref based on the deviation Iq. The two-phase / three-phase conversion unit 67 uses the corrected rotation angle θc2 to convert a two-phase voltage consisting of the d-axis voltage command value Vdref and the q-axis voltage command value Vqref into a three-phase voltage (A-phase voltage command value Varef, B-phase voltage command value Vbref, and C-phase voltage command value Vcref), for example, by space vector modulation (space vector transformation). The PWM control unit 68 generates a control signal (PWM signal) for controlling the drive circuit 16 by PWM control, based on the A-phase voltage command value Varef, the B-phase voltage command value Vbref, and the C-phase voltage command value Vcref.

[0056] 4, the correction amount setting unit 36 ​​calculates, based on the peak values ​​of the sine signal SIN0 and the cosine signal COS0 output from the magnetic sensor 19, a first gain G1 for correcting the amplitude error of the cosine signal COS0, a sine offset correction value Cs for correcting the offset error of the sine signal SIN0, and a cosine offset correction value Cc for correcting the offset error of the cosine signal COS0.

[0057] Specifically, the correction amount setting unit 36 ​​obtains the maximum value max(COS0) and minimum value min(COS0) which are peak values ​​of the cosine signal COS0, and also obtains the maximum value max(SIN0) and minimum value min(SIN0) which are peak values ​​of the sine signal SIN0. The correction amount setting unit 36 ​​calculates the amplitude Ax of the cosine signal COS0=(max(COS0)-min(COS0)) / 2 and the amplitude Ay of the sine signal SIN0=(max(SIN0)-min(SIN0)) / 2.

[0058] The correction amount setting unit 36 ​​calculates the ratio (Ay / Ax) of the amplitude Ay to the amplitude Ax as a first gain G1. Furthermore, the correction amount setting unit 36 ​​calculates a sine offset correction value Cs=(max(SIN0)+min(SIN0)) / 2 and a cosine offset correction value Cc=(max(COS0)+min(COS0)) / 2.

[0059] Next, the correction amount setting unit 36 ​​calculates a second gain G2 that corrects the phase error between the cosine signal COS0 and the sine signal SIN0, based on the peak value of the sum (COS1+SIN1) of the cosine signal COS1 in which the amplitude error and offset error have been corrected and the sine signal SIN1 in which the offset error has been corrected, and the peak value of the difference (COS1-SIN1). Specifically, the maximum value max(COS1+SIN1) and minimum value min(COS1+SIN1) which are the peak values ​​of the sum (COS1+SIN1) are obtained. Also, the maximum value max(COS1-SIN1) and minimum value min(COS1-SIN1) which are the peak values ​​of the difference (COS1-SIN1) are obtained.

[0060] The correction amount setting unit 36 ​​calculates the ratio ((max(COS1+SIN1)-min(COS1+SIN1)) / (max(COS1-SIN1)-min(COS1-SIN1))) that matches the amplitude of the difference (COS1-SIN1) to the amplitude of the sum (COS1+SIN1) as the second gain G2. As described above, the correction amount setting unit 36 ​​calculates the first gain G1, the sine offset correction value Cs, the cosine offset correction value Cc, and the second gain G2 based on the peak values ​​of the sine signal SIN0, the cosine signal COS0, the sum (COS1+SIN1), and the difference (COS1-SIN1). However, in order to accurately calculate this correction amount data G1, Cs, Cc, and G2, it is necessary to detect accurate peak values.

[0061] However, in a peak hold process (that is, a process for storing peak values) that simply compares the previous and current values ​​of these signals, the accurate peak value may not be detected due to the influence of noise. Noise contained in a signal can be removed by filtering using a low-pass filter, but the amplitude of the signal is attenuated by the filtering process, making it impossible to detect accurate peak values.

[0062] Therefore, the correction amount setting unit 36 ​​performs filtering using a low-pass filter on the sine signal SIN0, the cosine signal COS0, the sum (COS1+SIN1), and the difference (COS1-SIN1). Furthermore, the correction amount setting unit 36 ​​calculates the gain of the low-pass filter based on the known frequency characteristic of the low-pass filter and the rotation speed ω of the motor 20. Then, the sine signal SIN0, cosine signal COS0, sum (COS1+SIN1), and difference (COS1-SIN1) that have been filtered by the low-pass filter are corrected by the gain of the low-pass filter, and a corrected peak value, which is the peak value of the corrected signal, is detected.

[0063] Alternatively, the peak values ​​of the sine signal SIN0, cosine signal COS0, sum (COS1+SIN1) and difference (COS1-SIN1) that have been filtered by a low-pass filter may be detected, and then the peak values ​​may be corrected by the gain of the low-pass filter to obtain corrected peak values. This makes it possible to remove noise contained in the sine signal SIN0, the cosine signal COS0, the sum (COS1+SIN1), and the difference (COS1-SIN1), while maintaining the amplitudes of these signals. The correction amount setting unit 36 ​​calculates the correction amount data G1, Cs, Cc, and G2 based on the corrected peak value thus obtained.

[0064] 15 is a block diagram of an example of the functional configuration of the correction amount setting unit 36. The correction amount setting unit 36 ​​includes low-pass filters 70, 71, 72, 73, and 75, an angle difference calculation unit 74, a gain calculation unit 76, an amplitude correction unit 77, a peak hold unit 78, an implementation determination unit 79, and a correction amount calculation unit 80. In the drawings, the low-pass filter is referred to as "LPF." The gain calculation section 76, the amplitude correction section 77, and the peak hold section 78 are an example of a "peak value acquisition section."

[0065] Low-pass filters 70, 71, 72 and 73 perform filtering on the sine signal SIN0, the cosine signal COS0, the sum (COS1+SIN1) and the difference (COS1-SIN1), respectively. For example, a first-order LPF, a second-order Butterworth filter, or a four-point moving average filter may be used as the low-pass filters 70, 71, 72, 73, and 75. The frequency characteristics of the low-pass filters 70, 71, 72, 73, and 75 may be set appropriately according to the frequency at which the signal contains strong noise. For example, the frequency characteristics of the low-pass filters 70, 71, 72, 73, and 75 may be set so as to sufficiently attenuate high-frequency components including 1000 [Hz] components.

[0066] In the following, in this specification, an example in which four-point moving average filters are used as the low-pass filters 70, 71, 72, 73, and 75 will be described. The angle difference calculation unit 74 calculates the rotation speed ω of the motor 20 by calculating (i.e., differentiating) the change per unit time of the measured angle θ0. The low-pass filter 75 applies filtering to the rotation speed ω. The filtered rotation speed ω is input to the gain calculation unit 76. In this embodiment, the low-pass filter 75 is provided after the angle difference calculation unit 74, but instead, the low-pass filter 75 may be provided before the angle difference calculation unit 74.

[0067] Based on the rotation speed ω after filtering by the low-pass filter 75, the gain calculation unit 76 calculates a gain G3 of the low-pass filter 75 when the rotation speed of the motor 20 is the speed ω. For example, a four-point moving average is -n Using this, it is given by the following equation (9). H(z)=(1+z -1 +z -2 +z -3 ) / 4 …(9) When this is inverse z-transformed using a bilinear transformation, the following equation (10) is obtained.

number

[0068] Next, to obtain the gain characteristic, by substituting jω into the Laplace operator s in equation (10), the following equation (11) is obtained (j is the imaginary unit).

number

[0069] If the square root of the sum of the squares of the real and imaginary parts of the above equation (11) is calculated to obtain the gain characteristic, the following equation (12) is obtained.

number

[0070] The above formula (12) includes a square root operation, which may increase the processing load. Therefore, the approximation formula (1+a) n By utilizing ≈1+na, the above equation (12) may be approximated as the following equation (13).

number

[0071] The amplitude correction unit 77 corrects the sine signal SIN0, cosine signal COS0, sum (COS1+SIN1), and difference (COS1-SIN1) that have been filtered by the low-pass filters 70, 71, 72, and 73 by dividing these signals by a gain |G(ω)|. The peak hold unit 78 obtains the peak values ​​(maximum, minimum) of the sine signal SIN0, cosine signal COS0, sum (COS1+SIN1), and difference (COS1-SIN1) after they have been filtered by the low-pass filters 70, 71, 72, and 73 and corrected by the gain |G(ω)|.

[0072] The correction amount calculation unit 80 calculates the correction amount data G 1 , Cs, Cc, and G 2 based on the peak value acquired by the peak hold unit 78 . The correction amount calculation unit 80 may include a rate limiter that limits the rate of change of the correction amount data G1, Cs, Cc, and G2 in order to suppress abrupt fluctuations in the sum signal SA and the difference signal SD output from the detection signal correction unit 30. That is, the correction amount calculation unit 80 may gradually change the correction amount data G1, Cs, Cc, and G2.

[0073] The implementation decision unit 79 decides whether or not to cause the detection signal correcting unit 30 to correct the sine signal SIN0 and the cosine signal COS0, depending on whether or not the rotation speed ω is within a predetermined threshold range. For example, if the correction amount data G1, Cs, Cc, and G2 are set when the rotation speed ω is low (including a stopped state), it takes a long time to detect the maximum and minimum peaks, and errors occur due to temperature changes during that time. For this reason, the implementation judgment unit 79 may prohibit correction by the detection signal correction unit 30 when the rotation speed ω is below the lower limit. For example, the lower limit may be set based on the rate of temperature rise of the circuit and the temperature-error (offset, gain, phase) characteristics.

[0074] Also, for example, when the rotation speed ω is high, the error in peak detection during sampling is large. Therefore, the implementation determination unit 79 may prohibit the detection signal correction unit 30 from making correction when the rotation speed ω exceeds the upper limit. For example, the upper and lower limits may be set by simulation based on the allowable angle error and the sampling period. When the implementation determination unit 79 prohibits the detection signal correction unit 30 from making a correction, the peak hold unit 78 resets the stored peak value (i.e., the peak hold value). In addition, the correction amount calculation unit 80 resets the values ​​of the first gain and the second gain to "1" and resets the values ​​of the sine offset correction value and the cosine offset correction value to "0." As a result, the sine signal SIN0 and the cosine signal COS0 are no longer corrected.

[0075] FIG. 16 is a flowchart of an example of processing by the correction amount setting unit 36. In step S10, the angle difference calculation unit 74 calculates the rotation speed ω of the motor 20. In step S11, the implementation decision unit 79 decides whether or not the rotation speed ω is within a predetermined threshold range. If the rotation speed ω is within the predetermined threshold range (step S11: Y), the implementation decision unit 79 decides to perform correction by the detection signal correction unit 30, and the process proceeds to step S13. If the rotation speed ω is not within the predetermined threshold range (step S11: N), the implementation decision unit 79 decides to prohibit correction by the detection signal correction unit 30, and the process proceeds to step S12.

[0076] In step S12, the peak hold unit 78 resets the stored peak value (i.e., the peak hold value). The correction amount calculation unit 80 also resets the values ​​of the first gain G1 and the second gain G2 to "1" and resets the values ​​of the sine offset correction value Cs and the cosine offset correction value Cc to "0". After that, the process returns to step S10. In step S13, the peak hold unit 78 performs peak hold of the sine signal SIN0, cosine signal COS0, sum (COS1+SIN1) and difference (COS1-SIN1) after filtering by the low-pass filter and dividing by the gain of the low-pass filter, thereby updating the peak hold value.

[0077] In step S14, the correction amount calculation unit 80 determines whether or not the sine signal SIN0 and the cosine signal COS0 for one revolution of the electrical angle of the motor 20 have been input to the correction amount setting unit 36. If the signals for one revolution have been input (step S14: Y), the process proceeds to step S15. If the signals for one revolution have not yet been input (step S14: N), the process returns to step S10. In step S15, the correction amount calculation unit 80 calculates the correction amount data G1, Cs, Cc, and G2 based on the peak values ​​stored in the peak hold unit 78. The peak hold unit 78 also resets the peak hold values ​​stored therein. After that, the process ends.

[0078] 17 is a diagram illustrating the results of a simulation of the correction of sine signal SIN0 by low-pass filter 70 and amplitude correction unit 77. The dashed line indicates the amplitude value of sine signal SIN0 after filtering when the amplitude of sine signal SIN0 before filtering by low-pass filter 70 is set to "1", and the solid line indicates the amplitude value after correction by amplitude correction unit 77. As shown in FIG. 17, it can be seen that the value of the amplitude before the filtering process by the low-pass filter 70 is maintained by the correction by the amplitude correcting section 77.

[0079] (Effects of the embodiment) (1) A rotation angle detection device of an embodiment includes a magnet 24 fixed to a rotating shaft 21 of a motor 20, a magnetic sensor 19 that detects the direction of a magnetic field generated from the magnet 24, a rotation angle calculation unit 31 that calculates the rotation angle of the rotating shaft 21 based on a detection signal of the magnetic sensor 19, and a rotation angle correction unit 32 that calculates a current magnetic field generated at a position of the magnetic sensor by at least one of a power supply current and a multiphase current of a power converter that outputs a multiphase current to the motor 20, calculates an angle correction amount based on the ratio of the magnitude of the current magnetic field to the magnitude of the magnetic magnetic field and an angle difference that is the difference between the orientation of the magnetic magnetic field and the orientation of the current magnetic field, and corrects the rotation angle based on the angle correction amount. This makes it possible to suppress the effect on detection accuracy of the power supply current or the magnetic field caused by the multiphase current of the power converter that outputs the multiphase current to the motor 20 when the rotation angle of the rotating shaft 21 of the motor 20 is detected by the magnetic sensor 19.

[0080] (2) The rotation angle correction unit 32 may calculate the product of the ratio of the magnitude of the current magnetic field to the magnitude of the magnet magnetic field and the trigonometric function of the angle difference as the angle correction amount. This allows the angle correction amount to be calculated accurately. The rotation angle correction unit 32 may calculate the direction of the magnetic field of the magnet from the rotation angle calculated by the rotation angle calculation unit 31. In this way, the direction of the magnetic field of the magnet can be calculated. (3) The magnet 24 may further include a temperature sensor 15 that measures the temperature in the vicinity of the magnet 24 or a temperature estimation unit that estimates the temperature in the vicinity of the magnet 24. The rotation angle correction unit 32 may calculate the magnitude of the magnetic field of the magnet according to the temperature measured by the temperature sensor 15 or the temperature estimated by the temperature estimation unit. This allows the magnetic field to be calculated according to the temperature characteristics of the magnet 24.

[0081] (4) In addition, the rotation angle detection device of the embodiment includes a magnetic sensor 19 that outputs a sensor signal including a sine signal and a cosine signal in response to rotation of a rotating body such as the rotating shaft 21 of the motor 20, low-pass filters 70-73 to which the sensor signal output from the magnetic sensor 19 is input, a peak hold unit 78 that acquires a peak value of the sensor signal that has been filtered by the low-pass filters 70-73 and corrected by the gains of the low-pass filters 70-73, a correction amount calculation unit 80 that calculates a correction amount for correcting the sensor signal in response to the acquired peak value, a detection signal correction unit 30 that corrects the sensor signal output from the sensor based on the correction amount, and a rotation angle calculation unit 31 that calculates the rotation angle of the rotating body based on the sensor signal corrected by the detection signal correction unit 30. This makes it possible to remove noise contained in the sensor signals and maintain their amplitudes, so that the correction amount can be calculated based on accurate peak values.

[0082] (5) The gain calculation section 76 may calculate the gains of the low-pass filters 70 to 73 based on the amount of change over time in the rotation angle θ0. This makes it possible to calculate the gain according to the frequency characteristics of the low-pass filters 70-73. (6) An implementation decision unit 79 may be provided that decides not to correct the sensor signal based on the correction amount when the amount of change over time in the rotation angle is outside a predetermined threshold range. This makes it possible to avoid errors caused by temperature changes during the long period of time required to detect the maximum and minimum peaks when the correction amount is set when the rotation speed is low (including when the rotation speed is stopped), and also to avoid errors in peak detection during sampling when the rotation speed is high.

[0083] (7) The correction amount calculation section 80 may limit the rate of change of the correction amount according to the peak value. This makes it possible to suppress a sudden change in the sensor signal after correction by the detection signal correction unit 30. (8) The detection signal correction unit 30 may correct at least one of an offset error, an amplitude error, and a phase error of the sensor signal based on the correction amount. This makes it possible to correct errors that affect the first and second order components of the linearity error of the rotation angle calculated based on the sine and cosine signals. [Explanation of symbols]

[0084] 1...steering wheel, 2...column shaft, 3...reduction gear, 4a, 4b...universal joint, 5...pinion rack mechanism, 5a...pinion, 5b...rack, 6a, 6b...tie rod, 7a, 7b...hub unit, 8L, 8R...steered wheels, 9...torque sensor, 10...control device, 11...battery, 12...ignition key, 13...control board, 13a...processor, 13b...storage device, 14...power board, 15...temperature sensor, 16...drive circuit, 17, 18...current sensor, 19...magnetic sensor, 20...motor, 21...rotating shaft, 24...magnet, 30...detection signal correction unit, 31...rotation angle calculation unit, 32...rotation angle angle correction unit, 33...linearity correction unit, 34...origin correction unit, 35...motor control unit, 36...correction amount setting unit, 40...SIN offset correction unit, 41...COS offset correction unit, 42...COS gain correction unit, 43...adder, 44, 63, 64...subtractor, 45...phase error correction unit, 60...differentiator, 61...current command value calculation unit, 62...3-phase / 2-phase conversion unit, 65, 66...PI control unit, 67...2-phase / 3-phase conversion unit, 68...PWM control unit, 70, 71, 72, 73, 75...low-pass filter, 74...angle difference calculation unit, 76...gain calculation unit, 77...amplitude correction unit, 78...peak hold unit, 79...implementation determination unit, 80...correction amount calculation unit

Claims

1. A magnet fixed to a rotating shaft of a polyphase AC motor; a magnetic sensor for detecting a direction of a magnetic field generated by the magnet; a rotation angle calculation unit that calculates a rotation angle of the rotary shaft based on a detection signal of the magnetic sensor; a current magnetic field calculation unit that calculates a current magnetic field generated at a position of the magnetic sensor by at least one of a power supply current of a power converter that outputs a multiphase current to the multiphase AC motor and the multiphase current; an angle correction amount calculation unit that calculates, as an angle correction amount, a product of a ratio of the magnitude of the current magnetic field to the magnitude of the magnet magnetic field and a trigonometric function of an angle difference that is a difference between the orientation of the magnet magnetic field and the orientation of the current magnetic field; a rotation angle correction unit that corrects the rotation angle based on the angle correction amount; A rotation angle detection device comprising:

2. 2. The rotation angle detection device according to claim 1, wherein the angle correction amount calculation unit calculates the direction of the magnetic field of the magnet from the rotation angle calculated by the rotation angle calculation unit.

3. A temperature sensor for measuring a temperature in the vicinity of the magnet is further provided.

3. The rotation angle detection device according to claim 1, wherein the angle correction amount calculation unit calculates the magnitude of the magnetic field of the magnet in accordance with the temperature measured by the temperature sensor.

4. A temperature estimation unit that estimates a temperature in the vicinity of the magnet is further provided.

3. The rotation angle detection device according to claim 1, wherein the angle correction amount calculation unit calculates the magnitude of the magnetic field of the magnet in accordance with the temperature estimated by the temperature estimation unit.

5. A rotation angle detection device according to any one of claims 1 to 4, a drive unit that drives a polyphase AC motor based on the rotation angle corrected by the rotation angle correction unit; A motor control device comprising:

6. The motor control device according to claim 5 ; a polyphase AC motor controlled by the motor control device; An electric actuator product comprising:

7. The motor control device according to claim 5 ; a polyphase AC motor controlled by the motor control device; and applying a steering assist force to a steering system of a vehicle by the polyphase AC motor.

8. A rotation angle detection method for detecting a rotation angle of a rotating shaft of a polyphase AC motor by detecting a direction of a magnetic field generated from a magnet fixed to the rotating shaft of the motor using a magnetic sensor, comprising: Calculating the rotation angle based on a detection signal of the magnetic sensor; calculating a current magnetic field generated at a position of the magnetic sensor by at least one of a power supply current of a power converter that outputs a multiphase current to the multiphase AC motor and the multiphase current; calculating an angle correction amount by multiplying a ratio of the magnitude of the current magnetic field to the magnitude of the magnet magnetic field by a trigonometric function of an angle difference between the direction of the magnet magnetic field and the direction of the current magnetic field; correcting the rotation angle based on the angle correction amount; A rotation angle detection method comprising:

Images