JP7768038B2 - Rotation Angle Detection Device - Google Patents

Description

The present invention relates to a rotation angle detection device.

In a conventional rotation angle detection device that detects the rotation angle of a three-phase brushless motor using a rotation angle sensor that uses a magnetic resistance element or a Hall element, there is known technology for correcting errors in the angle detected by the rotation angle sensor.

For example, the rotation angle detection device disclosed in Patent Document 1 includes a first correction calculation unit that corrects angle errors caused by assembly errors in the rotation angle sensor, and a second correction calculation unit that corrects angle errors caused by leakage flux due to current flow through the windings. The angle error caused by leakage flux occurs when a composite wave of ±1 order sine waves corresponding to the number of pole pairs of the rotor magnetic poles is superimposed on the detection angle signal as noise.

Similarly, the control circuit of the rotation angle detection device disclosed in Patent Document 2 calculates the error angle caused by disturbance magnetic flux generated from the bus bar or coil when power is supplied to the coil via the bus bar as a correction angle for the rotation angle, and uses this correction angle to correct the rotation angle.

JP 2016-128772 A Japanese Patent Application Laid-Open No. 2017-143603

The prior art technologies in Patent Documents 1 and 2 calculate a correction angle according to the winding current, assuming that the temperature of the rotation angle sensor is a predetermined reference temperature, and do not take temperature changes into account. However, in a rotation angle detection device installed in an automobile, for example, the temperature of the rotation angle sensor changes due to changes in the outside air temperature in the area of use. When this happens, at temperatures higher than the reference temperature, the magnetic flux of the sensor magnet decreases, reducing the S/N ratio and increasing the error amplitude. Conversely, at temperatures lower than the reference temperature, the S/N ratio increases and the error amplitude decreases.

Therefore, if a correction angle based on a reference temperature is used uniformly regardless of the actual temperature, the correction will be insufficient at temperatures higher than the reference temperature and excessively corrected at temperatures lower than the reference temperature, reducing the accuracy of the corrected detected angle relative to the actual rotation angle. This will increase torque ripple in devices that control motor drive through feedback control using the detected angle. For example, in a drive device for a steering assist motor in an electric power steering device, motor torque ripple can cause vibrations in the steering wheel, potentially worsening the driver's steering feel.

The present invention was created in light of the above points, and its purpose is to provide a rotation angle detection device that accurately corrects the detected angle even when the temperature of the rotation angle sensor changes.

A rotation angle detection device according to one aspect of the present invention detects the rotation angle of a polyphase brushless motor (80) in a motor drive device (10) that controls current supply to windings (801, 802) by feeding back the rotation angle of the motor. The rotation angle detection device includes rotation angle sensors (301, 302), a first-order error elimination unit (43), a second-order error elimination unit (45), a rotation angle sensor temperature estimator (44), and an angle correction calculation unit (46).

The rotation angle sensor includes two or more Hall elements (331-334) mounted on a substrate and one or more sensor magnets (37) fixed to the shaft (87), which is the rotating axis of the motor.

The primary error elimination unit eliminates errors caused by the positional accuracy of the rotation angle sensor, which are included in the detected angles (θo1, θo2) of the rotation angle sensor, to calculate primary-corrected detected angles (θp1, θp2). The secondary error elimination unit calculates angle error correction amounts (θ#1, θ#2) to eliminate errors caused by leakage magnetic flux due to current flow through the windings. The rotation angle sensor temperature estimator calculates temperature estimates (TempS_est1, TempS_est2) of the rotation angle sensor based on the initial temperature detection value (Temp_0) of the rotation angle sensor before current is passed through the windings and the integrated value of power supplied to the windings, and notifies the secondary error elimination unit. The angle correction calculation unit calculates secondary-corrected detected angles (θm1, θm2) based on the primary-corrected detected angles and the angle error correction amounts.

The secondary error elimination unit calculates the angle error correction amount based on the temperature of the rotation angle sensor and a quantity correlated with the amplitude and phase of the current flowing through the winding. In the case of a three-phase motor, the "quantity correlated with the amplitude and phase of the current flowing through the winding" may be the q-axis current or the three-phase current.

In this invention, by correcting the detected angle after primary correction according to the correlation between the temperature of the rotation angle sensor and the winding current, the detected angle can be corrected with high accuracy even if the temperature of the rotation angle sensor changes. Therefore, torque ripple is reduced in devices that control motor drive through feedback control using the detected angle after secondary correction. For example, a good steering feel is ensured in the drive device of a steering assist motor in an electric power steering device.

1 is a configuration diagram of a column-type EPS to which a rotation angle detection device according to an embodiment is applied; 1 is a configuration diagram of a rack-type EPS to which a rotation angle detection device according to an embodiment is applied; FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3; FIG. 2 is a schematic diagram of a rotation angle sensor that detects two systems of rotation angles for each system according to one embodiment. 6 is a schematic diagram of a rotation angle sensor according to one embodiment, taken along arrow VI in FIG. 3 . FIG. 1 is a block diagram of a dual-system ECU (motor drive device) according to an embodiment. FIG. 2 is a block diagram of an angle correction unit of a dual-system microcomputer according to an embodiment. 10A and 10B are diagrams illustrating a detected angle after primary correction, an angle error correction amount, and a detected angle after secondary correction according to a comparative example. 6A and 6B are diagrams illustrating a detected angle after primary correction, an angle error correction amount, and a detected angle after secondary correction according to an embodiment. 4 is a conceptual diagram showing the relationship between the rotation angle sensor temperature and the angle error correction amount. 10 is a flowchart showing the process executed by the two-system secondary error elimination unit. FIG. 10 is a schematic diagram of a rotation angle sensor according to another embodiment that detects a rotation angle common to two systems. FIG. 10 is a block diagram of an angle correction unit of a microcomputer according to another embodiment.

One embodiment of a rotation angle detection device according to the present invention will be described with reference to the drawings. The rotation angle detection device of this embodiment detects the rotation angle of a motor in a motor drive device that controls the supply of electricity to a steering assist motor in a vehicle's electric power steering system. The motor in this embodiment is a three-phase brushless motor, i.e., a polyphase brushless motor. The ECU serving as the "motor drive device" controls the supply of electricity to the windings by feeding back the rotation angle of the three-phase brushless motor.

First, the configuration of the electric power steering device (hereinafter "EPS") and steering assist motor will be described with reference to Figures 1 to 5. Figure 1 shows the overall configuration of a steering system 99 including a column-type EPS 90, and Figure 2 shows a rack-type EPS 90. Figures 1 and 2 show an "electrically integrated motor" 800 in which the ECU 10 is integrated into one axial side of the motor 80. However, a "separate electromechanical configuration" in which the ECU 10 and motor 80 are connected by a harness may also be used. The motor 80 in this embodiment has two sets of three-phase windings, and the ECU 10 includes two drive control circuits corresponding to the two sets of three-phase windings.

The steering system 99 includes a steering wheel 91, a steering shaft 92, a pinion gear 96, a rack shaft 97, wheels 98, and an EPS 90. The steering wheel 91 is connected to the upper end of the steering shaft 92, and a pinion gear 96 that meshes with the rack shaft 97 is provided at the lower end of the steering shaft 92. When the driver turns the steering wheel 91, the rotational motion of the steering shaft 92 is converted into linear motion of the rack shaft 97 by the pinion gear 96. A pair of wheels 98 connected to both ends of the rack shaft 97 are steered to an angle that corresponds to the displacement of the rack shaft 97.

The EPS 90 includes an electromechanical integrated motor 800 in which the ECU 10 and motor 80 are integrated, a steering torque sensor 93, and a reduction gear 94. The steering torque sensor 93 is provided midway along the steering shaft 92 and detects the steering torque applied by the driver. In the configuration shown in Figures 1 and 2, the steering torques trq1 and trq2 detected by the steering torque sensor 93 are input to two ECUs 10, one for each system.

During power running, ECU 10 controls the drive of motor 80 based on steering torques trq1 and trq2 so that motor 80 generates the desired assist torque. In a column-type EPS, the assist torque output by motor 80 is transmitted to steering shaft 92 via reduction gear 94. In a rack-type EPS, the assist torque output by motor 80 is transmitted to rack 97 via reduction gear 94. Furthermore, during regenerative operation, ECU 10 regenerates the back electromotive force energy generated in motor 80 by reverse input or steering operation back into the power supply.

The rotation angle sensors 301, 302 of each system detect the rotation angles θ1, θ2 of the motor 80. The ECU 10 controls the energization of the motor 80 using the rotation angles θ1, θ2 of the motor 80. Specifically, the ECU 10 uses the electrical angle converted from the rotation angles θ1, θ2 of the motor 80 to perform coordinate transformation calculations such as converting three-phase currents into dq-axis currents. The detailed configuration of the rotation angle sensors 301, 302 will be described later with reference to Figure 5, etc.

Figures 3 and 4 show the schematic configuration of the electromechanical integrated motor 800. Note that the scale of each element in Figures 3 and 4 is not necessarily consistent. The lower side of Figure 3 corresponds to the front side where the output shaft of the motor 80 is provided, and the upper side of Figure 3 corresponds to the rear side where the connector is provided. The motor 80 rotates around a shaft 87, which is the rotation axis. The ECU 10 is disposed coaxially with the central axis O of the shaft 87 on the rear side of the motor 80.

The motor 80 includes a stator 84 and a rotor 86 housed in a motor case 83. The motor case 83 is formed in a generally cylindrical shape with a bottom, consisting of a bottom portion 831 and a cylindrical portion 832. A rear frame 88 is provided on the open side of the cylindrical portion 832.

The stator 84 has two sets of three-phase windings 801, 802 wound around an iron stator core 845 fixed inside the cylindrical portion 832 of the motor case 83. The stator core 845 is made of laminated steel plates or the like. When electricity is applied from the ECU 10 to the three-phase windings 801, 802 via motor wires 851, 852, a rotating magnetic field is formed in the stator 84.

The rotor 86 has multiple magnets 866 attached to the outer periphery of an iron rotor core 865. The rotor core 865 is made of laminated steel plates or the like. The rotor 86 rotates around a shaft 87 due to the rotating magnetic field formed in the stator 84. The shaft 87 fixed to the rotor 86 is rotatably supported by a front bearing 873 held in the bottom 831 of the motor case 83 and a rear bearing 874 held in the rear frame 88. A sensor magnet 37 is fixed to the rear end face of the shaft 87. In this embodiment, there is one sensor magnet 37.

In the configuration illustrated in Figure 4, the number P of magnets 866 in the rotor 86 is 10, and the number S of slots in the stator 84 is 12, expressed as "10P12S." The 10 magnets 866 form five magnetic pole pairs in which north and south poles are alternately arranged in the circumferential direction. In other words, the number of magnetic pole pairs in this configuration is five. Note that the number P of magnets and the number S of slots in the motor are not limited to these and may be set as appropriate.

The rear frame 88 supports the circuit board 13 of the ECU 10 and also functions as a heat sink to absorb heat generated by the elements mounted on the circuit board 13. On both sides of the circuit board 13, elements such as switching elements, microcomputers, ASICs, coils, and capacitors that make up two drive control circuits are mounted. The number of circuit boards is not limited to one, and two or more may be stacked.

One element of particular interest is the Hall IC 330, which has multiple built-in Hall elements and is located on the motor-side surface of the substrate 13 so as to face the sensor magnet 37. As will be described later with reference to Figure 5, the multiple Hall elements built into the Hall IC 330 and the sensor magnet 37 form two rotation angle sensors 301 and 302.

The cover 20 is made of a resin material and has a cylindrical shape with a bottom, a top plate portion 21, and an outer tube portion 22. It covers the circuit board 13 of the ECU 10. For example, the lower end of the outer tube portion 22 is inserted into and adhered to an annular groove formed in the rear frame 88. The top plate portion 21 is provided with a power supply connector 23 to which a power cable is connected, and a signal system connector 24 to which a signal cable is connected.

Referring to Figure 5, the configuration of rotation angle sensors 301, 302, which detect the rotation angles of the two systems, will be described. The lower part of Figure 5 shows a side or cross section of the sensor magnet 37 fixed to the rear end face of the shaft 87 and the Hall IC 330 mounted on the board 13. The upper part of Figure 5 shows the Hall IC 330 as viewed from the top of the board 13. Figure 5 is a schematic diagram and does not reflect the dimensional proportions of the actual components.

The motor rotation angle used in the drive control calculations for the first system is designated as the first rotation angle θ1, and the motor rotation angle used in the drive control calculations for the second system is designated as the second rotation angle θ2. Note that the stage symbols used in the angle correction described below are not taken into consideration here. The Hall IC 330 houses a set of two Hall elements 331, 332 that detect the first rotation angle θ1, and a set of two Hall elements 333, 334 that detect the second rotation angle θ2, coaxially on the central axis O.

Hall elements 331-334 use the Hall effect to output voltage signals proportional to the magnetic field generated by the current passing through windings 801 and 802. Because the magnetic field changes periodically as motor 80 rotates, the voltage signals output by Hall elements 331-334 change sinusoidally. Voltage signals that are 90° out of phase with each other are referred to as "sine signals and cosine signals." The rotation angle of motor 80 is detected by processing the sin signal and cos signal. A first rotation angle θ1 is detected by two Hall elements 331 and 332 arranged orthogonally to each other. A second rotation angle θ2 is detected by two Hall elements 333 and 334 arranged orthogonally to each other.

One rotation angle sensor is configured to include two or more pairs of Hall elements and one sensor magnet 37. In this embodiment, the sensor magnet 37 is included in common with the two systems of rotation angle sensors 301, 302. The first system of rotation angle sensor 301 includes Hall elements 331, 332 and the sensor magnet 37. The second system of rotation angle sensor 302 includes Hall elements 333, 334 and the sensor magnet 37.

Next, the electrical configuration of the dual-system ECU 10 and motor 80 will be described with reference to Figures 6 and 7. The symbols for the components of the first and second systems, or the symbols for current and angle, are suffixed with "1" and "2," respectively. The two systems are provided for redundancy, so that if one system fails, the other functioning system can continue to drive the motor 80.

As shown in Figure 6, motor 80 is a double-winding motor with two sets of three-phase windings 801, 802. The two sets of three-phase windings 801, 802 have the same electrical characteristics and are arranged on a common stator with a phase shift of, for example, 30 degrees. Accordingly, three-phase currents of equal amplitude and a phase shift of 30 degrees are passed through windings 801, 802.

The ECU 10, which functions as a "motor drive device," includes inverters 701 and 702, which function as two power converters, and microcomputers 401 and 402, which function as computing units. The inverters 701 and 702 energize two sets of three-phase windings 801 and 802 of the motor 80. The microcomputers 401 and 402 independently calculate the drive signals to be sent to the inverters 701 and 702 of each system.

The ECU 10 also includes an ASIC equipped with a pre-driver, a CPU, ROM, RAM, I/O, and bus lines connecting these components (not shown). The ECU 10 performs software processing by running pre-stored programs in the CPU, and hardware processing using dedicated electronic circuits.

Inverters 701 and 702 are configured with bridge-connected switching elements in the upper and lower arms of each of the U, V, and W phases. MOSFETs, for example, are used as the switching elements. Inverters 701 and 702 convert DC power into three-phase AC power by operating each switching element based on a voltage command, and supply it to two sets of three-phase windings 801 and 802. The first system of inverter 701 is connected to the U1, V1, and W1 terminals of the three-phase winding 801, and the second system of inverter 702 is connected to the U2, V2, and W2 terminals of the three-phase winding 802.

In the configuration example shown in Figure 7, two inverters 701 and 702 are connected individually to two DC power sources 601 and 602. In another configuration example, the two inverters 701 and 702 may be connected in parallel to a single DC power source. Smoothing capacitors 661 and 662 that smooth the input voltage are provided on the input sides of the inverters 701 and 702.

A current sensor 751 that detects three-phase currents Iu1, Iv1, and Iw1 is provided in the three-phase current path from the first system inverter 701 to the motor 80. A current sensor 752 that detects three-phase currents Iu2, Iv2, and Iw2 is provided in the three-phase current path from the second system inverter 702 to the motor 80.

The microcomputers 401 and 402 of each system include an angle correction unit 470 and a motor drive control unit 48. Because the first system microcomputer 401 and the second system microcomputer 402 have similar configurations, the first system microcomputer 401 will be mainly described as a representative. Each element within the microcomputer is assigned a common symbol, and the symbols for current and angle are suffixed with the number of each system.

The angle correction unit 470 of the first system removes errors contained in the detected angle θo1 of the rotation angle sensor 301 and outputs the corrected detected angle θm1 to the motor drive control unit 48. As information for angle correction, the angle correction unit 470 acquires the dq-axis currents Id1 and Iq1 from the motor drive control unit 48. Alternatively, as indicated by the dashed arrows, the angle correction unit 470 may acquire the three-phase currents Iu1, Iv1, and Iw1 independently from the current sensor 751. The angle correction unit 470 also acquires the initial temperature detection value Temp_0 of the rotation angle sensor 301 before current is applied to the winding 801 from the initial temperature sensor 76. The initial temperature sensor 76 may be, for example, an outside air temperature sensor or a substrate temperature sensor.

Furthermore, the angle correction units 470 of the first and second systems communicate information with each other. These details will be described later with reference to Figure 8. The rotation angle detection device 50 according to this embodiment is composed of rotation angle sensors 301, 302 and the angle correction units 470 of the microcomputers 401, 402 of each system. The rotation angle detection device 50 detects the rotation angle of the three-phase brushless motor 80 in the ECU 10, which feeds back the rotation angle of the motor 80 and controls the supply of current to the windings 801, 802.

The motor drive control unit 48 of the first system obtains the steering torque trq1 from the steering torque sensor 93 and obtains the three-phase currents Iu1, Iv1, and Iw1 from the current sensor 751. The motor drive control unit 48 also obtains the corrected detected angle θm1 from the angle correction unit 470. The motor drive control unit 48 converts the three-phase currents Iu1, Iv1, and Iw1 into d-axis and q-axis currents Id1 and Iq1 using the electrical angle converted from the corrected detected angle θm1. The motor drive control unit 48 calculates the drive signal to be sent to the inverter 701 using current feedback control.

Next, the detailed configuration of the angle correction unit 470 will be described with reference to Figure 8. As with Figure 7, the angle correction units 470 of the first system microcomputer 401 and the second system microcomputer 402 have the same configuration, so the angle correction unit 470 of the first system will be mainly described as a representative.

The angle correction unit 470 includes a first-order error elimination unit 43, a rotation angle sensor temperature estimation unit 44, a second-order error elimination unit 45, and an angle correction calculation unit 46. Here, "angle correction unit 470" is the name that indicates the comprehensive block related to angle correction, and "angle correction calculation unit 46" is the name that indicates the part of the angle correction unit 470 that calculates the final corrected detection angle θm1.

The primary error elimination unit 43 eliminates "errors due to the positional accuracy of the rotational angle sensor 301" contained in the detected angle θo1 of the rotational angle sensor 301, and calculates the detected angle θp1 after primary correction. Errors due to positional accuracy include errors in the individual components of the Hall IC 330 and sensor magnet 37, as well as assembly errors such as center misalignment and parallelism deviation during assembly. The function of the primary error elimination unit 43 conforms to Patent Document 1 (JP 2016-128772 A, corresponding US publication: US 2016/02020087 A1).

The rotation angle sensor temperature estimation unit 44 calculates the estimated temperature value TempS_est1 of the rotation angle sensor 301 based on the initial temperature detection value Temp_0 of the rotation angle sensor 301 before current is applied to the winding 801 and the integrated value of the power supplied to the winding 801, and notifies the second-order error elimination unit 45 of this.

Furthermore, for example, the rotational angle sensor temperature estimator 44 acquires the dq-axis currents Id1 and Iq1 flowing through the winding 801 and calculates the current amplitude. Alternatively, the rotational angle sensor temperature estimator 44 may calculate the current amplitude from the three-phase currents Iu1, Iv1, and Iw1. The rotational angle sensor temperature estimator 44 calculates an integrated power value from the product (RI ² ) of the winding resistance and the square of the current amplitude, and converts it into Joule heat. Furthermore, the rotational angle sensor temperature estimator 44 estimates the temperature rise due to heat transfer from the winding 801 to the rotational angle sensor 301 using a mathematical model that uses a transfer function. The rotational angle sensor temperature estimator 44 then calculates the estimated temperature value TempS_est1 of the rotational angle sensor 301 by adding the temperature rise to the initial temperature detection value Temp_0.

The second-order error elimination unit 45 acquires the temperature estimate TempS_est1 of the rotation angle sensor 301 and the q-axis current Iq1 flowing through the winding 801. The q-axis current Iq1 corresponds to "a quantity correlated with the amplitude and phase of the current flowing through the winding." Hereinafter, "a quantity correlated with the amplitude and phase of the current flowing through the winding" will be abbreviated to "winding current correlation quantity." Three-phase currents Iu1, Iv1, and Iw1 may be acquired as the winding current correlation quantity instead of the q-axis current Iq1.

In particular, the two-system secondary error elimination unit 45 has an own system angle error correction amount calculation unit 455 and an adder 456. The own system angle error correction amount calculation unit 455 calculates the own system angle error correction amount θ#1 based on the temperature of the rotation angle sensor 301 and the winding current correlation amount such as the q-axis current Iq1, so as to eliminate errors caused by leakage flux due to current flow to the winding 801. The above configuration is also the same for the angle correction unit 470 of the second system.

The explanation of errors caused by leakage magnetic flux follows that of Patent Document 1. Specifically, leakage magnetic flux occurs when current flows through motor wires 851 and 852, which are arranged radially outward on the mounting surface on which rotation angle sensors 301 and 302 are mounted. This leakage magnetic flux causes errors in the detected angles θo1 and θo2 of rotation angle sensors 301 and 302. However, the conventional technology of Patent Document 1 calculates angle correction values based solely on winding currents, without taking into account the temperature of the rotation angle sensors. In contrast, the secondary error elimination unit 45 of this embodiment calculates angle error correction amounts θ#1 and θ#2 based on the temperature of rotation angle sensors 301 and 302 in addition to the winding currents. The technical significance of this will be described later with reference to Figures 9 to 11.

In a double-winding motor such as that shown in Figure 6, the sum of the leakage magnetic flux due to the current flowing through the windings 801 and 802 of each system affects the rotation angle sensors 301 and 302. Therefore, the microcomputers 401 and 402 of the two systems communicate with each other and share the angle error correction amounts θ#1 and θ#2 of their own systems. The adder 456 of the secondary error elimination unit 45 of each system then adds up the angle error correction amounts θ#1 and θ#2 of the two systems to calculate the total angle error correction amount θ#sum.

The two microcomputers 401, 402 are set in a master-slave relationship, and it is possible, for example, to communicate the total angle error correction amount θ#sum calculated by the master microcomputer to the slave microcomputer. However, in this embodiment, the two microcomputers each calculate the total angle error correction amount θ#sum independently, so that if one microcomputer fails, the other microcomputer can continue to perform angle correction.

The angle correction calculation unit 46 calculates the second-order corrected detected angle θm1 based on the first-order corrected detected angle θp1 and the total angle error correction amount θ#sum, and outputs it to the motor drive control unit 48. In a single-system configuration, the angle error correction amount θ#1 of the system itself is used instead of the total angle error correction amount θ#sum. Furthermore, since the total angle error correction amount θ#sum includes the angle error correction amount θ#1 of the system itself, generally speaking, the angle correction calculation unit 46 calculates the second-order corrected detected angle based on the first-order corrected detected angle and the angle error correction amount.

Furthermore, when the angle error correction amount is calculated as shown in FIG. 10, the angle correction calculation unit 46 calculates the post-secondary correction detection angle θm1 by subtracting the total angle error correction amount θ#sum from the post-primary correction detection angle θp1. However, the sign of the angle error correction amount may be inverted, and the angle correction calculation unit 46 may calculate the post-secondary correction detection angle θm1 by adding the total angle error correction amount θ#sum to the post-primary correction detection angle θp1. Such changes in addition and subtraction are included in the expression "based on the post-primary correction detection angle and the angle error correction amount."

The effects of this embodiment will be explained in comparison with a comparative example, with reference to Figures 9 to 11. The comparative example shown in Figure 9 corresponds to the prior art disclosed in Patent Documents 1 and 2, in which the detected angle is corrected solely by the q-axis current flowing through the winding, regardless of the temperature of the rotation angle sensor. For simplicity, this section will be explained assuming a single-system configuration. The symbols and numbers at the end of the symbols of the rotation angle sensors will be omitted.

The top, middle, and bottom sections of Figures 9 and 10 are treated as a set of related diagrams. The top section shows the detected angle after primary correction, before the angle error caused by leakage flux is removed, and the bottom section shows the detected angle after secondary correction, after the angle error caused by leakage flux is removed. The horizontal axis in the top and bottom sections directly represents time. However, because time is converted to angle assuming a constant rotation speed, the horizontal axis is also shown in parentheses as a converted angle. The middle section shows a map of the angle error correction amount versus the detected angle. The detected angle after secondary correction in the bottom section is the value obtained by subtracting the angle error correction amount in the middle map from the detected angle after primary correction in the top section.

The angle error correction amount map in the middle of Figure 9 is represented by a composite wave of a fourth-order component (dashed line) and a sixth-order component (dashed line) at a reference temperature ST, such as standard ambient temperature (25°C). The fourth and sixth orders correspond to the (n±1) orders when the number of magnetic pole pairs n = 5 in equation (14) of Patent Document 1. Note that the phase difference (a±θu1) of the cosine wave in equation (14) of Patent Document 1 is assumed to be 0. The amplitude of the composite wave is determined based on the magnetic flux of the sensor magnet 37 at the reference temperature ST.

In the upper part of Figure 9, the actual detected angle after primary correction at the reference temperature ST (solid line) is represented by a waveform in which fourth- and sixth-order undulations are superimposed on the straight line B, which represents the ideal error-free detected angle. The undulations correspond to noise in the detected angle signal. When the angle error correction amount in the map is subtracted from the detected angle after primary correction, the detected angle after secondary correction at the reference temperature ST (solid line) matches the straight line B, which represents the ideal detected angle. In other words, in an environment of the reference temperature ST, the detected angle of the rotation angle sensor is accurately corrected using the technology of the comparative example.

Next, consider a case where the temperature of the rotation angle sensor deviates from the reference temperature ST. Temperatures higher than the reference temperature ST (e.g., 60 to 80°C) are referred to as "high temperatures HT," and temperatures lower than the reference temperature ST (e.g., -30 to -10°C) are referred to as "low temperatures LT." The magnetic flux of the sensor magnet 37 tends to decrease as the temperature increases. Therefore, in the upper part of Figure 9, at high temperature HT, the S/N ratio of the actual detected angle (long dashed line) is lower than at reference temperature ST, and the amplitude of the error is larger. At low temperature LT, the S/N ratio of the actual detected angle (short dashed line) is higher than at reference temperature ST, and the amplitude of the error is smaller.

Thus, even though the error amplitude changes depending on the temperature of the rotation angle sensor, the comparative example uses a uniform amount of angle error correction based on the reference temperature ST. As a result, at high temperature HT, correction is insufficient, and noise in the same direction as the detected angle after primary correction remains in the actual detected angle after secondary correction (long dashed line). Conversely, at low temperature LT, correction is excessive, and noise in the opposite direction to the detected angle after primary correction appears in the actual detected angle after secondary correction (short dashed line).

If a particular product is always used in a high-temperature environment or always in a low-temperature environment, it may be possible to adjust the optimal reference temperature ST depending on the operating temperature. However, operating temperatures may vary over a wide range, from low to high, depending on the season and weather. For example, in the column-type EPS shown in Figure 1, the motor 80 is installed near the air-conditioned passenger compartment, so the temperatures of the rotation angle sensors 301 and 302 are relatively stable. On the other hand, in the rack-type EPS shown in Figure 2, the motor 80 is exposed near the road surface, so the rotation angle sensors 301 and 302 are easily affected by the temperature of asphalt in summer and snowy roads in winter.

Therefore, in the comparative example, which uniformly uses an angle error correction amount based on the reference temperature ST regardless of the actual temperature, the accuracy of the detected angle after secondary correction relative to the ideal detected angle decreases due to temperature changes in the rotation angle sensor. As a result, in the motor drive device 10 of the EPS 90, feedback control using the detected angle increases the torque ripple of the motor 80, which could worsen the driver's steering feel.

In this embodiment, therefore, as shown in the map in the middle of Figure 10, the amplitude of the angle error correction amount is changed depending on the temperature of the rotation angle sensor. At high temperature HT, the amplitude of the angle error correction amount is set larger than at reference temperature ST, and at low temperature LT, the amplitude of the angle error correction amount is set smaller than at reference temperature ST.

As shown in more detail in Figure 11, the secondary error elimination unit 45 sets the amplitude of the angle error correction amount for the same winding current Iq in accordance with the rotational angle sensor temperature estimate TempS_est obtained from the rotational angle sensor temperature estimator 44. In contrast, in the comparative example, the amplitude of the angle error correction amount is set constant regardless of temperature changes in the rotational angle sensors 301 and 302.

The detection angles after primary correction for the high temperature HT and low temperature LT shown in the upper part of Figure 10 are the same as those in Figure 9. Note that the detection angle after primary correction for the reference temperature ST is not shown. In this embodiment, the angle error correction amount according to temperature is subtracted from the detection angle after primary correction, so the detection angles after secondary correction for the high temperature HT and low temperature LT shown in the lower part of Figure 10 all match line B, which is the ideal detection angle with no error.

In this way, in this embodiment, by correcting the detected angle after primary correction in accordance with the correlation between the temperature of the rotation angle sensor and the winding current, the detected angle can be corrected with high accuracy even if the temperature of the rotation angle sensor changes. Therefore, torque ripple is reduced in the ECU 10, which controls the drive of the motor 80 through feedback control using the detected angle after secondary correction. In particular, a good steering feel is ensured in the ECU 10 that drives the steering assist motor 80 of the EPS 90.

With reference to the flowchart in Figure 12, the processing executed by the second-order error elimination unit 45 of each system in a rotation angle detection device equipped with two microcomputers 401, 402 will be explained. In the explanation of the flowchart, the symbol "S" indicates a step. Here, the first system is the local system and the second system is the other system, and the explanation will be given from the perspective of the second-order error elimination unit 45 of the first system. The second-order error elimination unit 45 also performs similar processing.

In S1, the second-order error elimination unit 45 of the first system acquires the rotation angle sensor temperature estimate TempS_est1 of its own system and the q-axis current Iq1 flowing through its own system's winding 801. In S2, the second-order error elimination unit 45 of the first system calculates the angle error correction amount θ#1 of its own system. If inter-system communication between the microcomputers 401 and 402 is normal, a YES determination is made in S3, and the process proceeds to S4. In S4, the second-order error elimination unit 45 of the first system acquires the angle error correction amount θ#2 of the other system (i.e., the second system) through inter-system communication. The signal arrows for this process are shown in Figure 8.

In S6, the second-order error elimination unit 45 of the first system adds up the angle error correction amounts of the two systems to calculate the total angle error correction amount θ#sum (= θ#1 + θ#2). At this time, the second-order error elimination unit 45 of the second system also calculates the total angle error correction amount θ#sum in the same way. Because the total angle error correction amount θ#sum is calculated twice for both systems, even if the microcomputer of one system fails, appropriate angle correction can continue using the microcomputer of the other normal system.

On the other hand, if there is an abnormality in the inter-system communication between the microcontrollers 401 and 402, a NO determination is made in S3, and the process proceeds to S5. In S5, the secondary error elimination unit 45 of the first system replaces the angle error correction amount θ#2 of the other system (i.e., the second system) that cannot be shared with the angle error correction amount θ#1 of its own system. Therefore, in S6, the secondary error elimination unit 45 of the first system doubles the angle error correction amount θ#1 of its own system to calculate the total angle error correction amount θ#sum. This allows appropriate angle correction to continue even if there is an abnormality in the inter-system communication.

The routine in Figure 12 is repeated at a predetermined calculation cycle. During drive control of the motor 80, the total angle error correction amount θ#sum changes as the temperature of the rotation angle sensors 301, 302 and the amount of current flowing through the windings 801, 802 change. In this way, in this embodiment, the detected angle can be corrected with high accuracy even if the temperature of the rotation angle sensors 301, 302 changes.

Furthermore, if the abnormality in inter-system communication is temporary, it is possible to return to processing that shares information between the two systems once communication returns to normal. However, to prevent control hunting, it is also possible to continue alternative processing in the own system until a predetermined time has passed since the previous communication abnormality was detected. This will stabilize angle correction control.

(Other embodiments)
(a) The rotation angle sensors 301 and 302 illustrated in FIG. 5 detect the rotation angles of the two systems separately. The angle correction unit 470 of the microcomputers 401 and 402 illustrated in FIG. 8 calculates the second-order corrected detected angles θm1 and θm2 based on the detected angles θo1 and θo2 for each system. In contrast, FIGS. 13 and 14 show the configurations of the rotation angle sensor 30 that detects a rotation angle common to the two systems, and the angle correction unit 470 that calculates the second-order corrected detected angle θm based on the common detected angle θo. The notes for FIGS. 13 and 14 are the same as those for FIGS. 5 and 8, respectively. The configuration of the motor 80 itself to be applied is shown in FIGS. 3, 4, and 6.

As shown in FIG. 13, the Hall IC 335 contains two Hall elements 331, 332 arranged orthogonally to each other and which detect a single rotation angle θo. The rotation angle sensor 30 includes the two Hall elements 331, 332 and a sensor magnet 37. As shown in FIG. 14, the angle correction unit 470 of the microcomputer 40 corrects the detected angle θo to calculate a second-order corrected detected angle θm. The motor drive control unit 48 calculates drive signals to be sent to the inverters 701, 702 of each system based on the second-order corrected detected angle θm.

More specifically, the primary error elimination unit 43 eliminates errors resulting from the positional accuracy of the rotation angle sensor 30 and calculates the detected angle θp after primary correction. The rotation angle sensor temperature estimator 44 estimates the temperature estimate TempS_est of the rotation angle sensor 30 based on the integrated power value derived from the two dq-axis currents Id1, Iq1, Id2, and Iq2. The secondary error elimination unit 45 calculates the angle error correction amount θ# based on the total magnetic flux resulting from the two q-axis currents Iq1 and Iq2, so as to eliminate errors resulting from leakage magnetic flux due to the current flow through the windings 801 and 802. The angle correction calculation unit 46 subtracts the angle error correction amount θ# from the detected angle θp after primary correction to calculate the detected angle θm after secondary correction.

The motor drive control unit 48 performs drive control calculations for each system using the rotation angles θm1 and θm2 of each system calculated from the detected angle θm after secondary correction. For example, the rotation angle θm1 of the first system is calculated as θm1 = θm, and the rotation angle θm2 of the second system is calculated as θm2 = θm + 30 [deg].

The configuration in Figure 14 achieves a simple control configuration using a single microcomputer 40. Furthermore, because there is no communication between systems, no measures are required in the event of an abnormality in communication between systems. Note that the symbols and signs used only in Figures 13 and 14 will not be used as reference symbols or signs in the claims.

(b) The number of Hall elements in the rotation angle sensor per system is not limited to two, and may be three or more. Furthermore, the number of sensor magnets is not limited to one common to multiple systems, and multiple sensor magnets may be provided for each system, for example.

(c) Instead of estimating the rotation angle sensor temperature using the rotation angle sensor temperature estimator 44, the rotation angle sensor temperature may be detected, for example, by a temperature sensor installed near the Hall IC on the circuit board. If a temperature sensor for the inverter switching elements is installed near the Hall IC, the detected value may be used as the rotation angle sensor temperature.

(d) The number of phases in a "polyphase brushless motor" is not limited to three, but may be four or more. Furthermore, the number of magnetic pole pairs in the rotor and the number of slots in the stator may be set as appropriate. For the number n of magnetic pole pairs, (n±1)th-order noise components are superimposed on the angle detected by the rotation angle sensor.

(e) The motor may have three or more sets of polyphase windings, and the motor drive device may include three or more inverters that energize the three or more sets of polyphase windings of the motor, and three or more microcomputers. For example, in the case of three systems, the secondary error elimination unit of the microcomputer for the first system calculates a total angle error correction amount θ#sum by adding the angle error correction amount θ#1 of its own system to the angle error correction amounts θ#2 and θ#3 of the second and third systems obtained via communication.

(f) The rotation angle detection device of the present invention is not limited to EPS steering assist motors, but may also be used to detect the rotation angle of motors in motors for other applications mounted on vehicles, or in drive devices for various motors other than those for vehicles. The effects of the present invention are particularly effective in motor drive devices where the ambient temperature changes significantly and the effects of torque ripple generated by feedback control using the detected angle are a problem.

The present invention is not limited to the above-described embodiments, and can be implemented in various forms without departing from the spirit of the invention.

The invention of "a rotation angle detection device according to claim 1 or 2 that detects the rotation angle of a steering assist motor in an electric power steering device of a vehicle" may be specified as "a rotation angle detection device according to any one of claims 1 to 6 that detects the rotation angle of a steering assist motor in an electric power steering device of a vehicle" if the recitation requirements are permitted.

The computing unit and method described in this disclosure may be implemented by a special-purpose computer configured with a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the computing unit and method described in this disclosure may be implemented by a special-purpose computer configured with a processor comprising one or more dedicated hardware logic circuits. Alternatively, the computing unit and method described in this disclosure may be implemented by one or more special-purpose computers configured with a combination of a processor and memory programmed to perform one or more functions and a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory tangible recording medium.

10...ECU (motor drive device),
301, 302...Rotation angle sensors,
331-334: Hall element, 37: Sensor magnet,
401, 402...microcomputer (arithmetic unit),
43: First-order error elimination unit; 44: Rotation angle sensor temperature estimation unit;
45... Secondary error removal section, 46... Angle correction calculation section,
701, 702... inverters (power converters),
80: motor; 801, 802: windings; 87: shaft.

Claims (6)

A rotation angle detection device for detecting the rotation angle of a polyphase brushless motor (80) in a motor drive device (10) that controls current supply to windings (801, 802) by feeding back the rotation angle of the motor, comprising:
a rotation angle sensor (301, 302) including two or more Hall elements (331-334) mounted on a substrate and one or more sensor magnets (37) fixed to a shaft (87) that is a rotation axis of the motor;
a first-order error removal unit (43) that removes an error caused by the positional accuracy of the rotation angle sensor and included in the detection angles (θo1, θo2) of the rotation angle sensor, and calculates first-order corrected detection angles (θp1, θp2);
a secondary error elimination unit (45) that calculates angle error correction amounts (θ#1, θ#2) so as to eliminate errors caused by leakage flux due to current flow through the windings;
a rotation angle sensor temperature estimating unit (44) that calculates temperature estimates (TempS_est1, TempS_est2) of the rotation angle sensor in accordance with an initial temperature detection value (Temp_0) of the rotation angle sensor before current is applied to the winding and an integrated value of power supplied to the winding, and notifies the second-order error elimination unit of the calculated temperature estimates;
an angle correction calculation unit (46) that calculates second-order corrected detected angles (θm1, θm2) based on the first-order corrected detected angles and the angle error correction amount;
Equipped with
The second-order error elimination unit calculates the angle error correction amount in accordance with a quantity correlated to the temperature of the rotation angle sensor and the amplitude and phase of the current flowing through the winding. the motor has multiple sets of multi-phase windings;
The motor drive device includes a plurality of power converters (701, 702) that energize a plurality of sets of polyphase windings of the motor, and a plurality of computing units (401, 402) that independently compute drive signals to be issued to the power converters of the respective systems, the computing units including the first-order error elimination unit, the second-order error elimination unit, and the angle correction computation unit;
2. The rotation angle detection device according to claim 1 , wherein the second-order error elimination unit of each system calculates the angle error correction amount for each system in accordance with an amount correlated with the amplitude and phase of the current flowing through the winding of that system. The computing units of the plurality of systems communicate with each other and share the angle error correction amounts of their own systems;
3. The rotation angle detection device according to claim 2 , wherein the secondary error elimination unit of each system calculates a total angle error correction amount (θ#sum) by adding up the angle error correction amounts of all systems. A rotation angle detection device for detecting the rotation angle of a polyphase brushless motor (80) having a plurality of sets of polyphase windings in a motor drive device (10) that controls current supply to windings (801, 802) by feeding back the rotation angle of the motor,
a rotation angle sensor (301, 302) including two or more Hall elements (331-334) mounted on a substrate and one or more sensor magnets (37) fixed to a shaft (87) that is a rotation axis of the motor;
a first-order error removal unit (43) that removes an error caused by the positional accuracy of the rotation angle sensor and included in the detection angles (θo1, θo2) of the rotation angle sensor, and calculates first-order corrected detection angles (θp1, θp2);
a secondary error elimination unit (45) that calculates angle error correction amounts (θ#1, θ#2) according to amounts correlated with the temperature of the rotation angle sensor and the amplitude and phase of the current passed through the windings so as to eliminate errors caused by leakage magnetic flux due to current passing through the windings ;
an angle correction calculation unit (46) that calculates second-order corrected detected angles (θm1, θm2) based on the first-order corrected detected angles and the angle error correction amount;
Equipped with
The motor drive device includes a plurality of power converters (701, 702) that energize a plurality of sets of polyphase windings of the motor, and a plurality of computing units (401, 402) that independently compute drive signals to be issued to the power converters of the respective systems, the computing units including the first-order error elimination unit, the second-order error elimination unit, and the angle correction computation unit;
the secondary error elimination unit of each system calculates the angle error correction amount for each system in accordance with an amount correlated to the amplitude and phase of the current passed through the winding of that system;
The computing units of the plurality of systems communicate with each other and share the angle error correction amounts of their own systems;
The secondary error elimination unit of each system calculates a total angle error correction amount (θ#sum) by adding up the angle error correction amounts of all systems . When a communication error occurs between the computing units of the plurality of systems,
5. The rotation angle detection device according to claim 3 , wherein the computing unit of each system substitutes the angle error correction amount of the other system that cannot be shared with the angle error correction amount of its own system. 5. The rotation angle detection device according to claim 1, wherein the rotation angle of a steering assist motor is detected in an electric power steering device of a vehicle.