Motor control device and electric power steering system equipped therewith

Abstract

The present invention provides a motor control device and an electric power steering system equipped therewith, which can vary the gain of motor back electromotive force compensation according to the steering state, thereby suppressing the generation of minute currents that act as brakes due to motor back electromotive force. [Solution] In a motor control device that drives and controls a motor using current FB control based on a current command value, and compensates for the motor back electromotive force using a back electromotive force compensation signal based on the motor angle or motor angular velocity, a gain variable unit that varies the gain is provided in the path for compensating the motor back electromotive force.

Description

[Technical Field]

[0001] The present invention relates to a motor control device that drives a motor with current feedback (FB) based on a current command value calculated based on steering torque, and controls the motor's actual current to follow the current command value, and to an electric power steering system equipped with the motor control device that applies motor-assisted force (steering assist force) to the vehicle's steering system based on the current command value. In particular, the present invention relates to a motor control device that can suppress damage to the ECU (Electric Control Unit) and suppress the generation of a small current that acts as a brake due to the motor's back electromotive force when the motor is rotating in the direction that returns the steering wheel to the neutral position, by multiplying the back electromotive force compensation value by a variable gain calculated based on steering state information and correcting it, and to an electric power steering system equipped with the motor control device that can suppress damage to the ECU (Electric Control Unit) and suppress the generation of a small current that acts as a brake due to the motor's back electromotive force. [Background technology]

[0002] An electric power steering system (EPS) equipped with a motor control device provides assist force to the vehicle's steering mechanism using the rotational force of a motor. The motor's driving force, controlled by an inverter, is transmitted to the steering shaft or rack axis via a transmission mechanism such as gears to provide assist force. Such electric power steering systems generally employ motor current feedback control to accurately generate the torque of the assist force. Feedback control adjusts the motor applied voltage so that the difference between the current command value (steering assist command value) and the motor current detection value is small. This adjustment of the motor applied voltage is generally performed by adjusting the duty cycle of PWM (Pulse Width Modulation) control.

[0003] A typical configuration of an electric power steering system is shown in Figure 1. The steering column shaft (steering shaft, steering wheel shaft) 2 of the steering wheel 1 is connected to the steering wheels 8L and 8R via a reduction gear 3, universal joints 4a and 4b, a pinion rack mechanism 5, tie rods 6a and 6b, and further via hub units 7a and 7b. The steering column shaft 2 is also equipped with a torque sensor 10 for detecting the steering torque Th of the steering wheel 1 and a steering angle sensor 14 for detecting the steering angle θh. A motor 20 that assists the steering force of the steering wheel 1 is connected to the steering column shaft 2 via a reduction gear 3. Power is supplied to the control unit (ECU) 30 that controls the electric power steering system from the battery 13, and an ignition key signal is input via the ignition key 11. The control unit 30 calculates the current command value for the assist (steering assistance) command based on the steering torque Th detected by the torque sensor 10 and the vehicle speed Vs detected by the vehicle speed sensor 12, and controls the current supplied to the motor 20 by a voltage control command value Vref obtained by applying compensation to the current command value.

[0004] While the steering angle θh is detected by the steering angle sensor 14, it is also possible to obtain the steering angle from a rotation sensor such as a resolver connected to the motor 20.

[0005] The control unit 30 is connected to a CAN (Controller Area Network) 40 for exchanging various vehicle information, and the vehicle speed Vs can also be received from the CAN 40. In addition, the control unit 30 can also be connected to a non-CAN 41 for exchanging communications other than CAN 40, such as analog / digital signals and radio waves.

[0006] The control unit 30 is mainly composed of a CPU (Central Processing Unit) (including an MPU (Micro Processor Unit) and an MCU (Micro Controller Unit), etc.), and Figure 2 shows the general functions that are executed by programs within that CPU.

[0007] Referring to Figure 2, the control unit 30 is described as follows: The steering torque Th detected by the torque sensor 10 and the vehicle speed Vs detected by the vehicle speed sensor 12 (or from CAN 40) are input to the current command value calculation unit 31, which calculates the current command value Iref1. Based on the input steering torque Th and vehicle speed Vs, the current command value calculation unit 31 uses an assist map or the like to calculate the current command value Iref1, which is the control target value for the current supplied to the motor 20. The current command value Iref1 is input to the current limiting unit 33 via the adder 32A, and the current command value Irefm, with the maximum current limited, is input to the subtractor 32B, where the current deviation ΔI (=Irefm-Im) with the feedback motor current Im is calculated, and the current deviation ΔI is input to the PI (Proportional-Integral) control unit 34 for improving the characteristics of the steering operation. The voltage control command value Vref, whose characteristics have been improved by the PI control unit 34, is input to the PWM control unit 35, and the motor 20 is further PWM driven via the inverter 36. The current Im of the motor 20 is detected by the motor current detector 37 and fed back to the subtraction unit 32B.

[0008] A rotation sensor 21, such as a resolver, is connected to the motor 20. The rotation sensor 21 outputs the motor angle θm, and the motor angular velocity ωm is calculated by the motor speed calculation unit 22.

[0009] Furthermore, the compensation signal CM from the compensation signal generation unit 38 is added to the summing unit 32A. The addition of the compensation signal CM compensates for the characteristics of the steering system, improving convergence and inertial characteristics. The compensation signal generation unit 38 adds the self-aligning torque (SAT) 38-1 and inertia 38-2 in the summing unit 38-4, and then adds convergence 38-3 to the summing result in the summing unit 38-5, with the summing result of the summing unit 38-5 being the compensation signal CM.

[0010] In such electric power steering systems, the motor control device generates a back electromotive force (EMF) when the motor is driven. Therefore, compensation is necessary to suppress or attenuate this EMF. The reason for this is explained below.

[0011] When the control system in which the motor 20 is driven from the current command value Irefm is expressed by a transfer function, it becomes as shown in FIG. 3. The current command value Irefm is input to the subtraction unit 104 through the control filter (G FF ) 101, and the current deviation e1 from the actual motor current Imn is calculated. The current deviation e1 is input to the subtraction unit 105 through the control filter (G FB ) 102. In the subtraction unit 105, the back electromotive force EMF of the motor 20 is subtracted, and the difference e3 passes through the electrical system characteristic unit 110 (1 / (L·s + R)) of the motor 20, and further passes through the torque constant Kt [Nm / A] and is input to the mechanical system characteristic unit 120 (1 / (J·s + D)). Hereinafter, "s" is a Laplace operator. The back electromotive force EMF is obtained by multiplying the motor angular velocity (motor rotation speed) ωm, which is the output of the mechanical characteristic unit 120, by the back electromotive force constant Ke [V / (rad / s)]. The motor current Im from the electrical system characteristic unit 110 is detected and fed back. Actually, however, current detection noise Ni is mixed in and fed back as the actual motor current Imn.

[0012] Note that "L" in the electrical system characteristic unit 110 is the motor inductance [H], "R" is the motor resistance [Ω], "J" in the mechanical system characteristic unit 120 is the motor inertia moment [Kg·m 2 , and "D" is the motor viscous coefficient [Nm / (rad / sec)].

[0013] In order to make the system from the current command value Irefm to the motor current Im a first-order filter (1 / (T4·s + 1)) that is easy to control the frequency band as shown in FIG. 4, with T1 to T4 as time constants, the transfer function of the control filter (G FF ) 101 is set by Equation (1) below, and the transfer function of the control filter (G FB ) 102 is set by Equation (2) below.

[0014]

Equation

[0015]

Equation

[0016]

Equation

[0017]

Equation

[0018] Thus, the control filter (G FF ) 101 and the control filter (G FBIn setting 102, the inclusion of motor back electromotive force (EMF) is not taken into consideration. However, the generation of motor back electromotive force (EMF) affects the current command value, which poses a significant problem in accurately controlling the motor output. As a countermeasure, motor back electromotive force compensation can be considered. For example, in Japanese Patent Application Publication No. 2013-219870 (Patent Document 1), the motor back electromotive force is estimated based on the voltage command value and the current detection value, and the estimated back electromotive force is added to the current command value. In addition, in Japanese Patent Application Publication No. 2012-236472 (Patent Document 2), the back electromotive force is estimated based on the rotational angular velocity, and a back electromotive force compensation control value is calculated by multiplying this estimated back electromotive force by a compensation coefficient, and the back electromotive force compensation control value is added to the base voltage to obtain the voltage command value.

[0019] All of the back EMF compensation methods described above assume that position and rotational speed detection noise is not introduced. However, in reality, detection noise is introduced, which presents a challenge in accurately tracking the motor output in response to the current command value. [Prior art documents] [Patent Documents]

[0020] [Patent Document 1] Japanese Patent Publication No. 2013-219870 [Patent Document 2] Japanese Patent Publication No. 2012-236472 [Patent Document 3] Patent No. 6638471 [Overview of the Initiative] [Problems that the invention aims to solve]

[0021] As a method for solving the above-mentioned problems, a motor control device disclosed in Japanese Patent No. 6638471 (Patent Document 3) is known. Specifically, the motor control device disclosed in Patent Document 3 (hereinafter referred to as the "conventional device") compensates for the generation of back electromotive force during motor drive without changing the sensitivity to noise, and also inserts an angle filter for compensation error cancellation that compensates for noise compensation and LPF (Low Pass Filter) compensation into the feedback path. In this way, the actual motor current is made to follow the current command value accurately and without delay without changing the sensitivity to noise.

[0022] However, in the conventional device described above, overcompensation of back EMF can generate eddy currents. Therefore, constant settings are configured to avoid overcompensation, taking into account motor temperature changes and variations. Consequently, when motor temperature changes or variations occur, the motor back EMF cannot be completely offset. Therefore, for example, when the motor is rotating in the direction that returns the handle to the neutral position due to SAT, if the motor back EMF cannot be completely compensated, a small current that acts as a brake on the motor is generated by the motor back EMF, resulting in a problem where the handle return is impaired.

[0023] The present invention has been made in accordance with the circumstances described above, and the object of the present invention is to provide a motor control device and an electric power steering device equipped therewith that can vary the gain of motor back electromotive force compensation according to steering state information and suppress the generation of minute currents that act as brakes due to motor back electromotive force. [Means for solving the problem]

[0024] The present invention relates to a motor control device that drives and controls a motor using current feedback control based on a current command value, and compensates for the motor back electromotive force using a back electromotive force compensation signal based on the motor angle or motor angular velocity. The above objective of the present invention is achieved by providing a gain variable unit in the path for compensating the motor back electromotive force, which varies the gain according to steering state information. [Effects of the Invention]

[0025] In this invention, a variable gain section is provided in the path that compensates for the motor back electromotive force, which varies according to the steering state. Therefore, when the motor is rotating in the direction that returns the steering wheel to the neutral position due to SAT, increasing the gain of the back electromotive force compensation suppresses the generation of a small current that acts as a brake due to the motor back electromotive force, thereby improving the steering wheel return performance. Furthermore, since the gain of the back electromotive force compensation is limited to around 1 in a specific range, for example, when the motor is rotating at high speed or under high load torque, the generation of overcurrent due to back electromotive force overcompensation can be suppressed, preventing damage to the ECU. [Brief explanation of the drawing]

[0026] [Figure 1] This is a diagram illustrating the configuration of an electric power steering system. [Figure 2] This is a block diagram showing an example configuration of a control unit (ECU) for an electric power steering system. [Figure 3] This is a block diagram showing the path of back electromotive force generation in a motor control device (transfer function). [Figure 4] This is a frequency response diagram used to explain the characteristics of a control filter. [Figure 5] This is a frequency response diagram used to explain the characteristics of a control filter. [Figure 6] This is a diagram showing an example of the configuration of the present invention. [Figure 7] This is a block diagram showing an example of a back electromotive force compensation configuration (conventional device) in a motor control device (transfer function). [Figure 8] This is a block diagram showing the configuration of a conventional device. [Figure 9] This is a block diagram showing an example of the configuration of back electromotive force compensation (with angle FB filter) in the motor control device (transfer function) of the present invention. [Figure 10] This is a block diagram showing an example of the configuration of the gain adjustment section. [Figure 11] This is a characteristic diagram showing an example of the characteristics of the gain section (current command value). [Figure 12] This is a characteristic diagram showing an example of the gain section (motor angular velocity). [Figure 13] This is a conditional diagram showing the operation of the gain determination unit. [Figure 14] This is a block diagram showing an example of the configuration of back electromotive force compensation (without angle FB filter) in the motor control device (transfer function) of the present invention. [Figure 15] This is a block diagram showing an example configuration of a vector control system (3-phase FB) to which the present invention can be applied. [Figure 16] This block diagram shows an example configuration of a vector control system (2-phase FB) to which the present invention can be applied. [Modes for carrying out the invention]

[0027] In this invention, the gain of motor back EMF compensation is varied according to steering state information (current command value, steering angle or motor angle, motor angular velocity) to suppress the generation of minute currents that act as brakes due to motor back EMF. Figure 6 shows an example configuration of the present invention corresponding to Figure 2, and includes a back EMF estimation unit 300 to which motor angle θm and motor angular velocity ωm are input, and a gain variable unit 310 to which current command value Irefm, steering angle θh and motor angular velocity ωm are input. The back EMF estimate value EMFc calculated by the back EMF estimation unit 300 is corrected by the multiplication unit 311 with the gain G calculated by the gain variable unit 310 to calculate the back EMF compensation signal EMFe. The back EMF compensation signal EMFe corrects the voltage command value Vref from the PI control unit 34 by the addition unit 302 to compensate the motor back EMF EMF.

[0028] Before describing the back electromotive force compensation of the present invention, we will first describe the conventional apparatus that forms the basis of the present invention with reference to Figures 7 and 8. The present invention relates to the angle FB filter (G) in the conventional apparatus. ANG This does not assume the use of an angle FB filter (G ANG This also applies when a provision is in place.

[0029] Figure 7 shows an example configuration for compensating the motor back electromotive force (EMF) based on the motor angle θm detected by the rotation sensor 21, corresponding to Figure 3. The motor angle θm is differentiated in the differential unit 130, but in reality, the rotation sensor 21 contains noise Nr, and the motor angle θmr mixed with noise Nr in the summator 133 is input to the differential unit 130. The motor angular velocity ωn differentiated in the differential unit 130 is input to the LPF 131 for noise removal, whose transfer function is represented by equation 5. The motor angular velocity ωn', from which the noise Nr has been removed in the LPF 131, is multiplied by the back electromotive force compensation constant Ke' in the back electromotive force compensation constant unit 132 and input to the summator 106 of the current control system as the back electromotive force compensation signal EMFc. Note that "ωL" in LPF 131 is the cutoff frequency f c For this, ωL = 2πf c They have a relationship.

[0030]

number

[0031] Due to the filtering process of the LPF131, as the motor speed frequency increases, the phase lags behind the motor back electromotive force (EMF), potentially preventing complete cancellation of the EMF. This cancellation error can enter the current control system as a disturbance, preventing the actual motor current Im, which is the role of feedback (FB) control, from tracking the current command value Irefm. If the back electromotive force compensation were perfect, the relationship shown in equation 6 below should hold true. (Math 6) TIFF2026057018000007.tif12150 However, due to the inclusion of noise Nr, the above equation 6 does not hold true. In the first place, the main role of current feedback control is to ensure that the actual current flows without delay according to the current command value. With control by filtering, the higher the control bandwidth, the better the tracking performance can be, but the sensitivity to noise also increases, and in electric power steering systems, the steering feel deteriorates.

[0032] To address this, an angle FB filter (G) is used such that the current tracking characteristic is Im / Irefm = 1 / (T4·s+1). ANG )200 is inserted into the motor control feedback path. Figure 8 shows the configuration corresponding to Figure 7. The transfer function from the current command value Irefm to the motor current Im output by the electrical system characteristics unit 110 is given by the following equation 7. Control filter (G FF The transfer function of )101 is the above equation 1, and the control filter (G FB The transfer function of 10² is given by the above equation 2.

[0033]

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[0034]

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[0035]

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[0036]

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[0037]

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[0038]

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[0039] Therefore, in this invention, the back electromotive force compensation signal EMFc is gain-variable according to the steering state, and back electromotive force compensation is performed with the back electromotive force compensation signal EMFd after gain variation. Figure 9 shows the configuration corresponding to Figure 8, and includes a gain-variable unit 310 that inputs the current command value Irefm, steering angle θh, and motor angular velocity ωn' indicating the steering state, as well as a multiplier unit 311 that multiplies the back electromotive force compensation signal EMFc by the gain Gd from the gain-variable unit 310 and outputs the corrected back electromotive force compensation signal EMFd. The motor angle θm may be used instead of the steering angle θh. In this example, the current command value Irefm, steering angle θh, and motor angular velocity ωn' are shown as steering state information, but either the current command value Irefm or the motor angular velocity ωn' may be used along with the steering angle θh (or motor angle θm).

[0040] The detailed configuration of the gain variable unit 310 is shown in Figure 10. The current command value Irefm is input to the absolute value unit 320 and output as the current command absolute value |Irefm|, which is then input to the gain unit 321. An example of the characteristics of the gain unit 321 is shown in Figure 11. It outputs the maximum gain Gimax when the current command absolute value |Irefm| is from "0" to |Irefm-1|, and outputs the minimum gain Gimin when the current command absolute value is |Irefm-2| (>|Irefm-1|) or greater. The gain Gi from the gain unit 321 is input to the minimum value selection unit 313, which selects and outputs the minimum value.

[0041] Furthermore, the motor angular velocity ωn' is input to the absolute value unit 330 and output as the absolute value of the motor angular velocity |ωn'|, which is then input to the gain unit 331. An example of the characteristics of the gain unit 331 is shown in Figure 12, where the maximum gain G is reached when the absolute value of the motor angular velocity |ωn'| is between "0" and |ωn'-1|. ωnmax The output is generated, and the minimum gain G is obtained when the absolute value of the motor angular velocity is greater than or equal to |ωn'-2| (>|ωn'-1|). ωnmin The output is configured to be as follows: The gain Gωn from the gain unit 331 is input to the minimum value selection unit 313, which selects and outputs the minimum value.

[0042] The minimum value selection unit 313 selects the minimum value from the input gains Gi and Gωn and outputs it as gain Gmin, which is then input to the gain determination unit 314. If the current command value Irefm is not used as information about the steering state, the absolute value unit 320, gain unit 321, and minimum value selection unit 313 are unnecessary, and the gain Gωn from the gain unit 331 is input to the gain determination unit 314. Also, if the motor angular velocity ωn' is not used as information about the steering state, the absolute value unit 330, gain unit 331, and minimum value selection unit 313 are unnecessary, and the gain Gi from the gain unit 321 is input to the gain determination unit 314.

[0043] Maximum gain Gimax and maximum gain G of the gain section 321 ωnmax It is desirable to set this to around "1.15 (115%)" considering temperature changes and manufacturing variations. On the other hand, the minimum gain Gimin and G ωnmin While a value of 1x (100%) is desirable, it may be set to a value other than 1x (0.9 to 1.15) to account for temperature changes and manufacturing variations. Electric power steering systems generally use synchronous motors with a magnetic structure, and neodymium magnets, which have strong magnetic force, are often used for the magnets. The temperature coefficient of neodymium magnets is approximately -0.1 [% / °C], and when the temperature condition of the back EMF constant Ke is set to 60°C, the motor back EMF increases by about 10% in a low-temperature environment of -40°C, and decreases by about 5% in a high-temperature environment of +110°C.

[0044] Furthermore, manufacturing variations also cause variations in the motor back electromotive force, with a variation of ±5% being assumed. In this invention, the motor is assumed to be rotating in the direction that returns the steering wheel to the neutral position due to SAT, so low load (10-20% or less of the maximum current command value) and low speed rotation (steering wheel steering speed of 50-100 [deg / sec] or less) are assumed. Accordingly, the section transitioning from the maximum gain Gimax to the minimum gain Gimin shown in Figure 11, that is, the section from the absolute current command value |Irefm-1| to the absolute current command value |Irefm-2|, is set to 10-20% of the maximum current command value. Also, the maximum gain G shown in Figure 12ωnmax Minimum gain G from Gimax ωnmin The transition interval, that is, the interval from the absolute value of the motor angular velocity |ωn'-1| to the absolute value of the motor angular velocity |ωn'-2|, is defined as a steering speed of 50 to 100 [deg / sec]. To convert the steering speed to motor angular velocity, it is necessary to multiply by the gear ratio Gr, so the conversion to motor angular velocity is 50 × Gr to 100 × Gr [deg / sec].

[0045] Furthermore, the steering angle θh is input to the absolute value unit 340 to obtain the absolute steering angle |θh|, which is then added to the subtraction unit 342 and input to the past value storage unit 341, which holds the value from the previous cycle. The absolute past value |θh'| from the past value storage unit 341 is subtracted to the subtraction unit 342, and the difference steering angle θe (=|θh|-|θh'|) is output from the subtraction unit 342 and input to the gain determination unit 314.

[0046] The gain determination unit 314 performs a gain determination as shown in Figure 13, outputs a gain Gda, and outputs a gain Gd after passing through a rate limiter 315 to limit the rate of change of the signal. Note that the rate limiter 315 is not mandatory. As shown in Figure 13, the gain determination unit 314 outputs the gain Gmin from the minimum value selection unit 313 as the gain Gda when the differential steering angle θe is greater than 0 (θe > 0), and outputs a constant "1.0" when the differential steering angle θe is 0 or less (θe ≤ 0). Hysteresis may be added to the conditions to prevent chattering in the output (Gda) of the gain determination unit 314.

[0047] The gain Gd from the gain variable unit 310 is input to the multiplier unit 311, and is multiplied with the back electromotive force compensation signal EMFc from the back electromotive force compensation constant unit 132 which constitutes the back electromotive force estimation unit. The multiplied and corrected back electromotive force compensation signal EMFd is input to the adder unit 106. The adder unit 106 is connected to a control filter (G FB The deviation e2 from 102 is input, and the signal e4, which has been compensated by the back electromotive force compensation signal EMFd, is added to the subtraction unit 105, and the above operation is performed.

[0048] In the above embodiment, an angle FB filter (G) is used in the motor control feedback path to cancel out the back EMF compensation error, which is the difference between the motor back EMF and the back EMF compensation signal. ANG The example described uses 200, but the angle FB filter (G ANG A motor control device without 200 is also acceptable.

[0049] Here, motor back EMF compensation is feedforward (FF), and overcompensation of back EMF can cause overcurrent. Therefore, constant settings are configured to avoid overcompensation, taking into account motor temperature changes, manufacturing variations, etc. With these constant settings, in the conventional situation where the motor is rotating in the direction that returns the handle to the neutral position by SAT, if the motor back EMF cannot be fully compensated, a small current that acts as a brake on the motor may be generated due to the motor back EMF. As a result, the motor friction may increase slightly, potentially worsening the handle return. This invention solves this problem. When the motor is rotating in the direction that returns the handle to the neutral position, increasing the gain of back EMF compensation suppresses the generation of the small current that acts as a brake due to the motor back EMF, thereby improving the handle return performance.

[0050] The present invention can also be applied to a dq-axis vector control system for driving and controlling a brushless three-phase motor. The vector control system and the motor back electromotive force compensation according to the present invention will be described below.

[0051] In the vector control system (3-phase feedback type) shown in Figure 15, the d-axis current command value i d and q-axis current command value i q A current command value calculation unit 220 is provided to calculate and correct the current command value, and the steering torque Th, vehicle speed Vs, motor angle θm from the rotation sensor 100A connected to the motor 100, and motor angular velocity ωm calculated by the angular velocity calculation unit 226 are input to the current command value calculation unit 220. d and q-axis current command value i qThe current is input to the 2-phase / 3-phase conversion unit 221, which converts the motor angle θm into 3 phases in synchronization with the motor angle θm, and is converted into 3-phase current command values ​​Iuref, Ivref, Iwref in synchronization with the motor angle θm. The 3-phase current command values ​​Iuref, Ivref, Iwref are input to the subtraction unit 222 (222u, 222v, 222w), and the deviations ΔIu, ΔIv, ΔIw from the motor currents Imu, Imv, Imw detected by the current detection circuit 225A are calculated. The calculated deviations ΔIu, ΔIv, ΔIw are input to the PI control unit 223, and the current-controlled 3-phase voltage control command values ​​Vuref, Vvref, Vwref are input to the PWM control unit 224, and the motor 100 is driven via the inverter 225 based on the phase duty cycle calculated by the PWM control unit 224.

[0052] In this embodiment, the back electromotive force estimation unit 300A receives the motor angle θm and motor angular velocity ωn as inputs, and the gain variable unit 310A receives the motor angular velocity ωn, steering angle θh, and q-axis current command value i q The following is input. The back electromotive force compensation signal EMFc from the back electromotive force estimation unit 300A is input to the multiplication unit 311A, and the gain Gd obtained by the gain variable unit 310A as described above is also input to the multiplication unit 311A, and the back electromotive force compensation signal EMFe calculated by the multiplication unit 311A ​​is input to the summation unit 226A of the current control system, and back electromotive force compensation is performed.

[0053] Furthermore, in the vector control system (two-phase feedback type) shown in Figure 16, a back electromotive force compensation estimation unit 300A and a gain variable unit 310A similar to those in the above embodiment are provided, and a gain-corrected back electromotive force compensation signal EMFe is generated. The d-axis current command value i calculated by the current command value calculation unit 220 d and q-axis current command value i qThe currents are input to the subtraction unit 222 (222d, 222q), and the current deviations Δid and Δiq are calculated. The current deviations Δid and Δiq are controlled by the PI control unit 223 to the voltage control command values ​​Vdref and Vqref. The voltage control command values ​​Vdref and Vqref are input to the addition unit 226B, added with the back EMF compensation signal EMFe, and the back EMF-compensated voltage command values ​​Vdrefm and Vqrefm are input to the 3-phase / 2-phase conversion unit 221, which converts to 2 phases in synchronization with the motor angle θm. The voltage control command values ​​Vurefm, Vvrefm and Vwrefm converted to 3 phases by the 3-phase / 2-phase conversion unit 221 are input to the PWM control unit 224, and the same operation as described above is performed thereafter. [Explanation of Symbols]

[0054] 1 handle 2. Column axis (steering shaft, steering wheel axis) 10 Torque Sensor 12. Vehicle speed sensor 14. Steering angle sensor 20, 100 motors 30 Control Unit (ECU) 31, 220 Current command value calculation unit 33 Current limiting section 34 Compensation signal generation section 35, 223 PI control unit 36, 224 PWM control unit 37,225 Inverter 50 CAN 101 Control filter (G FF ) 102 Control filter (G FB ) 110 Electrical System Characteristics Section 120 Mechanical System Characteristics Section 131 LPF 132 Back EMF Compensation Constant Section 200 Angle FB Filter (G ANG ) 300, 300A Back EMF Estimation Unit 310, 310A Gain Variable Section 313 Minimum Value Selection Section 314 Gain determination unit 315 Rate Limiter 320, 330, 340 Absolute value part 321, 331 Gain section

Claims

1. A motor control device that drives and controls a motor using current feedback control based on a current command value, and compensates for the motor back electromotive force using a back electromotive force compensation signal based on the motor angle or motor angular velocity, characterized in that a gain variable unit that varies the gain according to steering state information is provided in the path for compensating the motor back electromotive force.

2. The motor control device according to claim 1, wherein the steering state information comprises at least one of the current command value and the motor angular velocity, and the steering angle or the motor angle.

3. The motor control device according to claim 1 or 2, wherein the gain of the gain variable unit is increased when the motor is rotating in the direction returning to the operating point.

4. The motor control device according to claim 1 or 2, wherein an angle feedback filter is provided in the motor control feedback path to cancel out a back electromotive force compensation error, which is the difference between the motor back electromotive force and the back electromotive force compensation signal.

5. The motor control device according to claim 1 or 2, wherein the motor control is dq-axis vector control, the current command value is a dq-axis current command value, and the control unit is a two-phase feedback type vector control system.

6. The motor control device according to claim 1 or 2, wherein the motor control is dq-axis vector control, the current command value is a dq-axis current command value, and the control unit is a three-phase feedback type vector control system.

7. An electric power steering system equipped with a motor control device according to any one of claims 1 to 6.

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