JP6638471B2 - Motor control device and electric power steering device equipped with the same - Google Patents

Description

  The present invention provides a motor control device that drives a motor with current feedback based on a current command value, controls the current command value by following a motor actual current, and includes the motor control device, and at least a current command calculated based on a steering torque. The present invention relates to an electric power steering device that applies an assist force by a motor to a steering system of a vehicle according to a value. In particular, a motor control device in which a back electromotive voltage during motor driving is canceled without changing the sensitivity to noise, and a compensation error canceling angle filter for noise compensation and LPF compensation inserted in a feedback path, and a motor control device therefor. The present invention relates to an electric power steering device equipped with a.

  2. Description of the Related Art An electric power steering device (EPS) equipped with a motor control device applies a steering assisting force (assisting force) to a steering mechanism of a vehicle by a rotational force of a motor. A steering assist force is applied to the steering shaft or the rack shaft by a transmission mechanism such as a gear. Such a conventional electric power steering device performs feedback control of a motor current in order to accurately generate a torque of a steering assist force. The feedback control is to adjust the motor applied voltage so that the difference between the steering assist command value (current command value) and the detected motor current value is small. The adjustment of the motor applied voltage is generally performed by PWM (pulse width). Modulation) control by adjusting the duty.

  A general configuration of the electric power steering apparatus will be described with reference to FIG. 1. 6b, and further connected to steered wheels 8L, 8R via hub units 7a, 7b. The column shaft 2 is provided 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 θ, and a motor 20 for assisting the steering force of the steering wheel 1 is provided with a reduction gear. 3 is connected to the column shaft 2. The control unit (ECU) 30 that controls the electric power steering device is supplied with electric power from the battery 13 and receives an ignition key signal via the ignition key 11. The control unit 30 calculates a current command value of an assist (steering assist) 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 compensates for the current command value. The current supplied to the EPS motor 20 is controlled by the voltage control command value Vref subjected to the above.

  The steering angle θ is detected from the steering angle sensor 14, and the steering angle can be obtained from a rotation sensor such as a resolver connected to the motor 20.

  The control unit 30 is connected to a CAN (Controller Area Network) 40 for transmitting and receiving various information of the vehicle, and the vehicle speed Vs can be received from the CAN 40. The control unit 30 can also be connected to a non-CAN 41 other than the CAN 40 for transmitting and receiving communications, analog / digital signals, radio waves, and the like.

  The control unit 30 is mainly composed of a CPU (including an MPU and an MCU), and FIG. 2 shows general functions executed by a program in the CPU.

  Referring to FIG. 2, the control unit 30 will be described. The steering torque Th detected by the torque sensor 10 and the vehicle speed Vs detected by the vehicle speed sensor 12 (or from the CAN 40) are determined by a current command for calculating a current command value Iref1. The value is input to the value calculator 31. The current command value calculation unit 31 calculates a current command value Iref1, which is a control target value of the current supplied to the motor 20, using an assist map or the like based on the input steering torque Th and vehicle speed Vs. The current command value Iref1 is input to the current limiting unit 33 via the adding unit 32A, and the current command value Irefm of which the maximum current is limited is input to the subtracting unit 32B, and the deviation ΔI (=) from the motor current value Im being fed back. Irefm−Im) is calculated, and the deviation ΔI is input to the PI 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 PWM-driven via the inverter 36. The current value Im of the motor 20 is detected by the motor current detector 37 and is fed back to the subtractor 32B. The inverter 36 is configured by an FET bridge circuit as a semiconductor switching element.

  A rotation sensor 21 such as a resolver is connected to the motor 20. The rotation sensor 21 outputs a motor rotation angle θ, and a motor speed ω is calculated by a motor speed calculation unit 22.

  Further, the compensation signal CM from the compensation signal generator 38 is added to the adder 32A, and the characteristics of the steering system are compensated by adding the compensation signal CM, so that the convergence and the inertia characteristics are improved. ing. The compensation signal generation unit 38 adds the self-aligning torque (SAT) 38-1 and the inertia 38-2 in the addition unit 38-4, and further adds the convergence 38-3 to the addition result in the addition unit 38-5. Then, the addition result of the addition section 38-5 is used as the compensation signal CM.

  In such a motor control device of the electric power steering device, since the motor 20 generates a back electromotive voltage when the motor is driven, compensation for suppressing or attenuating the motor back electromotive voltage is necessary. The reason will be described below.

FIG. 3 shows a control system in which the motor 20 is driven from the current command value Iref by using a transfer function. The current command value Iref is inputted to the subtraction unit 104 via the control filter _(G FF) 101, the deviation _{e 1} between the actual motor current Imn is calculated. Deviation _{e 1} is input to the subtraction unit 105 via the control filter _{(G FB),} the counter electromotive voltage EMF of the motor 20 is subtracted by the subtraction unit 105, an electrical system characteristics unit 110 of the difference _{e 3} the motor 20 (1 / (L · s + R)), and further input to the mechanical characteristic unit 120 (1 / (J · s + D)) via a torque constant Kt [Nm / A]. The back electromotive voltage EMF is obtained by multiplying the motor angular velocity (motor rotation speed) ωm output from the mechanical characteristic unit 120 by the back electromotive voltage constant Ke [V / (rad / s)]. The motor current Im from the electric system characteristic unit 110 is detected and fed back. However, actually, the current detection noise Ni is mixed and fed back as the actual motor current Imn.

L of an electrical system characteristics 110 mode tie inductance [H], R is the motor resistance [Omega], the J of the mechanical system characteristics unit 120 motor inertia moment [Kg · m ^2], D is the motor coefficient of viscosity [Nm / (rad / s)].

The system from the current command value Iref until the motor current Im, FIG. 4 to control the frequency band as shown in easily primary filter _{(1 / (T 4 · s} + 1)) and to _order, time constant T 1 through T ₄ The transfer function of the control filter (G _FF ) 101 is set by the following equation 1, and the transfer function of the control filter (G _FB ) 102 is set by the following equation 2.

即ち、電流指令値Ｉｒｅｆからモータ電流Ｉｍまでの系を“１／（Ｔ_４・ｓ＋１）”（数３）とし、時定数Ｔ_４の設定で電流指令値Ｉｒｅｆからモータ電流Ｉｍまでの特性である電流制御帯域を決定（１次フィルタ）するために、制御フィルタ（Ｇ_ＦＦ）１０１及び制御フィルタ（Ｇ_ＦＢ）１０２の特性を決定する。

That is, the system from the current command value Iref to the motor current Im is represented by “1 / (T ₄ · s + 1)” (Equation 3), and the characteristics from the current command value Iref to the motor current Im by setting the time constant T _4. In order to determine the current control band (primary filter), the characteristics of the control filter (G _FF ) 101 and the control filter (G _FB ) 102 are determined.

そして、制御フィルタ（Ｇ_ＦＢ）１０２を含む電流制御のフィードバック閉ループの系では、逆起電圧ＥＭＦを０として、数４及び図５に示すように、外乱の電流検出ノイズ（Ｎｉ）除去用の２次フィルタ（時定数Ｔ_２，Ｔ_３）と１次位相進みフィルタ（Ｔ_１）となる構成を採る。１次位相進みフィルタ（Ｔ_１）の項がないと、制御フィルタ（Ｇ_ＦＦ）１０１の分子の微分項が２次になってしまい、非常に不安定になるからである。要するに、制御フィルタ（Ｇ_ＦＦ）１０１は、電流指令値Ｉｒｅｆからモータ電流Ｉｍまでの特性を決めるフィルタであり、制御フィルタ（Ｇ_ＦＢ）１０２は、電流検出ノイズＮｉを除去するフィルタを含めた、電流指令値Ｉｒｅｆからモータ電流Ｉｍまでの特性を決めるフィルタと言える。

Then, in the current control feedback closed loop system including the control filter (G _FB ) 102, the back electromotive force EMF is set to 0, and as shown in Expression 4 and FIG. A configuration is adopted that serves as a next-order filter (time constants T ₂ and T ₃ ) and a first-order phase advance filter (T ₁ ). This is because if there is no term of the first-order phase advance filter (T ₁ ), the differential term of the numerator of the control filter (G _FF ) 101 becomes second-order and becomes very unstable. In short, the control filter (G _FF ) 101 is a filter for determining characteristics from the current command value Iref to the motor current Im, and the control filter (G _FB ) 102 is a filter including a filter for removing the current detection noise Ni. It can be said that this is a filter that determines characteristics from the command value Iref to the motor current Im.

上記数１及び数４をＧ_ＦＢについて解くと、制御フィルタ（Ｇ_ＦＢ）１０２は上記数２となる。

When Equations 1 and 4 are solved for G _FB , the control filter (G _FB ) 102 becomes Equation 2 above.

As described above, the setting of the control filter (G _FF ) 101 and the control filter (G _FB ) 102 does not take into account the mixing of the motor back electromotive voltage EMF. However, since the generation of the motor back electromotive voltage EMF affects the current command value, it is a serious problem in accurately controlling the motor output. As such a countermeasure, compensation of a motor back electromotive voltage can be considered. For example, in Japanese Patent Application Laid-Open No. 2013-219870 (Patent Document 1), a back electromotive voltage of a motor is estimated based on a voltage command value and a current detection value. The back electromotive force estimated value is added to the current command value. In Japanese Patent Application Laid-Open No. 2012-236472 (Patent Document 2), a back electromotive force is estimated based on a rotational angular velocity, and a back electromotive voltage compensation control value is calculated by multiplying the estimated back electromotive voltage by a compensation coefficient. The electromotive voltage compensation control value is added to the basic voltage to obtain a voltage command value.

JP 2013-219870 A JP 2012-236472 A

  All of the above-mentioned back electromotive force compensations are performed on the assumption that detection noise of position and rotation speed does not mix. However, there is a problem that the motor output cannot be followed.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to change the characteristics of a back electromotive force and a back electromotive voltage compensation path in a feedback path without delay over a wide range without changing the sensitivity to noise. It is an object of the present invention to provide a motor control device for compensating and reliably tracking an actual current to a current command value, and to provide an electric power steering device with improved steering feeling.

  The present invention relates to a motor control device that controls driving of a motor by current feedback control based on a current command value and compensates for a motor back electromotive voltage by a back electromotive force compensation signal based on a motor angle or a motor angular velocity. An object of the present invention is to provide an LPF for removing noise in a path for compensating the motor back electromotive voltage, and to provide a back electromotive force, which is a difference between the motor back electromotive voltage and the back electromotive voltage compensation signal, in a feedback path of the motor control. This is achieved by providing an angle feedback filter that cancels the voltage compensation error.

  The object of the present invention is that the motor control is dq-axis vector control, or the current command value is a dq-axis current command value, and the control unit is a two-phase feedback vector control system. Alternatively, the current command value is a dq-axis current command value, and the control unit is a three-phase feedback vector control system, which is more effectively achieved. By mounting, an electric power steering device with a good steering feeling can be provided.

  According to the motor control device of the present invention, in the motor control device having the function of compensating for the motor back electromotive voltage at the time of driving the motor, the feedback path includes a back electromotive force that is a difference between the motor back electromotive voltage and the back electromotive voltage compensation signal. Since the angle feedback filter for canceling the voltage compensation error is interposed, the following characteristic of the motor can be improved without delay without changing the sensitivity to noise.

1 is a configuration diagram illustrating an outline of an electric power steering device. FIG. 2 is a block diagram illustrating a configuration example of a control unit (ECU) of the electric power steering device. It is a block diagram which shows the path | route of generation | occurence | production of a back electromotive voltage in a motor control apparatus (transfer function). FIG. 4 is a frequency response diagram for explaining characteristics of a control filter. FIG. 4 is a frequency response diagram for explaining characteristics of a control filter. FIG. 2 is a block diagram illustrating a configuration example of a vector control system (three-phase FB) to which the present invention can be applied. FIG. 3 is a block diagram illustrating a configuration example of a vector control system (two-phase FB) to which the present invention can be applied. It is a block diagram which shows the example of a structure of the back electromotive force compensation in a motor control apparatus (transfer function). FIG. 4 is a diagram illustrating frequency characteristics of gain / phase and a frequency characteristic showing an effect of the present invention when an LPF is used for back electromotive force compensation. FIG. 1 is a block diagram illustrating an example of an embodiment of the present invention.

The motor control apparatus of the present invention, without altering the sensitivity to noise, both when performing the compensation of the back electromotive voltage generated at motor drive, feedback the angular filter for compensating the error offset for compensating for noise compensation and LPF path Has been inserted. This allows the actual motor current to accurately follow the current command value without delay without changing the sensitivity to noise .
Since the present invention can be applied to a vector control system for driving and controlling a brushless motor, the vector control system will be described first.

The vector control system of FIG. 6, and the current command value calculating section 220 is provided to correct by calculating the d-axis current command value i _d and the q-axis current command value i _q, steering the current command value calculating section 220 The torque Th, the vehicle speed Vs, the motor angle (rotation angle) θ _e from the rotation sensor 100A connected to the motor 100, and the motor angular speed ω calculated by the angular speed calculation unit 226 are input. D-axis current command value i _d and the q-axis current command value i _q calculated by the current command value calculating unit 220 is input to the 2-phase / 3-phase conversion unit 221, three-phase current in synchronization with the motor angle theta _e It is converted into command values Iuref, Ivref, Iwref. The three-phase current command values Iuref, Ivref, Iwref are input to the subtraction unit 222 (222u, 222v, 222w), and deviations ΔIu, ΔIv, ΔIw from the motor currents Imu, Imv, Imw detected by the current detection circuit 225A are calculated. Is calculated. The calculated deviations ΔIu, ΔIv, ΔIw are input to the PI control unit 223, and the current-controlled three-phase voltage control command values Vuref, Vvref, Vwref are input to the PWM control unit 224, and are calculated by the PWM control unit 224. The motor 100 is driven via the inverter 225 based on the duty of each phase.

  Although the current detection circuit 225A is provided in the inverter 225 in FIG. 6, the current detection circuit 225A can also detect a supply line to the motor 100 or the like.

Also, in the vector control system of FIG. 7, the current detection circuit 225A with the detected three-phase motor current Imu, Imv, 3-phase converted to 2-phase in synchronism with the motor angle theta _e the Imw / 2 phase converter 227 Is provided. D-axis current command value computed is corrected by the current command value calculating section 220 _{i d} and the q-axis current command value _{i q} is input to the subtraction unit 222 (222d, 222q), 3-phase / 2-phase conversion by the subtraction unit 222 2-phase current Imd from part 227, the deviation .DELTA.i _d with imq, .DELTA.i _q is calculated. Deviation .DELTA.i _d, .DELTA.i _q are input to the 2-phase / 3-phase conversion unit 221, converted three-phase current command values Iuref, Ivref, Iwref is input to the PI control unit 223, since, like the case of FIG. 4 Operation is performed.

  The control system of FIG. 6 is a three-phase feedback vector control system in which three-phase motor currents Imu, Imv, Imw are fed back. The control system of FIG. 7 has two-phase motor currents Imu, Imv, Imw of two. This is a two-phase feedback vector control system that is converted into phase currents Imd and Imq and fed back. The present invention can be applied to both the three-phase feedback vector control system and the two-phase feedback vector control system.

  FIG. 8 shows a configuration example in which the back electromotive force EMF is compensated based on the motor angle θm detected by a rotation sensor (for example, a resolver), corresponding to FIG. Although the motor angle θm is differentiated by the differentiator 130, the rotation sensor (for example, a resolver) actually includes noise Nr, and the motor angle θmr to which the noise Nr is added (mixed) by the adder 133 is differentiated. Input to the unit 130. The motor angular velocity ωn differentiated by the differentiator 130 is input to a noise removal low-pass filter (LPF) 131 whose transfer function is expressed by Equation 5, and the motor angular velocity ωn ′ from which the noise Nr has been removed by the LPF 131 is inversed. The voltage is multiplied by the back electromotive force compensation constant Ke ′ in the electromotive force compensation constant unit 132 and input to the adding unit 106 as the back electromotive force compensation signal EMFc.

Incidentally, omega _L of LPF131 have a relation of ω _L = 2πf _c relative to the cutoff frequency _{f c} (e.g. 40 Hz).

この逆起電圧補償はモータ角度θｍ（モータ角速度ωｍ）に依存しており、ノイズＮｒの混入がなければＬＰＦ１３１は不要である。しかし、実際には回転センサから混入するノイズＮｒの影響があり、その影響を除去若しくは低減するＬＰＦ１３１を具備している。フィルタ処理を行わないと、電動パワーステアリング装置では操舵感が悪化してしまうからである。

This back electromotive force compensation depends on the motor angle θm (motor angular velocity ωm), and the LPF 131 is not required unless the noise Nr is mixed. However, there is actually an effect of noise Nr mixed from the rotation sensor, and the LPF 131 is provided to eliminate or reduce the effect. This is because the steering feeling is deteriorated in the electric power steering apparatus unless the filter processing is performed.

  When the frequency of the motor rotation speed increases due to the filter processing of the LPF 131, the phase is delayed with respect to the motor back electromotive voltage EMF, and there is a possibility that the motor back electromotive voltage EMF cannot be completely canceled. This cancellation error enters the current control system as a disturbance, and it becomes impossible to cause the actual motor current Im, which plays a role of feedback control, to follow the current command value Iref. If the back electromotive force compensation is perfect, the relationship of the following equation 6 should be satisfied.

(Equation 6)
EMFc−EMF = 0
However, Equation 6 does not hold due to the mixing of the noise Nr. In the first place, the main role of the current feedback control is to flow the actual current without delay according to the current command value. In the control by the filter processing, the higher the control band, the better the followability can be, but the sensitivity to noise also increases, and the steering feeling of the electric power steering device deteriorates.

  FIG. 9 shows frequency characteristics when back electromotive force compensation is performed using an LPF, and FIG. 9 (A) shows the frequency characteristics of the gain. Before the countermeasure according to the present invention, the gain in the frequency range of 10 to 100 Hz is obtained. Are concavely lowered. FIG. 9B shows the frequency characteristics of the phase. Before the countermeasure according to the present invention, there is a delay and advance of the phase, so that the characteristics are not flat, and the back electromotive force EMF cannot be completely compensated. The compensation cancellation error is mixed in the control loop as a disturbance, and as a result, the detected current cannot follow the current command value.

As a countermeasure, in the present invention, an angle feedback (FB) filter (G _ANG ) 200 having a current follow-up characteristic of Im / Iref = 1 / (T ₄ · s + 1) is inserted in a feedback path for motor control. . FIG. 10 shows the configuration corresponding to FIG.

When the range from the current command value Iref to the motor current Im output by the electric system characteristic unit 110 is represented by a transfer function, the following equation 7 is obtained. The transfer function of the control filter (G _FF ) 101 is the above equation (1), and the transfer function of the control filter (G _FB ) 102 is the above equation (2).

そして、理想的には数７が上記数３の特性のように、下記数８で表わされれば良い。

Ideally, Equation 7 may be represented by Equation 8 below, like the characteristic of Equation 3 above.

そのためには、数７の分母の（）内が０になれば良い。即ち、下記数９が成立すれば良い。

For this purpose, the value in the parentheses of the denominator of Equation 7 should be 0. That is, the following equation 9 may be satisfied.

換言すれば、数７の分母の（）内を０とする数９が成立するような、角度フィードバックフィルタ（Ｇ_ＡＮＧ）２００をフィードバック経路に介挿すれば良い。

In other words, an angle feedback filter (G _ANG ) 200 that satisfies _Expression 9 where the value in parentheses of the denominator of Expression 7 is 0 may be inserted into the feedback path.

Therefore, when the angle feedback filter _GANG is calculated from _Expression 9, _Expression 10 is obtained.

数１０で決定された角度フィードバックフィルタ（Ｇ_ＡＮＧ）を電流指令値Ｉｒｅｆに適用すると、電流値Ｉｍは下記数１１で表わされ、数１１にＧ_ＦＦの伝達関数（数１）及びＧ_ＦＢの伝達関数（数２）を代入すると数１２となり、数１２の時定数Ｔ_４の調整により所望の特性を得ることができる。

When the angle feedback filter (G _ANG ) determined in Expression 10 is applied to the current command value Iref, the current value Im is expressed by Expression 11 below, and the transfer function of G _FF (Expression 1) and the transfer function of G _FB the number 12 becomes substituting the transfer function (equation 2), it is possible to obtain desired characteristics by adjusting the constant T ₄ when the number 12.

図９は、操舵時に、検出電流が電流指令値に追従しない問題におけるメカニズムをボード線図で比較しており、対策前では逆起電圧補償ロジックにはＬＰＦ（４０Ｈｚ）があり、逆起電圧を完全に補償できない。この相殺誤差が外乱として制御ループに混入し、これが要因となって検出電流が電流指令値に追従できない。しかし、上述したモータ逆起電圧と逆起電圧補償信号との差である逆起電圧補償誤差を相殺する角度フィードバックフィルタ２００（Ｇ_ＡＮＧ）を設けることにより、対策前の特性が改善されていることが分かる。即ち、ゲイン特性も位相特性も平坦な特性となっている。

FIG. 9 compares the mechanism in the problem that the detected current does not follow the current command value at the time of steering with a Bode diagram. Before the countermeasure, the back electromotive voltage compensation logic has an LPF (40 Hz). I cannot fully compensate. This canceling error enters the control loop as a disturbance, and as a result, the detected current cannot follow the current command value. However, by providing the angle feedback filter 200 (G _ANG ) for canceling the back electromotive force compensation error, which is the difference between the motor back electromotive force and the back electromotive force compensation signal, the characteristics before the countermeasure are improved. I understand. That is, both the gain characteristics and the phase characteristics are flat characteristics.

1 Handle 2 Column shaft (steering shaft, handle shaft)
10 Torque sensor 12 Vehicle speed sensor 20, 100 Motor 30 Control unit (ECU)
31, 220 Current command value calculation unit 34, 223 PI control unit 35, 224 PWM control unit 36, 225 Inverter 101, 102 Control filter 110 Electric system characteristic unit 120 Mechanical system characteristic unit 131 Low pass filter (LPF)
200 Angle feedback (FB) filter 221 2-phase / 3-phase converter 227 3-phase / 2-phase converter

Claims (5)

In a motor control device that drives and controls a motor by current feedback control based on a current command value and compensates for a motor back electromotive voltage by a back electromotive force compensation signal based on a motor angle or a motor angular velocity,
An LPF for removing noise is provided in a path for compensating the motor back electromotive voltage, and a back electromotive voltage compensation error which is a difference between the motor back electromotive voltage and the back electromotive voltage compensation signal is provided in the motor control feedback path. A motor control device, comprising: an angle feedback filter for canceling out. The motor control device according to claim 1, wherein the control of the motor is dq-axis vector control. The motor control device according to claim 2, wherein the current command value is a dq-axis current command value, and the control unit is a two-phase feedback vector control system. The motor control device according to claim 2, wherein the current command value is a dq-axis current command value, and the control unit is a three-phase feedback vector control system. An electric power steering device equipped with the motor control device according to claim 1.

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