JP5188376B2 - Electric power steering control device - Google Patents

Description

  The present invention relates to an electric power steering apparatus mounted on an automobile or the like, and more particularly to improvement of a steering feeling (also referred to as steering feeling) felt by a driver.

  2. Description of the Related Art Conventionally, there is a motor control device that estimates a motor rotation angle and controls the motor based on the estimated value (see, for example, Patent Document 1). The apparatus described in Patent Document 1 is not limited to an electric power steering apparatus, but relates to a brushless motor control method, and does not include a motor rotation angle sensor (also referred to as a rotor position sensor) that detects a rotation angle of the motor. This is called sensorless control in which the motor rotation angle is estimated and the motor is controlled based on the estimated value.

  In Patent Document 1, the motor rotation angle estimation means includes two means in different manners, and is switched according to the rotation speed of the motor. When the motor is stopped and when it rotates at a low speed, a high-frequency voltage is applied and the motor rotation angle is estimated from the response current. This is a method using the saliency of the motor. However, in general, this method needs to apply a voltage for estimation, so that the voltage utilization efficiency is reduced, and the power supply voltage allocated to the voltage used for the output of the original motor torque is equal to the high frequency applied voltage. It is known that it is not suitable for driving at high speed rotation that requires a higher voltage than at low speed rotation.

  On the other hand, at the time of medium / high speed rotation, a method of estimating the motor rotation angle based on the induced voltage of the motor is used. This method pays attention to the fact that the induced voltage changes based on the magnetic pole position of the rotor. In general, it is not necessary to apply a voltage for estimation, and during medium and high speed rotation where the induced voltage is relatively large. Although it is suitable, it is known that the estimation accuracy deteriorates at the time of stopping and at a low speed.

  Another example of a conventional device is an electric power steering device that estimates and controls a motor rotation angle (see, for example, Patent Document 2). This patent document 2 also estimates and controls the motor rotation angle in a brushless motor that does not have a motor rotation angle sensor. In recent years, research and development has been conducted on such a configuration also in an electric power steering apparatus. Yes. As described in paragraph 0007 of the problem to be solved by the invention of Patent Document 2, it is indicated that it is desirable to switch the estimation method of the motor rotation angle according to the motor rotation angular velocity.

  Furthermore, as another example of a conventional device, there is an electric power steering device that performs torque ripple compensation that suppresses torque ripple (see, for example, Patent Document 3). In brushless motors, it is known that ripples (pulsations) occur in the output torque, and in electric power steering devices, deterioration of steering feeling due to the torque ripples is often pointed out, and the improvement thereof is a problem. To solve this problem, one method for suppressing torque ripple by control has been proposed. Patent Document 3 describes torque ripple compensation that suppresses torque ripple based on a current command, a motor rotation angle, and a motor rotation angular velocity that is a derivative thereof.

  As described above, it is generally known that it is effective to use the motor rotation angle and the motor rotation angular velocity in the torque ripple compensation, and various methods other than this document have been proposed. In addition, as shown in this document, the motor rotation angular velocity is not limited to torque ripple compensation, but various improvements that improve steering feeling other than torque ripple, such as damping compensation (also called convergence compensation or viscosity compensation). This is also used in various compensation controls.

Japanese Patent No. 3695342 JP 2007-307940 A Japanese Patent No. 4033030

  However, in an apparatus such as Patent Document 3, for a brushless motor with a motor rotation angle sensor, torque ripple compensation for suppressing torque ripple, and convergence compensation for compensating convergence (damping compensation, or Although it is also referred to as viscosity compensation), a method for optimally performing these compensations in a configuration that is a brushless motor and does not have a motor rotation angle sensor is not shown.

  Various methods other than Patent Document 3 have been proposed for various compensation controls such as torque ripple compensation, damping compensation, inertia compensation, friction compensation, etc., all of which are brush motors that do not require a motor rotation angle sensor. Alternatively, a brushless motor with a motor rotation angle sensor is targeted.

  In order to realize these various compensation controls, it is necessary to incorporate state quantities such as motor rotation angle, motor rotation angular velocity, and motor rotation angular acceleration as signals into the control device by detection or estimation. Affects the effectiveness of the control.

  For example, in torque ripple compensation control, it is necessary to calculate a compensation current command suitable for the frequency or phase of torque ripple based on the motor rotation angle or motor rotation angular velocity, and the motor rotation angle or motor rotation angular velocity is detected or estimated. If the signal error increases, the error from the compensation current command suitable for the frequency or phase of the original torque ripple also increases as the compensation current command, the effect of suppressing the torque ripple decreases, and the steering feeling is reduced. Getting worse.

  The same can be said for other compensation controls. In the damping compensation and friction compensation, the motor rotational angular velocity is used. In the inertia compensation, the motor rotational angular acceleration, which is a derivative of the motor rotational angular velocity, is used. Decreases, the compensation control cannot be performed with an appropriate phase, frequency, and magnitude, and the effect of the compensation control is reduced.

  Therefore, when it is necessary to perform motor control using two or more types of motor rotation angle estimation means, such as a brushless motor without a motor rotation angle sensor, the estimation signals output by these estimation means are compensated for in various ways. It must be used appropriately in control. If the signals estimated by the two types of motor rotation angle estimation means are used for various compensation controls without switching or without appropriate switching, a region with low accuracy is generated. As described above, the effects of various compensation controls are reduced, and the steering feeling is deteriorated.

  Note that the method of estimating the motor rotation angle based on the induced voltage of the motor and the method of estimating the motor rotation angle based on the response current of the applied high-frequency voltage have superiority or inferior accuracy depending on the operation region. The method of estimating the motor rotation angle based on the induced voltage of the motor is more accurate in the region, and if the method of estimating the motor rotation angle from the response current of the applied high frequency voltage is used, the accuracy of each method in that region is The accuracy is reduced by the difference. The reverse is also true.

  However, no method has been presented so far in which two or more types of motor rotation angle estimation means are used for various compensation controls.

  The present invention has been made to solve the above-described problems, and in an electric power steering apparatus using a brushless motor without a motor rotation angle sensor, the motor rotation angle estimated by two or more types of methods. Electric power steering control device that can improve the steering feeling felt by the driver by appropriately performing various compensation controls such as torque ripple compensation and damping compensation by appropriately using the estimated value of The purpose is to obtain.

An electric power steering control device according to the present invention includes a current command generating means for calculating a current command corresponding to a target value of assist torque, a voltage command for each phase, a motor rotation angle signal, and a current command and a current signal. comprising a current control means for calculating the motor rotational angular velocity signal, a current detection section for outputting a current signal by detecting the current flowing through each phase of the probe Rashiresumota, controls the brushless motor based on the current command, the operation An electric power steering control device for generating a motor torque for assisting a person's steering, wherein the current command generation means calculates a damping compensation current command based on the motor rotation angular velocity signal, and the motor rotation Calculate inertia compensation current command based on motor rotation angular acceleration obtained by differentiating angular velocity signal And a friction compensator that calculates a friction compensation current command based on the motor rotational angular velocity signal, and is calculated based on one or more compensation current commands of the compensator and a steering torque. Current command is calculated according to the assist current command, and the current control means includes two types of motor rotation angle estimation means for calculating a motor rotation angle estimation value by two different methods , the motor rotation angle signal, Dq axis current control means for outputting the voltage command in response to the current command and the current signal, and the motor rotation angle estimation value output by the two motor rotation angle estimation means based on the motor rotation angular velocity. while select calculates the motor rotational angle signal and the motor rotation angular speed signal, smoothing the motor rotational angle signal or the motor rotation angular speed signal is calculated for The motor rotation angle signal or the motor rotational angular velocity signal smoothed by smoothing processing means, given as a motor rotation angle signal or the motor rotation angular speed signal to one of the compensator of the current command generating means, are the smoothed The voltage command is calculated by the dq-axis current control means based on the motor rotation angle signal that is not present.

  According to the present invention, the motor rotation angle signal and the motor rotation angular velocity signal obtained with high accuracy can be obtained by switching the estimated value of the motor rotation angle or the motor rotation angular velocity estimated by two or more methods by an appropriate method. Because it can be used for compensation control such as torque ripple compensation, damping compensation, inertia compensation, friction compensation, etc., the effect of improving torque ripple, convergence, friction feeling, inertia feeling, etc. can be obtained sufficiently and the driver feels It is possible to achieve a remarkable effect that is not achieved in the past, such as a good steering feeling.

Embodiment 1 FIG.
An electric power steering control apparatus according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 is a diagram showing a configuration of an electric power steering apparatus according to Embodiment 1 of the present invention. In the following, in each figure, the same reference numerals indicate the same or corresponding parts.

  In FIG. 1, the left and right wheels 4 a and 4 b are steered via a rack and pinion gear 3 in accordance with the rotation of the steering shaft 2 connected to the steering wheel 1. A brushless motor (hereinafter simply referred to as a motor) 5 is connected to the steering shaft 2 via a motor reduction gear 6, and can apply torque generated by the motor 5 to the steering shaft 2. A torque sensor 8 is disposed on the steering shaft 2 and detects a steering torque acting on the steering shaft 2. The vehicle speed of the vehicle is detected by a vehicle speed sensor 9. The electric power steering control device 10 controls a current flowing from the power source (battery) 7 to the motor 5 in order to cause the motor 5 to generate a predetermined assist torque in accordance with detection signals of the torque sensor 8 and the vehicle speed sensor 9.

  FIG. 2 is a block diagram showing a configuration of an electric power steering control device 10 (also referred to as a controller unit) of the electric power steering device according to Embodiment 1 of the present invention. In FIG. 2, the electric power steering control device 10 detects a current flowing through each phase of the motor 5 through a current command generating means 11 for calculating a current command corresponding to the target value of the assist torque and an inverter to detect a current. A current detection circuit 15 for outputting a signal, a current command and a voltage command for each phase in accordance with the current signal, a current control means 12 for calculating a motor rotation angle signal and a motor rotation angular velocity signal, and PWM modulating the voltage command. A switching element drive circuit 13 that outputs a switching operation signal to the inverter, and chopper-controls the switching elements 61a to 63a and 61b to 63b based on the switching operation signal, and supplies electric current to the motor 5 by electric power supplied from the power supply 7. The inverter 14 is provided. Of the constituent elements of the controller unit 10, the constituent elements other than the current detection circuit 15, the switching element drive circuit 13, and the inverter 14 are usually implemented as microcomputer software.

  Next, the operation of the electric power steering apparatus according to the first embodiment will be described with reference to the drawings. In FIG. 1, a steering torque applied to a steering wheel 1 by a driver (not shown) passes through a torque sensor 8 and a steering shaft 2 and is transmitted to a rack via a rack and pinion gear 3 to steer wheels 4a and 4b. .

  A brushless motor 5 (also referred to as a motor) is connected to the steering shaft 2 via a motor reduction gear 6. Assist torque (hereinafter also referred to as motor torque) generated from the motor 5 is transmitted to the steering shaft 2 via the motor reduction gear 6 to reduce the steering torque applied by the driver during steering. The motor 5 uses a synchronous motor such as a brushless motor. In the present embodiment, a brushless motor having three phases of U phase, V phase, and W phase is assumed.

  The torque sensor 8 detects a steering torque applied to the steering shaft when the driver steers the steering wheel 1. The controller unit 10 determines the direction and magnitude of the assist torque applied by the motor 5 according to the steering torque signal detected by the torque sensor 8 and the vehicle speed signal detected by the vehicle speed sensor 9, and this assist torque is determined by the motor 5. The current flowing from the power source 7 to the motor 5 is controlled so as to generate the current.

  In FIG. 2, the current command generation means 11 for calculating the current command Ir corresponding to the target value of the assist torque includes the steering torque signal detected by the torque sensor 8 and the motor torque corresponding to the vehicle speed signal detected by the vehicle speed sensor 9. By determining the direction and size, a basic current command is calculated. Further, as will be described in detail later, as shown in FIG. 4, compensators 23 to 26 that implement various compensation controls for improving the steering feeling according to the steering torque signal and the motor rotational angular velocity signal are provided. The current command is corrected by the added value of the compensation current command output from the meter.

  The current detection unit 15 detects a current flowing through each phase of the motor 5 via the current sensor 19 inside the inverter 14 and outputs a current signal. In addition, although the example which detects all three phases is shown here, generally, since the three-phase equilibrium condition that the sum of three-phase currents becomes zero is satisfied, only two of the phases may be detected.

  The current control means 12 calculates the voltage commands Vur, Vvr, Vwr of each phase, the motor rotation angle signal θest, and the motor rotation angular velocity signal ωest according to the current command and the current signal. The calculation method will be described later.

  The switching element drive circuit 13 performs PWM modulation on the voltage command and instructs the inverter 14 to perform a switching operation. The inverter 14 receives the switching operation signal, realizes chopper control of the switching elements 61 a to 63 a and 61 b to 63 b, and causes a current to flow to the motor 5 by the power supplied from the power supply 7. This current generates motor torque, that is, assist torque.

  Next, the calculation contents of the current control means 12 will be described with reference to FIG. However, this content may be the same as that of the control device 4 described in Patent Document 1. The current control unit 12 includes a dq-axis current control unit 31 that calculates voltage commands Vur, Vvr, and Vwr based on the current command Ir, the current signals Iu, Iv, Iw, the motor rotation angle signal θest, and the estimation voltage command Vh. The motor rotation angle estimation means A32 for estimating the rotation angle of the motor 5 that calculates the motor rotation angle estimated value θA based on the current signal, and the motor rotation angle estimation means B33 for calculating the motor rotation angle estimated value θB based on the current signal And a switching means 34 for switching the motor rotation angle estimation means in accordance with the calculation result of the motor rotation angular velocity.

  The motor rotation angle estimation means A32 uses a method of applying an estimation voltage and estimating based on the response current. This method uses the saliency of the motor, and gives a voltage command Vh for estimation, which is a relatively high-frequency periodic signal, to the dq axis current control means 31, and as a result, a response corresponding to the magnetic pole position of the motor 5. Based on the same frequency component as that of the estimation voltage command, the motor rotation angle is estimated from the current signal that detects the current generated as follows, and the motor rotation angle estimated value θA is calculated. In detail, for example, it may be the same as the carrier wave synchronization type position estimating means described in Patent Document 1.

  The motor rotation angle estimation means B33 uses a method of estimating based on the induced voltage of the motor 5. This method uses the fact that the induced voltage changes according to the rotation angle of the motor, and the induced voltage becomes relatively large during medium and high speed rotation. There is no need to apply a voltage for estimation. A motor rotation angle is estimated based on a current signal obtained by detecting a current generated as a response to the induced voltage, and a motor rotation angle estimated value θB is calculated. Specifically, for example, the same potential type position estimation means described in Patent Document 1 may be used. A method using an observer based not only on a current signal but also on a voltage command is generally known, and this method may be used.

  The switching means 34 calculates the motor rotation angular velocity and switches the motor rotation angle estimation means in accordance with the calculation result, and includes an angle switching unit 41 and a speed calculation unit 42 as shown in FIG. Based on the input motor rotation angular velocity signal ωest, the angle switching unit 41 outputs one of the motor rotation angle estimation values θA and θB output from the two motor rotation angle estimation means A32 and the motor rotation angle estimation means B33, respectively. This is selected and output as a motor rotation angle signal θest. The speed calculation unit 42 calculates the motor rotation angular velocity signal ωest by differentiating based on the motor rotation angle signal θest output from the angle switching unit 41. In detail, it may be the same as any one of the magnetic pole position switching means described in Examples 1 to 5 of Patent Document 1, for example. In particular, the method shown in the fourth embodiment of this document gradually switches the ratios reflected in the motor rotation angle signals of the two estimating means according to the speed, so that the torque fluctuation at the time of switching is suppressed and the switching is performed smoothly. Can do.

  The dq axis current control means 31 calculates voltage commands Vur, Vvr, Vwr based on the current command Ir, the current signals Iu, Iv, Iw, the motor rotation angle signal θest, and the estimation voltage command Vh. Basically, it is composed of dq conversion, three-phase conversion, PI controller, etc. (not shown) so as to implement control called dq control which is a general control method. The estimation voltage command Vh is added to a q-axis voltage command (not shown) that is a variable inside the dq control, or is three-phase converted and added to the voltage commands Vur, Vvr, and Vwr to be corrected. Used in the method. Since the contents of the dq control are general, a description thereof will be omitted. The current command Ir is used as the q-axis current command, and the d-axis current command is zero in this embodiment, but other values may be used.

  Next, the current command generation means 11 will be described with reference to FIG. A steering torque signal, a vehicle speed signal, a motor rotation angle signal θest, and a motor rotation angular velocity signal ωest are input to the current command generation unit 11. Here, the motor rotation angle signal θest and the motor rotation angular velocity signal ωest are signals output by the switching unit 34 described above, and are signals obtained by appropriately switching the estimation unit.

  However, in the first embodiment, the motor rotation angle signal θest is not used by the current command generation means 11 and therefore need not be input. A usage example of the motor rotation angle signal θest is shown in the second embodiment. In the first embodiment, when the motor rotation angle signal θest is used instead of the motor rotation angular velocity signal ωest, the motor rotation angle signal θest is differentiated in the current command generation unit 11 to obtain the motor rotation angular velocity signal ωest. It only has to be obtained.

  The phase compensator 22 performs phase compensation on the steering torque signal. The assist current calculator 21 stores in advance as map values the steering torque signal after the phase compensation output from the phase compensator 22 and the value of the assist current command corresponding to the vehicle speed signal detected by the vehicle speed sensor 9. An assist current command corresponding to the subsequent steering torque signal and vehicle speed is calculated.

  A damping compensator 23 (also referred to as a viscosity compensator or a convergence compensator) calculates a damping compensation current command from the motor rotational angular velocity ωest. The damping compensation current command has the effect of improving the convergence of the steering wheel and stabilizing the steering.

  The friction compensator 24 calculates a friction compensation current command from the sign of the motor rotational angular velocity. The friction compensation current command is a current for causing the motor 4 to generate a torque for canceling the friction existing in the steering mechanism, and has an effect of improving the steering feeling such as improving the steering wheel return when the hand is released.

  The angular acceleration calculator 27 differentiates the motor rotation angular velocity to calculate the motor angular acceleration. The inertia compensator 25 calculates an inertia compensation current command from the motor angular acceleration. Since the inertia compensation current command cancels the inertia force of the motor, the delay due to the inertia force is improved, the quick response is improved, and the steering feeling is improved. For details of the assist current calculator 21, the damping compensator 23, the friction compensator 24, and the inertia compensator 25, the conventional electric power steering control described in Mitsubishi Electric Technical Report Vol. 70 No. 9 P43 to P48 is described. It may be similar to the device.

  The torque ripple compensator 26 extracts, for example, a torque ripple component from the steering torque signal according to the motor rotational angular velocity, and calculates a torque ripple compensation current command according to the extraction result. For example, FIG. As shown, the torque ripple extractor 50 and the torque ripple suppression controller 53 are configured. Details will be described later. The torque ripple compensation current command can reduce pulsations such as cogging torque and steering torque due to torque ripple.

  Assist current command from assist current calculator 21, damping compensation current command from damping compensator 23, friction compensation current command from friction compensator 24, inertia compensation current command from inertia compensator 25, and torque ripple compensator 26 Is added to the torque ripple compensation current command to obtain a current command Ir.

  Next, the torque ripple compensator 26 will be described with reference to FIG. The torque ripple extractor 50 removes the steering component of the driver from the steering torque signal detected by the torque sensor 8 and a noise component in a higher frequency region than the pulsation component, and the pulsation component of the steering torque due to the cogging torque or torque ripple. Extract.

In the motor 5, cogging torque resulting from the motor structure such as the number of motor poles and slots, or manufacturing errors, and torque ripple caused by induced voltage waveform distortion, iron core magnetic saturation, and the like accompany rotation of the electric motor. Occur. Here, assuming that the number of pole pairs Pn of the motor and the electrical angle θe of the motor (corresponding to the motor rotation angle signal θest), the mechanical angle θm of the motor is expressed by Equation (1).
θm = θest / Pn (1)

A value obtained by dividing the number of torque pulsations generated per rotation of the motor by the number of pole pairs Pn is defined as a torque ripple generation harmonic order n. In general, there are multiple torque ripple generation harmonic orders n of an electric motor, but n is an integer, and components such as n = 1, 2, 6, 12 are generated. The frequency fn [Hz] of the torque ripple of the generated harmonic order n-order component is expressed by Equation (2-1).
fn = (dθm / dt) × Pn × n / (360) (2-1)

That is, the torque ripple frequency fn [Hz] changes according to the motor rotational angular velocity dθm / dt. Therefore, the center frequency fc of the bandpass filter is set to be equal to fn as shown in Equation (2-2).
fc = fn (2-2)

Further, the time constant Tc of the bandpass filter is set by the equation (2-3).
Tc = 1 / (2πfc) (2-3)

  Applying a time constant variable filter that sets the time constant of the bandpass filter using Equation (2-3) to the steering torque signal removes the driver's steering components and relatively high frequency noise components from the steering torque signal. In addition, the pulsation component of the steering torque due to the cogging torque or torque ripple can be extracted.

  Calculations from Expression (2-1) to Expression (2-3) are performed by the time constant calculator 51 shown in FIG. However, (dθm / dt) × Pn in Expression (2-1) uses the motor rotation angular velocity signal ωest.

  As the band-pass filter 52, for example, a fourth-order band-pass filter including a multiple root shown in Expression (3) is used. In Expression (3), Gbpf is a filter transfer function, and s is a Laplace operator. K1 is a correction gain for a gain of -12 dB at the center frequency fc [Hz], and K1 is set so that the gain is 0 dB at the center frequency fc [Hz].

  When the bandpass filter is configured by a fourth order including a multiple root, a pulsation component can be extracted with a gain of 0 dB and a phase delay of 0 (zero) at the center frequency fc, and other components can be extracted at -40 dB / decade in both the low frequency range and the high frequency range. Therefore, the pulsation component can be extracted with high accuracy.

  In the torque ripple suppression controller 53 shown in FIG. 6, a torque ripple compensation current command for reducing the pulsation component is calculated according to the pulsation component extracted by the torque ripple extractor 50. For example, a torque ripple compensation current command is obtained by multiplying the pulsation component extracted by the torque ripple extractor 50 by a proportional gain.

  As described above, the torque ripple compensator 26 is configured. However, the present invention is not limited to this, and other configurations may be used.

  As described above, according to the method shown in the first embodiment, the estimated value of the motor rotation angle or the motor rotation angular velocity estimated by two or more kinds of methods is switched with an appropriate method, so that it can be obtained with high accuracy. The motor rotation angle signal and motor rotation angular velocity signal can be used for any compensation control such as torque ripple compensation, damping compensation, inertia compensation, friction compensation, etc., improving torque ripple, convergence, friction feeling, inertia feeling, etc. The effect can be sufficiently obtained, and an unprecedented remarkable effect that the steering feeling felt by the driver is improved can be achieved.

Embodiment 2. FIG.
In the second embodiment, an electric power steering control device in which the current command generation means 11 of the first embodiment is replaced with that shown in FIG. 7 will be described. The description will be made only on the difference from the first embodiment, that is, only the signal input to the torque ripple compensator 26 and the contents of the torque ripple compensator 26. Signals input to the torque ripple compensator 26 are a steering torque signal, a motor rotation angular velocity signal, and a motor rotation angle signal. The torque ripple compensator 26 will be described with reference to FIGS.

The torque ripple compensator 26 is a sine wave component sin (nP _m θ _m ) and cosine based on the motor mechanical angle rotation angle signal θ _m , the target harmonic generation n of the torque ripple, and the motor pole pair number P _m. A reference wave vector ν [sin (nP _m θ _m ) cos (nP _m θ _m )] composed of the wave component cos (nP _m θ _m ) is calculated, and the steering torque signal detected by the torque sensor 8 and the reference wave vector are calculated. To calculate the coefficient vector φ = [φ ₁ φ ₂ ] for adjusting the phase and amplitude of the torque ripple compensation current command for canceling the torque ripple.

Here, the torque ripple generated harmonic order is a value obtained by dividing the number of torque pulsations generated per motor revolution by the pole pairs P _m. In general, there are a plurality of torque ripple generation harmonic orders of an electric motor. The motor mechanical angle rotation angle signal theta _m is obtained by dividing the motor rotational angle signal θest in pole pairs P _m. The reference wave vector is composed of a sine wave and a cosine wave having the same frequency as the torque ripple. Further, sin (nP _m θ _m ) is set as a reference wave of torque ripple having a harmonic order n of torque ripple generation.

Next, a torque ripple compensation current command for canceling the torque ripple is calculated from the reference wave vector ν and the coefficient vector φ. Here, assuming that the torque ripple acting on the motor shaft is T _g , the torque ripple becomes a pulsation depending on the motor rotation angle, and therefore can be expressed by Expression (4-1). Estimated value of torque ripple acting on motor shaft estimated by torque ripple compensator

Is expressed by equation (4-2).

That is, by sequentially adjusting the coefficient vector φ, the torque ripple amplitude and the phase difference of the torque ripple with respect to the reference wave can be estimated. As a result, the torque ripple compensation current command I _comp for canceling the torque ripple is expressed by the following equation (5). _Kt is a torque constant of the motor.

  In addition, since the coefficient vector φ is sequentially adjusted every calculation cycle of the microcomputer, it is possible to appropriately suppress the torque ripple in response to changes in the amplitude and phase of the torque ripple.

Next, the torque ripple compensator 26 will be described based on the block diagram shown in FIG. 8 and the flowchart shown in FIG. For example, when the ignition switch is closed, the flowchart of FIG. 9 is repeatedly executed at the calculation cycle of the microcomputer after the initial value of the coefficient vector φ = [φ ₁ φ ₂ ] is set. The initial value of the coefficient vector φ is set based on the average value of the phase difference with respect to the amplitude of the torque ripple and the electrical angle measured in advance. As a result, convergence of the estimated torque ripple amplitude and phase difference to the true value is accelerated. However, the initial value may be φ = [0 0].

In S1 of FIG. 9, the steering torque signal T _s and the motor mechanical angle rotation angle signal θ _m are stored in the memory. Also defines a value obtained by dividing the number of torque pulsations generated per motor revolution by the pole pairs P _m and the torque ripple generated harmonic order. In general, there are a plurality of torque ripple generation harmonic orders of an electric motor. In S2 in FIG. 9 (reference wave vector calculator 81 in FIG. 8), the torque ripple generation harmonic order of the torque ripple to be suppressed is n, and a reference wave vector composed of a sine wave and a cosine wave having the same frequency as the torque ripple is obtained. It calculates according to Formula (6). A sine wave table stored in the ROM of the microcomputer is used for the calculation of the trigonometric function. Further, sin (nP _m θ _m ) is set as a reference wave for the torque ripple of the generated harmonic order n.
ν [sin (nP _m θ _m ) cos (nP _m θ _m )] (6)

In S3, the motor rotation angular velocity signal ωest is read. In S4, it determines the calculated motor rotation angular speed signal if a predetermined motor rotational angular velocity threshold omega ₁ smaller. Motor when the rotational angular velocity signal is a motor rotational angular velocity threshold omega ₁ smaller, the process proceeds to S5. Motor rotational angular velocity signal when the motor rotation angular speed threshold omega ₁ or more, the process proceeds to S8.

When the motor rotation angular velocity increases, the torque ripple frequency increases as described in the first embodiment. When the frequency of the torque ripple is sufficiently high, there is a band where the pulsation of the steering torque is sufficiently attenuated due to the attenuation characteristic of the steering mechanism. Therefore, to set the motor rotation angular velocity pulsation of the steering torque by the torque ripple is sufficiently attenuated and the motor rotational angular velocity threshold omega _1.

In S5, the detected steering torque signal T _s is subjected to a high-pass filter process to remove a low frequency component from the steering torque, and a new steering torque signal T _s2 is obtained. The steering torque signal T _s includes a steering component by the driver in addition to a pulsation component due to torque ripple. Since the driver's steering is usually about 5 Hz or less, the steering component of the driver can be removed from the steering torque signal T _s by setting the cutoff frequency of the high-pass filter in the vicinity of 5 Hz, and the torque ripple is estimated. Accuracy can be improved.

In S6, phase compensation, for example, phase advance compensation, is further performed on the steering torque T _s2 subjected to the high-pass filter processing in S5 to obtain a new steering torque T _s3 . If the phase compensation is configured by the first order, the phase can be advanced by 90 deg at the maximum (180 deg for the second order). As a result, the phase delay in the transfer characteristic from the target current of the motor to -T _{s obtained} by multiplying the steering torque by gain -1 can be reduced by 90 degrees at the maximum, and the estimation accuracy of torque ripple can be improved. In this embodiment, the steering wheel is fixed, and the torque sensor output that is output when the motor current flows in the negative direction is positive. Note that the processing of S5 and S6 corresponds to the operation of the filter processor 82 shown in FIG.

In S7, the coefficient vector φ is calculated from the reference wave vector ν [sin (nP _m θ _m ) cos (nP _m θ _m )] and the steering torque T _s3 from the equation (7). That is, the gain multiplier 83 shown in FIG. 8 multiplies the reference wave vector ν by the feedback gain K, and further multiplies the filtered steering torque T _s3 by the multiplier 84 for time integration by the integrator 85. The calculation result of the integrator 85 is defined as a coefficient vector φ.

  In the present embodiment, the feedback gain K is a negative value. In the case of a negative value, the coefficient vector φ estimates the torque ripple amplitude and the phase difference of the torque ripple with respect to the reference wave. Accordingly, the motor outputs a torque that cancels the torque ripple by the compensation current command shown in the equation (5), and the pulsation of the steering torque can be suppressed.

In S8, since the motor rotation angular speed signal threshold omega ₁ or more, the calculation of the coefficient vector φ shown in S5~S7 is not performed, the less than 1 positive, or gain L coefficient vector φ 0 (previous value) Multiply the coefficient vector φ. Thereby, without changing the phase difference of the torque ripple with respect to the reference wave of the compensation current, the amplitude of the compensation current is reduced by L times, and as described above, in the region where the motor rotational angular velocity is high and the steering torque pulsation due to the torque ripple is small, The torque ripple compensation current command can be gradually reduced.

S9 corresponds to the operation of the compensation current calculator 86 and the gain 87. The calculation shown in the equation (5) is performed to calculate the torque ripple compensation current command I _comp .

  Since the torque ripple compensator 26 configured in this manner outputs torque that cancels torque ripple, torque ripple can be suppressed and pulsation of steering torque can be suppressed.

  As described above, the torque ripple compensator is configured. However, the present invention is not limited to this, and other configurations may be used.

  As described above, according to the method shown in the second embodiment, similarly to the first embodiment, the estimated value of the motor rotation angle or the motor rotation angular velocity estimated by two or more methods is switched by an appropriate method. Therefore, since the motor rotation angle signal and motor rotation angular velocity signal obtained with high accuracy can be used for compensation control such as torque ripple compensation, damping compensation, inertia compensation, friction compensation, etc., torque ripple, convergence, friction feeling, The effect of improving the feeling of inertia can be sufficiently obtained, and a remarkable effect that has not been achieved so far, such as the steering feeling felt by the driver being improved, can be achieved.

Embodiment 3 FIG.
In the third embodiment, as shown in FIG. 10, smoothing means 43 and 44 are sandwiched between the current control means 12 and the current command generation means 11 of the first and second embodiments, and the electric power steering is configured. The control device will be described. In the description, only differences from the first and second embodiments will be described.

  The angle smoothing processing means 43 performs a smoothing process on the motor rotation angle signal θest output from the switching means 34 and calculates a second motor rotation angle signal θest2. This is input to the current command generation means 11 as a motor rotation angle signal.

  Further, the speed smoothing processing unit 44 performs a smoothing process on the motor rotation angular velocity signal ωest output from the switching unit 34 and calculates a second motor rotation angular velocity signal ωest2. This is input to the current command generation means 11 as a motor rotation angular velocity signal.

  The specific method of the smoothing process in the angle smoothing processing unit 43 and the speed smoothing processing unit 44 may be a well-known method. For example, a low-pass filter or a moving average may be used. Good.

  The estimated signals from the motor rotation angle estimation means A32 and B33 may contain larger noise or pulsation error than the signals detected by the motor rotation angle sensor. In particular, since the motor rotation angle estimation means A32 estimates with a response obtained by adding a voltage command of a high-frequency periodic signal, noise or pulsation error in the estimation result tends to be larger than the estimation means B33.

  In addition, the motor rotation angle signal and the motor rotation angular velocity signal used for the current command generation means 11 can sufficiently obtain various effects of compensation control even if the delay is relatively large compared to that used for current control. Often done. In general, when the smoothing process is performed, the frequency band in which the signal is delayed tends to decrease and the delay tends to increase, but the signal used for the current command generation unit can be smoothed.

  Therefore, as shown in FIG. 10, the smoothing means 43 and 44 perform a smoothing process only on the motor rotation angle signal and the motor rotation angular velocity signal used for the current command generation means 11 in this embodiment. Proposed in

  In the electric power steering control apparatus according to this embodiment, since the smoothing process is performed only on the motor rotation angle and the motor rotation angular velocity estimation signal used for the current command generation means 11, the current control can be performed without delay. Since the command and the actual current are accurately followed, and the signal used for the current command generation means 11 is smoothed by reducing noise and pulsation, compensation control such as torque ripple compensation, damping compensation, inertia compensation, friction compensation, etc. It is possible to obtain the above effect satisfactorily. As a result, a good steering feeling can be obtained.

Embodiment 4 FIG.
In the present fourth embodiment, as shown in FIG. 11, an electric power steering system in which a current command switching unit 28 is sandwiched between the current control unit 12 and the current command generation unit 11 of the first and second embodiments. The control device will be described. In the description, only differences from the first and second embodiments will be described.

  The current command switching means 28 calculates the motor rotation angular velocity and switches the motor rotation angle estimation means according to the calculation result. As shown in FIG. 11, the angle switching section 41B, the speed calculation section 42B, the angle A smoothing processing means 43 and a speed smoothing processing means 44 are provided. The angle switching unit 41B selects one of the motor rotation angle estimation values θA and θB output from the two motor rotation angle estimation means A32 and B33, respectively, based on the input second motor rotation angular velocity signal ωest2. Then, it is output as a motor rotation angle signal θest2. The speed calculation unit 42B calculates the second motor rotation angular velocity signal ωest2 by differentiating the motor rotation angle signal θest2 output from the angle switching unit 41B and further performing smoothing processing by the speed smoothing processing unit 44. To do. The angle smoothing processing means 43 performs a smoothing process on the motor rotation angle signal θest output from the switching means 34 and calculates a second motor rotation angle signal θest2.

  The current command switching means 28 is the same as any one of the magnetic pole position switching means described in Examples 1 to 5 of Patent Document 1 with respect to the details other than the angle smoothing processing means 43 and the speed smoothing processing means 44. It may be the same. In particular, the method shown in the fourth embodiment of this document gradually switches the ratios reflected in the motor rotation angle signals of the two estimating means according to the speed, so that the torque fluctuation at the time of switching is suppressed and the switching is performed smoothly. Can do. The ratio to be reflected may be set to a ratio different from the switching means 34 in the current command switching means 28.

  Next, the second motor rotation angle signal θest2 and the second motor rotation angular velocity signal ωest2 are input to the current command generation unit 11 as a motor rotation angle signal and a motor rotation angular velocity signal, respectively.

  The specific method of the smoothing process in the angle smoothing processing unit 43 and the speed smoothing processing unit 44 may be a well-known method. For example, a low-pass filter or a moving average may be used. Good.

  As described in the third embodiment, the motor rotation angle signal and the motor rotation angular velocity signal used for the current command generation means 11 can be allowed even if the delay is relatively large compared to that used for current control. Therefore, in the fourth embodiment, the two kinds of estimation signals are switched by the current command switching means 28 provided separately from the switching means 34 in the current control means 12.

  In the electric power steering control apparatus according to the fourth embodiment, since the estimation signal without delay is used for the current control, the current command and the actual current can be accurately followed, and various compensation controls can be performed. In addition to current control, the current command switching means 28 can be used to perform switching suitable for compensation control. Therefore, the motor rotation angle signal and the motor rotation angular velocity signal used for the current command generation means 11 reduce noise and pulsation. Thus, the effects of compensation control such as torque ripple compensation, damping compensation, inertia compensation, and friction compensation can be obtained satisfactorily. As a result, a good steering feeling can be obtained.

  More specifically, if the current command switching means 28 is used, the motor rotation angular velocity signal ωest2 used for the angle switching section 41B is smoothed and noise and pulsation are reduced. Switching can be performed more smoothly than the switching means 34. Therefore, the motor rotation angle signal and the motor rotation angular velocity signal used for the current command generation unit 11 are smoothed by reducing noise and pulsation, so that the effects of compensation control such as torque ripple compensation, damping compensation, inertia compensation, and friction compensation can be achieved. It is possible to obtain well. As a result, a good steering feeling can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of the electric power steering apparatus by Embodiment 1-4 of this invention. It is a block diagram which shows the electric power steering control apparatus by Embodiment 1 and 2 of this invention. It is a block diagram which shows the current control means 12 by Embodiment 1 and 2 of this invention. It is a block diagram which shows the electric current command production | generation means 11 by Embodiment 1 of this invention. It is a block diagram which shows the switching means 34 by Embodiment 1-4 of this invention. It is a block diagram which shows the torque ripple compensator by Embodiment 1 of this invention. It is a block diagram which shows the electric current command production | generation means 11 by Embodiment 2 of this invention. It is a block diagram which shows the torque ripple compensator by Embodiment 2 of this invention. It is a flowchart which shows the torque ripple compensator by Embodiment 2 of this invention. It is a block diagram which shows the principal part of the electric power steering control apparatus by Embodiment 3 of this invention. It is a block diagram which shows the principal part of the electric power steering control apparatus by Embodiment 4 of this invention.

Explanation of symbols

  5 brushless motor, 10 electric power steering control device, 11 current command generation means, 12 current control means, 23 damping compensator, 24 friction compensator, 25 inertia compensator, 26 torque ripple compensator, 28 switching means for current command, 32 motor rotation angle estimation means A, 33 motor rotation angle estimation means B, 34 switching means, 43 angle smoothing processing means, 44 speed smoothing processing means.

Claims (5)

Current command generating means for calculating a current command corresponding to the target value of the assist torque;
Current control means for calculating a voltage command, a motor rotation angle signal, and a motor rotation angular velocity signal of each phase according to the current command and the current signal;
A current detecting section for outputting a current signal by detecting the current flowing through each phase of the probe Rashiresumota
With
An electric power steering control device for controlling the brushless motor based on the current command and generating a motor torque for assisting a driver's steering,
The current command generation means includes
A damping compensator for calculating a damping compensation current command based on the motor rotation angular velocity signal;
An inertia compensator for calculating an inertia compensation current command based on a motor rotation angular acceleration obtained by differentiating the motor rotation angular velocity signal;
A friction compensator for calculating a friction compensation current command based on the motor rotation angular velocity signal;
Calculating a current command according to one or more compensation current commands of the compensator and an assist current command calculated based on a steering torque;
The current control means includes
Two types of motor rotation angle estimation means for calculating motor rotation angle estimation values by two different methods ,
Dq axis current control means for outputting the voltage command in response to the motor rotation angle signal, the current command, and the current signal ;
Calculates the motor rotational angle signal and the motor rotation angular speed signal by selecting one of the motor rotation angle estimates two motor rotation angle estimating means for outputting based on the motor rotational angular velocity, calculated the motor rotation angle signal Alternatively, the motor rotation angle signal or the motor rotation angular velocity signal smoothed by the smoothing processing means for smoothing the motor rotation angular velocity signal is used as a motor rotation angle signal or motor rotation to any compensator of the current command generation means. The electric power steering control apparatus characterized in that the voltage command is calculated by the dq axis current control means based on the motor rotation angle signal which is given as an angular velocity signal and is not smoothed . In the electric power steering control device according to claim 1,
The current command generation means further includes a torque ripple compensator that calculates a torque ripple compensation current command based on the motor rotation angular velocity signal or the motor rotation angle signal, and includes at least one including a torque ripple compensator. An electric power steering control device that calculates a current command in accordance with the compensation current command of and the assist current command calculated based on the steering torque. In the electric power steering control device according to claim 1 or 2,
An electric power steering control device further comprising a smoothing processing means for smoothing a motor rotation angle signal or a motor rotation angular velocity signal given from the current control means to the current command generation means. In the electric power steering control device according to claim 1 or 2,
Switching between the two motor rotation angle estimation means according to a motor rotation angular velocity, and a current command switching means for estimating a rotation angle of the brushless motor and calculating a motor rotation angle signal;
The current command switching means provides the calculated motor rotation angle signal or a motor rotation angular velocity signal obtained by differentiating it as a motor rotation angle or a motor rotation angular velocity to any of the compensators. Electric power steering control device. In the electric power steering control device according to claim 4,
The current command switching means includes a smoothing processing means for smoothing a motor rotation angular velocity, and switches the two motor rotation angle estimation means according to the smoothed motor rotation angular velocity, and the rotation angle of the brushless motor. An electric power steering control device characterized by estimating the motor rotation angle signal.

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