JP6413633B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering device that applies assist force by an electric motor to a steering mechanism of a vehicle.

  An electric power steering device (EPS) detects a steering torque applied by a driver to a steering wheel by a torque sensor, supplies a current to the electric motor according to the detected steering torque, and decelerates a worm gear mechanism or the like. An assist force is applied to a steering mechanism such as a rack and pinion mechanism via a gear mechanism.

  Since the resonance between the reduction gear mechanism and the mechanical structure on the vehicle side affects the steering feeling, various countermeasures have been proposed in order to suppress the occurrence of such resonance (for example, Patent Documents). 1).

  Patent Document 1 discloses specific frequency extraction means for extracting a frequency component (for example, around 40 Hz) in a specific frequency band that resonates with a vehicle-side mechanical structure from a motor signal indicating the rotation state of the motor, and specific frequency extraction means. Based on the extracted frequency component, the vibration suppression basic component calculation means for calculating the vibration suppression basic component to reduce the vibration of the steering mechanism, and the phase advance compensation for the frequency component extracted by the specific frequency extraction means An electric power steering apparatus is disclosed that includes a phase advance compensation unit that adjusts the phase characteristic of the vibration suppression compensation component by performing the above.

JP 2011-88491 A

  However, in the steering mechanism, when the steering angular velocity increases, vibrations with a frequency outside the specific frequency band that resonates with the mechanical structure on the vehicle side from the reduction gear mechanism may occur. In such a case, in the electric power steering device described in Patent Document 1, since the specific frequency band extracted from the motor signal is fixed, vibration from the reduction gear mechanism may not be suppressed. In particular, when the vehicle is of a quiet type such as a hybrid vehicle or an electric vehicle, even a slight vibration or vibration noise may cause discomfort or anxiety to the driver or passenger of the vehicle.

  Accordingly, an object of the present invention is to provide an electric power steering device capable of suppressing vibration and vibration noise generated from a reduction gear mechanism.

In order to achieve the above object, the present invention provides a stator that is attached to the inside of a motor case, a motor that is rotatably supported by the motor case and that rotates with respect to the stator, and a drive source for the motor. A steering assist mechanism for applying an assist force for assisting a steering operation to the steering mechanism via a reduction gear mechanism, motor rotation angle detection means for detecting a rotation angle of the motor and outputting a motor rotation angle signal, and the steering by detecting the steering torque accompanying the operation and the steering torque detecting means for outputting a steering torque signal, and assist control means for generating an assist control signal based on the vehicle speed signal indicating the speed of the steering torque signal and vehicle, before Symbol deceleration extracting a frequency component of the vibration generated from the gear mechanism from the motor rotational angle signal, to suppress the vibration of the frequency component Generates a vibration suppression signal, the and a vibration suppression means to impart to the driving system of the current command signal to the vibration suppression signal obtained by adding the assist control signal the motor, the vibration suppressing means, using a band-pass filter Extracting the frequency component of vibration generated from the reduction gear mechanism, and shifting the frequency characteristic of the bandpass filter to a higher side as the steering angular velocity increases with the steering operation. An electric power steering device is provided in which the range in which the center frequency of the frequency band that can pass through the vehicle can be changed is wider than the resonance frequency band of the vehicle .

  The vibration suppression means is a frequency extraction means for extracting the frequency corresponding to the steering angular velocity from the motor rotation angle signal, and a gain of the steering angular velocity is calculated by the gain of the steering angular velocity and the frequency extraction means extracts the gain of the steering angular velocity. It is preferable that a steering angular velocity calculation unit for multiplying the obtained signal and a gain calculation means for calculating a gain of the steering torque and multiplying the signal extracted by the frequency extraction means by the steering torque gain.

  It is preferable that the frequency component extracted by the vibration suppression unit includes a resonance frequency band of the vehicle when the steering angular velocity is a predetermined value.

  According to the present invention, it is possible to suppress vibration and vibration noise generated from the reduction gear mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of the configuration of an electric power steering device and its surroundings according to an embodiment of the present invention. It is a block diagram which shows the structural example of ECU. It is a block diagram which shows the structural example of a vibration suppression compensation control part. It is a graph which shows the frequency characteristic of the band pass filter which a frequency variable process part has.

  Embodiments of the present invention will be described with reference to FIGS. Note that the embodiment described below is shown as a preferred specific example when the electric power steering apparatus of the present invention is implemented, and specifically illustrates various technical matters that are technically preferable. However, the technical scope of the present invention is not limited to this embodiment.

(Overall configuration of electric power steering device)
FIG. 1 is a schematic diagram showing an example of the configuration of an electric power steering apparatus and its surroundings according to an embodiment of the present invention. The electric power steering apparatus 1 includes a steering shaft 2 to which a steering wheel 10 that is rotated by a driver is coupled so as not to be relatively rotatable, a rack shaft 3 that linearly moves by a rotational force transmitted from the steering shaft 2, and a steering shaft 2. A steering assist mechanism 4 for applying a steering assist force (assist force) to the steering assist mechanism 4 and an ECU 5 as a control device for controlling the electric motor 40 of the steering assist mechanism 4 are provided. The steering shaft 2 forms a steering mechanism together with the rack shaft 3.

  The steering shaft 2 includes a column shaft 21 to which the steering wheel 10 is fixed at one end, a pinion shaft 23 that forms the rack and pinion mechanism 1 a together with the rack shaft 3, and an intermediate shaft that connects the column shaft 21 and the pinion shaft 23. 22. The column shaft 21 and the intermediate shaft 22 are connected by a universal joint 201. The intermediate shaft 22 and the pinion shaft 23 are connected by a universal joint 202.

  The rack shaft 3 is accommodated in a cylindrical rack housing 30 so as to be movable in the axial direction. Rack teeth 31 are formed along the axial direction of the rack shaft 3, and the rack teeth 31 mesh with the pinion teeth 231 of the pinion shaft 23. Ball joint sockets 32 are fixed to both ends of the rack shaft 3, and tie rods 11 connected to these ball joint sockets 32 are connected to the left and right steered wheels 100 via knuckle arms (not shown). Further, on the outer peripheral side of the ball joint socket 32, a boot 12 made of bellows-like rubber or resin is disposed.

  When the steering wheel 10 is rotated, the pinion shaft 23 connected to the steering wheel 10 via the column shaft 21 and the intermediate shaft 22 rotates, and the rack shaft 3 is moved by the engagement of the pinion teeth 231 and the rack teeth 31. It moves linearly in the axial direction. The steered wheel 100 is steered through the tie rod 11 by the linear motion of the rack shaft 3.

  The steering assist mechanism 4 includes an electric motor 40 and a worm wheel 41 that meshes with a worm gear 401 provided on the output shaft of the electric motor 40. The steering assist mechanism 4 applies an assist force for assisting the steering operation to the steering shaft 2 through the worm gear 401 and the worm wheel 41 using the electric motor 40 as a drive source. The reduction ratio of the rotation of the worm wheel 41 with respect to the rotation of the worm gear 401 is 20, for example. In the present embodiment, the worm wheel 41 is fixed to the column shaft 21. The worm wheel 41 may be fixed to the pinion shaft 23. The worm wheel 41 and the worm gear 401 are an example of a reduction gear mechanism.

  The electric motor 40 includes a stator attached to the inside of the motor case, and a rotor that is rotatably supported by the motor case and rotates with respect to the stator. The electric motor 40 is, for example, a brushless motor, receives supply of three-phase (U, V, W) drive power from the ECU 5, and applies assist force to the steering assist mechanism 4 by torque generated by the drive power.

  The column shaft 21 is provided with a torque sensor 24. The torque sensor 24 detects a steering torque τ accompanying the steering operation and outputs a steering torque signal Sτ. Specifically, the torque sensor 24 detects torsion of the torsion bar 211 provided on the column shaft 21 based on a change in magnetic field, and outputs a steering torque signal Sτ corresponding to the steering torque τ to the ECU 5. The torque sensor 24 is an example of a steering torque detection unit.

  The ECU 5 is connected to a vehicle speed sensor 101 that detects the vehicle speed V and outputs a vehicle speed signal. The vehicle speed sensor 101 outputs a vehicle speed signal indicating the detected vehicle speed V to the ECU 5.

  The ECU 5 controls the assist torque generated by the electric motor 40 based on the steering torque signal Sτ detected by the torque sensor 24 and the vehicle speed V detected by the vehicle speed sensor 101, thereby providing an assist force applied to the steering mechanism. Control.

(Control system for electric power steering device)
FIG. 2 is a block diagram showing a control system of the electric power steering apparatus 1. As shown in the figure, the ECU 5 includes a microcomputer 51 that outputs a motor control signal and a drive circuit 50 that supplies three-phase drive power to the electric motor 40 based on the motor control signal.

  The ECU 5 is connected to a current sensor 43 that detects an actual current value I that is supplied to the electric motor 40 and a rotation angle sensor 44 that detects a motor rotation angle θ of the electric motor 40 and outputs a motor rotation angle signal. Yes. The rotation angle sensor 44 is an example of a motor rotation angle detection unit.

  The microcomputer 51 outputs to the drive circuit 50 based on the vehicle state quantities (V, τ), the actual current value I of the electric motor 40 and the motor rotation angle θ detected by the current sensor 43 and the rotation angle sensor 44. A motor control signal is generated.

  The microcomputer 51 outputs the motor control signal generated as described above to the drive circuit 50, and the drive circuit 50 supplies three-phase drive power based on the motor control signal to the electric motor 40, whereby the steering assist mechanism. 4 is controlled.

  Specifically, the microcomputer 51 calculates a current command value calculation unit that calculates a current command value I * as a current command signal corresponding to a target value of assist force applied to the steering mechanism (hereinafter referred to as “target assist force”). 53, a motor control signal output unit 52 that outputs a motor control signal based on the current command value I * calculated by the current command value calculation unit 53, and a phase compensation control unit that performs phase compensation processing on the steering torque signal Sτ 54. The motor control signal output unit 52 constitutes a motor drive system.

  The motor control signal output unit 52 performs feedback control so that the actual current value I follows the current command value I * corresponding to the target assist force.

  That is, the motor control signal output unit 52 includes the current command value I * calculated by the current command value calculation unit 53, the actual current value I detected by the current sensor 43, and the motor rotation angle detected by the rotation angle sensor 44. A motor control signal is generated based on θ, and the motor control signal is output to the drive circuit 50.

  Specifically, the motor control signal output unit 52 receives the current command value I * as the q-axis current command value, and based on the motor rotation angle θ detected by the rotation angle sensor 44, the phase current values (Iu, Iv , Iw) is converted into d and q axis current values in the d / q coordinate system (d / q conversion). Next, the motor control signal output unit 52 calculates the d and q axis voltage command values based on the d and q axis current values and the q axis current command value. Next, the motor control signal output unit 52 calculates the phase voltage command value (Vu *, Vv *, Vw *) by performing d / q reverse conversion on the d, q axis voltage command value, and the phase voltage command value. A motor control signal is generated based on

  The phase compensation control unit 54 performs phase compensation processing (filter processing) on the steering torque signal Sτ output from the torque sensor 24, and outputs the obtained steering torque τ to the current command value calculation unit 53.

  The current command value calculation unit 53 calculates a current command value I * corresponding to the target assist force, and outputs the current command value I * to the motor control signal output unit 52.

  Specifically, the current command value calculation unit 53 calculates a basic assist control amount Ias * that is a basic component of the assist force that should be generated by the steering assist mechanism 4, and the basic assist control amount Ias *. A vibration suppression compensation control unit 56 for calculating a vibration suppression compensation amount Ivs * for canceling a torque ripple in a vibration frequency band (for example, 15 to 75 Hz) generated from the reduction gear mechanism, and a basic assist control unit. An assist gradient compensation control unit 57 for performing assist gradient compensation control for generating a control signal corresponding to each compensation control in order to change the characteristics of various compensation controls in accordance with the assist gradient Ra input from 55, and basic assist control. As a compensation component to be added to the amount Ias *, it is based on a differential value (steering torque differential value dτ) of the steering torque τ by the differentiator 60a. A torque inertia compensation control unit 58 for calculating the torque inertia compensation amount Iti *, and an adder 59 for adding various compensation amounts to the basic assist control amount Ias * calculated by the basic assist control unit 55. The differentiator 60b generates a motor angular speed ω by differentiating the motor rotation angle θ associated with the steering operation, and outputs a motor angular speed signal indicating the motor angular speed ω. The basic assist control unit 55 is an example of assist control means.

  The basic assist control unit 55 calculates a basic assist control amount Ias * as an assist control signal based on the steering torque signal indicating the steering torque τ and the vehicle speed signal indicating the vehicle speed V. The basic assist control unit 55 calculates the basic assist control amount Ias * having a larger absolute value as the absolute value of the input steering torque τ is larger and the vehicle speed V is smaller. In the present embodiment, particularly in relation to the steering torque τ, the larger the steering torque τ, the larger the assist gradient Ra, which is the ratio of the change in the basic assist control amount Ias * to the change in the steering torque τ. Designed to be The basic assist control unit 55 outputs the calculated basic assist control amount Ias * to the adder 59.

  The torque inertia compensation control unit 58 executes torque inertia compensation control based on each state quantity of the steering torque differential value dτ and the vehicle speed V. The torque inertia compensation control is a control that compensates for the influence of the EPS inertia, such as a motor, that is, after the catch at the start of turning in steering operation (following delay) and suppresses the flow feeling at the end of turning (overshoot). It is control for. In addition, the torque inertia compensation control has an effect of suppressing the vibration generated in the steering mechanism due to the cogging torque of the electric motor 40, the distortion of the induced voltage waveform, or the meshing of the gear in the reduction gear mechanism.

  Specifically, the torque inertia compensation control unit 58 associates the first map (not shown) in which the steering torque differential value dτ and the torque inertia basic compensation amount εti are associated, and the vehicle speed V and the interpolation coefficient A. A second map (not shown). In the first map, the basic torque inertia compensation amount εti is the basic assist control amount Ias * (absolute value) calculated by the basic assist control unit 55 as the absolute value of the input steering torque differential value dτ increases. It is set so as to increase the value. Further, in the second map, the interpolation coefficient A is set so as to increase as the vehicle speed V increases in the low vehicle speed region, and to decrease as the vehicle speed increases in the high vehicle speed region. The torque inertia compensation control unit 58 calculates the torque inertia compensation amount Iti * by multiplying the torque inertia basic compensation amount εti and the interpolation coefficient A obtained by referring to these maps, and the torque inertia compensation The quantity Iti * is output to the adder 59.

  The assist gradient compensation control unit 57 performs assist gradient compensation control for generating a control signal corresponding to each compensation control in order to change the characteristics of various compensation controls in accordance with the assist gradient Ra input from the basic assist control unit 55. Do.

  Specifically, the assist gradient compensation controller 57 includes a filter constant calculator 57a that calculates a filter constant Af, and an assist gradient gain calculator 57b that calculates an assist gradient gain Ka. Here, the filter constant Af and the assist gradient gain Ka are examples of control signals for changing the above characteristics.

  The filter constant calculation unit 57a calculates the filter constant Af based on the input assist gradient Ra, and provides the filter constant Af to the phase compensation control unit 54. The phase compensation control unit 54 changes the characteristics of the phase compensation process based on the filter constant Af.

  The assist gradient gain calculator 57b calculates an assist gradient gain Ka based on the input assist gradient Ra, and provides the assist gradient gain Ka to the torque inertia compensation controller 58. The torque inertia compensation control unit 58 changes the characteristics of the torque inertia compensation control based on the assist gradient gain Ka.

  Here, the change in the assist gradient is equivalent to the change in the spring constant of the torsion bar 211 that constitutes the torque sensor 24 provided in the middle of the steering shaft 2. Therefore, vibration tends to occur more easily as the assist gradient becomes larger. However, the problem of the increase in vibration caused by the increase in assist gradient is a characteristic change of phase compensation control, specifically, a filter in the phase compensation processing. It can be suppressed by keeping the gain of the characteristic low. And the said filter constant calculating part 57a calculates the filter constant Af which reduces the gain of a filter characteristic according to the raise of assist gradient Ra, The structure which suppresses the vibration increase accompanying the raise of assist gradient Ra, and It has become.

  In addition, torque inertia compensation control based on the steering torque differential value dτ has an effect of suppressing vibration generated in the steering mechanism, but the steering feeling deteriorates due to excessive rise of the assist torque (so-called “cut-off” “ There is a risk of causing a feeling of slipping ”) or instability (vibration) in control.

  In view of this point, in the present embodiment, the assist gradient gain Ka that reduces the torque inertia compensation amount Iti * in the small assist gradient region in which the assist gradient gain calculation unit 57b is not required to rapidly increase the assist torque. Is output. As a result, in addition to the change in the characteristics of the phase compensation control, a configuration that achieves a good steering feeling is achieved.

  The adder 59 calculates the basic assist control amount Ias * calculated by the basic assist control unit 55, the torque inertia compensation amount Iti * calculated by the torque inertia compensation control unit 58, and the vibration suppression compensation control unit 56 described later. The obtained vibration suppression compensation amount Ivs * is added. The vibration suppression compensation control unit 56 is an example of a vibration suppression unit.

  The current command value calculation unit 53 calculates the current command value I * based on a value obtained by adding the torque inertia compensation amount Iti * and the vibration suppression compensation amount Ivs * to the basic assist control amount Ias * in the adder 59.

(Functional configuration of vibration suppression compensation controller)
FIG. 3 is a block diagram illustrating an example of the configuration of the vibration suppression compensation control unit 56. The vibration suppression compensation control unit 56 extracts a frequency component of vibration generated from the worm wheel 41 and the worm gear 401 according to the steering angular velocity ωs from the motor rotation angle signal indicating the motor rotation angle θ, and suppresses the vibration of the frequency component. The vibration suppression compensation amount Ivs * is generated as a vibration suppression signal, and a current command value I * obtained by adding the vibration suppression compensation amount Ivs * to the basic assist control amount Ias * is given to the motor control signal output unit 52. That is, the motor rotation angle θ, the motor angular velocity ω (a differential value of the motor rotation angle θ by the differentiator 60b), the steering torque τ, and the vehicle speed V are input to the vibration suppression compensation control unit 56. Then, the vibration suppression compensation control unit 56 calculates a vibration suppression compensation amount Ivs * based on these state quantities.

  Based on the motor rotation angle θ as a motor signal output from the rotation angle sensor 44, the vibration suppression compensation control unit 56 reduces vibration for reducing torque ripple in a specific frequency band that resonates with the mechanical structure on the vehicle side. The specific frequency extraction unit 560 that calculates the suppression basic compensation amount εvs, the steering angular velocity gain calculation unit 562 that calculates the steering angular velocity gain Kωs for correcting the vibration suppression basic compensation amount εvs based on the steering angular velocity ωs, and the steering torque τ A steering torque gain calculating unit 563 for calculating a steering torque gain Kτ for correcting the vibration suppression basic compensation amount εvs based on the vehicle speed V, and a vehicle speed gain Kv for correcting the vibration suppression basic compensation amount εvs based on the vehicle speed V. The vehicle speed gain calculation unit 564 and the vibration suppression basic compensation amount εvs output from the specific frequency extraction unit 560 are multiplied by various gains. A gain calculator 565 for, and a guard calculation unit 566 for performing guard processing to the output of the gain calculation unit 565.

  The steering angular velocity gain calculation unit 562 calculates the steering angular velocity ωs based on the input motor angular velocity ω, and when the steering angular velocity ωs is not within a predetermined steering angular velocity region where torque ripple in a specific frequency band is likely to occur, vibration suppression compensation is performed. A steering angular velocity gain Kωs that reduces the amount Ivs * is calculated. Specifically, when the steering angular velocity ωs is not within the predetermined steering angular velocity region, a steering angular velocity gain Kωs less than “1” is calculated, and the gain calculation unit 565 multiplies it by the vibration suppression basic compensation amount εvs. Thus, the vibration suppression compensation amount Ivs * is reduced.

  The gain calculation unit 565 adds the steering angular velocity gain Kωs output from the steering angular velocity gain calculation unit 562 and the steering torque output from the steering torque gain calculation unit 563 to the vibration suppression basic compensation amount εvs output from the specific frequency extraction unit 560. The gain Kτ and the vehicle speed gain Kv output from the vehicle speed gain calculation unit 564 are multiplied, and the value obtained by the multiplication is output to the guard calculation unit 566 as a corrected vibration suppression basic compensation amount εvsa.

  The guard calculation unit 566 performs vibration suppression compensation on the value subjected to guard processing so that the absolute value of the corrected vibration suppression basic compensation amount εvsa does not exceed a predetermined value necessary for suppressing torque ripple in a specific frequency band in which resonance occurs. The quantity Ivs * is output to the adder 59 (see FIG. 2).

  In the reduction gear mechanism, when vibration or vibration noise is generated due to meshing between the teeth of the worm wheel 41 and the teeth of the worm gear 401, particularly when the vehicle is a quiet type such as a hybrid vehicle or an electric vehicle, the driver or There is a risk of discomfort and anxiety being detected by passengers. When the vibration frequency generated from the reduction gear mechanism exists in a resonance frequency band (for example, 20 to 50 Hz) Fr (see FIG. 4) that resonates with a vehicle-side mechanical structure (for example, a frame or a body), By the process of suppressing the torque ripple corresponding to the resonance frequency band, vibration and vibration noise from the reduction gear mechanism can also be suppressed. However, the vibration and vibration sound generated from the reduction gear mechanism increase in frequency as the steering angular velocity increases, and may deviate from the resonance frequency band with the vehicle side. Further, if the vibration or vibration sound that can be generated from the reduction gear mechanism at any steering angular velocity is to be suppressed in a fixed frequency band, the steering characteristics are deteriorated. Therefore, the vibration suppression compensation control unit 56 according to the present embodiment includes a frequency variable processing unit 561 that shifts a frequency characteristic of a bandpass filter described later to a higher level as the steering angular velocity increases.

  Note that the frequency F of vibration generated from the reduction gear mechanism changes in proportion to the steering angular velocity ωs in accordance with the reduction ratio of the reduction gear mechanism based on the ratio of the number of teeth of the worm wheel 41 and the number of teeth of the worm gear 401.

  FIG. 4 is a graph showing the frequency characteristics of the bandpass filter included in the frequency variable processing unit 561. The frequency variable processing unit 561 calculates a steering angular velocity ωs based on the input motor angular velocity ω, and extracts a frequency band (a hatched area in FIG. 4) extracted as a specific frequency band by a bandpass filter. Change according to. This band pass filter is configured such that a center frequency Fc of a passable frequency band (for example, 10 Hz) can be changed. In the case shown in FIG. 4, the center frequency Fc is minimized at the steering angular velocity ωs1, and the center frequency Fc is maximized at the steering angular velocity ωs2. The center frequency Fc is configured to be changeable within a range of 20 Hz to 70 Hz including a vehicle resonance frequency band (for example, 20 to 50 Hz) Fr.

(Operation of this embodiment)
Next, an outline of the operation of the vibration suppression compensation control unit 56 according to the present embodiment will be described. The basic assist control unit 55 calculates the basic assist control amount Ias * and the assist gradient Ra based on the vehicle speed V detected by the vehicle speed sensor 101 and the steering torque τ output from the phase compensation control unit 54, and the basic assist is calculated. The control amount Ias * is output to the adder 59, and the assist gradient Ra is output to the assist gradient compensation control unit 57.

  The filter constant calculation unit 57 a of the assist gradient compensation control unit 57 calculates the filter constant Af based on the assist gradient Ra, and outputs the filter constant Af to the phase compensation control unit 54. The assist gradient gain calculator 57b of the assist gradient compensation controller 57 calculates the assist gradient gain Ka based on the assist gradient Ra, and outputs the assist gradient gain Ka to the torque inertia compensation controller 58.

  The torque inertia compensation control unit 58 calculates the torque inertia compensation amount Iti * based on the vehicle speed V, the steering torque differential value dτ, and the assist gradient gain Ka, and outputs the torque inertia compensation amount Iti * to the adder 59.

  When the motor rotation angle θ is input, the specific frequency extraction unit 560 performs a bandpass filter process, extracts a frequency component in a specific frequency band from the motor rotation angle signal, and calculates a vibration suppression basic compensation amount εvs. At that time, the frequency variable processing unit 561 calculates the steering angular velocity ωs based on the input motor angular velocity ω, and changes the specific frequency band extracted by the bandpass filter according to the steering angular velocity ωs.

  The steering angular velocity gain calculation unit 562 calculates the steering angular velocity ωs from the input motor rotation angle, and calculates the steering angular velocity gain Kωs for correcting the vibration suppression basic compensation amount εvs based on the steering angular velocity ωs. The steering torque gain calculation unit 563 calculates a steering torque gain Kτ for correcting the vibration suppression basic compensation amount εvs based on the steering torque τ. The vehicle speed gain calculation unit 564 calculates a vehicle speed gain Kv for correcting the vibration suppression basic compensation amount εvs based on the vehicle speed V.

  The gain calculation unit 565 multiplies the vibration suppression basic compensation amount εvs by the steering angular velocity gain Kωs, the steering torque gain Kτ, and the vehicle speed gain Kv, and sets the value obtained by the multiplication as the corrected vibration suppression basic compensation amount εvsa, the guard calculation unit 566. Output to.

  The guard calculation unit 566 uses the value obtained by performing the guard process so that the absolute value of the corrected vibration suppression basic compensation amount εvsa does not exceed a predetermined value necessary for suppressing torque ripple in the specific frequency band, as the vibration suppression compensation amount Ivs. * Is output to the adder 59.

  The adder 59 calculates the basic assist control amount Ias * calculated by the basic assist control unit 55, the torque inertia compensation amount Iti * calculated by the torque inertia compensation control unit 58, and the vibration suppression compensation control unit 56 described later. The obtained vibration suppression compensation amount Ivs * is added.

  The motor control signal output unit 52 sets the current command value I * calculated by the current command value calculation unit 53, the actual current value I detected by the current sensor 43, and the motor rotation angle θ detected by the rotation angle sensor 44. Based on this, a motor control signal is generated, and the motor control signal is output to the drive circuit 50.

(Operation and effect of the present embodiment)
According to the present embodiment, the following operations and effects are achieved.

(1) Since the vibration suppression compensation control unit 56 suppresses the torque ripple of the frequency component of the vibration generated from the reduction gear mechanism over the entire range of the steering angular velocity, the frequency of the vibration generated from the reduction gear mechanism is the resonance frequency of the vehicle. Even at frequencies other than those described above, vibrations and vibration noises generated from the reduction gear mechanism can be suppressed. Therefore, even when the vehicle is of a quiet type such as a hybrid vehicle or an electric vehicle, unpleasant vibration or vibration noise is hardly given to the person who is on the vehicle.

(2) Since the vibration frequency suppressed by the vibration suppression compensation control unit 56 is a region overlapping with the vehicle resonance frequency, the vehicle resonance can be suppressed by suppressing the vibration generated from the reduction gear mechanism. it can.

  In addition, the said embodiment can also be implemented with the following aspects which changed this suitably. For example, in the above embodiment, the frequency variable processing unit 561 and the steering angular velocity gain calculating unit 562 calculate the steering angular velocity ωs based on the motor angular velocity ω obtained by differentiating the motor rotation angle θ of the electric motor 40. However, the steering shaft 2 The angular velocity obtained by differentiating the sensor output of the rotation angle may be the steering angular velocity ωs.

DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 1a ... Rack and pinion mechanism, 2 ... Steering shaft, 3 ... Rack shaft, 4 ... Steering assist mechanism, 7 ... Ignition switch, 10 ... Steering wheel, 11 ... Tie rod, 12 ... Boot, 21 ... Column shaft, 22 ... Intermediate shaft, 23 ... Pinion shaft, 24 ... Torque sensor, 30 ... Rack housing, 31 ... Rack teeth, 32 ... Ball joint socket, 40 ... Electric motor, 41 ... Worm wheel, 401 ... Worm gear, 43 ... Current sensor 44 ... Rotation angle sensor 50 ... Drive circuit 51 ... Microcomputer 52 ... Motor control signal output unit 53 ... Current command value calculation unit 54 ... Phase compensation control unit 55 ... Basic assist control unit 56 ... Vibration suppression compensation control unit 57... Assist gradient compensation control unit 57 a. Filter constant calculation unit, 57b ... assist gradient gain calculation unit, 58 ... torque inertia compensation control unit, 59 ... adder, 60a, 60b ... differentiator, 100 ... steered wheel, 101 ... vehicle speed sensor, 201, 202 ... universal joint, 211 ... Torsion bar, 231 ... Pinion teeth, 560 ... Specific frequency extraction unit, 561 ... Frequency variable processing unit, 562 ... Steering angular velocity gain calculation unit, 563 ... Steering torque gain calculation unit, 564 ... Vehicle speed gain calculation unit, 565 ... Gain Calculation unit, 566 ... guard calculation unit, Af ... filter constant, dτ ... steering torque differential value, I ... actual current value, I * ... current command value, Ias * ... basic assist control amount, Iti * ... torque inertia compensation amount, Ivs *: vibration suppression compensation amount, Ka: assist gradient gain, Kωs: steering angular velocity gain, Sτ: steering torque signal, V: vehicle speed, θ: motor rotation Angle, τ: Steering torque, ω: Motor angular velocity, ωs, ωs1, ωs2: Steering angular velocity, Fc: Center frequency, Fr: Resonance frequency band

Claims (3)

A stator attached to the inside of the motor case, and a motor having a rotor that is rotatably supported by the motor case and rotates with respect to the stator;
A steering assist mechanism for applying an assist force for assisting a steering operation to the steering mechanism via a reduction gear mechanism using the motor as a drive source;
Motor rotation angle detection means for detecting a rotation angle of the motor and outputting a motor rotation angle signal;
Steering torque detection means for detecting steering torque associated with the steering operation and outputting a steering torque signal;
Assist control means for generating an assist control signal based on the steering torque signal and a vehicle speed signal indicating a vehicle speed;
The frequency components of the vibration generated from the previous SL reduction gear mechanism extracted from the motor rotation angle signal, and generates a suppressing vibration suppression signal vibrations of the frequency components, obtained by adding the vibration suppression signal to the assist control signal current a command signal and a vibration suppression means to impart to the driving system of the motor,
The vibration suppression means extracts a frequency component of vibration generated from the reduction gear mechanism using a bandpass filter, and increases the frequency characteristic of the bandpass filter as the steering angular velocity increases with the steering operation. Shift to
The range in which the center frequency of the frequency band that can pass through the bandpass filter can be changed is wider than the resonance frequency band of the vehicle,
Electric power steering device. The vibration suppressing means extracts a frequency component corresponding to the steering angular velocity from the motor rotation angle signal, calculates a steering angular velocity gain, and extracts the steering angular velocity gain by the frequency extracting means. A steering angular velocity calculation unit that multiplies the generated signal, and a gain calculation unit that calculates the gain of the steering torque and multiplies the steering torque gain by the signal extracted by the frequency extraction unit,
The electric power steering apparatus according to claim 1. The frequency component extracted by the vibration suppression unit includes a resonance frequency band of the vehicle when the steering angular velocity is a predetermined value.
The electric power steering apparatus according to claim 1 or 2.

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