JP2009006985A - Electric power steering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering apparatus capable of accurately estimating steering torque by taking into consideration reaction from a road surface. <P>SOLUTION: This electric power steering apparatus has a first torque command value calculating means 31 that calculates a first torque command value on the basis of steering torque detected by a steering torque detecting means 14, a torque detecting part abnormality detecting means 33 that detects abnormality of the steering torque detecting means 14 and a self-aligning torque estimating means 321 that estimates self-aligning torque transmitted from the road surface side to a steering mechanism, and has a second torque command value calculating means 32 that calculates a torque command value on the basis of the self-aligning torque estimated by the self-aligning torque estimating means 321, and an abnormal time switching means 34 that selects the second torque command value calculating means instead of the first torque command value calculating means when detecting abnormality of the steering torque detecting means by the torque detecting part abnormality detecting means 33. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides a torque command value calculating means for calculating a torque command value based on at least a steering torque, an electric motor for applying a steering assist force to a steering mechanism, and a motor control means for controlling the electric motor based on the torque command value. And an electric power steering apparatus.

2. Description of the Related Art Conventionally, an electric power steering apparatus that applies a steering assist force to a steering mechanism by driving an electric motor in accordance with a steering torque that a driver steers a steering wheel has become widespread as a steering apparatus.
In this type of electric power steering apparatus, as the vehicle to be mounted increases in size, the output of the electric power steering apparatus increases, the motor torque increases, and the increase in current increases.

As described above, when the output of the electric power steering device is increased, the steering torque at the time of manual steering with the electric power steering device stopped is increased, and the steering becomes difficult.
Conventionally, when an abnormality occurs in the steering torque sensor or the like, the electric power steering device is stopped to ensure safety. However, since steering torque becomes too large during manual steering, steering becomes difficult. Even when an abnormality occurs in the steering torque sensor or the like, it is desired to continue the generation of the steering assist force by controlling the driving of the electric motor.

For this reason, conventionally, when the steering torque sensor fails, the steering torque estimating means estimates the steering torque based on the vehicle speed signal and the steering angle signal, and controls the drive of the electric motor based on the estimated steering torque. Such an electric power steering device is known (see, for example, Patent Document 1).
Japanese Patent No. 3390333 (first page, FIG. 2)

  However, in the conventional example described in Patent Document 1, the steering torque is estimated based on the vehicle speed signal and the steering angle signal, and the drive control of the electric motor is performed based on the estimated steering torque. Steering torque cannot be recognized correctly by the steering torque, and the steering wheel is turned into the steering wheel without permission. As a result, an alarm lamp indicating an abnormality of the electric power steering device is turned on to give the driver a sense of anxiety, and thus there is an unsolved problem of giving the driver a greater sense of discomfort.

Moreover, since the reaction force from the road surface is not considered in the estimation of the steering torque, the torque cannot be estimated correctly if it is not considered in the torque estimation model such as a low road surface friction coefficient. There are unresolved issues.
Accordingly, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and provides an electric power steering device capable of continuing the generation of the steering assist force in consideration of the reaction force from the road surface. The purpose is to do.

  In order to achieve the above object, an electric power steering apparatus according to a first aspect of the present invention is based on steering torque detection means for detecting steering torque input to a steering mechanism, and at least steering torque detected by the steering torque detection means. A first torque command value calculating means for calculating a steering assist torque command value; an electric motor for generating a steering assist torque to be applied to the steering mechanism; and a motor control means for controlling the driving of the electric motor based on the current command value. An electric power steering apparatus comprising: a torque detection unit abnormality detecting unit that detects abnormality of the steering torque detecting unit; and a self-aligning unit that estimates a self-aligning torque transmitted from the road surface to the steering mechanism. Torque estimation means and a cell estimated by the self-aligning torque estimation means A second torque command value calculating means for calculating a torque command value based on the aligning torque; and when the abnormality of the steering torque detecting means is detected by the torque detector abnormality detecting means, the first torque command value An abnormality time switching means for selecting the second torque command value calculation means is provided instead of the calculation means.

  In the first aspect of the invention, the self-aligning torque estimating means estimates the self-aligning torque transmitted from the road surface to the steering mechanism, and the second torque command value calculating means is based on the estimated self-aligning torque. When the torque command value is calculated and the abnormality of the steering torque detection means is detected, the abnormality switching means stops the output of the torque detection value from the steering torque detection means, and the first torque command value calculation means Instead, by selecting the second torque command value calculation means, it is possible to obtain an accurate torque detection value in consideration of the self-aligning torque transmitted from the road surface.

According to a second aspect of the present invention, there is provided an electric power steering apparatus according to the first aspect of the present invention, further comprising a steering angle detecting means for detecting a steering angle of the steering mechanism, and the self-aligning torque estimating means The self-aligning torque is estimated based on the above-described configuration.
In the invention according to claim 2, since the self-aligning torque is estimated based on the steering angle, the self-aligning torque according to the steering state of the steering mechanism can be accurately detected.

  Furthermore, the electric power steering apparatus according to claim 3 is the invention according to claim 1 or 2, further comprising: a steering angle detection unit that detects a steering angle of the steer mechanism, and a vehicle speed detection unit that detects a vehicle speed of the vehicle. And the self-aligning torque estimating means is configured to estimate the self-aligning torque based on the steering angle and the vehicle speed.

The electric power steering apparatus according to claim 3 estimates the self-aligning torque on the basis of the steering angle and the vehicle speed in the invention according to claim 1, and therefore more accurate self-aligning in consideration of the running state of the vehicle. Torque can be estimated.
Furthermore, the electric power steering apparatus according to claim 4 is the invention according to claim 2 or 3, further comprising lateral force detecting means for detecting lateral force acting on a front wheel of the vehicle, and the self-aligning torque estimating means. Is configured to correct the self-aligning torque based on the lateral force.

In the invention according to claim 4, since the self-aligning torque is corrected based on the lateral force, a more accurate self-aligning torque can be estimated.
According to a fifth aspect of the present invention, there is provided the electric power steering apparatus according to any one of the second to fourth aspects, further comprising friction coefficient estimating means for estimating a friction coefficient between a road surface and a wheel, and the self-steering device. The aligning torque estimating means is configured to correct the self-aligning torque based on the friction coefficient.

In the invention according to claim 5, since the self-aligning torque is corrected based on the friction coefficient, the more accurate self-aligning torque can be estimated in consideration of the road surface condition.
Further, an electric power steering apparatus according to a sixth aspect of the invention according to the fifth aspect includes an anti-skid control means for controlling a braking force of the wheel when detecting a tendency of the wheel to lock during braking. The friction coefficient estimating means is configured to estimate the friction coefficient based on an operating state of the anti-skid control means.

In the invention according to claim 6, since the friction coefficient is estimated based on the operating state of the anti-skid control means, the friction coefficient can be estimated with high accuracy.
Further, an electric power steering apparatus according to a seventh aspect is the invention according to the fifth or sixth aspect, wherein the reference yaw rate estimating means for estimating the reference yaw rate of the vehicle according to the steering angle, and the actual yaw rate of the vehicle are detected. The friction coefficient estimating means is configured to estimate the friction coefficient based on a difference between the standard yaw rate and the actual yaw rate.

In the invention according to claim 7, since the friction coefficient is estimated based on the difference between the standard yaw rate and the actual yaw rate, the friction coefficient can be estimated with high accuracy.
Furthermore, an electric power steering apparatus according to an eighth aspect of the present invention is the invention according to any one of the second to seventh aspects, wherein the steering angle detecting means detects wheel speeds of left and right front wheels of the vehicle. The steering angle is detected on the basis of the wheel speed detected in (1).

In the invention according to claim 8, the steering angle is detected based on the left and right wheel speeds of the front wheels. Therefore, the steering mechanism is used in an antilock brake system or the like without providing a steering angle detecting means. Wheel speed detection means can be used, and the number of parts can be reduced.
Still further, an electric power steering apparatus according to a ninth aspect is the invention according to any one of the second to seventh aspects, wherein the steering angle detecting means detects wheel speeds of left and right front wheels of the vehicle. The steering angle is detected from the rudder angle and the relative rudder angle calculated on the basis of the wheel speed detected in step (b).

In the invention according to the ninth aspect, the steering angle is calculated based on the wheel speeds of the left and right front wheels of the vehicle, and the steering angle is detected from the calculated steering angle and the relative steering angle. Therefore, the steering angle is detected more accurately. be able to.
An electric power steering apparatus according to a tenth aspect is the invention according to any one of the first to ninth aspects, wherein the second torque command value calculation means is a self-estimation estimated by the self-aligning torque estimation means. A feature is that the torque command value is calculated by multiplying the aligning torque by a gain smaller than one.

  In the invention according to the tenth aspect, the torque command value is calculated by multiplying the self-aligning torque by a gain smaller than 1. Therefore, an optimum torque command value corresponding to the reaction force from the road surface can be calculated.

  According to the present invention, the second torque command value calculating means calculates the torque command value based on the self-aligning torque estimated by the self-aligning torque estimating means. When the vehicle is detected, it is possible to obtain an accurate torque detection value that takes into account the self-aligning torque transmitted from the road surface, and the steering assist control can be continued without giving the driver a sense of incongruity even after the failure of the steering torque detection means. The effect that it can do is acquired.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, where SM is a steering mechanism. This steering mechanism SM has a steering shaft 2 having an input shaft 2a to which a steering force applied from a driver is transmitted to the steering wheel 1 and an output shaft 2b connected to the input shaft 2a via a torsion bar (not shown). It has. The steering shaft 2 is rotatably mounted on the steering column 3, one end of the input shaft 2a is connected to the steering wheel 1, and the other end is connected to a torsion bar (not shown).

  The steering force transmitted to the output shaft 2b is transmitted to the intermediate shaft 5 via the universal joint 4 composed of the two yokes 4a and 4b and the cross connecting portion 4c for connecting them, It is transmitted to the pinion shaft 7 through a universal joint 6 composed of yokes 6a and 6b and a cross connecting portion 6c for connecting them. The steering force transmitted to the pinion shaft 7 is converted into a straight movement in the vehicle width direction by the steering gear mechanism 8 and transmitted to the left and right tie rods 9, and the steered wheels W are steered by these tie rods 9.

A steering assist mechanism 10 for transmitting a steering assist force to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2. The steering assist mechanism 10 includes a reduction gear 11 connected to the output shaft 2b, and an electric motor 12 composed of, for example, a brushless motor as an electric motor that generates a steering assist force connected to the reduction gear 11. .
Further, a steering torque sensor 14 as a steering torque detecting means is disposed in a housing 13 connected to the steering wheel 1 side of the reduction gear 11. The steering torque sensor 14 detects a steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a. For example, a torsion bar (not shown) in which the steering torque is interposed between the input shaft 2a and the output shaft 2b. The torsional angular displacement is converted into a non-contact magnetic sensor.

  The steering torque detection value T output from the steering torque sensor 14 is input to the controller 15 as shown in FIG. The controller 15 includes, in addition to the torque detection value T from the steering torque sensor 14, a vehicle speed Vs detected by the vehicle speed sensor 16, motor currents Iu to Iw flowing in the electric motor 12, a resolver, an encoder, and the like. The rotation angle θ of the electric motor 12 detected at 17 and the steering angle φ detected by the steering angle sensor 18 as a steering angle detection means for detecting the steering angle of the steering shaft 2 are also input, and the input torque detection value T and vehicle speed are input. A steering assist torque command value Iref is calculated as a current command value for causing the electric motor 12 to generate a steering assist force corresponding to the detected value V, and is calculated based on the rotation angle θ with respect to the calculated steering assist torque command value Iref. Two-phase / three-phase conversion after performing various compensation processes based on motor angular velocity ω and motor angular acceleration α and then converting to dq axis current command value Thus, the three-phase current command values Iuref to Iwref are calculated, and the drive current supplied to the electric motor 12 based on the three-phase current command values Iuref to Iwref and the motor currents Iu to Iw is subjected to feedback control processing, and the electric motor 12 Motor currents Iu, Iv and Iw for controlling the driving of the motor are output.

  That is, the controller 15 calculates the steering assist torque command value Iref as a current command value based on the steering torque T and the vehicle speed Vs, and the steering calculated by the torque command value calculator 21. A torque command value compensation unit 22 for compensating the auxiliary torque command value Iref, and a dq axis current command value is calculated based on the post-compensation steering assist torque command value Iref ′ compensated by the command value compensation unit 22. The dq-axis current command value calculating unit 23 calculates the three-phase current command values Iuref, Ivref and Iwref by performing two-phase / three-phase conversion on the dq-axis current command value, and the dq-axis current command value. A motor current is generated based on the current command values Iuref, Ivref, and Iwref output from the calculation unit 23 and the motor current detection values Iu, Iv, and Iw to generate an electric motor. And a motor current control unit 24 that drives and controls the 12.

  The steering assist torque command value calculation unit 21 calculates a first steering assist torque command value Iref1 based on the steering torque T input from the steering torque sensor 14 and the vehicle speed Vs input from the vehicle speed sensor 16. A second steering assist torque based on the steering angle φ input from the steering assist torque command value calculation unit 31, the steering angle sensor 18 that detects the steering angle φ of the steering shaft 2, and the vehicle speed Vs input from the vehicle speed sensor 16. A second steering assist torque command value calculation unit 32 for calculating the command value Iref2, a torque sensor abnormality detection unit 33 for detecting abnormality of the steering torque sensor 14, and an abnormality detection signal output from the torque sensor abnormality detection unit 33 An abnormal time-out for selecting either the first steering assist torque command value calculator 31 or the second steering assist torque command value calculator 32 based on A command value selector 34 as a replacement means is provided.

  The first steering assist torque command value calculation unit 31 refers to the steering assist torque command value calculation map shown in FIG. 3 based on the steering torque T and the vehicle speed Vs, and determines the steering assist torque command value Irefb that is a current command value. A torque command value calculation unit 311 to calculate, a phase compensation unit 312 that calculates a phase compensation value Irefb ′ by performing phase compensation of the steering assist torque command value Irefb output from the torque command value calculation unit 311, and a steering torque sensor Based on the steering torque T input from 14, the control responsiveness in the vicinity of the steering neutral is improved, and the steering torque T is differentially processed to ensure the stability in the assist characteristic dead zone so as to realize smooth and smooth steering. A center responsiveness improving unit 313 for calculating a center responsiveness improving command value Ir for compensating for static friction, and a phase compensating output and a center of the phase compensating unit 312. And an adder 314 for calculating a first steering assist torque command value Iref1 by adding the center response improving command value Ir of motor response improving unit 313.

  Here, the steering assist torque command value calculation map referred to by the torque command value calculation unit 311 takes the steering torque T on the horizontal axis and the steering assist torque command value Irefb on the vertical axis, as shown in FIG. It consists of a characteristic diagram represented by a parabolic curve with the vehicle speed Vs as a parameter, and the steering assist torque command value Irefb is "0" while the steering torque T is between "0" and the set value Ts1 in the vicinity thereof. When the steering torque T exceeds the set value Ts1, initially, the steering assist torque command value Irefb increases relatively slowly as the steering torque T increases. However, when the steering torque T further increases, Thus, the steering assist torque command value Irefb is set so as to increase steeply, and this characteristic curve is set so that the inclination becomes smaller as the vehicle speed increases.

  The second torque command value calculation unit 32 includes a self-aligning torque estimation unit 321 that estimates the self-aligning torque SAT based on the steering angle φ and the vehicle speed Vs from the steering angle sensor 18, and the self-aligning torque estimation unit. The amplifying unit 322 calculates the second steering assist torque command value Iref2 by amplifying the self-aligning torque SAT estimated at 321 with a gain less than “1”.

  Here, in the self-aligning torque estimation unit 321, the parameter is changed by the vehicle speed Vs input from the vehicle speed sensor 16 expressed by the following equation (1) based on the steering angle φ input from the steering angle sensor 18. By calculating using a self-aligning torque estimation model having a second-order transfer function Tsat, the self-aligning torque SAT input to the rack shaft of the steering gear mechanism 8 from the road surface is estimated.

Tsat = (c ₀ s ² + c ₁ s + c ₂ ) / (s ² + a ₁ s + a ₂ ) (1)
Here, a ₁ , a ₂ , c ₀ , c ₁ , and c ₂ are coefficients that are changed by the vehicle speed Vs.

  Specifically, as shown in FIG. 4, the self-aligning torque estimation model refers to a nominal value calculation map based on the steering angle φ, and calculates a nominal value SATn of the self-aligning torque. Unit 321a, gain calculation unit 321b that calculates vehicle speed gain Kv with reference to the vehicle speed gain calculation map based on vehicle speed Vs, nominal value SATn of self-aligning torque calculated by nominal value calculation unit 321a, and vehicle speed gain calculation A multiplier 321c that multiplies the vehicle speed gain Kv calculated by the unit 321b, and a primary low-pass filter 321d that performs low-pass filter processing on the multiplication output of the multiplier 321c.

  Here, as shown in FIG. 5, when the steering wheel 1 is in the neutral position (straight traveling position) and the steering angle φ is “0”, the nominal value calculation map shows that the nominal value SATn of the self-aligning torque is “ In this state, when the steering wheel 1 is turned to the right (or left) and the steering angle φ increases in the positive (or negative) direction, the nominal value SATn is substantially reduced as the steering angle φ increases. When it increases linearly in the positive direction (or negative direction) and reaches a predetermined steering angle φ1 (−φ1), the nominal value SATn reaches a positive (or negative) peak, and then the steering angle φ is positive (or negative). The characteristic curve L1 is set so that the nominal value SATn decreases in the positive direction (or negative direction) in accordance with the increase in the) direction.

  Further, as shown in FIG. 6, the vehicle speed gain calculation map shows that when the vehicle speed Vs is “0”, the vehicle speed gain Kv also becomes “0”, but when the vehicle speed Vs increases from “0”, the vehicle speed gain Kv increases abruptly. The characteristic curve L2 is set so as to increase and then gradually increase as the vehicle speed Vs increases.

  The torque sensor abnormality detection unit 33 receives the steering torque T detected by the steering torque sensor 14, and the steering torque T is set in advance when the steering torque T continues to remain unchanged for a predetermined time when the vehicle travels. The steering torque sensor abnormality detection condition such as when the state exceeding the abnormal set value due to the power fault has continued for a predetermined time or more, or when the steering torque T has continued below the abnormal threshold value due to the preset ground fault for a predetermined time or longer, etc. When satisfied, the abnormality detection signal Sa is set to a logical value “1”, for example, and when the steering torque sensor abnormality detection condition is not satisfied, the abnormality detection signal Sa is set to a logical value “0”.

  Further, the command value selection unit 34 calculates the first torque command value calculation unit 31 described above when the abnormality detection signal Sa output from the torque sensor abnormality detection unit 33 is a logical value “0”. When the steering assist torque command value Iref1 is selected and the abnormality detection signal Sa is the logical value “1”, the second steering assist torque command value Iref2 calculated by the second torque command value calculation unit 32 is used. The selected first torque command value Iref1 or second torque command value Iref2 is output to the adder 46 described later as the torque command value Iref.

  The command value compensation unit 22 differentiates the motor rotation angle θ detected by the rotation angle sensor 17 and the electric angle conversion unit 40 that converts the motor rotation angle θ detected by the rotation angle sensor 17 into the electric angle θe. An angular velocity calculator 41 that calculates an angular velocity ω, an angular acceleration calculator 42 that calculates a motor angular acceleration α by differentiating the motor angular velocity ω calculated by the angular velocity calculator 41, and a motor calculated by the angular velocity calculator 41. A convergence compensator 43 that compensates the convergence of the yaw rate based on the angular velocity ω and a torque equivalent generated by the inertia of the electric motor 12 based on the motor angular acceleration α calculated by the angular acceleration calculator 42 are compensated. And an inertia compensator 44 for preventing deterioration of inertia or control responsiveness.

  Here, the convergence compensation unit 43 receives the vehicle speed Vs detected by the vehicle speed sensor 16 and the motor angular velocity ω calculated by the angular velocity calculation unit 41, and the steering wheel 1 swings in order to improve the yaw convergence of the vehicle. A convergence convergence compensation value Ic is calculated by multiplying the motor angular velocity ω by a convergence control gain Kc that is changed according to the vehicle speed Vs so as to apply a brake to the turning operation.

  Then, the inertia compensation value Ii calculated by the inertia compensation unit 44 and the convergence compensation value Ic calculated by the convergence compensation unit 43 are added by the adder 45 to calculate the command compensation value Icom, and this command compensation value Icom is added to the steering assist torque command value Iref output from the steering assist torque command value calculation unit 21 by the adder 46 to calculate a compensated steering assist torque command value Iref ′, and this compensated steering assist torque command value Iref is calculated. 'Is output to the dq-axis current command value calculation unit 23.

  Further, the dq-axis current command value calculation unit 23 calculates a d-axis current command value Idref based on the compensated steering assist torque command value Iref ′ and the motor angular velocity ω, Based on the electrical angle θe output from the electrical angle conversion unit 40 and the motor angular velocity ω output from the angular velocity calculation unit 41, a dq EMF component ed (θ) of a dq axis induced voltage model EMF (Electro Magnetic Force) and Induced voltage model calculation unit 52 for calculating q-axis EMF component eq (θ), d-axis EMF component ed (θ), q-axis EMF component eq (θ) and d-axis output from this induced voltage model calculation unit 52 A q-axis current command value Iqref is calculated based on the d-axis current command value Idref output from the current command value calculation unit 51, the post-compensation steering assist torque command value Iref ′, and the motor angular velocity ω. Q-axis current command value calculation unit 53, d-axis current command value Idref output from d-axis current command value calculation unit 51, and q-axis current command value Iqref output from q-axis current command value calculation unit 53. And a two-phase / three-phase converter 54 for converting into three-phase current command values Iuref, Ivref and Iwref.

  The motor current control unit 24 includes a motor current detection unit 60 that detects motor currents Iu, Iv, and Iw supplied to the phase coils Lu, Lv, and Lw of the electric motor 12, and a dq-axis current command value calculation unit 23. The motor currents Iu, Iv, and Iw detected by the motor current detector 60 are individually subtracted from the current command values Iuref, Ivref, and Iwref that are input from the two-phase / three-phase converter 54 of each phase, and current deviations ΔIu, ΔIv for each phase And subtractors 61u, 61v, and 61w for calculating ΔIw, and a PI current control unit 62 for calculating voltage command values Vu, Vv, and Vw by performing proportional integral control on the obtained phase current deviations ΔIu, ΔIv, and ΔIw. It has.

  The motor current control unit 24 receives the voltage command values Vu, Vv, and Vw output from the PI current control unit 62, performs a duty calculation based on the voltage command values Vu, Vv, and Vw, and performs an electric motor. The pulse width modulation unit 63 that calculates the duty ratio of each phase of 12 and forms an inverter control signal composed of a pulse width modulation (PWM) signal, and 3 based on the inverter control signal output from the pulse width modulation unit 63 And an inverter 64 that generates phase motor currents Ia, Ib, and Ic and outputs them to the electric motor 12.

Next, the operation of the above embodiment will be described.
Assuming that the steering torque sensor 14 is in a normal state, the steering torque T detected by the steering torque sensor 14 in the torque sensor abnormality detection unit 33 provided in the torque command value calculation unit 21 satisfies the torque sensor abnormality detection condition. By not doing so, an abnormality detection signal Sa having a logical value “0” is output to the command value selector 34. Therefore, the first steering assist torque command value calculator 31 is selected by the command value selector 34, and the first steering assist torque command value Iref1 output from the first steering assist torque command value calculator 31 is selected. Is output to the adder 46 as the steering assist torque command value Iref.

  At this time, it is assumed that the vehicle is stopped with the steering wheel 1 in a neutral position in a straight traveling state. When the steering wheel 1 is not being steered in this state, the steering torque T detected by the steering torque sensor 14 is “0”, and the vehicle speed Vs is also “0”. When the torque command value calculation unit 311 of the value calculation unit 31 refers to the steering assist torque command value calculation map based on the steering torque T and the vehicle speed Vs, the steering assist torque command value Irefb becomes “0”, and the first steering The auxiliary torque command value Iref1 is also “0”.

  At this time, since the electric motor 12 is also stopped, the motor angular velocity ω calculated by the angular velocity calculating unit 41 of the command value compensating unit 22 and the motor angular acceleration α calculated by the angular acceleration calculating unit 42 are both “0”. Since the convergence compensation value Ic calculated by the convergence compensation unit 43 and the inertia compensation value Ii calculated by the inertia compensation unit 44 are both “0”, the command compensation value Icom is also “0”. The post-compensation steering assist torque command value Iref ′ output from 46 is also “0”.

  For this reason, the three-phase current command values Iuref, Ivref, and Iwref calculated by the dq-axis current command value calculation unit 23 are also zero, and the electric motor 12 is stopped, so that it is detected by the motor current detection unit 60. Since the motor currents Iu, Iv, and Iw are also “0”, the current deviations ΔIu, ΔIv, and ΔIw that are output from the subtractors 61u, 61v, and 61w are also “0”, and thus are output from the PI current control unit 62. The voltage command values Vu, Vv and Vw are also “0”, the output of the inverter control signal from the pulse width modulation unit 63 is stopped, and the inverter 64 is stopped, so that the motor current Iu supplied to the electric motor 12 Iv and Iw continue to be “0”, and the electric motor 12 continues to be stopped.

  When the vehicle is stopped and the steering wheel 1 is steered to perform a so-called stationary operation, the steering torque T detected by the steering torque sensor 14 becomes a relatively large value in response to this, so that the first steering is performed. The steering assist torque command value Iref1 calculated by the assist torque command value calculation unit 31 increases rapidly according to the steering torque T.

  Even in this state, since the electric motor 12 is stopped, the motor angular velocity ω and the motor angular acceleration α also continue to be “0”, and the convergence compensation value Ic calculated by the convergence compensation unit 43 of the command value compensation unit 22 and The inertia compensation value Ii calculated by the inertia compensation unit 44 is also maintained at “0”, and the command compensation value Icom is also “0”.

  Therefore, the steering assist torque command value Iref is supplied as it is from the adder 36 to the dq axis current command value calculation unit 23, and the dq axis current command value calculation unit 23 responds to the steering assist torque command value Iref. Three-phase current command values Iuref, Ivref and Iwref are output to the motor current control unit 24.

  Accordingly, the three-phase current command values Iuref, Ivbref, and Iwref are output as they are as current deviations ΔIu, ΔIv, and ΔIw from the subtractors 61u, 61v, and 61w, and the voltage command values Vu, Vv after the PI control is performed by the current control unit 62. And Vw and supplied to the pulse width modulation unit 63, an inverter control signal is output from the pulse width modulation unit 63, and this is supplied to the inverter 64, whereby the three-phase motor current is output from the inverter 64. Ia, Ib, and Ic are output, the electric motor 12 is rotationally driven, and a steering assist force corresponding to the steering torque T is generated.

  The steering assist force generated by the electric motor 12 is transmitted to the steering shaft 2 to which the steering force from the steering wheel 1 is transmitted via the speed reduction mechanism 11, whereby the steering force and the steering assist force are transmitted to the steering gear mechanism. 8 is converted into a linear motion in the vehicle width direction, and the left and right steered wheels W are steered via the tie rods 9, and the steered wheels W can be steered with light steering torque.

  When the electric motor 12 is driven and controlled, the motor angular acceleration ω calculated by the angular velocity calculating unit 41 of the command value compensating unit 22 and the motor angular acceleration α increased by the angular acceleration calculating unit, whereby the command value compensating unit 22, the convergence compensation value Ic and the inertia compensation value Ii are calculated, and these are added to calculate the command compensation value Icom, which is supplied to the adder 46, whereby the command compensation value is added to the steering assist torque command value Iref. Icom is added to calculate a post-compensation steering assist torque command value Iref ′, so that command value compensation processing is performed, and the center responsiveness improvement unit 313 of the first steering assist torque command value calculation unit 31 The steering torque T is subjected to differential calculation processing to ensure stability in the assist characteristic dead zone and to compensate for static friction, and the phase compensation unit 312 performs the first steering assist torque command value I. Phase compensation is performed on ref1.

  When the vehicle is started, the steering assist torque calculated by the torque command value calculation unit 311 in the first steering assist torque command value calculation unit 31 according to the increase in the vehicle speed Vs detected by the vehicle speed sensor 16. As the command value Irefb decreases, the optimum steering assist torque command value Iref1 corresponding to the vehicle running state is set, and the optimum steering assistance control corresponding to the vehicle running state is performed.

  However, when the steering torque sensor 14 is in an abnormal state while the vehicle is running and the steering torque T satisfies the steering torque sensor abnormality detection condition in the torque sensor abnormality detection unit 33, the torque sensor abnormality detection unit. When the abnormality detection signal Sa having the logical value “1” is output from 33 to the command value selection unit 34, the command value selection unit 34 replaces the first steering assist torque command value calculation unit 31 described above with a second value. The steering assist torque command value calculation unit 32 is selected.

  Therefore, the nominal value calculation unit 321a of the self-aligning torque estimation unit 321 refers to the nominal value calculation map of FIG. 5 based on the steering angle φ, and the self input to the rack shaft of the steering gear mechanism 8 from the road surface. The nominal value SATn of the aligning torque is calculated, and the vehicle speed gain Kv is calculated by the vehicle speed gain calculation unit 321b with reference to the vehicle speed gain calculation map shown in FIG. 6 based on the vehicle speed Vs. Then, the nominal value SATn of the calculated self-aligning torque and the vehicle speed gain Kv are multiplied by the multiplier 321c, and the multiplication output of the multiplier 321c is low-pass filtered by the low-pass filter 321d, whereby the self-aligning torque is obtained. The SAT is estimated, and the second steering assist torque command value Iref2 is calculated by multiplying the self-aligning torque SAT by a gain K less than “1” by the amplifying unit 322.

  At this time, since the vehicle speed Vs detected by the vehicle speed sensor 16 is “0” when the vehicle is stopped, the vehicle speed gain Kv calculated by the vehicle speed gain calculation unit 321b is “0”. Even if the nominal value SATn of the self-aligning torque calculated by the value calculating unit 321a is a relatively large value, the output of the multiplier 321c is “0”, and the self-aligning torque SAT output from the low-pass filter 321d is also The second steering assist torque command value Iref2 output from the amplifying unit 322 becomes “0”. For this reason, in the stationary state when the vehicle is stopped, even if the driver steers the steering wheel 1, the electric motor 12 remains in the stopped state, and the steering assist force cannot be generated.

  However, when the steering wheel 1 is steered in a state where the vehicle is in a starting state, the vehicle speed gain Kv calculated by the vehicle speed gain calculating unit 321b is not increased even if the vehicle speed Vs is slightly increased due to the start of the vehicle. As the road surface frictional force acting on the steered wheels W decreases rapidly, the steering wheel 1 can be steered, and the steering detected by the steering angle sensor 18 by steering the steering wheel 1. When the angle φ increases, for example, in the positive direction from the neutral position, a nominal value SATn of the positive self-aligning torque corresponding to the steering angle φ is output from the nominal value calculation unit 321a accordingly, and a vehicle speed gain calculation unit 321b is output thereto. Is multiplied by a multiplier 321c, and the multiplication output is obtained by a low-pass filter 321d. By performing the low bus process, it is possible to accurately estimate the self-aligning torque SAT input from the road surface to the rack shaft of the steering gear mechanism 8 when the vehicle is traveling.

  Then, the estimated self-aligning torque SAT is amplified by the amplifying unit 322, thereby calculating a second steering assist torque command value Iref2 in consideration of the self-aligning torque SAT, and this is transmitted via the command value selecting unit 34. Therefore, the compensated steering assist torque command value Iref ′ obtained by adding the command compensation value Icom by the adder 46 is supplied to the dq axis current command value calculation unit 23, and this dq By supplying the three-phase current command values Iuref, Ivref and Iwref calculated by the shaft current command value calculation unit 23 to the motor current control unit 24, the motor current control unit 24 detects the motor detected by the motor current detection unit 60. By performing feedback control based on the currents Iu, Iv, and Iw, the motor currents Ia, Ib, and Ic are changed to the electric motor 12. Supplying to, to generate steering assist force in consideration of the self aligning torque SAT by the electric motor 12, it is possible to continue the steering assist control.

  As described above, according to the above embodiment, when the steering torque sensor 14 is in an abnormal state, the self-aligning torque estimation unit 321 estimates the reaction force from the road surface, and the second force required according to the reaction force. Since the steering assist torque command value Iref2 is calculated and the electric motor 12 is driven and controlled based on the second steering assist torque command value Iref2, the steering assist force corresponding to the reaction force from the road surface is generated by the electric motor 12. The steering assist control necessary for steering can be continued even after the steering torque sensor 14 becomes abnormal. Therefore, since the reaction force from the road surface is taken into account, even when traveling on a rainy road, a frozen road, a snowy road, etc. with a low road surface friction coefficient, an optimal steering assist force is generated according to the change in the steering angle φ. be able to.

In the above-described embodiment, the case where the steering angle φ when the steering wheel 1 is steered is detected by the steering angle sensor 18 is not limited to this, but is not limited thereto, and an anti-lock brake system or a traction control system. The steering angle φ may be detected using the wheel speeds V _FL and V _FR of a wheel speed sensor that detects the wheel speeds of the left and right front wheels used in the above.

That is, the steering angle φ is calculated by detecting the wheel speeds V _FL and V _FR of the left and right front wheels of the vehicle, and performing the calculation of the following equation (2) based on the front wheel speeds V _FL and V _FR. May be.
sin (2φ) = k _F (V _FL −V _FR ) / (V _FL + V _FR ) (2)
Here, k _F is a constant.

Thus, when the steering angle φ is calculated based on the wheel speeds V _FL and V _FR , it is not necessary to provide the steering angle sensor 18 as in the above-described embodiment, and the wheel speed used in other control systems is not necessary. Since the sensor can be used, an increase in the number of parts can be suppressed and the cost can be reduced. Further, the steering angle φ can be obtained by adding the rotation angle θ of the motor detected by the rotation angle sensor 17 as a relative steering angle to the steering angle φ estimated from the wheel speed.

  In the above embodiment, the case where the self-aligning torque estimator 321 estimates the self-aligning torque SAT based on the steering angle φ and the vehicle speed Vs has been described. However, the present invention is not limited to this. The self-aligning torque SAT may be estimated based only on the angle φ.

  Further, in the above embodiment, the case where the vehicle speed gain Kv is set to be “0” when the vehicle speed Vs is “0” has been described, but the present invention is not limited to this, and the vehicle speed Vs is “ When the vehicle speed gain Kv is fixed to a predetermined value, the steering angular velocity ωφ obtained by differentiating the steering angle φ is calculated, the angular velocity gain Kω corresponding to the steering angular velocity ωφ is set, and the vehicle speed gain Kv and The gain may be set by multiplying by the angular velocity gain Kω. In this case, the value obtained by multiplying the vehicle speed gain Kv and the steering angular velocity gain Kω is set to a value that generates a torque command value about immediately before the steered wheels W are steered when the vehicle is stopped. It becomes possible to stand up with a light steering force.

  Similarly, the steering torque sensor 14 is in an abnormal state by setting the steering angular velocity gain Kω and calculating the second steering assist torque command value Iref2 corresponding to the steering angular velocity ωφ even when the vehicle is traveling. Even in such a state, it is possible to continue the optimal steering assist control according to the steering state of the steering wheel 1.

  Furthermore, in the above-described embodiment, the case where the dq-axis current command value calculation unit 23 is provided with the two-phase / three-phase conversion unit 54 has been described. The conversion unit 54 is omitted, and a three-phase / two-phase conversion unit is provided on the output side of the motor current detection unit 60 instead of the conversion unit 54 to convert the d-axis current Id and the q-axis current Iq, and the two subtraction units perform d-axis The deviation between the current command value Idref and the q-axis current command value Iqref and the d-axis current Id and the q-axis current Iq of the motor may be calculated.

  Furthermore, in the above-described embodiment, the case where the controller 15 is configured by hardware has been described. However, the present invention is not limited to this, and the steering assist torque command value calculation unit 21, command value compensation is applied by applying a microcomputer. The functions of the subtractor 61u to 61w, the PI current control unit 62, and the pulse width modulation unit 63 of the unit 22, the dq axis current command value calculation unit 23, and the motor current control unit 24 can be processed by software. In this case, the microcomputer may execute the steering torque sensor abnormality detection process shown in FIG. 7 and the steering assist control process shown in FIG.

  Here, as shown in FIG. 7, the steering torque sensor abnormality detection process is executed as a timer interruption process every predetermined time (for example, 1 msec). First, the steering torque T detected by the steering torque sensor 14 in step S1. Then, the process proceeds to step S2, where it is determined whether or not the read steering torque T satisfies the torque sensor abnormality detection condition set in the torque sensor abnormality detection unit 33, and the torque sensor abnormality detection condition is determined. Is satisfied, the steering torque sensor 14 is determined to be normal, the process proceeds to step S3, and the torque sensor abnormality flag Fa is reset to “0” indicating that the steering torque sensor 14 is normal. When the timer interrupt process is completed and the torque sensor abnormality detection condition is satisfied, it is determined that the steering torque sensor 14 is abnormal, and step S Migrated, the torque sensor malfunction flag Fa steering torque sensor 14 is completed timer interrupt processing is set to "1" indicating that it is an abnormal.

  Further, as shown in FIG. 8, the steering assist control process is executed as a timer interrupt process every predetermined time (for example, 1 msec). First, in step S11, the steering torque sensor 14, the vehicle speed sensor 16, and the rotation angle sensor 17 are executed. Then, the detection values of various sensors such as the steering angle sensor 18 and the motor current detection unit 60 are read, and then the process proceeds to step S12, where the sensor abnormality flag Fa set in the torque sensor abnormality detection process of FIG. It is determined whether or not it is set, and when the sensor abnormality flag Fa is reset to “0”, the process proceeds to step S13. In step S13, the steering assist torque command value Irefb is calculated based on the steering torque T with reference to the steering assist torque command value calculation map shown in FIG. 3, and then the process proceeds to step S14.

  In step S14, a phase compensation process is performed on the calculated steering assist torque command value Irefb to calculate a post-phase compensation steering assist torque command value Irefb '. Then, the process proceeds to step S15 to differentiate the steering torque T. The center responsiveness improvement command value Ir is calculated, and then the process proceeds to step S15, where the center responsiveness improvement command value Ir is added to the phase-compensated steering assist torque command value Irefb 'to obtain the first steering assist torque command value. Iref1 (= Irefb ′ + Ir) is calculated and updated as a steering assist torque command value Iref in a torque command value storage area of a storage device such as a RAM, and then the process proceeds to step S22 described later.

  On the other hand, when the determination result of step S11 indicates that the sensor abnormality flag Fa is set to “1”, it is determined that the steering torque sensor 14 is abnormal, and the process proceeds to step S17, where the steering angle φ is determined. The self-aligning torque nominal value SATn is calculated with reference to the above-described nominal value calculation map of FIG. 5, and then the process proceeds to step S18 to refer to the above-described vehicle speed gain calculation map of FIG. 6 based on the vehicle speed Vs. Then, the vehicle speed gain Kv is calculated, and then the process proceeds to step S19 where the nominal value SATn of the self-aligning torque is multiplied by the vehicle speed gain Kv, and the process proceeds to step S20 where the multiplied value Kv × SATn is low-pass filtered. After calculating the self-aligning torque SAT, the process proceeds to step S21.

In this step S21, the self-aligning torque SAT is gain K less than “1”.
The second steering assist torque command value Iref2 is calculated, and this is updated and stored in the torque command value storage area of the storage device such as the RAM described above as the steering assist torque command value Iref.
In step S22, the motor rotational angle θ is differentiated to calculate the motor angular velocity ω, then the process proceeds to step S23, the motor angular speed ω is differentiated to calculate the motor angular acceleration α, and then the process proceeds to step S24. Then, similarly to the convergence compensation unit 43, the motor angular speed ω is multiplied by the compensation coefficient Kc set according to the vehicle speed Vs to calculate the convergence compensation value Ic, and then the process proceeds to step S25.

  In step S25, similar to the inertia compensation unit 44, the inertia compensation value Ii is calculated based on the motor angular acceleration α, and then the process proceeds to step S26 and stored in the torque command value storage area of a storage device such as a RAM. Then, the post-compensation steering assist torque command value Iref ′ is calculated by adding the convergence compensation value Ic and the inertia compensation value Ii calculated in steps S24 and S25 to the steering assist torque command value Iref, and then the process proceeds to step S27.

  In this step S27, a dq-axis current command value calculation process similar to that of the dq-axis current command value calculation unit 23 is performed on the calculated post-compensation steering assist torque command value Iref ′, and the d-axis current command value Idref and The q-axis current command value Iqref is calculated, and then the process proceeds to step S28 to perform a two-phase / three-phase conversion process to calculate motor current command values Iuref to Iwref.

  Next, the process proceeds to step S29, where the motor currents Iu to Iw are subtracted from the motor current command values Iuref to Iwref to calculate the current deviations ΔIu to ΔIw, and then the process proceeds to step S30, where PI for the current deviations ΔIu to ΔIw. Control processing is performed to calculate voltage command values Vu to Vw, and then the process proceeds to step S31 to perform pulse width modulation processing based on the calculated voltage command values Vu to Vw to form an inverter gate signal, and then to step S32 Then, after the formed inverter gate signal is output to the inverter 64, the steering assist control process is terminated and the process returns to the predetermined main program.

  The process of FIG. 7 corresponds to the torque detection unit abnormality detection means. In the process of FIG. 8, the process of step S12 corresponds to the abnormal time switching means, and the processes of steps S13 to S16 are the first torque command value calculation means. The processing of steps S17 to S21 corresponds to the second torque command value calculation means, and the processing of steps S22 to S30 corresponds to the motor control means.

  As described above, when the torque sensor abnormality detection process of FIG. 7 and the steering assist control process of FIG. 8 are executed by the microcomputer, the steering of FIG. 8 is performed when the steering torque sensor 14 is normal as in the above-described embodiment. Steps S13 to S16 in the auxiliary control process are executed to calculate the first steering assist torque command value Iref1, and when the steering torque sensor 14 is abnormal, steps S17 to S21 in the steering assist control process of FIG. By executing the processing and calculating the second steering assist torque command value Iref2, the self-aligning torque SAT, which is the reaction force from the road surface input to the rack shaft of the steering gear mechanism 8, is estimated, and the estimated self A second steering assist torque command value Ire is obtained by multiplying the aligning torque SAT by a gain K less than “1”. 2 is calculated. For this reason, when the steering torque sensor 14 is normal, the electric motor 12 is driven and controlled based on the first steering assist torque command value Iref1 to perform accurate steering assist control. If it has occurred, the self-aligning torque SAT is estimated based on the steering angle φ and the vehicle speed Vs, and the estimated self-aligning torque SAT is multiplied by a gain K less than “1” to obtain a second steering assist torque command. Since the value Iref2 is calculated, even when the steering torque sensor 14 changes from a normal state to an abnormal state, optimal steering assist control in consideration of the road surface reaction force is performed based on the second steering assist torque command value Iref2. You can do this if you continue.

  In the above embodiment, the case where the present invention is applied to a brushless motor has been described. However, the present invention is not limited to this, and when applied to a motor with a brush, as shown in FIG. Based on the motor current detection value Im output from the motor current detection unit 60 and the motor terminal voltage Vm output from the terminal voltage detection unit 70 in the unit 41, the calculation of the following equation (4) is performed to calculate the motor angular velocity ω. At the same time, the dq-axis current command value calculation unit 23 is omitted, and the compensated steering assist torque command value Iref ′ is directly supplied to the motor current control unit 24. Further, the motor current control unit 24 is divided into one subtraction unit 61, What is necessary is just to comprise with the PI current control part 62, and also to change the inverter 64 into the H bridge circuit 71.

ω = (Vm−Im · Rm) / K ₀ (4)
Here, Rm is the motor winding resistance, and K ₀ is the electromotive force constant of the motor.

  Further, in the above-described embodiment, the self-aligning torque SAT is estimated based on the steering angle φ and the vehicle speed Vs. The self-aligning torque estimator 321 applies this self-aligning torque SAT to the front wheels. You may make it correct | amend based on the lateral force Fy to perform, and the friction coefficient (mu) between a road surface and a wheel.

  First, as shown in FIG. 10, a lateral force Fy acting on the front wheel of the vehicle may be input from the lateral force sensor 19, and the self-aligning torque SAT may be corrected based on the lateral force Fy. That is, as the lateral force Fy increases, the nominal value calculation unit 321a corrects the nominal value SATn of the self-aligning torque, or the amplification unit 322 corrects the gain for amplifying the self-aligning torque SAT. The self-aligning torque SAT is increased. Thereby, the self-aligning torque SAT can be estimated more accurately.

  In addition, as shown in FIG. 11, a friction coefficient μ between the road surface and the wheel (tire) may be input, and the self-aligning torque SAT may be corrected based on the friction coefficient μ. That is, the nominal value calculation unit 321a corrects the nominal value SATn of the self-aligning torque, or the amplification unit 322 corrects the gain for amplifying the self-aligning torque SAT, so that the friction coefficient μ increases. The nominal value SATn of the self-aligning torque is increased. Thereby, the self-aligning torque SAT can be estimated more accurately in consideration of the road surface condition.

  The friction coefficient μ is estimated from the operating state of an ABS device (anti-skid control device) that controls the braking force of the wheel when a tendency to lock the wheel during braking is detected, or the ABS device estimates the friction coefficient μ. In the case of the configuration, the estimated friction coefficient μ may be read. That is, it is estimated that the friction coefficient μ between the road surface and the wheel is smaller as the braking force at the time of detecting the locking tendency is smaller or the wheel deceleration at that time is larger. As a result, the friction coefficient μ can be estimated with high accuracy, and as a result, the self-aligning torque SAT can be estimated more accurately.

Further, the standard yaw rate γ _{M of the} vehicle is estimated according to the steering angle φ, the actual yaw rate γ _{R of the} vehicle is detected by the yaw rate sensor, and friction is performed based on the difference Δγ between the standard yaw rate γ _M and the actual yaw rate γ _R. The coefficient μ may be estimated. That is, it is estimated that the smaller the difference Δγ between the reference yaw rate γ _M and the actual yaw rate γ _R is, the larger the friction coefficient μ between the road surface and the wheel is. As a result, the friction coefficient μ can be estimated with high accuracy, and as a result, the self-aligning torque SAT can be estimated more accurately.

  In addition, the friction coefficient μ between the road surface and the wheel may be estimated based on the steering angle, the yaw rate, the lateral acceleration, the vehicle speed, and the like.

1 is a diagram illustrating a schematic configuration of an electric power steering apparatus according to a first embodiment of the present invention. It is a block diagram which shows the specific example of the controller which concerns on this invention. It is a characteristic diagram which shows the steering assist torque command value calculation map which shows the relationship with the steering assist torque command value which uses vehicle speed as a parameter. It is a block diagram which shows the specific structure of a self aligning torque estimation part. FIG. 6 is a characteristic diagram showing a nominal value calculation map representing a relationship between a steering angle and a nominal value of self-aligning torque. It is a characteristic diagram which shows the vehicle speed gain calculation map showing the relationship between a vehicle speed and a vehicle speed gain. It is a flowchart which shows an example of the torque sensor abnormality detection process procedure performed with a microcomputer. It is a flowchart which shows an example of the steering assistance control processing procedure performed with a microcomputer. It is a block diagram which shows embodiment at the time of applying the motor with a brush to this invention. It is a block diagram which shows embodiment in the case of correct | amending self-aligning torque based on a lateral force. It is a block diagram which shows embodiment in the case of correct | amending self-aligning torque based on a friction coefficient.

Explanation of symbols

  SM ... steering mechanism, 1 ... steering wheel, 2 ... steering shaft, 2a ... input shaft, 2b ... output shaft, 3 ... steering column, 4, 6 ... universal joint, 5 ... intermediate shaft, 8 ... steering gear mechanism, 9 ... Tie rod, W ... steered wheel, 10 ... steering assist mechanism, 11 ... reduction gear, 12 ... electric motor, 14 ... steering torque sensor, 15 ... controller, 16 ... vehicle speed sensor, 17 ... rotation angle sensor, 18 ... steering angle sensor, DESCRIPTION OF SYMBOLS 21 ... Steering assist torque command value calculating part, 22 ... Command value compensation part, 23 ... dq-axis current command value calculating part, 24 ... Motor current control part, 31 ... 1st steering assist torque command value calculating part, 311 ... torque command value calculation unit, 312 ... phase compensation unit, 313 ... center response improvement unit, 314 ... adder, 32 ... second steering assist torque command value calculation 33 ... Torque sensor abnormality detection unit, 34 ... Command value selection unit, 321 ... Self-aligning torque estimation unit, 322 ... Amplification unit, 41 ... Angular velocity calculation unit, 42 ... Angular acceleration calculation unit, 43 ... Convergence compensation unit, 44 ... inertia compensation unit, 45, 46 ... adder, 60 ... motor current detection unit, 61u to 61w ... subtraction unit, 62 ... PI current control unit, 63 ... pulse width modulation unit, 64 ... inverter

Claims (10)

Steering torque detection means for detecting a steering torque input to the steering mechanism; first torque command value calculation means for calculating a steering assist torque command value based on at least the steering torque detected by the steering torque detection means; An electric power steering apparatus comprising: an electric motor that generates a steering assist torque to be applied to a steering mechanism; and a motor control unit that drives and controls the electric motor based on the current command value.
Torque detection unit abnormality detection means for detecting abnormality of the steering torque detection means, self-aligning torque estimation means for estimating self-aligning torque transmitted from the road surface side to the steering mechanism, and self-aligning torque estimation means When the abnormality of the steering torque detecting means is detected by the second torque command value calculating means for calculating the torque command value on the basis of the self-aligning torque estimated in step 1 and the torque detecting portion abnormality detecting means, An electric power steering apparatus comprising: an abnormality switching unit that selects the second torque command value calculation means instead of the torque command value calculation means. Steering angle detection means for detecting the steering angle of the steering mechanism;
The electric power steering apparatus according to claim 1, wherein the self-aligning torque estimating unit is configured to estimate a self-aligning torque based on the steering angle. Steering angle detection means for detecting the steering angle of the steer mechanism, and vehicle speed detection means for detecting the vehicle speed of the vehicle,
The electric power steering apparatus according to claim 1, wherein the self-aligning torque estimating means is configured to estimate a self-aligning torque based on the steering angle and the vehicle speed. Lateral force detection means for detecting lateral force acting on the front wheels of the vehicle;
The electric power steering apparatus according to claim 2 or 3, wherein the self-aligning torque estimating means is configured to correct the self-aligning torque based on the lateral force. A friction coefficient estimating means for estimating a friction coefficient between the road surface and the wheel;
5. The electric power steering apparatus according to claim 2, wherein the self-aligning torque estimating unit is configured to correct the self-aligning torque based on the friction coefficient. 6. . Having anti-skid control means for controlling the braking force of the wheel when detecting the tendency of the wheel to lock during braking,
6. The electric power steering apparatus according to claim 5, wherein the friction coefficient estimating means is configured to estimate the friction coefficient based on an operating state of the anti-skid control means. A standard yaw rate estimation unit that estimates a standard yaw rate of the vehicle according to the steering angle; and an actual yaw rate detection unit that detects an actual yaw rate of the vehicle;
The electric power steering apparatus according to claim 5 or 6, wherein the friction coefficient estimating means is configured to estimate the friction coefficient based on a difference between the reference yaw rate and the actual yaw rate.   8. The steering angle detecting means is configured to detect a steering angle based on a wheel speed detected by a wheel speed detecting means for detecting a wheel speed of left and right front wheels of the vehicle. The electric power steering device according to any one of the above.   The steering angle detection means is configured to detect a steering angle from a steering angle and a relative steering angle calculated based on a wheel speed detected by a wheel speed detection means for detecting a wheel speed of the left and right front wheels of the vehicle. The electric power steering apparatus according to any one of claims 2 to 7, wherein the electric power steering apparatus is provided.   The second torque command value calculating means is configured to calculate a torque command value by multiplying the self-aligning torque estimated by the self-aligning torque estimating means by a gain smaller than 1. The electric power steering apparatus according to any one of claims 1 to 9.

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