JP5272905B2 - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of accurately estimating a steering torque in consideration of a reaction force from a road surface. <P>SOLUTION: The electric power steering device comprises a first torque command value calculating means 31 for calculating a first torque command value based on the steering torque detected by a steering torque detecting means 14, a torque detecting part abnormality detecting means 33 for detecting the abnormality of the steering torque detecting means 14, and a self-aligning torque estimating means 321 for estimating a self-aligning torque transmitted from the road surface side to a steering mechanism based on a wheel rotation speed. The electric power steering device is equipped with a second torque command value calculating means 32 for calculating the torque command value based on the self-aligning torque estimated by the self-aligning torque estimating means 321, and an abnormal time switching means 34 which 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)2010,JPO&amp;INPIT

Description

  The present invention relates to a torque command value calculating means for calculating a torque command value based on at least a steering torque, an electric motor for generating a steering assist force applied to a steering mechanism, and a motor for controlling the electric motor based on the torque command value. The present invention relates to an electric power steering apparatus including a control unit.

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 required for manual steering with the electric power steering device stopped is increased, and 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, but the steering torque necessary for manual steering becomes too large and steering becomes difficult. Therefore, it is desired to continue the generation of the steering assist force by controlling the driving of the electric motor even when an abnormality occurs in the steering torque sensor or the like.

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 correctly estimated if the torque estimation model such as a road surface with a low road surface friction coefficient is not considered. There is an unresolved issue.
Accordingly, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and an electric power steering capable of continuing the generation of the steering assist force in consideration of the reaction force actually generated from the road surface. The object is to provide a device.

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. First torque command value calculating means for calculating a first torque command value, an electric motor for generating a steering assist torque to be applied to the steering mechanism, and motor control for driving and controlling the electric motor based on the torque command value An electric power steering device comprising means,
Torque detection unit abnormality detection means for detecting abnormality of the torque detection means, wheel rotation speed detection means for detecting wheel rotation speed of the vehicle, and second rotation based on the wheel rotation speed detected by the wheel rotation speed detection means When an abnormality of the torque detection means is detected by a second torque command value calculation means for calculating a torque command value and the torque detection unit abnormality detection means, the first torque command value calculation means is replaced with the first torque command value calculation means. An abnormal time switching means for selecting a second torque command value calculation means and outputting a second torque command value to the motor control means , wherein the second torque command value calculation means determines the wheel rotation speed. Based on the self-aligning torque estimating means for estimating the self-aligning torque transmitted from the road surface side to the steering mechanism, and the self-aligning torque estimating means Gain adjusting means for calculating the second torque command value by multiplying the ruf aligning torque by gain, and wheel rotation detected by the wheel rotation speed detecting means for the second torque command value calculated by the gain adjusting means. Torque limiting means for limiting based on at least one of the vehicle speed calculated based on the speed and the vehicle speed detected by the vehicle speed detecting means and the motor angular speed calculated by the motor angular speed calculating means is provided .

  In the first aspect of the invention, when the second torque command value calculation means calculates the torque command value based on the wheel rotation speed detected by the wheel rotation speed detection means and detects an abnormality in the steering torque detection means. In addition, by selecting the second torque command value calculation means instead of the first torque command value calculation means by the abnormal time switching means, an accurate torque detection value considering the road surface reaction force based on the wheel rotational speed can be obtained. Can be sought. Moreover, the wheel rotational speed detecting means used in the antilock brake system or the like can be used, and the number of parts can be reduced.

In the invention according to claim 1 , the second torque command value after gain adjustment is limited based on at least one of the vehicle speed and the motor angular velocity, so that the control output abnormality in the high vehicle speed region and the high motor angular velocity region is prevented. Can be suppressed.
Still further, in the electric power steering device according to claim 2 , in the invention according to claim 1 , the gain adjusting means is estimated by the motor rotation information detected by the motor rotation information detecting means and the self-aligning torque estimating means. It is characterized by having a steering state gain adjusting means for determining the steering state based on the self-aligning torque and adjusting the steering state sensitive gain based on the determination result of the steering state.

According to the second aspect of the present invention, the optimum steering state sensitive gain according to the steering state can be adjusted, and the optimum second torque command value can be calculated according to the steering state.
According to a third aspect of the present invention, in the electric power steering apparatus according to the first or second aspect , the gain adjusting means detects the vehicle speed and the vehicle speed detected based on the wheel rotational speed detected by the wheel rotational speed detecting means. The vehicle speed gain adjusting means for adjusting the vehicle speed sensitive gain based on one of the vehicle speeds detected by the means is provided.

In the invention according to claim 3 , since the vehicle speed sensitive gain can be adjusted according to the vehicle speed, the steering feeling of the vehicle can be improved.
Furthermore, an electric power steering apparatus according to a fourth aspect is the invention according to any one of the first to third aspects, wherein the gain adjusting means includes motor rotation information detected by a motor rotation information detecting means and the wheel rotation speed. The self-aligning torque gain is adjusted based on the deviation between the self-aligning torque calculated based on the wheel rotational speed detected by the detecting means and the self-aligning torque estimated value estimated by the self-aligning torque estimating means. And a self-aligning torque gain adjusting means.

According to the fourth aspect of the present invention, the self-aligning torque setting means performs self-alignment based on a deviation between the self-aligning torque calculation value calculated based on the motor rotation information and the wheel rotation speed and the self-aligning torque estimated value. Since the aligning torque gain is set, when an error occurs in the estimated self-aligning torque calculated based on the wheel speed, the error can be suppressed.

Furthermore, the electric power steering apparatus according to claim 5 is the invention according to any one of claims 1 to 4 , wherein the gain adjusting means is driven based on a wheel rotational speed detected by the wheel speed detecting means. Drive wheel slip gain adjusting means for estimating the wheel slip state and adjusting the drive wheel slip sensitive gain based on the estimated drive wheel slip state is provided.

According to the fifth aspect of the present invention, when the driving wheel slip affects the estimated self-aligning torque, the influence of the driving wheel slip can be suppressed.
Still further, according to a sixth aspect of the present invention, in the electric power steering apparatus according to the first aspect , the gain adjusting means multiplies the self-aligning torque estimated by the self-aligning torque estimating means by a gain smaller than one. The second torque command value is configured to be calculated.

In the invention according to the sixth aspect , since the torque command value is calculated by multiplying the self-aligning torque by a gain smaller than 1, an optimum torque command value corresponding to the reaction force from the road surface can be calculated.
The electric power steering apparatus according to a seventh aspect is the invention according to any one of the first to sixth aspects, wherein the self-aligning torque estimating means estimates a vehicle side slip angle based on the wheel rotation speed. Vehicle slip angle estimating means is included, and self-aligning torque is estimated based on the vehicle slip angle estimated by the vehicle skid angle estimating means.

In the invention according to claim 7 , the vehicle side slip angle of the vehicle is estimated based on the wheel rotational speed, and the self-aligning torque is estimated based on the estimated vehicle side slip angle. Accurate self-aligning torque can be estimated.

Furthermore, the electric power steering apparatus in claim 8, in the invention according to claim 7, before Symbol vehicle slip angle estimating means estimates the vehicle sideslip angle based on the wheel rotational speed, the motor rotates the slip angle estimated The present invention is characterized in that the correction is made based on the motor rotation information detected by the information detection means.

In the invention according to the eighth aspect , the side slip angle of the vehicle is estimated based on the wheel rotational speed of the vehicle, and the estimated side slip angle is corrected based on the motor rotation information. The side slip angle can be estimated.
Furthermore, the electric power steering apparatus according to claim 9, in the invention according to any one of claims 1 to 6, prior Symbol self-aligning torque estimating means, with the wheel rotational speed and the motor rotational information detecting means The self-aligning torque is estimated based on the detected motor rotation information.

In the invention according to claim 9 , since the self-aligning torque is estimated based on the left and right wheel rotation speeds of the vehicle and the motor rotation information, more accurate self-aligning torque is estimated according to the steering state of the vehicle. Can do.
Still further, 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 abnormal time switching means is replaced with the first torque command value calculating means. When the second torque command value calculation means is selected, the first torque command value is gradually changed to the second torque command value.

In the invention according to claim 10 , since the torque command value is gradually changed when switching from the first torque command value to the second torque command value, a sudden change in the steering assist force generated by the electric motor is prevented. Thus, a stable steering assist state can be continued.

  According to the present invention, since the torque command value is calculated based on the wheel rotational speed by the second torque command value calculation means, an accurate torque considering the road surface condition is detected when an abnormality of the steering torque detection means is detected. The detection value can be obtained, and the effect that the steering assist control can be continued without giving the driver a sense of incongruity even after the failure of the steering torque detecting means is obtained.

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 block diagram which shows the specific structure of the self-aligning torque estimation part which comprises a controller. It is a characteristic diagram which shows a self-aligning torque initial estimated value calculation map. 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 the specific example of the controller which shows the 2nd Embodiment of this invention. It is a block diagram which shows the specific structure of a steering state sensitive gain setting part. It is a characteristic diagram which shows the steering state sensitive gain calculation map applied to a steering state sensitive gain setting part. It is a characteristic diagram which shows the vehicle speed sensitive gain calculation map applied to a vehicle speed sensitive gain setting part. It is a block diagram which shows the specific structure of a self aligning torque gain setting part. It is a block diagram which shows the specific structure of the self-aligning torque calculating part of FIG. It is a characteristic diagram which shows the self-aligning torque gain calculation map applied to the gain calculation part of FIG. It is a block diagram which shows the specific structure of a driving wheel slip gain setting part. It is a characteristic diagram which shows the driving wheel slip gain calculation map applied to a driving wheel slip gain setting part. It is a characteristic diagram which shows the vehicle speed limit value calculation map applied to a torque limit value setting part, and a motor angular speed limit value calculation map. It is explanatory drawing which shows a wheel vehicle behavior in case the tire diameter of a left side wheel is large. It is a flowchart which shows an example of the steering assistance control processing procedure performed with the microcomputer of the 2nd Embodiment of this invention. It is a block diagram which shows the specific structure of the self-aligning torque estimation part which shows the 3rd Embodiment of this invention. It is a characteristic diagram which shows the hysteresis characteristic of the self-aligning torque initial estimated value with respect to the actual self-aligning torque. It is a block diagram of a controller showing a 4th embodiment of the present invention. It is a block diagram which shows the specific example of the self-aligning torque estimation part in 4th Embodiment. It is a characteristic diagram which shows a vehicle sideslip angle calculation map. It is a characteristic diagram which shows a self-aligning torque initial estimated value calculation map. It is a whole block diagram at the time of applying 3rd Embodiment to 2nd Embodiment. It is a whole block diagram at the time of applying 4th Embodiment to 2nd Embodiment.

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 WL and WR 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 speed reduction mechanism 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 speed reduction mechanism 11. .

  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 speed reduction mechanism 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 torsional angular displacement, and this torsional angular displacement is detected by 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 rotational angle θ of the electric motor 12 detected at 17 and the wheel rotational speeds VwL and VwR of the left and right of the vehicle detected by the wheel rotational speed sensors 18L and 18R are also input.

  In the state where the steering torque sensor 14 is normal in the controller 15, the first steering assist torque as a current command value for causing the electric motor 12 to generate a steering assist force corresponding to the input torque detection value T and the vehicle speed detection value Vs. The command value Iref1 is calculated, and various compensation processes are performed on the calculated steering assist torque command value Iref1 based on the motor angular velocity ω and the motor angular acceleration α calculated based on the rotation angle θ, and then the electric motor 12 is driven and controlled. To do. When the steering torque sensor 14 is abnormal, the second steering assist torque command value Iref2 is calculated based on the wheel rotational speeds VwL and VwR of the left and right driven wheels, and the second steering assist torque command value Iref2 is calculated. Based on this, drive control of the electric motor 12 is performed.

  That is, as shown in FIG. 2, the controller 15 includes a rotation information calculation unit 20 that calculates a motor angular velocity ω and a motor angular acceleration α based on the motor rotation angle θ detected by the rotation angle sensor 17, and a steering assist torque command value. The steering assist torque command value calculator 21 for calculating the torque, the torque command value compensator 22 for compensating the torque command value Iref calculated by the steering assist torque command value calculator 21, and the command value compensator 22 compensated for the torque command value Iref. A current limiting unit 23 that limits the maximum current of the post-compensation steering assist torque command value Iref ′, and a motor current is generated based on the post-compensation steering assist torque command value Iref ″ that is current limited by the current limiting unit 23 to generate electric current. The motor driving circuit 24 controls the driving of the motor 12.

  The rotation information calculation unit 20 differentiates the motor rotation angle θ detected by the rotation angle sensor 17 to calculate the motor angular velocity ω, and the motor angular velocity ω calculated by the motor angular velocity calculation unit 201. A motor angular acceleration calculation unit 202 for differentiating and calculating the motor angular acceleration α.

  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 command value Iref2 is calculated based on the wheel rotation speeds VwL and VwR input from the steering assist torque command value calculation unit 31 and the wheel rotation speed sensor 18 that detects the left and right wheel rotation speeds. Steering assist torque command value calculation unit 32, torque sensor abnormality detection unit 33 for detecting abnormality of the steering torque sensor 14, and the first steering based on the abnormality detection signal output from the torque sensor abnormality detection unit 33. A command value selection unit serving as an abnormal time switching means for selecting one of the auxiliary torque command value calculation unit 31 and the second steering assist torque command value calculation unit 32 4, and a suppressing rate limit 35 an abrupt change in the command value selected by the command value selecting unit 34.

  The first steering assist torque command value calculation unit 31 refers to the steering assist torque command value calculation map shown in FIG. 2 based on the steering torque T and the vehicle speed Vs, and the steering assist torque command value Irefb that is a current command value. A torque command value calculation unit 311 that calculates the phase, a phase compensation unit 312 that calculates the 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 the steering torque Based on the steering torque T input from the sensor 14, the steering torque T is differentiated to improve the control responsiveness near the neutral position of the steering wheel and realize smooth and smooth steering. A center response improvement unit 313 for calculating a center response improvement command value Ir for ensuring and compensating for static friction; and a phase compensation output of the phase compensation 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 printer 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. And a characteristic diagram represented by a parabolic curve with the vehicle speed Vs as a parameter.

  The second torque command value calculation unit 32 includes a self-aligning torque estimation unit 32A as self-aligning torque estimation means for estimating the self-aligning torque transmitted from the road surface to the steering mechanism, and the self-aligning torque estimation unit. The amplifying unit 32B is a gain adjusting unit that amplifies the self-aligning torque SAT estimated at 321 with a gain less than “1” and calculates a second steering assist torque command value Iref2.

  As shown in FIG. 3, the self-aligning torque estimating unit 32A estimates the self-aligning torque initial estimated value SATi based on the wheel rotational speeds VwL and VwR input from the wheel rotational speed sensors 18L and 18R. Torque (SAT) initial estimation unit 321, low-pass filter 322 for removing noise of self-aligning torque initial estimated value SATi estimated by self-aligning torque estimation unit 321, and wheel rotational speed sensors 18L and 18R are input. An adder 323 that adds the wheel rotation speeds VwL and VwR, an average value calculation unit 324 that calculates 1/2 of the addition value of the wheel rotation speeds VwL and VwR to calculate the vehicle speed equivalent value Vs ′, and this average value calculation Based on the vehicle speed equivalent value Vs ′ calculated by the unit 324, the low-pass filter 3 And a phase correcting section 325 that calculates a self aligning torque estimation value SAT performs phase correction of the noise reduction is output from the 2 self aligning torque initial estimate SAT '.

Here, the self-aligning torque initial estimation unit 321 performs the calculation of the following equation (1) based on the wheel rotation speeds VwL and VwR detected by the wheel rotation speed sensors 18L and 18R, and the left and right according to the vehicle speed are calculated. A wheel rotation speed difference ΔVw is calculated.
ΔVw = (VwL−VwR) / {(VwL + VwR) / 2} (1)

Next, based on the left and right wheel rotational speed difference ΔVw, the self-aligning torque SATi is calculated with reference to the self-aligning torque calculation map shown in FIG.
As shown in FIG. 4, the self-aligning torque calculation map shows that the self-aligning torque SAT is “0” in the state where the left and right wheel rotational speed difference ΔVw is zero, that is, the straight traveling state. When the rotational speed difference ΔVw becomes a positive value, that is, when the vehicle turns to the right, the self-aligning torque SAT increases. When the left and right wheel rotational speed difference ΔVw becomes equal to or greater than the predetermined value ΔVw1, the left and right wheel rotational speed difference ΔV increases. Therefore, the rate of increase of the self-aligning torque SAT is set to a characteristic line that gradually decreases. Similarly, the self-aligning torque SAT decreases from “0” until the left and right wheel rotational speed difference ΔVw becomes a predetermined value −ΔV1. The characteristic curve is such that the rate of decrease of the self-aligning torque SAT gradually decreases when the difference between the left and right wheel rotational speeds -ΔVw1 is exceeded.

  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 set as the torque command value Iref, and a rapid change in the torque command value Iref is suppressed by the rate limiter 35, and then output to an adder 46 described later. To do.

  The command value compensator 22 includes a convergence compensator 43 that compensates for the convergence of the yaw rate based on the motor angular velocity ω calculated by the motor angular velocity calculator 201 of the rotation information calculator 20, and a motor angle of the rotation information calculator 20. At least an inertia compensation unit 44 that compensates for the torque equivalent generated by the inertia of the electric motor 12 based on the motor angular acceleration α calculated by the acceleration calculation unit 202 and prevents deterioration of the sense of inertia or control responsiveness.

Here, the convergence compensation unit 43 receives the motor angular velocity ω calculated by the motor angular velocity calculation unit 201 and applies a brake to the operation of the steering wheel 1 swinging in order to improve the yaw convergence of the vehicle. As shown in FIG. 5, the convergence value Ic is calculated by multiplying the motor angular velocity ω by the convergence control gain Kc.
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 ′. The value Iref ′ is output to the current limiting unit 23.

Next, the operation of the above embodiment will be described.
Now, 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, both the motor angular velocity ω calculated by the motor angular velocity calculating unit 201 of the rotation information calculating unit 20 and the motor angular acceleration α calculated by the motor angular acceleration calculating unit 202 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 also “0”, the command compensation value Icom is also “0”. The post-compensation steering assist torque command value Iref ′ output from the adder 46 is also “0”.

For this reason, the post-compensation steering assist torque command value Iref "output from the current limiting unit 23 is also" 0 ", the motor drive current output from the motor drive circuit 24 is also" 0 ", and the electric motor 12 is stopped. Continue state.
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 directly supplied from the adder 46 to the current limiter 23, and the compensated steering assist torque command value Iref ″ whose maximum value is limited is supplied from the current limiter 23 to the motor drive circuit 24. Is output.

Therefore, a motor drive current corresponding to the post-compensation steering assist torque command value Iref ″ is output from the motor drive circuit 24 to the electric motor 12, and the electric motor 12 is rotationally driven, and a steering assist force corresponding to the steering torque T is obtained. Occur.
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, the left and right steered wheels WL and WR are steered via the tie rods 9 after being converted into a linear motion in the vehicle width direction, and the steered wheels WL and WR can be steered with light steering torque.

  When the electric motor 12 is driven and controlled, the motor angular velocity ω calculated by the motor angular velocity calculation unit 201 of the rotation information calculation unit 20 and the motor angular acceleration α calculated by the motor angular acceleration calculation unit 202 increase. As a result, the command value compensation unit 22 calculates the convergence compensation value Ic and the inertia compensation value Ii, and adds them to calculate the command compensation value Icom, which is supplied to the adder 46, whereby the steering assist torque. The command compensation value Icom is added to the command value Iref to calculate a post-compensation steering assist torque command value Iref ′. In this way, the command value compensation unit 22 performs the command value compensation process, and the center response improvement unit 313 of the first steering assist torque command value calculation unit 31 performs differential calculation processing of the steering torque T to assist characteristics. Stability is ensured in the dead zone and static friction is compensated, and the phase compensation unit 312 performs phase compensation on the first steering assist torque command value Iref1.

  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.

  At this time, in the second steering assist torque command value calculation unit 32, the wheel rotation speeds VwL and VwR of the left and right wheels WL and WR are detected by the wheel rotation speed sensors 18L and 18R, and the detected wheel rotation speeds VwL and VwR are detected. It is supplied to the self-aligning torque estimation unit 32A. Therefore, the vehicle speed equivalent value Vs ′ is calculated by the average value calculation unit 324 of the self-aligning torque estimation unit 32A, and the self-aligning torque initial estimation unit 321 calculates the vehicle speed based on the left and right wheel rotational speeds VwL and VwR. Calculation of the formula (1) is performed to calculate the wheel rotational speed difference ΔVw, and based on the calculated wheel rotational speed difference ΔVw, the self-aligning torque initial estimated value SATi is referred to with reference to the self-aligning torque calculation map of FIG. Is estimated.

  Then, the estimated self-aligning torque initial estimated value SATi is low-pass filtered by the low-pass filter 322 to obtain a self-aligning torque initial estimated value SATi ′ from which noise is removed. This self-aligning torque The initial estimated value SATi ′ is subjected to phase correction by the vehicle speed equivalent value Vs ′ by the phase correction unit 325 to calculate a self-aligning torque estimated value, and further multiplied by the gain K to obtain the second steering assist torque command value Iref2. Is calculated.

When the vehicle is traveling and is in a straight traveling state, since the wheel rotational speed difference ΔVw calculated by the equation (1) is “0”, the self-aligning torque initial estimated value SATi is also “0”. Thus, the electric motor 12 maintains the stopped state.
However, when the steering wheel 1 is steered from the straight traveling state to shift to the turning traveling state, there is a difference between the left and right wheel rotational speeds VwL and VwR according to the turning radius of the turning traveling state. Therefore, the wheel rotational speed difference ΔVw becomes a relatively small value because the difference between the left and right wheel rotational speeds VwL and VwR, which are numerators, is extremely small when the vehicle speed Vs is low. At 321, the self-aligning torque initial estimated value SATi calculated with reference to the self-aligning torque initial estimated value calculation map of FIG. 4 becomes a relatively small value. This self-aligning torque initial estimated value SATi is low-pass processed by the low-pass filter 322, and the phase correction unit 325 performs phase correction by the vehicle speed equivalent value Vs', so that the rack shaft of the steering gear mechanism 8 is moved from the road surface when the vehicle is traveling. The input self-aligning torque SAT can be accurately estimated.

  Then, the estimated self-aligning torque estimated value SAT is amplified by the amplifying unit 32B, thereby calculating a second steering assist torque command value Iref2 in consideration of the self-aligning torque SAT. This is a command value selecting unit 34. Is supplied to the adder 46 via the rate limiter 35, and the compensated steering assist torque command value Iref ′ obtained by adding the command compensation value Icom by the adder 46 is supplied to the current limiter 23. By supplying the compensated auxiliary torque command value Iref ″ with a limited current to the motor drive circuit 24, the motor drive circuit 24 generates a steering assist force in consideration of the self-aligning torque SAT, and continues the steering assist control. can do.

  Further, when the vehicle speed Vs of the vehicle is high, the difference between the left and right wheel rotation speeds VwL and VwR becomes a large value, so the wheel rotation speed difference ΔVw calculated by the equation (1) becomes a large value. Accordingly, the self-aligning torque initial estimation unit 321 refers to the self-aligning torque initial estimated value calculation map of FIG. 4 and the self-aligning torque initial estimated value SATi is a relatively large value. This self-aligning torque initial estimated value SATi is low-pass processed by the low-pass filter 322, and the phase correction unit 325 performs phase correction by the vehicle speed equivalent value Vs', so that the rack shaft of the steering gear mechanism 8 is moved from the road surface when the vehicle is traveling. The input self-aligning torque SAT can be accurately estimated.

  Then, the estimated self-aligning torque estimated value SAT is amplified by the amplifying unit 32B, thereby calculating a second steering assist torque command value Iref2 in consideration of the self-aligning torque SAT. This is a command value selecting unit 34. To the adder 46 via the rate limiter 35. Therefore, the steering assist force can be generated in the motor drive circuit 24 in consideration of the self-aligning torque SAT, and the steering assist control can be continued.

  As described above, according to the above embodiment, when the steering torque sensor 14 is in an abnormal state, the self-aligning torque estimating unit 32A 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 addition, since the self-aligning torque initial estimated value SATi is calculated using the wheel rotational speed sensors 18L and 18R used in other anti-lock braking systems, the increase in the number of parts is suppressed and the cost is reduced. Can do.
Furthermore, in the first embodiment, the case where the controller 15 is configured by hardware has been described. However, the present invention is not limited to this, and a microcomputer is applied to the rotation information calculation unit 20, steering assist. The functions of the torque command value calculation unit 21, the command value compensation unit 22, the current limiting unit 23, and the motor drive circuit can be processed by software. In this case, the microcomputer may execute the steering torque sensor abnormality detection process shown in FIG. 5 and the steering assist control process shown in FIG.

  Here, as shown in FIG. 5, 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. 6, 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 wheel rotation speed sensors 18L and 18R are read, and then the process proceeds to step S12, and the sensor abnormality flag Fa set in the torque sensor abnormality detection process of FIG. 5 is set to “1”. 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 aforementioned steering assist torque command value calculation map, 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 S16, 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 S19 described later.

  On the other hand, if the determination result of step S12 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 wheel rotational speeds VwL and VwR are set. Based on this, the wheel rotational speed difference ΔVw in the equation (1) is calculated. Then, based on the calculated wheel rotation speed difference ΔVw, the self-aligning torque initial estimated value SATi is calculated with reference to the self-aligning torque calculation map shown in FIG. 4, and the self-aligning torque initial estimated value SATi is low-passed. A self-aligning torque estimated value SAT is calculated through filter processing and phase correction processing. Next, the process proceeds to step S18 to calculate a second steering assist torque command value Iref2 by multiplying the calculated self-aligning torque estimated value SAT by a gain K less than “1”, and this is calculated as the steering assist torque command value. After being updated and stored in the torque command value storage area of the storage device such as RAM described above as Iref, the process proceeds to step S19.

  In step S19, the motor rotational angle θ is differentiated to calculate the motor angular velocity ω, then the process proceeds to step S20, the motor angular speed ω is differentiated to calculate the motor angular acceleration α, and then the process proceeds to step S21. 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 S22.

  In step S22, 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 S23 where it is stored in a 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 S21 and S22 to the steering assist torque command value Iref, and the process proceeds to step S24.

  In step S24, a maximum value limiting process is performed on the calculated post-compensation steering assist torque command value Iref ′ to calculate a post-limit torque assist command value Iref ″. The torque assist command value Iref ″ is output to the motor drive circuit 24 to drive the electric motor 12.

  The process of FIG. 5 corresponds to the torque detection unit abnormality detection means. In the process of FIG. 6, the process of step S12 corresponds to the abnormality time switching means, and the processes of steps S13 to S16 are the first torque command value calculation means. The processing of steps S17 and S18 corresponds to the second torque command value calculation means, and the processing of steps S19 to S25 corresponds to the motor control means.

  As described above, when the torque sensor abnormality detection process of FIG. 5 and the steering assist control process of FIG. 6 are executed by the microcomputer, the steering of FIG. 6 is performed when the steering torque sensor 14 is normal as in the above-described embodiment. The first steering assist torque command value Iref1 is calculated by executing the processes of steps S13 to S16 in the assist control process. Further, when the steering torque sensor 14 is abnormal, the process of steps S17 and S18 in the steering assist control process of FIG. 6 is executed to calculate the second steering assist torque command value Iref2, whereby the rack of the steering gear mechanism 8 is obtained. The self-aligning torque SAT, which is a reaction force from the road surface input to the shaft, is estimated, and the estimated self-aligning torque SAT is multiplied by a gain K less than “1” to obtain a second steering assist torque command value Iref2. calculate.

  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 occurs, the self-aligning torque SAT is estimated based on the wheel rotational speeds VwL and VwR, and the estimated self-aligning torque SAT is multiplied by a gain K less than “1” to obtain a second steering assist torque command. The value Iref2 is calculated. Therefore, even when the steering torque sensor 14 changes from a normal state to an abnormal state, it is possible to continue the optimal steering assist control in consideration of the road surface reaction force based on the second steering assist torque command value Iref2. it can.

Next, a second embodiment of the present invention will be described with reference to FIGS.
In the second embodiment, a gain adjustment unit having a plurality of adjustment units is applied in place of the amplifier 32B serving as a gain adjustment unit of the second steering assist torque command value calculation unit 32. In the second embodiment, the rotation information calculation unit 20 is configured including the rotation sensor 17, and the wheel rotation speed sensor 18 includes the wheel speeds VwFL and VwFR of the front left and right wheels and the wheel speeds of the left and right wheels of the rear wheel. VwRL and VwRR are detected, the average value of the left wheel speeds VwFL and VwRL is defined as the left wheel speed VwL, and the average value of the right wheel speeds VwFR and VwRR is defined as the right wheel speed VwR.

  In the second embodiment, as shown in FIG. 7, the second steering assist torque command value calculation unit 32 includes a self-aligning torque estimation unit 32A having the configuration shown in FIG. 3 and the self-aligning torque. The gain adjusting unit 32C as gain adjusting means for calculating the second steering assist torque command value Iref2 by multiplying the self-aligning torque SAT estimated by the estimating unit 32A by the gain, and the self adjusted by the gain adjusting unit 32C. The torque limiting unit 32D is a torque limiting unit that limits the aligning torque.

The gain adjusting unit 32C includes a steering state gain adjusting unit 36, a vehicle speed gain adjusting unit 37, a self-aligning torque gain adjusting unit 38, and a driving wheel slip gain adjusting unit 39.
The steering state gain adjustment unit 36 receives the self-aligning torque estimated value SAT output from the self-aligning torque estimation unit 32A and the motor angular velocity ω calculated by the motor angular velocity calculation unit 201, and increases based on these values. A steering state gain setting unit 36A that detects a steering state of a steering state, a switchback state, and a steered state, and sets a steering state gain K0 according to the detected steering state, and is set by the steering state gain setting unit 36A The steering state gain K0 is multiplied by the self-aligning torque estimation value SAT output from the self-aligning torque estimation unit 32A, and a gain multiplication unit 36B that outputs a gain multiple output Iref3 is configured.

  Here, as shown in FIG. 8, the specific configuration of the steering state gain setting unit 36A is that the self-aligning torque estimated value SAT and the motor angular velocity ω are input, and the increased state, the reverted state, and the steered state. And a steering state gain calculation unit 362 that calculates a steering state gain K0 based on the determination result of the steering state determination unit 361 and the motor angular velocity ω.

  When the sign of the self-aligning torque estimated value SAT and the sign of the motor angular velocity ω coincide with each other, the steering state determining unit 361 determines that the steering state is increasing, and the sign of the self-aligning torque estimated value SAT and the motor acceleration ω When the signs do not match, it is determined that the switch-back state is established, and when the absolute value | ω |

  The steering state gain calculation unit 362 calculates a steering state gain K0 with reference to the steering state gain calculation map shown in FIG. 9 based on the input steering state and motor angular velocity ω. As shown in FIG. 9, in the steering state gain calculation map, when the steering state is the steering holding state, the characteristic line Lh is set so as to maintain the predetermined gain K0h regardless of the value of the motor angular velocity ω. When the motor angular speed ω is in the increased state, the predetermined gain K0i that is larger than the predetermined gain K0h is maintained between the motor angular speed ω and the predetermined value ω1, and when the motor angular speed ω exceeds the predetermined value ω1, the motor angular speed ω increases. Accordingly, when the characteristic line Li is set so that the gain increases with a relatively large gradient and the steering state is the switchback state, the motor angular speed ω is a value smaller than the predetermined gain K0h between zero and the predetermined value ω1. When the motor angular speed ω exceeds the predetermined value ω1, the characteristic line Ld is set so that the gain decreases with a relatively small gradient as the motor angular speed ω increases. It has been determined.

Further, the vehicle speed gain adjusting unit 37 outputs a vehicle speed gain calculating unit 37A for calculating the vehicle speed sensitive gain K1, and a gain output from the steering state gain adjusting unit 36 for the vehicle speed sensitive gain K1 set by the vehicle speed gain setting value unit 37A. A gain multiplication unit 37B that multiplies the double output Iref3 by a vehicle speed sensitive gain K1 and outputs a gain double output Iref4.
The vehicle speed gain calculation unit 37A calculates a vehicle speed sensitive gain K1 with reference to the vehicle speed sensitive gain calculation map shown in FIG. 10 based on the input vehicle speed Vs. Here, as shown in FIG. 10, the vehicle speed sensitive gain calculation map maintains the predetermined value Kv when the vehicle speed Vs is between zero and the predetermined value Vs1, and when the vehicle speed Vs exceeds the predetermined value Vs1, the vehicle speed Vs increases. The characteristic line Lv is such that when the vehicle speed Vs exceeds a predetermined value Vs2 greater than the predetermined value Vs1, the gain decreases with a relatively small gradient as the vehicle speed Vs increases. Is set.

  The self-aligning torque gain adjusting unit 38 is set by the self-aligning torque gain setting unit 38A that calculates the self-aligning torque calculation value SATo and sets the correction gain K2, and the self-aligning torque gain setting unit 38A. The gain multiplier 38B is configured to multiply the self-aligning torque gain K2 by the gain multiple output Iref4.

  As shown in FIG. 11, the self-aligning torque gain setting unit 38A uses the vehicle model based on the four-wheel wheel speeds VwFL to VwRR inputted from the four-wheel wheel speed sensor 18 and the motor angle θ. A self-aligning torque calculation unit 381 for calculating an aligning torque calculation value SATo and a self-aligning torque calculation unit 381 calculated from the self-aligning torque estimation value SAT estimated by the self-aligning torque estimation unit 32 described above. A subtractor 382 for subtracting the lining torque calculation value SATo, an absolute value calculation unit 383 for converting the subtraction output of the subtractor 382 into an absolute value and calculating a self-aligning torque deviation ΔSAT (= | SAT−SATo |); Self-aligning torque deviation ΔS calculated by the absolute value calculator 383 Based on the T and a gain calculation unit 384 that calculates a self aligning torque gain K2 by referring to the self-aligning torque gain calculating map shown in FIG. 12.

  Here, the self-aligning torque calculation unit 381 calculates the average value of the wheel rotation speeds VwFL to VwRR of the four wheels as the vehicle speed V, sets the motor angle θ as the estimated steering angle θ, and sets the vehicle specification constant as (2 By substituting in the equation of motion (state equation) in the lateral direction of the vehicle, which is the vehicle model represented by equation (1), and using the self-aligning torque calculation value equation (output equation) represented by equation (3) below, A self-aligning torque calculation value SATo is calculated.

Vehicle specification constant m: Vehicle mass I: Vehicle inertia moment lf: Distance between vehicle center of gravity and front axle rr: Distance between vehicle center of gravity and rear axle Kf: Cornering power of front tire Kr: Cornering power of rear tire V: Vehicle speed N: Overall steering angle ratio θ: Estimated steering angle δf: Actual steering angle (δf = θ / N)
β: Side slip angle of vehicle center of gravity γ: Yaw rate ε: Trail

In order to perform the above calculation, a specific configuration of the self-aligning torque calculation unit 381 is configured as shown in FIG.
That is, the motor angle θ as the estimated steering angle is input to a multiplier 381a that multiplies 1 / N to calculate the actual steering angle δf. Actual steering angle δf output from the multiplier 381a is supplied to a multiplier 381b for multiplying the coefficients b ₁₁ of the aforementioned (2), the output of the multiplier 381b is supplied to the adder 381 c. The added output of the adder 381c is input to the integrator 381d and integrated to calculate the side slip angle β of the vehicle center of gravity, and the calculated side slip angle β of the vehicle center of gravity is the coefficient of the equation (3). is supplied to a multiplier 381e for multiplying the C _11, it is supplied to a multiplier 381g for multiplying the multiplier 381f and the (2) the coefficient of formula a ₂₁ is multiplied by a coefficient a ₁₁ of the (2) equation. Then, the multiplication outputs of the multiplier 381f and a multiplier 381n, which will be described later, are supplied to the adder 381c and added to the multiplication output of the multiplier 381b, thereby calculating the side slip angular velocity β ′. The side slip angular velocity β ′ is integrated by the integrator 381d to calculate the side slip angle β.

On the other hand, the actual steering angle δf output from the multiplier 381a is supplied to the multiplier 381h that multiplies the coefficient b ₂₁ of the equation (2), and the multiplication output output from the multiplier 381h is supplied to the adder 381i. Then, the addition output of the adder 381i is supplied to the integrator 381j and integrated, whereby the yaw rate γ is calculated. Then, the calculated yaw rate γ is supplied to the multiplier 381k that multiplies the coefficient c ₁₂ of the equation (3), and the multiplier 381m that multiplies the coefficient a ₂₂ of the equation (2) and the equation (2). It is supplied to a multiplier 381n for multiplying the coefficients a ₁₂ in.

Then, the multiplication output of the multiplier 381m and the multiplication output of the multiplier 381g are supplied to the adder 381i and added to the multiplication output of the multiplier 381h to calculate the yaw angular acceleration γ ′. 'Is integrated by the integrator 381j to calculate the yaw rate γ.
Furthermore, actual steering angle δf output from the multiplier 381a is, the equation (3) is supplied to the coefficient d ₁₁ to the multiplier 381O for multiplying of the multiplication output outputted from the multiplier 381O, the multiplier mentioned above The multiplication outputs output from 381e and 381k are added by an adder 381p to calculate a self-aligning torque calculation value SATo.

Further, the gain calculation unit 384 refers to the self-aligning torque gain calculation map shown in FIG. 13 based on the absolute value | ΔSAT | of the self-aligning torque deviation output from the absolute value calculation unit 383. Torque gain K2 is calculated.
Here, as shown in FIG. 13, the self-aligning torque gain calculation map has an absolute value | ΔSAT of the self-aligning torque deviation when the absolute value | ΔSAT | of the self-aligning torque deviation is between 0 and the set value ΔSAT1. The self-aligning torque gain K2 decreases with a relatively gentle slope in accordance with the increase of |, and the comparison is made until the absolute value | ΔSAT | of the self-aligning torque deviation exceeds the set value ΔSAT1 and reaches the set value ΔSAT2. When the self-aligning torque gain K2 decreases at a steep slope and exceeds the set value SAT2, the self-aligning torque gain K2 has a relatively gentle slope as the absolute value | ΔSAT | of the self-aligning torque deviation increases. The characteristic line Ls is set so as to decrease.

The drive wheel slip gain adjustment unit 39 sets a drive wheel slip gain K3 based on the wheel speeds VwL and VwR detected by the wheel speed sensor 18, and the drive wheel slip gain setting unit 39A. And a gain multiplication unit 39B that multiplies the gain multiple output Iref5 by the drive wheel slip gain K3 set in (1).
As shown in FIG. 14, the driving wheel slip gain setting unit 39A receives the left and right wheel speeds VwFL and VwFR of the front wheels and the left and right wheel speeds VwRL and VwRR detected by the wheel speed sensor 18, and the left and right wheels of the front wheels are input. An adder 391 that adds the speeds VwFL and VwFR, a multiplier 392 that multiplies the addition output of the adder 391 by one half to calculate the front wheel average value VwF, and the left and right wheel speeds VwRL and VwRR of the rear wheels. An addition unit 393 for adding, a multiplier 394 for multiplying the addition output of the addition unit 393 by one half to calculate the rear wheel average value VwR, and a multiplication unit from the front wheel average value VwF output from the multiplier 392 A subtraction unit 395 that calculates a driving wheel wheel speed deviation ΔVw by subtracting the rear wheel average value VwR output from 394, and a driving wheel wheel speed output from the subtraction unit 395. An absolute value circuit 396 that converts the difference ΔVw into an absolute value, and a gain calculation unit 397 that calculates a drive wheel slip sensitive gain K4 based on the absolute value | ΔVw | of the drive wheel wheel speed deviation output from the absolute value circuit 396; It has.

  Here, the gain calculation unit 397 calculates the drive wheel slip sensitivity gain K3 with reference to the drive wheel slip sensitivity gain calculation map shown in FIG. 13 based on the absolute value | ΔVw | of the input drive wheel wheel speed deviation ΔVw. To do. As shown in FIG. 15, this driving wheel slip sensitive gain calculation map is such that the driving wheel slip gain K3 gradually decreases as the absolute value | ΔVw | of the driving wheel wheel speed deviation ΔVw increases from zero. A characteristic line Lw consisting of a next curve is set.

Further, the torque limiting unit 32D limits the gain double output Iref6 by the torque limit value setting unit 40 and the torque limit value Tlim set by the torque limit value setting unit 40, thereby obtaining the second steering assist torque command value Iref2. And a limiter unit 41 for outputting.
The torque limit value setting unit 40 receives the vehicle speed Vs and the motor angular speed ω, calculates the vehicle speed limit value Limv based on the vehicle speed Vs with reference to the vehicle speed limit value calculation map shown in FIG. Based on ω, the motor angular speed limit value Limm is calculated with reference to the motor angular speed limit value calculation map shown in FIG. 16B, and the vehicle speed limit value Limv and the motor angular speed limit value Limm are compared to limit any smaller value. The value Lim is output to the limiter unit 41.

Here, as shown in FIG. 16A, the vehicle speed limit value calculation map maintains the maximum limit value Limmax until the vehicle speed Vs reaches a predetermined value Vs3 from zero, and the vehicle speed Vs exceeds the predetermined value Vs3. A characteristic line Lv1 is set in which the vehicle speed limit value Limv decreases while a gentle arc is drawn in accordance with the increase in the vehicle speed Vs.
Further, as shown in FIG. 16 (b), the motor angular velocity limit value calculation map shows a maximum limit value Limmax until the motor angular velocity ω reaches zero from the zero to the set angular velocity ω2 generated by the driver's steering or road reaction force. When the motor angular velocity ω exceeds the set angular velocity ω2, the characteristic line Lω is set such that the motor angular velocity limit value Limm decreases with a relatively large gradient as the motor angular velocity ω increases.

Next, the operation of the second embodiment will be described.
When the steering torque sensor 14 is normal, the torque sensor abnormality detection unit 33 outputs the abnormality detection signal Sa having the logical value “0” to the command value selection unit 34, as in the first embodiment. . 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. For this reason, steering assist control according to the steering torque T detected by the steering torque sensor 14 is performed, and a steering assist force according to the steering torque T is generated from the electric motor 12, which is transmitted via the speed reduction mechanism 11 to the steering wheel. By transmitting the steering force from 1 to the transmitted steering shaft 2, the steering force and the steering assist force are converted into a linear motion in the vehicle width direction by the steering gear mechanism 8, and the left and right steered wheels via the tie rod 9. WL and WR are steered, and steered wheels WL and WR can be steered with light steering torque.

  On the other hand, when the steering torque sensor 14 is in an abnormal state while the vehicle is running and the torque sensor abnormality detection unit 33 enters a state where the steering torque T satisfies the steering torque sensor abnormality detection condition, 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.

  In the second steering assist torque command value calculation unit 32, the self-aligning torque estimation unit 32 sets the left and right wheel speeds VwL and VwR output from the wheel speed sensor 18 in the same manner as in the first embodiment described above. Based on this, a self-aligning torque estimated value SAT is calculated. Various gain adjustments are performed on the calculated self-aligning torque estimated value SAT by the gain adjusting unit 32C.

  In other words, the steering state gain adjustment unit 36 determines whether the steering state of the steering wheel 1 is in the increased state, the return state, or the steered state. In this case, the determination is made based on whether or not the sign of the self-aligning torque estimated place SAT and the sign of the motor angular speed ω coincide with each other. When the value | ω | is equal to or less than the set angular velocity ωt, it is determined that the steering is maintained.

  Then, any one of the characteristic lines Li, Ld, and Lh in FIG. 9 is selected according to the determined steering state, and the steering state sensitive gain K0 is set from the motor angular velocity ω based on the selected characteristic line. Therefore, when the steering state of the steering wheel 1 is the steered state, the steering state sensitive gain K0 maintains the predetermined value K0h, so that the neutral steering state gain K0 corresponding to the steered state can be set. . For this reason, the steering state gain K0 can be multiplied by the steering state gain KO and the self-aligning torque estimated value SAT output from the self-aligning torque estimation unit 32A to obtain a gain doubled output Iref3 that is optimal for the steered state. .

  On the other hand, the vehicle speed sensitive gain K1 is set by the vehicle speed sensitive gain setting unit 37A with reference to the vehicle speed sensitive gain setting map shown in FIG. 10 based on the vehicle speed Vs in the steering state, and the set vehicle speed sensitive gain K1 is multiplied by the gain. The unit 37B multiplies the gain double output Iref3 to calculate the gain double output Iref4 (= Iref3 * K1), and outputs this gain double output Iref4.

That is, when the vehicle speed Vs is smaller than the set vehicle speed Vs1, a relatively large vehicle speed sensitive gain K1 is set, thereby generating a second steering assist force that generates a large steering assist force such as when the vehicle is stationary. 2 steering assist torque command value Iref2 can be calculated.
Further, when the vehicle speed Vs exceeds the set vehicle speed Vs1, the vehicle speed sensitive gain K1 decreases with a relatively large decrease rate as the vehicle speed Vs increases, and when the vehicle speed Vs exceeds the set vehicle speed Vs2. Decreases at a relatively small decrease rate as the vehicle speed Vs increases, and the second self-aligning torque command value Iref2 is calculated by optimizing the self-aligning torque estimated value SAT according to the vehicle speed Vs. Steering feeling can be improved.

  In the self-aligning torque gain setting unit 38A, the self-aligning torque calculation unit 381 calculates the self-aligning torque calculation value SATo using the vehicle model based on the motor angle θ and the wheel speeds VwFL to VwRR of the four wheels. calculate. Then, a subtractor 382 calculates a deviation ΔSAT between the calculated self-aligning torque calculation value SATo and the self-aligning torque estimation value SAT estimated by the self-aligning torque estimation unit 32A, and calculates the calculated deviation ΔSAT as an absolute value calculation. The absolute value | ΔSAT | is calculated by making it an absolute value in the unit 383. Then, the gain calculating unit 384 calculates the self-aligning torque gain K2 with reference to the self-aligning torque gain calculation map shown in FIG. 13 based on the calculated absolute value | ΔSAT |.

Then, the calculated self-aligning torque gain K2 is multiplied by the gain multiplication output Iref4 output from the gain multiplication unit 37B by the gain multiplication unit 38B to calculate the gain multiplication output Iref5 (= Iref4 * K2), and this gain multiplication output Iref5 is output.
For this reason, if one of the tires is punctured and an emergency tire is installed, the tire pressure varies, or the wear degree of the left and right wheels is different, the outer diameter of the left and right wheels is different, When traveling on a so-called split μ road where one side is a low friction coefficient road surface such as a snowy road, a frozen road, a dredging, or a puddle, and the other side is a high friction coefficient road surface such as a dry road surface, a wheel speed difference occurs between the left and right sides of the vehicle. become.

Thus, when a wheel speed difference occurs between the left and right sides of the vehicle, for example, as shown in FIG. 17, when the tire outer diameter on the left wheel side of the vehicle is larger than the tire outer diameter on the right wheel side, the arrow A Since the yaw motion in the clockwise direction is generated as shown by, in order to drive the vehicle straight, it is necessary to steer the steering wheel 1 to the left as shown by the arrow B to give the steering torque.
However, since the wheel speed VwL on the left side of the vehicle is faster than the wheel speed VwR on the right side, the self-aligning torque estimation unit 32A erroneously determines that the vehicle is turning right, and assists in turning right. A self-aligning torque estimated value SAT is calculated. For this reason, when the self-aligning torque estimated value SAT is set to the second steering assist torque command value Iref2, the control abnormal state in which a reverse steering assist force that assists the right steering is generated by the electric motor 12 is generated. End up.

  At this time, the self-aligning torque gain setting unit 38A calculates the self-aligning torque calculation value SATo using the vehicle model based on the motor angle θ and the wheel speeds VwFL to VwRR of the four wheels. Since the motor angle θ of the self-aligning torque calculation value SATo is “0”, the actual steering angle δf calculated by the multiplier 381a of the self-aligning torque calculation unit 381 shown in FIG. 12 is also “0”. Since the actual steering angle Δf becomes “0” in this way, the self-aligning torque calculation value SATo calculated by the self-aligning torque calculation unit 381 also becomes “0”, and the self-aligning torque output from the subtractor 382. The deviation ΔSAT from the estimated value SAT increases, and the absolute value | ΔSAT | calculated by the absolute value calculator 383 increases. Therefore, the self-aligning torque gain K2 calculated with reference to FIG. 13 decreases as the absolute value | ΔSAT | of the deviation ΔSAT increases.

  Therefore, since the gain multiplying unit 38B multiplies the gain multiplying output Iref4 output from the gain multiplying unit 37B by the self-aligning torque gain K2, the gain multiplying output Iref5 output from the gain multiplying unit 38B decreases. As a result, the second steering assist torque command value Iref2 decreases, and the steering assist force in the reverse direction generated by the electric motor 12 is suppressed.

  On the other hand, for example, when traveling on a split μ road where the left wheel side is a low friction coefficient road surface and the right wheel side is a high friction coefficient road surface, the wheel speed of the drive wheel on the left wheel side is the same as when the tire outer diameter is different. Is increased, the wheel speed VwL of the left wheel becomes faster than the wheel speed VwR of the right wheel. However, in the traveling state on the split μ road, the grip force of the drive wheel on the right wheel side is larger than the grip force of the drive wheel on the left wheel side, and thus the yaw motion in the counterclockwise direction is generated in the vehicle. For this reason, in order to drive the vehicle straight, the driver steers the steering wheel 1 to the right to generate a steering torque.

At this time, the self-aligning torque estimated value SAT estimated by the self-aligning torque estimating unit 32A is determined to be in the right-turning state because the wheel speed VwL of the left wheel is faster than the wheel speed VwR of the right wheel. It becomes the direction which assists a person's steering torque.
For this reason, it is not necessary to suppress the self-aligning torque estimated value SAT, but since the driving wheel on the left wheel side runs on the low friction coefficient road surface, the wheel speed rapidly increases, and the difference between the left and right wheel speeds ΔVw increases rapidly, and accordingly, the self-aligning torque estimated value SAT becomes larger than the actual self-aligning torque. Therefore, the second steering assist torque command value Iref2 becomes a large value as it is, and a self-steering state in which the steering assist force generated by the electric motor 12 becomes excessive is brought about.

  In this case, the absolute value | ΔSAT | of the deviation ΔSAT between the estimated self-aligning torque value SAT calculated by the self-aligning torque gain calculation unit 38A and the calculated self-aligning torque value SATo becomes a large value. As a result, the self-aligning torque gain K2 calculated with reference to FIG. 13 in the gain calculation unit 384 becomes a smaller value, and this self-aligning torque gain K2 becomes the gain multiplied output Iref4 in the gain multiplication unit 38B. Multiplication is performed to calculate a gain doubled output Iref5 (= Iref4 * K2). As a result, the second steering assist torque command value Iref2 is decreased and adjusted to a value commensurate with the steering holding torque. As a result, the steering assist force generated by the electric motor 12 is controlled to an appropriate value while suppressing self-steer. Therefore, appropriate steering assist control can be performed without causing the driver to feel uncomfortable.

  Further, when driving wheel slip occurs at the time of starting, the wheel speeds of the driving wheels increase, so that the left and right wheel speeds VwL and VwR also increase. For this reason, the left and right wheel rotational speed difference ΔVw calculated by the above-described equation (1) becomes larger than the actual wheel rotational speed difference, and the self calculated by referring to the self-aligning torque calculation map shown in FIG. The aligning torque estimated value SAT may be set to a value larger than the actual self-aligning torque. In this case, since the second steering assist torque command value Iref2 also increases, the electric motor 12 enters a self-steer state in which a steering assist force not intended by the driver is generated.

  For this reason, the driving wheel slip gain setting unit 39A calculates the driving wheel slip ratio and refers to the driving wheel slip gain calculation map shown in FIG. 15 on the basis of the calculated driving wheel slip ratio. A drive wheel slip gain K3 that decreases as it increases is calculated, and a gain multiplier output Iref6 (= Iref5 * K3) is calculated by multiplying the calculated drive wheel slip gain K3 by the gain multiplier 39B to the gain multiple output Iref5. Thus, the self-steering state due to the drive wheel slip is suppressed.

  Further, when the vehicle speed Vs and the motor angular speed ω are input to the torque limit value setting unit 40 of the torque limiter 32D, the vehicle speed Vs is determined based on the vehicle speed Vs with reference to the vehicle speed limit value calculation map of FIG. A vehicle speed limit value Limv that limits the output of the control output and control abnormality output by self-steering in a high region is calculated, and the motor angular speed is referred to the motor angular speed limit value calculation map of FIG. 16B based on the motor angular speed ω. When ω becomes equal to or higher than the speed generated by the driver's steering or road surface reaction force, a motor angular speed limit value Limm for limiting the output of the control output by the self-steer and the control abnormality output is calculated.

  Therefore, when the vehicle speed Vs is high, the vehicle speed limit value Limv becomes a small value, whereby the second steering assist torque command value Iref2 is limited to the vehicle speed limit value Limv, and the steering assist force generated by the electric motor 12 is also small. Limited. Similarly, when the motor angular speed ω becomes equal to or higher than the speed ω2 generated by the driver's steering or road reaction force, the motor angular speed limit value Limm gradually decreases as the motor angular speed ω increases, so that the second steering The auxiliary torque command value Iref2 is limited to the motor angular velocity limit value Limm, and the steering assist force generated by the electric motor 12 is limited. As a result, since there is a high possibility of a control abnormality output state in a high vehicle speed region or a region where the motor angular velocity ω is high, it is possible to suppress the control output abnormality by limiting the second steering assist torque command value Iref2.

  In the second 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 rotation information calculation unit 20 and the steering assist torque are applied by applying a microcomputer. The functions of the command value calculation unit 21, the command value compensation unit 22, the current limiting unit 23, and the motor drive circuit can be processed by software. As processing in this case, the microcomputer may execute the steering torque sensor abnormality detection processing shown in FIG. 5 and the steering assist control processing shown in FIG.

  Here, as shown in FIG. 18, the steering assist control process is executed as a timer interrupt process every predetermined time (for example, 1 msec). First, in step S31, the steering torque sensor 14, the vehicle speed sensor 16, and the rotation angle sensor are executed. 17, the detection values of various sensors such as the wheel rotation speed sensors 18L, 18R are read, then the process proceeds to step S32, the motor rotation angle θ is differentiated to calculate the motor angular speed ω, and then the process proceeds to step S33. After the motor angular speed ω is differentiated to calculate the motor angular speed α, the process proceeds to step S34.

In this step S34, it is determined whether or not the sensor abnormality flag Fa set in the torque sensor abnormality detection process of FIG. 5 is set to “1”, and when the sensor abnormality flag Fa is reset to “0”. The process proceeds to steps S35 to S38.
In these steps S35 to S38, processing similar to that in steps S13 to S16 in FIG. 6 in the first embodiment described above is performed to calculate the first steering assist torque command value Iref1, and the calculated first steering is calculated. After the auxiliary torque command value Iref1 is updated and stored in the predetermined command value storage area as the steering auxiliary torque command value Iref, the process proceeds to step S50.

If the determination result of step S34 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 S39. The first embodiment described above. The same processing as step S17 is performed to calculate the self-aligning torque estimated value SAT.
Next, the process proceeds to step S40, where it is determined whether the steering state is the increased state, the reverted state, or the steered state based on the calculated self-aligning torque estimated value SAT and the motor angular velocity ω. The steering state sensitive gain K0 is calculated with reference to the steering state sensitive gain calculation map of FIG.

Next, the process proceeds to step S41, and the gain double output Iref3 (= SAT * K0) is calculated by multiplying the calculated steering state sensitive gain K0 by the estimated self-aligning torque SAT calculated in step S39.
Next, the process proceeds to step S42, the vehicle speed sensitive gain K1 is calculated based on the vehicle speed Vs with reference to the vehicle speed sensitive gain calculation map shown in FIG. 10, and then the process proceeds to step S43, where the calculated vehicle speed sensitive gain K1 is obtained. The gain double output Iref4 (= Iref3 * K1) is calculated by multiplying the gain double output Iref3.

  Next, the process proceeds to step S44, and the self-aligning torque is calculated by performing the calculations of the above-described equations (2) and (3) using the vehicle model based on the wheel speeds VwFL to VwRR of the four wheels and the motor angle θ. A calculated value SATo is calculated, a deviation ΔSAT between the calculated self-aligning torque calculated value SATo and the estimated self-aligning torque SAT calculated in step S39 is calculated, and based on the absolute value | ΔSAT | of the calculated deviation ΔSAT. The self-aligning torque gain K2 is calculated with reference to the self-aligning torque gain calculation map shown in FIG.

Next, the process proceeds to step S45, and the gain double output Iref5 (= Iref4 * K2) is calculated by multiplying the calculated self aligning torque gain K2 by the gain double output Iref4.
Next, the process proceeds to step S46, where the aforementioned drive wheel slip ratio ΔVw is calculated based on the four-wheel wheel speeds VwFL to VwRR, and the drive wheel slip gain calculation map of FIG. 15 is referred to based on the absolute value | ΔVw | Then, the drive wheel slip gain K3 is calculated.

Next, the process proceeds to step S47, and the gain double output Iref6 (= Iref5 * K3) is calculated by multiplying the calculated drive wheel slip gain K3 by the gain double output Iref5.
Next, the process proceeds to step S48, where the vehicle speed limit value Limv is calculated based on the vehicle speed Vs with reference to the vehicle speed limit value calculation map shown in FIG. 16A, and based on the motor angular speed ω, as shown in FIG. The motor angular speed limit value Limm is calculated with reference to the motor angular speed limit value calculation map shown in FIG. 5 and the smaller one of the calculated vehicle speed limit value Limv and motor angular speed limit value Limm is set as the limit value Lim.

Next, the process proceeds to step S49, the gain multiplication output Iref6 is limited by the set limit value Lim to calculate the second steering assist torque command value Iref2, and the calculated second steering assist torque command value Iref2 is steered. After updating and storing the auxiliary torque command value Iref in a predetermined command value storage area, the process proceeds to step S50.
In this step S50, a convergence compensation value Ic (= Kc * ω) is calculated by multiplying the motor angular velocity ω by the convergence gain Kc, and then the routine proceeds to step S51, where the inertia compensation value is based on the motor angular acceleration α. Ti is calculated.

Subsequently, the process proceeds to step S52, and the post-compensation steering assist torque command value Iref ′ is calculated by adding the convergence compensation value Ic and the inertia compensation value Ii to the steering assist torque command value Iref stored in the command value storage area. To do.
Next, the process proceeds to step S53, where the calculated post-compensation steering assist torque command value Iref ′ is subjected to the maximum current limiting process to calculate the post-limit steering assist torque command value Iref ″, and then the process proceeds to step S54. The post-restricted steering assist torque command value Iref ″ is output to the motor response circuit 24, the electric motor 12 is driven, the timer interruption process is terminated, and the process returns to the predetermined main program.

In the process of FIG. 6, the process of step S34 corresponds to the abnormal time switching means, the processes of steps S35 to S38 correspond to the first torque command value calculation means, and the processes of steps S39 to S49 are the second torque. Corresponding to the command value calculating means, among these, the processing of steps S40 to S49 corresponds to the gain adjusting means, and the processing of S50 to S54 corresponds to the motor control means.
As described above, when the torque sensor abnormality detection process of FIG. 5 and the steering assist control process of FIG. 18 are executed by the microcomputer, the steering torque sensor 14 is normal as in the second embodiment described above. The process of steps S35 to S38 in the steering assist control process of 18 is executed to calculate the first steering assist torque command value Iref1. Further, when the steering torque sensor 14 is abnormal, the process of steps S39 to S49 in the steering assist control process of FIG. 18 is executed to calculate the second steering assist torque command value Iref2, whereby the rack of the steering gear mechanism 8 is obtained. A self-aligning torque SAT that is a reaction force from the road surface input to the shaft is estimated, and various gain adjustments are performed on the estimated self-aligning torque SAT to calculate a second steering assist torque command value Iref2.

  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 occurs, the self-aligning torque SAT is estimated based on the wheel rotation speeds VwL and VwR, and the second self-aligning torque command value Iref2 is calculated by adjusting the gain of the estimated self-aligning torque SAT. For this reason, even when the steering torque sensor 14 changes from a normal state to an abnormal state, the road surface reaction force is considered based on the second steering assist torque command value Iref2, and the vehicle steering state and traveling state are further changed. A more optimal steering assist control can be continued by performing a corresponding gain adjustment.

In the second embodiment, the case where the vehicle speed gain adjustment, the steering state gain adjustment, the self-aligning torque gain adjustment, and the drive wheel slip gain adjustment are described has been described. However, the present invention is not limited to this and is necessary. Depending on the above, any one of the above adjustments may be selected, or a plurality may be selected and combined.
In the above embodiment, the vehicle speed sensitive gain adjusting unit 37 calculates the vehicle speed sensitive gain K1 based on the vehicle speed Vs. However, the present invention is not limited to this, and the four wheel speeds VwFL to VwRR are not limited thereto. You may make it apply an average value or the average value of the wheel speed of a driven wheel as a vehicle speed.

Next, a third embodiment of the present invention will be described with reference to FIGS.
In the third embodiment, an angular velocity correction value based on the motor angular velocity ω with respect to the self-aligning torque initial estimated value SATi estimated by the self-aligning torque initial estimating unit 321 in the first and second embodiments described above. This is to be corrected.
That is, in the third embodiment, the motor angular velocity ω calculated by the rotation information calculating unit 20 is supplied to the amplifier 326 in which the angular velocity gain Khys is set to calculate the hysteresis correction value Ahys, and the calculated hysteresis correction value Ahys is calculated. This is supplied to an adder 327 interposed between the self-aligning torque initial estimation unit 321 and the low-pass filter 322 to correct the hysteresis characteristic of the self-aligning torque initial estimated value SATi.

  In the first and second embodiments described above, the relationship between the self-aligning torque SAT actually generated in the vehicle and the self-aligning torque initial estimated value SATi estimated by the self-aligning torque initial estimating unit 321 is shown in FIG. As shown by the broken line, it has a relatively large hysteresis characteristic. For this reason, in the second embodiment, the hysteresis correction value Ahys is calculated based on the motor angular velocity ω, and this hysteresis correction value Ahys is added to the self-aligning torque initial estimated value SATi. By correcting in accordance with the steering angular speed, the hysteresis characteristic width can be narrowed as shown by the solid line in FIG. 20 to calculate the more accurate self-aligning torque initial estimated value SATi.

Next, a fourth embodiment of the present invention will be described with reference to FIGS.
In the fourth embodiment, instead of directly calculating the self-aligning torque estimated value from the wheel rotational speeds VwL and VwR, the vehicle side slip angle β is estimated based on the wheel rotational speeds VwL and VwR, and the estimation is performed. The self-aligning torque initial estimated value SATi is calculated based on the vehicle side slip angle β.

That is, in the fourth embodiment, as shown in FIG. 21, the motor rotation angle θ and the motor angular speed ω are supplied to the self-aligning torque estimation unit 32A in addition to the wheel rotation speeds VwL and VwR. The self-aligning torque estimated value unit 32A has the configuration shown in FIG.
This self-aligning torque estimation unit 32A calculates a side slip angle estimation unit 328 that estimates the vehicle side slip angle β based on the left and right wheel rotation speeds VwL and VwR, and calculates the angle change amount Δθ by inputting the motor rotation angle θ. An angle change amount calculation unit 329, an amplifier 330 in which a slip angle correction gain Kslp to which the angle change amount Δθ calculated by the angle change amount calculation unit 329 is input, and a slip angle correction value calculated by the amplifier 330 are set. An adder 331 that corrects the amount of tire twist by adding Aslp to the skid angle β estimated by the skid angle estimator 328, and an amplifier 326 and an adder 327 similar to those of the second embodiment described above are provided. ing.

  Here, the skid angle estimation unit 328 calculates the wheel rotation speed difference ΔVw by performing the calculation of the above-described equation (1) in the first embodiment, and based on the calculated wheel rotation speed difference ΔVw in FIG. The vehicle side slip angle β is estimated with reference to the vehicle side slip angle calculation map shown. As shown in FIG. 23, the vehicle side slip angle calculation map is represented by a characteristic diagram obtained from a measured value of an actual vehicle with the wheel rotational speed difference ΔVw on the horizontal axis and the vehicle side slip angle β on the vertical axis. A characteristic curve L is set such that when the rotational speed difference ΔVw is near zero, a relatively gentle gradient is obtained, and when the wheel rotational speed difference ΔVw is larger than this, a relatively steep slope is set.

  On the other hand, the self-aligning torque initial estimation unit 321 estimates the self-aligning torque initial estimated value SATi with reference to the self-aligning torque initial estimated value calculation map shown in FIG. 24 based on the vehicle side slip angle β. As shown in FIG. 24, this self-aligning torque initial estimated value calculation map is obtained from the measured values of the actual vehicle with the vehicle sideslip angle β on the horizontal axis and the self-aligning torque initial estimated value SATi on the vertical axis. A linear section Ls in which the inclination angle increases as the vehicle speed equivalent value Vs ′ becomes a large value using the vehicle speed equivalent value Vs ′ as a parameter, and a saturation section La extending from both ends of the linear section Ls. The characteristic line is set.

According to the third embodiment, the self-aligning torque estimation unit 32A constituting the second steering assist torque command value calculation unit 32 calculates the wheel rotation speed difference ΔVw between the left and right wheel rotation speeds VwL and VwR of the driven wheel. Based on the vehicle side slip angle calculation map shown in FIG. 23, the vehicle side slip angle β is calculated, and the calculated vehicle side slip angle β is converted to the slip angle correction value Aslp based on the angle change amount Δθ of the motor rotation angle θ. As a result of the correction, the error due to the torsion amount of the tire can be corrected to improve the estimation accuracy of the vehicle side slip angle β.

  Then, the self-aligning torque initial estimation unit 321 estimates the self-aligning torque initial estimated value SATi with reference to the self-aligning torque initial estimated value calculation map shown in FIG. 24 based on the estimated skid angle β, At this time, the optimum self-aligning torque initial estimated value SATi corresponding to the vehicle speed equivalent value Vs ′ can be estimated by selecting a characteristic line of inclination corresponding to the vehicle speed equivalent value Vs ′.

  Then, the estimated self-aligning torque initial estimated value SATi is corrected with the hysteresis correction value Ahys based on the motor angular velocity ω as in the above-described third embodiment, thereby correcting the hysteresis characteristic and more accurate self-aligning. The torque initial estimated value SATi can be estimated, and the second steering assist torque command value Iref2 is calculated by multiplying the self-aligning torque initial estimated value SATi by a gain K equal to or less than “1”. The steering torque command value Iref2 can be calculated.

In the fourth embodiment, the case where the vehicle speed equivalent value Vs ′ calculated based on the wheel rotation speeds VwL and VwR is supplied to the self-aligning torque initial estimation unit 321 has been described. However, the present invention is not limited to this. Instead, the vehicle speed Vs detected by the vehicle speed sensor 16 may be supplied to the self-aligning torque initial estimation unit 321.
Similarly, in the first to fourth embodiments, the vehicle speed equivalent value Vs ′ calculated based on the wheel rotation speeds VwL and VwR is supplied to the phase correction unit 325 constituting the self-aligning torque estimation unit 32A. However, the present invention is not limited to this, and the vehicle speed Vs detected by the vehicle speed sensor 16 may be supplied.

  Further, the overall configuration diagram when the third embodiment and the fourth embodiment are applied to the second embodiment described above is as shown in FIGS. 25 and 26, and the self-aligning torque estimation unit 32A. You can change the input of.

  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, WL, WR ... steered wheel, 10 ... steering assist mechanism, 11 ... deceleration mechanism, 12 ... electric motor, 14 ... steering torque sensor, 15 ... controller, 16 ... vehicle speed sensor 16 ... rotation angle sensor, 18L, 18R ... wheel Rotational speed sensor 20 ... Rotation information calculation unit 201 ... Motor angular velocity calculation unit 212 ... Motor angular acceleration calculation unit 21 ... Steering assist torque command value calculation unit 22 ... Command value compensation unit 23 ... Current limit unit 24 ... Motor drive circuit, 31 ... first steering assist torque command value calculation unit, 311 ... torque command value calculation unit, 312 ... complementary 313 ... Center response improvement part, 314 ... Adder, 32 ... Second steering assist torque command value calculation part, 32A ... Self-aligning torque estimation part, 32B ... Amplification part, 32C ... Gain adjustment part, 32D ... Torque limiter 321 ... Self-aligning torque initial estimator 322 ... Robas filter 324 ... Average value calculator 325 ... Phase corrector 326 ... Amplifier 327 ... Adder 328 ... Side slip angle estimator 329 ... An angle change amount calculation unit, 330 ... Amplifier, 33 ... Torque sensor abnormality detection unit, 34 ... Command value selection unit, 36 ... Steering state gain adjustment unit, 37 ... Vehicle speed sensitive gain adjustment unit, 38 ... Self-aligning torque gain adjustment 38A ... Self-aligning torque gain setting unit 38B ... Gain multiplying unit 381 ... Self-aligning torque calculating unit 382 ... Calculator: 383: Absolute value calculation unit, 384: Gain calculation unit, 39: Drive wheel slip gain adjustment unit, 40: Torque limit value setting unit, 41: Limiter unit, 43: Convergence compensation unit, 44 ... Inertia compensation unit 45, 46 ... adders

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 first 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 the steering mechanism; and a motor control unit that drives and controls the electric motor based on the torque command value.
A torque detector abnormality detecting means for detecting an abnormality of the torque detecting means;
Wheel rotation speed detection means for detecting the wheel rotation speed of the vehicle;
Second torque command value calculation means for calculating a second torque command value based on the wheel rotation speed detected by the wheel rotation speed detection means;
When the abnormality of the torque detection means is detected by the torque detection unit abnormality detection means, the motor control means is selected by selecting the second torque command value calculation means instead of the first torque command value calculation means. And an abnormal time switching means for outputting the second torque command value,
The second torque command value calculating means includes self-aligning torque estimating means for estimating self-aligning torque transmitted from the road surface side to the steering mechanism based on the wheel rotation speed, and the self-aligning torque estimating means. Gain adjusting means for calculating the second torque command value by multiplying the self-aligning torque estimated in step 1 by gain, and detecting the second torque command value calculated by the gain adjusting means by the wheel rotation speed detecting means. Torque limiting means for limiting based on at least one of the vehicle speed calculated based on the wheel rotational speed and the vehicle speed detected by the vehicle speed detecting means and the motor angular speed calculated by the motor angular speed calculating means. It shall be the electric power steering apparatus. The gain adjusting means determines the steering state based on the motor rotation information detected by the motor rotation information detecting means and the self-aligning torque estimated by the self-aligning torque estimating means, and based on the determination result of the steering state 2. The electric power steering apparatus according to claim 1 , further comprising steering state gain adjusting means for adjusting a steering state sensitive gain. The gain adjusting means has vehicle speed gain adjusting means for adjusting a vehicle speed sensitive gain based on one of the vehicle speed calculated based on the wheel rotational speed detected by the wheel rotational speed detecting means and the vehicle speed detected by the vehicle speed detecting means. The electric power steering apparatus according to claim 1 or 2 , wherein The gain adjustment means includes a self-aligning torque calculation value calculated based on the motor rotation information detected by the motor rotation information detection means and the wheel rotation speed detected by the wheel rotation speed detection means, and the self-aligning torque estimation means. according to any one of claims 1 to 3, characterized in that it has a self-aligning torque gain adjusting means for adjusting the self-aligning torque gain based in the deviation between the estimated self aligning torque estimated value Electric power steering device. The gain adjusting means estimates a driving wheel slip state based on the wheel rotational speed detected by the wheel speed detecting means, and adjusts a driving wheel slip sensitive gain based on the estimated driving wheel slip state. The electric power steering apparatus according to any one of claims 1 to 4 , further comprising means. The gain adjusting means is configured to calculate the second torque command value by multiplying the self-aligning torque estimated by the self-aligning torque estimating means by a gain smaller than 1. Item 4. The electric power steering device according to Item 1 . The self-aligning torque estimating means includes vehicle side-slip angle estimating means for estimating a vehicle side-slip angle based on the wheel rotational speed, and the self-aligning torque based on the vehicle side-slip angle estimated by the vehicle side-slip angle estimating means. The electric power steering apparatus according to claim 1 , wherein the electric power steering apparatus is configured to estimate The vehicle side slip angle estimating means is configured to estimate a vehicle side slip angle based on the wheel rotation speed, and to correct the estimated side slip angle based on motor rotation information detected by the motor rotation information detecting means. The electric power steering apparatus according to claim 7 . The self-aligning torque estimating means, according to claim 1, characterized in that it is configured to estimate the self aligning torque on the basis of the the motor rotation information detected by the wheel rotational speed and the motor rotational information detecting means The electric power steering device according to any one of 1 to 6 . The abnormal time switching means changes from the first torque command value to the second torque command value when the second torque command value calculation means is selected instead of the first torque command value calculation means. The electric power steering apparatus according to any one of claims 1 to 9 , wherein the electric power steering apparatus is gradually changed.

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