JP6012824B1 - Vehicle steering apparatus and vehicle steering control method - Google Patents

Abstract

Interference with driver steering in a vehicle steering apparatus that converges lateral displacement to a target travel line with simple control by calculating a target steering angle based on lateral velocity controlled so that lateral displacement is reduced. The present invention provides a vehicle steering device and a vehicle steering control method capable of preventing the occurrence of the above and the unstable behavior of the vehicle. According to the present invention, feedback control and feedforward control of a target vehicle state quantity are properly used, according to comparison with threshold values of lateral displacement, inclination of a target travel line, vehicle speed, travel path recognition rate, steering torque, switching of an operation switch, and the like. The target torque is set by changing the ratio of the feedback control type target torque signal and the feedforward control type target torque signal to the target torque signal. [Selection] Figure 6

Description

  The present invention relates to a vehicle steering apparatus and a vehicle steering control method for assisting a driver's steering by applying an assist torque to a steering mechanism so that the vehicle travels while maintaining the center of the lane.

  In recent years, by using a camera attached to the front of the vehicle to detect the driving lane and applying assist steering torque to the steering by electric power steering, steering wobble or lane departure caused by driver's side-view driving, diffuse driving, or snoozing driving A lane keeping control device (lane keeping system) that reduces the burden on the driver while preventing the vehicle has been developed.

  As for a conventional vehicle steering apparatus having a lane keeping control function, as shown in Patent Document 1 below, steering is performed so that an estimated travel locus approaches a target locus set based on the travel path shape of the vehicle. When controlling an auxiliary part, what corrects a control gain for making a run locus close to a target locus based on curvature is disclosed.

  According to this conventional apparatus, the control gain for bringing the travel locus close to the target locus is corrected based on the detected curvature, so that the control gain for bringing the travel locus close to the target locus according to the curvature of the vehicle travel path. This has the effect of not giving the driver a sense of incongruity when correcting the travel line.

JP 2001-001921 A

  However, the device described in Patent Document 1 only discloses a method of multiplying a future lateral deviation by a control gain for setting a control torque for the steering assist unit, and it is unknown whether the travel locus converges to the target locus. It is. Still further, for example, the yaw rate of the vehicle is not specifically described and not considered. Therefore, there is a possibility that the vehicle cannot travel following the target travel line.

  The present invention has been made to solve the above-described problems in the conventional apparatus. The lateral displacement at the forward gazing point distance is converged to the target travel line, and further, the occurrence of interference with the driver steering and the behavior of the vehicle are reduced. It is an object of the present invention to provide a vehicle steering device and a vehicle steering control method that prevent instability.

  The present invention provides a vehicle state quantity detection unit that detects a vehicle state quantity of a vehicle in a vehicle steering device that applies a steering torque to a steering mechanism so that the vehicle travels along a traveling path and performs a steering assist of a driver. A travel path recognition unit that recognizes the travel path on which the vehicle travels, a target travel line setting unit that sets a target travel line for the vehicle to travel following the travel path, and a front side of the vehicle A lateral displacement calculation unit that calculates a lateral displacement that is a difference in position between the target travel line and the vehicle at a gaze point distance; a target vehicle state quantity calculation unit that calculates a target vehicle state quantity so as to reduce the lateral displacement; A first steering torque for realizing the target vehicle state quantity is calculated by feedback control of the vehicle state quantity based on a deviation between the target vehicle state quantity and the vehicle state quantity. A feedback control type torque calculation unit; a feedforward control type torque calculation unit that calculates a second steering torque for realizing the target vehicle state quantity by feedforward control of the vehicle state quantity based on the target vehicle state quantity; A target torque setting unit for setting the target torque by adding the first steering torque and the second steering torque according to the state of the vehicle; and an assist motor for applying a steering torque to the steering mechanism based on the target torque; The target vehicle state quantity calculation unit controls a lateral speed that is a change amount of the lateral displacement so that the lateral displacement is reduced, and calculates the target vehicle state quantity based on the lateral speed. It is in a steering device for a vehicle.

  In this invention, the lateral displacement at the forward gazing point distance is converged to the target travel line, and further, the occurrence of interference with the driver steering and the instability of the behavior of the vehicle are prevented, and the vehicle steering device A control method can be provided.

It is a block diagram which shows the steering mechanism of the steering apparatus for vehicles which concerns on one embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a functional block diagram showing an electric power steering control device of a vehicle steering device and peripheral devices thereof according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a functional block diagram showing a lane keeping control device and its peripheral devices for a vehicle steering system according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view for explaining a positional relationship and parameters between a host vehicle and a lane in a vehicle steering apparatus according to an embodiment of the present invention. It is a figure which shows the relationship of the reference | standard road surface reaction force gradient (ratio of a road surface reaction force and a steering angle) with respect to the vehicle speed in the vehicle steering device which concerns on one embodiment of this invention. It is an operation | movement flowchart which shows the processing content of the target torque setting part in the lane keeping control apparatus of the steering apparatus for vehicles which concerns on one embodiment of this invention. It is explanatory drawing at the time of comprising the electric power steering control apparatus and lane keeping control apparatus of the steering apparatus for vehicles which concern on one embodiment of this invention with a microprocessor, respectively.

  First, when the lateral displacement at the forward gazing point distance is converged to the target travel line, it is necessary to consider the occurrence of interference with the driver steering and the unstable behavior of the vehicle.

  As a control method of the target steering angle, there are feedback control that calculates assist steering torque based on a deviation between a target vehicle state quantity (steering angle, yaw rate, lateral acceleration, etc.) for approaching the target travel line and an actual vehicle state quantity. There is feedforward control that calculates assist steering torque based only on the target vehicle state quantity.

  In the feedback control, since the steering torque changes every time a deviation between the target value and the actual value occurs, the tracking accuracy to the target travel line is high, but the frequency of interference with the driver is high. On the other hand, the feedforward control has a lower frequency of interference with the driver because the steering torque value fluctuates less frequently than the feedback control, but has low disturbance resistance against crosswinds and cants, and the tracking accuracy to the target travel line is low. Therefore, it is preferable to properly use feedback control and feedforward control according to the situation.

  In the present invention, the target rudder angle is calculated based on the lateral speed that is controlled so that the lateral displacement is reduced, so that the lateral displacement is converged to the target travel line by simple control. By properly using feedback control and feedforward control according to the relative position between the vehicle and the host vehicle, it is possible to prevent occurrence of interference with driver steering and instability of vehicle behavior.

  Hereinafter, a vehicle steering apparatus and a vehicle steering control method according to the present invention will be described with reference to the drawings according to each embodiment. In each embodiment, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing a steering mechanism of a vehicle steering apparatus according to an embodiment of the present invention.
In FIG. 1, the steering mechanism 1 includes a steering wheel 2, a steering shaft 3, a pinion gear 4, a steering angle detection unit 5, a torque sensor 6 as a steering torque detection unit, an assist motor 7, a motor gear 8, a rack shaft 9, a tire 10, An electric power steering control device 100 and a lane keeping control device 200 are provided. In addition, a traveling vehicle speed detection unit 11 is connected to the electric power steering control device 100, and a traveling vehicle speed detection unit 11, a camera unit 12, a yaw rate detection unit 13, and a lateral acceleration detection unit 14 are connected to the lane keeping control device 200. The

  A steering wheel 2 that is steered by an automobile driver is connected to one end of a steering shaft 3. Further, a steering angle detector 5 that detects a steering angle and outputs a steering angle signal θs is attached to the handle 2. A torque sensor 6 is attached to the steering shaft 3 for detecting a steering torque Td by the driver's steering and outputting a steering torque signal Ts. An electric assist motor 7 that generates a motor torque Tm that assists the driver's steering torque Td is attached to the steering shaft 3 via a motor gear 8.

  The pinion gear 4 is connected to the end of the steering shaft 3 and corresponds to the rotational direction of the steering shaft 3 that rotates based on the combined torque obtained by adding the steering torque Td and the motor torque Tm by the driver. Is converted into a linear motion in the axial direction of the rack shaft 9 in the direction. The tire 10 is connected to the pinion gear 4 via the rack shaft 9.

  The electric power steering control device 100 includes a steering torque signal Ts of the torque sensor 6, a vehicle speed signal Vs of the traveling vehicle speed detection unit 11, a motor current detection signal Is of the assist motor 7, and a motor voltage detection signal Es of the assist motor 7. The target torque signal Ttg of the lane keeping control device 200 is input. The electric power steering control device 100 calculates a target current value for driving the assist motor 7 based on the above inputs, and outputs an applied voltage E generated from the target current value to the assist motor 7. Further, the road surface reaction force torque signal Trs calculated based on the steering torque signal Ts and the motor current detection signal Is is output to the lane keeping control device 200.

  The lane keeping control device 200 includes a steering angle signal θs of the steering angle detector 5, a steering torque signal Ts of the torque sensor 6, a vehicle speed signal Vs of the traveling vehicle speed detector 11, a video signal Ms of the camera unit 12, and a yaw rate detector 13. The yaw rate signal γs, the lateral acceleration signal Gs of the lateral acceleration detector 14, and the road surface reaction force torque signal Trs of the electric power steering control device 100 are input. The lane keeping control device 200 calculates an assist torque for performing lane keeping control based on the above inputs, and outputs a target torque signal Ttg to the electric power steering control device 100.

  In particular, the present invention is characterized by the configuration and control processing of a vehicle steering control device including the lane keeping control device 200 and its peripheral devices.

  FIG. 2 is a functional block diagram showing the electric power steering control device on the output side of the vehicle steering device shown in FIG. 1 together with peripheral devices.

  In FIG. 2, the electric power steering control device 100 includes a steering assist current calculation unit 101, a lane keeping current calculation unit 102, an applied voltage calculation unit 103, and a road surface reaction force torque calculation unit 104. Note that a general electric power steering control device does not necessarily have all of these, and the above describes the configuration necessary for describing the present embodiment.

  For example, as shown in FIG. 7, the electric power steering control device 100 is a microprocessor having a CPU for electric power steering control, a memory M that stores programs and data necessary for processing, and an interface I / F. Configured. Each functional block shown in FIG. 2 of the electric power steering control device 100 is recorded as software in the memory M and executed by the CPU for electric power steering control. Further, the electric power steering control device 100 generates an applied voltage E corresponding to the target current and outputs it to the assist motor 7.

  The steering assist current calculation unit 101 is based on the steering torque signal Ts of the torque sensor 6 and the vehicle speed signal Vs of the traveling vehicle speed detection unit 11, and the steering assist current Ia for the steering torque signal Ts and the vehicle speed signal Vs stored in the memory M in advance. The steering assist current Ia is calculated with reference to the output map that defines the above and is output to the applied voltage calculation unit 103. The calculation of the steering assist current Ia is the same as that of an electric power steering device for assisting general driver steering, and although details are omitted, actually, a plurality of compensation controls are combined in addition to this. Thus, the steering assist current Ia is calculated.

  The lane keeping current calculation unit 102 converts the target torque signal Ttg of the lane keeping control device 200 into a current value based on the torque constant of the assist motor 7, calculates the lane keeping control current Ib, and outputs it to the applied voltage calculation unit 103.

  The applied voltage calculation unit 103 receives the steering assist current Ia of the steering assist current calculation unit 101, the lane maintenance control current Ib of the lane maintenance current calculation unit 102, the motor current detection signal Is of the assist motor 7 and the motor voltage detection signal Es. Is done. The applied voltage calculation unit 103 adds the steering assist current Ia and the lane keeping control current Ib, and calculates a target current value for driving the assist motor 7. Further, the applied voltage E is generated from the target current value based on the motor current detection signal Is and the motor voltage detection signal Es of the assist motor 7 and is output to the assist motor 7.

  The road surface reaction force torque calculation unit 104 calculates the road surface reaction force torque signal Trs from the equation (1) and outputs the road surface reaction force torque signal Trs to the lane keeping control device 200.

Trs = Ts + Kt · Is (1)
Kt: Motor torque constant

  FIG. 3 is a functional block diagram showing the lane keeping control device 200 of the vehicle steering device shown in FIGS.

  In FIG. 3, the lane keeping control device 200 includes a travel path recognition unit 201, a target travel line setting unit 202, a lateral displacement calculation unit 203, a target travel line inclination calculation unit 204, a target vehicle state quantity calculation unit 205, a feedback control type torque. A calculation unit 206, a feedforward control type torque calculation unit 207, and a target torque setting unit 208 are included. Note that a general vehicle fiber control device does not necessarily have all of these, and the above describes the configuration necessary for explaining the present embodiment.

  In addition, it is not necessary to configure all these functions of the lane keeping control device 200 with a single control unit, and the functions are distributed to a plurality of control units, and the calculation results are acquired from each other by wire or wireless communication. You may make it meet. Further, a part of the functions of the lane keeping control device 200 may be configured to be performed by, for example, the camera unit 12 on the input side or the electric power steering control device 100 on the output side. In the description of the present embodiment, for convenience of explanation, these functions will be described as being included in the lane keeping control device 200.

  Similarly to the electric power steering control device 100, the lane keeping control device 200 includes a CPU for lane keeping control, a memory M storing data necessary for programs and processing, and an interface, as shown in FIG. And a microprocessor having an I / F. Each functional block shown in FIG. 3 of the lane keeping control device 200 is recorded as software in the memory M and executed by the CPU for lane keeping control.

  The travel path recognition unit 201 detects the left and right white lines of the host vehicle from the video signal Ms output from the camera unit 12. Further, a travel path recognition rate rs, which is the reliability of the detected white line, is calculated. As a method of detecting the left and right white lines, an image ahead of the host vehicle is acquired from the input video signal Ms, binarized image processing and edge detection processing are performed, and left and right white lines of the host vehicle are detected by Hough transform or the like. In general, the relative position of the left and right white lines with respect to the host vehicle is detected and used as the forward travel path information. Various methods other than these have been proposed for detecting the white line on the road surface. However, in this embodiment, any method can be used to detect the white line on the left and right sides to achieve the effect of the present invention. Has no effect.

  FIG. 4 is a plan view for explaining the positional relationship and parameters between the host vehicle and the traveling lane in the present invention. The target travel line setting unit 202, the lateral displacement calculation unit 203, and the target line inclination calculation unit 204 will be described with reference to FIG. 4 in addition to FIG.

  The target travel line setting unit 202 sets a target travel line that is a target when the vehicle travels following the travel path in the travel path based on the forward travel path information obtained by the travel path recognition unit 201. In the present embodiment, as shown in FIG. 4, the target travel line is set at a position away from the lane boundary line that is the right travel lane, for example, 1/2 of the travel path width, but the present invention is not limited to this. Instead, for example, the driver's preference may be changed as appropriate. Also, the distance from the right or left lane boundary line of the host vehicle is obtained.

  The lateral displacement calculation unit 203 is based on the distance of the vehicle position from the lane boundary line with respect to the vehicle position obtained by the travel path recognition unit 201 and the target travel line set by the target travel line setting unit 202 as shown in FIG. The lateral displacement yLd at the forward gazing point distance Ld shown in FIG. If there is a distance from the right lane boundary of the host vehicle, a value obtained by subtracting the position of the target travel line from this value is the lateral displacement yLd. In this case, when the vehicle is on the left side with respect to the target travel line, the value is on the + side. If the distance from the right lane boundary or the right lane boundary cannot be detected and only the distance from the left lane boundary or the lane boundary is detected, the left lane boundary from the road width Since the value obtained by subtracting the distance from is the distance from the right lane boundary line, the value obtained by subtracting the position of the target travel line from this value may be used as the lateral displacement yLd.

  The target line inclination calculation unit 204 calculates the target travel line inclination eLd at the forward gazing distance Ld shown in FIG. 4 from the lane boundary inclination at the forward gazing distance Ld. However, one value is enough, so if the lane boundary slope on both sides can be acquired, it can be set to one value by processing such as averaging, and only one lane boundary slope can be acquired. Can be used as is.

  The target vehicle state quantity calculation unit 205 calculates the target vehicle state quantity Ptg based on the information obtained above, and outputs it to the feedback control type torque calculation unit 206 and the feedforward control type torque calculation unit 207.

  Here, the target vehicle state quantity Ptg is any one of the target steering angle θtg, the target yaw rate γtg, the target lateral acceleration Gtg, and the target road surface reaction force Trtg. Thereby, the kind of target vehicle state quantity can be arbitrarily set according to the kind of sensor which detects a vehicle state quantity, and the presence or absence of a sensor.

  Since the target yaw rate γtg, the target lateral acceleration Gtg, and the target road surface reaction force Trtg can be calculated from the target steering angle θtg, a method for calculating the target steering angle θtg will be described here. A method for obtaining the target yaw rate γtg, the target lateral acceleration Gtg, and the target road surface reaction force Trtg from the target steering angle θtg will be described later.

  Regarding the calculation of the target steering angle θtg, in order to make the vehicle position at the forward gazing point distance Ld follow the target travel line, a steering angle at which these differences approach 0 may be obtained as the target steering angle. Therefore, a lateral speed y′Ld, which is a change speed of the lateral displacement yLd, is considered with respect to the lateral displacement yLd that is the difference between the target travel line and the vehicle position at the forward gazing point distance Ld. If the lateral velocity y′Ld is controlled so that the lateral displacement yLd decreases, the lateral displacement yLd approaches 0. Therefore, the lateral velocity y′Ld may be controlled so as to satisfy Expression (2).

  y′Ld = −λ · yLd (2)

However,
y′Ld: lateral velocity at the forward gazing point yLd: lateral displacement from the target travel line at the forward gazing point λ: yLd attenuation characteristic parameter that takes a positive value. The larger the value, the faster the response of the control becomes unstable. Tend to be

Here, assuming that the vehicle is traveling on a high-standard trunk road, the following conditions are satisfied.
1) The horizontal speed is sufficiently smaller than the vertical speed.
2) Longitudinal acceleration is negligibly small.
3) The difference between the target travel line and the vehicle direction is sufficiently small.
4) The yaw rate γs is sufficiently small.

  When the conditions 1) to 4) are applied to the two-wheel model of the vehicle, the lateral speed y′Ld is expressed by Expression (3).

here,
L _f : Center-of-gravity-front wheel axle distance L _r : Center-of-gravity-rear wheel axle distance C _f : Front wheel side force stiffness C _r : Rear wheel side force stiffness

  Therefore, when Expression (3), which is the lateral velocity, is substituted into Expression (2) and rearranged into the expression of the target rudder angle θtg, Expression (4) is obtained.

  Vs: Speed signal (vehicle speed V)

  Finally, in equation (4), when the coefficients k1 to k3 are set as in equations (5) to (7), equation (8) is obtained.

  θtg = k1 · yLd + k2 · eLd−k3 · γs (8)

here,
θtg: Target steering angle (target vehicle state quantity)
k1 to k3: coefficient yLd: lateral displacement at the front gaze distance eLd: target travel line inclination at the front gaze distance γs: yaw rate

Regarding the values included in the coefficients k1 to k3, L _f and L _r are values determined for each vehicle because of the distance between the center of gravity and the wheel axis, but C _f and C _r are values related to the frictional force of the tire and are road surface conditions. It varies with the tire and the like, and λ is a value related to the control response. Furthermore, k1 and k3 also include a speed signal Vs indicating the vehicle speed V, and Ld may be changed in accordance with the vehicle speed. Therefore, the coefficients k1 to k3 may be changed in accordance with the vehicle state quantity. vehicle speed and impact of the vehicle behavior change is large relative to the change, may in a low μ road C _f must suppress the response of the steering angle control _is changed in accordance with the road surface friction coefficient high impact on the C _r.

  The target yaw rate γtg, the target lateral acceleration Gtg, and the target road surface reaction force Trtg are obtained from the following equations (9) to (11).

here,
A: Stability factor L: Wheelbase Kalign: Standard road surface reaction force gradient, “Ratio of steering angle to road reaction force” in the linear region of tire characteristics
It is.

  FIG. 5 shows the relationship between the reference road surface reaction force gradient (road surface reaction force / steering angle) Kalign and the vehicle speed signal Vs. FIG. 5 shows that when the vehicle speed signal Vs is small, the standard road surface reaction force gradient Kalign is small, and the standard road surface reaction force gradient Kalign increases as the vehicle speed signal Vs increases. These A, L and Kalign are vehicle-specific parameters. Therefore, the target yaw rate γtg, the target lateral acceleration Gtg, and the target road surface reaction force Trtg can be easily calculated from the target steering angle θtg without adding a sensor or the like.

The feedback control type torque calculation unit 206 calculates a feedback control type target torque signal Ttg_FB by feedback control of the sensor signal Ps with respect to the target vehicle state quantity Ptg obtained by the target vehicle state quantity calculation unit 205, and sets a target torque. The data is output to the unit 208.
here,
When the target vehicle state quantity Ptg is the target steering angle θtg, the sensor signal Ps is converted into the steering angle signal θs,
When the target vehicle state quantity Ptg is the target yaw rate γtg, the sensor signal Ps is changed to the yaw rate signal γs,
When the target vehicle state quantity Ptg is the target lateral acceleration Gtg, the sensor signal Ps is converted into the lateral acceleration signal Gs,
When the target vehicle state quantity Ptg is the target road surface reaction torque Trtg, the sensor signal Ps is the road surface reaction torque signal Trs,
And it is sufficient.

  Feedback control of the sensor signal Ps with respect to the target vehicle state quantity Ptg can be realized by PID control, and is calculated from the following equations (12) and (13). Expression (12) is a deviation e between the target vehicle state quantity Ptg and the sensor signal Ps, and Expression (13) is an expression for calculating the feedback control type target torque signal Ttg_FB by PID control.

here,
Kp: proportional control gain,
Ki: integral control gain,
Kd: differential control gain. Further, since it is not desirable that the steering angle changes suddenly, an upper limit value may be provided for the deviation e between the target vehicle state quantity Ptg and the sensor signal Ps.

The feedforward control type torque calculation unit 207 calculates a feedforward control type target torque signal Ttg_FF from the target vehicle state quantity Ptg obtained by the target vehicle state quantity calculation unit 205 and the speed signal Vs indicating the traveling vehicle speed, and sets a target torque. The data is output to the unit 208.
The feedforward control type target torque signal Ttg_FF is expressed by the following equations (14) to (17).
When the target vehicle state quantity Ptg is the target steering angle θtg, the equation (14)
When the target vehicle state quantity Ptg is the target yaw rate γtg,
When the target vehicle state quantity Ptg is the target lateral acceleration Gtg, the equation (16)
When the target vehicle state quantity Ptg is the target road surface reaction force Trtg, the equation (17)
It is represented by

The target torque setting unit 208
A feedback control type target torque signal Ttg_FB;
Feedforward control type target torque signal Ttg_FF
Are appropriately added and output to the electric power steering control device 100 as the target torque signal Ttg. Here, the ratio of the feedback control type target torque signal Ttg_FB to the target torque signal Ttg is α_FB. Therefore, the target torque signal Ttg is expressed by equation (18).

FIG. 6 is a flowchart showing the processing contents of the target torque setting unit 208.
In FIG. 6, first, in step S101, it is determined whether or not the lateral displacement yLd exceeds the lateral displacement threshold yLd_th. If the lateral displacement yLd exceeds the lateral displacement threshold yLd_th, the process proceeds to step S102. When the lateral displacement yLd is equal to or smaller than the lateral displacement threshold yLd_th, the process proceeds to step S108. As a result, when the lateral displacement yLd is equal to or less than the threshold value, it is determined that the deviation tendency of the host vehicle from the traveling lane is small, and the target in which the ratio of the feedforward control type target torque signal Ttg_FF is higher than the feedback control type target torque signal Ttg_FB. Interference with the driver can be prevented by setting the torque Ttg.

  In step 102, it is determined whether the target travel line slope eLd exceeds the target travel line slope threshold eLd_th. If the target travel line slope eLd exceeds the target travel line slope threshold eLd_th, the process proceeds to step 103. When the target travel line inclination eLd is equal to or less than the target travel line inclination threshold eLd_th, the process proceeds to step S108. As a result, when the target travel line inclination eLd is equal to or less than the threshold value, it is determined that the tendency of the vehicle to deviate from the travel lane is small, and the ratio of the feedforward control type target torque signal Ttg_FF is higher than the feedback control type target torque signal Ttg_FB. By setting the target torque Ttg, it is possible to prevent interference with the driver.

  In step S103, it is determined whether or not the vehicle speed (signal) Vs is less than the vehicle speed threshold value Vs_th. If the vehicle speed Vs is equal to or higher than the vehicle speed threshold value Vs_th, the process proceeds to step S108. If the vehicle speed Vs is less than the vehicle speed threshold Vs_th, the process proceeds to step 104. When the vehicle speed is high, the change rate of the vehicle behavior with respect to the change of the steering angle is large, and therefore the vehicle speed range in which the feedback control can be used is limited by the accuracy of the sensor signal Ps. Therefore, when the vehicle speed Vs is equal to or higher than the threshold value, the behavior of the vehicle becomes unstable by setting the target torque Ttg in which the ratio of the feedforward control type target torque signal Ttg_FF is higher than the feedback control type target torque signal Ttg_FB. Can be prevented.

  In step S104, it is determined whether the travel path recognition rate rs exceeds the travel path recognition rate threshold rs_th. If the travel path recognition rate rs exceeds the travel path recognition rate threshold rs_th, the process proceeds to step S105. If the travel path recognition rate rs is less than or equal to the travel path recognition rate threshold value rs_th, the process proceeds to step S108 if it is less. When the travel path recognition rate is low, the variation in white line information is large. Therefore, when the target torque calculated by feedback control is used, the frequency of interference with the driver increases. Therefore, when the travel path recognition rate rs is less than or equal to the threshold value, the frequency of interference with the driver is reduced by setting the target torque Ttg in which the ratio of the feedforward control type target torque signal Ttg_FF is higher than the feedback control type target torque signal Ttg_FB. Can be suppressed.

  In step S105, it is determined whether or not the steering torque Ts is less than the steering torque threshold value rs_th. If the steering torque Ts is greater than or equal to the steering torque threshold value Ts_th, the process proceeds to step S108. If the steering torque Ts is less than the steering torque threshold Ts_th, the process proceeds to step S106. When the steering torque is greater than or equal to the steering torque Ts, it can be determined that the interference with the driver is large. Therefore, when the steering torque Ts is equal to or greater than the threshold, the ratio of the feedforward control type target torque signal Ttg_FF is higher than the feedback control type target torque signal Ttg_FB. By setting the target torque Ttg, interference with the driver can be prevented.

  In step S106, it is determined whether the state of the mode selector switch SW shown in FIG. 3, for example, that can be switched by the driver is the first mode or the second mode. The process proceeds to step S107, and if it is the second mode, the process proceeds to step S108. Thereby, it is possible to switch to a target torque having a higher ratio of the feedforward control type target torque signal Ttg_FF than the feedback control type target torque signal Ttg_FB, and to prevent interference with the driver.

  In step S107, the target torque signal Ttg is output with the ratio α_FB of the feedback control type target torque signal Ttg_FB to the target torque signal Ttg set to a value larger than 0.5. That is, the target torque signal Ttg in which the ratio of the feedback control type target torque signal Ttg_FB is set higher than the feedforward control type target torque signal Ttg_FF is output.

  In step S107, the target torque signal Ttg is output with the ratio α_FB of the feedback control type target torque signal Ttg_FB to the target torque signal Ttg set to a value smaller than 0.5. That is, the target torque Ttg in which the ratio of the feedforward control type target torque signal Ttg_FF is set higher than the feedback control type target torque signal Ttg_FB is output.

In FIG. 6, steps S101 to S106 do not necessarily have to determine the ratio α_FB of the feedback control type target torque signal Ttg_FB with respect to the target torque signal Ttg based on all the conditions, and any one of steps S101 to S106. Alternatively, the ratio α_FB may be determined according to the conditions of a plurality of steps.
Here, the ratio α_FB is
Target torque Ttg =
Target torque Ttg_FB × a% + target torque Ttg_FF × b%
However, a + b = 100%
Represents a% when the target torque Ttg is set.

The electric power steering control device 100, the steering angle detection unit 5, the yaw rate detection unit 13, the lateral acceleration detection unit 14, the torque sensor 6 that is a steering torque detection unit, the traveling vehicle speed detection unit 11, and the camera unit 12 are in a vehicle state. A quantity detection unit is configured.
Further, the feedback control type target torque signal Ttg_FB corresponds to the first first steering torque, and the feedforward control type target torque signal Ttg_FF corresponds to the second steering torque.

  As described above, according to the present embodiment, by calculating the target steering angle based on the lateral speed that is controlled so that the lateral displacement is reduced, the lateral displacement can be converged to the target travel line with simple control. In the steering device, the use of feedback control and feedforward control according to the vehicle state quantity and the relative position between the target travel line and the host vehicle makes it possible to generate interference with driver steering and make vehicle behavior unstable. Can be prevented.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are within the scope of the present invention. Those skilled in the art will appreciate that this is possible.

1 steering mechanism, 2 steering wheel, 3 steering shaft, 4 pinion gear,
5 Steering angle detector, 6 Torque sensor, 7 Assist motor, 8 Motor gear,
9 rack shaft, 10 tires, 11 traveling vehicle speed detector, 12 camera unit,
13 yaw rate detector, 14 lateral acceleration detector,
100 electric power steering control device, 101 steering assist current calculation unit,
102 Lane maintaining current calculation unit, 103 Applied voltage calculation unit,
104 road surface reaction torque calculation unit, 200 lane keeping control device,
201 travel path recognition unit, 202 target travel line setting unit,
203 lateral displacement calculation unit, 204 target travel line inclination calculation unit,
205 target vehicle state quantity calculation unit, 206 feedback control type torque calculation unit,
207 Feedforward control type torque calculation unit, 208 Target torque setting unit,
SW mode selector switch.

Claims (14)

In a vehicle steering apparatus that applies a steering torque to a steering mechanism so that a vehicle travels along a traveling path and performs steering assist of a driver,
A vehicle state quantity detection unit for detecting a vehicle state quantity of the vehicle;
A travel path recognition unit that recognizes the travel path on which the vehicle travels;
A target travel line setting unit for setting a target travel line for the vehicle to travel following the travel path;
A lateral displacement calculation unit that calculates a lateral displacement that is a difference in position between the target travel line and the vehicle at a forward gazing distance of the vehicle;
A target vehicle state quantity calculation unit for calculating a target vehicle state quantity so as to reduce the lateral displacement;
A feedback control type torque calculation unit for calculating a first steering torque for realizing the target vehicle state quantity by feedback control of the vehicle state quantity based on a deviation between the target vehicle state quantity and the vehicle state quantity;
A feedforward control type torque calculation unit that calculates a second steering torque that realizes the target vehicle state quantity by feedforward control of the vehicle state quantity based on the target vehicle state quantity;
A target torque setting unit that sets the target torque by adding the first steering torque and the second steering torque according to the state of the vehicle;
An assist motor for applying a steering torque to the steering mechanism based on the target torque;
With
The target vehicle state quantity calculation unit controls a lateral speed that is a change amount of the lateral displacement so that the lateral displacement is reduced, and calculates the target vehicle state quantity based on the lateral speed. A vehicle speed detector for detecting the vehicle speed of the vehicle;
A yaw rate detector for detecting the yaw rate of the vehicle;
A target travel line inclination calculating unit for obtaining a target travel line inclination that is an inclination between the vehicle and the target travel line at a forward gazing distance of the vehicle;
Further comprising
The vehicle steering apparatus according to claim 1, wherein the target vehicle state quantity calculation unit calculates the target vehicle state quantity using the vehicle speed, the yaw rate, the target travel line inclination, and the lateral displacement.   The target torque setting unit sets a ratio of the first steering torque to the target torque higher than a ratio of the second steering torque when both the lateral displacement and the target travel line inclination exceed the respective threshold values. The ratio of the second steering torque to the target torque is set to be higher than the ratio of the first steering torque when either the lateral displacement or the target travel line inclination is equal to or less than the threshold value. The vehicle steering device according to claim 1.   The target torque setting unit sets a ratio of the first steering torque to the target torque higher than the ratio of the second steering torque when the vehicle speed is less than a threshold, and when the vehicle speed is equal to or higher than the threshold, The vehicle steering apparatus according to claim 2 or 3, wherein a ratio of the second steering torque to a target torque is set to be higher than a ratio of the first steering torque.   The target torque setting unit sets a ratio of the first steering torque to the target torque higher than a ratio of the second steering torque when a travel path recognition rate of the travel path recognition unit exceeds a threshold value, The ratio of the said 2nd steering torque with respect to the said target torque is set higher than the ratio of the said 1st steering torque when a travel path recognition rate is below the said threshold value, The any one of Claim 1 to 4 Vehicle steering system. A steering torque detector for detecting the steering torque of the driver;
The target torque setting unit sets a ratio of the first steering torque to the target torque higher than a ratio of the second steering torque when the steering torque is less than a threshold, and the steering torque is greater than or equal to the threshold. The vehicle steering apparatus according to any one of claims 1 to 5, wherein a ratio of the second steering torque to the target torque is sometimes set higher than a ratio of the first steering torque. It has a switch that can select the first mode and the second mode by operating the driver,
The target torque setting unit sets the ratio of the first steering torque to the target torque higher than the ratio of the second steering torque when the first mode is selected by the switch, and the second mode The vehicle steering apparatus according to any one of claims 1 to 6, wherein a ratio of the second steering torque to the target torque is set to be higher than a ratio of the first steering torque when is selected. .   The vehicle steering apparatus according to any one of claims 1 to 7, wherein the target vehicle state quantity is a target steering angle. The target vehicle state quantity is a target steering angle,
The target vehicle state quantity calculation unit calculates the target steering angle,
θtg = k1 · yLd + k2 · eLd−k3 · γs
8 tg: target steering angle k1 to k3: coefficient yLd: lateral displacement at the forward gazing point distance eLd: target traveling line inclination at the forward gazing point distance γs: yaw rate The calculation according to any one of claims 2 to 7. Vehicle steering system.   The vehicle steering apparatus according to claim 9, wherein the target vehicle state quantity calculation unit changes the coefficients k1 to k3 according to the vehicle state quantity.   The vehicle steering apparatus according to claim 1, wherein the target vehicle state quantity is a target yaw rate.   The vehicle steering apparatus according to any one of claims 1 to 7, wherein the target vehicle state quantity is a target lateral acceleration.   The vehicle steering apparatus according to any one of claims 1 to 7, wherein the target vehicle state quantity is a target road surface reaction force. In a vehicle steering control method in which a steering torque is applied to a steering mechanism so that a vehicle travels along a traveling path and a driver assists steering,
Detecting a vehicle state quantity of the vehicle;
Recognizing the travel path on which the vehicle travels;
Set a target travel line for the vehicle to travel following the travel path,
Calculating a lateral displacement, which is a difference in position between the target travel line and the vehicle at a forward gazing distance of the vehicle;
Calculating a target vehicle state quantity so as to reduce the lateral displacement;
A first steering torque for realizing the target vehicle state quantity is calculated by feedback control of the vehicle state quantity based on a deviation between the target vehicle state quantity and the vehicle state quantity;
Calculating a second steering torque for realizing the target vehicle state quantity by feedforward control of the vehicle state quantity based on the target vehicle state quantity;
Adding the first steering torque and the second steering torque according to the state of the vehicle to set a target torque;
A steering torque is applied to the steering mechanism by the assist motor based on the target torque,
A vehicle steering control method, wherein a lateral speed that is a change amount of the lateral displacement is controlled so as to reduce the lateral displacement, and the target vehicle state quantity is calculated based on the lateral speed.

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