JP2005041386A - Steering controlling device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform a road surface friction adaptive control by a simple constitution without newly providing a special sensor or the like to at least one of steering controls for the front wheels and the rear wheels of a vehicle. <P>SOLUTION: At a feed forward control section FF, a first target value is calculated in response to a norm yaw rate and a norm lateral acceleration based on a front wheel rudder angle (steering angle). At the same time, at a feed back control section FB, an (actual) yaw rate and an actual lateral acceleration are respectively compared with the norm yaw rate and the norm lateral acceleration, and a second target value is calculated based on a yaw rate deviation and a lateral acceleration deviation of the comparison result. In addition, at a road surface friction estimating section ES, respective sections are adjusted in response to a set road surface friction corresponding gain, based on a correlation between yaw rate identified models of the front wheel and rear wheel rudder angles and the (actual) yaw rate, and the road surface friction adaptive control is performed. Then, an actuator is controlled by a rear wheel rudder angle servo control section SC based on a target rear wheel rudder angle for which the second target value is added to the first target value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vehicle steering control device, and more particularly to a steering control device that controls a steering angle of at least one of a front wheel and a rear wheel by feedback control.

  Recently, a vehicle steering control device that controls the steering angle of at least one of the front and rear wheels of a vehicle by a control system that performs feedback control so that the actual state amount of the vehicle follows a predetermined target state amount has been attracting attention. ing. For example, as a rear wheel steering control device, a rear wheel steering control device has been proposed that can significantly reduce the man-hours for setting the gain of the target rear wheel steering angle with respect to the front wheel steering angle, as described in Patent Document 1 below. In the patent document 1, when setting the transfer function of the rear wheel steering angle with respect to the front wheel steering angle, attention is paid to a specific physical quantity expressing the motion of the vehicle, and predetermined characteristic parameters of the theoretical transfer function of the specific physical quantity with respect to the front wheel steering angle are set. The transfer function obtained by multiplying each variable constant input by the variable constant input means is the target transfer function, and the equivalent transfer function of the specific physical quantity with respect to the front wheel steering angle is the transfer function of the rear wheel steering angle with respect to the front wheel steering angle and the front wheel The rear wheel steering angle relative to the front wheel steering angle so that the equivalent transfer function is equivalent to the target transfer function when expressed by the theoretical transfer function of the specific physical amount relative to the steering angle and the theoretical transfer function of the specific physical amount relative to the rear wheel steering angle. And the target rear wheel steering angle is calculated based on the transfer function of the rear wheel steering angle with respect to the set front wheel steering angle.

  On the other hand, as means for estimating the road surface friction of the vehicle traveling road surface, the following Patent Document 2 describes a road surface friction coefficient that can easily estimate the friction coefficient of the vehicle traveling road surface with good accuracy before the vehicle behavior reaches the limit. An estimation device has been proposed. This device is configured to calculate the characteristic of the steering torque detected by the steering torque detection means with respect to the steering angle detected by the steering angle detection means, and to estimate the friction coefficient of the road surface on which the wheel contacts the ground based on the calculation result. Yes.

  Further, a slip control device for a vehicle is proposed in Patent Document 3 below, and “a first road surface μ based on lateral acceleration and a second road surface μ based on vehicle body longitudinal acceleration are estimated and predetermined. The slip control is performed according to the road surface μ that is selected according to the selection condition, that is, more accurately reflects the actual road surface μ. However, the patent document 3 states that “a specific driving state such as when the vehicle is spinning, that is, when the vehicle is sliding or drifting, when the driven wheel is locked, or when the slip of the driving wheel is extremely large. In this case, since it is difficult to accurately estimate the road surface μ in any case, it is necessary to select the road surface μ before the specific operation state, that is, the previously selected road surface μ as the current road surface μ. Is preferred. "

JP 2001-334949 A Japanese Patent Laid-Open No. 11-287749 JP-A-5-170087

  The above-mentioned Patent Document 1 sets a target state so that the vehicle has a desired characteristic and performs rear wheel steering control so as to achieve the desired characteristic. The desired characteristic is on a normal road surface (such as a dry asphalt road). This is a characteristic, and if the conditions change like a snowy road, the operation may be adversely affected. Specifically, the desired characteristic reflects the steering characteristic on the normal road surface, and the yaw rate gain is high. However, if the gain is high on the road surface with low friction, there is a possibility of causing resonance with the steering operation by the driver. is there. Therefore, it is necessary to take a separate measure in such a case.

  As countermeasures against this, it is conceivable to perform the road surface friction adaptive control by changing the target state in the rear wheel steering control according to the road surface friction (for example, the road surface friction coefficient μ), but accurately estimate the road surface friction. It is not easy. For example, in Patent Document 2 described above, when the steering wheel is increased, the amount of change in the steering torque with respect to the amount of change in the rotation angle (steering wheel angle) is obtained, and the friction coefficient of the road surface is calculated from this value. As a premise, steering torque must be measured, and when a new steering torque sensor is attached, the cost increases considerably.

  Further, in Patent Document 3 described above, since the previous road surface friction coefficient is selected at the time of wheel spin detection, the road surface friction coefficient is fixed when the wheel is not spinning. Particularly in the rear wheel steering control device, it is necessary to detect the road surface friction state successively and accurately only in such a state. Therefore, it is not appropriate to use the road surface friction coefficient estimating means described in Patent Document 3 for the rear wheel steering control device.

  Therefore, the present invention provides a steering control device capable of performing road surface friction adaptive control with a simple configuration without providing a new special sensor or the like for steering control of at least one of the front and rear wheels of a vehicle. Is an issue.

  In order to achieve the above object, the present invention provides a control system that performs feedback control so that the actual state quantity of the vehicle follows a predetermined target state quantity, and the steering angle of at least one of the front and rear wheels of the vehicle is set. In the vehicle steering control apparatus to be controlled, as described in claim 1, vehicle state detection means for detecting the actual state quantity of the vehicle, and the actual state quantity of the vehicle detected by the vehicle state detection means Set the vehicle state model identified in the normal driving range on the road surface of the high road surface friction coefficient, and based on the correlation between the vehicle state model and the actual state quantity, the road surface friction corresponding to the road surface friction state of the traveling road surface of the vehicle Based on the road surface friction estimation means for setting the gain and the road surface friction corresponding gain set by the road surface friction estimation means, at least a reference state quantity and a feedback gain for the control system are reduced. It is obtained by a further comprising an adjustment means for adjusting one.

  As described in claim 2, the road surface friction estimation means calculates the actual state amount of the vehicle detected by the vehicle state detection means in a normal driving range on a road surface having a predetermined high road surface friction coefficient (in an ideal state). Vehicle state model setting means for setting the identified vehicle state model, and a correlation value for sequentially calculating a correlation value between the output value of the model set by the vehicle state model setting means and the actual state quantity detected by the vehicle state detection means It is preferable to include calculation means and gain setting means for setting a road surface friction corresponding gain according to the road surface friction state of the traveling road surface of the vehicle based on the correlation value calculated by the correlation value calculation means. In addition, it is good also as performing smoothing by performing a filter process to the sequential calculation result of the said correlation value, and setting a road surface friction corresponding | compatible gain based on the correlation value after a filter process.

  According to a third aspect of the present invention, the correlation value calculation means sequentially uses at least one of a correlation coefficient, a square error integral value, and an error absolute value integral value as the correlation value at predetermined time intervals. It can be configured to operate. According to a fourth aspect of the present invention, the vehicle state detection means detects at least one of a front wheel steering angle and a rear wheel steering angle, a yaw rate, and a lateral acceleration of the vehicle as the actual state quantity of the vehicle. The vehicle state model setting means is configured to identify at least one of yaw rate and lateral acceleration and set a front wheel steering angle identification model and a rear wheel steering angle identification model for the front wheels and the rear wheels of the vehicle. It is good to configure.

  And, as described in claim 5, the adjusting means sets at least one of a standard yaw rate and a standard lateral acceleration for the vehicle as the standard state quantity, and adjusts based on the road surface friction corresponding gain. Configure.

  Since this invention is comprised as mentioned above, there exist the following effects. That is, in the vehicle steering control apparatus according to claim 1, the vehicle surface model in which the actual state quantity of the vehicle is identified in the normal driving range on the road surface having a predetermined high road surface friction coefficient is set by the road surface friction estimating means. Based on the correlation between the vehicle state model and the actual state amount, a road surface friction corresponding gain according to the road surface friction state of the traveling road surface is set. Based on the road surface friction corresponding gain, at least the reference state amount and the feedback gain for the control system are set. Since it is configured to adjust one, optimal control according to road surface friction, that is, road surface friction adaptive control is realized with a relatively small amount of computation by using only existing sensors without providing a special sensor or the like. It is possible to eliminate problems on slippery road surfaces and the like.

  The road surface friction estimation means includes vehicle state model setting means, correlation value calculation means, and gain setting means as described in claim 2, and sequentially calculates the correlation value between the vehicle state model output value and the actual state quantity. Since it is configured to calculate and set the road surface friction corresponding gain based on the correlation value, an appropriate road surface friction corresponding gain according to the road surface friction state of the traveling road surface can be easily set. In the correlation value calculating means, as described in claim 3, as the correlation value, a correlation coefficient, an integral value of a square error, and an integral of an absolute value of an error are calculated as the correlation value sequentially calculated at a predetermined time interval. If at least one of the values is used and these are sequentially calculated at predetermined time intervals, the correlation value can be easily calculated, and the road surface friction can be estimated easily and accurately. The normative state quantity etc. can be adjusted appropriately.

  Further, if the vehicle state quantity detection means is configured as described in claim 4, the actual state quantity of the vehicle can be easily detected by using only existing sensors. Further, as described in claim 5, the adjustment means can be configured simply by setting at least one of the standard yaw rate and the standard lateral acceleration as the standard state quantity, and an inexpensive device can be provided. Can be provided.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of a vehicle steering control device according to an embodiment of the present invention. In the vehicle 1, front wheels 3 and 3 are steered in response to an operation of a steering wheel 2, and rear wheels are accordingly moved. The steering angles of the wheels 4 and 4 are controlled by the actuator 5 to constitute a four-wheel steering control system (4WS). A steering angle (steering wheel angle), which is the steering angle of the front wheels 3 and 3, is detected by the front wheel steering angle sensor 6, and the front wheel steering angle δf is obtained based on the detection signal. On the other hand, the actuator 5 is driven and controlled by the controller 10, and the rear wheels 4 and 4 connected to the actuator 5 are steered. The steering angle is detected by the rear wheel steering angle sensor 7, and the detection is performed. The rear wheel steering angle δr is obtained based on the signal.

  In the present embodiment, the front wheel rudder angle δf has a one-to-one correspondence with the steering angle (handle angle), but the front wheels 3 and 3 are mechanically separated from the steering wheel 2 and controlled independently. When configured in this manner (for example, so-called steer-by-wire), the front wheel steering angle δf and the steering angle (steering wheel angle) do not correspond one to one. In this case, these rotation angles are detected separately, and the front wheel rudder angle is controlled independently in the same manner as the rear wheel rudder angle, but in this case as well, the same control as in this embodiment is performed. Can do.

  Further, a wheel speed sensor 11 is disposed on each of the front wheels 3 and 3 and the rear wheels 4 and 4, and these are connected to the controller 10, and a pulse signal proportional to the rotational speed of each wheel, that is, the wheel speed. Is input to the controller 10. A yaw rate sensor 12 for detecting the yaw rate γ of the vehicle, a lateral acceleration sensor 13 for detecting the lateral acceleration gy of the vehicle, and the like are mounted and connected to the controller 10. Thus, these constitute vehicle state detection means for detecting the yaw rate γ and the lateral acceleration gy as the actual state quantities of the vehicle 1. In the present embodiment, the mode changeover switch 14 is connected to the controller 10 so that four-wheel steering control and normal two-wheel (front wheel) steering control can be switched.

  In the controller 10, a CPU, ROM and RAM (not shown) for steering control are arranged. By these, a term controlled by feedforward control based on a front wheel steering angle δf (steering angle), and a front wheel A term for calculating a reference state quantity (reference yaw rate and reference lateral acceleration) representing the reference vehicle state based on the steering angle δf, and feedback-controlling a difference from the actual state quantity (yaw rate γ and lateral acceleration gy) showing the actual vehicle state. A basic system is configured in which the target rear wheel steering angle is set as the target and the rear wheel steering actuator 5 is servo-controlled.

  In the present embodiment, a road surface friction estimation means (which includes a vehicle state model setting means, a correlation value calculation means, and a gain setting means) and an adjustment means are configured in the controller 10, and in the road surface friction estimation means, A vehicle state model in which the actual state quantity of the vehicle is identified in the normal driving range on the road surface having a predetermined high road surface friction coefficient is set, and based on the correlation between the vehicle state model and the actual state quantity, the road surface friction state of the traveling road surface of the vehicle is set. A road surface friction corresponding gain is set according to the road surface friction, and based on this road surface friction corresponding gain, the adjustment means adjusts the reference state quantity (reference yaw rate and reference lateral acceleration) and / or the feedback gain.

  Specifically, it is configured as shown in the control block diagram of FIG. 2, and based on the front wheel steering angle δf (steering angle) detected by the front wheel steering angle sensor 6 in the feedforward control unit FF, The first target value is calculated according to the standard yaw rate γr and the standard lateral acceleration gyr calculated by the calculation units RY and RG based on the above. In parallel with the processing of the feedforward control unit FF, feedback control is executed in the feedback control unit FB. That is, the (actual) yaw rate γ and the lateral acceleration gy detected by the yaw rate sensor 12 and the lateral acceleration sensor 13 are compared with the standard yaw rate γr and the standard lateral acceleration gyr, respectively, and based on the yaw rate deviation and lateral acceleration deviation of the comparison result, The second target value is calculated in the feedback control unit FB.

  Then, the final target rear wheel steering angle is obtained by adding the second target value calculated by the feedback control unit FB to the first target value calculated by the feedforward control unit FF. The actuator 5 is servo-controlled by the rear wheel steering angle servo controller SC based on the rear wheel steering angle. In the present embodiment, both the yaw rate γ and the lateral acceleration gy are used as actual state quantities, but only one of them may be used.

  Further, in the present embodiment, the feedforward control unit FF, the feedback control unit FB, and the calculation units RY and RG are configured to be adjusted by the road surface friction estimation unit ES. That is, in each control unit, a transfer function is calculated by the following control equations [Equation 1] to [Equation 4], and coefficients and constants therein are set as described later in the road surface friction estimation unit ES. The road surface friction adaptive control is performed according to the road surface friction corresponding gain.

ここで、Ｇbdf(0)及びＧbdr(0)はゲイン定数で、ｎ０乃至ｎ２及びｄ１乃至ｄ３は車速依存係数である。尚、ｓはラプラス演算子を示す。 First, in the feedforward control unit FF, a control transfer function of the following [Equation 1] is set.

Here, Gbdf (0) and Gbdr (0) are gain constants, and n0 to n2 and d1 to d3 are vehicle speed dependent coefficients. Note that s represents a Laplace operator.

ここで、ｎｒ０乃至ｎｒ４、ｎｇ０乃至ｎｇ４、及びｄｇ０乃至ｄｇ４は車速依存係数、γｒは規範ヨーレイト、γは（実）ヨーレイト、ｇｙｒは規範横加速度、ｇｙは（実）横加速度である。 Next, in the feedback control unit FB, a control transfer function of the following [Equation 2] is set.

Here, nr0 to nr4, ng0 to ng4, and dg0 to dg4 are vehicle speed dependence coefficients, γr is a reference yaw rate, γ is a (real) yaw rate, gyr is a reference lateral acceleration, and gy is a (real) lateral acceleration.

ここで、Ｇrdf(0)及びＧrdr(0)はゲイン定数、Ｔｒ及びＴｒ'は車速依存係数、ζは減衰係数、ωｎは固有周波数である。 On the other hand, the reference yaw rate transfer function is set as in the following [Equation 3].

Here, Grdf (0) and Grdr (0) are gain constants, Tr and Tr ′ are vehicle speed dependent coefficients, ζ is an attenuation coefficient, and ωn is a natural frequency.

ここで、Ｇrdfgy(0)及びＧrdrgy(0)はゲイン定数、Ｔ１，Ｔ２，Ｔ１',Ｔ２'は車速依存係数、ζは減衰係数、ωｎは固有周波数である。 The reference lateral acceleration transfer function is set as shown in the following [Equation 4].

Here, Grdfgy (0) and Grdrgy (0) are gain constants, T1, T2, T1 ′ and T2 ′ are vehicle speed dependent coefficients, ζ is an attenuation coefficient, and ωn is a natural frequency.

  The coefficients and constants in the above equations [Equation 1] to [Equation 4] are variable depending on the road surface friction corresponding gain set by the road surface friction estimation unit ES as follows. The road surface friction estimation unit ES sequentially calculates at least one of a correlation coefficient, an integral value of a square error, and an integral value of an error absolute value as a correlation value at a predetermined time interval, and travels based on the correlation value. A road surface friction corresponding gain is set according to the road surface friction state of the road surface.

  FIG. 3 shows a configuration example of the road surface friction estimation unit ES. The front wheel rudder angle δf and the rear wheel rudder angle δr input as the actual state quantity of the vehicle are expressed as the high road surface friction coefficient in an ideal state (for example, a dry road). Vehicle state model setting means YM for identifying the normal driving range (linear area) on the road surface and setting the yaw rate model as the vehicle state model, and the correlation value between the model output value of this vehicle state model setting means YM and the actual state quantity Correlation value calculation means CE that sequentially calculates and performs a predetermined filter process on the calculation result, and gain setting means SG that sets a road surface friction corresponding gain according to the road surface friction state of the traveling road surface based on the correlation value after the filter processing Has been. Hereinafter, each means will be described sequentially.

  In the vehicle state model setting means YM, the front wheel rudder angle input yaw rate identification model YM1 that performs identification using the actual data of the yaw rate with respect to the front wheel rudder angle δf and represents a linear model, and the actual data of yaw rate with respect to the rear wheel rudder angle δr A rear-wheel steering angle input yaw rate identification model YM2 that is identified by using and is expressed as a linear model is configured, and the outputs of both models are added. Although the yaw rate model is used in the present embodiment, a lateral acceleration model may be used, and both may be used in combination.

また、後輪舵角入力ヨーレイト同定モデルＹＭ２は下記［数６］式で表される。

上記２式において、ｎｆ０乃至ｎｆ４、ｄｆ０乃至ｄｆ４、ｎｒ０乃至ｎｒ４、及びｄｒ０乃至ｄｒ４は車速依存係数、δｆは前輪舵角、δｒは後輪舵角である。 The front wheel steering angle input yaw rate identification model YM1 is expressed by the following [Equation 5].

The rear wheel steering angle input yaw rate identification model YM2 is expressed by the following [Equation 6].

In the above two formulas, nf0 to nf4, df0 to df4, nr0 to nr4, and dr0 to dr4 are vehicle speed dependent coefficients, δf is a front wheel steering angle, and δr is a rear wheel steering angle.

  Next, in the correlation value calculation means CE, the outputs of the front wheel steering angle input yaw rate identification model YM1 and the rear wheel steering angle input yaw rate identification model YM2 are added, and the addition result (yaw rate) and the actual state quantity (yaw rate γ) As a correlation value, at least one of a correlation coefficient, an integral value of a square error, and an integral value of an absolute value of an error is sequentially calculated at a predetermined time interval and smoothed at a predetermined time by a predetermined filter process. .

In the present embodiment, the correlation coefficient is obtained based on the following [Equation 7].

  Then, the gain setting means SG sets the road surface friction coefficient μ according to the correlation coefficient based on the correlation value-road surface μ table FT (for example, the map shown in FIG. 4), and further, the road surface μ-gain table GT ( For example, the road surface friction corresponding gain is set according to the road surface friction coefficient μ based on the map shown in FIG. Thus, as shown in FIG. 3, the standard state quantity (standard yaw rate and standard lateral acceleration) and / or feedback gain are adjusted based on the road surface friction corresponding gain, and the coefficient of each means is adjusted.

  FIG. 6 shows an example of the simulation result of the above-described road surface friction adaptive control, and FIG. 7 shows the contrast of a conventional four-wheel steering control system (4WS) in which this adaptive control is not performed. As shown in FIG. 7 of the latter, in the conventional system, for example, when the vehicle is traveling on a low friction coefficient road surface (low μ road) and the control gain at 4WS is high, the steering operation by the driver and resonance are generated. It may happen. That is, on the low μ road, as shown at the first rise of FIG. 7A, when the front wheel steering angle (in this case, the steering angle) is changed by the steering operation, when the control gain is high, The rear wheel rudder angle, slip angle, yaw rate, and lateral acceleration change as shown in FIGS. 7B to 7E.

  On the other hand, according to this embodiment, since it is configured as shown in FIG. 2, the above-described road surface friction adaptive control can be realized only with existing sensors at a relatively low calculation cost (calculation amount). As shown in FIG. 6G, when the vehicle moves from a road surface with a high friction coefficient (high μ road) to a low μ road, if the control gain is high, the control gain of 4WS is increased by road surface friction adaptive control. Adjusted to decrease. Thus, as shown in FIGS. 6B to 6E, the rear wheel rudder angle, slip angle, yaw rate, and lateral acceleration converge without causing resonance, ensuring stable running even on slippery road surfaces. Is done. Note that, unlike the present embodiment, the same road surface as described above for the front wheel steering angle control also in the steering control device configured to mechanically separate the front wheels 3 and 3 from the steering wheel 2 and to control them independently. Friction adaptive control (not shown) can be applied.

It is a lineblock diagram showing one embodiment of a steering control device of vehicles of the present invention. It is a block diagram which shows the control aspect in one Embodiment of this invention. It is a block diagram which shows the structural example of the road surface friction estimation means in one Embodiment of this invention. It is a graph which shows the map which sets a road surface friction coefficient according to a correlation coefficient in one Embodiment of this invention. It is a graph which shows the map which sets the road surface friction corresponding | compatible gain according to a road surface friction coefficient in one Embodiment of this invention. It is a graph which shows an example of the simulation result of the road surface friction adaptive control in one embodiment of the present invention. It is a graph which shows an example of the simulation result in the conventional four-wheel steering control system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Steering wheel 3 Front wheel 4 Rear wheel 5 Actuator 6 Front wheel rudder angle sensor 7 Rear wheel rudder angle sensor 10 Controller 11 Wheel speed sensor 12 Yaw rate sensor 13 Lateral acceleration sensor 14 Mode change switch

Claims (5)

  In a vehicle steering control device for controlling a steering angle of at least one of the front and rear wheels of a vehicle by a control system that performs feedback control so that the actual state quantity of the vehicle follows a predetermined target state quantity, Vehicle state detection means for detecting an actual state quantity; and a vehicle state model in which the actual state quantity of the vehicle detected by the vehicle state detection means is identified in a normal driving range on a road surface having a predetermined high road surface friction coefficient, Based on the correlation between the vehicle state model and the actual state quantity, road surface friction estimation means for setting a road surface friction corresponding gain according to the road surface friction state of the traveling road surface of the vehicle, and the road surface friction set by the road surface friction estimation means A vehicle steering system comprising: an adjusting unit that adjusts at least one of a reference state quantity and a feedback gain for the control system based on a corresponding gain. Control device.   The road surface friction estimating means sets a vehicle state model setting means for setting a vehicle state model that is identified in a normal driving range on a road surface of a predetermined high road surface friction coefficient, the actual state amount of the vehicle detected by the vehicle state detecting means, Correlation value calculation means for sequentially calculating a correlation value between the output value of the model set by the vehicle state model setting means and the actual state quantity detected by the vehicle state detection means; and the correlation value calculated by the correlation value calculation means The vehicle steering control device according to claim 1, further comprising gain setting means for setting a road surface friction corresponding gain according to a road surface friction state of the traveling road surface of the vehicle.   The correlation value calculating means is configured to sequentially calculate at least one of a correlation coefficient, an integral value of a square error, and an integral value of an absolute value of the error as the correlation value at a predetermined time interval. The vehicle steering control device according to claim 2.   The vehicle state detection unit is configured to detect at least one of a front wheel steering angle and a rear wheel steering angle, a yaw rate and a lateral acceleration of the vehicle as an actual state quantity of the vehicle, and the vehicle state model setting unit includes The front wheel rudder angle identification model and the rear wheel rudder angle identification model are set by identifying at least one of yaw rate and lateral acceleration with respect to the front wheel and the rear wheel of the vehicle. Or the steering control device of the vehicle according to 3. 5. The adjustment means is configured to set at least one of a reference yaw rate and a reference lateral acceleration for the vehicle as the reference state quantity, and adjust based on the road friction corresponding gain. Vehicle steering control device.

Images