Patent Description:
Patent Literature <NUM> discloses a driving assist device that assists driving of a vehicle. When detecting an obstacle around the vehicle, the driving assist device determines a braking control amount for avoiding collision based on possibility of collision with the obstacle. Here, when a driver of the vehicle performs a steering operation in a direction away from the obstacle, the driving assist device corrects the braking control amount to be smaller. <CIT> discloses the preamble of the independent claims and shows a vehicle control system providing automated turning control of a wheel.

A case where a vehicle of a steer-by-wire type has a function of driving assist control that assists driving of the vehicle is considered. For example, the driving assist control automatically turns (steers) the vehicle independently of a steering operation by a driver. Meanwhile, reaction force control that applies a steering reaction force to a steering wheel is performed in the case of the vehicle of the steer-by-wire type. The reaction force control may be performed in conjunction with the vehicle turning caused by the driving assist control. Depending on conditions, the driver may have a feeling of strangeness about the reaction force control performed in conjunction with the vehicle turning caused by the driving assist control.

An object of the present disclosure is to provide a technique that can reduce the driver's feeling of strangeness about the reaction force control performed in conjunction with the vehicle turning caused by the driving assist control, in the vehicle of the steer-by-wire type.

A first aspect is directed to a vehicle control system that controls a vehicle of a steer-by-wire type.

The vehicle control system includes one or more processors.

The one or more processors are configured to execute:.

The conjunction reaction force control includes:.

The adjustment process acquires the second system turn angle by adjusting the first system turn angle such that the difference between the second system turn angle and the driver turn angle becomes smaller than a difference between the first system turn angle and the driver turn angle.

A second aspect is directed to a vehicle control method that controls a vehicle of a steer-by-wire type.

According to the present disclosure, the conjunction reaction force control that applies the steering reaction force component to the steering wheel in conjunction with the vehicle turning caused by the driving assist control is performed. The steering reaction force component for the conjunction reaction force control is generated based on the difference between the driver turn angle and the system turn angle. At this time, the adjustment of the system turn angle is performed according to the steering intention of the driver. Then, the steering reaction force component for the conjunction reaction force control is generated by using the second system turn angle after the adjustment instead of the first system turn angle before the adjustment. The difference between the second system turn angle after the adjustment and the driver turn angle becomes smaller than the difference between the first system turn angle before the adjustment and the driver turn angle. Therefore, when the driver has the steering intention, the steering reaction force component for the conjunction reaction force control is suppressed. As a result, the driver's feeling of strangeness about the conjunction reaction force control is reduced.

Embodiments of the present disclosure will be described below with reference to the attached drawings.

<FIG> is a schematic diagram showing a configuration example of a vehicle <NUM> and a vehicle control system <NUM> according to the present embodiment. The vehicle <NUM> is provided with a wheel <NUM> and a steering wheel <NUM>. The steering wheel <NUM> is an operation member that a driver of the vehicle <NUM> uses for a steering operation. A steering shaft <NUM> is coupled with the steering wheel <NUM> and rotates together with the steering wheel <NUM>. The vehicle <NUM> is a vehicle of a steer-by-wire type, and the wheel <NUM> and the steering wheel <NUM> are mechanically disconnected from each other.

The vehicle control system <NUM> controls the vehicle <NUM> of the steer-by-wire type. The vehicle control system <NUM> includes a turning device <NUM>, a reaction force device <NUM>, a driving environment information acquisition device <NUM>, and a control device <NUM>.

The turning device <NUM> turns the wheel <NUM>. Here, turning the wheel <NUM> means changing a direction of the wheel <NUM> for making a turn. The turning device <NUM> includes a turning actuator <NUM> for turning the wheel <NUM>. For example, the turning actuator <NUM> is a turning motor. A rotor or the turning motor is connected to a turning bar <NUM> through a speed reducer <NUM>. The turning bar <NUM> is coupled with the wheel <NUM>. When the turning motor rotates, its rotational motion is converted into a linear motion of the turning bar <NUM>, and thereby the wheel <NUM> turns (i.e. changes its direction). That is, actuating the turning motor makes it possible to turn the wheel <NUM>. The operation of the turning actuator <NUM> is controlled by the control device <NUM>.

The reaction force device <NUM> applies a steering reaction force (reaction torque) to the steering wheel <NUM>. The reaction force device <NUM> includes a reaction force actuator <NUM> for applying the steering reaction force to the steering wheel <NUM>. For example, the reaction force actuator <NUM> is a reaction force motor. Actuating the reaction force motor makes it possible to apply the steering reaction force to the steering shaft <NUM> and thus to the steering wheel <NUM>. The operation of the reaction force actuator <NUM> is controlled by the control device <NUM>.

The driving environment information acquisition device <NUM> acquires driving environment information ENV indicating a driving environment for the vehicle <NUM>. The driving environment information acquisition device <NUM> includes a vehicle state sensor <NUM>, a recognition sensor <NUM>, and the like.

The vehicle state sensor <NUM> detects a state of the vehicle <NUM>. The vehicle state sensor <NUM> includes a steering angle sensor <NUM>, a steering torque sensor <NUM>, a rotational angle sensor <NUM>, a rotational angle sensor <NUM>, a turning current sensor <NUM>, a vehicle speed sensor <NUM>, and the like. The steering angle sensor <NUM> detects a steering angle θs (i.e., a steering wheel angle) of the steering wheel <NUM>. The steering torque sensor <NUM> detects a steering torque Ts applied to the steering shaft <NUM>. The rotational angle sensor <NUM> detects a rotation angle Φ of the reaction force actuator <NUM> (e.g., the reaction force motor). The rotational angle sensor <NUM> detects a rotation angle of the turning actuator <NUM> (e.g., the turning motor). The rotation angle of the turning motor corresponds to a turn angle (i.e., an actual turn angle δa) of the wheel <NUM>. It can be also said that the rotational angle sensor <NUM> detects the actual turn angle δa of the wheel <NUM>. The turning current sensor <NUM> detects a turning current Im that drives the turning actuator <NUM>. The vehicle speed sensor <NUM> detects a vehicle speed V being a speed of the vehicle <NUM>. In addition, the vehicle state sensor <NUM> may include a yaw rate sensor and an acceleration sensor.

The recognition sensor <NUM> recognizes (detects) a situation around the vehicle <NUM>. Examples of the recognition sensor <NUM> include a camera, a LIDAR (Laser Imaging Detection and Ranging), a radar , and the like.

The driving environment information acquisition device <NUM> may further include a position sensor that acquires a position of the vehicle <NUM>. The position sensor is exemplified by a GPS (Global Positioning System) sensor. The driving environment information acquisition device <NUM> may acquire map information.

The driving environment information ENV includes vehicle state information and surrounding situation information. The vehicle state information indicates the vehicle state detected by the vehicle state sensor <NUM>. The surrounding situation information indicates results of recognition by the recognition sensor <NUM>. For example, the surrounding situation information includes an image captured by the camera. The surrounding situation information may include object information about objects around the vehicle <NUM>. Examples of the objects around the vehicle <NUM> include a pedestrian, another vehicle (e.g., a preceding vehicle, a parked vehicle, etc.), a sign, a white line, a roadside structure, and the like. The object information indicates a relative position and a relative velocity of the object with respect to the vehicle <NUM>. The driving environment information ENV may further include the position information of the vehicle <NUM>, the map information, and the like.

The control device (controller) <NUM> controls the vehicle <NUM>. The control device <NUM> includes one or more processors <NUM> (hereinafter simply referred to as a processor <NUM>) and one or more memory devices <NUM> (hereinafter simply referred to as a memory devices <NUM>). The processor <NUM> executes a variety of processing. For example, the processor <NUM> includes a CPU (Central Processing Unit). The memory device (memory) <NUM> stores a variety of information necessary for the processing by the processor <NUM>. Examples of the memory device <NUM> include a volatile memory, a nonvolatile memory, an HDD (Hard Disk Drive), an SSD (Solid State Drive), and the like. The control device <NUM> may include one or more ECUs (Electronic Control Units).

The variety of processing by the control device <NUM> is implemented by the processor <NUM> executing a control program being a computer program. The control program is stored in the memory device <NUM>. As another example, the control program may be recorded on a non-transitory computer-readable recording medium.

The control device <NUM> (i.e., the processor <NUM>) acquires the driving environment information ENV from the driving environment information acquisition device <NUM>. The driving environment information ENV is stored in the memory device <NUM>.

<FIG> is a block diagram showing a functional configuration of the control device <NUM>. The control device <NUM> includes a turning control unit <NUM>, a reaction force control unit <NUM>, and a driving assist control unit <NUM> as functional blocks. These functional blocks are realized by a cooperation of the processor <NUM> executing the control program and the memory device <NUM>. It should be noted that the turning control unit <NUM>, the reaction force control unit <NUM>, and the driving assist control unit <NUM> may be realized by different control devices, respectively. In that case, the control devices are communicably connected to each other and communicate necessary information with each other.

Hereinafter, each of the turning control unit <NUM>, the reaction force control unit <NUM>, and the driving assist control unit <NUM> will be described in more detail.

The turning control unit <NUM> executes "turning control" that turns the wheel <NUM>. More specifically, the turning control unit <NUM> turns (i.e., changes a direction of) the wheel <NUM> by controlling the turning actuator <NUM> of the turning device <NUM>.

The turning control unit <NUM> executes the turning control in response to a steering operation of the steering wheel <NUM> performed by the driver. For example, the turning control unit <NUM> calculates a target turn angle δt based on the steering angle θs and the vehicle speed V. The steering angle θs is detected by the steering angle sensor <NUM>. As another example, the steering angle θs may be calculated from the rotation angle Φ detected by the rotational angle sensor <NUM>. The vehicle speed V is detected by the vehicle speed sensor <NUM>. The turning control unit <NUM> turns the wheel <NUM> according to the target turn angle δt. The actual turn angle δa of the wheel <NUM> is detected by the rotational angle sensor <NUM>. The turning control unit <NUM> controls the turning actuator <NUM> such that the actual turn angle δa follows the target turn angle δt. More specifically, the turning control unit <NUM> generates a control signal for driving the turning actuator <NUM> based on a deviation between the target turn angle δt and the actual turn angle δa of the wheel <NUM>. The turning actuator <NUM> is driven according to the control signal, and thereby the wheel <NUM> is turned. It should be noted a current driving the turning actuator <NUM> at this time is the turning current Im.

Moreover, the turning control unit <NUM> executes the turning control according to a request from the driving assist control unit <NUM> described later. In this case, the turning control unit <NUM> acquires a target control amount from the driving assist control unit <NUM> and executes the turning control according to the target control amount.

The reaction force control unit <NUM> executes "reaction force control" that applies the steering reaction force (reaction torque) to the steering wheel <NUM>. More specifically, the reaction force control unit <NUM> applies the steering reaction force to the steering wheel <NUM> by controlling the reaction force actuator <NUM> of the reaction force device <NUM>.

The reaction force control unit <NUM> executes the reaction force control in response to the steering operation of the steering wheel <NUM> performed by the driver. For example, the reaction force control unit <NUM> calculates a target steering reaction force (spring component) corresponding to a self-aligning torque applied to the wheel <NUM>, based on the steering angle θs and the vehicle speed V. The target steering reaction force may further include a damping component according to a steering speed (dθs/dt). The reaction force control unit <NUM> controls the reaction force actuator <NUM> so as to generate the target steering reaction force. More specifically, the reaction force control unit <NUM> generates a control signal for driving the reaction force actuator <NUM> based on the target steering reaction force. The reaction force actuator <NUM> is driven according to the control signal, and thereby the steering reaction force is generated.

Moreover, the reaction force control unit <NUM> may execute the reaction force control according to a request from the driving assist control unit <NUM> described later. Furthermore, the reaction force control unit <NUM> may execute the reaction force control in conjunction (collaboration) with the driving assist control by the driving assist control unit <NUM>. Details of the reaction force control performed in conjunction with the driving assist control will be described later.

The driving assist control unit <NUM> executes "driving assist control" that assists driving of the vehicle <NUM>. The driving assist control automatically controls travel of the vehicle <NUM> independently of a driving operation by the driver. In the present embodiment, the driving assist control related to steering will be considered in particular. Examples of such the driving assist control include automated driving control, risk avoidance control, lane keep assist control (LTA: Lane Tracing Assist), lane departure suppression control (LDA: Lane Departure Alert), and the like.

The automated driving control controls automated driving of the vehicle <NUM>. More specifically, the driving assist control unit <NUM> generates a travel plan of the vehicle <NUM> based on the driving environment information ENV. Examples of the travel plan include keeping a current travel lane, making a lane change, making a right or left turn, avoiding an obstacle, and the like. Furthermore, the driving assist control unit <NUM> generates a target trajectory TRJ necessary for the vehicle <NUM> to travel in accordance with the travel plan, based on the driving environment information ENV. The target trajectory TRJ includes a target position and a target speed. Then, the driving assist control unit <NUM> performs vehicle travel control such that the vehicle <NUM> follows the target trajectory TRJ.

More specifically, the driving assist control unit <NUM> calculates a deviation (e.g., a lateral deviation, a yaw angle deviation, and a speed deviation) between the vehicle <NUM> and the target trajectory TRJ, and calculates a target control amount necessary for reducing the deviation. Examples of the target control amount include a target turn angle, a target yaw rate, a target speed, a target acceleration, a target deceleration, a target current, and the like. The driving assist control unit <NUM> performs the vehicle travel control according to the target control amount. The vehicle travel control includes turning control, acceleration control, and deceleration control. The turning control is performed through the turning control unit <NUM> described above. The acceleration control and the deceleration control are performed by controlling a driving device and a braking device (not shown) of the vehicle <NUM>.

<FIG> is a conceptual diagram for explaining the risk avoidance control. The risk avoidance control is the driving assist control for reducing a risk of collision with an object existing ahead of the vehicle <NUM>. Examples of the object as the avoidance target include a pedestrian, a bicycle, a motorcycle, an animal, another vehicle, and the like. The driving assist control unit <NUM> recognizes the object existing ahead of the vehicle <NUM> based on the surrounding situation information (object information) included in the driving environment information ENV. For example, when the risk of collision with the recognized object exceeds a threshold, the driving assist control unit <NUM> executes the risk avoidance control. More specifically, the driving assist control unit <NUM> generates a target trajectory TRJ moving in a direction away from the object in order to secure a lateral distance to the object. Then, the driving assist control unit <NUM> performs the vehicle travel control such that the vehicle <NUM> follows the target trajectory TRJ. The vehicle travel control here includes at least one of the turning control and the deceleration control. The turning control is performed through the turning control unit <NUM> described above.

<FIG> is a conceptual diagram for explaining the lane keep assist control. The lane keep assist control is the driving assist control for assisting the vehicle <NUM> to travel along a lane center LC. The lane is an area sandwiched between left and right lane boundaries LB. Examples of the lane boundary LB include a white line (lane marking), a curb, and the like. The lane center LC is a center line of the lane. The driving assist control unit <NUM> recognizes the lane boundary LB and the lane center LC based on the surrounding situation information included in the driving environment information ENV. When the vehicle <NUM> deviates from the lane center LC, the driving assist control unit <NUM> executes the lane keep assist control. More specifically, the driving assist control unit <NUM> executes the turning control such that the vehicle <NUM> returns back to the lane center LC. The turning control is performed through the turning control unit <NUM> described above.

<FIG> is a conceptual diagram for explaining the lane departure suppression control. The lane departure suppression control is the driving assist control for suppressing the vehicle <NUM> from departing from a travel lane. The driving assist control unit <NUM> recognizes the lane boundary LB based on the surrounding situation information included in the driving environment information ENV. When a distance between the vehicle <NUM> and the lane boundary LB becomes less than a predetermined threshold, the driving assist control unit <NUM> executes the lane departure suppression control. More specifically, the driving assist control unit <NUM> notifies the driver of a possibility of the lane departure. For example, the driving assist control unit <NUM> vibrates the steering wheel <NUM> by controlling a steering wheel vibration mechanism (not shown). The driving assist control unit <NUM> may output an alert through display and/or audio. Moreover, the driving assist control unit <NUM> may execute the turning control such that the vehicle <NUM> moves toward the lane center LC. The turning control is performed through the turning control unit <NUM> described above.

Next, cooperation of the driving assist control and the reaction force control will be considered. For example, a case where the reaction force control is performed in conjunction (collaboration) with turning of the vehicle <NUM> caused by the driving assist control will be considered. Such the reaction force control performed in conjunction with turning of the vehicle <NUM> caused by the driving assist control is hereinafter referred to as "conjunction reaction force control.

The conjunction reaction force control is intended to move (rotate) the steering wheel <NUM> in conjunction with the turning of the vehicle <NUM> (i.e., changing a direction of the wheel <NUM>) caused by the driving assist control when the driving assist control is in operation. For that purpose, the conjunction reaction force control applies a steering reaction force component for making the steering wheel <NUM> follow the turning of the vehicle <NUM> caused by the driving assist control to the steering wheel <NUM>.

First, a comparative example will be explained with reference to <FIG>. The reaction force control unit <NUM> includes a conjunction reaction force control unit <NUM>. The conjunction reaction force control unit <NUM> calculates a target control amount CON_C for generating the steering reaction force component for the conjunction reaction force control. The conjunction reaction force control unit <NUM> includes a driver turn angle acquisition unit <NUM>, a difference calculation unit <NUM>, and a control amount calculation unit <NUM>.

The driver turn angle acquisition unit <NUM> acquires the steering angle θs (i.e., the steering wheel angle) of the steering wheel <NUM> included in the vehicle state information. Further, the driver turn angle acquisition unit <NUM> calculates a target turn angle δt corresponding to the steering angle θs of the steering wheel <NUM> based on a variable gear ratio and the like. The calculation of the target turn angle δt is the same as that by the turning control unit <NUM> described above. For convenience sake, the target turn angle δt corresponding to the steering angle θs of the steering wheel <NUM> is hereinafter referred to as a "driver turn angle δx.

On the other hand, a "system turn angle δy" is a target turn angle δt required by the driving assist control. As described above, the system turn angle δy is determined by the driving assist control unit <NUM>. The conjunction reaction force control unit <NUM> acquires the system turn angle δy determined by the driving assist control unit <NUM>.

The difference calculation unit <NUM> calculates a difference (deviation) between the driver turn angle δx and the system turn angle δy.

The control amount calculation unit <NUM> calculates the target control amount CON_C for generating a steering reaction force component in a direction of reducing the difference between the driver turn angle δx and the system turn angle δy. For example, the control amount calculation unit <NUM> calculates the target control amount CON_C such that the steering reaction force component increases as the difference becomes larger.

It should be noted that the reaction force control unit <NUM> calculates a final target control amount by combining the target control amount CON_C caused by the conjunction reaction force control and another target control amount caused by another type of reaction force control. Then, the reaction force control unit <NUM> executes the reaction force control by controlling the reaction force actuator <NUM> of the reaction force device <NUM> in accordance with the final target control amount.

As described above, the conjunction reaction force control calculates the difference between the driver turn angle δx and the system turn angle δy, and applies the steering reaction force component in a direction of reducing the difference to the steering wheel <NUM>. However, depending on conditions, the driver may have a feeling of strangeness about such the conjunction reaction force control. For example, when the driver has a positive steering intention, the conjunction reaction force control may cause the driver to feel that the steering wheel <NUM> is heavy. As another example, the conjunction reaction force control may cause the driver to feel that the steering wheel <NUM> is strongly returned back.

In view of the above, the present embodiment proposes a technique that can reduce the driver's feeling of strangeness about the conjunction reaction force control.

<FIG> is a block diagram showing the conjunction reaction force control unit <NUM> according to the present embodiment. As compared with the case of the comparative example shown in <FIG>, the conjunction reaction force control unit <NUM> further includes an adjustment unit <NUM>.

The adjustment unit <NUM> executes an "adjustment process" that adjusts the system turn angle δy. For convenience sake, the system turn angle δy required by the driving assist control, that is, the system turn angle δy determined by the driving assist control unit <NUM> is hereinafter referred to as a "first system turn angle δy1. " The adjustment unit <NUM> acquires the first system turn angle δy1 and adjusts the first system turn angle δy1 according to a steering intention of the driver. The system turn angle δy after the adjustment is hereinafter referred to as a "second system turn angle δy2. " That is, the adjustment unit <NUM> acquires the second system turn angle δy2 by adjusting the first system turn angle δy1 according to the driver's steering intention.

The driver's steering intention is reflected in a steering parameter Ps. For example, the steering parameter Ps is the driver turn angle δx. As another example, the steering parameter Ps may be a difference between the driver turn angle δx and the first system turn angle δy1. As still another example, the steering parameter Ps may be the steering torque Ts detected by the steering torque sensor <NUM>. The adjustment unit <NUM> acquires the second system turn angle δy2 by adjusting the first system turn angle δy1 according to the steering parameter Ps.

A relationship between the first system turn angle δy1 and the second system turn angle δy2 is as follows. A first difference d1 is a difference (deviation) between the first system turn angle δy1 before the adjustment and the driver turn angle δx. On the other hand, a second difference d2 is a difference (deviation) between the second system turn angle δy2 after the adjustment and the driver turn angle δx. The adjustment unit <NUM> acquires the second system turn angle δy2 by adjusting the first system turn angle δy1 such that an absolute value of the second difference d2 becomes smaller than an absolute value of the first difference d1.

After that, the difference calculation unit <NUM> calculates the second difference d2 between the driver turn angle δx and the second system turn angle δy2. Then, the control amount calculation unit <NUM> calculates a target control amount CON_C for generating a steering reaction force component in a direction of reducing the second difference d2. For example, the control amount calculation unit <NUM> calculates the target control amount CON_C such that the steering reaction force component increases as the second difference d2 becomes larger.

As described above, in the conjunction reaction force control according to the present embodiment, the adjustment of the system turn angle δy is performed according to the steering intention of the driver. Then, the steering reaction force component for the conjunction reaction force control is generated by using the second system turn angle δy2 after the adjustment instead of the first system turn angle δy1 before the adjustment. The second difference d2 between the second system turn angle δy2 after the adjustment and the driver turn angle δx becomes smaller than the first difference d1 between the first system turn angle δy1 before the adjustment and the driver turn angle δx. Therefore, when the driver has the steering intention, the steering reaction force component for the conjunction reaction force control is suppressed. As a result, the driver's feeling of strangeness about the conjunction reaction force control is reduced.

It should be noted that the adjustment of the system turn angle δy is performed only in the conjunction reaction force control for applying the steering reaction force to the steering wheel <NUM>. The driving assist control unit <NUM> performs the driving assist control including the turning control based on the system turn angle δy determined by itself (i.e., the first system turn angle δy1). Therefore, in the driving assist control, the vehicle turning is achieved as intended. That is to say, performance of the driving assist control is never deteriorated.

<FIG> is a block diagram showing a configuration example of the adjustment unit <NUM> of the conjunction reaction force control unit <NUM>. The adjustment unit <NUM> includes a gain setting unit <NUM> and a multiplier unit <NUM>. The gain setting unit <NUM> executes a "gain setting process" that sets a conjunction reaction force gain Gc. The gain setting unit <NUM> sets the conjunction reaction force gain Gc according to the driver's steering intention, that is, the steering parameter Ps. Then, the multiplier unit <NUM> calculates the second system turn angle δy2 by multiplying the first system turn angle δy1 by the conjunction reaction force gain Gc (i.e., δy2 = Gc × δy1).

The gain setting unit <NUM> sets the conjunction reaction force gain Gc such that the second difference d2 between the second system turn angle δy2 and the driver turn angle δx becomes smaller than the first difference d1 between the first system turn angle δy1 and the driver turn angle δx. Hereinafter, various configuration examples of the gain setting unit <NUM> will be described.

<FIG> is a block diagram showing a first configuration example of the gain setting unit <NUM>. The gain setting unit <NUM> includes a difference calculation unit <NUM> and a gain map unit <NUM>.

The difference calculation unit <NUM> calculates the first difference d1 between the first system turn angle δy1 and the driver turn angle δx. It should be noted that in the first configuration example, the driver turn angle δx or the first difference d1 between the first system turn angle δy1 and the driver turn angle δx corresponds to the steering parameter Ps.

The gain map unit <NUM> sets the conjunction reaction force gain Gc based on the first difference d1. For example, when the driver turn angle δx is larger than the first system turn angle δy1, the conjunction reaction force gain Gc is set to a value larger than <NUM> in order to make the second system turn angle δy2 be more closer to the driver turn angle δx. On the other hand, when the first system turn angle δy1 is larger than the driver turn angle δx, the conjunction reaction force gain Gc is set to a value smaller than <NUM> in order to make the second system turn angle δy2 be more closer to the driver turn angle δx. As a result, the second difference d2 between the second system turn angle δy2 and the driver turn angle δx becomes smaller than the first difference d1 between the first system turn angle δy1 and the driver turn angle δx.

The gain map unit <NUM> may set the conjunction reaction force gain Gc in consideration of the vehicle speed V together with the first difference d1.

<FIG> is a block diagram showing a second configuration example of the gain setting unit <NUM>. The gain setting unit <NUM> includes the difference calculation unit <NUM>, a lateral G conversion unit <NUM>, and a gain map unit <NUM>. The difference calculation unit <NUM> is the same as in the case of the first configuration example.

The lateral G conversion unit <NUM> converts the first difference d1 between the first system turn angle δy1 and the driver turn angle δx into a dimension of the lateral acceleration, based on the vehicle speed V. The vehicle speed V is obtained from the vehicle state information. As a result of the conversion, a lateral acceleration deviation d1' corresponding to the first difference d1 is acquired.

The gain map unit <NUM> sets the conjunction reaction force gain Gc based on the lateral acceleration deviation d1' instead of the first difference d1. A policy of setting the conjunction reaction force gain Gc is the same as in the case of the gain map unit <NUM> in the above-described first configuration example. It should be noted that the gain map unit <NUM> is simplified as compared with the gain map unit <NUM> in the first configuration example, because the gain map unit <NUM> does not depend on the vehicle speed V.

<FIG> is a block diagram showing a third configuration example of the gain setting unit <NUM>. The gain setting unit <NUM> includes a driver's steering determination unit <NUM> and a gain switching unit <NUM>.

The driver's steering determination unit <NUM> determines whether or not the driver has a steering intention. For that purpose, the driver's steering determination unit <NUM> determines whether or not the steering parameter Ps reflecting the driver's steering intention exceeds a threshold. For example, the steering parameter Ps is the steering torque Ts detected by the steering torque sensor <NUM>. As another example, the steering parameter Ps may be the first difference d1 between the driver turn angle δx and the first system turn angle δy1. As still another example, the steering parameter Ps may be the lateral acceleration deviation d1' that is acquired by converting the first difference d1 into the dimension of the lateral acceleration. When the steering parameter Ps exceeds the threshold, the driver's steering determination unit <NUM> determines that the driver has a steering intention.

The gain switching unit <NUM> switches the conjunction reaction force gain Gc according to the result of determination by the driver's steering determination unit <NUM>. More specifically, when it is determined that the driver has no steering intention, the gain switching unit <NUM> sets the conjunction reaction force gain Gc to "<NUM>. " On the other hand, when it is determined that the driver has the steering intention, the gain switching unit <NUM> sets the conjunction reaction force gain Gc to a value α different from <NUM>.

For example, the third configuration example is applied to a case where a steering direction by the driver and a turning direction by the driving assist control are in opposite phase. In the case of the opposite phase, the value α is less than <NUM>. By using the conjunction reaction force gain Gc less than <NUM>, the second difference d2 between the second system turn angle δy2 and the driver turn angle δx becomes smaller than the first difference d1 between the first system turn angle δy1 and the driver turn angle δx.

In a case where the steering direction by the driver and the turning direction by the driving assist control are in phase, the value α varies depending on a magnitude relationship between the driver turn angle δx and the first system turn angle δy1. When the driver turn angle δx is larger than the first system turn angle δy1, the value α is set to a value larger than <NUM>. On the other hand, when the first system turn angle δy1 is larger than the driver turn angle δx, the value α is set to a value smaller than <NUM>. As a result, the second difference d2 between the second system turn angle δy2 and the driver turn angle δx becomes smaller than the first difference d1 between the first system turn angle δy1 and the driver turn angle δx.

<FIG> is a block diagram showing a modification example of the adjustment unit <NUM> of the conjunction reaction force control unit <NUM>. As compared with the examples shown in <FIG>, the adjustment unit <NUM> further includes a guard unit <NUM>. The guard unit <NUM> gradually changes the conjunction reaction force gain Gc in order to suppress a rapid change in the steering reaction force.

<FIG> is a diagram for explaining an example of the change in the conjunction reaction force gain Gc. In the example shown in <FIG>, the conjunction reaction force gain Gc gradually changes from "<NUM>" to "α. " For example, a variation time of the conjunction reaction force gain Gc is set to half the "inverse number of a main frequency component of the first system turn angle δy1. " Thus, a variation gradient of the second system turn angle δy2 becomes less than a variation gradient of the original first system turn angle δy1. As a result, a rapid change in the steering reaction force is suppressed.

As described above, according to the present embodiment, the conjunction reaction force control that applies the steering reaction force component to the steering wheel <NUM> in conjunction with the turning of the vehicle <NUM> caused by the driving assist control is performed. The steering reaction force component for the conjunction reaction force control is generated based on the difference between the driver turn angle δx and the system turn angle δy. At this time, the adjustment of the system turn angle δy is performed according to the steering intention of the driver. Then, the steering reaction force component for the conjunction reaction force control is generated by using the second system turn angle δy2 after the adjustment instead of the first system turn angle δy1 before the adjustment. The second difference d2 between the second system turn angle δy2 after the adjustment and the driver turn angle δx becomes smaller than the first difference d1 between the first system turn angle δy1 before the adjustment and the driver turn angle δx. Therefore, when the driver has the steering intention, the steering reaction force component for the conjunction reaction force control is suppressed. As a result, the driver's feeling of strangeness about the conjunction reaction force control is reduced.

It should be noted that the adjustment of the system turn angle δy is performed only in the conjunction reaction force control for applying the steering reaction force to the steering wheel <NUM>. The turning control in the driving assist control is performed based on the original first system turn angle δy1. Therefore, in the driving assist control, the vehicle turning is achieved as intended. That is to say, performance of the driving assist control is never deteriorated.

Furthermore, according to the present embodiment, not the driver turn angle δx but the system turn angle δy is multiplied by the conjunction reaction force gain Gc. Therefore, the driver turn angle δx reflecting the driver's steering intention is not affected. Influence of the driver turn angle δx in the reaction force control is not reduced, and thus the reaction force control according to the driver's steering intention is achieved.

Claim 1:
A vehicle control system (<NUM>) that controls a vehicle (<NUM>) of a steer-by-wire type,
the vehicle control system (<NUM>) comprising one or more processors (<NUM>) configured to execute:
driving assist control that assists driving of the vehicle (<NUM>); and
conjunction reaction force control that applies a steering reaction force component to a steering wheel (<NUM>) in conjunction with turning of the vehicle (<NUM>) caused by the driving assist control, wherein
the conjunction reaction force control includes:
acquiring a driver turn angle (δx) that is a target turn angle corresponding to a steering angle (θs) of the steering wheel (<NUM>);
acquiring a first system turn angle (δy1) that is a target turn angle required by the driving assist control; and
an adjustment process that acquires a second system turn angle (δy2) by adjusting the first system turn angle (δy1) according to a steering intention of a driver of the vehicle (<NUM>);
characterised in that the conjunction reaction force control includes:
applying a steering reaction force component to the steering wheel (<NUM>) in a direction of reducing a difference (d2) between the driver turn angle (δx) and the second system turn angle (δy2), and
the adjustment process acquires the second system turn angle (δy2) by adjusting the first system turn angle (δy1) such that the difference (d2) between the second system turn angle (δy2) and the driver turn angle (δx) becomes smaller than a difference (d1) between the first system turn angle (δy1) and the driver turn angle (δx).