Vehicle steering system

Abstract

A vehicle steering system of the present application includes a steering control amount operation section (10) that operates a steering control amount for causing a vehicle to approach a target travel route; a lateral acceleration detection section (2) that detects a lateral acceleration of the vehicle; a steering control amount limit value operation section (12) that operates a steering control amount limit value that limits the lateral acceleration to a lateral acceleration limit value based on the lateral acceleration; a limit determination section (11) that determines at least the lateral acceleration to determine whether the steering control amount limit is effective or ineffective; and a steering control amount limiting section (13) that limits the steering control amount based on the steering control amount limit value in a case where the limit determination section (11) determines that the limit is effective.

Description

Technical Field

[0001] This application relates to vehicle steering systems, and more particularly to vehicle steering systems that assist steering operations to enable a vehicle to follow a target driving path. Background Technology

[0002] Previously, there were known technologies that provided steering assistance or automatic steering to enable vehicles to follow a desired target driving path.

[0003] For example, firstly, as shown in Patent Document 1, there is a technology that uses a camera installed in front of the vehicle to identify the white lines on the road, thereby performing steering control to keep the vehicle in the center of the lane (hereinafter referred to as a lane keeping system). Secondly, as shown in Patent Document 2, there is a technology that uses satellite information to determine the vehicle's position, the driver's pre-set target location, map data, etc., and then calculates a target trajectory to perform steering control by following that target trajectory. Existing technical documents Patent documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2015-13545 Patent Document 2: Japanese Patent Application Publication No. 2005-67484 Summary of the Invention The technical problem that the invention aims to solve

[0005] In the existing vehicle steering systems described in Patent Documents 1 and 2, in order to provide steering assistance by following a target driving route based on camera or satellite information, the vehicle steering system makes sharp turns according to the target driving route, resulting in increased lateral acceleration of the vehicle, which can cause insecurity or discomfort to the driver. In particular, for example, if the camera or satellite information is misidentified, causing the vehicle steering system and the driver to turn the vehicle in an undesirable direction, the insecurity and discomfort experienced by the driver are significant.

[0006] This application was made to solve the problems mentioned above, and its purpose is to provide a vehicle steering system that reduces the burden on the driver caused by insecurity and discomfort. Technical solutions to solve technical problems

[0007] The vehicle steering system disclosed in this application includes: a steering control quantity calculation unit that calculates a steering control quantity for bringing the vehicle closer to a target driving path; a lateral acceleration detection unit that detects the lateral acceleration of the vehicle; a steering control quantity limit value calculation unit that calculates and limits the lateral acceleration to a steering control quantity limit value based on the lateral acceleration; a limit determination unit that determines whether the steering control quantity limit is valid or invalid based at least on the lateral acceleration; and a steering control quantity limiting unit that limits the steering control quantity based on the steering control quantity limit value when the limit determination unit determines that the limit is valid. Invention Effects

[0008] According to the vehicle steering system disclosed in this application, the lateral acceleration of the vehicle is limited to a steering control amount limit value, which is the same as the lateral acceleration limit value. The steering control amount is limited based on the steering control amount limit value. Therefore, the lateral angular velocity of the vehicle generated by the system can be limited regardless of the driving environment such as vehicle deviation or the slope angle of the driving path, thereby reducing the burden on the driver caused by the driver's sense of insecurity and discomfort. Attached Figure Description

[0009] Figure 1 This is a functional block diagram representing the vehicle steering system according to Embodiment 1. Figure 2 This is a diagram showing the hardware structure of the vehicle steering device in the vehicle steering system according to Embodiment 1. Figure 3 This is a flowchart illustrating the operation of the steering control quantity limit value calculation unit in the vehicle steering system according to Embodiment 1. Figure 4 This is a functional block diagram representing the vehicle steering system involved in Embodiment 2. Figure 5 This is a flowchart illustrating the operation of the steering control quantity limit value calculation unit in the vehicle steering system according to Embodiment 2. Figure 6 This is a functional block diagram representing a variation of Implementation 1, namely a vehicle steering system. Figure 7 This is a functional block diagram representing a variation of implementation 2, namely a vehicle steering system. Detailed Implementation

[0010] Implementation method 1. The vehicle steering system disclosed in this application will now be described with reference to the accompanying drawings, based on embodiments. Figure 1This is a functional block diagram illustrating the structure of the vehicle steering system according to Embodiment 1. For example... Figure 1 As shown, the vehicle steering system includes: a vehicle steering device 1 (hereinafter sometimes referred to as "steering device 1"), a lateral acceleration detection unit 2, a driving path recognition unit 3, and a steering actuator 4. Furthermore, in the following description, the vehicle equipped with the steering device 1 will be referred to as "this vehicle".

[0011] The steering device 1 includes a steering control quantity calculation unit 10, a limit determination unit 11, a steering control quantity limit value calculation unit 12, and a steering control quantity limit unit 13. The lateral acceleration detected by the lateral acceleration detection unit 2 is input to the limit determination unit 11 and the steering control quantity limit value calculation unit 12, and the driving path information detected by the driving path recognition unit 3 is input to the steering control quantity calculation unit 10, which outputs the steering control quantity. Here, the steering device 1 may also have the control functions of a general electric power steering device.

[0012] The lateral acceleration detection unit 2 is, for example, a lateral G-sensor that detects the lateral acceleration of the vehicle and outputs it to the steering device 1. Alternatively, the lateral acceleration detection unit 2 can also detect the yaw rate and vehicle speed of the vehicle, outputting the values ​​of yaw rate and vehicle speed as the lateral acceleration, and its detection method is not limited.

[0013] The driving path recognition unit 3 is, for example, a camera that captures an image of the road ahead of the vehicle. Based on the captured image, it recognizes lane boundary lines such as the outer lane line, lane edge line, and lane center line of the driving path ahead. Then, based on the position of the lane boundary lines in the vehicle's coordinate system, it identifies the driving lane of the vehicle and outputs this driving road information to the steering device 1. The vehicle's coordinate system is a coordinate system centered on a base point obtained on the vehicle.

[0014] The steering actuator 4 generates a target torque, i.e., steering power (driving torque), equivalent to the steering control amount input from the steering device 1, to steer the steering wheels of the vehicle. The steering actuator 4 can be, for example, an electric power steering motor or a hydraulic motor. The type of motor is not particularly limited; a DC motor or an AC motor can be used.

[0015] Next, the internal structure of the steering device 1 will be described. The steering control quantity calculation unit 10 sets a target driving route within the driving route based on the driving route information in the vehicle coordinate system, and outputs a steering control quantity for the vehicle to follow the target driving route.

[0016] Here, the target driving route is set, for example, at a position in the vehicle coordinate system that is a predetermined distance (e.g., half the width of the driving road) away from the right lane boundary line, i.e., at the center of the driving lane. Furthermore, the predetermined distance can be appropriately changed according to the driver's preferences, the surrounding environment, etc. Additionally, the method for calculating the steering control quantity in the steering control quantity calculation unit 10 is well known in technologies that provide steering assistance or automatic steering to the steering wheels in a manner that follows the desired target driving route. For example, the target torque for driving the steering actuator disclosed in Japanese Patent No. 6012824 can be used as the steering control quantity, regardless of the method used.

[0017] The limitation determination unit 11 compares the lateral acceleration of the vehicle with a preset arbitrary lateral acceleration limit value to determine whether the steering control quantity is limited, and outputs a limitation determination flag to the steering control quantity limit value calculation unit 12. The limitation determination flag is set to limited if the lateral acceleration of the vehicle is at least above the lateral acceleration limit value, and is set to unrestricted if the lateral acceleration of the vehicle is at least less than the lateral acceleration limit value.

[0018] Here, the lateral acceleration limit value used in determining whether there is a restriction or not is the same as the lateral acceleration limit value used in the steering control amount limit value calculation unit 12 described later, but different values ​​can also be set for each. Alternatively, the lateral acceleration limit values ​​for determining whether there is a restriction or not can be set to different values, thus setting a hysteresis. Alternatively, the determination can be based not only on the lateral acceleration of the vehicle, but also on the relationship between the steering control amount limit value and the steering control amount in the steering control amount limit value calculation unit 12. In this case, for example, the limit determination unit can determine the limit determination flag as follows. (a) When the lateral acceleration of the vehicle is above the lateral acceleration limit and the steering control amount limit is greater than the steering control amount, the limit judgment flag output is limited. (b) When the steering control limit value is less than the steering control value, the limit determination flag outputs no limit. (c) In cases other than those described above, the restriction decision flag retains the previous output value. By making the above judgments, even when the lateral acceleration of the vehicle is below the lateral acceleration limit, the steering control quantity limit is reduced, and the output continues to be limited until it matches the value of the steering control quantity. Therefore, it can suppress the change in steering control quantity, which is equivalent to the difference between the steering control quantity limit and the steering control quantity when switching from limited to unlimited. This helps to reduce the burden on the driver caused by the driver's sense of insecurity and discomfort.

[0019] The steering control quantity limit calculation unit 12 calculates a steering control quantity limit value that makes the lateral acceleration generated by the vehicle below a preset arbitrary lateral acceleration limit value based on the input lateral acceleration, steering control quantity, and limit determination flag, and outputs it to the steering control quantity limit unit 13.

[0020] The steering control quantity limiting unit 13 limits the steering control quantity to below the steering control quantity limit value based on the input steering control quantity and the steering control quantity limit value, and outputs it to the steering actuator 4.

[0021] exist Figure 2 In, it is shown Figure 1 The modules of the steering device 1 shown (steering control quantity calculation unit 10, limit determination unit 11, steering control quantity limit value calculation unit 12, and steering control quantity limit unit 13) represent the hardware structure when a processor such as a CPU (Central Processing Unit) or DSP (Digital Signal Processor) is used. In this case, the functions of each module of the steering device 1 are implemented by software (software, firmware, or a combination of software and firmware). The software is expressed in the form of a program and stored in the memory 103 (storage device).

[0022] The interface (I / F) 101 controls the input and output of signals to external devices such as the driving path recognition unit 3. Figure 2 Only the structure of the steering actuator 4 connected via I / F 101 is shown. The CPU 102 executes various processes according to the program stored in the memory 103 to realize the functions of each module of the steering device 1. These I / F 101, CPU 102, and memory 103 are connected to each other via a bus.

[0023] Figure 3 This is a flowchart illustrating the operation of the steering control quantity limiting unit 12. First, in step S101, the steering control quantity limit value calculation unit 12 reads the lateral acceleration output by the lateral acceleration detection unit 2, the steering control quantity output by the steering control quantity calculation unit 10, and the limit determination flag output by the limit determination unit 11.

[0024] Next, in step S102, a conditional branch determination based on the restriction determination flag is performed. If the restriction determination flag has a restriction, the process proceeds to step S103; otherwise, the process proceeds to step S104.

[0025] In step S103, a conditional branch determination based on the restriction determination flag is further performed. If the restriction determination flag changes from unrestricted to restricted, that is, if the lateral acceleration of the vehicle reaches the lateral acceleration limit value from a value less than any lateral acceleration limit value, the process proceeds to step S105. Otherwise, the process proceeds to step S106.

[0026] In steps S104 to S106, the steering control quantity limit values ​​corresponding to each limit determination flag are calculated.

[0027] In step S104, since the restriction determination flag indicates no restriction, meaning the lateral acceleration of the vehicle is less than the lateral acceleration limit value, and it is in a state where steering control amount does not need to be restricted, the steering control amount limit value is reset to a value where the steering control amount is not restricted in the steering control amount restriction unit 13. For example, a value larger than the steering control amount that the vehicle's steering system can obtain. Furthermore, any value that is not restricted in the steering control amount restriction unit 13 is acceptable, and its setting value is not limited.

[0028] In step S105, when the limit determination flag changes from unrestricted to restricted, that is, when the lateral acceleration of the vehicle reaches the lateral acceleration limit value from a value less than any lateral acceleration limit value, the steering control amount limit value is set as the steering control amount to prevent the lateral acceleration of the vehicle from increasing further. In other words, it can be said that the steering control amount limit value is set as the steering control amount when the lateral acceleration of the vehicle is equivalent to the lateral acceleration limit value.

[0029] In step S106, since the limit determination flag is in a limited state, indicating a desire to continue limiting the lateral acceleration of the vehicle, the steering control amount limit value remains the previous value, i.e., the value set at the time of step S105. By maintaining the steering control amount at the moment when the lateral acceleration of the vehicle reaches the lateral acceleration limit value through steps S105 and S106, it is possible to prevent the lateral acceleration of the vehicle from increasing further.

[0030] As described above, the calculation limits the vehicle's lateral acceleration to a steering control amount limit value, similar to the lateral acceleration limit value. By limiting the steering control amount based on the steering control amount limit value, the lateral angular velocity of the vehicle generated by the system can be limited regardless of the driving environment, such as vehicle deviation or the slope angle of the driving path. This can reduce the driver's burden caused by the driver's insecurity and discomfort.

[0031] In addition, in order to limit the steering control amount of the vehicle's steering system, it is easy to make the steering control amount a continuous action before and after the limitation, and the lateral acceleration will not be discontinuous, which helps to reduce the burden on the driver caused by the driver's sense of insecurity and discomfort.

[0032] Implementation method 2. In Embodiment 1, the steering control quantity limit value calculation unit 12 sets the steering control quantity limit value to the steering control quantity at the moment when the lateral acceleration of the vehicle reaches the lateral acceleration limit value, thereby limiting the lateral acceleration of the vehicle to any lateral acceleration limit value or below. In contrast, in this embodiment 2, a vehicle steering system using a vehicle steering device 1a is described, which includes a steering control amount limit value calculation unit 12a that calculates the steering control amount limit value based on the deviation between the lateral acceleration limit value and the lateral acceleration of the vehicle.

[0033] Figure 4 This is a functional block diagram showing the structure of the vehicle steering system in Embodiment 2. Parts labeled with the same reference numerals as in Embodiment 1 are the same or equivalent parts.

[0034] The steering control quantity limit value calculation unit 12a in the vehicle steering device 1a includes a deviation calculator 120, an integrator 121, and a gain multiplier 122. The lateral acceleration detected by the lateral acceleration detection unit 2 is input to the deviation calculator 120. The limit determination flag calculated by the limit determination unit 11 and the steering control quantity calculated by the steering control quantity calculation unit 10 are respectively input to the integrator 121. The calculation makes the lateral acceleration generated by the vehicle become a steering control quantity limit value below an arbitrarily set lateral acceleration limit value, and outputs it to the steering control quantity limit unit 13.

[0035] Next, the internal structure of the steering control quantity limit value calculation unit 12a will be explained. The deviation calculator 120 calculates the deviation between any lateral acceleration limit value and the absolute value of lateral acceleration based on lateral acceleration, and outputs it as the lateral acceleration deviation to the integrator 121.

[0036] Integrator 121 calculates and outputs the integral value of lateral acceleration corresponding to the limit decision flag based on the limit decision flag, steering control quantity, and lateral acceleration deviation.

[0037] Gain multiplier 122 multiplies a preset arbitrary gain with the integral value of lateral acceleration and outputs it as a steering control quantity limit value. Here, the multiplied gain can also be a value that can change according to the vehicle speed. In this case, for example, the gain can be obtained by referring to a mapping corresponding to the detected vehicle speed. It has the function of bias amplifier 123, which amplifies the output of bias amplifier 120 through integrator 121 and gain multiplier 122.

[0038] Figure 5This is a flowchart illustrating the operation of the steering control quantity limit value calculation unit 12a. First, in step S201, the steering control quantity limit value calculation unit 12a reads the lateral acceleration output by the lateral acceleration detection unit 2, the steering control quantity output by the steering control quantity calculation unit, and the limit determination flag output by the limit determination unit 11.

[0039] Next, in step S202, the operation in the deviation calculator 120 is performed as shown in the following formula (1), and the deviation between the lateral acceleration limit value and the absolute value of the lateral acceleration is calculated as the lateral acceleration deviation. dGy=Gy_limit-|Gy|·····(1) in, dGy: Lateral acceleration deviation Gy_limit: Lateral acceleration limit value Gy: Lateral acceleration

[0040] Next, in steps S203 to S206, the calculations in integrator 121 are performed. First, in step S203, a conditional branch determination based on the limit determination flag is performed. If the limit determination flag is limited, that is, if the lateral acceleration of the vehicle is above the lateral acceleration limit value, the process proceeds to step S204. Otherwise, the process proceeds to step S205. In step S204, the lateral acceleration integral value is calculated by the lateral acceleration integral value calculation (A) of the following equation (2). I_Gy=I_Gy last value+dGy×dT……(2) in, I_Gy: Integral value of lateral acceleration dT: Integration period Gy_limit: Lateral acceleration limit value Gy: Lateral acceleration

[0041] In step S205, the lateral acceleration integral value is calculated using the lateral acceleration integral value calculation (B) according to the following formula (3). That is, by setting the lateral acceleration integral value to the value corresponding to the steering control amount limit value, when the limit determination flag is unrestricted, the steering control amount is not restricted in the steering control amount restriction unit 13. In addition, when the limit determination flag changes from unrestricted to restricted, the steering control amount limit value is discontinuous relative to the steering control amount when the steering control amount restriction begins, thus preventing discontinuity in the steering control amount. I_Gy=Q_ctr / KI·····(3) in, I_Gy: Integral value of lateral acceleration Q_ctr: Steering control quantity KI: Gain

[0042] Next, in step S206, the operation in the gain multiplier 122 is performed using the following formula (4), multiplying the integral value of the lateral acceleration by a preset arbitrary gain, and using it as the steering control quantity limit value. Q_limit=KI×I_Gy·····(4) in, Q_limit: Steering control limit value

[0043] As described above, when the lateral acceleration of the vehicle exceeds the lateral acceleration limit, the steering control amount limit is adjusted based on the deviation between the lateral acceleration limit and the lateral acceleration. Therefore, compared with the case of maintaining the steering control amount limit in Embodiment 1, the lateral acceleration of the vehicle can be limited with higher precision for changes in the driving environment such as vehicle deviation or the slope angle of the driving path. Thus, it can improve the effect of reducing the driver's burden caused by the driver's sense of insecurity and discomfort, regardless of the driving environment such as vehicle deviation or the slope angle of the driving path.

[0044] Here, in this embodiment 2, the steering control quantity limit value calculation unit 12a is a structure that calculates the steering control quantity limit value based solely on the integral element of the lateral acceleration deviation, which is the deviation between the lateral acceleration limit value and the absolute value of the lateral acceleration. However, it can also be a structure that incorporates a proportional element or a differential element of the lateral acceleration deviation. For example, when a proportional element is incorporated, the following ability of the lateral acceleration limit value can be improved. When a proportional element is incorporated, the lateral acceleration integral value reset process in equation (3) of step S205 can be replaced with the following equation (5), and the gain multiplication process in equation (4) of step S206 can be replaced with the following equation (6). I_Gy=Q_ctr / KI-KP×dGy·····(5) in, KP: Scale Element Gain Q_limit=KI×I_Gy+KP×dGy·····(6)

[0045] Furthermore, in Embodiments 1 and 2, a camera is used as the driving path recognition unit 3 to identify the driving path ahead. However, the driving path can also be identified by means other than a camera, achieving the same effect as the vehicle steering device shown in this embodiment. For example, it can be configured to identify the driving path ahead based on the vehicle's own position and map information received from a communicable satellite, or it can be configured to identify the driving path ahead based on the trajectory of a vehicle traveling ahead obtained by radar, a camera, or the like, regardless of the means used.

[0046] <Modifications of the Implementation> In addition, the steering control quantity is, for example, the target torque (driving torque) used to drive the steering actuator 4, but it can also be the target steering angle used to steer the vehicle to follow the target driving route.

[0047] The functional block diagram representing the structure of the vehicle steering system according to Embodiment 1 in this case is, for example, as shown below. Figure 6 As shown, the steering control quantity and steering control quantity limit value in the steering control quantity limit calculation unit 12 and the steering control quantity limit unit 13 are also called the target steering angle and the target steering angle limit value, respectively. In addition, in this case, the configuration includes a steering angle detection unit 5 and a steering angle control unit 14. The steering angle detection unit 5 detects the steering angle of the vehicle and outputs it to the steering angle control unit 14. In the steering angle control unit 14, based on the steering control quantity input from the steering control quantity limit unit 13, i.e., the target steering angle, and the steering angle input from the steering angle detection unit 5, the target torque (drive torque) that the steering angle of the vehicle follows the target steering angle is calculated, and output to the steering actuator 4.

[0048] Here, the calculation of the target torque (driving torque) in the steering angle control unit 14 can be performed using known control methods based on proportional elements, integral elements, etc., of the deviation between the target steering angle and the steering angle, regardless of the calculation method. With this structure, in the steering control quantity limit value calculation unit 12, by maintaining the steering control quantity, i.e., the steering angle, at the moment when the lateral acceleration of the vehicle reaches the lateral acceleration limit value, similar to Embodiment 1, it is possible to prevent the lateral acceleration of the vehicle from further increasing, that is, to limit the lateral acceleration of the vehicle to the lateral acceleration limit value.

[0049] Furthermore, the functional block diagram illustrating the structure of the vehicle steering system according to Embodiment 2 in this case is, for example, as shown below. Figure 7 As shown, with Figure 6 It also has a structure that includes a steering angle detection unit 5 and a steering angle control unit 14.

[0050] With this structure, in the steering control quantity limit value calculation unit 12a, when the lateral acceleration of the vehicle is greater than the lateral acceleration limit value, the steering control quantity, i.e. the steering angle, is adjusted based on the deviation between the lateral acceleration limit value and the lateral acceleration. Similar to Embodiment 2, this can prevent the lateral acceleration of the vehicle from increasing further, i.e., it can limit the lateral acceleration of the vehicle to the lateral acceleration limit value with higher precision.

[0051] Although this application describes various exemplary embodiments and examples, the various features, methods and functions described in one or more embodiments are not limited to the application of a particular embodiment and can be applied to the embodiment individually or in various combinations. Therefore, it can be assumed that numerous variations not illustrated are also included within the scope of the technology disclosed in this application. For example, this includes cases involving modifications, additions, or omissions of at least one constituent element, as well as cases involving the extraction of at least one constituent element and its combination with constituent elements of other embodiments. Label Explanation

[0052] 1. Steering device; 2. Lateral acceleration detection unit; 3. Driving path recognition unit; 4. Steering actuator; 5. Steering angle detection unit; 10. Steering control quantity calculation unit; 11. Limit determination unit; 12. Steering control quantity limit value calculation unit; 13. Steering control quantity limit unit; 14. Steering angle control unit.

Claims

1. A vehicle steering system that assists in steering operations to enable a vehicle to follow a target driving path, characterized in that it comprises: A steering control quantity calculation unit calculates a steering control quantity for making the vehicle approach the target driving route; A lateral acceleration detection unit that detects the lateral acceleration of the vehicle; A steering control quantity limit value calculation unit that limits the lateral acceleration to a steering control quantity limit value such as the lateral acceleration limit value based on the lateral acceleration calculation. The limitation determination unit determines whether the steering control amount limitation is effective or ineffective based at least on the lateral acceleration. as well as A steering control amount limiting unit, which limits the steering control amount based on the steering control amount limiting value when the limiting determination unit determines that the limiting is effective. The steering control quantity limit value calculation unit includes: A deviation calculator that calculates the deviation between the lateral acceleration limit value and the lateral acceleration; as well as A bias amplifier amplifies the output of the bias arithmetic unit. The steering control quantity limit calculation unit calculates the steering control quantity limit value based on the output of the deviation amplifier.

2. The vehicle steering system as claimed in claim 1, characterized in that, The limitation determination unit determines whether the steering control amount limitation is valid or invalid based at least on the lateral acceleration and the steering control amount limitation value.

3. The vehicle steering system as claimed in claim 1, characterized in that, The steering control quantity limit calculation unit uses the steering control quantity at the moment when the lateral acceleration reaches the lateral acceleration limit value as the steering control quantity limit value.

4. The vehicle steering system as claimed in claim 1, characterized in that, The bias amplifier includes at least an integrator that integrates the output of the bias arithmetic unit.

5. The vehicle steering system as claimed in claim 4, characterized in that, When the limitation determination unit determines that the limitation is invalid, the deviation amplifier sets the integral element of the integrator to a value that is consistent with the steering control quantity limit value and the steering control quantity.

6. The vehicle steering system as claimed in any one of claims 1 to 5, characterized in that, This includes steering actuators that steer the vehicle's steering wheels. The steering control quantity is the driving torque of the steering actuator. The steering control limit value calculated by the steering control limit value calculation unit is the drive torque limit value. The steering control quantity limiting unit limits the driving torque of the steering actuator to the driving torque limit value.

7. The vehicle steering system as claimed in any one of claims 1 to 5, characterized in that, include: A steering angle detection unit that detects the steering angle of the vehicle's steering wheels; A steering actuator that steers the vehicle's steering wheels; as well as A steering angle control unit drives a steering actuator such that the steering control amount is a target steering angle of the vehicle, causing the steering angle to follow the target steering angle. The steering control limit value calculated by the steering control limit value calculation unit is the target steering angle limit value. The steering control quantity limiting unit limits the target steering angle to a target steering angle limit value.

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