Curvature estimation device, vehicle control device and curvature estimation program

Abstract

To provide a curvature estimation device, a vehicle control device and a curvature estimation program which can accurately acquire a curvature of a travel trajectory of a vehicle.SOLUTION: A curvature estimation device 100 comprises an actual curvature acquisition section 102 that acquires an actual curvature which is a curvature of a travel trajectory of a vehicle 10. The actual curvature acquisition section 102 acquires a first curvature calculation value which is a calculation value of the curvature of the travel trajectory based on a yaw rate as the actual curvature when a vehicle speed is equal to or greater than a first speed determination value. The actual curvature acquisition section 102 also acquires a second curvature calculation value which is a calculation value of the curvature of the travel trajectory based on a speed difference between rear wheels 23 and 24 when the vehicle speed is less than the first speed determination value as the actual curvature.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a curvature estimation device, a vehicle control device, and a curvature estimation program. [Background technology]

[0002] Patent Document 1 describes a vehicle control device that controls the steering angle of a vehicle to make the vehicle travel along a target trajectory. The vehicle control device calculates the steering angle of the vehicle based on the deviation between a target position set on the target trajectory and the current position. The vehicle control device then executes steering control of the vehicle based on the calculated steering angle of the vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-32828 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned vehicle control device, in order to improve the braking of the steering control, it is desirable to obtain the current position of the vehicle with high accuracy. As an example, the current position of the vehicle can be obtained from the actual curvature, which is the curvature of the vehicle's traveling path. In other words, if the vehicle control device can obtain the actual curvature with high accuracy, it can obtain the current position of the vehicle with high accuracy. [Means for solving the problem]

[0005] A curvature estimation device that solves the above problem includes a state variable acquisition unit that acquires the wheel speed of the right wheel and the wheel speed of the left wheel of the vehicle based on the detection results of a wheel speed sensor, and acquires the yaw rate of the vehicle based on the detection results of a yaw rate sensor, and an actual curvature acquisition unit that acquires an actual curvature, which is the curvature of the vehicle's driving trajectory, and when the vehicle body speed is equal to or greater than a first speed determination value, the actual curvature is acquired as a first curvature calculation value, which is a calculation value of the curvature of the driving trajectory based on the yaw rate, and when the vehicle body speed is less than the first speed determination value, the actual curvature is acquired as a second curvature calculation value, which is a calculation value of the curvature of the driving trajectory based on the speed difference between the wheel speed of the right wheel and the wheel speed of the left wheel.

[0006] The vehicle control device that solves the above problem is applied to a vehicle that has a wheel having a right wheel and a left wheel, and a steering device that adjusts the steering angle of the wheel, and assists the vehicle in traveling along a target trajectory by outputting a command steering angle to the steering device, and is equipped with the above-mentioned curvature estimation device.

[0007] A curvature estimation program that solves the above problem is a curvature estimation program that causes a vehicle control device to execute a state variable acquisition process that acquires the wheel speed of the right wheel and the wheel speed of the left wheel of the vehicle based on the detection results of a wheel speed sensor, and acquires the yaw rate of the vehicle based on the detection results of a yaw rate sensor, and an actual curvature acquisition process that acquires the actual curvature, which is the curvature of the vehicle's driving trajectory, wherein the actual curvature acquisition process acquires a first curvature calculation value, which is a calculation value of the curvature of the driving trajectory based on the yaw rate, as the actual curvature when the vehicle body speed is equal to or greater than a first speed determination value, and acquires a second curvature calculation value, which is a calculation value of the curvature of the driving trajectory based on the speed difference between the wheel speed of the right wheel and the wheel speed of the left wheel, as the actual curvature, when the vehicle body speed is less than the first speed determination value. Effect of the Invention

[0008] The curvature estimation device, the vehicle control device, and the curvature estimation program can accurately obtain the curvature of the vehicle's travel trajectory. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle. [Diagram 2] FIG. 2 is a schematic diagram showing an example of a target trajectory of a vehicle during automatic parking. [Diagram 3] FIG. 3 is a flowchart showing the flow of processing executed by the vehicle control device to output the command steering angle. [Figure 4] FIG. 4 is a flowchart showing the flow of the process performed by the vehicle control device to obtain the actual curvature. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of a vehicle control device and a vehicle control program will be described below. <Configuration of this embodiment> As shown in FIG. 1, a vehicle 10 includes front wheels 21, 22, rear wheels 23, 24, a drive device 30, a steering device 40, a detection system 50, a driving assistance device 60, and a vehicle control device .

[0011] <Drive unit and steering unit> The drive device 30 includes a motor generator 31 that generates a drive force for the wheels 21-24, and a drive control unit 32 that controls the motor generator 31. The drive control unit 32 is an electronic control unit having a CPU and a memory. The drive control unit 32 controls the motor generator 31 based on a command drive force output from the vehicle control device 70. The power of the motor generator 31 is then transmitted to the wheels 21-24, causing the vehicle 10 to run.

[0012] The steering device 40 includes a steering actuator 41 that adjusts the steering angle of the front wheels 21, 22, and a steering control section 42 that controls the steering actuator 41. The steering control section 42 is an electronic control device having a CPU and a memory. The steering control section 42 controls the steering actuator 41 based on a command steering angle output from the vehicle control device 70. Then, when the steering angle of the front wheels 21, 22 is adjusted by the output of the steering actuator 41, the vehicle 10 becomes able to turn. In this embodiment, of the multiple wheels 21-24, the front wheels 21, 22 correspond to the steered wheels.

[0013] <Detection system> The detection system 50 detects the state of the vehicle 10 that changes while the vehicle 10 is traveling. The detection system 50 has a steering angle sensor 51, a plurality of wheel speed sensors 52, and a yaw rate sensor 53 as a plurality of sensors that detect the state of the vehicle 10. These multiple sensors 51 to 53 output signals according to the detection results to the vehicle control device 70.

[0014] The steering angle sensor 51 detects the steering angle of the front wheels 21, 22. The multiple wheel speed sensors 52 correspond to the multiple wheels 21-24, respectively. The multiple wheel speed sensors 52 individually detect the rotation speeds of the multiple wheels 21-24 as wheel speeds. The yaw rate sensor 53 detects the yaw rate of the vehicle 10.

[0015] <Driving assistance device> The driving assistance device 60 is an electronic control device having a CPU and a memory. In the driving assistance device 60, the CPU executes programs stored in the memory to realize various driving assistance functions. The driving assistance functions are functions that assist the driver in driving the vehicle 10. The driving assistance functions include, for example, automatic parking, lane keep assist, and adaptive cruise control. In the following description, automatic parking will be described in detail.

[0016] As shown in FIG. 2, automatic parking automatically parks the vehicle 10 in the parking area AR by turning the vehicle 10 while moving it backward. The driving support device 60 starts automatic parking control when there is a request to perform automatic parking from the driver or the like. In the automatic parking control, the driving support device 60 generates a target trajectory TR from the current position P1 of the vehicle 10 to a target position P2 set in the parking area AR. The target trajectory TR is an ideal turning trajectory when moving the vehicle 10 from the current position P1 to the target position P2. If an obstacle exists between the current position P1 and the target position P2, it is preferable that the target trajectory TR is generated so as to avoid the obstacle. Next, the driving support device 60 generates a target curvature Kt, which is the curvature of the target trajectory TR. Then, the driving support device 60 outputs the target curvature Kt to the vehicle control device 70.

[0017] In the following description, the curvature of the travel path when the vehicle 10 turns right is taken as positive, and the curvature of the travel path when the vehicle 10 turns left is taken as negative. In other words, when the target trajectory TR curves to the right as it moves forward, the target curvature Kt is a positive value, and when the target trajectory TR curves to the left as it moves forward, the target curvature Kt is a negative value. In addition, when the target trajectory TR is a straight trajectory moving forward, the target curvature Kt is "0". Note that the relationship between the left-right direction of the vehicle 10 and the positive and negative values ​​of the target curvature Kt may be reversed.

[0018] <Vehicle control device> As shown in Fig. 1, the vehicle control device 70 includes a processing circuit 80. The processing circuit 80 is, for example, an electronic control device having a CPU 81 and a memory 82. The memory 82 stores a vehicle control program executed by the CPU 81. The processing circuit 80 controls the drive device 30 and the steering device 40 as a result of the CPU 81 executing the vehicle control program. The vehicle control program is a program targeted at the control device of the vehicle 10. The vehicle control program includes a curvature estimation program.

[0019] <Functional configuration of the processing circuit> The processing circuit 80 functions as a target curvature acquisition unit 91, a command steering angle calculation unit 92, a steering angle command unit 93, and a curvature estimation device 100 as a result of the CPU 81 executing a vehicle control program. The curvature estimation device 100 functions as a state variable acquisition unit 101 and an actual curvature acquisition unit 102. These will be described in detail below.

[0020] <Target curvature acquisition part> The target curvature acquisition unit 91 acquires the target curvature Kt output from the driving support device 60. <State variable acquisition section> The state variable acquisition unit 101 acquires state variables of the vehicle 10 based on the detection signal output from the detection system 50. More specifically, the state variable acquisition unit 101 acquires the steering angle of the front wheels 21, 22 based on the detection result of the steering angle sensor 51. The state variable acquisition unit 101 acquires the yaw rate of the vehicle 10 based on the detection result of the yaw rate sensor 53. The state variable acquisition unit 101 acquires the wheel speeds of the multiple wheels 21-24 based on the detection result of the wheel speed sensor 52. Furthermore, the state variable acquisition unit 101 calculates the vehicle body speed Vb based on the wheel speeds of the multiple wheels 21-24. The steering angle, wheel speed, and yaw rate are examples of state variables.

[0021] <Actual curvature acquisition section> The actual curvature acquisition unit 102 acquires the actual curvature, which is the curvature of the travel path of the vehicle 10, based on state variables such as the steering angle, the wheel speed, and the yaw rate.

[0022] The actual curvature acquisition unit 102 can obtain a first curvature calculation value K1, which is a calculation value of the curvature of the travel path of the vehicle 10 based on the yaw rate, as shown in the following (Equation 1), where "Y" is the yaw rate.

[0023] K1=Y / Vb…(Formula 1) The actual curvature acquisition unit 102 can determine a second curvature calculation value K2, which is a calculation value of the curvature of the travel path of the vehicle 10 based on the speed difference between the wheel speed of the left rear wheel 23 and the wheel speed of the right rear wheel 24 (hereinafter referred to as the "rear wheel speed difference"), as shown in the following (Equation 2). Here, "Vrl" is the wheel speed of the left rear wheel 23, "Vrr" is the wheel speed of the right rear wheel 24, and "d" is the tread base length.

[0024] K2=(Vrl-Vrr) / d(Vrl+Vrr)...(Formula 2) The actual curvature acquisition unit 102 can obtain a third curvature calculation value K3, which is a calculation value of the curvature of the travel path of the vehicle 10 based on the steering angle, as shown in the following (Equation 3), where "δ" is the steering angle of the front wheels 21, 22, and "L" is the wheelbase length.

[0025] K3=δ / L…(Equation 3) The actual curvature acquisition unit 102 acquires one of the first curvature calculation value K1, the second curvature calculation value K2, and the third curvature calculation value K3 as the actual curvature based on the vehicle body speed Vb and the target curvature Kt. When the yaw rate, the rear wheel speed difference, and the steering angle are compared, the state variable that best represents the turning behavior of the vehicle 10 is the yaw rate. Therefore, the actual curvature acquisition unit 102 basically acquires the first curvature calculation value K1 based on the yaw rate as the actual curvature.

[0026] The effect of the vehicle speed Vb on the calculation accuracy of the curvature calculation value will be described. As shown in (Equation 1), the first curvature calculation value K1 is calculated by dividing the yaw rate by the vehicle body speed Vb. Therefore, when the vehicle body speed Vb is low, the effect of the error contained in the yaw rate on the first curvature calculation value K1 becomes large. In other words, when the vehicle body speed Vb is low, the calculation accuracy of the first curvature calculation value K1 is likely to be low. In the following description, a judgment value for judging the calculation accuracy of the first curvature calculation value K1 based on the yaw rate, in other words, a judgment value for judging whether the vehicle body speed Vb is low or not, is referred to as a first speed judgment value Vth1.

[0027] When the vehicle speed Vb is equal to or greater than the first speed determination value Vth1, the actual curvature acquisition unit 102 acquires the first curvature calculation value K1 based on the yaw rate as the actual curvature. On the other hand, when the vehicle speed Vb is less than the first speed determination value Vth1, the actual curvature acquisition unit 102 acquires either the second curvature calculation value K2 based on the speed difference between the wheel speeds or the third curvature calculation value K3 based on the steering angle as the actual curvature.

[0028] The number of pulses output by the wheel speed sensor 52 per unit time increases as the wheel speed of the wheel corresponding to the wheel speed sensor 52 increases. The more pulses the wheel speed sensor 52 outputs per unit time, the more accurately the wheel speed is detected. Therefore, when the vehicle body speed Vb is equal to or greater than the first speed determination value Vth1 and when the vehicle body speed Vb is slightly lower than the first speed determination value Vth1, the number of pulses output by the wheel speed sensor 52 per unit time is greater than the number of pulses required to accurately calculate the wheel speed. Therefore, the calculation accuracy of the second curvature calculation value K2 based on the rear wheel speed difference is relatively high. On the other hand, when the vehicle body speed Vb is much lower than the first speed determination value Vth1, the number of pulses output by the wheel speed sensor 52 per unit time is likely to be less than the number of pulses required to accurately calculate the wheel speed. Therefore, the calculation accuracy of the second curvature calculation value K2 based on the rear wheel speed difference is relatively low.

[0029] On the other hand, when the vehicle 10 turns, a slip angle occurs, which is a deviation between the direction in which the front wheels 21, 22 face and the traveling direction of the front wheels 21, 22. The slip angle tends to become smaller as the vehicle speed Vb becomes lower. That is, when the vehicle speed Vb is much lower than the first speed determination value Vth1, the deviation between the direction in which the front wheels 21, 22 face and the traveling direction of the front wheels 21, 22 becomes smaller. Therefore, the calculation accuracy of the third curvature calculation value K3 based on the steering angle is likely to be high in that the correlation between the steering angle of the front wheels 21, 22 and the turning behavior of the vehicle 10 becomes stronger. On the other hand, when the vehicle speed Vb is equal to or higher than the first speed determination value Vth1 and when the vehicle speed Vb is slightly lower than the first speed determination value Vth1, the deviation between the direction in which the front wheels 21, 22 face and the traveling direction of the front wheels 21, 22 becomes larger. Therefore, the correlation between the steering angle of the front wheels 21, 22 and the turning behavior of the vehicle 10 becomes weak, and the calculation accuracy of the third curvature calculation value K3 based on the steering angle is likely to be low.

[0030] From the above, when the vehicle speed Vb is slightly lower than the first speed determination value Vth1, the calculation accuracy of the second curvature calculation value K2 based on the rear wheel speed difference becomes high, while the calculation accuracy of the third curvature calculation value K3 based on the steering angle becomes low. Also, when the vehicle speed Vb is much lower than the first speed determination value Vth1, the calculation accuracy of the second curvature calculation value K2 based on the rear wheel speed difference becomes low, while the calculation accuracy of the third curvature calculation value K3 based on the steering angle becomes high. In the following description, the second speed determination value Vth2 is used as a determination value for determining the calculation accuracy of the second curvature calculation value K2 and the third curvature calculation value K3, in other words, a determination value for determining whether the vehicle speed Vb is very low or not. The second speed determination value Vth2 is a value smaller than the first speed determination value Vth1.

[0031] When the vehicle speed Vb is less than the first speed determination value Vth1 and is equal to or greater than the second speed determination value Vth2, the actual curvature acquisition unit 102 acquires the second curvature calculation value K2 based on the rear wheel speed difference as the actual curvature. When the vehicle speed Vb is less than the second speed determination value Vth2, the actual curvature acquisition unit 102 acquires the third curvature calculation value K3 based on the steering angle as the actual curvature.

[0032] In this embodiment, the actual curvature acquisition unit 102 acquires the actual curvature when the vehicle 10 is automatically parked. For this reason, the first speed determination value Vth1 and the second speed determination value Vth2 are both set to values ​​according to the traveling speed when parking. Although it varies depending on the accuracy of the sensor, as an example, the first speed determination value Vth1 is set to a speed of about 10 km per hour, and the second speed determination value Vth2 is set to a speed of about several km per hour.

[0033] The effect of the target curvature Kt on the calculation accuracy of the curvature calculation value will be described. The first curvature calculation value K1 is calculated based on the yaw rate. Here, consider a case where the first curvature calculation value K1 includes an error of 0.1% with respect to the true curvature. In this case, if the turning radius of the vehicle 10 is 10 m, an error of 1 cm may occur in the radial direction perpendicular to the turning direction of the vehicle 10 when the vehicle 10 turns 90°. On the other hand, if the turning radius of the vehicle 10 is 2 m, an error of 0.2 cm may occur in the radial direction perpendicular to the turning direction of the vehicle 10 when the vehicle 10 turns 90°.

[0034] That is, when the turning radius of the vehicle 10 is large, the deviation between the first curvature calculation value K1 and the true curvature becomes larger than when the turning radius of the vehicle 10 is small. In other words, when the turning radius of the vehicle 10 is large, the calculation accuracy of the first curvature calculation value K1 decreases than when the turning radius of the vehicle 10 is small. Since the turning radius of the vehicle 10 increases as the target curvature Kt decreases, it can be said that the calculation accuracy of the first curvature calculation value K1 decreases as the target curvature Kt decreases.

[0035] The same tendency is observed for the second curvature calculation value K2 based on the rear wheel speed difference and the third curvature calculation value K3 based on the steering angle. However, due to the nature of errors contained in the sensors, even if the target curvature Kt is small, the calculation accuracy of the second curvature calculation value K2 tends to be higher than the calculation accuracy of the first curvature calculation value K1, and the calculation accuracy of the third curvature calculation value K3 tends to be higher than the calculation accuracy of the second curvature calculation value K2.

[0036] In this embodiment, high calculation accuracy of the actual curvature means that the deviation between the calculated actual curvature and the true curvature is small, and does not mean that the value obtained by dividing the deviation by the actual curvature is small. Incidentally, when the vehicle 10 is automatically parked, the allowable deviation between the target parking position and the actual parking position does not change regardless of the turning radius of the vehicle 10.

[0037] The actual curvature acquisition unit 102 uses the first curvature judgment value Kth1 to determine whether the calculation accuracy of the first curvature calculation value K1 is high. For example, when the absolute value of the target curvature Kt is equal to or greater than the first curvature judgment value Kth1, the calculation accuracy of the first curvature calculation value K1 is deemed to be high. On the other hand, when the absolute value of the target curvature Kt is less than the first curvature judgment value Kth1, the calculation accuracy of the first curvature calculation value K1 is deemed to be low. In addition, the actual curvature acquisition unit 102 uses a second curvature judgment value Kth2 that is less than the first curvature judgment value Kth1 to determine whether the calculation accuracy of the second curvature calculation value K2 is high. For example, when the absolute value of the target curvature Kt is equal to or greater than the second curvature judgment value Kth2, the calculation accuracy of the second curvature calculation value K2 is deemed to be high. On the other hand, when the absolute value of the target curvature Kt is less than the second curvature judgment value Kth2, the calculation accuracy of the second curvature calculation value K2 is deemed to be low. The first curvature determination value Kth1 and the second curvature determination value Kth2 may be fixed values ​​or may be variable values ​​that become higher as the vehicle body speed Vb becomes slower.

[0038] Then, when the vehicle speed Vb is equal to or greater than the first speed determination value Vth1 and the absolute value of the target curvature Kt is equal to or greater than the first curvature determination value Kth1, the actual curvature acquisition unit 102 acquires the first curvature calculation value K1 as the actual curvature. On the other hand, even if the vehicle speed Vb is equal to or greater than the first speed determination value Vth1, when the absolute value of the target curvature Kt is less than the first curvature determination value Kth1, the actual curvature acquisition unit 102 does not acquire the first curvature calculation value K1 as the actual curvature. In this case, when the absolute value of the target curvature Kt is equal to or greater than the second curvature calculation value K2, the actual curvature acquisition unit 102 acquires the second curvature calculation value K2 as the actual curvature, and when the absolute value of the target curvature Kt is less than the second curvature calculation value K2, the actual curvature acquisition unit 102 acquires the third curvature calculation value K3 as the actual curvature.

[0039] Furthermore, when the vehicle body speed Vb is equal to or greater than the second speed determination value Vth2 and less than the first speed determination value Vth1, and the absolute value of the target curvature Kt is equal to or greater than the second curvature determination value Kth2, the actual curvature acquisition unit 102 acquires the second curvature calculation value K2 as the actual curvature. On the other hand, even when the vehicle body speed Vb is equal to or greater than the second speed determination value Vth2 and less than the first speed determination value Vth1, when the absolute value of the target curvature Kt is less than the second curvature determination value Kth2, the actual curvature acquisition unit 102 acquires the third curvature calculation value K3 as the actual curvature.

[0040] <Indicated steering angle calculation unit> The commanded rudder angle calculation unit 92 calculates the commanded rudder angle by feedback control based on the target curvature Kt and the actual curvature so that the actual curvature approaches the target curvature Kt. More specifically, the commanded rudder angle calculation unit 92 calculates the commanded rudder angle by feedback control based on the deviation between the target curvature Kt and the actual curvature. The feedback control is, for example, PID control.

[0041] <Steering angle indicator> The steering angle instruction unit 93 outputs an instruction steering angle to the steering control unit 42. If the instruction steering angle is a positive value, the steering angle of the front wheels 21, 22 is adjusted so that the vehicle 10 can turn to the right. On the other hand, if the instruction steering angle is a negative value, the steering angle of the front wheels 21, 22 is adjusted so that the vehicle 10 can turn to the left. Also, if the instruction steering angle is "0", the steering angle of the front wheels 21, 22 is adjusted so that the vehicle 10 can go straight.

[0042] <Processing contents of the processing circuit> The process executed by the processing circuit 80 to determine the command steering angle will be described with reference to Fig. 3 and Fig. 4. This process is repeatedly executed in a predetermined control cycle while the driving assistance device 60 is performing automatic parking control. This process is executed by the CPU 81 by executing a vehicle control program stored in the memory 82.

[0043] As shown in Fig. 3, the processing circuit 80 acquires the target curvature Kt output from the driving support device 60 (S11). Next, the processing circuit 80 performs an actual curvature acquisition process for acquiring an actual curvature (S12). After that, the processing circuit 80 calculates an instructed steering angle based on the target curvature Kt acquired in step S11 and the actual curvature acquired in step S12 (S13). Then, the processing circuit 80 outputs the instructed steering angle to the steering control unit 42 (S14). After that, the processing circuit 80 ends this process.

[0044] The actual curvature acquisition process in step S12 will be described with reference to FIG. As shown in Fig. 4, the processing circuit 80 acquires state variables such as a steering angle, a wheel speed, and a yaw rate based on the detection results of a plurality of sensors (S21). Next, the processing circuit 80 judges whether or not the vehicle body speed Vb is equal to or greater than a first speed judgment value Vth1 (S22). If the vehicle body speed Vb is equal to or greater than the first speed judgment value Vth1 (S22: YES), the processing circuit 80 judges whether or not the target curvature Kt acquired in step S11 is equal to or greater than the first curvature judgment value Kth1 (S23). If the target curvature Kt is equal to or greater than the first curvature judgment value Kth1 (S23: YES), the processing circuit 80 acquires a first curvature calculation value K1 based on the yaw rate as an actual curvature (S24). After that, the processing circuit 80 temporarily ends this process.

[0045] In step S22, if the vehicle body speed Vb is less than the first speed determination value Vth1 (S22: NO), the processing circuit 80 determines whether the vehicle body speed Vb is equal to or greater than the second speed determination value Vth2 (S25). If the vehicle body speed Vb is equal to or greater than the second speed determination value Vth2 (S25: YES), the processing circuit 80 determines whether the target curvature Kt is equal to or greater than the second curvature determination value Kth2 (S26). If the target curvature Kt is equal to or greater than the second curvature determination value Kth2 (S26: YES), the processing circuit 80 acquires the second curvature calculation value K2 based on the rear wheel speed difference as the actual curvature (S27). After that, the processing circuit 80 temporarily ends this process.

[0046] In step S25, if the vehicle speed Vb is less than the second speed determination value Vth2 (S25: NO), the processing circuit 80 acquires the third curvature calculation value K3 based on the steering angle as the actual curvature (S28). After that, the processing circuit 80 temporarily ends this process.

[0047] In step S23, if the target curvature Kt is less than the first curvature determination value Kth1 (S23: NO), the processing circuit 80 shifts the process to step S27 or step S28. In this case, the processing circuit 80 acquires the second curvature calculation value K2 or the third curvature calculation value K3 as the actual curvature. In step S26, if the target curvature Kt is less than the second curvature determination value Kth2 (S26: NO), the processing circuit 80 shifts the process to step S28. In this case, the processing circuit 80 acquires the third curvature calculation value K3 as the actual curvature.

[0048] In this embodiment, step S21 corresponds to the "state variable acquisition process". Steps S22 to S28 correspond to the "actual curvature acquisition process". Step S11 corresponds to the "target curvature acquisition process". Step S13 corresponds to the "instructed steering angle calculation process". The process of step S21 is performed by the state variable acquisition unit 101. The processes of steps S22 to S28 are performed by the actual curvature acquisition unit 102. The process of step S11 is performed by the target curvature acquisition unit 91. The process of step S13 is performed by the instructed steering angle calculation unit 92. The process of step S14 is performed by the steering angle instruction unit 93.

[0049] <Actions and Effects of the Present Embodiment> When vehicle 10 is automatically parked, vehicle control device 70 calculates a command steering angle by feedback control based on the deviation between target curvature Kt and actual curvature. Then, vehicle control device 70 outputs the calculated command steering angle to steering device 40. Steering actuator 41 operates in response to the command steering angle, causing vehicle 10 to travel along target trajectory TR.

[0050] Here, the vehicle control device 70 switches the calculation method of the actual curvature used in the feedback control according to the driving conditions of the vehicle 10 during automatic parking. In detail, the vehicle control device 70 acquires the curvature calculation value with the highest calculation accuracy as the actual curvature from among three curvature calculation values ​​calculated by different calculation methods based on the vehicle body speed Vb and the target curvature Kt. Therefore, the vehicle control device 70 can calculate the command steering angle based on the target curvature Kt and the actual curvature with the highest calculation accuracy according to the driving conditions of the vehicle 10. Therefore, it becomes possible to make the vehicle 10 run along the target trajectory TR.

[0051] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0052] The curvature estimation device 100 can also be applied to a position estimation device that estimates the current position of the vehicle 10 based on the actual curvature. The curvature estimation device 100 may obtain any one of the first curvature calculation value K1, the second curvature calculation value K2, and the third curvature calculation value K3 as the actual curvature based only on the vehicle body speed Vb. That is, in the flowchart shown in FIG. 4, steps S23 and S26 may be omitted.

[0053] The curvature estimation device 100 may acquire either the first curvature calculation value K1 or the second curvature calculation value K2 as the actual curvature based on the vehicle body speed Vb and the target curvature Kt. That is, in the flowchart shown in FIG. 4, steps S25, S26, and S28 may be omitted.

[0054] The curvature estimation device 100 may obtain either the first curvature calculation value K1 or the second curvature calculation value K2 as the actual curvature based only on the vehicle body speed Vb. That is, in the flowchart shown in FIG. 4, steps S23, S25, S26, and S28 may be omitted.

[0055] After calculating the first curvature calculation value K1, the second curvature calculation value K2, and the third curvature calculation value K3, the curvature estimation device 100 may select a curvature calculation value to be the actual curvature from among these three curvature calculation values ​​based on the vehicle body speed Vb and the target curvature Kt. Furthermore, when the curvature estimation device 100 calculates one curvature calculation value to be the actual curvature based on the vehicle body speed Vb and the target curvature Kt, it is not necessary to calculate the other two curvature calculation values.

[0056] The curvature estimation device 100 may calculate the second curvature calculation value K2 based on the speed difference between the wheel speed of the left front wheel 21 and the wheel speed of the right front wheel 22 (hereinafter referred to as the "front wheel speed difference"). In the above embodiment, so-called reverse parking is given as an example of automatic parking. However, the driving assistance device may also implement automatic parking control for automatically performing so-called forward parking and parallel parking.

[0057] In the vehicle 10, both the front wheels 21, 22 and the rear wheels 23, 24 may be steerable wheels. Also, in the vehicle 10, of the front wheels 21, 22 and the rear wheels 23, 24, only the rear wheels 23, 24 may be steerable wheels.

[0058] In the vehicle 10, the motor generator 31 can be replaced with an internal combustion engine. The vehicle control device 70 and the curvature estimation device 100 are not limited to processing circuits having a CPU and a ROM and executing software processing. For example, the vehicle control device 70 and the curvature estimation device 100 may be equipped with a dedicated hardware circuit that executes at least a part of the various processes executed in the above-described embodiment. An example of the dedicated hardware circuit is an ASIC. ASIC is an abbreviation for "Application Specific Integrated Circuit." In other words, the vehicle control device 70 and the curvature estimation device 100 may have any one of the following configurations (a) to (c).

[0059] (a) A processing circuit including a processing device that executes all of the above processes according to a program, and a program storage device such as a ROM that stores the program. (b) A processing circuit having a processing device and a program storage device for executing part of the above processing in accordance with a program, and a dedicated hardware circuit for executing the remaining processing.

[0060] (c) A processing circuit having dedicated hardware circuitry for performing all of the above processes. Here, there may be a plurality of software execution devices each having a processing device and a program storage device, and a plurality of dedicated hardware circuits.

[0061] <Technical philosophy> The technical ideas that can be understood from the above-described embodiment and modified examples will be described. A curvature estimation method comprising: a state variable acquisition process for acquiring the wheel speed of a right wheel and the wheel speed of a left wheel of a vehicle based on the detection results of a wheel speed sensor, and acquiring a yaw rate of the vehicle based on the detection results of a yaw rate sensor; and an actual curvature acquisition process for acquiring an actual curvature, which is the curvature of a driving trajectory of the vehicle, wherein the actual curvature acquisition process acquires, when the vehicle body speed is equal to or greater than a first speed determination value, a first curvature calculation value, which is a calculation value of the curvature of the driving trajectory based on the yaw rate, as the actual curvature, and acquires, when the vehicle body speed is less than the first speed determination value, a second curvature calculation value, which is a calculation value of the curvature of the driving trajectory based on the speed difference between the wheel speed of the right wheel and the wheel speed of the left wheel, as the actual curvature. [Explanation of symbols]

[0062] 10. Vehicle 21~24…Wheel 40...Steering device 51...Steering angle sensor 52...Wheel speed sensor 53...Yaw rate sensor 70...Vehicle control device 91…Target curvature acquisition unit 92…Instruction rudder angle calculation unit 100...Curvature estimation device 101...Status variable acquisition unit 102…Actual curvature acquisition unit K1: First curvature calculation value K2: Second curvature calculation value K3: 3rd curvature calculation value Kt…Target curvature Kth1: First curvature judgment value Kth2: Second curvature judgment value Vb: Vehicle speed Vth1: First speed judgment value Vth2: Second speed judgment value

Claims

1. a state variable acquisition unit that acquires a wheel speed of a right wheel of the vehicle and a wheel speed of a left wheel of the vehicle based on a detection result of a wheel speed sensor, and acquires a yaw rate of the vehicle based on a detection result of a yaw rate sensor; an actual curvature acquisition unit that acquires an actual curvature that is a curvature of a running path of the vehicle; The actual curvature acquisition unit is When the vehicle speed is equal to or greater than a first speed determination value, a first curvature calculation value, which is a calculation value of the curvature of the travel path based on the yaw rate, is acquired as the actual curvature; When the vehicle speed is less than the first speed determination value, a second curvature calculation value, which is a calculation value of the curvature of the travel path based on a speed difference between the wheel speed of the right wheel and the wheel speed of the left wheel, is acquired as the actual curvature. Curvature estimation device.

2. the state variable acquisition unit acquires a steering angle of a steered wheel of the vehicle based on a detection result of a steering angle sensor; The actual curvature acquisition unit acquires, as the actual curvature, a third curvature calculation value that is a calculation value of a curvature of the traveling path based on the steering angle when the vehicle speed is less than a second speed determination value that is smaller than the first speed determination value. The curvature estimation device according to claim 1 .

3. A vehicle control device that is applied to a vehicle including a wheel having the right wheel and the left wheel and a steering device that adjusts a steering angle of the wheel, and supports traveling of the vehicle along a target trajectory by outputting a command steering angle to the steering device, The curvature estimation device according to claim 1 ; a target curvature acquisition unit that acquires a target curvature that is a curvature of the target trajectory; a command steering angle calculation unit that calculates the command steering angle by feedback control based on the target curvature and the actual curvature so that the actual curvature approaches the target curvature, The actual curvature acquisition unit acquires the second curvature calculation value as the actual curvature when the target curvature is less than the first curvature determination value even when the vehicle speed is equal to or greater than the first speed determination value. Vehicle control device.

4. A vehicle control device that is applied to a vehicle including a wheel having the right wheel and the left wheel and a steering device that adjusts the steering angle of the wheel, and supports traveling of the vehicle along a target trajectory by outputting a command steering angle to the steering device, The curvature estimation device according to claim 2 ; a target curvature acquisition unit that acquires a target curvature that is a curvature of the target trajectory; a command steering angle calculation unit that calculates the command steering angle by feedback control based on the target curvature and the actual curvature so that the actual curvature approaches the target curvature, The actual curvature acquisition unit is Even when the vehicle speed is equal to or greater than the first speed determination value, when the target curvature is less than the first curvature determination value and equal to or greater than a second curvature determination value that is smaller than the first curvature determination value, the second curvature calculation value is acquired as the actual curvature, Even when the vehicle speed is equal to or greater than the second speed determination value, if the target curvature is less than the second curvature determination value, the third curvature calculation value is acquired as the actual curvature. Vehicle control device.

5. a state variable acquisition process for acquiring a wheel speed of a right wheel of the vehicle and a wheel speed of a left wheel of the vehicle based on a detection result of a wheel speed sensor, and acquiring a yaw rate of the vehicle based on a detection result of a yaw rate sensor; and an actual curvature acquisition process for acquiring an actual curvature, which is a curvature of a travel path of the vehicle, The actual curvature acquisition process includes: When the vehicle speed is equal to or greater than a first speed determination value, a first curvature calculation value, which is a calculation value of the curvature of the travel path based on the yaw rate, is acquired as the actual curvature; When the vehicle speed is less than the first speed determination value, a second curvature calculation value, which is a calculation value of the curvature of the travel path based on a speed difference between the wheel speed of the right wheel and the wheel speed of the left wheel, is acquired as the actual curvature. Curvature estimation program.

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