Vehicle control device, vehicle control method and vehicle control system

Abstract

Vehicle control device comprising: - a target tire lateral force input section configured to receive an input of a target tire lateral force that should be generated at a wheel section of a vehicle, the target tire lateral force being detected on the basis of a specified route that the vehicle is to travel, - a target tire longitudinal force input section configured to receive an input of a target tire longitudinal force that should be generated at the wheel section, the target tire longitudinal force being detected based on the set route; - an actuator output section configured to output an instruction to achieve an optimal slip ratio according to a minimum value of a sum of a first difference and a second difference to an actuator with respect to braking / driving the vehicle, wherein the first difference is a difference between a tire lateral force and the target tire lateral force at each slip ratio in a correlative relationship between slip ratio and tire lateral force of a tire of the wheel section, wherein the second difference is a difference between a tire longitudinal force and the target tire longitudinal force at each slip ratio in a correlative relationship between slip ratio and tire longitudinal force; - a maximum tire lateral force input section configured to receive an input of a maximum tire lateral force that can be generated at the wheel section, wherein the maximum tire lateral force is detected based on the tire lateral force generated at the wheel section and the slip ratio, which are detected based on vehicle behavior information acquired by a vehicle behavior detection section configured to detect a behavior of the vehicle; and - a maximum tire longitudinal force input area configured to receive an input of a maximum tire longitudinal force that can be generated at the wheel area, wherein the maximum tire longitudinal force is detected based on the maximum tire lateral force, - wherein the actuator output section detects the correlative relationship between the slip ratio and the tire lateral force based on the maximum tire lateral force and detects the correlative relationship between the slip ratio and the tire longitudinal force based on the maximum tire longitudinal force.

Description

Area of ​​application

[0001] The present invention relates to a vehicle control apparatus, a vehicle control method and a vehicle control system. State of the art

[0002] PTL1 discusses a technique that determines a target slip ratio of each wheel based on a target tire lateral force and a target tire longitudinal force of each wheel, and controls an actuator to achieve the determined target slip ratio. Citation listPatent literature [PTL1] JP 2008 - 247 067 A JP 2003 - 159 966 A DE 100 03 681 A1 DE 699 34 161 T2 Summary of the inventionTechnical problem

[0003] However, the conventional configuration described above involves a problem that a balance between the target tire lateral force and the target tire longitudinal force cannot be optimized because there is a difference between a tire lateral force characteristic and a tire longitudinal force characteristic with respect to the slip ratio.

[0004] One of the objects of the present invention is to provide a vehicle control apparatus, a vehicle control method and a vehicle control system capable of optimizing the balance between the target tire lateral force and the target tire longitudinal force. Solution to the problem

[0005] This problem is solved by the features of the independent claims. The subclaims contain advantageous embodiments of the invention.

[0006] According to one aspect of the present invention, a vehicle control device outputs an instruction to achieve an optimal slip ratio according to a minimum value of a sum of a first difference and a second difference to an actuator related to braking / driving of a vehicle. The first difference is a difference between a tire lateral force and a target tire lateral force with respect to an arbitrary slip ratio in a correlative relationship between a slip ratio and the tire lateral force of a tire of a wheel portion. The second difference is a difference between a tire longitudinal force and a target tire longitudinal force with respect to the arbitrary slip ratio in a correlative relationship between the slip ratio and the tire longitudinal force.

[0007] Therefore, the present invention can optimize the balance between the target tire lateral force and the target tire longitudinal force. Brief description of the drawings Fig. 1 illustrates a configuration of a vehicle control system 1 relating to autonomous driving according to a first embodiment. Fig. 2 is a control block diagram of a vehicle slip control section 8d. Fig. 3 is a flowchart illustrating a processing flow for calculating an optimal slip ratio executed by a VMCU8. Fig. 4 is a flowchart illustrating a processing flow for calculating a tire lateral force maximum value. Fig. Figure 5 shows an example of a normalized slip ratio-tire lateral force characteristic map. Fig. 6 is a flowchart showing the processing flow for calculating the optimal slip ratio. Fig. Figure 7 shows an example of a normalized map of the slip ratio-tire longitudinal force characteristic. Fig. Figure 8 shows an example of a normalized slip ratio-tire lateral force characteristic map. Fig. Figure 9 shows an example of a second difference with respect to each slip ratio. Fig. Figure 10 shows an example of a first difference with respect to each slip ratio. Fig. 11 illustrates an example of a minimum value of a total value of the first difference and the second difference with respect to each slip ratio. Fig. 12 shows an example of a slip ratio tire lateral force characteristic and a slip ratio tire longitudinal force characteristic. Fig. Figure 13 shows an example of a tire longitudinal force and a tire lateral force realized by the optimal slip ratio. Description of Embodiments[First Embodiment]

[0008] Fig. 1 illustrates a configuration of a vehicle control system 1 relating to autonomous driving according to a first embodiment.

[0009] The vehicle control system 1 is mounted on the vehicle and uses an engine as its driving source. The vehicle control system 1 includes a locator 3, a camera unit 4, a radar 5, a vehicle behavior sensor unit 6 (a vehicle behavior detection section), an autonomous driving control unit 7 (hereinafter referred to as ADCU), and a vehicle motion control unit 8 (a vehicle motion control device, hereinafter referred to as VMCU).

[0010] The localizer 3 includes a GNSS (Global Navigation Satellite System) receiver and an inertial sensor, such as a gyroscope sensor. The localizer 3 measures a position of a test vehicle based on signals from a plurality of artificial satellites received by the GNSS receiver and a measurement result from the inertial sensor. The position of the test vehicle is defined as a center of gravity of the vehicle, a geometric center, or a center of a rear axle.

[0011] The camera unit 4 includes a stereo camera that images a predetermined area in front of the test vehicle using two CCDs. The camera unit 4 calculates a difference between images captured by the stereo camera to detect an object (an obstacle) based on a baseline length and calculates a distance to the object.

[0012] For example, radar 5 transmits a millimeter wave from a transmitting antenna in front of the test vehicle. Radar 5 receives the millimeter wave reflected from the object using a receiving antenna and calculates the distance to the object.

[0013] The vehicle behavior sensor unit 6 is a unit that integrally includes sensors each detecting a vehicle behavior such as a lateral acceleration, a longitudinal acceleration, a yaw rate, and a wheel speed.

[0014] The ADCU7 estimates a current position of the test vehicle from the correspondence of the position of the test vehicle measured by the locator 3 with a dynamic map. At this time, the ADCU7 serves to improve estimation accuracy by recognizing a situation surrounding the test vehicle based on the distance to the object calculated by the camera unit 4 and the radar 5 and by referring to the situation surrounding the test vehicle. Examples of the situation surrounding the test vehicle include a curvature (a radius of curvature) of a curve, a turning angle, and road information such as a curve.a starting position, a moving object (a pedestrian, a bicycle, a motorcycle, a vehicle traveling ahead of the test vehicle, a vehicle traveling in an adjacent lane, and the like), and a stationary object (a dropped object on a road, a traffic light, a guardrail, a curb, a traffic sign, a lane marking, a lane marking, a tree, and the like). The ADCU7 outputs a target input by a driver shift operation or the like, the estimated current position of the test vehicle, and the surrounding situation to the VMCU8.

[0015] The VMCU8 generates a target trajectory of the test vehicle and also outputs an instruction for implementing the target trajectory to respective control units (an engine control unit 13, a brake control unit 14, and an electric power steering control unit 15) of actuators (the engine 2, a brake unit 9, and an electric power steering device 10) mounted on the test vehicle. The engine control unit 13, the brake control unit 14, and the electric power steering control unit 15 control the corresponding actuators according to the instruction output from the VMCU8. The brake unit 9 can individually control a wheel cylinder hydraulic pressure at each of the wheels (a wheel section) represented by a side-slip prevention device and a braking torque to be provided to each of the wheels.The power steering device 10 can rotate front wheels, which are steered wheels, to an arbitrary angle using an output torque of an electric motor.

[0016] The VMCU8 includes a driving position control section 8a, a vehicle stability control section 8b, a tire force control section 8c, a wheel slip control section 8d, and an actuator output section 8e.

[0017] The driving position control section 8a generates the target trajectory of the test vehicle with respect to autonomous driving based on the target and the current position. The target trajectory is a target trajectory point (a target position) of the test vehicle after a forward gaze time (a forward gaze distance / a vehicle speed). Furthermore, the driving position control section 8a generates a target vehicle body speed at the generated target trajectory point. The driving position control section 8a calculates a target lateral force and a target longitudinal force of the vehicle to realize the target trajectory point and the target vehicle body speed.

[0018] The vehicle stability control section 8b corrects the calculated target lateral force and target longitudinal force of the vehicle based on the situation surrounding the test vehicle (the obstacle or the like). Furthermore, the vehicle stability control section 8b generates a target yaw rate at the target trajectory point and calculates a target yaw moment that should be provided to the vehicle to realize the target yaw angle. The yaw angle is an angle formed between a longitudinal axis direction of the test vehicle and a reference axis direction specified on a road surface (e.g., an x-axis direction in a coordinate system specified on the road surface).

[0019] The tire force control section 8c (a target tire lateral force calculation section and a target tire longitudinal force calculation section) calculates a target tire lateral force and a target tire longitudinal force of each of the wheels to realize the corrected target lateral force, target longitudinal force, and target yaw moment of the vehicle. Now, it is assumed that the target tire lateral force and the target tire longitudinal force are the values ​​that prioritize the target vehicle lateral force and the target vehicle yaw moment over the target vehicle longitudinal force. Specifically, the target tire lateral force and the target tire longitudinal force of each of the wheels are adjusted so that deviations between the target lateral force and the target yaw moment and the actual lateral force and the actual yaw moment fall below a deviation between the target longitudinal force and the actual longitudinal force. Consequently, spin avoidance and lane tracking can be realized simultaneously.The tire force control section 8c determines a duty share assigned to each of the actuators (the engine 2, the brake control unit 9, and the electric power steering device 10) for realizing the target tire lateral force and the target tire longitudinal force of each of the wheels, and generates a wheel turning instruction according to the duty share assigned to the electric power steering device 10.

[0020] The wheel slip control section 8d calculates an optimal slip ratio of each of the wheels to realize the specific task shares assigned to the motor 2 and the brake unit 9, and generates braking and driving force commands to achieve the optimal slip ratio at each of the wheels. A method for calculating the optimal slip ratio is described below.

[0021] The actuator output section 8e outputs the generated wheel turning command to the electric power steering control unit 15 and the generated braking and driving force commands to the engine control unit 13 and the brake control unit 14.

[0022] Fig. 2 is a control block diagram of the vehicle slip control section 8d.

[0023] A slip ratio calculation section 21 calculates the slip ratio of each of the wheels. The slip ratio is defined as a value calculated by dividing an absolute value of a difference between the wheel speed and the vehicle body speed detected by the vehicle ratio sensor unit 6 by the vehicle body speed. The vehicle body speed is estimated from the wheel speed of each of the wheels. A highest value among the individual wheel speeds is selected as the vehicle body speed at the time of braking, and a lowest value among the individual wheel speeds is selected as the vehicle body speed at the time of acceleration.

[0024] A tire lateral force calculation section 22 calculates the tire lateral force of each of the wheels using a two-wheel model of the vehicle based on the yaw rate, lateral acceleration, and longitudinal acceleration detected by the vehicle behavior sensor unit 6.

[0025] A tire lateral force maximum value calculation section 23 (a maximum tire lateral force calculation section) calculates a tire lateral force maximum value, which is a maximum tire lateral force that each of the wheels can generate, based on the slip ratio and tire lateral force of each of the wheels. Details of a calculation method are described below.

[0026] A tire lateral force maximum value storage area 24 stores the calculated tire lateral force maximum value of each of the wheels as a stored value of a tire lateral force maximum value. The stored value of the tire lateral force maximum value is updated each time the tire lateral force maximum value of each of the wheels is calculated.

[0027] A tire longitudinal force maximum value calculation section 25 (a tire longitudinal force maximum calculation section) calculates a tire longitudinal force maximum value, which is a maximum tire lateral force that each of the wheels can generate, based on the tire lateral force maximum value of each of the wheels. Details of a calculation method are described below.

[0028] An optimal slip ratio calculation section 26 includes a target tire lateral force input section 26a, a target tire longitudinal force input section 26b, a tire lateral force maximum value input section 26c (a maximum tire lateral force input section), a tire longitudinal force maximum value input section 26d (a maximum tire longitudinal force input section), a tire lateral force maximum value storage input section 26e (a stored maximum tire lateral force input section), a tire lateral force difference calculation section 26f, and a tire longitudinal force difference calculation section 26g.

[0029] The target tire lateral force input section 26a inputs the target tire lateral force of each of the wheels. The target tire longitudinal force input section 26b inputs the target tire longitudinal force of each of the wheels. The tire lateral force maximum value input section 26c inputs the tire lateral force maximum value of each of the wheels. The tire longitudinal force maximum value input section 26d inputs the tire longitudinal force maximum value of each of the wheels. The tire lateral force maximum value storage input section 26e inputs the storage value for the tire lateral force maximum value of each of the wheels.

[0030] The tire lateral force difference calculation section 26f calculates a first difference, which is an absolute value of a difference between the tire lateral force and the target tire lateral force at each slip ratio in a current tire lateral force characteristic with respect to each of the wheels.

[0031] The tire longitudinal force difference calculation section 26g calculates a second difference which is an absolute value of the difference between the tire longitudinal force and the target tire longitudinal force at each slip ratio of the current tire longitudinal force characteristic with respect to each of the wheels.

[0032] The optimal slip ratio calculation section 26 calculates a slip ratio at which a sum of the first difference and the second difference is minimized as an optimal slip ratio with respect to each of the wheels. In the following description, a processing flow for calculating the optimal slip ratio with respect to Fig. 3 described.

[0033] Fig. Figure 3 is a flowchart illustrating the processing flow for calculating the optimal slip ratio, which is executed by the VMCU8. A process in each of the steps is executed with respect to all wheels.

[0034] In step S1, the VMCU8 determines whether the slip ratio calculated by the slip ratio calculation section 21 falls within an expected normal range. If the determination in step S1 is yes, the flow proceeds to step S2. If the determination in step S1 is no, the flow proceeds to step S5.

[0035] In step S2, the VMCU8 calculates the maximum tire lateral force value. Fig. 4 is a flowchart showing a processing flow for calculating the tire lateral force maximum value.

[0036] In step S21, the VMCU8 determines whether the tire lateral force calculated by the tire lateral force calculation section 22 falls within an expected normal range. If the determination in step S21 is yes, the flow proceeds to step S22. If the determination in step S21 is no, the flow proceeds to step S24.

[0037] In step S22, the VMCU8 calculates a normalized tire lateral force by referring to a normalized slip ratio-tire lateral force characteristic map according to an actual tire slip angle based on the current slip ratio. Fig. Figure 5 shows an example of the normalized slip ratio-tire lateral force characteristic map. This map represents a relationship between the slip ratio S and the tire lateral force Fy, which is normalized such that the tire lateral force maximum value Fyimax coincides with 1 from the slip ratio-tire lateral force characteristic map. The normalized tire lateral force normalizedFyi can be determined from the current slip ratio Si by referring to this map.

[0038] In step S23, the VMCU8 calculates the tire lateral force maximum value Fyimax using the following equation based on the current tire lateral force Fyicurrent and the normalized tire lateral force normalizedFyi. Fyimax=Fyicurrent / normalizedFyi

[0039] In step S24, the VMCU8 sets the storage value of the tire lateral force maximum value as the tire lateral force maximum value Fyimax.

[0040] In step S3, the VMCU8 calculates the maximum tire longitudinal force value Fximax based on the maximum tire lateral force value Fyimax, assuming a perfect tire wear circle. In other words, the VMCU8 sets Fximax = Fyimax.

[0041] In step S4, the VMCU8 calculates the optimal slip ratio. Fig. 6 is a flowchart showing a processing flow for calculating the optimal slip ratio.

[0042] In step S41, the VMCU8 calculates the tire longitudinal force Fxi (Si) corresponding to each slip ratio Si by referring to the normalized slip ratio-tire longitudinal force characteristic map based on the tire longitudinal force maximum value Fximax as shown in Fig. 7 shown.

[0043] In step S42, the VMCU8 calculates the tire lateral force Fyi (Si) corresponding to each slip ratio Si using the normalized slip ratio-tire lateral force characteristic map based on the tire lateral force maximum value Fyimax as shown in Fig. 8 shown.

[0044] In step S43, the VMCU8 calculates the second difference FxiDifference(Si), which is the absolute value | Fxi(Si) - FxiTarget | of the difference between the target tire longitudinal force FxiTarget and the tire longitudinal force Fxi(Si) corresponding to each slip ratio Si. Fig. Figure 9 shows an example of the second difference with respect to each slip ratio.

[0045] Furthermore, the VMCU8 calculates the first difference FyiDifference(Si), which is the absolute value | Fyi(Si) - FyiTarget | of the difference between the target tire lateral force FyiTarget and the tire lateral force Fyi(Si) corresponding to each slip ratio Si. Fig. Figure 10 shows an example of the first difference in slip ratio.

[0046] In step S44, the VMCU8 applies weights to the first difference FyiDifference (Si) and the second difference FxiDifference (Si) and calculates a corresponding total value FiDifference (Si). FiDifference(Si)=ωx×FxiDifference(Si)+ωy×FyiDifference(Si).

[0047] Now, assume that a relationship ωx + ωy = 1 is established between the weight ωx applied to the tire longitudinal force and the weight ωy applied to the tire lateral force. The weights ωx and ωy serve to determine the characteristics of the vehicle's behavior and can be preset according to the intended vehicle type to be designed. Furthermore, or alternatively, the weights ωx and ωy can be changed in real time according to the driving condition or the like.

[0048] In step S45, the VMCU8 calculates the slip ratio Si at which the total value FiDifference(Si) matches the minimum value FiDifference(Si)min and sets this value as the optimal slip ratio Sioptimal, as shown in Fig. 11 shown.

[0049] In step S5, the VMCU8 sets the preset predetermined slip ratio as the optimal slip ratio Sioptimal.

[0050] Next, advantageous effects of the first embodiment will be described.

[0051] Fig. 12 shows an example of the slip ratio tire lateral force characteristic and the slip ratio tire longitudinal force characteristic at a certain slip angle. As in Fig. As shown in Figure 12, there is a difference between the tire lateral force characteristic and the tire longitudinal force characteristic with respect to the slip ratio, so that slip ratios that respectively satisfy the target tire lateral force and the target tire longitudinal force rarely match each other.

[0052] Therefore, the optimal slip ratio calculation section 26 according to the first embodiment sets the slip ratio as the optimal slip ratio Sioptimal at which the total value FiDifference (Si) of the first difference FyiDifference (Si), which is the absolute value of the difference between the target tire lateral force FyiDesired and the tire lateral force Fyi (Si), and the second difference FxiDifference (Si), which is the absolute value of the difference between the target tire longitudinal force FxiDesired and the tire longitudinal force Fxi (Si), is minimized. In other words, as in Fig.As shown in Figure 13, the point closest to the target point can be searched from a solution space, even if it is impossible to realize the target point that satisfies both the target tire lateral force and the target tire longitudinal force. The balance between the target tire lateral force and the target tire longitudinal force can be optimized by setting the slip ratio as the optimal slip ratio at this point.

[0053] Controlling the vehicle's lateral and longitudinal forces, especially on a low-μ road surface, is of utmost importance for ensuring robustness for vehicles equipped with the autonomous driving function. The tire lateral and longitudinal forces of each wheel can be accurately controlled independently of the driving surface μ (a road surface friction coefficient between the tire and the road surface) using the optimal slip ratio control according to the first embodiment. Consequently, the vehicle's lateral and longitudinal forces can be controlled with improved accuracy, and therefore, both spin avoidance and lane tracking can be realized simultaneously.

[0054] The conventional sideslip prevention device is configured to detect a disturbance in the vehicle behavior and control slip in a direction to reduce the wheel slip ratio. On the other hand, the optimal slip ratio control according to the first embodiment is configured to control slip to optimize the balance between the target tire lateral force and the target tire longitudinal force in a state where the vehicle ratio is not disturbed, that is, in a state where the sideslip prevention device is not operating. Therefore, the optimal slip ratio control according to the first embodiment can increase the wheel slip ratio depending on the optimal slip ratio even in a scene where the conventional sideslip prevention device would not increase the slip ratio.

[0055] The optimal slip ratio calculation section 26 weights the first difference FyiDifference(Si) and the second difference FxiDifference(Si) using ωy and ωx that satisfy ωx + ωy = 1, and sets the slip ratio at which the total value FiDifference(Si) after weighting is minimized as the optimal slip ratio Sioptimal. This enables the vehicle to take appropriate action according to the vehicle characteristics and the driving state. For example, setting ωx and ωy to values ​​preset based on vehicle specifications enables the vehicle to take appropriate action according to the vehicle characteristics. Further, variably controlling ωx and ωy according to the driving state of the vehicle enables the vehicle to take appropriate action according to the vehicle condition.

[0056] The tire lateral force maximum value calculation section 23 calculates the normalized tire lateral force normalizedFyi based on the current slip ratio Sicurrent using the normalized slip ratio-tire lateral force characteristic map, and calculates the tire lateral force maximum value Fyimax based on the normalized tire lateral force normalizedFyi and the current tire lateral force Fyicurrent. Acquiring the tire lateral force maximum value Fyimax enables the acquisition of the current slip ratio-tire lateral force characteristic from the normalized slip ratio-tire lateral force characteristic map. The tire longitudinal force maximum value calculation section 25 calculates the tire longitudinal force maximum value Fximax based on the tire longitudinal force maximum value Fyimax, hypothetically assuming that the tire wear circle is a perfect circle.Detecting the maximum tire longitudinal force value Fximax allows the current slip ratio-tire longitudinal force characteristic to be detected from the normalized slip ratio-tire longitudinal force characteristic map. Therefore, in the first embodiment, the correlative relationship between the current slip ratio and the tire force (the tire lateral force and the tire longitudinal force) can be detected without estimating a wheel load of each of the wheels and the road surface μ.

[0057] The tire lateral force maximum value calculation section 23 sets the tire lateral force maximum value stored in the tire lateral force maximum value storage section 24 as the tire lateral force maximum value Fyimax when the tire lateral force calculated by the tire lateral force calculation section 22 is outside the normal range. Due to this configuration, the optimal slip ratio Sioptimal can be calculated even if an abnormality has occurred in the vehicle behavior sensor unit 6, and therefore autonomous driving can continue.

[0058] The optimal slip ratio calculation section 26 sets the preset predetermined slip ratio as the optimal slip ratio Sioptimal when the slip ratio calculated by the slip ratio calculation section 21 is outside the normal range. Consequently, the target tire lateral force and the target tire longitudinal force can be prevented from becoming unbalanced due to the inappropriate optimal slip ratio Sioptimal.

[0059] The actuator output section 8e generates the braking and driving force commands to achieve the optimal slip ratio Sioptimal at each of the wheels. Consequently, the optimal slip ratio Sioptimal can be achieved at all wheels, thus enabling both spin avoidance and lane tracking to be realized simultaneously. [Other embodiments]

[0060] Having described the embodiment for carrying out the present invention, the specific configuration of the present invention is not limited to the configuration of the embodiment, and the present invention also includes design modifications and the like made within a range that does not deviate from the spirit of the present invention, if at all. Furthermore, the individual components described in the claims and the specification can be arbitrarily combined or omitted within a range that allows them to remain capable of achieving at least part of the above-described objects or producing at least part of the above-described advantageous effects.

[0061] The present invention is applicable as long as there is at least one wheel other than the wheel for which the optimal slip ratio control is used. For example, the VMCU8 can select a wheel with the largest wear circle among the four wheels and apply the optimal slip ratio control to that wheel. Alternatively, the optimal slip ratio control can be used only for the front or rear wheel.

[0062] The vehicle control system 1 may be configured such that at least one driving position control section 8a, one vehicle stability control section 8b and / or one tire force control section 8c or all of them are provided outside the VMCU8 (in the ADCU7 or another external control unit).

[0063] The vehicle control system 1 may be configured such that at least one of a slip ratio calculation section 21, a tire lateral force calculation section 22, a tire lateral force maximum value calculation section 23, a tire lateral force maximum value storage section 24, and / or a tire longitudinal force maximum value calculation section 25, or all of them, are provided outside the VMCU8 (in the ADCU7 or another external control unit).

[0064] The tire lateral force and slip ratio can be calculated by any method.

[0065] The following description describes other configurations that can be recognized from the embodiment described above.

[0066] In one configuration, a vehicle control device includes a target tire lateral force input section configured to receive an input of a target tire lateral force that should be generated at a wheel portion of a vehicle. The target tire lateral force is detected based on a set route on which the vehicle is to travel. The vehicle control device further includes a target tire longitudinal force input section configured to receive an input of a target tire longitudinal force that should be generated at a wheel portion. The target tire longitudinal force is detected based on the set route. The vehicle control device further includes an actuator output section configured to output an instruction for achieving an optimal slip ratio according to a minimum value of a sum of a first difference and a second difference to an actuator with respect to braking / driving the vehicle.The first difference is a difference between a tire lateral force and the target tire lateral force with respect to any slip ratio, in a correlative relationship between a slip ratio and the tire lateral force of a tire of the wheel area. The second difference is a difference between a tire longitudinal force and the target tire longitudinal force with respect to the arbitrary slip ratio, in a correlative relationship between the slip ratio and the tire longitudinal force.

[0067] According to another configuration, in the configuration described above, the vehicle control device further includes a maximum tire lateral force input section configured to receive an input of a maximum tire lateral force that can be generated at the wheel section. The maximum tire lateral force is detected based on the tire lateral force generated at the wheel section and the slip ratio detected based on vehicle behavior information acquired by a vehicle behavior detection section configured to detect a behavior of the vehicle. The vehicle control device further includes a maximum tire longitudinal force input section configured to receive an input of a maximum tire longitudinal force that can be generated at the wheel section. The maximum tire longitudinal force is detected based on the maximum tire lateral force.The actuator output section detects the correlative relationship between the slip ratio and the tire lateral force based on the maximum tire lateral force and detects the correlative relationship between the slip ratio and the tire longitudinal force based on the maximum tire longitudinal force.

[0068] According to another configuration, in each of the configurations described above, the optimal slip ratio is obtained by adding a first weighted difference, which is the first difference with a first weight applied thereto, and a second weighted difference, which is the second difference with a second weight applied thereto.

[0069] According to yet another configuration, in each of the configurations described above, assuming that ωx represents the first weight and ωy represents the second weight, the following equation ωx + ωy = 1 is satisfied.

[0070] According to yet another configuration, in each of the configurations described above, the first weight and the second weight are preset based on vehicle specifications.

[0071] According to yet another configuration, in each of the configurations described above, the first weight and the second weight are changed according to a driving state of the vehicle.

[0072] According to yet another configuration, in each of the configurations described above, the vehicle control device further includes a maximum tire lateral force input area configured to receive an input of a stored maximum tire lateral force stored in a maximum tire lateral force storage area configured to store the maximum tire lateral force. When an abnormality has occurred in the vehicle behavior detection area, the stored maximum tire lateral force is input to the stored maximum tire lateral force input area, and a stored maximum tire longitudinal force detected based on the stored maximum tire lateral force is input to the maximum tire longitudinal force input area instead of the maximum tire lateral force.

[0073] According to still another configuration, in each of the configurations described above, when an abnormality has occurred in the vehicle behavior detection section, the actuator output section outputs an instruction to achieve a predetermined slip ratio detected on the basis of the target tire longitudinal force inputted to the target tire longitudinal force input section to the actuator instead of the instruction to achieve the optimal slip ratio.

[0074] According to yet another configuration, in each of the configurations described above, the actuator output section outputs an instruction to the actuator to achieve the optimal slip ratio for all wheels of the wheel section.

[0075] According to yet another configuration, in each of the configurations described above, the actuator output section outputs an instruction to the actuator to achieve the optimal slip ratio on at least one wheel of the wheel section.

[0076] According to another aspect, a vehicle control method, in a related configuration, includes receiving inputs of a target tire lateral force and a target tire longitudinal force that should be generated at a wheel portion of a vehicle. The target tire lateral force and the target tire longitudinal force are acquired based on a set route on which the vehicle is to travel. The vehicle control method further includes outputting an instruction to achieve an optimal slip ratio according to a minimum value of a sum of a first difference and a second difference to an actuator related to braking / driving the vehicle. The first difference is a difference between a tire lateral force and the target tire lateral force with respect to any slip ratio in a correlative relationship between a slip ratio and the tire lateral force of a tire of the wheel portion.The second difference is a difference between a tire longitudinal force and the target tire longitudinal force with respect to the arbitrary slip ratio in a correlative relationship between the slip ratio and the tire longitudinal force.

[0077] In another configuration, in the configuration described above, the vehicle control method further comprises receiving an input of a maximum tire lateral force that can be generated at the wheel portion. The maximum tire lateral force is detected based on the tire lateral force generated at the wheel portion and the slip ratio detected based on the detected vehicle behavior information. The vehicle control method further comprises receiving an input of a maximum tire longitudinal force that can be generated at the wheel portion. The maximum tire longitudinal force is detected based on the maximum tire lateral force. The vehicle control method further comprises detecting the correlative relationship between the slip ratio and the tire lateral force based on the maximum tire lateral force and detecting the correlative relationship between the slip ratio and the tire longitudinal force based on the maximum tire longitudinal force.

[0078] According to another configuration, in each of the configurations described above, the optimal slip ratio is obtained by adding a first weighted difference, which is the first difference with a first weight applied thereto, and a second weighted difference, which is the second difference with a second weight applied thereto.

[0079] According to yet another configuration, in each of the configurations described above, assuming that ωx represents the first weight and ωy represents the second weight, the following equation ωx + ωy = 1 is satisfied.

[0080] In another aspect, a vehicle control system in an associated configuration includes a vehicle behavior detection section configured to detect a behavior of a vehicle, a tire lateral force calculation section configured to detect a tire lateral force generated at a wheel portion of the vehicle based on the vehicle behavior information detected by the vehicle behavior detection section, a slip ratio calculation section configured to detect a slip ratio of the wheel portion based on the vehicle behavior information, a target tire lateral force calculation section configured to detect a target tire lateral force that should be generated at the wheel portion based on a set route on which the vehicle is to travel, a target tire longitudinal force calculation section configured to detect a target tire longitudinal force,which should be generated at the wheel portion based on the specified route, a tire lateral force difference calculation portion configured to detect a first difference, which is a difference between the tire lateral force and the target tire lateral force with respect to any slip ratio in a correlative relationship between the slip ratio and the tire lateral force of a tire of the wheel portion, a wheel longitudinal force difference calculation portion configured to detect a second difference, which is a difference between the tire longitudinal force and the target tire longitudinal force with respect to the arbitrary slip ratio in a correlative relationship between the slip ratio and the tire longitudinal force, an optimal slip ratio calculation portion configured to detect an optimal slip ratio according to a minimum value of a sum of the first difference and the second difference,and an actuator output section configured to output an instruction to achieve the optimal slip ratio to the actuator with respect to braking / driving the vehicle.

[0081] According to another configuration, in the configuration described above, the vehicle control system further includes a maximum tire lateral force calculation section configured to detect a maximum tire lateral force that can be generated at the wheel section based on the tire lateral force detected by the tire lateral force calculation section and the slip ratio detected by the slip ratio calculation section, and a maximum tire longitudinal force calculation section configured to detect a maximum tire longitudinal force that can be generated at the wheel section based on the maximum tire lateral force.The tire lateral force difference calculation section detects the correlative relationship between the slip ratio and the tire lateral force based on the maximum tire lateral force, and the tire longitudinal force difference calculation section detects the correlative relationship between the slip ratio and the tire longitudinal force based on the maximum tire longitudinal force.

[0082] According to another configuration, in each of the configurations described above, the optimal slip ratio is obtained by adding a first weighted difference, which is the first difference with a first weight applied thereto, and a second weighted difference, which is the second difference with a second weight applied thereto.

[0083] According to yet another configuration, in each of the configurations described above, assuming that ωx represents the first weight and ωy represents the second weight, the following equation ωx + ωy = 1 is satisfied.

[0084] This application claims priority under the Paris Convention to Japanese Patent Application No. 2017-180314, filed on September 20, 2017. The entire disclosure of Japanese Patent Application No. 2017-180314, filed on September 20, 2017, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety. List of reference symbols 1 vehicle control system 2 Motor (actuator) 6 Vehicle behavior sensor unit (vehicle behavior detection area) 7 autonomous drive control unit 8 Vehicle movement control unit 8c Tire force control range (target tire lateral force calculation range and target tire longitudinal force calculation range) 8d Wheel slip control range 8e Actuator output range 9 Brake unit (actuator) 21 Slip ratio calculation range 22 Tire lateral force calculation range 26 optimal slip ratio calculation range 26a Target tire lateral force input range 26b Target tire longitudinal force input range 26f Tire lateral force difference calculation range 26g tire longitudinal force difference calculation range

Claims

[1] Vehicle control device comprising: - a target tire lateral force input section configured to receive an input of a target tire lateral force that should be generated at a wheel section of a vehicle, the target tire lateral force being detected on the basis of a specified route that the vehicle is to travel, - a target tire longitudinal force input section configured to receive an input of a target tire longitudinal force that should be generated at the wheel section, the target tire longitudinal force being detected based on the set route; - an actuator output section configured to output an instruction to achieve an optimal slip ratio according to a minimum value of a sum of a first difference and a second difference to an actuator with respect to braking / driving the vehicle, wherein the first difference is a difference between a tire lateral force and the target tire lateral force at each slip ratio in a correlative relationship between slip ratio and tire lateral force of a tire of the wheel section, wherein the second difference is a difference between a tire longitudinal force and the target tire longitudinal force at each slip ratio in a correlative relationship between slip ratio and tire longitudinal force; - a maximum tire lateral force input section configured to receive an input of a maximum tire lateral force that can be generated at the wheel section, wherein the maximum tire lateral force is detected based on the tire lateral force generated at the wheel section and the slip ratio, which are detected based on vehicle behavior information acquired by a vehicle behavior detection section configured to detect a behavior of the vehicle; and - a maximum tire longitudinal force input area configured to receive an input of a maximum tire longitudinal force that can be generated at the wheel area, wherein the maximum tire longitudinal force is detected based on the maximum tire lateral force, - wherein the actuator output section detects the correlative relationship between the slip ratio and the tire lateral force based on the maximum tire lateral force and detects the correlative relationship between the slip ratio and the tire longitudinal force based on the maximum tire longitudinal force. [2] Vehicle control device according to claim 1, - wherein the optimal slip ratio is detected by adding a first weighted difference, which is the first difference with a first weight applied thereto, and a second weighted difference, which is the second difference with a second weight applied thereto. [3] Vehicle control device according to claim 2, - where, assuming that ωx represents the first weight and ωy represents the second weight, the following equation ωx + ωy = 1 is satisfied. [4] Vehicle control device according to claim 3, - where the first weighting and the second weighting are preset based on vehicle specifications. [5] Vehicle control device according to claim 3, - wherein the first weight and the second weight are changed according to a driving condition of the vehicle. [6] A vehicle control device according to claim 1, further comprising a stored maximum tire lateral force input area configured to receive an input of a stored maximum tire lateral force stored in a maximum tire lateral force storage area configured to store the maximum tire lateral force, - wherein, when an abnormality has occurred in the vehicle behavior detection area, the stored maximum tire lateral force is input into the stored maximum tire lateral force input area, and a stored maximum tire longitudinal force detected on the basis of the stored maximum tire lateral force is input into the maximum tire longitudinal force input area instead of the maximum tire lateral force. [7] Vehicle control device according to claim 1, - wherein, when an abnormality has occurred in the vehicle behavior detection section, the actuator output section outputs an instruction to achieve a predetermined slip ratio detected on the basis of the target tire longitudinal force input to the target tire longitudinal force input section to the actuator instead of the instruction to achieve the optimal slip ratio. [8] Vehicle control device according to claim 1, - wherein the actuator output section outputs an instruction to the actuator to achieve the optimal slip ratio at all wheels of the wheel section. [9] Vehicle control device according to claim 1, - wherein the actuator output section outputs an instruction to the actuator to achieve the optimal slip ratio on at least one wheel of the wheel section. [10] Vehicle control method comprising the following steps: - receiving inputs of a target lateral tire force and a target longitudinal tire force that should be generated at a wheel portion of a vehicle, wherein the target lateral tire force and the target longitudinal tire force are detected based on a specified route that the vehicle is to travel; - issuing an instruction to achieve an optimal slip ratio according to a minimum value of a sum of a first difference and a second difference to an actuator relating to braking / driving of the vehicle, wherein the first difference is a difference between a tire lateral force and the target tire lateral force at each slip ratio in a correlative relationship between slip ratio and tire lateral force of a tire of the wheel region, wherein the second difference is a difference between a tire longitudinal force and the target tire longitudinal force at each slip ratio in a correlative relationship between slip ratio and tire longitudinal force;Receiving a maximum tire lateral force input that can be generated at the wheel region, wherein the maximum tire lateral force is detected based on the tire lateral force generated at the wheel region and the slip ratio detected based on detected vehicle behavior information; - Receiving a maximum longitudinal tire force input that can be generated at the wheel area, wherein the maximum longitudinal tire force is detected based on the maximum lateral tire force; - Determining the correlative relationship between the slip ratio and the tire lateral force based on the maximum tire lateral force; and - Determine the correlation between the slip ratio and the tire longitudinal force based on the maximum tire longitudinal force. [11] A vehicle control method according to claim 10, wherein the optimal slip ratio is detected by adding a first weighted difference, which is the first difference with a first weight applied thereto, and a second weighted difference, which is the second difference with a second weight applied thereto. [12] A vehicle control method according to claim 11, wherein, assuming that ωx represents the first weight and ωy represents the second weight, the following equation ωx + ωy = 1 is satisfied. [13] Vehicle control system comprising: - a vehicle behavior detection area configured to detect a behavior of a vehicle; - a tire lateral force calculation section configured to detect a tire lateral force generated at a wheel portion of the vehicle based on vehicle behavior information detected by the vehicle behavior detection section; - a slip ratio calculation section configured to detect a slip ratio of the wheel section based on vehicle behavior information; - a target tire lateral force calculation section configured to detect a target tire lateral force that should be generated at the wheel section based on a specified route that the vehicle is to travel; - a target tire longitudinal force calculation section configured to detect a target tire lateral force that should be generated at the wheel area based on the specified route, - a tire lateral force difference calculation section configured to detect a first difference, the first difference being a difference between the tire lateral force and the target tire lateral force at each slip ratio in a correlative relationship between slip ratio and tire lateral force of a tire of the wheel section; - a tire longitudinal force difference calculation section configured to detect a second difference, the second difference being a difference between the tire longitudinal force and the target tire longitudinal force at each slip ratio in a correlative relationship between slip ratio and tire longitudinal force; - an optimal slip ratio calculating section configured to detect an optimal slip ratio according to a minimum value of a sum of the first difference and the second difference; - an actuator output section configured to output an instruction to achieve the optimal slip ratio to an actuator related to braking / driving the vehicle; a maximum tire lateral force calculation section configured to detect a maximum tire lateral force that can be generated at the wheel section based on the tire lateral force detected by the tire lateral force calculation section and the slip ratio detected by the slip ratio calculation section; and - a maximum tire longitudinal force calculation section configured to detect a maximum tire longitudinal force that can be generated at the wheel area based on the maximum tire lateral force, - wherein the tire lateral force difference calculation section detects the correlative relationship between the slip ratio and the tire lateral force based on the maximum tire lateral force, and the tire longitudinal force difference calculation section detects the correlative relationship between the slip ratio and the tire longitudinal force based on the maximum tire longitudinal force. [14] A vehicle control system according to claim 13, wherein the optimum slip ratio is detected by adding a first weighted difference, which is the first difference with a first weight applied thereto, and a second weighted difference, which is the second difference with a second weight applied thereto. [15] A vehicle control system according to claim 14, wherein, assuming that ωx represents the first weight and ωy represents the second weight, the following equation ωx + ωy = 1 is satisfied.

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