Vehicle control device, vehicle control method, and vehicle control system

Abstract

According to the vehicle control apparatus, the vehicle control method, and the vehicle control system, in one embodiment, a target vehicle motion amount indicating a target yaw rate or a target lateral acceleration is acquired based on an operation angle of a steering wheel, and when a steering angle of a steering wheel cannot be detected, the steering angle of the steering wheel is detected based on the target vehicle motion amount. A control command for causing the vehicle to generate a yaw moment through wheels other than the steering wheel is output, and a braking driving force command for applying a braking driving force to the steering wheel is output based on a steering angle estimated by a difference between an actual vehicle motion amount generated in the vehicle according to the control command and a target vehicle motion amount. Thus, even if the information of the steering angle is lost, the steering control based on the braking driving force can be implemented with high precision.

Description

Technical Field

[0001] The present invention relates to a vehicle control device, a vehicle control method and a vehicle control system. Background Art

[0002] Patent Document 1 discloses a failure detection / management system for a steering angle sensor of a steer-by-wire system.

[0003] The failure detection / management system of Patent Document 1 determines an estimated steering angle based on the yaw rate or lateral acceleration and compares the estimated steering angle with the steering angle detected by the steering angle sensor, thereby detecting a failure of the steering angle sensor.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-256095 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] However, when the steer-by-wire system fails (malfunctions) and the steering wheel cannot be turned, by controlling the difference between the braking force applied to the wheel on the inside of the turn and the braking force applied to the wheel on the outside of the turn, the vehicle can generate a yaw moment, causing the vehicle to turn in the direction of the steering wheel operation.

[0009] However, when performing turning control based on such braking / driving force, if information on the steering angle of the steered wheel is lost, the braking / driving force cannot be controlled to be appropriate according to the steering angle, resulting in a problem of reduced accuracy of turning control.

[0010] The present invention has been completed in view of previous actual situations, and its purpose is to provide a vehicle control device, vehicle control method and vehicle control system that can implement turning control based on braking and driving forces with high accuracy even if the information of the steering angle of the steering wheel is lost.

[0011] Means for solving problems

[0012] According to the vehicle control device, vehicle control method and vehicle control system involved in the present invention, in one of their modes, based on the operating angle of the steering wheel, a target vehicle motion amount indicating a target yaw rate or target lateral acceleration to be generated by the vehicle is obtained, and when the detectability information as information related to whether the steering angle of the steering wheel can be detected is information indicating that it cannot be detected, a control instruction for causing the vehicle to generate a yaw moment through the wheels of the vehicle other than the steering wheel is output based on the target vehicle motion amount, an actual vehicle motion amount corresponding to the target vehicle motion amount generated in the vehicle according to the control instruction is obtained, an estimated steering angle as an estimated value of the steering angle of the steering wheel is obtained based on the difference between the target vehicle motion amount and the actual vehicle motion amount, and a first braking-driving force instruction for applying a braking-driving force to the steering wheel is output based on the estimated steering angle.

[0013] Effects of the Invention

[0014] According to the present invention, even if information on the steering angle of the steered wheel is lost, turning control based on the braking / driving force can be performed with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a diagram showing the overall structure of the vehicle control system.

[0016] Figure 2 This is a block diagram schematically showing each control system of the vehicle control system.

[0017] Figure 3 This is a flowchart showing the process of turning control in which the steering angle is estimated based on the yaw rate difference.

[0018] Figure 4 This is a flowchart showing the process of turning control in which the steering angle is estimated based on the yaw rate difference.

[0019] Figure 5 This is a state diagram illustrating the control state of the braking and driving forces when estimating the steering angle.

[0020] Figure 6 This is a state diagram illustrating a control state of the braking / driving force using an estimated steering angle.

[0021] Figure 7 This is a flowchart showing the process of turning control in which the steering angle is estimated based on the lateral acceleration difference.

[0022] Figure 8 This is a flowchart showing the process of turning control in which the steering angle is estimated based on the lateral acceleration difference. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of a vehicle control device, a vehicle control method, and a vehicle control system according to the present invention will be described with reference to the accompanying drawings.

[0024] Figure 1 1 is a diagram showing the overall configuration of a vehicle control system 100 provided in the vehicle 10 .

[0025] Figure 2 This is a block diagram schematically showing each control system of braking, driving, and steering in the vehicle control system 100 .

[0026] The vehicle 10 includes a pair of left and right front wheels 11 and 12 and a pair of left and right rear wheels 13 and 14 .

[0027] The vehicle 10 also includes a motor 71 for applying driving force to the front wheels 11 and 12 and a motor 72 for applying driving force to the rear wheels 13 and 14 as driving force actuators 70 for applying driving force to the vehicle 10 .

[0028] The driving force control unit 31 obtains information on the operation amount of the accelerator pedal 73 from the accelerator pedal sensor 74, and outputs a control signal corresponding to the target driving force based on the operation amount of the accelerator pedal 73 to the motors 71 and 72, thereby imparting a driving force corresponding to the operation amount of the accelerator pedal 73 to the front wheels 11 and 12 and the rear wheels 13 and 14.

[0029] Furthermore, the vehicle 10 includes a steer-by-wire system 40 as a steering device in which the steering wheel 51 is mechanically separated from the front wheels 11 and 12 serving as steerable wheels.

[0030] The steer-by-wire system 40 includes a reaction force actuator 41 that applies an operational reaction force torque to the steering wheel 51, a wheel actuator 42 that applies a steering force to the front wheels 11 and 12, a steering angle sensor 43 that detects the steering angle δ of the front wheels 11 and 12 (in other words, the tire angle of the front wheels 11 and 12), and a steering control unit 32 that controls the reaction force actuator 41 and the wheel actuator 42.

[0031] Furthermore, the steering wheel 51 includes an operation angle sensor 52 that detects an operation angle θ, which is a rotation angle of the steering wheel 51 .

[0032] The steering angle sensor 43 detects the steering angle δ of the front wheels 11 and 12 by detecting the rotation angle of the steering motor constituting the wheel actuator 42 and the rack position of a rack and pinion mechanism that converts the rotational force of the steering motor into linear motion.

[0033] The steering control unit 32 obtains information on the operating angle θ of the steering wheel 51 detected by the operating angle sensor 52 and obtains a target steering angle and a target reaction torque based on the operating angle θ as a steering angle command.

[0034] Then, the steering control unit 32 controls the wheel actuator 42 so that the steering angle δ detected by the steering angle sensor 43 approaches the target steering angle, and controls the reaction force actuator 41 so that the target reaction force torque is applied to the steering wheel 51 .

[0035] Furthermore, the vehicle 10 includes a braking device.

[0036] The braking device includes a braking control unit 33, a brake pedal sensor 62 for detecting the amount of operation of the brake pedal 61, brake actuators 15, 16, 17, 18 provided on each wheel 11, 12, 13, 14, and brake thrust sensors 21, 22, 23, 24 for respectively detecting the thrust generated by the brake actuators 15, 16, 17, 18.

[0037] The brake control unit 33 controls the braking force applied to the wheels 11 , 12 , 13 , 14 by the brake actuators 15 , 16 , 17 , 18 based on the output of the brake pedal sensor 62 and the outputs of the brake thrust sensors 21 , 22 , 23 , 24 .

[0038] Furthermore, the brake actuators 15 , 16 , 17 , 18 and the driving force actuator 70 constitute a brake drive actuator of the vehicle control system 100 .

[0039] The driving force control unit 31 , the steering control unit 32 , and the brake control unit 33 include microcomputers 31A, 32A, and 33A, respectively.

[0040] Furthermore, each of the microcomputers 31A, 32A, and 33A includes an MPU (Microprocessor Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown). The MPU executes a program stored in the ROM as a storage unit, thereby realizing various functions.

[0041] Furthermore, the driving force control unit 31 , the steering control unit 32 , and the braking control unit 33 constitute a vehicle control device 30 that controls the vehicle 10 .

[0042] Furthermore, the microcomputers 31A, 32A, and 33A function as a control unit 30A of the vehicle control device 30 .

[0043] Furthermore, the vehicle 10 includes a yaw rate sensor 81 that detects the yaw rate γ of the vehicle 10 and a lateral acceleration sensor 82 that detects the lateral acceleration Gy of the vehicle 10 as sensors that detect the behavior of the vehicle 10 .

[0044] Furthermore, the vehicle 10 includes wheel speed sensors 83 that detect wheel speeds V1 to V4 of the wheels 11 to 14 , respectively.

[0045] The control unit 30A obtains output signals from the yaw rate sensor 81 , the lateral acceleration sensor 82 , and the wheel speed sensor 83 .

[0046] In the vehicle control system 100 , the control unit 30A, specifically the microcomputer 32A of the steering control unit 32 diagnoses whether or not there is an abnormality in the steering function of the steer-by-wire system 40 .

[0047] In addition, the abnormality of the steering function is a state in which the front wheels 11 and 12, which serve as steering wheels (steering wheels), cannot steer and cannot control the steering angle δ to the target steering angle corresponding to the operating angle θ of the steering wheel 51. It is caused by a failure of the wheel actuator 42, an abnormality in the drive circuit of the wheel actuator 42, a failure of various sensors, etc.

[0048] Then, if the control unit 30A obtains information indicating an abnormality in the steering function of the wire-controlled steer system 40, it outputs a braking-driving force instruction to generate a braking-driving force difference between the left and right wheels, thereby causing the vehicle 10 to generate a yaw moment corresponding to the operating angle θ of the steering wheel 51, causing the vehicle 10 to turn in the operating direction of the steering wheel 51.

[0049] The control for generating a braking-driving force difference between the front wheels 11, 12 is a control in which, when the driving force is set as a positive physical quantity and the braking force is set as a negative physical quantity, one of the total value of the driving force and the braking force applied to the front wheel on the outer side of the turning of the front wheels 11, 12 and the total value of the driving force and the braking force applied to the front wheel on the inner side of the turning of the front wheels 11, 12 is made larger than the other.

[0050] Here, between the front wheels 11 and 12, whether the braking / driving force on the outer side of the turn is smaller than the braking / driving force on the inner side of the turn, or vice versa, is determined based on the alignment characteristics of the front wheels 11 and 12, specifically, based on the setting of the scrub radius.

[0051] When the kingpin offset of the front wheels 11 , 12 is negative, the vehicle control device 30 outputs a braking / driving force command in the braking / driving force control of the front wheels 11 , 12 so that the braking / driving force on the outer side of the turn is smaller than the braking / driving force on the inner side of the turn.

[0052] When the kingpin offset of the front wheels 11, 12 is negative, for example, when braking force is applied to the right front wheel 12 for a right turn, the front wheels 11, 12 face to the left, which is opposite to the target turning direction. Similarly, when braking force is applied to the left front wheel 11 for a left turn, the front wheels 11, 12 face to the right, which is opposite to the target turning direction.

[0053] That is, when the kingpin offset of the front wheels 11 and 12 is negative, if the braking-driving force on the inner side of the turn is made smaller than the braking-driving force on the outer side of the turn, the steering angle δ of the front wheels 11 and 12 changes in the direction of offsetting the yaw moment generated by the difference in braking-driving force between the front wheels 11 and 12.

[0054] Furthermore, if the influence of the yaw moment caused by the change in the steering angle δ is large, the vehicle may turn in the opposite direction to the turning direction expected based on the difference in braking and driving forces applied to the front wheels 11 and 12 .

[0055] Therefore, when the kingpin offset of the front wheels 11 and 12 is negative, the control unit 30A outputs the braking / driving force command so that the braking / driving force on the outer side of the turn is smaller than the braking / driving force on the inner side of the turn.

[0056] Thus, the front wheels 11 and 12 can be steered in a direction corresponding to the operating angle θ of the steering wheel 51 , and the vehicle 10 can be turned in a direction corresponding to the operating angle θ of the steering wheel 51 using the tire lateral force generated by the steering of the front wheels 11 and 12 in the turning direction.

[0057] On the other hand, when the kingpin offset of the front wheels 11 and 12 is positive, the direction of the change in the steering angle due to the left-right braking-driving force difference is opposite to that in the negative case.

[0058] Therefore, when the kingpin offset of the front wheels 11 and 12 is positive, the control unit 30A outputs a braking-driving force instruction in such a manner that the braking-driving force on the inner side of the turn among the front wheels 11 and 12 is smaller than the braking-driving force on the outer side of the turn, so that the vehicle 10 generates a yaw moment by utilizing the steering caused by the positioning characteristics and the difference in braking-driving forces on the left and right.

[0059] Furthermore, the influence of the kingpin offset as a positioning characteristic is relatively small on the rear wheels 13 and 14 that are not steering wheels.

[0060] Therefore, when the control unit 30A controls the braking and driving forces of the rear wheels 13 and 14 to cause the vehicle 10 to generate a yaw moment, when the driving force is set to a positive physical quantity and the braking force is set to a negative physical quantity, the braking and driving force instructions for the rear wheels 13 and 14 are output in such a manner that the total value of the driving force and the braking force applied to the rear wheel on the inner side of the turn is smaller than the total value of the driving force and the braking force applied to the rear wheel on the outer side of the turn.

[0061] Furthermore, the configuration may be such that abnormality information of the steering function in the steer-by-wire system 40 detected by the microcomputer 32A of the steering control unit 32 is transmitted to the driving force control unit 31 and the braking control unit 33 via the upper vehicle integrated control unit of the vehicle control device 30 .

[0062] In addition, the following structure can also be set: the upper unit such as the vehicle integrated control control unit diagnoses whether there is any abnormality in the steering function of the wire-controlled steering system 40. When an abnormality occurs in the steering function, the abnormality information is output from the upper unit to the driving force control unit 31 and the braking control unit 33 as the lower units.

[0063] However, when the control unit 30A implements turning control that generates a difference in braking-driving force between the left and right wheels, if the detection information that is information representing the detection value of the steering angle δ is lost, in other words, if the steering angle δ cannot be detected, it is impossible to control the appropriate braking-driving force that takes into account the lateral force generated by the steering angle δ, and the accuracy of the turning control is reduced.

[0064] Therefore, when the detection information of the steering angle δ is lost, the control unit 30A estimates the steering angle δ based on the motion equation of the vehicle 10 and uses the information of the estimated steering angle δ for turning control.

[0065] As a process for estimating the steering angle δ, the control unit 30A outputs a control command to generate a target yaw rate according to the operation angle θ of the steering wheel 51 in braking / driving force control of the rear wheels 13 and 14 , which are wheels other than the steered wheels.

[0066] Then, the control unit 30A estimates the steering angle δ based on the difference between the actual yaw rate generated during the braking / driving force control on the rear wheels 13 , 14 and the target yaw rate.

[0067] Here, the control unit 30A does not generate a braking-driving force difference in the front wheels 11 and 12 serving as steering wheels in the estimation process of the steering angle δ, but generates a braking-driving force difference in the rear wheels 13 and 14. This is because if a braking-driving force difference is generated in the front wheels 11 and 12, the steering angle δ will change according to the positioning characteristics as described above, and the estimation accuracy of the steering angle δ will be reduced.

[0068] Therefore, when the control unit 30A is unable to detect the steering angle δ, it causes the vehicle 10 to generate a yaw moment by controlling the braking and driving force of the wheels other than the steered wheels, i.e., the rear wheels 13 and 14. After estimating the steering angle δ based on the generation condition of the yaw moment at this time, it uses the information of the estimated steering angle δ to implement braking and driving force control of the front wheels 11 and 12 that are steered wheels.

[0069] Hereinafter, turning control (in other words, a vehicle control method) when an abnormality occurs in the steering function of the steer-by-wire system 40 will be described in more detail.

[0070] Figure 3 and Figure 4 3 is a flowchart showing the procedure of turning control executed by the control unit 30A.

[0071] In step S201 , the control unit 30A determines whether the drive system (drive force actuator 70 ) and the brake system (brake actuators 15 , 16 , 17 , 18 ) are both normal and in a state where the braking and driving forces can be controlled.

[0072] Furthermore, the driving force control unit 31 diagnoses whether there is an abnormality in the driving system, and the brake control unit 33 diagnoses whether there is an abnormality in the braking system.

[0073] If both the braking system and the driving force system are normal, the control unit 30A proceeds to step S202. If at least one of the braking system and the driving force system is abnormal, turning control based on the braking or driving force cannot be performed, and thus this routine ends.

[0074] In step S202 , the control unit 30A determines whether information indicating an abnormality in the steering function in the steer-by-wire system 40 has been acquired. Specifically, the control unit 30A determines whether an abnormality in the steering function has been diagnosed by the steering control unit 32 .

[0075] Then, if the steering function of the steer-by-wire system 40 is abnormal, the control unit 30A proceeds to step S203.

[0076] On the other hand, if the steering function of the steer-by-wire system 40 is normal and the front wheels 11 and 12 are steered according to the operation angle θ of the steering wheel 51, the control unit 30A does not need turning control based on braking or driving force, and thus ends this routine.

[0077] In step S203 , the control unit 30A determines whether information indicating that detection is impossible or information indicating that detection is possible is obtained as information on whether the steering angle δ can be detected.

[0078] In other words, the control unit 30A determines in step S203 whether the steering angle δ is unknown or whether the steering angle δ can be detected normally.

[0079] If the steering angle δ is detectable, the control unit 30A proceeds to step S204 and performs turning control based on the braking / driving force using the steering angle δ detected by the steering angle sensor 43 .

[0080] On the other hand, if the steering angle δ cannot be detected, that is, if the information of the steering angle δ is lost, the control unit 30A enters step S209 and implements turning control based on the braking / driving force, including processing to obtain an estimated steering angle δe as an estimated value of the steering angle δ.

[0081] First, the turning control after step S204 when the steering angle δ can be detected will be described below.

[0082] In step S204, the control unit 30A calculates the target yaw rate γ based on the operating angle θ of the steering wheel 51 detected by the operating angle sensor 52 and the vehicle speed V (in other words, the vehicle body speed) obtained from the signal of the wheel speed sensor 83. as the target vehicle motion amount.

[0083] Next, in step S205, the control unit 30A calculates the target longitudinal acceleration α based on the operation amount of the brake pedal 61 detected by the brake pedal sensor 62 and the operation amount of the accelerator pedal 73 detected by the accelerator pedal sensor 74. .

[0084] Then, in step S206, the control unit 30A determines the target yaw rate γ based on the target yaw rate γ. , target front and rear acceleration α In addition, the information of the steering angle δ detected by the steering angle sensor 43 is used to calculate the target yaw rate γ and the target front and rear acceleration α The target braking and driving forces Ffl, Ffr, Frl, and Frr of each wheel 11-14 are as follows.

[0085] Hereinafter, unless otherwise specified, the target braking / driving force of each wheel will be collectively represented as “Fxx”.

[0086] Next, in step S207 , the control unit 30A calculates the target braking force Tbxx of each wheel 11 - 14 generated by the brake actuators 15 , 16 , 17 , 18 and the driving torque Tmxx of each wheel 11 - 14 generated by the motors 71 , 72 based on the target braking / driving force Fxx of each wheel 11 - 14 .

[0087] Then, in step S208 , the control unit 30A outputs a braking force command as a control command to the brake actuators 15 , 16 , 17 , and 18 based on the target braking force Tbxx, and outputs a driving force command as a control command to the driving force actuator 70 based on the target driving torque Tmxx.

[0088] That is, when the steering function of the steer-by-wire system 40 is abnormal, if the steering angle δ can be detected, the estimation process of the steering angle δ is unnecessary, and the braking / driving force control using the detected value of the steering angle δ can be performed.

[0089] Therefore, the control unit 30A does not perform processing for estimating the steering angle δ by applying braking or driving force only to the rear wheels 13 and 14 described later, but estimates the steering angle δ based on the target yaw rate γ. The braking / driving force command for applying braking / driving force to the front wheels 11 and 12 is output.

[0090] In addition, based on the target yaw rate γ The braking / driving force command φ φ corresponds to a second braking / driving force command for applying braking / driving force to the front wheels 11 and 12 based on the target vehicle motion amount.

[0091] As described above, when the steering function of the steer-by-wire system 40 is abnormal, if the control unit 30A can detect the steering angle δ, the braking and driving forces applied to the front wheels 11, 12 and the rear wheels 13, 14 are controlled in consideration of the information of the steering angle δ, so that the vehicle 10 generates the yaw moment required by the driver of the vehicle 10.

[0092] In other words, when the steering function of the steer-by-wire system 40 is abnormal and the steering angle δ can be detected, the control unit 30A controls the vehicle based on the target yaw rate γ. The braking / driving force command for applying braking / driving force to the front wheels 11 and 12 and the rear wheels 13 and 14 is output.

[0093] Next, the turning control after step S209 which is performed when the steering function of the steer-by-wire system 40 is abnormal and the steering angle δ cannot be detected will be described below.

[0094] First, in step S209, the control unit 30A calculates a target yaw rate γ as a target vehicle motion amount based on the operating angle θ of the steering wheel 51 and the vehicle speed V. .

[0095] In addition, the control unit 30A can adjust the target yaw rate γ according to the vehicle state. Make corrections.

[0096] Next, in step S210, the control unit 30A calculates the target longitudinal acceleration α based on the operation amount of the brake pedal 61 and the operation amount of the accelerator pedal 73. .

[0097] Then, in step S211, the control unit 30A determines the target yaw rate γ based on the target yaw rate γ. and the target front and rear acceleration α Target braking / driving forces Frl and Frr of the rear wheels 13 and 14 other than the steering wheels are obtained.

[0098] That is, the control unit 30A controls the braking and driving forces of the rear wheels 13 and 14 so that the vehicle 10 generates the target yaw rate γ The target braking and driving forces Frl and Frr of the rear wheels 13 and 14 are determined in this manner.

[0099] Next, in step S212, the control unit 30A calculates the target braking forces Tbrl and Tbrr of the rear wheels 13 and 14 generated by the brake actuators 17 and 18 and the driving torques Tmrl and Tmrr of the rear wheels 13 and 14 generated by the motor 72 based on the target braking and driving forces Frl and Frr of the rear wheels 13 and 14.

[0100] Then, in step S213, the control unit 30A controls the brake actuators 17 and 18 of the rear wheels 13 and 14 based on the target braking forces Tbr1 and Tbrr, and controls the electric motor 72 that drives the rear wheels 13 and 14 based on the target driving torques Tmrl and Tmrr.

[0101] Next, in step S214 , the control unit 30A detects the vehicle speed V based on the signal from the wheel speed sensor 83 .

[0102] Then, in step S215 , the control unit 30A determines whether the vehicle speed V is equal to or greater than a threshold value VT, which is a predetermined value.

[0103] Here, the threshold value VT of the vehicle speed V in step S215 is a value used by the control unit 30A to switch between detecting the yaw rate γ actually generated in the vehicle 10 using the yaw rate sensor 81 and estimating the yaw rate γ actually generated in the vehicle 10 based on the driving conditions of the vehicle 10 .

[0104] Since the detection accuracy of the yaw rate γ by the yaw rate sensor 81 decreases as the vehicle speed V decreases, the lower limit value of the vehicle speed V at which the yaw rate sensor 81 can detect the yaw rate γ with necessary and sufficient accuracy is set as the threshold value.

[0105] That is, when the vehicle speed V is greater than the threshold value VT, the yaw rate sensor 81 ensures the detection accuracy of the yaw rate γ. When the vehicle speed V is less than the threshold value VT, the yaw rate sensor 81 cannot detect the yaw rate γ with necessary and sufficient accuracy.

[0106] Therefore, when the control unit 30A determines in step S215 that the vehicle speed V is equal to or greater than the threshold value VT, the process proceeds to step S216 to detect the actual yaw rate γa as the actual vehicle motion amount based on the output signal of the yaw rate sensor 81 .

[0107] On the other hand, when the control unit 30A determines that the vehicle speed V is less than the threshold value VT, the process proceeds to step S217 and estimates the actual yaw rate γa as the actual vehicle motion amount according to equation 1 based on the wheel speed detected by the wheel speed sensor 83 and the wheel tread of the vehicle 10.

[0108] [Mathematical formula 1]

[0109]

[0110] In Mathematical Formula 1, V1 is the wheel speed of the inner turning wheel, V2 is the wheel speed of the outer turning wheel, and d is the vehicle wheelbase.

[0111] When the vehicle 10 does not include the yaw rate sensor 81 or the yaw rate sensor 81 included in the vehicle 10 fails and cannot detect the yaw rate γ, the control unit 30A can perform the process of step S217 to estimate the actual yaw rate γa based on the wheel speed and the like.

[0112] After the control unit 30A obtains the actual yaw rate γa in step S216 or step S217, the process proceeds to step S218 to obtain the target yaw rate γ The difference Δγ (Δγ=γ -γa).

[0113] Next, in step S219, the control unit 30A determines the target yaw rate γ based on the target yaw rate γ. The difference Δγ from the actual yaw rate γa, in other words, the estimated steering angle δe as the estimated value of the steering angle δ at the current moment is obtained based on the difference between the target vehicle motion amount and the actual vehicle motion amount.

[0114] Specifically, in step S219 , the control unit 30A calculates the estimated steering angle δe based on the difference Δγ according to the motion equation of the vehicle 10 shown in Formula 2.

[0115] [Mathematical formula 2]

[0116]

[0117] In Mathematical Formula 2, Kf is a proportionality constant representing the cornering force of the front wheels 11 , 12 , Kr is a proportionality constant representing the cornering force of the rear wheels 13 , 14 , V is the vehicle body speed, m is the inertial mass of the vehicle 10 , β is the slip angle of the vehicle body, β (with dot) is the time derivative of the slip angle β, Lf is the distance from the vehicle's center of gravity to the front wheels 11 , 12 , and Lr is the distance from the vehicle's center of gravity to the rear wheels 13 , 14 .

[0118] Furthermore, the control unit 30A can determine the slip angle β of the vehicle body from, for example, the lateral acceleration Gy and the vehicle body speed V of the vehicle 10 .

[0119] In the next step S220, the control unit 30A determines the target yaw rate γ based on the target yaw rate γ. , target front and rear acceleration α , and the estimated steering angle δe to calculate the target yaw rate γ and the target front and rear acceleration α The target braking and driving forces Ffl, Ffr, Frl, and Frr of each wheel 11-14 are as follows.

[0120] Next, in step S221 , the control unit 30A calculates target braking forces Tbxx of the wheels 11 - 14 generated by the brake actuators 15 , 16 , 17 , 18 and driving torques Tmxx of the wheels 11 - 14 generated by the motors 71 , 72 based on the target braking / driving forces Fxx of the wheels 11 - 14 .

[0121] Then, in step S222, the control unit 30A outputs a braking force instruction to the brake actuators 15, 16, 17, and 18 of the front wheels 11, 12 and the rear wheels 13, 14 based on the target braking force Tbxx, and outputs a driving force instruction to the electric motors 71 and 72 of the driving force actuators 70 of the front wheels 11, 12 and the rear wheels 13, 14 based on the target driving torque Tmxx.

[0122] Specifically, after obtaining the estimated steering angle δe by controlling the braking and driving forces of the rear wheels 13 and 14 , the control unit 30A outputs a braking and driving force command, ie, a first braking and driving force command, for applying braking and driving forces to the front wheels 11 and 12 based on the estimated steering angle δe.

[0123] As described above, the braking / driving force command output by the control unit 30A in step S222 for applying braking / driving force to the front wheels 11 and 12 is determined based on whether the kingpin offset setting of the front wheels 11 and 12 is negative or positive.

[0124] That is, when the kingpin offset of the front wheels 11 and 12 is negative, the control unit 30A outputs the braking / driving force command so that the braking / driving force on the outer side of the turn is smaller than the braking / driving force on the inner side of the turn.

[0125] Thus, the front wheels 11 and 12 can be steered in a direction corresponding to the operating angle θ of the steering wheel 51 , and the vehicle 10 can be turned in a direction corresponding to the operating angle θ of the steering wheel 51 using the tire lateral force generated by the steering of the front wheels 11 and 12 in the turning direction.

[0126] On the other hand, when the kingpin offset in the front wheels 11, 12 is positive, the control unit 30A outputs a braking-driving force instruction in such a manner that the braking-driving force on the inner side of the turn in the front wheels 11, 12 is smaller than the braking-driving force on the outer side of the turn, so that the vehicle 10 generates a yaw moment by utilizing the steering caused by the positioning characteristics and the left and right braking-driving force difference.

[0127] Figure 5 、 Figure 6 This diagram schematically illustrates the braking / driving force control (in other words, the vehicle control method) executed by the control unit 30A when the steering function in the steer-by-wire system 40 is abnormal and the steering angle δ cannot be detected.

[0128] and, Figure 5 The target yaw rate γ is generated by controlling the braking and driving forces of the rear wheels 13 and 14. The state diagram when Figure 6 The target yaw rate γ is generated by controlling the braking and driving forces of the front wheels 11 and 12 and the rear wheels 13 and 14 based on the estimated steering angle δe. State diagram when .

[0129] also, Figure 5 、 Figure 6 As an example, a case where the driver of the vehicle 10 operates the steering wheel 51 in a right turning direction is taken.

[0130] That is, the driver requests the generation of a yaw moment in the direction of turning the vehicle 10 right by operating the steering wheel 51 , but the steer-by-wire system 40 fails and the direction of the front wheels 11 , 12 , which are steerable wheels, cannot be changed to the right.

[0131] At this time, the control unit 30A does not first perform braking / driving force control for generating a yaw moment on the front wheels 11 and 12, which are steered wheels, but instead outputs braking / driving force commands to the rear wheels 13 and 14, which are wheels other than the steered wheels, thereby generating a target yaw rate γ, which is the yaw moment requested by the driver. (Reference Figure 5 ).

[0132] like Figure 5As shown, the braking / driving force command for the rear wheels 13 and 14 is, for example, a command to apply braking force to the right rear wheel 14 .

[0133] That is, when the driving force is set to a positive physical quantity and the braking force is set to a negative physical quantity, the control unit 30A outputs a braking-driving force instruction so that the total value of the driving force and the braking force applied to the right rear wheel 14, which is the wheel on the inner side of the turn of the vehicle 10, is smaller than the total value of the driving force and the braking force applied to the left rear wheel 13, which is the wheel on the outer side of the turn of the vehicle 10, where the rear wheels 13, 14 are wheels other than the front wheels 11, 12 that serve as steering wheels.

[0134] Then, the control unit 30A adjusts the yaw rate γ actually generated by controlling the braking and driving forces of the rear wheels 13 and 14 and the target yaw rate γ. The difference Δγ is used to calculate the estimated steering angle δe at the current moment.

[0135] Furthermore, if the front wheels 11 and 12 are included in the braking / driving force control targets for calculating the estimated steering angle δe, the steering angle δ of the front wheels 11 and 12 changes with the braking / driving force control, thereby reducing the calculation accuracy of the estimated steering angle δe.

[0136] Therefore, the control unit 30A improves the calculation accuracy of the estimated steering angle δe by excluding the front wheels 11 and 12, which are steered wheels, from the objects of the braking and driving force control used to calculate the estimated steering angle δe, and performing braking and driving force control on the rear wheels 13 and 14, which are wheels other than the steered wheels.

[0137] If the steering angle δ is estimated, the estimated steering angle δe can be used in the braking / driving force control for generating the yaw moment requested by the driver. By using the estimated steering angle δe, the control accuracy of the yaw moment is improved.

[0138] Therefore, the control unit 30A takes the estimated steering angle δe into consideration and determines the value for achieving the target yaw rate γ and the target front and rear acceleration α The target braking-driving forces Fxx of the front wheels 11, 12 and the rear wheels 13, 14 are calculated.

[0139] Then, the control unit 30A controls the braking and driving forces of the front wheels 11 and 12 and the rear wheels 13 and 14 based on the target braking and driving force Fxx, thereby generating the yaw moment requested by the driver, that is, the target yaw rate γ (Reference Figure 6 ).

[0140] That is, when the control unit 30A is unable to detect the steering angle δ, as a first stage, the control unit 30A controls the braking driving force on the rear wheels 13 and 14 to generate a yaw moment for the vehicle 10, and then, as a second stage, outputs a braking driving force instruction for applying a braking driving force to the front wheels 11 and 12 serving as steering wheels, thereby generating a yaw moment for the vehicle 10, wherein the rear wheels 13 and 14 are wheels other than the front wheels 11 and 12 serving as steering wheels.

[0141] Furthermore, the first stage provides the actual yaw rate γa and the target yaw rate γ that can be generated according to the actual The difference Δγ is used to estimate the steering angle δ with higher accuracy. In the second stage, when the braking-driving force is applied to the front wheels 11 and 12 serving as steering wheels, the estimated result of the steering angle δ is reflected in the control of the braking-driving force, thereby generating a yaw moment corresponding to the driver's operation of the steering wheel 51 with high accuracy.

[0142] Therefore, when the steering function of the steer-by-wire system 40 malfunctions, the control unit 30A can perform turning control based on the braking and driving forces with high accuracy even if information on the steering angle δ of the front wheels 11 and 12 serving as steerable wheels is lost.

[0143] However, instead of calculating the estimated steering angle δe based on the yaw rate difference Δγ, the control unit 30A may calculate the estimated steering angle δe based on the actual lateral acceleration Gya and the target lateral acceleration Gy The estimated steering angle δe is calculated by using the difference ΔGy, where the actual lateral acceleration Gya is used as the target lateral acceleration Gy. This is actually generated as a result of controlling the braking and driving forces of the rear wheels 13 and 14.

[0144] Furthermore, the yaw rate γ has a delay and less noise than the lateral acceleration Gy.

[0145] Therefore, the process of calculating the estimated steering angle δe from the yaw rate difference Δγ enables higher-precision turning control compared to the process of calculating the estimated steering angle δe from the lateral acceleration difference ΔGy.

[0146] Figure 7 as well as Figure 8 The flowchart shows a turning control procedure in the case where the estimated steering angle δe is calculated based on the difference ΔGy of the lateral acceleration Gy.

[0147] The following mainly describes Figure 7 as well as Figure 8 The steps S301 to S322 of the flowchart of Figure 3 as well as Figure 4Steps S201 to S222 of the flowchart have different processing contents, and detailed descriptions of the steps with the same processing contents are omitted.

[0148] If the steering function of the steer-by-wire system 40 is abnormal but the steering angle δ can be detected, the control unit 30A calculates the target lateral acceleration Gy generated by the vehicle 10 based on the operating angle θ of the steering wheel 51 and the vehicle speed V in step S304. .

[0149] Then, in step S306, the control unit 30A determines the target lateral acceleration Gy , target front and rear acceleration α In addition, the information of the steering angle δ detected by the steering angle sensor 43 is used to calculate the target lateral acceleration Gy and the target front and rear acceleration α The target braking and driving forces Ffl, Ffr, Frl, and Frr of each wheel 11-14 are as follows.

[0150] On the other hand, if the steering function of the steer-by-wire system 40 is abnormal and the steering angle δ cannot be detected, the control unit 30A calculates the target lateral acceleration Gy generated by the vehicle 10 based on the operating angle θ of the steering wheel 51 and the vehicle speed V in step S309. .

[0151] Then, in step S311, the control unit 30A calculates the target lateral acceleration Gy based on the target lateral acceleration Gy. and the target front and rear acceleration α The target braking / driving forces Frl and Frr of the rear wheels 13 and 14 , which are wheels other than the steered wheels, are calculated.

[0152] Next, in steps S312 and S313 , the control unit 30A controls the braking force and the driving force of the rear wheels 13 and 14 based on the target braking / driving forces Frl and Frr.

[0153] In steps S315 to S317 , the control unit 30A obtains the actual lateral acceleration Gya when the braking / driving forces of the rear wheels 13 and 14 are controlled based on the target braking / driving forces Frl and Frr.

[0154] Furthermore, when the vehicle speed V is less than a threshold value or when the lateral acceleration sensor 82 cannot detect the lateral acceleration, the control unit 30A can estimate the actual lateral acceleration Gya by substituting the actual yaw rate γa obtained according to Formula 1 and V=(V1+V2) / 2 into Gya=V·γa.

[0155] Then, the control unit 30A obtains the actual lateral acceleration Gya and the target lateral acceleration Gy in step S318. The difference ΔGy (ΔGy=Gy -Gya).

[0156] Next, in step S319 , the control unit 30A calculates the estimated steering angle δe based on the difference ΔGy according to the motion equation of the vehicle 10 shown in Formula 3.

[0157] [Mathematical formula 3]

[0158]

[0159] Formula 3 is based on γ=Gy / V and is obtained by substituting ΔGy / V into Δγ in Formula 1.

[0160] After the control unit 30A obtains the estimated steering angle δe in step S319, it calculates the estimated steering angle δe in step S320 based on the target lateral acceleration Gy , target front and rear acceleration α In addition, and by estimating the steering angle δe, the target lateral acceleration Gy is calculated. and the target front and rear acceleration α The target braking / driving forces Ffl, Ffr, Frl, and Frr of each wheel.

[0161] Then, in step S321, the control unit 30A calculates the target braking force Tbxx and driving torque Tmxx for each wheel 11-14 respectively, and in the following step S322, controls the brake actuators 15, 16, 17, and 18 based on the target braking force Tbxx, and controls the electric motors 71 and 72 serving as the driving force actuator 70 based on the target driving torque Tmxx.

[0162] When the control unit 30A determines the estimated steering angle δe from the lateral acceleration difference ΔGy, the control unit 30A also performs braking / driving force control on wheels other than the steered wheel during the braking / driving force control for determining the estimated steering angle δe. Therefore, the estimated steering angle δe can be determined with high accuracy.

[0163] Furthermore, the control unit 30A performs braking / driving force control of each wheel 11-14 in consideration of the estimated steering angle δe. Therefore, even if information on the steering angle δ of the steered wheel is lost, turning control based on the braking / driving force can be performed with high accuracy.

[0164] The technical concepts described in the above embodiments can be used in appropriate combination as long as no contradiction occurs.

[0165] Furthermore, while the present invention has been described in detail with reference to preferred embodiments, it is apparent that a person skilled in the art can employ various modifications based on the basic technical concept and teachings of the present invention.

[0166] The steer-by-wire system in the above embodiment is a steering system for steering the front wheels of the vehicle. However, the vehicle may be a work vehicle such as a forklift or construction machinery equipped with a steer-by-wire system for steering the rear wheels.

[0167] In the case of a vehicle equipped with a steer-by-wire system for steering the rear wheels, the control unit of the vehicle control device can control the braking and driving force of the front wheels, which are wheels other than the steered wheels, so as to generate a target yaw rate or a target lateral acceleration, and estimate the steering angle δ of the rear wheels, which are the steered wheels, based on the difference between the actual yaw rate or actual lateral acceleration generated at this time and the target, and implement the braking and driving force control of the rear wheels by reflecting the estimated result of the steering angle δ of the rear wheels.

[0168] In addition, in a vehicle control system including a driving force control unit 31, a steering control unit 32 and a braking control unit 33, in which the control unit of each actuator is provided with a higher-level control unit such as a vehicle integrated control unit, when an abnormality occurs in the steering function of the wire-controlled steering system, the higher-level control unit can output a control instruction of the braking driving force to the control unit of each actuator.

[0169] In this case, the host control unit corresponds to a vehicle control device including a control unit.

[0170] Description of Reference Signs

[0171] 10…Vehicle; 11, 12…Front wheels (steering wheels); 13, 14…Rear wheels; 15, 16, 17, 18…Brake actuator; 30…Vehicle control device; 30A…Control unit; 40…Steering-by-wire system; 51…Steering wheel; 70…Drive force actuator; 81…Yaw rate sensor; 100…Vehicle control system.

Claims

1. A vehicle control device, which is provided on a vehicle, The vehicle has a steer-by-wire system that steers a steering wheel of the vehicle that is mechanically decoupled from a steering wheel. The vehicle control device includes a control unit: acquiring detection capability information as information regarding whether the steering angle of the steering wheel can be detected; obtaining a target vehicle motion amount indicating a target yaw rate or a target lateral acceleration to be generated in the vehicle based on the steering wheel operation angle; outputting a control command for causing the vehicle to generate a yaw moment at a wheel of the vehicle other than the steered wheel based on the target vehicle motion amount when the detection capability information indicates that the detection capability information is not detectable; Obtaining an actual vehicle motion amount corresponding to the target vehicle motion amount generated on the vehicle according to the control instruction; obtaining an estimated steering angle as an estimated value of the steering angle of the steered wheel based on a difference between the target vehicle motion amount and the actual vehicle motion amount; as well as Based on the estimated steering angle, a first braking / driving force command for applying a braking / driving force to the steerable wheel is output.

2. The vehicle control device according to claim 1, wherein: The target vehicle motion amount is a target yaw rate, and the actual vehicle motion amount is an actual yaw rate.

3. The vehicle control device according to claim 1, wherein: The target vehicle motion amount is a target lateral acceleration, and the actual vehicle motion amount is an actual lateral acceleration.

4. The vehicle control device according to claim 1, wherein: The control unit: When information indicating an abnormality in the steering function of the steer-by-wire system is acquired and the detectability information indicates detectability, a second braking / driving force command for applying braking / driving force to the steered wheel is output based on the target vehicle motion amount.

5. The vehicle control device according to claim 1, wherein: The steering wheel is any one of the front and rear wheels of the vehicle.

6. The vehicle control device according to claim 5, wherein: The steering wheel is the front wheel.

7. The vehicle control device according to claim 5, wherein: The control instruction is a braking-driving force instruction that makes the total value of the driving force and the braking force applied to the wheels on the inner side of the turn of the vehicle among the wheels other than the steering wheel smaller than the total value of the driving force and the braking force applied to the wheels on the outer side of the turn of the vehicle when the driving force is set to a positive physical quantity and the braking force is set to a negative physical quantity.

8. The vehicle control device according to claim 5, wherein: The first braking-driving force instruction is a braking-driving force instruction that causes one of the total value of the driving force and the braking force applied to the steerable wheel on the outer side of the vehicle when the driving force is a positive physical quantity and the braking force is a negative physical quantity to be greater than the other value of the total value of the driving force and the braking force applied to the steerable wheel on the inner side of the vehicle when the steerable wheel is a positive physical quantity and the braking force is a negative physical quantity. The braking / driving force command is obtained based on the setting of the kingpin offset of the steered wheel.

9. The vehicle control device according to claim 5, wherein: In the vehicle, the kingpin offset of the steering wheel is set to negative, The first braking-driving force instruction is a braking-driving force instruction that makes the total value of the driving force and the braking force applied to the steering wheel on the outer side of the vehicle turning less than the total value of the driving force and the braking force applied to the steering wheel on the inner side of the vehicle turning when the driving force is set to a positive physical quantity and the braking force is set to a negative physical quantity.

10. The vehicle control device according to claim 5, wherein: The first braking-driving force instruction is a braking-driving force instruction that makes the total value of the driving force and the braking force applied to the steering wheel on the inner side of the vehicle turning less than the total value of the driving force and the braking force applied to the steering wheel on the outer side of the vehicle turning when the driving force is set to a positive physical quantity and the braking force is set to a negative physical quantity.

11. The vehicle control device according to claim 1, wherein: The control unit: The actual vehicle motion amount is estimated based on the wheel speed of the vehicle in any of the following cases: when the vehicle speed is less than a prescribed value, when the yaw rate of the vehicle cannot be detected, and when the lateral acceleration of the vehicle cannot be detected.

12. A vehicle control method, executed by a control unit provided on a vehicle, The vehicle has a steer-by-wire system that steers a steering wheel of the vehicle that is mechanically decoupled from a steering wheel. The control unit: acquiring detection capability information as information regarding whether the steering angle of the steering wheel can be detected; obtaining a target vehicle motion amount indicating a target yaw rate or a target lateral acceleration to be generated in the vehicle based on the steering wheel operation angle; outputting a control command for causing the vehicle to generate a yaw moment at a wheel of the vehicle other than the steered wheel based on the target vehicle motion amount when the detection capability information indicates that the detection capability information is not detectable; Obtaining an actual vehicle motion amount corresponding to the target vehicle motion amount generated on the vehicle according to the control instruction; obtaining an estimated steering angle as an estimated value of the steering angle of the steered wheel based on a difference between the target vehicle motion amount and the actual vehicle motion amount; as well as Based on the estimated steering angle, a first braking / driving force command for applying a braking / driving force to the steerable wheel is output.

13. A vehicle control system comprising: A steer-by-wire system that steers a vehicle's steering wheel that is mechanically decoupled from the steering wheel; a control unit that, when the steering angle of the steerable wheel cannot be detected, generates a yaw moment for the vehicle by wheels of the vehicle other than the steerable wheel and then outputs a braking / driving force command for applying a braking / driving force to the steerable wheel; and The braking drive actuator applies a braking drive force to the steerable wheel based on the braking drive force command.

Images