Vehicle control system

Abstract

The present invention provides a vehicle control device that can improve vehicle stability in a control system that generates braking force by changing the steering angle of a malfunctioning wheel. [Solution] The vehicle control device 1 of the present invention comprises a first control unit 3, a wheel failure management unit 5, and a second control unit 4. When the wheel failure management unit 5 determines that one or more wheels have failed, the second control unit 4 performs special control by changing the steering angle of the failed wheel using the corresponding actuators 21 to 25 so that braking force is generated on the failed wheel. When the special control is performed, the first control unit 3 acquires information on the steering angle of the failed wheel that has been changed by the special control, and controls the driving force, steering angle, and braking force of each wheel other than the failed wheel using the corresponding actuators 21 to 25 based on the driver input or vehicle motion control request and the acquired information on the steering angle of the failed wheel.

Description

[Technical Field]

[0001] This invention relates to a vehicle control device. [Background technology]

[0002] The vehicle control device is configured to control the corresponding tire forces (e.g., longitudinal force and lateral force) of each wheel based on target values ​​of the six components of the vehicle's center of gravity force (longitudinal force, lateral force, vertical force, roll moment, pitch moment, and yaw moment). The tire forces are applied by various actuators. For example, Japanese Patent Application Publication No. 2022-165535 discloses a method to prevent the search for a solution from being slowed down when there are constraints on the tire forces in calculating the optimal tire force to achieve the target. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-165535 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In a vehicle in which at least one pair of left and right wheels are configured to be independently driveable and independently steerable, if a failure in braking force occurs in one wheel, the steering angle of the wheel with the failure can be changed (for example, by changing it to the toe-in side) to generate braking force in the wheel with the failure. This braking force (hereinafter also referred to as "camber braking force") is generated because the direction of travel of the vehicle and the direction of rotation of the tires are different.

[0005] If only one wheel loses braking force, the steering angle of the wheel with the faulty brake changes, resulting in a diagonal braking force on that wheel. In this case, the wheel with the faulty brake may continue to dig into the soil or sand on the road surface, potentially generating a large diagonal braking force. Such bulldozing-induced braking disturbances are difficult to predict. An unexpected braking force applied to one wheel affects vehicle stability.

[0006] The object of the present invention is to provide a vehicle control device that can improve vehicle stability in a control system that generates braking force by changing the steering angle of a lost wheel. [Means for solving the problem]

[0007] The present invention provides a vehicle control device that controls a vehicle using a plurality of actuators based on driver input or a vehicle motion control request, and comprises a plurality of wheels, each configured to be independently steerable and independently drivable, including one or more pairs of left and right wheels, a first control unit that controls the corresponding actuator based on driver input or a vehicle motion control request, a failure management unit that determines whether or not there is a failure in the braking force of each wheel, and a second control unit. When the failure management unit determines that one or more of the wheels have failed, the second control unit executes a special control to change the steering angle of the failed wheel using the corresponding actuator so that braking force is generated on the failed wheel. When the special control is executed, the first control unit acquires information on the steering angle of the failed wheel that has changed due to the special control, and controls the driving force, steering angle, and braking force of each of the wheels other than the failed wheel using the corresponding actuator based on the driver input or the vehicle motion control request and the acquired information on the steering angle of the failed wheel. [Effects of the Invention]

[0008] According to the present invention, the other wheels are controlled based on the steering angle of the malfunctioning wheel after special control. In other words, the state of the steering angle of the malfunctioning wheel is taken into consideration and reflected in the calculation of the control of the other wheels. This enables control that is more appropriate to the actual situation and improves vehicle stability. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing the configuration of the vehicle control device of this embodiment. [Figure 2] This is a block diagram showing the calculation and control flow of this embodiment. [Figure 3] This is a conceptual diagram illustrating the special control of this embodiment. [Modes for carrying out the invention]

[0010] Hereinafter, a vehicle control device 1, which is one embodiment of the present invention, will be described in detail with reference to the drawings. In addition to the embodiments described below, the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. This embodiment will be described with reference to the prior art (Japanese Patent Application Publication No. 2022-165535).

[0011] As shown in Figure 1, the vehicle control device 1 comprises a plurality of wheels, an actuator group 2, and a controller 30. The plurality of wheels consist of one or more pairs of left and right wheels. In this embodiment, the plurality of wheels consist of four wheels: one pair of left and right front wheels and one pair of left and right rear wheels. Each of the plurality of wheels is configured to be independently steerable and independently drivable.

[0012] The controller 30 is composed of a computer (which can also be called an electronic control unit) having one or more processors and one or more memories. The controller 30, when its functions are represented by functional blocks, comprises a first control unit 3, a second control unit 4, and a failure management unit 5. The first control unit 3 controls the vehicle using the actuator group 2 (multiple actuators) based on driver input or vehicle motion control requests. The second control unit 4 and the failure management unit 5 will be described later.

[0013] The controller 30 is connected to the accelerator sensor 91, brake sensor 92, steering sensor 93, and actuator group 2. The controller 30 may be composed of multiple computers. For example, the first control unit 3 and the second control unit 4 may each be composed of separate computers capable of communicating with each other. That is, the first control unit may be composed of a first controller, and the second control unit 4 may be composed of a second controller separate from the first controller.

[0014] The accelerator sensor 91 is a sensor that detects the amount of operation of the accelerator (e.g., accelerator pedal) by the driver. The brake sensor 92 is a sensor that detects the amount of operation of the brake (e.g., brake pedal) by the driver. The steering sensor 93 is a sensor that detects the amount of operation of the steering member (e.g., steering wheel) by the driver. The controller 30 acquires each of these detected values.

[0015] Actuator group 2 consists of multiple actuators for performing vehicle control. Actuator group 2 includes a drive actuator 21, a brake actuator 22, a steering actuator 23, an active stabilizer 24, and an active suspension 25.

[0016] The drive actuator 21 controls the driving force of the vehicle based on the command of the first control unit 3. The drive actuator 21 of the present embodiment is an in-wheel motor provided for each wheel. Each drive actuator 21 can be independently controlled and can generate a driving force independently for each wheel. Further, each drive actuator 21 can also generate a braking force independently by means of a regenerative braking force.

[0017] The brake actuator 22 is a device that applies a braking force to the tire based on the command of the first control unit 3. The brake actuator 22 is incorporated in, for example, a hydraulic brake system. The brake actuator 22 can, for example, independently control the braking force of each wheel, or can independently control the braking force of the front wheels and the braking force of the rear wheels. Since the vehicle of the present embodiment is configured to exert a braking force using a regenerative braking force instead of a hydraulic braking force, the drive actuator 21 and the brake actuator 22 are configured to include an electric motor which is a single common member.

[0018] The steering actuator 23 is a device that steers the steered wheels based on the command of the controller 30. All the wheels (four wheels) are steered wheels. The steering actuator 23 controls the steering angle of the steered wheels. The steering actuator 23 may be a part of an electric power steering or may be a part of a steer-by-wire.

[0019] The active stabilizer 24 controls the torsion angle of the stabilizer bar based on the command of the first control unit 3. The active stabilizer 24 is provided, for example, at the front and the rear of the vehicle respectively. The active stabilizer 24 may not be a control target of the first control unit 3 (may not be included in the actuator group 2), and may be a mere stabilizer.

[0020] The active suspension 25 controls the suspension characteristics based on commands from the first control unit 3. The active suspension 25 controls the suspension reaction force by adjusting extension and compression through hydraulic or pneumatic control. The active suspension 25 may also control the damping force characteristics. The active suspension 25 does not have to be a control target of the first control unit 3 (it does not have to be included in the actuator group 2), and may be a simple suspension.

[0021] The controller 30 acquires vehicle status information, which is information relating to the vehicle's state, from the status detection device 8. The vehicle status information is information acquired from the status detection device 8. The status detection device 8 includes, for example, acceleration sensors in each direction (e.g., front / rear, left / right, up / down, yaw rate, etc.), wheel speed sensors provided on each wheel, surrounding monitoring sensors (e.g., LiDAR, etc.), ZMP sensors, and / or road surface information storage devices associated with map data. The controller 30 is connected to the status detection device 8 and vehicle position information (e.g., GPS receiver). The vehicle speed is calculated, for example, based on the detection results of the wheel speed sensors.

[0022] (Control of actuator groups) The first control unit 3 sets target control values ​​for the actuator group 2 based on detected values ​​related to driver input (detected values ​​from various sensors 91-93) or vehicle motion control requests transmitted from other ECUs (e.g., an autonomous driving ECU). Vehicle motion control requests are, for example, motion commands in autonomous driving control. An example of calculating target control values ​​will be briefly explained with reference to Figure 2. Figure 2 shows the control flow during autonomous driving of the vehicle.

[0023] The first control unit 3 calculates the sideslip angle, yaw angular velocity, and yaw angular acceleration by applying motion commands (longitudinal acceleration, front wheel steering angle, rear wheel steering angle) corresponding to driver input or vehicle motion control requests to a planar motion model. The planar motion model reflects, for example, the dynamic characteristics of the vehicle. For example, a two-wheel model can be used as the planar motion model. The first control unit 3 calculates the three components of planar forces (longitudinal force, lateral force, and yaw moment) from the sideslip angle, yaw angular velocity, and yaw angular acceleration using the planar motion model. A well-known method can be used for this calculation. Furthermore, during automatic driving control, it can also be explained as follows: The first control unit 3 calculates the target vehicle speed and target curvature based on the vehicle motion control request. The first control unit 3 calculates the target three components of planar forces based on the target vehicle speed and target curvature (i.e., target path). This process of calculating the target three components of planar forces is a calculation process for following the target path and can be called a "following calculation process".

[0024] The first control unit 3 uses an inertial motion model to calculate the three components of sprung mass forces (vertical force, roll moment, and pitch moment) from the three components of planar forces of the vehicle. The inertial motion model is a coupled model (relative motion model between sprung mass and unsprung mass) that takes into account inertial forces and suspension reaction forces. A known model can be applied as the coupled model. In this way, the first control unit 3 calculates the six components of the target center of gravity of the vehicle (longitudinal force, lateral force, vertical force, yaw moment, roll moment, and pitch moment) based on driver input or vehicle motion control requests. This process can also be called a calculation process for rollover suppression by ZMP, and is referred to here as the "center of gravity force calculation process". Note that since the target control value can also be calculated from the three components of planar forces, the calculation of the three components of sprung mass forces, i.e., the center of gravity force calculation process, may be omitted.

[0025] The first control unit 3 calculates the controllable forces to be distributed to each wheel, that is, the tire three-component forces (longitudinal force, lateral force, vertical force) generated at each wheel, by using the component force calculation formula (y = C × u), which is a matrix operation, in order to achieve the target center-of-gravity six-component forces. In the component force calculation formula, y is the vector of the center-of-gravity six-component forces, u is the vector of the tire three-component forces, and C is the coefficient matrix. It can be said that the component force calculation formula represents the relationship between the "tire three-component forces of each wheel" and the "center-of-gravity six-component forces of the vehicle". The first control unit 3 calculates the tire three-component forces of each wheel corresponding to the target center-of-gravity six-component forces based on the vehicle's ground contact load and predetermined rules (constraint conditions, etc.) from a number of solutions that can be calculated by the component force calculation formula.

[0026] The first control unit 3 calculates the target driving force and / or target steering angle of each wheel based on the calculated tire three-component forces of each wheel. The process of calculating the tire three-component forces of each wheel in this way and calculating the target driving force and target steering angle of each wheel based on the calculation results is referred to as the "distribution calculation process".

[0027] The component force calculation formula is represented by, for example, the following Equation 1. The tire three-component forces are represented as the longitudinal force F ix , lateral force F iy , and vertical force F iz . The subscript i represents the position of the wheel. For the subscript i, in a four-wheel vehicle, the right front wheel is represented as fr, the left front wheel as fl, the right rear wheel as rr, and the left rear wheel as fl. The center-of-gravity six-component forces are represented as the longitudinal force F x , lateral force F y , vertical force F z , roll moment M x , pitch moment M y , and yaw moment M z . The coefficient matrix C is determined based on, for example, the suspension and vehicle specifications (e.g., tread width). The number of rows m of the coefficient matrix C corresponds to the number of center-of-gravity forces (number of types), and the number of columns n corresponds to the degree of freedom of the tire forces (C = [m × n]).

Equation

[0028] The first control unit 3 recognizes failures related to the braking and driving force of the wheels (hereinafter also referred to as braking and driving force failures), such as electric motor failure, based on notifications from the failure management unit 5. The failure management unit 5 determines whether or not there is a braking and driving force failure for each wheel based on the detection values ​​of various sensors. Since the braking and driving force in this embodiment is realized by the electric motor of each wheel, it can be said that the failure management unit 5 determines whether or not there is a failure of the electric motor of each wheel. The failure management unit 5 may be configured to detect only failures related to braking force. In addition, the failure management unit 5 may be composed of a computer separate from the controller 30.

[0029] When the first control unit 3 receives loss information from the loss management unit 5, it sets the three tire component forces of the lost wheel to fixed values ​​and then calculates the three tire component forces of the wheels other than the lost wheel. Details of the distribution calculation process when there is a lost wheel will be described later.

[0030] The first control unit 3 controls the actuator group 2 based on the calculated target braking force and target steering angle for each wheel. This process involves applying a control current to the corresponding actuator group 2 and can be described as "servo processing." The operation of the actuator group 2 causes the vehicle to move, and the actual vehicle speed and curvature, including disturbances (effects of bulldozing), are revealed.

[0031] The second control unit 4 recognizes a wheel with a brake failure based on information from, for example, the wheel failure management unit 5, and when the vehicle requires braking force, it overrides the servo processing to change the steering angle of the wheel with the brake failure. In other words, when braking force is requested from the vehicle while a brake failure has occurred in one or more of the multiple wheels, the second control unit 4 performs special control to change the steering angle of the wheel with the brake failure so that braking force is generated in that wheel.

[0032] The second control unit 4 controls the steering angle of the lost wheel as a special control, overriding (forcibly) the servo processing of the first control unit 3. For example, when braking force is required while a vehicle with a lost wheel is moving straight, the second control unit 4 changes the steering angle of the lost wheel to, for example, the toe-in side, generating a braking force on the lost wheel due to friction with the road surface. A braking force (hereinafter also called special braking force) is generated because the rotation direction of the lost wheel and the direction of travel of the vehicle are different. In this case, the axis of rotation of the lost wheel is tilted with respect to the lateral direction of the vehicle. If both left and right wheels are changed to the toe-in or toe-out side in order to maintain balance, when viewed from above, the tires appear in a V-shape. For this reason, the special braking force can also be called V-shape braking force. The special braking force (V-shape braking force) is generated by the special control (override of steering angle change) by the second control unit 4 on the lost wheel. The second control unit 4 can also be called a special control unit.

[0033] When special control is performed, the first control unit 3 acquires information on the steering angle of the lost wheel that changes due to the special control, and controls the driving force, steering angle, and braking force of each wheel other than the lost wheel using the corresponding actuator based on the driver input or vehicle motion control request and the acquired information on the steering angle of the lost wheel. At this time, the first control unit 3 sets at least the longitudinal force and lateral force of the lost wheel to fixed values ​​according to the state of the lost wheel. The first control unit 3 sets the fixed value (set value) corresponding to the steering angle of the lost wheel that is overridden to the lateral force F of the tire 3 component of the lost wheel. iy This applies to the first control unit 3, which has a fixed value set as the lateral force of the lost wheel, corresponding to the override amount by special control (change in steering angle or steering angle after override).

[0034] In the distribution calculation process, the first control unit 3 applies a lateral force F to the lost wheel. iy Set to a fixed value, and longitudinal force F ixThe vertical force of the wheel that has lost traction is also set to a fixed value (e.g., 0), and the three component forces of the tires other than the wheel that has lost traction are calculated. The vertical force of the wheel that has lost traction may also be set to a fixed value. In the distribution calculation process, at least the longitudinal force and lateral force of the wheel that has lost traction are not treated as variables, but as fixed values ​​corresponding to special control. This makes it possible to perform distribution calculations that take into account the effect of the special braking force of the wheel that has lost traction, and to control the wheels other than the wheel that has lost traction in a way that is closer to the actual wheel state.

[0035] Thus, according to this embodiment, the other wheels are controlled based on the steering angle of the malfunctioning wheel after special control. In other words, the state of the steering angle of the malfunctioning wheel is taken into consideration and reflected in the calculation of the control of the other wheels. This enables control that is more appropriate to the actual situation and improves vehicle stability.

[0036] The configuration of this embodiment can be summarized as follows: The vehicle is an autonomously driven vehicle. Each wheel is configured to be independently steerable and independently driveable. The vehicle is configured to be braked not by hydraulic braking force, but by regenerative braking force from each wheel, and a special braking force is generated for wheels that lose braking force. The power supply configuration is a redundant configuration with two batteries.

[0037] As shown in Figure 3, the technology of this disclosure is particularly effective when, for example, a vehicle attempts to apply braking force while moving in a straight line (for example, while driving in an autonomous manner), and the regenerative function of one of the wheels is lost due to a power failure or the like. In the event of a failure, the second control unit 4 changes the steering angle of the wheel with the failure to apply a special braking force (a V-shaped braking force). This applies the special braking force, but the bulldozing caused by the wheel with the failure causes the tire force (tire-generated force) to rise rapidly, generating a yaw moment in the vehicle.

[0038] In conventional control systems, the first control unit 3 updates the constraint conditions in the distribution calculation process so that it does not issue a regenerative command (setting and commanding target regenerative braking force) for the wheel that has failed to regenerate when the wheel failure management unit detects that the wheel failure is not regenerative. As a result, the first control unit 3 performs the distribution of target braking force (distribution calculation process, servo processing) without issuing a regenerative command for the wheel failure. In this situation, the second control unit 4, upon detecting the wheel failure, overrides the target steering angle of the wheel failure and changes the target steering angle so that a special braking force is generated. If a rapid increase in tire force occurs due to bulldozing at this point, a yaw moment is generated in the vehicle.

[0039] In conventional control systems, the first control unit 3 attempts to compensate for the generation of yaw moment using feedback control, but it calculates the distribution of the target steering angle including the wheel that has lost its position. However, since the target steering angle of the wheel that has lost its position is overridden by special control, the feedback control is not performed as calculated.

[0040] In the distribution calculation process of this embodiment, the longitudinal and lateral forces of the lost wheel are treated as fixed values ​​corresponding to the steering angle after special control, so that the target steering angle of the lost wheel, which has been changed by special control, is reflected in the distribution calculation. With fixed values ​​applied to at least the longitudinal and lateral forces of the lost wheel, the longitudinal and lateral forces of the other wheels are calculated so that the target center of gravity 6-component force is achieved. As a result, the tire force due to the steering angle of the lost wheel after special control is reflected in the calculation as a fixed value, so that the capabilities of the wheels other than the lost wheel (target braking force and target steering angle) can be fully utilized in redistribution (optimization). In other words, the performance of feedback control is improved. It also becomes possible to respond more appropriately to the occurrence of bulldozing than before. For example, if the lost wheel is one wheel on one side (left or right), in order to maintain straight-line movement after special control, the steering angles of the wheels on the other side (left or right) are also changed by the distribution calculation process, resulting in a V-shape.

[0041] The vehicle control device 1 is applicable to vehicles with two or more wheels, where the sum of the degrees of freedom of the inputs for each wheel is greater than the number of target center of gravity forces to be controlled. For example, if the target center of gravity forces consist of three types: longitudinal force, lateral force, and yaw moment (hereinafter also referred to as "three-component plane forces"), the vehicle control device 1 can be applied to any vehicle with four or more wheels that can control the longitudinal force (each wheel having 1 degree of freedom). The sum of the degrees of freedom of the inputs for each wheel corresponds to the number of columns n in the coefficient matrix C, and corresponds to the degrees of freedom of the actuator group 2 (the sum of the degrees of freedom of each actuator). The number of rows m in the coefficient matrix is ​​less than the number of columns n.

[0042] (Summary of one component of the disclosed technology) The vehicle control device 1 of this embodiment is a device that controls the vehicle using a plurality of actuators 21 to 25 based on driver input or vehicle motion control requests. The vehicle control device 1 comprises a plurality of wheels, a first control unit 3, a failure management unit 5, and a second control unit 4. Each of the plurality of wheels is configured to be independently steerable and independently drivable, and includes one or more pairs (preferably two or more pairs, i.e., four or more wheels) on the left and right sides. The first control unit 3 controls the corresponding actuators 21 to 25 based on driver input or vehicle motion control requests. The failure management unit 5 determines whether or not there is a failure in braking force for each wheel. When the failure management unit 5 determines that one or more wheels have failed, the second control unit 4 performs special control by changing the steering angle of the failed wheel using the corresponding actuators 21 to 25 so that braking force is generated on the failed wheel. When special control is performed, the first control unit 3 acquires information on the steering angle of the wheel that has lost traction due to the special control, and controls the driving force, steering angle, and braking force of each wheel other than the wheel that has lost traction using the corresponding actuators 21 to 25 based on the driver input or vehicle motion control request and the acquired information on the steering angle of the wheel that has lost traction.

[0043] In the above configuration, the first control unit 3 calculates at least the longitudinal force and lateral force of each wheel based on driver input or vehicle motion control request, and controls the corresponding actuators 21 to 25 based on the calculation results. Furthermore, when special control is performed, the first control unit 3 sets at least the longitudinal force and lateral force of the malfunctioning wheel to fixed values ​​corresponding to the steering angle of the malfunctioning wheel, and calculates target values ​​for the driving force, steering angle, and braking force of each wheel other than the malfunctioning wheel.

[0044] In the above configuration, each wheel is provided with an electric motor that can independently drive and brake the wheel. The failure management unit 5 determines whether or not there is a failure of the electric motor (e.g., power failure). When special control is performed, the first control unit 3 sets the longitudinal force of the failed wheel to 0, sets the lateral force of the failed wheel to a fixed value corresponding to the steering angle of the failed wheel, and calculates target values ​​for the driving force, steering angle, and braking force of each wheel other than the failed wheel.

[0045] In the technology disclosed herein, vertical control of the vehicle is not required. In the calculation, at least the longitudinal force and lateral force of the three components of the tire force are used, and at least the braking force and steering angle of the wheels are controlled. Furthermore, the braking force of the vehicle is not limited to regenerative braking force, but may also be hydraulic braking force. [Explanation of Symbols]

[0046] 1...Vehicle control device, 21-25...Actuators, 3...First control unit, 4...Second control unit, 5...Loss management unit.

Claims

1. A vehicle control device that performs vehicle control using multiple actuators based on driver input or vehicle motion control requests, Each wheel is configured to be independently steerable and independently driven, and includes multiple wheels, including one or more pairs on the left and right sides. A first control unit controls the corresponding actuator based on driver input or vehicle motion control request, A failure management unit that determines whether or not there is a loss of braking force for each of the aforementioned wheels, When the wheel failure management unit determines that one or more of the wheels have failed, and braking force is requested from the vehicle, the second control unit performs special control by changing the steering angle of the failed wheel using the corresponding actuator so that braking force is generated on the failed wheel. Equipped with, When the special control is performed, the first control unit acquires information on the steering angle of the lost wheel that changes as a result of the special control, and controls the driving force, steering angle, and braking force of each wheel other than the lost wheel using the corresponding actuator based on the driver input or the vehicle motion control request and the acquired information on the steering angle of the lost wheel. Vehicle control device.

2. The first control unit calculates at least the longitudinal force and lateral force of each wheel based on the driver input or the vehicle motion control request, and controls the corresponding actuator based on the calculation results. When the special control is performed, the first control unit sets at least the longitudinal force and lateral force of the lost wheel to fixed values ​​corresponding to the steering angle of the lost wheel, and calculates target values ​​for the driving force, steering angle, and braking force of each wheel other than the lost wheel. The vehicle control device according to claim 1.

3. Each of the wheels is provided with an electric motor that can independently drive and brake the wheel. The failure management unit determines whether or not the electric motor has failed, When the special control is executed, the first control unit sets the longitudinal force of the lost wheel to zero, sets the lateral force of the lost wheel to a fixed value corresponding to the steering angle of the lost wheel, and calculates target values ​​for the driving force, steering angle, and braking force of each wheel other than the lost wheel. The vehicle control device according to claim 2.

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