Control allocation system for path following in a vehicle

Abstract

A control allocation system for a vehicle includes an electric power steering (EPS) system, one or more redundant drive systems for controlling a plurality of wheels of the vehicle, and one or more controllers in electronic communication with the EPS system and the one or more redundant drive systems. The one or more controllers execute instructions to determine tracking errors and vehicle dynamics states based on a plurality of local path planning references and receive a fault signal indicative of a failure of the EPS system. In response to receiving the fault signal, the one or more controllers determine a plurality of correction constraints in real-time. The one or more controllers solve a real-time constraint optimization problem for each sampling interval of the control allocation system to determine a plurality of control actions based on the plurality of correction constraints and the tracking errors.

Description

Technical Field

[0001] This disclosure relates to a control distribution system for guiding a vehicle along a planned driving path when electric power steering (EPS) is not in operation. More specifically, the disclosed control distribution system guides the vehicle in real time along a planned driving path using an existing drive system when the EPS system is not in operation. Background Technology

[0002] Semi-autonomous and autonomous vehicles are becoming increasingly common on the road. Autonomous vehicles execute various path planning algorithms to determine the planned driving path that the vehicle may follow. In addition, autonomous vehicles also include an electric power steering (EPS) system, which includes an electric motor driven by a software-driven steering module, and a torque sensor for measuring driver input.

[0003] Sometimes, the electric motor in an EPS system may stop working due to overheating or the infiltration of water, dirt, or other contaminants, and may fail to function properly. In some cases, the steering module may stop working due to a problem with the electronic board or circuitry that is part of the steering module. Additionally, torque sensors (especially contact torque sensors) may also malfunction in certain situations. Furthermore, the EPS system may sometimes exhibit performance degradation and may fail to transmit requested commands. When the EPS is not working, it is difficult to control the vehicle to follow the planned path, even if the driver attempts to manually control it.

[0004] Therefore, while the current system achieves its intended purpose, there is still a need in the art for an improved system that can address the path tracking gap problem when the EPS system is not working. Summary of the Invention

[0005] According to several aspects, a control distribution system for a vehicle including an electric power steering (EPS) system is disclosed, comprising one or more redundant drive systems for controlling multiple wheels of the vehicle, and one or more controllers in electronic communication with the EPS system and the one or more redundant drive systems. The one or more controllers execute instructions to determine tracking errors and vehicle dynamic states based on multiple local path planning references. The one or more controllers execute instructions to receive a fault signal indicating that the EPS system is not operating. In response to receiving the fault signal, the one or more controllers execute instructions to determine multiple correction constraints for controlling the EPS system and the one or more redundant drive systems in real time. The one or more controllers execute instructions to solve a real-time constraint optimization problem for each sampling interval of the control distribution system, thereby determining multiple control actions based on the multiple correction constraints and tracking errors. The one or more controllers execute instructions to distribute the multiple control actions to the one or more redundant drive systems.

[0006] In one aspect, the controller executes instructions to determine a state-space formula based on tracking error, vehicle dynamics, and tire lateral forces, wherein the state-space formula includes high-level control variables and driver Boolean matrices.

[0007] In another aspect, the driver Boolean matrix indicates one or more redundant drive systems in the vehicle that can be used to guide the vehicle when the EPS system is not in operation.

[0008] In another aspect, multiple correction constraints are determined based on high-level control variables.

[0009] In one aspect, fault signals include fault codes indicating conditions that cause the EPS system to malfunction.

[0010] On the other hand, fault signals include one or more of the following: EPS fault flag, EPS fault mode message, fault steering angle message, and EPS operating boundary message.

[0011] In one aspect, multiple correction constraints include correction equality constraints and correction boundary constraints.

[0012] In another aspect, one or more redundant drive systems for controlling multiple wheels of a vehicle include at least one of the following: an active rear steering (ARS) system, a torque vectoring (TV) and differential braking (DB) combined system, or an ARS system and a TV and DB combined system.

[0013] In another aspect, tracking errors include lateral distance errors and heading orientation errors, and vehicle dynamics include vehicle lateral velocity and yaw rate.

[0014] In one aspect, multiple control actions include front wheel steering angle, rear wheel steering angle, and external yaw moment at the vehicle's center of gravity.

[0015] On the other hand, when the EPS system is not working, multiple control actions instruct one or more redundant drive systems to guide the vehicle along a planned driving path.

[0016] In one aspect, a method for determining control actions to guide a vehicle along a planned driving path via a control distribution system is disclosed. The method includes determining a tracking error and vehicle dynamics state by one of a plurality of controllers of the vehicle based on multiple local path planning references. The method also includes receiving a fault signal indicating that the EPS system is not operating by one or more controllers. In response to receiving the fault signal, the method includes determining multiple correction constraints for controlling the EPS system and one or more redundant drive systems in real time. The method further includes solving a real-time constraint optimization problem for each sampling interval of the control distribution system to determine multiple control actions based on the multiple correction constraints and the tracking error. Finally, the method includes distributing the control actions to one or more redundant drive systems for controlling multiple wheels of the vehicle.

[0017] In one aspect, the method also includes approximating the state-space formula based on tracking error, vehicle dynamics, and tire lateral force, wherein the state-space formula includes high-level control variables and driver Boolean matrices.

[0018] In another aspect, the driver Boolean matrix indicates one or more redundant drive systems in the vehicle that can be used to guide the vehicle when the EPS system is not in operation.

[0019] In one aspect, a control distribution system for a vehicle including an EPS system is disclosed, comprising one or more redundant drive systems for controlling multiple wheels of the vehicle, wherein the one or more redundant drive systems include at least one of the following: an ARS system, a TV and DB combined system, and an ARS system and a TV and DB combined system. The system also includes one or more controllers in electronic communication with the EPS system and the one or more redundant drive systems. The one or more controllers execute instructions to determine tracking errors and vehicle dynamic states based on multiple local path planning references. The one or more controllers execute instructions to determine a state-space formula based on the tracking errors, vehicle dynamic states, and tire lateral forces, wherein the state-space formula includes high-level control variables and a driver Boolean matrix. The one or more controllers execute instructions to receive a fault signal indicating that the EPS system is not operating. In response to receiving the fault signal, the one or more controllers determine multiple correction constraints for controlling the EPS system and the one or more redundant drive systems in real time. The one or more controllers execute instructions to solve a real-time constraint optimization problem for each sampling interval of the control distribution system, thereby determining multiple control actions based on the multiple correction constraints and the tracking error. Finally, the one or more controllers execute instructions to distribute the control actions to the one or more redundant drive systems.

[0020] In one aspect, the drive Boolean matrix indicates one or more redundant drive systems in a vehicle that can be used to guide the vehicle when the EPS system is not in operation.

[0021] On the other hand, fault signals include fault codes indicating conditions that cause the EPS system to malfunction.

[0022] In another aspect, fault signals include one or more of the following: EPS fault flag, EPS fault mode, fault steering angle message, and EPS operating boundary message.

[0023] In one aspect, multiple correction constraints include correction equality constraints and correction boundary constraints.

[0024] On the other hand, multiple control actions include front wheel steering angle, rear wheel steering angle, and external yaw moment at the vehicle's center of gravity.

[0025] Further areas of application become apparent from the description provided herein. It should be understood that the descriptions and specific examples are intended for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0026] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure in any way.

[0027] Figure 1This is a schematic diagram of a vehicle including the disclosed control distribution system according to an exemplary embodiment. The control distribution system includes one or more controllers that communicate electronically with an electric power steering (EPS) system, an active rear wheel steering (ARS) system, and a torque vectoring (TV) and differential braking (DB) combination system.

[0028] Figure 2 This is illustrated according to an exemplary embodiment. Figure 1 The diagram shows the planned driving path of the vehicle.

[0029] Figure 3 According to exemplary embodiments, such as Figure 1 The block diagram shown illustrates one or more controllers used to determine control actions assigned to one or more redundant drive systems that are part of the vehicle; and

[0030] Figure 4 The exemplary embodiment illustrates the determination of the method used along... Figure 2 The diagram shows the process flow of the method for planning a driving path to guide the vehicle's control actions. Detailed Implementation

[0031] The following description is merely exemplary in nature and is not intended to limit this disclosure, its application, or its uses.

[0032] refer to Figure 1 A schematic diagram of an exemplary vehicle 10 is shown, which includes a control distribution system 12 for providing control to a plurality of wheels 14. The control distribution system 12 includes one or more controllers 20 that electronically communicate with an electric power steering (EPS) system 22 and one or more redundant drive systems 32. Specifically, in an embodiment, the redundant drive system 32 includes an active rear wheel steering (ARS) system 24, a torque vectoring (TV) and differential braking (DB) combination system 26, or an ARS system 24 and a TV and DB combination system 26. The EPS system 22 guides a pair of front wheels 30A of the vehicle 10, and the one or more redundant drive systems 32 provide control to the rear wheels 30B of the vehicle 10, or the front wheels 30A and the rear wheels 30B. As explained in detail below, one or more controllers 20 send control actions 28 to instruct the drives associated with the EPS system 22, the ARS system 24, and the TV and DB combination system 26 to guide the wheels 30 along a planned driving path 16 when the EPS system 22 is not in operation. Figure 2 ) Guide vehicle 10.

[0033] EPS system 22 includes an EPS controller 40 that electronically communicates with electric motor 42, steering torque sensor 46, steering angle sensor 47, and steering motor sensor 48. Electric motor 42 provides auxiliary torque to steering system 44. Steering system 44 includes numerous gears, links, and other components for controlling the front wheel steering angle δf of the front wheels 30A of vehicle 10. ARS system 24 includes a rear wheel steering drive 56 for controlling the rear wheel steering angle δr of the rear wheels 30B of vehicle 10 independently of driver input. The torque vectoring system of TV and DB combination system 26 differentially applies torque from an engine or motor (not shown) to multiple wheels 30 of vehicle 10, and the differential braking system independently changes the braking force of the wheels 30 of vehicle 10.

[0034] Figure 2 This diagram illustrates vehicle 10 traveling along road 38 and simultaneously along the planned travel path 16. (Reference) Figure 1 and 2 In the absence of EPS system 22, vehicle 10 may deviate from the planned travel path 16. For example, the electric motor 42 of EPS system 22 may fail to provide auxiliary torque due to overheating or the infiltration of water, dirt, or other contaminants. As explained in detail below, the disclosed control distribution system 12 transmits control actions 28 in real time to instruct one or more redundant drive systems 32 on vehicle 10 (i.e., the rear wheel steering drive 48 of the ARS system 24 and / or the combined TV and DB system 26) to guide vehicle 10 along the planned travel path 16.

[0035] Vehicle 10 can be any type of vehicle, such as, but not limited to, a sedan, truck, SUV, van, or motorhome. In one non-limiting embodiment, vehicle 10 can be a fully automated vehicle including an automated driving system (ADS) for performing all driving tasks, or alternatively, a semi-automated vehicle including an advanced driver assistance system (ADAS) for assisting the driver in steering, braking, and / or acceleration. However, it should be understood that in another embodiment, vehicle 10 can also be a non-automatic or manually driven vehicle.

[0036] Figure 3 This is a block diagram of one or more controllers 20. The one or more controllers 20 include a path tracking module 50 and a control allocation module 52. The path tracking module 50 determines control actions 28 to be sent to the control allocation module 52. Control actions 28 include front wheel steering angle δf, rear wheel steering angle δr, and external yaw moment ΔM at the center of gravity. zThe path tracing module 50 includes a control formula block 60, an EPS monitoring and prediction block 62, a driver constraint block 64, and a model predictive control (MPC) block 66. It should be understood that the control formula block 60 determines the driver Boolean matrix offline; however, the remaining blocks 62, 64, and 66 are executed in real time.

[0037] refer to Figure 1 and 3 Control formula block 60 from vehicle 10 ( Figure 1 Part of the local path planning module 72 receives multiple local path planning references 70. The multiple local path planning references 70 include vehicle position coordinates X, Y, and vehicle heading angle Ψ. The control formula block 60 determines a driver Boolean matrix indicating a specific driver control configuration for the vehicle 10. The specific driver control configuration indicates one or more drivers available on the vehicle 10 for guiding the wheels 30 along the planned travel path 16 when the EPS system 22 is not operating. Figure 2 The vehicle 10 is guided. Specifically, the control formula block 60 first determines the tracking error and vehicle dynamics state based on multiple local path planning references 70. The tracking error includes lateral distance error e. y and heading and orientation error e Ψ Furthermore, the vehicle dynamics state includes the vehicle's lateral velocity and yaw rate. Control formula block 60 can determine the state-space formula based on the tracking error, vehicle dynamics state, and tire lateral forces. Tire lateral forces can be implemented using various methods, such as the Fiala brush tire model or the affine tire model.

[0038] The state-space formula includes high-level control variables and driver Boolean matrices, and is expressed in equations 1, 2, 3, and 4 as follows:

[0039]

[0040] y = C c x Equation 2

[0041] x = [e y v y e Ψ r] T Equation 3

[0042] y = [e y e Ψ ] T Equation 4

[0043] Where v is a vector containing the high-level control variables, It is a system matrix. It is a control input matrix. It is an additional item for estimating tire lateral force and lateral stiffness. It is the output matrix, B a It is a Boolean matrix for the driver. The vector of the advanced control variable v is determined based on one or more redundant drive systems 32 on vehicle 10, and is used to travel along the planned driving path 16 when the EPS system 22 is not in operation. Figure 2 Guide vehicle 10, as shown in Table 1, and explained in more detail below.

[0044] Continue to refer to Figure 1 and 3 The driver Boolean matrix indicates one or more redundant drive systems 32 available in vehicle 10 for guiding the wheels 30 of vehicle 10 when EPS system 22 is not in operation. For example, vehicle 10 may include EPS system 22, ARS system 24, and a combined TV and DB system 26. In this example, the driver Boolean matrix listed in row 1 of Table 1 (shown below) is selected. Alternatively, vehicle 10 may include only EPS system 22 and ARS system 24, and the driver Boolean matrix listed in row 2 of Table 1 is used. In another example, vehicle 10 includes only EPS system 22 and TV / DB combined system 26, and the driver Boolean matrix in row 3 is used.

[0045]

[0046] Table 1

[0047] refer to Figure 1 and 3 The EPS monitoring and prediction block 62 of the path tracking module 50 monitors the EPS controller 40 in real time to obtain a fault signal 80 indicating that the EPS system 22 is not working. In an embodiment, the fault signal 80 includes a fault code indicating a condition causing the EPS system 22 to malfunction. In an embodiment, the fault signal 80 includes one or more of the following: an EPS fault flag, an EPS fault mode message, a fault steering angle message, and an EPS operating boundary message. The EPS fault flag can indicate a fault in the EPS system 22 by outputting a false value such as 0. The EPS fault mode message can, for example, indicate the presence of steering sticking. The fault steering angle message indicates the current steering angle measurement when in sticking mode, or the real-time steering change when in free-rotation mode.

[0048] During normal operation of the EPS system 22, the driver constraint block 64 determines standard constraints, which include equality constraints and boundary constraints. Standard operation refers to the operating conditions under which the EPS system 22 operates normally (i.e., the EPS controller 40 does not generate a fault signal 80). Specifically, in this embodiment, the equality constraints are represented by Formula 5, and the boundary constraints are represented by Formula 6:

[0049] Av = b Equation 5

[0050] lb≤v≤ub Equation 6

[0051] Where A is a predetermined coefficient, and b is based on the operation of EPS system 22 as the main drive system for traveling along the planned driving path 16. Figure 2 )Guide vehicle 10 ( Figure 1 The setpoints for the front wheel 30A under assumed conditions are as follows: v is the high-level control variable (vector), lb is the lower limit vector of the high-level control variable v, and ub is the upper limit vector of the high-level control variable v. In the embodiment, during normal operation, the entries corresponding to the upper limit ub and lower limit lb of the ARS system 24 and the TV and DB combined system 26 are set to zero to disable the ARS system 24, the TV and DB combined system 26, or both.

[0052] In response to receiving a fault signal 80 indicating that the EPS system 22 is not operating from the EPS monitoring and prediction block 62, the driver constraint block 64 determines multiple correction constraints for controlling the EPS system 22 and one or more redundant drive systems 32. The multiple correction constraints are determined based on high-level control variables and driver Boolean matrices. The multiple correction constraints include correction equality constraints and correction boundary constraints. Specifically, in an embodiment, the equality constraints are represented by Equation 7, and the boundary constraints are represented by Equation 8:

[0053] Av = b f Equation 7

[0054] lb f ≤v≤ub f Equation 8

[0055] Where A is a predetermined coefficient, b f This is a setpoint based on one or more redundant drive systems 32 available in vehicle 10 to guide the wheels 30 of vehicle 10 when EPS system 22 is not working; v is an advanced control variable; lb f It is the lower bound vector of the higher-level control variable v, ub f This is the upper bound vector of the higher-level control variable v. The correction equality constraint can be fixed to a constant value (e.g., in hysteresis mode) and is used by the EPS system 22. The lower bound vector lb f and upper bound vector ub f Indicates the range of the control variable v (e.g., the front steering angle, rear steering angle, and external yaw moment under non-operating conditions), where this range may be determined by the mass capacity. These lower bound vectors lb f and upper bound vector ub f This is part of the MPC optimization problem, and it is guaranteed that the control action 28 generated by the MPC module 66 is feasible. Then, the correction constraints are sent to the MPC module 66.

[0056] The MPC module 66 can determine in real time that the EPS system 22 is not working because the correction constraints are sent to the MPC module 66 in real time. Therefore, the MPC module 66 updates the control action 28 in real time, which in turn allows the control allocation module 52 to allocate the control action 28 to one or more redundant drive systems 32 to guide the vehicle 10 in real time along the planned driving path 16. Specifically, the MPC module 66 receives the correction constraints (i.e., correction equality constraints and correction boundary constraints) and the tracking error (i.e., lateral distance error e). y and heading and orientation error e Ψ MPC block 66 solves the real-time constraint optimization problem for each sampling interval of control allocation system 12, thereby determining control action 28 based on correction constraints and tracking error. In an embodiment, control action 28 includes front wheel steering angle δf, rear wheel steering angle δr, and external yaw moment ΔM at the center of gravity. z It should be understood that the MPC module 66 executes a cost-minimizing control strategy to track the current path that the vehicle 10 is traveling on when the EPS system 22 is not working, while adhering to correction constraints to determine updated control and predicted vehicle and path states.

[0057] Then, the MPC block 66 can transmit the control action 28 to the control distribution module 52, and the control distribution module 52 distributes the control action 28 to one or more redundant drive systems 32 to guide the steering wheels 30 along the planned driving path 16. Figure 2 The vehicle 10 is guided. Specifically, the front wheel steering angle δf is sent to the EPS system 22, the rear wheel steering angle δr is sent to the ARS system 24, and the external yaw moment ΔM at the center of gravity is... z It is sent to the TV and DB combined system 26. In an embodiment, the external yaw moment ΔM at the center of gravity is... z In the case of a torque vectoring system, this is converted into torque applied to the wheels 30A and 30B of vehicle 10. Figure 1 The differential torque command is converted into independent braking force when a differential braking system is included.

[0058] Figure 4 The diagram illustrates the method for determining the driving path 16 along the planned route. Figure 2 A flowchart illustrating an exemplary method 200 for guiding control actions 28 of vehicle 10. (See reference...) Figure 1-4 This method 200 can begin at block 202. In block 202, the control formula block 60 determines the tracking error and vehicle dynamics state based on multiple local path planning references 70. As mentioned above, the tracking error includes lateral distance error e. y and heading and orientation error e ΨFurthermore, the vehicle dynamics state includes the vehicle's lateral velocity and yaw rate. Method 200 then proceeds to block 204.

[0059] In block 204, control formula block 60 determines the state-space formula based on tracking error, vehicle dynamics state, and tire force approximations. The state-space formula indicates the high-level control variable v and the driver Boolean matrix. This method 200 then proceeds to block 206.

[0060] In block 206, the EPS monitoring and prediction block 62 of the path tracing module 50 receives a fault signal 80 indicating that the EPS system 22 is not working. The method 200 then proceeds to block 208.

[0061] In block 208, in response to receiving fault signal 80, the driver constraint block 64 of path tracking module 50 determines in real time multiple correction constraints for controlling EPS system 22 and one or more redundant drive systems 32. This method 200 then proceeds to block 210.

[0062] In block 210, the MPC module 66 of the path tracking module 50 solves the real-time constraint optimization problem for each sampling interval of the control allocation system 12, thereby determining the control action 28 based on multiple correction constraints and tracking errors. This method 200 then proceeds to block 212.

[0063] In block 212, control distribution module 52 distributes control action 28 to one or more redundant drive systems 32. The method 200 then terminates, or, optionally, returns to block 202.

[0064] Referring to the accompanying drawings, the disclosed control distribution system addresses path tracking discrepancies that may occur when the EPS system is not operational by utilizing redundant existing drives, thereby providing various technical effects and benefits. Specifically, in response to determining a fault within the EPS system, the disclosed control distribution system updates control actions in real time. Furthermore, the disclosed control distribution system includes a reconfigurable multi-layered structure adaptable to various drive configurations. Specifically, the drive Boolean matrix can be used to accommodate various types of drive configurations. While the control distribution system is particularly convenient for use in automatic and semi-automatic vehicles, the control drive system can also be used as a steering backup control for manually driven vehicles.

[0065] A controller can refer to electronic circuitry, combinational logic circuitry, a field-programmable gate array (FPGA), a processor (shared, dedicated, or grouped) that executes code, or a combination thereof, such as in a system-on-a-chip. Alternatively, the controller can be microprocessor-based, such as a computer having at least one processor, memory (RAM and / or ROM), and associated input and output buses. The processor can operate under the control of an operating system residing in memory. The operating system can manage computer resources so that computer program code embodied as one or more computer software applications (e.g., applications residing in memory) can have instructions executed by the processor. In alternative embodiments, the processor can directly execute the application, in which case the operating system can be omitted.

[0066] The descriptions in this disclosure are merely exemplary in nature, and any changes that do not depart from the spirit and scope of this disclosure are intended to fall within its scope. Such changes should not be considered as departing from the spirit and scope of this disclosure.

Claims

1. A control distribution system for a vehicle including an electric power steering (EPS) system, the control distribution system comprising: One or more redundant drive systems for controlling multiple wheels of the vehicle; as well as One or more controllers communicate electronically with the EPS system and the one or more redundant drive systems, wherein the one or more controllers execute instructions to: Based on multiple local path planning references, the tracking error and vehicle dynamics state are determined. Receive a fault signal indicating that the EPS system is not working; In response to receiving the fault signal, multiple correction constraints for controlling the EPS system and the one or more redundant drive systems are determined in real time. Solve the real-time constraint optimization problem of each sampling interval of the control allocation system, and thus determine multiple control actions based on the multiple correction constraints and the tracking error; as well as The multiple control actions are distributed to the one or more redundant drive systems.

2. The control and distribution system according to claim 1, wherein, The controller executes instructions to: Based on the tracking error, the vehicle dynamics state, and the tire lateral force, a state-space formula is determined, wherein the state-space formula includes high-level control variables and a driver Boolean matrix.

3. The control and distribution system according to claim 2, wherein, The driver Boolean matrix indicates one or more redundant drive systems in the vehicle that can be used to guide the vehicle when the EPS system is not working.

4. The control and distribution system according to claim 2, wherein, The multiple correction constraints are determined based on the high-level control variables.

5. The control and distribution system according to claim 1, wherein, The fault signals include fault codes indicating conditions that cause the EPS system to malfunction.

6. The control and distribution system according to claim 5, wherein, The fault signals include one or more of the following: EPS fault flag, EPS fault mode message, fault steering angle message, and EPS operation boundary message.

7. The control and distribution system according to claim 1, wherein, The multiple correction constraints include correction equality constraints and correction boundary constraints.

8. The control and distribution system according to claim 1, wherein, The one or more redundant drive systems for controlling multiple wheels of the vehicle include at least one of the following: an active rear-wheel steering (ARS) system, a torque vectoring (TV) system, and a differential braking (DB) system.

9. The control and distribution system according to claim 1, wherein, The tracking error includes lateral distance error and heading orientation error, and the vehicle dynamics state includes vehicle lateral speed and yaw rate.

10. The control and distribution system according to claim 1, wherein, The multiple control actions include front wheel steering angle, rear wheel steering angle, and external yaw moment at the vehicle's center of gravity.

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