Driver direction control during brake-steered manual driving using model predictive control

Abstract

The invention relates to driver direction control during brake-steered manual driving using model predictive control. A number of variations are disclosed, including methods, systems, or computer products for determining an expected yaw or yaw angular velocity desired by a driver using a model, comparing the yaw or yaw angular velocity to an actual vehicle yaw or yaw angular velocity to determine a yaw error or yaw angular velocity error, and determining a yaw error or yaw angular velocity error. Model predictive control is used to determine the brake pressure required to minimize or reduce yaw error or yaw angular velocity error to zero.

Description

Technical Field

[0001] The field to which the present disclosure relates generally includes vehicle steering and braking control. Background Art

[0002] Some methods used in vehicles to determine the brake pressure required to achieve the desired yaw control rely on traditional methods, such as pressure gauges based on speed and lateral acceleration. Such methods cannot actively reduce yaw error in relation to the yaw movement desired by the driver. Summary of the invention

[0003] A number of variations may include a method, system, or computer product for determining an expected yaw or yaw rate desired by a driver using a model, comparing the yaw or yaw rate to an actual vehicle yaw or yaw rate to determine a yaw error or yaw rate error, and determining a brake pressure required to minimize or reduce the yaw error or yaw rate error to zero using model predictive control.

[0004] Other illustrative variations within the scope of the invention will become apparent from the detailed description provided below. It should be understood that the detailed description and specific examples, while disclosing variations of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Selected variations within the scope of the invention will be more fully understood from the detailed description and accompanying drawings, in which:

[0006] Figure 1 Methods and systems according to a number of variations are shown.

[0007] Figure 2 Illustrative variations of vehicles and systems having steer-by-wire systems are depicted.

[0008] Figure 3 Illustrative variations of vehicles and systems are depicted having connected power steering systems. DETAILED DESCRIPTION

[0009] The following description of variations is merely illustrative in nature and is in no way intended to limit the scope of the invention, its application, or uses.

[0010] Multiple variations can use vehicles equipped with electric power steering systems with traditional systems (with an intermediate connecting shaft between the steering column and the steering rack) or steer-by-wire systems, and the steering system can experience electrical or mechanical failures. In these situations, the driver can use brake steer (BTS) to achieve lateral control of the vehicle. Lateral control of the vehicle can be achieved using differential braking, such as but not limited to when a brake-by-wire system is used. However, the methods, systems, and computer products described herein can use model predictive control to determine brake pressure and / or powertrain commands even when components of the vehicle have not failed.

[0011] In the event of a failure in the connected steering system, the driver inputs a torque on the steering wheel which then drives the steering rack causing the vehicle to undergo a yaw motion and causing a certain lateral acceleration. The yaw rate so achieved will be less than normal for a system with an intact primary steering system in operation. In a number of variations, the ideal yaw rate may be estimated by using vehicle speed / lateral acceleration and / or a predicted bicycle model or by characterizing the vehicle. The ideal yaw rate may then be compared to the actual yaw rate. The error so calculated may be passed to a model predictive control (MPC) block or module which will use a state-space based representation of the vehicle operating the BTS system to predict an optimal set of brake pressures on all wheels to achieve zero yaw rate error or minimize the yaw rate error.

[0012] In the case of a steer-by-wire system, the method described above for a mechanically coupled steering system would be the same, with the difference that the driver cannot introduce any yaw in the vehicle because the steering column is not mechanically coupled to the steering rack and the steering rack fails. In this case, the predicted yaw can be estimated with the steering column angle sensor as an input parameter to the vehicle speed / lateral acceleration and / or a predictive bicycle model or by characterizing the vehicle. The method can also be used for coupled systems with an external / redundant steering column angle (steering angle) sensor.

[0013] The bicycle model takes a four-wheel model and combines the front and rear wheels separately to form a two-wheel model (hence the name bicycle model). MPC helps the vehicle predict and plan for future events by continuously generating a series of control actions that bring the vehicle closer to its desired trajectory. The MPC algorithm can handle nonlinear and complex vehicle dynamics, such as tire force models and actuator models, thus allowing precise and accurate trajectory tracking. At each time stamp, MPC receives measured outputs to predict the current state. Then, MPC calculates a series of control inputs that minimize the cost within the prediction horizon by solving a constrained optimization problem. The optimization problem depends on the vehicle model, reference values, and current state. Finally, the MPC controller or module applies the first calculated control input to the vehicle and ignores the subsequent inputs. The process is repeated for the next time stamp. In other words, MPC predicts the control input within the prediction horizon so that the predicted output will be merged with the reference trajectory. Then, MPC uses only the predicted control input at that time for actuation.

[0014] Figure 1A system and method 10 is shown, which may include a model predictive control module 16 that receives vehicle data 14, which may include, but is not limited to, steering angle, yaw, yaw rate, vehicle speed or velocity, wheel speed, lateral acceleration, brake pressure at each vehicle wheel, and / or powertrain data or commands. The model predictive control module uses the vehicle data 14 to predict and plan future events by continuously generating a series of control actions that will bring the vehicle closer to its desired trajectory as intended by the driver, which may be determined based on the vehicle data 14. For example, the model predictive control module may use an algorithm that uses a model to determine an expected yaw or yaw rate desired by the driver, which model may be based on vehicle speed or velocity and lateral acceleration, or based on a bicycle model, or other representation of the vehicle. The model predictive control module performs a method that may include comparing the driver desired yaw or yaw rate with the actual vehicle yaw or yaw rate to determine a yaw error or yaw rate error. Thereafter, the model predictive control module uses the yaw error or yaw rate error to determine brake pressure to minimize or reduce the yaw error or yaw rate error to zero. The model predictive control module may send a brake pressure command 18 to a brake-steering module 20, which may use the brake pressure command and other vehicle data to send a second set of commands 22 to each brake 24 to steer or assist in steering the vehicle. The model predictive control module 16 may also determine a powertrain or propulsion command 26 that may be sent to a powertrain module 28, which may use the powertrain or propulsion command 26 and other vehicle data to send a second set of powertrain commands 30 to a powertrain system 32. Alternatively, the brake pressure command 18 may be sent directly to the brakes 24, and the powertrain command 26 may be sent directly to the powertrain system 32.

[0015] Figure 2 A vehicle with steer-by-wire functionality and a system for performing the methods described herein are shown. Figure 3 A vehicle having a mechanical steering linkage and a system for performing the method described herein are shown. Figure 2 The vehicle retains the steer-by-wire function and Figure 3 If the vehicle retains the mechanical steering linkage, Figure 2 and Figure 3 Components and systems are interchangeable.

[0016] Figure 2Depicted are illustrative variations of various portions of a vehicle equipped with hardware sufficient to perform at least some of the systems and methods described herein. The vehicle 750 may include a controller 712 that is constructed and arranged to provide a brake-steer function in the vehicle 750. The controller 712 may be in operative communication with a wire-steer system 715 and an electronic brake system 716. The wire-steer system 715 may be composed of a steering wheel actuator 746 and a wheel actuator 714. The wire-steer system 715 may be constructed and arranged to rotate at least one wheel 742. The electronic brake system 716 may apply a braking force or braking torque 710 to the determined appropriate wheel 742. The driver may provide a driver input 734 for lateral movement using a steering wheel 744 that includes at least one steering wheel actuator 746 and send a steering command to the wire-steer system 715 and the wheel actuator 714. The electronic brake system 716 may be in operable communication with the controller 712 and a driver brake input system 752 such as a brake pedal system to receive driver brake input. According to some variations, the steering wheel actuator 746 may be in operable communication with the controller 712, the steer-by-wire wheel actuator 714, or the electronic brake system 716. In some variations, the steering wheel actuator 746 may be in a fault state 748 or disconnected from or unable to communicate with the steer-by-wire wheel actuator 714. In such variations, the steering wheel actuator 746 may transmit a steering command to the controller 712, and the controller 712 may receive health status information of the steer-by-wire system 715. In the case where the controller 712 receives steer-by-wire system 715 information indicating a steer-by-wire system 715 fault 748 or a wheel actuator 714 fault, the controller 712 may convert the steering command from the steering wheel actuator 746 into a braking force or braking torque command to be transmitted to the electronic brake system 716. The controller 712 may include instructions that may include algorithms for performing MPC. The electronic braking system 716 may apply a braking force or braking torque 710 to the determined appropriate wheel 742 to implement lateral movement of the vehicle in accordance with the driver's input 734 via the steering wheel 744. The controller 712 may also send powertrain commands to the powertrain system 708. The control device 712 and any other control devices (e.g., controller 768) may be provided to perform one or more functions described herein and may include a processor 760, a memory 762, wherein instructions 764 stored in the memory 762 may be executed by the processor 760.

[0017] Reference now Figure 3, shows an illustrative variation of a vehicle equipped with hardware that allows the execution of at least some of the methods disclosed herein. The vehicle 801 is equipped with a wheel 802 and a steering wheel 803 for rotating the wheel 802 via a gear 804, the gear 804 meshing with a rack 805, and the rack 805 is constructed and arranged to rotate the wheel 802. In the illustrative variation shown, the steering wheel 803 is equipped with a steering wheel torque sensor 806 and a steering wheel angle sensor 807, so that any rotation of the steering wheel can generate sensor data, which can be transmitted to or accessed by the controller 808. The controller 808 can provide all other functions described herein, including MPC, steer-by-wire control, powertrain control, brake control, and / or control vehicle systems, or one or more other controllers can be provided to perform the same operations. Although in this illustrative variation, the controller 808 is shown as being onboard the vehicle, the controller can also be located somewhere outside the vehicle and communicate wirelessly with the sensor or the vehicle. The gear 804 may be equipped with a gear torque sensor 809 so that any rotation of the gear can be observed by or transmitted to the controller 808 and utilized by the methods described herein. In the illustrated illustrative variation, the rack 805 is equipped with a rack force sensor 810 so that any rack force detected during driving can be observed by or transmitted to the controller 808 and utilized by the methods described herein. The vehicle may have a steering shaft 814 connecting the steering wheel or steering interface 803 to the gear 804. An electric steering assist or hydraulic power steering device 836 may be connected to the shaft 814 to help the driver steer the wheels of the vehicle by reducing the force or torque that the driver would need to apply to the steering wheel or steering interface 803 in the absence of the power steering device 836. It is also shown in this illustrative variation that the wheel 802 may be equipped with a wheel sensor so that any wheel data detected during driving can be observed by or transmitted to the controller 808 and utilized by the methods described herein. Furthermore, in the illustrated illustrative variation, the brake 812 is located near the wheel 802. Another controller 818 may be provided and may include a processor 820, a memory 822, wherein instructions 824 stored in the memory 822 may be executed by the processor 820 to determine whether the steering wheel angle sensor 807 or the gear 804, the rack 805, the gear sensor 809, or the rack sensor 810 has failed. Additionally, the instructions 824 stored in the memory 822 may be executed by the processor 820 to implement any of the methods described herein or to implement any of the functions described herein.

[0018] The modules and controllers described herein may include software, hardware, or computing devices including non-transitory computer-readable media, such as but not limited to memory having instructions stored thereon, and a processor for executing instructions to implement the actions, steps, methods, and functions described herein. Multiple modules and controllers and their associated actions, steps, methods, and functions may be included in or implemented by one or more computing devices.

[0019] The following description of the variations merely illustrates the parts, elements, actions, products and methods that are considered to be within the scope of the present invention, and is by no means intended to limit such scope with specific disclosures or unspecified content. The parts, elements, actions, products and methods described herein may be combined and rearranged in ways other than those explicitly described herein, and are still considered to be within the scope of the present invention.

[0020] Variant 1 may include a method comprising: determining an expected yaw or yaw rate desired by a driver using a model; comparing the expected yaw or yaw rate to an actual vehicle yaw or yaw rate to determine a yaw error or yaw rate error; and using the determined yaw error or yaw rate error in a model predictive control module to determine a brake pressure to minimize or reduce the yaw error or yaw rate error to zero.

[0021] Variation 2 may include the method as set forth in Variation 1 wherein the model is a vehicle bicycle model.

[0022] Variation 3 may include the method of Variation 1 wherein the model is based on vehicle speed and lateral acceleration.

[0023] Variation 4 may include the method of Variation 1 further comprising issuing a braking command based on the determined brake pressure to minimize or reduce the yaw error or yaw rate error to zero.

[0024] Variation 5 may include a method as set forth in Variation 1 further comprising sending powertrain commands to achieve the desired yaw or yaw rate.

[0025] Variation 6 may include a computer readable medium including a non-transitory memory operable for machine instructions to be executed by an electronic processor, the instructions when executed by the electronic processor performing functions including: determining an expected yaw or yaw rate desired by a driver using a model; comparing the expected yaw or yaw rate to an actual vehicle yaw or yaw rate to determine a yaw error or yaw rate error; and using the determined yaw error or yaw rate error in a model predictive control module to determine a brake pressure to minimize or reduce the yaw error or yaw rate error to zero.

[0026] Variation 7 may include a computer readable medium as set forth in Variation 6 wherein the model is a vehicle bicycle model.

[0027] Variation 8 may include a computer readable medium as set forth in Variation 6 wherein the model is based on vehicle speed and lateral acceleration.

[0028] Variation 9 may include the computer readable medium of Variation 6 further comprising: sending a braking command based on the determined braking pressure to minimize or reduce the yaw error or yaw rate error to zero.

[0029] Variation 10 may include a computer readable medium as set forth in Variation 6 further comprising sending a powertrain command to achieve the desired yaw or yaw rate.

[0030] Variant 11 may include a system comprising a model predictive control module, wherein the model predictive control model comprises a non-transitory memory having instructions stored thereon, and the instructions are executable by an electronic processor to perform the following actions: receiving vehicle data and determining an expected yaw or yaw rate desired by a driver from the data using a model; comparing the expected yaw or yaw rate to an actual vehicle yaw or yaw rate to determine a yaw error or yaw rate error; and using the determined yaw error or yaw rate error to determine a brake pressure to minimize or reduce the yaw error or yaw rate error to zero.

[0031] Variation 12 may include the system of Variation 11 wherein the model predictive control module uses a vehicle bicycle model.

[0032] Variation 13 may include the system of Variation 11 wherein the model predictive control module uses vehicle speed and lateral acceleration.

[0033] Variation 14 may include the system of Variation 11 further comprising: sending a braking command to a brake steering module based on the determined brake pressure to minimize or reduce the yaw error or yaw rate error to zero.

[0034] Variation 15 may include the system of Variation 11 further comprising sending a powertrain command to a powertrain module to achieve the desired yaw or yaw rate.

[0035] The above description of selected examples of the present invention is merely illustrative in nature and, thus, variations or modifications thereof should not be regarded as a departure from the spirit and scope of the present invention.

Claims

1. A method comprising: Using the model, determine the expected yaw or yaw rate desired by the driver; comparing the expected yaw or yaw rate with an actual vehicle yaw or yaw rate to determine a yaw error or yaw rate error; The determined yaw error or yaw rate error is used in a model predictive control module to determine a brake pressure in order to minimize or reduce the yaw error or yaw rate error to zero.

2. The method according to claim 1, wherein: The model is a vehicle bicycle model.

3. The method according to claim 1, wherein: The model is based on vehicle speed and lateral acceleration.

4. The method according to claim 1, further comprising: A braking command is issued based on the determined brake pressure to minimize or reduce the yaw error or yaw rate error to zero. 5 . The method of claim 1 , further comprising sending powertrain commands to achieve the desired yaw or yaw rate.

6. A computer readable medium comprising non-transitory storage operable for machine instructions to be executed by an electronic processor, the instructions, when executed by the electronic processor, performing functions comprising: Using the model, determine the expected yaw or yaw rate desired by the driver; comparing the expected yaw or yaw rate with an actual vehicle yaw or yaw rate to determine a yaw error or yaw rate error; The determined yaw error or yaw rate error is used in a model predictive control module to determine a brake pressure in order to minimize or reduce the yaw error or yaw rate error to zero.

7. The computer-readable medium of claim 6, wherein: The model is a vehicle bicycle model.

8. The computer-readable medium of claim 6, wherein: The model is based on vehicle speed and lateral acceleration.

9. The computer-readable medium of claim 6, further comprising: A braking command is issued based on the determined brake pressure to minimize or reduce the yaw error or yaw rate error to zero.

10. The computer readable medium of claim 6, further comprising sending powertrain commands to achieve the desired yaw or yaw rate.

11. A system comprising a model predictive control module, wherein: The model predictive control model includes a non-transitory memory having instructions stored thereon, and the instructions are executable by an electronic processor to perform the following actions: receiving vehicle data and determining from the data an expected yaw or yaw rate desired by a driver using a model; comparing the expected yaw or yaw rate with an actual vehicle yaw or yaw rate to determine a yaw error or yaw rate error; The determined yaw error or yaw rate error is used to determine the brake pressure in order to minimize or reduce the yaw error or yaw rate error to zero.

12. The system according to claim 11, wherein: The model predictive control module uses a vehicle bicycle model.

13. The system according to claim 11, wherein: The model predictive control module uses vehicle speed and lateral acceleration.

14. The system of claim 11, further comprising: A braking command is sent to a brake steering module based on the determined brake pressure to minimize or reduce the yaw error or yaw rate error to zero.

15. The system of claim 11 further comprising sending a powertrain command to a powertrain module to achieve the desired yaw or yaw rate.

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