Vehicle Steering Control via Differential Wheel Torque Actuators
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Solution Overview
Problem
Current steering systems in vehicles, particularly in trucks, face challenges with malfunctions leading to impaired steering capabilities, increased risk of accidents, and the need for limp-home modes, which compromise drivability and safety.
Innovation Solution
A method and system that utilize individually controllable wheel torque actuators on the front axle to determine and adjust the steering angle by applying differential torque, accounting for parameters like scrub radius, camber, and cornering stiffness, allowing for precise control of the steering system, even in malfunctioning conditions, without relying on yaw rate determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a primary steering system is used to control the vehicle, then steering functionality is achieved under normal conditions, but the system becomes unreliable when malfunctions occur
Solution Approach 1:
The steering control function is segmented into two independent systems: a primary steering system for normal operation and a secondary torque-based steering system for backup. Each system operates independently with its own control logic, allowing the vehicle to maintain steering capability even when one system fails. The secondary system uses individual wheel torque actuators rather than a centralized steering mechanism.
Solution Approach 2:
The invention changes the control parameter from steering angle (in the primary system) to wheel torque (in the secondary system). By applying differential torque to individual wheels, the system achieves steering effect without relying on the traditional steering mechanism. This parameter change allows the backup system to function using a different physical principle, improving reliability.
2Measurement precision
If traditional steering control methods are used, then steering accuracy is maintained under normal conditions, but the system fails to provide steering control when malfunctions occur
Solution Approach 1:
The invention introduces an intermediary control layer that monitors the primary steering system and can activate the secondary torque-based steering system when malfunctions are detected. This intermediary layer includes a control unit that receives steering angle requests and distributes them to appropriate actuators, ensuring continuous steering control availability.
Solution Approach 2:
The system implements feedback control by continuously monitoring the actual steering angle and comparing it with the requested steering angle. When the difference exceeds a threshold indicating a malfunction, the system automatically switches to the secondary torque-based control mode, maintaining steering functionality through adaptive feedback response.
3Reliability
If wheel torque actuators are used for steering control, then redundant steering capability is achieved, but energy consumption increases
Solution Approach 1:
The system dynamically switches between primary and secondary steering modes based on operational needs and system status. The secondary torque-based system remains dormant during normal operation and is activated only when the primary system malfunctions or during specific maneuvering conditions, optimizing energy consumption while maintaining redundancy.
Solution Approach 2:
The wheel torque actuators serve multiple functions: they provide primary propulsion/braking control and simultaneously serve as a backup steering mechanism. This multi-functionality reduces the need for dedicated backup steering components and minimizes overall system energy consumption by utilizing existing actuators for dual purposes.
Data Source
AI summary
The present invention relates to a method for controlling a steering system of a vehicle (100). The steering system comprises individually controllable wheel torque actuators (103, 105) on a respective left (104) and right (106) steerable wheel of the vehicle, wherein the wheel torque actuators (103, 105) are controlled during a turning maneuver of the vehicle.