Steer-by-Wire Active Return Torque Control
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Solution Overview
Problem
Steer-by-wire steering systems lack effective self-alignment into a neutral position, leading to rapid steering wheel return and potential overshooting, which is disturbing for drivers and requires a more robust active return function compared to electromechanical systems.
Innovation Solution
A method for controlling a steer-by-wire steering system that includes determining base and hands-off self-aligning torques, calculating a resulting self-aligning torque based on the driver's operating state, and using a feedback actuator to rotate the steering wheel into a defined position at a pleasant self-aligning speed, with a weighting unit adapting the steering feel to ensure smooth alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the active return function is implemented in steer-by-wire steering systems, then the steering wheel can self-align into a neutral position, but the steering wheel may turn back too rapidly and cause overshooting
Solution Approach 1:
The system dynamically adjusts the self-aligning torque based on the detected operating state (hands-on or hands-off). When hands-off state is detected, the system reduces the self-aligning torque to prevent rapid steering wheel return and overshooting, while maintaining adequate self-alignment capability when the driver's hands are on the wheel
Solution Approach 2:
A steering wheel monitoring means continuously detects the operating state (hands-on/hands-off) and provides feedback to the control unit, which then adjusts the active return function accordingly. This closed-loop feedback mechanism ensures the steering wheel returns to neutral position appropriately without causing disturbing movements
2Speed
If the self-aligning torque is increased for rapid centering, then the steering wheel returns to neutral position faster, but it causes disturbing movements and overshooting
Solution Approach 1:
The system changes the parameter of self-aligning torque based on the detected operating state. In hands-off state, the self-aligning torque is reduced to a lower value that prevents overshooting, while in hands-on state, the normal self-aligning torque is maintained. This parameter adaptation allows rapid centering when needed while preventing harmful movements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method ensures the steering wheel self-aligns into a neutral position without uncontrolled movements, providing a pleasant and stable steering experience by adapting the self-aligning torque to the driver's state, preventing overshooting and ensuring smooth centering.
Implementation Method 1
a feedback actuator (FPA) to be provided on the steering wheel or the steering column, which feedback actuator imparts a steering feel
Implementation Method 2
This uses a torque sensor (TSU) to measure the manual torque at the steering wheel
Data Source
AI summary
A method of controlling a steer-by-wire steering system for motor vehicles is disclosed for the calculation of a resulting self-aligning torque of a feedback actuator in a manner which is dependent on an operating state (hands-on/hands-off). The method includes determining of a base self-aligning torque for a first operating state, in which there is hand contact by a driver on a steering wheel, determining a hands-off self-aligning torque for a second operating state, in which there is no hand contact by the driver on the steering wheel, determining a self-aligning speed of the steering wheel for the first operating state and for the second operating state, and determining the resulting self-aligning torque on the basis of the base self-aligning torque or the hands-off self-aligning torque, as a result of which the steering wheel rotates at the defined self-aligning speed into the defined position.