Steering Reaction Force Limiting for Vehicle Stability Control
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Solution Overview
Problem
Conventional stability control systems for vehicles cause an unpleasant sensation for drivers due to fluctuating steering reaction forces when correcting for external disturbances, such as crosswinds, as they require imparting a steering reaction force component to urge a turn.
Innovation Solution
A stability control device that limits the steering reaction force to a predetermined value or less, using a steer-by-wire system to control the turning part based on the steering unit's turning amount and yaw angle, and employs feedback controls to reduce yaw angle and lateral position deviations without necessitating a steering reaction force for external disturbance suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a steering reaction force component is imparted to suppress external disturbance, then vehicle stability is improved, but driver comfort deteriorates due to unpleasant sensation
Solution Approach 1:
The patent segments the steering reaction force into multiple components: a basic steering reaction force for normal steering operation and a separate external disturbance suppression component. By dividing the total steering reaction force into these distinct segments, the system can independently control each component, allowing the suppression force to be applied without affecting the basic steering feel, thus resolving the contradiction between vehicle stability and driver comfort
Solution Approach 2:
The patent changes the parameters of the steering reaction force by introducing a predetermined threshold value. The external disturbance suppression steering reaction force is calculated based on yaw rate and vehicle speed, but is limited to not exceed the threshold. This parameter change allows the system to provide sufficient suppression force for stability while preventing excessive force that would cause unpleasant sensations, thereby resolving the contradiction
2Reliability
If steering reaction force is increased to suppress yaw angle, then vehicle stability is improved, but steering reaction force fluctuation increases causing unpleasant sensation
Solution Approach 1:
The patent employs feedback control by continuously monitoring the calculated external disturbance suppression steering reaction force and comparing it against the predetermined threshold. When the calculated force exceeds the threshold, the feedback mechanism limits it to the threshold value. This feedback loop ensures that yaw angle suppression is maintained while preventing excessive fluctuations in steering reaction force, resolving the contradiction between yaw suppression effectiveness and steering reaction force stability
Data Source
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AI summary
A stability control device capable of reducing an unpleasant sensation imparted to a driver is provided. [Solution] When left and right front wheels 5FL, 5FR mechanically separated from a steering wheel 6 are to be controlled, the turning angle is controlled based on a SBW command turning angle that corresponds to a steering angle of the steering wheel 6 and an external disturbance suppression command turning angle for suppressing a yaw angle and displacement from the center of the lane, and meanwhile, the steering reaction force corresponding to the external disturbance suppression command turning angle for suppressing the yaw angle is limited to a predetermined value or less.