Steering Control Device Hysteresis Adaptation
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Solution Overview
Problem
Existing steering control devices for steer-by-wire systems face challenges in accurately calculating and maintaining the hysteresis width of the axial force with respect to the steering angle, leading to discomfort in steering wheel movement and feedback.
Innovation Solution
A steering control device that includes a processing circuit capable of calculating a torque command value by adding a calculational hysteresis component to a torque component. The processing circuit adjusts the origin used to calculate the hysteresis component based on changes in vehicle speed and steering states, ensuring a consistent hysteresis width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a calculational hysteresis component is added to reflect the actual hysteresis status of axial force with respect to steering angle, then the accuracy of steering reaction force calculation is improved, but sudden changes in hysteresis width may cause discomfort in steering wheel movement and feedback
Solution Approach 1:
The patent applies dynamics by making the hysteresis width adaptive rather than fixed. The control device dynamically adjusts the hysteresis width of the calculational hysteresis component based on vehicle speed and steering angle conditions. This allows the system to reflect actual hysteresis status accurately while preventing sudden changes that would cause steering discomfort, thereby resolving the contradiction between measurement precision and harmful factors.
Solution Approach 2:
The patent changes the hysteresis width parameter based on operating conditions. Specifically, the hysteresis width is adjusted according to vehicle speed and steering angle, allowing the system to maintain high calculation accuracy across different conditions while avoiding sudden parameter changes that would manifest as steering wheel movement discomfort or abnormal feedback.
2Measurement precision
If the hysteresis width is increased to reflect actual hysteresis status at low vehicle speeds, then the accuracy of axial force calculation is improved, but the steering wheel movement may become unstable
Solution Approach 1:
The patent makes the hysteresis width dynamic rather than static. At low vehicle speeds where actual hysteresis is larger, the system increases the calculational hysteresis width to improve accuracy. However, it also implements rate limiting or smoothing mechanisms that prevent sudden jumps in hysteresis width, thereby maintaining steering wheel movement stability while improving calculation accuracy.
Solution Approach 2:
The patent applies preliminary action by anticipating potential instability before it occurs. When vehicle speed changes or steering conditions transition, the system proactively adjusts the hysteresis width in a controlled manner rather than allowing abrupt changes. This preliminary control prevents steering wheel movement instability while still achieving accurate axial force calculation.
3Speed
If the hysteresis width is decreased for high vehicle speeds, then the steering response becomes more responsive, but the accuracy of reflecting actual hysteresis status deteriorates
Solution Approach 1:
The patent changes the hysteresis width parameter based on vehicle speed. At high speeds where actual hysteresis is smaller, the system decreases the calculational hysteresis width to improve steering responsiveness. The parameter is adjusted according to pre-defined speed thresholds, allowing the system to optimize between responsiveness and accuracy for different operating conditions.
Data Source
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AI summary
In a steering control device configured to control a steering system (2) where a steering torque required for steering a steering wheel (3) is changed using a motor torque, a processing circuit includes a first calculation situation where a calculational hysteresis component for adding a first hysteresis characteristic to a torque component is calculated and a second calculation situation where the calculational hysteresis component for adding a second hysteresis characteristic to the torque component is calculated. In the second calculation situation after change from the first calculation situation, the processing circuit calculates a value corresponding to an origin in the second hysteresis characteristic at a time when the calculational hysteresis component enabling a value of the calculational hysteresis component at a timing of the change from the first calculation situation to be maintained is calculated, and calculates the calculational hysteresis component using the calculated value as the origin.