Steering Control Torque Calculation for Stability
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Solution Overview
Problem
Steering control systems in steer-by-wire systems face challenges in accurately transmitting road surface information to drivers, leading to issues with vibration characteristics and control stability due to changes in axial force gradients and hysteresis widths at different vehicle speeds.
Innovation Solution
A steering control device that calculates a torque command value using separate components for different vehicle speed situations, adjusting the axial force gradient to manage hysteresis characteristics and reduce vibration, by employing a torque component calculating unit that accounts for both angle and current axial forces, and a mediation unit to smoothly transition between calculation situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the distribution proportion of the current axial force is increased to accurately transmit road surface information, then the axial force gradient increases and road surface information transmission improves, but the hysteresis width decreases and control stability deteriorates
Solution Approach 1:
The patent dynamically adjusts the distribution proportion between angle axial force and current axial force based on vehicle speed. At low speeds, the angle axial force proportion is increased to maintain larger hysteresis width and better control stability. At high speeds, the current axial force proportion is increased to improve road surface information transmission accuracy. This dynamic adjustment resolves the contradiction by adapting the force distribution to operating conditions.
Solution Approach 2:
The patent changes the distribution proportion parameter of axial forces based on vehicle speed thresholds. By adjusting this parameter dynamically, the system optimizes both control stability and road surface information transmission accuracy for different operating conditions, resolving the contradiction between these two requirements.
2Measurement precision
If the axial force gradient is increased to improve road surface information transmission, then the steering reaction force accuracy improves, but vibration characteristics appear and control stability deteriorates
Solution Approach 1:
The patent dynamically adjusts the axial force gradient based on vehicle speed. At low speeds, a smaller axial force gradient is used to avoid excessive vibrations. At high speeds, a larger axial force gradient is applied to improve steering reaction force accuracy. This dynamic adjustment resolves the contradiction between accuracy and vibration.
Solution Approach 2:
The patent changes the axial force gradient parameter according to vehicle speed conditions. By adjusting this parameter dynamically, the system achieves high steering reaction force accuracy at high speeds while maintaining control stability and minimizing vibrations at low speeds.
3Measurement precision
If the hysteresis width is increased to reflect actual hysteresis status, then the steering reaction force accuracy improves, but the axial force gradient decreases and control responsiveness deteriorates
Solution Approach 1:
The patent dynamically adjusts the hysteresis width based on vehicle speed. At low speeds, a larger hysteresis width is used to accurately reflect actual hysteresis status and improve steering reaction force accuracy. At high speeds, a smaller hysteresis width is applied to maintain control responsiveness. This dynamic adjustment resolves the contradiction between accuracy and responsiveness.
Data Source
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AI summary
A steering control device (1) includes a torque command value calculating unit (52) configured to calculate a torque command value which is a target value of a motor torque when operation of a motor is controlled such that the motor torque is generated. The torque command value calculating unit (52) includes a first component calculating unit configured to calculate a first component, a second component calculating unit configured to calculate a second component, and a torque component calculating unit configured to calculate a torque component. The first component calculating unit is configured to add a calculational hysteresis component to the first component such that hysteresis characteristics with respect to change of a specific state variable are provided. The torque component calculating unit (52) is configured to perform calculation in a first calculation situation and calculation in a second calculation situation.