Steering Control System Abnormal Vehicle Speed Handling
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Solution Overview
Problem
Existing steering control systems face challenges in accurately determining vehicle speed, leading to inappropriate steering wheel operations when the vehicle speed value is abnormal, as they may incorrectly enable rotation angle feedback control, preventing users from properly operating the steering wheel.
Innovation Solution
A steering control system with a steering operation processing circuit that includes a basic controlled variable calculation, rotation angle command value calculation, feedback calculation processing, control processing, and limited-state setting circuit, which sets a provisional vehicle speed value during abnormality determination periods to limit the influence of rotation angle feedback control, ensuring users can operate the steering wheel effectively, even when the vehicle is stationary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rotation angle feedback control is enabled based on abnormal vehicle speed value, then the system attempts to maintain steering assistance, but the user cannot appropriately operate the steering wheel
Solution Approach 1:
The system applies preliminary anti-action by detecting abnormal vehicle speed values and proactively limiting the rotation angle feedback control before it can adversely affect steering wheel operability. The control limitation is enacted in advance to prevent the harmful effect of inappropriate feedback control during abnormal conditions.
Solution Approach 2:
The system extracts the rotation angle feedback control function from the overall steering control system during abnormal vehicle speed conditions. By separating and limiting this specific control component, the system maintains other steering assistance functions while preventing the harmful effects of feedback control when vehicle speed data is unreliable.
2Measurement precision
If the system uses detected vehicle speed value for control, then it achieves accurate steering assistance, but the control accuracy deteriorates when vehicle speed value is abnormal
Solution Approach 1:
The system introduces an intermediary mechanism that mediates between the detected vehicle speed value and the control variable calculation. When the detected vehicle speed is abnormal, the intermediary limits the influence of this inaccurate data on the control variable, preventing propagation of measurement errors to the control output.
Solution Approach 2:
The system changes the parameter usage by detecting abnormalities in the vehicle speed parameter and adjusting how this parameter influences the control variable. When abnormality is detected, the system modifies the control strategy to limit the weight or influence of the suspicious vehicle speed parameter, thereby maintaining control accuracy despite poor measurement quality.
3Ease of operation
If the system limits the second component variation range during abnormality determination period, then steering wheel operability is maintained, but the rotation angle feedback control effectiveness is reduced
Solution Approach 1:
The system applies dynamics by making the control parameter (second component variation range) adjustable based on operating conditions. During abnormality determination periods, the variation range is dynamically limited to maintain steering wheel operability. When normal conditions are restored, the limitation is removed to recover full feedback control effectiveness.
Data Source
AI summary
The microcomputer calculates a first assist component based on a vehicle speed value and a steering torque, calculates a rotation angle command value based on at least the vehicle speed value and a first assist component, and calculates a second assist component by adjusting a rotation angle to the rotation angle command value through feedback control. The microcomputer sets a limited state 1 where the second assist component is disabled when a vehicle is stationary. During an abnormality determination period during which the vehicle speed value is determined to be abnormal, the microcomputer sets the vehicle speed value to a provisional vehicle speed value. Further, in a limited state 2 that is set when the vehicle is stationary during the abnormality determination period, the microcomputer calculates the first assist component based on a provisional vehicle speed value, and disables the second assist component.