Vehicle Steering Torque Control for Rotation Stepping Prevention
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Solution Overview
Problem
In vehicle steering systems with electric power steering (EPS), the efficiency of torque transfer from the electric motor to the steering mechanism can fluctuate, leading to 'rotation stepping' where the electric motor stops or decreases in rotation, preventing intended vehicle behavior during high-torque steering assist controls like lane departure prevention.
Innovation Solution
A steering control apparatus that calculates a target yaw rate and torque, and includes a target torque corrector to increase the torque by applying a correction gain when the motor rotation angle variation is within a set value, thereby preventing rotation stepping by stabilizing torque transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-torque steering assist control is applied, then steering assist effectiveness is improved, but rotation stepping occurs causing unstable vehicle behavior
Solution Approach 1:
The control apparatus predicts future steering torque requirements based on current steering angle and rate of change, then proactively adjusts motor output torque before the actual torque demand occurs. This preliminary action prevents torque deficiency that would otherwise cause rotation stepping and unstable vehicle behavior during high-torque steering assist operations.
Solution Approach 2:
The system dynamically adjusts the steering assist torque by calculating a predicted torque component based on real-time steering angle and its rate of change. This dynamic adjustment allows the motor output torque to adapt to varying steering conditions, maintaining stable vehicle behavior while providing effective steering assist across different operating scenarios.
2Speed
If torque transfer efficiency is increased, then steering response is improved, but rotation stepping occurs due to torque fluctuation
Solution Approach 1:
By predicting future torque demands and adjusting motor output accordingly, the system ensures continuous smooth torque transfer to the steering mechanism. This prevents torque fluctuations that would cause rotation stepping, thereby maintaining both fast steering response and stable torque transfer throughout the steering operation.
3Power
If steering assist torque is increased for lane departure prevention, then lane departure prevention effectiveness is improved, but rotation stepping occurs preventing intended vehicle behavior
Solution Approach 1:
The control apparatus calculates predicted steering torque based on current steering angle and rate of change, then proactively adjusts motor output torque before high-torque demands occur during lane departure prevention. This ensures the motor can deliver the required torque without rotation stepping, enabling reliable execution of intended vehicle behavior for lane departure prevention.
Solution Approach 2:
The system dynamically adjusts torque output based on real-time steering conditions, providing high torque when needed for lane departure prevention while preventing rotation stepping through continuous adaptation. This maintains both the effectiveness of lane departure prevention and the reliability of vehicle behavior execution.
Data Source
AI summary
A steering control apparatus of vehicle includes a target yaw rate calculator, a target torque calculator, and a target torque corrector. The target yaw rate calculator calculates a target yaw rate that allows a vehicle to travel along a traveling course. The target torque calculator calculates target torque that is torque of an electric motor and allows the target yaw rate to be generated. The target torque corrector performs a correction process that calculates a correction gain directed to the target torque and corrects, with the correction gain, the target torque to cause the target torque to be increased. The target torque corrector performs the correction process when an instruction value based on the target torque is varied at a constant rate and on a condition that an absolute value of a motor rotation angle variation amount becomes equal to or less than a set value.