Motor Driven Power Steering Torque Control for Rack Collision Prevention
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Solution Overview
Problem
In motor driven power steering systems, the collision between the stopper of a rack-bar and the inner ball joint socket (housing) of a gearbox during full steering turns causes noise and mechanical damage, which existing systems fail to adequately mitigate.
Innovation Solution
A control method and apparatus that set a reference point for the motor angle, estimate steering angular speed and angle, and adjust output torque using a control unit, reducing impact by detecting decouple and vehicle speed gains, and compensating torque to prevent collision between the rack-bar stopper and IBJ socket.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the steering angle is increased to achieve full turn steering, then the steering performance is improved, but the collision between the stopper and IBJ socket causes noise and mechanical damage
Solution Approach 1:
The control unit applies a counteracting torque to the motor before the rack-bar stopper collides with the IBJ socket. When the steering angle reaches a predetermined range approaching the full turn position, the control unit generates a torque opposite to the steering direction to reduce the impact force, preventing mechanical damage and noise while allowing the steering operation to complete
Solution Approach 2:
The system detects the steering angle and angular speed to predict the collision risk in advance. Before the actual collision occurs, the control unit adjusts the motor torque to minimize impact, performing the protective action preemptively rather than reactively after collision detection
2Power
If the output torque is increased to assist steering, then the steering assist performance is improved, but the impact during full turn causes mechanical damage and noise
Solution Approach 1:
The control unit dynamically adjusts the output torque based on real-time steering conditions. During normal steering operations, high torque is provided for excellent assist performance. When the steering angle approaches the full turn position and collision risk increases, the torque is automatically reduced or reversed to prevent impact, maintaining both performance and reliability across different operating conditions
Solution Approach 2:
The system changes the torque parameter dynamically based on steering angle and angular speed. By monitoring these parameters, the control unit identifies when the system is approaching a hazardous state (full turn collision) and adjusts the torque parameter accordingly to prevent damage while maintaining assist performance during safe operating ranges
Data Source
AI summary
A method for controlling a motor driven steering system includes setting a reference point of a motor angle by a control unit, estimating a steering angular speed and a steering angle using the reference point by the control unit, determining whether the steering angle is included within a predetermined setting range by the control unit, and controlling an output torque of the motor driven steering system by the control unit using the steering angular speed and the steering angle, when the steering angle is included within the setting range.