Motor-Driven Power Steering Torque Compensation for Sensor Failure
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Solution Overview
Problem
Conventional loss of assist mitigation (LOAM) compensation logic in motor-driven power steering systems is inadequate for high-performance vehicles, leading to excessive steering effort when the torque sensor fails, as it cannot effectively manage the higher steering loads and torque requirements of these vehicles.
Innovation Solution
A system and method that includes a steering condition-dependent compensation device to adjust the steering torque assist compensation amount based on the steering wheel's position and movement, reducing the basic steering torque assist compensation when returning the wheel to the center or releasing it, thereby reducing driver effort and maintaining proper steering effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LOAM compensation logic is applied to high-performance vehicles, then basic steering torque assist compensation is provided, but steering effort becomes excessively heavy when returning the steering wheel to center
Solution Approach 1:
The patent applies dynamics by making the steering torque compensation amount variable based on steering conditions. The controller dynamically adjusts the compensation amount using different gain values (first gain during steering, second gain when returning to center) according to the steering wheel's position and movement state, thereby optimizing steering effort across different operating conditions rather than using a fixed compensation value.
Solution Approach 2:
The patent changes the parameter of steering torque compensation amount based on steering conditions. By detecting steering angle and steering speed, the system switches between different gain parameters (first gain > second gain) to adjust the compensation magnitude, ensuring appropriate steering effort whether the wheel is being turned or returned to center position.
2Speed
If high gear ratio and reducer are equipped in steering gearbox for faster steering response, then steering response speed is improved, but steering load increases leading to heavier steering effort
Solution Approach 1:
The patent compensates for the increased steering load caused by high gear ratio and reducer by dynamically adjusting the motor torque compensation parameter. The controller calculates appropriate compensation amounts based on steering conditions (angle and speed), effectively counterbalancing the mechanical advantage gained from the high gear ratio while offsetting the increased return spring force that causes heavy steering effort during wheel return.
3Reliability
If high grip tires are equipped to improve driving limit, then contact grip with ground is increased, but steering load increases causing heavier steering effort
Solution Approach 1:
The patent addresses the increased steering load from high grip tires by implementing conditional torque compensation. The controller adjusts the steering assist torque parameter based on detected steering conditions, providing sufficient compensation to counterbalance the higher friction and grip forces from performance tires, thereby maintaining acceptable steering effort despite the increased mechanical resistance.
Data Source
AI summary
A system and a method of controlling a motor-driven power steering are disclosed. A basic steering torque assist compensation is made according to a LOAM compensation logic under a steering condition such as steering of a steering wheel and holding of the steering wheel after steering, and an additional steering torque compensation is made to reduce the basic steering torque assist compensation amount when returning the steering wheel to the center or releasing the steering wheel in a restoring direction, thereby reducing steering effort felt by a driver when returning the steering wheel to the center or releasing the steering wheel in the restoring direction, and thus maintaining proper steering effort when a torque sensor of a high-performance vehicle fails.