Steering Return Control Damping Compensation for MDPS
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Solution Overview
Problem
Conventional Motor Driven Power Steering (MDPS) systems experience a slight sense of difference in the on-center region when returning the steering wheel after a large steering angle, due to insufficient self-alignment torque and frictional behavior, leading to overshoot and reduced return velocity.
Innovation Solution
A steering return control apparatus and method that includes sensors for column torque, steering angle, vehicle velocity, and lateral acceleration, with a damping controller adjusting damping compensation gains to increase return velocity by decreasing damping slope based on column velocity, and linearly controlling gains for column torque, velocity, and lateral acceleration to minimize differences in the on-center region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the damping amount is adjusted to increase return velocity, then the return performance is improved, but overshoot occurs in the on-center region
Solution Approach 1:
The damping amount is made dynamically adjustable based on the steering angle. The controller increases damping amount when the steering angle is large to prevent overshoot, and decreases damping amount when the steering angle is small to allow faster return. This dynamic adjustment resolves the contradiction by adapting the damping characteristic to the current operating state.
Solution Approach 2:
The damping amount parameter is changed according to the steering angle threshold. When steering angle exceeds the threshold, damping amount is increased to suppress overshoot; when steering angle is below the threshold, damping amount is decreased to improve return velocity. This parameter change strategy resolves the contradiction by optimizing damping for different operational phases.
2Stability of the object's composition
If the damping amount is adjusted to reduce overshoot, then the stability is improved, but the return velocity is lowered
Solution Approach 1:
The damping amount is dynamically adjusted based on the steering angle. High damping is applied only when necessary (large steering angle) to reduce overshoot, while low damping is applied during the return phase (small steering angle) to maintain high return velocity. This dynamic control resolves the contradiction by applying different damping levels at different stages of the steering return process.
Solution Approach 2:
The damping amount parameter is changed based on the steering angle threshold comparison. When steering angle is below the threshold, damping amount is set to a lower value to maximize return velocity; when steering angle exceeds the threshold, damping amount is increased to minimize overshoot. This parameter switching resolves the contradiction by optimizing for different performance requirements at different operating points.
3Productivity
If the damping amount is properly adjusted, then the return performance is optimized, but a slight sense of difference occurs in the on-center region when driver turns at similar velocity
Solution Approach 1:
The damping amount parameter is changed based on steering angle threshold. When steering angle is small (in on-center region), damping amount is decreased to match the driver's steering velocity and eliminate the sense of difference. When steering angle is large, damping amount is increased to ensure proper return performance. This parameter adjustment resolves the contradiction by adapting damping to match driver input characteristics in the on-center region.
Solution Approach 2:
The damping amount is dynamically adjusted based on the steering angle and driver input characteristics. In the on-center region where driver turns at velocity similar to return velocity, damping is reduced to create a natural feel. During large angle returns, damping is increased to ensure controlled return. This dynamic adaptation resolves the contradiction by optimizing both return performance and driver comfort.
Data Source
AI summary
A steering return control apparatus of MDPS may include: a column torque sensor configured to sense a column torque of a steering wheel; a steering angle sensor configured to measure a steering angle of the steering wheel; a column velocity calculator configured to calculate a column velocity at which a steering column is rotated; a vehicle velocity sensor configured to sense a vehicle velocity; a lateral acceleration sensor configured to sense a lateral acceleration of the vehicle; and a damping controller configured to detect a damping compensation gain in an on-center region according to at least one of the column torque, the column velocity and the lateral acceleration, and applies the damping compensation gain to a default damping amount, when the steering angle falls within the on-center region while at least one of the column torque, the column velocity and the vehicle velocity satisfies a preset damping compensation condition.