MDPS Friction Compensation Torque Gain Adjustment
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Solution Overview
Problem
In motor-driven power steering (MDPS) systems, friction compensation and damping control torques overlap in the middle/high-speed region, degrading damping control performance and affecting on-center steering feeling, vehicle recoverability, torque build-up, and hand-free stability.
Innovation Solution
A friction compensation control apparatus and method that adjusts friction compensation torque based on damping torque, using a gain adjusting unit to decouple damping and friction compensation periods, reducing friction compensation torque when damping torque increases and increasing it when damping torque decreases, thereby preventing performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If friction compensation torque is applied continuously, then steering smoothness is improved, but damping control performance deteriorates in middle/high-speed region
Solution Approach 1:
The friction compensation torque is made dynamic by adjusting its gain based on the damping torque magnitude. When damping torque is large (middle/high-speed region), the gain is reduced to prevent interference with damping control. When damping torque is small (low-speed region), the gain is increased to improve steering smoothness. This dynamic adjustment resolves the contradiction between continuous friction compensation and damping control performance.
Solution Approach 2:
The gain parameter of the friction compensation torque is changed according to the damping torque magnitude. The control system monitors the damping torque and adjusts the friction compensation gain accordingly, transforming the friction compensation from a static continuous signal to a dynamic parameter-adjusted signal that adapts to operating conditions, thereby resolving the performance conflict.
2Adaptability or versatility
If friction compensation and damping control are performed simultaneously, then comprehensive steering control is achieved, but control periods overlap causing performance degradation
Solution Approach 1:
The system dynamically adjusts the friction compensation gain based on the damping torque magnitude, allowing the two control functions to coexist without fixed temporal separation. This dynamic parameter adjustment enables comprehensive control while preventing period overlap interference, as the friction compensation automatically adapts its strength based on the damping control needs.
3Measurement precision
If friction compensation torque is increased, then steering precision is improved, but hand-free stability deteriorates due to excessive torque interference
Solution Approach 1:
The friction compensation torque parameter (gain) is changed dynamically based on the damping torque magnitude. In regions where damping torque is large, the gain is reduced to maintain hand-free stability. In regions where damping torque is small, the gain is increased to improve steering precision. This parameter adaptation resolves the contradiction between precision and stability.
Data Source
AI summary
A friction compensation control apparatus of a motor driven power steering (MDPS) system may include: a damping control unit configured to detect a damping torque of the MDPS system; and a friction compensation control module configured to detect a friction compensation torque using a column torque, a motor speed, and a vehicle speed, and adjust the detected friction compensation torque according to the magnitude of the damping torque.