MDPS Steering Control With Adaptive Filtering for Stable Response
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Solution Overview
Problem
Existing Motor Driven Power Steering (MDPS) systems face challenges in enhancing responsiveness during autonomous driving while maintaining stability, particularly in emergency situations, due to noise interference and belt slip issues, which can lead to reduced control performance and safety risks.
Innovation Solution
An apparatus and method that includes a filtering unit to remove specific frequency components from the steering angle, a command steering angle control unit to adjust the cut-off frequency of a Low Pass Filter based on steering conditions, and a responsiveness improvement unit to compensate for steering angle errors, using a combination of band stop filters, notch filters, and lead-lag filters to enhance stability and responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the responsiveness of MDPS is increased during autonomous driving, then the ability to respond to emergency situations is improved, but control stability deteriorates due to vibration and noise
Solution Approach 1:
The system dynamically adjusts the cut-off frequency of the low pass filter based on driving conditions (autonomous vs. manual mode) and operational state (normal vs. belt slip). During autonomous driving, a higher cut-off frequency is applied to improve responsiveness, while during manual driving or normal operation, a lower cut-off frequency maintains stability. This dynamic adaptation resolves the contradiction between responsiveness and stability.
Solution Approach 2:
The invention changes the parameter of cut-off frequency according to different operating conditions. By adjusting this critical parameter, the system optimizes the balance between responsiveness (higher frequency passes through) and stability (lower frequency filtering applied) without requiring a fixed design compromise.
2Reliability
If a low pass filter is applied to remove noise from command steering angle, then the robustness to noise is improved, but the responsiveness and performance of the position controller deteriorate
Solution Approach 1:
The cut-off frequency of the low pass filter is made dynamic rather than fixed. During autonomous driving emergencies, the system temporarily increases the cut-off frequency to allow faster response, while during normal operation or manual driving, it maintains a lower frequency for noise filtering. This dynamic adjustment resolves the trade-off between noise robustness and responsiveness.
Solution Approach 2:
The system changes the cut-off frequency parameter based on operational context. By adjusting this parameter, the low pass filter becomes adaptive - providing strong noise filtering when needed while allowing high-frequency emergency commands to pass through when responsiveness is prioritized.
3Stability of the object's composition
If the cut-off frequency of the low pass filter is lowered to filter noise, then the stability is improved, but the responsiveness to emergency steering commands deteriorates
Solution Approach 1:
The system dynamically adjusts the cut-off frequency based on the driving mode and emergency detection. When an emergency situation is detected during autonomous driving, the cut-off frequency is temporarily raised to improve responsiveness. During normal operation or manual driving, the lower cut-off frequency maintains stability. This dynamic behavior resolves the contradiction.
Solution Approach 2:
The cut-off frequency parameter is adjusted according to operational conditions. The system transitions between different parameter settings (low for stability during normal operation, high for responsiveness during emergencies) based on real-time detection of driving mode and emergency situations.
4Speed
If the MDPS uses motor angle for control instead of steering angle, then the responsiveness is improved, but the reliability deteriorates due to belt slip
Solution Approach 1:
The system continuously monitors belt tension and detects belt slip conditions. When belt slip is detected, the feedback mechanism triggers a mode switch from motor angle control to steering angle control, ensuring reliability during critical events while maintaining responsiveness during normal operation.
Solution Approach 2:
The control parameter is dynamically changed based on belt slip detection. During normal operation, motor angle provides high responsiveness. When belt slip occurs, the system switches to steering angle as the control parameter, maintaining reliability despite the slight reduction in responsiveness.
Data Source
AI summary
An apparatus for controlling an MDPS may include: a filtering unit configured to filter a specific frequency from a first current steering angle provided from a steering angle sensor; a command steering angle control unit configured to remove noise of a first command steering angle inputted from an autonomous driving system, and output a second command steering angle; a steering angle position control unit configured to compensate for a first steering angle error corresponding to the difference between the second command steering angle and the first current steering angle filtered by the filtering unit, and output a first command current; and a responsiveness improvement unit configured to compensate for a second steering angle error corresponding to the difference between the second command steering angle and a second current steering angle provided from a motor, and apply the compensation result value to the steering angle position control unit.