Phase-lead filter decouples power steering stability from driver feel
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power steering servo-control methods face challenges in reconciling effective assistance, comfortable steering feel, and stability, particularly due to the interdependence of assist gain and derivative gain, which limits the optimization of both assistance and feeling feedback.
Innovation Solution
A servo-control method that generates the motor torque setpoint from a filtered proportional component using a phase-lead filter and a derivative feedback component, allowing for independent adjustment of assist and derivative gains to enhance stability and feeling feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a high assist gain is used to provide effective steering assistance and good maneuver comfort, then the steering assistance and maneuverability are improved, but the servo-control stability deteriorates and oscillations occur
Solution Approach 1:
The control signal is segmented into two independent components: a proportional component filtered by a phase-lead filter for stability, and a derivative feedback component for feeling optimization. This segmentation allows each component to be optimized independently without compromising the other.
Solution Approach 2:
The invention changes the parameter structure by introducing a phase-lead filter with specific frequency characteristics (first and second cutoff frequencies) to modify the proportional component's frequency response, enabling high assist gain while maintaining stability through frequency-domain parameter optimization.
2Ease of operation
If a derivative feedback is introduced to improve steering feeling and reduce stick-slip effects, then the steering responsiveness and feeling are improved, but the servo-control stability deteriorates
Solution Approach 1:
The control signal is segmented into two independent components: a proportional component filtered by a phase-lead filter for stability, and a derivative feedback component for feeling optimization. This segmentation allows each component to be optimized independently without compromising the other.
3Ease of operation
If the assist gain and derivative gain are both maximized to optimize assistance and feeling independently, then the steering assistance and feeling feedback are improved, but the interdependence causes stability to deteriorate
Solution Approach 1:
The control signal is segmented into two independent components: a proportional component filtered by a phase-lead filter for stability, and a derivative feedback component for feeling optimization. This segmentation allows each component to be optimized independently without compromising the other.
Solution Approach 2:
The phase-lead filter acts as an intermediary that processes the proportional component to provide phase lead compensation, enabling high assist gain while maintaining stability. This intermediary allows the derivative gain to be optimized independently for feeling feedback.
Data Source
AI summary
A method for controlling a power steering device including a steering assist motor and a steering wheel. In the method, a steering wheel torque setpoint is generated, the actual steering wheel torque actually exerted by the driver on the steering wheel is measured, the difference, the so-called “steering wheel torque error”, between the steering wheel torque setpoint and the actual steering wheel torque is determined, then a motor torque setpoint for the steering assist motor is generated from a first filtered proportional component on one hand, obtained by filtering via a phase-lead filter the steering wheel torque error weighted by a first assist gain, and from a second derivative return component on the other hand, obtained by calculating the time derivative of the actual steering wheel torque and weighting the derivative by means of a second derivative gain.