Steering Torque Control With Phase-Advanced Derivative Feedback
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Solution Overview
Problem
Existing steering control systems face challenges in balancing stability and responsiveness, particularly in steer-by-wire systems where mechanical connection between the steering wheel and steered wheels is disconnected.
Innovation Solution
A steering control device and method that utilizes a proportional and derivative element with an enlarging phase controller to enhance the phase advancement of the derivative element relative to the proportional element, improving responsiveness and stability by controlling steering torque through a motor mechanically connected to the operating member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control is performed on steering torque using conventional proportional and derivative elements, then steering torque can be controlled to target value, but responsiveness and stability cannot be sufficiently improved due to limited phase advancement
Solution Approach 1:
The patent changes the phase parameter of the derivative element by introducing an enlarging phase controller that increases the phase advancement of the derivative element relative to the proportional element. This parameter change allows the system to achieve both improved stability and responsiveness by optimizing the phase relationship between control components.
Solution Approach 2:
The patent employs feedback control where the actual steering torque is continuously measured and compared with the target steering torque, and the difference (error) is used to adjust the control output. The enlarging phase controller enhances this feedback mechanism by optimizing the phase characteristics of the derivative term, allowing for better damping of oscillations while maintaining rapid response.
2Speed
If the phase advancement of the derivative element is increased to improve responsiveness, then steering response improves, but system stability may deteriorate due to excessive phase shift
Solution Approach 1:
The enlarging phase controller dynamically adjusts the phase advancement parameter of the derivative element within optimal ranges. By carefully controlling the degree of phase advancement rather than maximizing it indiscriminately, the system achieves improved responsiveness while preventing excessive phase shift that would cause instability.
Solution Approach 2:
The patent introduces dynamic phase adjustment through the enlarging phase controller, which adapts the phase characteristics of the derivative element based on operating conditions. This dynamic adjustment allows the system to optimize responsiveness when needed while maintaining stability under varying steering conditions, rather than using fixed phase parameters.
Data Source
AI summary
A steering torque control process includes a process of calculating a manipulated variable for controlling steering torque to target steering torque by using a proportional element and a derivative element according to a difference between the steering torque and the target steering torque. At least one of the two elements, namely the proportional element and the derivative element, includes an enlarging phase controller. The enlarging phase controller is a controller that enlarges a degree to which a phase of the derivative element is advanced with respect to a phase of the proportional element.