Virtual Steering Model Torque Control for Nonlinear Handling
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Solution Overview
Problem
Conventional motor driven power steering control systems using open loop-based methods require repetitive tuning and struggle to accurately vary target steering torque with large steering angles, limiting their performance and efficiency.
Innovation Solution
A virtual steering system model is implemented, where the column stiffness torque is determined using torsional displacement, with varying rates of change across different displacement amplitudes, and the target steering torque is calculated as a sum of column stiffness and damping torques, incorporating vehicle speed for assist gain, enabling feedback control to track the determined torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional open loop-based control is used, then the control system is simple to implement, but the control performance varies according to hardware dispersion and requires repetitive tuning
Solution Approach 1:
The patent implements closed-loop feedback control by measuring the actual steering torque and comparing it with the target steering torque generated from the virtual steering system model. The controller adjusts the motor output based on the torque difference, ensuring consistent control performance that compensates for hardware variations and eliminates the need for repetitive tuning.
2Productivity
If conventional virtual steering system model is used, then development efficiency is improved through feedback control, but the target steering torque cannot vary according to steering angle change in large steering angle regions
Solution Approach 1:
The patent introduces dynamic characteristics into the virtual steering system model by incorporating column damping torque that varies with steering angle velocity and column stiffness torque that varies with torsional displacement. This allows the target steering torque to dynamically adapt to different steering conditions, particularly in large steering angle regions, while maintaining the development efficiency benefits of virtual modeling.
3Device complexity
If linear column stiffness torque characteristics are used, then the control logic is simple, but the steering performance cannot be optimized in off-center regions with large steering angles
Solution Approach 1:
The patent applies local quality by making the column stiffness and damping characteristics position-dependent. The virtual steering system model uses different stiffness and damping parameters for different steering angle regions, allowing optimized steering performance in off-center regions while maintaining simpler characteristics in center regions. This localized optimization improves overall steering performance without requiring completely complex control logic throughout the entire system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for improved steering performance and tuning efficiency by enabling nonlinear characteristics in target steering torque, particularly in off-center regions with large steering angles, enhancing driver control and system robustness.
Implementation Method 1
determining a column stiffness torque using torsional displacement of the column as a variable in the set virtual steering system model
Implementation Method 2
determining a column stiffness torque using torsional displacement of the column
Implementation Method 3
a column damping torque determined using a change rate of the torsional displacement of the column as a variable
Data Source
AI summary
A motor driven power steering control method may include setting a virtual steering system model including a column connecting a steering wheel to a rack gear, determining a column stiffness torque using torsional displacement of the column in the set virtual steering system model, and determining a target steering torque based on the determined column stiffness torque.