Steering Wheel Torque Estimation via Driver Model
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Solution Overview
Problem
The existing electric power steering systems face challenges in accurately estimating driver steering wheel torque due to nonlinear characteristics of the mechanism, leading to inaccuracies in torque sensing and steering intention detection, which affects the precision of feedback control.
Innovation Solution
A method that models the steering system using state variables to estimate driver steering wheel torque, compensating for differences between sensed and actual torque, and uses this estimation to improve feedback control logic, thereby enhancing the precision of steering assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If torque sensing values from torque sensors are used directly as driver steering wheel torque for controlling the electric power steering system, then the control system is simple and easy to implement, but the measurement precision deteriorates because the sensed torque does not accurately reflect the actual driver steering intention due to nonlinear mechanism characteristics
Solution Approach 1:
A driver model is introduced as an intermediary between the torque sensor and the control system. The driver model processes the torque sensor signal and vehicle speed information to generate an estimated driver steering wheel torque that more accurately reflects the driver's intended steering action, while the overall system remains relatively simple
Solution Approach 2:
The direct mechanical torque sensing approach is replaced with a computational estimation approach using a driver model that combines torque sensor data with vehicle speed information. This substitution allows the system to infer driver intention more accurately without requiring complex mechanical modifications
2Measurement precision
If a driver model based on vehicle speed and torque sensor signal is constructed to estimate driver steering wheel torque, then the measurement precision of driver steering intention improves, but the device complexity increases due to additional modeling and computation requirements
Solution Approach 1:
The driver model serves multiple functions simultaneously: it filters torque sensor signals, compensates for nonlinear mechanism characteristics, incorporates vehicle speed information, and generates estimated driver steering torque. This multi-functionality reduces the need for separate components and maintains system simplicity while improving measurement precision
3Ease of operation
If the torque sensing value is used directly without compensation, then the ease of operation is maintained, but the reliability of steering control deteriorates due to inaccurate representation of driver steering intention
Solution Approach 1:
The driver model implements a feedback mechanism where the estimated driver steering wheel torque is fed back to the control system to replace the raw torque sensor signal. This feedback loop continuously adjusts the control commands based on the more accurate torque estimation, improving steering control reliability while maintaining ease of operation through automated compensation
Data Source
AI summary
A method of operating a motor vehicle includes sensing a sensed torque based on a driver interaction with a steering wheel that is part of an electric power steering system, the sensed torque being sensed using a torque sensor, calculating driver steering wheel torque using state variables of a steering system model based on the electric power steering system, and controlling a difference between the driver steering wheel torque calculated from the steering system model and sensed torque sensed by the torque sensor to converge to zero through a controller.