Electric Power Steering Motor Torque Limiting via Virtual Torsion-Bar
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional electric power steering systems cannot limit the torque of the electric motor effectively in automated driving scenarios with transverse guidance, as the driver does not apply a torsion-bar torque to the steering wheel.
Innovation Solution
A method and control device that limit the control variable for the motor of an electric power steering system by determining a virtual torsion-bar torque using a setpoint steering angle and an actual steering angle, and then applying limiting values to the control variable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional torque limiting based on torsion-bar torque is used, then the electric motor torque can be limited in manual driving, but the limitation cannot be applied in automated driving scenarios where the driver does not apply torsion-bar torque
Solution Approach 1:
The patent replaces the mechanical torsion-bar torque sensing system with an electronic control system that calculates virtual torsion-bar torque based on steering angle deviations. This substitution enables torque limitation to function in automated driving scenarios where no physical torsion-bar torque is applied, while maintaining reliable torque control through electronic calculation and control variable adjustment.
Solution Approach 2:
The patent introduces a virtual torsion-bar torque calculation as an intermediary mechanism. Instead of directly sensing physical torsion-bar torque, the system calculates a virtual representation based on steering angle deviations from the setpoint. This intermediary enables the torque limitation function to operate effectively in automated driving scenarios by translating steering angle information into equivalent torque limitation control.
2Reliability
If the control variable is limited based on virtual torsion-bar torque calculated from steering angle deviations, then hazardous situations can be prevented in automated driving, but the system complexity increases
Solution Approach 1:
The patent makes the existing steering angle control system multi-functional by having it simultaneously perform steering control and torque limitation functions. The steering angle controller uses the same steering angle deviation calculations for both steering control and for determining virtual torsion-bar torque for torque limitation, thereby preventing hazardous situations without adding separate dedicated hardware systems.
Solution Approach 2:
The patent merges the torque limitation function with the existing steering angle control function. Both functions utilize the same steering angle sensor data and control variables, combining what were previously separate control paths into a unified control system. This integration reduces overall system complexity while maintaining hazard prevention capabilities.
Data Source
AI summary
A method limits a control variable for a motor of an electric power steering system for a motor vehicle having automated lateral control. The method receives a setpoint steering angle, determines the control variable in accordance with the setpoint steering angle, receives an actual steering angle, determines a virtual torsion-bar torque in accordance with the setpoint steering angle and the actual steering angle, determines at least one limit value for the control variable in accordance with the virtual torsion-bar torque, and limits the control variable in accordance with the at least one limit value.