Motor Driven Power Steering Virtual Torque Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional motor driven power steering systems (MDPS) fail to maintain normal operation and driving stability when an error occurs in the torque sensor, as they typically limit output or convert to manual mode, disrupting steering performance.
Innovation Solution
A motor driven power steering system and method that generates a virtual torque based on sensed motor position, steering angle, and current, using a virtual torque estimation unit and assist torque calculation unit to continuously provide assist torque, even with a torque sensor error, thereby ensuring normal steering operation and vehicle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fail safe logic limits output or converts to manual mode when torque sensor error occurs, then system safety is improved, but steering operation normality deteriorates
Solution Approach 1:
The patent creates a virtual torque signal that copies the functional role of the failed torque sensor signal. By generating a virtual torque value through alternative sensors (steering angle sensor, motor current sensor, encoder) and calculation algorithms, the system reproduces the necessary input for assist torque generation without relying on the defective torque sensor, thus maintaining normal steering operation while ensuring safety through virtual rather than direct physical sensing.
Solution Approach 2:
The patent introduces a virtual torque estimation unit as an intermediary between the failed torque sensor and the assist torque calculation. This intermediary component bridges the gap by using other available sensors and mathematical models to generate a substitute torque signal, allowing the control system to continue functioning normally without directly using the erroneous torque sensor data.
2Stability of the object's composition
If torque sensor output is limited when error occurs, then system stability is improved, but steering performance deteriorates
Solution Approach 1:
The patent changes the parameters used for torque estimation by switching from direct torque sensor output to a virtual torque calculation based on multiple alternative parameters (steering angle, motor current, motor position, vehicle speed). This parameter substitution allows the system to maintain stable operation while preserving steering performance through continuous and accurate virtual torque generation rather than limited output.
Solution Approach 2:
The virtual torque estimation creates a functional copy of the torque signal that maintains the dynamic characteristics and responsiveness needed for normal steering performance. By copying the essential information through alternative sensing and calculation methods, the system avoids the performance degradation that would result from output limiting.
3Reliability
If manual mode is used when torque sensor fails, then system reliability is improved, but automation level deteriorates
Solution Approach 1:
The patent enables the system to serve itself by automatically detecting torque sensor failures and generating virtual torque signals through alternative sensors and internal calculations. The control system performs self-diagnosis and self-correction without requiring manual intervention or mode switching, maintaining full automation while ensuring reliability through autonomous fault tolerance mechanisms.
Solution Approach 2:
The virtual torque estimation unit acts as an automated intermediary that mediates between the failed torque sensor and the control system. This automated mediation eliminates the need for manual mode conversion by providing continuous, reliable torque information through alternative computational paths, thereby maintaining the automated steering operation.
Data Source
AI summary
A motor driven power steering system may include: a steering angle sensor configured to sense a steering angle of a steering wheel; a motor current sensor configured to sense a current of a motor; an encoder configured to sense a position of the motor; a vehicle speed sensor configured to sense a speed of a vehicle; a virtual torque estimation unit configured to estimate, when an error of a torque sensor is detected, a virtual torque using the position of the motor, the steering angle of the steering wheel, and the current of the motor; and an assist torque calculation unit configured to calculate an assist torque for operation of the motor using the steering angle of the steering wheel, the speed of the vehicle, and the virtual torque.