Steering Sensor Cross-Check Fault Handling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric power assisted steering systems face challenges in safely applying assistance torque when a fault is detected in dual channel torque sensors, as it is unclear which channel is faulty and there is no protection against subsequent faults in the remaining good channel.
Innovation Solution
A combined angular position and torque sensor assembly that includes multiple sensors and a processing unit to produce absolute angular position signals, cross-check these signals for errors, and learn expected variations to flag errors, ensuring robust operation even with faulty sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dual channel torque sensor is used to provide fault safety margin, then safety is improved, but the system cannot continue to apply assistance torque when one channel is faulty
Solution Approach 1:
The system implements a cross-check mechanism where the first and second absolute angular position signals are continuously compared. When a discrepancy is detected indicating a sensor fault, the feedback loop triggers a fault flag that allows the system to maintain assistance torque application while protecting against further errors, thus resolving the contradiction between safety and productivity
Solution Approach 2:
The system changes the operational parameter from complete torque shutdown to reduced or monitored torque application when faults are detected. By modifying the control strategy based on fault detection parameters, the system maintains productivity while implementing safety measures through learned expected variations and error flagging
2Reliability
If dual channel torque sensor is used, then fault detection capability is improved, but device complexity increases
Solution Approach 1:
The patent combines angular position sensing and torque measurement functions into a single integrated sensor assembly. The first and second angular position sensors are merged with the torque sensor structure, sharing common components such as the torsion bar and signal processing circuitry. This merging reduces overall system complexity while maintaining dual-channel fault detection capability
Solution Approach 2:
The sensor assembly is designed to perform multiple functions: measuring torque, determining absolute angular position, and providing redundant fault detection channels. The first and second angular position sensors serve both position measurement and fault detection purposes, eliminating the need for separate dedicated fault detection hardware and thereby reducing device complexity
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 solution enables the electric power assisted steering system to safely apply assistance torque by accurately identifying and handling sensor faults, providing a more robust and reliable operation.
Implementation Method 1
The torsion bar twists causing the two angular position sensors to move out of alignment
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A combined angular position and torque sensor assembly for use in an electric power assisted steering system comprises an input part for connection to an upper column shaft, an output part for connection to a lower column shaft, a torsion bar that interconnects the input shaft and the output shaft, a first and second upper column angular position sensing means that each produce at least one output signal that is dependent on the angular position of the upper column shaft; and a processing means which produces a first torque signal indicative of the torque carried by the torsion bar. The processing means further includes means for producing a first absolute angular position signal by processing the output signals of the first and secondary sensors in a first way and a second absolute angular positon signal processing the output of the same two sensors in a different way, and further comprises a cross checker that performs a cross check between the two absolute position signals.