Steering Wheel Angular Position Estimation Using Stored Offset
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Solution Overview
Problem
Existing power steering systems face challenges in quickly and reliably estimating the absolute angular position of the steering wheel after vehicle startup, leading to temporary unavailability of dependent functions due to the need for acquiring sufficient dynamic data and scoring iterations.
Innovation Solution
A method that records the switching off offset value and uses it to calculate the total compensation offset upon restart, allowing for immediate determination of the absolute angular position by weighting the memorized offset based on its reliability, thereby retaining the learning from previous sessions and ensuring continuity in the estimation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system acquires sufficient dynamic data and performs multiple scoring iterations to ensure reliable estimation of absolute angular position, then the reliability of the estimation is improved, but the time required for startup increases
Solution Approach 1:
The system performs preliminary actions during the vehicle shutdown phase by storing the final compensation offset value in non-volatile memory. This preliminary data preparation eliminates the need to start from scratch during startup, allowing the system to immediately resume using the stored offset value and achieve reliable estimation much faster than traditional iterative approaches.
2Measurement precision
If the system uses sensor technology to measure steering wheel relative position and applies dynamic models with multiple iterations, then the precision of the angular position assessment is improved, but the complexity of the system increases
Solution Approach 1:
The invention extracts and stores only the essential compensation offset value in non-volatile memory, separating this critical parameter from the complex dynamic models and iterative calculation processes. This extraction allows the system to maintain high measurement precision while reducing operational complexity during startup, as the stored offset can be directly applied without re-running complex models.
3Reliability
If the system resets the compensation offset after vehicle shutdown and restarts the iterative process, then the reliability of the estimation is maintained, but the productivity of the system decreases
Solution Approach 1:
The system maintains continuity of useful action by persisting the compensation offset value across shutdown and startup cycles. Instead of resetting and restarting the estimation process, the stored offset enables immediate resumption of accurate angular position assessment, ensuring continuous availability of steering angle information for vehicle control functions.
Data Source
AI summary
A method for estimating the absolute angular position of a steering wheel equipping a power-steering device, referred to as “relative steering wheel position”, of the shaft of a power-steering motor is assessed, a first estimation (Angle1) of the absolute angular position of the steering wheel is assessed from at least one first model using the speed difference between the left and right rear wheels, a first dynamic offset equal to the difference between the first estimation (Angle1) of the absolute angular position of the steering wheel and the relative steering wheel position is estimated, and the absolute angular position of the steering wheel is calculated by adding to the relative steering wheel position a total compensation offset determined from the first dynamic offset, also when restarting the vehicle, a switching-off offset corresponds to the value of the total compensation offset at the time when the vehicle was previously switched off.