Steering Angle Sensor Stability Monitoring via Nonius Principle
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Solution Overview
Problem
Existing electromechanical power steering systems face instability issues in calculating the steering shaft angle due to sub-gear angle errors, which are not adequately addressed by current software solutions.
Innovation Solution
A method and device for determining the risk of instability in steering shaft angle calculations using a stability margin calculation, where the angles of multiple gear wheels are monitored, and fine-adjustment values are applied to correct asymmetry and recalibrate sensor readings, ensuring accurate steering angle determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a software calculation algorithm is used to determine steering shaft angle from sub-gear angles, then measurement precision is improved, but reliability deteriorates when critical error limits are exceeded
Solution Approach 1:
The patent applies preliminary action by calculating the stability margin before the instability occurs. The method continuously monitors the stability margin t = round(k) - k, where k is derived from the steering shaft angle calculation. When the stability margin exceeds a threshold (0.5 or -0.5), the system detects potential instability in advance and can take corrective measures, preventing the calculation output from becoming instable.
Solution Approach 2:
The patent implements feedback by continuously monitoring the stability margin and using it to adjust or reset the steering shaft angle calculation. When instability is detected through the stability margin threshold, the system provides feedback to recalculate the angle or reset the calculation, ensuring the output remains stable and reliable while maintaining high precision through the Nonius principle.
2Measurement precision
If multiple gear wheels with different tooth counts are used to determine unambiguous steering angle, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the steering angle measurement into multiple independent sub-gear angle measurements. Instead of using a single complex sensor, the system uses multiple simpler angle sensors to measure the angles of different sub-gear wheels (with tooth counts m and m+1), then combines these measurements through calculation to achieve high-precision unambiguous steering angle determination.
Solution Approach 2:
The patent applies universality by making the angle sensors serve multiple functions. The same type of angle sensor is used to measure multiple sub-gear angles, and through the Nonius calculation algorithm, these measurements collectively provide both the magnitude and the unambiguous direction of the steering shaft angle, eliminating the need for different specialized sensors.
Data Source
AI summary
A method for determining a risk of instability of a calculation of an angle ϕ of a steering shaft of a motor vehicle can be employed where a first gear wheel is fixed to the steering shaft and cooperates with a second gear wheel and a third gear wheel, which are smaller than the first gear wheel. The number of teeth of the first gear wheel is n. The number of teeth of the second gear wheel is m. And the number of teeth of the third gear wheel is m+1. The angles θ and ψ of the two smaller gear wheels are determined and the angular position ϕ of the steering shaft is calculated by evaluating the equationϕ=m*ψ+(m+1)*θ-(2m+1)*k*Ω2n,with Ω being an angle of the sensor range and a whole number k given byk=round((m+1)*θ-m*ψΩ),wherein the risk of instability is determined by calculation of a stability margin t according tot=k-((m+1)*θ-m*ψΩ).