Steering Wheel Angle Sensing Using Correlation-Based Code Reading
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Solution Overview
Problem
Existing methods for determining the absolute angular position of a motor vehicle's steering wheel are sensitive to interference from dirt and electromagnetic pulses, leading to measurement errors that cannot be corrected.
Innovation Solution
A process that correlates the sensor array's output signal with a reference signal using a correlation filter to determine the best coincidence point, reducing the impact of local interference and ensuring valid angle determination by comparing the correlation function's maximum value with a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If edge-based evaluation is used to determine angular position, then the process can achieve theoretical accuracy, but the system becomes highly sensitive to interference from dirt and electromagnetic pulses
Solution Approach 1:
The patent introduces a correlation filter as an intermediary between the sensor array and the evaluation process. This filter correlates the sensor output signal with a reference signal representing the encoding, thereby mediating the measurement process to reject interference while preserving the true angular position information.
Solution Approach 2:
The patent merges the entire output signal from all sensor elements into a single correlation operation. By combining all sensor outputs and correlating with the reference encoding pattern, the system achieves interference rejection through statistical averaging while maintaining measurement precision.
2Reliability
If the entire output signal is used for evaluation, then insensitivity to local interference is achieved, but the computational complexity increases
Solution Approach 1:
The patent replaces complex mechanical or algorithmic interference rejection methods with a mathematical correlation operation. The correlation filter provides a computationally efficient way to achieve reliability by substituting mathematical processing for physical or procedural complexity.
3Reliability
If correlation filtering is applied to reduce interference, then measurement reliability improves, but the processing time increases
Solution Approach 1:
The patent applies preliminary action by pre-storing the reference signal representing the encoding pattern. This reference signal is prepared in advance and used for correlation with the sensor output, enabling rapid interference rejection without requiring complex real-time computation of the reference pattern.
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 approach significantly increases insensitivity to external influences, allowing for reliable angular position measurement even in the presence of interference, while balancing certainty and availability by adjusting the correlation threshold.
Implementation Method 1
a transceiver (10) comprising a light source (11) and a sensor array (12) having a plurality of optoelectronic transducers (12.1)
Data Source
AI summary
A method for determining the absolute value of a rotational angle includes imaging a continuous segment of a code track of a code carrier on a sensor array such that the sensor array generates a corresponding output signal. The code track includes a code provided over an angular range of 360°. The code contains a plurality of code words with each code word respectively corresponding to an angular value in the angular range. The output signal is correlated with a reference signal in a correlation filter to produce a correlation function signal. The reference signal is indicative of the code and the angular values corresponding to the code words. The correlation function signal is processed to determine the code word of the imaged segment of the code track as a function of the angular value where the output signal best coincides with the reference signal.