Steering Wheel Angular Position Sensor Correlation Filter
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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 signal interference from dirt and electromagnetic interference, leading to incorrect measurements that cannot be corrected.
Innovation Solution
A correlation filter is used to evaluate the output signal of a sensor array by forming a correlation function with a reference signal, determining the maximum value and comparing it to a correlation threshold to validate the code word for the angle value, thereby reducing the impact of local disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If edge-based evaluation method is used to determine angular position, then measurement speed is improved, but measurement precision deteriorates due to sensitivity to signal interference from dirt and electromagnetic interference
Solution Approach 1:
The patent divides the code track into multiple evaluation zones (first evaluation zone with first code elements and second evaluation zone with second code elements). Instead of evaluating the entire code track at once or relying on a single edge detection point, the measurement is segmented into multiple independent zones. This segmentation allows the system to process multiple segments in parallel and select the most reliable measurement, thereby maintaining high speed while improving precision by avoiding interference-affected zones.
Solution Approach 2:
The patent implements a feedback mechanism where the plausibility of measurement results is continuously checked. The system evaluates multiple measurement segments and uses plausibility checks to identify and reject measurements affected by interference (such as dirt or electromagnetic interference). This feedback loop ensures that only valid measurements are accepted, significantly improving measurement precision while maintaining the speed advantages of edge-based detection.
2Reliability
If multiple evaluation zones are used to improve measurement reliability, then insensitivity to external influences is improved, but device complexity increases
Solution Approach 1:
The patent designs the code track to serve multiple functions simultaneously. The same code elements in the code track are used both for generating the measurement signal and for plausibility checking. The code structure itself (with its specific pattern of code elements) provides both the measurement information and the reference for validating measurements. This multi-functionality reduces device complexity by eliminating the need for separate validation components while still achieving improved reliability through multiple evaluation zones.
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 accurate determination of the steering angle despite interference, with the ability to tolerate certain levels of contamination and interference while maintaining system availability.
Implementation Method 1
a transmitter/receiver unit comprising a light source and a sensor array
Implementation Method 2
sensor array having a large number of optoelectronic transducer elements
Data Source
Figure 1
AI summary
The invention relates to a method for the absolute determination of a rotation angle, in particular the angular position of the steering wheel of a motor vehicle, by means of a transmitter-receiver unit comprising a light source and a sensor array with a plurality of optoelectronic transducer elements, and a code carrier rotatably arranged relative to this unit and having a unique, single-track encoding of the angle values, wherein a contiguous segment of the encoding is mapped onto the sensor array, and the output signal of the sensor array is evaluated to determine a codeword corresponding to the current angle value. The present invention is intended to further develop such a method in such a way that a significantly increased insensitivity to external influences, in particular from contamination or electromagnetic interference, is achieved.According to the invention, this is achieved by correlating the output signal of the sensor array with a reference signal representing the entire angular information of the coding using a correlation filter, and determining the position of the best match between the output signal and the reference signal as the current codeword.