Capacitive Contact Detection Using Phase Signals for Wire Breakage
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Solution Overview
Problem
Conventional contact deciding apparatuses for detecting steering wheel holding states in autonomous vehicles require additional elements for wire breakage detection, complicating the system and potentially reducing reliability.
Innovation Solution
A contact deciding apparatus that utilizes a capacitive sensor to detect contact failures, such as wire breakage, by generating reference signals in-phase and out-of-phase with the detection signal, and analyzing the direct-current components of demodulation signals to determine the connection state between the sensor and detection circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional contact deciding apparatus uses separate wire breakage detection electrodes and signal wires to detect wire breakage, then wire breakage can be detected, but the device complexity increases and reliability may be reduced
Solution Approach 1:
The patent merges the wire breakage detection function with the existing capacitance detection function by using the same sensor electrode and signal processing circuitry. The detection circuit analyzes the phase relationship between the excitation signal and the detection signal to identify wire breakage, eliminating the need for separate detection electrodes and signal wires.
Solution Approach 2:
The sensor electrode and detection circuit are designed to perform multiple functions: capacitance measurement for contact detection and wire breakage detection through phase analysis. This multi-functionality reduces the number of dedicated components while maintaining both detection capabilities.
2Measurement precision
If additional constituent elements are added for wire breakage detection, then detection capability is improved, but the device becomes more complex and space requirements increase
Solution Approach 1:
The existing sensor system serves itself by using the same electrode and signal path for both capacitance measurement and wire integrity detection. The detection circuit automatically analyzes the phase relationship of the returned signal to identify wire breakage without requiring external detection components.
Solution Approach 2:
The patent detects wire breakage by monitoring changes in the phase parameter of the detection signal. When a wire breakage occurs, the phase relationship between the excitation and detection signals changes, providing a reliable indicator of wire integrity without additional hardware.
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
Enables reliable detection of contact failures without the need for dedicated wire breakage detection elements, ensuring accurate detection of driver interactions with the steering wheel and enhancing system reliability.
Implementation Method 1
a sensor unit that outputs a detection signal with a sine wave, the detection signal having an amplitude matching the capacitance between a detection target and a detection electrode
Implementation Method 2
a demodulation circuit that creates, as a first demodulation signal, a signal by multiplying the detection signal output from the sensor unit by the first reference signal, and also creates, as a second demodulation signal, a signal by multiplying the detection signal output from the sensor unit by the second reference signal
Implementation Method 3
a first low-pass filter that extracts a first direct-current signal, which is the direct-current component of the first demodulation signal; a second low-pass filter that extracts a second direct-current signal, which is the direct-current component of the second demodulation signal
Data Source
AI summary
A contact deciding apparatus includes: reference signal creating units that create first and second reference signals, with a sine wave, that have the same frequency as a detection signal output from a sensor unit, and are respectively in phase with and out of phase with the detection signal; a demodulation circuit that creates first and second demodulation signals by multiplying the detection signal respectively by the first and second reference signals; low-pass filters that extract first and second direct-current signals, which are respectively the direct-current components of the first and second demodulation signals; and a contact deciding unit that makes a decision about contact according to the first direct-current signal. The contact deciding unit decides that the connection state between the sensor unit and the detection circuit is abnormal when the first and second direct-current signals change in the same direction and normal when these signals change in opposite directions.