Capacitive Position Sensing on Metal Beams
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Solution Overview
Problem
Current position sensing systems for automotive safety sensors face challenges in recalibration, especially in harsh environments, due to sensitivity to alignment errors and contamination, and require active components and periodic target release, which increases complexity and cost.
Innovation Solution
A capacitive sensing system that uses mutual capacitive sensing to detect the absolute position of moving targets along a metal beam with a minimal number of sensors, employing a gray code-based Rx sensor pattern and a processing device to determine target position without electronic feedback, allowing simultaneous detection of multiple targets and minimizing scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional position sensing systems are used in automotive safety sensors, then position detection can be achieved, but the system is sensitive to alignment errors and contamination requiring periodic target release and active components which increases complexity and cost
Solution Approach 1:
The patent replaces traditional mechanical or optical position sensing systems with a capacitive sensing system. The capacitive sensors detect position through electrical field interactions with the target, eliminating the need for mechanical alignment components and optical paths that are sensitive to contamination. This substitution reduces device complexity while improving reliability in harsh automotive environments.
Solution Approach 2:
The capacitive sensing system automatically detects target position without requiring periodic manual intervention for target release or recalibration. The system continuously monitors capacitance changes and self-adjusts to maintain accurate position detection, eliminating the need for external calibration procedures and reducing operational complexity.
2Measurement precision
If traditional position sensing systems with active components are used, then position detection can be achieved, but periodic target release is required which increases operation time and reduces productivity
Solution Approach 1:
The capacitive sensing system implements continuous periodic scanning of target position without requiring the target to be released or reset. Multiple capacitive sensors continuously monitor position changes, enabling real-time tracking and eliminating downtime associated with periodic target release operations, thus improving productivity while maintaining measurement precision.
3Measurement precision
If capacitive sensing with multiple sensors is used for absolute position detection, then detection accuracy is improved, but the number of sensors and wiring increases complexity
Solution Approach 1:
The patent combines multiple capacitive sensing elements into an integrated sensor array where sensors are closely spaced and electrically connected through shared signal paths. This merging approach maintains the measurement precision benefits of multiple sensors while reducing wiring complexity through common signal lines and integrated circuitry, making the system practical for automotive applications.
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 solution provides accurate and efficient absolute position detection with reduced alignment errors and no need for active components or periodic target release, enhancing recalibration precision and reducing complexity and cost in automotive applications.
Implementation Method 1
Capacitive sense arrays function by measuring the capacitance of a capacitive sense element and evaluating for a delta in capacitance indicating a touch or presence of a conductive object.
Implementation Method 2
There are two typical types of capacitance: 1) mutual capacitance where the capacitance-sensing circuit measures a capacitance formed between two electrodes coupled to the capacitance-sensing circuit
Implementation Method 3
2) self-capacitance where the capacitance-sensing circuit measures a capacitance of a single electrode
Data Source
AI summary
The embodiments described herein are directed to systems and devices for electronically measuring the absolute position of one or more moving targets e.g., along the length of a metal beam using mutual capacitive sensing. The beam may be made of metal and may have a limited inset area to fit a position detection sensor device along its length. The moving targets may have no active elements and the position of multiple targets may be detected simultaneously along the beam. The systems and devices described herein do not utilize electronic position feedback and instead rely on an integrated ruler and minimize the total number of sensors required to support recalibration, thereby minimizing scan time (more sensors results in a linear increase in scan time).