Capacitive Sensing Control Element Tolerance Compensation
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Solution Overview
Problem
Force-sensitive user-actuated devices, such as drills and power tools, face challenges in accurately controlling operations due to variations in capacitance caused by changes in electrode distance and tilting, which affect the reliability of resistive actuators.
Innovation Solution
A capacitance-based sensing technique using multiple electrically conductive electrodes configured as capacitors, where a movable electrode moves relative to fixed electrodes, changing capacitance is detected by a capacitive sensing circuit, and the detected changes control the device's operation, automatically compensating for variations in distance and tilting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistive actuator is used to control device operation based on user force, then the device can respond to user input, but the control accuracy deteriorates due to variations in capacitance caused by electrode distance changes and tilting
Solution Approach 1:
The patent divides the single capacitance measurement into multiple measurements using separate electrode pairs. Each electrode pair measures capacitance in a specific direction, allowing the system to segment the measurement task to achieve compensation for distance variations and tilting effects that would otherwise degrade measurement precision
Solution Approach 2:
The patent implements feedback by using the capacitance measurements from multiple electrode pairs to detect and compensate for electrode distance variations and tilting. The system continuously monitors capacitance changes and adjusts control signals accordingly, maintaining measurement precision despite mechanical variations in the actuator assembly
2Ease of operation
If the movable electrode moves relative to fixed electrodes to detect capacitance changes, then device operation control is enabled, but control precision deteriorates due to mechanical tolerance variations in electrode distance
Solution Approach 1:
The patent segments the capacitance sensing into multiple independent electrode pairs, each sensitive to different spatial variations. This segmentation allows the system to maintain control functionality while compensating for mechanical tolerances by combining information from multiple measurement channels
Solution Approach 2:
The patent changes the measurement parameters by using multiple electrode pairs with different orientations and positions. This allows the system to detect capacitance changes from multiple perspectives, enabling accurate device control despite variations in electrode distance caused by mechanical tolerances
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 ensures precise control of device functions, such as motor speed, by accurately measuring changes in capacitance, thereby improving the reliability and consistency of user-actuated equipment operations.
Implementation Method 1
A capacitance sensing circuit is coupled to the first and second electrodes. The capacitive sensing circuit is configured to determine a capacitance using the first and second electrodes.
Data Source
AI summary
An apparatus includes a first electrode, a second electrode, and a third electrode having first and second opposing surfaces. The first opposing surface is adjacent the first electrode and separated from the first electrode by a first distance, and the second opposing surface is adjacent the second electrode and separated from the second electrode by a second distance. The third electrode is configured to move relative to the first and second electrodes. A capacitance sensing circuit is coupled to the first and second electrodes. The capacitive sensing circuit is configured to determine a capacitance using the first and second electrodes.