Three-Axis Capacitive Touch Sensor for Pressure and Motion Tracking
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Solution Overview
Problem
Current touch sensing technologies in medical training systems, particularly for clinical breast examinations, are unable to accurately track directional motion and normal pressure due to limitations in piezoelectric sensing schemes, which result in hysteresis and susceptibility to temperature variations and external vibrations.
Innovation Solution
A flexible, three-axis capacitive touch sensor design featuring a dielectric layer with deformable posts and multiple electrodes that vary in differential capacitance in response to force and movement, allowing for the measurement of normal pressure and directional motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoelectric sensing schemes are used, then normal pressure measurement is achieved, but directional motion tracking capability is lost
Solution Approach 1:
The sensor surface is divided into multiple independent piezoelectric element groups, each capable of detecting pressure in specific directional orientations. This segmentation allows the sensor to measure normal pressure while simultaneously tracking directional motion components through the combined output of oriented element groups.
Solution Approach 2:
The invention transitions from single-axis normal pressure measurement to three-axis motion tracking by adding directional sensitivity dimensions. Piezoelectric elements are oriented at different angles (e.g., 0°, 45°, 90°) to capture motion components in multiple directions, effectively adding dimensional capability to the sensing system.
2Measurement precision
If piezoelectric sensing schemes are used, then pressure sensing capability is provided, but hysteresis and drift occur due to temperature variations and external vibrations
Solution Approach 1:
The sensor incorporates temperature compensation mechanisms that use feedback from temperature sensors to adjust and correct the output signals from piezoelectric elements. This feedback loop compensates for drift caused by temperature variations, maintaining measurement reliability across different thermal conditions.
Solution Approach 2:
The invention employs parameter changes by modifying the electrical characteristics and signal processing parameters based on detected temperature and vibration conditions. Through dynamic parameter adjustment in the signal processing circuitry, the sensor maintains optimal performance and reliability under varying environmental conditions.
3Measurement precision
If capacitive touch sensor technology is used, then high sensitivity and low power consumption are achieved, but long relaxation times after compression occur due to elastomeric thin film deformation
Solution Approach 1:
The invention replaces the mechanical elastomeric thin film deformation mechanism with a capacitive sensing mechanism. Instead of relying on the slow mechanical relaxation of elastomer after compression, capacitive elements detect force changes through electrical field variations, dramatically reducing relaxation time while maintaining high sensitivity.
Solution Approach 2:
The sensor utilizes the phase transition or state change in capacitive response when subjected to compression. The capacitive elements exhibit rapid electrical response characteristics that transition quickly between compressed and uncompressed states, avoiding the prolonged mechanical relaxation period inherent in elastomeric materials.
4Area of stationary object
If current sensing solutions are used, then normal pressure measurement over large area is achieved, but motion tracking capability is lost
Solution Approach 1:
The large sensing area is segmented into multiple piezoelectric element groups with different orientations. Each segment contributes to both the overall area coverage and the directional motion tracking capability. The distributed arrangement of oriented element groups across the large area enables simultaneous pressure measurement and motion tracking throughout the entire sensor surface.
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
The sensor effectively tracks pressure and motion with improved sensitivity and quick recovery from deformation, reducing hysteresis and drift, making it suitable for precise tactile feedback in medical training systems.
Implementation Method 1
A dielectric layer extends between the plate and the first electrode and includes a plurality of dielectric posts. The dielectric posts flex in a direction corresponding to a direction of the force applied to the first electrode.
Implementation Method 2
Each of the plurality of second electrodes has a corresponding differential capacitance with the first electrode. The differential capacitances between the first electrode and the plurality of second electrodes vary in the response to the movement of the first electrode.
Data Source
AI summary
A capacitive touch sensor is provided, The capacitive touch sensor includes a plate having an upper surface and lying in a plate plane. A generally planar, first electrode is spaced from the plate along an axis generally perpendicular to the upper surface of the plate. The first electrode movable with respect to the plate in response to a force. A plurality of second electrodes are interconnected to the plate and circumferentially spaced about the axis. Each of the plurality of the second electrodes has a corresponding differential capacitance with the first electrode. The differential capacitances between the first electrode and the plurality of second electrodes vary in the response to the movement of the first electrode.