Sheet-like tactile sensor with inverted protrusions for curved surfaces
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Solution Overview
Problem
Existing tactile sensor systems for robots face challenges in accurately detecting shearing forces due to issues with cantilever electrode alignment and deformation on curved or uneven surfaces, leading to reduced detection resolution and accuracy.
Innovation Solution
A sheet-like tactile sensor system with a three-layer structure, including an exterior sheet layer, an intermediary viscoelastic layer, and a force detection sheet layer, where protrusions on both layers engage with the intermediary layer to transmit deformation and detect forces, including shearing forces, using central and edge detection sensor devices for differential detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If cantilever electrodes are used to detect shearing force, then detection capability for shearing force is improved, but detection resolution and accuracy deteriorate due to pull-in failure or misalignment on curved surfaces
Solution Approach 1:
The sensor surface is divided into multiple independent detection regions, each with its own force detection protrusion and electrode structure. This segmentation allows each region to independently detect local forces without interference from adjacent areas, preventing pull-in failure propagation and maintaining detection accuracy across the entire sensor surface.
Solution Approach 2:
Instead of using traditional cantilever electrodes that stand erect and are prone to pull-in failure, the invention inverts the structure by using force detection protrusions that extend from the sensor surface outward. This inverted configuration eliminates the pull-in problem while maintaining the ability to detect shearing forces through differential measurement of normal forces on opposite sides.
2Adaptability or versatility
If cantilever-type sensor units are mounted on curved or uneven surfaces, then adaptability to robot surfaces is improved, but detection accuracy deteriorates due to curvature-induced misalignment
Solution Approach 1:
The sensor unit is constructed as a thin, flexible sheet that can conform to curved or uneven surfaces without compromising the orientation of the force detection protrusions. The flexible substrate allows the sensor to adapt to various surface geometries while maintaining the perpendicular alignment of protrusions relative to the local surface tangent, ensuring accurate force detection.
Solution Approach 2:
Each local region of the sensor surface has force detection protrusions that are oriented perpendicular to the local tangent of the surface at that position. This local orientation ensures that each detection region accurately measures forces normal to its specific location on the curved surface, maintaining detection accuracy across the entire non-planar sensor area.
3Measurement precision
If force detection protrusions are made small for high resolution, then detection resolution is improved, but deformation amount decreases leading to reduced detection sensitivity
Solution Approach 1:
The invention transitions from detecting shearing force directly (one-dimensional measurement) to detecting the difference in normal forces on opposite sides of a protrusion (three-dimensional measurement). This dimensional change allows small protrusions to produce measurable effects through differential normal force detection, maintaining both high resolution and sensitivity simultaneously.
Solution Approach 2:
The invention replaces the mechanical cantilever bending measurement system with an electrostatic capacitance measurement system. By measuring changes in capacitance between electrodes and the force detection protrusion, the system can detect extremely small displacements with high sensitivity, overcoming the limitation of small protrusion deformation while maintaining high resolution.
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 configuration enhances detection resolution and accuracy for both normal and shearing forces, prevents detection failures, and maintains product quality by allowing sufficient deformation of force detection protrusions, while ensuring a smooth surface for human-robot interaction.
Implementation Method 1
an intermediary layer portion (220) having flexibility and sandwiched between the exterior sheet layer portion (210) and the force detection sheet layer portion (230)
Implementation Method 2
a plurality of normal stress detection sensor units (300) that detect a force acting on an outer surface of the sheet layer portion (200) are buried in the force detection sheet layer portion (230)
Data Source
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AI summary
Provided are multiple normal stress detection sensor units 300 capable of detecting a normal stress, and a sheet layer portion 200. The sheet layer portion 200 includes an exterior sheet layer portion 210, a force detection sheet layer portion 230 incorporating normal stress detection units 300, and an intermediary layer 220 sandwiched between the exterior sheet layer portion 210 and the force detection sheet layer portion 230. The exterior sheet layer portion 210 and the force detection sheet layer portion 230 include multiple protrusions 212 and 232 protruding in directions opposed to each other, and are disposed such that the protrusions 212 and 232 engage each other with the intermediary layer 220 interposed therebetween. Each normal stress detection sensor unit 300 includes a central portion detection sensor device 310 disposed immediately below a central portion of the protrusions 232 provided on the force detection sheet portion 230, and at least two edge detection sensor devices 321 to 324 disposed immediately below edge portions of the protrusion 232 provided on the force detection sheet portion 230.