Optical Tactile Sensor for Multi-Force Measurement
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Solution Overview
Problem
Conventional tactile sensors, including mechanical and optical types, face challenges such as insufficient durability, complexity in manufacturing, difficulty in detecting friction coefficients, and inability to simultaneously measure multi-dimensional mechanical quantities, particularly in a compact and cost-effective manner.
Innovation Solution
An optical tactile sensor featuring an optically transparent elastic body with a convex curved surface and a marker portion on the surface, utilizing imaging means to capture deformation and process image data for simultaneous measurement of normal force, tangential force, coefficient of friction, and torque without the need for internal strain gauges or multiple sensor types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical tactile sensors with strain gauges are used to measure pressure distribution and slip, then measurement precision is improved, but device complexity and manufacturing difficulty increase due to the need to arrange multiple strain gauges within elastic bodies
Solution Approach 1:
The patent replaces the mechanical strain gauge system with an optical imaging system. Instead of using multiple strain gauges embedded in elastic bodies to measure deformation, the invention uses a single camera to capture images of the elastic body's surface deformation. This substitution eliminates the complexity of arranging and wiring multiple strain gauges while maintaining the ability to measure pressure distribution and slip through image analysis.
Solution Approach 2:
The patent creates an optical copy (image) of the elastic body's deformation state rather than directly measuring mechanical strain. By capturing the deformation pattern as an image and analyzing it computationally, the system obtains measurement data without the physical complexity of multiple strain gauges. The image serves as a copy that contains all the deformation information needed for precise measurement.
2Ease of manufacture
If optical tactile sensors with flat contact surfaces are used, then ease of manufacture is improved, but measurement precision deteriorates because the coefficient of friction cannot be detected
Solution Approach 1:
The patent applies curvature to the contact surface of the optical tactile sensor. By making the contact surface curved rather than flat, the sensor can detect the coefficient of friction between the object and the tactile portion. The curvature enables the detection of slip patterns that are necessary for friction coefficient measurement, while still maintaining the simplicity and ease of manufacture associated with optical sensor designs.
3Device complexity
If finger-like tactile sensors are used to measure contact state and pressure, then device complexity is reduced, but measurement precision deteriorates because multi-dimensional mechanical quantities including friction coefficient cannot be simultaneously measured
Solution Approach 1:
The patent creates a universal optical tactile sensor that can simultaneously measure multiple mechanical quantities including normal force, tangential force, coefficient of friction, and torque. By using a single camera-based system that captures comprehensive deformation patterns of the curved elastic body, the sensor performs multiple measurement functions that would otherwise require different specialized sensors, thereby maintaining simplicity while achieving multi-dimensional measurement capability.
4Measurement precision
If combinations of mechanical and optical tactile sensors are used to measure multi-dimensional mechanical quantities, then measurement precision is improved, but device complexity increases and productivity decreases due to the need for multiple sensor types
Solution Approach 1:
The patent merges the functions of mechanical and optical tactile sensors into a single optical sensor system. By integrating the measurement capabilities that would require separate mechanical strain gauge sensors and optical sensors into one unified camera-based optical system, the invention achieves multi-dimensional mechanical quantity measurement with reduced device complexity and improved productivity, as only one sensor type needs to be manufactured and maintained.
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 solution enables accurate and simultaneous measurement of various mechanical quantities with a simple and compact structure, enhancing durability and manufacturing ease while providing accurate force determination and grip control, suitable for robotic applications.
Implementation Method 1
a tactile portion made of an optically transparent elastic body which includes a convex curved surface and has a marker portion disposed on the convex curved surface
Implementation Method 2
imaging means for imaging behavior of the marker portion while an object is in contact with the convex curved portion
Data Source
AI summary
An optical tactile sensor has a touch pad and a CCD camera for imaging behavior of the touch pad. A CPU processes image information from the CCD camera, extracts information on the size, shape, and center of gravity of a contact region, and extracts information on the size of a fixation region. The CPU obtains a normal force from the size of the contact region, obtains a tangential force from the shape of the contact region and the center of gravity of the contact region, and obtains a friction coefficient from the ratio of the size of the fixation region to the size of the contact region.