Vision-Based Tactile Sensor for Shear and Torque Detection
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Solution Overview
Problem
Conventional tactile sensors in robotics are limited in measuring compressive forces and fail to detect shear movement, torque, and other types of forces, leading to inaccurate object gripping and assembly, which can result in failed assembly, damaged parts, and equipment damage.
Innovation Solution
A tactile sensor with multiple micro mechanical pins attached to an elastomeric cap that translates patterns of forces into measurable quantities, featuring micro mechanical pins with lever arms and fiducial markers, allowing for sensitive detection of compressive forces, shear, torque, and other forces through machine vision algorithms and image processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional pressure sensors are used to measure compressive forces, then the sensor structure is simple, but the sensor cannot detect shear movement, torque, and other types of forces
Solution Approach 1:
The sensor surface is divided into multiple discrete pin locations, each capable of independent deflection and force detection. This segmentation allows the sensor to detect multiple force types (compressive, shear, torque) across different locations simultaneously, increasing versatility while maintaining a relatively simple overall structure based on the elastomeric membrane with embedded pins
Solution Approach 2:
The elastomeric membrane with pins serves multiple functions: it detects compressive forces through pin deflection, detects shear forces through lateral pin movement, and detects torque through rotational pin displacement. A single sensor structure thus performs multiple detection functions that would otherwise require separate sensors
2Measurement precision
If micro mechanical pins with lever arms are used to amplify motion, then the sensitivity is enhanced, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical linkages with a simplified optical detection system. Instead of using elaborate mechanical amplification mechanisms, the system uses simple pin deflections coupled with optical sensors (cameras, photodetectors) to detect and amplify the motion signals, achieving high sensitivity with reduced mechanical complexity
Solution Approach 2:
The patent changes the physical parameters of the pins, such as their length, diameter, and material properties, to optimize the deflection characteristics and sensitivity. By adjusting these parameters, the system achieves enhanced measurement precision while keeping the basic pin structure relatively simple
3Measurement precision
If multiple pins with fiducial markers are used for machine vision tracking, then the measurement accuracy is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent uses fiducial markers with distinct visual characteristics (colors, patterns, reflectivity) on the pins to enable easy detection by machine vision systems. These markers can be applied through simple coating or printing processes during manufacturing, improving measurement accuracy without significantly complicating the fabrication process
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 provides enhanced sensitivity and accuracy in detecting various forces, enabling precise object gripping and assembly by amplifying the motion of micro mechanical pins, resulting in improved robotic grasping and assembly processes.
Implementation Method 1
an elastomeric tactile sensor having multiple micro mechanical pins attached to an underside of an elastomeric cap and upon exterior forces applied to a top surface, translates a pattern of forces into measurable quantities
Implementation Method 2
the motion of deflection of the elastomeric cap, under pressure, offset pressure, shear, or torque, can be recorded
Implementation Method 3
The pin can be modified to include one or more lever arm extending away from the pin, i.e. similar to a tree like figure or shape; wherein at a tip of each lever arm may include at least one trackable mark. Based upon experimentation, the addition of the one or more lever arm on the pin resulted in a level of magnification of sensitivity that is higher
Implementation Method 4
using one or more video camera or webcam(s). The one or more video camera views the marks or fiducial marks, by non-limiting example, at an oblique (zero to ̃20) degree angle, or at some other angle
Data Source
AI summary
A tactile sensor including a cap having a top surface and an undersurface. The undersurface includes pins, each pin has a mark. A portion of the undersurface is attachable to a device. A camera positioned in view of the marks, captures images of the marks placed in motion by elastic deformation of the top surface of the cap. A processor receives the captured images and determines a set of relative positions of the marks in the captured images, by identifying measured image coordinates of locations in images of the captured images. Determine a net force tensor acting on the top surface using a stored machine vision algorithm, by matching the set of relative positions of the marks to a stored set of previously learned relative positions of the marks placed in motion. Control the device via a controller in response to the net force tensor determined in the processor.