Compliant Tactile Sensor for Robotic Grasping
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Solution Overview
Problem
Robotic and prosthetic systems face challenges in delicately handling fragile objects due to high impact forces from collisions and difficulties in precise contact detection, leading to potential damage or failure in grasping and collision prevention.
Innovation Solution
A compliant tactile sensor using a sponge-like material with a flexible skin and fluid pressure sensing, allowing for sensitive contact detection and cushioning of impact forces, integrated into robotic systems to enhance safety and grasping capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If rigid mechanical linkages and high-quality position and force encoders are used to achieve fast-reacting systems, then response speed and control precision are improved, but system cost and complexity increase
Solution Approach 1:
The patent replaces complex mechanical linkages, high-quality position encoders, and force encoders with a compliant tactile sensor that directly senses contact. The sensor uses a compliant structure with embedded pressure sensors to detect contact forces, eliminating the need for complex mechanical transmission and multiple sensing components while achieving fast response and precise measurement.
Solution Approach 2:
The patent changes the mechanical parameters of the robotic system by introducing compliant structures with specific stiffness values (e.g., 100-1000 N/m) that allow controlled deformation under load. This enables the system to respond to contact forces through material deformation rather than rigid mechanical transmission, simplifying the overall system architecture while maintaining sensitivity.
2Speed
If DC motors with high closing speed are used in prosthetic hands, then grasping speed is improved, but stalling forces and risk of damage increase
Solution Approach 1:
The patent incorporates compliant tactile sensors with controlled stiffness into the prosthetic hand structure before grasping occurs. These sensors act as mechanical cushions that limit the maximum force transmitted to both the object and the motor during closing, preventing stalling forces of 50-100 N from occurring while maintaining fast closing speed capability.
Solution Approach 2:
The patent implements real-time feedback from compliant tactile sensors that detect contact forces during the grasping process. This feedback enables the control system to modulate motor commands dynamically, reducing power delivery as contact forces increase, thereby preventing motor stalling and protecting both the prosthetic and the grasped object from damage.
3Measurement precision
If high-level visual attention is used to precisely time stopping the hand, then grasping precision is improved, but operator cognitive burden and reaction time increase
Solution Approach 1:
The patent enables the prosthetic hand to perform contact detection autonomously through compliant tactile sensors that continuously monitor contact forces. The system self-regulates the grasping process by detecting contact and automatically modulating motor commands, eliminating the need for the operator to maintain high-level visual attention and precisely time stopping commands, thereby reducing cognitive burden and reaction time.
4Measurement precision
If stiff mechanical linkages are used in robotic systems, then position control accuracy is improved, but collision impact forces and safety risks increase
Solution Approach 1:
The patent changes the stiffness parameter of the robotic system's mechanical linkages from high (rigid) to controlled low (compliant) values. By designing linkages with specific compliance characteristics, the system maintains sufficient position control accuracy for normal operation while dramatically reducing impact forces during collisions, thereby improving safety without sacrificing functional performance.
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 compliant tactile sensor provides robust and sensitive contact detection, reducing collision forces and enabling safer handling of fragile objects by interpreting data to minimize impact and improve grasp stability, thus alleviating cognitive burdens on operators.
Implementation Method 1
The sponge-like material may be saturated with a fluid
Implementation Method 2
compress in response to force applied to the sponge-like material
Implementation Method 3
The fluid pressure sensor may sense changes in pressure in fluid that is within the sponge-like material caused by a force applied to the flexible skin
Data Source
AI summary
A compliant tactile sensor may include sponge-like material, a flexible skin, and a fluid pressure sensor. The flexible skin may have a shape, absorb fluid, compress in response to force applied to the sponge-like material, and decompress and return to its original shape when the force is removed. The flexible skin may cover an outer surface of the sponge-like material. The fluid pressure sensor may sense changes in pressure in fluid that is within the sponge-like material caused by a force applied to the flexible skin. A robotic system may include a movable robotic arm, a compliant tactile sensor on the movable robotic arm that senses contact between the compliant tactile sensor and an object during movement of the movable robotic arm and that cushions the effect of that contact, and a reflex system that causes the moveable robotic arm to move in response to commands.