Tactile Sensor Module for Robot Hand Grasping

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Solution Overview

Problem

Conventional robot-hands lack precise control over grasping force, especially when handling soft objects, due to the inability to accurately measure tactile characteristics like stiffness and softness, leading to potential deformation and sliding during grasping operations.

Innovation Solution

A robot-hand equipped with a tactile sensor module featuring force sensors on a three-dimensional Flexible Printed Circuit Board (FPCB) assembly and phalange sensor modules, which measure normal force and rotational displacement to adjust grasping force based on object stiffness, minimizing deformation and sliding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If conventional distance sensors and visual feedback are used for grasping control, then the device complexity is reduced, but the measurement precision of tactile characteristics like stiffness and softness deteriorates

Engineering Contradiction:

Improvegrasping control systemVSAvoidtactile characteristics measurement

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent replaces conventional distance sensors and visual feedback systems with a tactile sensor module that directly measures mechanical forces. The force sensor mounted on the FPCB assembly measures normal force applied during grasping, providing direct tactile feedback about object stiffness and softness rather than inferring these properties from distance or visual data.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The FPCB assembly acts as an intermediary structure that mounts the force sensor and transfers mechanical stress from the gripping surface to the sensor. This intermediary arrangement enables precise force measurement while maintaining the structural integrity needed for grasping operations.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If grasping force is increased to prevent sliding of soft objects, then the stability of grasping is improved, but the deformation of the object increases

Engineering Contradiction:

Improvegrasping stabilityVSAvoidobject deformation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback control system where the force sensor continuously measures the normal force applied to the object during grasping. The controller receives this force data and adjusts the grasping force in real-time to maintain optimal levels - sufficient to prevent sliding but minimal enough to avoid excessive deformation of soft objects.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The grasping force is made dynamic rather than static. The system continuously adapts the grasping force based on real-time feedback from the force sensor, allowing the robot hand to apply different force levels during approach, contact, and holding phases of grasping soft objects with varying stiffness.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If the force sensor is mounted directly on the gripping surface, then the measurement precision is improved, but the device complexity and difficulty of integration increase

Engineering Contradiction:

Improveforce measurementVSAvoidsensor integration structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The FPCB assembly serves multiple functions: it provides the gripping surface, mounts the force sensor, transfers mechanical stress, and enables electrical connections. This multi-functional design integrates the sensing capability into the existing gripper structure without requiring separate mounting mechanisms or complex integration processes.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Measurement precision

If tactile sensor module is added to measure normal force and rotational displacement, then the measurement precision of object stiffness is improved, but the device complexity increases

Engineering Contradiction:

Improveobject stiffness measurementVSAvoidtactile sensor module

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines the force sensor, FPCB assembly, and control unit into an integrated tactile sensor module that is incorporated into the robot hand structure. The force sensor measures normal force while the rotational displacement sensor measures motor rotation, and the controller processes both data streams together to calculate object stiffness, merging multiple measurement functions into a unified system.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS11633850B2Tactile sensor module for robot-hand and grasping method using the same

Publication Date: 2023.04.25 KOREA INST OF SCI & TECH

AI summary

This disclosure relates to a technology for grasping an object while adjusting a grasping force according to stiffness of the object measured by a tactile sensor module, especially to a robot-hand, which includes a tactile sensor module for measuring a normal force applied when grasping an object, a phalange sensor module having an actuator to generate a driving force and configured to measure a rotational displacement of a motor, and a hand back control unit for operating the actuator by generating a desired displacement signal to control a grasping force so that a grasping motion is stably and accurately achieved by applying a minimum grasping force to soft object with no sliding and minimized deformation, wherein the desired displacement signal is generated based on stiffness which is calculated from the normal force data and the rotational displacement data.