Temperature-Compensated Force Sensor for Human-Robot Collaboration

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Solution Overview

Problem

Existing human cooperative robot systems face challenges in accurately monitoring contact force between humans and robots due to temperature-induced changes in force sensor readings, leading to potential harm from undetected robot interactions.

Innovation Solution

Incorporating temperature detection elements into the load detector and robot controller to monitor temperature changes and stop robot operations based on predetermined thresholds, ensuring safe human-robot collaboration by correcting for temperature-induced strain variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the threshold for contact force detection is set to a small value to ensure safety, then the robot can detect contact forces more sensitively, but the detection accuracy deteriorates due to temperature-induced changes in force sensor readings

Engineering Contradiction:

Improvesafety detection sensitivityVSAvoidcontact force detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the temperature detection element continuously monitors temperature changes and feeds this information back to the robot controller. The controller then adjusts the contact force threshold dynamically based on the detected temperature, compensating for thermal expansion effects on the force sensor. This closed-loop feedback system maintains both sensitivity and accuracy across varying temperature conditions.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the threshold parameter dynamically based on temperature conditions. Instead of using a fixed threshold, the system adjusts the contact force threshold as a function of detected temperature, thereby compensating for temperature-induced sensor drift and maintaining accurate detection across different thermal environments.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If a fixed threshold is used for contact force detection, then the system is simpler to operate, but the detection accuracy deteriorates under varying temperature conditions

Engineering Contradiction:

Improvethreshold setting simplicityVSAvoidcontact force detection accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The system performs self-adjustment by automatically modifying the contact force threshold based on temperature detection. The robot controller autonomously compensates for temperature effects without requiring manual recalibration or complex user intervention, maintaining both operational simplicity and detection accuracy through self-service temperature compensation.

Inventive Principle:

Principle #25Self-service

3Productivity

If the robot operates in a shared workspace with humans, then productivity increases through collaborative work, but the risk of harm to humans increases due to potential contact

Engineering Contradiction:

Improvecollaborative work efficiencyVSAvoidrisk of harm to humans

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent implements preliminary safety measures by continuously monitoring temperature and proactively adjusting the contact force threshold before harmful contact can occur. The system prepares compensation values in advance based on detected temperature trends, enabling preventive safety intervention that allows collaborative work while mitigating harm risks.

Inventive Principle:

Principle #10Preliminary action

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 solution enhances safety by minimizing the risk of human harm by accurately detecting contact forces and preventing robot operations when temperature-related inaccuracies occur, thereby improving the reliability of human cooperative robot systems.

Implementation Method 1

the volume of the metal force sensor body can change due to the change in temperature of the surroundings of the robot

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the amount of strain on the force sensor body is detected by the strain gauge

Methodology Applied

Scientific EffectStrain measurement: Deformation

Data Source

PatentUS9903774B2Robot system for monitoring contact force of robot and human

Publication Date: 2018.02.27 FANUC LTD

AI summary

The human cooperative robot system according to the present invention includes a robot, a force sensor detecting a load applied to a robot, and a robot controller controlling the robot. The force sensor includes at least one temperature detection element detecting temperature, incorporated therein. The robot controller determines whether or not to stop the operation of the robot based on the detected temperature output from the temperature detection element.