Robotic Force Torque Sensor Thermal Conduction
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Solution Overview
Problem
Existing force/torque sensors in robotics face inaccuracies due to thermal changes, which cause resistance variations and material expansion, leading to errors in force and torque measurements, especially with uneven heating patterns that current compensation techniques struggle to address effectively.
Innovation Solution
A robotic force/torque sensor design that channels heat generated by a tool radially through a thermally conductive member to the center of the sensor body, while using a thermally insulating member to isolate other parts, ensuring all transducers experience a uniform thermal load, thereby eliminating thermal gradients and enhancing the effectiveness of temperature compensation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heat is conducted through the sensor body from the tool interface, then thermal equilibrium is achieved, but thermal gradients across transducers cause measurement errors
Solution Approach 1:
The patent applies local quality by creating different thermal conduction paths in different regions of the sensor body. A thermally conductive member is placed at the center to conduct heat radially outward, while thermally insulating members are positioned at radial locations to block heat conduction in those directions. This creates controlled thermal gradients that ensure all transducers experience uniform temperature changes, eliminating differential thermal expansion errors while maintaining thermal equilibrium.
2Area of stationary object
If transducers are positioned at different distances from the heat source, then coverage is improved, but differential thermal loading causes measurement errors
Solution Approach 1:
The patent uses asymmetry in the thermal conduction structure to achieve symmetric thermal loading on transducers. The thermally conductive member is positioned asymmetrically at the center, creating radial heat flow paths of equal length to all transducer locations. This asymmetric placement of the heat conduction pathway ensures that despite transducers being at different radial distances from the tool interface, they all experience the same temperature changes simultaneously.
3Stability of the object's composition
If thermal insulation is applied to block heat conduction, then thermal stability is improved, but heat dissipation is reduced
Solution Approach 1:
The patent segments the thermal conduction paths by dividing the sensor body into distinct thermal zones using thermally insulating members positioned at radial locations. This segmentation allows heat to be conducted efficiently along controlled paths through the thermally conductive member while blocking unwanted heat conduction in other directions. The segmented approach maintains thermal stability in transducer regions while allowing heat dissipation through designated pathways.
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 design significantly reduces thermal-induced errors by ensuring all transducers experience temperature changes simultaneously, allowing for more accurate force and torque measurements by simplifying temperature compensation and improving the rejection of common-mode signals in differential circuit topologies.
Implementation Method 1
channels heat generated by a tool radially through a thermally conductive member to the center of the sensor body
Implementation Method 2
using a thermally insulating member to isolate other parts, ensuring all transducers experience a uniform thermal load
Implementation Method 3
strain gage Temperature Coefficient of Resistance (TCR) arises as the resistance of a silicon strain gage changes with its temperature
Implementation Method 4
sensor body material expansion, as well as other effects
Data Source
AI summary
A robotic force/torque (FT) sensor restricts the conduction of heat, generated by an attached tool, through the FT sensor body to a radial direction. Heat from the tool is channeled to the center of the FT sensor body by a thermally conductive member. Additionally, heat from the tool is insulated from portions of the FT sensor body other than its center by a thermally insulating member. Transducers, such as strain gages attached to the surfaces of deformable beams, are disposed at a substantially equal distance from the center of the FT sensor body. Accordingly, as heat conducts through the FT sensor body from the center radially outwardly, all transducers experience substantially equal thermal load at any given time. Embodiments of the present invention substantially eliminate thermal gradients across groups of transducers that are wired in differential circuit topologies, such as half-bridge or quarter-bridge, enhancing the ability of such circuits to reject a common-mode signal component caused by thermal changes to the FT sensor body or the transducers themselves. Elimination of thermal gradients in the FT sensor body, other than one in the radial direction, enhances the effectiveness of known temperature compensation techniques.