Six-Axis Force Torque Transducer Using Segmented U-Beams
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Solution Overview
Problem
Traditional six-axis force torque transducers (FTTs) are costly and difficult to manufacture due to the need for specialized tools and high-skilled labor for strain gauge attachment, and they face challenges with temperature compensation and mechanical complexity, leading to high production costs and reduced accuracy.
Innovation Solution
A compact six-axis FTT design featuring a U-shaped flexural beam with strain gauges arranged to measure shear strain, connected via a PCB, allowing for manual attachment without special equipment and efficient temperature compensation, utilizing all accessible surfaces for strain measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are attached to surfaces on different tangent planes at 90 degrees offset to measure all six force and torque components, then measurement precision is improved, but device complexity and manufacturing difficulty increase due to the need for specialized tools and high-skilled labor
Solution Approach 1:
The FTT is divided into multiple independent flexural beams, each equipped with strain gauges on accessible surfaces. Each beam independently measures specific force and torque components, and the results are combined to obtain complete six-axis measurements. This segmentation allows strain gauges to be attached to easily accessible surfaces while maintaining measurement precision.
Solution Approach 2:
The patent utilizes the third dimension (depth/thickness) of the flexural beams by attaching strain gauges to top and bottom surfaces that are easily accessible. This dimensional approach allows measurement of multiple components without requiring gauges on hard-to-reach side surfaces, thereby simplifying manufacturing while maintaining measurement capability.
2Measurement precision
If multiple flexural beams with strain gauges on all surfaces are used to resolve three orthogonal forces and three orthogonal torques, then measurement precision is improved, but ease of manufacture deteriorates due to difficult access for wire attachment and soldering
Solution Approach 1:
The FTT structure is segmented into multiple flexural beams, each responsible for measuring specific force and torque components. This segmentation allows strain gauges to be attached to the top and bottom surfaces of each beam, which are easily accessible, rather than requiring attachment to all surfaces including hard-to-reach side surfaces.
Solution Approach 2:
A PCB (printed circuit board) is introduced as an intermediary to connect the strain gauges electrically. The PCB provides accessible connection points on the outer perimeter, eliminating the need for complex wire routing and soldering operations on the flexural beams themselves, thereby significantly improving ease of manufacture.
3Ease of manufacture
If external sensors are used for temperature compensation on non-stressed surfaces, then ease of manufacture is improved, but temperature compensation accuracy deteriorates due to slow heat transfer and temperature drift
Solution Approach 1:
Temperature compensation strain gauges are merged with the load-bearing flexural beams and attached to the same stressed surfaces as the measurement strain gauges. This ensures both sets of gauges experience identical temperature conditions and mechanical stresses, enabling accurate temperature compensation while maintaining ease of manufacture through consistent attachment procedures.
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 design enables the production of ultra-compact, high-performance FTTs with reduced manufacturing costs and improved accuracy, compatible with industrial robotic systems, without requiring special assembly skills or tools, and effectively compensates for temperature fluctuations.
Implementation Method 1
Strain gauge sensors are used to translate the deformation to a change in resistance, voltage, capacitance or current
Implementation Method 2
The strain gauges are either combined in quarter bridges and/or in half bridges to resolve the necessary two components of each beam
Data Source
AI summary
A six-axis Force Torque Transducer (FTT) including a hub and at least one flexural beam disposed on the hub and extending outwardly from the hub. Each of the at least one flexural beams including a U-beam having a substantially U-shaped cross section and at least one beam plate attached to the U-beam at a portion of the U-beam that is remote from the hub. A first strain gauge carrier, including at least one strain gauge, is mounted on an exterior surface of the at least one U-beam. A second strain gauge carrier, including at least one strain gauge, is mounted on an exterior surface of the at least one beam plate. A connection element electrically connects the strain gauges of the first strain gauge carrier and the strain gauges of the second strain gauge carrier in a bridge configuration.