S-Shaped Tactile Load Cell for Six-Degree-of-Freedom Robotic Finger Sensing
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Solution Overview
Problem
Existing load measurement systems for robotic fingers, such as single axis contact sensors and commercial load cells, fail to provide accurate six-degrees of freedom load resolution due to size constraints and inability to measure forces along multiple axes, limiting their application in dexterous robotic systems.
Innovation Solution
A tactile load cell with a flexible strain element featuring S-shaped members and eight strain gauge pairs, allowing for compact integration within robotic fingers to measure forces in six-degrees of freedom, including three linear and three rotational directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single axis contact sensors are used to measure load on robotic fingers, then the device complexity is reduced, but the measurement precision is insufficient because they cannot measure forces acting along more than one axis
Solution Approach 1:
The load cell is segmented into multiple S-shaped members (first and second S-shaped members) with multiple sections each, allowing independent measurement of forces along different axes. Each S-shaped member can deform independently in response to forces applied in different directions, enabling multi-axis load measurement while maintaining a relatively simple overall structure.
Solution Approach 2:
The invention transitions from single-axis measurement to six-degrees-of-freedom measurement by adding dimensional capability. The S-shaped members are configured to detect forces in multiple directions (x, y, z axes and rotational moments), effectively adding spatial dimensions to the measurement capability without proportionally increasing structural complexity.
2Measurement precision
If commercial load cells are used to measure load values, then the measurement precision is improved, but the volume is too large to be housed inside every section of a finger of the robotic hand
Solution Approach 1:
The load cell employs flexible S-shaped members as strain elements instead of rigid commercial load cell structures. These flexible members can be made thin and compact while maintaining the ability to detect forces and moments. The flexibility allows the strain elements to deform under load and transfer this deformation to strain gauges for measurement, achieving accurate load sensing in a compact form factor suitable for integration within robotic finger sections.
Solution Approach 2:
The invention achieves six-degrees-of-freedom measurement capability in a compact volume by using multiple S-shaped members with multiple sections. This multi-sectional design allows the load cell to capture complex force and moment information without requiring the large volume of traditional commercial load cells, enabling integration within the constrained space of robotic finger sections.
3Measurement precision
If multiple strain gauge pairs are mounted on S-shaped members to measure six-degrees of freedom, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The S-shaped members serve multiple functions: they act as structural elements connecting different parts of the load cell, as sensing elements that deform under various types of loads, and as mounting substrates for strain gauges. Each S-shaped member with multiple sections can detect different components of the six-degrees-of-freedom load, making the structure universal and multi-functional rather than requiring separate dedicated sensors for each measurement axis.
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
Enables precise load measurement in six-degrees of freedom, providing direction and orientation information for applied loads, and identifying potential malfunctions like slippage, while being compact enough to fit within the robotic hand's phalanges.
Implementation Method 1
eight strain gauge pairs where each strain gauge pair is mounted to opposing surfaces of one of the sections of the S-shaped members where the strain gauge pairs provide strain measurements in six-degrees of freedom
Data Source
AI summary
A tactile load cell that has particular application for measuring the load on a phalange in a dexterous robot system. The load cell includes a flexible strain element having first and second end portions that can be used to mount the load cell to the phalange and a center portion that can be used to mount a suitable contact surface to the load cell. The strain element also includes a first S-shaped member including at least three sections connected to the first end portion and the center portion and a second S-shaped member including at least three sections coupled to the second end portion and the center portion. The load cell also includes eight strain gauge pairs where each strain gauge pair is mounted to opposing surfaces of one of the sections of the S-shaped members where the strain gauge pairs provide strain measurements in six-degrees of freedom.