Three-Dimensional Load Cell With Pivoting Torque Decoupling
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Solution Overview
Problem
Existing three-dimensional load cells are unable to decouple torque from linear force measurements, leading to inaccurate readings and potential damage due to spurious forces, particularly in multidimensional force applications.
Innovation Solution
A pivotally movable load element with radially symmetric beams and strain gauges that allow the load element to pivot and align with the force vector, decoupling torque by independently measuring component forces using a sensor with radially symmetric beams spaced about a central axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If three-dimensional load cells are used to measure forces in three perpendicular directions, then multidimensional force measurement capability is achieved, but torque coupling occurs and measurement accuracy deteriorates
Solution Approach 1:
The load cell is divided into three independent linear force sensing elements arranged orthogonally, each measuring force in a specific direction. By segmenting the measurement function into separate orthogonal components, the system achieves multidimensional measurement capability while preventing torque coupling between axes, as each element independently measures only its designated linear force component.
Solution Approach 2:
Each sensing element is designed with specific local properties optimized for measuring linear force in its respective direction, with geometric configurations and material characteristics tailored to respond only to axial loading. This local optimization ensures that each element maintains high measurement precision for its specific function while being insensitive to torque and lateral forces.
2Measurement precision
If conventional load cells are used for force measurement, then linear force measurement is achieved, but torque and off-center loads cause measurement errors and potential damage
Solution Approach 1:
The design accepts that torque and off-center loads will occur in practice, but configures the three orthogonal sensing elements such that these harmful effects produce equal responses in multiple elements that can be mathematically differentiated and eliminated. The harmful torque effects are converted into useful information that helps identify and remove their influence from the final measurement through computational algorithms.
Solution Approach 2:
The load cell structure serves multiple functions simultaneously: it measures linear forces in three orthogonal directions, detects torque components, and provides geometric alignment references. The same structural elements that measure linear force also detect torque through their response patterns, allowing the system to universally handle both measurement tasks with a single integrated device.
3Measurement precision
If S-beam load cells are used for force measurement, then weight or force measurement capability is achieved, but the cells become very sensitive to torque and off-center loads
Solution Approach 1:
The measurement system transitions from a single-dimensional S-beam configuration to a three-dimensional orthogonal arrangement of sensing elements. By adding spatial dimensions to the measurement architecture, the system maintains the force measurement capability of the original S-beam design while eliminating its torque sensitivity through the orthogonal geometry that naturally decouples linear force from rotational moment measurements.
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
Accurate measurement of three-dimensional force vectors is achieved by decoupling torque, ensuring precise force readings without parasitic loads and sensor damage, suitable for applications requiring multidimensional force interaction.
Implementation Method 1
A strain gauge is an electrically resistant wire gauge that is bonded to a member to measure surface strains. A strain gauge will measure the change in deformation by providing a signal in the form of resistance
Implementation Method 2
by knowing its sensitivity to strain, referred to as the gauge factor, Hooke's law may be used to determine the stress
Implementation Method 3
When a force is applied, the middle of the beam acts as a spring and compresses or elongates by elastic deformation proportional to the force applied
Implementation Method 4
Shear beam load cells measure the shear strain on the beam
Data Source
AI summary
Disclosed herein is a torque insensitive three dimensional force measurement device and load cell therefor. A pivotally movable load element eliminates torque by moving independently of a sensor. The load element aligns with the direction of an input force. The pivotally movable load element decomposes an input force vector into force components that are measured by at least three radially symmetric beams spaced about a central axis. Each of the beams has a fixed end and a free end. The beams are operatively constrained at their fixed end and free to deflect at their free end. Each of the beams is disposed to deflect independently from a component force transmitted by the load element. Each beam has at least one strain gauge operatively bonded thereto. A force measurement device further comprises a base, circuit board, nonvolatile memory, random access memory, a processor, and a display screen.