Torque Measurement Flexplate Strain Sensor Neutral Axis Placement
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Solution Overview
Problem
Conventional torque measurement flexplates using SAW sensing elements face inaccuracies due to unwanted strains from out-of-plane bending and axial loads, as the simplistic approach of locating sensors on a single 'local neutral axis' fails to account for multiple neutral axes, leading to incomplete strain cancellation and measurement inaccuracies.
Innovation Solution
The torque measurement flexplate features a strain sensor positioned proximate to one of the local neutral axes, with radial slots and reduced thickness circumferential webs to decouple the sensor from twisting forces and reduce bending stiffness, allowing for common mode signal subtraction and enhanced strain measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SAW sensing elements are placed on the flexplate to measure torque, then torque measurement capability is achieved, but measurement precision deteriorates due to unwanted strains from out-of-plane bending and axial loads
Solution Approach 1:
The sensing element is divided into multiple active regions arranged at specific orientations (e.g., 0°, 45°, 90°, 135°) around the flexplate. Each active region measures strain in a different direction, and through signal processing (difference and sum operations), the system separates useful torque signals from unwanted bending and axial strain signals, achieving rejection of harmful factors while maintaining measurement precision
Solution Approach 2:
The patent places sensing elements at specific locations and orientations where they can selectively measure different strain components. By positioning active regions at particular angles and depths, the system creates local measurement zones that are sensitive to torque while being less sensitive to bending and axial loads, thereby improving measurement precision without being affected by unwanted strains
2Measurement precision
If multiple sensing elements are installed on the flexplate to improve measurement accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The sensing element is designed as a multi-functional device where a single integrated sensor structure performs multiple measurement functions simultaneously. The sensing element measures torque, bending strains, and axial loads through its multiple active regions, and the system processes these signals to extract pure torque measurements, thereby achieving high measurement precision without requiring multiple separate sensing devices
Solution Approach 2:
The patent combines multiple strain measurement functions into a single integrated sensing element. By merging multiple active regions at different orientations into one sensor component, the system achieves comprehensive strain measurement capability while simplifying the overall device structure, reducing the number of separate components needed, and maintaining measurement precision
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 configuration significantly reduces unwanted strains by at least 50% compared to conventional designs, improving torque measurement accuracy and minimizing the impact of twisting and bending forces, while maintaining non-contact communication without active electronic components.
Implementation Method 1
the sensor lies at least proximate to one of the local neutral axes relating to one of a plurality of unwanted strains to which the flexplate is subject in use
Implementation Method 2
SAW sensing elements advantageously permit wireless interrogation without requiring an installed power supply at the sensing elements and have a frequency response sensitive to strain at UHF, for instance, 420-450 MHz
Data Source
AI summary
A torque measurement flexplate (20) includes a substantially planar body (54) which defines a plurality of circumferentially distributed axial through apertures (22), a radial web (24) extending between each pair of adjacent axial apertures (22). The flexplate (20) further defines a plurality of circumferentially distributed axial outer fastening holes (26) for attachment to an output member. The flexplate (20) includes a strain sensor (28) for measuring the shear strain field on the flexplate (20). The flexplate (20) defines a recess (30) in which the strain sensor (28) is located, the recess (30) being defined in an axial surface (32) of one of the radial webs (24) such that, in use, the sensor (28) lies at least proximate to one of the local neutral axes (34) relating to one of a plurality of unwanted strains (36) to which the flexplate (20) is subject in use.