Rotational Torque Measurement via Phase Difference Detection
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Solution Overview
Problem
Torque measurement devices face challenges with measurement errors due to inertia of rotating components and the inapplicability of strain gauges to rotating members, which affect accuracy and reliability.
Innovation Solution
A device and method utilizing first and second torsion reference members fixedly coupled to a rotating member, with detectors generating signals based on the passage of these members, allowing a controller to calculate the phase difference and determine the torque loading by comparing the phase difference to a reference value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are used to measure torque, then torque measurement is achieved, but measurement error occurs due to inertia of rotating components and wires are required which make them inapplicable to rotating members
Solution Approach 1:
The patent replaces the mechanical strain gauge system with an optical measurement system. Optical encoders detect the rotational position of the shaft, and the control unit calculates torque based on the phase difference between signals from multiple encoders, eliminating the need for mechanical strain gauges on rotating components.
Solution Approach 2:
The patent introduces optical encoders as intermediary devices that indirectly measure torque. Instead of directly measuring stress on the rotating shaft, the encoders detect rotational position, and the control unit derives torque information from the phase difference, using the encoders as mediators between the shaft and measurement system.
2Adaptability or versatility
If strain gauges are attached to deformable members, then torque can be converted to electrical signal, but the wires make them inapplicable to rotating members
Solution Approach 1:
The patent replaces the wire-based electrical strain gauge system with a contactless optical measurement system. Optical encoders mounted on the rotating shaft generate signals detected by stationary sensors, eliminating the need for flexible wires and making the system suitable for rotating applications.
Solution Approach 2:
The patent uses optical encoders that create optical copies or representations of the shaft's rotational position. The encoders transfer positional information through optical fields rather than physical wire connections, enabling measurement without mechanical or electrical contacts to the rotating member.
3Measurement precision
If phase difference calculation method is used, then measurement error due to inertia is minimized, but device complexity increases with multiple detectors and controllers
Solution Approach 1:
The patent divides the measurement system into multiple independent optical encoders positioned at different locations on the shaft. Each encoder generates its own signal, and the control unit processes these segmented signals by calculating phase differences, allowing inertia effects to be eliminated through comparative analysis.
Solution Approach 2:
The control unit continuously monitors the phase difference between signals from multiple encoders and uses this feedback to calculate torque. The system continuously compares the rotational positions detected by different encoders, providing real-time torque measurement that compensates for inertial effects through active feedback processing.
Data Source
AI summary
A device for measuring torque applied through a rotating member. A first torsion reference member is fixedly coupled to the rotating member at a first axial position and a second torsion reference member is fixedly coupled to the rotating member at a second axial position. A first detector detects the passage of the first torsion reference member past the first detector upon each full rotation of the rotating member and to generate a first signal upon each passage of the first torsion reference member. A second detector detects the passage of the second torsion reference member past the second detector upon each full rotation of the rotating member and to generate a second signal upon each passage of the second torsion reference member. A controller calculates a phase difference between the first signal and the second signal relative during rotation of the rotating member under a torsional load.