Torque Measurement on Rotating Shafts Using Elastic Deformation
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Solution Overview
Problem
Existing torque measurement systems for rotating shafts are cumbersome and costly due to the need for speed sensors placed far apart, making it difficult to accurately measure torque on short rotating shafts.
Innovation Solution
A compact torque measurement system that uses elastically deformable elements and magnetic sensors to detect rotational angle displacement, allowing for precise torque measurement without the need for extensive sensor placement, by observing the rotational angle shift between deformable housing portions and a static frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two speed sensors are placed at each extremity of the rotating shaft to measure torque, then torque measurement is achieved, but the distance between sensors increases the cost and size of the system
Solution Approach 1:
The patent combines the torque measurement function with a single speed sensor by using the elastic deformation of the shaft itself as the measurement element. The strain gauges are mounted on the shaft at a single location, and the shaft's elastic deformation under torque is measured to calculate torque, eliminating the need for two separate speed sensors placed far apart.
Solution Approach 2:
The patent introduces elastic deformation as an intermediary mechanism between the applied torque and the measurement. The shaft's elastic deformation serves as a mediator that converts the torque into a measurable displacement, which is then detected by strain gauges and processed through a Wheatstone bridge to obtain the torque value.
2Measurement precision
If strain gauges are mounted on a rotating shaft to measure torque, then torque measurement is possible, but supplying power to and extracting signals from the rotating shaft becomes difficult
Solution Approach 1:
The patent replaces the direct mechanical connection method with an electrical measurement approach. Instead of mechanically tracking the rotation to measure torque, strain gauges are used to detect the shaft's elastic deformation electrically, and the Wheatstone bridge circuit converts these deformation signals into measurable electrical outputs, simplifying power supply and signal extraction.
3Measurement precision
If speed sensors are placed far apart to measure torque on a rotating shaft, then torque measurement is achieved, but the system becomes costly and unsuitable for short shafts
Solution Approach 1:
The patent merges the torque measurement capability into a compact form by using the shaft's own elastic properties as the measurement element. This allows torque measurement on short shafts by utilizing the shaft's deformation characteristics rather than requiring long baseline distances between sensors.
Solution Approach 2:
The patent changes the measurement parameter from rotational speed difference (requiring long distances) to elastic deformation (which can be measured locally). By measuring the shaft's elastic deformation under torque at a single location, the system can accurately measure torque on short shafts without requiring the shaft to span a large distance.
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 system provides accurate and cost-effective torque measurement on short rotating shafts, such as those in electrical bicycles, by translating rotational angle shifts into measurable sensor signals, enhancing the efficiency and compactness of the measurement process.
Implementation Method 1
a first housing portion (104) including one or more elastically deformable elements (34)
Implementation Method 2
a sensor (306) observing the second end (310) of the first housing portion (104) and the second housing portion (304)
Data Source
Figure 1
Figure 2
Figure 2A
AI summary
A torque measurement system for measuring a torque acting on a rotatable shaft is provided. The torque measurement system includes a first housing portion having a first end adapted to be fixedly coupled to the rotatable shaft and a second end. The torque measurement system includes a second housing portion having a first end spaced apart from the second end of the first housing portion so as to define a gap between the first housing portion and the second housing portion. The second housing portion is adapted to be fixedly coupled to the rotatable shaft. The torque measurement system includes at least one sensor that observes at least one of the second end of the first housing portion, the first end of the second housing portion and the gap and generates sensor signals based on the observation. The sensor signals are indicative of a torque acting on the rotatable shaft.