Elastic Torque Sensor with Load Path Extraction
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Solution Overview
Problem
Existing torque sensors integrated into the load path of planar torsion springs suffer from positional lag and hysteresis, leading to inaccurate torque calculations due to the load being subjected to the sensor components.
Innovation Solution
A configuration of sensors and sensor disks positioned outside the load path, with the disks attached to the input and output sides of the planar torsion spring, allowing for accurate measurement of angular deflection and torque calculation without being affected by the load, using a spring constant to determine the torque applied based on measured angular movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If torque sensors are integrated into the load path of the planar torsion spring, then torque measurement capability is achieved, but measurement precision deteriorates due to positional lag and hysteresis
Solution Approach 1:
The patent extracts the sensor components from the load path by positioning them on the stationary support structure rather than integrating them into the moving parts. The stationary sensor detects position of the moving component through non-contact means (optical, magnetic, or capacitive fields), allowing torque measurement without subjecting the sensor to mechanical loads, thereby eliminating hysteresis and positional lag while maintaining measurement capability.
2Difficulty of detecting and measuring
If sensor components are subjected to the load in the load path, then torque detection is enabled, but measurement precision deteriorates due to hysteresis
Solution Approach 1:
The patent introduces an intermediary field (optical, magnetic, or capacitive) that transfers position information from the moving component to the stationary sensor without direct mechanical contact. This intermediary mechanism enables torque detection while isolating the sensor from load-induced hysteresis, maintaining both detection capability and measurement precision.
3Strength
If the spline stiffness is increased to reduce deflection, then structural strength improves, but the spring characteristics and torque measurement range are reduced
Solution Approach 1:
The patent applies different material properties and structural characteristics to different regions of the planar torsion spring. The spline can have varying thickness, width, or material composition along its length to optimize the balance between structural strength and elastic deflection. This localized quality adjustment allows the spring to maintain adequate strength while preserving sufficient compliance for accurate torque measurement across a desired range.
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 hysteresis, achieving accurate torque measurements with hysteresis factors as low as 0.25% of the maximum load, and maintains calibration even under shock loads, enabling precise torque calculation and improved sensor accuracy.
Implementation Method 1
The splines (and thus the planar torsion spring) are not completely stiff but rather have a spring coefficient. The spring constant can be used to calculate the degree of movement of either the input side or output side relative to movement of one side in response to a quantity of a torque force.
Implementation Method 2
The sensor used as described herein may be used to determine angular movement or spring deflection. The stationary sensor component detects each marker of the sensor disk that passes in front of the stationary sensor. The stationary sensor may send a signal to a computer, programmable controller or similar device to count the number of markers that have passed per unit of time.
Data Source
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AI summary
An elastic torque sensor utilizing a torsion spring and components to measure the movement of the spring output side and input side. The torque sensor is in communication with a programmable controller. The components detecting movement or distortion of the either side of the torsion spring are not positioned within the load path experienced by the torsion spring. This configuration allows the detected position of the spring input and output sides not to be distorted by hysteresis. The components comprise a sensor disk that is attached to either the spring input or output side. The sensor disk is not within the spring load path. The sensor disk rotates with the torsion spring. The sensor disk is mark so that the degree of rotation can be detected by a stationary sensor also not in the load path. The sensor disk can send a signal to a programmable controller.