Actuator Load Sensing via Torsional Spring Segmentation
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Solution Overview
Problem
Conventional electro-mechanical actuators are unable to accurately sense actuator output load across a large operating range without compromising structural stiffness, as traditional load sensors have a minimum sensed load capability of about 5% to 10% of the maximum load, limiting their sensitivity and accuracy.
Innovation Solution
An electro-mechanical actuator with a wide operating range load feedback mechanism, featuring a speed summed differential coupled to a shaft, a torsional spring, and a rotary position sensor, which measures output torque and load without deforming the sensor element, allowing for accurate load detection from zero to maximum load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional load sensor is used to measure actuator output load, then load measurement capability is provided, but the sensor cannot accurately sense loads across a large operating range (minimum sensed load is 5% to 10% of maximum load) and compromises structural stiffness
Solution Approach 1:
The load measurement function is segmented from the main actuator structure through the use of a separate torsional spring element. This spring element is specifically designed to deform only under load conditions, while the main actuator structure maintains its structural stiffness. The segmentation allows the sensor component to be optimized for measurement sensitivity without compromising the overall structural integrity.
Solution Approach 2:
A torsional spring element is introduced as an intermediary between the actuator output and the load sensor. This spring element transfers the load information to the sensor while isolating the sensor from the high-stiffness requirements of the main actuator structure. The spring acts as a mechanical mediator that converts large-scale structural forces into measurable deformations suitable for the sensor's operating range.
2Strength
If the actuator structure is made stiffer to maintain structural integrity, then structural stiffness is improved, but the ability to sense small loads is reduced
Solution Approach 1:
The system is divided into two functional segments: the main actuator structure optimized for strength and stiffness, and a separate sensing segment using a torsional spring optimized for measurement sensitivity. This segmentation allows each component to be optimized for its specific function without compromise.
Solution Approach 2:
Different parts of the system have different mechanical properties: the main actuator structure has high stiffness for structural integrity, while the torsional spring element has low stiffness for sensitivity. This local differentiation of mechanical properties allows the system to simultaneously achieve both structural strength and measurement sensitivity.
3Reliability
If a load sensor is integrated into the actuator, then load feedback is provided, but the sensor element deforms under load which limits the operating range and compromises calibration
Solution Approach 1:
The torsional spring serves as a mediator that protects the sensor element from direct exposure to full load conditions. The spring absorbs the mechanical stress and presents a scaled, manageable deformation to the sensor, maintaining calibration stability across the full operating range while enabling reliable load feedback.
Solution Approach 2:
The system changes the mechanical parameter (deformation magnitude) through the torsional spring, transforming large load-induced deformations into smaller, sensor-appropriate deformations. This parameter transformation allows the sensor to operate within its calibrated range while measuring loads across the entire actuator operating 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
Enables accurate measurement of both small and large loads without compromising structural stiffness, maintaining sensor calibration and sensitivity across the entire operating range, thereby improving the actuator's performance and reliability.
Implementation Method 1
a torsional spring coupled to the speed summed differential by way of a rotary position sensor
Implementation Method 2
a rotary position sensor for detecting the rotation of the shaft thereby measuring the output torque of the shaft
Data Source
Figure 1~2
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AI summary
An electro-mechanical actuator (100; 200) with wide operating range load includes a shaft (102; 202) and a speed summed differential (110; 210) coupled to rotate the shaft. A prime mover (120; 220) is coupled to the speed summed differential and is configured to react to an output torque of the screw shaft. A torsional spring (130; 230) coupled to the speed summed differential by way of a rotary position sensor (132; 232) for detecting the rotation of the screw shaft thereby measuring the output torque of the shaft for control of the prime mover.