Torsion-Bar Force Balance Sensing for Actuator Torque Mismatch
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Solution Overview
Problem
Conventional force balance sensors for flight control surfaces face challenges in accurately measuring torque differences between actuators, leading to potential position errors and reduced service life due to increased force differences and compromised torsion bar stiffness from multiple pressure sensors or torque sensors.
Innovation Solution
A force balance sensor with a mechanical strain amplification system, including a sensor torsion member, strain sensors, and torsional stiffening members coupled to a torque member, which increases mechanical strain to bring electrical signals above noise thresholds, reducing complexity and sensor error while measuring torque differentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple pressure sensors are used to sense pressure differential across actuators, then force balance error can be determined, but the force difference increases and creates counterproductive results
Solution Approach 1:
The patent extracts the sensing function from the actuator load path by placing sensors on the torsion bar itself, rather than using multiple pressure sensors across actuators. This single sensor approach measures torque differential directly without adding force to the system.
Solution Approach 2:
The torsion bar serves as an intermediary element that transfers torque from both actuators to a single sensor location. This mediator allows measurement of the net torque differential without requiring multiple sensors that would each add force to the system.
2Measurement precision
If torque sensors are placed in series between horns and torsion bar, then force balance error can be determined, but the stiffness of the torsion bar is compromised and reduced to the stiffness of the torque sensors
Solution Approach 1:
The patent applies local quality by creating a specific sensing zone on the torsion bar where strain measurements are taken, while maintaining the full stiffness of the torsion bar throughout its structure. The sensor measures local strain without compromising overall structural rigidity.
Solution Approach 2:
The patent replaces mechanical torque sensors (which would be placed in series and compromise stiffness) with strain sensors mounted on the torsion bar. This substitution maintains the torsion bar's full stiffness while still enabling torque differential measurement through strain measurement.
3Measurement precision
If strain sensors are used directly on the torque member, then torque differences can be measured, but the electrical signals are below noise thresholds
Solution Approach 1:
The patent transitions from measuring torque directly (one dimension) to measuring mechanical strain (another dimension) and then converting to electrical signals through a bridge circuit. This dimensional transformation amplifies the signal and improves the signal-to-noise ratio.
Solution Approach 2:
The patent uses a Wheatstone bridge circuit to convert small mechanical strain into amplified electrical signals. This substitution of mechanical measurement with electrical bridge measurement significantly improves signal detectability and reduces noise impact.
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 solution effectively measures torque differences between actuators, reduces sensor error, and maintains torsion bar stiffness, improving the accuracy and service life of flight control surfaces by amplifying mechanical strain to usable signal levels.
Implementation Method 1
a sensor torsion member having a first end and a second end spaced from one another along a longitudinal axis of the sensor torsion member
Implementation Method 2
at least one strain sensor coupled to the sensor torsion member between the first and second ends
Implementation Method 3
a first torsional stiffening member coupled to the first end of the sensor torsion member, and a second torsional stiffening member coupled to the second end of the sensor torsion member
Data Source
AI summary
A force balance sensor including a mechanical strain amplification system including a sensor torsion member having a first end and a second end spaced from one another along a longitudinal axis of the sensor torsion member, at least one strain sensor coupled to the sensor torsion member between the first and second ends, a first torsional stiffening member coupled to the first end of the sensor torsion member, and a second torsional stiffening member coupled to the second end of the sensor torsion member, wherein the first torsional stiffening member and the second torsional stiffening member are coupled to a torque member.