Deformable Cover Pressure Sensor for Robotic Landing Gear
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Solution Overview
Problem
Current force sensors for robotic landing gear (RLG) face challenges in sensitivity, robustness, and durability, particularly in detecting low forces and withstanding harsh environments, with existing technologies like resistive film sensors, load cells, and magnet-based sensors exhibiting inconsistencies, lack of redundancy, and susceptibility to electromagnetic interference.
Innovation Solution
A sensing device comprising a pressure sensor, a deformable cover, and a deformable cavity filled with fluid, where the deformable cover deforms under external force, altering the pressure sensed by the pressure sensor, allowing for sensitive detection of low forces and high durability, with the ability to withstand forces up to 10 kilonewtons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resistive film sensors are used for force measurement, then the sensors are simple to implement, but they lack consistency and robustness, requiring calibration before each flight and cracking after limited usage
Solution Approach 1:
The patent replaces resistive film sensors with a capacitive sensing system that uses electromagnetic fields to detect force. The capacitive sensor measures changes in capacitance caused by deformation of the robotic leg structure, eliminating the mechanical contact and wear issues of resistive films while maintaining simplicity of implementation
Solution Approach 2:
The patent changes the measurement parameter from electrical resistance to electrical capacitance. By measuring capacitance changes rather than resistance changes, the system achieves better stability and consistency without requiring frequent calibration, as capacitance measurements are less susceptible to drift over time
2Strength
If load cells are used to withstand the entire weight of the aircraft, then the sensors are robust, but they do not have sufficient sensitivity at small loads and add significant weight to the system
Solution Approach 1:
The patent divides the force measurement function into two separate systems: a capacitive sensor for measuring small contact forces during landing, and the robotic leg structure itself for withstanding the aircraft's full weight. This segmentation allows each component to be optimized for its specific function without compromise
Solution Approach 2:
The patent introduces the robotic leg structure as an intermediary element between the capacitive sensor and the ground. The leg structure absorbs and withstands the majority of the load, while the capacitive sensor measures only the small contact forces, enabling both robustness and sensitivity
3Measurement precision
If load cells are used for ground contact sensing, then the sensors can measure force, but they suffer from inertial effects where vibrations produce erroneous force readings
Solution Approach 1:
The patent replaces the mechanical load cell with a capacitive sensing system that measures force through electromagnetic field changes rather than mechanical deformation. This substitution eliminates inertial effects because the capacitive measurement is not subject to the same dynamic response issues as mechanical sensors
Solution Approach 2:
The patent creates an electrical copy of the force measurement function using capacitance changes rather than direct mechanical measurement. By measuring the electrical field changes caused by leg deformation, the system obtains force information without the harmful inertial effects of mechanical sensors
4Adaptability or versatility
If magnet-based sensors are used to estimate contact force, then the sensors enable tailoring of sensor properties, but they are susceptible to electromagnetic interference that skews measurements
Solution Approach 1:
The patent converts the potential harm of electromagnetic interference into a benefit by using capacitive sensing, which is inherently less susceptible to EMI than magnetic field-based sensors. The capacitive measurement approach naturally filters out electromagnetic interference while still allowing for tailored sensor properties through adjustable capacitance values
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 provides a robust and sensitive force measurement system capable of detecting forces as low as 1 millinewton while withstanding up to 10 kilonewtons, offering improved durability and redundancy, suitable for harsh environments and complex terrains.
Implementation Method 1
The deformable cavity and the sensor cavity can contain a fluid, such that when an external force is applied to a surface of the deformable cover, the deformable cavity deforms and alter a volume of the deformable cavity to alter a pressure sensed by the pressure sensor
Implementation Method 2
The deformable cover can comprise a polymer or an elastomer... when an external force is applied to a surface of the deformable cover, the deformable cavity deforms
Data Source
AI summary
A sensing device includes a pressure sensor and a deformable cover. A fluid cavity engineered between the deformable cover and the pressure sensor changes shape and ultimately collapses as force is applied to the sensing device. The shape and collapse of the engineered cavity, along with the entire structure of deformable cover and the pressure sensor, govern the force vs. pressure behavior of the sensing device and can be tailored as desired. A first benefit includes providing tailored properties of the sensing device by varying the structure of the deformable cover. A second benefit includes that if too much force is applied, excess force—beyond that which is required to collapse the engineered cavity—does not produce excess pressure which would cause damage to the pressure sensor. As such the sensing device is protected from accidental, or intended, over loading.