Rotorcraft Cable Angle Detection Using Linear Displacement Sensors
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Solution Overview
Problem
Existing methods for determining the position of hanging loads on rotary-wing aircraft are unreliable in low visibility environments and add complexity or weight to the aircraft, such as using video cameras or ball joints with sensors.
Innovation Solution
A pair of linear displacement sensors mounted on the rotorcraft and cable to measure the angle of the cable relative to the rotorcraft, providing a low-cost, reliable, and lightweight solution that operates independently of environmental conditions like fog or rain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If video cameras are used to determine payload position, then the system can visualize the payload, but it fails in low visibility environments like fog, rain, or dust
Solution Approach 1:
The patent replaces the optical-based video camera system with a mechanical sensing system using linear displacement sensors that directly measure cable angle through physical displacement detection. This substitution eliminates dependence on visual conditions, allowing reliable operation in fog, rain, or dust where cameras fail.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using the cable itself as the sensing element. Instead of trying to see the payload directly, the system measures the cable's angular position through displacement sensors mounted on the cable, which translates mechanical displacement into position information without requiring line-of-sight visibility.
2Measurement precision
If an inverted joystick approach with a ball joint is used to measure payload position, then the system can measure movement, but the ball joint must support the full payload weight adding significant size and weight
Solution Approach 1:
The patent segments the measurement function from the support function. Instead of using a single ball joint that must both support the payload weight and measure movement, the system uses separate linear displacement sensors mounted on the cable that only measure angle without bearing the payload weight. This segmentation allows the measurement components to be lightweight while the cable structure handles the weight support.
Solution Approach 2:
The patent extracts the measurement function from the structural support function. The linear displacement sensors are mounted on the cable rather than requiring a heavy ball joint structure. This extraction allows the sensing elements to be lightweight and simple, while the cable and mounting structure handle the weight support separately.
3Measurement precision
If an inverted joystick approach with sensors is used, then payload movement can be measured, but the sensor complexity increases the risk of system failure
Solution Approach 1:
The patent uses simple, inexpensive linear displacement sensors that are easier to manufacture and less prone to failure compared to complex ball joint sensor systems. These sensors can be readily replaced if needed and do not require the complex calibration and alignment of sophisticated orientation sensors.
Solution Approach 2:
The patent replaces complex mechanical orientation sensors with simple linear displacement sensors that measure only the angular position of the cable through cable displacement. This substitution dramatically simplifies the sensing system while maintaining measurement capability, reducing both complexity and failure risk.
4Measurement precision
If specialized visual markers are applied to the payload for camera-based tracking, then accurate payload location is achieved, but the system fails when markers are forgotten or invisible
Solution Approach 1:
The patent uses the cable as an intermediary element that connects the rotorcraft to the payload. Instead of marking the payload directly, the system measures the cable's angular position, which indirectly indicates payload location. This intermediary approach eliminates the need for visual markers on the payload, as the cable's motion naturally traces the payload's position path.
Solution Approach 2:
The patent creates a mechanical copy of the payload's motion path through the cable's movement. By measuring the cable's angular displacement, the system obtains a scaled and transformed representation of the payload's position, eliminating the need for direct visual observation of the payload itself.
Data Source
AI summary
Embodiments described herein provide for detecting an angle of a cable attached to a rotorcraft for transporting a hanging payload using a pair of linear displacement sensors that are coupled to both the rotorcraft and the cable. One embodiment is a cable angle detector mounted to an underside of a rotorcraft. A cable has one end coupled to the rotorcraft and another end coupled to a payload. A pair of linear displacement sensors has one end coupled to the underside of the rotorcraft and another end coupled to the cable. The detector measures the displacement of the sensors and calculates an angle of the cable relative to the rotorcraft based on the measurements.