Stabilized UAV Recovery System Ship Motion Compensation
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Solution Overview
Problem
Current UAV recovery systems face challenges in accommodating a wide range of UAV sizes, managing wave-induced ship motions, and handling vertical flight path errors, particularly for larger UAVs, and struggle with the handling and placement of captured UAVs after recovery.
Innovation Solution
A computer-controlled robot arm with a kinematic arrangement similar to a backhoe, equipped with a capture mechanism including an arresting line and winch, ship motion sensors, and a UAV position sensing system, which compensates for ship motion and vertical flight path errors, and features an arresting hook on the UAV fuselage for stable capture and handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hanging cable system is used for UAV recovery, then capture over the side of the ship is enabled, but the UAV structure must be heavily modified to withstand severe turning moments and cable impacts
Solution Approach 1:
Instead of having the cable hang vertically from above and the UAV turn sharply to capture it, the system inverts the approach by having the UAV maintain a relatively straight flight path and the cable system adapt its position and angle to meet the UAV. The robotic arm with multiple joints positions the cable intercept point dynamically, allowing the UAV to capture the cable with minimal structural stress while the system does the work of adaptation.
Solution Approach 2:
The cable intercept point is made dynamic through a robotic arm with multiple actuated joints rather than being fixed. The system continuously adjusts the position, height, and angle of the cable intercept point in real-time based on UAV position, ship motion, and flight path variations, transforming a static structural challenge into a dynamic control solution.
2Ease of operation
If an arresting line system is used for UAV recovery, then capture over the side of the ship is achieved, but the system cannot accommodate significant vertical flight path errors caused by wind buffeting or guidance errors
Solution Approach 1:
The system incorporates continuous feedback from sensors tracking UAV position, velocity, and orientation, as well as ship motion from inertial measurement units. This feedback drives real-time adjustments of the robotic arm and cable position to maintain optimal intercept geometry despite vertical flight path errors, allowing the system to accommodate wind buffeting and guidance variations.
Solution Approach 2:
The cable intercept point's vertical position is dynamically adjusted through the robotic arm's degrees of freedom, allowing the system to track and compensate for vertical deviations in the UAV's flight path. The robotic arm actively positions the cable at the appropriate height and angle to match the UAV's actual trajectory rather than requiring the UAV to follow a perfectly predetermined path.
3Device complexity
If a fixed boom system is used for UAV recovery, then a simple capture mechanism is provided, but the boom rotates upwards and downwards with ship rolls and heaves, complicating the hook capture task
Solution Approach 1:
Instead of a fixed boom that passively rotates with ship motion, the system uses an actively controlled robotic arm with multiple joints. The robotic arm dynamically compensates for ship rolls and heaves by adjusting its own configuration, maintaining a stable and predictable cable intercept point relative to the approaching UAV despite the moving ship platform.
Solution Approach 2:
The robotic arm acts as an intermediary between the ship's moving platform and the cable capture system. It isolates the capture mechanism from direct ship motion effects by providing an actively controlled linkage that can compensate for platform movements, delivering a stable target for the UAV hook.
4Ease of operation
If net-based capture is used for UAV recovery, then shipboard recovery is enabled, but there is risk of damage to the UAV and potential for the UAV to be ensnared in the net
Solution Approach 1:
The system extracts the UAV from the hazardous environment of the ship's air wake and turbulence by enabling capture over the side of the ship, away from the superstructure. The cable-based mechanism provides a clean, simple capture interface that avoids the entanglement risks of nets while maintaining effective recovery capability.
Solution Approach 2:
The system uses a simple, replaceable cable segment at the intercept point rather than a complex or fragile capture device. The cable can be quickly replaced if needed, providing a reliable and maintainable capture interface that doesn't risk damaging the expensive UAV.
5Ease of operation
If water landing is used for UAV recovery, then shipboard recovery is enabled, but the UAV must be heavily modified for water landings and must be recovered from the water after landing
Solution Approach 1:
The system extracts the recovery process from the water environment entirely, performing capture in the air over the side of the ship. This eliminates the need for UAV modifications related to water landings and removes the subsequent step of recovering the UAV from water, keeping the airframe design simpler and the recovery process more direct.
Data Source
AI summary
A stabilized UAV recovery system is disclosed. In the illustrative embodiment for UAV recovery over water, the system includes ship-based elements and UAV-based elements. The ship-based elements include a robot arm that holds a capture mechanism over the side of the ship while compensating for wave-induced ship motion. The UAV-based elements include a hook mounted to the top of the UAV fuselage. With the capture mechanism held stable from the perspective of a UAV approaching from behind or in front of the mechanism, the UAV is flown under it, snagging an arresting line with the hook. With continued forward motion of the UAV, the arresting line pulls out of a winch drum that is coupled to a brake, bringing the UAV to rest.