Researchers invented a hinge that improves how quickly a quadrotor the size of a king-sized mattress can ascend from the ground to the rooftop of a two-story building, particularly with large payloads. The hinge is located at the root of the quadrotor blade next to the hub so that the blade pitch changes with rotor speed.

As quadrotors and similar aircraft are scaled up, the extra inertia of the rotor blade slows them down. It can take a long time for lightweight electric motors to change the rotor speed and thrust, which ultimately impacts the vehicle's speed, range, and flight stability. With the new coupling, the thrust becomes more sensitive to changes in rotation per minute (RPM).

The difference is that large quadrotors carrying these loads could climb roughly 25 feet in as little as two seconds with the hinge, instead of three or four seconds without it.

Increasing the thrust sensitivity to changes in the RPM will allow for greater control authority and more agility. Helicopters with four rotors, commonly referred to as quadrotors or quadcopters, are part of a family of unmanned aircraft systems that have two pairs of counter-rotating rotors and propellers. These vehicles can hover, fly forward, and perform vertical takeoffs and landings, similar to helicopters.

Common requirements for Army quadcopters include speed, flexibility, adaptability, providing real-time surveillance and carrying payloads. This invention will likely improve agility without fully committing to a swashplate and the weight penalties associated with it.

Designs usually are made around the issues of responsiveness in one of two ways. A swashplate is added to actively control the blade pitch or smaller rotors are put on the aircraft like an octacopter. Both of these solutions weigh more, which means the aircraft can't carry as much gear, cameras, or batteries.

For more information, contact DEVCOM, Army Research Laboratory Public Affairs at 703-693-6477.


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This article first appeared in the May, 2021 issue of Tech Briefs Magazine.

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