Download "World's Smallest Cyclocopter (Texas A&M University)"

The world’s smallest cycloidal-based rotorcraft, or cyclocopter, has been recently designed, built and test flown successfully at Texas A&M University, Advanced Vertical Flight Laboratory under the direction of Dr. Moble Benedict, with graduate students Carl Runco and David Coleman. Weighing only 29 grams, it utilizes the latest advances in microelectronics technology and carbon fiber composite construction, as well as extensive experimental data for design and optimization. The cyclorotor, unlike traditional helicopter rotors, utilizes a horizontal axis of rotation with the blade span parallel to this axis. With the blades cyclically pitched such that each blade has a positive geometric angle of attack at the top and bottom of the circular trajectory, a net thrust is produced. The mechanism that generates this pitching motion allows complete 360 degree thrust vectoring capabilities, one major advantage of the cyclocopter which allows the vehicle to fly in flight regimes unsuitable for traditional helicopters and multi-copters. Additionally, recent studies have shown that a cyclorotor can achieve higher hover efficiency than a conventional rotor at smaller scales, because of uniform lift distribution and favorable unsteady aerodynamic environment along the blade span. For these reasons, the cyclocopter is advantageous for applications such as search and rescue operations and indoor to outdoor surveillance and reconnaissance in which high hover efficiency, agility and gust-tolerance are needed. The current vehicle prototype utilizes cantilevered rotor blades with a semi-elliptical planform shape, resulting in a novel, lightweight cyclorotor design. To minimize blade bending, a unique, high strength-to-weight ratio unidirectional carbon-fiber based structural design is employed, and the blades are fabricated using a specialized manufacturing process which ensures consistency and lightweight results (0.12 grams each). During flight, roll is controlled by varying the differential rotational speed of the main cyclorotors, which generates a lift imbalance about the longitudinal axis of the vehicle. Pitch is controlled by changing the tail rotor RPM, which, due to the variation in vertical thrust, creates a moment about the pitching axis. Finally, yaw is controlled by tilting one cyclorotor thrust vector forward and the other backward. Additionally, both can be tilted in the same direction for forward or backward translation. Therefore, unlike a traditional hybrid aircraft such as a tilt-rotor, a cyclocopter can transition from hover to high-speed forward flight without any configuration change due to its thrust vectoring capability. A closed-loop proportional-derivative control strategy is implemented on a custom-built 1.3 gram autopilot which senses the vehicle motion and corrects the motor RPMs and tilts the thrust vectors accordingly. By careful tuning of feedback gains the vehicle has demonstrated stable hovering flight. More information could be obtained from our 2016 AIAA SciTech paper: https://arc.aiaa.org/doi/abs/10.2514/6.2016-1255