Inspired by one of the most abundant insects on the planet, a species of horned beetle called Allomyrina dichotoma, researchers at South Korea’s Konkuk University have created a tailless flying robot they call KUBeetle-S. Insects like the horned beetle species lack a tail control surface, yet are able to modify their wing kinematics to produce control force for attitude change during flight. These modifications include shifting the stroke plane position or flapping angle range — complex kinematics that is a challenging task to mimic in robotics.
For an insect-like, tailless, flapping-wing robot like the KUBeetle-S, incorporating a control mechanism that produces sufficient flight force, is lightweight enough to not exceed the limited take-off weight, and produces enough control torques for altitude change pose significant hurdles. For this reason, this new development from Konkuk is one of the few such robots ready for free flight.
The flapping-wing mechanism is composed of two deformable wings actuated by a 3.5 g coreless motor through a gearbox to amplify torque and a transmission linkage system to convert rotary motion to flapping. The control moment generator installed can alter the wing stroke plain to the right or left, front or back, enabling the redirection of its vertical flight as desired. This generator, integrated with lightweight servo motors, is controlled electronically with both a control board and a feedback control system developed by the researchers. The hover-capable robot can ultimately change its stroke plane and wing twist simultaneously for pitch and roll controls and modulate wing root spars asymmetrically for yaw control. Additionally, the control mechanism requires less actuation torques from actuators, allowing for the use of smaller, lighter actuators.
Several tests conducted by researchers prove the ability of the control mechanism to generate both force and torque enough for attitude changes. With the implemented feedback control system, careful attention to wing loading to mimic that of a real beetle, and the use of a low-voltage power source, the beetle bot is currently able to hover for almost nine minutes. It is also able to move in any direction, fly outdoors, and carry extra payloads, making it suitable for real-world applications. Future directions for the research include the use of KUBeetle-S to better study insects and the mechanisms behind their movements either through fine-tuning its own mechanisms or deployment into natural habitats to collect data. In fact, the next step is even longer flight time and onboard vision systems, and the final goal is the autonomous flight of the KUBeetle-S.