Design and Development of Swashplateless Micro Helicopter with Pitch-Lag Coupling

This paper presents the design and development of a swashplateless micro helicopter with a target endurance of more than 30 minutes using an optimized direct drive rotor connected to a unique rotor hub that has blades with a flap hinge and proprietary skewed-lag hinge with pitch-lag kinematic coupling. This obviates the need for conventional swashplate based cyclic pitch control, as the cyclic variation in control angle is achieved by cyclically varying the motor RPM. UP12 underactuated propulsion system developed by VertiQ is used for the baseline design. The blades in this propulsion system are optimized using Blade Element Momentum Theory (BEMT) analysis with lookup table to enhance its performance. BEMT is validated using experimental measurements and then used to optimize the geometry of the rotor. The optimized blades offer better performance and are 30% lighter than the original 3D-printed plastic blades. The prototyping of the Micro Aerial Vehicle (MAV) is completed by fabricating the airframe and using off-the-shelf electronic components. Tabletop tests are carried out using a yawing test stand to tune the yaw attitude gains for the MAV. A coupled flap-lag rotor dynamics is combined with the motor angular speed dynamics to simulate the dynamics of the system to carry out fundamental understanding of the control power being generated by the swashplateless system. The swashplateless rotor design is able to generate significant propulsive and side forces, however it is unable to generate control moments which may be inadequate for aggressive maneuvering warranted by small agile MAV.