US Patent 9914535 Passive rotor control mechanism for micro air vehicles

Technology for achieving the behavior and benefits of traditional cyclic control in one rotor may be implemented with a simple under-actuated passive mechanism. An air vehicle employing the disclosed technology maintains lifting thrust by regulating the average rotor speed and generates control moments through coordinated pulsing of the motor torque. Rapid pulsing of the motor torque induces oscillations in propeller angle of attack, and so causes “cyclic control” without requiring the traditional auxiliary actuators and linkages. The MAV propulsion system is capable of using a minimum number of actuators in dual roles of thrust and moment objectives.