Hover Control of an Underactuated Nonlinear Quadrotor Aerial Robot

Abstract

Quadrotor aerial robot is an under actuated system with nonlinearities. It has 6 DOF with only four actuators.  Actuators are the propellers with fixed pitch mounted on brushless DC motors. The actuators perform three basic operations for flight control of a quadrotor aerial robot; to generate lift force against gravity; to produce thrust force for flight in forward, backward, left and right directions against air drag; to balance weight at specific altitude during hover. Both translational and rotational motions of quadrotor aerial robot are controlled by varying relative propeller angular speed. The purpose of research work is to stabilize roll, pitch and yaw motions of a quadrotor during hover condition. To stabilize the system, an optimal model of quadrotor is presented. The model comprises of determining equations of motion of quadrotor, deriving the DC motor model and deriving the control inputs in terms of motor speeds. An optimal PD controller is designed, implemented in Simulink/Matlab and analyzed the performance of quadrotor in roll, pitch and yaw motions during hover.

Keywords: Hover, Under activated, Quadrotor, Aerial robot, PD controller.