Control System Design for Tiltable Quad-rotor with Propeller Failure

The traditional quad-rotor UAV is an under-driven system, and it is difficult to ensure stability when the actuator fails. In this paper, a new mechanical structure is adopted on the traditional quad-rotor to enable the rotors to tilt around the arm that the 4 additional actuated dofs are added and the full controllability over the quad-rotor attitude is obtained. The dynamics and kinematics models of the quad-rotor with the new structure are established and be linearized at a given equilibrium point. Based on the linearization model, the controller based on the linearized feedback method is designed to stabilize the system when the two opposing propellers failed. Numerical simulation and a quad-rotor prototype experiment are provided to verify the effectiveness of the proposed new mechanical structure and control algorithm.

I. Introduction

In recent years, quad-rotor have become more and more widely used in civil unmanned aerial vehicles (UAVs), especially consumer UAVs due to their small size, simple structure, and easy handling. However, as the application scenarios of quad-rotor become increasingly complex, collisions may occur during flight, causing irreversible damage to the propulsion system (e.g. propeller break or motor stop). Traditional quad-rotor, as a typical under-driven controlled object, have relatively low reliability. Once a propeller or motor fails, it will almost certainly crash or destroy the aircraft. Although [1] realized the space position control when one or two propeller failures under the traditional quad-rotor structure, the aircraft was always in the state of spinning around the yaw axis during the flight. As a result, the method provided by [1] cannot satisfy the stable control of the attitude angle, i.e., it will cause damage to the airborne equipment. The safety problem has dramatically limited the broader application of quad-rotor.