Cascaded Attitude Control For Heterogeneous Multirotor UAS For Enhanced Disturbance Rejection

Abstract

Multirotor unmanned aircraft systems (UAS) have enjoyed much popularity of late due to their excellent manoeuvrability, VTOL capability, precise hovering, simple deign and satisfactory speed. But they do lack in terms of energy efficiency and endurance when compared to helicopter and fixed wing counterparts. This paper explores a heterogeneous multirotor configuration which attains the benefits of both helicopter and multirotor. The design employs a single large central rotor for the lift and three tilted small boom rotors for control. Three single loop PI cascade control system is designed to control the attitude of the rotorcraft. Motor dynamics of each rotor are also considered in the multirotor model and a novel motor control loop is implemented for enhanced disturbance rejection in turblent environment. The presented configuration has been explored previously mainly focusing on energy efficiency but reported degraded attitude performance of the UAV. This work mainly focuses on the control system strategies to improve the robustness and stability of the system. We demonstrate the proposed control strategy with stable attitude performance, reference tracking and disturbance rejection by means of Simulink simulation. Deigning prototype is also in progress which will demonstrate its flight.