Angular Acceleration Observer Design for Jerk-level Control of Tiltrotors Based on the High-order Fully Actuated System Approaches

Multirotors with tilting actuators, called tiltrotors, have been a research highlight in recent years. Servos are usually used to generate the tilting action. Acceleration-level controllers of tiltrotors might generate discontinuous tilting signals, which will lead to the gear wear of the servos. Jerk-level controllers, which generate continuous tilting signals, are more suitable for the control of tiltrotors, by which the acceleration of target trajectory can be tracked. However, the performance of jerk-level attitude controllers is limited by the lack of accurate estimation of the angular acceleration. In order to address this problem, this paper proposes a design method of angular acceleration observer based on the high-order fully actuated system approaches. The nonlinear jerk-level attitude model of the tiltrotor is converted into a fully-measured system, and the observation error system is turned into a linear constant one. A twelve-input overactuated tiltrotor is adopted as the plant in the simulations. A LQR controller is employed to implement the jerk-level control. Simulations demonstrate the effectiveness of the proposed method.