Multirate Attitude Control of Dual-Rotor System Considering Propeller Loss of Effectiveness

This paper presents a two-degree-of-freedom control system for improving the attitude control performance under the existence of propeller's loss of effectiveness (LoE). To deal with the long sampling time of attitude measurements, a multirate observer is designed to estimate the attitudes at every control period of the propeller actuator. Using the estimated attitudes, the LoEs are identified via recursive least squares (RLS) algorithm. Using the identified LoEs, the propeller speed references are adjusted to compensate the fault effect on the system. Some physical parameters of the attitude dynamics are also identified to adaptively update the feedforward controller. In summary, the proposed system only consists of practical algorithms which can be implemented conveniently in real applications. Experiments using a dual-rotor testbench show that the proposed system can quickly identify the time-varying LoEs. In comparison with a conventional singlerate control system without fault tolerance, the proposed system can reduce the pitch angle and yaw angle tracking errors by 69.3 % and 39.6 %, respectively.