Sensor Fault-Tolerant Control for Unmanned Helicopter Based on Nonlinear Observer

In this paper, a fault-tolerant control scheme for sensor bias fault of the unmanned helicopter (UH) is proposed. The attitude control design for the UH is divided into two loops based on active disturbance rejection control (ADRC). The attitude angles controller and attitude rates controller are designed for the outer loop and inner loop, respectively. The bias of the fault sensor is estimated by using the nonlinear adaptive observer. The fault-tolerant scheme is designed by compensating the estimated bias in the basic attitude controllers. Finally, the simulation results show that the fault-tolerant scheme is effective for the attitude angles control of the UH with sensor bias fault.