Document Type : Original Article
Advanced Robotics &amp; Automated Systems (ARAS), Faculty of Electrical Engineering, K. N. Toosi University of Technology, Tehran, Iran
Department of Electrical Engineering, K. N. Toosi University of Technology, Tehran, Iran
Mechanical Engineering Department Faculty of Engineering- Branch 3 Lebanese University Beirut, Lebanon
This paper proposes a nonlinear robust passive fault tolerance controller for recovering faults and perturbation that affect the actuators of multirotor unmanned aerial vehicles. This approach is applied to a coaxial octorotor drone, benefiting from its actuator redundancy. The proposed controller is based on a second order super twisting sliding mode controller, which attenuates the chattering effect caused by first order sliding manifold. An active fault tolerance approach is also proposed based on both offline and online strategies for tolerating total effectiveness loss of actuators for an octorotor. A nonlinear Thau observer is designed firstly to detect actuator fault. Then two different control recovery algorithms are designed to compensate the fault, whenever it is detected to maintain the stability and desired behavior of the drone. The proposed algorithms are simulated and tested under fault free conditions and several fault conditions with various fault scenarios affecting the actuators through a complex 3D trajectory maneuver performed by the UAV. A new case study is presented to compare the behavior of the octorotor in case of successive total actuators loss. A novel comparison criterion for comparing various methods of fault tolerance controllers is introduced considering the design simplicity, implementation complexity, and system performance. The obtained results present suitable tracking performance for the desired trajectory, despite of different injected faults, with desirable recovery time. In addition, a weighting table is constructed to show the strength of each method.