Trajectory Tracking of Unmanned Helicopter Using Super Twisting Control

The autonomous operation of unmanned helicopters (UHs) is a necessary but challenging task and a topic well attempted by the scientific community. Trajectory tracking is pivotal to the autonomous operation of UH. In this paper, a small scale helicopter model derived from first principles is used. It is made to follow a pre-defined trajectory in the presence of disturbance. The control strategy consists of two loops: inner comprises of fast varying attitude angles which determine the stability; outer comprises of position dynamics which are slow varying and used to trace the trajectory. Inner loop stabilization is achieved with particle swarm optimized (PSO) LQR controller. To make the trajectory tracking operation invariant to disturbance, we employ sliding mode control (SMC) derived from super-twisting algorithm, also tuned using PSO, which is a continuous form of sliding mode control. Super twisting control (STC) provides both disturbance rejection and reduced chattering in the control input generally associated with SMC. The efficacy of the proposed control law in fulfilling the post stated objectives is demonstrated by simulation results.