Trajectory tracking controller for miniature unmanned helicopters with position and velocity constrains

A trajectory tracking controller with position and velocity constraints is developed for miniature unmanned helicopters flying in narrow space. The helicopter model is firstly simplified to one with unmolded dynamics. Based on this model, the constrained backstepping technique is applied to design the controller, in which the barrier Lyapunov functions, instead of traditional pure quadratic Lyapunov functions, are introduced to the position control loop for maintaining the position and velocity constraints. Command filters are utilized to estimate derivatives of the virtual controls during the backstepping progress such that complex analytical calculations can be avoided. Furthermore, upper bounds of the disturbances due to the unmodeled dynamics and command filter errors are estimated and compensated with adaptive algorithms. The stability analysis shows that tracking errors of the closed-loop helicopter system are ultimately uniformly bounded and its position and velocity are restricted in the prescribed sets during the tracking progress. Simulation results validate the effectiveness of the proposed controller. © 2015, Editorial Department of Journal of Control Theory & Applications. All right reserved.