Robust altitude tracking of a helicopter using sliding mode control structure

This paper focuses on Lyapunov stability analysis and sliding mode controller for time varying reference altitude tracking of a helicopter. A nonlinear mathematical model of heave dynamics of the helicopter is used for analysis and controller design. Control Lyapunov functions are designed using direct Lyapunov method to stabilize the heave dynamics of the system. Tracking sliding mode controller uses conventional sliding surface nd equivalent contol technique in a novel manner to achieve altitude tracking/stabilization of the helicopter. Reachability of the system is proved and condition on initial conditions is derived for finite time convergence for the proposed sliding surface. It is proved that finite time convergence results are valid for conventional sliding surface independent of the application or plant under consideration. Simulations are performed with matched and unmatched disturbance and bounds for matched disturbance are calculated.