Model-Free Sliding Mode Control Method

In this paper, a model-free sliding mode controller is developed and demonstrated on a second order nonlinear system. The proposed controller is based solely on state measurements and previous control inputs, thus, a system model is not required. The underlying knowledge required about the system is its order and the bounds of the input matrix, if it is non-unitary. In order to handle system uncertainties, a discontinuous term is added to the controller form and is designed using Lyapunov’s stability theorem to guarantee asymptotically stability during the reaching phase of the state trajectories. The discontinuous term creates an undesirable effect i.e., chattering, which is impractical for implementation of the controller in actual system types. A time-varying smoothing boundary layer is used to eliminate chattering and is also developed in this work. Finally, the controller is tested using a nonlinear second order system with and without including sensor measurement noise effects simulating real-world effects.