Abstract-The control of nonlinear system is the hotspot in the control field. The paper proposes an algorithm to solve the tracking and robustness problem for the discrete-time nonlinear system. The completed control algorithm contains three parts. First, the dynamic linearization model of nonlinear system is designed based on Model Free Adaptive Control, whose model parameters are calculated by the input and output data of system. Second, the model error is estimated using the Quasi-sliding mode control algorithm, hence, the whole model of system is estimated. Finally, the neural network PID controller is designed to get the optimal control law. The convergence and BIBO stability of the control system is proved by the Lyapunov function. The simulation results in the linear and nonlinear system validate the effectiveness and robustness of the algorithm. The robustness effort of Quasi-sliding mode control algorithm in nonlinear system is also verified in the paper.Keywords-dynamic linearization model, quasi-sliding mode control, nonlinear system, neural network
IntroductionWith increasing demands on the improvement of the precision control, the control problem of nonlinear system is attracting more and more attention [1]. Especially, the robustness problem of nonlinear control system model has gradually become an important topic in control theory. In general, control algorithms of nonlinear system mainly contain the neural network control, fuzzy logic control, the sliding mode control and model free adaptive control (MFAC).From universal approximation theory, a single hidden layer neural network can approximate any nonlinear function to any prescribed accuracy if sufficient hidden neurons are provided [2]. However, the training examples are usually much larger than the hidden nodes, and selecting the appropriate number of hidden nodes is the key factor which determining the error of the prediction model. And the algorithm of the control system can't ensure the global optimal value of weight [3]. The fuzzy logic system can also approximate any nonlinear function to any prescribed accuracy, and it has the advantages in dealing with the time-delay, time-varying, multi input single output nonlinear system [4]. Especially, the combination between fuzzy control and PID iJOE