Adaptive secure control for connected nonlinear servo systems with constraints through observer

In this paper, the problem of adaptive secure control of a nonlinear servo system subject to state constraints, disturbance and denial-of-service (DoS) attacks is studied. An adaptive backstepping control scheme is developed. Firstly, a model of connected servo motors suffer from state constraints and disturbance is established. Then, in order to estimate the prior knowledge of the disturbance, a disturbance observer is proposed and the convergence of the observer is proved. Thirdly, an adaptive backstepping control strategy is designed for the system without DoS attacks, and a barrier Lyapunov function is proposed to solve the state constraints of the system. Furthermore, the adaptive backstepping security control approach is presented for the system under DoS attacks and it is shown that the convergence of the system under DoS attacks is maintained as long as each attack time is less than a specific constant. Finally, the simulation results demonstrate the effectiveness of the proposed methods.