This article deals with robust fixed-time stability and stabilization. First, new global robust fixed-time stability results are proposed for scalar systems by using constant and variable exponent coefficients. Then, they are applied to global robust fixed-time stabilization of a class of uncertain nonlinear second order systems by using sliding mode control. All the results are illustrated in simulation.

With the developments of wireless data communication and network technology, time-delays are widely found in nowadays' control systems, e.g. networked control systems, mobile robot systems, and multi-agent systems. Predictor-based control is an effective method dealing with long time-delays because it can generally lead to a delay-free closed-loop system by introducing a prediction for future states. Recently, various predictor-based control methods have been developed for numerous control systems subject to different time-delays, which motivates this survey. This paper presents a comprehensive review of the up-to-date results on the predictor-based control of time-delay systems. Firstly, the ordinary differential equation-based approaches for designing and analysing predictor-based controllers are summarised. Secondly, one reports an alternative method of predictor-based control, in which the systems/controllers are understood in the sense of partial differential equations. Next, several integration-free predictor-based controllers are introduced: by abandoning the infinite-dimensional integral terms, the control laws become easier to realise in practice. Hereafter, the paper discusses the real-time implementations and the practical applications of predictor-based control methods to several particular control systems. Finally, this paper suggests some new trends of predictor-based control for future research.

A shift in paradigm from dedicated to open communication channels in power systems have made them prone to constant and time varying delays. This paper tackles a novel load frequency control (LFC) problem in the presence of constant and time varying delays in state and control input under load disturbances. The presence of time delays can deteriorate the performance of the controller or even destabilize the system. The above problem is addressed through a prediction-based super twisting sliding mode control (ST-SMC) using a state and disturbance observer. The proposed design achieves finite time convergence of frequency and tie line power deviation. The said design is validated under ramp and random step disturbance, with nonlinearities like generation rate constraints and governor deadband, with an integration of renewable energy and also with IEEE 39 bus power system. The closed loop stability is proven thanks to candidate Lyapunov function and verified by simulations.

International audienceThe stability of a prediction-based controller for LTI systems is studied in presence of time-varying input and output delays. The uncertain delay case is treated as well as the partial state knowledge case. The reduction method is used in order to prove the convergence of the closed-loop system including the state-observer, the predictor and the plant. Explicit conditions that guarantee the closed-loop stability are given thanks to a Lyapunov-Razumikhin analysis. The results are illustrated thanks to simulations