Asian Journal of Control最新文献

This paper is concerned with the stability analysis problems of asynchronous sampled-data systems via an input-delay approach. Between two sequential sampling times, a sampled-data system is controlled by previously sampled states and thus can be modeled as a time-delay system with a saw-tooth delay. Inevitably, information at the sampling instants have played essential roles in controlling the systems and reducing the conservatism of the stability criteria. Therefore, to further utilize the information at sampling instants, this paper proposes novel looped functionals consisting of integral state variables and their interval-normalized terms. Three numerical examples including a practical helicopter system demonstrate the effectiveness of the proposed approaches in terms of allowable sampling intervals.

Practical stability refers to the notion that the origin is not an equilibrium point (EP) and that the system states tend to converge toward a sphere centered at the origin. The first goal of this paper is to analyze the concept of “practical stability” in Caputo–Hadamard fractional-order derivative (CHFOD) systems. Then, using the Lyapunov approach, a polynomial fuzzy (PF) observer-based controller for stabilizing CHFOD PF systems is created. The observer-based control is innovative since it was created and proven using the sum-of-squares (SOS) method. In conclusion, a numerical illustration is provided to corroborate the theoretical findings.

In this letter, an adaptive fixed-time integral sliding mode (ISM) controller is exploited for the stabilization of disturbed planar high-order nonlinear systems. The exploited controller is designed by constructing a novel fixed-time ISM surface to tackle the high-order power. Moreover, the parametric adaptive technique is embedded to estimate the square of the upper bound of the disturbance. In this way, the exploited controller has no obvious chattering problem and can maintain the high control accuracy simultaneously. The resultant closed-loop system is proved to be practically fixed-time stable through the bilimit homogeneous theory and fixed-time Lyapunov stability theory. Lastly, two simulated examples are carried out to demonstrate the derived results.

This paper investigates prediction-based robust super-twisting sliding mode controller design for nonlinear systems with input delay and external disturbances. A novel predictor feedback is introduced based on state predictions of the original and transformed models. To cope with the external disturbances, a set of disturbance observers are utilized which estimate the future values of disturbances asymptotically. Super-twisting sliding mode control is used to avoid chattering phenomenon which is also able to handle external disturbances. Proposed design can handle all external disturbances that their derivatives vanish at infinity. Stability proof of the closed-loop is given in details ensuring the asymptotic stability of the tracking errors and finite time vanishing of the sliding surface. To illustrate effectiveness and applicability, the proposed design is applied to a two-link robot and a serial variable stiffness actuator. Simulation results show that input delays of the robot and actuator are compensated, and external disturbances are correctly estimated and attenuated.

This paper considers a rotating Euler-Bernoulli beam system with no dampings, where disturbances and references are generated from a block diagonalizable exosystem. Two tracking errors are the only measurable outputs for the output regulation of the beam system. Firstly, a nominal exosystem is chosen to generate the same signals, and a nominal beam is obtained by finding the specially known coefficients of the disturbances and references. This makes a tracking error-based observer easily designed for the nominal partial differential equation-ordinary differential equation (PDE-ODE) system. Observer-based robust controls are then designed for the nominal beam system and further proved to guarantee the asymptotic convergence of the tracking errors and the boundedness of the states, although under unknown disturbances and references. Two simulation examples are provided to describe the effectiveness of the controls.

This paper researches the time-varying formation tracking (TVFT) problem of linear multi-agent systems (MASs). By designing a compensator, the problem of time-varying formation can be considered as the output regulation problem. Thereby, the distributed output feedback controller combined with an adaptive technique is proposed. With this controller, follower agents achieve the desired time-varying formation and follow the trajectory of the leader agent. Furthermore, extending the designed controller to the case where the leader agent equips with unknown control input. Using Lyapunov stability theory, it is demonstrated that under proper conditions the given protocol is implementable. Simulation example is presented at the end of the paper to illustrate the effectiveness of designed control mechanism.