Showing papers on "Terminal sliding mode published in 2000"

Robust global terminal sliding mode control of SISO nonlinear uncertain systems

Abstract: A global terminal sliding mode controller is proposed for higher order SISO nonlinear dynamic systems by employing the fast terminal sliding mode concept in both the reaching phase and the sliding phase. The inherent dynamical properties of the fast terminal sliding modes and the recursive mechanism for application in higher order systems are explored. A control design procedure is developed. It is shown that, by suitably choosing the parameters of the fast terminal sliding modes, the system state variables will reach the fast terminal sliding manifolds within a desired finite time, and stay in the sliding modes thereafter, resulting in the convergence to the equilibrium in a finite time which can also be prespecified. The control law designed, which is called "the global terminal sliding mode control", is nonlinear and continuous. It does not cause chattering in the reaching phase and sliding phase. The robustness analysis shows that the proposed global terminal sliding mode controller has superior robustness in system uncertainties and external disturbances. Simulation studies are presented to validate the proposed scheme.

Sliding mode model predictive control with terminal constraints

Abstract: A new model predictive control scheme is proposed, which combines the receding horizon control and sliding mode variable structure control. By predicting the system states, the pre-designed switching function is predicted, then the control law can be found by solving the constrained open-loop optimal control problem based on the given cost function. The current control is implemented, and at the next sampling time the optimizing procedure is repeated. The proposed scheme has advantage of receding horizon control and sliding mode variable structure control, can deal with constraints online, and has strong robustness on the sliding surface. Furthermore, by constraining terminal sliding mode to be zero, the stability of closed-loop systems is guaranteed. Another scheme, which relaxes equality constraints to inequality constraints, is suggested for less calculation. In addition, the proposed method can be extended to nonlinear systems, and a nonlinear sliding mode predictive control scheme is acquired.

A new fuzzy sliding mode control scheme

Abstract: In this paper, a new fuzzy sliding mode control scheme is proposed for second-order linear time-varying systems in order to obtain faster error convergence and desired error dynamics. It is well known that a second-order linear time-varying system can be used to model higher order linear time invariant systems piece-wise. Therefore, it is necessary to do deep investigation for the stability and robustness analysis and the design of advanced tracking controllers for second-order linear time-varying systems. It is shown that the design of sliding mode control system is divided into two steps. A linear sliding mode controller is designed first to speed up the error convergence when the error is greater than one. A terminal sliding mode controller is then designed to guarantee that the error can converge to zero in a finite time when the error is around the system origin. In order to have a smooth switching from the linear sliding mode control to the terminal sliding mode control, a fuzzy logic technique is used to connect two sliding mode surfaces. The stability of the proposed fuzzy sliding mode controller is analyzed, and the convergence and robustness properties are demonstrated in a simulation example with a second-order system.

Finite-time tracking for robot manipulators with singularity-free continuous control: a passivity-based approach

Abstract: Terminal attractors are introduced in dynamic sliding mode error coordinates in order to obtain two control schemes for robot manipulators that guarantee globally finite-time convergence of tracking errors. The simple passivity-based design yields a chattering-free controller with singularity-free closed-loop dynamics. The controllers render better stability properties in comparison to an ill-posed class of static terminal sliding mode control, with simpler control structures in comparison to a class of dynamic sliding mode controllers. Simulation data show the performance of the controllers.

Dynamic modeling and adaptive VSC of two-link flexible manipulators using a hybrid sliding surface

Abstract: To suppress the resonance modes of flexible manipulator and to expedite the convergence, a hybrid sliding mode consisting of frequency shaped optimal sliding mode (FSOSM) and terminal sliding mode (TSM) is proposed and applied to two-link flexible manipulator, which is an extension of the authors' previous work (2000). An adaptive variable structure control (AVSC) is designed to estimate the upper bounds on the norm of uncertainties. The adaptation law generates a relatively small gain in the initial stage to reduce the impact to the system and a higher gain at the equilibrium to lower steady state error. Dead zone scheme is introduced to further improve system robustness. Attractiveness of the dead zone for the proposed AVSC is proven. Simulation results demonstrate the effectiveness of the proposed method.

A robust terminal sliding composite adaptive control scheme for rigid robots

Abstract: In this article is presented a robust adaptive control scheme for mechanical manipulators with finite error convergence time. The design combines, on the one hand, a composite adaptive controller that implements a feedback linearization control law that compensates the modelled dynamics, and, on the other hand, a terminal sliding mode control law that overcomes the uncertainties usually present in the real systems. Then, to avoid the chattering phenomenon inherent to the sliding schemes, the control law is also smoothed out. It is proved that the resulting closed loop system is stable and that the trajectory-tracking error converges to zero in finite time. Moreover, an upper bound of this error convergence time is calculated. Finally, the design is evaluated by means of simulations.