Fast Finite-time Research Articles

Robust fast finite-time sliding mode control for industrial robot manipulators

In this work, a robust fast finite-time sliding mode control (RFFTSMC) approach is developed for industrial robot manipulator (IRM) system involved for tasks of interactive manipulation. The robust position tracking control is accomplished by the design of non-singular fast terminal sliding mode controller (TSMC) with disturbance estimator and tested using a two-link IRM system influenced by parameter uncertainties and external disturbances. This arrangement not only guarantees finite and faster convergence of the systems states to the equilibrium from anywhere in the phase-plane but also remove the difficulty of singularity associated with traditional TSMC. Additionally, owing to the interfering observer augmented in said control law, the overall stability of the closed-loop system is enhanced. The practicality of suggested RFFTSMC is acknowledged by carrying out the comparative study of the well-known controllers from the literature. Simulation results demonstrate that the tracking error can be reduced efficiently and robustness of the closed loop system has been enhanced.

Robust spacecraft attitude tracking control with integral terminal sliding mode surface considering input saturation

This paper studies the finite time spacecraft attitude tracking control problem, while considering modeling uncertainty, external disturbances and control input saturation. A novel integral terminal sliding mode surface (ITSMS) is designed by combining the fast terminal sliding mode surface (FTSMS) with a low pass filter to achieve a fast finite time convergence rate for the control system, without input singularity. An auxiliary signal is used to compensate for the effects of actuator saturation. The basic controller is first formulated based on the ITSMS, fast-TSM-type reaching law and auxiliary system, in the presence of an external disturbance and input saturation. Then, an adaptive control procedure is introduced, which simultaneously handles modeling uncertainty and external disturbance, thereby creating an adaptive attitude tracking controller. The proposed controller provides a fast finite time convergence rate for the control system, based on the newly designed ITSMS, while simultaneously compensating for modeling uncertainty, external disturbances and input saturation, without restricting the parameter selection process nor requiring repeated differentiation of nonlinear functions. Finally, digital simulation results are presented and demonstrate the effectiveness of the proposed controllers.

Design, development and control of a 2PRP-2PPR planar parallel manipulator for lower limb rehabilitation therapies

This paper proposes a vertical planar 2PRP-2PPR parallel manipulator along with a serial planar RRR passive orthosis (exoskeleton/supporting system) for performing sitting/lying type (stationary trainer) lower limb rehabilitation therapies in the sagittal plane. Proposed system's kinematic arrangement along with forward and inverse solutions is presented. System dynamics is derived to understand the behavior of the over-constrained manipulator-orthosis system. Further, a robust motion control scheme is proposed and the motion control scheme is based on non-singular fast terminal sliding mode control along with a nonlinear disturbance observer. The effectiveness and usefulness of the proposed manipulator is shown with the implementation of the motion controller through computer based numerical simulations using a clinical gait motion pattern. The proposed motion control scheme is also validated on an in-house fabricated prototype through motion control experiments. The controller parameter sensitivity and controller robustness are further analyzed at different working conditions. In comparison to the conventional controllers, the proposed control scheme possess few advantages namely better robustness, less chattering, high precision and fast finite time convergence, and can work in the presence of parameter uncertainties. From the demonstration, the proposed manipulator has certain advantages over existing stationary lower limb rehabilitation trainers namely, simple design, larger workspace, higher stiffness, modular design and low cost.

Fast Finite-Time Consensus Tracking of Second-Order Multi-Agent Systems with a Virtual Leader

Fast Finite-Time Consensus Tracking of Second-Order Multi-Agent Systems with a Virtual Leader

Fast Finite-Time Consensus Tracking of Heterogeneous Multi-Agent Systems with a Virtual Leader

This paper proposes a novel finite-time consensus tracking protocol for guaranteeing heterogeneous multi-agent systems with a virtual leader to achieve the fast finite-time consensus tracking. The Lyapunov function method, algebra graph theory, homogeneity with dilation and some other techniques are employed to prove that heterogeneous multi-agent systems with a virtual leader applying the proposed protocol can reach the finite-time consensus tracking. Numerical simulations indicate that compared with traditional finite-time consensus tracking protocols, the proposed protocol can accelerate the convergence speed of the finite-time consensus tracking.

Fast Finite-Time Consensus Tracking of First-Order Multi-Agent Systems with a Virtual Leader

This paper proposes a novel finite-time consensus tracking protocol for guaranteeing first-order multi-agent systems with a virtual leader to achieve the fast finite-time consensus tracking. The Lyapunov function method, algebra graph theory, homogeneity with dilation and some other techniques are employed to prove that first-order multi-agent systems with a virtual leader applying the proposed protocol can reach the finite-time consensus tracking. Furthermore, theoretical analysis and numerical simulations show that compared with the traditional finite-time consensus tracking protocols, the proposed protocol can accelerate the convergence speed of achieving the finite-time consensus tracking.

Multi-surface sliding control for fast finite-time leader-follower consensus with high order SISO uncertain nonlinear agents

SUMMARY In this paper, multi surface sliding cooperative control scheme is presented and new multiple sliding surfaces are proposed. It is proven that, for the setup that each agent is described by a chain of integrators, where the last integrator is perturbed by a bounded disturbance, leader–follower consensus can be achieved on these sliding surfaces if the communication graph has a directed spanning tree. Also, sliding variables can be driven to the sliding surfaces in fast finite time by the nonsmooth control law. The fast finite-time Lyapunov stability theorem, the terminal sliding control technique, and the adding a power integrator design approach are used in our proposed control. Simulation results demonstrate the effectiveness of the proposed scheme. Copyright © 2013 John Wiley & Sons, Ltd.

Adaptive fast finite-time multiple-surface sliding control for a class of uncertain non-linear systems

This paper concerns the adaptive fast finite-time multiple-surface sliding control (AFFTMSSC) problem for a class of high-order uncertain non-linear systems of which the upper bounds of the system uncertainties are unknown. By using the fast control Lyapunov function and the method of so-called adding a power integrator merging with adaptive technique, a recursive design procedure is provided, which guarantees the fast finite-time stability of the closed-loop system. Further, it is proved that the control input is bounded.

Fast Finite-Time Consensus Tracking of Second-Order Multi-Agent Systems with a Virtual Leader

Fast Finite-Time Consensus Tracking of Second-Order Multi-Agent Systems with a Virtual Leader