Shafiqul Islam

Robust Sliding Mode Control for Robot Manipulators

In the face of large-scale parametric uncertainties, the single-model (SM)-based sliding mode control (SMC) approach demands high gains for the observer, controller, and adaptation to achieve satisfactory tracking performance. The main practical problem of having high-gain-based design is that it amplifies the input and output disturbance as well as excites hidden unmodeled dynamics, causing poor tracking performance. In this paper, a multiple model/control-based SMC technique is proposed to reduce the level of parametric uncertainty to reduce observer-controller gains. To this end, we split uniformly the compact set of unknown parameters into a finite number of smaller compact subsets. Then, we design a candidate SMC corresponding to each of these smaller subsets. The derivative of the Lyapunov function candidate is used as a resetting criterion to identify a candidate model that approximates closely the plant at each instant of time. The key idea is to allow the parameter estimate of conventional adaptive sliding mode control design to be reset into a model that best estimates the plant among a finite set of candidate models. The proposed method is evaluated on a 2-DOF robot manipulator to demonstrate the effectiveness of the theoretical development.

Robust Control of Four-Rotor Unmanned Aerial Vehicle With Disturbance Uncertainty

This paper addresses the stability and tracking control problem of a quadrotor unmanned flying robot vehicle in the presence of modeling error and disturbance uncertainty. The input algorithms are designed for autonomous flight control with the help of an energy function. Adaptation laws are designed to learn and compensate the modeling error and external disturbance uncertainties. Lyapunov theorem shows that the proposed algorithms can guarantee asymptotic stability and tracking of the linear and angular motion of a quadrotor vehicle. Compared with the existing results, the proposed adaptive algorithm does not require an a priori known bound of the modeling errors and disturbance uncertainty. To illustrate the theoretical argument, experimental results on a commercial quadrotor vehicle are presented.

Robust Adaptive Fuzzy Output Feedback Control System for Robot Manipulators

In this paper, we propose a novel hybrid control system for the trajectory tracking control problem of robotic systems. The design combines fuzzy system with robust adaptive control algorithm. The fuzzy system approximates the certainty equivalent-based optimal controller, while a robustifying adaptive control term is used to cope with uncertainties due to the presence of the external disturbance, fuzzy approximation errors, and other modeling errors. Using the Lyapunov method, we first develop a stable hybrid controller by assuming that the system output and its derivatives are available for feedback control design. Then, an output-feedback form of the position-velocity (state-feedback) controller is proposed, where the unknown velocity signal is replaced by the output of a model-free linear estimator. We show that the tracking of the output-feedback design can converge asymptotically to the performance achieved under the state-feedback control design. Finally, the proposed method is evaluated on a robotic system to demonstrate the theoretical development.

Bilateral Control of Teleoperation Systems With Time Delay

In this paper, we address the stability and tracking control problem of constant input-based bilateral teleoperation systems in the presence of time-varying delay. The teleoperation algorithm comprises delayed position and position-velocity signals with undelayed position and velocity signals of the master and slave manipulators. An adaptation law is employed locally to learn and compensate uncertain parameters associated with the gravity loading vector of the master and slave manipulators. Lyapunov-Krasovskii functions are employed to derive stability and tracking properties of the position, velocity, and synchronizing error of the master and slave manipulator. These properties are established in the presence of symmetrical and unsymmetrical time-varying delays under constant input interaction forces between human and master manipulator and between environment and slave manipulator. Finally, evaluation results are presented to illustrate the theoretical development of this paper.

PD Output Feedback Control Design for Industrial Robotic Manipulators

This paper presents an output feedback PD-type controller for the trajectory tracking control of robotic manipulators. A linear observer is used to estimate the unknown velocity signals of the nonlinear manipulator. In the first part of this paper, we propose a PD-like output-feedback control law. The Lyapunov method is used to characterize the asymptotic property of all the signals in the closed-loop error model dynamics. This property sets the bound on the tracking error trajectory of the closed-loop system. In the second part, we remove the nominal model dynamics from the control design to formulate a model-independent PD-type output feedback approach. Using an asymptotic analysis for the singularly perturbed closed-loop model, we guarantee that all the signals under the proposed PD output feedback design are bounded and their bounds can be made arbitrarily small by using observer-controller gains. Implementation results demonstrate the potential application of the proposed method on real systems.

A review on the platform design, dynamic modeling and control of hybrid UAVs

This article presents a review on the platform design, dynamic modeling and control of hybrid Unmanned Aerial Vehicles (UAVs). For now, miniature UAVs which have experienced a tremendous development are dominated by two main types, i.e., fixed-wing UAV and Vertical Take-Off and Landing (VTOL) UAV, each of which, however, has its own inherent limitations on such as flexibility, payload, axnd endurance. Enhanced popularity and interest are recently gained by a newer type of UAVs, named hybrid UAV that integrates the beneficial features of both conventional ones. In this paper, a technical overview of the recent advances of the hybrid UAV is presented. More specifically, the hybrid UAVs platform design together with the associated technical details and features are introduced first. Next, the work on hybrid UAVs flight dynamics modeling is then categorized and explained. As for the flight control system design for the hybrid UAV, several flight control strategies implemented are discussed and compared in terms of theory, linearity and implementation.

Teleoperation Systems With Symmetric and Unsymmetric Time Varying Communication Delay

This paper addresses the stability and tracking control problem for passive and nonpassive input-based teleoperation systems under time varying telecommunication delays. The design comprises delayed position signals with the local velocity and known structure of the master and slave manipulator dynamics. Using Lyapunov-Krasovskii-like functional, we derive the stability condition for the closed-loop teleoperators under symmetrical and unsymmetrical time varying delays. These conditions ensure the control stability and tracking of the closed-loop teleoperation systems in the presence of passive and nonpassive input forces. Finally, various simulation results are presented to confirm the validity of the proposed designs for real-time teleoperation application.

New stability and tracking criteria for a class of bilateral teleoperation systems

Abstract In this paper, hybrid position and impedance reflection based strategies are presented for bilateral teleoperation systems in the presence of time varying delay. The local and remote platform is coupled by delaying position, position-velocity and impedance reflection characteristics of the input interaction forces between human–master and slave–environment. An adaptation law is used locally to estimate uncertain impedance characteristics of the interaction forces between human and master and between slave and remote environment. The estimated parameter of the impedance characteristics of the interaction force between slave and remote environment are then transmitted with delay back to the master manipulator to adjust the parameter of the target impedance at the human operator hand. Adaptive control terms are also used locally to deal with the uncertainty associated with gravity loading of the master and slave manipulator. By choosing Lyapunov–Krasovskii-like functional, we establish the stability and transparency property of the closed loop teleoperator systems under both symmetrical and unsymmetrical time varying delays. Finally, simulation results are presented to demonstrate the validity of the proposed design for real-time applications.

Output feedback sliding mode control for robot manipulators

In this work, we propose an output feedback sliding mode control (SMC) method for trajectory tracking of robotic manipulators. The design process has two steps. First, we design a stable SMC controller by assuming that all state variables are available. Then, an output feedback version of this SMC design is presented, which incorporates a model-free linear observer to estimate unknown velocity signals. We then show that the tracking performance under the output feedback design can asymptotically converge to the performance achieved under state-feedback-based SMC design. A detailed stability analysis is given, which shows semi-global uniform ultimate boundedness property of all the closed-loop signals. The proposed method is implemented and evaluated on a robotic system to illustrate the effectiveness of the theoretical development.

Bilateral shared autonomous systems with passive and nonpassive input forces under time varying delay.

In this paper, we address stability and tracking control problem of bilateral shared autonomous systems in the presence of passive and nonpassive input interaction forces. The design comprises delayed position and position-velocity signals with the known and unknown structures of the master and slave manipulator dynamics. Using novel Lyapunov-Krasovskii functional, stability and tracking conditions of the coupled master-slave shared autonomous systems are developed under symmetrical and unsymmetrical time varying data transmission delays. This condition allows the designer to estimate the control design parameters to ensure position, velocity and synchronizing errors of the master and slave manipulators. Finally, evaluation results are presented to demonstrate the validity of the proposed design for real-time teleoperation applications.