Sanjoy Mondal

Adaptive second order terminal sliding mode controller for robotic manipulators

Abstract In this paper an adaptive second order terminal sliding mode (SOTSM) controller is proposed for controlling robotic manipulators. Instead of the normal control input, its time derivative is used in the proposed controller. The discontinuous sign function is contained in the derivative control and the actual control obtained after integration is continuous and hence chatterless. An adaptive tuning method is utilized to deal with the system uncertainties whose upper bounds are not required to be known in advance. The performance of the proposed control strategy is evaluated through the control of a two-link rigid robotic manipulator. Simulation results demonstrate the effectiveness of the proposed control method.

Chattering free adaptive multivariable sliding mode controller for systems with matched and mismatched uncertainty.

In this paper, a chattering free adaptive sliding mode controller (SMC) is proposed for stabilizing a class of multi-input multi-output (MIMO) systems affected by both matched and mismatched types of uncertainties. The proposed controller uses a proportional plus integral sliding surface whose gain is adaptively tuned to prevent overestimation. A vertical take-off and landing (VTOL) aircraft system is simulated to demonstrate the effectiveness of the proposed control scheme.

A fast converging robust controller using adaptive second order sliding mode.

This paper proposes an adaptive second order sliding mode (SOSM) controller with a nonlinear sliding surface. The nonlinear sliding surface consists of a gain matrix having a variable damping ratio. Initially the sliding surface uses a low value of damping ratio to get a quick system response. As the closed loop system approaches the desired reference, the value of the damping ratio gets increased with an aim to reducing the overshoot and the settling time. The time derivative of the control signal is used to design the controller. The actual control input obtained by integrating the derivative control signal is smooth and chattering free. The adaptive tuning law used by the proposed controller eliminates the need of prior knowledge about the upper bound of system uncertainties. Simulation results demonstrate the effectiveness of the proposed control strategy.

Second order sliding mode controller for twin rotor MIMO system

In this paper a twisting algorithm based second order sliding mode controller (SMC) is proposed to control a laboratory helicopter called the twin rotor multi-input multi-output (MIMO) system (TRMS). The TRMS model is pseudo decomposed into two subsystems and the coupling between them is considered as an uncertainty. A proportional integral based sliding surface is used for the vertical subsystem to reduce the steady state error. The proposed second order sliding mode technique shows robustness against the uncertainties and disturbances present in the TRMS system. Apart from imparting robustness, the proposed second order SMC law reduces the chattering effect in the control input. The performance of the proposed control scheme is demonstrated through simulation.

Improved adaptive control of nonlinear uncertain systems through second order sliding mode controller

This paper proposes an adaptive second order sliding mode (SOSM) control strategy to tackle nonlinear uncertain systems. For effective handling of the uncertain system, prior knowledge about the upper bound of the system uncertainty is a prerequisite for the sliding mode control (SMC). In order to remove this constraint, an adaptive tuning law based SMC was designed recently where the upper bounds of the uncertainties were not required to be known in advance. However, such controllers were found to suffer from the drawback of the high frequency chattering in the control input. In this paper an improved adaptive second order sliding mode controller is proposed to alleviate the undesired chattering phenomenon. The proposed control strategy uses an adaptive tuning law for the sliding mode controller which is of the second order. A simulation example illustrates the benefits of the proposed scheme.

Homogeneous Finite-Time Consensus Control for Higher-Order Multi-Agent Systems by Full Order Sliding Mode

This paper investigates the distributed finite-time consensus tracking problem for higher-order nonlinear multi-agent systems (MASs). The distributed finite-time consensus protocol is based on full order sliding surface and super twisting algorithm. The nominal consensus control for the MASs is designed based on the geometric homogeneous finite time control technique. The chattering is avoided by designing a full order sliding surface. The switching control is constructed by integrating super twisting algorithm, hence a chattering alleviation protocol is obtained to maintain a smooth control input. The finite time convergence analysis for the leader follower network is presented by using strict Lyapunov function. Finally, the numerical simulations validate the proposed homogeneous full-order sliding mode control for higher-order MASs.

An Adaptive Finite-Time Consensus Control for Higher-Order Nonlinear Multi-agent Systems

This chapter presents a finite-time consensus problem of higher-order nonlinear multi-agent systems (MAS) in the presence of bounded disturbances. The nominal control is designed by homogeneous finite-time technique to track the desired target trajectories. The chattering is mitigated by designing an integral sliding surface using adaptive super twisting algorithm (STA). The design parameters of super twisting controller are estimated adaptively without knowing the bounds a priori. The finite time convergence of the consensus protocol for the higher-order MAS is presented using Lyapunov analysis. Simulation results shows the effectiveness of the proposed homogeneous adaptive sliding mode control for the MAS.

Disturbance observer based consensus control for higher order multi-agent systems with mismatched uncertainties

A robust consensus controller is proposed for heterogeneous higher order nonlinear multi-agent systems (MAS), when the agent dynamics are potentially affected by mismatched uncertainties. A distributed consensus protocol based on finite time disturbance observer(FTDO) and sliding mode control is designed to realize the network consensus of higher order MAS. The control law can be used to solve the homogeneous as well as heterogeneous consensus problem simultaneously, where some agents have different nonlinear dynamics. FTDO is designed to estimate the uncertainties. The use of FTDO allows to neglect the effect of mismatched uncertainties during the sliding mode. For dismissing the chattering phenomenon and finite time convergence of the sliding surface, control law is designed using the super twisting algorithm. Finally numerical simulations are given to illustrate the validity of the proposed method.

A step by step adaptive super twisting controller for mismatched uncertain system

In this paper a step by step adaptive super twisting controller is designed for second order nonlinear strict feedback system with mismatched uncertainty. The design procedure is carried out by considering a virtual controller at each step. After obtaining the first step the desired dynamic model for each state is defined by the previous one and finally the actual control law is obtained. The design parameters of super twisting controller are estimated adaptively. The proposed method can be used for disturbance estimation also. The finite time convergence has been obtained by using a strict Lyapunov function. Simulation results demonstrate the efficacy of the proposed controller.

Chattering-Free Adaptive Second-Order Terminal Sliding-Mode Controller for Uncertain System

In this paper, an adaptive second-order terminal sliding-mode (SOTSM) controller is proposed for controlling uncertain systems. The design procedure is carried out in two parts. A linear sliding surface is designed first, and then, using the linear sliding surface, the terminal sliding manifold is obtained. Instead of the normal control input, its time derivative is used by the proposed control law. The actual control is obtained by integrating the derivative control input. The discontinuous sign function is contained in the derivative of the control input, and hence, chattering is eliminated in the actual control. An adaptive tuning method is designed to deal with the unknown system uncertainties, and their upper bounds are not required to be known apriori. System stability is proved by using the Lyapunov criterion. Simulation results demonstrate the effectiveness of the proposed controller for both the single-input single-output (SISO) and multi-input multi-output (MIMO) uncertain systems.