Robust Terminal Sliding Mode Control Research Articles

A non-singular predefined-time sliding mode tracking control for space manipulators

This research presents a predefined-time control strategy for the trajectory tracking of a space manipulator subjected to parametric uncertainty and time-varying disturbance. Firstly, a nonlinear disturbance observer with predefined time convergence is constructed to achieve accurate estimation of the lumped disturbance without requiring any prior information. Subsequently, a unique predefined-time terminal sliding surface containing arctan function is proposed, which avoids the singularity problem that exists in traditional terminal sliding surfaces. Afterwards, a novel robust terminal sliding mode control law is designed based on the estimated knowledge. The developed controller ensures the predefined time stability of the closed-loop system, and the convergence time’s upper bound can be explicitly defined in advance through two specific parameters for any initial conditions. Finally, numerical simulations and comparative tests verify the effectiveness and superiority of the suggested controller.

ANFIS-RTSMC based MPPT for a hybrid PV-diesel-battery water pumping system

This paper introduces a novel hybrid method for achieving Maximum Power Point Tracking (MPPT) in a photovoltaic-diesel-battery hybrid water pumping system driven by an induction motor drive (IMD). The innovative MPPT control strategy uniquely combines the rapid response and minimal oscillations of the Adaptive Neuro Fuzzy Inference System with the high robustness of Robust Terminal Sliding Mode Control (RTSMC). This combination ensures unprecedented steady-state resilience to changes in solar irradiance, enhancing system stability across a variety of IMD speeds, and making the system robust to parameter variations. Unlike traditional approaches, this two-stage photovoltaic (PV) setup integrates a regulated boost converter for MPPT control and a three-phase inverter using Space Vector Pulse Width Modulation (SVPWM) to regulate the DC link voltage (Vdc). Extensive MATLAB Simulink simulations demonstrate the proposed method’s superior efficiency in power extraction and its resilience under varying operating conditions, showcasing its originality and effectiveness.

Adaptive Robust Terminal Sliding Mode Control with Integral Backstepping Synthesized Method for Autonomous Ground Vehicle Control

Autonomous ground vehicles (AGVs) operating in complex environments face the challenge of accurately following desired paths while accounting for uncertainties, external disturbances, and initial conditions, necessitating robust and adaptive control strategies. This paper addresses the critical path-tracking task in AGVs through a novel control framework for multilevel speed AGVs, considering both structured and unstructured uncertainties. The control system introduced in this study utilizes a nonlinear adaptive approach by integrating integral backstepping with terminal sliding mode control (IBTSMC). By incorporating integral action, IBTSMC continuously adjusts the control input to minimize tracking errors, improving tracking performance. The hybridization of the terminal sliding mode method enables finite time convergence, robustness, and a chatter-free response with reduced sensitivity to initial conditions. Furthermore, adaptive control compensators are developed to ensure robustness against unknown but bounded external disturbances. The Lyapunov stability theorem is employed to guarantee the global asymptotic stability of the closed-loop system and the convergence of tracking errors to the origin within finite time. To validate the effectiveness of the proposed control scheme, high-fidelity cosimulations are conducted using CarSim and MATLAB. Comparative analysis is performed with other methods reported in the literature. The results confirm that the proposed controller demonstrates competitive effectiveness in path-tracking tasks and exhibits strong efficiency under various road conditions, parametric uncertainties, and unknown disturbances.

Adaptive neuro-fuzzy inference system algorithm-based robust terminal sliding mode control MPPT for a photovoltaic system

The non-linear power-current characteristics of a photovoltaic generator (GPV) present a challenge in maximizing power production. To address this issue, Maximum Power Point Tracking (MPPT) methods, such as the Adaptive Neuro-Fuzzy Inference System (ANFIS), are commonly used due to their quick response and minimal oscillation. As well, sliding mode control (SMC) is a popular method for controlling linear and nonlinear systems because of its high robustness. In this study, the principal purpose is to develop a new approach based on the combination of ANFIS and Terminal Robust Sliding Mode Control (ANFIS-TRSMC) to resist the PV system against uncertain conditions and track the optimal power point. The simulation results show that the ANFIS-TRSMC controller has an accurate, fast, and robust response in comparison with other algorithms such as perturb and observe and the maximum power voltage–based TRSMC controller.

Control of a Hydraulic Generator Regulating System Using Chebyshev-Neural-Network-Based Non-Singular Fast Terminal Sliding Mode Method

A hydraulic generator regulating system with electrical, mechanical, and hydraulic constitution is a complex nonlinear system, which is analyzed in this research. In the present study, the dynamical behavior of this system is investigated. Afterward, the input/output feedback linearization theory is exerted to derive the controllable model of the system. Then, the chaotic behavior of the system is controlled using a robust controller that uses a Chebyshev neural network as a disturbance observer in combination with a non-singular robust terminal sliding mode control method. Moreover, the convergence of the system response to the desired output in the presence of uncertainty and unexpected disturbances is demonstrated through the Lyapunov stability theorem. Finally, the effectiveness and appropriate performance of the proposed control scheme in terms of robustness against uncertainty and unexpected disturbances are demonstrated through numerical simulations.

Robust Terminal Sliding Mode Control on SE(3) for Gough–Stewart Flight Simulator Motion Platform with Payload Uncertainty

This work proposes a robust terminal sliding mode control scheme on Lie group space SE(3) for Gough–Stewart flight simulator motion systems with payload uncertainty. A complete dynamic model with geometric mechanical structures and a computer dynamic model built in the MATLAB/Simulink package are briefly presented. The robust control strategy on the Lie group SE(3) is applied at the workspace level to counteract the effects of imperfect compensation due to model simplification and payload uncertainty in flight simulator application. With exponential coordinates for configuration error and adjoint operator on Lie algebra se(3), the robust control strategy is designed to guarantee almost global finite-time convergence over state space through the Lyapunov stability theory. Finally, a describing function and a step acceleration response to characterize the performance of a flight simulator motion base are employed to compare the robustness performance of the proposed controller on SE(3) with the conventional terminal sliding mode controller on Cartesian space. The comparison experimental results verify that the proposed controller on SE(3) provides better robustness than the conventional controller on Cartesian space, which means higher bandwidth in two degrees of freedom and faster response with smaller tracking error in six degrees of freedom.

Neural‐network‐based robust terminal sliding‐mode control of quadrotor

AbstractA novel robust terminal sliding‐mode control (RTSMC) based on radial basis function (RBF) neural network is proposed firstly for controlling the attitude and position of the quadrotor, guaranteeing the system converged to stability point in a limited time. After establishing the nonlinear kinematics and dynamics models of the system, robust control is adopted in the RBF neural network terminal sliding‐mode controller such that the impact of external interference is reduced effectively. Resorting to the Lyapunov function, the asymptotically stable condition for the considered system is obtained, in which the convergence of the system is deduced in a finite time. Furthermore, simulation results are given to show the faster convergence speed and strong robustness for the considered system with RBF and RTSMC. Finally, the effectiveness and robustness of the developed control strategy is validated experimentally.

Design of a secure communication system between base transmitter station and mobile equipment based on finite-time chaos synchronisation

This paper proposes a chaotic secure communication system between a base transmitter station and mobile equipment. To make the chaotic keys, the Chua chaotic systems are used in the mobile equipment and base transmitter station. Chaotic oscillators are perturbed by external disturbances and parametric uncertainties. Based on the Lyapunov stability theory and the finite-time synchronisation concept, a robust terminal sliding mode controller is designed. In the first step, we aimed to achieve chaos synchronisation under external disturbances and parametric uncertainties in a finite time. In the second step, to enhance security in the communication system, a combination of the chaotic encryption method as multi-shift cipher encryption and double chaotic masking has been suggested. The simulation outcomes are presented to show the applicability and performance of the proposed method.

Terminal sliding mode control-based MPPT for a photovoltaic system with uncertainties

Over the past few decades, the world demand for energy has risen steadily, forcing the world communities to look for alternative sources. Photovoltaic (PV) is seen as the most appropriate solution for this demand. In this context, this paper presents a robust terminal sliding mode control (RTSMC) method for maximum power tracking of stand-alone PV systems. The design method provides good robustness properties in the face of the system uncertainties and change of environment conditions. Starting from the mathematical dependence between the open-circuit voltage (Voc) and the optimal operating voltage (Vop), an MPPT design method is given. To eliminate the tracking voltage error, a RTSMC method is introduced thereafter. A pulse width modulator (PWM) is used to maintain the switching frequency constant. Compared to the P&O algorithm, the proposed methodology reduces the oscillations around the maximum power point (MPP) and provides better performance proprieties. Also, the simulations results prove the robustness qualities of the TSMC-MPPT design method.

Robust terminal sliding mode control for automotive electronic throttle with lumped uncertainty estimation

In this study, we propose a robust terminal sliding mode (TSM) control scheme for automotive electronic throttle (ET) valve. Compared with the conventional throttle control systems, a TSM controller is developed where the lumped uncertainty is estimated by using a finite-time exact observer (FEO), such that the effects of the parameter uncertainties and nonlinearities including friction, return spring limp-home and gear backlash can be eliminated. It is shown that since the designed FEO can well estimate the lumped uncertainty, it is much easier to select the TSM control gains and a robust tracking performance can be ensured in the presence of the parametric variations and disturbances. The comparative simulations and experiments are provided to verify the excellent transient and steady-state tracking performance of the proposed TSM controller for ET systems.

Robust terminal sliding mode control for automotive electronic throttle with lumped uncertainty estimation

In this study, we propose a robust terminal sliding mode (TSM) control scheme for automotive electronic throttle (ET) valve. Compared with the conventional throttle control systems, a TSM controller is developed where the lumped uncertainty is estimated by using a finite-time exact observer (FEO), such that the effects of the parameter uncertainties and nonlinearities including friction, return spring limp-home and gear backlash can be eliminated. It is shown that since the designed FEO can well estimate the lumped uncertainty, it is much easier to select the TSM control gains and a robust tracking performance can be ensured in the presence of the parametric variations and disturbances. The comparative simulations and experiments are provided to verify the excellent transient and steady-state tracking performance of the proposed TSM controller for ET systems.

Nonlinear disturbance observer based sliding mode control of a human-driven knee joint orthosis

The present paper deals with the control of a knee joint orthosis intended to be used for rehabilitation and assistive purposes. A model, integrating human shank and orthosis, is presented. To reduce the influence of the uncertainties in muscular torque modeling on the system control, a nonlinear observer is proposed to estimate the muscular torque developed by the wearer. Additionally, a robust terminal sliding mode control approach combined with the nonlinear observer is presented. To illustrate the effectiveness of the proposed control method, a comparison with two control methods, basic sliding mode and sliding mode with nonlinear observer, are also given. The asymptotic stability of the presented approaches and observer convergence are proved by means of a Lyapunov analysis. Furthermore, the proof of advantage of the robust terminal sliding mode control method with the nonlinear observer (improving the tracking precision and reducing the required time for eliminating external disturbances) is proposed as well. The experiment results show that the robust terminal sliding mode control approach combined with the nonlinear observer has a significant advantage with respect to the position tracking and robustness regarding the modeling identification errors and external disturbances.

Quad-rotor unmanned helicopter control via novel robust terminal sliding mode controller and under-actuated system sliding mode controller

This paper uses the recently developed novel robust terminal sliding mode control (NRTSMC) and under-actuated system sliding mode control (USSMC) approaches to solve the strong coupling and under-actuated problems of a small quad-rotor unmanned helicopter (QRUH). The two controllers have been widely adopted to act as a single control algorithm in many fields, respectively. However, this paper just displays the useful composite application of the two controllers. The QRUH model can be divided into two subsystems, including a fully actuated subsystem (FAS) and an under-actuated subsystem (UAS). For the FAS, the NRTSMC is used to solve the strong coupling problem, it can guarantee the FAS states converge to the desired equilibrium in a very short time, then the states are treated as time invariants and the UAS gets simplified. For the UAS, the USSMC is utilized to solve the under-actuated problem. The obtained simulation results show the applicability of the composite control when faced with external disturbances.

Position and attitude tracking control for a quadrotor UAV

A synthesis control method is proposed to perform the position and attitude tracking control of the dynamical model of a small quadrotor unmanned aerial vehicle (UAV), where the dynamical model is underactuated, highly-coupled and nonlinear. Firstly, the dynamical model is divided into a fully actuated subsystem and an underactuated subsystem. Secondly, a controller of the fully actuated subsystem is designed through a novel robust terminal sliding mode control (TSMC) algorithm, which is utilized to guarantee all state variables converge to their desired values in short time, the convergence time is so small that the state variables are acted as time invariants in the underactuated subsystem, and, a controller of the underactuated subsystem is designed via sliding mode control (SMC), in addition, the stabilities of the subsystems are demonstrated by Lyapunov theory, respectively. Lastly, in order to demonstrate the robustness of the proposed control method, the aerodynamic forces and moments and air drag taken as external disturbances are taken into account, the obtained simulation results show that the synthesis control method has good performance in terms of position and attitude tracking when faced with external disturbances.

A new control method for leveling output frequency fluctuations in an autonomous PV/FC/UC network with maximum power point tracking of the photovoltaic system

This paper presents a study on isolated hybrid distributed generation (DG) system combining solar photovoltaic (PV), fuel cell (FC) and ultra-capacitor (UC) for improving the frequency profile. The PV system is used as the main power generation source, while the long-term energy balance is supposed to be generated by FC, besides, as for the short-term compensation the UC is used. The PV is controlled to track the maximum power point at all operating conditions by employing an efficient robust terminal sliding mode controller (TSMC). The proposed MPPT controller guarantees fast convergence of MPP tracking and high robustness against PV system parameters variation. In this part, to demonstrate the effectiveness and reliability of the TSMC controller, comparison with Proportional Integral (PI) control was performed. In the following, with the optimization of droop controller by applying the Improved Particle Swarm Optimization (IPSO) algorithm the frequency deviation in the various states changing of generated power and consumed power declines significantly. To demonstrate the effectiveness of proposed frequency controller, optimal droop frequency controller using IPSO algorithm, is compared with conventional and improved droop controllers. Employing matlab/simulink® environment based on nonlinear detailed mathematical and dynamic models, simulation results under the real weather data and practical load demand profile are presented to validate the proposed scheme.

Fast Terminal Sliding Mode Control for the Ship Steering Problem

In this paper we propose the application of a robust terminal sliding mode control with fast sliding surface to the ship control problem, which consists of leading the ship along the desired course via automatic changes in the rudder blade deflections. In spite of its robustness to system parameter variations and external disturbances, normal terminal sliding mode control (NTSMC) has a limitation of shattering the input rudder angle command particularly when the ship steering mechanism has a big time constant. Through comparative simulations, we show that the proposed controller with fast sliding surface outperforms NTSMC controller in reducing the chattering in the input signal and the initial swing of the rudder angle in the presence of external disturbances and model uncertainties.

Global Robust Terminal Sliding Mode Control for PMLSM Servo System

Permanent Magnet Linear Synchronous Motor (P MLSM was hard to control with traditional control strategy for parameters variation and external load disturbance, a global robust terminal sliding mode control (GRTSMC) was designed for PMLSM servo system, the sliding mode surface function was designed, the robust sliding mode control law was deduced and the stability was proved by Lyapunov theory. With the mathematical models of PMLSM, the simulation was taken with traditional PID control, SMC control and GRTSMC control proposed in this paper, the robust performance be found with GRTSMC control when motor parameters and external load changed, the efficiency and advantages of this robust control strategy was successfully demonstrated.

Robust Terminal Sliding Mode Control for Robotic Manipulators with Actuator Dynamics

A novel robust terminal sliding mode control is studied for robotic manipulators with actuator dynamics. It is seen that the developed scheme can ensure a finite-time error convergence and the stability of the closed-loop system in the presence of uncertain parameters in both the manipulator and actuator dynamics. The detailed stability analysis is presented to lay a foundation for the readers’ understanding of generic theoretical aspects and safe operation for real systems. An illustrative example is bench-tested to validate the effectiveness of the proposed algorithm.

On the Cascaded Robust Terminal Sliding Mode Control of Robotic Manipulators Including Actuator Dynamics

AbstractIn this study, a novel cascaded robust terminal sliding mode control approach is developed for robotic manipulators including actuator dynamics. The proposed approach can achieve finite-time stability in the presence of arbitrary uncertain mechanical and electrical parameters of the robot model. Corresponding stability analysis is presented to lay a foundation for analytical understanding in generic theoretical aspects and safe operation for real systems. An illustrative example is bench tested to validate the effectiveness of the proposed approach.

Synchronization of chaotic systems with uncertainties using robust terminal sliding mode control

A novel robust terminal sliding mode control based on fast fuzzy disturbance observer is designed for a class of chaotic systems with uncertainties. To deal with the shortcoming of slow learning of traditional fuzzy disturbance observer when the approximation errors are very small, a fast fuzzy disturbance observer is designed which improves the learning speed. It is rigorously proved that the synchronization error and approximation error converge to very small values in finite time. Finally, simulation results of the Duffing-Holmes chaotic system demonstrate the effectiveness of the presented closed-loop control scheme.