Terminal Sliding Mode Controller Design Research Articles

Disturbance‐observer‐based fault‐tolerant control of robotic manipulator: A fixed‐time adaptive approach

AbstractThe concurrent existence of model uncertainties, external disturbances, and actuator faults in a nonlinear system such as a robotic manipulator can significantly affect the trajectory tracking performance of these systems. Therefore this study is devoted to proposing a control approach based on fixed‐time control theory to improve the trajectory tracking performance of the robotic manipulator in the presence of lumped disturbance, including uncertainties, external disturbances, and actuator faults. The control approach in this paper is designed based on the integration of a fixed‐time adaptive sliding mode observer and a fixed‐time non‐singular fast terminal sliding mode control design strategy. Firstly, a new fixed‐time adaptive sliding mode observer is designed based on fixed‐time theory and adaptive control theory to estimate the lumped disturbance present in the system. Then, using the information from the disturbance observer, the fixed‐time non‐singular fast terminal sliding mode control is devised based on a non‐singular fixed‐time sliding surface and a fixed‐time reaching approach. Furthermore, in the sense of the Lyapunov theorem, through rigorous analysis, it is demonstrated that the tracking errors of the closed‐loop system converge to a small neighbourhood within a fixed time, regardless of the information about the initial conditions of the states of the system. Finally, extensive comparative simulations are performed using the PUMA560 robot to manifest the feasibility and validity of the proposed control strategy in terms of trajectory tracking accuracy and fast convergence in the presence of uncertainties, disturbances, and actuator faults.

Terminal Sliding Mode Controller Design Based on Barrier for UAVs With Mismatched Disturbances

Terminal Sliding Mode Controller Design Based on Barrier for UAVs With Mismatched Disturbances

Robust finite-time integral terminal sliding mode control design for maximum power extraction of PMSG-based standalone wind energy system

This paper introduces a novel control strategy called Finite-time Integral Terminal Sliding Mode Control (FITSMC), explicitly designed for a permanent-magnet synchronous generator (PMSG)-based standalone Wind Energy Conversion System (WECS). The primary objective of the FITSMC strategy is to regulate the operation of the wind turbine efficiently and maximize power extraction from the WECS. To achieve this, the system is driven onto a sliding surface within a predefined terminal time, ensuring rapid convergence and overall stability. An important advantage of the FITSMC strategy is its ability to maintain a standalone wind power system close to the maximum power point, even under varying wind conditions and load changes. In addition, the controller demonstrates robustness against uncertainties and disturbances, making it highly suitable for real-world applications. Extensive simulations and analyses have been conducted to validate the effectiveness of the proposed FITSMC. The results show a superior control performance compared to traditional methods. Consequently, the FITSMC strategy represents a promising advancement in control techniques for standalone wind power systems, providing an efficient and reliable approach for harnessing power from wind energy.

Non‐singular terminal sliding mode controller design for nonlinear systems with prescribed convergence time guarantees

AbstractThis paper considers the prescribed‐time non‐singular terminal sliding mode control (TSMC) for nonlinear systems with uncertainties bounded by non‐negative functions. At first, a new Lyapunov theorem for prescribed‐time stability is introduced. Then, a novel terminal sliding surface together with a non‐singular TSMC input is constructed by using a time‐varying scaling function. Strict analysis shows that the proposed controller is able to ensure the exact reaching of the sliding surface as well as the system states to zero in a prescribed time independent of the system initial conditions. Moreover, all the state signals and the control input remain uniformly bounded. Finally, simulation comparison with the existing fixed‐ and prescribed‐time TSMC is given to verify the effectiveness of the theoretical results.

Novel Explicit Reference Governor-Based Adaptive Terminal Sliding Mode Control Design for Reentry Vehicles Equipped with Strapdown Seeker

Novel Explicit Reference Governor-Based Adaptive Terminal Sliding Mode Control Design for Reentry Vehicles Equipped with Strapdown Seeker

Adaptive terminal sliding mode controller design for cyber‐physical systems under external disturbance and actuator cyber‐attack

SummaryThis article studies a novel technique of the adaptive terminal sliding mode (TSM) control for the finite time stabilization of cyber‐physical systems (CPSs). By using the proposed nonlinear sliding surface, the reaching mode is eliminated and the entire system robust procedure is ameliorated. The used adaptive laws are dealt with the cyber‐attacks and external disturbances which their upper bounds are not needed to be recognized, where suggested approach is more pliable in the real performance. The presented new adaptive TSM control technique guarantees the system robustness versus cyber‐attacks and external disturbances. Furthermore, the proposed control method obliterated the chattering behavior utilizing the hyperbolic tangent function and the continuous adaptive parameters in the control law. Numerical simulation results indicate the proposed adaptive TSM control technique's effectiveness and success compared to the results of state feedback control, conventional sliding mode control (SMC), traditional integral‐type SMC, and adaptive integral‐type SMC methods.

Dynamic Event-Triggered Terminal Sliding Mode Control Under Binary Encoding: Analysis and Experimental Validation

This paper designs a novel nonsingular terminal sliding mode control (TSMC) scheme for a class of nonlinear systems under binary encoding transmission. To further ease the communication overheads between the plant and the controller, a dynamic event-triggered mechanism is also introduced to the TSMC design. Sufficient conditions are proposed, respectively, for guaranteeing the reachability to a practical sliding mode and the ultimate boundedness of the closed-loop system, in which the effects from the binary encoding and the dynamic event-triggered protocol are quantified clearly. The Zeno phenomena for the developed dynamic event-triggered mechanism is excluded via an explicit analysis. Finally, the feasibility and effectiveness of the proposed scheme are demonstrated by a numerical example and a real experiment on permanent magnet synchronous motor speed regulation system.

Neuro-adaptive fixed-time non-singular fast terminal sliding mode control design for a class of under-actuated nonlinear systems

This paper presents a fixed-time neuro-adaptive control design for a class of uncertain under-actuated nonlinear systems (UNS) using a non-singular fast terminal sliding mode control (TSMC) with a radial basis function (RBF)-based estimator to achieve the convergence and robustness against the uncertainties. The mathematical model of the considered class is reduced into an equivalent regular form. A fast TSMC is designed for the transformed form to improve the control performance and annihilate the associated singularity problem of the conventional TSMC. Lyapunov stability theory ensures the steering of the sliding manifold and system states in fixed time. RBF neural networks are adaptively estimate the nonlinear drift functions. The theoretical design, analysis, and simulations of cart-pendulum and quadcopter demonstrate the feasibility and benefits of the regular form transformation and the designed control design. Comparing the proposed synthesis with the standard literature presents the attractive nature of proposed method for such a class.

Event-based fast terminal sliding mode control design for a class of uncertain nonlinear systems with input delay: A quantized feedback control

This paper deals with the problem of regulation and tracking tasks for nonlinear dynamic systems that use a network medium to transmit state measurements. A novel quantized event-triggered fast terminal sliding mode controller (SMC) is proposed to reduce communication resources and computation loads while increase robustness against packet dropout, uncertainties, and disturbances. Then, new criteria are defined for the dynamic quantizer based on the event-triggering error, which increases the accuracy and facilitates the implementation procedures. In practice, delay-free systems are not realistic considerations, thus, their stability is analyzed in the presence of a dynamic quantizer and input delay under the proposed controller scheme. Then, the minimum inter-sampling time is derived, which guarantees the Zeno-free behavior and provides information about the cyber layer bandwidth in cyber-physical systems. Finally, three simulations on an unstable numerical model, the model of an inertia wheel inverted pendulum, and the mass-spring-damper model validate the effectiveness of the proposed methodology.

출력 예측 성능을 갖는 제어 입력 변환 터미널 적분 슬라이딩 모드 제어

In this note, the discontinuous and continuous control input transformation integral terminal sliding mode control(TSMC)s by using the integral sliding surface without the reaching phase and with the output prediction performance as the one approach are presented for second order uncertain plants. Theoretically discontinuous and practically continuous control input transformed TSMCs are proposed when Δb ≠ 0, while it is assumed that Δb=0 in most of the TSMCs for easy design. Applying the idea of [32] for the linear sliding mode control(LSMC), the integral sliding surface without the reaching phase is suggested for the TSMCs. The exponent of the power function can be any positive numbers satisfying q＞p＞0 such that 0＜p/q＜1. The ideal sliding dynamics of the integral sliding surface is derived and the real robust output can be predicted, predesigned, predetermined by means of the solution of the ideal sliding dynamics. The transformed control input is suggested for generating the sliding mode for the entire trajectory from any given initial condition to the origin based on defining a new auxiliary nonlinear state. The closed loop exponential stability together with the existence condition of the sliding mode on the predetermined sliding surface is investigated theoretically for the complete formulation of the TSMC design for the output prediction performance. As a remedy of the singularity, a certain limit is imposed on the new auxiliary nonlinear state. For practical applications, a continuous approximation of the discontinuous TSMC is made by means of the modified boundary layer function. In addition, the closed loop bounded stability together with the existence condition of the sliding mode by the continuous TSMC is analyzed. The discontinuity of the control input as the inherent property of the sliding mode control is much improved in view of the practical applications. Through a design example and simulation studies, the effectiveness of the proposed discontinuous and continuous control input transformed TSMCs is verified.

Fast terminal sliding mode control design for position control of induction motors using adaptive quantum neural networks

In this work, an efficient robust control scheme is proposed for position control of induction motors based on field-oriented control (FOC). The proposed control scheme consists of three interior loops. In the outer loop, the central controller based on the nonsingular fast terminal sliding mode control (NFTSM) is designed. The objective of this loop is to provide the required stator current in the q-axis for regulating the electromagnetic torque. In the inner loops, two fractional-order PI (FOPI) controllers are designed to provide the stator voltages. Besides, since induction motors have a complex mathematical model, time-varying dynamics, and non-linear structure, to deal with these challenges in the controller design, the quantum neural network (QNN) is presented with a novel framework and employed to estimate the lumped uncertainties. This makes the main contribution of the paper. In addition, to further improve system performance, the parameters of the FOPI controllers are tuned by employing the artificial bee colony (ABC) optimization algorithm. The stability of the proposed control approach is proved by Lyapunov’s stability theory. According to the results of the comparative simulation, the superiority of this approach is confirmed.

Adaptive nonsingular fast terminal sliding mode controller design for a smart flexible satellite in general planar motion

In this research, a new mathematical modeling is obtained for a smart satellite with flexible appendages in general planar motion by considering two control thrust forces, a control torque and piezoelectric actuators and sensors. The satellite consists of a central rigid body and two flexible appendages modeled as Euler-Bernoulli beams. It has ability to translate and rotate in the plane of motion. Moreover, its flexible appendages can arbitrarily vibrate in the satellite's moving plane. The Lagrange method based on the Rayleigh-Ritz method is employed to derive the governing equations of motion and the sensors equations. The nonlinearity of the satellite's motion equations is the result of considering large angle rotation. Continuous terminal sliding mode and adaptive nonsingular fast terminal sliding mode controllers are designed to control the smart flexible satellite's position and attitude and suppress vibrations of the flexible appendages in the presence of uncertainties and external disturbances simultaneously. Finally, numerical simulations are presented in order to validate the proposed dynamic model and demonstrate the performance of the proposed controllers.

Decentralized adaptive terminal sliding mode control design for nonlinear connected system in the presence of external disturbance

SummaryIn this article, a decentralized adaptive integral terminal sliding mode control is presented for a class of nonlinear connected systems. It is assumed that the system is also confronted by unknown disturbances, while the interconnections between subsystems are assumed unknown. An integral terminal sliding surface for each subsystem is locally considered to guarantee the stability of the closed‐loop system, and to increase the convergence speed during a tracking task. The unknown interconnections between subsystems are estimated using adaptive rules. An appropriate Lyapunov candidate is chosen to perform global stability analysis. In this regard, design parameters are chosen such that the closed‐loop stability is ensured. Performance of the proposed method for a mechanical connected system, including two chaotic subsystems, is shown through simulations.

Fixed-time ESO based fixed-time integral terminal sliding mode controller design for a missile

This paper studies a novel fixed-time extended state observer based fixed-time integral terminal sliding mode controller for partial integrated guidance and control design. Firstly, a class of arbitrary-order systems with fixed-time stability is proposed by utilizing homogeneous approach, whose upper bound of convergence time is given. Then, an arbitrary-order fixed-time integral terminal sliding mode control is designed based on the proposed arbitrary-order fixed-time stable system, which avoids the singular problem. Subsequently, this paper constructs a new fixed-time extended state observer to further actively compensate for the disturbance caused by unknown target acceleration. Finally, numerical simulations show the effectiveness of the proposed controller.

A discrete-time terminal sliding mode controller design for an autonomous underwater vehicle

Autonomous underwater vehicle (AUV) are underwater robotic devices intended to explore hostiles territories in underwater domain. AUVs research gaining popularity among underwater research community because of its extensive applications and challenges to overcome unpredictable ocean behavior. The aim of this paper is to design discrete time terminal sliding mode control (DTSMC) reaching law-based employed to NPS AUV II purposely to improve the dynamic response of the closed loop system. This is accomplished by introducing a nonlinear component to sliding surface design in which the system state accelerated, and chattering effect is suppressed. The nonlinear component consist of fractional power is to ensure steeper slope of the sliding surface in the vicinity of the equilibrium point which lead to quicker convergence speed. Thus, the chattering effect in the control action suppressed as the convergence of the system state accelerated. The stability of the control system is proven by using Sarpturk analysis and the performance of the DTSMC is demonstrated through simulation study. The performance of DTSMC is benchmarked with DSMC and PID controller

Neuro-adaptive fast integral terminal sliding mode control design with variable gain robust exact differentiator for under-actuated quadcopter UAV

In this paper, a robust global fast terminal attractor based full flight trajectory tracking control law has been developed for the available regular form which is operated under matched uncertainties. Based on the hierarchical control principle, the aforesaid model is first subdivided into two subsystems, i.e., a fully-actuated subsystem and an under-actuated subsystem. In other words, the under-actuated subsystem is further transformed into a regular form whereby the under-actuated characteristics are decoupled in terms of control inputs. In the proposed design, the nonlinear drift terms, which certainly varies in full flight, are estimated via functional link neural networks to improve the performance of the controller in full flight. Besides, a variable gain robust exact differentiator (VG-RED) is designed to provide us with estimated flight velocities. It has consequently reduced the noise in system’s velocities and has mapped this controller as a practical one. The finite-time sliding mode enforcement and the states’ convergence are shown, for all flight loops, i.e., forward flight and backward flight, via the Lyapunov approach. All these claims are verified via numerical simulations and experimental implementation of the quadcopter system in a Matlab environment. For a more impressive presentation, the developed simulation results are compared with standard literature.

Finite-Time Control of Myringotomy Surgical Device Based on Nonsingular Terminal Sliding Disturbance Observer

This paper presents a disturbance observer-based nonsingular terminal sliding mode control design for a myringotomy surgical device. The methodology is established to control a semi-automated hand-held ear surgical device for the treatment of otitis media with effusion. Otitis media with effusion is the collection of bacterial fluid in the middle ear space which can potentially lead to hearing loss and chronic infections. A finite-time terminal sliding surface is proposed and a nonsingular terminal sliding control is constructed. The control approach fulfils precise tracking of the desired motion trajectory in the presence of disturbances, nonlinearities and uncertainties. The stability of the control approach is analyzed. In addition, the tracking control of the myringotomy surgical device is proven mathematically and the simulation results confirm the applicability and efficiency of the proposed approach and a precise tracking performance following desired motion trajectory is demonstrated in the simulations.

Free-will Arbitrary Time Terminal Sliding Mode Control

In this technical note, free-will arbitrary time terminal sliding mode control design is proposed. With such a design, it is possible to control the time duration of sliding in the sliding phase. Under the assumption that the chosen arbitrary time is greater than the reaching phase time (tr), it is shown that the nth order chain of integrators converges to zero within the selected arbitrary time. An algorithm is also proposed for the case when tr is not known to the designer. Stability analysis based on Lyapunov theory has been provided.

Barrier Lyapunov function based sliding mode control for Mars atmospheric entry trajectory tracking with input saturation constraint

The nature of the bank angle modulation technique based on the low lift-to-drag aerodynamic configuration of the entry vehicle inevitably introduces the problem of input saturation, which would lead to unexpected tracking performance degradation. To this end, a barrier Lyapunov function (BLF) based sliding mode control is proposed for the Mars atmospheric entry trajectory tracking in this paper. A variable gain super-twisting (VGST) based terminal sliding mode controller is firstly presented. By introducing a novel logarithm-type BLF, the proposed terminal sliding mode controller is proved stable with bounded convergence time in the presence of input saturation and external disturbance. Then, based on the numerical predictor–corrector strategy, the variable gain of terminal sliding mode controller is adjusted onboard to satisfy the constraint of input saturation. The Mars Science Laboratory Mission based atmospheric entry scenario is utilized in the numerical simulation to verify the proposed trajectory tracking method, demonstrating the effectiveness of method of BLF based terminal sliding mode controller design.

Fuzzy Non-singular Terminal Sliding Mode Controller Design for Nonlinear Systems with Input Saturation

The current work has proposed an approach to the controller design of a fuzzy non-singular terminal sliding mode (NTSM) for a type of planar systems with input saturation. On the basis of a modified version of NTSM, a category of saturated NTSM controller is first constructed to ensure that the states can reach the sliding surface and finite-time converge to the origin. On this basis, a fuzzy logic controller including two fuzzy input variables and a fuzzy output variable is developed to adaptively adjust the control gain such that the gain of the NTSM controller can be automatically minimized. This also implies that the chattering phenomenon encountered by most conventional sliding mode control (SMC) schemes can be significantly attenuated without sacrificing inherent properties. Finally, in comparison with a traditional SMC method, the superiority of the presented algorithm is confirmed by the comparative simulation results in terms of chattering alleviation and robustness.