Search

This paper introduces the innovative Adaptive Backstepping Fast Terminal Sliding Mode Control (AB-FTSMC) for Unmanned Aerial Vehicles (UAVs), a groundbreaking approach designed to address the complex challenges in UAV dynamics, such as perturbations, disturbances, and the intricate inter-coupling of control systems. What sets the AB-FTSMC apart is its unique integration of the robust Fast Terminal Sliding Mode Control with the layered approach of Backstepping Control. This combination not only offers enhanced adaptability to a range of uncertainties including actuator failures and unmodeled states, but it also represents a significant leap in UAV control technology. The control process of AB-FTSMC is strategically divided into two distinct phases. The initial phase employs Newton-Euler formalism to develop a comprehensive mathematical model of the UAV, incorporating key concepts of observability and controllability for assured stability. The subsequent phase involves the implementation of a robust AB-FTSMC controller, meticulously designed to precisely regulate the UAV's pitch and yaw angles, effectively countering issues such as gyroscopic torque and parametric uncertainties. The novelty of this research lies in its methodical approach to tackling the traditionally complex problem of UAV control. By merging two sophisticated control strategies, the AB-FTSMC method not only mitigates common UAV control issues but also ensures a higher degree of stability and rapid convergence of state variables. The practical effectiveness of this novel control system is underscored through extensive real-time simulation responses of a UAV hardware prototype, clearly demonstrating its superior performance and adaptability under various perturbations. [ABSTRACT FROM AUTHOR]

Introduction. This study presents a robust control method for the path following problem of the PUMA560 robot. The technique is based on the Adaptive Fuzzy Type-2 Fast Terminal Sliding Mode Control (AFT2FTSMC) algorithm and is designed to handle actuator faults, uncertainties (such as payload change), and external disturbances. The aim of this study is to utilize the Fast Terminal Sliding Mode Control (FTSMC) approach in order to ensure effective compensation for faults and uncertainties, minimize tracking error, reduce the occurrence of chattering phenomena, and achieve rapid transient response. A novel adaptive fault tolerant Sliding Mode Control (SMC) approach is developed to address the challenges provided by uncertainties and actuator defects in real robotics tasks. Originality. The present work combined the AFT2FTSMC algorithm in order to give robust controllers for trajectory tracking of manipulator’s robot in presence parameters uncertainties, external disturbance, and faults. We use an adaptive fuzzy logic system to estimate the robot’s timevarying, nonlinear, and unfamiliar dynamics. A strong adaptive term is created to counteract actuator defects and approximation errors while also guaranteeing the convergence and stability of the entire robot control system. Novelty. The implemented controller effectively mitigates the chattering problem while maintaining the tracking precision and robustness of the system. The stability analysis has been conducted using the Lyapunov approach. Results. Numerical simulation and capability comparison with other control strategies show the effectiveness of the developed control algorithm. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study of dynamics identification‐driven diving control for unmanned underwater vehicles (UUVs). Initially, a diving dynamics model of UUVs is established, serving as the foundation for the development of subsequent algorithms. A noise‐reduction least squares (NRLS) algorithm is then derived for parameter identification, demonstrating convergence under measurement noise from a probabilistic perspective. A notable feature of this algorithm is its skill in correcting raw data, thereby improving parameter identification accuracy. Based on the identified model, an improved fast terminal sliding mode control (FTSMC) algorithm is introduced for diving control, consistently ensuring rapid convergence under 16 scenarios. Importantly, the proposed diving control algorithm effectively mitigates chattering by incorporating a dedicated filter, adaptively adjusting the switching gain, and substituting saturation function for sign function. Through experimental validation, the NRLS algorithm's advantage over the traditional least squares method becomes evident, with depth errors consistently below 3.5 cm. This indicates that the identified model closely aligns with the actual model, showcasing a commendable fit. Additionally, when compared to the traditional sliding mode controller and the proportional‐integral‐derivative algorithm, the FTSMC algorithm has superior performance, as indicated by a mean absolute percentage error consistently below 4%. [ABSTRACT FROM AUTHOR]

This paper presents a novel control framework for enhancing the attitude stabilization of multirotor UAVs using Control Moment Gyros (CMGs) and a Disturbance Robust Drive Law (DRDL). Due to their lightweight and compact structure, multirotor UAVs are highly susceptible to disturbances such as wind, making it challenging to achieve stable attitude control using rotor thrust alone. To address this issue, we employ CMGs to provide robust attitude control and apply Fast Terminal Sliding Mode Control (FTSMC) to ensure fast and accurate convergence within a finite time. The combination of CMGs' torque amplification capability with the DRDL enables the system to effectively avoid singularities and maintain stable control performance in the presence of disturbances. Simulation results demonstrate that the CMG-equipped hexarotor utilizing the DRDL rapidly converges to the target attitude despite external disturbances, while minimizing oscillations in both motor speed and gimbal movement. Additionally, compared to the pseudo-inverse control method, the proposed approach significantly improves singularity avoidance and disturbance mitigation. The proposed control framework enhances the stability and reliability of UAV operations and demonstrates its potential for high-performance control in challenging disturbance environments. [ABSTRACT FROM AUTHOR]

Introduction. This study presents a robust control method for the path following problem of the PUMA560 robot. The technique is based on the Adaptive Fuzzy Type-2 Fast Terminal Sliding Mode Control (AFT2FTSMC) algorithm and is designed to handle actuator faults, uncertainties (such as payload change), and external disturbances. The aim of this study is to utilize the Fast Terminal Sliding Mode Control (FTSMC) approach in order to ensure effective compensation for faults and uncertainties, minimize tracking error, reduce the occurrence of chattering phenomena, and achieve rapid transient response. A novel adaptive fault tolerant Sliding Mode Control (SMC) approach is developed to address the challenges provided by uncertainties and actuator defects in real robotics tasks. Originality. The present work combined the AFT2FTSMC algorithm in order to give robust controllers for trajectory tracking of manipulator’s robot in presence parameters uncertainties, external disturbance, and faults. We use an adaptive fuzzy logic system to estimate the robot’s time-varying, nonlinear, and unfamiliar dynamics. A strong adaptive term is created to counteract actuator defects and approximation errors while also guaranteeing the convergence and stability of the entire robot control system. Novelty. The implemented controller effectively mitigates the chattering problem while maintaining the tracking precision and robustness of the system. The stability analysis has been conducted using the Lyapunov approach. Results. Numerical simulation and capability comparison with other control strategies show the effectiveness of the developed control algorithm. References 53, table 1, figures 8.

A fast trajectory tracking controller is designed for the airship, involving dynamic uncertainties of parameters, capable of guaranteeing the prescribed performance of tracking errors, and fast response of the closed-loop system. To achieve the decoupling of velocity control and attitude control of the airship, a new guidance and control integration framework is proposed first. Then, based on the dynamics model established by the spinor method, the lumped disturbance, caused by unknown aerodynamic parameter uncertainties and exogenous disturbances, is estimated online using a high-order finite-time observer. The control performance, namely, overshoot and steady-state performance of tracking errors, is significantly improved by utilizing the prescribed output performance constraints, while the convergence rate is further enhanced by combining the finite-time convergence property of the fast terminal sliding mode control. Simulation results attest to the effectiveness of the strategy in this paper. Compared with the adaptive fast terminal sliding mode control, the strategy effectively utilizes the capability of the actuator within the allowed range and reduces the convergence time by more than half with similar control inputs. [ABSTRACT FROM AUTHOR]

This paper presents a novel control framework for enhancing the attitude stabilization of multirotor UAVs using Control Moment Gyros (CMGs) and a Disturbance Robust Drive Law (DRDL). Due to their lightweight and compact structure, multirotor UAVs are highly susceptible to disturbances such as wind, making it challenging to achieve stable attitude control using rotor thrust alone. To address this issue, we employ CMGs to provide robust attitude control and apply Fast Terminal Sliding Mode Control (FTSMC) to ensure fast and accurate convergence within a finite time. The combination of CMGs’ torque amplification capability with the DRDL enables the system to effectively avoid singularities and maintain stable control performance in the presence of disturbances. Simulation results demonstrate that the CMG-equipped hexarotor utilizing the DRDL rapidly converges to the target attitude despite external disturbances, while minimizing oscillations in both motor speed and gimbal movement. Additionally, compared to the pseudo-inverse control method, the proposed approach significantly improves singularity avoidance and disturbance mitigation. The proposed control framework enhances the stability and reliability of UAV operations and demonstrates its potential for high-performance control in challenging disturbance environments.

In addressing the control of asynchronous motors in the remote conductivity of fertigation machines, this study proposes a joint control strategy based on the Fast Terminal Sliding Mode Control-Disturbance Observer (FTSMC-DO) system for asynchronous motors. The goal is to enhance the dynamic performance and disturbance resistance of asynchronous motors, particularly under low-speed operating conditions. The approach involves refining the two-degree-of-freedom internal model controller using fractional-order functions to explicitly separate the controller's robustness and tracking capabilities. To mitigate the motor's sensitivity to external disturbances during variable speed operations, a load disturbance observer is introduced, employing hyperbolic tangent and Fal functions for real-time monitoring and compensation, seamlessly integrated into the sliding mode controller. To address issues related to low-speed chattering typically associated with sliding mode controllers, this study introduces a revised non-singular fast terminal sliding mode surface. Additionally, guided by fuzzy control principles, the study enables real-time selection of sliding mode approaching law parameters. Experimental results from the asynchronous motor control platform demonstrate that FTSMC-DO control significantly reduces adjustment time and speed fluctuations during operation, minimizing the impact of load disturbances on the system. The system exhibits robust disturbance rejection, improved robustness, and enhanced control capability. Furthermore, field tests validate the effectiveness of the FTSMC-DO system in regulating remote electrical conductivity (EC) levels. The control time is observed to be less than 120 s, overshoot less than 16.1%, and EC regulation within 0.2 mS·cm−1 over a pipeline distance of 120 m. The FTSMC-DO control consistently achieves the desired EC levels with minimal fluctuation and overshoot, outperforming traditional PID and SMC methods. This high level of precision is crucial for ensuring optimal nutrient delivery and efficient water usage in agricultural irrigation systems, highlighting the system's potential as a valuable tool in modern, sustainable farming practices. [ABSTRACT FROM AUTHOR]

The purpose of this article is to present a fast terminal sliding mode control scheme for constrained mobile manipulators with both holonomic and non-holonomic constraints while taking uncertainties and external disturbances into account. Existing techniques cannot manage this kind of system because of the unavoidable errors in a mobile manipulator's dynamical model. In order to improve position/force tracking performance of constrained mobile manipulators, a control scheme is presented that combines the advantages of fast terminal sliding mode control and neural networks. Without the requirement for offline training, the manipulator's unknown dynamics are learned using a radial basis function neural network. Using an adaptive bound component, the bounds on uncertainties and neural network reconstruction error are quantified. The stability of the system and the convergence of the tracking errors are investigated using the Lyapunov theory. Analyzed simulation results indicate the proposed controller's robust performance in a variety of circumstances. [ABSTRACT FROM AUTHOR]

In order to improve the performance and suppress the chattering problem of variable structure control system, a nonlinear novel quick reaching law with dynamic power term is suggested, which could enhance the convergence rate whenever the system state position is near to or far from the manifold. Furthermore, a novel fast terminal sliding surface with additional nonlinear terms is developed and designed. The combination of these structure propositions can minimize both the reaching time and sliding time convergence. The finite-time stability of the proposed control paradigm is demonstrated via the Lyapunov criteria method. Moreover, in order to see the superior performance of the compound control, a disturbed DC-DC buck converter is selected as plant in this work. In addition, the extended state observer is designed and added in feedforward path of control law of sliding mode structure. In order to estimate the unknown uncertainties, the results demonstrate that the nonlinear novel fast terminal sliding mode with variable quick reaching law brings the system at equilibrium point more rapidly than the traditional manifolds and reaching laws. More than that, the closed-loop system performance has better transient response, lower steady state error and lesser sensitivity to disturbances. [ABSTRACT FROM AUTHOR]

Copyright of Control Theory & Applications / Kongzhi Lilun Yu Yinyong is the property of Editorial Department of Control Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, the position and attitude tracking finite-time adaptive control problem of a type of vertical take-off and landing (VTOL) aircraft system is studied. Here, the dynamic of the VTOL aircraft is subjected to external disturbances and unknown nonlinearities. Firstly, radial basis function neural networks are introduced to approximate these unknown nonlinearities, and adaptive weight update laws are proposed to replace unknown ideal weights. Secondly, for the errors generated in the approximation process and the external disturbances of the aircraft system, adaptive parameter update laws are presented. After that, based on the designed global fast terminal sliding mode control functions and adaptive update laws, we present the position tracking control laws and the roll angle control law. Then, based on this, the adaptive global fast terminal sliding control laws for the given aircraft system are finally obtained. Meanwhile, the stability of the aircraft control system is proven by using Lyapunov stability theory and designed adaptive control laws. It is not only ensured that the outputs of the aircraft system can track the given trajectories, but also ensured that the tracking errors can converge to approximately zero within a finite time. Finally, the validity of the designed adaptive control laws is verified through three numerical examples. It can be obtained that the finite-time tracking problems of the given aircraft system can be achieved at 18.8766 s and 14.6340 s under the given parameters. The results are consistent with the theoretical analysis. In addition, under the control laws proposed in this work, the aircraft system can achieve tracking after 9.443 s and 9.674 s and the tracking errors are basically close to zero, which is significantly superior to other control methods considered in this work. [ABSTRACT FROM AUTHOR]

To overcome the sensitivity of voltage source inverters (VSIs) to parameter perturbations and their susceptibility to load variations, a fast terminal sliding mode control (FTSMC) method is proposed as the core and combined with an improved nonlinear extended state observer (NLESO) to resist aggregate system perturbations. Firstly, a mathematical model of the dynamics of a single-phase voltage type inverter is constructed using a state-space averaging approach. Secondly, an NLESO is designed to estimate the lumped uncertainty using the saturation properties of hyperbolic tangent functions. Finally, a sliding mode control method with a fast terminal attractor is proposed to improve the dynamic tracking of the system. It is shown that the NLESO guarantees convergence of the estimation error and effectively preserves the initial derivative peak. The FTSMC enables the output voltage with high tracking accuracy and low total harmonic distortion and enhances the anti-disturbance ability. [ABSTRACT FROM AUTHOR]

In addressing the control of asynchronous motors in the remote conductivity of fertigation machines, this study proposes a joint control strategy based on the Fast Terminal Sliding Mode Control-Disturbance Observer (FTSMC-DO) system for asynchronous motors. The goal is to enhance the dynamic performance and disturbance resistance of asynchronous motors, particularly under low-speed operating conditions. The approach involves refining the two-degree-of-freedom internal model controller using fractional-order functions to explicitly separate the controller’s robustness and tracking capabilities. To mitigate the motor’s sensitivity to external disturbances during variable speed operations, a load disturbance observer is introduced, employing hyperbolic tangent and Fal functions for real-time monitoring and compensation, seamlessly integrated into the sliding mode controller. To address issues related to low-speed chattering typically associated with sliding mode controllers, this study introduces a revised non-singular fast terminal sliding mode surface. Additionally, guided by fuzzy control principles, the study enables real-time selection of sliding mode approaching law parameters. Experimental results from the asynchronous motor control platform demonstrate that FTSMC-DO control significantly reduces adjustment time and speed fluctuations during operation, minimizing the impact of load disturbances on the system. The system exhibits robust disturbance rejection, improved robustness, and enhanced control capability. Furthermore, field tests validate the effectiveness of the FTSMC-DO system in regulating remote electrical conductivity (EC) levels. The control time is observed to be less than 120 s, overshoot less than 16.1%, and EC regulation within 0.2 mS·cm−1 over a pipeline distance of 120 m. The FTSMC-DO control consistently achieves the desired EC levels with minimal fluctuation and overshoot, outperforming traditional PID and SMC methods. This high level of precision is crucial for ensuring optimal nutrient delivery and efficient water usage in agricultural irrigation systems, highlighting the system’s potential as a valuable tool in modern, sustainable farming practices.

In this study, to improve the speed tracking performance of the switched reluctance motor (SRM), a control scheme combining fast terminal sliding mode (FTSM) control and radial basis function (RBF) neural network is proposed. First, the convergence characteristic of the FTSM control is derived, and a basic control scheme is designed to ensure the fast convergence of SRM speed tracking errors. Second, the RBF neural network with adaptive parameters is introduced to replace the equivalent control law, which avoids the requirement for the precise mathematical model information of the system. At the same time, considering the network approximation error and unknown external disturbances, an adaptive control law with variables gain is designed. The chattering phenomenon is suppressed and the robustness of the system is enhanced. The updated law of the controller and the stability of the closed‐loop system are derived based on the Lyapunov stability theory. Finally, the simulation and experimental results of the SRM drive system show that the proposed control scheme has an excellent performance in terms of tracking accuracy, response speed, and robustness. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Summary: The problem of attitude tracking control for quadrotor in presence of actuator faults and external disturbances is investigated in this article. By using fast terminal sliding mode control combined with prescribed performance technique, an adaptive control strategy capable of accommodating actuator faults and suppressing external disturbances is designed to achieve attitude finite‐time tracking control with guaranteed performance. In particular, with the help of Nussbaum functions, actuator faults are passively handled without extra development of fault detection and diagnosis mechanism. The finite‐time stability of attitude system under actuator faults and external disturbances is analyzed by Lyapunov stability criterion. Moreover, in order to demonstrate the effectiveness and superiority of proposed control scheme, numerical simulations in different cases are performed and presented in simulation section. [ABSTRACT FROM AUTHOR]

A multi-axis gimbal tracking device is necessary for the micro spacecraft to detect the target. The movement of the tracking device can generate a marked impact on its carrier in the microgravity environment, which should be taken into account when high accuracy is required. The model of the micro spacecraft and the gimbal tracking device can be regarded as a multi-axis open-chain manipulator composed of rigid bodies and joints. Then the dynamics of the model is established by the twist–wrench formulation. A novel dual-loop integral-type fast terminal sliding mode control scheme is proposed to improve the attitude tracking performance of the micro spacecraft. The attitude dynamics of the micro spacecraft is decomposed into two parts, which are used to design controllers to track the angle and the dummy angular velocity signals, respectively. An adaptive disturbance observer is designed to estimate and compensate for the external disturbance. To maintain high positioning accuracy and restrict excessive control torque, a modified nonsingular fast terminal sliding mode controller is proposed for the gimbal tracking device. Accordingly, the proposed schemes have the advantages of nonsingularity, fast convergence, good robustness, and high tracking accuracy. The simulation results demonstrate the feasibility of the modeling method and the effectiveness of the control schemes. • Dynamics of spacecraft with GTD is established by twist–wrench formulation. • Adaptive disturbance observer estimates torque interferences. • Double-loop integral-type FTSMC achieves high tracking accuracy. • Modified NFTSMC restricts control output caused by large error. [ABSTRACT FROM AUTHOR]

In the SPMSM no-speed control system, the traditional SMC speed controlling led to a difference in adjustment speed, a large amount of overshoot and obvious chattering. In order to solve this problem, a new non-singular fast Terminal-SMC speed controller is designed and the continuous function υ(s) is used to replace the traditional symbolic function, which effectively improves the observation accuracy, and reduces the system chattering. The Lyapunov function is designed to prove the system’s stability. The simulation results show that the new NSFT-SMC has faster responded speed, stronger system robustness, and less chattering during stable operation. Comparing with traditional SMC speed control and hyperbolic tangent function SMC speed control, it has better control performance.

In this work, the position and attitude tracking finite-time adaptive control problem of a type of vertical take-off and landing (VTOL) aircraft system is studied. Here, the dynamic of the VTOL aircraft is subjected to external disturbances and unknown nonlinearities. Firstly, radial basis function neural networks are introduced to approximate these unknown nonlinearities, and adaptive weight update laws are proposed to replace unknown ideal weights. Secondly, for the errors generated in the approximation process and the external disturbances of the aircraft system, adaptive parameter update laws are presented. After that, based on the designed global fast terminal sliding mode control functions and adaptive update laws, we present the position tracking control laws and the roll angle control law. Then, based on this, the adaptive global fast terminal sliding control laws for the given aircraft system are finally obtained. Meanwhile, the stability of the aircraft control system is proven by using Lyapunov stability theory and designed adaptive control laws. It is not only ensured that the outputs of the aircraft system can track the given trajectories, but also ensured that the tracking errors can converge to approximately zero within a finite time. Finally, the validity of the designed adaptive control laws is verified through three numerical examples. It can be obtained that the finite-time tracking problems of the given aircraft system can be achieved at 18.8766 s and 14.6340 s under the given parameters. The results are consistent with the theoretical analysis. In addition, under the control laws proposed in this work, the aircraft system can achieve tracking after 9.443 s and 9.674 s and the tracking errors are basically close to zero, which is significantly superior to other control methods considered in this work.

Quad-rotor unmanned aerial vehicles (UAV) are prone to external interference during aerial photography of farmland environments. For example, they are affected by external airflow and load, resulting in route deviation and irregular image overlap, which seriously affects image quality. An aerial trajectory tracking controller is designed for this aerial photography process. To ensure that a drone can fly according to the established route during the aerial photography process and meet the requirements of large-scale topographic map stereo mapping for the flight control accuracy of the drone platform, the system was divided into a full-drive subsystem and an underactuated subsystem. The full-drive subsystem uses a fast terminal sliding mode controller to ensure that the variable (z , ψ) reaches the desired value. The under-actuated subsystem adopts the second-order sliding mode control was used to achieve effective position and attitude tracking of variables (x , y , ϕ , θ). The flight controllers are derived by using Lyapunov theory. Finally, with the aerial trajectory of a farmland taken as an example, the flight path control of the UAV is simulated. Simulation results show that the designed control system can be applied to the aerial photography process of the UAV and has strong anti-system parameter perturbation, robustness and good trajectory tracking. [ABSTRACT FROM AUTHOR]

This research article presents a process control application of a single-input single-output (SISO) level control system using the combination of fast terminal sliding mode control (FTSMC) and optimization method. Non-dominated sorted genetic algorithm-ii (NSGA-ii); a modern optimization technique is used to optimized the parameters of FTSMC. Here, a comparative analysis of conventional sliding mode control (SMC), FTSMC, NSGA tuned FTSMC and NSGA-ii tuned FTSMC has being carried out through MATLAB/ Simulink. The performance indices such as integral absolute error (IAE), integral square error (ISE), and integration of weighted errors have been considered as the objective functions. The robustness of the controller is tested through real-time experimentation. The stability is obtained by using Lyapunov stability criteria. Simulation and experimental results show that NSGA-ii tuned FTSMC method outperforms the conventional methods and the error is converging to zero in a finite-time. Also, NSGA-ii tuned FTSMC provides better-estimated setpoint and disturbance rejection responses. • An optimization of fast terminal sliding mode control strategy has been proposed for level control system. • Performance of conventional controllers have been compared with evolutionary algorithm based method through simulation and real-time experimentation. • Proposed method shows good tracking performance and better robustness against setpoint change, external disturbances, and parametric uncertainties. [ABSTRACT FROM AUTHOR]

The most important issue in the use of wind energy conversion systems (WECS) is to ensure maximum power extraction for attaining increased efficiency. In this study, maximum power extraction frameworks operating the state-of-the-art optimization methods are presented for permanent magnet synchronous generator (PMSG) based WECS. These frameworks consist of a fast terminal sliding mode control (FTSMC) based MPPT controller and a hybrid MPPT approach that combines chaotic based particle swarm optimization (PSO) derivatives and optimal relation based (ORB) method. Chaotic dynamic weight PSO (CDW-PSO) and Gauss map based chaotic PSO (GM-CPSO), which are remarkable and recent optimization techniques, are utilized to achieve optimum coefficients to ensure efficient MPPT operation. After acquiring the optimum coefficients, the framework passes to ORB operation part. Moreover, the proposed frameworks track extracted power within certain limits during the operation of WECS and make transition between the best coefficients if necessary. On the other hand, FTSMC is used to track the MPPT references that are determined via hybrid MPPT algorithms. To validate the proposed frameworks, they are tested in Matlab/Simulink environment for three specific wind speed scenarios. GM-CPSO based ORB and CDW-PSO based ORB MPPT methods are compared with ORB and tip speed ratio (TSR) methods under these scenarios. Consequently, it is revealed that proposed methods contribute to MPPT efficiency by providing higher power extraction than other conventional methods.

This paper proposes a robust control scheme to accomplish the interaction control problem between a series elastic actuator (SEA) and a flexible environment. The adaptability of the controller to unknown variations and robustness of the controller during interaction of the system with environment are the main aims. The control scheme is based on a fuzzy impedance control approach and consists of an inner fast terminal sliding mode force control loop. An experimental setup is designed to prove the efficiency of the developed controller. The experimental results confirm that the proposed fuzzy logic controller guarantees the sensitivity of the controlled system to unpredictable variations. Moreover, by applying the fast terminal sliding mode algorithm for the inner force control loop, the system has faster convergence to the reference path compared with similar control methods found in the literature. [ABSTRACT FROM AUTHOR]

To overcome the sensitivity of voltage source inverters (VSIs) to parameter perturbations and their susceptibility to load variations, a fast terminal sliding mode control (FTSMC) method is proposed as the core and combined with an improved nonlinear extended state observer (NLESO) to resist aggregate system perturbations. Firstly, a mathematical model of the dynamics of a single-phase voltage type inverter is constructed using a state-space averaging approach. Secondly, an NLESO is designed to estimate the lumped uncertainty using the saturation properties of hyperbolic tangent functions. Finally, a sliding mode control method with a fast terminal attractor is proposed to improve the dynamic tracking of the system. It is shown that the NLESO guarantees convergence of the estimation error and effectively preserves the initial derivative peak. The FTSMC enables the output voltage with high tracking accuracy and low total harmonic distortion and enhances the anti-disturbance ability.

This article proposes a characteristic model-based adaptive fault tolerant control scheme to deal with actuator failure in four-motor synchronization systems, which usually causes sudden inertia ratio change and backlash increase. Firstly, the characteristic modeling method is applied into servo system to obtain a simplified system model without losing high-order features. Also, this model could reflect real-time system status through three characteristic parameters. Secondly, a particle swarm optimization algorithm-based estimator is designed to identify characteristic parameters online. By this way, the characteristic model could react to inertia ratio changes quickly and eliminate its negative effect in signal tracking. Thirdly, an improved adaptive electric anti-backlash method is used to restrain backlash. Compared to regular anti-backlash technique, this adaptive one uses a neural network-based fault detector to monitor motors and adjust bias current according to different actuator status, even when one motor breaks down. With these three steps combined, a fast terminal sliding mode controller is finally designed as fault tolerant controller and the stability of this closed-loop system is guaranteed by Lyapunov stability theorem. At last, the simulation and experiment results prove the effectiveness of the proposed control scheme in system control and fault tolerance. [ABSTRACT FROM AUTHOR]

This paper proposes a novel non-singular fast terminal sliding control technique for underactuated robotic manipulators. The proposed approach combines the robustness properties of sliding mode-based control approaches with the approximation accuracy of disturbance observers to suppress both matched and mismatched uncertainties. It also solves the singularity and complex-value number problems associated with fast terminal sliding mode control (FTSMC), while guaranteeing fast convergence rate, robustness and tracking accuracy. The performance of the proposed approach is assessed using a three-link underactuated robotic manipulator with and without holding brakes. The obtained results confirmed the fast convergence rate of the disturbance approximation and position tracking errors along with the excellent robustness and dynamic performance of the proposed control approach. Additionally, due to the estimation properties of the disturbance observer, fast and excellent tracking performance was achieved without the use of large feedback gains.

Under the noncascade structure, the balance between q-axis current constraint and dynamic performance in permanent-magnet synchronous motor system has become a critical problem. On the one hand, large transient current is required to provide high torque to achieve fast dynamic performance. On the other hand, current constraint becomes a state constraint problem, instead of governing q-axis reference current in the cascade structure directly. Aiming at this issue, a novel fast terminal sliding mode control (FTSMC)-based controller with current constraint is developed in this paper. The novelty of this scheme is related to the proposed penalty function based on interior point method, which is established in control action directly. Unlike ordinary solutions, the suggested solution combined with sliding mode variable can achieve current constraint of q-axis without scarifying dynamic performance. Furthermore, by adopting the FTSMC-type surface and new reaching law, the proposed implementation guarantees high performance with significant reduction of chattering phenomenon and has fast convergence characteristics. Then, the stability proof of the whole closed-loop system by employing the Lyapunov method is given in detail. Finally, series of simulations are provided to evaluate the performance of the presented FTSMC-type controller, in terms of current constraint, dynamic performance, and chattering reduction. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive neural network based output feedback backstepping fast terminal sliding mode control (NN-BFTSMC) for continuous polymerization reactor with external disturbances and parametric uncertainties. Firstly, neural networks (NN) are employed to approximate the uncertain nonlinear functions. Next, the average molecular weight and the reactor temperature tracking controllers are designed based on the finite-time NN-BFTSMC. In addition, the NN-BFSMC effectively estimates and compensates the upper bounds of the external disturbances. Moreover, the chattering effect is eliminated without losing the robustness accuracy. The finite-time stability of the closed-loop system is proved by Lyapunov theory. At last, numerical simulations and comparative studies are introduced to illustrate the superior performance of the proposed method. [ABSTRACT FROM AUTHOR]

In the SPMSM no-speed control system, the traditional SMC speed controlling led to a difference in adjustment speed, a large amount of overshoot and obvious chattering. In order to solve this problem, a new non-singular fast Terminal-SMC speed controller is designed and the continuous function υ(s) is used to replace the traditional symbolic function, which effectively improves the observation accuracy, and reduces the system chattering. The Lyapunov function is designed to prove the system's stability. The simulation results show that the new NSFT-SMC has faster responded speed, stronger system robustness, and less chattering during stable operation. Comparing with traditional SMC speed control and hyperbolic tangent function SMC speed control, it has better control performance. [ABSTRACT FROM AUTHOR]

This paper proposes a distributed secondary voltage control method based on extended state Kalman-Bucy filter (ESKBF) and fast terminal sliding mode (FTSM) control for the resilient operation of an islanded microgrid (MG) with inverter-based distributed generations (DGs). To tackle the co-existence of multiple uncertainties, a unified modelling framework is proposed to represent the set of different types of disturbances, including parameter perturbation, measurement noise, and immeasurably external variables, by an extended state method. Kalman-Bucy filter is then applied to accurately estimate the state information of the extended DG model. In addition, based on the accurate estimation, a fast terminal sliding mode (FTSM) surface with terminal attractors is designed to maintain the system stability and accelerate the convergence of consensus tracking, which significantly improves the performance of secondary voltage control under both normal and plug-and-play operation. Finally, case studies are conducted in both MATLAB/Simulink and an experimental testbed to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The paper addresses an adaptive robust position control for tracking control of a manipulator under the presence of the uncertainties, such as variant payload, modeling error, friction, and external disturbance. The proposed control uses radial basis function neural networks (RBFNN)s to approximate and cancel the uncertainties. The nonsingular fast terminal sliding mode control (NFTSMC) of the proposed control is developed to guarantees a finite-time convergence and to solve the singular issue of the terminal sliding mode control. Moreover, the learning laws are derived from the Lyapunov approach to ensure the stability and robustness of the whole system. The proposed control is compared with other controllers through both simulations and experiments on a 3-DOF manipulator to exhibit its efficiency with the variant payload and the uncertainties. [ABSTRACT FROM AUTHOR]

In this paper, a control strategy is proposed to improve the tracking performance of the lower limb exoskeleton (LLE). The proposed active disturbance rejection control (ADRC) with fast terminal sliding mode control (FTSMC) can not only alleviate the disturbance but also converge to a bounded region fast. Based on the robotics analysis, a dynamic model for the LLE was established. To achieve decoupling control for a coupled system, the virtual control input was introduced, where the system uncertainty and external disturbances were regarded as lumped disturbances. To validate the feasibility of the proposed control strategy, the simulations and experiments were both carried out. The numerical simulation results were shown that the proposed control strategy and ADRC can remarkably reduce the chattering phenomena, which is owing to the estimation ability of extended state observer (ESO). Both the simulations and the experiments results were shown that this strategy was better than the conventional proportional-integral-derivative (PID) and ADRC in terms of tracking performance. With the proposed ADRC-FTSMC, the LLE system can achieve higher tracking precision and faster response.

The performance of the pilot solenoid valve (PSV) has a significant impact on the efficiency and service life of an automatic transmission (AT) in automobiles, and it is very difficult to achieve a perfect pressure tracking performance due to the sophisticated combination of mechanical, hydraulic and electromagnetic characteristics inside the PSV. In this paper, based on a nominal nonlinear dynamic model of the PSV including uncertainties and an external disturbance, a fast terminal sliding-mode control (FTSMC) method is developed to achieve tracking precision and robustness in the pressure control of the PSV. To alleviate the chattering phenomenon in the control input signal, fuzzy logic rules are established to tune the switching control coefficient of the control law in FTSMC controller. Compared with the trend-law-based sliding-mode control (TLSMC) method and PID method, the developed fuzzy-type fast terminal sliding-mode control (F-FTSMC) method achieves the shortest settling time, the smallest tracking error at steady state and almost no chattering in the control input by intelligently changing the control law. Simulations and experiments are demonstrated to verify the effectiveness and excellent advantages of the proposed controller.

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents an optimized sliding mode controller (OPSMC) for vibration control of active suspension systems. The proposed controller consists of two parts: the first is the fast terminal sliding mode controller which performs fast convergence, and the second is the particle swarm optimization algorithm which is used to achieve the optimal controller's' parameters. The merit of OPSMC has quite simple structure and easy to be regulated, as well as improve the tracking performance. The half-car active suspension systems with non-linearity such as the parameters variation and external disturbance are simultaneously taken into account to provide a realistic framework. The control objective is to deal with the classical conflict between minimizing vertical and angular chassis accelerations to increase the ride comfort. Versus, to keep minimum dynamic wheel loads and suspension deflections to ensure the ride safety. Finally, to show the performance of the proposed OPSMC, the comparison with a recently developed efficient method called optimization and static output-feedback control (OPSOFC) is conducted with different roads disturbances. [ABSTRACT FROM AUTHOR]

Summary: A favorable option to supply unbalanced loads and provide the neutral wire is the four‐leg inverter. Controllers with high robustness and dynamic response should be used to adjust the inverter load voltages for unknown, unbalanced, and nonlinear loads. Sliding mode controls (SMCs) have a simple structure, good robustness against model parameter uncertainties, and desirable transient response. However, chattering phenomena, variable switching frequency, and error convergence to the operating point on infinite time are the main weaknesses of the conventional SMC method. In this paper, to restrict the conversion time to a finite and controllable value, terminal sliding mode control (TSMC) and fast terminal sliding mode control (FTSMC) procedures are proposed to regulate the load voltages of the four‐leg inverter. In these methods, a continuous control output is suggested to fix the switching frequency and reduce chattering phenomena significantly. Furthermore, the proposed methods are highly robust against model parameter uncertainties. Different simulation and experimental results on a 3‐kW test bench under different loading conditions are done to validate the significant performance of the proposed methods. [ABSTRACT FROM AUTHOR]

Featured Application: Featured Application: This paper proposed the control synthesis, which can be performed in the trajectory tracking control for various robot manipulators as well as in other mechanical systems, the control of the higher-order system, several uncertain nonlinear systems, or chaotic systems. This paper comes up with a novel Fast Terminal Sliding Mode Control (FTSMC) for robot manipulators. First, to enhance the response, fast convergence time, against uncertainties, and accuracy of the tracking position, the novel Fast Terminal Sliding Mode Manifold (FTSMM) is developed. Then, a Supper-Twisting Control Law (STCL) is applied to combat the unknown nonlinear functions in the control system. By using this technique, the exterior disturbances and uncertain dynamics are compensated more rapidly and more correctly with the smooth control torque. Finally, the proposed controller is launched from the proposed sliding mode manifold and the STCL to provide the desired performance. Consequently, the stabilization and robustness criteria are guaranteed in the designed system with high-performance and limited chattering. The proposed controller runs without a precise dynamic model, even in the presence of uncertain components. The numerical examples are simulated to evaluate the effectiveness of the proposed control method for trajectory tracking control of a 3-Degrees of Freedom (DOF) robotic manipulator. [ABSTRACT FROM AUTHOR]

For the hypersonic vehicle with external disturbance, input saturation, model parameter uncertainties and prescribed performance constraint, the tracking control strategy is studied in the thesis. Firstly, a prescribed performance function is introduced into the control design by transforming auxiliary variable errors, which guarantees tracking performance of the control system. On the basis of second-order system model of hypersonic vehicle, an adaptive anti-saturation terminal sliding mode (TSM) controller with prescribed performance is presented by using the adaptive control theory and TSM control. The stability theory of the control law is presented by Lyapunov stability theory and the numerical simulations are conducted to indicate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

This paper presents an integrated vehicle chassis control (IVCC) strategy to improve vehicle handling and stability by coordinating active front steering (AFS) and direct yaw moment control (DYC) in a hierarchical way. In high-level control, the corrective yaw moment is calculated by the fast terminal sliding mode control (FTSMC) method, which may improve the transient response of the system, and a non-linear disturbance observer (NDO) is used to estimate and compensate for the model uncertainty and external disturbance to suppress the chattering of FTSMC. In low-level control, the null-space-based control reallocation method and inverse tyre model are utilized to transform the corrective yaw moment to the desired longitudinal slips and the steer angle increment of front wheels by considering the constraints of actuators and friction ellipse of each wheel. Finally, the performance of the proposed control strategy is verified through simulations of various manoeuvres based on vehicle dynamic software CarSim. [ABSTRACT FROM AUTHOR]

This paper comes up with a novel Fast Terminal Sliding Mode Control (FTSMC) for robot manipulators. First, to enhance the response, fast convergence time, against uncertainties, and accuracy of the tracking position, the novel Fast Terminal Sliding Mode Manifold (FTSMM) is developed. Then, a Supper-Twisting Control Law (STCL) is applied to combat the unknown nonlinear functions in the control system. By using this technique, the exterior disturbances and uncertain dynamics are compensated more rapidly and more correctly with the smooth control torque. Finally, the proposed controller is launched from the proposed sliding mode manifold and the STCL to provide the desired performance. Consequently, the stabilization and robustness criteria are guaranteed in the designed system with high-performance and limited chattering. The proposed controller runs without a precise dynamic model, even in the presence of uncertain components. The numerical examples are simulated to evaluate the effectiveness of the proposed control method for trajectory tracking control of a 3-Degrees of Freedom (DOF) robotic manipulator.