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Summary: This paper presents a composite continuous fast nonsingular terminal sliding mode (CCFNTSM) trajectory tracking control method for Mars entry vehicle. Firstly, the trajectory tracking is transferred into the tracking of the pre‐designed drag acceleration. Secondly, the finite‐time disturbance observer (FTDO) is introduced to estimate the matched and mismatched disturbances. And then, the dynamical fast nonsingular terminal sliding mode manifold is designed based on the estimation information. Finally, the CCFNTSM controller is constructed and its continuity is guaranteed by employing the power function of sliding variable to replace the constant switching gain. Numerical simulation results validate the effectiveness of the proposed control method. [ABSTRACT FROM AUTHOR]

ObjectiveThis paper seeks to solve the problem of the partial failure of the actuator of an underwater salvage robot caused by a decrease in the shipborne power supply voltage or corrosion of the control system circuit. Methods Considering the influence of complex ocean conditions on deep-sea torpedoes, cargo shipwrecks, and other engineering salvage operations, the terminal sliding mode observer is used to observe the uncertain disturbance of the system, while the fault-tolerant control method and finite-time control method are used to estimate the fault coefficient of the actuator on-line, and a finite-time trajectory tracking fault-tolerant control scheme with a terminal sliding mode observer is designed. ResultThe system output of this scheme is smooth, stable, and can reach the desired trajectory quickly. At the same time, compared with the traditional fault-tolerant control scheme, the steady-state time of the underwater salvage robot's control system is reduced (the lateral displacement is reduced by 10 s and the longitudinal displacement by 15 s).ConclusionThis study has practical engineering significance and can provide theoretical references for the trajectory tracking of underwater construction machinery.

This study examines stability improvement of the power system which includes Double Feed Induction Generators (DFIGs) and Static Series Synchronous Compensator (SSSC). The proposed nonlinear controller is designed based on the terminal sliding mode control theory. A sliding mode observer is also developed to remove the need to access the information of all the state variables. The final closed-loop of the power system modeling is robust against parameter variations and uncertainties. The limitations of the control signals in the process of controller design are also considered. The application of such a method increases the stability margins and results in higher robustness degrees. A comparison with other nonlinear approaches such as back-stepping and feedback linearization approaches is carried out. The results show the faster and more reliable convergence rate of the power system-controlled trajectories to reach back to the equilibrium point after occurring a sudden fault. The results are obtained by performing a simulation on the standard 39-Bus, 10 machines NEW ENGLAND power system.

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.)

This paper introduces a control strategy to recover from various spin motions to level trim flight conditions, utilizing a fixed-time nonsingular terminal sliding mode approach to minimize altitude loss. Firstly, an integral terminal sliding mode surface is constructed to guarantee the tracking errors of the spin recovery system converge to the origin within a fixed time and avoid the singularity problem. Next, a fixed-time type reaching law is proposed to weaken the chattering phenomenon and guarantee terminal sliding hyperplanes converge to zero in a fixed time. Furthermore, the stability analysis indicates the fixed-time convergence stability of the spin recovery control system and provides an accurate calculation of the settling time. Finally, comparative simulations are performed to validate the effectiveness and superiority of the developed spin recovery control scheme. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai University of Engineering Science / Shanghai Gongcheng Jishu Daxue Xuebao is the property of Journal of Shanghai University of Engineering Science 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 study examines stability improvement of the power system which includes Double Feed Induction Generators (DFIGs) and Static Series Synchronous Compensator (SSSC). The proposed nonlinear controller is designed based on the terminal sliding mode control theory. A sliding mode observer is also developed to remove the need to access the information of all the state variables. The final closedloop of the power system modeling is robust against parameter variations and uncertainties. The limitations of the control signals in the process of controller design are also considered. The application of such a method increases the stability margins and results in higher robustness degrees. A comparison with other nonlinear approaches such as back-stepping and feedback linearization approaches is carried out. The results show the faster and more reliable convergence rate of the power system-controlled trajectories to reach back to the equilibrium point after occurring a sudden fault. The results are obtained by performing a simulation on the standard 39-Bus, 10 machines NEW ENGLAND power system. [ABSTRACT FROM AUTHOR]

In this paper, a fast terminal sliding mode control strategy based on a novel reaching law and fixed-time disturbance observer is proposed to improve the tracking performance of robot manipulators in the presence of disturbance. Firstly, aiming at the problems of chattering and slow convergence rate of traditional reaching laws, a novel variable exponential power reaching law is designed to adaptively change the convergence rate according to the system’s initial state, and its characteristic of finite time convergence is analyzed as well. Secondly, a fixed-time disturbance observer is constructed to approximate the lumped disturbance and realize online compensation for the controller. Thirdly, to solve the problems of singularity and slow convergence rate associated with the traditional terminal sliding mode surface, a fast non-singular terminal sliding mode surface is proposed, which guarantees the tracking error converges to zero in a finite time. Finally, a fast non-singular terminal sliding mode tracking controller for the manipulator is designed, and the system stability is proved by the Lyapunov theorem. Moreover, a large number of simulation experiments are carried out to verify the validity and superiority of the proposed controller.

The ideal fuel rail pressure is a significant component to keep the high-pressure common rail (HPCR) system work stably. The influence of time-varying fuel injection disturbance of the HPCR system is neither fully considered nor well dealt with in traditional rail pressure control approaches. To this end, the rail pressure tracking problem of an HPCR system is investigated in this paper using a generalized proportional integral observer (GPIO)-based composite control algorithm. A nonlinear model of the HPCR system is first established based on fluid dynamics and mechanics laws. Then, a GPIO is utilized to observe the time-varying fuel injection disturbance. Based on the design of a nonlinear sliding surface using the disturbance estimation, a GPIO-based nonsingular terminal sliding mode control (NTSMC) method is proposed to achieve a better rail pressure tracking control performance and a stronger robustness. Finally, a group of simulations in the MATLAB/Simulink environment and experiments in a more realistic Advanced Modeling Environment for performing Simulation of engineering systems (AMESim) environment are conducted, the results of which demonstrate the advantage and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

To further improve the response speed and anti-interference capability of permanent magnet synchronous motors (PMSMs), many advanced control algorithms have been developed. Among the various advanced controls, the fixed-time terminal sliding mode control is one of the effective methods. However, there are still some problems, e.g., too many parameters imposed on the control design in the existing results. In this paper, a fixed-time non-singular terminal sliding mode control (FTNTSMC) method is proposed for the speed loop of a PMSM drive system. First, to improve the closed-loop performance of the PMSM drive system, the relationship between the reference q-axis current and the speed of the PMSM is described in a second-order model. Next, a sliding mode surface with variable exponential coefficients is selected, and the expression of the controller is given. Then, the stability of the PMSM drive system is demonstrated by using Lyapunov functions. Using this method, the fixed-time convergence of the PMSM drive system can be realized and the occurrence of singularity phenomena can be avoided in a simpler and easier method. Finally, the effectiveness of the proposed method is verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

As most of the current dynamic positioning systems are based on model ships, they cannot accurately reflect the motion state, position changes, and mutual influence of each part of the dynamic positioning system of actual ships in complex environments. Other actual ships such as cargo ships cannot add various sensors and auxiliary equipment to verify and analyze the positioning system. This article takes the intelligent research and training dual-use ship of Dalian Maritime University, which integrates scientific research and training, as the object of study. This ship will not be affected by the voyage period and route and can choose a suitable sea area for research. Therefore, in order to improve the accuracy and reliability of the dynamic positioning system, research on the ship's dynamic positioning system was carried out. Firstly, an accurate mathematical model was developed to simulate ship motion, focusing on the use of the Dalian Maritime University's intelligent and practical training dual-purpose vessel as the modeling object. Through this approach, a more detailed understanding of the effects of actual environmental perturbations on ship control and positioning can be obtained, as well as more realistic ship control and positioning results. The hydrodynamic derivatives of ship model motion were obtained by numerical calculation and applied to the three-degree-of-freedom model of the intelligent research and training dual-use ship. Then, the model was used as part of the closed-loop simulation model of the ship's dynamic positioning system, and the terminal sliding mode controller was used for simulation and emulation, thereby obtaining ideal simulation test results. Our results deepen the understanding of DPS accuracy and are consistent with the theory of terminal slip modes for ship power positioning control systems. This has implications for improving the accuracy of ship power positioning systems, as previously discussed in previous authors. In conclusion, this study not only improves the accuracy and reliability of the DPS but also proposes the use of the terminal slip film for a ship power positioning control system modeled on the Dalian Maritime University intelligent and practical dual-purpose vessel. These contributions are significant in improving the efficiency, safety, and environmental sustainability of ship operations. [ABSTRACT FROM AUTHOR]

In this study, a novel adaptive nonsingular terminal sliding mode (ANTSM) control frame combined with a modified extended state observer (MESO) is presented to enhance the anti-interference performance of the permanent magnet synchronous motor (PMSM) system. In the face of time-varying disturbances with unknown upper bounds, traditional nonsingular terminal sliding mode (NTSM) controllers typically utilize the large control gain to counteract the total disturbance, which will cause unsatisfactory control performances. To address this tough issue, an ANTSM control technique was constructed for the PMSM system by tuning the control gain automatically without overestimation. On this basis, the MESO was adopted to estimate the unknown total disturbance, whose estimation was offset to the ANTSM control input. By applying finite-time techniques, the estimation error will finite-time converge to zero. The proposed MESO has a more rapid estimation speed than the traditional extended state observer (ESO). Finally, the validity of the ANTSM + ESO composite control algorithm is confirmed by comprehensive experiments.

ObjectiveThis study addresses the engineering problem of underwater tracked dredging robots sliding due to insufficient adhesion when dredging caissons in bridge construction. Therefore, a trajectory tracking controller based on the barrier Lyapunov function (BLF) is designed. MethodThe algorithm considers the non-coincidence of the centroid and geometric center, influence of unknown bounded disturbances and system dynamic uncertainty to establish kinematic and dynamic motion models. A terminal sliding mode observer (TSMO) is used to approximate external disturbances and system dynamic uncertainty in finite time. The stability of the control system is verified by time-varying symmetric finite time BLF stability analysis, and control failure is prevented by limiting the velocity state of the system. ResultsThe simulation results show that the robot reaches the desired trajectory smoothly and quickly under the control of the designed controller. ConclusionThe proposed algorithm can limit the velocity state of the robot system to an interval that conforms to the actual engineering practice.

• A novel I&I adaptive scheme is presented. • Immersion and invariance based adaptive terminal sliding mode control is proposed. • Immersion and invariance based adaptive terminal sliding mode control with saturation compensation is presented. This work investigates attitude control of spacecraft with uncertainties and input saturation. An immersion and invariance based adaptive robust control (IIARC) is proposed to improve tracking performance of spacecraft. The proposed approach consists of an immersion and invariance (I&I) estimator, a robust adaptive law, and a terminal sliding mode control (TSMC). The continuous fast TSMC is designed to stabilize the system and obtain fast convergence rate. To estimate the disturbances and uncertainties, I&I methodology is introduced into the proposed approach. The robust adaptive law is applied such that the prior information of disturbances is not required. IIARC with saturation compensation (IIARCSC) is presented to reduce the effect of input saturation on the attitude tracking of spacecraft. It is proved that the developed approach could guarantee the finite-time convergence (FTC). Extensive comparative simulations demonstrate the effectiveness of the presented scheme. [ABSTRACT FROM AUTHOR]

This paper studies the fixed-time coordinated tracking problem of second-order nonlinear multi-agent systems with unknown disturbances. Based on the fixed-time distributed observer, a non-singular terminal sliding mode protocol is proposed, which could avoid singularity and achieve exact convergence. By using graph theory and Lyapunov stability method, sufficient conditions and the upper bound of setting time for fixed-time coordinated tracking are obtained. Numerical examples are given to show the effectiveness of theoretical results. [ABSTRACT FROM AUTHOR]

In this paper, a direct yaw-moment control strategy based on the adaptive terminal sliding mode (TSM) control technique and disturbance observer (DOB) is developed to promote the safety driving under extreme situations for in-wheel electric vehicles. First of all, the ideal yaw rate is calculated through a two-degree-of-freedom vehicle model. A traditional TSM control scheme is designed to ensure that the yaw rate can approximate the ideal value as closely as possible. Since a large gain is always needed in the TSM controller to overcome the unknown disturbance, an adaptive TSM controller is constructed to attenuate the chattering. The key merit of the proposed adaptive TSM controller lies in that it can automatically search the minimum gain satisfying the reaching condition of sliding mode. To further facilitate the performance improvement, a new nonlinear DOB is constructed to estimate the disturbance and a composite adaptive TSM control framework is designed by combining the proposed adaptive TSM controller and the given DOB. Simulation results under a professional software verify the presented methods. [ABSTRACT FROM AUTHOR]

In this paper, a novel backstepping terminal super-twisting sliding mode (TSTSM) with high order sliding mode observer (HOSMO) is proposed to control the two degrees of freedom (DOFs) Serial Elastic Actuator (SEA), inspired by a lower limb of humanoid robots. First, the dynamic model, extended from our previous study, is presented for developing the control algorithm. Secondly, the backstepping technique is utilized to separate the overall system into two subsystems. One of the challenges of SEA is to deal with the evident oscillations caused by the elastic element, which might lead to the degrading performance of load position control. In order to reduce this adverse effect, a TSTSM is proposed to control the position tracking of two subsystems. The advantages of TSTSM are the finite-time convergence despite the bounded perturbation and the dramatic reduction of the chattering phenomenon. To construct and implement the TSTSM controller, it requires the knowledge of all states, which is not available in the current lower limb system setup. Therefore, a HOSMO is utilized to estimate the unknown states. Finally, experiment results are carried out to assess the effectiveness of the proposed controller and compare it with those of different control schemes. [ABSTRACT FROM AUTHOR]

Piezoelectric micropositioning systems (PMSs) have been widely utilized in the high-precision manipulation applications, but are also subjected to undesired nonlinearities, like hysteresis, and parameter uncertainties. To solve this problem, this paper proposes a new robust sliding mode control scheme for a class of nonlinear PMSs with time-varying uncertainties. Different from the conventional sliding mode control (SMC), the proposed controller further combines the Fourier series-based function estimation technique, fuzzy logic system and adaptive learning algorithm to realize online estimation and compensation of system time-varying uncertainties without their boundary information. The adaptive laws of Fourier coefficients and fuzzy adjustable parameters are obtained via the Lyapunov stability theory. Compared with the existing SMC methods, the proposed control effectively eliminates the control chattering problem, and guarantees the convergence of the tracking error in finite time in the presence of time-varying uncertainties. Theoretical analysis and numerical simulation results show that the proposed control strategy can meet the high-speed, high-precision robust tracking performance requirements of PMSs for micro/nano-manipulation applications. [ABSTRACT FROM AUTHOR]

This paper proposes a new fixed-time sliding mode (FSM) control, where the settling time for reaching the system origin is bounded to a constant independent of the initial condition; this is in contrast to the initial condition-dependent constants used in the traditional linear sliding mode (LSM) and terminal sliding mode (TSM) controls. First, a new sliding mode control with a single power term is discussed, where the power term can have any nonnegative value. Except for the traditional LSM and TSM controls, a new sliding mode control called power sliding mode (PSM) is proposed, whose power term is larger than 1. Then, a new FSM control with two power terms is investigated, whose design is based on the combination of TSM and PSM. In particular, the two power terms on the plane in the first quadrant are carefully discussed, and a detailed classification is provided. Here, the first quadrant can be classified into six categories, including LSM, generalized LSM, TSM, fast TSM (FTSM), PSM, and FSM. Furthermore, the analytical settling time is calculated, and three different estimation bounds of the settling time are given for reaching the origin under any initial condition. It is also interesting to derive the lowest bound for the settling time. Finally, FSM control design for general nonlinear dynamical systems with the relative degree from the control input to the output is also discussed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology 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.)

Copyright of Journal of Chongqing University of Posts & Telecommunications (Natural Science Edition) is the property of Chongqing University of Posts & Telecommunications 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.)

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.)

This study proposes an adaptive nonsingular integral dynamic terminal sliding mode tracker/synchronizer for disturbed nonlinear systems along with its usage in safe communication systems. The convergence of the closed-loop structure under unknown uncertainty and disturbances is guaranteed via Lyapunov analysis. Furthermore, a parameter-tuning method is planned to approximate the upper bound of uncertainty and disturbance terms, since this latter is typically unknown in practice. The proposed approach is used to design a digital secure transmission scheme according to the chaotic systems. The effectiveness of the suggested approach is validated using computer simulations on a benchmark example of chaotic system. The obtained outcomes clearly confirm the ability of the planned control approach enables to attain the desired tracking/synchronizing performance despite the disturbances. Additionally, when implemented to the data encryption of a communication system, the proposed control and secure communication techniques enabled the complete and secure retrieval of the original digital sequences. [ABSTRACT FROM AUTHOR]

In this article, the finite-time output feedback sliding mode control problem is investigated for a class of continuous-time linear systems with unmeasurable states. First, a novel terminal sliding mode observer is established to estimate the unmeasured system states. Second, a novel integral sliding surface is introduced with tunable parameters. Then, an output feedback sliding mode controller with power terms is constructed to drive the given system to the origin in a finite time. A switching from the terminal sliding mode to a usual sliding manifold is taken to avoid singularity problem. Finally, two application-oriented examples are offered to verify the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

A new bilateral continuous terminal sliding mode control method is proposed to attenuate the high-order time-varying disturbance in teleoperation systems based on enhanced nonlinear disturbance observer (ENDOB). Firstly, the control task of the teleoperation systems is transformed into stabilization of the position and force tracking errors. And then, the ENDOBs are introduced to estimate the high-order lumped disturbances in position and force tracking error subsystems. Finally, based on the estimation of lumped disturbances, a bilateral continuous terminal sliding mode controller is developed. The proposed bilateral controller not only guarantees the continuity of the control action but also guarantees the position and force tracking errors converge to a small bounded region even when there exist high-order time-varying disturbances. The effectiveness of the proposed method is validated by its applications on a bilateral lift robot system. [ABSTRACT FROM AUTHOR]

This paper describes a control algorithm for the sliding mode of a lower-extremity exoskeleton model with a neural network for elimination of external perturbances and uncertainties. The sliding control of rapid action is used for achievement of rapid convergence in finite time, absence of singularity, and suppression of oscillations. The neural network allows the efficiency of the regulator inside the boundary layer to be improved. The analysis of the asymptotic stability of the closed system is confirmed by the Lyapunov stability criterion guaranteeing the condition of sliding. The efficiency of the proposed control method has been proven using simulation in the MATLAB software, including the construction of a five-joint mathematical model of a lower-extremity exoskeleton. [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.)

This paper introduces a control strategy to recover from various spin motions to level trim flight conditions, utilizing a fixed-time nonsingular terminal sliding mode approach to minimize altitude loss. Firstly, an integral terminal sliding mode surface is constructed to guarantee the tracking errors of the spin recovery system converge to the origin within a fixed time and avoid the singularity problem. Next, a fixed-time type reaching law is proposed to weaken the chattering phenomenon and guarantee terminal sliding hyperplanes converge to zero in a fixed time. Furthermore, the stability analysis indicates the fixed-time convergence stability of the spin recovery control system and provides an accurate calculation of the settling time. Finally, comparative simulations are performed to validate the effectiveness and superiority of the developed spin recovery control scheme.

As most of the current dynamic positioning systems are based on model ships, they cannot accurately reflect the motion state, position changes, and mutual influence of each part of the dynamic positioning system of actual ships in complex environments. Other actual ships such as cargo ships cannot add various sensors and auxiliary equipment to verify and analyze the positioning system. This article takes the intelligent research and training dual-use ship of Dalian Maritime University, which integrates scientific research and training, as the object of study. This ship will not be affected by the voyage period and route and can choose a suitable sea area for research. Therefore, in order to improve the accuracy and reliability of the dynamic positioning system, research on the ship’s dynamic positioning system was carried out. Firstly, an accurate mathematical model was developed to simulate ship motion, focusing on the use of the Dalian Maritime University’s intelligent and practical training dual-purpose vessel as the modeling object. Through this approach, a more detailed understanding of the effects of actual environmental perturbations on ship control and positioning can be obtained, as well as more realistic ship control and positioning results. The hydrodynamic derivatives of ship model motion were obtained by numerical calculation and applied to the three-degree-of-freedom model of the intelligent research and training dual-use ship. Then, the model was used as part of the closed-loop simulation model of the ship’s dynamic positioning system, and the terminal sliding mode controller was used for simulation and emulation, thereby obtaining ideal simulation test results. Our results deepen the understanding of DPS accuracy and are consistent with the theory of terminal slip modes for ship power positioning control systems. This has implications for improving the accuracy of ship power positioning systems, as previously discussed in previous authors. In conclusion, this study not only improves the accuracy and reliability of the DPS but also proposes the use of the terminal slip film for a ship power positioning control system modeled on the Dalian Maritime University intelligent and practical dual-purpose vessel. These contributions are significant in improving the efficiency, safety, and environmental sustainability of ship operations.

This study focuses on addressing the tracking control problem for a coaxial unmanned aerial vehicle (UAV) without any prior knowledge of its dynamic model. To overcome the limitations of model-based control, a model-free approach based on terminal sliding mode control is proposed for achieving precise position and rotation tracking. The terminal sliding mode technique is utilized to approximate the unknown nonlinear model of the system, while the global stability with finite-time convergence of the overall system is guaranteed using the Lyapunov theory. Additionally, the selection of control parameters is addressed by incorporating the accelerated particle swarm optimization (APSO) algorithm. Finally, numerical simulation tests are provided to demonstrate the effectiveness and feasibility of the proposed design approach, which demonstrates the capability of the model-free control approach to achieve accurate tracking control even without prior knowledge of the system’s dynamic model.

In this article, a predictor‐based robust synchronization control scheme is proposed for a non‐collocated nonlinear master–slave system with any large networked communication time delays. In contrast to traditional collocated teleoperation systems, enhanced flexibility, and operation capacity will be obtained under the non‐collocated system structure in this article. Yet, due to the introduced input delays, existing control strategies for teleoperation systems are no longer applicable. Aiming at this problem, the terminal sliding mode (TSM) admittance control approach is proposed for the master robot to improve system transparency by receiving the contact force from the slave robot to the local side, first. Moreover, complete position synchronization performance is realized by developing a predictor‐based TSM control method for the slave robot while the closed‐loop system is subject to time‐variant large delays. It is mathematically proved that the synchronization errors between the master and the slave will converge to zero completely in finite time by compensating the effect of time delays. Finally, numerical simulations and comparisons are executed to illustrate the superior performance of the posed control algorithms. [ABSTRACT FROM AUTHOR]

In this article, the steady‐state behaviors of discrete‐time nonsingular terminal sliding mode (NTSM) control systems are investigated for the explicit and implicit Euler integration schemes. It is demonstrated that implicit Euler method can guarantee the global convergence of both system states and sliding variable for discrete‐time NTSM control systems, whereas explicit Euler approximation does not. For explicit discrete‐time NTSM, the range of quasi sliding mode band is deduced on the basis of the reachability condition of discrete SM, showing that discretized NTSM can achieve higher control accuracy than the discrete‐time linear sliding mode. By analyzing the distribution features of steady‐state points, the upper bound for steady states is obtained to estimate chattering amplitude, which establishes the influence relationship of sampling time, switching gain and movement characteristics on the bound of steady states. Simulations are presented to validate the theoretical results. [ABSTRACT FROM AUTHOR]

This article proposes a novel robust control scheme for the trajectory tracking control of a cable-driven aerial manipulator in joint space, combining an adaptive fractional-order nonsingular terminal sliding mode (FONTSM) manifold and a nonlinear disturbance observer (NDOB). The proposed control scheme mainly consists of three aspects, i.e., an NDOB used to estimate the unmodeled dynamics and external disturbances, a FONTSM applied to guarantee the control accuracy of the tracking performance, and an adaptive reaching law applied to improve the robustness. The proposed scheme is based on the model-free idea that can reduce the difficulty of controller design without knowing the precise dynamics of the plant. The experimental results show that the proposed controller can ensure better transient performance and stronger robustness against lumped disturbances than two other existing controllers. [ABSTRACT FROM AUTHOR]

Nowadays, research on electric drive control has become popular because hybrid methods to collect the advantages of individual controllers. Moreover, these methods aim to reach better performance and robust control even in the presence of uncertainties and disturbances which are typically evident in high-speed dynamics where the influence of external disturbances and modeling errors are more evident. Therefore, in this paper, a novel hybrid controller is proposed between the super-twisting algorithm based on high order design (HO-STA) and terminal sliding mode control (T-SMC) applied on a permanent magnet synchronous motor PMSM. Whereas, it accounts to deal with the weaknesses of both terminal sliding mode control and super twisting algorithm (STA) and at the same time combining their advantages; furthermore, it provides exceptional characteristics, including fast finite-time convergence, stabilization of the performance and its reaching law developer based on new design which contributes to reducing the chattering problems afflicted by C-SMC. This proposed hybrid technique contributes to gaining robust control under variation between slow, medium, and high speed levels, no matter what load torque is applied or whatever PMSM parameters change. Moreover, it also offers optimum performance characteristics such as smaller settling time and steady state error. Whereas, the control efficiency is demonstrated by Matlab/Simulink simulation to confirm our design parameters. [ABSTRACT FROM AUTHOR]

• This paper adopts a unified algorithm to handle disturbances at different locations, which has a wider adaptability. • This paper only requires that the disturbance is bounded, which broadens the premise and has good practical engineering application ability. • This paper accelerates the convergence speed of the system after disturbance and improves the dynamic performance of the system. The large-scale application of measurement devices, programmable controllers, and power electronic devices increases the likelihood of distributed energy storage systems suffering from various disturbances, thus affecting the stable operation of the system. In this paper, an adaptive finite time fast resilient control strategy is proposed for the unknown transmission disturbance in the control channel of distributed energy storage system. Firstly, the adverse effects of sensor and actuator disturbances on conventional consensus-based secondary control strategies are quantitatively analyzed. Secondly, an resilient control protocol with adaptive compensation mechanism based on terminal sliding mode is proposed, and the suppression mechanism of the controller to the unknown disturbance of the sensor and the actuator is analyzed, and the finite time convergence of the proposed distributed resilient secondary control strategy is proved theoretically. Experimental results show that the proposed control strategy is correct and effective. [ABSTRACT FROM AUTHOR]

In this study, with the help of a disturbance observer, an adaptive fractional-order sliding mode control scheme is designed to achieve trajectory tracking control of indeterminate manipulators. Firstly, the fractional-order non-singular fast terminal sliding mode (FO-NFTSM) surface is presented to increase the convergence velocity of the controller. Secondly, the adaptive reaching law is designed on the strength of the super-twisting algorithm to ensure the control performance of the approaching stage. Meanwhile, aiming at the compound disturbance existing in the manipulator system, an adaptive fixed-time sliding mode disturbance observer (AFSMDO) is introduced to settle the problem, which can estimate the lumped disturbance in real-time. Moreover, compensate for the system and raise the precision of the controller. The Lyapunov method is applied to certify the stability of the control system. Simulation experiments verify the superior property of the controller designed in this article.

This paper presents an active disturbance rejection control (ADRC) method for modular robot manipulators (MRMs) based on extended state observer (ESO), which solves the problem of trajectory tracking when modular robot manipulators facing the emotional physical human-robot interaction (pHRI). The dynamic model of MRMs is formulated via joint torque feedback (JTF) technique that is deployed for each joint module to design the model compensation controller. ESO is used to estimate the interconnected dynamic coupling (IDC) term and the interference term caused by emotional pHRI. An uncertainty decomposition-based robust control is developed to compensate the friction term. The terminal sliding mode control (TSMC) algorithm is introduced to the controller to provide faster convergence and higher precision control effect. Based on the Lyapunov theory, the tracking error is proved to be ultimately uniformly bounded (UUB). Finally, experiments demonstrate advantages of the proposed method.

Achieving compliance and flexibility under the premise of ensuring trajectory tracking performance and also reflecting the wearer's movement intention, has not yet been well solved in the field of prosthesis. The aim of this paper is to provide a compliant, robust, and continuous control scheme for robotic knee prosthesis to solve the contradictory problems of trajectory tracking performance and compliance. The proposed scheme are based on the admittance model and radial basis function (RBF) neural network–enhanced nonsingular fast terminal sliding-mode controller (NFTSMC). The desired trajectory of the prosthetic knee joint is driven by humans and reshaped to reference trajectory by an admittance model, so that the prosthetic leg can reflect the human's movement intention and being compliant. RBF neural network is introduced to achieve adaptive approximation of unknown models and ensure that the controller does not depend on the mathematical model of the "human-in-the-loop" prosthesis system. A novel NFTSMC was proposed to deal with the influence of ground reaction forces (GRFs) and fitting errors of the RBF neural network, which make the tracking error converge to zero in a finite time. The adaptive law of the RBF neural network is obtained by the Lyapunov method, and the stability and finite-time convergence of the closed-loop system are rigorously proved and analyzed mathematically. The simulation results prove the feasibility and effectiveness of the propose control scheme. [ABSTRACT FROM AUTHOR]

A novel sliding mode control strategy is proposed to solve the trajectory tracking control problem of an offshore antenna platform, which uses a Stewart-type parallel mechanism and has a large orientation workspace. To obtain comprehensive posture parameters of the offshore antenna platform, a posture compensation algorithm using the information of azimuth and elevation is proposed. Considering known limb lengths, a state observer which based on a super-twisting algorithm is presented to obtain limb velocities. To solve the trajectory-tracking control problem of the platform, a modified nonsingular terminal integral sliding mode controller is proposed. To reduce chattering, the sliding mode controller is equipped with a higher order super-twisting algorithm. The Lyapunov theory was used to prove its stability. Simulation results on a large-orientation workspace offshore antenna platform demonstrate its superiority over three other controllers. Compared with the traditional sliding mode controller with super-twisting algorithm, the integral of the squared error of the proposed control strategy is 49.49% lower. • Trajectory tracking control of Stewart-type offshore antenna platform with a large orientation workspace. • A modified nonsingular terminal integral sliding mode surface is employed. • The superiority of the proposed strategy has been verified using the simulation. • The proposed strategy can reduce the chattering greatly. [ABSTRACT FROM AUTHOR]

Due to the unknown disturbance caused by the harsh environment in deep water, the stability of Underwater Tracked Remotely Opreated Vehicle (UTROV) trajectory tracking control is affected; especially the resistance forces of random vibrations caused by non-differentiable random disturbance resistance, which has become one of the main problems in controller design. Considering engineering practice, a stochastic model and new dynamic damping-based terminal sliding mode event-triggered fault-tolerant controller were designed in this paper. Firstly, based on the random resistance pre-compensation theory for the first time, a stochastic model was designed for differential drive UTROV. Meanwhile, a new nonsingular terminal sliding mode and dynamic damping reaching law were designed to achieve global finite-time convergence and reduce chattering with better robust response speed. Furthermore, to deal with the wear and tear caused by actuator failure and fixed sampling rate transmission, a new dynamic event trigger mechanism was designed and the faults analyzed. On this basis, combined with the finite-time adaptive on-line estimation technology, it can not only better reduce the transmission frequency, but also the finite-time dynamic active fault-tolerant compensation. The control scheme has semi-globally finite-time stability in probability and is proved by theory, which is compliant with engineering requirements. Then, according to characteristics of innovation, the three groups of simulation of control methods are designed to compare the methods in this paper. Finally the advantages of the method are verified by simulation to achieve the design expectations. [ABSTRACT FROM AUTHOR]