Showing papers on "Terminal sliding mode published in 2018"
TL;DR: A novel nonlinear sliding mode control approach dealing with the formation control of under-actuated ships is presented and a distributed controller is designed for individual under-Actuated ship to achieve the given formation pattern within a finite time.
Abstract: A novel nonlinear sliding mode control approach dealing with the formation control of under-actuated ships is presented in this paper To avoid the singularity problem, state space of the system is partitioned into two regions, with one region bounded for terminal sliding mode control and its complement singular for that And a linear auxiliary sliding mode controller is designed for system trajectories starting from the complement region With the application of nonlinear sliding mode control approach and finite-time stability theory, a distributed controller is designed for individual under-actuated ship to achieve the given formation pattern within a finite time Finally, two simulation examples are provided to verify the effectiveness and performance of the proposed approach
230 citations
TL;DR: The finite-time multivariable terminal sliding mode control and composite-loop design are pursued to enable integration into the FTC, which can ensure the safety of the postfault vehicle in a timely manner.
Abstract: This paper proposes a fault-tolerant control (FTC) scheme for a hypersonic gliding vehicle to counteract actuator faults and model uncertainties. Starting from the kinematic and aerodynamic models of the hypersonic vehicle, the control-oriented model subject to actuator faults is built. The observers are designed to estimate the information of actuator faults and model uncertainties, and to guarantee the estimation errors for converging to zero in fixed settling time. Subsequently, the finite-time multivariable terminal sliding mode control and composite-loop design are pursued to enable integration into the FTC, which can ensure the safety of the postfault vehicle in a timely manner. Simulation studies of a six degree-of-freedom nonlinear model of the hypersonic gliding vehicle are carried out to manifest the effectiveness of the investigated FTC system.
202 citations
TL;DR: Rigorous analysis is provided to demonstrate that the fast terminal SMC law can offer a higher accuracy than the traditional linear SMClaw and show the advantages of the present discrete-time fast terminalSMC approach over some existing approaches, such as discrete- time linear sliding mode control approach and the PID control method.
Abstract: The main objective of this paper is to solve the position tracking control problem for the permanent magnet linear motor by using the discrete-time fast terminal sliding mode control (SMC) method. Specifically, based on Euler's discretization technique, the approximate discrete-time model is first obtained and analyzed. Then, by introducing a new type of discrete-time fast terminal sliding surface, an improved discrete-time fast SMC method is developed and an equivalent-control-based fast terminal SMC law is subsequently designed. Rigorous analysis is provided to demonstrate that the fast terminal SMC law can offer a higher accuracy than the traditional linear SMC law. Numerical simulations and experimental results are finally performed to demonstrate the effectiveness of the proposed approach and show the advantages of the present discrete-time fast terminal SMC approach over some existing approaches, such as discrete-time linear sliding mode control approach and the PID control method.
201 citations
TL;DR: In this paper, robust and adaptive nonsingular fast terminal sliding-mode (NFTSM) control schemes with known or unknown upper bound of the system uncertainty and external disturbances are proposed.
Abstract: In this paper, robust and adaptive nonsingular fast terminal sliding-mode (NFTSM) control schemes for the trajectory tracking problem are proposed with known or unknown upper bound of the system uncertainty and external disturbances. The developed controllers take the advantage of the NFTSM theory to ensure fast convergence rate, singularity avoidance, and robustness against uncertainties and external disturbances. First, a robust NFTSM controller is proposed which guarantees that sliding surface and equilibrium point can be reached in a short finite-time from any initial state. Then, in order to cope with the unknown upper bound of the system uncertainty which may be occurring in practical applications, a new adaptive NFTSM algorithm is developed. One feature of the proposed control law is their adaptation techniques where the prior knowledge of parameters uncertainty and disturbances is not needed. However, the adaptive tuning law can estimate the upper bound of these uncertainties using only position and velocity measurements. Moreover, the proposed controller eliminates the chattering effect without losing the robustness property and the precision. Stability analysis is performed using the Lyapunov stability theory, and simulation studies are conducted to verify the effectiveness of the developed control schemes.
169 citations
TL;DR: The results show that the motor control system based on the proposed SMC method has good speed and current tracking performance and strong robustness.
Abstract: A terminal sliding mode control (SMC) method based on nonlinear disturbance observer is investigated to realize the speed and the current tracking control for the permanent magnet synchronous motor (PMSM) drive system in this paper. The proposed method adopts the speed-current single-loop control structure instead of the traditional cascade control in the vector control of the PMSM. First, considering the nonlinear and the coupling characteristic, a single-loop terminal sliding mode controller is designed for PMSM drive system through feedback linearization technology. This method can make the motor speed and current reach the reference value in finite time, which can realize the fast transient response. Although the SMC is less sensitive to parameter uncertainties and external disturbance, it may produce a large switching gain, which may cause the undesired chattering. Meanwhile, the SMC cannot keep the property of invariance in the presence of unmatched uncertainties. Then, a nonlinear disturbance observer is proposed to the estimate the lump disturbance, which is used in the feed-forward compensation control. Thus, a composite control scheme is developed for the PMSM drive system. The results show that the motor control system based on the proposed method has good speed and current tracking performance and strong robustness.
144 citations
TL;DR: This paper presents a practical discrete-time fractional order terminal sliding mode (DFOTSM) control strategy for high-precision tracking tasks based on a linear motor and synthesizes a novel DFOTSM control law to drive the sliding mode dynamics into the stable region in finite steps theoretically.
Abstract: This paper presents a practical discrete-time fractional order terminal sliding mode (DFOTSM) control strategy for high-precision tracking tasks based on a linear motor. In particular, the practical parametric uncertainties involving sliding friction, uncertain payload, and disturbance in tracking tasks are considered in this paper. Combining Grunwald–Letnikov fractional order definition and terminal sliding mode technique, the proposed method synthesizes a novel DFOTSM control law to drive the sliding mode dynamics into the stable region in finite steps theoretically, even though the system is suffering from uncertainties and disturbances, and the motion on the surface can guarantee higher tracking precision than the conventional discrete-time terminal sliding surface by selecting suitable controller parameters. The theoretical analyses give out the guideline of parameter selection, and experiments are carried out on the linear-motor-based test platform to demonstrate that the proposed controller is easily implemented and can achieve high-precision tracking, fast response, and considerable robustness to uncertainties.
133 citations
TL;DR: Simulation results demonstrate that the composite learning can efficiently estimate the system uncertainty and the tracking performance under the proposed controllers can be enhanced.
Abstract: This paper addresses two composite learning controller designs of quadrotor dynamics with unknown dynamics and time-varying disturbances using the terminal sliding mode For unknown system dynamics, the single-hidden-layer feedforward network is employed for approximation which provides the information for the disturbance observer Based on composite learning using neural approximation and disturbance estimation, the terminal sliding mode control (TSMC) is synthesized to obtain the finite-time convergence performance To overcome the singularity problem, nonsingular TSMC is proposed The closed-loop system stability under the two proposed controllers is presented via Lyapunov approach and the system trajectory will converge to the region caused by approximation error and disturbance estimation error Simulation results demonstrate that the composite learning can efficiently estimate the system uncertainty and the tracking performance under the proposed controllers can be enhanced
119 citations
TL;DR: A practical tracking control scheme of an AET system is developed using a continuous fast nonsingular terminal sliding mode (CFNTSM) technique based on uncertainty observer, and the closed-loop stability and finite-time convergence are presented based on the Lyapunov stability theory.
Abstract: The control of automobile electronic throttle (AET) systems is a challenging task owing to multiple nonlinearities, i.e., transmission friction, gear backlash, limp-home spring set, and external load disturbance. In this paper, a practical tracking control scheme of an AET system is developed using a continuous fast nonsingular terminal sliding mode (CFNTSM) technique based on uncertainty observer. By using the prescribed CFNTSM surface and fast terminal sliding mode-based reaching element, the proposed control implementation guarantees the fast error convergence characteristic and high tracking accuracy under parameter uncertainties and perturbations. Furthermore, due to the adoption of the finite-time exact observer (FEO) for the lumped uncertainty estimation in the controller, the ease of the selection of the control gains is well-achieved since they only depend on the uncertainty estimation error. The closed-loop stability and finite-time convergence are presented based on the Lyapunov stability theory. Experimental verifications are conducted to validate the remarkable performance of the proposed control, in terms of the step and sinusoidal tracking as well as anti-disturbance ability.
115 citations
TL;DR: This paper develops an enhanced robust fault tolerant control using a novel adaptive fuzzy proportional-integral-derivative-based nonsingular fast terminal sliding mode (AF-PID-NFTSM) control for a class of second-order uncertain nonlinear systems.
Abstract: This paper develops an enhanced robust fault tolerant control using a novel adaptive fuzzy proportional-integral-derivative-based nonsingular fast terminal sliding mode (AF-PID-NFTSM) control for a class of second-order uncertain nonlinear systems. In this approach, a new type of sliding surface, called proportional-integral-derivative (PID)-nonsingular fast terminal sliding mode (NFTSM) (PID-NFTSM) which combines the benefits of the PID and NFTSM sliding surfaces, is proposed to enhance the robustness and reduce the steady-state error, whilst preserving the great property of the conventional NFTSM controller. A fuzzy approximator is designed to approximate the uncertain system dynamics and an adaptive law is developed to estimate the bound of the approximation error so that the proposed robust controller does not require a need of the prior knowledge of the bound of the uncertainties and faults and the exact system dynamics. The proposed approach is then applied for attitude control of a spacecraft. The simulation results verify the superior performance of the proposed approaches over other existing advanced robust fault tolerant controllers.
112 citations
TL;DR: A novel nonsingular Terminal Sliding surface is proposed for the finite-time robust stabilization of second order nonlinear plants with matched uncertainties such that a fixed bound naturally exists for the settling time of the state variable, once the surface has been reached.
108 citations
TL;DR: The six-degree-of-freedom dynamic model of the VTVL is developed, and then the error tracking state equation is established as well, and a novel fixed-time extended state observer is presented to estimate the error state and the total disturbances in the presence of nonlinear, couplings, uncertain parameters and external disturbances.
TL;DR: This paper proposes an adaptive super-twisting decoupled terminal sliding mode control technique for a class of fourth-order systems using the adaptive-tuning law to eliminate the requirement of the knowledge about the upper bounds of external perturbations.
Abstract: This paper proposes an adaptive super-twisting decoupled terminal sliding mode control technique for a class of fourth-order systems. The adaptive-tuning law eliminates the requirement of the knowledge about the upper bounds of external perturbations. Using the proposed control procedure, the state variables of cart-pole system are converged to decoupled terminal sliding surfaces and their equilibrium points in the finite time. Moreover, via the super-twisting algorithm, the chattering phenomenon is avoided without affecting the control performance. The numerical results demonstrate the high stabilization accuracy and lower performance indices values of the suggested method over the other ones. The simulation results on the cart-pole system as well as experimental validations demonstrate that the proposed control technique exhibits a reasonable performance in comparison with the other methods.
TL;DR: Two new definitions and related theorems in analyzing the transient behavior of terminal sliding mode control (TSMC) for nonlinear systems are proposed and their associated rigorous proofs can be used to comprehensively describe the dynamic behavior of TSMC and NTSMC.
Abstract: This paper proposes two new definitions and related theorems in analyzing the transient behavior of terminal sliding mode control (TSMC) for nonlinear systems. The first one is named critical trajectory (CT), which is used to characterize the system dynamics for both TSMC and its nonsingular version, i.e., nonsingular TSMC (NTSMC). The second one is named constrained surface (CS), which is used to characterize the phase trajectory for NTSMC. Based on these two terms, we further propose two new theorems and their associated rigorous proofs that can be used to comprehensively describe the dynamic behavior of TSMC and NTSMC. In addition to theoretical analyses, we also present two case studies, i.e., one numerical example and one two-link manipulator system, to verify the effectiveness of the proposed theoretical research.
TL;DR: Lyapunov analysis and multiple-time scale principle ensure the realization of control goal in finite-time and the effectiveness of the proposed FMNNDO and controllers are verified by numerical simulations.
Abstract: The distributed finite-time formation tracking control problem for multiple unmanned helicopters is investigated in this paper. The control object is to maintain the positions of follower helicopters in formation with external interferences. The helicopter model is divided into a second order outer-loop subsystem and a second order inner-loop subsystem based on multiple-time scale features. Using radial basis function neural network (RBFNN) technique, we first propose a novel finite-time multivariable neural network disturbance observer (FMNNDO) to estimate the external disturbance and model uncertainty, where the neural network (NN) approximation errors can be dynamically compensated by adaptive law. Next, based on FMNNDO, a distributed finite-time formation tracking controller and a finite-time attitude tracking controller are designed using the nonsingular fast terminal sliding mode (NFTSM) method. In order to estimate the second derivative of the virtual desired attitude signal, a novel finite-time sliding mode integral filter is designed. Finally, Lyapunov analysis and multiple-time scale principle ensure the realization of control goal in finite-time. The effectiveness of the proposed FMNNDO and controllers are then verified by numerical simulations.
TL;DR: A new adaptive nonsingular fast terminal sliding mode surface (ANFTSMS) is developed that has both the merits of the NFTSM avoiding singularity and the adaptive method regulating the relative weighting of parameters, and provides designers a new way to improve the control performance.
TL;DR: Using the proposed global sliding surface, the reaching period is omitted and the robust performance of the whole system is improved, and the chattering phenomenon is removed using the adaptive-tuning parameters and hyperbolic tangent function in the reaching control law.
Abstract: This paper proposes an adaptive global terminal sliding mode control scheme for tracking control of uncertain nonlinear systems Using the proposed global sliding surface, the reaching period is omitted and the robust performance of the whole system is improved The discontinuous sign function is involved in the controller derivative and then, the control signal achieved after integration is continuous and attenuates the chattering problem Two adaptation laws are employed to cope with the uncertainties and disturbances whose upper bounds are not required to be known, where the proposed technique is more flexible in the real implementations This method guarantees robustness against uncertainties, disturbances and nonlinearities of the system Moreover, the proposed scheme removes the chattering phenomenon using the adaptive-tuning parameters and hyperbolic tangent function in the reaching control law Numerical simulations display the success and applicability of the proposed scheme in comparison with the results of the other method
TL;DR: A robust adaptive integral terminal sliding mode control strategy is proposed to deal with unknown but bounded dynamic uncertainties of a nonlinear system and no prior knowledge of the exact dynamic model and upper bounds of uncertainties is required.
TL;DR: This study investigates a continuous sliding mode tracking problem for robot manipulators under the presence of parametric uncertainty and external disturbances and proposes a chattering-free integral terminal sliding mode control scheme.
Abstract: This study investigates a continuous sliding mode tracking problem for robot manipulators under the presence of parametric uncertainty and external disturbances. A chattering-free integral terminal sliding mode control scheme is first proposed by integrating an integral terminal sliding surface with an observer. Lypaunov stability theory is employed to prove the global finite-time tracking of robotic system. The appealing advantages of the proposed controller are that it is easy to implement with the continuous sliding mode control featuring chattering-free, fast transient and high steady-state tracking precision. Extensive simulations on two degree of freedoms (DOFs) are presented to demonstrate the effectiveness and improved performance of the proposed approach.
TL;DR: The proposed model-free based adaptive nonsingular fast terminal sliding mode control which comprises three parts: the intelligent PI controller, time-delay estimation, and adaptive sliding mode compensator shows improved tracking performance compared with the existing model free controller in co-simulations.
TL;DR: In this study, time delay estimation (TDE)-based model-free fractional-order nonsingular fast terminal sliding mode control (MFF-TSM) is proposed for the lower-limb robotic exoskeleton in the existence of uncertainties and external disturbance.
Abstract: A robotic exoskeleton is a nonlinear system, which is subjected to parametric uncertainties and external disturbances. Due to this reason, it is difficult to obtain the exact model of the system, a...
TL;DR: A time-specified nonsingular terminal sliding mode control (TS-NTSMC) scheme is proposed to address the problem of trajectory tracking for robotic airships, which can avoid the singularity problem and specify the convergence time of terminal sliding Mode control.
Abstract: The robotic airships provide potential aerial platforms for various applications and require robust trajectory tracking to support these tasks. A time-specified nonsingular terminal sliding mode control (TS-NTSMC) scheme is proposed to address the problem of trajectory tracking for robotic airships, which can avoid the singularity problem and specify the convergence time of terminal sliding mode control. First, the problem of trajectory tracking of robotic airships is formulated. Second, a nonsingular terminal sliding manifold consisting of pre-specified nonlinear functions is proposed, and the TS-NTSMC law is designed for trajectory tracking. Time-specified convergence and stability of the closed-loop system can be guaranteed by Lyapunov theory. Finally, compared experimental simulations are given to illustrate the advantages of TS-NTSMC against NTSMC.
TL;DR: A novel attitude control scheme is proposed based on nonsingular fast terminal sliding mode (NFTSM) technique and the extended state observer (ESO) is constructed to provide the estimate of the modeling uncertainties and unknown disturbances.
Abstract: The attitude control problem is addressed for a quadrotor system subject to the modeling uncertainties and unknown disturbances. A novel attitude control scheme is proposed based on nonsingular fast terminal sliding mode (NFTSM) technique. First, the tracking differentiator (TD) is designed to obtain the smooth tracking signal and its derivative. Then, the extended state observer (ESO) is constructed to provide the estimate of the modeling uncertainties and unknown disturbances. With the designed TD and ESO, a novel NFTSM controller is developed such that tracking error converges to zero in finite time. The transient-state and the steady-state performances are both achieved with the new controller. Finally, the simulation and real experiment results verify the effectiveness and superiority of the proposed control method.
TL;DR: This brief investigates the finite-time consensus tracking control problem for networked uncertain mechanical systems on digraphs and develops a new terminal sliding-mode-based cooperative control scheme to guarantee that the tracking errors converge to an arbitrarily small bound around zero in finite time.
Abstract: This brief investigates the finite-time consensus tracking control problem for networked uncertain mechanical systems on digraphs. A new terminal sliding-mode-based cooperative control scheme is developed to guarantee that the tracking errors converge to an arbitrarily small bound around zero in finite time. All the networked systems can have different dynamics and all the dynamics are unknown. A neural network is used at each node to approximate the local unknown dynamics. The control schemes are implemented in a fully distributed manner. The proposed control method eliminates some limitations in the existing terminal sliding-mode-based consensus control methods and extends the existing analysis methods to the case of directed graphs. Simulation results on networked robot manipulators are provided to show the effectiveness of the proposed control algorithms.
TL;DR: A robust adaptive integral terminal sliding mode (AITSM) control scheme with an uncertainty observer (UO) is developed for automobile electronic throttle (AET) systems and the quantitive root mean square values and the maximum values of the sampled tracking errors are demonstrated to validate the superior performance of the proposed control.
Abstract: A robust adaptive integral terminal sliding mode (AITSM) control scheme with an uncertainty observer (UO) is developed for automobile electronic throttle (AET) systems. Distinguished from the ordinary sliding mode (SM)-based AET control systems, by using a novel integral terminal sliding surface (SS) to force the closed-loop system to start on the SS at the very beginning, an excellent error convergence and tracking accuracy as well as robustness of the closed-loop system against uncertainties and nonlinearities including transmission friction, return spring limp-home, and gear backlash can be assured. Also, in order to achieve a stably excellent performance for different tracking commands, the sliding parameters are updated by the designed adaptive laws in Lyapunov sense. Moreover, for reducing the control chattering caused by the large switching gain in conventional SM control, an SM-based UO is introduced to provide with the online estimation for the system lumped uncertainty and conduct the feed-forward compensation in the control design. In addition, model-free robust exact differentiators (MRED) are presented to obtain the accurate angular velocity and acceleration information from the unique angle sensors with measurement noises. Not only the comparative experimental results from a real-time digital signal processor (DSP)-based AET plant but also the quantitive root mean square (RMS) values and the maximum (MAX) values of the sampled tracking errors are demonstrated to validate the superior performance of the proposed control. In particular, in the disturbance rejection test by combining trapezium and sinusoidal reference commands, the proposed control exhibits the smallest RMS error values of 0.6832 deg (37% and 27% of the ones of the nonsingular terminal sliding mode and the proportional-integral-derivative controllers), and the smallest MAX values of 2.9352 deg (67% and 35% of the ones of the comparative controllers, respectively).
TL;DR: The global terminal sliding mode control based on the quick reaching law is designed and used to control the unmanned surface vehicle and results show that the control method has better control performance than the conventional methods.
Abstract: In order to overcome the disadvantages of the conventional sliding mode reaching law, such as the large chattering and the slow convergence rate, an improved quick reaching law is proposed. The reaching law is composed of two terms which can, respectively, play the leading role when the system is far away from or near to the sliding mode surface. Thus, the system can arrive at the sliding mode surface with the faster convergence rate from beginning to end. Some other advantages of the reaching law, such as converging to the sliding mode surface in a finite time, and the second-order sliding mode characteristic are proved. Furthermore, in order to speed up the convergence rate to the equilibrium point along the sliding mode surface, the global terminal sliding mode control based on the quick reaching law is designed. It is used to control the unmanned surface vehicle. Simulation results show that the control method has better control performance than the conventional methods.
TL;DR: A robust finite time trajectory tracking control approach is proposed for autonomous underwater vehicle (AUV), which belongs to the class of highly nonlinear, coupled dynamics with motion in 6-degrees-of-freedom (DOF) and has been extended to task space control problem of an AUV - manipulator system employed for underwater manipulation tasks.
TL;DR: Comparison experiments show that the load torque rejection of the IM speed loop is significantly enhanced by using the proposed approach, combining the conventional PI control with a high-order fast terminal sliding-mode (HOFTSM) load torque observer.
Abstract: Speed loop is the key factor affecting the performance of induction machine (IM) drives. Conventionally, the proportional integral (PI) controller is applied for its simple implementation and static-errorless; however, its performance degrades apparently under sudden external load torque changes. To address this problem, this paper presents a nonlinear control strategy, combining the conventional PI control with a high-order fast terminal sliding-mode (HOFTSM) load torque observer. The external load torque is estimated online by the proposed HOFTSM observer, and then the estimated torque is used as feed-forward compensation for the PI controller. Moreover, the designed HOFTSM observer shows superiorities in fast convergence rate and chattering elimination. Comparison experiments show that the load torque rejection of the IM speed loop is significantly enhanced by using the proposed approach.
TL;DR: A comparative analysis of linear and non-linear feedback control techniques based on investigation of time, control energy and tracking error to obtain best control performance for the IP system indicates that ISMC over-performs compared to other control techniques in terms of reduced chattering, less settling time and small steady state error.
TL;DR: The presented method can avoiding dynamical obstacles whilst satisfying the requirements of autonomous rendezvous and can save more energy than the traditional APF-SMC and also have better control accuracy than the SDRE.