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Since the complexity nonlinearities generated by discontinuous control and event‐triggered scheme, fixed‐time formation in event‐based framework is a more challenging issue compared with the continuous‐time control. This paper focuses on fixed‐time leaderless formation problem for multi‐agent systems with undirected topology. We propose a distributed robust event‐triggered control strategy for the fixed‐time formation where predictor‐based state transformation is employed to deal with input delay and sliding mode technology is implemented to solve bounded disturbances. We also obtain that the upper bound of the formation settling time is only determined by delay time, control design parameters, network connectivity, and independent of the initial conditions. In addition, the lower bound for the interexecution time is calculated to ensure that there is no Zeno behavior occurs. Finally, some numerical simulations are presented to show the effectiveness of the strategies. [ABSTRACT FROM AUTHOR]

In this article, a novel robust finite‐time tracking control scheme is proposed for a class of uncertain nonlinear systems subject to the model uncertainty, external disturbance, and input saturation. A barrier function based disturbance observer (BFDO) with finite‐time convergence performance is developed to estimate the non‐smooth nonlinear compound disturbance, which includes the uncertainty, disturbance of system and input saturation. In addition, an adaptive continuous nonsingular terminal sliding mode controller, based on the barrier function and the estimate of the BFDO is developed. The Lyapunov stability and finite‐time convergence of the proposed control scheme are proved. The effectiveness and performance advantage of the proposed control scheme is demonstrated by numerical simulations and comparison with existing works. [ABSTRACT FROM AUTHOR]

This paper proposes a new hybrid robust control method for control of an autonomous underwater vehicle. Fractional sliding mode control (FSMC) is robust against external disturbances. The main drawback of the FSMC method is creating a chattering phenomenon. Therefore, a compound control method is applied, which benefits in both robustness of the FSMC method and chattering elimination by the new control algorithm. A random noise is applied in order to verify the robustness of the proposed control method. The stability of FSMC and proposed compound control method has been verified by Lyapunov theory. The effectiveness of the proposed control method is compared with FSMC, which numerical simulation results confirm the best performance of the proposed control method. [ABSTRACT FROM AUTHOR]

Summary: For the high precise tracking control purpose of a cable‐driven manipulator under lumped uncertainties, a novel adaptive fractional‐order nonsingular terminal sliding mode control scheme based on time delay estimation (TDE) is proposed and investigated in this paper. The proposed control scheme mainly has three elements, ie, a TDE element applied to properly compensate the lumped unknown dynamics of the system resulting in a fascinating model‐free feature; a fractional‐order nonsingular terminal sliding mode (FONTSM) surface element used to ensure high precision in the steady phase; and a combined reaching law with adaptive technique adopted to obtain fast convergence and high precision and chatter reduction under complex lumped disturbance. Stability of the closed‐loop control system is analyzed with the Lyapunov stability theory. Comparative simulations and experiments were performed to demonstrate the effectiveness of our proposed control scheme using 2‐DOF (degree of freedom) of a cable‐driven manipulator named Polaris‐I. Corresponding results show that our proposed method can ensure faster convergence, higher precision, and better robustness against complex lumped disturbance than the existing TDE‐based FONTSM and continuous FONTSM control schemes. [ABSTRACT FROM AUTHOR]

Abstract In this paper, two control methods are proposed to control mismatched dc–dc buck converters. In the first method, called Method I, a multiple surface sliding mode control is proposed to handle mismatched load uncertainty. A major problem associated with multiple surface sliding mode control viz. 'explosion of terms' is handled by a disturbance observer. Another method, Method II, based on simultaneous state and disturbance observer is proposed as a further improvement over Method I in terms of sensor requirement. The practical stability of the proposed schemes is proved. The performance of both the methods are assessed for regulation and tracking of output voltage under various uncertainties and is compared with a method based on extended state observer. It is shown by simulation and experimentation that the transient and steady state performance of both the controllers are satisfactory. Highlights • Two new control methods are proposed to control a mismatched buck dc–dc converter. • One of the control methods overcomes the problem of 'explosion of terms's associated with multiple surface sliding control as well as it reduces the requirement of load current sensor. • In the second method, a simultaneous state and disturbance observer is proposed so as to save on load current as well as inductor current sensors. • Both the control methods are validated by simulation and experimentation. • Both methods can regulate the output voltage and can track the desired reference voltage. [ABSTRACT FROM AUTHOR]

Summary: Novel robust finite‐time stabilizing algorithms are developed side by side for the state and output feedback designs. Being initially developed for a nonlinear cascade second‐order system, these algorithms are straightforwardly extendible to electromechanical systems of relative degree two. The proposed synthesis is based on the disturbance compensation, relying on the dirty differentiation and sliding mode approach, and it is applicable to a wider class of disturbances than that addressed in the literature. Simulation results illustrate the efficiency of the resulting synthesis procedure and support analytical results. [ABSTRACT FROM AUTHOR]

This paper investigates an adaptive observer-based consensus control strategy for general nonlinear multi-agent systems (MASs). The distributed control of leader–follower MASs is studied in the presence of unknown parts in the dynamical equations of the followers which may be due to model simplification, parameter uncertainties and/or external disturbances. In order to decrease the conservatism of robust analysis, the upper bound of unknown terms are considered as unknown positive constants and are obtained through the adaptation laws. Additionally, it is assumed that all the agents' states are not directly measurable and nonlinear distributed observers are designed. Furthermore, the robust consensus is achieved via distributed adaptive observer-based sliding mode controllers. In this regard, a theorem is given and it is proved that the consensus error converges to zero. Finally, computer simulations are performed and the theoretical results are verified. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

SUMMARY: This paper presents a fractional-order sliding mode control scheme equipped with a disturbance observer for robust impedance control of a single-link flexible robot arm when it comes into contact with an unknown environment. In this research, the impedance control problem is studied for both unconstrained and constrained maneuvers. The proposed control strategy is robust with respect to the changes of the environment parameters (such as stiffness and damping coefficient), the unknown Coulomb friction disturbances, payload, and viscous friction variations. The proposed control scheme is also valid for both unconstrained and constrained motions. Our novel approach automatically switches from the free to the constrained motion mode using a simple algorithm of contact detection. In this regard, an impedance control scheme is proposed with the inner loop position control. This means that in the free motion, the applied force to the environment is zero and the reference trajectory for the inner loop position control is the desired trajectory. However, in the constrained motion the reference trajectory for the inner loop is determined by the desired impedance dynamics. Stability of the closed loop control system is proved by Lyapunov theory. Several numerical simulations are carried out to indicate the capability and the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

This paper introduces an observer-based sliding mode control strategy for stabilizing the attitude of flapping micro-air vehicles in the presence of unknown uncertainties and external disturbances. First, a finite-time observer is designed to estimate the lumped disturbances. Next, a controller is developed to provide attitude stabilization with high robustness where the lumped disturbances could be completely rejected after a finite amount of time. The stability of the closed-loop system is rigorously proven. By employing MATLAB/Simulink software, a numerical simulation example including a comparison between the proposed method and a conventional sliding mode controller is provided to illustrate the effectiveness of the proposed method and to confirm the theoretical results. [ABSTRACT FROM AUTHOR]

The comprehensive design of uniform robust exact disturbance observer (UREDO) and fixed-time controller for reusable launch vehicles is investigated. A UREDO which can estimate the disturbance after a fixed-time independent of the initial error is presented. Based on the disturbance estimation, a non-singular terminal sliding mode controller is designed to ensure that the guidance command can be tracked within a fixed-time in the presence of model uncertainties and external disturbances. A proof of the fixed-time convergence of the closed-loop system under the control scheme is derived with complete stability analysis using the Lyapunov technique. The features of the proposed control scheme contain that the disturbance estimation, as well as the attitude tracking, can be achieved within a fixed-time, which is independent of initial conditions and the derivative information of states is not essential, which is valuable in engineering application. Numerical simulations are performed to demonstrate the fixed-time convergence performance of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Sliding mode control is an efficient and robust control method widely used in nonlinear systems. Power systems are one of the largest nonlinear dynamic systems which their transient stability analyses have a lot of importance. In this paper, sliding mode control is applied for improving the low frequency oscillations damping of a single machine connected to an infinite bus. The performance of the system is analyzed in normal mode operation, post-fault state, after operation of relays (and opening the breakers in the both ends of the faulty line), and reclosing mechanism which returns the line to service. Here, TCSC is employed as an oscillation damper. TCSC can be considered as a controllable impedance determined by the sliding mode control. In addition, a dynamical observer is proposed for the sliding mode controller. Simulation results demonstrate that, the performance of the power system in damping the low frequency oscillations is improved significantly. [ABSTRACT FROM AUTHOR]

This paper introduces an adaptive control method for finite-time modified function projective lag synchronization of uncertain hyperchaotic systems. Based upon novel nonsingular terminal sliding mode surfaces and the adaptive super-twisting algorithm, a controller is proposed to provide robustness, high precision and fast and finite-time modified function projective lag synchronization without the knowledge of the upper bound of uncertainties and unknown external disturbances. In addition, chattering is significantly attenuated due to the inherited continuity of the proposed controller. The global stability and finite-time convergence are rigorously proven. Numerical simulation is presented to demonstrate the effectiveness and feasibility of the proposed strategy and to verify the theoretical results. [ABSTRACT FROM AUTHOR]

The sliding mode control (SMC) strategy is employed to a permanent magnet synchronous motor (PMSM) vector control system in this study to improve system robustness against parameter variations and load disturbance. To decrease the intrinsic chattering behavior of SMC, a speed SMC with an adaptive law and an extended state observer (ESO) is proposed. In this method, based on the Lyapunov stability theorem, adaptive estimation laws are deduced to estimate uncertainties of a PMSM caused by parameter variations and unmodeled dynamics. Online estimated uncertainties can be used to eliminate the effect caused by the real uncertainties. In addition, an ESO is applied to observe the load disturbance in real time. The load disturbance observed value is then utilized to the output side of the speed adaptive SMC controller as feed-forward compensation. Both the simulation and experiment results demonstrate that the proposed approach effectively alleviates system chattering and enhances system robustness against uncertainty and load disturbance. [ABSTRACT FROM AUTHOR]

In this manuscript, we have studied the adaptive sliding mode synchronization of commensurate fractional order Genesio-Tesi system with disturbance. Firstly, we have discussed the fractional order disturbance observer (FODO) which is based on adaptive sliding mode control laws for a commensurate fractional order Genesio-Tesi system with unknown bounded disturbance. Appropriate control gain parameters have been chosen in such a manner, so that the disturbance observer can approximate the unknown disturbance well. Further, we have designed a simple sliding mode surface based on sliding mode control technique, incorporating the designed fractional order disturbance observer for developing a bounded synchronization control scheme. Finally, the viability and the efficacy of the proposed sliding mode control scheme in the presence of external bounded unknown disturbance for fractional order Genesio-Tesi system is established by the numerical simulation results. We have observed that for different parameters and fractional orders of Genesio-Tesi system the synchronization time varies, which is also demonstrated in numerical simulations. To visualize the robustness and effectiveness of proposed methodology we have compared our results with earlier published results as well. Moreover, as an application, the proposed scheme is then applied to a secure communication scheme. Simulation results verify the proposed schemes success in the communication application. [ABSTRACT FROM AUTHOR]

This paper deals with the design of a robust sliding mode-based extremum-seeking controller aimed at the online optimization of a class of uncertain reaction systems. The design methodology is based on an input-output linearizing method with variable-structure feedback, such that the closed-loop system converges to a neighborhood of the optimal set point with sliding mode motion. In contrast with previous extremum-seeking control algorithms, the control scheme includes a dynamic modelling-error estimator to compensate for unknown terms related with model uncertainties and unmeasured disturbances. The proposed online optimization scheme does not make use of a dither signal or a gradient-based optimization algorithm. Practical stabilizability for the closed-loop system around to the unknown optimal set point is analyzed. Numerical experiments for two nonlinear processes illustrate the effectiveness of the proposed robust control scheme. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Environmental disturbances and systematical uncertainties are the main obstacles for ship motion control. This paper devotes to enhancing the control system robustness of underactuated surface ships with model uncertainties and environmental disturbances. A novel nonlinear robust adaptive scheme with sliding mode control is proposed for underactuated ships to track the desired path generated by the logical virtual ship in the presence of unknown plant parameters and environmental disturbances. Compared with the existing results, the proposed controller is designed based on the combination of PI sliding mode control and the upper bound estimation of disturbances. With the proposed design, the control scheme could not only obtain a better performance of the control system, the continuous scheme also reduce the chattering of system by a special construction of the sliding manifolds. Numerical simulations are given to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A robust consensus controller is proposed for heterogeneous higher-order nonlinear multi-agent systems, when the agent dynamics are involved with mismatched uncertainties. A distributed consensus protocol based on a time-varying nonhomogeneous finite-time disturbance observer and sliding mode control is designed to realize the network consensus of higher-order multi-agent systems. The time-varying finite-time disturbance observer overcomes the problem of peaking value near the initial time caused by the constant gain one and is designed to estimate the uncertainties and to mitigate the effect of mismatched uncertainties during the sliding mode. To eliminate the chattering phenomenon and ensure finite-time convergence to the sliding surface, the control law is designed by using the super twisting algorithm. Finally numerical simulations are given to illustrate the validity of the proposed method. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this study, the implementation of the sliding mode control method regarding a varying sliding surface on a electromechanical fin actuation system is dealt with. First, the mathematical model of the considered control actuation system is derived and then a control system considering the sliding mode control approach is designed upon the mentioned model. In this extent, the sliding mode controllers with both constant and varying sliding surfaces are evaluated individually. For the varying sliding surface case, the variation of the surface is described by means of a time dependent first order linear function. Moreover, the ajdustment is tried to be done regarding appropriately-constructed fuzzy functions, too. For comparison purpose, a classical control system accounting the PID (proportional plus integral plus derivative) control action is also designed. At the end of the study, the responses of all the proposed control schemes are evaluated altogether. [ABSTRACT FROM AUTHOR]

This article deals with the design and real-time implementation of three second order sliding mode controllers for the altitude tracking of a quadrotor aircraft. A comparative study based on the analysis of the tracking error was performed in order to determine the controller presenting the best performance in a real-time application at outdoors environments. The compared strategies were the Classical First Order Sliding Mode Controller, the Super Twisting Sliding Mode Controller, the Modified Super Twisting Sliding Mode Controller and the Nonsingular Terminal Super Twisting Sliding Mode Controller. The last three controllers are based on the second order sliding mode technique, and they ensure robustness with respect to modeling errors even under external disturbances while reducing the chattering phenomenon in comparison with first order sliding mode controllers. Lyapunov stability theory is used to prove convergence in finite time of the altitude tracking error in the different proposed control laws. In order to demonstrate the effectiveness of the proposed solutions, an extensive set of simulation and real-time experimental results are presented. [ABSTRACT FROM AUTHOR]

This paper deals with a comparative analysis of the performances of sliding mode controller (SMC) and fractional-order sliding mode controller (FOSMC) when applied to the problem of trajectory control of ball in a ball and plate (BP) system. Owing to the open-loop instability, inherent nonlinearity, and under actuation, the BP system is considered a benchmark platform for testing the efficacies of different control algorithms. In this work, a robust cascaded SMC is initially designed to track the desired trajectory and tackle the uncertainties present in the system. In order to improve the speed of response, an FOSMC is designed thereafter. The two-control algorithms are simulated on MATLAB-Simulink environment and the experimental validation is later carried out on a BP laboratory set-up (Feedback Instruments Model No. 033-240). The simulation results and experimental validation convey that FOSMC performs better than SMC in regard to speed of response and tracking accuracy without increasing the level of chattering and control effort. [ABSTRACT FROM AUTHOR]

A robust entry guidance law based on terminal sliding mode and second-order differentiator is designed for trajectory tracking in this paper. The bank angle is regarded as the control variable. A novel nonlinear compound controller is designed to make the system with the trajectory-tracking error and its rate as states be input-to-state stable (ISS) with respect to uncertainties. The terminal sliding mode controller is designed to the problem of entry guidance by using the second-order differentiator to estimate the total disturbances. The proposed nonlinear compound control law by employing the second-order differentiator and the terminal sliding mode controller, provide robustness, higher control precision. Also, simulation results are presented to illustrate the effectiveness of the control strategy. [ABSTRACT FROM AUTHOR]

A Fault Tolerant Attitude Control algorithm for the spacecraft using Single Gimbal Control Moment Gyros (SGCMGs) as actuator is proposed. The controller is designed using the sliding mode control theory to control the gimbal rate directly and there is no singular point in the control algorithm, which means that we don't need to design the steering laws again and the singularity problems can be avoided. Also the gimbal rate saturation is considered when designing the control method. The adaptive control algorithm is used to estimate the disturbance and the boundary of the fault and saturation, which means that no prior information of the fault is needed. Although the controller is designed based on the SGCMGs, it can also be employed when reaction wheels work as the actuator of the spacecraft. Also the complete failure of several SGCMGs is allowed. It is proved based on the Lyapunov stability theorem that the designed control algorithm can achieve the attitude asymptotic stability both on the fault or fault-free condition. The simulation results show that the proposed method has a strong robustness. [ABSTRACT FROM AUTHOR]

This paper proposes a fractional order sliding mode control for the deployment of tethered space systems with the consideration of uncertainty of external disturbances and unmodeled system dynamics. The proposed fractional order sliding mode control consists of two sub-sliding manifolds that are defined separately for the actuated and unactuated states. This, in turn, generates a control scheme to make all states move toward to the desired states. The stability analysis of the proposed control law indicates not only all states converge to the desired states at equilibrium but also disturbances caused by the uncertainty can be suppressed satisfactorily. Parametric studies are conducted to investigate the influences of fractional order and sub-sliding manifold of unactuated states on the performance of the proposed control law. The performance is compared with the sliding mode, PD and fractional order PD control laws for a baseline scenario of tether deployment. The proposed control law performs better than others in the settling time and the maximum pitch angle control in the presence of unwanted disturbances. Effectiveness and robustness of the proposed control law are demonstrated by computer simulations. [ABSTRACT FROM AUTHOR]

This paper introduces an adaptive fractional-order sliding-mode controller for stabilization of a two-axis gimbal platform in the presence of the torque disturbance effects. To tend the angular velocities of the inner gimbal in the elevation and azimuth axes to zero, an adaptive fractional-order sliding-mode approach is utilized. To achieve this goal, fractional-order sliding surfaces in both azimuth and elevation axes and the corresponding adaptive controllers with adjustable parameters tuned according to Lyapunov-based adaptation mechanisms are employed. The optimal value of the fractional order is obtained through an integral square error performance index minimization. The moments products uncertainties are incorporated in the design procedure. The numerical simulations demonstrate that the proposed control approach is robust against the moments products variations. [ABSTRACT FROM AUTHOR]

This paper presents a composite control strategy integrating adaptive sliding-mode control and the linear quadratic regulator (LQR) technology for a wheeled inverted pendulum (WIP) vehicle system. The system can be partitioned into an actuated rotational subsystem and an underactuated longitudinal subsystem based on the different control input in the mathematical model. In particular, the instability analysis of zero dynamic for the underactuated longitudinal subsystem is investigated in detail using the feedback linearisation technology. Then, an adaptive sliding-mode control is designed for the trajectory tracking, where an adaptive algorithm is developed to handle with the parameter uncertainties. In addition, the LQR technique is employed to guarantee zero dynamics stability so as to achieve simultaneously the vehicle body stabilisation at the upright position. Simulation results show the good performance and strong robustness of the proposed control schemes. [ABSTRACT FROM AUTHOR]

This paper proposes, for a class of uncertain nonlinear systems, an adaptive controller based on adaptive second-order sliding mode control and integral sliding mode control concepts. The adaptation strategy solves the problem of gain tuning and has the advantage of chattering reduction. Moreover, limited information about perturbation and uncertainties has to be known. The control is composed of two parts: an adaptive one whose objective is to reject the perturbation and system uncertainties, whereas the second one is chosen such as the nominal part of the system is stabilised in zero. To illustrate the effectiveness of the proposed approach, an application on an academic example is shown with simulation results. [ABSTRACT FROM AUTHOR]

Event-triggering strategy is one of the real-time control implementation techniques which aims at achieving minimum resource utilisation while ensuring the satisfactory performance of the closed-loop system. In this paper, we address the problem of robust stabilisation for a class of nonlinear systems subject to external disturbances using sliding mode control (SMC) by event-triggering scheme. An event-triggering scheme is developed for SMC to ensure the sliding trajectory remains confined in the vicinity of sliding manifold. The event-triggered SMC brings the sliding mode in the system and thus the steady-state trajectories of the system also remain bounded within a predesigned region in the presence of disturbances. The design of event parameters is also given considering the practical constraints on control execution. We show that the next triggering instant is larger than its immediate past triggering instant by a given positive constant. The analysis is also presented with taking delay into account in the control updates. An upper bound for delay is calculated to ensure stability of the system. It is shown that with delay steady-state bound of the system is increased than that of the case without delay. However, the system trajectories remain bounded in the case of delay, so stability is ensured. The performance of this event-triggered SMC is demonstrated through a numerical simulation. [ABSTRACT FROM AUTHOR]

The lane keeping problem of automatic driving for vehicles was studied based on the simplified linear lateral dynamic model which was divided into a translation subsystem and a rotation subsystem. The rotation subsystem was defined as an inner loop and the translation subsystem was defined as an outer loop. With the separation design strategy of inner loop and outer loop, a kind of angle stable controller was designed to make the rotation subsystem stable. The inner angle stable subsystem was driven by the outer translation subsystem which was controlled by the error signal of vehicle position. The inner loop was cascaded with outer loop and both loops were designed by the sliding mode method. At last, detailed numerical simulations were done and simulation results were compared with other three methods to explain the physical meanings of design and its three advantages. [ABSTRACT FROM AUTHOR]

A kind of backstepping sliding mode control law was proposed to solve the lane keeping problem where the automatic driving system was simplified to be a kind of linear lateral dynamic model. And the dynamic response characteristic of tire steering system was described to be a first order system with a proper delay time constant. First, the complex system was divided into a relative accurate subsystem and an uncertain subsystem. Second, the proposed backstepping sliding mode method was proposed to eliminate the lateral position error which can make use of the advantage of sliding mode method that it can improve the robustness of the whole system. The backstepping strategy was adopted for the accurate inertial delay dynamic of tire steering system. Third, a kind of soft function was used to reduce the oscillation caused by sliding mode control. And a Lyapunov function was constructed to guarantee all signals of close loop system are stable. At last, 100 times of random numerical simulations were done to testify the rightness and stability of the proposed method applied in the situation that the tire coefficients are uncertain. [ABSTRACT FROM AUTHOR]

In the future, large satellites may be automatically assembled on-orbit in order to reduce weight and increase volume efficiency in launchers. During this process, it may be important to maintain satellite attitude. This paper presents a dynamic model, including reaction wheels and a twisting-algorithm-based sliding-mode controller, to maintain attitude during a simple self-assembly process. Simulation results of this controller are compared with results from other controllers found in the literature. [ABSTRACT FROM AUTHOR]

ROV accurate path following is challenging due to system unmodeled dynamics, disturbances and navigation sensors error. The model uncertainty and disturbances are commonly treated using robust methods such as the sliding mode controller where by incorporating an integral action in the zero tracking error is also guaranteed. Practically, the ROV position data is often computed using low cost inertial measurement unit (IMU) with outputs contaminated with bias and noise. Failure of mission is an immediate consequence of employing such biased sensors. However, the problem can be circumvented using the concept of redundant measurements and data fusion. In this respect, a set of 12 measurements from IMU, magnetometer and Doppler velocity log (DVL) are employed where the last two are aided sensors. The set up is shown to be capable of providing ROV path following with zero (in average) steady state tracking error irrespective of its dynamic parameters, environmental disturbances and erroneous data; as if it enjoys the exact values of the position of the ROV. It means that the combined DVL and magnetometer are sufficient for filtering the IMU biased measurements. Various simulations conducted confirm the results. [ABSTRACT FROM AUTHOR]

This study is concerned with the asynchronous bumpless transfer (ABT) problem for a class of switched linear systems with external disturbances. Asynchronous switching or transfer implies that the transfers between sub-controllers and between sub-plants are asynchronous, and ABT is to ensure that there is no controller/plant-induced bumps or undesirable transients to the process. Specifically, the ABT process is first divided into two parts: robust performance bumpless transfer (RPBT) between sub-plants and robust control bumpless transfer (RCBT) between sub-controllers. Then, with a set of pre-given sub-plants under disturbances and corresponding sub-controllers, the RPBT and RCBT design schemes are, respectively, proposed. The designed RPBT and RCBT compensators are based on model reference adaptive sliding mode control such that the switched system can perform smooth transitions during the whole asynchronous switching process. Furthermore, by using average dwell time technique, the condition for guaranteeing the switched closed-loop system to be stable under ABT is developed. Finally, numerical simulations demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The camera always suffers from image instability on the moving vehicle due to the unintentional vibrations caused by road roughness. This paper presents a novel adaptive neural network based on sliding mode control strategy to stabilize the image captured area of the camera. The purpose is to suppress vertical displacement of sprung mass with the application of active suspension system. Since the active suspension system has nonlinear and time varying characteristics, adaptive neural network (ANN) is proposed to make the controller robustness against systematic uncertainties, which release the model-based requirement of the sliding model control, and the weighting matrix is adjusted online according to Lyapunov function. The control system consists of two loops. The outer loop is a position controller designed with sliding mode strategy, while the PID controller in the inner loop is to track the desired force. The closed loop stability and asymptotic convergence performance can be guaranteed on the basis of the Lyapunov stability theory. Finally, the simulation results show that the employed controller effectively suppresses the vibration of the camera and enhances the stabilization of the entire camera, where different excitations are considered to validate the system performance. [ABSTRACT FROM AUTHOR]

This article investigates transient and steady state performance of sliding mode control using fractional calculus and fuzzy logic system. Sliding mode control is robust to uncertainties but its major disadvantage is severe chattering. To overcome the problem, boundary layer design is used at the cost of loss of robustness. Steady state performance is guaranteed by introducing integral sliding mode control (ISMC); however, the transient response degrades. This work proposes a new sliding mode control method using fractional operator and fuzzy logic system which recovers transient performance and ensures steady performance with minimum chattering. Fuzzy logic system is used to adjust the order of fractional operator. The proposed method is derived for position control of servo system which is subjected to nonlinear disturbance. Numerical simulations confirm superiority of proposed method. [ABSTRACT FROM AUTHOR]

A continuous stirred tank reactor (CSTR) is a typical example of chemical industrial equipment, whose dynamics represent an extensive class of second order nonlinear systems. It has been witnessed that designing a good control algorithm for the CSTR is very challenging due to the high complexity. The two difficult issues in CSTR control are state estimation and external disturbance attenuation. In general, in industrial process control a fast and robust response is essential. Driven by these challenging issues and desired performance, this paper proposes an output feedback terminal sliding mode control (TSMC) framework which is developed for CSTR, and can estimate the system states and stabilize the system output tracking error to zero in a finite time. The corresponding stability analysis is presented in terms of the Lyapunov method. Illustrative examples are demonstrated by using Matlab simulations to validate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper considers the attitude tracking problem of a rigid spacecraft involving inertia matrix uncertainty and external disturbance. First, an adaptive integral sliding mode control (ISMC) is proposed for when the upper bound on the lumped uncertainty is unknown in advance. It is shown that such a combination can produce a much smaller switching gain than the current adaptive sliding mode control (ASMC); hence, the overadaptation problem in existing ASMC design is effectively solved. Additionally, the system performance is improved by virtue of the global sliding mode feature of ISMC. A similar, but more flexible, ASMC design is introduced to further enhance the results; this design is developed on the basis of the reference trajectory scheme. The validity of the proposed strategies is verified by both theoretical analysis and simulation results. [ABSTRACT FROM AUTHOR]

A neural network-based global fast terminal sliding mode control method with non-linear differentiator (NNFTSMC) is proposed in this paper to design the dynamic control system for three-axis stabilized platform. The dynamic model of the three-axis stabilized platform is established with various uncertainties and unknown external disturbances. To overcome the external disturbance and reduce the output chatter of the classical sliding mode control (SMC) system, the improved global fast terminal sliding mode control method using the nonlinear differentiator and neural network techniques is proposed and implemented in the three-axis stabilized platform system. The global fast terminal sliding mode controller can make the controlled state approach to the sliding surface in a finite time. To eliminate the system output chatter, the nonlinear differentiator is employed to obtain the differentiation of the signal. The neural network is introduced to estimate the uncertainties disturbances to improve the stability and the robustness of the control system. The stability and the robustness of the proposed control method are analyzed using the Lyapunov theory. The performance of the proposed NNFTSMC method is verified and compared with the classical proportion-integral-differential (PID) controller, SMC controller and fast terminal sliding mode controller (FTSMC) through the computer simulation. Results validate the effectiveness and robustness of the proposed NNFTSMC method in presence of uncertainties and unknown external disturbances. [ABSTRACT FROM AUTHOR]

This paper investigates the tracking control problem for the air-to-air missile with lateral thrusters and aerodynamic surfaces. An integral sliding mode manifold which is suitable for solving the problem of the input constraint is first given based on the saturation function. By using the integral sliding mode manifold, a finite-time controller without singularity is designed to deal with the input saturation and bounded disturbances. Then, the control moment is mapped to the control commands for the aerodynamic deflector and thrust engine array respectively, by using the dynamic control allocation. Finally, theoretical analysis and numerical simulations are presented to prove that the robust controller can make the missile follow a reference signal in finite time. [ABSTRACT FROM AUTHOR]