Adaptive Terminal Sliding Mode Control Research Articles

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

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

A novel model-free adaptive terminal sliding mode controller for bridge cranes

To achieve stabilisation control of an underactuated bridge crane system, a new robust control strategy for the sliding mode is proposed in this paper. It can realise finite-time-convergent stabilisation control under the conditions of model uncertainty, parameter perturbation and external interference. In contrast to the existing methods, our method does not need prior information of the dynamic characteristics of the bridge crane system, and can make the system converge to the equilibrium state at the preset time. Specifically, the nonlinear model of the bridge crane system is linearised with partial feedback, and adaptive signals are introduced. Then, according to the form of the transformed system, a fast terminal sliding mode surface is constructed, and an adaptive terminal sliding mode controller is designed. According to strict analysis, the proposed control law ensures that the system converges to the equilibrium point in finite time and provides the convergence time. Finally, the effectiveness and robustness of the proposed control method are verified by comparing the simulation and experimental results with existing methods.

Decoupled adaptive terminal sliding mode control strategy for a 6-DOF electro-hydraulic suspension test rig with RBF coupling force compensator

Aiming at the problems of poor tracking accuracy, low convergence speed, weak robustness of a 6-DOF electro-hydraulic suspension test system under system uncertainties and external disturbance, this article proposes double closed-loop control scheme. In the outer loop controller, this article designs a new decoupled adaptive fast nonsingular terminal sliding mode (DAFNTSM) control to achieve fast convergence rate, high accurate and adaptive disturbances estimation during trajectory tracking. Additionally, a coupling force compensator based on RBF neural network is employed, which can reduce online calculation quantity and guarantee accuracy. For six inner loop controllers, each hydraulic actuator can precisely follow the required force solved by outer loop controller. The hard-in-loop experiment results reveal that the control approach we proposed in this paper realize superior trajectory tracking characteristics in comparison with the conventional nonsingular terminal sliding mode (CNTSM) method.

Control of Quadrotor Based on RBF Neural Network Adaptive Fast Terminal Sliding-Mode Strategy

I The purpose of this paper is to propose a fast adaptive terminal sliding mode control method for quadrotor unmanned aerial vehicles (UAVs) under dynamic uncertainties and external interference. Firstly, a complete mathematical dynamics model of a quadrotor UAV is presented. Secondly, a robust dual-loop nonlinear control law for the quadrotor velocity and attitude tracking is designed. Through the introduction of equivalent control inputs, the attitude control channels can be decoupled and attitude stabilized controllers can be designed separately. For velocity tracking and altitude tracking control, coupled controllers are designed to ensure velocity tracking based on the stability of altitude tracking control. The attitude loop adopts RBF neural network sliding mode control, to compensate for model disturbance uncertainty, adjust its gain in real time, and suppress chattering problems. Finally, the experimental results show that the designed controller can not only suppress external interference, but also achieve accurate tracking of the desired flight command.

LQR-based adaptive TSMC for nuclear reactor in load following operation

This paper concerns with the design of LQR-based adaptive terminal sliding-mode control (TSMC) for nuclear reactor in load following operation. For this purpose, the reactor nonlinear model is firstly converted into linear parameter varying (LPV) system. Then, based on this model a referenced control law is designed by integrating the LQR-based control with the TSMC. In order to obtain high precision control as well as convergence in finite time a nonlinear sliding surface is defined. Afterwards, a control law is derived to ensure the global asymptotic stability of the whole system. Numerical simulations are performed. Furthermore, the developed control law is compared against an LQR-based and PID control laws. It results that the derived control law not only offers remarkable performance to the system in load following operation in the presence of varying uncertainties but also performs better than the foresaid control laws.

Adaptive integral‐type terminal sliding mode control: Application to trajectory tracking for mobile robot

SummaryThis paper presents an Adaptive Terminal Integral Sliding Mode Control (ATISMC) scheme for trajectory tracking problems applied to a differential Wheeled Mobile Robot (WMR). First, a terminal integral sliding variable is designed. Based on the finite‐time concept, an adaptive control law has been developed in which a switching gain is adjusted adaptively by using a novel strategy. This control method aims to deal with unknown bounded disturbances and uncertainties. Moreover, it allows fast convergence of the system states to an equilibrium point. The main features of the proposed ATISMC are its robustness, fast convergence rate, and chattering avoidance. To realize trajectory tracking for WMR, the ATISMC is incorporated into a double closed loop scheme. Stability analysis is performed using the Lyapunov stability theory. Numerical simulations and real‐time experiments demonstrate the feasibility of the proposed controller scheme. A comparison study with the classical ISMC was performed to show the superiority of the developed method.

Finite-Time Attitude Tracking Control for Hypersonic Flight Vehicles with Actuator Saturation

This paper investigates finite-time attitude tracking control strategies for hypersonic flight vehicles (HFVs) with parameter uncertainties, external disturbances, and actuator saturations by applying sliding model control, adaptive mechanism, and nonlinear disturbance observer techniques. A nonlinear dynamic model of HFV attitude system in reentry flight phase is established. Then, a basic attitude control method of the HFV system is designed based on a terminal sliding mode control (TSMC) scheme to accommodate the system-lumped disturbance torques and guarantee the finite-time stability. To relax the prior knowledge of bounded lumped disturbance of the TSMC-based HFV attitude system, an adaptive TSMC (ATSMC) scheme is proposed. In order to relax the limit of compound uncertainties and attenuate chattering phenomenon of the TSMC-based HFV attitude system, a nonlinear disturbance observer-based TSMC (DO-TSMC) scheme is presented, which enhances the disturbance attenuation and robust tracking performance. Finally, simulation results of a generic X-33 nonlinear model exhibit the effectiveness of the proposed TSMC, ATSMC, and DO-TSMC schemes.

Online Reinforcement-Learning-Based Adaptive Terminal Sliding Mode Control for Disturbed Bicycle Robots on a Curved Pavement

The reaction wheel is able to help improve the balancing ability of a bicycle robot on curved pavement. However, preserving good control performances for such a robot that is driving on unstructured surfaces under matched and mismatched disturbances is challenging due to the underactuated characteristic and the nonlinearity of the robot. In this paper, a controller combining proximal policy optimization algorithms with terminal sliding mode controls is developed for controlling the balance of the robot. Online reinforcement-learning-based adaptive terminal sliding mode control is proposed to attenuate the influence of the matched and mismatched disturbance by adjusting parameters of the controller online. Different from several existing adaptive sliding mode approaches that only tune parameters of the reaching controller, the proposed method also considers the online adjustment of the sliding surface to provide adequate robustness against mismatched disturbances. The co-simulation experimental results in MSC Adams illustrate that the proposed controller can achieve better control performances than four existing methods for a reaction wheel bicycle robot moving on curved pavement, which verifies the robustness and applicability of the method.

Chattering-free nested adaptive terminal sliding mode control for PEMFC air supply system with event-triggered communication

Aiming at the proton exchange membrane fuel cell air supply system subject to time-varying external load, system uncertainty and limited network communication resources, a chattering-free event-triggered nested adaptive terminal sliding mode controller is first developed to achieve the tracking control of oxygen excess ratio. First, an integral terminal sliding mode function with recursive structure is designed to eliminate the reaching phase of sliding mode control and ensure that the high-frequency switching term only appears in the first derivative of control law. Then, to alleviate the communication burden, an event-triggered control strategy is adopted for the controller-to-actuator channel. Furthermore, a nested dual-layer adaptive law is constructed to adaptively update the robust gain without overestimation, so as to counteract the composite disturbance composed of the lumped system uncertainty and event-triggering error, which does not require priori upper bounds of the composite disturbance and its derivative. Besides, it is theoretically proved that the output tracking error can converge to the origin in finite time and the Zeno behavior can be strictly excluded. Finally, the adaptability and superiority of the proposed event-triggered nested adaptive terminal sliding mode controller are fully validated by a series of numerical simulations and comparative analysis.

Two-stage isolated AC/DC converter and its compound control strategy.

With the continued development of the new energy vehicle industry, two-stage isolated AC/DC converters are widely used because of their simple topology and easy control characteristics. In this study, we investigate the front-stage Buck power factor correction (PFC) converter and rear-stage full-bridge converter. The main circuit design and component selection were completed through a detailed analysis of the circuit characteristics. In terms of the control strategy, the front-stage adopting PI control and parameter adaptive terminal sliding mode control strategy were proposed for the rear-stage full-bridge converter. This new compound control strategy ensures an optimal regulation of the system under different operating conditions. Simulation analysis verified the correctness of the system topology and control strategy. Based on an analysis of the main parameters of the system, a low-power experimental prototype was trial-produced. The experimental results show that under the same load switching conditions, the parameter-adaptive terminal sliding mode control enhanced faster dynamic regulation and stronger robustness than the conventional PI control. The study is also a good reference in terms of engineering work.

Finite-Time Synchronization of Uncertain Fractional-Order Delayed Memristive Neural Networks via Adaptive Sliding Mode Control and Its Application

Finite-time synchronization (FTS) of uncertain fractional-order memristive neural networks (FMNNs) with leakage and discrete delays is studied in this paper, in which the impacts of uncertain parameters as well as external disturbances are considered. First, the fractional-order adaptive terminal sliding mode control scheme (FATSMC) is designed, which can effectively estimate the upper bounds of unknown external disturbances. Second, the FTS of the master–slave FMNNs is realized and the corresponding synchronization criteria and the explicit expression of the settling time (ST) are obtained. Finally, a numerical example and a secure communication application are provided to demonstrate the validity of the obtained results.

Design of adaptive continuous barrier function finite time stabilizer for TLP systems in floating offshore wind turbines

This essay discusses the finite-time stabilization of Tension Leg Platforms (TLP), one of the most considerable offshore floating wind turbine systems. The most critical issue in installing such turbines is controlling and balancing them on the water. In order to stabilize the TLP systems in floating offshore wind turbines, an adaptive terminal sliding mode controller is designed. Because the discontinuous signal function is one of the most important disadvantages of common sliding mode controllers, which causes an undesirable chattering phenomenon in the control law, the suggested approach introduces a new Lyapunov candidate function based on the adaptive continuous barrier function technique, so that the planned control law on TLP systems is obtained continuously and smoothly. The mentioned improved control method uses Lyapunov's stability theory and satisfies the convergence of states around the switching surface in a finite time. In this way, the proposed method removes the chattering phenomenon and operates with higher accuracy than the conventional controllers. In addition, the unknown bound of external disturbance is estimated using the adaptive control scheme. Finally, based on the simulation results, it can be seen that all the state variables of the TLP system are asymptotically stable in the presence of external disturbance and converge to zero, which indicates the efficiency of the proposed technique for stabilizing the tension leg platforms in offshore floating wind turbines.

A novel composite adaptive terminal sliding mode controller for farm vehicles lateral path tracking control

A novel composite adaptive terminal sliding mode controller for farm vehicles lateral path tracking control

Adaptive attitude maneuver control for satellite with large scale antenna in space thermal environment

The attitude precision requirement for satellite with large scale antenna is increasingly higher with progress of space missions. In the space environment, the drastic changes of temperature not only excite thermal vibration of antenna but also change the mode shapes and nature frequencies significantly. Under these circumstances, in order to improve satellite attitude precision, an adaptive attitude maneuver control scheme is proposed for the attitude tracking task in this paper. Firstly, a novel robust input shaper is designed based on impulse vector diagrams for vibration suppression. Secondly, an adaptive terminal sliding mode controller with radial basis function neural network and anti-windup modular is proposed and the stability is proved by Lyapunov theorem. The effectiveness of the control scheme is validated under different space thermal environments. The antenna vibration is suppressed effectively and the attitude maneuvering can be achieved in a finite time, when the mode shapes and nature frequencies of antenna change in a wide range with temperature.

An Adaptive Terminal Sliding Mode Control Scheme via Neural Network Approach for Path-following Control of Uncertain Nonlinear Systems

An Adaptive Terminal Sliding Mode Control Scheme via Neural Network Approach for Path-following Control of Uncertain Nonlinear Systems

Trajectory tracking of multi-legged robot based on model predictive and sliding mode control

To address the problem of achieving accurate tracking control of multi-legged robots, which is difficult due to their strong coupling structure, this paper decomposes the trajectory tracking of the whole-body into body-level and limb-level sub-control systems. First, a tracking controller based on the model predictive control strategy is designed for the body-level subsystem, and the general projection neural network method is used to quickly solve for the optimal control signal that satisfies stride constraints. Then, a robust adaptive terminal sliding mode controller is designed for the limb-level subsystem to resist the influence of model uncertainties and external disturbances on tracking performance. The designed gait mode generator and stride solver modules serve as two bridges connecting the body- and limb-level subsystems, thus coalescing the entire control system into a closed loop, which greatly improves the tracking accuracy of the whole system. Finally, two cases, the directed curved-trajectory tracking with tripod gait and the undirected polyline-trajectory tracking with quadruped gait, are given to illustrate the omnidirectional mobility of the multi-legged robot, and to demonstrate the effectiveness and practicability of the proposed control strategy.

Adaptive terminal sliding mode control of a regulated multidimensional electrospinning device for polymeric structures

This study intends to present an automatic control design for a Cartesian electrospinning system with a dual moving platforms for the collector and the syringe subsystems which are mobilized using linear actuators. The proposed device is including a set of dual robotized structures, that is also carrying a structure to create the Taylor cone that regulates the nano-fiber deposition over the supporting platform. The suggested control form considers the synchronization between the syringe tip and the collector using a cascade tracking structure. A class of distributed state-dependent terminal sliding mode control form solves the tracking problem that yields the syringe-collector pair moves in a synchronized form tracking a bidimensional design that should be reproduced with the fibers deposition made of polyvinyl acid–based polymer. This controller also considers the working space restrictions in the Cartesian electrospinning system device using state-dependent gains which are obtained using a control barrier Lyapunov function. The application of the second stability method of Lyapunov serves to both design the state-dependent gains and prove that the tracking error trajectory is ultimate bound. The proposed controller is evaluated using a cyber-physical representation of the Cartesian electrospinning system device where the proposed controller is evaluated. This evaluation considers a comparison of the control effectiveness (using the root mean square value of the tracking error) with a traditional non-adaptive state feedback and a first-order sliding mode control. This comparison shows that the proposed adaptive controller induces the smallest root mean square among the tested control forms while reducing the magnitude of the overshoot for each actuator.

Control of Time Delay Force Feedback Teleoperation System With Finite Time Convergence.

In order to make the teleoperation system more practical, it is necessary to effectively control the tracking error convergence time of the teleoperation system. By combining the terminal sliding mode control method with the neural network adaptive control method, a bilateral continuous finite time adaptive terminal sliding mode control method is designed for the combined teleoperation system. The Lyapunov theory is used to analyze the stability of the closed-loop system, and the position tracking error is able to effectively converge in time. Finally, the effectiveness of the proposed control scheme is verified by MATLAB Simulink numerical simulation, and the numerical analysis of the results shows that the method has better system performance. Compared with the traditional two-sided control method (TPDC) of PD time-delay teleoperation system, the control method in this paper has good performance, improves stability, and makes steady-state errors smaller and better tracking.

Optimization of Grid-Connected Photovoltaic Power Generation Technology Based on Nonlinear Back-Stepping Controller

To address the issue of energy scarcity and to use solar photovoltaic energy as a renewable source, a three-phase grid-connected photovoltaic inverter system with uncertain system model parameters is investigated, which converts DC power into AC power, feeds it into the grid, and maintains the grid-connected part’s quality. An enhanced back-stepping approach is proposed to explore the control strategy of three-phase solar grid-connected inverter, which includes adaptive control, dissipative theory, sliding mode control, and rapid terminal sliding mode control, respectively. It is verified that the system is subjected to external interference F = 5 during 0.5 s–0.8 s. As per the simulation results, the improved adaptive terminal sliding mode control method can suppress the interference to a certain extent and has strong robustness to the external interference. When compared with the adaptive sliding mode control approach, the anti-interference ability is better, and the system stability is improved. Then, to improve the above approach, a high speed terminal sliding mode control method is proposed, which can swiftly converge in finite time and the estimated value of uncertain parameters is closer to the actual value, thereby boosting the system’s robustness.

Prescribed Performance-Based Adaptive Terminal Sliding Mode Control for Virtual Synchronous Generators

Due to the lack of inertia and damping in the distributed power system with power electronic devices as interface, the stability of the power system will be adversely affected when the distributed power system is connected to the grid. In order to solve the problem of low inertia and improve stability, an adaptive terminal sliding mode control method based on the electromagnetic transient characteristics of virtual synchronous generators is proposed. During the design process, projection operators and parameter adaptive law control methods are introduced to compensate for parameter errors caused by environmental interference. Furthermore, by utilizing a prescribed performance function, the terminal sliding surface of the system will have the desired dynamic response, and variations of the system tracking error can be restricted. Simulation results show that the proposed controller has improved control accuracy and response speed, frequency stability, and power response.