Sliding mode fault tolerant consensus control for multi-agent systems based on super-twisting observer

The fault-tolerant consensus problem for leader-following nonlinear multi-agent systems with actuator faults is mainly investigated.A new super-twisting sliding mode observer is constructed to estimate the velocity and undetectable fault information simultaneously.The time-varying gain is introduced to solve the initial error problem and peak value problem,which makes the observation more accurate and faster.Then,based on the estimated results,an improved sliding mode fault-tolerant consensus control algorithm is designed to compensate the actuator faults.The protocol can guarantee the finite-time consensus control of multi-agent systems and suppress chattering.Finally,the effectiveness and the superiority of the observer and control algorithm are proved by some simulation examples of the multi-aircraft system.

Revised barrier function-based adaptive finite-and fixed-time convergence super-twisting control

This paper presents an adaptive gain,finite-and fixedtime convergence super-twisting-like algorithm based on a revised barrier function,which is robust to perturbations with unknown bounds.It is shown that this algorithm can ensure a finite-and fixed-time convergence of the sliding variable to the equilibrium,no matter what the initial conditions of the system states are,and maintain it there in a predefined vicinity of the origin without violation.Also,the proposed method avoids the problem of overestimation of the control gain that exists in the current fixed-time adaptive control.Moreover,it shows that the revised barrier function can effectively reduce the computation load by obviating the need of increasing the magnitude of sampling step compared with the conventional barrier function.This feature will be beneficial when the algorithm is implemented in practice.After that,the estimation of the fixed convergence time of the proposed method is derived and the impractical requirement of the preceding fixed-time adaptive control that the adaptive gains must be large enough to engender the sliding mode at time t=0 is discarded.Finally,the outperformance of the proposed method over the existing counterpart method is demonstrated with a numerical simulation.

Modified grey wolf optimised adaptive super-twisting sliding mode control of rotary inverted pendulum system

This paper proposes a modified grey wolf optimiser-based adaptive super-twisting sliding mode control algorithm for the trajectory tracking and balancing of the rotary inverted pendulum system.The super-twisting sliding mode algorithm severely alleviates the chattering present in the classical sliding mode control.It provides robustness against model uncertainties and external disturbances with the knowledge of the upper bounds of the uncertainties and disturbances.The gains of the super-twisting sliding mode algorithm are selected through adaptive law.Parameters of the adaption law are tuned using a modified grey wolf optimisation algorithm,a meta-heuristic optimisation technique.Lyapunov stability analysis is carried out to analyse the overall control system stability.The performance of the proposed control algorithm is compared with two other sliding mode control strategies present in the literature,therein showing better performance of the proposed control scheme.

A sliding mode control algorithm based on improved super-twisting and its application to quadrotors

This paper presents a fast terminal sliding mode control strategy based on improved supertwistingalgorithm (IST-FTSMC) for quadrotors with external disturbances. First, the dynamicmodel of quadrotors is described. Then, a control strategy based on fast terminal sliding modewith improved super-twisting algorithm is proposed for attitude subsystem and position subsystem.Finally, some comparative results show superior tracking performance of the proposedmethod in this paper under external disturbances.

Second-order terminal sliding mode control for hypersonic vehicle in cruising flight with sliding mode disturbance observer

This paper focuses on the design of nonlinear robust controller and disturbance observer for the longitudinal dynamics of a hypersonic vehicle （HSV） in the presence of parameter uncertainties and external disturbances. First, by combining terminal sliding mode control （TSMC） and second-order sliding mode control （SOSMC） approach, the second- order terminal sliding control （2TSMC） is proposed for the velocity and altitude tracking control of the HSV. The 2TSMC possesses the merits of both TSMC and SOSMC, which can provide fast convergence, continuous control law and high- tracking precision. Then, in order to increase the robustness of the control system and improve the control performance, the sliding mode disturbance observer （SMDO） is presented. The closed-loop stability is analyzed using the Lyapunov technique. Finally, simulation results illustrate the effectiveness of the proposed method, as well as the improved overall performance over the conventional sliding mode control （SMC）.

Second-order Sliding Mode Approaches for the Control of a Class of Underactuated Systems

In this paper, first-order and second-order sliding mode controllers for underactuated manipulators are proposed. Sliding mode control(SMC) is considered as an effective tool in different studies for control systems. However, the associated chattering phenomenon degrades the system performance. To overcome this phenomenon and track a desired trajectory, a twisting, a supertwisting and a modified super-twisting algorithms are presented respectively. The stability analysis is performed using a Lyapunov function for the proposed controllers. Further, the four different controllers are compared with each other. As an illustration, an example of an inverted pendulum is considered. Simulation results are given to demonstrate the effectiveness of the proposed approaches.

Fuzzy super-twisting sliding mode control for municipal wastewater nitrification process

A fuzzy super-twisting algorithm sliding mode controller is developed for the dissolved oxygen concentration in municipal wastewater nitrification process. First, a fuzzy neural network(FNN) model is designed to approach the oxygen dynamics with unmeasurable disturbances, then the established model consists of the nominal system model and the modelling error. Second,based on the FNN model, a super-twisting sliding mode controller is employed to stabilize the nominal system and to suppress the modelling error. Moreover, the stability of the system is investigated and an adaption law is applied to ensure the robustness of the closed-loop system. Finally, the comparison experiments on benchmark simulation model no. 2(BSM2) of wastewater treatment show the advantages of the proposed method in multiple-units oxygen concentration control.

Match and mismatched second-order sliding mode finite-time control with simple parameter conditions and its applications

In this paper,a class of second-order sliding mode controller is proposed for nonlinear uncertain systems.The finite-time stability of the nonlinear uncertain systems is achieved when the sliding mode is matched or unmatched.Compared with the previous second-order sliding mode controller,the parameter conditions of the controller are simple and can be given explicitly,and easy to obtain.Finally,the simulation results of dc motor system and dc–dc buck converter verify the effectiveness of the proposed controller in the case of matching and mismatching.

Saturated super-twisting sliding mode missile guidance

This paper concentrates on developing a missile terminal guidance law against a highly maneuvering target whose maneuvering acceleration is very close to that of the missile or even exceeds the missile normal acceleration in a finite period of time.A new saturated super-twisting algorithm is proposed and applied to the design of missile guidance law.The proposed algorithm has the advantages of simple structure,easy parameter tuning rules and a full utilization of the limit control input.The designed saturated super-twisting sliding mode guidance law is then employed in a missile guidance system.Simulation and its superior performance against strong maneuvering targets is demonstrated.

Finite-time sliding mode attitude control for a reentry vehicle with blended aerodynamic surfaces and a reaction control system

This paper proposes a finite-time robust flight controller, targeting for a reentry vehicle with blended aerodynamic surfaces and a reaction control system（RCS）. Firstly, a novel finite-time attitude controller is pointed out with the introduction of a nonsingular finite-time sliding mode manifold. The attitude tracking errors are mathematically proved to converge to zero within finite time which can be estimated. In order to improve the performance, a second-order finite-time sliding mode controller is further developed to effectively alleviate chattering without any deterioration of robustness and accuracy. Moreover, an optimization control allocation algorithm, using linear programming and a pulse-width pulse-frequency（PWPF） modulator, is designed to allocate torque commands for all the aerodynamic surface deflections and on–off switching-states of RCS thrusters.Simulations are provided for the reentry vehicle considering uncertain parameters and external disturbances for practical purposes, and the results demonstrate the effectiveness and robustness of the attitude control system.

Sliding Mode Formation Control of Nonlinear Multi-Agent Systems with Local Lipschitz Continuous Dynamics

In this paper, the multi-agent formation problem of networked nonlinear multi-agent systems with local Lipschitz continuous dynamics under directed interaction topology, is investigated. Based on the nonlinear dynamics satisfying locally Lipschitz continuous conditions, three kinds of sliding mode controllers are proposed to solve the problem of multi-agent formation control. Using integral sliding mode controller in first-order system, formation shape is achieved within finite time. For second-order system, on the one hand, non-singular terminal sliding mode function is adopted to accomplish the system asymptotic convergence. Furthermore, super-twisting algorithm is proposed to make multi-agent achieve the desired formation within finite time. Lyapunov functions are applied in the whole paper to ensure the system stability. Numerical simulation examples are provided to demonstrate the effectiveness of the proposed sliding mode control methods.

非线性动力学模型中的分步式超扭曲/终端滑模协议:在气垫船等混沌系统的应用

Fractional terminal and super-twisting as two types of fractional sliding mode controller are addressed in the present paper.The proposed methodologies are planned for both the nonlinear fractional-order chaotic systems and the nonlinear factional model of Hovercraft.The suggested procedure guarantees the asymptotic stability of fractional-order chaotic systems based on Lyapunov stability theorem,by presenting a set of fractional-order laws.Compared to the previous studies that concentrate on sliding mode controllers with unwanted chattering phenomena,the proposed methodologies deal with chattering reduction of terminal sliding mode controller/super twisting to converge to desired value in finite time,consequently.The main advantages of the offered controllers are 1)closed-loop system stability,2)robustness against external disturbances and uncertainties,3)finite time zero-convergence of the output tracking error,and 4)chattering phenomena reduction.Finally,the simulation results show the performance of the approaches both on the chaotic and Hovercraft models.

High-order sliding mode control of a doubly salient permanent magnet machine driving marine current turbine

Due to the harsh and changeable marine environment,one low speed stator-permanent magnet machine named doubly salient permanent magnet machine with toothed pole is applied for marine current energy conversion system.Indeed,this machine has simple structure,intriguing fault tolerance,and higher power density,which could adequately satisfy the different complicated operation conditions.However,its permanent magnet flux-linkage has the same variation period as the inductance which leads to a strong nonlinear coupling system.Moreover,the torque ripple caused by this special characteristics,uncertainty of system parameters and disturbance of load greatly increases the difficulty of control in this strongly coupling system.Consequently,the classical linear PI controller is difficult to meet the system requirement.In this paper,the high-order sliding mode control strategy based on the super-twisting algorithm for this system is creatively utilized for the first time.The stability of the system within a limited time is also proved with a quadratic Lyapunov function.The relative simulation results demonstrate convincingly that,the high-order sliding mode control has little chattering,high control accuracy and strong robustness.

Integrated Path‑Following and Fault‑Tolerant Control for Four‑Wheel Independent‑Driving Electric Vehicles

Autonomous vehicles are prone to instability when the motors of the four-wheel independent-driving electric vehicles fail at high driving speed on low-adhesion roads.To improve the vehicle tracking performance in the expected path and ensure vehicle stability when the motor fails,this paper designs an integrated path-following and passive fault-tolerant controller.The path-following controller is designed to improve the vehicle path-following performance based on model predictive control(MPC),while the passive fault-tolerant controller is used to ensure vehicle stability when the motor fails.First,a vehicle dynamic model is established and simplified,and an MPC controller based on a state-space equation is designed.Then,taking the motor fault as a fault factor,a first-order sliding mode fault-tolerant controller is developed.The first-order sliding mode fault-tolerant controller takes the vehicle’s yaw rate and sideslip angle into account.Furthermore,to address the chattering problem of the traditional first-order sliding mode fault-tolerant controller,a second-order sliding mode fault-tolerant controller with a disturbance observer is developed.Finally,the developed controller is tested using the Simulink/Carsim platform and applied to a Raspberry Pi 4B for controller hardware-in-the-loop experiment.Simulation and experi-ment results show the practicability and effectiveness of the proposed integrated control strategy.

Comparative study of three types of controllers for DFIG in wind energy conversion system

This paper presents an enhanced control strategy for Wind Energy Conversion System(WECS)using Doubly-Fed Induction Generator(DFIG).A robust Super-Twisting(STW)sliding mode control for variable speed wind turbine is developed to produce the optimal aerodynamic torque and improve the dynamic performance of the WECS.The electromagnetic torque of the DFIG is directly tracked using the proposed control to achieve maximum power extraction.The performance and the effectiveness of the STW control strategy are compared to conventional Sliding Mode(SM)and Proportional-Integral(PI)controllers.The proposed STW algorithm shows interesting features in terms of chattering reduction,finite convergence time and robustness against parameters variations and system disturbances.