Practical bipartite consensus for multi-agent systems:A barrier function-based adaptive sliding-mode control approach

This paper is concerned with bipartite consensus tracking for multi-agent systems with unknown disturbances.A barrier function-based adaptive sliding-mode control(SMC)approach is proposed such that the bipartite steady-state error is converged to a predefined region of zero in finite time.Specifically,based on an error auxiliary taking neighboring antagonistic interactions into account,an SMC law is designed with an adaptive gain.The gain can switch to a positive semi-definite barrier function to ensure that the error auxiliary is constrained to a predefined neighborhood of zero,which in turn guarantees practical bipartite consensus tracking.A distinguished feature of the proposed controller is its independence on the bound of disturbances,while the input chattering phenomenon is alleviated.Finally,a numerical example is provided to verify the effectiveness of the proposed controller.

Sliding-mode observers for systems with unknown inputs and measurement disturbances

The method to design sliding-mode observers for systems with unknown inputs and measurement disturbances is presented in the paper. An augmented system is constructed by viewing the measurement disturbances as unknow inputs. For such an augmented system, the so-called observer matching condition is not satisfied. Based on the construction of auxiliary outputs, the observer matching condition may be satisfied. High-order sliding-mode differentiators are developed to obtain the estimates of those unmeasurable variables contained in the auxiliary output vector. Employing the estimate of auxiliary output vector, a sliding-mode observer is designed. The simulation results to a real model show that the proposed method is effective.

Adaptive sliding-mode path following control system of the underactuated USV under the influence of ocean currents

The path-following control of the asymmetry underactuated unmanned surface vehicle(USV) under external disturbances such as unknown constant and irrational ocean currents is discussed, and an adaptive sliding-mode path-following control system is proposed, which comprises a path-variable updated law,a modified integral line-of-sight(ILOS) guidance law based on a time-varying lookahead distance and adaptive feedback linearizing controllers combined with sliding-mode technique. A more accurate USV model without the assumption of having diagonal inertia and damping matrices is first presented, aiming at improving the performance of the path-following control. Next, the coordinate transformation is adopted to decouple the sway dynamic from the rudder angle, and the path-following errors dynamics without non-singular problem are presented in the moving Frenet-Serret frame. Then, based on the cascaded theorem and the adaptive sliding-mode method, the adaptive control law of position errors and course error are designed, among which the lookahead distance and integral gain are all computed as different functions of cross-track error to estimate and compensate the sideslip angle caused by external disturbances adaptively. Finally, according to the Lyapunov and cascaded theorem, the control system proposed is proved to be uniform globally asymptotic stability(UGAS) and uniform semiglobal exponential stability(USGES) when the control objectives are all achieved. Simulation results illustrate the precision and high-quality performance of this new controller.

Adaptive Sliding-Mode Control of an Automotive Electronic Throttle in the Presence of Input Saturation Constraint

In modern vehicles, electronic throttle(ET) has been widely utilized to control the airflow into gasoline engine. To solve the control difficulties with an ET, such as strong nonlinearity,unknown model parameters and input saturation constraints,an adaptive sliding-mode tracking control strategy for an ET is presented. Compared with the existing control strategies for an ET, input saturation constraints and parameter uncertainties are adequately considered in the proposed control strategy. At first, the nonlinear dynamic model for control of an ET is described. According to the dynamical model, the nonlinear adaptive sliding-mode tracking control method is presented,where parameter adaptive laws and auxiliary design system are employed. Parameter adaptive law is given to estimate the unknown parameter with an ET. An auxiliary system is designed,and its state is utilized in the tracking control method to handle the input saturation. Stability proof and analysis of the adaptive sliding-mode control method is performed by using Lyapunov stability theory. Finally, the reliability and feasibility of the proposed control strategy are evaluated by computer simulation.Simulation research shows that the proposed sliding-mode control strategy can provide good control performance for an ET.

Distributed Secondary Control of AC Microgrids With External Disturbances and Directed Communication Topologies:A Full-Order Sliding-Mode Approach

This paper addresses the problem of distributed secondary control for islanded AC microgrids with external disturbances.By using a full-order sliding-mode(FOSM)approach,voltage regulation and frequency restoration are achieved in finite time.For voltage regulation,a distributed observer is proposed for each distributed generator(DG)to estimate a reference voltage level.Different from some conventional observers,the reference voltage level in this paper is accurately estimated under directed communication topologies.Based on the observer,a new nonlinear controller is designed in a backstepping manner such that an FOSM surface is reached in finite time.On the surface,the voltages of DGs are regulated to the reference level in finite time.For frequency restoration,a distributed controller is further proposed such that a constructed FOSM surface is reached in finite time,on which the frequencies of DGs are restored to a reference level in finite time under directed communication topologies.Finally,case studies on a modified IEEE 37-bus test system are conducted to demonstrate the effectiveness,the robustness against load changes,and the plug-and-play capability of the proposed controllers.

Sliding-mode control for a rolling-missile with input constraints

This paper investigates the overload stabilization problem of the rolling-missile subject to parameters uncertainty and actuator saturation. In order to solve this problem, a sliding-mode control(SMC) scheme is technically employed by using the backstepping approach to make the dynamic system stable. In addition,SMC with the tanh-type switching function plays an important role in reducing intrinsic vibration. Furthermore, an auxiliary system(AS) is developed to compensate for nonlinear terms arising from input saturation. Finally, the simulation results provide a solution to demonstrate that the suggested SMC and the AS methodology have advantages of strong tracking capability, anti-interference ability and anti-saturation performance.

Robust fuzzy sliding-mode control for T-S model based permanent magnet synchronous motor

A fuzzy sliding-mode control (FSMC) scheme based on T-S fuzzy models was proposed for the permanent magnet synchronous motor (PMSM) drive system to solve the speed tracking problem. A T-S fuzzy model was firstly formed to represent the nonlinear system of PMSM. For converting the tracking control into a stabilization problem, a new control design was proposed to define the internal desired states. Then, the FSMC controller for PMSM system with parameter variation and load disturbance was designed based on the fuzzy model. The performance of the proposed controller was verified by experimental results on PMSM system. The results show that the FSMC scheme can drive the dynamics of PMSM into a designated sliding surface in finite time and guarantee the property of asymptotical stability. The information of upper bound of modeling errors as well as perturbations is not required when using the FSMC controller.

A Novel Sliding-mode Guidance Law Based on Lie-group Method

Although the channel-decoupling assumption is often used in design of three-dimensional guidance laws, it loses its rationality for aircrafts with strong kinematics coupling because body rotation arises. To overcome this trouble, a novel guiding method was proposed based on Lie-group. After a model of 3D guidance is formulated using vectors, the precision guidance with ending angular constraints can be transformed into a problem involving the relation between directional angles and rotational angular velocities of certain vectors. When the guidance model is imposed a SO(3)-based description, a novel 3D sliding mode guidance law with ending angular constraints can be developed via Lie-group control method and variable structure control theory. Finally, the feasibility and performance of the guidance law were shown by simulating the examples.

Sliding-Mode Control Based on Index control Law for MPPT in Photovoltaic Systems

A novel maximum power point tracking method based on sliding mode control and average state model of PV generation systems is developed.This method consists of two parts:term of constant control and term of index control.It is different from the conventional sliding mode control which uses a constant speed control law.The developed method uses a controllable sliding mode switching function which can automatically adjust the approaching speed,so as to enable the photovoltaic system to achieve fast dynamic response and stable output power.System simulations using MATLAB are performed.Compared with conventional methods,simulation results show that maximum power point tracking times for the novel method both in start-up phase and in cases of environmental changes can be shorten by more than 50%.A experimental platform of 150W PV system has been established to conduct tests.Experimental results show that the maximum power point tracking times both in start-up phase and in load stepping phase including the illumination change phase,can be significantly decreased.These results indicate that the developed method owns better dynamic response than constant speed control law.It can be used in photovoltaic generation system.

Adaptive Sliding-Mode Disturbance Observer-Based Nonlinear Control for Unmanned Dual-Arm Aerial Manipulator Subject to State Constraints

The unmanned dual-arm aerial manipulator system is composed of a multirotor unmanned aerial vehicle(UAV)and two manipulators.Compared to a single manipulator,dual-arm always provides greater°exibility and versatility in both goods delivery and complex task execution.However,the practical application of the system is limited due to nonlinearities and complex dynamic coupling behavior between the multirotor and the manipulator,as well as the one between the inner and outer loop of the multirotor.In this paper,a holistic model of the dual-arm aerial manipulator system is¯rst derived with complete model information.Subsequently,an adaptive sliding-mode disturbance observer(ASMDO)is proposed to handle external disturbances and unmeasurable disturbances caught by unmeasurable angular velocity and acceleration of the manipulators.Moreover,for safety concerns and transient performance requirements,the state constraints should be guaranteed.To this end,an auxiliary term composed of constrained variable signals is introduced.Then,the performance of the designed method is proven by rigorous analysis.Finally,the proposed method is validated through two sets of simulation tests.

Distributed Finite-Time Integral Sliding-Mode Control for Multi-Agent Systems with Multiple Disturbances Based on Nonlinear Disturbance Observers

This paper proposes a finite-time consensus control algorithm based on nonlinear integral sliding-mode control for second-order multi-agent systems(MASs)with mismatched and matched disturbances.Firstly,a nonlinear finite-time disturbance observer is established to estimate the states and mismatched disturbances of the agent.Secondly,a dynamic integral sliding-mode(ISM)surface is designed by employing the estimates of mismatched disturbances.Then,based on the designed ISM and disturbance observer,the discontinuous or continuous campsite control protocols are respectively developed to guarantee the consensus for MASs in finite time with active anti-disturbance control.Finally,numerical simulation results illustrate the effectiveness of the proposed consensus control algorithm.

Optimal predictive sliding-mode guidance law for intercepting near-space hypersonic maneuvering target

The design of optimal guidance law for intercepting a near-space hypersonic maneuvering target with bounded inputs is considered. Firstly, a maneuvering model for near-space hypersonic aircraft is given. Then, the aircraft acceleration prediction can be obtained using this model with two neural networks. By using the target acceleration prediction, which is taken into account when calculating the Zero Effort Miss(ZEM), an optimal sliding-mode guidance law is proposed to fulfill the guidance task. An adaptive sliding-mode switch term is designed to deal with actuator saturation and prediction errors. Finally, numerical simulations show that the proposed guidance law can reduce the energy consumption and the terminal acceleration command of the interceptor effectively.

A sliding-mode variable-structure controller based on exact feedback linearization for automatic navigation system

In order to improve the path tracking accuracy and robustness of the agricultural machinery navigation system,a sliding-mode variable-structure controller based on exact feedback linearization was presented.Firstly,based on the differential geometry theory and the affine nonlinear kinematics model,the corresponding nonlinear coordinate change matrix and nonlinear state variable feedback equations were deduced,and an exact feedback linearization model was then established.Secondly,based on the exact feedback linearization model,a sliding-mode variable-structure controller was designed by selecting suitable linear switching function and exponential reaching law.Finally,the comparative experiments were carried out.And the experimental results indicated that the proposed method had a high tracking accuracy and robustness.The maximum lateral error of the straight line tracking was less than 0.06 m,and maximum lateral error of the curve path tracking was less than 0.09 m.Experimental results show that the transplanter based on this automatic navigation system can effectively track the predefined path.

A sliding-mode triboelectric nanogenerator with chemical group grated structure by shadow mask reactive ion etching

With the support by the National Natural Science Foundation of China,a collaboration by the research groups led by Prof.Cheng Gang(程纲)from Henan University and Prof.Wang Zhonglin(王中林)from Beijing Institute of Nanoenergy and Nanosystems,Chinese Academy of Sciences,invents'a sliding-mode triboelectric nanogenerator with chemical group grated structure by shadow mask reactive ion etching',which was published in ACS Nano(2017,11(9):8796-8803).

Cascaded Sliding-mode Observer and Its Applications in Output Feedback Control Part II:Adaptive Output Feedback Control

Part II proposes a cascaded sliding-mode observer based output feedback controller for control of multi-input multi-output(MIMO)system.The controller,designed based on feedback linearization control strategy,requires the information of the states and perturbations of the system for realization of disturbance rejection.The observer studied in part I[1]is then utilized to provide the accurate estimates of states and perturbations.As is proved,the proposed observer-based controller can ensure Lyapunov stability of the closed-loop system.Also,it can be used for output tracking control.Simulation studies are carried out on a single-wind-energy-conversion-system-infinite-bus(SWNCSIB)system to test the performances of the proposed observer-based output feedback controller.

Cascaded Sliding-mode Observer and Its Applications in Output Feedback Control Part I:Observer Design and Stability Analysis

This paper proposes a cascaded sliding-mode observer for systems with high relative degree and studies its applications in output feedback controller design.In part I,the working principle and parameter design of the proposed observer are discussed in detail.It is proved that,within a sufficiently short period of time,the states of the proposed observer will reach the intersection of all the sliding surfaces.On sliding surfaces,the observation error of the proposed observer will converge to sufficiently small values.Compared with traditional high-gain observers,the proposed observer has smaller gain coefficients.In addition,the peaking-phenomenon occurred in the proposed observer is less severe.Furthermore,the proposed observer has a convergence rate of observation error as fast as that of traditional high-gain observers.Simulation studies are carried out on a fifth-order system to verify the properties of the proposed observer.

Efficient maximum power point tracker based on neural network and sliding-mode control for buck converters

This paper presents detailed design steps of an effective control system aiming to increase the solar energy harvested via photovoltaic power-generation systems.The design of an intelligent maximum power point tracker(MPPT)supported by a robust sliding-mode(SM)controller is discussed in this study.The proposed control scheme is designed to track the MPP and provide a smooth system response by removing the overshoot in the load current during any variation in the connected load.Such a system is suitable for DC-DC buck converter applications.The study begins with modelling the buck converter for a continuous current mode operation.The reference voltage of the tracking system is produced by the proposed neural network(NN)algorithm.The proposed intelligent MPPT integrated with an SM controller is simulated in a MATLAB®/Simulink®platform.The simulation results are analysed to investigate and confirm the satisfaction level of the adopted four-serially connected PV-modules system.The system performance is evaluated at a light intensity of 500 W/m^(2) and an ambient temperature of 25°C.Applying only the proposed NN algorithm guarantees the MPP tracking response by delivering 100 W at a resistive load of 13Ω,and 200 W at a load of 6.5Ω,respectively,with 99.77%system efficiency.However,this simultaneously demonstrates a current spike of~0.5 A when the load is varied from 50%to 100%.The integrated SM controller demonstrates a robust and smooth response,eliminating the existing current spike.

A Synthesized Design of Adaptive and Sliding-Mode Observer-Based Incipient Fault Detection for a Quadrotor

This study in westigatn the fault detection and fault atimation problem of a quadrotar with disturbanea.A synthesiand design of adaptive and sliding mode obeerver is propoeed to addres the efkctive detection and atimation of inepient faulta.First,the decom pased subaystems are obtalned through the coardinate transdormation,and the in Stial and ineipkent faults are sea rated from the disturbanon.Second,an adaptive obeerver is applied to the decamposd un petubad subaystem to atimate ineipient faults,while the sliding mode obearver remalns robust to disturbanos for the perturbed subaytem.Lyapumov stahility theory mmas the mavergenae o dynamic erors and the stability of the quadrotor ayatem.Pinally,the dfc tiveess of the proposed synthated algod thm of ineipient fault detection is weified by the quadrotor simulation.

Sliding Mode Control Approach with Integrated Disturbance Observer for PMSM Speed System

The research on high-performance vector control of permanent magnet synchronous motor(PMSM)drive system plays an extremely important role in electrical drive system.To further improve the speed control performance of the system,a fast non-singular end sliding mode(FNTSM)surface function based on traditional NTSM control is developed.The theoretical analysis proves that the FNTSM surface function has a faster dynamic response and more finite-time convergence.In addition,for the self-vibration problem caused by high sliding mode switching gain,an FNTSM control method with anti-disturbance capability was designed based on the linear disturbance observer(DO),i.e.the FNTSMDO method was employed to devise the PMSM speed regulator.The comparative simulation and experiment results with traditional PI control and NTSM control methods indicate that the FNTSMDO method could improve the dynamic performance and anti-interference of the system.

Nonsingular Terminal Sliding Mode Control With Ultra-Local Model and Single Input Interval Type-2 Fuzzy Logic Control for Pitch Control of Wind Turbines

As wind energy is becoming one of the fastestgrowing renewable energy resources,controlling large-scale wind turbines remains a challenging task due to its system model nonlinearities and high external uncertainties.The main goal of the current work is to propose an intelligent control of the wind turbine system without the need for model identification.For this purpose,a novel model-independent nonsingular terminal slidingmode control(MINTSMC)using the basic principles of the ultralocal model(ULM)and combined with the single input interval type-2 fuzzy logic control(SIT2-FLC)is developed for non-linear wind turbine pitch angle control.In the suggested control framework,the MINTSMC scheme is designed to regulate the wind turbine speed rotor,and a sliding-mode(SM)observer is adopted to estimate the unknown phenomena of the ULM.The auxiliary SIT2-FLC is added in the model-independent control structure to improve the rotor speed regulation and compensate for the SM observation estimation error.Extensive examinations and comparative analyses were made using a real-time softwarein-the-loop(RT-SiL)based on the dSPACE 1202 board to appraise the efficiency and applicability of the suggested modelindependent scheme in a real-time testbed.