Variable Structure Control Strategy Research Articles

GENERALIZED SYNCHRONIZATION OF A CLASS OF HETEROGENEOUS DRIVE RESPONSE NETWORKS WITH TIME DELAY BASED ON VARIABLE STRUCTURE CONTROL

In this study, the problem of synchronization of heterogeneous-driven response networks is introduced by using variable structure control strategy. First, the mathematical model of the heterogeneous-driven response network is described, and the development history of variable structure control is outlined. Second, considering the coupling time delay of the heterogeneous-driven response network, two types of variable structure controls are designed based on sliding mode control and soft variable structure control theories. Finally, the effectiveness of the two variable structure controls is verified through numerical simulation experiments, and a discussion on their advantages and disadvantages is provided.

Grid-Connected PV Inverter Control Strategy Based on the Sliding Mode

The Photovoltaic grid-connected inverter is an essential equipment of photovoltaic grid-connected system. Due to the disadvantages of the traditional PI control method for grid-connected photovoltaic inverters, this paper adopts the integral sliding mode variable structure to control grid-connected inverters. Grid inverter DC control mode was introduced in detail in the sliding mode variable structure control strategy. Using Matlab simulation platform to compare and analyze the traditional PI voltage compensation control strategy and sliding mode variable structure control strategy. From the waveform of the simulation output, the current harmonic at the output of the grid-connected inverter is reduced, and the power factor is increased, with the power factor is close to 1. The control precision, robustness and anti-interference ability of grid-connected system are improved. Which proved the feasibility and the superiority of the proposed control strategy.

Self-Docking Characteristics and Sliding Mode Control on Space Electromagnetic Docking Mechanism

Electromagnetic docking technology can realize the flexible docking and safe separation of spacecraft, and presents broad application prospects. However, an electromagnetic force with nonlinearity and uncertainty properties increases the difficulties of the electromagnetic docking control. In this work, the magnetic dipole far-field model of a single coil has been established by simplifying the electromagnetic docking device. Afterward, the electromagnetic force and electromagnetic torque models were obtained during space electromagnetic docking. The space electromagnetic docking dynamics model was established by analyzing the influences of disturbance force and disturbance torque caused by a geomagnetic field. According to the one-dimensional docking reference trajectory, the sliding mode variable structure controllers based on exponential reaching law were proposed and verified. The quasi-sliding mode control method has been adopted to solve the chattering problem in sliding mode variable structure control. The simulation results show that it is necessary to design and add an electromagnetic controller to achieve flexible docking. The sliding mode variable structure controller based on quasi sliding mode can realize one-dimensional electromagnetic flexible docking, and have made good tracking effect on the reference trajectory. Compared with the control method based on exponential reaching law, it can reduce the chattering phenomenon in the control process. The sliding mode variable structure control strategy based on quasi sliding mode presented good robustness. Therefore, it can provide theoretical guidance and control reference for the flexible docking process between electromagnetic satellites.

Multi-Degree-of-Freedom Manipulator Joint Trajectory Tracking Control Method Based on Decision Tree

For industrial-grade manipulators, the study of trajectory tracking control issues provides an important guarantee for accurate and safe work. Therefore, the trajectory control input driving torque can meet the requirements of the robot arm to accurately track a given target trajectory, and the process of building a decision tree is a process of dividing the feature space. For a given training data set, a set of if-then is summarized the rule of. Based on this, this paper launches the research of multi-degree-of-freedom manipulator joint trajectory tracking control method based on decision tree. Based on the established kinematics and dynamics model of the manipulator, this paper uses a proportional-integral-derivative (PID) sliding mode controller based on the sliding mode surface of the manipulator to perform the trajectory tracking control of the end of the manipulator, and the simulation results of the improved sliding mode control are compared with the simulation results of the improved sliding mode control. The simulation results of the PID controller and the traditional sliding mode controller are compared. This paper finally verifies the effectiveness of the proposed new sliding mode controller based on the expanded state observer through the experimental platform. The speed and chattering problems of the trajectory tracking at the end of the manipulator are better than those of the controller on the experimental platform. Finally, this paper adopts the sliding mode variable structure control strategy combining the double-power reaching law and the improved terminal sliding mode surface to study the trajectory tracking control of the planar two-degree-of-freedom manipulator.

New Control Approaches for Trajectory Tracking and Motion Planning of Unmanned Tracked Robot

This work proposes new control approaches for tracking and motion planning of Unmanned Ground Vehicles (UGVs) that utilize skid steering system. This work proposes an energy based Variable Structure Control (VSC) scheme, in which two independent Sliding Control Surfaces (SCS)s are designed based on the system states. Particularly, the controller is designed based on the assessment and the minimization of the systems total energy by finding an explicit relation between the controller gains and the slope of the sliding surface. The work also discusses a new fuzzy potential approach for motion planning of UGV. The Fuzzy system generates an attractive force that pulls the UGV effectively toward a moving or stationary target, and a repulsive force, which is required to avoid any stationary or moving obstacles. Both, the VSC and the motion planning were validated by a nonlinear model of an Unmanned Tracked Robot (UTR) on different trajectories, and was compared with different control schemes. Simulation results show superiority of the proposed VSC over other methods with less control effort. Furthermore, the new motion planning controller proved its high capacity in producing a smooth and dynamic trajectory to allow an UGV to track a target and to avoid obstacles.

Position Control Study on Pump-Controlled Servomotor for Steam Control Valve

In steam turbine control and actuation, the steam control valve plays a key role in operability and reliability. The electrohydraulic regulating system for the steam control valve, usually called the servomotor, needs to be reliable and high performing under nonlinear excitation interference in actual conditions. Currently, electrohydraulic servo valve control technology is widely used in servomotors. Although this technology has good control performance, it still has some technical defects, such as poor antipollution ability, low energy efficiency, large volume size, and limited installation space. Aiming at the abovementioned technical shortcomings of electrohydraulic servo valve control technology, a servomotor-pump-hydraulic cylinder volume control scheme is proposed in this paper, forming a pump-controlled servomotor for the steam control valve. By analyzing the working principle of the pump-controlled servomotor position control in the steam control valve, the mathematical model of a pump-controlled servomotor for the steam control valve is established. The sliding mode variable structure control strategy is proposed, and the variable structure control law is solved by constructing a switching function. To verify the performance of the proposed control method, experimental research was conducted. The research results show that the proposed sliding mode variable structure control strategy has a good control effect, which lays the theoretical and technical foundation for the engineering application and promotion of pump-controlled servomotors for steam control valves and helps the technical upgrade and product optimization of steam turbines.

Direct Torque Control of Two Series Connected Six-Three phases Motor Fed by Single Six Phases VSI Based on Optimum Vectors Selection

In this paper, a direct torque control (DTC) is developed for a two series connected six-phase & three-phase motor drive (IMs) with sinusoidal distributed windings and fed by single six-phase voltage source inverter (VSI). Direct torque control also considered as a variable structure control strategy with simplicity, fast response and tolerance to motor parameter variations; it provides direct control of stator flux and torque by optimally selecting the inverter states in each sampling period. In case of multi-phase system drive, the increased number of voltages vectors offers greater flexibility in optimizing the selection of the inverter states. The technique elaborated in this work based direct torque control allows independently control of the system fed by single inverter. The effectiveness and capability of the proposed method are shown by computer simulation.

Dynamic Modeling and Error Analysis of a Cable-Linkage Serial-Parallel Palletizing Robot

The efficiency and accuracy for parallel robot play a significant role in the industrial production process. In order to further improve the motion performance of parallel robot, this paper focuses on the study of mechanism design, dynamic modeling and error analysis of a cable-linkage serial-parallel palletizing robot (CSPR). Firstly, the CSPR is designed as a series-parallel hybrid mechanism driven by flexible cables, which can effectively reduce the inertia and improve the dynamic response. As is known that kinematic design optimization of compliant mechanisms requires accurate yet efficient mathematical models, the kinematics and dynamic models are established by the homogeneous coordinate transformation method and Lagrange equation. Based on the dynamic mathematical model of the robot, a variety of sensors are chosen to construct the hardware control system and the sliding mode variable structure control strategy is also designed based on motion errors. Then, the motion performance and load carrying capacity of the CSPR were analyzed and compared in different operating conditions respectively, and the results verify the validity and efficiency of the mechanism.

An MPPT Control of a PMSG-Based WECS with Disturbance Compensation and Wind Speed Estimation

The paper presents simulation research on a variable structure control scheme of a small variable-speed fixed-pitch wind energy conversion system (WECS) with a three-phase permanent magnet synchronous generator (PMSG) in variable wind conditions. The WECS is connected to a power grid through two back-to-back voltage source converters (VSCs) with a DC link. The presented control algorithm is based on feedforward compensation of the wind turbine aerodynamic torque estimated using a linear disturbance observer (DOB). The torque estimate is employed to determine the effective wind speed, required for setting the reference angular speed, using numerical zero search of a nonlinear function. The simulation model, built in the Matlab/Simulink environment using the Simscape Electrical toolbox, includes the field-oriented control of the PMSG via the machine VSC, performed by cascaded angular velocity and current/torque PI controllers, as well as synchronization with the grid and the reactive power control via the grid VSC. The presented results are focused on the performance of the proposed control in the maximum power point tracking (MPPT) operating region of the WECS for various wind speed profiles.

Virtual synchronous motor based-control of Vienna rectifier

Vienna rectifiers are widely used because of their advantages of high power-factor, low voltage stress on the power semiconductor switches, high power density, stable output voltage, low current harmonic content, and good economics. And gradually applied to the front stage AC/DC part of the electric vehicle charger. Traditional Vienna rectifier control methods include double closed-loop control, hysteresis current control, and Sliding mode variable structure control strategy, but all strategies usually regulate DC-Voltage and keep the unity power factor. However, if it is used for the interface part of the electric vehicle charger with frequent load switching, it is necessary not only to ensure the stability of the output voltage and low THD of the current, but also to be able to respond to the fluctuation of the voltage and frequency of the power system and improve the inertia and damping at the interface. Thereby, the stability of the power grid is improved to a certain extent, and fast-charging is ensured while being grid-friendly. Therefore, this paper proposes to apply the virtual synchronous motor control to the Vienna rectifier to improve the adaptability of the grid to the large-scale access of electric vehicles. Build the topology of the Vienna rectifier in simlink and the modulation method using SVPWM to build a complete model on the basis of VSM.

Variable Structure Control of a Small Ducted Wind Turbine in the Whole Wind Speed Range Using a Luenberger Observer

This paper proposes a new variable structure control scheme for a variable-speed, fixed-pitch ducted wind turbine, equipped with an annular, brushless permanent-magnet synchronous generator, considering a back-to-back power converter topology. The purpose of this control scheme is to maximise the aerodynamic power over the entire wind speed range, considering the mechanical safety limits of the ducted wind turbine. The ideal power characteristics are achieved with the design of control laws aimed at performing the maximum power point tracking control in the low wind speeds region, and the constant speed, power, and torque control in the high wind speed region. The designed control laws utilize a Luenberger observer for the estimation of the aerodynamic torque and a shallow neural network for wind speed estimation. The effectiveness of the proposed method was verified through tests in a laboratory setup. Moreover, a comparison with other solutions from the literature allowed us to better evaluate the performances achieved and to highlight the originality of the proposed control scheme.

Adaptive control realization for canonic Caputo fractional-order systems with actuator nonlinearity: application to mechatronic devices

Nonlinearities, such as dead-zone, backlash, hysteresis, and saturation, are common in the mechanical and mechatronic systems’ components and actuators. Hence, an effective control strategy should take into account such nonlinearities which, if unaccounted for, may cause serious response problems and might even result in system failure. Input saturation is one of the most common nonlinearities in practical control systems. So, this article introduces a novel adaptive variable structure control strategy for nonlinear Caputo fractional-order systems despite the saturating inputs. Owing to the complex nature of the fractional-order systems and lack of proper identification strategies for such systems, this research focuses on the canonic systems with complete unknown dynamics and even those with model uncertainties and external noise. Using mathematical stability theory and adaptive control strategy, a simple stable integral sliding mode control is proposed. The controller will be shown to be effective against actuator saturation as well as unknown characteristics and system uncertainties. Finally, two case studies, including a mechatronic device, are considered to illustrate the effectiveness and practicality of the proposed controller in the applications.

Variable Structure Controller for Chaos Elimination in a Single Ended Primary Inductance Converter

The paper attempts to off-set the circuit parasitics and the inherent switching nature of the power switch in a SEPIC (Single Ended Primary Inductance Converter) that eclipses its performance from theoretical predictions. The focus orients to design a control strategy that offers a chaotic free operation of the SEPIC. It envisages the use of a Variable Structure Control (VSC) strategy to irradiate the adverse effects of non-linear dynamics and assuage the operating range of the converter. The scheme projects the creation and elimination of this nonlinear property through time domain waveforms and phase portraits. The methodology underscores the theory to ensure an uniform rate of charging and discharging for the inductor current during the process of the converter operating the load. The scheme realizes the benefits of the mechanism through a correlation between the open and closed loop inductor current time domain waveform, with the help of adjustments in the parametric variations. The effort involves evaluating the performance using MATLAB simulation and experimental validation in a DSPIC (Digital signal peripheral interface controller) environment to illustrate its suitability for practical applications.

Sliding mode and predictive current control strategy of the three-phase Vienna rectifier

This study involves the design and implementation of a novel double closed-loop control of the three-phase Vienna rectifier. To achieve the unit power factor operation of the rectifier and reduce the harmonic content of the grid side, the double closed-loop control strategy is proposed on the basis of the voltage control of the outer loop and the current control of the inner loop. The voltage outer loop adopts the sliding-mode variable structure control strategy based on the improved reaching law; this strategy can effectively suppress switching jitter. The current inner loop adopts an improved predictive current control strategy that combines the traditional finite control set model predictive control (FCS-MPC) with the space vector modulation method (SVPWM), such that the optimal switching state obtained by the predictive controller is modulated to generate a switching signal. Moreover, the switching frequency can be controlled by adjusting the frequency of the carrier, and the switching frequency is fixed while preserving the advantages of model prediction control. The primary advantages of the proposed double closed-loop control strategy are as follows: (1) it does not require proportional–integral controllers in the current control loops, and (2) it keeps the output voltage stable. The Vienna rectifier simulation is performed on MATLAB. Then an experimental prototype based on SiC devices is developed to verify the excellent performance of the proposed strategy in steady and transient states.

Finite-time projective synchronization of fractional-order chaotic systems via soft variable structure control

The finite-time projective synchronization of two fractional-order chaotic systems with control constraints is investigated in this study. A soft variable structure control scheme is first introduced for finite-time synchronization. A controller is then proposed for finite-time generalized projective synchronization. The finite-time stability of the error systems is rigorously proven. The control parameters of the controller are limited by the soft variable structure method considering the constraints of the controller. Finally, numerical simulation results are presented to demonstrate the effectiveness and feasibility of the proposed strategy and verify the theoretical results.

Adaptive Bipartite Consensus of Second-Order Multi-Agent Systems With Bounded Disturbances

This paper investigates distributed adaptive bipartite consensus for second-order multi-agent systems (MASs) with bounded disturbances under a signed graph. Based on adaptive variable structure control strategies, an adaptive bipartite consensus protocol is proposed, which guarantees that the bipartite consensus can be realized if the signed graph is structurally balanced and connected. Furthermore, the external disturbances are attenuated effectively by the variable structure control. And the obtained results are applied to adaptive consensus of disturbed second-order MASs under cooperative networks. Finally, a numerical simulation is presented to demonstrate the theoretical finding.

An Approach to Improve System Performance in the Vehicle-Grid System Using Sliding Mode Control Under Multiple Operation Conditions

To improve the performance of vehicle-grid system under multiple operation conditions and suppress the low-frequency oscillation (LFO) in electrified railways, this paper proposed a control strategy of electric multiple units (EMUs) traction line-side converter (LSC) based on sliding mode control (SMC). First, the accurate model of EMUs is established and then the mathematical model of it in the d-q frame is derived. Then, the application of sliding mode variable structure control strategy in the LSC of EMUs is presented in detail, which includes the design of outer loop voltage sliding mode surface and inner loop current control law. Moreover, the control performance for EMUs based on SMC and traditional linear proportional integral (PI) control is compared under multiple operation conditions in the case of one traction drive unit of EMUs and multi-EMUs, respectively. Finally, experiments are implemented on the hardware in the loop simulation platform based on software StarSim. The experiments results show that, compared with PI control, SMC owns better control performance, such as the lower total harmonic distortion of traction line-side current under multiple conditions, lower voltage fluctuation when braking occurs, better anti-interference ability with the change of system parameters, and can effectively suppress the LFO occurs under operation mode.

Adaptive Fuzzy Variable Structure Control for Permanent Magnet Linear Servo System

In order to improve the immunity of AC permanent magnet linear servo system to parameter perturbation, end effect and load resistance, an intelligent sliding mode variable structure control scheme based on adaptive neuro-fuzzy inference system ANFIS is proposed. The adaptive neuro-fuzzy inference system ANFIS is introduced into the traditional sliding mode variable structure control to weaken the inherent chattering of sliding mode control and eliminate the end effect of permanent magnet linear synchronous motor. The simulation and experimental results show that the intelligent sliding mode variable structure control method based on ANFIS is simple, has good dynamic performance and good robustness.

Robust adaptive synchronization of complex network with bounded disturbances

In this paper, we investigate distributed robust adaptive synchronization for complex networked systems with bounded disturbances. We propose both average synchronization protocol and leader-following synchronization protocol based on adaptive control and variable structure control strategies. The synchronization conditions do not require any global information except a connection assumption under the adaptive control method. Furthermore, the external disturbances are attenuated effectively. Finally, we present numerical simulations to illustrate the theoretical findings.

Sliding Mode Variable Structure Control Strategy Applied on Position Servo System of EMA

This paper introduces the basic elements of Electronic-Mechanical Actuator (EMA), and gives the equations. The mathematical model-state equations is established based on the basic equations, and the sliding mode variable structure control strategy, based on the reaching law is applied to control the position servo of EMA. We design a position-speed integrated sliding mode variable structure controller. The models of EMA machinery, electrical motor and controller are established in AMESim and Matlab, and joint simulation is carried out. Finally, this control strategy is compared with the three loop PID control strategy, and the experiment is carried out. The result shows that the sliding mode variable structure control strategy based on reaching law used to control EMA can improve the frequency response and control accuracy of the system, can also improve the dynamic performance of the position servo system.