Equivalent Sliding Mode Control Research Articles

Sliding Mode with Equivalent Control for Induction Motor Drive Based on Multi-Pulse VSC

In this work, the application of a sliding mode equivalent control for an induction motor drive based on a multi-pulse Voltage Source Converter is proposed. This is accomplished by transforming the squirrel-cage induction motor mathematical model into a block control form. The equivalent control method is applied to the sliding manifold, where the voltages are obtained in the stationary reference frame to control the angular velocity of the motor. In addition, a proportional-integral control is designed and applied to the motor represented in this form in order to make performance comparisons with the equivalent control method. Multi-pulse converters of 6, 12, and 84 pulses are used directly to feed the plant that is being controlled. The outcomes of using these power electronics devices are used to perform comparisons among the velocity tracking performance, control voltages in stationary reference frame, tracking errors, and rejection of external disturbances. Furthermore a dynamic and steady-state analysis of the velocity tracking performance is executed. The energy profiles for the startup, torque variations, and steady-state are also obtained. Additionally, total harmonic distortion values are added. All comparisons are carried out using the established plan for the motor, both with and without the use of power electronics converters, and with both control algorithms. The obtained results demonstrate that the use of a high-quality voltage source converter, along with a good control strategy, allows for a general improvement in the overall system and a significant reduction in energy usage, whilst also reducing controller complexity.

The adaptive neural network fuzzy sliding mode control for the 3-RRS parallel manipulator

In order to improve the high-precision tracking control of angle variables and the sliding mode equivalent control part for the 3-RRS parallel manipulator, an adaptive neural network fuzzy sliding mode control algorithm with self-adjusting switching gain is proposed. Firstly, considering the uncertainty of the constrained force between derived links and the moving platform, the complete dynamic model including ideal and non-ideal constrained force is established by combining with the Udwadia-Kalaba(U-K) equation and Lagrange method. Secondly, the neural network sliding mode controller is designed to realize the approximate solution of the sliding mode equivalent control part. At the same time, in order to reduce the chattering phenomenon of the neural network sliding mode controller, a fuzzy adjustment rule of switching gain is designed to better compensate for the uncertain terms. And then the stability of the control system is proved by the Lyapunov method. Finally, the proposed control algorithm is simulated on the 3-RRS parallel manipulator. The simulation results show that the chattering phenomenon is overcome. The high-precision control of angle variables and the sliding mode equivalent control part is realized.

Equivalent SM Controller for Load-Sharing and Dynamic Performance in a DC Microgrid Application

Load-sharing and voltage regulation are key challenges in low voltage dc microgrid systems. Droop-based decentralized control methods are used to control dc grids which cannot achieve these challenges simultaneously due to unequal voltages and load power variations. Centralized control schemes can achieve these challenges using high bandwidth communication. However, the failure of a single central controller can degrade performance and reliability. In addition, cascaded proportional-integral (PI) type controllers are used to control the voltage and current loop of each power electronic converter. These controllers suffer stability and show slower dynamic responses. Furthermore, control parameters cannot be optimized for different operating conditions. To address these challenges, a distributive control method using an equivalent sliding mode (SM) controller utilizing low bandwidth communication is proposed in this paper. The distributive method improves reliability and achieves load sharing and voltage regulation simultaneously. Furthermore, in SM, both voltage and current loop operate in the parallel configuration which improves the dynamic response and shows stability in all operating conditions. To analyze, a system model is developed, and existence and stability conditions are verified. Detailed simulations are carried out to show the steady-state and transient performance. The presented results show the effectiveness of the proposed scheme.

Recursive Terminal Sliding-Mode Control Method for Nonlinear System Based on Double Hidden Layer Fuzzy Emotional Recurrent Neural Network

Aiming at the problem of the coexistence of nonlinearity and uncertainty in the control systems, a novel control method which combines the double hidden layer fuzzy emotional recurrent neural network (DHLFERNN) and the recursive terminal sliding mode control (RTSMC) is proposed. Firstly, a novel double hidden layer fuzzy emotional recurrent neural network (DHLFERNN) is designed. The proposed DHLFERNN can be considered as a combination of a fuzzy neural network (FNN) and a double hidden layer recurrent neural network (DHLRNN) in the framework of brain emotional learning (BEL), which could make the controller obtain higher nonlinear approximation ability. Secondly, a recursive terminal sliding mode control (RTSMC) method based on the DHLFERNN is proposed. In this method, the nonlinear sliding-mode equivalent control term is approximated by the proposed DHLFERNN, which makes the controller possess a good nonlinear approximation ability when the nonlinear model cannot be obtained exactly. Finally, the stability of closed-loop system is proved by the Lyapunov method, and the adaptive law of each parameter in DHLFERNN is derived. The proposed method is verified on an inverted pendulum system, and the comparison with other control methods proves that the proposed method has faster convergence speed and higher control accuracy.

Guidance Law with Desired Impact Time and FOV Constrained for Antiship Missiles Based on Equivalent Sliding Mode Control

Impact time control guidance (ITCG) is an important approach to achieve saturation attack on targets. With the increasing complexity of warfare requirements for missiles, an ITCG with field-of-view (FOV) constrained for antiship missiles is proposed based on equivalent sliding mode control. Firstly, in view of the accuracy of the calculation of remaining impact time for guidance law, the large initial lead angle is taken into consideration in the estimation of remaining flying time in which there is no need for the assumption of small angle approximation. Besides, for the sake of promoting the practical application value of the proposed guidance law, FOV is considered so that it can satisfy the actual working performance of the seeker. Then, combined with the concept of predicted interception point (PIP), the proposed guidance law is applied to attack a moving target. Numerical analysis is carried out for different initial lead angles, various impact time, different methods of estimating remaining flying time, and cooperative attack conditions. Compared with proportion navigation guidance (PNG), the feasibility and effectiveness of the guidance law are verified. Simulation results demonstrate that the proposed guidance law can guarantee the constraints of both impact time and FOV effectively.

Fuzzy Multiple Hidden Layer Recurrent Neural Control of Nonlinear System Using Terminal Sliding-Mode Controller.

This study designs a fuzzy double hidden layer recurrent neural network (FDHLRNN) controller for a class of nonlinear systems using a terminal sliding-mode control (TSMC). The proposed FDHLRNN is a fully regulated network, which can be simply considered as a combination of a fuzzy neural network (FNN) and a radial basis function neural network (RBF NN) to improve the accuracy of a nonlinear approximation, so it has the advantages of these two neural networks. The main advantage of the proposed new FDHLRNN is that the output values of the FNN and DHLRNN are considered at the same time, and the outer layer feedback is added to increase the dynamic approximation ability. FDHLRNN was designed to approximate the nonlinear sliding-mode equivalent control term to reduce the switching gain. To ensure the best approximation capability and control performance, the proposed FDHLRNN using TSMC is applied for the second-order nonlinear model. Two simulation examples are implemented to verify that the proposed FDHLRNN has faster convergence speed and the FDHLRNN with TSMC has good dynamic property and robustness, and a hardware experimental study with an active power filter proves the feasibility of the method.

Global-Equivalent Sliding Mode Control Method for Bridge Crane

A wide application of sliding mode variable structure control as a nonlinear robust control method, has been witnessed in anti-swing positioning control of bridge crane system. Aiming at the problem that the sliding mode variable structure control system of bridge crane is not robust in approaching process, a new Global-Equivalent Sliding Mode Controller (GESMC) based on bridge crane system is proposed. This controller can realize the anti-sway positioning control of the bridge crane system under the condition of uncertain model parameters and external disturbance. The proposed controller, different from the traditional sliding mode control, excels in improving system robustness through keeping the system states in the sliding surface during the whole response process. Specifically, it initiates with the design of a global sliding surface, which can eliminate the sliding mode approach process of the system and achieve global robustness in the system. Afterwards, a new switching function combined with the equivalent sliding mode control method is incorporated to effectively reduce the chattering generated when the system reaches the sliding mode manifold. Its asymptotic stability is proven without a priori knowledge on the bounds of unknown disturbances by using the Lyapunov stability theory. Lastly, the simulation conducted verifies the effectiveness and robustness of the GESMC proposed in this paper and meanwhile demonstrates a comparatively favorable performance for the GESMC in reducing chattering.

Sliding-Mode Direct-Voltage Control of Voltage-Source Converters With LC Filters for Pulsed Power Loads

This article proposes a direct-voltage controller, based on sliding modes, for regulating the output voltage of voltage-source converters (VSCs) equipped with LC filters. Grid-forming VSCs used in microgrids with pulsed loads must provide fast dynamic response and strong rejection of load perturbations. The new voltage control scheme uses a single-stage sliding-mode voltage controller with state feedback. The typical two-loop cascaded topology using a current controller in the inner loop and a voltage controller in the outer loop is not employed. The sliding-mode control (SMC) contains three components: 1) a feedforward effort that sets the ideal operating point, 2) a switching control law based on SMC, and 3) a sliding-mode equivalent control. The sliding variable is defined with proportional-derivative (PD) dynamics, and thus, it provides inherent active damping properties. The SMC improves the robustness with respect to load perturbations and modeling errors, whereas the equivalent control adds damping and reduces the response time to large load transients. The article describes the design and gain selection, and provides a simulation-based sensitivity analysis for this scheme. Two variants are tested in standalone operation: with and without the P term of the PD component. Experimental results show that, in both cases, the response to pulsed loads is very fast (about 1 ms) and accurate.

Analysis of a DC–DC quadratic type step‐down converter for wider low voltage conversion

This study proposes a new transformerless DC–DC step-down converter having the quadratic type of wider voltage gain, for point-of-load applications. In comparison to existent quadratic buck converter variants, the proposed topology offers better switch utilisation at small output voltages and reduced voltage/current stress on components. The stress minimisation benefit helps to select low ON-state resistance switch in the proposed converter, thereby decreasing its conduction losses. Qualitative steady-state analysis is carried out under continuous inductor current mode and design criteria for L-C components are established. State-space average model is derived and subsequently, an equivalent sliding mode control law based on just source side inductor current dynamics and integral of load voltage error is constituted to regulate the output. Salient operational characteristics of the converter are studied analytically and illustrated thereafter using experimental outcomes on a laboratory prototype.

Strongly perturbed sliding mode adaptive control of vehicle active suspension system considering actuator nonlinearity

Aiming at the problem of improving driving comfort under the condition of ensuring driving safety and limited suspension travel, this paper proposes a sliding mode adaptive controller suitable for strong disturbance action. Considering the nonlinear characteristics of the hydraulic actuator, a one-half vehicle suspension model with uncertain parameters and external disturbances is established. In the sliding mode design part of the controller, the sliding mode equivalent control items of the vertical and pitch subsystems are derived, and the optimised constant velocity approach law is adopted. The sliding mode switching control item is given to ensure that the controller can effectively adjust the vehicle body posture when the system is subjected to strong external disturbance. Finally, by selecting the adaptive law, the controller can adapt to the uncertainty of the vehicle body parameters. The simulation results for the specific example considered in this work show that the control strategy can greatly improve the ride comfort under the premise of ensuring the safety of the vehicle and the stability of the steering. Compared with the backstepping adaptive control, the control strategy of this paper shows superiority when the system is subjected to strong disturbance.

Bionic Visual Control for Probe-and-Drogue Autonomous Aerial Refueling

The probe-and-drogue autonomous aerial refueling (AAR) docking suffers the multiwind disturbances leading to the low accuracy of receiver position control and drogue relative position estimation. This article proposes a bionic visual navigation control system in a hardware-in-loop simulation environment and further develops an AAR outfield experiment platform for promoting the success of probe-and-drogue AAR docking. The drogue region and markers are detected by the biological method imitating the eagle-eye color vision mechanism. The different visual navigation methods based on the ellipse fitting, marker matching, and marker prediction are, respectively, applied to the three possible situations in AAR docking for precise pose estimation. Moreover, a relative position control scheme of the receiver, which is constructed by back-stepping design technique and gain-adaptive equivalent sliding mode control, is proposed to compensate multi-wind disturbances and model uncertainties. Fuzzy logic position strategy is designed to compensate swing of the drogue caused by the multiwind disturbances. The AAR outfield experiment platform contains two unmanned aerial vehicles to verify a part of the proposed navigation control method. Extensive experimental results are presented to demonstrate the effectiveness of the bionic visual navigation control system for the high accuracy of the visual navigation and antidisturbance position control.

Multimotor Improved Relative Coupling Cooperative Control Based on Sliding-Mode Controller

To provide cooperative control under complex working conditions of a filling multimotor system, this paper proposes a relative coupling control strategy with a switching system structure. Firstly, a multistation transmission system composed of a filling motor and a transfer motor is designed according to different filling processes. Secondly, a stable sliding-mode surface common to the multimotor system is selected, and an equivalent sliding-mode controller corresponding to each motor is designed. Thirdly, public Lyapunov stability theory is used to prove that the switched system can move from any initial state to the common sliding surface of the system, thereby ensuring the asymptotic stability of the entire system. Simulation results show that this method has a more significant control effect on the system error of each motor in comparison with the traditional relative coupling control structure.

Robust Reconstruction of Current Sensor Faults for PMSM Drives in the Presence of Disturbances

The reliability and availability of a permanent magnet synchronous motor (PMSM) drive system are of increasing importance in industrial applications. Occurrence of current sensor faults in the system can lead to system degradation. Therefore, early detection of the faults has become an important problem. However, various exogenous disturbances seriously affect the accuracy of the faults detection. This paper presents a method of reconstructing current sensor faults for a PMSM drive containing unknown disturbances. An equivalent-input-disturbance approach is devised to reject the effects of unknown disturbances on system performance and reconstruction of faults And an integral observer is designed to approximately separate faults from the measured output to eliminate the interference to disturbance rejection. Then, a sliding-mode observer is designed for the disturbance-rejected system with current sensor faults. And the faults are reconstructed based on sliding-mode equivalent control methodology. The presented scheme has good performance in terms of faults reconstruction and is robust to time-varying unknown disturbances. Simulations and experiments validate the effectiveness of the method.

The Equivalent Sliding Mode Tension Control of Carbon Fiber Multilayer Diagonal Loom

In order to enhance the tension control performance of the carbon fiber multilayer diagonal loom, two control methods based on the yarn warping and the curling control are proposed. The tension control mathematical models of carbon fiber multilayer diagonal loom, the yarn warping control model and the curling control model, are reestablished by the force analysis of the warping and the curling systems. Some technological process movements, such as the opening and the beating-up, are regarded as the disturbances. Based on the equivalent sliding mode control theory, the tension control strategies of the warping and the curling are constructed. Lyapunov method is used to prove the stability of the systems. Simulation results show that both the two methods could control the tension of the yarn, and the control results have good robustness to the disturbances.

Estimation of sensor faults and unknown disturbance in current measurement circuits for PMSM drive system

Current sensor faults leads to system degradation of a permanent magnet synchronous motor (PMSM) drive. Accurate estimation of the faults for fault-tolerant control has become an important issue. However, unknown disturbance in measurement circuits greatly aggravates the difficulty of the estimation and seriously influences the performance of the estimation. This paper presents a new estimation method of sensor faults and unknown disturbance in current measurement circuits for an interior PMSM drive system. The system model, which contains faults of virtual sensors for αβ axis currents and the unknown disturbance, is first constructed. Then, the model is transformed into a model with actuator faults by a first-order low-pass filter. Moreover, the faults and disturbance in the model are decoupled by coordinate transformation. And sliding-mode observers are designed based on the new decoupled system. Single and simultaneous faults of current sensors and an unknown disturbance are accurately estimated based on sliding-mode equivalent control methodology. An experiment is carried out to demonstrate the validity and effectiveness of the method.

Quadratic feedback–based equivalent sliding mode control of wind turbine blade section based on rigid trailing-edge flap

Modeling of aeroelastic system of wind turbine blade section based on chordwise rigid trailing-edge flap has been investigated. The flutter suppression of blade section exhibiting flap-wise bending and twist deformation is performed by equivalent sliding mode control. Aerodynamic expressions are based on the modified quasi-steady model which is attached to the influences of trailing-edge flap. The continuous equivalent sliding mode control algorithm based on quadratic feedback parameter is applied to realize flutter suppression, with displacements and velocities, control input of angle of trailing-edge flap and sliding mode function demonstrated. To facilitate the process of computer implementation, the discrete equivalent sliding mode control algorithm is discussed in detail, with better control effects and angle control of trailing-edge flap demonstrated. The quadratic feedback–based equivalent sliding mode control algorithm, including continuous equivalent sliding mode control and discrete equivalent sliding mode control, realizes the analysis of control effects based on feedback parameter with empirical adjustment coefficient. This provides schemes of not only theoretical simulation but also real-time implementation for the application of equivalent sliding mode control in different engineering projects.

GA/PSO Robust Sliding Mode Control of Aerodynamics in Gas Turbine

Abstract In gas turbine process, the axial compressor is subjected to aerodynamic instabilities because of rotating stall and surge associated with bifurcation nonlinear behaviour. This paper presents a Genetic Algorithm and Particle Swarm Optimization (GA/PSO) of robust sliding mode controller in order to deal with this transaction between compressor characteristics, uncertainties and bifurcation behaviour. Firstly, robust theory based equivalent sliding mode control is developed via linear matrix inequality approach to achieve a robust sliding surface, then the GA/PSO optimization is introduced to find the optimal switching controller parameters with the aim of driving the variable speed axial compressor (VSAC) to the optimal operating point with minimum control effort. Since the impossibility of finding the model uncertainties and system characteristics, the adaptive design widely considered to be the most used strategy to deal with these problems. Simulation tests were conducted to confirm the effectiveness of the proposed controllers.

Modeling and Sliding Mode Control for Cement Particle Size

Considering the characteristics of large time delay and vulnerable to interference of cement particle size control. Firstly, through the rise curve of the production process to identify the transfer function with time delay by least squares algorithm. Secondly, translate the time delay system into a form of state space equation with no delay by a method of state transition. Finally, an equivalent sliding mode control is applied to control the particle size and the stability conditions of sliding mode control are given. The simulation results show it can achieve a desirable control effect in cement particle size control.

Adaptive Neural Network Sliding Mode Control for Quad Tilt Rotor Aircraft

A novel neural network sliding mode control based on multicommunity bidirectional drive collaborative search algorithm (M-CBDCS) is proposed to design a flight controller for performing the attitude tracking control of a quad tilt rotors aircraft (QTRA). Firstly, the attitude dynamic model of the QTRA concerning propeller tension, channel arm, and moment of inertia is formulated, and the equivalent sliding mode control law is stated. Secondly, an adaptive control algorithm is presented to eliminate the approximation error, where a radial basis function (RBF) neural network is used to online regulate the equivalent sliding mode control law, and the novel M-CBDCS algorithm is developed to uniformly update the unknown neural network weights and essential model parameters adaptively. The nonlinear approximation error is obtained and serves as a novel leakage term in the adaptations to guarantee the sliding surface convergence and eliminate the chattering phenomenon, which benefit the overall attitude control performance for QTRA. Finally, the appropriate comparisons among the novel adaptive neural network sliding mode control, the classical neural network sliding mode control, and the dynamic inverse PID control are examined, and comparative simulations are included to verify the efficacy of the proposed control method.

Generalized projective synchronization between controlled master and multiple slave TLFMs with modified adaptive SMC

The problem of projected work space trajectory synchronization for multiple two link flexible manipulators is considered here. Generalized projective synchronization between a controlled master and multiple slave manipulators is presented in this paper. The master and slave manipulators are non-identical. A low frequency chaotic signal and an exponentially varying signal are used as the desired trajectories. An equivalent sliding mode controller is designed for the master manipulator to track the desired trajectory. A modified adaptive equivalent sliding mode controller is designed for the slave manipulators to be projectively synchronized with the controlled master. Two scaling factors are used for the projective synchronization. Simulation results, with disturbances and payload variation reveal that the master and multiple slaves are synchronized with their respective desired trajectories. Such projective synchronization between one master and multiple slaves using the proposed control techniques to track a low frequency chaotic desired signal is not found in the literature. Such projective synchronization to track a chaotic signal is considered as the novelty of this paper. The performances of the proposed control techniques are found to be better in terms of link deflections and control effort when compared with three other sliding mode control techniques.