Showing papers on "Variable structure control published in 2019"

Trajectory Tracking of Autonomous Vehicle with the Fusion of DYC and Longitudinal-Lateral Control

Abstract: The current research of autonomous vehicle motion control mainly focuses on trajectory tracking and velocity tracking. However, numerous studies deal with trajectory tracking and velocity tracking separately, and the yaw stability is seldom considered during trajectory tracking. In this research, a combination of the longitudinal–lateral control method with the yaw stability in the trajectory tracking for autonomous vehicles is studied. Based on the vehicle dynamics, considering the longitudinal and lateral motion of the vehicle, the velocity tracking and trajectory tracking problems can be attributed to the longitudinal and lateral control. A sliding mode variable structure control method is used in the longitudinal control. The total driving force is obtained from the velocity error in order to carry out velocity tracking. A linear time-varying model predictive control method is used in the lateral control to predict the required front wheel angle for trajectory tracking. Furthermore, a combined control framework is established to control the longitudinal and lateral motions and improve the reliability of the longitudinal and lateral direction control. On this basis, the driving force of a tire is allocated reasonably by using the direct yaw moment control, which ensures good yaw stability of the vehicle when tracking the trajectory. Simulation results indicate that the proposed control strategy is good in tracking the reference velocity and trajectory and improves the performance of the stability of the vehicle.

Automatic Steering Control Strategy for Unmanned Vehicles Based on Robust Backstepping Sliding Mode Control Theory

Abstract: Automatic steering system of self-driving vehicles has significant influence on vehicle safety. The performance of automatic steering system is affected by external disturbance, parameter perturbation, and real-time ability of control algorithm. First, to develop a high-performance automatic steering control strategy, a vehicle-road system model based on vehicle dynamics and kinematics is established. Then, the system state equation with direction-angle and lateral-position deviations is derived to describe the tracking accuracy. Finally, based on the sliding mode variable structure control method, an automatic steering control algorithm is proposed and verified. The results show that the dynamic quality of the system is improved with the optimization of the sliding mode. Furthermore, good robustness against vehicular velocity, real-time performance, and tracking accuracy is achieved.

Corrections to “A New Load Torque Identification Sliding Mode Observer for Permanent Magnet Synchronous Machine Drive System”

Abstract: Effective identification of the load torque is one of the key aspects in improving the performance of servo drive systems against load disturbances. Sliding mode variable structure control has become a popular method in the development of a load torque identification (LTID) algorithm due to its parameter insensitivity and easy realization features. However, existing LTID sliding mode observers (SMO) with conventional structure have the disadvantages of high-frequency chattering and poor estimation accuracy, which limit its application in high-performance servo systems. In this paper, the mathematical model of the conventional LTID-SMO is deduced and analyzed. A new LTID-SMO is proposed by replacing the sign function with a saturation function and an additional feedback loop in the load torque observer. The effectiveness of the proposed observer is verified by various experiments. The results show that compared to conventional load torque observer, the proposed observer can identify the load torque with higher accuracy and faster response in different operational conditions.

Hierarchical Fuzzy Logic-Based Variable Structure Control for Vehicles Platooning

Abstract: This paper proposes a variable structure control approach for vehicles platooning based on a hierarchical fuzzy logic. The leader-follower vehicle dynamics with model uncertainties is discussed from the viewpoint of a consensus problem. A practical two-layer fuzzy control for the platooning is designed by employing two common spacing policies to ensure system robustness in different scenarios. The two policies, i.e., constant distance and constant time headway, utilize the predecessor-successor information flow from the immediate predecessor and follower other than controlled vehicles. The first layer of the fuzzy system combines spacing control with velocity-acceleration control to achieve a rapid tracking for the desired control commands, and the second layer combines the sliding mode control to adaptively compensate for reducing the state errors caused by parameter uncertainties and disturbances. Shift between different controller parameters is based on performance boundaries to guarantee the stability of individual vehicle and platooning for arbitrary initial spacing and velocity errors. These performance boundaries can be determined by using a Lyapunov method with exponential stability. Simulation of a ten-vehicle large platooning with two spacing policies shows that the control performance of the newly proposed method is effective and promising.

Adaptive sliding mode enhanced disturbance observer-based control of surgical device.

Abstract: This paper presents an enhanced adaptive robust disturbance observer-based motion tracking control methodology. This control approach is established and investigated for a semi-automated hand-held ear surgical device for the treatment of Otitis Media with Effusion. The proposed control methodology is utilised for tracking a desired motion trajectory in the presence of unknown or uncertain system parameters, nonlinearities including hysteresis, and disturbances in the motion system. The stability of the control approach is analysed. The convergence of position and velocity tracking errors is proven theoretically. A precise tracking performance following desired motion trajectory is demonstrated in the experimental study.

Neural Network Sliding Mode Control of Intelligent Vehicle Longitudinal Dynamics

Abstract: Longitudinal dynamics control is the basis for autonomous driving of intelligent vehicles, which have great significance to the development of intelligent transportation system (ITS). To solve the problems of traditional sliding mode control method when applied to intelligent vehicle longitudinal dynamics, such as large velocity tracking errors, strong chattering phenomenon and so on, a new sliding mode control strategy based on RBF (Radical Basis Function) neural network is presented in this paper. Firstly, a nonlinear mathematical model of the intelligent vehicle longitudinal motion is established by considering the dynamics of the engine, the torque converter, the automatic transmission and the brake system. On the basis of the system model, a variable structure control system with sliding mode is introduced to design a sliding mode variable controller with RBF neural network. This controller can adaptively adjust the switching gain and its stability is proved based on the Lyapunov theory. Finally, the effectiveness of the designed longitudinal velocity control strategy is verified by simulation under typical driving conditions. The simulation results show that the improved control algorithm can effectively suppress chattering, obtain the higher precision and stronger robustness than the traditional sliding mode control. Thus, the longitudinal motion control performance of intelligent vehicles is improved effectively.

Picking Robot Visual Servo Control Based on Modified Fuzzy Neural Network Sliding Mode Algorithms

Abstract: Through an analysis of the kinematics and dynamics relations between the target positioning of manipulator joint angles of an apple-picking robot, the sliding-mode control (SMC) method is introduced into robot servo control according to the characteristics of servo control. However, the biggest problem of the sliding-mode variable structure control is chattering, and the speed, inertia, acceleration, switching surface, and other factors are also considered when approaching the sliding die surface. Meanwhile, neural network has the characteristics of approaching non-linear function and not depending on the mechanism model of the system. Therefore, the fuzzy neural network control algorithm can effectively solve the chattering problem caused by the variable structure of the sliding mode and improve the dynamic and static performances of the control system. The comparison experiment is carried out through the application of the PID algorithm, the sliding mode control algorithm, and the improved fuzzy neural network sliding mode control algorithm on the picking robot system in the laboratory environment. The result verified that the intelligent algorithm can reduce the complexity of parameter adjustments and improve the control accuracy to a certain extent.

Quality Inspection of Remote Radio Units Using Depth-Free Image-Based Visual Servo With Acceleration Command

Abstract: In this paper, the problem of quality inspection of remote radio units (RRUs) is approached using the image-based visual servo control. A novel computer vision pipeline is designed that recognizes the power port of RRU and tracks it from the stream of images. For the control part, a new depth-independent interaction matrix is designed that relates the depth information with the area of the region of interest surrounding the power port. Based on this, an acceleration command is generated to drive the robot's trajectories. Furthermore, a propotional-derivative (PD)-type controller is designed based on the idea of sliding surface in variable structure control. This reduces the number of design parameters to a single parameter. The designed controllers are proven to be stable using the Lyapunov stability analysis. Simulation results and experimental validations are provided to support the research arguments.

Consensus-Based Odor Source Localization by Multiagent Systems

Abstract: This paper presents an investigation of the task of localizing an unknown source of an odor by heterogeneous multiagent systems. A hierarchical cooperative control strategy has been proposed as a potential candidate to solve the problem. The agents are driven into consensus as soon as the information about the location of source is acquired. The controller has been designed in a hierarchical manner of group decision making, agent path planning, and robust control. In group decision making, the particle swarm optimization algorithm has been used along with the information of the movement of odor molecules to predict the odor source location. Next, a trajectory has been mapped using this predicted location of source, and the information is passed to the control layer. A variable structure control has been used in the control layer due to its inherent robustness and disturbance rejection capabilities. Cases of movement of agents toward the source under consensus and parallel formation have been discussed. The efficacy of the proposed scheme has been confirmed by simulations.

Performance Evaluation of Variable Structure Controller Based on Sliding Mode Technique for a Grid-Connected Solar Network

Abstract: Generating electric power from solar energy is a vastly growing technology worldwide. This paper investigates and evaluates the performance of a solar power generation system utilizing variable structure control with sliding mode for maximum power point tracking (MPPT). This controller is implemented on a buck–boost dc–dc power converter to track the maximum power point (MPP). The suggested controlled solar energy system also includes a dc-link capacitance, a voltage-source inverter, and a grid filter. Energy-based control is performed for the voltage of the dc-link capacitor. Space vector pulsewidth modulation (SVPWM) with current control in dq rotating frame is utilized to govern the inverter. The suggested system is simulated and subjected to various operating conditions. The results demonstrate the power captured from photovoltaic (PV) panels and delivered to the grid while tracking the MPP. For more confidence on the MPPT controller, practical experimentation is introduced using a real PV panel and power circuit with interfacing to a personal computer (PC). The proposed design is subjected to various experimental tests to ensure its validity.

Decentralized Optimal Control of a Microgrid with Solar PV, BESS and Thermostatically Controlled Loads

Abstract: Constructing microgrids with renewable energy systems could be one feasible solution to increase the penetration of renewable energy. With proper control of the battery energy storage system (BESS) and thermostatically controlled loads (TCLs) in such microgrids, the variable and intermittent energy can be smoothed and utilized without the interference of the main power grid. In this paper, a decentralized control strategy for a microgrid consisting of a distributed generator (DG), a battery energy storage system, a solar photovoltaic (PV) system and thermostatically controlled loads is proposed. The control objective is to maintain the desired temperature in local buildings at a minimum cost. Decentralized control algorithm involving variable structure controller and dynamic programming is used to determine suitable control inputs of the distributed generator and the battery energy storage system. The model predictive control approach is utilized for long-term operation with predicted data on solar power and outdoor temperature updated at each control step.

Control of chaos in vehicle lateral motion using the sliding mode variable structure control

Abstract: A 3-degree of freedom (DOF) nonlinear model including yaw, lateral, and roll motions was constructed, and a numerical simulation of chaotic behavior was performed using the Lyapunov exponent method...

Research on High Precision Control of Joint Position Servo System for Hydraulic Quadruped Robot

Abstract: Electro-hydraulic servo valve-controlled cylinder(EHSVCC) is a highly integrated and high-performance electro-hydraulic servo driving unit(EHSDU), which is the basic driving unit of the leg joint for hydraulic quadruped robot. The robot impedance control mostly adopts control methods based on position inner loop and impedance outer loop, the high precision control of position inner loop is the key to improve impedance control. Therefore, it is of great significance to study a high precision position control method. Firstly, the electro-hydraulic servo drive unit of the foot robot is taken as the research object. The model of the nonlinear system is established, and the feedback linearization of the system is carried out. Secondly, in order to improve the tracking performance and anti-jamming ability of the position inner loop input/output a sliding mode variable structure robust controller(SMVSRC) with switching function, variable structure control rate and improved boundary layer function is designed. Finally, the electro-hydraulic servo drive unit(EHSDU) and the hydraulic foot robot test platform are tested, the influence of the two control algorithms on the position response and tracking error for EHSDU is analyzed and compared under the control of sinusoidal signals with different amplitudes and frequencies and diagonal gait signals. The experimental results show that the improved SMVSRC algorithm is feasible and effective, which provides a theoretical basis for the later study of impedance control based on position inner loop.

Sliding Mode Control for Position Tracking of Servo System with a Variable Loaded DC Motor

Abstract: In this paper, the real-time position control of servo system is carried out using sliding mode control (SMC) method based on variable structure control (VSC). As DC Motors are commonly used in many industrial applications and robotics, studies in this paper have are tested on a DC servo system, which is designed and produced by Quanser Inc. Three different types of sliding mode controllers are designed for position control of servo system and, later, performance comparison of DC Motor on Servo system is made. According to results obtained from real-time servo system, it is shown that SMC method is robust against to disturbing effects, variabilities, and uncertainties on the systems. Outstanding part of this paper is that designed controllers are implemented to servo system in real-time with a variable loaded DC Motor. Moreover, this study shows that this control structure can be performed as high performance in the real-time motor control applications.

Robust adaptive synchronization of complex network with bounded disturbances

Abstract: 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.

Non-linear extended state observer-based sliding mode control for a direct-driven wind energy conversion system with permanent magnet synchronous generator

Abstract: Considering the internal and external disturbances of direct-driven wind turbine-based permanent magnet synchronous generation system, an extended state observer (ESO)-based sliding mode variable structure control strategy is proposed to improve the maximum power tracking performance of the system. The ESO is used to estimate the effects of the disturbances, such as dynamical uncertainties, modelling error, external forces, variety of wind speed and so on, and eliminate the disturbances by the feedforward compensation. The simulation results show that the control system not only effectively improves the anti-disturbance ability of the system, but also solves the chattering problem of sliding mode control system to a certain extent.

Sliding Mode Variable Structure Control for Surface Permanent Magnet Synchronous Motors Based on a Fuzzy Exponential Reaching Law

Abstract: In order to handle heavy chattering and negative robustness caused by time-varying system parameters and external load disturbance of the speed control system, thereby having high-precision control over surface permanent magnetic synchronous machine (PMSM), this paper combines the advantages of sliding mode variable structure control (SMVSC) and fuzzy control. Firstly, a fuzzy sliding mode variable structure control (FUZZY-SMVSC) method is proposed, based on the vector control foundation framework of surface PMSM (SPMSM). It effectively reduces chattering while keeping sliding mode, according to the fuzzy rules formulated based on fuzzy control principle. Secondly, integral sliding mode surface is used and integration element is introduced into fuzzy control input, thereby reducing the static error of the conventional fuzzy control. Simulation and experimental results show that the proposed fuzzy sliding mode variable structure control reduces chattering by fuzzy reasoning and softening. Also, it still can maintain the strong robustness of sliding mode variable structure and ensures the fine dynamics of the system, against time-varying system parameters and external load disturbance.

State Constrained Variable Structure Control for Active Heave Compensators

Abstract: Heave compensation systems are widely used to decouple the load motion from wave-induced vessel motion for the equipment handling on the ocean. Researches have been made to achieve successful compensation, yet few of them discusses the inherent constraints of the systems, such as bounded compensator’s stroke and max actuator’s velocity. This paper presents a solution for active heave compensation systems with such constraints by means of variable structure control. The controller’s complexity on design procedures and effectiveness are compared with a trajectory planning control method which turns out that the variable structure controller is more suitable to apply to the active heave compensators. The back-stepping method is used to robustly stabilize this variable structure system and for the aim of a decrease on the high robust gain due to uncertain friction term, a modified decoupled friction observer is used which is also verified by both theoretical and experimental analyses. To compensate for the time delay of the motion reference unit (MRU), a heave prediction algorithm is used. The experimental results show that most heave motion can be compensated when the motion and its velocity are feasible, while no hit occurs otherwise.

Vibration control of a structure using sliding-mode hedge-algebras-based controller

Abstract: Sliding-mode control is known as a popular approach of robust control methods. Fuzzy sliding-mode control method has been commonly used to prevent chattering phenomenon, drastic change of control factor, around sliding surface in sliding-mode control. In Hedge-algebras theory, inherent order relationships among linguistic values of each linguistic variable are always guaranteed and these values are determined by isomorphism mapping called semantically quantifying one based on a few fuzziness parameters of each linguistic variable instead of using fuzzy sets. In this paper, sliding-mode hedge-algebras-based controller is designed and applied in active control of a structure subjected to earthquake in order to show advantages of the proposed method.

Fuzzy sliding mode control of servo control system based on variable speeding approach rate

Abstract: In order to optimize the speed control performance of the permanent-magnet synchronous motor system with different disturbances and uncertainties, this paper proposes a fuzzy sliding mode variable structure control (fuzzy-SMC) strategy. First, a variable speed reaching rate is introduced to solve the deficiency of the exponential reaching rate widely used in conventional sliding mode variable structure control (SMC) strategy. Then, a fuzzy controller is designed to adjust the control parameters to overcome the control deviation and improve the dynamic performance of the system. Simulation and experimental results show that when the steady state is reached, the proposed fuzzy-SMC strategy has better response speed than the proportional integral differential strategy and the conventional SMC strategy. It has smaller speed fluctuation, is more robust, and effectively suppresses the chattering phenomenon.

Improved Adaptive Backstepping Approach on STATCOM Controller of Nonlinear Power Systems

Abstract: This paper proposes an improved backstepping control approach which uses error-compensation and the sliding mode variable structure control to achieve stability for a single machine infinite bus system (SMIBS) with a static synchronous compensator (STATCOM). An adaptive sliding mode control was also utilised to obtain strong response performance in order to avoid excitation and the unknown parameters generated by the recursive steps of traditional backstepping control. Increasing the error-compensation term was used to generate a new virtual control to guarantee that the system states are more rapid stable and eliminate system chattering effectively generated by traditional sliding mode control. The boundedness and convergence of the closed-loop system were then obtained based on Lyapunov stability theory. Finally, a simulation is demonstrated to illustrate the effectiveness and the practicality of the proposed control method.

Variable structure control for an isolated boost converter used in fuel cell applications

Abstract: In recent years fuel cells have become prominent as an alternative source of energy to meet the society’s energy requirements. A control strategy derived from variable structure theory known as Sliding Mode Control (SMC) was proposed for an Isolated Boost topology which was mostly used in fuel cell systems. Converter operation and its detailed mathematical modelling are also presented. Then the converter with the control strategy suggested is simulated in MATLAB/SIMULINK and compared with other controllers. The results show that transient response of the converter is very fast and steady state error is reduced throughout the load change period with proposed control topology.

Low-Impact Contact Between Electrodes of Pneumatic Servo Welding Gun Using Segmented Sliding-Mode Control

Abstract: In automobile manufacturing, improving the quality and efficiency of resistance spot welding and avoiding the damage caused by excessive impact force are of significance. This paper proposes a low-impact contact evaluation method for the pneumatic servo welding gun and the concept of optimal cushioning distance. A segmented sliding-mode control method is used. By analyzing the electrode contact mechanism, the gradual progress of spot welding is controlled by the method proposed in this paper. The cushioning effects of PID control, sliding-mode variable structure control, and segmented sliding-mode variable structure control are compared by experiments. The results show that the contact force during the 0.05 s after the electrode contact is not more than 10% of the welding force using sliding-mode control, approximately 0.2 kN, which satisfies the proposed low-impact contact requirements.

Online Stator and Rotor Resistance Estimation Scheme Using Sliding Mode Observer for Indirect Vector Controlled Speed Sensorless Induction Motor

Abstract: Recently, many works have been made to improve the performance of sensorless induction motor drives. However, parameter variations and low-speed operations are the most critical aspects affecting the accuracy and stability of sensorless drives. This work presents a sensorless vector control scheme consisting of the first hand of a velocity estimation algorithm that overcomes the need for sensor velocity and secondly a robust variable structure control law that compensates for the uncertainties present in the system. Simulation results confirm the efficacy of the proposed approach.

Quasi-Soft Variable Structure Control of Discrete-Time Systems With Input Saturation

Abstract: In the effort to improve the convergence rate of linear controllers, at the same time avoiding abrupt input transitions and implementation difficulties of time-optimal ones, soft variable structure control (VSC) may be considered. The classical formulation of soft VSC in continuous time domain assumes smooth, yet instantaneous switching in an infinite pool of controllers, which is not possible in the now commonplace digital control schemes. In discrete-time systems, the control structure may be changed only at the sampling instants, which results at best in quasi-soft behavior. This brief presents a design of quasi-soft VSC system, which by directly covering the discretization effects, permits maintaining the favorable properties of fast convergence and smooth inputs in discrete time domain, thus bringing the realization of soft VSC closer to the industrial reality. The properties of the presented control system are formally proved and verified experimentally.