Switching Control Action Research Articles

Variable Structure Controller for Energy Savings in an Underwater Sensor Platform.

This paper introduces a new variable structure controller designed for depth control of an autonomous underwater sensor platform equipped with a variable buoyancy module. To that end, the prototype linear model is presented, and a finite element-based method is used to estimate one of its parameters, the hull deformation due to pressure. To manage potential internal disturbances like hull deformation or external disturbances like weight changes, a disturbance observer is developed. An analysis of the observer steady-state estimation error in relation to input disturbances and system parameter uncertainties is developed. The locations of the observer poles according to its parameters are also identified. The variable structure controller is developed, keeping energy savings in mind. The proposed controller engages when system dynamics are unfavorable, causing the vehicle to deviate from the desired reference, and disengages when dynamics are favorable, guiding the vehicle toward the target reference. A detailed analysis determines the necessary switching control actions to ensure the system reaches the desired reference. Finally, simulations are run to compare the proposed controller's performance with that of PID-based controllers recently developed in the literature, assessing dynamic response and energy consumption under various operating conditions. Both the VBM- and propeller-actuated vehicles were evaluated. The results demonstrate that the proposed controller achieves an average energy consumption reduction of 22% compared to the next most efficient PID-based controller for the VBM-actuated vehicle, though with some impact on control performance.

Optimal Energy Management System Control of Permanent Magnet Direct Drive Linear Generator for Grid-Connected FC-Battery-Wave Energy Conversion

The Wave Energy Conversion System (WECS) control strategy is presented in this study to make sure the system operates at its best under fluctuating wave resource situations. The suggested system consists of a MOPSO based MPC approach, a point absorber WEC oscillating in heave, back-to-back power converter for grid connections, and a linear permanent magnet generator. Despite the benefits of model predictive control, problems including switching frequency variations, steady-state errors, high processing costs, and constrained prediction horizons continue to exist. The article presents a method that incorporates the switching control action into the cost function while maintaining the finite nature of a model predictive control to handle the switching frequency issue. In order to minimise switching frequency variations while also addressing other control goals, such as regulating the direct current linked voltage and controlling the flow of active and reactive power, the switching control weight factors are optimised. In order to increase power quality, a fuel cell-based short-term energy storage system is also included to direct current link between the back-to-back converters.

Design and implementation of finite control set MPC with an LCL filter for grid-tied PMSG based wind turbine

This paper presents a grid-connected wind energy conversion system (WECS) that leverages the benefits of a permanent magnet synchronous generator and a finite control set model predictive control (FCS MPC) strategy. Despite the advantages offered by FCS MPC, challenges such as fluctuations in switching frequency, steady-state errors, high computational demands, and limited prediction horizons still persist. To address the switching frequency issue, the study introduces an approach incorporating the switching control action within the cost function while preserving the finite character of FCS MPC. The weight factors for switching control are optimized to reduce the switching frequency fluctuations while addressing other control objectives, such as regulating the DC-link voltage and controlling the flow of active and reactive power. The grid currents on the d and q axes are controlled to limit the amount of active and reactive electricity entering the grid. The proposed system also includes a modified third-order LCL filter, which is optimized by the predictive controller’s regulation of switching frequency, reducing design complexities and ensuring effective performance. A simulation of the proposed WECS with FCS MPC and a modified LCL filter has been performed using the MATLAB/Simulink environment. The dSpace DS1202 controller has been used to create an experimental setup suitable for a lab setting. The simulation and experimental findings confirm the controller and filter’s effectiveness under dynamic and steady-state operating circumstances. This research provides a promising solution for future wind energy conversion systems, advancing the field and establishing a foundation for further exploration.

Multi‐input enhanced model reference adaptive control strategies and their application to space robotic manipulators

AbstractThe Enhanced Model Reference Adaptive Control (EMRAC) algorithm, augmenting the MRAC strategy with adaptive integral and adaptive switching control actions, is an effective solution to impose reference dynamics to plants affected by parameter uncertainties, unmodeled dynamics and disturbances. However, the design of the EMRAC solutions has so far been limited to single‐input systems. To cover the gap, this paper presents two extensions of EMRAC to multi‐input systems. The adaptive mechanism of both solutions includes the ‐modification strategy to assure the boundedness of the adaptive gains also in presence of persistent disturbances. The closed‐loop system is analytically studied, and conditions for the asymptotic convergence of the tracking error are presented. Furthermore, when the plant is subjected to unmatched disturbances, the ultimate boundedness of the closed‐loop dynamics, which are made discontinuous by the adaptive switching control actions, is systematically proven by using Lyapunov theory for Filippov systems. The problem of trajectory tracking for space robotic arms in presence of unknown and noncooperative targets is used to test the effectiveness of the novel multi‐input EMRAC algorithms for taming uncertain systems. Four EMRAC solutions are designed for this engineering application, and tested within a high fidelity simulation framework based on the Robot Operating System. Finally, the tracking performance of the EMRAC implementations is quantitatively evaluated via a set of key performance indicators in the joint space and operational space, and compared with that of four benchmarking controllers.

Global stability of a Lotka-Volterra piecewise-smooth system with harvesting actions and two predators competing for one prey

The global dynamics of a three-dimensional Lotka-Volterra system described by two predator species competing for one prey and with human harvesting action on the predator species is studied in this paper. The harvesting action is introduced by means of two switching control actions defined on the predator species. A well-known result in the study of ecosystem modeling is that there are two states of coexistence of one of the predatory species with the prey species assuming that the principle of competitive exclusion or coexistence of competing species is fulfilled. In this sense, the three species cannot coexist in this class of system. In this work, it is proved that there is a global stable equilibrium point where the three species can coexist due to the proposed harvesting action.

Ergodic switching control for diffusion-type processes

We consider the control of the discrete component $ n_t $ of a switching Markov process $ x_t = ( z_t, n_t) $ when there is a running cost and an immediate cost $ c(i, j) $ for switching $ n_t $ from $ i $ to $ j $. We study the minimization of the ergodic (or long-term average) total cost. Essentially, this paper treats the case where, for $ n_t=n $ fixed, $ z_t $ is a reflected diffusion or a reflected diffusion with jumps, $ n_t $ being, for fixed $ z $, a continuous-time Markov chain. Using the vanishing discount approach, we extend existing results dealing with the situation where $ n_t $ evolves only by the switching control action and the diffusion is non-degenerate. Moreover, we solve the ergodic problem for a class of diffusions which can be degenerate and for an example with absorbing state.

2-D path following for fixed wing UAV using global fast terminal sliding mode control

This paper considers the finite time convergence problem of 2-D path following for fixed wing unmanned air vehicle. Firstly, the UAV path following model is divided into an outer guidance loop and an inner control loop. Then, the guidance loop and control loop controllers of the UAV are derived by global fast terminal sliding mode control technique, which is able to guarantee the system state variables converge to expected values in finite time and eliminate the chattering phenomenon caused by the switching control action. Furthermore, the stability of the two-loops system is proven by Lyapunov stability theory. Finally, the simulation results are shown to verify the performance of the proposed method.

Research of Robust Trajectory Tracking Control and Attenuated Chattering: Application on Quadrotor

In this paper, we presented a strategy for accurate trajectory tracking control of a quadrotor with unknown disturbances. To guarantee that the tracking errors of all system state variables converge to zero in finite time and eliminate the chattering phenomenon caused by the switching control action, a control strategy that combines linear prediction model of disturbances and fuzzy sliding mode control (SMC) based on logical framework with side conditions (LFSC) was designed. LFSC was applied for both position and attitude tracking of the quadrotor. Firstly, a linear prediction method was devised to minimize the effects of external disturbances. Secondly, a new fuzzy law was implemented to eliminate the chattering phenomenon. In addition, the stabilities of position and attitude were demonstrated by using Lyapunov theory, respectively. Simulation results and comprehensive comparisons demonstrated the superior performance and robustness of the proposed LFSC scheme in the case of external disturbances.

An Adaptive Switching-Gain Sliding-Mode-Assisted Disturbance Observer for High-Precision Servo Control

Active disturbance compensation is crucial for realizing high-precision servo control. However, the suppression of rapidly changing disturbances is still a challenging issue. In this article, observer-based disturbance-rejection control is investigated, and an observer with adaptive switching gain is proposed for improved robustness against changing disturbances. First, a disturbance observer (DOB) is established, based on the tracking differentiator technique. Second, a sliding-mode-assisted observer with an adaptive law is designed to estimate the residual-disturbance estimation error of the DOB. The proposed scheme instantly increases the switching gain when the state deviates from a preset boundary, thus eliminating the tuning time. The switching control action with an immediately large switching gain is robust against suddenly changing disturbances. Moreover, the switching gain then decays to zero, reducing chattering in the steady state. The gain adjustment process is designed to have the same dynamic characteristics as the proposed DOB, which guarantees the convergence of the proposed scheme. This method is not only suitable for linear systems, but also extendable to nonlinear systems. The proposed scheme was evaluated experimentally; the results showed that it improves disturbance rejection and decreases servo error.

H ∞ bipartite consensus of nonlinear multi-agent systems over a directed signed graph with a leader of non-zero input

This paper examines the bipartite tracking consensus for nonlinear multi-agents over a directed signed graph under bounded disturbances and a non-zero bounded input of the leader. For dealing with disturbances, the control theory has been adopted to develop a robust bipartite tracking consensus protocol. An additional switching control action is proposed to counteract the bounded matching input of the leader. The proposed control ensures the asymptotic convergence of the consensus error for known matching bounded input at the leader without disturbances, and an performance criterion from bounded disturbances to the consensus error has been provided. Contrary to the traditional consensus frameworks, our approach considers the nonlinear agents to resolve the bipartite consensus, disturbances for a robust distributed control, directed signed graphs, and bounded non-zero input at the leader for dealing with a realistic consensus scenario. Two simulation examples are provided for illustration.

Higher order networked sliding mode controller for heat exchanger connected via data communication network

Heat Exchanger (HE) is a widely used device in industrial applications for both cooling and heating processes because it can sustain a wide range of temperature and pressure parameters without affecting the output performance of the system. In this paper, we propose a Higher-Order Sliding Mode (HOSM) controller for HE connected via a data communication network. The higher-order sliding mode controller is well known for chattering attenuation which occurs due to switching control action in a sliding mode control technique. The HOSM controller based on super-twisting algorithm is proposed to compensate for the random communication network delay and process delay in the presence of model uncertainties of HE. The sufficient condition for stability is ensured by the trivial Lyapunov function. The simulation results demonstrate the efficacy of the designed controller for the HE in terms of chattering, delay compensation, and faster convergence. Further, the performance of HE is compared in two ways. In first case, the proposed controller performance is compared for a HE system with network delay and without network delay. In the second case, the performance of the proposed controller is compared with the conventional constant plus proportional rate reaching law based controller.

An Energy Management System-Based Control Strategy for DC Microgrids with Dual Energy Storage Systems

In this work, a control strategy is developed for different components in DC microgrids where set points for all controllers are determined from an energy management system (EMS). The proposed EMS-based control scheme is developed for DC microgrids with solar photovoltaic (PV) systems as the primary generation units along with energy storage systems. In this work, the concept of dual energy storage systems (DESSs) is used, which includes a battery energy storage system (BESS) and supercapacitor (SC). The main feature of this DESS is to improve the dynamic performance of DC microgrids during severe transients appearing from changes in load demands as well as in the output power from solar PV units. Furthermore, the proposed EMS-based control scheme aims to enhance the lifetime of the BESS in DC microgrids with DESSs and voltage stability as compared to the same without SCs. The proposed EMS-based control strategy uses proportional-integral (PI) controllers to regulate the switching control actions for different converters within the DC microgrid based on the decision obtained from the EMS in order to achieve the desired control objectives. The performance of the proposed scheme was analyzed through simulation results in terms of improving the voltage stability, maintaining the power balance, and enhancing the lifetime of BESSs within a DC microgrid framework incorporated with the DESS. The simulations are carried out in the MATLAB/SIMULINK simulation platform and compared with a similar approach having only a single energy storage system, i.e., the BESS.

A novel nonsingular terminal sliding mode control combined with global sliding surface for uncertain nonlinear second-order systems

This paper proposes a novel nonsingular terminal sliding mode control combined with global sliding surface for a class of uncertain nonlinear second-order systems. The suggested control approach is developed based on the Lyapunov theory. The sliding mode reaching the sliding surface in finite time can be guaranteed. Furthermore, chattering phenomenon caused by the switching control action can be eliminated theoretically, and desirable control performance is realized. The simulation and tank test results for heave control of a remotely operated vehicle are presented to verify the effectiveness of the proposed method.

Global fast dynamic terminal sliding mode control for a quadrotor UAV

A control method based on global fast dynamic terminal sliding mode control (TSMC) technique is proposed to design the flight controller for performing the finite-time position and attitude tracking control of a small quadrotor UAV. Firstly, the dynamic model of the quadrotor is divided into two subsystems, i.e., a fully actuated subsystem and an underactuated subsystem. Secondly, the dynamic flight controllers of the quadrotor are formulated based on global fast dynamic TSMC, which is able to guarantee that the position and velocity tracking errors of all system state variables converge to zero in finite-time. Moreover, the global fast dynamic TSMC is also able to eliminate the chattering phenomenon caused by the switching control action and realize the high precision performance. In addition, the stabilities of two subsystems are demonstrated by Lyapunov theory, respectively. Lastly, the simulation results are given to illustrate the effectiveness and robustness of the proposed control method in the presence of external disturbances.

Continuous higher-order sliding mode control with time-varying gain for a class of uncertain nonlinear systems

This paper presents a continuous higher-order sliding mode (HOSM) control scheme with time-varying gain for a class of uncertain nonlinear systems. The proposed controller is derived from the concept of geometric homogeneity and super-twisting algorithm, and includes two parts, the first part of which achieves smooth finite time stabilization of pure integrator chains. The second part conquers the twice differentiable uncertainty and realizes system robustness by employing super-twisting algorithm. Particularly, time-varying switching control gain is constructed to reduce the switching control action magnitude to the minimum possible value while keeping the property of finite time convergence. Examples concerning the perturbed triple integrator chains and excitation control for single-machine infinite bus power system are simulated respectively to demonstrate the effectiveness and applicability of the proposed approach.

A modified sliding mode approach for synchronization of fractional-order chaotic/hyperchaotic systems by using new self-structuring hierarchical type-2 fuzzy neural network

This paper presents a new adaptive sliding mode control approach for the synchronization of the uncertain fractional-order chaotic systems. A self-structuring hierarchical type-2 fuzzy neural network (SHT2FNN) is proposed for estimation of uncertainties. Also the switching control action in the conventional sliding mode scheme is replaced by combination type-2 fuzzy neural network (T2FNN) with hyperbolic tangent function. In SHT2FNN, the number of rules is determined by a proposed algorithm. Adaptation laws of all trainable parameters of T2FNN and the consequent parameters of SHT2FNN, are derived based on Lyapunov stability analysis. The simulation results on two kind systems: Genio-Tesi and Coullet System and fractional-order hyper-chaotic Lorenz system, confirm the efficacy of the proposed scheme in synchronization of the uncertain fractional-order hyperchaotic and fractional-order chaotic systems.The proposed controller is robust against the approximation error and external disturbance. The proposed self-structuring algorithm in this paper is simple and it can be applied in the high dimensional problems. Furthermore, the proposed algorithm can delete unimportant rules. Adjusting the structure of the T2FNN in the hierarchical form ensures that the estimation error is very small so it can be negligible. Furthermore, the proposed strategy guarantees the robustness of controller.

An adaptive chattering-free PID sliding mode control based on dynamic sliding manifolds for a class of uncertain nonlinear systems

This paper proposes a new dynamic PID sliding mode control technique for a class of uncertain nonlinear systems. The offered controller is formulated based on the Lyapunov stability theory and guarantees the existence of the sliding mode around the sliding surface in a finite time. Furthermore, this approach can eliminate the chattering phenomenon caused by the switching control action and can realize high-precision performance. Moreover, an adaptive parameter tuning method is proposed to estimate the unknown upper bounds of the disturbances. Simulation results for an inverted pendulum system demonstrate the efficiency and feasibility of the suggested technique.

Integral Sliding Mode Control for Fast Tool Servo Diamond Turning of Micro-Structured Surfaces

Fast Tool Servo (FTS) diamond turning is a promising machining process for fabricating high precision micro-structured surfaces. However, the dynamics of FTS affects its performance and causes form error in the machined surfaces, thus shortening the useful bandwidth of the FTS for precision machining. In this paper, an Integral Sliding Mode Control (ISMC) algorithm is proposed to control the FTS in order to achieve the desired closed-loop dynamics. The robustness of the ISMC to disturbance and model uncertainties or variations is ensured by the implementation of disturbance estimation and an integral switching control action. The influence of the FTS dynamics can thereby be minimized by modifying the tool path offline with the inverse of the desired dynamics. Experiments on machining of typical micro-structured surfaces show that the proposed method is effective in reducing the FTS dynamics induced form error in the machined surface.

Constrained switching stabilization of linear uncertain switched systems using piecewise linear Lyapunov functions

The problem of switching stabilizability of linear uncertain switched systems with unstable modes has recently attracted increased interest. For a given collection of unstable linear uncertain subsystems, the problem is to determine asymptotically stabilizing switching signals or to ascertain the absence of such laws. In this paper, we deal with the switching stabilizability problem for a class of autonomous continuous-time switched linear systems with time-varying parametric uncertainties in the presence of additional state constraints. With a special emphasis on two-dimensional systems we extend previous relevant results in the literature, and we propose a computational technique that generates piecewise linear Lyapunov functions of a convex or non-convex nature. The algorithm is graph-based and consists of determining controlled invariant polytopes induced by systematic conic decompositions of the state-space and corresponding state-dependent switching control actions. Further extension of this computational tool to higher dimensional systems is also discussed.

A novel dynamic terminal sliding mode control of uncertain nonlinear systems

A new dynamic terminal sliding mode control (DTSMC) technique is proposed for a class of single-input and single-output (SISO) uncertain nonlinear systems. The dynamic terminal sliding mode controller is formulated based on Lyapunov theory such that the existence of the sliding phase of the closed-loop control system can be guaranteed, chattering phenomenon caused by the switching control action can be eliminated, and high precision performance is realized. Moreover, by designing terminal equation, the output tracking error converges to zero in finite time, the reaching phase of DSMC is eliminated and global robustness is obtained. The simulation results for an inverted pendulum are given to demonstrate the properties of the proposed method.