Decentralized Control Configuration Research Articles

Model validation and Robust State Feedback control for nonlinear subway traffic networks

This paper develops a nonlinear Discrete-Event (DE) model for Intersecting Lines (ILs) of a Subway Network (SN). A class of Monte Carlo (MC) methods based on repeated random values is employed to validate the model. Model validation is performed by generating random values for delay rates and external disturbances. After model validation, a Robust State Feedback (RSF) controller is designed to compensate the delays caused by disturbances. Simulations are performed based on the characteristics and actual data of lines 2 and 4 of the Tehran subway to demonstrate the effectiveness of the proposed approach. Simulation results show the accuracy and proper performance of the proposed model. In addition, the closed-loop responses demonstrate the effectiveness of the proposed RSF controller for centralized and decentralized control configurations.

Active Vibration Mitigation of Bladed Structures With Piezoelectric Patches by Decentralized Positive Position Feedback Controller

Abstract This paper proposes an active damping system to mitigate the vibration of bladed assemblies. The damping system consists of multiple pairs of piezoelectric patches accompanied by a decentralized control configuration. To maximize the control authority, the size and the location of the patches are optimized based on maximizing the strain energy. In each pair, one patch is used as a sensor and the other one as an actuator. As the control plants of such configuration have no high-frequency roll-off, a second-order low-pass filter known as a positive position feedback (PPF) controller is considered as the control law. The parameters of the controller are tuned based on maximizing the closed-loop damping of the first family of modes. This active damping system is implemented on a monobloc bladed rail which is representative of a portion of bladed drum, i.e., BluM. Numerical simulations are performed to assess the performance of the designed control system and experimental tests are carried out to validate the numerical design.

A decentralized multivariable controller for hydrostatic wind turbine drivetrain

AbstractA hydrostatic drivetrain transmits wind turbine energy to a generator. One hydrostatic transmission system (HTS) configuration utilizes a fixed displacement pump and a variable displacement motor. The system dynamics are captured in a nonlinear multi‐input multi‐output mathematical model. This paper introduces a decentralized control configuration based on this model to achieve two desired objectives: maximizing the harvested energy without direct measurement of wind and regulating the frequency of the generator without using power electronic converters. To accomplish these objectives, suitable pairing of control actuators and system responses are identified through nonlinear relative gain arrays (RGA) analysis. The pairing also provides a strong decoupling of control loops. So maximum power point tracking (MPPT) is achieved independently while the generator speed is regulated to maintain the frequency of generated power at 60 Hz. Simulation results demonstrate robust performance of MPPT and frequency regulation in the presence of uncertainties in the turbine and HTS model. We also demonstrate that the RGA paired input‐out control configuration offers superior performance over other possible input–output paired control configurations.

Dynamic Modeling of a Parabolic Trough Solar Thermal Power Plant with Thermal Storage Using Modelica

ABSTRACTConcentrating solar power (CSP) technology with thermal energy storage is a renewable and emerging technology. In this work, dynamic models for analyzing and evaluating energy storage concepts and its interaction with the solar field and the power block have been developed. A physical model of a 50 MW CSP plant has been implemented in the modeling language Modelica. The models are developed in a modular, flexible structure with a well-defined interface to easily replace and test modules of various detail and complexity. Models include turbine island, steam generator, solar field, and thermal energy storage system. In addition, a decentralized control configuration has been developed. Results have been successfully validated against the reference plant key steady-state data. Dynamic response of the power block has shown expected behavior, and transient durations were comparable with settling times predicted in literature. Furthermore, the performance of the plant has been evaluated during a typical summer day including effects such as variation of solar irradiance, charging and discharging the heat storage system, and dumping excess heat in the solar field. The summer day scenario results agreed with published performance of the plant.

Control configuration synthesis using agglomerative hierarchical clustering: A graph-theoretic approach

This paper addresses the synthesis of control configurations that have optimal structural coupling characteristics between manipulated inputs and controlled outputs in terms of relative degrees. A recently developed agglomerative hierarchical clustering approach is reformulated in a graph theoretic setting. This allows the efficient generation of decentralized control configuration as well as the entire hierarchy of block decentralized control configurations. In addition, a notion of modularity is used to evaluate the compactness and separation of the resulting clusters, allowing the identification of optimal control configurations. The application of the proposed method is illustrated through case studies on an energy integrated fuel-cell system and a heat exchanger network.

Augmented Lagrangian Genetic Algorithm Based Decentralized Control Configuration Design for Fluid Catalytic Cracking Units

In this work, three decentralized control configuration designs—independent, sequential and simultaneous designs—were used in multivariable feedback configurations for PI control of the riser and regenerator temperatures of FCCU in order to compare their performances. Control design was formulated as optimization problem to minimize infinity norm of weighted sensitivity functions subject to μ-interaction measure bound on diagonal complementary functions of the closed loop system. The optimization problem was solved using augmented Lagrangian genetic algorithm. Simulation results show that simultaneous and independent designs give good response with less overshoot and with no oscillation. Bound on μ-interaction measure is satisfied for both designs meaning that their nominal stabilities are guaranteed; however, it is marginal for simultaneous design. Simultaneous design outperforms independent design in term of robust performance while independent design gives the best performance in terms of robust stability. Sequential design gives the worst performance out of the three designs.

Decentralized Control Framework and Stability Analysis for Networked Control Systems

The combination of decentralized control and networked control where control loops are closed through a network is called decentralized networked control system (DNCS). This paper introduces a general framework that converts a generic decentralized control configuration of non-networked systems to the general setup of networked control systems (NCS). Two design methods from the literature of decentralized control for non-networked systems were chosen as a base for the design of a controller for the networked systems, the first being an observer-based decentralized control, while the second is the well-known Luenberger combined observer–controller. The main idea of our design is to formulate the DNCS in the general form and then map the resulting system to the general form of the NCS. First, a method for designing decentralized observer-based controller is discussed. Second, an implementation using a network is analyzed for the two designs. Third, two methods to analyze the stability of the DNCS are also introduced. Fourth, perturbation bounds for stability of the DNCS have been derived. Finally, examples and simulation results are shown and discussed.

Automated synthesis of control configurations for process networks based on structural coupling

In this paper, a method to systematically synthesize control configurations with favorable structural coupling is developed, using relative degree as a measure of such coupling. Initially, an integer optimization problem is formulated to identify optimal distributions of inputs and outputs (decentralized control configurations) that minimize the overall structural coupling in the network. Then, a hierarchical clustering procedure, which allows identifying groups of inputs and outputs that are strongly connected topologically (block decentralized control configurations), is proposed. The application of the method is illustrated through an example process network.

(Un)conditional consensus emergence under perturbed and decentralized feedback controls

We study the problem of consensus emergence in multi-agent systems via external feedback controllers. We consider a set of agents interacting with dynamics given by a Cucker-Smale type of model, and study its consensus stabilization by means of centralized and decentralized control configurations. We present a characterization of consensus emergence for systems with different feedback structures, such as leader-based configurations, perturbed information feedback, and feedback computed upon spatially confined information. We characterize consensus emergence for this latter design as a parameter-dependent transition regime between self-regulation and centralized feedback stabilization. Numerical experiments illustrate the different features of the proposed designs.

Selection of Sensors for Hydro-Active Suspension System of Passenger Car With Input–Output Pairing Considerations

With respect to weight, energy consumption, and cost constraints, hydro-active suspension system is a suitable choice for improving vehicle ride comfort while keeping its handling. The aim of sensors selection is determining number, location, and type of sensors, which are the best for control purposes. Selection of sensors is related to the selection of measured variables (outputs). Outputs selection may limit performance and also affect reliability and complexity of control systems. In the meanwhile, hardware, implementation, maintenance, and repairing costs can be affected by this issue. In this study, systematic methods for selecting the viable outputs for hydro-active suspension system of a passenger car are implemented. Having joint robust stability and nominal performance of the closed loop is the main idea in this selection. In addition, it is very important to use these methods as a complementation for system physical insights, not supersedes. So, in the first place the system is described and the main ideas in ride comfort control are addressed. An 8 degrees of freedom model of vehicle with passive suspension system is derived and validated. Both linear and nonlinear models of the car which is equipped with hydro-active subsystem are derived. After selecting the outputs, for benefiting from minimum loop interactions, the control configuration is systematically determined. The main goal of selecting control configuration is assessing the possibility of achieving a decentralized control configuration. Finally, the system behavior is controlled by a decentralized proportional–integral–differential (PID) controller. The results indicate the efficiency of the controlled hydro-active suspension system in comparison with the passive system.

Optimal Operation of an Industrial PVC Dryer

This article describes the design of a control structure architecture for an industrial polyvinyl chloride (PVC) dryer, currently operating at Braskem Company (Marechal Deodoro, Alagoas, Brazil). The underlying motivation is to search for a control configuration that leads to optimal economic operation, while promptly rejecting disturbances at lower layers in the control hierarchy. We start by optimizing a nonlinear model of the process with respect to reducing energy consumption as a criterion of optimization for different disturbance scenarios. The results show that it is optimal to control the temperature level of the utilities serving the dryer and the outlet PVC moisture contents at their respective upper bounds. In addition, the flow of air to the dryer should be fixed at its optimum nominal setpoint despite disturbances. Application of this strategy results in a reduction of about 16% in energy consumption with respect to the current dryer operation policy and a 22% increase in throughput under nominal operation. In addition, almost perfect indirect control of the outlet PVC moisture was achieved by tightly controlling a temperature difference in the dryer. The proposed decentralized control configuration gives good dynamic performance for the outlet PVC moisture content with maximum settling time of about 1.8 h for the more difficult disturbance of increasing the inlet slurry moisture content by 40% and magnitude of overshoot of ca. 5% w.r.t. the optimum setpoint for an increase of 20% in PVC feed flow rate to the dryer.

Lithium ion battery system using amorphous carbon in negative electrode and its management technology for HEV applications

We have developed the lithium ion battery system using amorphous carbon in negative electrode and its management technology for hybrid electric vehicle (HEV) applications. The cell has an output power density as high as 3000 W/kg at 50 % state of charge (SOC) and 25 deg.C, and the 48-cell battery module has an output power of 43 kW. To enable effective and adequate use of this high power battery, we have developed new architecture characterized by the newly developed battery control IC, daisy chain communication circuit without isolator and the decentralized control configuration of cell controller and battery controller. Then, we have determined suitable battery control parameters, such as SOC, state of health (SOH) and allowable current/power, taking into consideration the battery characteristics which mainly result from amorphous carbon, system particulars of IIEVs, and the purpose of these parameters. They were adopted into the software of the battery controller. Both software and hardware of the battery controller is made in the form of platform. Because of the excellent characteristics of this battery, its intrinsically reliable controllability, and the platform for battery control technologies, the battery system is promising not only for HEVs, but also for other applications that require both high power and reliability such as a hybrid electric train.

Semicontinuous, middle-vessel, extractive distillation

A decentralized control configuration is proposed for the semicontinuous, extractive distillation of a low-boiling azeotropic mixture of acetone and methanol. The separation is performed in a middle-vessel column (MVC), having a large external middle vessel, from which the column is fed, and to which a full-liquid sidedraw from the stage above the feed tray is sent. The extractive agent, water, feeds the column on a scheduled basis of facilitate the separation. Based upon the simplicity of a decentralized configuraiton and the desire to avoid controller overrides, a DB-control configuration is selected. This configuration, in which the distillate flow rate is manipulated to control the composition of the distillate, and the bottoms flow rate is manipulated to control the composition of the bottoms product, has been widely labeled as inoperable. Herein, the configuration is shown to perform satisfactorily when a middle vessel with a full-liquid sidedraw is utilized. A cyclic campaign is simulated showing the satisfactory performance of the DB-MVC control configuration. The advantages of the control configuration are discussed and design specifics are provided. An analysis of the campaign, highlighting the problems overcome, is given.