Control System Design Tools Research Articles

Real-time energy-efficient operation of a dedicated mechanical subcooling based transcritical CO2 heat pump water heater via multi-input single-output extreme seeking control

In the field of transcritical CO2 systems applied research, dedicated mechanical subcooling (DMS) is one of the most recently investigated and promising solutions, especially for space heating. However, this kind of system brings with it an intrinsic complexity, and to pursue effective and efficient operation, it requires suitable control and optimization strategies. The paper considers a combined transcritical CO2 and R134a -based DMS system and depicts the benefits of using a Multi-Input-Single-Output (MIMO) Extremum Seeking Control (ESC) approach. The real-time optimization strategy was obtained through a Computer-Aided Control System Design (CACSD) tool, exploiting an ad hoc Dymola model of the DMS system that has been validated and tested by using experimental data. The performance of the proposed approach has been compared with standard solutions relying on physical correlations. The MISO-ESC strategy always performed better in terms of system Coefficient of Performance (COP), under both fixed and variable ambient temperature conditions. Finally, the influence of the different refrigerants in the combined DMS system was analyzed from both heating capacity and performance points of view.

Remote Control of a Robotic Unit: A Case Study for Control Engineering Formation

Hands-on experimentation has widely demonstrated its efficacy in engineering training, especially in control formation, since experimentation using computer-aided control system design (CACSD) tools is essential for future engineers. In this context, this article describes a case study for Control Engineering formation, based on a new lab practice for the linear and angular velocity control for a commercial P3-DX robot platform, to teach industrial control. This lab proposal includes all the stages involved in the design of a real control system, from plant identification from an open-loop test to real experimentation of the designed control system. The lab practices proposed have a twofold objective: First, it is an interdisciplinary approach that allows students to put into practice the skills from other subjects in the curriculum, facilitating the integration of knowledge. In addition, it allows increasing the motivation of the students by working with a complex and realistic plant. The proposal has been evaluated through the grades of the students, as well as the perception of both students and instructors, and the results obtained allow to confirm the benefits of the proposal.

Complex State Variables as Analytical Tool for Control System Design of Medium-Voltage Drives

Complex state variables are used to analyze the dynamics of medium-voltage drives. These operate at low switching frequency to reduce the dynamic losses of the power semiconductor devices. It results in a low sampling rate of the digital signal processing system, causing signal delays that deteriorate the dynamic behavior. Undesired cross-coupling results between the current components id and iq. The effect is shown to be even more adverse than described by the conventional control theory. The solution is modeling the system by single-complex state variables. These permit designing a current controller of high dynamic performance, which exhibits zero cross-coupling. Improved performance at very low switching frequency is demonstrated by experimental results.

Experimental measurement for non-spherical bulk materials flow behaviour in rectangular enclosure

Dust control is a major concern in food industries since dust emission is generally unavoidable during bulk material handling. Obtaining a better understanding of the way particles are pulled away from a stream of particles and the generation of a dust cloud will assist in the design of more efficient dust control systems. In this paper, the particles- air interactions during free fall of bulk powder is reviewed. An experimental investigation was performed to elucidate the effect of conveying velocity and particle properties on velocity profiles. The Laser Doppler Anemometry (LDA) technique was employed to measure the particle velocity during free fall. Results revealed that the particle properties (particles with flaky shapes and lower bulk density) had a great influence on dust cloud generation as compared to the conveying velocity. The results presented here may facilitate the development of a quantitative tools for dust control system design that deal with a falling stream of bulk powder.

An ontology-based approach to knowledge representation for Computer-Aided Control System Design

Different approaches have been used in order to represent and build control engineering concepts for the computer. Software applications for these fields are becoming more and more demanding each day, and new representation schemas are continuously being developed. This paper describes a study of the use of knowledge models represented in ontologies for building Computer Aided Control Systems Design (CACSD) tools. The use of this approach allows the construction of formal conceptual structures that can be stated independently of any software application and be used in many different ones. In order to show the advantages of this approach, an ontology and an application have been built for the domain of design of lead/lag controllers with the root locus method, presenting the results and benefits found.

Multi-objective optimization based tuning tool for industrial 2doF PID controllers

A computer-aided control system design tool is presented. This tool is able to take advantage of a database of Pareto optimal PID controllers. The idea is to give to the control engineer an useful tool to close the gap between the optimization procedure and the final selection of the parameters. The input to the tool are the allowed degradation of the considered cost functions, the desired level of robustness and the information of the plant, in the form of second order plus time delay model or a set of input-output data. The tool is written as a graphical user interface in MATLAB© and freely available to anyone.

A Light-Weight Rapid Control Prototyping System Based on Open Source Hardware

In this paper, we propose a light-weight rapid control prototyping (RCP) system based on off-the-shelf open source hardware to achieve high performance computing, cost effectiveness, portability, and easy accessiblity. The proposed RCP system consists of a PC-based computer-aided control system design (CACSD) tool for computing control action and tiny palm-sized open source hardware for input and output (I/O) operation and data transfer through a built-in high-speed USB interface. The popular-priced and portable open source hardware is used as a bridge between CACSD tools and real plants to deliver the control and sensor data at the sampling time points. Ten I/O function blocks written in C code are developed based on the CACSD tool employed for the proposed light-weight RCP system in order to handle I/O operation in a simple way. In addition, we suggest two practical strategies, a batch transfer strategy and a variable sampling period method, to increase the sampling rate of the control system. It is shown through experiment that the proposed light-weight RCP system works well up to a sampling rate of 2 kHz without adopting expensive hardware and C code generators. It is expected that the proposed RCP system will be considered as affordable and readily available to schools for mass education.

An Experience of CACSD for Networked Control Systems: From Mechatronic Platform Identification to Control Implementation

Continual advances in information and communication technologies (ICT) are revolutionizing virtual education and bringing new tools on the market that provide virtual solutions to a range of problems. Nevertheless, nonvirtual experimentation using computer-aided control system design tools is still fundamental for future engineers. This paper describes a control course laboratory element, which is designed to teach electronic control engineering, in which students use a networked control system to steer and drive an electric car prototype. Multidisciplinary in nature, this laboratory allows students to take advantage of their previous academic training, as they model the plant from an open-loop test and contrast the simulated behavior with experimental results obtained on the prototype. A goal in this work was that students, across multiple engineering disciplines, should be able to integrate the knowledge acquired throughout their degree studies. An evaluation of students' grades, and their perception of the course, was conducted; this confirmed the educational benefits of the approach.

Modeling of Energy Demand of a High-Tech Greenhouse in Warm Climate Based on Bayesian Networks

This work analyzes energy demand in a High-Tech greenhouse and its characterization, with the objective of building and evaluating classification models based on Bayesian networks. The utility of these models resides in their capacity of perceiving relations among variables in the greenhouse by identifying probabilistic dependences between them and their ability to make predictions without the need of observing all the variables present in the model. In this way they provide a useful tool for an energetic control system design. In this paper the acquisition data system used in order to collect the dataset studied is described. The energy demand distribution is analyzed and different discretization techniques are applied to reduce its dimensionality, paying particular attention to their impact on the classification model’s performance. A comparison between the different classification models applied is performed.

Linear covariance techniques for closed-loop guidance navigation and control system design and analysis

While linear covariance analysis is widely used for navigation system design and analysis, it is often overlooked as a tool for closed-loop guidance navigation and control (GN&C) system design and analysis. This article presents an overview of the techniques and methods required to develop a linear covariance analysis tool for a close-loop GN&C system. Then, using a simple nonlinear closed-loop GN&C problem as a guide, the capabilities of linear covariance analysis for the design and analysis of closed-loop systems are demonstrated. It is shown that linear covariance can be accurately applied to a closed-loop system with time-to-go guidance, dead-reckoning navigation, and a Kalman filter for state estimation. The accuracy and efficiency of linear covariance analysis is shown by direct comparison to Monte Carlo analysis results, and the value of linear covariance analysis is highlighted by presenting several analysis capabilities that are often required in the design and analysis of closed-loop GN&C systems. It is also shown how the efficiency of linear covariance enables new design methodologies, one of which is presented in this article, that would otherwise be prohibitive with Monte Carlo analysis.

Constrained Nonlinear Polynomial Time-Delay Systems: A Sum-of-Squares Approach to Estimate the Domain of Attraction

A sum-of-squares (SOS) approach is proposed to estimate the domain of attraction (DoA) of regulated nonlinear polynomial time-delay systems subject to input constraints. It will be shown that the joint use of semialgebraic geometric arguments and semidefinite programming methods provides an efficient tool for Lyapunov-based control system analysis and design for this class of nonlinear delayed systems. Specifically, a two-step procedure is presented which consists of deriving first a Lyapunov-Krasovskii functional/controller pair complying with the prescribed constraints and computing then an estimate of the DoA.

The State-of-the-Art of Gas-Liquid Cylindrical Cyclone Control Technology: From Laboratory to Field

Conventional gas-liquid separators are vessel-type with simple level and pressure control since the residence time is large. Compact gas-liquid separators, such as gas-liquid cylindrical cyclone (GLCC©—gas-liquid cylindrical cyclone—copyright, University of Tulsa, 1994), have emerged recently as alternatives to reduce size and increase separation efficiency for onshore, offshore, and subsea applications. As compared with the vessel-type separators, compact separators are simple, low-cost, low-weight, require little maintenance and are easy to install and operate. However, the residence time of the GLCC is very small. Consequently, it can be destabilized easily due to high flow variations at the inlet, for example, slugging, without the aid of fast and accurate control systems. In the past, lack of understanding of control system dynamics and design tools has prevented this technology from fast field deployment. The objective of this study is to present a review of the compact gas-liquid separator (GLCC) control technology. This includes the development of control strategies, control system design, dynamic simulation, experimental investigation, and field applications. The performance of compact gas-liquid separator (GLCC) strongly depends on the liquid level and/or separating pressure. In this investigation, several control strategies have been presented for field applications of gas-liquid compact separators. Especially, an optimal control strategy was developed for handling slug flow and optimizing the system performance in terms of reduced or eliminated liquid carry-over or gas carry-under. The developed strategies have been used for the design of several hundreds of GLCC applications, currently in operation in the field. Details of some of these applications are also presented. This study provides the state-of-the-art of gas-liquid compact separator control technology from the laboratory to the field.

System GAMMA: the directives of finite‐frequency identification

PurposeThe purpose of this paper is to present the results in the area of modern computer‐aided control system design tools relating to system identification.Design/methodology/approachThe finite‐frequency identification method was designed for the needs of active identification. The test signal represents the sum of harmonics with automatically tuned (self‐tuned) amplitudes and frequencies where the number of harmonics does not exceed the state space dimension of the plant. The self‐tuning of amplitudes is carried out to satisfy those requirements on the bounds of the input and output which hold true in the absence of a test signal.FindingsIn this paper, the software implementation of finite‐frequency identification method in the system GAMMA is considered. GAMMA is the two‐level computer‐aided design (CAD) tool for identification and controllers algorithms synthesis for linear plants.Practical implicationsThe system GAMMA is the complete and really working system.Originality/valueA new structure of the CAD tool for engineers‐developers of control systems is proposed and its program implementation is described. The new variant of finite‐frequency identification method with self‐tuning of identification parameters (test signal and identification time) is considered.

A31 EXCEL VBAによる制御系設計ソフトウェアの開発(制御系設計とモデリング)

A31 EXCEL VBAによる制御系設計ソフトウェアの開発(制御系設計とモデリング)

Global optimization toolbox for maple [Product review

Global optimization seeks to find the best solution to a constrained nonlinear optimization problem by performing a complete search over a set of feasible solutions. The global optimization toolbox for Maple provides a widely applicable, fully integrated development environment that can support control engineering applications and help realize the significant potential that global optimization has a valuable tool in control system design.

LEARNING ABOUT FLIGHT CONTROL USING AIRBORNE SIMULATION

The article deals with an educational concept in the field of experimental flight systems and applied flight control. Within the scope of a university teaching position at the Technical University of Berlin, the author provides students with theoretical information and practical experiences in flight control and flight-testing. The students come from different branches of aeronautical education and have very different previous knowledge. Within two semesters the students learn in the lectures about particular aspects of theoretical and applied flight control, aircraft dynamics, man/machine systems, real-time simulation, flight-testing, software engineering concepts, etc. In laboratory courses the students work with a modern computer based simulation and control system design tool. They learn how to analyze dynamic systems and how they can be influenced by feedforward and feedback controllers. In the last part of the second semester the designed controllers are implemented in the fly by wire system of DLRs flying test-bed ATTAS (Advanced Technologies Testing Aircraft System). The flight-tests are performed by DLR test pilots. After the two semesters the students have to write a report including all theoretical results and flight-test data evaluations and they have to pass an oral examination.

HIFOO - A MATLAB PACKAGE FOR FIXED-ORDER CONTROLLER DESIGN AND H∞ OPTIMIZATION

H∞ controller design for linear systems is a difficult, nonconvex and typically nonsmooth (nondifferentiable) optimization problem when the order of the controller is fixed to be less than that of the open-loop plant, a typical requirement in e.g. embedded aerospace control systems. In this paper we describe a new MATLAB package called HIFOO, aimed at solving fixed-order stabilization and local optimization problems. It depends on a new hybrid algorithm for nonsmooth, nonconvex optimization based on several techniques, namely quasi-Newton updating, bundling and gradient sampling. The user may request HIFOO to optimize one of several objectives, including H∞ norm, which requires either the Control System Toolbox for MATLAB or, for much better performance, the linorm function in the SLICOT package. No other external package is required, but the quadratic programming code quadprog from either MOSEK or the Optimization Toolbox for MATLAB is recommended. Numerical experiments on benchmark problem instances from the COMPleib database indicate that HIFOO could be an efficient and reliable computer-aided control system design (CACSD) tool, with a potential for realistic industrial applications.

Contraction analysis of non-linear distributed systems

Contraction theory is a comparatively recent dynamic analysis and non-linear control system design tool based on an exact differential analysis of convergence. This paper extends contraction theory to local and global stability analysis of important classes of non-linear distributed dynamics, such as convection-diffusion-reaction processes, Lagrangian and Hamilton–Jacobi dynamics, and optimal controllers and observers. By contrast with stability proofs based on energy dissipation, stability and convergence can be determined for energy-based systems excited by time-varying inputs. The Hamilton–Jacobi–Bellman controller and a similar optimal non-linear observer design are studied based on explicitly computable conditions on the convexity of the cost function. These stability conditions extend the well-known conditions on controllability and observability Grammians for linear time-varying systems, without requiring the unknown transition matrix of the underlying differential dynamics.

Interactive control system design

This contribution describes a LabVIEW-based interactive computer-aided control system design tool. Although it does not provide the flexibility of common low-level design tools, it offers a set of comfortable, ready-to-use solutions for plant identification, loop-shaping or LQR/LQG-controller design and controller implementation. The tool integrates into industrial plant control and enables engineers to efficiently do the control system design from plant identification to controller implementation on the same platform. The user interface with convenient system editors and analysis tools facilitates the user to interactively attain the design goals. If desired, a configurable wizard leads the user through the design process.

MODELCAT – A MODEL CATALOGUE BASED APPROACH TO PROCESS MODELLING

The paper describes a new approach to generate plant models automatically at the end of the plant engineering process using a simulation model catalogue. Such a model can be used to test the functionality of the plant by simulation before it is built and to simulate and optimise the integrated control functions using Computer Aided Control System Design (CACSD) tools. To demonstrate the feasibility of the proposed approach, the prototype software module Modelcat (industrial Model Catalogue) was realised. Modelcat is based on the plant CAE system Comos PT and makes use of the simulation tools Matlab/Simulink and gProms.