Dynamics Of Control System Research Articles

High-Bandwidth Sensorless Algorithm for AC Machines Based on Square-Wave-Type Voltage Injection

This paper describes a new control algorithm which can enhance the dynamics of a sensorless control system and gives a precise sensorless control performance. Instead of the conventional sinusoidal-type voltage injection, a square-wave-type voltage injection incorporated with the associated signal processing method is proposed in this paper. As a result, the error signal can be calculated without low-pass filters and time delays, and the position estimation performance can be enhanced. Using the proposed method, the performance of the sensorless control can be enhanced; the bandwidth of the current controller was enhanced up to 250 Hz, and that of the speed controller was up to 50 Hz.

Model-based characterization of ventilatory stability using spontaneous breathing

Cyclic ventilatory instabilities are widely attributed to an increase in the sensitivity or loop gain of the chemoreflex feedback loop controlling ventilation. A major limitation in the conventional characterization of this feedback loop is the need for labor-intensive methodologies. To overcome this limitation, we developed a method based on trivariate autoregressive modeling using ventilation, end-tidal Pco(2) and Po(2); this method provides for estimation of the overall "loop gain" of the respiratory control system and its components, chemoreflex gain and plant gain. Our method was applied to recordings of spontaneous breathing in 15 anesthetized, tracheostomized, newborn lambs before and after administration of domperidone (a dopamine D(2)-receptor antagonist that increases carotid body sensitivity). We quantified the known increase in hypoxic ventilatory sensitivity in response to domperidone; controller gain for O(2) increased from 0.06 (0.03, 0.09) l·min(-1)·mmHg(-1) to 0.09 (0.08, 0.13) l·min(-1)·mmHg(-1); median (interquartile-range). We also report that domperidone increased the loop gain of the control system more than twofold [0.14 (0.12, 0.22) to 0.40 (0.15, 0.57)]. We observed no significant changes in CO(2) controller gain, or plant gains for O(2) and CO(2). Furthermore, our estimate of the cycle duration of periodic breathing compared favorably with that observed experimentally [measured: 7.5 (7.2, 9.1) vs. predicted: 7.9 (7.0, 9.2) breaths]. Our results demonstrate that model-based analysis of spontaneous breathing can 1) characterize the dynamics of the respiratory control system, and 2) provide a simple tool for elucidating an individual's propensity for ventilatory instability, in turn allowing potential therapies to be directed at the underlying mechanisms.

Codimension-two singularities on the stability boundary in 2D Filippov systems

AbstractBifurcation theory provides powerful tools for the analysis of the dynamics of open-loop or closed-loop nonlinear control systems. These systems are Filippov (or piecewise smooth) when the dynamics depends discontinuously on the state, for example as a consequence relay feedback actions. In this paper we contribute to the analysis of codimension-two bifurcations in Filippov systems by reporting some results on the equilibrium bifurcations of 2D systems that involve a sliding limit cycle. There are only two such local bifurcations: a degenerate boundary focus that we call homoclinic boundary focus; and the boundary Hopf. We address both of them, and provide the complete set of curves that exist around such codimension-two bifurcation points. Existing numerical software can be used to exploit these results for the analysis of the stability boundaries of nonlinear piecewise smooth control systems. In the final part of this paper, we discuss a 2D Filippov system modelling an ecosystem subject to on-off harvesting control that exhibits both codimension-two bifurcations.

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.

The Feedback Control of Drives with Low Acceleration and Deceleration Rate of Motor

The paper proposes an algorithm for control of processes based on variable-speed drives with low acceleration and deceleration rate of the motor, which determines the dynamics of the whole control system. The results of investigation of the controller based on the proposed algorithm are presented and discussed. The controller provides good transient performance of the control system response in case when the drives with different motor acceleration and deceleration rates are used.

Two-mode dynamics in pulse-modulated control systems

Pulse-modulated converter systems play an important role in modern power electronics. Systems of this type also deserve considerable theoretical interest because of the complex interplay they exhibit between ordinary (smooth) bifurcations and so-called border-collision bifurcations generated by the switching dynamics. Particularly interesting are the unusual transitions to torus dynamics, i.e., to a mode of behavior in which the regular switching dynamics is modulated by another oscillatory mode that may arise through instability in the feedback control. Using the model of a two-level DC/DC converter as an example the paper provides a survey of three new mechanisms of torus bifurcation that can be observed in pulse-modulated control systems. The paper concludes with a discussion of the influence that operation in the torus regimes will have on the efficiency of the converter.

A novel optical granulometry algorithm for ore particles

This paper proposes a novel algorithm to detect the particle size distribution of ores with irregular shapes and dim edges. This optical granulometry algorithm is particularly suitable for blast furnace process control, so its result can be used directly as a reliable basis for control system dynamics optimization. The paper explains the algorithm and its concept, as well as its method, which consists of five steps to detect ore granularity and distribution. A series of comparative experiments under industrial environments proved that this novel algorithm, compared with conventional ones, improves the accuracy of granulometry.

Improved 48-pulse static synchronous compensator for high-voltage applications

A modified three-level 48-pulse ±100 MVAr static synchronous compensator (STATCOM) employing four pairs of elementary six-pulse neutral-point diode-clamped gate turn-off thyristor-based voltage source converters with fundamental frequency switching modulation is realised using angle control methodology and pre-calculated dead angle (the duration in which converter-terminal voltage is clamped to zero) in d–q synchronous rotating frame. With a magnetics configuration designed for summing up of output voltages of four converter pairs and simultaneously stepping up of its voltage to the transmission level, and employing proportional and integral controllers in the control, the operating performance equivalent to 96-pulse STATCOM is achieved through optimising harmonics distortion. This compensator is modelled and its performance is simulated in MATLAB using SimPowerSystem toolbox for voltage regulation in transmission system. The obtained results show reasonably good characteristics of the compensator to control system dynamics under steady-state and dynamic system conditions.

Laboratory tutorial practice with facility for attitude control simulation

The paper presents a combined approach to teaching of Spaceflight Dynamics, Theoretical Mechanics and Control Theory. In addition to a standard lecture course, this approach provides hands-on training at the laboratory, offering to the student a possibility to develop, design, assemble and test his/her own project of a nanosatellite attitude control system. We describe the software for mathematical modeling, the facilities for laboratory simulation of controlled system dynamics and student training based on these facilities.

Characterization of Semi-active Control System Dynamics with Magneto-rheological Suspensions

This paper characterizes two semi-active control algorithms through strategy analysis and parametric simulation study. A brief literature review discloses two kinds of semi-active controls: non-model based skyhook-like control policy (or skyhook variations), and model-based clipped semi-active control strategies. Both can be formulated as a bi-state control algorithm. In this paper, the no-jerk skyhook control policy is chosen to represent bi-state strategies, while a nonlinear adaptive semi-active control algorithm without need of clipping control signals is selected for comparison study. Then the studied MR suspension and its model setup are presented. In the paper we explain dynamic analysis approach and controller tuning for this simulation study. While analytic analysis of strategies is based on linear base-excited vibration systems by using transmissibility plots, simulation study adopts sine-sweep excitations so that comparison of transient dynamics could be stressed out and simultaneously the vibration isolation capability compared in the frequency domain by directly observing the time domain data. In addition, one pure-tone excitation case is simulated to explain higher harmonics inherent with bi-state skyhook controls. From the simulation study, the effectiveness of both semi-active controls can be observed for vibration isolation. In addition, the adaptability of both selected controls is compared regarding plant variations and different excitation profiles, both of which are typical in vehicle suspension systems. Finally the characteristics of these two semi-active controls are summarized from the simulation findings.

Démarche d'aide à la conception par approche multimode des SED

Base sur la theorie du controle par supervision (TCS), nous proposons une demarche d'aide a l'etude de la dynamique des Systemes a Evenements Discrets (SED). Situee en amont du cycle de conception des lois de commande des SED, notre proposition concerne la gestion des modes de fonctionnement. L'objectif est de permettre tout d'abord l'etude formelle de la dynamique du systeme controle dans chaque mode puis celle de la succession de ces dynamiques. Dans cet article nous insisterons particulierement sur la presentation des differentes etapes de construction et de generation automatique des modeles ainsi que sur les possibilites de validation de ceux-ci. Based on the Supervisory Control Theory, this paper introduces a framework to help study the dynamics of Discrete Event Systems (DES). Upstream of the design process of control law in DES, the proposal focuses on the management modes of operation. The goal is to first allowing a formal study of the controlled system's dynamics in each mode and secondly studying the mode switching. This article is focused on the presentation of the different stages of design, the automatic generation of models and the possibilities of validating them.

Analysis of dynamics of electric-mode control system for an arc steel furnace

Recommendations on the stabilization of dynamic processes and extension of the range of stable electric-mode control for arc steel furnaces with differential error meters are presented.

Hopf bifurcation and oscillations in a communication network with heterogeneous delays

In this paper, we investigate stability, bifurcation and oscillations arising in a single-link communication network model with a large number of heterogeneous users adopting a Transmission Control Protocol (TCP)-like rate control scheme with an Active Queue Management (AQM) router. In the system considered, different user delays are known and fixed but taken from a given distribution. It is shown that for any given distribution of delays, there exists a critical amount of feedback (due to AQM) at which the equilibrium loses stability and a limit cycling solution develops via a Hopf bifurcation. The nature (criticality) of the bifurcation is investigated with the aid of Lyapunov–Schmidt perturbation method. The results of the analysis are numerically verified and provide valuable insights into dynamics of the AQM control system.

Static synchronous compensators (STATCOM): a review

Fast acting static synchronous compensator (STATCOM), a representative of FACTS family, is a promising technology being extensively used as the state-of-the-art dynamic shunt compensator for reactive power control in transmission and distribution system. Over the last couple of decades, researchers and engineers have made path-breaking research on this technology and by virtue of which, many STATCOM controllers based on the self-commutating solid-state voltage-source converter (VSC) have been developed and commercially put in operation to control system dynamics under stressed conditions. Because of its many attributes, STATCOM has emerged as a qualitatively superior controller relative to the line commutating static VAR compensator (SVC). This controller is called with different terminologies as STATic COMpensator advanced static VAR compensator, advanced static VAR generator or static VAR generator, STATic CONdenser, synchronous solid-state VAR compensator, VSC-based SVC or self-commutated SVC or static synchronous compensator (SSC or S2C). The development of STATCOM controller employing various solid-state converter topologies, magnetics configurations, control algorithms, switching techniques and so on, has been well reported in literature with its versatile applications in power system. A review on the state-of-the-art STATCOM technology and further research potential are presented classifying more than 300 research publications.

Learning from neural control of nonlinear systems in normal form

A deterministic learning theory was recently proposed which states that an appropriately designed adaptive neural controller can learn the system internal dynamics while attempting to control a class of simple nonlinear systems. In this paper, we investigate deterministic learning from adaptive neural control (ANC) of a class of nonlinear systems in normal form with unknown affine terms. The existence of the unknown affine terms makes it difficult to achieve learning by using previous methods. To overcome the difficulties, firstly, an extension of a recent result is presented on stability analysis of linear time-varying (LTV) systems. Then, with a state transformation, the closed-loop control system is transformed into a LTV form for which exponential stability can be guaranteed when a partial persistent excitation (PE) condition is satisfied. Accurate approximation of the closed-loop control system dynamics is achieved in a local region along a recurrent orbit of closed-loop signals. Consequently, learning of control system dynamics (i.e. closed-loop identification) from adaptive neural control of nonlinear systems with unknown affine terms is implemented.

Large Scale Nonlinear Control System Fine-Tuning Through Learning

Despite the continuous advances in the fields of intelligent control and computing, the design and deployment of efficient large scale nonlinear control systems (LNCSs) requires a tedious fine-tuning of the LNCS parameters before and during the actual system operation. In the majority of LNCSs the fine-tuning process is performed by experienced personnel based on field observations via experimentation with different combinations of controller parameters, without the use of a systematic approach. The existing adaptive/neural/fuzzy control methodologies cannot be used towards the development of a systematic, automated fine-tuning procedure for general LNCS due to the strict assumptions they impose on the controlled system dynamics; on the other hand, adaptive optimization methodologies fail to guarantee an efficient and safe performance during the fine-tuning process, mainly due to the fact that these methodologies involve the use of random perturbations. In this paper, we introduce and analyze, both by means of mathematical arguments and simulation experiments, a new learning/adaptive algorithm that can provide with convergent, an efficient and safe fine-tuning of general LNCS. The proposed algorithm consists of a combination of two different algorithms proposed by Kosmatopoulos (2007 and 2008) and the incremental-extreme learning machine neural networks (I-ELM-NNs). Among the nice properties of the proposed algorithm is that it significantly outperforms the algorithms proposed by Kosmatopoulos as well as other existing adaptive optimization algorithms. Moreover, contrary to the algorithms proposed by Kosmatopoulos , the proposed algorithm can operate efficiently in the case where the exogenous system inputs (e.g., disturbances, commands, demand, etc.) are unbounded signals.

Control Communication Complexity of Nonlinear Systems

The interaction of information and control has been a topic of interest to system theorists that can be traced back at least to the 1950's when the fields of communications, control, and information theory were new but developing rapidly. Recent advances in our understanding of this interplay have emerged from work on the dynamical effect of state quantization together with results connecting communication channel data rates and system stability. Although this work has generated considerable interest, it has been centrally concerned with the relationship between control system performance and feedback information processing rates while ignoring the complexity (i.e. the cost of information processing). The concepts of communication and computation complexity of a controlled dynamical system based on digitized information lie in what is largely an uncharted area. In our recent work an attempt was made to explore this area by introducing a new measure of communication complexity for a two-player distributed control system. This complexity is named control communication complexity (CCC). It is based on the communication complexity concept defined in distributed computing and seeks to connect the complexity of information exchange over finite bandwidth channels with the control system dynamics. The purpose of the present paper is to extend the study of control communication complexity to an interesting class of continuous-time control systems that have appeared in the recent literature dealing with quantum communication and control systems. An interesting aspect of this extension is that it brings together heretofore independent research themes that have been prominent in the research career of Roger Brockett.

A New Speed Observer Based on Fuzzy Sliding Mode Sensorless Control Scheme for a High- Performance Induction Motor Drive

The subject of the paper is the implementation of fuzzy sliding mode control conception for robust accurate tracking of induction motor drive operating in a high-performance drives environment. The introducing of fuzzy sliding mode in the control system helps to achieve a good dynamic response, disturbance rejection and low to plant parameter variations of the A.C drive. The fuzzy sliding mode controller combines the advantages of both fuzzy controllers and sliding mode controllers. By combining variable structure systems theory and fuzzy logic concept, a new algorithm is developed. The proposed control scheme can drive the dynamics of controlled system into a designed sliding surface in finite time and guarantee the property of asymptotical stability. The synthesis of sliding mode control and the control laws for the controls of speed are described. In order to verify the performances of the proposed observers and control algorithms and to test behaviour of the controlled system, numerical and real experiments are achieved.

Fractional optimal control problem of a distributed system in cylindrical coordinates

In this work, Fractional Optimal Control Problem (FOCP) of a Distributed system is investigated in cylindrical coordinates. Axis-symmetry naturally arises in the problem formulation. The fractional time derivative is described in the Riemann–Liouville (RL) sense. The performance index of a FOCP is considered as a function of state and control variables and system dynamics are given as a Partial Fractional Differential Equation (PFDE). The method of separation of variables is used to find the solution of the problem. Eigenfunctions are used to eliminate the terms containing space parameters and to define the problem in terms of a set of generalized state and control variables. For numerical computations, Grünwald–Letnikov (GL) approach is used. A time-invariant example is considered to demonstrate the effectiveness of the formulation. The comparison of analytical and numerical solutions is given using simulation results and also it can be seen that analytical and numerical results converge each other. In addition, simulation results for different values of order of derivative, time discretizations and eigenfunctions are analyzed.

Washout Control for Manual Operations

It is known that limitations of human accuracy in manual manipulation hinder the quality of work performed by human operators of manual control systems. Indeed, movements of operators are apt to cause undesirable vibrations in manual control systems. In this paper, we propose a new operator-support control scheme for suppressing harmful oscillatory motions in such systems without disturbing human operator's manipulation. The proposed scheme is based on the fact that steady-state blocking zeros of a feedback controller do not affect the steady-state control input. A finite-dimensional feedback controller with steady-state blocking zeros, called a washout controller in this paper, plays the central role in support for operator's manipulation. However, the dynamics of a manual control system may become different significantly from its initial model used for the design of an initial washout controller when it is applied to the manual control system. Such difference can result in poor performance of operator-support control. In order to improve it, an iterative procedure is presented for redesign of washout controllers based on closed-loop subspace identification. Closed-loop identification is performed to refine the model for the control design, and then a more sophisticated washout controller is obtained using the identified model. The effectiveness of the proposed scheme is demonstrated by an experiment on manual control of an inverted pendulum.