Showing papers on "Control theory published in 2001"

Design and control of an LCL-filter-based three-phase active rectifier

Abstract: This paper proposes a step-by-step procedure for designing the LCL filter of a front-end three-phase active rectifier. The primary goal is to reduce the switching frequency ripple at a reasonable cost, while at the same time achieving a high-performance front-end rectifier (as characterized by a rapid dynamic response and good stability margin). An example LCL filter design is reported and a filter has been built and tested using the values obtained from this design. The experimental results demonstrate the performance of the design procedure both for the LCL filter and for the rectifier controller. The system is stable and the grid current harmonic content is low both in the lowand high-frequency ranges. Moreover, the good agreement that was obtained between simulation and experimental results validates the proposed approach. Hence, the design procedure and the simulation model provide a powerful tool to design an LCL-filter-based active rectifier while avoiding trial-and-error procedures that can result in having to build several filter prototypes.

Switched reluctance motor drives : modeling, simulation, analysis, design, and applications

Abstract: PRINCIPLE OF OPERATION OF THE SWITCH RELUCTANCE MOTOR (SRM) Introduction Background Elementary Operation of the Switch Reluctance Motor Principle of Operation of the Switched Reluctance Motor Derivation of the Relationship Between Inductance and Rotor Position Equivalent Circuit SRM Configurations Linear Switched Reluctance Machines References DERIVATION OF SRM CHARACTERISTICS Introduction Data for Performance Computation Analytic Method for the Computation of Machine Characteristics Computation of Unaligned Inductance Computation of Aligned Inductance Computation of Inductance vs. Rotor Position vs. Excitation Current Comparison of Measured, Analytic and Finite Element Results References DESIGN OF SRM Introduction Derivation of Output Equation Selection of Dimensions Design Verification Operational Limit Selection of Number of Phases Selection of Poles Ratio of Pole-Arc to Pole-Pitch Selection of Pole Base Selection of Pole-Arcs Measurement of Inductance Calculation of Torque Design of Linear Switched Reluctance Machine (LSRM) References CHAPTER 4: CONVERTERS FOR SRM DRIVES Converter Configurations Asymmetric Bridge Converter Asymmetric Converter Variation Single Switch per Phase Converters m Switches and 2m Diodes m Switches and 2m Diodes with Independent Phase Current Control (m+1) Switch and Diode Configurations One Common Switch Configuration Minimum Switch Topology With Variable DC Link Variable DC Link Voltage with Buck Boost Converter Topology 1.5m Switches and Diodes Configuration Comparison of Some Power Converters Two Stage Power Converter Resonant Converter Circuits for Switched Reluctance Motor Drives References CONTROL OF SRM DRIVE Introduction Control Principle Closed Loop Speed Controlled SRM Drive Design of Current Controllers Flux Linkage Controller Torque Control Design of the Speed Controller References MODELING AND SIMULATION OF SRM DRIVE SYSTEM Introduction Modeling Simulation References ACOUSTIC NOISE AND ITS CONTROL IN SRM Introduction Sources of Acoustic Noise in Electrical Machines Noise Sources Noise Mitigation Qualitative Design Measures to Reduce Noise Measurement of Acoustic Noise and Vibrations Future Directions Appendix-1: Derivation of First Mode Frequency of SRM References SENSORLESS OPERATION OF SRM DRIVES Introduction Current Sensing Rotor Position Measurement Methods Rotor Position Estimation References APPLICATION CONSIDERATIONS AND APPLICATIONS Introduction Review of SRM Drive Features for Application Consideration Applications Emerging applications References

Delay-dependent robust stabilization of uncertain state-delayed systems

Abstract: This paper concerns a problem of robust stabilization of uncertain state-delayed systems. A new delay-dependent stabilization condition using a memoryless controller is formulated in terms of matrix inequalities. An algorithm involving convex optimization is proposed to design a controller guaranteeing a suboptimal maximal delay such that the system can be stabilized for all admissible uncertainties.

On designing improved controllers for AQM routers supporting TCP flows

Abstract: In this paper we study a previously developed linearized model of TCP and active queue management (AQM). We use classical control system techniques to develop controllers well suited for the application. The controllers are shown to have better theoretical properties than the well known RED controller. We present guidelines for designing stable controllers subject to network parameters like load level propagation delay etc. We also present simple implementation techniques which require a minimal change to RED implementations. The performance of the controllers are verified and compared with RED using ns simulations. The second of our designs, the proportional integral (PI) controller is shown to outperform RED significantly.

Putting energy back in control

Abstract: Energy is one of the fundamental concepts in science and engineering practice, where it is common to view dynamical systems as energy-transformation devices. This perspective is particularly useful in studying complex nonlinear systems by decomposing them into simpler subsystems that, upon interconnection, add up their energies to determine the full system's behavior. The action of a controller may also be understood in energy terms as another dynamical system. The control problem can then be recast as finding a dynamical system and an interconnection pattern such that the overall energy function takes the desired form. This energy-shaping approach is the essence of passivity-based control (PBC), a controller design technique that is very well known in mechanical systems. Our objectives in the article are threefold. First, to call attention to the fact that PBC does not rely on some particular structural properties of mechanical systems, but hinges on the more fundamental (and universal) property of energy balancing. Second, to identify the physical obstacles that hamper the use of standard PBC in applications other than mechanical systems. In particular, we show that standard PBC is stymied by the presence of unbounded energy dissipation, hence it is applicable only to systems that are stabilizable with passive controllers. Third, to revisit a PBC theory that has been developed to overcome the dissipation obstacle as well as to make the incorporation of process prior knowledge more systematic. These two important features allow us to design energy-based controllers for a wide range of physical systems.

Vibration-to-electric energy conversion

Abstract: A system is proposed to convert ambient mechanical vibration into electrical energy for use in powering autonomous low power electronic systems. The energy is transduced through the use of a variable capacitor. Using microelectromechanical systems (MEMS) technology, such a device has been designed for the system. A low-power controller IC has been fabricated in a 0.6-/spl mu/m CMOS process and has been tested and measured for losses. Based on the tests, the system is expected to produce 8 /spl mu/W of usable power. In addition to the fabricated programmable controller, an ultra low-power delay locked loop (DLL)-based system capable of autonomously achieving a steady-state lock to the vibration frequency is described.

Hand-actuated articulating surgical tool

Abstract: A double cylinder system is disclosed, comprising at least one controller being adapted to transmit hydraulic control signals; at least one slave being in fluid communication with the controller and being configured to respond to the hydraulic control signals transmitted by the controller; and at least one control line providing hydraulic communication between the controller and the slave. Also disclosed is a surgical device, comprising at least one controller located at a proximal end of the device, the controller being adapted to transmit hydraulic control signals; at least one manipulator, the manipulator being configured to be controlled by a human hand and to actuate the controller; at least one slave located at a distal end of the device, the slave being in fluid communication with the controller and being configured to respond to the hydraulic control signals transmitted by the controller; and at least one control line providing hydraulic communication between the controller and the slave.

MOSAIC Model for Sensorimotor Learning and Control

Abstract: Humans demonstrate a remarkable ability to generate accurate and appropriate motor behavior under many different and often uncertain environmental conditions. We previously proposed a new modular architecture, the modular selection and identification for control (MOSAIC) model, for motor learning and control based on multiple pairs of forward (predictor) and inverse (controller) models. The architecture simultaneously learns the multiple inverse models necessary for control as well as how to select the set of inverse models appropriate for a given environment. It combines both feedforward and feedback sensorimotor information so that the controllers can be selected both prior to movement and subsequently during movement. This article extends and evaluates the MOSAIC architecture in the following respects. The learning in the architecture was implemented by both the original gradient-descent method and the expectation-maximization (EM) algorithm. Unlike gradient descent, the newly derived EM algorithm is robust to the initial starting conditions and learning parameters. Second, simulations of an object manipulation task prove that the architecture can learn to manipulate multiple objects and switch between them appropriately. Moreover, after learning, the model shows generalization to novel objects whose dynamics lie within the polyhedra of already learned dynamics. Finally, when each of the dynamics is associated with a particular object shape, the model is able to select the appropriate controller before movement execution. When presented with a novel shape-dynamic pairing, inappropriate activation of modules is observed followed by on-line correction.

Novel maximum-power-point-tracking controller for photovoltaic energy conversion system

Abstract: A novel maximum-power-point-tracking (MPPT) controller for a photovoltaic (PV) energy conversion system is presented. Using the slope of power versus voltage of a PV array, the proposed MPPT controller allows the conversion system to track the maximum power point very rapidly. As opposed to conventional two-stage designs, a single-stage configuration is implemented, resulting in size and weight reduction and increased efficiency. The proposed system acts as a solar generator on sunny days, in addition to working as an active power line conditioner on rainy days. Finally, computer simulations and experimental results demonstrate the superior performance of the proposed technique.

Adaptive state feedback and tracking control of systems with actuator failures

Abstract: Direct adaptive-state feedback control schemes are developed for linear time-invariant plants with actuator failures with characterizations that some of the plant inputs are stuck at some fixed or varying values which cannot be influenced by control action. Conditions and controller structures for achieving plant-model state matching in the presence of actuator failures are derived. Adaptive laws are designed for updating the controller parameters when both the plant parameters and actuator-failure parameters are unknown. Closed-loop stability and asymptotic-state tracking are ensured. Simulation results show that desired system performance is achieved with the developed adaptive actuator failure compensation control designs.

Control theory for linear systems

Abstract: Control Theory for Linear Systems deals with the mathematical theory of feedback control of linear systems. It treats a wide range of control synthesis problems for linear state space systems with inputs and outputs. The book provides a treatment of these problems using state space methods, often with a geometric flavour. Its subject matter ranges from controllability and observability, stabilization, disturbance decoupling, and tracking and regulation, to linear quadratic regulation, $H_2$ and $H_\infty$ control, and robust stabilization. Each chapter of the book contains a series of exercises, intended to increase the reader's understanding of the material. Often, these exercises generalize and extend the material treated in the regular text.

Non-linear Control for Underactuated Mechanical Systems

Abstract: From the Publisher: This book deals with the application of modern control theory to some important underactuated mechanical systems. It presents modelling and control of the following systems:||- the inverted pendulum||- a convey-crane system||- the pendubot system||- the Furuta pendulum||- the inertia wheel pendulum||- the planar flexible-joint robot||- the planar manipulator with two prismatic and one revolute joints||- the ball & beam system||- the hovercraft model||- the planar vertical and take-off landing (PVTOL) aircraft||- the helicopter model on a platform||- the helicopter model||In every case the model is obtained in detail using either the Euler-Lagrange formulation or the Newton's second law. We develop control algorithms for every particular system using techniques such as passivity, energy-based Lyapunov functions, forwarding, backstepping or feedback linearization techniques.||This book will be of great value for PhD students and researchers in the areas of non-linear control systems.

Impulsive Control Theory

Abstract: Preliminaries.- Linear Impulsive Control.- Comparison Methods.- Impulsive Control with Fixed-time Impulses.- Impulsive Control with Impulses at Variable Time.- Practical Stability of Impulsive Control.- Other Impulsive Control Strategies.- Impulsive Computational Verb Control.- Impulsive Control of Periodic Motions.- Impulsive Control of Almost Periodic Motions.- Applications to Nanoelectronics.

Universal single-input-single-output (SISO) sliding-mode controllers with finite-time convergence

Abstract: An universal controller is constructed, formulated in input-output terms only, which causes the output of any uncertain smooth single-input single-output (SISO) minimum-phase dynamic system with known relative degree to vanish in finite time. This allows exact tracking of arbitrary real-time smooth signals. Only one parameter is to be adjusted. Since the approach is based on higher order finite time-convergence sliding modes, the control can be made arbitrarily smooth, providing for the arbitrarily-high tracking-accuracy order with respect to the sampling step.

Inverse control of systems with hysteresis and creep

Abstract: Since the beginning of the 1990s, hysteresis operators have been employed on a larger scale for the linearisation of hysteretic transducers. One reason for this is the increasing number of mechatronic applications that use solid-state actuators based on magnetostrictive or piezo-electric material or shape memory alloys. All of these actuator types show strong hysteretic effects. In addition to hysteresis, piezo-electric actuators show strong creep effects. Thus, the objective of the paper is to enlarge the operator-based methodology of hysteresis operators by elements that allow the description of systems with hysteresis and creep. To reach this objective, following the procedure used for hysteretic systems, creep operators are introduced to form, together with the hysteresis operators, a system operator for the simultaneous consideration of both phenomena. With regard to applications in control and measurement technology, the existence, uniqueness, Lipschitz continuity and thus input-output stability of its inverse operator are theoretically supported by functional analytical methods. Subsequently, the efficiency of this new concept is demonstrated, in practice, by a real-time inverse feedforward controller for piezo-electric actuators. Using this control concept, the tracking errors caused by hysteretic and creep effects are reduced by approximately one order of magnitude.

Stable Adaptive Control and Estimation for Nonlinear Systems: Neural and Fuzzy Approximator Techniques

Abstract: From the Publisher: A powerful, yet easy-to-use design methodology for the control of nonlinear dynamic systems A key issue in the design of control systems is proving that the resulting closed-loop system is stable, especially in cases of high consequence applications, where process variations or failure could result in unacceptable risk. Adaptive control techniques provide a proven methodology for designing stable controllers for systems that may possess a large amount of uncertainty. At the same time, the benefits of neural networks and fuzzy systems are generating much excitement-and impressive innovations-in almost every engineering discipline. Stable Adaptive Control and Estimation for Nonlinear Systems: Neural and Fuzzy Approximator Techniques brings together these two different but equally useful approaches to the control of nonlinear systems in order to provide students and practitioners with the background necessary to understand and contribute to this emerging field. The text presents a control methodology that may be verified with mathematical rigor while possessing the flexibility and ease of implementation associated with "intelligent control" approaches. The authors show how these methodologies may be applied to many real-world systems including motor control, aircraft control, industrial automation, and many other challenging nonlinear systems. They provide explicit guidelines to make the design and application of the various techniques a practical and painless process. Design techniques are presented for nonlinear multi-input multi-output (MIMO) systems in state-feedback, output-feedback, continuous or discrete-time, or even decentralized form. To help students and practitioners new to the field grasp and sustain mastery of the material, the book features: Background material on fuzzy systems and neural networksStep-by-step controller designNumerous examplesCase studies using "real world" applicationsHomework problems and design projects

An optimal fuzzy PID controller

Abstract: This paper introduces an optimal fuzzy proportional-integral-derivative (PID) controller. The fuzzy PID controller is a discrete-time version of the conventional PID controller, which preserves the same linear structure of the proportional, integral, and derivative parts but has constant coefficient yet self-tuned control gains. Fuzzy logic is employed only for the design; the resulting controller does not need to execute any fuzzy rule base, and is actually a conventional PID controller with analytical formulae. The main improvement is in endowing the classical controller with a certain adaptive control capability. The constant PID control gains are optimized by using the multiobjective genetic algorithm (MOGA), thereby yielding an optimal fuzzy PID controller. Computer simulations are shown to demonstrate its improvement over the fuzzy PID controller without MOGA optimization.

Tracking control of unicycle-modeled mobile robots using a saturation feedback controller

Abstract: The tracking control problem with saturation constraint for a class of unicycle-modeled mobile robots is formulated and solved using the backstepping technique and the idea from the LaSalle's invariance principle. A global result is presented in which several constraints on the linear and the angular velocities of the mobile robot from recent literature are dropped. The proposed controller can simultaneously solve both the tracking and regulation problems of a unicycle-modeled mobile robot. With the proposed control laws, the robot can globally follow any path specified by a straight line, a circle or a path approaching the origin using a single controller. As demonstrated, the circular and parallel parking control problem are solved using the proposed controller. Computer simulations are presented which confirm the effectiveness of the proposed tracking control law. Practical experimental results validate the simulations.

Microprocessor for controlling the speed and frequency of a motor shaft in a power tool

Abstract: A control system for driving a power tool is provided comprising a power source, a motor adapted to drive a shaft, a power switching unit interconnecting the power source and the motor, and a controller The power switching unit applying a pulse width modulated (PWM) drive signal from the power source to the motor The controller monitoring at least one electrical characteristic of at least one of the power source, motor and power switching unit and adjusting the operating duty cycle of the PWM drive signal based on the electrical characteristics

Method and apparatus for acoustically controlling liquid solutions in microfluidic devices

Abstract: Acoustic energy is used to control motion in a fluid. According to one embodiment, the invention directs acoustic energy at selected naturally occurring nucleation features to control motion in the fluid. In another embodiment, the invention provides focussed or unfocussed acoustic energy to selectively placed nucleation features to control fluid motion. According to one embodiment, the invention includes an acoustic source, a controller for controlling operation of the acoustic source, and one or more nucleation features located proximate to or in the fluid to be controlled.

A new controller architecture for high performance, robust, and fault-tolerant control

Abstract: We propose a new feedback controller architecture. The distinguished feature of our new controller architecture is that it shows structurally how the controller design for performance and robustness may be done separately which has the potential to overcome the conflict between performance and robustness in the traditional feedback framework. The controller architecture includes two parts: one part for performance and the other part for robustness. The controller architecture works in such a way that the feedback control system can be solely controlled by the performance controller when there is no model uncertainties and external disturbances and the robustification controller can only be active when there are model uncertainties or external disturbances.

Coil winding number variable type motor and coil winding number varying method for varying cooling and heating capacity of reciprocating compressor

Abstract: A coil winding number variable type motor for varying a cooling and heating capacity of a reciprocating motor includes: a plurality of coils separately wound and connected in series to each other so as to vary turn ratio among motor coils; a plurality of relays respectively connected between adjacent coils among the plurality of coils; and a relay controller for outputting and ON/OFF control signal for varying the winding number of the motor coil and controlling the relays according to a change in a load and a power supply voltage. The coil wound in the motor of the reciprocating compressor is divided into the main coil and the plurality of sub-coils and the winding number of the motor coil is varied by itself to control the stroke of the reciprocating compressor, thereby effectively coping with the change in the voltage or the load.

Adaptive method and apparatus for forecasting and controlling neurological disturbances under a multi-level control

Abstract: A method and apparatus for forecasting and controlling neurological abnormalities in humans such as seizures or other brain disturbances. The system is based on a multi-level control strategy. Using as inputs one or more types of physiological measures such as brain electrical, chemical or magnetic activity, heart rate, pupil dilation, eye movement, temperature, chemical concentration of certain substances, a feature set is selected off-line from a pre-programmed feature library contained in a high level controller within a supervisory control architecture. This high level controller stores the feature library within a notebook or external PC. The supervisory control also contains a knowledge base that is continuously updated at discrete steps with the feedback information coming from an implantable device where the selected feature set (feature vector) is implemented. This high level controller also establishes the initial system settings (off-line) and subsequent settings (on-line) or tunings through an outer control loop by an intelligent procedure that incorporates knowledge as it arises. The subsequent adaptive settings for the system are determined in conjunction with a low-level controller that resides within the implantable device. The device has the capabilities of forecasting brain disturbances, controlling the disturbances, or both. Forecasting is achieved by indicating the probability of an oncoming seizure within one or more time frames, which is accomplished through an inner-loop control law and a feedback necessary to prevent or control the neurological event by either electrical, chemical, cognitive, sensory, and/or magnetic stimulation.

Analysis of communication losses in vehicle control problems

Abstract: In this paper we study the effect of communication packet losses in the feedback loop of a control system. Our motivation is derived from vehicle control problems where information is communicated via a wireless local area network. For such problems, we consider a simple packet-loss model for the communicated information and note that results for discrete-time linear systems with Markovian jumping parameters can be applied. The goal is to find a controller (if one exists) such that the closed loop is mean square stable for a given packet loss rate. A linear matrix inequality (LMI) condition is developed for the existence of a stabilizing dynamic output feedback controller. This LMI condition is used to study the effect of communication losses on a vehicle following problem. In summary, these results can be used not only to design controllers but also give a 'worst-case' performance specification (in terms of packet-loss rate) for an acceptable communications system.

Robust Adaptive Variable Structure Control of Spacecraft Under Control Input Saturation

Abstract: In this paper we propose two globally stable control algorithms for robust stabilization of spacecraft in the presence of control input saturation, parametric uncertainty, and external disturbances. The control algorithms are based on variable structure control design and have the following properties: 1 ) fast and accurate response in thepresenceofbounded external disturbancesand parametricuncertainty;2 )explicit accounting forcontrol input saturation; 3 ) computational simplicity and straightforward tuning. We include a detailed stability analysis for the resulting closed-loop system. The stability proof is based on a Lyapunov-like analysis and the properties of the quaternion representation of spacecraft dynamics. It is also shown that an adaptive version of the proposed controller results in substantially simpler stability analysis and improved overall response. We also include numerical simulations to illustrate the spacecraft performance obtained using the proposed controllers.

Unconstrained receding-horizon control of nonlinear systems

Abstract: It is well known that unconstrained infinite-horizon optimal control may be used to construct a stabilizing controller for a nonlinear system. We show that similar stabilization results may be achieved using unconstrained finite horizon optimal control. The key idea is to approximate the tail of the infinite horizon cost-to-go using, as terminal cost, an appropriate control Lyapunov function. Roughly speaking, the terminal control Lyapunov function (CLF) should provide an (incremental) upper bound on the cost. In this fashion, important stability characteristics may be retained without the use of terminal constraints such as those employed by a number of other researchers. The absence of constraints allows a significant speedup in computation. Furthermore, it is shown that in order to guarantee stability, it suffices to satisfy an improvement property, thereby relaxing the requirement that truly optimal trajectories be found. We provide a complete analysis of the stability and region of attraction/operation properties of receding horizon control strategies that utilize finite horizon approximations in the proposed class. It is shown that the guaranteed region of operation contains that of the CLF controller and may be made as large as desired by increasing the optimization horizon (restricted, of course, to the infinite horizon domain). Moreover, it is easily seen that both CLF and infinite-horizon optimal control approaches are limiting cases of our receding horizon strategy. The key results are illustrated using a familiar example, the inverted pendulum, where significant improvements in guaranteed region of operation and cost are noted.

A novel current-tracking method for active filters based on a sinusoidal internal model [for PWM invertors]

Abstract: A new current control method based on the internal model principle in control theory is proposed. It introduces a sinusoidal internal model into the control system. It does not use any coordinate transformations. The method can be used for tracking an arbitrary number of harmonics: a DC component or fundamental frequency component signal. It is applied to a single-phase pulsewidth modulation inverter and active filter. The validity is confirmed by simulation and experimental results.

Diagnostics in a process control system

Abstract: A diagnostic tool automatically collects and stores data indicative of a variability parameter, a mode parameter, a status parameter and a limit parameter associated with each of the different devices, loops or function blocks within a process control system, processes the collected data to determine which devices, loops or function blocks have problems that result in reduced performance of the process control system, displays a list of detected problems to an operator and then suggests the use of other, more specific diagnostic tools to further pinpoint or correct the problems. When the diagnostic tool recommends and executes a data intensive application as the further diagnostic tool, it automatically configures a controller of the process control network to collect the data needed for such a tool.