Non-singular terminal sliding mode guidance and control with terminal angle constraints for non-maneuvering targets

In this paper guidance laws to intercept stationary and constant velocity targets at a desired impact angle, based on sliding mode control theory, are proposed. The desired impact angle, which is defined in terms of a desired line-of-sight (LOS) angle, is achieved in finite time by selecting the missile's lateral acceleration (latax) to enforce non-singular terminal sliding mode on a switching surface designed using this desired LOS angle and based on non-linear engagement dynamics. Numerical simulation results are presented to validate the proposed guidance laws for different initial engagement geometries and impact angles.

Continuous-time and discrete-time sliding mode control accomplished using a computer

A computer-based sliding mode control (SMC) is analysed. The control law is accomplished using a computer and A/D and D/A converters. Two SMC designs are presented. The first one is a continuous-time conventional SMC design, with a variable structure law, which does not take into consideration the sampling period. The second one is a discrete-time SMC design, with a smooth sliding law, which does not have a structure variable and takes into consideration the sampling period. Both techniques are applied to control an inverted pendulum system. The performance of both the continuous-time and discrete-time controllers are compared. Simulations and experimental results are shown and the effectiveness of the proposed techniques is analysed.

CONTROL OF UNCERTAIN DYNAMIC-SYSTEMS USING STRICTLY POSITIVE REAL SYSTEMS

This paper presents necessary and sufficient conditions to turn a linear time-invariant system with p outputs, m inputs, p greater-than-or-equal-to m and using only inputs and outputs measurements into a Strictly Positive Real (SPR).Two results are presented. In the first, the system compensation is made by two static compensators, one of which forward feeds the outputs and the second back feeds the outputs of the nominal system.The second result presents conditions for the Walcott and Zak variable structure observer-controller synthesis. In this problem, if the nominal system is given by {A,B,C}, then the compensated system is given by {A+GC,B,FC} where F and G are the constant compensation matrices. These results are useful in the control system with uncertainties.

Mathematical modelling and optimal multivariable control of chemical processes

This work reports the developnent of a mathenatical model and distributed, multi variable computer-control for a pilot plant double-effect climbing-film evaporator. A distributed-parameter model of the plant has been developed and the time-domain model transformed into the Laplace domain. The model has been further transformed into an integral domain conforming to an algebraic ring of polynomials, to eliminate the transcendental terms which arise in the Laplace domain due to the distributed nature of the plant model. This has made possible the application of linear control theories to a set of linear-partial differential equations. The models obtained have well tracked the experimental results of the plant. A distributed-computer network has been interfaced with the plant to implement digital controllers in a hierarchical structure. A modern rnultivariable Wiener-Hopf controller has been applled to the plant model. The application has revealed a limitation condition that the plant matrix should be positive-definite along the infinite frequency axis. A new multi variable control theory has emerged fram this study, which avoids the above limitation. The controller has the structure of the modern Wiener-Hopf controller, but with a unique feature enabling a designer to specify the closed-loop poles in advance and to shape the sensitivity matrix as required. In this way, the method treats directly the interaction problems found in the chemical processes with good tracking and regulation performances. Though the ability of the analytical design methods to determine once and for all whether a given set of specifications can be met is one of its chief advantages over the conventional trial-and-error design procedures. However, one disadvantage that offsets to some degree the enormous advantages is the relatively complicated algebra that must be employed in working out all but the simplest problem. Mathematical algorithms and computer software have been developed to treat some of the mathematical operations defined over the integral domain, such as matrix fraction description, spectral factorization, the Bezout identity, and the general manipulation of polynomial matrices. Hence, the design problems of Wiener-Hopf type of controllers and other similar algebraic design methods can be easily solved.

Vibration of ship structures and its control

Noise and vibration in complex ship structures are becoming a prominent issue for ship building industry and ship companies due to the constant demand of building faster ships of lighter weight, and the stringent noise and libration regulation of the industry. In order to retain the full benefit of building faster ships without compromising too much on ride comfort and safety, noise and vibration control needs to be implemented. Due to the complexity of ship structures, the coupling of different wave types and multiple wave propagation paths, active control of global hull modes is difficult to implement and very expensive. Traditional passive control such as adding damping materials is only effective in the high frequency range. However, most severe damage to ship structures is caused by large structural deformation of hull structures and high dynamic stress concentration at low frequencies. The most discomfort and fatigue of passengers and the crew onboard ships is also due to the low frequency noise and vibration. Innovative approaches are therefore, required to attenuate the noise and vibration at low frequencies. This book was developed from several specialized research topics on vibration and vibration control of ship structures, mostly from the author's own PhD work at the University of Western Australia. The book aims to provide a better understanding of vibration characteristics of ribbed plate structures, plate/plate coupled structures and the mechanism governing wave propagation and attenuation in periodic and irregular ribbed structures as well as in complex ship structures. The book is designed to be a reference book for ship builders, vibro-acoustic engineers and researchers. The author also hopes that the book can stimulate more exciting future work in this area of research. It is the author's humble desire that the book can be some use for those who purchase it. This book is divided into eight chapters. Each chapter focuses on providing solution to address a particular issue on vibration problems of ship structures. A brief summary of each chapter is given in the general introduction. All chapters are inter-dependent to each other to form an integration volume on the subject of vibration and vibration control of ship structures and alike. I am in debt to many people in completing this work. In particular, I would like to thank Professor J. Pan, Dr N.H. Farag, Dr K. Sum and many others from the University of Western Australia for useful advices and helps during my times at the University and beyond. I would also like to thank my wife, Miaoling Wang, my children, Anita, Sophia and Angela Lin, for their sacrifice and continuing supports to make this work possible. Financial supports from Australian Research Council, Australian Defense Science and Technology Organization and Strategic Marine Pty Ltd at Western Australia for this work is gratefully acknowledged.

Fast Direct Torque Control of an Open-End Induction Motor Drive Using 12-Sided Polygonal Voltage Space Vectors

A torque control scheme, based on a direct torque control (DTC) algorithm using a 12-sided polygonal voltage space vector, is proposed for a variable speed control of an open-end induction motor drive. The conventional DTC scheme uses a stator flux vector for the sector identification and then the switching vector to control stator flux and torque. However, the proposed DTC scheme selects switching vectors based on the sector information of the estimated fundamental stator voltage vector and its relative position with respect to the stator flux vector. The fundamental stator voltage estimation is based on the steady-state model of IM and the synchronous frequency of operation is derived from the computed stator flux using a low-pass filter technique. The proposed DTC scheme utilizes the exact positions of the fundamental stator voltage vector and stator flux vector to select the optimal switching vector for fast control of torque with small variation of stator flux within the hysteresis band. The present DTC scheme allows full load torque control with fast transient response to very low speeds of operation, with reduced switching frequency variation. Extensive experimental results are presented to show the fast torque control for speed of operation from zero to rated.

Control of self-organized low-dimensional morphology in Poly(styrene-b-4vinylpyridine)/polystyrene blend thin films

The surface morphologies of poly(styrene-b-4vinylpyridine) (PS-b-P4VP) diblock copolymer and homopolystyrene (hPS) binary blend thin films were investigated by atomic force microscopy as a function of total volume fraction of PS (phi(PS)) in the mixture. It was found that when hPS was added into symmetric PS-b-P4VP diblock copolymers, the surface morphology of this diblock copolymer was changed to a certain degree. With phi(PS) increasing at first, hPS was solubilized into the corresponding domains of block copolymer and formed cylinders. Moreover, the more solubilized the hPS, the more cylinders exist. However, when the limit was reached, excessive hPS tended to separate from the domains independently instead of solubilizing into the corresponding domains any longer, that is, a macrophase separation occurred. A model describing transitions of these morphologies with an increase in phi(PS) is proposed. The effect of composition on the phase morphology of blend films when graphite is used as a substrate is also investigated.

水-岩土反应的力学与环境效应研究

The research on mechanical effects of water-rock and soil interaction on deformation and failure of rocks and soils involves three aspects of mechanics, physics and chemistry. It is the cross between geochemistry and rock mechanics and soil mechanics. To sum up, the mechanical effects of water-rock and soil interaction is related to many complex processes. Research in this respect has been being an important forward field and has broad prospects. In connection with the mechanism of the effects of the chemical action of water-rock on deformation and failure of rocks and soils, the research significance, the present state, the developments in this research domain are summarized. Author prospects the future of this research. The research of the subject should be possessed of important position in studying engineering geology and will lead directly to a new understand on geological hazard and control research. In order to investigation the macroscopic mechanics effects of chemical kinetics of water-rock interaction on the deformation and failure, calcic rock, red sandstone and grey granite reacting chemically with different aqueous solution at atmospheric temperature and atmospheric pressure are uniaxially compressed. The quantitative results concerning the changes of uniaxially compressive strength and elastic modulus under different conditions are obtained. It is found that the mechanical effects of water on rock is closely related to the chemical action of water-rock or the chemical damage in rock, and the intensity of chemical damage is direct ratio to the intensity of chemical action in water-rock system. It is also found that the hydrochemical action on rock is time-dependent through the test. The mechanism of permeation and hydrochemical action resulting in failure of loaded rock mass or propagation of fractures in rocks would be a key question in rock fracture mechanics. In this paper, the fracture mechanical effects of chemical action of water-rock and their time- and chemical environment-dependent behavior in grey granite, green granite, grey sandstone and red sandstone are analyzed by testing K_(IC) and COD of rock under different conditions. It is found that: ①the fracture mechanical effect of chemical action of water-rock is outstanding and time-dependent, and high differences exist in the influence of different aqueous solution, different rocks, different immersion ways and different velocity of cycle flow on the fracture mechanical effects in rock. ②the mechanical effects of water-rock interaction on propagation of fractures is consistent with the mechanical effects on the peak strength of rock. ③the intensity of the mechanical fracture effects increases as the intensity of chemical action of water-rock increases. ④iron and calcium ion bearing mineral or cement in rock are some key ion or chemical composition, and especially iron ion-bearing mineral resulting in chemical action of water-rock to be provided with both positive and negative mechanical effects on rock. Through the above two tests, we suggest that primary factors influencing chemical damage in rock consist of the chemical property of rock and aqueous solution, the structure or homogeneity of rocks, the flow velocity of aqueous solution passing through rock, and cause of formation or evolution of rock. The paper explores the mechanism on the mechanical effects of water-rock interaction on rock by using the theory of chemistry and rock fracture mechanics with chemical damage proposed by author, the modeling method and the energy point of view. In this paper, the concept of absorbed suction between soil grains caused by capillary response is given and expounded, and the relation and basic distinction among this absorbed suction, surface tension and capillary pressure of the soil are analyzed and established. The law of absorbed suction change and the primary factors affecting it are approached. We hold that the structure suction are changeable along with the change of the saturation state in unsaturated soils. In view of this, the concept of intrinsic structure suction and variable structure suction are given and expounded, and this paper points out: What we should study is variable structure suction when studying the effective stress. By IIIy κHH's theory of structure strength of soils, the computer method for variable structure suction is analyzed, the measure method for variable structure suction is discussed, and it reach the conclusions: ①Besides saturation state, variable structure suction is affected by grain composition and packing patter of grains. ②The internal relations are present between structure parameter N in computing structure suction and structure parameter D in computing absorbed suction. We think that some problems exit in available principle of effective stress and shear strength theory for unsaturated soil. Based on the variable structure suction and absorbed suction, the classification of saturation in soil and a principle of narrow sense effective stress are proposed for unsaturated soils. Based on generalized suction, the generalized effective stress formula and a principle of generalized effective stress are proposed for unsaturated soils. The experience parameter χ in Bishop's effective stress formula is defined, and the principal factors influencing effective stress or χ. The primary factor affecting the effective stress in unsaturated soils, and the principle classifying unsaturated soils and its mechanics methods analyzing unsaturated soils are discussed, and this paper points out: The theory on studying unsaturated soil mechanics should adopt the micromechanics method, then raise it to macromechanics and to applying. Researching the mechanical effects of chemical action of water-soil on soil is of great importance to geoenvironmental hazard control. The texture of soil and the fabric of soil mass are set forth. The tests on physical and mechanical property are performed to investigate the mechanism of the positive and negative mechanical effects of different chemical property of aqueous solution. The test results make clear that the plastic limit, liquid limit and plasticity index are changed, and there exists both positive and negative effects on specimens in this test. Based on analyzing the mechanism of the mechanical effects of water-soil interaction on soil, author thinks that hydrochemical actions being provided with mechanical effects on soil comprise three kinds of dissolution, sedimentation or crystallization. The significance of these tests lie in which it is recognized for us that we may improve, adjust and control the quality of soils, and may achieve the goal geological hazard control and prevention.The present and the significance of the research on environmental effects of water-rock and soil interaction. Various living example on geoenvironmental hazard in this field are enumerated. Following above thinking, we have approached such ideals that: ①changing the intensity and distribution of source and sink in groundwater flow system can be used to control the water-rock and soil interaction. ②the chemical action of water-rock and soil can be used to ameliorate the physical and mechanical property of rocks and soils. Lastly, the research thinking and the research methods on mechanical effects and environmental effects of water-rock and soil interaction are put forward and detailed.

Path planning of robots in noisy workspaces using learning automata

The problem of a manipulator operating in a noisy workspace and required to move from an initial fixed position P0 to a final position Pf is considered. However, Pf is corrupted by noise, giving rise to Pˆf, which may be obtained by sensors. The use of learning automata is proposed to tackle this problem. An automaton is placed at each joint of the manipulator which moves according to the action chosen by the automaton (forward, backward, stationary) at each instant. The simultaneous reward or penalty of the automata enables avoiding any inverse kinematics computations that would be necessary if the distance of each joint from the final position had to be calculated. Three variable-structure learning algorithms are used, i.e., the discretized linear reward-penalty (DLR-P, the linear reward-penalty (LR-P ) and a nonlinear scheme. Each algorithm is separately tested with two (forward, backward) and three forward, backward, stationary) actions.

Controlador em modo dual adaptativo robusto - DMARC

The so-called Dual Mode Adaptive Robust Control (DMARC) is proposed. The DMARC is a control strategy which interpolates the Model Reference Adaptive Control (MRAC) and the Variable Structure Model Reference Adaptive Control (VS-MRAC). The main idea is to incorporate the transient performance advantages of the VS-MRAC controller with the smoothness control signal in steady-state of the MRAC controller. Two basic algorithms are developed for the DMARC controller. In the first algorithm the controller's adjustment is made, in real time, through the variation of a parameter in the adaptation law. In the second algorithm the control law is generated, using fuzzy logic with Takagi-Sugeno s model, to obtain a combination of the MRAC and VS-MRAC control laws. In both cases, the combined control structure is shown to be robust to the parametric uncertainties and external disturbances, with a fast transient performance, practically without oscillations, and a smoothness steady-state control signal

Controle adaptativo robusto para um modelo desacoplado de um robô móvel

This thesis presents a new structure of robust adaptive controller applied to mobile robots (surface mobile robot) with nonholonomic constraints. It acts in the dynamics and kinematics of the robot, and it is split in two distinct parts. The first part controls the robot dynamics, using variable structure model reference adaptive controllers. The second part controls the robot kinematics, using a position controller, whose objective is to make the robot to reach any point in the cartesian plan. The kinematic controller is based only on information about the robot configuration. A decoupling method is adopted to transform the linear model of the mobile robot, a multiple-input multiple-output system, into two decoupled single-input single-output systems, thus reducing the complexity of designing the controller for the mobile robot. After that, a variable structure model reference adaptive controller is applied to each one of the resulting systems. One of such controllers will be responsible for the robot position and the other for the leading angle, using reference signals generated by the position controller. To validate the proposed structure, some simulated and experimental results using differential drive mobile robots of a robot soccer kit are presented. The simulator uses the main characteristics of real physical system as noise and non-linearities such as deadzone and saturation. The experimental results were obtained through an C++ program applied to the robot soccer kit of Microrobot team at the LACI/UFRN. The simulated and experimental results are presented and discussed at the end of the text

Avaliação de robustez, desempenho e aplicação do controlador adaptativo por posicionamento de pólos e estrutura variável

In this work, the variable structure adaptive pole placement controller (VS-APPC) robustness and performance are evaluated and this algorithm is applied in a motor control system. The controller robustness evaluation will be done through simulations, where will be introduced in the system the following adversities: time delay, actuator response boundeds, disturbances, parametric variation and unmodeled dynamics. The VS-APPC will be compared with PI control, pole placement control (PPC) and adaptive pole placement controller (APPC). The VS-APPC will be simulated to track a step and a sine reference. It will be applied in a three-phase induction motor control system to track a sine signal in the stator reference frame. Simulation and experimental results will prove the efficiency and robustness of this control strategy

Técnica de controle adaptativo robusto aplicada a filtros ativos de potência e paralelo

The Methods for compensation of harmonic currents and voltages have been widely used since these methods allow to reduce to acceptable levels the harmonic distortion in the voltages or currents in a power system, and also compensate reactive. The reduction of harmonics and reactive contributes to the reduction of losses in transmission lines and electrical machinery, increasing the power factor, reduce the occurrence of overvoltage and overcurrent. The active power filter is the most efficient method for compensation of harmonic currents and voltages. The active power filter is necessary to use current and voltage controllers loop. Conventionally, the current and voltage control loop of active filter has been done by proportional controllers integrative. This work, investigated the use of a robust adaptive control technique on the shunt active power filter current and voltage control loop to increase robustness and improve the performance of active filter to compensate for harmonics. The proposed control scheme is based on a combination of techniques for adaptive control pole placement and variable structure. The advantages of the proposed method over conventional ones are: lower total harmonic distortion, more flexibility, adaptability and robustness to the system. Moreover, the proposed control scheme improves the performance and improves the transient of active filter. The validation of the proposed technique was verified initially by a simulation program implemented in C++ language and then experimental results were obtained using a prototype three-phase active filter of 1 kVA

Uma abordagem indireta para o Controlador em Modo Dual Adaptativo Robusto

In this work is proposed an indirect approach to the DualMode Adaptive Robust Controller (DMARC), combining the typicals transient and robustness properties of Variable Structure Systems, more specifically of Variable Structure Model Reference Adaptive Controller (VS-MRAC), with a smooth control signal in steady-state, typical of conventional Adaptive Controllers, as Model Reference Adaptive Controller (MRAC). The goal is to provide a more intuitive controller design, based on physical plant parameters, as resistances, inertia moments, capacitances, etc. Furthermore, with the objective to follow the evolutionary line of direct controllers, it will be proposed an indirect version for the Binary Model Reference Adaptive Controller (B-MRAC), that was the first controller attemptting to act as MRAC as well as VS-MRAC, depending on a pre-defined fixed parameter

Controlador adaptativo por posicionamento de pólos e estrutura variável aplicado ao controle de geradores eólicos baseados em máquina de indução duplamente alimentada

In the last decade, the renewable energy sources have present a major propulsion in the world due to several factors: political, environmental, financial and others. Within this context, we have in particular the energy obtained through wind, wind energy - that has highlighted with rapid growth in recent years, including in Brazil, mostly in the Northeast, due to it s benefit-cost between the clean energies. In this context, we propose to compare the variable structure adaptive pole placement control (VS-APPC) with a traditional control technique proportional integral controller (PI), applied to set the control of machine side in a conversion system using a wind generator based on Double-Fed Induction Generator (DFIG). Robustness and performance tests were carried out to the uncertainties of the internal parameters of the machine and variations of speed reference.