Scalar Control System Research Articles

СИНТЕЗ ЭЛЕКТРОПРИВОДА КОМПРЕССОРНОЙ УСТАНОВКИ ЭЛЕКТРОВОЗА

The study objective is to improve the reliability and energy efficiency of the electric locomotive compressor drive. To achieve this, the required power of the electric motor was calculated the performance of the compressor unit, the volume of the main tanks and the selected electric motor were checked to start and adjust the capacity at low supply voltage. The task to which the paper is devoted is to design an electric drive for a compressor motor. A vector model of an asynchronous motor was made. The process of direct start-up and starting an asynchronous electric motor with the use of a scalar control system and IR compensation were modeled. Research methods: systematic approach; provisions of the theory of automatic control and electrical engineering; numerical PC simulation using Matlab software package. The novelty of the work is in the use of a frequency-controlled electric drive to start the asynchronous electric motor of the compressor unit instead of the normally installed starting capacitors. This design solution will significantly reduce the amplitude of the starting currents, which in turn will reduce the wear of the winding insulation. The study results are presented, based on the results of the constructed models, as graphs of the dependencies of speed and current during direct start of the electric motor and with the control system. Conclusions: the scalar control system, thanks to the introduction of an intensity setter, as well as IR compensation diagram, allow extending the transition time and controlling the value of the inrush current in acceptable values. Such an approach to make an electric drive compressor motor is able to significantly increase its reliability and service life, as well as to increase the overall energy efficiency of the system.

DEVELOPMENT AND CONFIGURATION OF A FULL-ORDER OBSERVER FOR «CABLE LINE – INDUCTION MOTOR» ELECTRICAL COMPLEX

Link for citation: Rakov I.V., Glazyrin A.S., Kladiev S.N. Development and configuration of a full-order observer for «cable line – induction motor» electrical complex. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 10, рр. 219-231. In Rus. The relevance. The task of oil production specialists is to minimize all types of energy consumption, ensuring an increase in oil production profitability because of the following reasons. First of all, availability of oil reserves with low energy consumption decreases, and the number of gushing wells reduces, along with increase in water content in the extracted liquid. One of the methods of reducing energy consumption in wells with low and moderate flow rate, equipped with electric submersible pumps, is a well transfer from continuous to periodic operation mode, namely cyclic well operation. This involves alternating short periods of oil production (up to 15 minutes) with liquid accumulation (up to 30 minutes) in the wellbore. Well switching to a cyclic operation mode leads to a 40 % reduction in electric power consumption by the submersible electric motor, as well as increase in oil production up to 3 %. This can be achieved by partial gravitational separation of the extracted liquid at the accumulation stage. However, a negative consequence of switching to a cyclic operation mode is a reduction in an average time between failures. This is due to increase in current surges and torque during rapid acceleration of the submersible electric motor to the rated speed. Transition from a scalar control system with an open loop to a vector control system without sensors can settle these problems. To implement a vector control system, it is necessary to obtain information about the state variables of a submersible electric motor. Construction of a full-order observer based on explicit mathematical models is considered as a promising method of obtaining information, taking into account the main advantages and disadvantages of direct measurement and indirect estimation of state variables. Based on the above, the urgent task is to develop a full-cycle observer for the electromechanical complex «cable line – induction motor» and a methodology for its configuration. The settlement of this issue will create prerequisites for implementation of a vector control system by a submersible electric motor. The main aim: to develop and experimentally validate the effectiveness of a full-order observer for the electrical complex «cable line – induction motor» using voltage and current measurements at a cable line input. Methods: literature analysis, system analysis, mathematical modeling, experimental research. Results. The authors have developed and tested a full-order observer for the «cable line – induction motor» electrical complex. The results of this study confirm the efficiency of the developed observer and its potential applicability for implementing a vector control system for electric submersible pumps. Ultimately, this will enable the transition of low- and medium-flow-rate oil wells to a cyclically operated mode without a significant reduction of the mean time between failures.

ПОВЫШЕНИЕ ЭНЕРГОЭФФЕКТИВНОСТИ АСИНХРОННОГО ЭЛЕКТРОПРИВОДА В СЕЛЬСКОМ ХОЗЯЙСТВЕ

The cost of electricity for the electric drive of technological installations is about 40 ... 50% of the total electricity consumed, depending on the type of enterprise. Two principles of control of an asynchronous electric motor are analyzed. Optimum from the point of view of energy efficiency, the scalar law of regulation of the supply voltage amplitude assumes the selection for each fixed value of the supply frequency and load moment of such a value of the voltage amplitude at which the losses in the motor are minimal and the efficiency is maximum. For these purposes, an additional controller is added to the composition of the electric drive, which, when the power frequency changes, corrects the value of the voltage amplitude obtained, according to the basic law, to a small extent, in such a way as to ensure the extremum of efficiency. As an objective function of the extremal controller (a criterion for the energy efficiency of an asynchronous electric motor), the following can be chosen: power losses in the motor based on the current in the stator winding or on the value of the main magnetic flux, maintaining a constant rotor slip, combinations of several parameters. A computer model of a scalar control system with a similar extremal controller, created in the SimInTech software package, is proposed. The use of the proposed regulator allows to increase the efficiency of the electric motor by 1.3 ... 11.2%, the largest increase in efficiency is achieved at a frequency of 20 Hz, and the smallest - at a frequency of 50 Hz. The proposed computer model is universal and allows you to explore various combinations of optimization criteria and algorithms for the extremal controller.

МЕТОДИКА ОЦЕНИВАНИЯ ПАРАМЕТРОВ ЭЛЕКТРОТЕХНИЧЕСКОГО КОМПЛЕКСА «КАБЕЛЬНАЯ ЛИНИЯ — АСИНХРОННЫЙ ДВИГАТЕЛЬ» НА ОСНОВЕ БАЛАНСА ПОТРЕБЛЯЕМОЙ МОЩНОСТИ

Relevance In the Russian Federation, 82 % of oil is produced using Electric Submersible Pumps (ESP), while only 63 % of wells are equipped with such pumps. Since more than half of the operating wells are equipped with ESP, developing methods to reduce operating costs for these wells is a rational and logical allocation of human, material, and financial resources. One method to increase the profitability of oil production from low- and medium-flow rate wells is to transition a well equipped with ESP from continuous operation to intermittent operation, specifically cyclic operation. Intermittent operation reduces energy consumption by up to 40 % and increases oil production by 3 % due to partial gravitational separation of the produced fluid during accumulation. However, the negative effect of transitioning to intermittent operation is reflected in the reduction of the average runtime before failure due to a decreased ESP hydroprotection resource, accelerated wear of the pump unit thrust bearings, and intermediate radial bearings. The cause of these negative effects is the increased vibration level during intensive startup. One way to address these issues is transitioning from the existing scalar open-loop control system to a vector sensorless control system for the ESP. To implement such a system, it is necessary to obtain information about the vector of the ESP state variables. A promising approach to obtaining information about the ESP state involves creating observers based on explicit mathematical models. To create an observer for the state variables, mathematical models for each component of the studied system must be developed and combined into a unified system. When measuring currents and voltages at the output of the step-up transformer, the studied system will be an electric complex «Cable Line — Induction Motor». To implement this observer, it is necessary to determine the parameters of the equivalent circuit of the studied complex. Based on the above, developing a methodology for identifying the parameters of the equivalent circuit of the electric complex «Cable Line — Induction Motor» when measuring currents and voltages on the surface is a timely and relevant task. Solving this task will create prerequisites for the implementation of a vector control system for the ESP, increasing the reliability of the ESP during intermittent operation, and consequently, increasing the profitability of oil production from low- and medium-flow rate oil wells. Aim of research To develop and experimentally confirm the effectiveness of a methodology for assessing the parameters of the electric complex «Cable Line — Induction Motor» based on the balance of consumed power. Research methods Analysis of literary sources, system analysis, mathematical modeling, experimental research. Results The effectiveness of the methodology for assessing the parameters of the electric complex «Cable Line — Induction Motor» based on the balance of consumed power has been experimentally tested and confirmed.

РАЗРАБОТКА НАБЛЮДАТЕЛЯ ЛЮЕНБЕРГЕРА ПОЛНОГО ПОРЯДКА ВЕКТОРА ПЕРЕМЕННЫХ СОСТОЯНИЯ УЧАСТКА КАБЕЛЬНОЙ ЛИНИИ С ПОВЫШЕННОЙ ПАРАМЕТРИЧЕСКОЙ РОБАСТНОСТЬЮ

In addition, in the Russian Federation, 75 % of oil-producing wells in operation at old fields are low- to medium-flow rate wells. One way to increase the profitability of oil production from low- to medium-flow rate wells using ESPs is to reduce the power consumption of the Submersible Electric Motor (SEM) by switching the ESP from a scalar open-loop control system to a sensorless vector control system. To implement the vector control system for ESPs, it is necessary to develop a methodology for identifying the parameters of the electrical equipment in the power channel of the ESP, as well as to implement a full-order observer of the SEM vector state variables to create a feedback channel for angular speed. One of the electrical components in the ESP power channel that affects the accuracy of the SEM vector state variable estimation is the power cable, which can reach up to 5 km in length. Such a long cable length results in the output voltage at the cable end being significantly different in amplitude and frequency from the measured input voltage, and the cable parameters themselves change as the temperature of the well varies depending on the depth. Failure to estimate the output voltage of the cable will result in incorrect estimation of the torque and angular speed of the SEM, which, in turn, may cause the angular speed of the SEM to oscillate and the ESP to trip at the bottom of the well. Due to the above factor, the development of a full-order observer for the vector state variables of the cable line with increased parametric robustness is a relevant and timely task

Analysis of the behavior of asynchronous electric drive with a closed scalar control system when changing the inductance of the magnetizing circuit

The article was devoted to the study of an automated electric drive with a scalar closed-loop speed control system. Severe duty and operating modes of electric drive determine the actual service life. Wear of the induction motor, as a key link of the electric drive, was associated with deviation from nominal parameters. The deviation of parameters of the induction motor equivalent circuit determined the resultant change of characteristics. The parameters of the equivalent circuit determined the accuracy of the adjustment of regulators and optimal algorithms in the control system of the electric drive. In continuous operation modes the possibility of auto-tuning regulators, which requires stopping or no-load mode, was excluded. The paper considered the influence of the magnetization circuit mutual inductance value of the induction motor on the behavior of the electric drive control system. Evaluation of the behavior of the scalar closed-loop speed control system was performed on the basic energy (power factor, efficiency factor) and mechanical (speed, electromagnetic torque) characteristics of the electric drive.

FREQUENCY-PARAMETRIC CONTROL SYSTEM OF AN ASYNCHRONOUS ELECTRIC DRIVE WITH AN OBSERVER OF THE ANGLE BETWEEN THE VECTORS OF THE STATOR CURRENT AND THE MAGNETIZATION CURRENT

In industry, especially metallurgy, a large number of previously installed electric drives based on an asynchronous motor with a phase rotor with uneconomical parametric control systems are used, the advantage of which is the possibility of removing part of the sliding energy from the rotor circuit, and the ability to obtain an increased inrush current multiplicity. The use of frequency converters in such an electric drive allows you to adjust the speed of rotation of the stator field and maintain sliding and losses in the rotor circuit at a minimum level. However, when the rotor windings are shorted, the multiplicity of the starting torque decreases. Additional possibilities for maintaining an increased starting torque of an asynchronous motor with a phase rotor with frequency control are provided by the inclusion of a frequency-dependent active-inductive resistance (IR) in the rotor circuit. In this case, the electric drive will be frequency-parametric. Using an observer of the mutual position of the stator and rotor current vectors, working on the basis of processing the measured signals of instantaneous values of the stator and rotor currents, allows you to build a scalar control system with stator current correction, bringing the operation of the electric drive to the mode with minimal losses in the motor windings.

МОДЕЛИРОВАНИЕ ЭЛЕКТРОПРИВОДА ПЕРЕМЕННОГО ТОКА С АЛГОРИТМАМИ ПРОСТРАНСТВЕННО-ВЕКТОРНОЙ МОДУЛЯЦИИ

The relevance of investigation of induction motor electric drives with frequency converters having voltage source inverter with space-vector modulation is shown. The brief survey of researches of such matter is carried out. The aim of this article is to develop mathematical and computer model of frequency converter with space-vector modulation algorithms by means of Matlab Simulink, this model has to be implemented into the Matlab models of AC electric drives with induction and synchronous motors. To achieve such an aim, it needs to introduce techniques of electric drive theory, numerical techniques, techniques of algebraic equations system solution, techniques of computer simulation. The still two-phase framework is applied to describe the converter model. The two-level voltage source inverter is chosen for the investigation of modulation algorithms. To verify the mathematical model of space-vector modulation, the model of 5.5 kW induction motor is used. Induction motor and power switches are modelled by means of Matlab SimPowerSystems units. The results of simulation show the adequacy of the developed model in both steady state and transient modes. One can conclude the dependence of total harmonic distortion of the induction motor stator current from load torque, switching frequency of voltage source inverter’s power switches and stator current frequency for the electric drive with scalar control system.

Development of a Robust Scalar Control System for an Induction Squirrel-cage Motor Based on a Linearized Vector Model

The paper considers the problem of developing a digital system for an induction motor speed control which has a sensor and a speed regulator to increase accuracy of speed control. Speed control is carried out by a scalar method due to consistent change in the stator frequency and voltage. To obtain the uniformity of the motor overload capability in a given range the control mode is used associated with maintaining uniformity of flux linkage of the motor stator. Induction motor scalar models do not possess high accuracy and their parameters and their parameters can vary over a wide range, which complicates the controller design and achievement of robustness of the speed control system. To eliminate these disadvantages, it is proposed to use a vector model in a rotating coordinate system having subjected it to linearization at different points of the operating mode with the account of the adopted law of frequency control, to ensure robust absolute stability of the system on the basis of application of a graphical method for constructing a modified amplitude-phase characteristic.

MINIMIZATION OF ELECTRICAL CONSUMPTION OF A FREQUENCY-REGULATION INDUCTION MOTOR WITH A FAN LOAD IN START-BRAKING REGIMES

Purpuse. To minimize the total power consumption in start-braking regimes by a three-phase squirrel-cage frequency-regulated induction motor, loaded a centrifugal fan (or smoke exhauster), and also to obtain analytical dependencies for calculating the optimal durations of acceleration and deceleration times, corresponding to minimizing the total energy consumption of this motor in start-braking regimes with the indicated type of load. Metodology. Based on the methods of calculus of variations and numerical solution of non-linear differential equations, the quasi-optimal type of trajectories of speed change (tachograms) of the motor with the considered load in start-braking regimes is determined. Using the methods of mathematical analysis and similarity, the acceleration and deceleration times of an induction motor with a fan load were optimized for different (linear, parabolic and quasi-optimal) types of tachograms. Using the method of computer simulation, the energy consumption in the start-braking regimes of an induction motor with the indicated load for these types of tachograms was quantified. Results. Refined analytical dependencies are obtained for calculating the consumed active power and energy in start-braking regimes by a frequency-regulated induction motor with a fan load for the mentioned various types of tachograms. Analytical optimization of the consumption of active energy of this motor in start-braking regimes has been carried out. The change at the optimal durations for the starting-braking regimes and the corresponding it’s total energy consumption of the motor with varying the maximum value of the motor speed in these regimes has been researched. A quantitative assessment of transient electromechanical and energy processes in the considered motor with a fan load has been carried out. For this motor, as applied to the non-regenerative version of the static frequency converter, a scalar automatic control system is proposed, by means of which the motor accelerates with a constant rotor flux linkage with a given (linear, parabolic or quasi-optimal) speed trajectory and brakes on freewheel. The expected annual saving of active energy by an induction motor, loaded with a smoke exhauster, in starting and braking regimes, achieved by optimizing the form of the tachograms and the duration of the acceleration and deceleration times, is determined. Originality. Analytical dependencies are obtained for calculating the optimal durations of the acceleration and deceleration times of an induction motor with a fan load, corresponding to minimizing the energy consumption of this motor in start-braking regimes. The "U"-shaped form of dependences of the total energy, consumed during acceleration (or the total generated energy during braking) of the induction motor in function the duration of the deceleration (or braking) times is established. An analytical dependence is obtained for changing the speed of a motor loaded by a fan or a smoke exhauster during the freewheel braking regime, and an analytical expression is proposed for determining the duration of the indicated braking time. Practical value. On the example of an induction motor loaded by a smoke exhauster, the possibility of saving the total energy consumption in start-braking regimes was identified: from 77 to 90 % – due to the use of the proposed quasi-optimal tachogram and the use of practically realizable optimal acceleration and deceleration times, and also in the amount of 10 % – through the transition from freewheel braking to regenerative braking. Figures 6, tables 6, references 22.

Improving the energy efficiency of electric drives for auxiliary units of traction rolling stock

The review of technical solutions and schematic characteristics of auxiliary drives for traction vehicles has shown that the most rational variant is an electric drive with an induction machine. Given the operating modes of the auxiliary drives and the share of their power consumption in the total locomotive power, the task of using scalar control systems for induction machines becomes relevant. Based on a mathematical model describing the dynamic energy conversion processes in the T-shape substitution circuit of an induction motor, taking into account stator steel losses and current displacement effects in the rotor winding and saturation along the main magnetic path, possibilities for reducing stator current have been investigated. In order to improve the energy efficiency of electric drives two variants of control system have been proposed. One based on search method of self-tuning to the stator current minimum and the other - on maintaining the power factor of induction motor at the level that ensures equality of active and reactive components of stator current. The hardware and software requirements for implementing control systems have been analysed. Modelling using Matlab has shown that both control systems work - power loss reduction can be as low as 50% and as high as 60% in certain modes.

Energy-efficient variable frequency asynchronous electric drive

Currently, there are quite a large number of various scientific papers on the creation of a controlled asynchronous engine and the optimization of its modes, and the availability of acceptable results for practical implementation, but there is still no single generally accepted approach to solving the problem. In this regard, the issue of synthesis of scalar control systems that provide the minimum value of one or another criterion of energy efficiency is relevant. In this paper, we consider the obtained mathematical model of an asynchronous engine (AE), which differs from the known ones in that the parameters of the substitution scheme are expressed in terms of the stator and rotor conductivities. The energy characteristics of the AE in the sliding function are obtained, which make it possible to determine the dependences of the active and reactive components of the AE current and the possibility of their redistribution within the nominal value of the AE phase current. The principle of optimal frequency-current control of AE is formulated, which differs from the known ones in that, as an energy efficiency indicator, the value of the maximum energy efficiency of AE is used, expressed as the ratio of the active resistance of the rotor circuit to the total conductivity of the AE phase.

RECIRCULATION PUMP SCALAR CONTROL SYSTEM ELECTRICAL DRIVE MODEL S DEVELOPMENT AND RESEARCH

On the basis of the analysis of the used models of the electric motor at synthesis of the asynchronous electric drive with frequency control mathematical and simulation models are received. The structural scheme of the three-circuit scalar control system of the electric drive of the recirculation pump in the form of the simulation model for which the parameters of the scalar control system were calculated is offered and realized. The calculation of parameters and coefficients of the mathematical model of the solar control system of the electric drive is given. The calculations of the pressure of the recirculation pump are presented. The scheme of the simulation model of the subsystem of the unit for calculating the performance and pressure of the recirculation pump is given. Calculations and simulation model of PI current regulator are presented. Calculations and simulation model of PID-speed controller subsystem are given. Calculations andsimulation model of PI-pressure regulator subsystem are presented. Calculations of scalar control system parameters in the form of MathCad scripts are presented. On the received model processes of work of the electric drive of the pump in normal and emergency operating modes were considered. Calculations and simulation model of voltage and frequency converter subsystem are given. Calculations of parameters and coefficients of the scalar control system are given. The simulation model of the sensor unit subsystem is given. The calculations of the frequency converter and the voltage converter are given. The transfer functions of the voltage and frequency converter of the scalar control system of the asynchronous electric drive of the recirculation pump are presented. The simulation model of the fan load subsystem of the scalar control system of the boiler's recirculation pump is presented. The table presents an analysis of the transient characteristics of a two-phase mathematical model of an induction motor. The analysis of transient characteristics of the scalar control system of the recirculation pump is presented.

Necessary and sufficient conditions for assignability of dichotomy spectra of continuous time-varying linear systems

We consider a version of the pole placement problem for continuous time-varying linear systems. Our purpose is to prove that uniform complete controllability is equivalent to possibility of arbitrary assignment of the dichotomy spectrum. The main ingredients of the proof are the reduction of system to upper triangular form and the use of the concept of uniform complete stabilization. To illustrate the theoretical result, we consider scalar continuous time-varying control systems. For these systems we provide a simple necessary and sufficient condition for uniform complete controllability and if this condition holds, then we construct an explicit control to assign the dichotomy spectrum.

Synthesis of a Scalar Automatic Control System of a Valve Engine with Field Control for a Rowing Electric Installation with an Azipod Propulsion and Steering System

The article deals with the main trends in the development of marine automatic AC electric drive systems. A variant of the implementation of an electric drive using an electromechanical converter of a synchronous machine with electromagnetic field excitation is presented. A promising electric drive system with a valve engine for the icebreaker's with the Azipod propulsion and steering system is proposed. The aim of the work is to eliminate the structural complexity and expand the functional capabilities of the electric drive by using a scalar automatic control system of the frequency of rotation in the two-zone control of the valve motor of the EPS. The novelty lies in the use of the approach and representation of the control object-a valve motor as an analog of a DC collector motor controlled by an armature and by a field. The analysis of control processes is directly related to the processes of electromechanical energy conversion occurring in a synchronous machine.

A System for Controlling the Thermal Behavior of Voltage Source Inverters

The thermal behavior of semiconductor devices of voltage source inverters for a traction frequency converter and its control systems are investigated. A test bed for studying thermal processes in steady state and transient modes occurring in semiconductor modules with air forced cooling systems is described. The results of an experimental investigation for the Infineon FF300R06KE3 module are analyzed and compared to the results of a mathematical model. Transfer functions of a semiconductor module as an object of temperature control are synthesized with respect to the collector current, cooling air flow, and frequency switching. The control system of thermal behavior of a voltage source inverter with two control actions on the object of temperature control (cooling air flow and frequency switching) is developed. It is proposed to use an electric drive with an induction motor and scalar control system for the purposes of regulating the cooling air flow. The effectiveness of the proposed control system is confirmed by means of simulation in MATLAB/Simulink in transient and steady-state modes.

RESEARCH OF SCALAR CONTROL SYSTEM OF TWO TRACTION INDUCTION MOTORS FROM BY ONE INVERTER

Most adjustable-speed AC drive systems are constructed in such a way that one motor receives power from one inverter and uses vector control as the basic control principle. However, in some cases there is a need to power several motors in parallel from a single inverter, that minimizes the size, weight and cost of such a system. The most common examples of such systems are rail and urban electric vehicles, where two to four induction motors are connected to drive in parallel. Control of such a system is a difficult task, especially in conditions of unbalanced loads on the motors, that can occur in conditions of different adhesion of wheels with rails. The inability to provide individual control of the motor when powered by a single inverter can lead to a decrease in the safety level of such a vehicle due to the loss of stability when changing the current value of the adhesion coefficient of individual wheel pairs. Mechanical processes in the traction system are analyzed, in which each wheel pair is driven by a separate motor powered by a common inverter. It is shown that the identity of the values of the adhesion coefficients is an important condition for the stability of such a system, that cannot be guaranteed in the actual practice of the operation of the vehicle. Therefore, the development and research of control systems that are capable of operating the system in a variety of rail / road conditions is an important direction for the further development of such systems. The structure of mathematical model of traction electromechanical system consisting of two induction motors powered by one inverter is proposed. The adjustable-speed control is based on the scalar control system, that is the easiest to implement because it does not require the estimation of the state variables of the system components. Sinusoidal pulse width modulation is selected as the switch control signal method. Operation of traction electromechanical system with scalar frequency control law is investigated by mathematical modeling. It has been proven that changing the characteristics of a single wheel pair's adhesion can lead to a loss of stability by a system that is unacceptable in terms of providing a comfortable and safe operation of the vehicle. Keywords: traction electric drive, scalar control, adhesion, mathematical model, frequency control

Ограничение колебаний электромагнитного момента асинхронного двигателя при скалярном частотном управлении

The paper presents mathematical models of induction motor as a system of equations and a structure. It also suggests the correction methods of induction motor with scalar control, which decrease fluctuations of electromagnetic torque. The graphs of the transients of the frequency-controlled electric drive with scalar control, obtained based on the mathematical model with and without additional correction device, are given. The presented scalar control system for induction motor allows starting the electric drive and regula­ting the speed with the stabilization of the electromagnetic torque of induction motor with a maximum deviation from the mean value under 5 %, as well as suppressing the engine speed fluctuations in transient modes. The frequency-controlled electric drives with induction motor and scalar control with improved dynamic properties can be applied in metallurgical mechanisms.

Bit Rate Conditions to Stabilize a Continuous-Time Scalar Linear System Based on Event Triggering

This technical note is mainly concerned with bit rate conditions to stabilize a continuous-time scalar linear control system which transmits its feedback information through digital communication networks. It shows that when a packet is received, not only the bits inside that packet but also the receiving time instant of that packet carry information. The latter could carry a huge amount of information and can be obtained through simply receiving a packet without additional communication cost. Therefore it is an efficient way to encode information into the receiving time instant of a packet. The receiving time instant, however, cannot be accurately controlled by the sensor/sampler which can determine only sampling time instants. The difference between the sampling and receiving time instants of a packet is up to two delays, including the delay to process and encode the packet and the network delay to transmit that packet. These delays cannot be precisely known and have negative effects on the amount of information carried by receiving time instants. Under the boundedness assumption of these delays, this technical note provides some bit rate conditions to guarantee the system's input-to-state stability by making a good use of receiving time instants. Through event-triggering schemes, we realize these conditions which may require much lower stabilizing bit rates than periodic sampling schemes. Simulations are done to confirm the effectiveness of the obtained stabilizing bit rate conditions.

Digital Control System of Two-Motor Ac Electrical Drive Built by Principles of Harland

Abstract In the paper, optimization of scalar control system of two-motor electrical ac drive with individual regulators of speed is investigated. Structural scheme of the drive is constructed via electromagnetic process agreement taking into account elasticitic shaft. The expressions for the optimal parameters of digital regulators for stator currents of the motors and speed of the drive are given. Modelling results obtained on the computer are given. The considered system of ac drive provides optimal dynamic character as well as automatic distribution of loading between the motors.