The possibility and desirability of damping the step response of stepper motors has been noted by many authors. A root locus interpretation is presented in this paper which shows concisely some aspects of the damping. A method for providing damping when using a Pulsewidth Modulation (PWM) chopper is presented and it is shown to be possible to introduce damping in single or multi-phase excitation modes. These ideas have been implemented by the authors on three different stepper motors and some practical conclusions are presented.
A new type of software system for an industrial sequence controller is proposed. In this system, a control program is described with the Petri net-like language named Control-net (C-net). This language improves control software maintainability and flexibility. An efficient C-net interpretation schema for real-time control is presented and an overhead time evaluation model of the proposed schema is developed. Through the model analysis and measurement of the response time of an interpreter on a microcomputer, it is proved that the interpretation schema satisfies the required response time. Finally, a microcomputer based controller named Station Controller (SCR) in which the presented C-net interpreter was installed is described and several applications of this controller to real systems are illustrated.
The conventional proportional P controller has been often used as the position controller of the dc servo motor. When the unknown and inaccessible load torque, such as the coulomb friction, the gravity, and so on, is imposed on the dc servo motor, this control system has the steady-and/or transient-state error.
A device is described for measuring temperature and other parameters of high-voltage transmission-line conductors. A transmitter at line potential sends data from seven multiplexed transducers to a ground-based receiver through a fiber-optic link. The system is linear in operation throughout, the data being encoded onto the optical fiber by a voltage-to-frequency converter.
A speed-control system with a separately controlled current source converter is proposed for a doubly fed synchronous motor. Conventional systems with a voltage-source converter develop negative damping torques and become unstable. The theoretical analysis for a linearized model shows that the proposed system eliminates negative damping torques. The digital simulation of a nonlinear model and experiments using a laboratory machine verify the theoretical predictions. The system has the advantages of a simple frequency converter construction and a wide-range speed control capability from standstill to supersynchronous speeds.
An efficient ac-to-dc converter with reversible power flow, which embodies an active, low-frequency filter, is presented. A nondissipatively controlled, nonlinear resonant oscillator is used to extract electric energy directly from the phase pairs of the polyphase supply line and to generate a mixed amplitude-and frequency-modulated carrier. The demodulated carrier and the resulting 20-kHz pulse train produces, after being processed by a high-frequency filter, an active, low-frequency filtering effect for attenuation of the 360-Hz ripple of the apparently ``rectified'' three-phase supply line. The system is governed by means of a pulse area control mechanism with a verified response time of one 10-kHz cycle, or 100 µs. The customary dc link between the three-phase line and the converter's 20-kHz pulse-processing mechanism in the form of a common rectifier-filter is completely eliminated. Data obtained from the test of a 3-kW feasibility model are analyzed in support of the presentation of the significant aspects of design and technology.
A new ac voltage regulator is proposed which employs thyristors as switching elements in the secondary of a power autotransformer.
Time-optimal feedback controllers are studied for systems with delay in control. The control input is assumed to be bounded. Design methods are presented for continuous-time as well as discrete-time controllers. Sensitivities of the control system performance due to mismatches between the model and the plant are also studied. Finally, an adaptive time-optimal feedback controller is investigated which is capable of updating model parameters during normal system operation.
A method to stabilize a phase-locked loop (PLL) dc motor control system is described. Integral square error (ISE) criterion is used to find out the constants of the stabilizing circuit for giving an optimum response. Transient response of the system is calculated for a sudden loading condition and changes in reference frequency. Experimental oscillograms are also included.
In this paper the extension of the subharmonic method for pulse-width modulation (PWM) systems, in the case in which the ratio between modulating and carrier wave amplitudes can be varied from 0 to ∞, is studied in an analytical way. This method allows us to obtain an inverter output waveform variable continuously from a nearly sinusoidal to a square wave and to increase somewhat the amplitude of the fundamental output wave without a significant worsening of the harmonic content, a feature particularly useful for drives with wide speed variations or which need an optimized use of dc power supply.
A microprocessor-based digital PLL speed control system for motor drives is discussed on its load characteristics, stability, and speed control accuracy. The digital and hybrid simulations as well as the Z transform are used to analyze these items of discussion. As the results of the analysis, two compensating methods, that is, the current compensator and the speed feedback loop are proposed for enlargement of both static and dynamic operating load torque ranges of the PLL-controlled motor. This effect of the compensators is predicted through theoretical procedures, assessed by the hybrid simulator, and confirmed by experiments. The effects due to the current compensator and the speed feedback loop on the stability and the speed control accuracy of the PLL system are inspected with the aid of digital and hybrid simulations. These compensators do not virtually affect the stability of the PLL system. The speed control accuracy of the PLL system can be increased by virtue of the speed feedback loop. Design examples based on the discussion in this paper are provided and the authors conclude that the methods for performance improvement have substantial effects on the practical design for the microprocessor-based digital PLL speed control system.
A design method, which decouples an interactive system by using a compensator obtained from the plant inverse matrix, which is often called the direct-decoupling method is modified in this paper. The modified direct-decoupling method uses the adjoint matrix instead of the inverse of the plant matrix to construct the compensator. The method uses a frequency-domain model-reduction method to simplify the degree of the given plant transfer function matrix and the obtained compensator. For an open-loop stable multivariable system, the proposed method gives a simple, practical, and realizable controller without using an unstable pole-zero cancellation approach.
The synchronization of a controlled oscillator with external frequencies is investigated, and conditions for synchronization without cycle skipping are ascertained. Locking requirements are determined analytically by an indirect approach for a class of PLL's embodying first-order linear filters. The validity of this analytical approach is supported by experimental observations and is justified by considerations on the region of attraction, which can be obtained by the procedure suggested.
Digital control of static power converters such as pulsewidth modulated (PWM) inverter realizes the precise waveform control which copes with interference problems by selective elimination of harmful harmonics not only in load voltage but also in source current. Moreover, software control has a great advantage in allowing such a flexible system design or adaptable modification of characteristics by only memory change or program revision with the hardware intact. In this paper, a novel system configuration technique using microprocessors is proposed.
This paper extends the novel application of the principle of pole-amplitude modulation to that in time for ac to ac conversion resulting in a single-phase frequency changer. A general method of suppressing a sideband frequency of the modulated public system and the results of the initial work carried out with a view to realizing a frequency changer are described. Herein is shown that for a given modulation ratio, depending on the modulating wave sequence, either of the sideband frequencies in relation to the public supply could be realized with the other completely eliminated. It is concluded that the amplitude-modulated power supply may well prove to be complimentary to the conventional cycloconverter in addition to the frequencies obtainable which are outside the frequencies available from a normal cycloconverter.
In the present work, an analysis concerning the torque performance of a two-phase induction motor is carried out. The analysis is based on the first-harmonic approximation of distorted by triac voltage waveforms and concerns the case where the motor is driven by two quadrature voltages one of which is controlled by a triac. As an extension to the above analysis, the unusual case in which the motor is driven by two in-phase voltages with the triac acting on one-phase winding, is also considered. For this case of motor driving, it is pointed out that a torque is developed in motor due to voltage phase shifting caused by triac nonlinear action. This could be perhaps of value for specially designed motors which would provide the ability of using triacs instead of capacitors for quadrature voltage production and torque generation.
Oscillatory processes in two dimensions are well known, and most of the electronic oscillators exhibit a dynamic behavior, which is related to them. The aim of the present paper is to demonstrate and analyze an oscillatory process in three dimensions. The mathematical model considered possesses, as solutions in steady state, three stable sinusoidal waveforms arranged symmetrically as is usual in a three-phase supply system. The dynamic behavior of the model is thoroughly investigated and it is shown that it is related to the dynamic behavior of a well-known symmetrical quadrature oscillator in two phases. This relationship suggests that a practical system realized according to the model equations should possess the properties of a high-quality quickly responding voltage-controlled oscillator (VCO). This useful feature has been demonstrated experimentally by investigating the performance of a corresponding instrument.
The specific objective of this paper is to develop multiloop controllers that would achieve asymptotic regulation in the presence of parameter variations and disturbance inputs for a tubular reactor used in ammonia synthesis. The dynamic model considered here has nine state variables, two control inputs, and two outputs. A systematic procedure for pairing the two inputs with the corresponding two outputs is presented. The two multiloop proportional controllers so configured are designed via the parameter plane method. This economic configuration of controllers maintains the temperature profile almost at the optimal value whereas the point controllers fail to do so.
This paper describes a microwave sweep frequency oscillator operated by means of a microprocessor. The frequency of the oscillation depends on the control of a YIG (Yittrium Iron Garnet) filter and an electronic phase shifter placed in a closed loop with amplifiers. The frequency is controlled directly by a Rockwell AIM 65 microprocessor in both fixed-and swept-frequency operating modes.
The design of a miniature, recording cardiotachometer is described. It is simple and can store digital data. Bench and field tests, using a hand-held display, are presented. Construction and principles of operation are discussed. Applications, with performing athlete subjects, are outlined.
