Showing papers presented at "International Symposium on Industrial Electronics in 1992"

The parallel operation of two UPS by the coupled-inductor method

Abstract: For expanding uninterruptible power supply (UPS) capacity, the coupled-inductor method is proposed for the parallel operation of two UPSs in this paper. Because of the use of the magnetic coupling concept, the circulating current flowing through the respective inverters can be avoided, and the load can be automatically shared between the two UPSs. In parallel operation with the coupled-inductor method, a little error of phase angle between the UPSs can be allowed, so the control circuit is simple to implement in the practical application. >

Tuning of PI controllers based on gain and phase margin specifications

Abstract: The authors examine a class of tuning formula associated with the relay auto-tuning, cross correlation auto-tuning and other self-tuning PI/PID controllers. These methods measure the ultimate gain, ultimate period, simplified process model parameters e.g. gain, time constant and dead-time or some related frequency response data e.g. a point on the Nyquist curve. The estimates are then used in the tuning formulae. It has been found from extensive simulation that the modified Ziegler-Nichols formulae give good responses over a wide range of process dynamics. A more general approach is to use the combined phase and gain margins approach. However, the method to date could only achieve a compromise in phase and gain margins by designing to move the compensated Nyquist curve to pass through a specified design point. The performance of this tuning formula, however, is found to be too conservative especially when the dead time is large. The authors propose an analytical method to tune/design the PI controller to pass through two design points and the Nyquist curve as specified by separate gain margin (A/sub m/) and phase margin. >

Sensorless force control of direct drive manipulator

Abstract: The authors describe a method of a sensorless force control of direct-drive robot which has three-degrees-of-freedom. In the proposed method, a disturbance observer, which estimates the total sum of disturbance effects, is employed in each joint. First, the robust motion controller is realized by the feedback of the estimated disturbance torque. Secondly, the reaction force (reaction torque) is calculated from the estimated disturbance torque and the motion equation of robot. Finally, the calculated reaction force is fed back to obtain the sensorless force controller. This method is so simple that the total algorithm is executed in the on-line calculation. Several experimental results are also shown to confirm the validity of the proposed method. >

PID auto-tuning controller using a single neuron for DC servomotor

Abstract: The single neuron used has three input connections that have associated weights. Each gain parameter corresponding with each weight of the single neuron is determined in accordance with the learning method based on the delta rule. The structure of this system is very simple and practical. The motor speed control system with 100 W DC servomotor has been simulated and experimented upon. These results show the good tuning performance of this controller. >

A new method for optimal output of a solar cell array

Abstract: A new method for optimizing the output of a solar cell array is presented Several curves printed under different solar radiation levels and temperatures is given out It is confirmed by an experimental setup that introducing this output control method, compared with using the traditional charging method, can obtain notably more power from the same solar cell array >

Control of indirect field-oriented induction motor drives considering the effects of dead-time and parameter variations

Abstract: In this paper, a speed controller considering the effects of system dead-time and parameter variations for indirect field-oriented induction motor drives is presented. Firstly, a two-degree-of-freedom speed controller is designed to math the prescribed speed command tracking and load regulation specifications. Then, a dead-time compensator and a model following controller are augmented to enhance the robustness of the speed controller. The simulated and experimental results show that good control performances both in the speed command tracking and the load regulation characteristics are achieved. >

Optimum design of single switch resonant induction heater

Abstract: The availability of low cost power switching devices has opened up the application of induction heating for domestic cooking. This paper describes a single switch resonant inverter for this application. A performance index for the switch (output power/switch VA rating) is proposed. The operating point can be selected to realize the best switch utilization. >

A new microprocessor based approach to an automatic control system for railway safety

Abstract: A new microprocessor based automatic control system for railway safety is presented in this paper. The advanced control system is called the Automatic Train Safety System (ATSS). For many years, safety has been one of the most important problems in railway traffic organization. In the design of the ATSS, a fault-tolerant computing technique is applied in both hardware and software for the reliability and safety of the system. In addition, the principle of fail-safe is employed at the system level. All of the programs in the system are designed using a modular structure. The authors' research is the first step towards the application of microprocessors in real-time railway control systems in China. >

A new method for leather texture image classification

Abstract: A new texture classification method intended for classifying leathers made of the same materials is presented. Unlike the conventional methods which mainly use global features, the authors use both global features extracted from the two dimensional power spectrum of enhanced leather trench image and the local features based on mathematical morphology operation of a segmented leather image. The experiment is conducted on a group of sample leathers and the results are satisfactory. >

Field oriented control of an asynchronous motor with a very wide region of flux weakening

Abstract: In the first part of the paper, the torque capability of an inverter-fed saturated induction motor is determined. The maximum torque being available for short-time duty and the corresponding flux are calculated considering the limitations of the current and the voltage only. The flux weakening region consists of two parts which require different control strategies. At partial load the efficiency can be optimized. The results are implemented in a field oriented control which makes use of a flux and a voltage controller. With regard to the coupling of the d-axis and the q-axis existing in the machine, priority is given to the control of the d-components. The improvement of the performance being achieved by the new control strategy is verified by experimental results. >

Operational characteristics of switched reluctance motor drives

Abstract: Renewed interest on switched reluctance motor drives has been motivated by its robustness and its relatively high performance in comparison to induction motor drives. This paper presents the operational characteristics of switched reluctance drives and discusses some design related issues affecting its performance. >

Sensor-based robot systems

Abstract: Sensor based robot control systems can overcome many of the difficulties of uncertain models and unknown environments which limit the domain of application of current robots used without external sensory feedback Among various sensors, vision is expected to play a very important role in control of intelligent robot In this paper robot control systems with vision are firstly discussed Then a control scheme for a robotic manipulator system is described, which uses visual information to position and orientate the end-effector Recently there has been increasing interest in upgrading robot intelligence by using multiple sensors Therefore this paper also focuses on the multiple sensor system, especially sensor integration or fusion schemes A navigation method for a mobile robot based on cooperation of vision and range sensors is described >

Design of an optimal robust model matching controller for the elimination of interarea power system oscillation

Abstract: A novel controller design approach and its measure of robustness are presented for the elimination of interarea power system oscillations. The design method involves the minimization of a suitably selected performance index to reflect a required model matching object. It can be used to eliminate low frequency oscillation between interarea power systems. >

A new design method for nonminimum phase MRACS in the presence of disturbances

Abstract: This paper presents a new design method for nonminimum phase MRACS (model reference adaptive control system) in the presence of disturbances. It is assumed that the unknown deterministic disturbances are described by a polynomial function of time with known degree and unknown coefficients. The proposed scheme uses only input and output data and the existence of bounds for all signals is proved, which assures the output error convergence to zero. Finally, the results of computer simulation are presented to illustrate the effectiveness of the proposed method. >

Real-time thresholding using histogram concavity (image processing)

Abstract: In this paper, the authors present a method of generating a real-time threshold for each incoming image frame using the histogram concavity technique. A real-time histogram hardware unit is built to facilitate such approach. The system can determine the optimal threshold value once the frame is obtained, and it takes about 10 ms to work out this value. >

Variable structure control with sliding mode for self-controlled synchronous motor drive speed regulation

Abstract: The variable structure control strategy is a potential tool for designing a closed-loop system which contains variable of indeterminate parameters. The application of variable structure theory to a self-controlled synchronous machine is discussed, in which a microprocessor-based digital regulator is used to make up a nonlinear regulation system. The simulation and experimental results show that the dynamic performance meets the given requirements. >

Variable structure predictor controller with quasi-sliding mode for systems with delay

Abstract: The main feature of variable structure control systems is the sliding mode. In the sliding mode, the eigenvalues of the system are specified and the system enjoys invariance to parameter variations and disturbances. Then, how can one apply this control method to the systems with time delay? In this paper, the discrete variable structure controller is first reviewed and discussed. Combined with the predictor control method, the authors propose a variable structure predictor controller with quasi-sliding mode. Simulation results are presented illustrating the effectiveness of the control method. >

Fast 2D convolution filter based on look up table FFT

Abstract: This paper shows a fast implementation method of a two dimensional (2D) filter. The filter design is based on fast convolution related to the fast Fourier transform (FFT) look up table. This is then extended to the 2D FFT. The design and implementation of the system gives a good accurate selection of the desired frequency. The system has a step advantage of a reduction in the operation time. >

Adaptive frequency measurement (AFM) for vortex flowmeter signal

Abstract: This paper proposes a new adaptive frequency measurement method (AFM) for vortex flowmeter signals. Based on AFM, one can construct a new adaptive vortex flowmeter. Theoretical analysis and experimental results have proven that this method is practical for improving the measurement accuracy of the vortex flowmeter in practice use, and that this method can also be used in the other measurement and instrumentation systems. >

A field acceleration method for induction motor drive using a novel space vector based current controller

Abstract: In this paper, a field acceleration method is proposed for controlling the motor torque directly to achieve instantaneous response without oscillation. One of the advantages is that no time varying coordinate transformation is required and the hardware implementation is greatly simplified. At the same time, a new space vector based current controller is proposed to effectively coordinate with the previous method. The new current controller is able to provide a sinusoidal current waveform and has very quick current response. In addition, it can take full advantage of the zero voltage-space-vector such that the switching frequency is much reduced without sacrificing the required performance. As a result, the inverter efficiency can be increased. It is seen that through the integration of the above two parts, the proposed drive system is extremely simple to implement and has excellent performance. >

On the initial conditions in learning control

Abstract: The effect of the initial conditions on establishing learning control schemes for nonlinear systems is studied in this paper. The quantitative boundedness of the output errors between the actual and the given trajectories is obtained in the presence of initial state errors when a so-called D-type learning control is used directly. The robustness of learning control law with respect to the existence of initial errors, fluctuations of system dynamics and measurement noises is discussed. If high-gain state feedback to the open-loop systems is employed before the learning control loop is enclosed, then the output errors of the system will be independent of the size of the initial state errors at every operation. >

The evolution of power electronics

Abstract: The author presents a meaningful definition of power electronics. The definition offered includes for two reasons the phrase 'by static means'. One is rather obvious, and that is to exclude equipment that intimately depends on components employing moving parts and mechanical switching. The other is perhaps less obvious; it is to allow the inclusion of magnetic amplifiers under the category of power electronics equipment. >

Effect of slot ripples on damper windings of synchronous machines

Abstract: The authors summarize the experimental results of the effect of slot ripples on damper windings of a synchronous machine under the steady state operation in a one-machine connected to an infinite-bus system. A new method of directly measuring damper winding currents inside a synchronous generator has been established. In particular, the physical relationship between airgap fluxes and damper winding currents both at no load and on-load has been made clear. The effect of saturation on damper currents are also examined. >

Development of CAPP system for removal operation of 3D free surfaces

Abstract: The authors deal with the development of a computer aided process planning system (CAPP) for manufacturing products having 3D free-form surfaces. It is difficult to perform a form feature modeling of free-form surfaces, and to clear the relationship between the removal form and cutting tool form. To solve these problems, the authors extract the concavity of the product model by paying attention to the product concavity. Considering that the concavity is the most important part in the machining of the free surface, a local concavity model is produced by judging concavo-convex. This model is analyzed and characterized with geometric shape and machining conditions. The connection relationship between each area is represented as graphs. The authors carried out the process planning using the form feature model. >

Control of stator voltage-controlled current source induction motor drive

Abstract: This paper presents a comprehensive study on the stability of several control schemes for the induction motor driven by current source inverters. A stator voltage-controlled current source inverter driven system without a speed sensor is investigated in order to find appropriate control schemes, which are primarily based on a direct or, alternatively, an indirect frequency control scheme. The overall control systems with either a voltage control loop or current and voltage control loops, provided in addition to each frequency control scheme, are analyzed by utilizing the root locus method and simulated by computer to show the validity of this analysis. >

High precision intelligent apparatus driven by a step motor for measuring liquid level

Abstract: This paper presents a steel rope float type apparatus driven by a step motor for measuring liquid level. The apparatus consists of a tank top gauge, a pulse power supply, a STD industrial computer (Z80CPU) and a multiplexer. This apparatus has the features of very simple mechanic construction of the top gauge, uncomplicated circuit, highly accurate measurement, almost no influence by surrounding temperature variation, low cost, convenient operation, and easy maintenance. It can be not only used in making a long distance tour of tank group measurements but also can be plugged into a distributed control system (DCS) so as to directly provide data. >

Programmed PWM inverter using PC for induction motor drive

Abstract: A PC/AT (Intel 80286 based) controlled transistorized inverter with programmed PWM technique for induction motor speed control is discussed. The switching angles for eliminating unwanted harmonics up to 600 Hz are predetermined such that the immediate dominant voltage harmonic is minimized. The realization aspects of the above technique and the method by which closed loop speed control is achieved are described. The performance features of the developed prototype are described by presenting the relevant waveforms obtained experimentally. >

A neural network adaptive observer for field oriented control

Abstract: A neural based adaptive observer is proposed for field oriented asynchronous machine control systems. It comprises two artificial neural networks (ANN) which are trained to learn the rotor flux and stator voltage dynamics respectively. After training, the ANN adjusts the slip signal command, thus providing decoupling of the flux terms. The ANN are subject to online training performed on the basis of voltage errors. Simulation results show that the proposed observer behaves very satisfactorily under rotor time constant changing conditions. >

A compact high performance 16-bit microprocessor controller AC-servodrive

Abstract: This paper describes a 16 bit microprocessor controlled 1 kVA AC servomotor drive system which has a high performance and a compact design. The servodrive has three main components, a high power factor rectifier, a highly integrated PWM VSI inverter and a microcontroller which all represent the latest technology in the field of servomotor drive systems. The microcontroller manages both modulation, field vector control with three control loops, monitoring and data acquisition. Test results show a fast response in the control loops as well as a unity power factor is achieved at line input. It is concluded that a reliable, flexible, highly integrated and compact servomotor drive system is realized. >

Modeling and analysis of losses within the switching process in real-time systems

Abstract: An analytical approach to analysis of losses within the switching process in real-time systems is considered by the author. Distributions of losses and other characteristics for priority disciplines of absolute and mixed types are given here. >