Prof. Dr. Joachim Holtz
Editor-in-Chief
|
Prof. Dr. Joachim Holtz |
IEEE Transactions on Industrial
Electronics
Volume 44, Number 3, June 1997
Special Section on Factory Automation
Abstract - The availability of considerable computer processing power,
at a low cost, as well as substantial advancement in software development
techniques, had a large impact on factory automation. Factory automation
is concerned with automation of processes of the kind found in
manufacturing, chemical process, power generation, and other industries.
Automation aims at replacing, or complementing, or assisting human
beings in activities requiring physical and/or intellectual effort.
The manufacturing industry is the one which felt the most impact of the
technological changes which took place in recent years. This is not
surprising, as this industry is largely responsible for production of
consumer goods. The growing international competition in the area of
consumer goods forced companies to adopt many new technologies to retain
competitiveness or gain new markets, mostly through low prices offered
and increased consumer satisfaction.
Factory automation involves technologies which are rooted in mechanical
engineering, electrical and electronic engineering, and computer science
and engineering.
This special section on Factory Automation reflects the
use of these technologies by practitioners from research establishments
and the industry. The section includes four papers. Two papers were
contributed by researches and practitioners from Japanese corporations:
Toshiba Corporation and Mitsubishi Electric Corporation. The work
reported in these two papers was motivated by needs for practical
solutions to increase productivity as well as improve quality and
reliability of the processes involved. The Guest Editor of this special
section on Factory Automation would like to thank the authors of these
two papers for the contribution. Two other papers were contributed by
researches and practitioners from industrial oriented research and
development establishments: INRIA-Lorraine, France and Institute of
Industrial Science, University of Tokyo.
The section begins with a paper by Yasuo Namioka, Toshikazu Tanaka,
Hiroyuki Mizutani und Takayuki Matsudaira of Toshiba Corporation. This
paper focuses on the sequence control program design. It introduces a
new planning-based visual programming method to increase productivity of
the design phase of the sequence control programs, and improve quality
and reliability of control specifications. The proposed planning method
is based on an equipment-level state space model for plants, and a new
scope-restricted Dijkstra algorithm for state space search.
The second paper in the section is by Masanori Akiyoshi of Mitsubishi Electric
Corporation and Shogo Nishida of Osaka University. In this paper, the
authors report on the development of a new approach to generating casual
explanations. Casual explanation can give insight into casual
relationship between events defining dynamics of a system. Thus allowing
for meaningful interpretation of numerical data obtained using
quantitative simulation techniques. The availability of casual
explanation can be of assistance to a decision maker in activities such
as process control and monitoring, for instance. The key aspect of the
aspects of the approach are qualitative modelling with the reduction of
the dependency structure of a detailed quantitative model, and
justification based simulation with quantitative data.
Next paper in this section is by Jean-Marie Proth, Nathalie Sauer and Xiaolan Xie of
INRIA-Lorraine. This paper deals with the issue of optimizing
transportation devices in a manufacturing system. The objectives are to
maximize productivity of a system and minimize the number of
transportation devices, which are usually very expensive. To solve this
very practical problem, the authors adopt Event Graph, a type of Petri
net model, to represent the manufacturing system, and propose a variant
of Branch and Bound algorithm to obtain optimal solution.
Finally, the last paper in the section is by Richard Zurawski of University of Tokyo.
This paper deals with the design stage of manufacturing systems using
Petri nets. The focus is on verification of the correctness of the
interfaces of the components of the design model. It introduces a
concept of functional abstractions which allow for the reduction of the
complexity of design models of large-scale manufacturing systems. The
paper also defines functional abstractions of models of typical
components of manufacturing systems.
We hope that the readers will find the material presented in this
special section on Factory Automation of interest to them. We also hope
that this section will help many of its readers develop better
understanding of the range and variety of issues involved in Factory
Automation.
Abstract - The planning method adopted in VIsual Programming System for Sequence control program SpeciFiCation Design (VIPS/S-SFCD) is described. VIPS/S-SFCD is based on two unique features: 1) an example-based programming technique in which designers specify the initial states and goal conditions of equipment blocks using visual representations; 2) a planning method that infers machine actions and generates control program specifications. The planning method is based on a state space model and uses scope to make the searches more efficient. To investigate the effectiveness of the method, VIPS/S-SFCD was used to experimentally generate control program specifications for an existing steel plant. The results showed that the quality of the control program specifications generated by the planner was equal to that achieved by a design specialist, and the time required for designing control programs was much shorter. Using VIPS/S-SFCD, errors in writing specifications are reduced because designers can easily understand the initial and goal state of an equipment block and the sequence of state transitions. The reliability of the specifications is improved because VIPS/S-SFCD generates valid segments of the specifications. The design time is also reduced because designers can use high-level instructions that closely reflect their thought processes.
Abstract - One of the central issues of Qualitative Reasoning is generating causal explanation in response to user's query. The construction of an adequate model is crucial to the generation of valid explanation in case of large-scale systems. This paper describes a new approach to the model construction based on using Causal Ordering algorithm and qualitative conversion of numerical data. Our approach involves two key ideas: A qualitative model is constructed from a unique quantitative model. Simulated qualitative behavior aspects are compared with numerical data. This approach is illustrated by using it to generate casual explanation related to the operation of a power plant.
Abstract - An important step when designing a Flexible Manufacturing System (FMS) using Automated Guided Vehicles (AGVs) is the definition of the number of AGVs to be used in order to reach a given productivity. A way to define this number is to consider several scenari, to define the minimal number of AGVs required by each scenario, and to keep the maximal of these numbers. In this paper, we propose a Branch and Bound (B&B) approach to define the minimal number of AGVs require for a scenario. This approach is based on an Event Graph (EG) formulation.
Abstract - One of the central issues of Qualitative Reasoning is generating causal explanation in response to user's query. The construction of an adequate model is crucial to the generation of valid explanation in case of large-scale systems. This paper describes a new approach to the model construction based on using Causal Ordering algorithm and qualitative conversion of numerical data. Our approach involves two key ideas: A qualitative model is constructed from a unique quantitative model. Simulated qualitative behavior aspects are compared with numerical data. This approach is illustrated by using it to generate casual explanation related to the operation of a power plant.
Regular Papers
Abstract - This paper presents the synthesis and performance of a shunt active power filter based on the three phase PWM voltage converter connected to the AC mains. Current harmonics and asymmetries caused by non-linear loads can be compensated. A decoupled system in Parks variables is achieved and so simple controllers with excellent performance can be used. The controllers are implemented directly in the Parks referential. Expressions for the controllers synthesis are derived. Experimental results from a 2kVA IGBT prototype showing excellent dynamic and steady state systems performances are presented. The control circuit is implemented with analogue and digital electronic circuits. A considerable amount of electronic circuits is needed. The method presented in this paper can also be implemented with a DSP.
Abstract - This paper presents an active power filter based on DSP controller with enhanced current control performance. A novel predictive current control method is introduced to compensate the phase error of harmonic components caused by discrete sampling and finite non-negligible execution time delay. The concept of average current control is also introduced that is adequate for digital current control. With a close coordination between the reference current prediction, PWM pattern generation, and control timing, a high performance control is achieved. Experimental results show that the developed system gives satisfactory performance in harmonic and reactive power compensation.
Abstract - This paper presents an active power filter based on DSP controller with enhanced current control performance. A novel predictive current control method is introduced to compensate the phase error of harmonic components caused by discrete sampling and finite non-negligible execution time delay. The concept of average current control is also introduced that is adequate for digital current control. With a close coordination between the reference current prediction, PWM pattern generation, and control timing, a high performance control is achieved. Experimental results show that the developed system gives satisfactory performance in harmonic and reactive power compensation.
Abstract - Parallel operation of two 6-pulse uncontrolled bridge rectifiers, to obtain a 12-pulse rectification, without an interphase transformer connected on the dc sides is investigated in this paper. The mechanism of interactions between the two 6-pulse bridges is analyzed. As the load current varies from no-load to the complete short-circuit value, seven modes of operation are recognized. Equations describing the mean output voltage and various operating angles of the rectifier circuit are given in terms of a reactance factor. Voltage regulation and variations of the ignition angle and the commutation overlap angle for rectifiers with and without an interphase transformer are also compared.
Abstract - In this paper, the imbricated cells multilevel converters are studied and modelled from a control view point. These converters make use of several switches connected in series which allows using switches with reduced voltage ratings; these low voltage switches have lower conduction losses and can switch at higher frequency. In addition to this feature common to all converters using series connected switches, the control signals of multilevel converters can be phase-shifted to increase the apparent switching frequency and improve the dynamic performances of the whole converter. It will be shown that a multilevel inverter leg composed of p pairs of switches and p-1 capacitors forms a multivariable non-linear system that cannot be properly modelled by standard methods such as state space averaging. The transient behaviour of this system depends on the current harmonics and their phase-shift with the different control signals. A specific model will be detailed, studied and used to illustrate the properties of these converters. In particular, the natural balancing of the voltage across the switches will be demonstrated and the time constants involved in this process will be determined.
Abstract - A three-phase rectifier employing three single-phase boost power factor correction circuits is analyzed. Each converteris ensured by a common voltage loop driving the individual current loops of the three converters. A suitable circuit arrangement is devised to limit phase interaction. The zero-voltage-transition technique (ZVT) is successfully Results of a 1800W, 100kHz experimental prototype are reported, which confirm the theoretical forecasts.
Abstract - This paper presents an active power filter based on DSP controller with enhanced current control performance. A novel predictive current control method is introduced to compensate the phase error of harmonic components caused by discrete sampling and finite non-negligible execution time delay. The concept of average current control is also introduced that is adequate for digital current control. With a close coordination between the reference current prediction, PWM pattern generation, and control timing, a high performance control is achieved. Experimental results show that the developed system gives satisfactory performance in harmonic and reactive power compensation.
Abstract - In this paper, we have evaluated the difference between the slip frequency type and the flux feedback type in discrete time. Both vector control systems in discrete time, designed equivalently in continuous time, have different discretization errors. Especially, in large sampling time region, the slip frequency type (using the rotor flux frame model) is less influenced by the discretization error than the flux feedback type (using the stator frame model). In this sense, the slip frequency type is superior to the flux feedback type. But the stator frame model is linear and the rotor flux frame model is nonlinear. The flux feedback type using the stator frame is easier to design the controller and the observer, Therefore we think that the vector controller and the observer should be designed using the stator frame model and that after transformed to the rotor flux frame model, it should be implemented.
Abstract - The use of modern identification techniques to the problem of determination of the values of the steady state equivalent circuit parameters of a three phase squirrel cage induction machine is discussed. The identification procedure is based on the steady state phase current versus slip and input power versus slip characteristics. The proposed identification algorithm is of a non-linear kind. The machine parameters are obtained as the solution of a minimization of least squares cost function of the difference between calculated and experimental steady state characteristics. Simulation as well as experimental results concerning the application of the proposed algorithm to the modeling of a 1.5kW wound rotor three phase induction machine are presented.
Abstract - A DSP-based permanent magnet (PM) synchronous motor (SM) drive with a proposed recursive least square (RLS) estimator and real-time integral-proportional (IP) position controller is introduced in this study. First, the rotor inertia constant, the damping constant, and the disturbed load torque of the synchronous motor are estimated by the proposed RLS estimator, which is composed of an RLS estimator and a torque observer. Next, the IP position controller is real-time designed according to the estimated rotor parameters to match the time-domain command tracking specifications. Then, the observed disturbance torque is fed forward to increase the robustness of the synchronous motor drive. The analysis, design,simulation, and implementation of the proposed controller are described. Good control performance, both in the command-tracking and the load-regulating characteristics of the rotor position, is achieved.
Abstract - Robotic manipulators are multi-variable nonlinear coupling dynamic systems. Industrial robots were controlled by using traditional controllers, whose control performance may chnage with respect to operating conditions. Since the robotic manipulators have complicated nonlinear mathematical models, control systems based on the system model are difficult to design. In this paper, a model-free hybrid fuzzy logic and neural network algorithm was proposed to control this multi-input/ multi-output (MIMO) robotic system. First, a fuzzy logic controller was designed to control individual joints of this four degree-of-freedom (DOF) robot. Secondly, a coupling neural network controller was introduced to take care of the coupling effect among joints and refine the control performance of this robotic system. The experimental results showed taht the application of this control strategy effectively improved the trajectory tracking precision.
Abstract - From the time of MAP (Manufacturing Automation Protocol) a decade ago up to recent field bus, the network communication protocol for distributed realtime control has been controversial, but has not been popularized as anticipated. On the other hand, it has been observed as a key element of Internet prosperity that once network based applications have been standardized, users can apply the best from existing and emerging communication mechanisms to fit their application. Proposed Integrated Instrument NETwork (IINET) protocol provides realtime-response and high-reliability network communication services as a communication mechanism for distributed controllers, and IINET LSI requires only a few external components for operation. IINET is eligible to be a network communication protocol in the era of distributed realtime control. In this paper, new token passing mechanism, Priority Token Passing, which features realtime access and fast detection and recovery of transmission errors is discussed in detail in comparison with standard token passing protocols, and its LSI oriented design concept is described. Priority Token Passing has only a small performance overhead, due to its switching capabilities, which can change network topology from ring to broadcast medium. A token-holding node passes the token to another node after determining the successor through priority comparison. Errors occurring during token passing can thus be detected and corrected simply and promptly. Priority Token Passing can be implemented by simple hardware, requiring only small additions to the frame control circuitry. The Priority Token Passing protocol and two other important network communication functions, dual ring network reconfiguration and HDLC NRM (Normal Response Mode) based message transmission, are designed as a single finite state machine, and implemented into a compact LSI chip.
Letters to the Editor
Abstract - The letter introduces an apparently new circuit component, the multi- hysteresis block. It consists of several hysteresis elements,having the same input signal. It is shown that this component could simplify the circuit of poly- phase square wave oscillators. Only one integrator is requested for any number of phase generations.
Abstract - A simple but accurate PSpice circuit model simulating the electrical characteristics of low pressure gaseous discharge lamp operating at high frequency is proposed. The model is constructed from a two-parameter equation and is suitable for computer simulation and analytic derivation in a preliminary design of electronic dimming ballasts. Simulated and measured results are used to verify the theoretical discussion.
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