Search

In the present paper, a control system for a Plastic Injection Mold Machine was proposed by using a Programmable Logic Controller (PLC) of type IMO iSmart ED-RD-20. The PLC is intended to be implemented in an automated industrial system to yield plastic products, such as flowerpots. For the practical implementation of a prototype of the system, besides the PLC, a power source (24 V DC), a temperature sensor, two DC motors, LEDs for signaling the inputs and outputs states, switches and buttons were also used. The project was realized in the Ladder Diagram (LD) language, comprising 8 LD programs and was simulated with the software simulator SMT. [ABSTRACT FROM AUTHOR]

Supervisory Control and Data Acquisition (SCADA) systems control and monitor industrial and critical infrastructure functions, such as electricity, gas, water, waste, railway, and traffic. The main objective of this work is to develop SCADA simulation model for packaging system in dry ice plant. Dry ice is an important refrigerant for keeping foods cold and preventing bacterial growth during shipment. Dry ice used for cooling or freezing foods must be very clean and considered food grade to ensure that food it may touch will not be contaminated. Some recent developments for its use include using the pellets in blasting or cleaning and its increasing use in transporting medical specimens, including hearts, limbs, and tissues, for reattachment and transplantation. The manufacturing process of dry ice has not changed significantly in many decades and is a relatively simple process of pressurizing and cooling gaseous carbon dioxide. But because of its growing demand, packaging becomes vital. An attempt has been made to develop and automate LOGIXPRO based SCADA simulations for dry ice plant to improve packaging and extensively reduce operating labor costs. [ABSTRACT FROM AUTHOR]

An approach to the construction and verification of LD programs of programmable logic controllers (PLC) for discrete problems is proposed. The specification of the program behavior is performed using the linear temporal logic language (LTL). Programming is performed using the Ladder Diagram (LD) language by the LTL specification. The correctness analysis of the LTL specification is performed using the Cadence SMV symbolic model-checking tool. An approach to programming and verifying the PLC LD programs is shown using an example. The LD program, its LTL specification, and an SMV model are given for a discrete problem. This article is aimed at the description of an approach to PLC programming that will provide the correctness analysis of PLC LD programs using the model-checking method. Therefore, the variation in each programmable variable is described using a pair of LTL formulas. The first LTL formula describes situations in which the corresponding variable increases and the second LTL formula specifies conditions leading to a decrease in the variable. LTL formulas, which are considered to specify the behavior of variables, are constructive in the sense that the PLC program corresponding to the temporal properties expressed by these formulas is constructed by them. Thus, PLC programming is reduced to the construction of the LTL specification for the behavior of each programmed variable. In addition, the SMV model of the PLC LD program is constructed by the LTL specification. Then, the SMV model is analyzed for correctness (relative to additional conventional general-programming LTL properties) by the Cadence SMV symbolic model-checking tool. [ABSTRACT FROM AUTHOR]

An ordinary Petri-net ( PN) based approach is proposed to design the programmable logical controller ( PLC) for preventing collisions between vehicles in an automated guided vehicles ( AGV) system. First, method is proposed to model an AGV system as an ordinary PN, called the plant PN. Second, for collision prevention in an AGV system, module control methods are proposed to design the PN supervisor (the closed-loop PN) by augmenting the plant PN. In detail, three modules are defined the line, divide, and merge modules, in the plant PN, and the control module methods are presented for each of these three modules. As a result, the closed-loop PN of an AGV system is obtained and can be analyzed using the PN theory. Finally, method is proposed to translate a closed-loop PN into a ladder diagram. Consequently, the PN supervisor is implemented by a PLC using these proposed methods. A laboratory AGV system is used to illustrate this approach. [ABSTRACT FROM AUTHOR]

The paper presents control water jets and the lights for a fountain with PLC. Command can be synchronized with a musical background or with a generated sequence of control of jets and lights. [ABSTRACT FROM AUTHOR]

Extended labeled Petri nets (ELPNs), i.e., labeled Petri nets with inhibitor arcs, are usually used to model the desired closed-loop behavior of a controlled discrete-event system, and, as such, their states are formed with both the controller and the plant states. However, the control logic is based on the controller states only and the interaction between controller and plant is carried out through sensor readings from the plant and control actions (forced events) from the controller. This makes ELPN not suitable for modeling the controller. Control interpreted Petri nets (CIPNs), on the other hand, include control actions in the places and sensor readings in the transitions as part of their formal structure, and so provide a better formalism for controller modeling. In this paper, we propose a two-step approach to discrete-event controller implementation, as follows: (i) we first propose a set of transformation rules to convert the initial ELPN to an equivalent CIPN, therefore extracting the control logic from the desired closed-loop behavior and (ii) we present a straightforward systematic way to translate the CIPN into a ladder diagram. We apply the results presented here to the implementation of the automation system of a plastic molding machine. [ABSTRACT FROM PUBLISHER]

In this document a methodological process is proposed, aimed to generate ladder diagrams from fuzzy Petri nets. The method is based on the "marks evolution analysis" concepts, which have been developed with the desire of implementing complex control systems expressed through fuzzy Petri nets, in programmable logical controllers (PLC). Furthermore the method is implemented using Matlab® as platform, getting a toolbox which allows: simulate the fuzzy Petri nets and generate the ladder diagram associated to that net. [ABSTRACT FROM AUTHOR]

Copyright of Tecnura is the property of Tecnura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Programmable logic controller (PLC) is one of the most important components in today’s manufacturing. Its performance-based microprocessor and software have been a bottleneck for improving its efficiency. To enhance the PLC performance and flexibility, a new PLC design based on field programmable gate array (FPGA) has been a hot topic because of its parallel execution mechanism and reconfigurable hardware structure. From practical viewpoint, in this paper, the authors propose an approach to implement the existing ladder diagram (LD) inside FPGA making full use of the advantage of FPGA device. The essential of this research includes two issues: (a) analyze the LD program and organize it with sequential and parallel structure and (b) implement the sequential and parallel structure of the LD program with hardware description language inside FPGA. To the first work, the condensed simultaneity graph theory is applied to optimize the LD program with sequential and parallel structure. To the second work, Boolean equations are taken as the bridge to convert the optimized LD program to the hardware description language program. Finite state machine is used to generate sensitive signals to guarantee that the performance of the converted very high-speed integrated circuit hardware description language design is the same as the original ladder diagram. A case study is practiced to verify the proposed approach in this paper. [ABSTRACT FROM AUTHOR]

Programmable logic controllers (PLCs) have been widely used in manufacturing systems for many years. PLC performance is highly constrained by speed of the microprocessor and real-time firmware of the PLC. To enhance conventional PLC performance and flexibility, this paper proposes a new PLC design based on field programmable gate array (FPGA) with parallel execution mechanism and reconfigurable hardware structure. Since ladder diagrams (LD) are the most popular programming language of PLCs, the essential approach of this research is to convert LD programs to equivalent and very high speed integrated circuit hardware description language programs (VHDL), which are the major programming language for FPGA design. This conversion process requires two steps. The first step is to convert the LD program to a VHDL program, in which the LD sequence is controlled by a state machine process. The second step is to optimize the state machine process with concurrent sensitive signals to assure that independent operations in the LD program can be executed in parallel in FPGA. Considering the diversity of LD instructions from different PLC providers, a universal converter with an extended Boolean equation as a bridge is introduced to implement the conversion of LD programs to VHDL. In the second step, the condensed simultaneity graph theory (CSG) is applied to optimize the converted VHDL program with concurrent sensitive signals, which is explained by a practical example. [ABSTRACT FROM AUTHOR]

We proposed an algorithm that converts the ladder diagrams (LDs) of the programmable logic controller (PLC) to the petri nets (PNs) using the module synthesis technique. By using the enabling arc, the reset arc, and the buffer place, we first converted the LD core functions such as contacts and coils to the corresponding PN modules. We then systematically synthesized these PN modules to convert any general LDs consisting of contacts and coils to the corresponding PNs. The generated PN can be served as an analysis tool for the original LD program. We also converted the counter and the timer function blocks of the function block diagram (FBD) to the PN modules because they were the functions supported by most of the commercially available PLCs. In converting these function blocks, we used the variable weight arc and the variable weight enabling arc. [ABSTRACT FROM AUTHOR]

Starting from the viewpoint that the constituent quark has its own structure and incorporating the hypothesis of maximum nonperturbative strong interaction reaction (MNSIR), which should be obeyed in high energy strong soft processes, we modified the field theory for soft Pomeron (ℙ) of Landshoff and Nachtmann and proposed a new structure model for the soft Pomeron ℙ and Reggeon ℝ. In this model a pair of constituent quarks coming from colliding hadron in strong soft processes are first disaggregated into a valance quark with a nonperturbative gluon cloud G wrapped about, or, according to the case, into a nonperturbative gluon wrapped by spinor cloud. Corresponding to such mechanism, the relevant structure of soft Pomeron ℙ or Region ℝ is represented by the sum of a series of cut ladder diagrams. In the multi-Regge region, where the energy of the system is very large and the momentum transfer |t| is very small, and in the approximation where only the leading order of log s is preserved, we calculated the $q\hbox{--}q(\bar q)$ scattering amplitude and its total cross-section from the sum of such ladder diagrams. The Regge-behavior factor in the form of an exponential power law of s does arise. We also get compact formulas for the trajectories of soft ℙ and ℝ. As example of application, an alternative mechanism of J/Ψ nonquarkonic-hadron decay is proposed. [ABSTRACT FROM AUTHOR]

Abstract: Electrocardiographic (ECG) rhythm analysis is inadequately taught in training programs, resulting in undertrained physicians reading a large percentage of the 40 million ECGs recorded annually. The effective use of simple tools (calipers, ruler, and magnifier) required for crucial measurements and comparisons of intervals requires considerable time for interactive instruction and is difficult to teach in the classroom. The ECGViewer (Blaufuss Medical Multimedia Laboratories, Palo Alto, Calif) program was developed using virtual tools easily manipulated by computer mouse that can be used to analyze archived scanned ECGs on computer screens and classroom projection. Trainees manipulate the on-screen tools from their seats by wireless mouse while the instructor makes corrections with a second mouse, in clear view of the trainees. An on-screen ladder diagram may be constructed by the trainee and critiqued by the instructor. The ECGViewer program has been successfully used and well received by trainees at medical school, residence, and subspecialty fellow level. [Copyright &y& Elsevier]

Abstract: Ladder diagrams are valuable teaching and interpretive tools in both human and veterinary electrocardiography. The purpose of this paper is to demonstrate how ladder diagrams can be used to help understand the possible mechanisms underlying atrial flutter and atrial fibrillation. [Copyright &y& Elsevier]

Abstract: Starting from the GW approximation (GWA) beyond density functional theory and solving the eigenvalue problem associated with the Bethe–Salpeter equation which accounts for the excitonic effect, I have determined optical properties of isolated Be, Mg and Ca atoms and Na2. In the representation of single electron wave functions, I have used the all-electron mixed basis approach in which both plane waves and atomic orbitals are used as a basis set. The resulting quasiparticle energies and optical absorption spectra are compared with available experimental data. [Copyright &y& Elsevier]

This research presents a Web-based learning and instructional system for Pneumatics. The system includes course material, remote data acquisition modules, and a pneumatic laboratory set. The course material is in the HTML format accompanied with text, still and animated images, simulation programs, and computer aided design tools. The data acquisition modules of the system can be connected through the computer I/O with actual devices to verify and implement simulation results to enhance the corresponding pneumatics learning. Therefore, this Web-based learning and instruction support system can be used to assist the pneumatics instruction, computer aided sequential control design and pneumatic laboratory practice. The course material is organized by chapters and sections, leads users from pneumatic devices to pneumatic systems. Programmable logic controller, PC-based sequential control, internet remote monitoring, and Web-based sequential control are also covered. In this study, combinations of software devices and hardware system circuit were used to demonstrate the motion of controlled system. To assist instruction for a pneumatics course, computer-aided pneumatic circuit design software and computer-aided electric circuit design software were fully integrated. In combining with the remote data acquisition modules, the Web-based sequential controller can be used to conduct pneumatic experiment. To gain consistency, this instructional system is mounted on a previously developed instructional platform. Under this Java-based platform, users can apply the communication tools of the platform to gain efficiency while in a non-co-located multiuser session. A database server is used to store circuit designs for all users. And, because the software has collaborative function, it allows all users to design on same circuits collaboratively. [Copyright &y& Elsevier]

The Ladder Diagram (LD) has been widely used in industry as a language for sequential control. However, the LD cannot represent sequential flows of control logic explicitly. This leads to difficulties for other engineers in understanding the control logic. To overcome this problem, the Sequential Function Chart (SFC) has been proposed. Because the SFC can represent sequential flow explicitly, it is expected to be used more widely. Since the LD has been widely used in the past, however, it is necessary to develop an algorithm for transformation from the LD to the SFC. In this paper, a technique to transform an LD to the corresponding SFC by using temporal logic is proposed. In the closed loop system which consists of the LD and the controlled plant, sequence information including parallel path divergences is extracted to develop the transformation algorithm. An example is presented to verify the feasibility of the proposed algorithm. © 1999 Scripta Technica, Electr Eng Jpn, 129(1): 74–81, 1999 [ABSTRACT FROM AUTHOR]

Dual-chamber pacemakers interact with cardiac rhythms in complex ways. The resultant surface electrocardiograms (ECGs) are often very difficult to interpret. A simple and automatic diagnostic diagram is described that graphically illustrates pacemaker-heart interactions. Pacemaker operation is explained by a continuous series of lines and symbols that interconnect any sequence of paced and sensed events in both chambers. Fixed, programmable, and adaptive pacemaker timing intervals are all shown in a simple format. The pacemaker diagnostic diagram is plotted directly below the ECG to help users interpret the paced cardiac rhythm. The pacemaker diagnostic diagram is generated by software in a pacemaker programmer from: (1) telemetered real-time event markers; (2) fixed and programmable timing parameters (lower rate, AV interval, etc.); (3) pacemaker conditional logic. If this computer analysis of the telemetered event markers is not consistent with normal pacemaker operation, a specific error-message is printed. The pacemaker diagnostic diagram should be useful for instruction, pacemaker follow-up, and troubleshooting. [ABSTRACT FROM AUTHOR]