IEEE Transactions on Industrial Electronics 

Volume 41,  Number 6, Dec 1994           Access to the journal on IEEE XPLORE     IE Transactions Home Page



41.6.1    R. Zurawski, MengChu Zhou, "Petri nets and industrial applications: A tutorial," IEEE Trans. on Industrial Electronics, vol. 41, no. 6, pp. 567-583, Dec 1994.   Abstract Link    Full Text

Abstract: Petri nets, as a graphical and mathematical tool, provide a uniform environment for modelling, formal analysis, and design of discrete event systems. The main objective of this paper is to introduce the fundamental concepts of Petri nets to researchers and practitioners, both from academia and industry, who are involved in the work in the areas of modelling and analysis of industrial types of systems, as well as those who may potentially be involved in these areas. The paper begins with an overview of applications of Petri nets, mostly industrial ones. Then, it proceeds with a description of Petri nets, properties, and analysis methods. The discussion of properties is put in the context of industrial applications. The analysis methods are illustrated using an example of a simple robotic assembly system. The performance analysis, using Petri nets, is discussed for deterministic and stochastic Petri nets. The presented techniques are illustrated by examples representing simple production systems. In addition, the paper introduces high-level Petri nets, fuzzy Petri nets, and temporal Petri nets. This is done in the context of application prospects. The paper also briefly discusses some of the reasons restricting the use of Petri nets, mostly, to academic institutions

41.6.2    R. Zurawski, "Systematic construction of functional abstractions of Petri net models of flexible manufacturing systems," IEEE Trans. on Industrial Electronics, vol. 41, no. 6, pp. 584-592, Dec 1994.   Abstract Link    Full Text

Abstract: The use of generic models in the synthesis of FMS systems, which allows for rapid modelling and analysis, does not ease the verification task difficulty. Even though generic modules can be verified separately, the verification of the interconnections between modules requires the whole model to be considered. A potential solution is to replace the generic modules with their functional abstractions which realize the external functional behavior of these modules. The number of places and transitions involved in realizing the required functionality is, typically, a fraction of that used to represent complete components. This reduces the complexity of the components of the modelled system, and thus the complexity of the verification model. The verification task can then focus on the correctness of the interfaces, rather then on the internal nature of the components. In this paper, for a class of Petri net models, which can be used to represent the primary components of AGV based FMS systems, a method that allows one to systematically construct functional abstractions is presented

41.6.3    Tien-Hsiang Sun, Chao-Weng Cheng, Li-Chen Fu, "A Petri net based approach to modeling and scheduling for an FMS and a case study," IEEE Trans. on Industrial Electronics, vol. 41, no. 6, pp. 593-601, Dec 1994.   Abstract Link    Full Text

Abstract: In this paper, a timed-place Petri net (TPPN) model for flexible manufacturing systems (FMSs) is constructed, which contains two major submodels: the stationary transportation model; and the variable process flow model. For multiple automated guided vehicle (AGV) systems, the authors embed a simple rule and introduce a push-AGV strategy in a TPPN model to solve the collision and traffic jam problems of such vehicles. Since a firing sequence of the TPPN from the initial marking to the final marking can be seen as a schedule of the modeled FMS, by using an A* based search algorithm, namely, the limited-expansion A algorithm, an effective schedule of the part processing can be obtained. To show the promising potential of the proposed work, a prototype FMS is used as a target system for implementation. The experiment results assert that the job-shop scheduling problem can always be satisfactorily solved

41.6.4    Doo Yong Lee, F. DiCesare, "Integrated scheduling of flexible manufacturing systems employing automated guided vehicles," IEEE Trans. on Industrial Electronics, vol. 41, no. 6, pp. 602-610, Dec 1994.   Abstract Link    Full Text

Abstract: Centralized and distributed automated guided vehicle system (AGVS) models for materials handling, and the model for part processing are integrated into a single coherent model. This formulation can be used to collectively schedule and control the entire flexible manufacturing system (FMS) as opposed to the traditional separate scheduling of part processing and material handling. The two AGVS models are based on Petri nets and can be directly used in the scheduling method that uses Petri nets for formulation and heuristic search for solution. This method employs a global search to seek the optimal operation of an entire FMS. Scheduling examples are presented and the method compares favorably with the results simulated using heuristic dispatch rules

41.6.5    K. Venkatesh, MengChu Zhou, R.J. Caudill, "Comparing ladder logic diagrams and Petri nets for sequence controller design through a discrete manufacturing system," IEEE Trans. on Industrial Electronics, vol. 41, no. 6, pp. 611-619, Dec 1994.   Abstract Link    Full Text

Abstract: Design methods for sequence controllers play a very important role in advancing industrial automation. The increasing complexity and varying needs of modern discrete manufacturing systems have challenged the traditional design methods such as the use of ladder logic diagrams (LLDs) for programmable logic controllers. The methodologies based on research results in computer science have recently received growing attention by academic researchers and industrial engineers in order to design flexible, reusable, and maintainable control software. Particularly, Petri nets are emerging as a very important tool to provide an integrated solution for modeling, analysis, simulation, and control of industrial automated systems. This paper identifies certain criteria to compare LLDs and Petri nets in designing sequence controllers and responding to the changing control requirements. The comparison is performed through a practical system after introducing “real-time Petri nets” for discrete-event control purposes. The results reported in this paper will help: (a) further establish Petri net based techniques for discrete-event control of industrial automated systems; and (b) effectively convince industrial practitioners and researchers that it is worthy and timely to consider and promote the applications of Petri nets to their particular discrete-event control problems

41.6.6    T. Cao, A.C. Sanderson, "Task decomposition and analysis of robotic assembly task plans using Petri nets," IEEE Trans. on Industrial Electronics, vol. 41, no. 6, pp. 620-630, Dec 1994.   Abstract Link    Full Text

Abstract: This paper describes a framework for robotic task sequence planning which decomposes tasks into operations sequences for a generic robotic workcell. The approach provides robust execution of tasks through properties of: traceability-implicit mapping operations representation, and viability-retaining multiple execution. Given the descriptions of the objects in the system and all feasible geometric configurations and relationships among these objects, an AND/OR net which describes the relationships of all feasible geometric states and associated feasibility criteria for net transitions is generated. This AND/OR net is mapped into a Petri net which incorporates all feasible sequences of high level operations. The resulting Petri net is then decomposed in a stepwise manner into lower level Petri nets of which each transition can be directly implemented by control commands or command sequences based on devices and objects in the system, or, by lower level planning transitions corresponding to path planning, grasp planning, fine motion planning, etc. The property analysis for different levels of decomposition is also presented, and the inheritance of properties between levels is defined. All possible task sequences could be found using a search algorithm based on feasible system states. The shortest sequence may be chosen from the lowest level decomposition and is guaranteed to be the optimal output of the hierarchical planning system to efficiently implement the desired tasks

41.6.7    B.J. McCarragher, "Petri net modelling for robotic assembly and trajectory planning ," IEEE Trans. on Industrial Electronics, vol. 41, no. 6, pp. 631-640, Dec 1994.   Abstract Link    Full Text

Abstract: A new approach to process modelling, task synthesis, motion control and trajectory planning for robotic assembly is presented. Assembly is modelled as a discrete event dynamic system using Petri nets, incorporating both discrete and continuous aspects of the process. A process monitor based on recognizing contact state transitions is presented. A discrete event controller is developed. The controller issues velocity commands that direct the system toward the next desired contact state, while maintaining currently desired contacts and avoiding unwanted transitions. A novel means of trajectory planning which incorporates the system's ability to both monitor and control the process is given. Experimental results are given for a dual peg-in-the-hole example. The experimental results not only demonstrate highly successful insertion along the desired trajectory, but also demonstrate the ability to detect, recognize, and recover from errors and unwanted situations

41.6.8    F.-Y. Wang, K. Gildea, H. Jungnitz, D.D. Chen, "Protocol design and performance analysis for manufacturing message specification: A Petri net approach," IEEE Trans. on Industrial Electronics, vol. 41, no. 6, pp. 641-653, Dec 1994.   Abstract Link    Full Text

Abstract: The manufacturing message specification (MMS) is the ISO standard communication protocol specific to manufacturing. To analyze MMS design and performance, service unit automats are introduced to represent individual MMS services, while service connection Petri Nets (PNs) are constructed from these automats to describe MMS service connections and processes. This approach makes MMS protocol specification and analysis possible in terms of well-developed concepts and methods in PN theory. It leads to a distributed and hierarchical model of MMS software system by integrating service connection PNs. A generalized stochastic PN for MMS performance evaluation is obtained by incorporating service parameters and time factors into the model. A technique based on T-invariants is used to simplify the performance analysis

41.6.9    T. D'Orazio, F.P. Lovergine, M. Ianigro, E. Stella, A. Distante, "Mobile robot position determination using visual landmarks," IEEE Trans. on Industrial Electronics, vol. 41, no. 6, pp. 654-662, Dec 1994.   Abstract Link    Full Text

Abstract: This paper is concerned with the problem of determining the position of a mobile vehicle during navigation. In order to achieve this objective a multisensor navigation system for self location of the robot has been developed. By tracking a few known landmarks with a vision module, the system is able to monitor continuously its position and to integrate these estimates with the measures provided by the vehicle odometers. This paper describes in detail the vision module used by the navigation system

41.6.10    G.S. Buja, F. Todesco, "Neural network implementation of a fuzzy logic controller," IEEE Trans. on Industrial Electronics, vol. 41, no. 6, pp. 663-665, Dec 1994.   Abstract Link    Full Text

Abstract: Fuzzy logic is an attractive technique for plant control but suffers from a heavy computation burden. A solution to this problem is proposed here and consists of implementing a fuzzy logic controller in a neural network. The solution is applied to the speed control of a DC motor drive and is validated by experimental results

41.6.11    N.M. Botros, M. Abdul-Aziz, "Hardware implementation of an artificial neural network using field programmable gate arrays (FPGA's)," IEEE Trans. on Industrial Electronics, vol. 41, no. 6, pp. 665-667, Dec 1994.   Abstract Link    Full Text

Abstract: In this paper, the authors present a hardware implementation of a fully digital multilayer perceptron artificial neural network using Xilinx Field Programmable Gate Arrays (FPGAs). Each node is implemented with two XC3042 FPGAs and a 1 K×8 EPROM. Training is done offline on a PC. The authors have tested successfully the performance of the network