Ladder diagrams (LDs) for a programmable logic controller are a dominant method in discrete event control of industrial automated systems. Yet, the ever-increasing functionality and complexity of these systems have challenged the use of LDs to design their discrete-event controllers. Researchers are constantly pursuing integrated tools that eliminate the limitations of LDs. These tools are aimed not only for control but also system analysis, evaluation, and simulation. For the past several decades, Petri nets (PNs) have emerged as an important tool to provide an integrated solution for modeling, analysis, simulation, and control of industrial automated systems. Different types of PN-based controllers are proposed and intended to apply in the industry. There is a need for more benchmark studies of PN and LD methods in order to form a structured and integrated framework for logic control software development. This paper, for the first time, presents a comprehensive survey on the recent methods for discrete event control design.

Production cycle time reduction in their discrete-event control systems (DECS) helps increase the productivity of automated manufacturing systems (AMS). Methods developed to evaluate the production cycle time are usually based on either the Design for Manufacture (DFM) or Design for Production (DFP) scheduling techniques. To evaluate the real cycle time at the programming level of controllers such as the ladder logic design of programmable logic controller (PLC) in DECS, this paper discusses a method to analyze the production cycle time based on the sensor-based stage Petri nets technique. The production time can be estimated at each stage directly from all the I/O sensors that are represented by the extended Petri nets: the sensor-based stage Petri net (SBSPN). The production cycle time required to complete each product is marked on the individual stage transition through the real timers in the SBSPN model. For the production of multiple products, different production cycles times are estimated through the stage-by-stage real timers of controller program. These production cycle times are able to evaluate the bottleneck of integrated manufacturing systems. An example is used to illustrate the approach.

Sequential function chart (SFC) is currently one of the design diagrams for automated control systems to capture the sequence of operations executed by the system's control software. This method grows so complex that locating the cause when a problem is detected becomes extremely difficult. Researchers are constantly pursuing to develop tools that eliminate the limitations and increase the design performance using SFCs. Petri nets are among the most widely used tools to model and evaluate the behaviour of automated control systems. Petri net control of real-worlds systems is achieved by mapping sensor signals and actuator commands to Petri net transitions. Being a well-defined and well-developed tool based on a mathematical formulation, PN models are used to analyze and implement real-time control for discrete industrial systems. This paper discusses a methodology to convert the SFC of an automated control system for design and analysis using the sensor-based stage Petri nets (SBSPN). Appropriate rules are suggested to convert all the I/O sensors of SFC into stages Petri net picture. A pneumatic control system is illustrated as an example to demonstrate the practical use of this technique.

Petri nets have been extensively applied for specification, design, verification, performance evaluation, and simulation of discrete event control systems (DECS). This paper proposes a real-time stage Petri net (RTSPN), to represent the stage programming of a programmable logic controller (PLC) for DECS. The new technique is able to simplify the design process of the complex PLC program without considering the interlocking problem within the ladder diagram. An illustrated example is used to explore the new methodology. The proposed method contains the power and flexibility of the Petri net analysis. It is believed that this technique is significant for the industry practice.

Petri nets have become a powerful tool for modeling, analysis, performance evaluation, simulation, and discrete-event control of automated manufacturing systems (AMS). A number of Petri net classes were proposed to facilitate in attacking various specific problems encountered in manufacturing automation. This paper presents a brief summary of those special yet important classes of Petri nets and their purposes. It, however, only covers a small number of these classes owing to the limited space.

Develops and evaluates an automated process sequential manufacturing system using stochastic Petri nets (SPN) theory. The proposed Petri net-based graphic model is used to generate a reachability tree. The tree is, in turn, converted to a state table representation of a Markov process model to investigate the model for liveness, boundedness, reversibility, and performance. Other important characteristics of a dynamic system, such as conflict, blocking, and deadlock can also be examined. Different configurations of an automated system are studied by SPN models to design an improved system.

Modern manufacturing systems have challenged the use of LDs for PLCs to design their discrete-event controllers. Researchers are constantly pursuing integrated tools that eliminate the limitations of LDs. These tools are aimed not only for control but also for system analysis, evaluation, and simulation. For the past decades, Petri nets (PNs) have emerged as an important tool to provide an integrated solution for modeling, analysis, simulation, and control of industrial automated systems Different types of PN-based controllers in academia are intended for application in industry. There is a need for more benchmark studies of PN and LD methods in order to form a structured and integrated framework for logic control software development. The paper surveys work on these methods with focus on the conversion methods between PNs and LDs.

Petri nets have been extensively applied for specification, design, verification, performance evaluation, and simulation of discrete-event control systems. A real-time Petri net is a further improvement over the timed Petri net. The paper proposes to use a real-time Petri net to represent the stage programming of a programmable logic controller for a discrete-event control system. An illustrated example is used to explore the Petri net-based PLC stage programming methodology.