G. Andrzejewski

Time Dependencies Modelling in Traffic Control Algorithms

The paper presents the concept of discrete control systems for traffic control implementation on PLC devices. A transformation of popular finite state machine (FMS) model to the form that allows to represent the time dependencies is presented. An example of lights control on a pedestrian crossing is presented. Two implementation methods that can be a reference for particular real-life traffic control examples are discussed. Results of implementation of the example are shown.

Hierarchical Petri Nets for Digital Controller Design

This paper presents a model of formal specification of reactive systems. It is a kind of an interpreted Petri net, extended by important properties: hierarchy, history, and time dependencies. The syntax definition is introduced and the principles of graphical representation drawing are characterized. Semantics and dynamic behavior are shown by means of a little practical example: automatic washer controller.

Block Programming Technique in Traffic Control

In the paper there are discussed benefits of using the block-oriented approach in programming the PLC controller. As an example there is taken a model of traffic junction with multiple traffic flow (including the railway crossing). The model is described and control system structure is presented. There are discussed principles of block-oriented programming approach in Ladder Diagram (LAD) language. Benefits of using this technique are shown and example is discussed.

Hierarchical Decomposition of Petri Nets for Digital Microsystems Design

In this paper an approach to hierarchical decomposition of Petri nets and of specification of a digital system behavior by means of hierarchical Petri nets is proposed.

Fault Detection Variants of the CloudBus Protocol for IoT Distributed Embedded Systems

Distributed embedded systems have become larger, more complex and complicated. More often, such systems operate accordingly to the IoT or Industry 4.0 concept. However, large number of ...

CloudBus protocol hardware multi-converter gateway for distributed embedded systems

The CloudBus protocol is one of the methods which is used for data exchange and concurrent process synchronization in the distributed embedded systems. It realizes decentralized (distributed) control method, where each node is equal to each other. This communication model allows the significant savings in the amount of transmitted data between end modules. However, there are many distributed embedded systems, which are already implemented and working in the field. Switching the entire communication interface to the another protocol would result in high costs and process control interruption. This paper proposes a hardware converter which provides the integration of the CloudBus protocol with most popular protocols used in the industry. It allows for the extension and connection of the existing systems with the distributed embedded systems based on the CloudBus protocol. The research results provide performance and resource usage analysis for different converter architectures. The verification was performed on the SoC research and development platform for distributed embedded systems, which is based on Xilinx Zynq-7000.

EmbedCloud – Design and Implementation Method of Distributed Embedded Systems

This paper presents a novel design and implementation methodology of the distributed embedded systems, called EmbedCloud. It defines structured implementation model for each module in the system. EmbedCloud forms the basis for the automatic code generation algorithm of the distributed embedded systems which accelerates and simplifies synthesis process of such systems. The EmbedCloud utilizes CloudBus protocol demonstrated in previous publications, which provides a process synchronization and control mechanism for a number of processing units distributed in a network. The CloudBus protocol allows to significant savings in the amount of transmitted data between end modules in the distributed embedded system, especially when compared with the other protocols used in the industry. To verify and evaluate the performance of the EmbedCloud, a concurrent process was described using Petri nets. Hardware tests and synthesis verification of the distributed embedded system was performed on the testing platform built with AVR, ATmega series microcontrollers. The tests confirmed the correctness of the developed source code and EmbedCloud method. Furthermore, resource requirements and reaction time analysis were performed.

SEMANTIC INTEGRITY OF FLAT AND HIERARCHICAL PETRI NETS

Abstract This paper presents a semantic integrity of classical flat interpreted Petri net and hierarchical net. There are some known algorithms for a flat net analysis (e.g. liveness, safeness, etc.). The paper shows some elements of behavioral description (which are characteristic for hierarchical Petri net), such as enabling and prohibiting arcs, time dependencies, history of macroplaces, preemption, etc., and representation of them with using of flat net.