Andrzej Kwiecień

Performance of HTTP Protocol in Networked Control Systems

Integration of Networked Control Systems is always an engineering challenge. Heterogeneous hardware and software environments combined with long lifetime of control systems makes this job particularly troublesome. Modern concepts of integration of automation systems are related to Service Oriented Architecture (SOA). While its suitability is proven in IT systems, SOA has not been adopted yet in commercial Programmable Logic Controllers (PLC), and thus cannot be considered as a solution for integration with already deployed control systems. However, during past years thousands of PLCs with embedded HTTP servers were deployed in the field. These devices, used together with modern PLC that acts as the HTTP client, enable unique opportunity of integration for control systems with soft real-time constraints. In the present study, the performance of PLC-to-PLC communications based on HTTP is evaluated and compared to Modbus TCP.

Using Cloud Storage in Production Monitoring Systems

Cloud Computing has received much rumour during the last year. Although the idea of lending processing power and data storage is, in essence, known since the very beginning of the computer industry, a new distributed computing platform coming from Microsoft is expected to have much impact on the enterprise software development and usage.

Dual Bus as a Method for Data Interchange Transaction Acceleration in Distributed Real Time Systems

The chapter presents considerations on data interchange acceleration method in distributed control systems by the use of dual data transmission line. The method is based on the construction of a system based on two buses: one with separated master bus and the other one with separated slave bus.

The Cost of Redundancy in Distributed Real-Time Systems in Steady State

The paper presents considerations that refer to introducing the term “cost of redundancy”, and indicates general assumptions that allow defining this term and its quantitative determination. However, “the cost of redundancy” does not apply in this case to financial expenses but only time loses (temporal cost) associated with the use of redundancy in industrial real-time distributed systems. Several computer systems architectures are analyzed from the point of view of that temporal redundancy cost.

The Concept of Using Multi-protocol Nodes in Real-Time Distributed Systems for Increasing Communication Reliability

The paper presents the considerations on the method which enables to accelerate the exchange of data in distributed control system, using multi-protocol nodes. The method presented in this paper is related to hardware and software, and based on new original communication protocol, which is used by the node for supporting various communication protocols to simultaneous data exchange via different buses. This method will enable to increase not only network bandwidth, but also the security of data transmission.

Reliability of Bluetooth Smart Technology for Indoor Localization System

The main objective of the paper was to test whether the devices compatible with Bluetooth Low Energy are reliable for indoor localization system. To determine the reliability of this technology several tests were performed to check if measured distance between Bluetooth transmitter and mobile device is close to the real value. Distance measurement focused on Bluetooth technology based mainly on received signal strength indicator (RSSI), which is used to calculate the distance between a transmitter and a receiver. As the research results show, the Bluetooth LE signal power cannot be the only reliable source of information for precise indoor localization.

Using HTTP as Field Network Transfer Protocol

Increasing popularity of Ethernet-based field networks is an opportunity to integrate heterogeneous automation devices and systems. To achieve this goal, a universally adopted open communication protocol is required. In general computing, Hypertext Transfer Protocol (HTTP) performs that role. In this paper, the HTTP is evaluated as a core data transfer protocol of industrial field networks, and compared to a proprietary Ether-S-Bus communication protocol of Saia Burgess PCD Series programmable logic controllers.

The Analysis of Microprocessor Instruction Cycle

Each microcontroller realizing the code saved in a program memory emits electromagnetic disturbances, both conducted that propagate through lines connected to the processor and radiated in the form of electromagnetic field. All of these undesirable signals emitted by the processor can be measured, received and interpreted by the appropriate methods. However, this subject requires a precise measurement and understanding of processes occurring inside the microprocessor during realization of the sequential instructions. The presented results of the influence of parameters such as data bus state, instruction argument, the result of operation on the voltage waveform on the power supply lines of microprocessor, enable to understand the processes occurring during the realization of following instructions by microprocessor unit.

The Method of Reducing the Cycle of Programmable Logic Controller (PLC) Vulnerable “to Avalanche of Events”

Reducing the cycle duration of PLC (Programmable Logic Controller) is one of the methods for increasing the access frequency of nodes in the real time distributed system into the transmission medium. The authors presents in this paper one of the methods developed by themselves for a rather specific use of a cases of avalanche of events.

Automatic Scenario Selection of Cyclic Exchanges in Transmission via Two Buses

The paper presents the theoretical and empirical tests which examine the algorithms of automatic scenario selection of cyclic exchange in transmission via two buses. The implemented method is the base for using the second (redundant) bus for data transmission. The main aim of this method is to build two-stream data transmission so that each data stream has similar, or even the same transmission time. The flexibility of the proposed solution results from the fact that it is useful not only for two-bus transmission, but also when the transmission is via only one bus. This method allows estimating the time of the network cycle and also indicates the values of the times for acyclic transmissions. The presented method is only the introduction to designing, developing and controlling the two-stream transmission.