Linux Based Real-Time Control over Industrial Networks

Linux Based Real-Time Control over Industrial Networks

Peter Fodrek, Michal Blaho, Martin Foltin, Matúš Lichý, Tomáš Murgaš
DOI: 10.4018/978-1-4666-0294-6.ch015
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This chapter deals with industrial networked control systems. These systems are the most modern means of industrial control. The current approach contains several problems. Mostly discussed problem in the control theory is a network-caused variable transport delay problem. On the software point of view there is problem of the system latency, which limits time period of the discrete control. State of art research in hardware part of the system shows that latency source and transport delay variations are caused by unpredictable hardware behavior as well. Another problem is the control system security. This was the case of the Mexico gulf oil rig disaster in 2010, as well as Iran nuclear program three months later the same year, caused by worm attack at its centrifuges. Therein lies the question; how can security issues be avoided? The authors demonstrate how via using GNU/Linux, which solves timing correctness by their project of the plasma cutting machine design.
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Hardware Configuration

In this section we are to describe used hardware and the lowest level of the software which is in lasagna code equal to hardware drivers. This is critical for hard real-time capabilities of the system. It is because when you are not successful in design of this layer then you are not able to achieve hard real-time capabilities. As Mr. Paul McKenney recognized in his 11th Real-Time Linux workshop in Dresden paper we are now to compensate not determinism in the hardware system especially in CPUs. He described that in 1979 then was 1 hardware problem of hard real-time per 29 software problems but in 2009 there were one software problem of hard real-time per 39 hardware problems. So there is critical to design hardware to software interaction layer. It is critical to patch hardware problems at lowest possible level not to cause too much bugs in the software.

Key Terms in this Chapter

Kernel: Most complicated and most important part of the operating systems. It contains static part that is used at anytime program works and modules that are loaded in case of their need. After loading module extends capabilities of the kernel and became its part until unloaded.

GUI: Graphical User Interface is type of computer program that solves Human-Machine interface tasks via using graphical objects like icons, Windows etc.

Latency: Is a technical term for delay caused by any technological system or software. It is often varying which is worst case for control systems to deal with. Latency is negative when certain value became available before it is needed.

Linux, GNU/Linux: Linux is a kernel of The GNU/Linux an Unix like operating system.

Networked Control: Is a type of automatic control where actuators, sensors man-machine interfaces and controllers are connected via industrial network.

Hard Real-Time: Is a state when system never exceeds deadline latency of the system response.

EtherCAT: Type of an industrial networks also knowns as field-buses which uses Ethernet infrastructure to interconnect devices.

Software: Complex set of computer programs to solve concrete type of tasks. Most complicated software is operating system that controls all computer components to work together and serves as interface for another software to deal with hardware.

CAN Bus: Controller Area Network is an type of two wired industrial network used mostly in car control systems as it was developed by BOSCH company in 1980’s.

CAD/CAM: Computer Aided Design software is software used to design machines, building or and any other things that needs mechanical drawing.

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