Control systems

Control-command systems are almost indispensable on any modern automated production line. It is almost unthinkable to manage industrial plants that cover hectares and hectares of land without supervision and remote control systems.

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The Scada (Supervisory Control and Data Acquisition) man-machine interfaces and systems are there to address this issue by allowing us to monitor and take control over complete remote installations.

A man-machine interface, in the more basic case, can be a few buttons and LEDs installed on the console of the control cabinet of a machine. This allows to supervise and control it.

In the case of medium-sized production lines, the control panel will be much more complex, including many more push buttons and LEDs, as well as supervisory panels that are small screens for graphical display These supervisory panels are found on special machines such as bagging machines, bottle packaging machines, control rooms in stations and airports, etc.

Control systems based on pushbuttons, indicators and tactile panels are inexpensive but they only allow the control of the machine or the installation locally. A problem therefore arises if we want to connect to our machine Although most of the trade supervision panels run on operating systems like Linux or Windows CE, it does not have large storage capacity which is limited in most cases to A memory card of a few gigas.To perform archiving of production data over a month or several years, these storage spaces may be insufficient. Other control devices such as industrial PCs or IPC are more adequate. To a screen, the IPC has a hard disk and can store large amounts of data.

Via the web server, it is possible to take control over a remote monitoring panel. These controls are often used for remote maintenance and not to supervise installations. Sometimes they are available only under a paid license.On the supervision panels, the archiving of Data can be made in binary format, text, CSV etc on the memory card.However, remote access to archived data is difficult. When the memory card is full or damaged, besides archiving becomes temporarily impossible, data Can be irrevocably lost as they are not configured in redundant systems.

The main advantage of supervision panels is their cost and simplicity of implementation. They are ideal for small stand-alone applications with limited functionality and little data to archive. However, if the user wants to manage an entire production line , Set monitoring parameters, collect and archive large amounts of data that can be accessed remotely in real time, perform production reports, it will be forced to turn to a Scada system. And there is all the nuance Between human machine interfaces (HMI) and Scada system.

A man-machine interface is a computer device that presents the processes to the human operator and allows it to control the process. HMIs are generally linked to the SCADA system database and programs capable of computing trends, selecting Diagnostic information and management information such as predictive maintenance procedures, logistical information, detailed diagrams of a sensor or a particular machine. A scada system is the set of hardware and software Real-time processing of a large number of telemetries and remote control of technical installations (cf wikipedia). The advantage of scada systems is that they are more reliable. They can be installed in redundant systems which allows to recover the data Archived in the event of a breakdown.

In the next article, we will see the main criteria for choosing a control-command system