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НаименованиеA Process Control System for Preparation of Concrete Mixtures

 

In 1993 the engineering firm Eltikon was commissioned to develop control systems for a series of mobile concrete facilities for the Russian Defense Ministry. These facilities had a capacity of from 20 cubic meters to 60 cubic meters of mix per hour and included four to six dosers, one or two mixers, cement storage of up to 80 tons, and component storage of from 40 to 60 tons.

We based the system configuration on an analysis of foreign and domestic hardware, taking into account the system requirements, cost, reliability and functionality. The resultant system has a service life of at least ten years, with a three-year guarantee and a full operating time of 50,000 hours. The operational temperature range (without using heating or cooling equipment) is from -20 degrees to +60 degrees Celsius, running on from 90 to 280 volts of power. Command execution time using a 386 processor (25MHz) with 1 MB of RAM and a 1 MB solid state disk is from 4 to 6 milliseconds. The system includes four ports (Centronics, RS-232c, RS-485/422, Ethernet 10) and an SVGA video card.

This system can run practically all the aggregate equipment of a mobile concrete facility or an individual section of a stationary plant.

We selected Borland Pascal 7.0 as the development language for the system's software. This language allows for the rapid development of applications of any degree of functional complexity. The commands of the execution module run under the control of a real-time operating system with a round robin planning algorithm, which ensures that all commands of the same priority level have equal access to processor time.

The software for the operator's station was developed using Delphi 2, which produces applications that run on Windows 95. A production cycle begins with the input of the order (for whom, what, how much), which takes three seconds. Then the operator merely monitors on a color terminal as the process unfolds, maintaining the ability to intervene in the process at any phase.

The process of developing and deploying such systems has proved fairly straightforward and has therefore been adapted for automating a mixed feed plant, which uses similar process, only on a larger scale. In all, since the end of 1993, about 20 such systems have been produced. During that time, various sensors and relay elements have failed but have been replaced by the clients' service personnel. No failures of a control computer have been recorded.


Automated Concrete Plant

Operator's Station

By Elticon