Structure and Hierarchical Organisation of Process Data

Abstract

In DDC of fast systems it is necessary to transmit process-data to the computer and control values to the process at high datarates. Depending on the use of the data different sampling rates are required. We di-stinguish three cases:

• 1) Electrical signals, mechanical oszillations etc., whose finctions of time have to be measured. Application: Computation of effective or mean values of non sinusoidal signals, surveillance of electronic power switching elements, detection of short peaks etc. Frequency: Very high, limited by the computation speed of the computer.

• 2) State values (means values), which are determining the control algorithms (input values to the computation). Application: Measurement of effective or filtered values of alternating or oscillating signals or signals with undesired harmonics. (Most of the signals belong to this category because of noise, etc.). Frequency: Lower limit: According to the shortest timeconstants of the controlled process. Upper limit: Determined by the frequency of harmonics, which have to be processed.

• 3) State values (mean values, supplied with gradients and statistical data), which characterize the behaviour of the process over a longer period of time. Application: Documentation, identification and parameteroptimisation of values with long time constants. Frequency: Upper limit determined by the capacity of the storage medium.

The paper will present a set of programs developed at the On-LINE LABORATORY of the Institute of Automatic Control, Swiss Federal Institute of Technology, Zürich, which organize the prozess data in memory, on disk and magnetic tape and allow the user to access them easily.