The test chamber (Fig. 1) was built on the roof of the Faculty of Civil Engineering, UL, Ljubljana (46.0° latitude, 300 m altitude). The test chamber has dimensions 1 m x 1 m x 1 m and is designed especially for control design purposes. The cell is shifted off the ground and the roof is ventilated in order to avoid the influence of overheating caused by direct radiation on the roof. Walls, floor and ceiling are built of lightweight brick blocks. Material properties are shown in Table 1.

Table 1 Material properties of the test chamber envelope

The south wall is completely glazed with double-glazing composed of two layers of standard clear glass and air fill, and the thickness of the wooden frame is 5 cm. The alternating geometry of the window is made with the moveable roller blind, the position of which can be automatically controlled.

With the measuring equipment the following values for outdoor and indoor conditions are measured:

• direct and reflected solar radiation with pyranomether CM-B (Kipp&Zonnen Delft BV),

• outdoor and indoor air temperature with thermocouples type T, and

• indoor illumination with luxmeter LUX cells.

The transparent area surface size of the envelope depends on the temporary roller blind position, and is expressed as the percentage of the shaded area related to the whole glazing area. The displacement sensor measures the exact roll position.

The regulation equipment enables the controlled optical response of the test chamber to the outside conditions. This equipment contains a programmable logic controller PLC, PC and operator panel. PLC sends the signals for proper functioning of the actuator — roller blind using electric engine. The illumination control algorithm was developed in the IDR BLOCK [7] environment and it is loaded on the PLC. Remote PC and control panel are used for the process supervision and they are also used for the visualization of experiments. The measured values and process variables are collected and stored in the PC, with an application in Factory Link environment developed for this purpose. For the realization of the introduced control system the following program tools were used:

• MAC Programmer is a software package for operator panel, which satisfies the demands for human-machine (PLC -Mitsubishi controller) communications.

• Melsec Meldoc Plus program for sequential control of the Mitsubishi programmable logic controller PLC.

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A system software package IDR BLOK for designing the control algorithm, which enables the PLC to perform the direct digital control DDC operations on the test chamber.

• Fuzzy logic controllers FLC implemented by Fuzzy blocks in an IDR BLOK program.

• The developed application in the Factory Link program environment used for the visualization of the experiments, data acquisition of the measurements and for preparing temperature and illumination set point values for experiments.