IEA Solar Heating & Cooling Programme Task 31: Daylighting ...

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position slightly too low is thus preferred to a position slightly too high.

When the blind movement is accepted by the time filter, it enters the minimum step filter:
the movement is applied only if it is larger than a fixed minimum value delta_alpha (in
our case, delta_alpha = 0.3, i.e. 30% of the movement between totally closed and totally
open). This value is reduced by half when there is a risk of glare (i.e. when alpha_max <
alpha_cur).

The control algorithm presented here deals only with one blind but in the LESO building
there are two blinds to control per room. The idea is to control independently the two
blinds with two similar algorithms. The unique difference is in the fuzzy rule base
"Illuminance" of the lower blind. A minimal opening of 0.4 is kept in order to allow
visual contact with the outdoor environment, which has been clearly shown as an
important criteria for user acceptance [Elder and Tibbott, 1981].

In the case of user absent, two steps have been taken to minimize the number of
movements (and prevents early mechanical wear). The first reduction of the number of
blind movements is realized with a minimum step filter (similar to the one used in the
user present case) that allows moving blind only if the movement is large enough (larger
than 40% of the movement between totally closed and totally open). The other reduction
is done through the use of the two blinds (in the case of the LESO building) in a
sequential way, that means to consider the two blinds as only one larger blind. In the
LESO building, one blind is above the other and a sequential control seems to be a
natural solution.

The idea is to use a parameter called Bi that describes the importance of blinds regarding
the illuminance provided.

0 < Bi < 1

Using Bi and the alpha value given by the controller, the blind position of the upper blind
alpha_1 and the lower blind alpha_2 are calculated as follows:

If alpha >= Bi then:

1
alpha_1 = (alpha-Bi)/(1-Bi) and alpha_2 = 1 (completely open)

If alpha <= Bi then:

2
alpha_1 = 0 (completely closed) and alpha_2 = alpha/Bi

The Bi parameter is continuously adapted together with the RI model adaptation
(described in a further section).

2.2.2 Electric Lighting System

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Summary :

1 Using Bi and the alpha value given by the controller, the blind position of the upper blind alpha_1 and the lower blind alpha_2 are calculated as follows: If alpha >= Bi then: 1 alpha_1 = (alpha-Bi)/(1-Bi) and alpha_2 = 1 (completely open) If alpha <= Bi then: 2 alpha_1 = 0 (completely closed) and alpha_2 = alpha/Bi The Bi parameter is continuously adapted together with the RI model adaptation (described in a further section).

Tags : two,blinds,moement,totally,case,only,control,alpha,alue,alpha1,alpha2,position,user
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