Wireless Sensor and Actuator Networks for Lighting Energy ...

tolerable range by relieving the equality constraints into inequality constraints as shown
in (6.6).
min d
1
, subject to
L sub
d E sub
+ tol
,
L sub
E
L sub
d E sub
tol
,
L sub d
sub
+ tol
E sub
+ tol ,
(6.6)
DimLevel min
d DimLevel max
6.3 Lighting Optimization Algorithm with Sensory Feedback
The basic optimal lighting actuation algorithm is a single-iteration operation that
assumes perfect illuminance model and no extraneous source of light. It is, however, not
possible to capture every detail of the room configuration and account for
manufacturing tolerances of the lights to generate accurate workplane level illuminance
models. More importantly, daylight will always be an uncontrollable external light
source for a daylight harvesting system, so the algorithm must be able to incorporate
available daylight for optimal lighting actuation. Therefore, the open-loop lighting
optimization algorithm is extended by closing the control loop with sensory feedback to
compensate for uncertainties and external light sources.
Figure 6-3 shows the block diagram of the extended lighting optimization
algorithm. The behaviors of the illuminance model generator, lighting optimizer and
wireless-enabled luminaires are exactly the same as those described before. The
photosensors placed at each of the locations of interest sense the light, which may be a
mixture of electric light and daylight, and transmit the measurement back to the lighting
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