Advanced Building Simulation

166 Mahdavi
practice, however, controllers for various systems and components are often interdependent.
A controller may need the information from another controller in order to
devise and execute control decisions. For example, the building lighting system may
need information on the building’s thermal status (e.g. heating versus cooling mode)
in order to identify the most desirable combination of natural and electrical lighting
options. Moreover, two different controllers may affect the same control parameter
of the same impact zone. For example, the operation of the window and the operation
of the heating system can both affect the temperature in a room. In such cases,
controllers of individual systems cannot identify the preferable course of action independently.
Instead, they must rely on a higher-level controller instance (a “metacontroller”,
(MC) as it were), which can process information from both systems
toward a properly integrated control response.
We conclude that the multitude of controllers in a complex building controls
scheme must be coupled appropriately to facilitate an efficient and user-responsive
building operation regime. Thus, control system features are required to integrate and
coordinate the operation of multiple devices and their controllers. Toward this end,
control functionalities must be distributed among multiple higher-level controllers or
MCs in a structured and distributed fashion. The nodes in the network of DCs and
MCs represent points of information processing and decision-making.
In general, “first-order” MCs are required: (i) to coordinate the operation of
identical, separately controllable devices and (ii) to enable cooperation between different
devices in the same environmental service domain. A simple example of the
first case is shown in Figure 7.5 (left), where an MC is needed to coordinate the operation
of two electric lights to achieve interior illuminance goals in a single control
zone. In the second case (see Figure 7.5, right), movable blinds and electric lights are
coordinated to integrate daylighting with electric lighting.
In actual building control scenarios, one encounters many different combinations of
the cases discussed here. Thus, the manner in which the control system functionality
DC
Light 1
MC
Lights
DC
Light 2
Light 1 Light 2
Sensor
DC
Light
MC
Visual
DC
Blinds
Light Blinds
Sensor
Figure 7.5 Left: MC for individually controllable identical devices; Right: MC for different devices
addressing the same control parameter.