Modulated Controls are control rules that provide for a continuous degree of control applied to a pump or flow regulator as determined by the value of some controller variable, such as water depth at a node, or by time. The functional relation between the control setting and the controller variable can be specificed by using a Control Curve, a Time Series, or a PID controller. Some examples of modulated control rules are:

RULE MC1

IF NODE N2 DEPTH >= 0

THEN WEIR W25 SETTING = CURVE C25

RULE MC2

IF SIMULATION TIME > 0

THEN PUMP P12 SETTING = TIMESERIES TS101

RULE MC3

IF LINK L33 FLOW <> 1.6

THEN ORIFICE O12 SETTING = PID 0.1 0.0 0.0

Note how a modified form of the action clause is used to specify the name of the control curve, time series or PID parameter set that defines the degree of control. A PID parameter set contains three values -- a proportional gain coefficient, an integral time (in minutes), and a derivative time (in minutes). Also, by convention the controller variable used in a Control Curve or PID Controller will always be the object and attribute named in the last condition clause of the rule. As an example, in rule MC1 above Curve C25 would define how the fractional setting at Weir W25 varied with the water depth at Node N2. In rule MC3, the PID controller adjusts the opening height of Orifice O12 to maintain a flow of 1.6 in Link L33.

To create a control curve to reference in the controls go to Components/SWMM Extensions/Control Curves. The units of the curve are determined by the units of the Control Set. If the selected unit for the Control Set is “SI Units – CMS, m, cubic m” then the curve assumed to be a depth (m) vs setting (unitless) curve on export.

To create a time series to be reference in the controls go to Components/SWMM Extensions/Time Series Control Data.