Page 438 - ExtendSim User Guide
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412 Delaying Flow
Controlling a Valve’s maximum rate
plished by using model conditions to explicitly control both when a Valve’s maximum rate is observed and when it is ignored.
Unlike the quantity and duration goals discussed earlier, where the conditions for applying the Valve’s maximum rate were entered in its dialog, hysteresis must always get its control infor- mation from outside the block. The hysteresis option always relies on the Valve’s start input connector to control when the Valve’s maximum rate will be observed and its stop input con- nector to control when the maximum rate will be ignored. When the maximum rate is ignored, the Valve’s dialog provides a popup menu for choosing if the flow stops or if the Valve does not constrain the flow.
Hysteresis model
In this model, the Filling valve opens when the Storage tank is empty and closes when the tank is full. Conversely, the Emptying valve opens when the Storage tank is full and closes when the tank is empty. As a result, the model repeatedly cycles through the following stages:
Hysteresis model
• Emptyingvalveclosesandfillingvalveopens • Storage tank starts accumulating flow
• Storage tank reaches the full state
• Emptyingvalveopensandfillingvalvecloses • Storagetankstartsemptying
• Storage tank reaches the empty state
Based on settings in its Indicators tab, the Storage tank's I (indicator) connector outputs a value of 0 when empty and 2 when it is full. (Tank indicators are discussed on page 351.)
The Filling valve’s Hysteresis set- tings are shown at the right. When this valve’s start connector gets a 0 from the Storage tank’s I output connector, the valve observes its maximum rate. When the Filling valve’s stop input connector gets a 2, the block shuts down.
Hysteresis settings: Filling valve
The Emptying valve’s hysteresis set- tings are the opposite of the Filling valve, as shown at the right. When
this valve’s start connector gets a 2
from the Storage tank’s I output con- nector, the valve observes its maxi- mum rate. When its stop input
connector gets a 0, the valve shuts down.
Hysteresis setting for Emptying valve
Discrete Rate


































































































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