Page 431 - ExtendSim User Guide
P. 431

Using the Flow Control tab
By default, the settings in a Valve’s Flow Control tab are disabled. Use the tab’s popup menu, shown at right, to choose either the Goal or Hys- teresis option.
If the Goal option is selected, an additional popup menu appears to the right. Use this second menu to choose:
• Goalasaquantity • Goalasaduration
Observing the maximum rate for a goal
Flow Control options
Delaying Flow 405
Controlling a Valve’s maximum rate
Whether you select a quantity or a duration goal, a Valve’s maximum rate is observed while a goal is On. While the goal is off, you have the option to choose whether the maximum rate is observed or not and whether the flow is stopped. Thus your purpose in using a goal could be to block flow for a period of time and allow it to move through when the goal is off, allow flow for a period of time and block it at other times, accept a certain quantity of flow but stop flow when the goal is off, and so forth. In fact, you can choose to observe the maximum rate when the goal is off. This can be useful for a quantity goal, when you just want the Valve to report when a goal is finished.
• If its maximum rate is 0 (zero), the Valve will block flow while its goal is On.
• Ifitsmaximumrateis>0,blank,orinfinite,theValvewillallowflowtopassthroughatthat rate while its goal is On. (If the maximum rate is blank, the Valve uses an infinite rate.)
☞ If a Valve’s maximum rate is zero and a quantity goal is On, no flow will go through the block and the goal will never end.
Options when goal is Off
Dialog options allow you to choose what will happen when the goal switches to Off: • Stoptheflow
• Ignore maximum rate (do not constrain flow) • Observe maximum rate
Setting a Valve’s quantity goal
Using popup menus in a Valve’s Control Flow tab, you can specify that the block has a goal to pass a certain quantity of flow from its inflow to its outflow. Additional options allow you to specify what the Valve should do once that quantity of flow has passed.
The quantity goal modulates a Valve's critical constraint (its maximum rate) by cycling between On and Off states.
• WhileaquantitygoalisOn,thevalueintheValvetab’sMaximumratefield,orthevalueat the block’s R (maximum rate) input connector, is observed. The goal remains On until either the amount of flow that has passed through the block reaches the target quantity, or the goal is interrupted. At that point the goal switches to the Off state.
• What happens when the goal switches to the Off state depends on the Off option selected in the block’s dialog: stop the flow, do not constrain flow, or observe maximum rate.
☞ To interrupt a goal, send a value to the Valve’s stop input connector.
Discrete Rate

   429   430   431   432   433