Set Pressure and Flow Rate in Simulink (SimHydraulics)
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David Yu
el 1 de Jul. de 2015
Comentada: David Yu
el 2 de Jul. de 2015
Hi!
I would like to ask if it is possible to set a user-defined pressure and flow rate in a model with Simulink.
I have tried using a "Hydraulic Flow Rate Source" together with a "Hydraulic Pressure Source", however by using the sensors I have noticed that if I check the flow rate after the pressure source, the values that I have set initially have changed.
I have uploaded a screenshot showing this issue.
Does anyone of you know if it is possible to set both values?
Thank you in advance!
Best Regards,
David
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Sebastian Castro
el 1 de Jul. de 2015
I don't believe that is possible, because the Ideal Flow Rate Source will provide whatever pressure is necessary to maintain a given flow rate. If you add more pressure drops in the system, the flow rate source will simply compensate for those.
Suppose you need 10 MPa to cause a desired flow rate. If you put a Pressure Source of 3 MPa in series, then all that will happen is that the Flow Rate Source will supply 7 MPa instead, because it's being "helped" by the other pressure source.
Another reason why your flows are different is that the flow in the left sensor has two possible pathways. Some of the fluid flows through the Pressure Source into the second sensor, but most of it ends up going down into that Hydraulic Reference block. So, it makes sense for those flow rates to not be the same.
- Sebastian
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Sebastian Castro
el 1 de Jul. de 2015
I can think of two tips that might help with that.
- You mentioned that after connecting a Pressure Sensor, your pressures drop to zero. This is likely because you're connecting the Pressure Sensor in series, thus causing an infinite resistance in the system. Try connecting the sensor in parallel (the P port at the node you want to measure, and the T port connected to a Hydraulic Reference).
- Typically, you have a constant pressure source and you control the flow rates by modifying the opening of the valves. I think you should keep the Pressure Sources there, and then measure flow rates into a closed-loop controller that modifies the openings of Valve1 and Valve2. This will let you control the flow rates at both systems.
For the valves, what are you using? Variable Orifice blocks, or something more elaborate?
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