Hydraulic Library User Manual - NUPET

Hydraulic Library 4.2User ManualSome very simple arithmetic gives two important points:1. If you want to see f Hz you need a communication interval no biggerthan about 1/(10f) seconds.2. A communication interval of x seconds enables you to see frequenciesdown to about 1/(10x) Hz. Thus with 0.1 seconds you can seedown to about 1 Hz.In the current example we are probably not interested below 1 Hz and 0.1seconds, HL01 and HL03 are very suitable. The following note is vitallyimportant.Note:It is a common mistake in modeling hydraulic systems to alwaysuse line submodels of high complexity. The correct procedure is touse the simplest line submodels that will achieve the modelingobjective. Be aware of the frequencies you are interested in andthe frequencies you can see with the current communicationinterval.If you make a bad choice, you may multiply the CPU time by 10 or100 and force the integrator to compute high frequencyphenomena which are of no interest to you and will be invisiblewith the communication interval set! The messages under theWarning tab are very helpful. Read them.See also Chapter 4:Selecting submodels for Hydraulic Lines.1.5 Example 4: Valves with duty cyclesFigure 1.27: Hydraulic system with servovalve.Objectives• Introduce valves controlled by duty cycles.• Use the plot manager to plot flow rates against differential pressure.21