Does anybody has any idea of how to implement in simscape pneumatic valve? Like the one in SimHydraulic. At some time I have to close one part of pneumatic circuit, but with available blockes I can't do it.
Thanks in advance.
Tomas
MATLAB: Pneumatic valve
pneumaticSimscape
Related Solutions
The attached model shows a small example of how Simscape works in evaluating Across and Through variables, and specifically how the constant area orifice(same as fixed orifice) block works. In the attached model example.mdl, two orifices connect into a double-acting hydraulic cylinder whose mechanical piston is connected to a mass-damper-spring system. One end of the orifices have a pressure source that maintains the pressure constant (-4e6) at this end. Since pressure is an across variable, both the lower ports of orifices o1, and o2 have the same constant pressure kept by the pressure source.
At the other end of the orifices, the pressure is determined by the hydraulic cylinder, specifically the variable volume chambers within this cylinder. (To see this block, right click on the cylinder and select look under mask. Note that this has 2 variable volume chambers). The variable volume chamber's initial condition(such as initial piston position,etc) determine the initial pressure at this end of the orifices. Once the pressure difference is determined across the orifices, the flow rate is found out based on the pressure-flowrate equation of the orifices, as mentioned in the doc link:
<http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/hydro/ref/fixedorifice.html>Once the current flow rate is obtained, the pressure of the orifices at the upper port at the next time is obtained from the current flow rate, and current pressure and the control signal input of the variable volume chamber, according to the flow rate-pressure equation shown in the below link:
<http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/simscape/ref/pistonchamber.html>Thus, the pressure is internally determined, and the flow rate across the orifices obtained directly from the equation of the orifice.
To read more about how Simscape works, and how across and through variables are used to resolve the blocks internally, please visit the following links:
<http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/simscape/ug/bq89sba-1.html#bq89sba-2> <http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/simscape/ug/bql2kkl-2.html>To read more about the Double acting Hydraulic cylinder, visit here:
<http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/hydro/ref/doubleactinghydrauliccylinder.html>A good debugging technique on a Simscape hydraulics model, is to use Ideal Pressure Sensors and Flow Rate Sensors at different points to measure the pressure and flow rates there. In the attached model, an ideal pressure sensor is used to measure the pressure at the lower ports of the orifices.(Please see the scope 'pressure at lower ports')
It might also be helpful to think of pressure-flowrate in the same terms as voltage-current, following kirchoffs laws.
There are three flow rate components associated with the moving piston:
- flow rate caused by the piston motion, q = A * v, - flow rate caused by the fluid compressibility, q = V/E * dp/dt - flow rate due to leakage, if any q = K_l * p.The flow rate associated with the piston velocity is accounted in the hydro-mechanical converter while the compressibility-caused flow is accounted in the variable volume chamber block. It gives you the possibility to build cylinder models with various level of idealization of a very limited set of building blocks.
Best Answer