4-way directional valve from matlab simscape calculates volume flow incorrectly.

I am building a model for a hydraulic 4-post susspension dynamometer as part of a master's thesis. For this I use Matlab Simscape functions, among others the "4-way directional valve" from the hydraulics segment.

For this I use the block as follows:

in a specially created test case to validate the block pair parameter

Now let's get to my problem. The flow into the valve is not the same as the flow out of my valve. Furthermore, I am not sure why there is only one volume flow at the negative valve stroke between A and B and not at the positive one during the complete valve stroke (maximum negative -> maximum positive).

The volume flows can be seen below:

top left -> volume flow from the pump

middle left -> its derivative

bottom left -> volume flow from outlet A and B

top right -> volume flow to the tank

middle right -> valve signal (from maximum negative -> maximum positive)

bottom right -> applied pressure of 100 bar

I now actually expect the same volume flow that goes from the pump to the valve also back to the tank.

Why the volume flow of A and B is only half, I am uncertain. But I can mirror the values of the "Opening Vector" and "Opening Area Vector" in the "4-Way Directional-Valve". Thereupon, the actual model no longer works, but that is another question.

Now the question, did I do something wrong or is this a bug?

[Yifeng Tang]

One observation: the v_A signal isn't the flow rate out of Port A. There is a branch before the flowrate sensor that returns to the tank.

[Felix Woltering]

Thank you very much, I must have been a bit blind after working for a long time.

[Yifeng Tang]

I'll copy my short "answer" into the Answer section so the question would appear answered :)

Answer 1

[Yifeng Tang]

The flow rate sensor that is supposed to measure the flow rate out of Port A, appears to have a branch before it, which allows the flow to return to the tank. It could contribute to the weird behavior you observed.