What is the mistake in the simulation, if the transient initialization at time x, solving for consistent states and modes, failed to converge?

Hey, I am using a 4-Way Directional Valve to controll a double-acting Actuator. To switch the valve I am using a valve actuator.

Error:An error occurred while running the simulation and the simulation was terminated

Caused by:

['test_dumm/Solver Configuration']: Transient initialization at time 0.06666666666666732, solving for consistent states and modes, failed to converge.

Nonlinear solver: Linear Algebra error. Failed to solve using iteration matrix.

all components and nodal across variables involved

Cannot solve for one or more variables, including dynamic variable derivatives:

Time derivative of 'Double_Acting_Actuator_IL.chamber_A.p_I' (Pressure of liquid volume)

Time derivative of 'Double_Acting_Actuator_IL.chamber_A.interface_displacement' (Interface displacement)

Time derivative of 'Double_Acting_Actuator_IL.chamber_B.p_I' (Pressure of liquid volume)

Time derivative of 'Double_Acting_Actuator_IL.chamber_B.interface_displacement' (Interface displacement)

Time derivative of 'Double_Acting_Actuator_IL.hard_stop.x' (Position)

Time derivative of 'Double_Acting_Actuator_IL.sensor.x' (Position)

Time derivative of 'Ideal_Translational_Motion_Sensor.x' (Position)

'Double_Acting_Actuator_IL.R.v' (Velocity)

'Double_Acting_Actuator_IL.chamber_A.R.v' (Velocity)

'Double_Acting_Actuator_IL.chamber_B.R.v' (Velocity)

'Double_Acting_Actuator_IL.hard_stop.R.v' (Velocity)

'Double_Acting_Actuator_IL.hard_stop.v' (Velocity)

'Double_Acting_Actuator_IL.sensor.R.v' (Velocity)

'Double_Acting_Actuator_IL.sensor.V' (V)

'Ideal_Translational_Motion_Sensor.R.v' (Velocity)

'Ideal_Translational_Motion_Sensor.V' (V)

'Translational_Free_End1.V.v' (Velocity)

'Translational_Free_End1.v' (Velocity)

The controlling structure for the valve actuator is correct

Can you tell me where I made mistakes?

Thank you

[Yifeng Tang]

The error message seems to suggest that there is something wrong with the way the model is assembled. Possibly overconstrained. But it's impossible to tell without seeing the modeling. If you can share the model here, I can help take a quick look. Or at least, a snapshot of the model (but I can do way less with only a picture).

[Emefun]

thats my model

Answer 1

[Yifeng Tang]

Hi Emefun,

It looks like the piston side of your hydraulic cylinder doesn't have any mass. Adding a mass block to the rod allow the model to simulate to completion. See below:

And now I understand what the error message is trying to say about time derivative: when you try to divide the force by the mass to get acceleration (derivative of velocity) but the mass is zero, the derivative goes crazy :p

With that fixed, I also believe the valve parameter needs some further work. As the input S varies between -5mm and 5mm, all the flow paths in this valves are open, so the piston isn't moving anywhere. You can right click on the valve -> Fluids -> Plot Valve Characteristics, and view the opening curves. I saw the following, and I'm not sure if it's the intended behavior.

Hope this helps.

Yifeng

[Yifeng Tang]

Also, it may be a good idea to think about putting some load at the end of the rod. The pressure building up inside the chambers and the speed of the rod may well depend on the external load as well.

[Emefun]

Thank you. I didn't think about that.

I know that i have to change the valves configuration, was just a test for now.

Do you know if it is possible to exchange the mass to another double-acting cylinder? like the rod of them is connected and like this connect two different hydraulic-cycles

[Yifeng Tang]

You can add another double-acting cylinder, but you probably also need to keep the mass. The rod side of the added cylinder has no mass either, so if there is ANY difference in the cylinder forces, the acceleration becomes inf. So, keep the mass, and set it as the same (or best guess) as the actual piston+rod mass.

[Emefun]

Thank you so much for the help. Im still in the beginning and its a lot to learn. Have a nice day