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

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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

##### 2 Comments

Yifeng Tang
on 12 Feb 2024

### Accepted Answer

Yifeng Tang
on 14 Feb 2024

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

##### 4 Comments

Yifeng Tang
on 15 Feb 2024

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