Translational Multibody Interface cannot solve velocity

Hi everyone,

I try to combine a multibody model with a hydraulic model. For this I used the Translational Multibody Interface block between the Double Acting Hydraulic Cylinder block and a prismatic Joint block with enabled velocity and force. But in this case the following error occurs:

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

Caused by:

• ['Knickgelenk_V03/Solver Configuration2']: Initial conditions solve failed to converge.
• Nonlinear solver: Linear Algebra error. Failed to solve using iteration matrix.
• The model may not give enough information to make it possible to solve for values of some of its variables. Specific advice is given below. all components and nodal across variables involvedCannot solve for one or more variables: 'Double_Acting_Hydraulic_Cylinder.C.v' (Velocity) 'Double_Acting_Hydraulic_Cylinder.R.v' (Velocity) 'Double_Acting_Hydraulic_Cylinder.conv_A.C.v' (Velocity) 'Double_Acting_Hydraulic_Cylinder.conv_A.R.v' (Velocity) 'Double_Acting_Hydraulic_Cylinder.conv_A.chosen_converter.C.v' (Velocity) 'Double_Acting_Hydraulic_Cylinder.conv_A.chosen_converter.R.v' (Velocity) 'Double_Acting_Hydraulic_Cylinder.conv_B.C.v' (Velocity) 'Double_Acting_Hydraulic_Cylinder.conv_B.R.v' (Velocity) 'Double_Acting_Hydraulic_Cylinder.conv_B.chosen_converter.C.v' (Velocity) 'Double_Acting_Hydraulic_Cylinder.conv_B.chosen_converter.R.v' (Velocity) 'Double_Acting_Hydraulic_Cylinder.hs.C.v' (Velocity) 'Double_Acting_Hydraulic_Cylinder.hs.R.v' (Velocity) 'Translational_Multibody_Interface1.C.v' (Velocity) 'Translational_Multibody_Interface1.R.v' (Velocity) Dependency found among topology equations. Check for missing reference node.

If the Translational Multibody Interface block and the Double Acting Hydraulic Cylinder block were replaced by Hydraulic Actuator Multibody block, the model seems to do something whenever not the things I want it to do, because the cylinder moves even when the valve is closed and doesn't change its motion if the valve setting changes.

I would be very happy to receive helpful answers and thank you in advance!

An overwhelmed Simscape apprentice

Answer 1

[Steve Miller]

The diagnostic indicates you are missing a reference node

Check for missing reference node.

The block you are likely missing is shown below.

--Steve

[Benedikt Wanke]

Thank you very much!

That was again one of those tiny little things that often only an outsider recognizes - within a second :'D

[Benedikt Wanke]

@Steve Miller

What am I doing wrong if the cylinder ALWAYS extends, regardless of the position of the valve?

Depending on the valve, the cylinder extends immediately, even if the valve is at zero from the start (3-Way Directional Valve) or it only extends when the valve is at >0, but does not retract again at <0 (4-Way Directional Valve)

[Steve Miller]

Guesses:

• Initial pressures are asymmetric
• Gravity, a spring, or some other force in the mechanical system is forcing the cylinder to move (requires leakage area to be high enough).
• Valve is not symmetrically parameterized (one side opens way more than the other - check units?)

--Steve

[Benedikt Wanke]

Thank you!

I checked all of your points but in the end it worked after reducing the mass acting on the cylinder.