Single acting actuator model interfacing with gas domain problem

I am building a Simscape model for a single-acting translational actuator and trying to map 3 to 15 psi input pressure to 0 to 14 mm displacement. However, I am getting negative interface force and Warning:First solve for initial conditions failed to converge. Trying again with all high priorities relaxed to low.

Current observations:

• chamber-->p_I is matching the source pressure.
• interface_displacement initializes correctly at 0.01 mm.
• interface_force is negative.
• chamber-->A-->p is not matching the desired pressure.
• Translational Spring-->x remains at 0 m, so the spring does not seem to deform.

My questions are:

1. How can I correct the negative displacement sign in this model?
2. What is the correct way to connect the actuator, spring, and reference so the force and displacement become positive?

Any guidance on proper Simscape connection, sign convention, and parameter settings would be appreciated.

Answer 1

[Abhipsa]

Hi @Viji,

The simulation appears to be failing during the initialization phase. This can occur when the target values and priorities specified for certain Simscape variables are inconsistent with the physical constraints of the model.

As a first step, I recommend using the Simscape Variable Viewer to inspect the initial conditions and identify variables that are unable to satisfy their initialization targets.

A good practice is to build and validate the model incrementally:

1. Verify the actuator subsystem independently.
2. Add the spring and validate the mechanical response.
3. Introduce additional components and initialization targets one at a time.
4. Check that all high-priority initialization targets are physically consistent.

Additional guidance on diagnosing initialization failures can be found in the following documentation:

https://www.mathworks.com/help/simscape/ug/troubleshooting-simulation-errors.html#:~:text=Simulation%20Issues).-,Initial%20Conditions%20Solve%20Failure,-The%20initial%20conditions

The information available so far suggests that the initialization issue should be resolved first. Once the model initializes successfully, it will be easier to investigate the negative interface force and the lack of spring deformation.