"This model is structurally singular. Check the equations."

We are trying to use PID controllers to control Mass flow Rate when the system senses a difference in pressure in the system. Attached we have our model. The simulation runs when we have our mass flow rate subsystem but when we add our pressue subsystem, we keep getting "This model is structurally singular. Check equations."

Answer 1

[Raj]

Hi @Neil Bernardino

As per my understanding, a structural singularity points to equations that are not lineraly independent.

There may be two types of structural singularity-

1. When a variable does not appear in any equation.
2. When some equations are degenerate in some ways. Tracing this down means looking for the places where you may find confliciting equations.

An example to structural singularity can be an instance of a vehicle model in which for example if we apply same velocity to all four wheels and then also apply a redundant constraint that forces the velocity to be the same on all 4 wheels. Check if there are similar instances in your model and update accordingly.

I hope this helps!