A Catapult to demonstrate locked states

The objective of this exercise is to obtain a partial equilibrium for a system using locked states.

Introduction to locked states

Locked states status

The Locked states facility applies only to stabilizing runs and can be very useful for the more advanced users but at first reading you may prefer to omit this example.

During a normal stabilizing run state variables are free to evolve, hopefully to some equilibrium position. A locked state is not allowed to evolve during a stabilizing run, it is held at its initial value. Simcenter Amesim provides a facility to give you control over which states are locked.

Sometimes it is useful to lock a sub-set of state variables and do the stabilizing runs on the rest of the state variables. The idea is that you lock the values of certain state variables, but you want the rest to evolve to be consistent with the ones you fix. Then the system is divided into two parts. Often these parts are in different domains. Thus we might have a hydraulic power system driving a mechanical load through an actuator. It might be useful to start the simulation with the hydraulic sub-system in equilibrium but with the mechanical system in some prescribed non-equilibrium state.

We describe the resulting system as being in a partial equilibrium state.