Have a look at
ConstantActuator and at
PermeanceActuator for an explanation of both converter
models.
Simulation of the force-stroke characteristic of the PermeanceActuator with a constant current I=3A and a forced armature movement (similar to measurements in reality) shows the dependency of both force-generating permeances G_ma and G_mb as well as inductance L on armature position x. Simulate for 8 s and plot vs. armature position feedX.flange_b.s (same physical quantities together in a common diagram for comparison):
feedX.flange_b.f // force of permeance model (permeance of stator iron neglected in this model) comparisonWithFEA.y[1] // force of FEA model with non-linear stator iron 1.0718 comparisonWithFEA.y[2] // force of FEA model with mu_rFe=const.=1000 actuator.g_ma.G_m // permeance G_ma actuator.g_mb.G_m // permeance G_mb actuator.L // inductance of permeance model comparisonWithFEA.y[3] // inductance of FEA model for comparison (mu_rFe=const.=1000).