.Modelica.Mechanics.Translational.Interfaces.PartialCompliantWithRelativeStates

Information

This is a 1-dim. translational component with a compliant connection of two translational 1-dim. flanges where inertial effects between the two flanges are neglected. The basic assumption is that the cut-forces of the two flanges sum-up to zero, i.e., they have the same absolute value but opposite sign: flange_a.f + flange_b.f = 0. This base class is used to built up force elements such as springs, dampers, friction.

The difference to base class "PartialCompliant" is that the relative distance and the relative velocity are defined as preferred states. The reason is that for a large class of drive trains, the absolute position is quickly increasing during operation. Numerically, it is better to use relative distances between drive train components because they remain in a limited size. For this reason, StateSelect.prefer is set for the relative distance of this component.

In order to improve the numerics, a nominal value for the relative distance should be set, since drive train distances are in a small order and then step size control of the integrator is practically switched off for such a variable. A default nominal value of s_nominal = 1e-4 is defined. This nominal value might also be computed from other values, such as "s_nominal = f_nominal / c" for a spring, if f_nominal and c have more meaningful values for the user.