Alibre Design

Chapter 19 - Alibre Motion• Prescribed Motion Actuators are Incompatible With Springs and DampersSince Springs and Dampers produce force or torque effects, any Prescribed Motionsacting on the same constraints will completely override them. In this situation, any Springsor Dampers will be automatically excluded from the simulation (Springs and Dampers onother constraints remain unaffected, and their effects will be calculated normally).• Prescribed Motion Actuators Can Produce LockingIf you prescribe a Motion that cannot continue past a certain point due to other constraints,then you have created a situation where an “irresistible force meets an immovable object”,as the Simulator does not decide which constraint or motion should be ignored at thatpoint. Metaphysical considerations aside, this produces a simulation condition for whichthere is no viable solution, so the simulation stops at that point, and a warning message isdisplayed.• Quasi-Kinematic Simulations Always Use Prescribed Motion TypesThe inputs to Quasi-Kinematic simulations that you create are always prescribed motions, as forces,torques and inertias are effectively ignored in this type of simulation. See Simulation Types andParameters for more on Quasi-Kinematic simulations. You can use prescribed motions in DynamicSimulations, as well.Specifying Harmonic FunctionsVarious quantities in Alibre Motion, including prescribed motions, forces, and torques, may bespecified as Harmonic or Sinusoidally varying functions of time. This enables you to create backand-forthmotions, for instance.513