Alibre Design

Chapter 19 - Alibre MotionIf you prescribe a Motion that cannot continue past a certain point due to otherconstraints, then you have created a situation where an “irresistable forcemeets an immovable object”, as the Simulator does not decide whichconstraint or motion should be ignored at that point. Metaphysicalconsiderations aside, this produces a simulation condition for which there is noviable 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 prescribedmotions, as forces, torques and inertias are effectively ignored in this type ofsimulation. See Simulation Types and Parameters for more on Quasi-Kinematicsimulations. You can use prescribed motions in Dynamic Simulations, as well.Specifying Harmonic FunctionsVarious quantities in Alibre Motion, including prescribed motions, forces, and torques,may be specified as Harmonic or Sinusoidally varying functions of time. This enablesyou to create back-and-forth motions, for instance.To completely specify a Sinusoidal function, three things must be known:• Period - The Period is the time taken for one complete cycle. You can enter the Periodin seconds, which is the time taken for one complete cycle, or the Frequency in Hertz,which is the number of cycles per second. Entering one automatically calculates the other.540