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How to Improve a Motion?

That is a very big question.

A good motion for one application may not be a good motion for another.

Assuming 
  • the cycle time of the overall motion design can not change (ie you don't want to reduce the speed of the machine!)
  • the motion is intended for a packaging machine where the mechanical output reciprocates or oscillates or indexes.

    Ask yourself these questions:
  • Are there any step changes in velocity?
    If there are, eliminate them from the motion design.  Step changes in velocity might reduce peak velocity and acceleration, but a step change will induce vibrations in the mechanical system so that the actual acceleration experienced by the system will be much greater than the motion design itself.
  • Are there any step changes in acceleration?
    If there are, eliminate them from the motion design.  Step changes in acceleration might reduce peak velocity and acceleration, but a step change will induce vibrations in the mechanical system so that the actual acceleration experienced by the system will be much greater than the motion design itself.
  • Are the peak values of acceleration of each of the segments similar?
  • Is it possible to increase the duration of the "move" segments (reducing the duration of other less critical segments) so that the peak accelerations are reduced?  Even a small increase in a segment duration will help.
  • Is it really necessary for your motion to have dwells? A blend-point with zero velocity,acceleration AND jerk as an "in-specification" and an "out-specification" gets pretty close to a dwell for a reasonable number of degrees without there being a dwell segment at all.
  • Can you reduce the distance a part is moved?

    Consider these issues too:

    Transient oscillations or vibrations will occur in mechanical systems as a result of moving them with a segment type (or sometimes called a motion or even a cam law) that has a discontinuity in the function at any derivative. 
    (A discontinuity in a motion means that there are two distinct Y-Values on a graph for a particular X-Value. This means that if the function is differentiated with respect to the time once more, the differentiated value will be infinite at the particular X-Value point that has the two values.).  The lower the order of the derivative in which the first discontinuity occurs, the more serious will be the resulting vibration.  

    When a motion design is to be saved and used for a cam or servo system, then it is critical that the motion has at least position continuity - this goes without saying. Velocity continuity is also important, although, many designs may be able to suffer (and I mean suffer) small discontinuities in velocity - but it is also extremely poor practice. Continuity in Acceleration is also important, and any system that requires precise following of the segment or motion design should be continuous in acceleration - this means that the jerk will remain finite through out the motion following.

    The jerk function is related to the rate of change of the strain energy of the system throughout the motion design. A high rate of change of acceleration, (that is high or even infinite jerk) anywhere in the motion will be accompanied by abrupt changes of torque in the drive and of forces on the cam and following system,  These abrupt changes will give rise to deflections in the parts concerned.  The importance of jerk depends on the magnitude of the deflections and their relationship to the desired accuracy.  Even with zero jerk, there will be deflections that are caused by the inertia and static loads depending on the elasticity of the system.  It must be borne in mind that a segment type with a zero jerk at the start and end of the segment will produce high maximum accelerations and therefore higher nominal forces, when the required displacements is to be reached within the same period.