motion-laws
The same rise, three ways
A 20-unit rise over 120°, then a dwell. Above, the displacement — all three do the same job and are hard to tell apart. Below, the acceleration, differentiated from those same curves. Constant acceleration peaks lowest at 5.556e-3 per degree² and arrives at the dwell with a step; cycloidal peaks highest at 8.727e-3 and arrives at zero. The smoothest law has the largest peak, which is the trade the whole of cam design turns on and which the displacement plot gives no hint of.
Where it is used
- Prescribing motion Prescribed motion
- The law that costs least is not the smoothest Prescribed motion
- Stopping thirty times a second Prescribed motion
- The arc that is concentric with the pivot Motion that stops
- The cam is not the valve Machines you have met
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