Monday, March 9, 2009

BASIC CURVE CLASSIFICATION

The basic curves of the rise-fall displacement diagram are primarily of two families: the simple polynomial and the trigonometric .The trigonometric curves are superior to the polynomial curves and give smoother action , easier layout , lower manufacturing cost, and less vibration , wear , stresses , noise and torque , in addition to smaller cams .

3.6.1. Simple polynomial curves:

The displacement equations of simple polynomial curves are of the form

Y=Cθn

Where n=any number.

C= a constant.

In this polynomial family, we have the following popular curves with integer powers:

Straight line, n=1;

Parabolic or constant acceleration, n=2;

Cubic or constant pulse, n=3.

Trigonometric curves:

The curves of trigonometric form are: simple harmonic motion (SHM) or crank curve, which has a cosine acceleration curve; cycloidal, which has a sine acceleration curve ; double harmonic ;and elliptical .

Other curves:

In addition to these two families, we have the miscellaneous little-used curves: modified straight-line circular arc and the circular arc curves. These are employed primarily as an improvement over the characteristics of the straight-line curve.

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