6 - 8
Pitch
Yaw
Roll
X
Z
Y
Figure 6.2-9 — Pitch, Yaw, and Roll Motion Axes
The problem with this definition is that, though correct, it is difficult to
remember. An expanded graphical representation is presented in Figure
6.2-10. Imagine a tiny carriage driven by a giant leadscrew. When the
carriage
rolls
sideways on the lead screw, we call it a
Roll
. When it rides
up and down on the lead screw
pitch
, we call that
Pitch
. And, when the
carriage deviates left or right from the straight direction (on an imaginary
Y
trajectory), we call it
Yaw
.
Screw
Pitch
Roll
Pitch
Yaw
Figure 6.2-10 — Pitch, Yaw and Roll
6.2.10 Wobble
This parameter applies only to rotary stages. It represents the deviation of
the axis of rotation during motion. A simple form of
Wobble
is a constant
one, where the rotating axis generates a circle (Figure
6.2-11).
Figure 6.2-11 — Wobble
A real rotary stage may have a more complex
Wobble
, where the axis of
rotation follows a complicated trajectory. This type of error is caused by
the imperfections of the stage machining and/or ball bearings.
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