Encoder Resolution
From the quadrature signal the SCORBOT-ER IX controller measures four counts
for each encoder slot, thus quadrupling the effective resolution of the encoder.
The resolution of the encoder is expressed as:
S
E
=
360°
n
Where:
S
E
is the resolution of the encoder.
n is the number of counts per encoder revolution.
The encoders used in the SCORBOT-ER IX have 512 slots, generating 2048 counts
per motor revolution. The encoder resolution is therefore:
S
E
=
360°
2048
=
.176°
When the encoder resolution is divided by the overall gear ratio of the axis, the
resolution of the joint is obtained.
Since the encoder is mounted on the motor shaft, and turns along with it, the
resolution of the joint is expressed as:
S
JOINT
=
S
E
N
AXIS
Thus, for example, the resolution of joint 3 of the SCORBOT-ER IX is therefore as
follows:
S
J3
=
0.176°
213.33
= 0.000825°
The resolution is the smallest possible increment which the control system can
identify and theoretically control. The accuracy of the axis—that is, the precision
with which it is positioned—is affected by such factors as backlash, mechanical
flexibility, and control variations.
User’s Manual 7 - 3 SCORBOT-ER IX
9603
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