Accuracy; Conveyor Resolution Error - YASKAWA MOTOMAN DX200 Instructions Manual

Conveyor Synchronized
Funciton with Shift
Functions
4.2
4.3
4 Playback

4.2 Accuracy

Accuracy
In the operation by the conveyor synchronized control, the manipulator
motion path taught on the conveyor in stop status is reproduced on the
conveyor in run status.
Therefore, the accuracy of the operation is determined by the amount of
difference between the taught motion path and the synchronized motion
path. Since the object is moving, it is impossible to appreciate the
accuracy in the same way as the repetitive positioning accuracy for still-
object.
The amount of difference between the taught motion path and the
synchronized motion path is resulted from the following factors. Even if
the following factors are adjusted not to cause the difference, the amount
of difference can be about ten times of the amount of difference resulted
from the repetitive positioning for still-object.
• Linearity of the conveyor in the synchronization section
• Conveyor movements that are not indicated in the pulse data from
the conveyor encoder
(such as swings with hanger conveyor)
• Difference between the manipulator actual dimensions and the
dimensions registered in the DX200
• Conversion resolution error that occurs when converting the pulse
data from the conveyor encoder to the conveyor travel amount in
mm
• Manipulator mechanical accuracy such as arm bending
• Follow-up delay due to the conveyor speed fluctuation
• Manipulator system lag time
• Difference between the conveyor moving direction and the travel-
axis moving direction when the synchronization is performed by the
travel-axis

Conveyor Resolution Error

The synchronization error resulted from the conveyor resolution setting
error increases as the conveyor position value increases. The farther the
conveyor moves, the bigger the synchronization error becomes. The
minimum value for conveyor positional resolution setting is 0.01 μm.
Therefore, a maximum error of 0.005 μm per pulse may occur.
Entering a correct resolution is especially required when using the
conveyor synchronized function with shift functions because of its large
follow-up distance.
For example, when the conveyor resolution is 10 μm per pulse and the
synchronization distance is 2 m, 200,000 pulses are output when the
conveyor moves for 2 m. Since the maximum error per pulse is 0.005 μm,
the following synchronization error may occur: 200,000 pulses × 0.005 μm
= 1 mm
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