Adept Python - Manual (Page 43)

Linear Module Options
Adept Python Modules User’s Guide, Rev. E 43
Acceleration
The maximum acceleration rate achievable for Python modules varies with ball screw
lead pitch, stroke length, module type, and payload. As payload and/or ball screw inertia
increase, the available torque to inertia ratio will decrease, limiting the maximum
acceleration rate. The ACCEL 100 values for Python are conservatively set in SPEC, so
they are achievable for all rated payload and screw combinations (see
Table 3-8 ). The user
is able to command higher acceleration values up to Accel 110 by modifying the Max
Accel value in SPEC. For short axes with light payloads, maximum acceleration rates 50%
higher than these values may be possible.
Resolution and Repeatability
The linear resolution of Python modules is a function of the encoder resolution and the
ball screw lead. Therefore, the values vary with module and ball screw type. See the
following table for details.
NOTE: The minimum incremental step size may be greater than the linear
resolution due to mechanical and/or servo limitations. Adept has
demonstrated consistent sub-micron incremental step performance on
standard modules under various payloads. Typically a Python module
motor will null to a single count, and the high stiffness and low friction in
the drive train of in-line modules will enable discrete step increments per
the previous table. However, Adept does not guarantee this performance
due to other variables that could have adverse effects.
Table 3-8. Linear Module ACCEL 100 Acceleration Rate (mm/s 2 )
Ball Screw
Lead (mm)
ACCEL
100 Rate
(mm/sec 2 )
5 4,000
10 8,000
20 16,000
Table 3-9. Linear Module Resolution
Module
type
Encoder
resolution
(counts/rev)
Linear resolution
(counts/mm)
Linear resolution
(µm/count)
Screw Lead Screw Lead
5 mm 10 mm 20 mm 5 mm 10 mm 20 mm
L18/L12 65536 n/a 6553.6 3276.8 n/a 0.153 0.305
L08 131072 26214.4 13107.2 6553.6 0.0381 0.0763 0.153