Danaher Motion
06/2005
Compensation Tables
M-SS-005-03 Rev
E
137
7.
COMPENSATION TABLES
Groups allow you to control multiple axes as a single mechanism. With
groups, the position command and feedback signals are no longer single
values, but instead, are vectors with two or three elements. Velocity and
acceleration no longer apply to a motor, but instead, apply to the combination
of two or three motors moving in concert.
Some applications require high accuracy in position, so compensate for
mechanical inaccuracies in the system is required. The MC allows you to
define a table of corrections for one or more axes. This table defines a
correction to the positioned command given to the axes, depending on its
location or other axes’ locations. This correction is achieved every SERCOS
cycle. The compensation table is usually created by high accuracy tools and
is then used by the MC to correct small inaccuracies. The correction can also
take affect when the target axis is part of a group.
7.1.1. Specification
The compensation table is constructed from
N
axes, for which compensation
is defined. The number of rows in the table will be k1*k2*….*k
n
, where k1
through k
n
are the number of correction points defined for the axes A1
through A
n,
respectively. The “source” positions (in source axis position
units) must be equally spaced and monotonously increasing, while the
“compensations” (in target user position units) are the corrections added to
the “target” axes.
A compensation table 3 axes source on 3 axes target is shown below.
The Header
3 10 2
“Source” axis location
“Target” axis compensation
1 3.1 4.5
0 0.5 0.9
2 3.1 4.5
0.9 0.51 0.2
------------------------------ ----------------------------------
6 3.1 4.5
2.0 0.5 0.9
1 3.2 4.5
0 0.1 0.9
2 3.2 4.5
0.65 0.01 0.9
------------------------------ ----------------------------------
6 3.2 4.5
3.0 0.22 0.9
------------------------------ ----------------------------------
6 4 4.5
2.0 0.2 0.9
1 3.1 5.0
0 0.1 0.87
------------------------------ ----------------------------------
6 4 5.0
1 1 1.2
The value in the table is locked and calculated according to the source axis'
PCMD
and is linearly transformed. The “source” axes determine the
correction value, depending on location. The “target” axes are corrected.
The table has a “header” which consists of the number of axes in the table
followed by the number of compensation points defined for each axis. The
table can be created the MC using
TARGETDATA
,
SOURCEDATA
, and
CREATECOMP
,
or can be loaded from a binary file with a .CMP extension.
The correction takes affect when ALL the “source” axis position feedbacks
reach the first (i.e., the minimal) value in the table. The target axes are added
and the value calculated in the table to its current
PCMD
and
PFB
.