Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Setting Up the Servo Loop
187
Entering 1D Tables
If the position compensation table to be entered has both the source and target motors equivalent to the
addressed (assigned) motor, and the table uses the actual position of this motor to calculate the
corrections, then there is no need to specify the motors in the DEFINE COMP command. The command
would look something like:
addressed (assigned) motor, and the table uses the actual position of this motor to calculate the
corrections, then there is no need to specify the motors in the DEFINE COMP command. The command
would look something like:
#2 DEFINE COMP 25, 500000
This command establishes a table using Motor 2 as both the source and target motor, using the actual
position to compute the corrections. The next 25 numerical constants sent to Turbo PMAC would be
entered into the table. The first value would be the correction at 500,000/25 = 20,000 counts. (20,000
here represents the uncorrected position.) The second value would be the correction at 40,000
uncorrected counts, and so on. The 25
position to compute the corrections. The next 25 numerical constants sent to Turbo PMAC would be
entered into the table. The first value would be the correction at 500,000/25 = 20,000 counts. (20,000
here represents the uncorrected position.) The second value would be the correction at 40,000
uncorrected counts, and so on. The 25
th
entry would be the correction at 500,000 counts; if I30 were set
to 1 at the time of entry, this would be the correction at 0 counts as well. The units of the correction itself
are 1/16 count.
are 1/16 count.
If you desire that either the source or target motors be different from the addressed motor, or you wish to
make the table a function of the source motor’s desired position, you must explicitly declare the motors in
the DEFINE COMP command. In this case, the command would look something like:
make the table a function of the source motor’s desired position, you must explicitly declare the motors in
the DEFINE COMP command. In this case, the command would look something like:
#1 DEFINE COMP 25, #2D, #2, 500000
This command establishes a table using Motor 2 both as the source, working from its net desired position,
and as the target to which the corrections are applied, even though the table is assigned to Motor 1. As in
the above case, the next 25 numerical constants would be entered into the table, with the first value being
the entry at 20,000 counts the second at 40,000 counts, and so on.
and as the target to which the corrections are applied, even though the table is assigned to Motor 1. As in
the above case, the next 25 numerical constants would be entered into the table, with the first value being
the entry at 20,000 counts the second at 40,000 counts, and so on.
1D Table Example
Below is a simple example of the entry of a 1D table
Below is a simple example of the entry of a 1D table
#1
DEFINE COMP 8,4000
; Table of 8 entries over 4000 cts belonging to
; motor 1 ; Uses motor 1 for source (actual pos)
;
& target because no other motors specified
-160
; Correction at 4000/8 (500) cts is -160/16 = -10 cts
80
; Correction at 1000 counts is 5 counts
120
; Correction at 1500 counts is 7.5 counts
96
; Correction at 2000 counts is 6 counts
20
; Correction at 2500 counts is 1.25 counts
-56
; Correction at 3000 counts is -4.5 counts
-12
; Correction at 3500 counts is -0.75 cts
0
; Correction at 4000 (and 0) cts is zero
In this example, the correction at a raw position of 1300 counts would be linearly interpolated between
the corrections at 1000 counts and 1500 counts, as follows:
the corrections at 1000 counts and 1500 counts, as follows:
counts
5
.
6
500
1000
1300
*
)
5
5
.
7
(
5
Correction
+
=
−
−
+
=
Entering 2D Tables
If the position-compensation table has two source motors, establishing a 2D, or planar table, the entry is a
little more complex. Declare the length of the table (in number of entries) in both dimensions, and the
span of the table in both dimensions. Declare both source motors, and usually the target motor (although
the default is the addressed motor). The command that establishes the table will look something like:
little more complex. Declare the length of the table (in number of entries) in both dimensions, and the
span of the table in both dimensions. Declare both source motors, and usually the target motor (although
the default is the addressed motor). The command that establishes the table will look something like:
#2 DEFINE COMP 15.20, #1D, #2D, #3, 20000, 15000
This command specifies that the table assigned to Motor 2 will have 15 rows and 20 columns. Therefore,
each row has 20 entries, and each column has 15 entries.
each row has 20 entries, and each column has 15 entries.