DMC-18x6 Command Reference
157
PL
FUNCTION: Pole
DESCRIPTION:
The PL command adds a low-pass filter in series with the PID compensation. The digital transfer
function of the filter is (1 - n) / (Z - n) and the equivalent continuous filter is A/(S+A) where
A is the filter cutoff frequency: A=(1/T) ln (1 / n) rad/sec and T is the sample time.
To convert from the desired crossover (-3 dB) frequency in Hertz to the value given to PL, use the
following formula:
2
·
·
-
=
c
f
T
e
n
where:
n is the argument given to PL
T is the controller's servo loop sample time in seconds (TM divided by 1,000,000)
f
c
is the crossover frequency in Hertz
Example: f
c
=36Hz TM=1000
n=e
-0.001·36·2
=0.8
n
0 0.2 0.4 0.6 0.8 0.999
F
c
(HZ)
(off)
256 145 81 36 0
ARGUMENTS: PL n,n,n,n,n,n,n,n or
PLA=n where
n is a positive number in the range 0 to 0.9999.
n = ? Returns the value of the pole filter for the specified axis.
USAGE:
DEFAULTS:
While Moving
Yes
Default Value
0.0
In a Program
Yes
Default Format
1.4
Not in a Program
Yes
Controller Usage
ALL CONTROLLERS
OPERAND USAGE:
_PLn contains the value of the pole filter for the specified axis.
RELATED COMMANDS:
Derivative
Proportional
Integral Gain
EXAMPLES:
PL .95,.9,.8,.822
Set A-axis Pole to 0.95, B-axis to 0.9, C-axis to 0.8, D-axis pole to
0.822
PL ?,?,?,?
0.9527,0.8997,0.7994,0.8244
Return all Poles
PL?
0.9527
Return A Pole only
PL,?
0.8997
Return B Pole only
