Danfoss MCO 305, Design Manual, Page: 142 / 242

MCO 305 Design Guide
__ Software Reference __
142
MG.33.L4.02 – VLT
®
is a registered Danfoss trademark
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PID
Summary Calculates PID filter.
Syntax u(n) = PID e(n)
Parameter e(n) = actual deviation (error) for which the PID filter should be used
Return Value u(n) = result of the PID calculation
Description A PID filter can be calculated with this function. The PID filter works according to
the following formula:
u(n) = ( KP * e(n) + KD *(e(n)-e(n–1)) + KI* ¦ e(n) ) / timer
where the following is true:
e(n) error occurring at time n
KP proportional factor of the PID
control
KD Derivative Value
KI Integral Factor (limited by
Integration Limit)
timer controller sample time
KDER
+
+
+
KPROP
KINT
KILIM
u(n) e(n)
The corresponding factors can be set with the following commands:
SET PID KPROP 1 /* set KP 1 */
SET PID KDER 1 /* set KD 1 */
SET PID KINT 0 /* set KI 0 */
SET PID KILIM 0 /* Integration limit 0 */
SET PID TIMER 1 /* Sample time = 1 */
The following syntax example also show the default allocation of the factors.
Command Group I/O
Syntax Example e = INAD 53
u = PID e
PRINT "input = ",e, "output = ",u
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POSA
Summary Positioning in relation to actual zero point.
Syntax POSA p
Parameter p = Position in user units (UU) absolute to the actual zero point; the UU
corresponds in the standard setting the number of quadcounts.
Description The axis can be moved to a position absolute to the actual zero position.
When the POSA command exceeds the Negative or Positive Software End Limit (para-
meters 33-41 or 33-42) the program continue with the next command after an error.
NB!:
If a temporary zero point, set via SET ORIGIN, exists and is active, then the
position result refers to this zero point.
NB!:
If an acceleration and/or velocity have not been defined at the time of the POSA
command, then the procedure will take place with the values of parameters 32-84
Default Velocity and 32-85 Default Acceleration .
Command Group ABS
Cross Index VEL, ACC, POSR, HOME, DEF ORIGIN, SET ORIGIN,
Parameters: 32-12 User Unit Numerato r, 32-11 User Unit Denominator
Syntax Example POSA 50000 /* move axis to position 50000 */
Program Sample POS_01.M