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It allows to set the value of PID output, automatically rating the single
percentages of proportional and integral action. Changing from manual to
automatical operation, PID output will assume the value entered in manual
function and it will start control action.
Consequently the function must be used only in manual control, to keep
PID output in line with value of manual control.
This function automatically cancels derivative action.
If the function is used with process value outside proportional band, integral
action will be set to 0.
2.2.24 Functions StartPOSPID and POSPID
Functions StartPOSPID and POSPID are conceived to assure a simple and
quick positioning by reading encoder 1 and by motor control with a tension
+/- 10V generated as differential by outputs AQ1and AQ2. Positioning is
achieved with PID algorithm, adding also action “F” , which is due to theoric
speed of axis motion.
Function StartPOSPID activates control action, setting the parameters as
required. The function can be activated once at starting but it may also be
recalled later for a quick change to control parameters. Integral action of
PID is initialized only starting this function and setting integral time to 0.
Otherwise , even in case of switch-off, the system will start regulation
keeping as reference the same percentage of integral action, therefore
limiting the time of transient.
Parameters required for function StartPOSPID are the following:
• Proportional band
• Integral time
• Derivative time
• Dead band
Parameters can be entered with numeric format or even referring to internal
variables. Integral time is expressed with time unit used to recall function
POSPID (ex. function POSPID recalled every 1 ms >> Integral time
expressed as milliseconds). Derivative time is expressed with one decimal
point more than integral time. Proportional band and dead band are
expressed as counts, since they refer to encoder 1.
Parameters required for function POSPID are the following
• Setpoint (counts)
• Value of action F (+/- 10000)
• Output limits (0…10000)
Function POSPID, after getting setpoint value expressed as counts, value
of action “F” and limit of output, will rate value of analogic outputs AQ1 and
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