7 APPLICATION INSTRUCTIONS
7.18 PID Instruction
733
7
Parameters
This section explains the parameters of the PID operation instruction (PID).
Sampling time (T
S
): (S3)
Setting range: 1 to 32767ms
Set the cycle (ms) for PID operation.
• PID control or auto tuning (limit cycle method)
"Operation cycle of programmable controller"<"sampling time"
• Auto tuning (step response method)
1000ms (1s) or more
■Maximum error
The maximum error of the sampling time (T
S
) ranges from -(1 operation cycle + 1ms) to + (1 operation cycle).
• When the sampling time (T
S
) is a small value
The variations of the above maximum error may become a problem. Execute the instruction in constant scan mode or
program it in the timer interrupt routine.
• When the sampling time is shorter than one operation cycle of programmable controller
A PID operation error (9106H) occurs but PID operation is executed assuming sampling time (T
S
) = operation cycle. In this
case, use the PID operation instruction in the timer interrupt, and clear (S3)+7 immediately before execution of the PID
operation instruction.
(1) Execute (S3)+7 (clear the internal processing register with the pulse conversion command during initial execution of the interrupt routine).
(2) Execute the PID operation.
MOVP
K0 D107
PID
D0
D1 D100
D150
X0
• • • (1)
• • • (2)
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