Mitsubishi Electric MELSEC iQ-R Series - Page 1156

1154
10 PID CONTROL INSTRUCTIONS
10.1 Overview
■Sampling period
Sampling period is a cycle in which PID operation is performed. The measurement time of a single scan is added to the total
measurement time up to the last scan every time the PIDCONT instruction is executed. The total measurement time reaches
or exceeds the set sampling period, PID operation of the corresponding loop is performed.
Set the sampling period used in PID operation in increments of 10ms.
Ex.
When the sampling period is 50ms
PV: Measured value
SV: Set value
Since the sampling period is measured at execution of the PIDCONT instruction, a value smaller than the
program scan time cannot be set as the sampling period. If set, PID operation is performed with a scan time.
19ms 19ms 19ms 19ms 19ms19ms 19ms
0
END
0
END
0
END
0
END
0
END
0
END
0
END
0
END
0ms 19ms
19+19=38ms 4+19=23ms26+19=45ms7+19=26ms38+19=57ms 45+19=64ms
PIDCONT
PIDINIT
PIDCONT PIDCONT PIDCONT PIDCONT PIDCONT PIDCONT PIDCONT
PV
PV<SV PV<SV PV<SV
PV<SV
PV<SV
PV<SV
PV>SV
PV>SV
Powering on the CPU module
Program
PID operation is performed
with the initial value.
PID operation is performed
with a sampling cycle of 50ms.
The measured value is
changed to 57-50=7ms.
PID operation is performed
with a sampling cycle of 60ms.
The measured value is
changed to 64-60=4ms.