Chapter 10 Built-in PID Functions
10 - 13
(8) _PIDn_AT_EN (PID Auto-Tuning ENable)
- Setting Area
K DEVICE AREA : m
Unit : Bit
This performs AT (Auto-tuning) of the corresponding PID loop. The approximate T_s (operation cycle) and
PID coefficients (K_p, T_i, T_d) of the systemare are determined through AT. Do not forget to set the
PIDn_HYS_val item before starting AT. The AT function is described in detail in 10.6.
If the corresponding bit is Off, the [Default] AT function is Disabled and AT is performed in the rising edge.
(9) _PIDn_MV_BMPL (PID MV BuMPLess changeover)
- Setting Area
K DEVICE AREA : m
Unit : Bit
This allows to not only determine an appropriate MV value through operation so that MV can continue
smoothly when the corresponding PID loop changes from manual to auto output mode, but also reflect the
MV value to the internal state so as to stabilize MV. This function shows an algorithm difference between
single operation and cascade operation, but both operations are performed by this bit.
If the corresponding bit (in cascade operation, the corresponding bit of the master loop) is On, Bumpless
changeover is performed. If it is Off, The [Default] Bumpless changeover function is Disabled.
Note
_PIDn_AT_EN
This bit is initialized as Off when the PLC changes to Run mode. If the PLC is stopped and
restarted with this bit On (eg. power outage), the system is initialized at the first scan but does
not enter into AT mode again. Since there is no change in the PID settings, the system
operates in the state before the PLC stops.
_PIDn_MV_BMPL
Assuming that the manual output value is 1000 and the auto output of 2000 is required, the
driver receives the value of 1000 for system operation and instantly receives 2000 at the time
of mode conversion. If the corresponding bit is On, the corresponding PID loop outputs 1000 at
the time of mode conversion and performs an operation in order that the output gradually
increases to 2000.
