Chapter 10 Built-in PID Functions
10 - 18
(16) _PIDn_ERR (PID ERRor value)
- Setting Prohibited
K DEVICE AREA : K1042+32n
Unit : DINT [ -2747483648 ~ 2747483647 ]
This is the current error value of the corresponding loop.
An error value in PID is defined as SV – PV. This is used as an indicator of how far the current state is from
the desired state. If the error is 0, it means the control system reaches its desired state. The control system
can be considered ideal if, when a control starts, the error rapidly decreases in the transient state and,
when it reaches the normal state, vibration is minimized and the offset(the error in the stable state) is kept
at 0.
(17) _PIDn_MV_p (PID MV Propotional component)
- Setting Prohibited
K DEVICE AREA : K1044+32n
Unit : REAL [ -3.4038 ~ -1.17549435e-38 , 0 , 1.17549435e-38 ~ 3.4038 ]
This displays the proportional control value of the corresponding loop. If the error of the current system is
known, its integral and derivative control output values can also be calculated independently. Comparing
the 3 output values enables to determine the exact operational state of the control system and PID control.
MV is the sum of MV_p, MV_i, and MV_d.
(18) _PIDn_MV_i (PID MV Integral component)
-
Setting
Prohibited
K DEVICE AREA : K1046+32n ~ K1047+32n
Unit : REAL [ -3.4038 ~ -1.17549435e-38 , 0 , 1.17549435e-38 ~ 3.4038 ]
This displays the integral control value of the corresponding loop.
(19) _PIDn_MV_d (PID MV Derivative component)
- Setting Prohibited
K DEVICE AREA : K1048+32n ~ K1049+32n
Unit : REAL [ -3.4038 ~ -1.17549435e-38 , 0 , 1.17549435e-38 ~ 3.4038 ]
This displays the derivative control value of the corresponding loop.
(20) _PIDn_DB_W (PID DeadBand Width)
- Setting Area
K DEVICE AREA : K1050+32n
Unit : WORD [ 0 ~ 65535 ]
This sets the deadband of the corresponding loop. The deadband is set to a positive value and operates in
the range from [SV – DB_W] ~ [SV + DB_W]. If PV enters the area, SV is assigned to the PV value. If this
value is set to 0, the corresponding function does not operate.
Note
Deadband
This is used to let PV fully approach SV during system control so as to eliminate fine output
viariations due to fine state changes. Input of a value to DB_W during PID control forms a
deadband from [SV – DB_W] ~ [SV + DB_W]. If PV follows SV into the deadband during control,
ERR is forcibly calculated as 0 and, as far as PV remains in this area, the MV variation stops. This
has the same effect as stopping the controller for a while in the stabilization area and helps
avoiding a heavy load on the driver during stabilization operation. It is recommended to fully
stabilize the system before use in the area to be set as the deadband. Otherwise, when entering
the deadband, the controller experiences a temporary output excess.
