Owner's manual

9-7
Proportional/Integral/Derivative (PID) Function Block
Bumpless Transfer and
Setpoint Tracking
You can configure the method for tracking the setpoint by configuring
the following control options (CONTROL_OPTS):
SP-PV Track in Man — Permits the SP to track the PV when the
target mode of the block is Man.
SP-PV Track in LO or IMan — Permits the SP to track the PV when
the actual mode of the block is Local Override (LO) or Initialization
Manual (IMan).
When one of these options is set, the SP value is set to the PV value
while in the specified mode.
You can select the value that a master controller uses for tracking by
configuring the Use PV for BKCAL_OUT control option. The
BKCAL_OUT value tracks the PV value. BKCAL_IN on a master
controller connected to BKCAL_OUT on the PID block in an open
cascade strategy forces its OUT to match BKCAL_IN, thus tracking the
PV from the slave PID block into its cascade input connection
(CAS_IN). If the Use PV for BKCAL_OUT option is not selected, the
working setpoint (SP_WRK) is used for BKCAL_OUT.
You can set control options in Manual or OutofService mode only.
When the mode is set to Auto, the SP will remain at the last value (it
will no longer follow the PV.
PID Equation Structures Configure the STRUCTURE parameter to select the PID equation
structure. You can select one of the following choices:
• PI Action on Error, D Action on PV
• PID Action on Error
• I Action on Error, PD Action on PV
Set RESET to zero to configure the PID block to perform integral only
control regardless of the STRUCTURE parameter selection. When
RESET equals zero, the equation reduces to an integrator equation
with a gain value applied to the error:
Reverse and Direct Action To configure the block output action, enable the Direct Acting control
option. This option defines the relationship between a change in PV and
the corresponding change in output. With Direct Acting enabled (True),
an increase in PV results in an increase in the output.
You can set control options in Manual or OutofService mode only.
NOTE
Track Enable, Track in Manual, SP-PV Track in Man, SP-PV Track in LO
or IMan, Use PV for BKCAL_OUT, and Direct Acting are the only
control options supported by the PID function block. Unsupported
options are not grayed out; they appear on the screen in the same
manner as supported options.
GAIN e s()×
s
-------------------------------
Where
GAIN: proportional gain value
e: error
s: laplace operator