Pid Control Block - rotork Mk3 Technical Manual

Foundation Fieldbus CP Option Card Technical Manual
Block Bit
DO 4 0
Mode 6: 1
2
3
4
5
6
7
Note: Ensure that parameters 65 (Control Mode) and 66 (Discrete Block Control) in the
Transducer block are set for the type of control and DO 4 mode required.
6.7

PID Control block

The actuator includes a standard three-term PID controller block for use in a control loop. The inputs
and outputs of this block are not directly linked to the actuator Transducer block. This allows the PID
controller to be used for controlling devices other than the actuator. With a PID function, as long as an
error exists between the set point (desired value) and the measured value feedback (process
variable), the controller will change the output in a direction to reduce the error.
The way in which the output changes is influenced by the actual error value, the time it is present and
the rate of change it undergoes. The PID settings applied integrate the error with respect to time
(RESET value), apply a proportional gain on the error (GAIN) and differentiate the rate of change in
the error (RATE); all these actions are combined to produce the OUTPUT.

PID
CAS_IN
SETPOINT
RCAS_IN
IN PV_TIME
Fig 6.11: PID Function block
The PID block must be connected and set up before it can be used. It is not pre-connected to any
input or output of the actuator transducer block and may be freely connected into a control loop. The
scheduler is used to allocate a time slot for the control algorithm to execute.
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Operation
Position control enable
Partial stroking
Close
Open
Stop
ESD
Set relay 1
Set relay 2
A stand-alone 3-term controller within the actuator.
BKCAL_OUT
RCAS_OUT
BYPASS
GAIN
SP
RESET
BAL_TIME
RATE
PV
Publication PUB089-005-00_0618
Read-back
Position control enabled
Partial stroking enabled
Close limit
Open limit
Actuator not moving
ESD
relay 1 set
relay 2 set
PID
BKCAL_IN
FF_VAL
ROUT_IN
FF_SCALE
FF_GAIN
TRK_IN_D
TRK_VAL
ROUT_OUT
OUTPUT
TRK_SCALE
OUT