Rockwell Automation 1760-xxxx Pico GFX-70 Controllers User Manual - Manual (Page 209)

Publication 1760-UM002B-EN-P - March 2005
Wiring with Pico GFX-70 4-99
• DC01ED to DC32ED:Activate the differential component;
• DC01SE to DC32SE:Activate the manual manipulated variable
Memory Requirement of the PID Controller
The PID controller function block requires 96 bytes of memory plus 4 bytes
per constant on the function block input.
Function of the PID Controller Function Block
The PID controller works on the basis of the PID algorithm. According to
this, the manipulated variable Y(t) is the result of the calculation of the
proportional component, an integral component and a differential
component.
Equation of PID controller:
Y(t) = Y
P
(t) + Y
I
(t) + Y
D
(t)
Y(t) = calculated manipulated variable with scan time t
Y
P
(t) = Value of the proportional component of the manipulated variable with scan time t
Y
I
(t) = Value of the integral component of the manipulated variable with scan time t
Y
D
(t) = Value of the differential component of the manipulated variable with scan time t
IMPORTANT
The PID controller must be enabled so that it can work.
Coil DC..EN is active. If coil DC..EN is not active, the
entire PID controller is deactivated and reset. The
manipulated variable is set to zero.
The corresponding coils for the P, I and D components
must be active.
Example: If only coils DC..EP and DC..EI are activated,
the controller operates as a PI controller.
IMPORTANT
The device calculates the manipulated variable every time
the scan time T
c
has elapsed. If the scan time is zero, the
manipulated variable is calculated every cycle.