Omron SYSMAC CS Series User Manual

192
Examples of Applied Control Types Section 5-2
PID1 of the primary loop indirectly controls the finite control element of the
secondary loop by controlling the setting value of PID2.
By this control, PID2 of the secondary loop absorbs the disturbance on the
secondary loop, and suppresses the influence of the disturbance on the sec-
ondary loop on the primary loop. (The effect on the disturbance on the sec-
ondary loop increases as the response of the secondary loop process
becomes faster than primary loop processes.)
Note This kind of cascade control has no effect on disturbance entering the primary
loop. Cascade control must be combined with feedforward control in this case.
Function blocks used: Two Advanced PID blocks (Block Model 012)
Example
MV output of one Advanced PID block is input to the Remote Set Point of the
other Advanced PID block.
Note In cascade control, when the secondary loop PID2 is set to Local, MV1 of the
primary loop PID1 must be tracked to changes on the Local Set Point setting
(LSP2) (matched to LSP2).
The Loop Controller is provided with a bumpless MV tracking function on the
primary and secondary sides during cascade processing in ITEM032 (bump-
less processing between primary/secondary loops) in the Basic PID block
(Block Model 011) and Advanced PID block (Block Model 012). The primary
side MV1 is overwritten with the Local Set Point of the local node when the
secondary side is local merely by setting 1 (bumpless processing ON) to
ITEM032 of the Basic PID or Advanced PID block on the secondary side.
Advanced PID
Block Model 012
PV1
Advanced PID
Block Model 012
MV1
PV2
RSP
MV2
PID1
Secondary
process
characteristics
+
−
PV1
Control
output
PID2
+
−
Primary
process
characteristics
Set PointMV1
PV2
MV2
Secondary loop
Primary loop
Disturbance
Set Point
SP1

Omron SYSMAC CS Series Specifications

General

Brand	Omron
Model	SYSMAC CS Series
Category	Controller
Language	English