Yokogawa RotaMASS 3-Series - Manual (Page 151)

APPENdIX 5. PId BLOCK
a-51
IM 01R04B05-00E-E 3rd edition July 30, 2010 -00 all Rights Reserved. Copyright © 2005, Rota Yokogawa
A5.7 Control Action By-
pass
the PID control computation can be bypassed
so as to set the SP value in the control output
out as shown below. Setting BYPaSS to “on”
bypasses the PID control computation.
Setpoint
Control
Feed-
forward
CaS_In
Filter In PV
BYPaSS
SP
RCaS_In
output out
Fa0502.EPS
A5.8 Feed-forward
Feed-forward is an action to add a compensa-
tion input signal FF_VaL to the output of the PID
control computation, and is typically used for feed-
forward control. the following figure illustrates the
action.
PID
computation
FF_SCaLE
out_SCaLE
PV out
FF_VaL
FF_GaIn
Fa0503.EPS
A5.9 Block Modes
the block mode is set in the parameter MoDE_
BLK.
Stipulates the target mode to which the
PID block transfers.
Indicates the current mode of the PID
block.
Stipulates all the modes that the PID
block can enter. the PID block is
prohibited to enter any mode other than
those set in this element.
Stipulates the mode in which the PID
block normally resides.
MoDE_
BLK target
actual
Permitted
normal
ta0505.EPS
there are eight modes for a PID block as shown
below.
Block
Mode
Description
Remote output mode, in which the PID block outputs
the value set in Rout_In.
Remote cascade mode, in which the PID block
carries out the PID control computation based on the
setpoint (SP) set via the remote cascade connection,
such as from a computer, and outputs the computed
result.
Cascade mode, in which the PID block carries out the
PID control computation based on the setpoint (SP)
set from another fieldbus function block, and outputs
the computed result.
the PID block carries out automatic control and
outputs the result computed by the PID control
computation.
Manual mode, in which the PID block outputs the
value set by the user manually.
the PID block outputs the value set in tRK_VaL.
Initialization and manual mode, in which the control
action is suspended. the PID block enters this mode
when the specified condition is met
(see Section a5.14).
out of service mode, in which neither the control
computation nor action is carried out, and the output
is kept at the value that was output before the PID
block entered into o/S mode.
Rout
RCas
Cas
auto
Man
Lo
IMan
o/S
ta0506.EPS