Yokogawa RotaMASS 3-Series - Manual (Page 154)

APPENdIX 5. PId BLOCK
a-54 IM 01R04B05-00E-E 3rd edition July 30, 2010 -00 all Rights Reserved. Copyright © 2005, Rota Yokogawa
A5.15 Manual Fallback
Manual fallback denotes an action in which a PID
block changes mode to Man (manual) and sus-
pends the control action. Manual fallback takes
place automatically as a means of abnormality
handling when the following condition is met:
• In.status is Bad except when the control action
bypass is on.
to enable the manual fallback action to take
place when the above condition is met, target to
Manual if BaD In must be specified beforehand in
StatuS_oPtS.
the table below shows the options in StatuS_
oPtS.
A5.15.1 STATUS_OPTS
options in
StatuS_oPtS
Description
Sets the sub-status component of
out.status to IFS if In.status is Bad
except when PID control bypass is on.
Sets the sub-status component of
out.status to IFS if CaS_In.status is
Bad.
Does not regard In as being in Bad
status when In.status is uncertain (to
prevent mode transitions from being
affected when it is uncertain).
automatically changes the value of
MoDE_BLK.target to Man when In falls
into Bad status.
automatically changes the value of
MoDE_BLK.target to auto (or to Man
if auto is not set in Permitted) when
CaS_In falls into Bad status.
IFS if BaD In
IFS if BaD CaS In
use uncertain
as Good
target to Manual
if BaD In
target to next
permitted mode
if BaD CaS In
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A5.16 Auto Fallback
auto fallback denotes an action in which a PID
block changes mode from CaS (cascade) to
auto (automatic) and continues automatic PID
control with the user-set setpoint. auto fallback
takes place automatically when the following con-
dition is met:
• In.status (data status of In) is Bad except
when the control action bypass is on.
to enable the manual fallback action to take place
when the above condition is met:
• target to next permitted mode if BaD CaS
In must be previously specified in StatuS_
oPtS.
- anD -
• auto must be previously set in MoDE_BLK.
permitted.
A5.17 Mode Shedding
upon Computer Fai-
lure
When the data status of RCaS_In or Rout_In,
which is the setting received from a computer as
the setpoint SP, falls to Bad while the PID block is
running in the RCaS (remote cascade) or Rout
(remote output) mode, the mode shedding occurs
in accordance with the settings in SHED_oPt.
A5.17.1 SHEd_OPT
the SHED_oPt setting stipulates the specifica-
tions of mode shedding as shown below. only
one can be set.
available Setting
for SHED_oPt
actions upon Computer Failure
Sets MoDE_BLK.actual to Cas*,
and leaves MoDE_BLK.target unchanged.
Sets both MoDE_BLK.actual and
MoDE_BLK.target to Cas*.
Sets MoDE_BLK.actual to auto**, and
leaves MoDE_BLK.target unchanged.
Sets both MoDE_BLK.actual and
MoDE_BLK.target to auto**.
Sets MoDE_BLK.actual to Man, and
leaves MoDE_BLK.target unchanged.
Sets both MoDE_BLK.actual and
MoDE_BLK.target to Man.
If Cas is in MoDE_BLK.target, sets
MoDE_BLK.actual to Cas*, and leaves
MoDE_BLK.target unchanged.
If Cas is not set in MoDE_BLK.target,
sets MoDE_BLK.actual to auto**, and
leaves MoDE_BLK.target unchanged.
If Cas is set in MoDE_BLK.target, sets
both MoDE_BLK.actual and
MoDE_BLK.target to Cas*.
If Cas is not set in MoDE_BLK.target,
sets MoDE_BLK.actual to auto**, and
MoDE_BLK.target to Cas.
normal shed,
normal return
normal shed,
no return
Shed to auto,
normal return
Shed to auto,
no return
Shed to Manual,
normal return
Shed to Manual,
no return
Shed to retained
target, normal
return
Shed to retained
target, no return
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