Yokogawa Electric Corporation - TC10 - ENGINEERING MANUAL - PAG. 16
[57] Auto - Auto tune selection
There are three auto-tune algorithms:
•
Oscillating auto-tune;
•
Fast auto-tune;
•
EvoTune.
1.
The
oscillating
auto-tune is the usual auto-tune and:
•
It is more accurate;
•
Can start even if PV is close to the set point;
•
Can be used even if the set point is close to the
ambient temperature.
2.
The
fast type
is suitable when:
•
The process is very slow and you want to be opera-
tive in a short time;
•
When an overshoot is not acceptable;
•
In multi loop machinery where the fast method reduces
the calculation error due to the effect of the other loops.
3.
The
EvoTune
type is suitable when:
•
You have no information about your process;
•
You can not be sure about the end user skills;
•
You desire an auto tune calculation independently
from the starting conditions (e.g. set point change
during tune execution, etc).
Note:
Fast auto-tune can start only when the measured
value (PV) is lower than (SP + 1/2 SP).
Available:
When [56] cont = PID
Range:
-4 to 8 where:
-4 =
Oscillating auto-tune with automatic restart
at all set point change;
-3 =
Oscillating auto-tune with manual start;
-2 =
Oscillating auto-tune with automatic start at
the first power up only;
-1 =
Oscillating auto-tune with automatic restart
at every power up;
0 =
Not used;
1 =
Fast auto tuning with automatic restart at
every power up;
2 =
Fast auto-tune with automatic start at the
first power up only;
3 =
FAST auto-tune with manual start;
4 =
FAST auto-tune with automatic restart at all
set point change.
5 =
EvoTune with automatic restart at every
power up;
6 =
EvoTune with automatic start at the first
power up only;
7 =
EvoTune with manual start;
8 =
EvoTune with automatic restart at all set
point change.
[58] Aut.r - Manual start of the auto-tune
Available:
When [56] cont = PID.
Range:
oFF = The instrument is not performing the auto-tune;
on =
The instrument is performing the auto-tune.
[59] SELF - Self-tune enable
The self-tuning is an adaptive algorithm able to optimize
continuously the PID parameter value.
This algorithm is specifically designed for all process subjected to
big load variation able to change heavily the process response.
Available:
When [56] cont = PID .
Range:
YES = self-tune active;
no =
self-tune not active.
[60] HSEt - Hysteresis of the ON/OFF control
Available:
When [56] cont is different from PID.
Range:
0 to 9999 engineering units.
[61] cPdt - Time for compressor protection
Available:
When [56] cont = nr.
Range:
OFF = Protection disabled
1 to 9999
seconds.
[62] Pb - Proportional band
Available:
When [56] cont = PID and [59] SELF = no.
Range:
1 to 9999 engineering units.
Note:
Auto-tune functions calculate this value.
[63] ti - Integral time
Available:
When [56] cont = PID and [59] SELF = no.
Range: •
OFF = Integral action excluded;
•
1 to 9999 seconds;
•
inF= Integral action excluded.
Note:
Auto-tune functions calculate this value.
[64] td - Derivative time
Available:
When [56] cont = PID and [59] SELF = no.
Range: •
oFF - derivative action excluded;
•
1 to 9999 seconds.
Note:
Auto-tune functions calculate this value.
[65] Fuoc - Fuzzy overshoot control
This parameter reduces the overshoot usually present at
instrument start up or after a set point change and it will be
active only in this two cases.
Setting a value between 0.00 and 1.00 it is possible to slow
down the instrument action during set point approach.
Setting
Fuoc = 1
this function is disabled.
PV
SP
time
2
1
3
Available:
When [56] cont = PID and [59] SELF = no.
Range:
0 to 2.00.
Note:
Fast auto-tune calculates the Fuoc parameter while
the oscillating one sets it equal to 0.5.
[66] tcH - Cycle time of the heating output
Available:
When at least one output is programmed in order
to be the heating output (H.rEG),
[56] cont = PID and [59] SELF = no.
Range:
1.0 to 130.0 seconds.
[67] rcG - Power ratio between heating and
cooling action (relative cooling gain)
The instrument uses the same PID parameter set for heat
and for cool action but the efficiency of the two actions are
usually different.
This parameter allows to define the ratio between the efficiency
of the heating system and the efficiency of the cooling one.
An example will help us to explain you the philosophy.
Consider one loop of a plastic extruder. The working
temperature is equal to 250°C.
When you want to increase the temperature from 250 to 270°C
(
D
T = 20°C) using 100% of the heating power (resistor), you
will need 60 seconds.
