Manual

8/16 CC1B-Hints-en Preliminary 04.02.2003 HVAC Products
2. Hints
2.7 Auto-tune (self-setting function)
RWF40 user manual section 6.2.4 and 9.1
The RW F40 User manual refers to a ‘self-setting-function’
that for the purposes of this manual will be refered to as ‘Auto-tune’.
Technical Explanation
Auto-tune is a self-setting software function,
that is integrated into the RWF40 controller,
and can be repeated as often as desired.
Auto-tune tests the reaction, in the modulating mode of operation,
of the process-control loop, to steps in the actuator position,
according to a special procedure.
The data, during the forced oscillations, is then recorded, and used to
calculate new values, that are optimized for your specific controlled
system.
Auto-tune items summary:
Values for Pb.1, dt, rt and dF1, can always be changed.
Auto-tune uses two different methods to force oscillations,
and will automatically select and use
, a method, based on,
at the start of Auto-tune, what the difference is,
between the setpoint (w), and the process value.
When Auto-tune is started with a large difference,
(typically before the process-control loop has stabilized)
Auto-tune performs a forced oscillation around a switching level.
When Auto-tune is started with a small difference,
(typically after the process-control loop has stabilized)
Auto-tune performs a forced oscillation, around the setpoint (w).
If for any reason the controller exceeds the switch off threshold (HYS3)
Auto-tune will be cancelled.
Conditions
The controller must be :
- in the modulating output mode (D1 is open and the step icon
is off)
- burner is released (green LED above
is on, relay 1, is activated,
contact between terminals Q14 and Q13 is closed)
- controller is not
in manual mode (red LED above is off)
Procedure
Start Auto-tune by pressing
and release.
The current temperature value, (175)
is shown in the actual value display.
The current function item (tunE)
is flashing in the setpoint display.
You can cancel Auto-tune while it is flashing
pressing
and releasing.
When tunE stops flashing on it’s own
Auto-tune is complete.
You can save the new values for Pb.1, dt, rt and dF1,
by pressing
, and holding for at least 2 seconds.
Possible results,and their correction. A favorable value for dt is rt/4.
Block diagram of Auto-tune.
Items at the user level that will affect Auto tune
SP 1 Set Point 1
HYS1 Switch-on threshold, HYSteresis 1
HYS3 Switch-off threshold, HYSteresis 3,
Items at the Parameter level that Auto-tune will adjust
Pb.1 Proportional band 1 (Factory setting 10)
dt derivative time (Factory setting 80)
rt Integral action time (Factory setting 350)
Item at the configuration level that Auto-tune will adjust
dF1 Time constant for digital Filter, analog 1