Beckett RWF40 Hints Manual - Manual (Page 10)

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 RWF40 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 S et P oint 1
HYS1 Switch-on threshold, HYS teresis 1
HYS3 Switch-off threshold, HYS teresis 3 ,
Items at the Parameter level that Auto-tune will adjust
Pb.1 P roportional b and 1 (Factory setting 10)
dt d erivative t ime (Factory setting 80)
rt Integ r al action t ime (Factory setting 350)
Item at the configuration level that Auto-tune will adjust
dF1 Time constant for d igital F ilter, analog 1