Beckhoff TwinCAT 3 Manual page 19

bSelCtrlParameterSet:= FALSE,
(* tuninig *)
iTuningMode := eCTRL_TuneMode_heating,
fYTuneHeating := 100.0,
fYTuneCooling := -100.0,
fEndTunePercentHeating := 80.0, (* switch to closed loop control when X > 0.8*W *)
fEndTunePercentCooling := -70.0, (* switch to closed loop control when X < 0.2*W *)
iReactionOnFailure := eCTRL_ReactionOnFailure_StopController,
TempLow := -50.0,
TempLowLow := -100.0,
TempHigh := 100.0,
TempHighHigh := 155.0,
TempAbsoluteHigh := 150.0,
TempAbsoluteLow := -95.0,
bEnablePreController := FALSE,
bEnableZones := FALSE,
bEnableCVFilter := FALSE,
iFilterType := eCTRL_FilterType_AVERAGE,
iControllerType := eCTRL_ControllerType_PID
);
The marked parameters are optional, and only need to be initialised if they are needed.
Assignment in the code can look like the following in ST:
sControllerParameter.tPWMCycleTime :=
t#100ms;
• Specification of the controller sampling time, that task cycle time and the PWM cycle time
The controller's sampling time must be adapted to the particular process. It should be selected to be equal to
or less than one tenth of the loop's dominant time constants. The task cycle time is specified by the PLC task
from which the controller block has been called. This value can be read from the task configuration (PLC
Control: Resources Task Configuration). The PWM cycle time is usually equal to the controller cycle time. If
the task cycle time is 10ms and the PWM cycle time (=controller sampling time) is chosen to be 100ms, then
a total of 10 levels (PWM cycle time / task cycle time) are available.
• Parameterisation of TwinCAT Scope
To check the results, a scope examination should always be made of the tuning process and of the closed
loop regulation behaviour. To do this, TwinCAT Scope View should be started and parameterised. The
following channels should be recorded: set value (fW1 or fW2), actual value (fX) and the analog control value
(fYAnalog).
• Switching off the Alarms during the Commissioning Phase
The alarms can be temporarily switched off during the commissioning phase. An appropriate bit mask must
be written into the dwAlarmSupp data word. If a bit is set in this data word, the corresponding alarm is
disabled. The assignment of the individual alarms is described here [} 33].
Warning: All the required alarms should be switched on again after the initial commissioning!
• Starting the Controller with Tuning
If the controller parameters are to be determined with the aid of the Tuning system, the bOn and bTune
inputs must both be TRUE. A fixed waiting period of 20s first elapses. During this waiting period the
temperature is monitored to ensure that it remains within a +-1°C band. If the temperature goes outside this
band, the waiting starts again. The process is then subjected to a step excitation with a magnitude of
fYTune. The process then reacts with the step response. As long as 80% of the set value is not reached, the
process parameters are determined using the inflectional tangent method. For safety reasons, after 80% of
the set value has been reached, control is switched over to closed loop control. If the temperature reaches
the 80% mark too quickly (with no clear inflection) then the value of fYTune is to be reduced. The parameters
determined in this way are used for the PID controller, and are provided in a structure at the output of the
controller.
TC3 Temperature Controller Version: 1.1
Configuration
19