Overview of the diagnosis
There are a number of reasons that can lead to the autotuning not starting, being cancelled or failing. In such a case, depending on the cause of failure, it can be possible to supply a parameter set. Every bit of the diagnostic word diag allows for a type of error to be created.
This word contains the current operating mode of the autotuning.
The following cases are explained:
This table contains the meaning of the diag elements of the data structure Info_AUTOTUNE
|
Bit
|
Meaning
|
|
Bit 0 = 1
|
Autotuning is running
|
|
Bit 1 = 1
|
Autotuning aborted
|
|
Bit 2 = 1
|
Parameter error
|
|
Bit 3 = 1
|
Alteration of parameters, which have just been set automatically
|
|
Bit 4 = 1
|
Stop as a consequence of system error
|
|
Bit 5 = 1
|
Process value saturated
|
|
Bit 6 = 1
|
Alteration too small
|
|
Bit 7 = 1
|
Sampling interval invalid
|
|
Bit 8 = 1
|
Incomprehensible reaction
|
|
Bit 9 = 1
|
Non-stabilized measuring at the start
|
|
Bit 10 = 1
|
Length of actuating pulse Stellimpulses (tmax) too short
|
|
Bit 1 1= 1
|
Too much noise/interference
|
|
Bit 12 = 1
|
Length of actuating pulse (tmax) too long
|
|
Bit 13 = 1
|
Process with significant exceeding of the thresholds
|
|
Bit 14 = 1
|
Process without minimum phase
|
|
Bit 15 = 1
|
Asymmetric process
|
|
Bit 16 = 1
|
Process with integral component
|
The following bits of the diagnostic word (diag element) show the status of the autotuning.
|
Bit
|
Meaning
|
|
|
1 = Autotuning running.
|
|
|
1 = Autotuning stopped
|
Bit 0 of the
diag element
This Bit indicates that the autotuning is running. On quitting autotuning or terminating using the START Bit, this is set to zero.
Bit 1 of the
diag element
This Bit indicates that the user stopped the last control using the START Bit or by setting the operating mode to Tracking.
The following bits of the diagnostic word (diag element ) indicate a faulty start.
|
Bit
|
Meaning
|
|
|
1 = Parameter error
|
|
|
1 = incorrect sampling interval
|
Bit 2 of the
diag element
The following causes can lead to a faulty start:
-
Length of actuating pulse too short (tmax < 4 s),
-
Amplitude too weak (step_ampl < 1% of the output range),
-
Cannot perform this protocol: if the output + n x the amplitude of the actuating pulse (where n = 1 for adjustment during a warm start and n = 2 for adjustment during a cold start) is outside the output range (out_inf, out_sup), then the test protocol cannot be used. The step_ampl value must be set to a value that is compatible with the current work point.
Bit 7 of the
diag element
If the sampling interval is too large in relation to the length of the actuating pulse (> tmax / 25), then the response test is too imprecise and autotuning will be blocked. This typically occurs during very rapid regular processes (where tmax is larger than the rise time of the process, a matter of a few seconds). In this case tmax can be increased, because the algorithm reacts only slightly to this parameter (in the ratio of 1 to 3), or alternatively, the sampling interval can be set to correspond.
