ABB AC 800M, Руководство по стилю объекта библиотеки, Страница: 102 / 120

Power Failure Behavior Section 6 Program Code Issues
102 3BSE042835-600
into consideration, when constructing the code of a control module or Function
Block.
Three alternatives exist:
1. Accept the error code and return failure back to the caller.
2. Ignore the -15 error code and return success back to the caller.
3. Retry the asynchronous procedure when error code is -15 until success or
another error emerges.
Which one of the alternatives to choose depends on the application. Often the only
solution is to pass on the problem to the user in terms of an extra module parameter.
In this case, an integer in the parameter ErrorHandling should be introduced with
the above possibilities and a default value of 1.
Power Failure Behavior
Outputs shall be ramped when the application is restarted after a power failure and if
an OSP value has been used.
State algorithms and bumpless parameters changes
Some parameter changes in algorithms that hold a state might cause a “bump” in the
output if the update of parameters are not done with care. An example is change of
filter time or gain for a filter algorithm. To avoid such bumps, the following method
should be used.
The parameter values from the last scan is stored and used for the calculation for the
new state. The output is computed and the last thing that is done is that the state is
adjusted to the value that would have given the same output with the new
parameters. The pseudo code below exemplifies the method:
NewState := UpdateState(OldState, In, SampleTime,
OldParameters);
Out := CalculateOut(NewState);
OldState := UpdateStateInverse(Out, In, SampleTime,
NewParameters);
OldParameters := NewParameters