Derivative (FB)

FUNCTION_BLOCK Derivative

This function block will approximate the first derivative of a function at the actual time with the respect to the values of the last three function calls according to the BDF method:

InOut:

Scope Name Type Comment Input xEnable BOOL reset lrInputValue LREAL actual function value udiTM UDINT length of time interval (equals time passed since last call to function) Output lrDerivative LREAL approxmated value of first derivative xValid BOOL Validity of result FALSE: If the number of calls neccessary for approximating has not been executed yet.