MATH.Derivative (FB)

(CAA_Mathematics.library)

This function will approximate the first derivative (gradient) of a functionat the actual time with respect to the values of the last three function calls according to the BDF method:

Input:

xEnable	BOOL	reset (see ⇘ “CAA 指南”)
lrInputValue	LREAL	actual function value
udiTM	UDINT	length of time interval (equals time passed since last call to function)

Output:

lrDerivative	LREAL	approximated value of first derivative
xValid	BOOL	validity of result; will be set to FALSE, if the number of calls necessary for approximating has not been executed yet