Exceeded value range at position output of the function block L_CamExtrapolate

What happens?
The function block output L_CamExtrapolate.dnPosOut_p may assume values outside the x-clock pulse length (0 ≤ x < xmax) for a short period of time. If this position value is continued to be used as master position for further function bocks of the cam technology consequences such as jerk of the drive axis in the cam zero crossing may occur.

When does the problem occur?
The problem may occur when using the absolute external master selection if a value interpolation is executed over several program cycles via the function block L_CamExtrapolate (e. g. when selecting the master value via the system bus).

Possible diagnostics?
The behaviour can be diagnosed if the function block output L_CamExtrapolate.dnPosOut_p is compared to the maximum clock pulse length (function block input L_CamExtrapolate.dnActXLength_p). At the end of the clock pulse it may happen that the interpolated position output assumes larger values than the maximum value selected via L_CamExtrapolate.dnActXLength_p. The error also occurs in the cam template since the function block L_ CamExtrapolate is used here, too.

Short-term measures/recommendations?
Via an additional network directly connected after the network with the function block L_CamExtrapolate the interpolated x-position can be transformed subsequently to the valid x-range (0 ≤ x < xmax). By means of DDS menu Project => Import insert the export file containing a subprogram CycleLimit for limiting the output signal of the L_CamExtrapolate function block into your project. The subprogram CycleLimit will be filed to the program group Blocks/UserExtensions. Please position it behind the L_CamExtrapolate function block as subprogram call, see sketch below. The presented subprogram CycleLimit corrects the position correspondingly.

Evaluation:
The problem occurs when using the external position master value and the interpolation function via function block L_CamExtrapolate at the same time. It can easily be avoided by applying the program addition mentioned above.