Using velocity override in absolute contouring mode

[Tulio]

Does a call to flex_load_velocity_override with overridePercentage parameter set zero affects a move in absolute contour mode ?

[Jochen]

The velocity of a contoured move is not determined by the velocity parameter but by the distance between the position points in the contour array. Thus in this case the velocity parameter has no effect and flex_load_velocity_override() doesn't change the velocity of contoured moves.

Best regards,

Jochen Klier
Applications Engineering Group Leader
National Instruments Germany GmbH

[Tulio]

Thanks Jochen !
I verified this in a small program that I wrote. But I need to ask because in the documentation (October 2003 Edition, Part Number 370538B-01) is stated the velocity override works in all operation modes:
"Velocity override scales velocity in all operation modes on all single axis and vector space moves including 2D and 3D linear interpolation and circular, helical, and spherical arcs."

[Jochen]

I read this, too but if you think of the way contouring works you will agree that it's not possible to change the velocity this way.

Anyway, the phrase you mention is a bit confusing so I will pass this information to the developers in order to change the documentation accordingly in the next revision.

[Tulio]

I agree with you Jochen.
But I need to implement a "pause function", and it will be highly desirable if it could be done during motion.
Any ideia of how it could be done ?

[Jochen]

In this case you should follow this sequence:

1. Halt Motion
2. Check the buffer (flex_check_buffer_rtn) so you know where you have stopped
3. Rewrite the buffer with data starting at the position where you have stopped motion
4. Wait for the time you want to pause motion
5. Start the move again.

[alex2020]

As mentioned in NI motion user manual, the controller create intermedite points using cubic spline algorithm. So, when it move from the first position point in contour array, must it start from zero velocity ? and end at zero velocity too when it come to the last position point in countour array? How about if i want to input contour array continuously. what would the velocity profile looks like ?