Questions about using blend motion!

[jihuang]

The manual of PCI-7344 mentions about by setting blend factor to -1 to get smooth motion path.
I have tried, but the outcome always changes the sharp corners into round corners with excessive r
values. If I set the blend factor to 0 or larger values, the sharp corners reserve, but it seems that we have lost the capability by keeping the velocity value and without the hasel to decelerate and accelerate all the time for continuous motions.

Furthermore, if the consecutive path lengths are comparatively short, it is very easy to
get "blend motion is issued at in-appropriate time" error from the motion control card.

The way that I use the blend motion is as follow:

load target positions
flex_start
flex_check_for_blend_com
plete

Is there any way that we could test and make sure that the motion command buffer is not full?
How should I do to prevent the error when using flex_blend?
How could I do to get sharper corners when setting the blend factor to -1?

[Jochen]

With the blend function the next move starts to accelerate when the first move starts to decelerate. So this is the reason why you get round corners. This is the effect that makes the moves smoother. A sharp corner always means extremely high accelerations and forces and they are not very conducive to the health of the mechanics.
Thus to get sharper corners you simply need to increase the values for acceleration/deceleration.

For very short consecutive moves it might become hard to avoid the error you described. You better should use contoured moves for this type of trajectory.

Regards,

Jochen Klier
Applications Engineering Group Leader
National Instruments Germany GMbH

[jihuang]

Dear Sir:

Your answer is very helpful, Thanks. After compared with some other motion control cards, some of them have equipped a command buffer for users to send in commands, and the control card would do the motion control automatically for users. It seems that PCI-7344 does not have this facility, therefore we will get the blend motion error easily. I wish that the PCI-7344 could offer this function in the future.

Sincerely

Jih-Jenn Huang

[algames]

The 7344 does offer this funcitonality and it is called Contouring mode, when you want to download several positions and spline throughthem , all you need to do is download the sequence of poinst you want to go though into a buffer and then run the move. Please refer to the example programs that ship with your driver for more information. Also, here is a LabVIEW example that demonstrates this functionality.

http://sine.ni.com/apps/we/niepd_web_display.DISPLAY_EPD4?p_guid=B8DD125379730531E034080020E74861&p_node=DZ52479&p_submitted=N&p_rank=&p_answer=&p_source=External