Position-Velocity-Time vs Position Profile

Hello,
I have a
question concerning the behavior of position profile and PVT contoured move.
In the topic
“Position Profile-Motion Assistant Help file” says:
“Position
profile moves give you maximum control over the position of the move …”.
And in “Position/Velocity/Time
(PVT)-Motion Assistant Help file” it says “PVT moves give you maximum control
over the velocity of the move at certain times throughout the move.”
So, it’s
correct to say that the position generated by a PVT based contoured move is “less
accurate” than the one generated by a position profile in respect to the
original data points?
If yes, is
there any way to know in advance maximum position error?

Hello DJ L,
The PVT
examples work fine. I’m using Motion Assistant 1.2.
I’m trying
to do a 2D move that have 2 different velocity profiles. I only have XY
coordinates, the maximum cruise velocity and the maximum acceleration that my setup
supports. One profile is used for straight (or almost straight) moves and the
second at a much lower speed in curves.
I think
that what is causing my problem is a constraint that is out of range like you
said. I managed to get a few points to be plotted by Motion Assistant. But the
resulting velocity profile is unacceptable for this application (see file
Profile1.png and PVT_Profile1.txt for data). Adjusting the time index by trial
and error I get a more appropriate velocity profile for my needs (see file
Profile2.png and PVT_Profile2.txt for data). The constraints for this
application are:
- Go to
the maximum cruise velocity in the least amount of time (given the maximum allowed
acceleration).
- Maintain this
cruise velocity with the minimum variation until the next change in velocity
profile.
- The XY
coordinates defines a cutting path, so distortions in position should be minimum.
I’m looking
for a set of equations that could generate data in the PVT format that meet
this requirements and it should be possible to put this in C++ program because adjusting
and testing in Motion Assistant application would not be possible. Could you help me in developing those equations?
The file “data_profile.xls”
is one real example and contains XY coordinates with the respective move
constraints.
Regards,
Attachments:
files.zip ‏141 KB

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