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Blend in PVT mode
#1
I have a motion profile that I run in PVT mode. I have attached the code. The motion loops for a certain number of cycles.

The Y axis motion has a sharp edge at the end of a cycle and beginning of next cycle due to direction reversal. I've marked this in the attached Y axis position plot.

How do I use the blend function to make this a smooth transition?


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#2
In PVT mode, observing the acceleration and velocity limits are the responsibility of the programmer, unlike in Linear blended mode.

You may find that letting Pmac do more control of the trajectories is easier than PVT.

See this example from the Turbo User manual:

SPLINE1 TM20
P1=0
WHILE (P1<10)
P2=0
WHILE (P2<359)
X(P1*SIN(P2))
P2=P2+1
ENDWHILE
X(P1*SIN(P2))
P1=P1+1
ENDWHILE

If you change the first line to LINEAR mode, then Pmac will observe acceleration and velocity limits while creating the overall trajectory.

'Not sure if this is exactly what you want, but something to consider.
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#3
With PVT mode your program has to be written to control the blend at such a transition acc/dec and velocity. This can be "fun" (sarcasm) at a direct reversal since you want to bring velocity to zero then back up to desired velocity. Therefore the block at reversal brings velocity to Zero and the next block set velocity back to desired velocity. Now acc/dec may need modification as well through the transition.

As Dave mentioned LINEAR with Lookahead active makes this very simple since the velocity Ixx16 and acc/dec limits Ixx17 are active and firmware prevents exceeding them through all moves of the program.


(08-02-2017, 06:00 AM)DaveBarnett Wrote: In PVT mode, observing the acceleration and velocity limits are the responsibility of the programmer, unlike in Linear blended mode.

You may find that letting Pmac do more control of the trajectories is easier than PVT.

See this example from the Turbo User manual:

SPLINE1 TM20
P1=0
WHILE (P1<10)
P2=0
WHILE (P2<359)
X(P1*SIN(P2))
P2=P2+1
ENDWHILE
X(P1*SIN(P2))
P1=P1+1
ENDWHILE

If you change the first line to LINEAR mode, then Pmac will observe acceleration and velocity limits while creating the overall trajectory.

'Not sure if this is exactly what you want, but something to consider.
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