How to anticipate velocity changes in lookahead

[Corentin]

Hello everyone,

I'm trying to synchronize my pumping system flow rate to my motion system commanded speed.
I am using a CK3E 8 axis, and my motors are defined in Coord[1] which uses a kinematic routine and lookahead (LHDistance = 250, SegMoveTime = 20).

Because my pumping system has a lot of inertia, I need to anticipate a change in XY velocity about 2 seconds before segment execution and change my pump speed command accordingly.

How can I achieve this ?

Best regards,
 

[DaveBarnett]

Maybe create a second motion program which mirrors the first, but is started 2 seconds earlier.  That program should stay in sync, and could use a phantom motor from which you could derive your pump speed command.  

[Corentin]

Thanks for the reply.

I need the time delay to be a parameter that can be changed by the operator while the Motion Program is running so this solution won't do it unfortunately. But I will keep it in mind, it might be useful for some testing.

I was thinking about reading the XYZ coordinates or Motor[x].DesPos from lookahead segments. I found Coord[x].LHData but it is undocumented and I could not find anything obvious. Maybe using the Coord[x].LHStart address + n * BlockSize and somehow read values from the memory directly ?

I'm sure there is a better way to do this but I can't figure it out at the moment.

[MoMo]

I think DaveBarnett's method is actually a good method.

You can ensure precise synchronization of the two coordinate systems through TimeBase and achieve precise delay through PLC0.
First set Coord[x].DesTimeBase=0 in the two coordinate systems, and then run the running program. At this time, the motor will remain stationary. Then first restore the Coord[x].DesTimeBase of the first coordinate system to Sys.ServoPeriod, and start the countdown, and then restore the Coord[x].DesTimeBase of the second coordinate system.