2012/5/2 Alexey Starikovskiy <aysta...@gmail.com>: > No, the question was quite simple. In your example of > velocity-controlled drive, it gets command > input once per ~1ms, thus you can't really give it any smooth curve as > velocity, as there is no way > to reliably smooth it between those points. You might have low-pass > filter in some MESA card, > you might have low-pass filter in the drive itself, and it may be any > combination of them. > What will be the typical (ac/de)celeration time? Is it much larger > than 1ms and we could assume > all the above is irrelevant? >
Well, then I think that this is general question, not related to s-curve velocity profile. Practice shows that 1 ms is short enough that vast majority of motors with their inertia and load cannot achieve any significant acceleration during this one servo thread period. 1 ms is short enough that most machines with velocities below 10-15 m/min have smooth velocity profiles without additional filtering. I think that successful PID loop with a 1ms update interval proves that it is sufficient for vast majority of machines. I guess that very strong linear servo motors with accelerations of 5G and more will require faster update rate, but they are so expensive that I doubt any LinuxCNC users will be able to afford them in any near future. Anywy the servo period length can be adjusted as well. I myself have set servo cycle at 1,5 kHz on D525MW based PC. I have read that other users have achieved even better numbers. Viesturs ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
