Depending on how the control software was written, a system that doesn't use an operating system, or uses an operating system like MSDOS with no multi-tasking or preemption can have really high performance on crummy hardware. It's really frustrating to use if you want to go beyond very simple activities, but the control performance is great. The Accurite control we have at work runs on a 486 (can see that as it is booting), and it is perfectly usable. Looking at all the nonsense that is running on a modern operating system, it's amazing you can get any performance at all out of them Eric Keller
On Fri, May 18, 2012 at 12:52 PM, Jon Elson <[email protected]> wrote: > Jan de Kruyf wrote: > > Jon: > > when I started working in the CNC field we had 20msec loops and they > > worked(cutting steel) from pure fanciness we would upgrade to 10msec, and > > with a well tuned servo drive you could feel the distinct steps of the > DAC > > while accelerating. > Yes, with velocity servo amps with tachometers, all the computer has to > deal with > is keeping the position within bounds. But, if there is no velocity > feedback > (current/torque-mode amps or pure voltage amps) then the computer has to > work > a lot harder at it. > > Afterwards I learned to tune a servo by holding the > > table feeling for those steps. > > Off course on a small high speed machine the picture changes > considerably. > > But at the same time I guess that the problem you are describing might be > > caused in the digital speed servoloop, by the jitter of the CPU board, > and > > / or a poor setup of the positioning loop. > > > > In any case: from the grumbles in this thread we might perhaps deduct > that > > there is money in a good micro stepping board, that takes position or > speed > > input every msec or so; for the stepper people. > > > Well, I make one of those, there are several other makes available, > too. My board, the > Universal Stepper Controller, turns a stepper into a servo. With no > encoders, the > "encoder" counter counts the step pulses, if you add an encoder, it > reads actual position. > LinuxCNC samples position typically every ms and sends a new velocity > command. > You can go to over 300K steps/second on each axis and still have > velocity granularity > of 3%. That can't be done in software. > > Jon > ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
