On Wed, May 06, 2009 at 04:37:07PM +1000, Frank Tkalcevic wrote: > I've just configured my first emc project, a 9x20 lathe conversion. I'm > using a large servo for the spindle - I'm hoping to be able to use it as a > 4th axis for some light engraving down the track. > > My problem - I've set up the servo for the spindle, but like a servo, it > responds imediately to change requests. I haven't put a chuck on it yet, > but it I'm sure it will break the belt when it tries to stop from 1000rpm to > 0, instantly. > > Any ideas on how I can soft start and stop it?
Send the commanded spindle speed through a limiter before pid, so that the pid 'command' value varies slowly. "limit2", "limit3", and "lowpass" are three built-in components that limit a signal: "limit2" limits the range and first derivative of a signal. "limit3" limits the range, first and second derivatives of a signal. "lowpass" uses an exponentially-weighted moving average to track an input signal. Here's a standalone hal setup I wrote to show the behavior of each of these limiters when fed a step signal: ######################################################################## loadrt threads period1=1000000 name1=thread loadrt siggen loadrt lowpass loadrt limit2 loadrt limit3 net square siggen.0.square => lowpass.0.in limit2.0.in limit3.0.in net lowpass <= lowpass.0.out net limit2 <= limit2.0.out net limit3 <= limit3.0.out setp siggen.0.frequency .1 setp lowpass.0.gain .9 setp limit2.0.maxv 2 setp limit3.0.maxv 2 setp limit3.0.maxa 10 addf siggen.0.update thread addf lowpass.0 thread addf limit2.0 thread addf limit3.0 thread start loadusr halscope ######################################################################## .. run it with 'halrun -I limiters.hal' at the terminal. In halscope, I selected the signals 'square', 'limit2', 'limit3' and 'lowpass' and captured a trace: http://emergent.unpy.net/files/sandbox/limiters.png Jeff ------------------------------------------------------------------------------ The NEW KODAK i700 Series Scanners deliver under ANY circumstances! Your production scanning environment may not be a perfect world - but thanks to Kodak, there's a perfect scanner to get the job done! With the NEW KODAK i700 Series Scanner you'll get full speed at 300 dpi even with all image processing features enabled. http://p.sf.net/sfu/kodak-com _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
