Certainly NOT complaining :-) I'm having fun learning about this. Machining stuff is (part of) what I do. Ninety percent of my machining only require wide tolerances, but it's not uncommon to have to work to +-0.0002" on manual machining. This 'theoretical' f-error of +-0.0003" is already outside that and I wouldn't expect the situation to improve downstream. But as yet, I don't actually know how this f-error will translate in the real world machining parts.
Thank you for taking the time to reply (I'm off to find out about double quantization noise :-) ) Richard Jon Elson wrote: > Richard Arthur wrote: > >> A couple more questions with reference to: >> >> http://imagebin.org/73098 >> >> Looks to me like harmonics in the constant speed section; any >> suggestions as to its source? >> There are spikes at the change constant speed/acceleration and vice >> versa. I wouldn't expect to see that in a smooth transition, any comments? >> >> My setup: >> Brushed DC motors with tacho feedback to servo amps (+-10v control >> > What are you COMPLAINING about???? The worst-case peak-peak error is in the > neighborhood of 300 uInch, or 0.0003". Unless you are diamond-turning > telescope > mirrors, this is probably FAR smaller than any other error in your machine. > Since these motors have discrete windings, commutator segments and maybe > belt drives, there will be perturbations as they turn. Also, you have > the inevitable > double quatization noise of the encoder. > > As for your spikes, you should plot velocity as well as position. There > is an acceleration > "jerk" at the transition from rest to constant accel, and then another > at the transition from > accel to constant velocity. (There is an experimental S-curve traj > planner, but I don't think > it was ever made mainstream.) I always view velocity (called "delta" on > my driver, but you > may have to manufacture such a signal with a hal component) with pid > error when tuning. > > Jon > > ------------------------------------------------------------------------------ > Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day > trial. Simplify your report design, integration and deployment - and focus on > what you do best, core application coding. Discover what's new with > Crystal Reports now. http://p.sf.net/sfu/bobj-july > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > > > ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
