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
