Jack Ensor wrote: > I've been trying to pin down follow tracking error in that after I run > Axis.ngc my dro doesn't agree with the position according to the Axis > display. After trying many things as far as acceleration and velocity > settings I thought maybe I ought to take a look at what was coming out > of emc. Using halscope connected to the parport pins that drive the > motor driver I could't believe what I was seeing. As I jogged at > maximum velocity hal showed an increasing frequency as the table > accelerated, but then the displayed frequency decreased after the > acceleration period and then increased again as it entered the > deceleration phase, finally decreasing to zero as the table stopped. If > the halscope scaling is correct, the max frequency reached was around > 400 hz during acceleration and deceleration After the acceleration > phase the frequency slowed to zero as the table stopped. The rise and > falltimes were 0.5 ms. Yes 500 uS.! Maybe I should mention that I am > using the quadrature stepper. > This is the classic aliasing error. The scope is sampling less frequently than the step pulse generating code. I'm not sure how fast you can get halscope to sample, I suppose it depends on the CPU speed.
Jon ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
