The rate of change of acceleration is "Jerk". Limiting Jerk literally make the machine less "Jerky" which is much more noticeable when running at high speeds.
Andy hinted at it with car braking.. Have you ever been in a car with a new driver? Oftentimes everyone suffers from a bit of whiplash due to the new drivers lousy braking and lack of control of the accelerator pedal. That is jerk. A while back, someone on this list mentioned that they had tweaked EMC2 to include jerk limiting and I believe they included a URL to their modified source code, if that is of interest to anyone. That was probably 6 months ago or so. But like Andy said, Jerk limiting is much different than dynamically adjusting acceleration rates based on motor speed. Dave On 9/20/2011 11:01 AM, craig wrote: > Although my education, long ago, was in physics, I do not really > understand the physics of electric motors. > > Are there reasons to limit the rate of change of acceleration? > > for example: Are there reasons that one would not want to go from max > acceleration in one direction to max acceleration is the opposite direction? > > If so under what circumstances? What kind of motors? > > Craig > > > > > > On 9/20/2011 6:56 AM, Dave wrote: > >> I would think that this would be very hard to implement successfully. >> You are talking about optimizing the acceleration settings to a >> particular motor/drive/load setup. >> >> I can only see this being of a benefit if you were running a fixed part >> with the same cutter over and over again with a undersized or poorly >> sized drive system. If you changed materials or cutters or the >> carriage mass you might have to >> retune everything. >> >> The norm is to make sure that you are not operating your motors that >> close to the edge of their torque curve. >> >> A machine with accels tightly fitted to the motor/drive/load would be >> very unforgiving. >> >> Servos can operate beyond their ratings for short periods of time which >> sometimes makes them more forgiving, especially if you increase the the >> max following error allowed. >> >> Dave >> >> On 9/19/2011 4:02 PM, Andrew wrote: >> >>> Thinking about decreasing stepper (and servo, to some extent) torque at >>> higher speeds, I just thought that having variable axis acceleration would >>> be perfect. I.e., the highest at lower speeds and lower at higher speeds. Is >>> that ever possible with EMC2? If no, is it hard to implement? >>> >>> Andrew >>> ------------------------------------------------------------------------------ >>> All the data continuously generated in your IT infrastructure contains a >>> definitive record of customers, application performance, security >>> threats, fraudulent activity and more. Splunk takes this data and makes >>> sense of it. Business sense. IT sense. Common sense. >>> http://p.sf.net/sfu/splunk-d2dcopy1 >>> _______________________________________________ >>> Emc-users mailing list >>> Emc-users@lists.sourceforge.net >>> https://lists.sourceforge.net/lists/listinfo/emc-users >>> >>> >>> >> ------------------------------------------------------------------------------ >> All the data continuously generated in your IT infrastructure contains a >> definitive record of customers, application performance, security >> threats, fraudulent activity and more. Splunk takes this data and makes >> sense of it. Business sense. IT sense. Common sense. >> http://p.sf.net/sfu/splunk-d2dcopy1 >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > > ------------------------------------------------------------------------------ > All the data continuously generated in your IT infrastructure contains a > definitive record of customers, application performance, security > threats, fraudulent activity and more. Splunk takes this data and makes > sense of it. Business sense. IT sense. Common sense. > http://p.sf.net/sfu/splunk-d2dcopy1 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > > ------------------------------------------------------------------------------ All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
