But you need to look at why you have your jerk limit is set to what it is in the first place. Is it not there so that the motor (joint) can accelerate in a controlled fashion as quickly as possible within its capabilities smoothly? Therefore the vector sum is also the vector sum of the combined joints capabilities, so shouldn't that also be the same amount higher?
Todd Zuercher P. Graham Dunn Inc. 630 Henry Street Dalton, Ohio 44618 Phone: (330)828-2105ext. 2031 -----Original Message----- From: Chris Albertson <albertson.ch...@gmail.com> Sent: Monday, August 23, 2021 3:39 PM To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] jerk control [EXTERNAL EMAIL] Be sure links are safe. On Mon, Aug 23, 2021 at 7:16 AM Todd Zuercher <to...@pgrahamdunn.com> wrote: > To my lay persons eyes I would think it would be enough to jerk limit > in joint space. The limiting in Cartesian space would then take care > of itself. > Let's work a simple example to see. Assume jerk is limited to 1 meter per second cubed. Assume the machine is just 2D, X and Y pen plotter. If both axes are running at the same speed and the current X and Y jerk is at the 1m/s^3 limit then the pen (Cartesian space) has jerk equal to 1.414 (square root of two) which is over the limit. Controllering only joint limits can't work if the cartesian motion can be expressed as the vector sum of joint motions because the sum of two vacters can have greater magnitude then either of the two joint vectors Simply not bumping into a limit is not really hard but it becomes a hard problem when you want to move as fast as possible, but no faster. You can't do it without doing a full simulation and numeric optimization. I think this is true on a 3-axis machine where all the axes are linear and orthogonal. Basically wherever "trivial kinematics" applies. > > As to the jogging question, does it matter? Why would jogging have to > have the same acceleration limits as planned motion? Set the jogging > limits to something safe and conservative that won't matter if they > are jerk limited. > > Todd Zuercher > P. Graham Dunn Inc. > 630 Henry Street > Dalton, Ohio 44618 > Phone: (330)828-2105ext. 2031 > > -----Original Message----- > From: andy pugh <bodge...@gmail.com> > Sent: Monday, August 23, 2021 4:50 AM > To: Enhanced Machine Controller (EMC) > <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] jerk control > > [EXTERNAL EMAIL] Be sure links are safe. > > On Mon, 23 Aug 2021 at 04:40, Chris Albertson > <albertson.ch...@gmail.com> > wrote: > > > Actually for a machine tool, why not run the simulation off-line and > > use as much time and computer power as it takes. > > Feed-override? > > Do you allow infinite jerk on abort? You might think that is an easy > question, except that continuous jog is implemented as a move to the > limit that is aborted on key release. > > And, do we need to jerk-limit in joint space or cartesian space, or both? > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > - George Fitch, Atlanta Constitution Newspaper, 1912 > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > > https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Flist > s.sourceforge.net%2Flists%2Flistinfo%2Femc-users&data=04%7C01%7Cto > ddz%40pgrahamdunn.com%7Cdd7544f442b14a481c5d08d9666dccd5%7C5758544c573 > f47cebee96c3e0806fb43%7C0%7C0%7C637653444482037937%7CUnknown%7CTWFpbGZ > sb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3 > D%7C3000&sdata=2OcIVDtgOdrHp0UmetoWxlAJ3mdvi%2FoT5hRpOH3Oc4Q%3D&am > p;reserved=0 > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Flist > s.sourceforge.net%2Flists%2Flistinfo%2Femc-users&data=04%7C01%7Cto > ddz%40pgrahamdunn.com%7Cdd7544f442b14a481c5d08d9666dccd5%7C5758544c573 > f47cebee96c3e0806fb43%7C0%7C0%7C637653444482037937%7CUnknown%7CTWFpbGZ > sb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3 > D%7C3000&sdata=2OcIVDtgOdrHp0UmetoWxlAJ3mdvi%2FoT5hRpOH3Oc4Q%3D&am > p;reserved=0 > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.sourceforge.net%2Flists%2Flistinfo%2Femc-users&data=04%7C01%7Ctoddz%40pgrahamdunn.com%7Cdd7544f442b14a481c5d08d9666dccd5%7C5758544c573f47cebee96c3e0806fb43%7C0%7C0%7C637653444482037937%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=2OcIVDtgOdrHp0UmetoWxlAJ3mdvi%2FoT5hRpOH3Oc4Q%3D&reserved=0 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
