Re: [Emc-users] jerk control
So for feed override. I think just having the planner generate a blended path using the "max' override speed. thus guaranteeing that no constraints could be violated for any range of the feed override. Otherwise you would need to regenerate the path based upon override speed as it changes thus the path would change as well (around blend points). I think that could be quite bad especially if your blending tolerances were set large (say for fast roughing passes). You boost up max override and all of a sudden your tool is running larger corners than it was prior and you break a tool. Naturally leading an operator to think "whoops too fast" when it may not have been the speed induced load that broke the toool but too much sudden overstepping. I think it would be prefered that the path remains identical at any feed speed. On Mon, Aug 23, 2021, 7:12 PM andy pugh wrote: > On Mon, 23 Aug 2021 at 21:27, andrew beck > wrote: > > > > Just had a look at tiny g looks great. > > I did try to implement a zero look-ahead finite jerk planner for laser > rastering. It was interesting, and I learned a bit. > > It is easier the less general you make it. > > Ideally LinuxCNC would have a 9-axis finite-jerk planner that handled > arbitrary kinematics with feed-override control. > > Tiny-G is a 3-axis (I think) planner with trivial kinematics and no > feed override (AFAIK). > > At the moment I would be happy just to see LinuxCNC handle more than > 3-axis blending. It's in Tormach. > > I have a feeling that kinematics is not a problem in most cases, the > kins functions run fast enough to be used for finite-difference > differentiation / numerical integration. > I am not sure about the more computationally intensive ones, such as > genserkins. (I think that is fast forwards, slow inverse) > > -- > 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://lists.sourceforge.net/lists/listinfo/emc-users > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] jerk control
Andy do you know what the tormach uses for more than 3 axis path blending? On Tue, Aug 24, 2021, 11:11 AM andy pugh wrote: > On Mon, 23 Aug 2021 at 21:27, andrew beck > wrote: > > > > Just had a look at tiny g looks great. > > I did try to implement a zero look-ahead finite jerk planner for laser > rastering. It was interesting, and I learned a bit. > > It is easier the less general you make it. > > Ideally LinuxCNC would have a 9-axis finite-jerk planner that handled > arbitrary kinematics with feed-override control. > > Tiny-G is a 3-axis (I think) planner with trivial kinematics and no > feed override (AFAIK). > > At the moment I would be happy just to see LinuxCNC handle more than > 3-axis blending. It's in Tormach. > > I have a feeling that kinematics is not a problem in most cases, the > kins functions run fast enough to be used for finite-difference > differentiation / numerical integration. > I am not sure about the more computationally intensive ones, such as > genserkins. (I think that is fast forwards, slow inverse) > > -- > 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://lists.sourceforge.net/lists/listinfo/emc-users > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] jerk and a bit of humor
Cute. Snap, crackle, pop. This page does a fairly good job of showing how jerk is derived and reasonably easy to follow. https://physics.info/kinematics-calculus/ John > -Original Message- > From: dave engvall [mailto:dengv...@charter.net] > Sent: August-23-21 1:14 PM > To: Enhanced Machine Controller (EMC) > Subject: [Emc-users] jerk and a bit of humor > > read all the way to the bottom for the humor. > > > https://www.linearmotiontips.com/how-to-reduce-jerk-in-linear-motion-systems/ > > Dave > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] jerk control
On Mon, 23 Aug 2021 at 21:27, andrew beck wrote: > > Just had a look at tiny g looks great. I did try to implement a zero look-ahead finite jerk planner for laser rastering. It was interesting, and I learned a bit. It is easier the less general you make it. Ideally LinuxCNC would have a 9-axis finite-jerk planner that handled arbitrary kinematics with feed-override control. Tiny-G is a 3-axis (I think) planner with trivial kinematics and no feed override (AFAIK). At the moment I would be happy just to see LinuxCNC handle more than 3-axis blending. It's in Tormach. I have a feeling that kinematics is not a problem in most cases, the kins functions run fast enough to be used for finite-difference differentiation / numerical integration. I am not sure about the more computationally intensive ones, such as genserkins. (I think that is fast forwards, slow inverse) -- 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://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] jerk control
It really does matter on a high speed vmc too. On Tue, Aug 24, 2021, 9:40 AM Chris Albertson wrote: > I think the reason for a jerk limit is to limit changes in the force > applied to the machine's structure.A high constant acceleration applies > a constant force and hence constant deflection. "A constant deflection" > is a fancy way to way "no motion". But any jerk means the force and > deflection is non-constant, a fancy way to so the machine's frame is > moving. > > This matters on 3D printers and other lightly constructed machines a lot > more than on a CNC mill. > > On Mon, Aug 23, 2021 at 1:45 PM Todd Zuercher > wrote: > > > 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 > > Sent: Monday, August 23, 2021 3:39 PM > > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] jerk control > > > > [EXTERNAL EMAIL] Be sure links are safe. > > > > On Mon, Aug 23, 2021 at 7:16 AM Todd Zuercher > > 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 > > > Sent: Monday, August 23, 2021 4:50 AM > > > To: Enhanced Machine Controller (EMC) > > > > > > Subject: Re: [Emc-users] jerk control > > > > > > [EXTERNAL EMAIL] Be sure links are safe. > > > > > > On Mon, 23 Aug 2021 at 04:40, Chris Albertson > > > > > > 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-usersdata=04%7C01%7Cto > > > ddz%40pgrahamdunn.com%7Cdd7544f442b14a481c5d08d9666dccd5%7C5758544c573 > > > f47cebee96c3e0806fb43%7C0%7C0%7C63765382037937%7CUnknown%7CTWFpbGZ > > > sb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3 > > > D%7C3000sdata=2OcIVDtgOdrHp0UmetoWxlAJ3mdvi%2FoT5hRpOH3Oc4Q%3D > > > 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-usersdata=04%7C01%7Cto > > >
Re: [Emc-users] jerk control
I think the reason for a jerk limit is to limit changes in the force applied to the machine's structure.A high constant acceleration applies a constant force and hence constant deflection. "A constant deflection" is a fancy way to way "no motion". But any jerk means the force and deflection is non-constant, a fancy way to so the machine's frame is moving. This matters on 3D printers and other lightly constructed machines a lot more than on a CNC mill. On Mon, Aug 23, 2021 at 1:45 PM Todd Zuercher wrote: > 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 > Sent: Monday, August 23, 2021 3:39 PM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] jerk control > > [EXTERNAL EMAIL] Be sure links are safe. > > On Mon, Aug 23, 2021 at 7:16 AM Todd Zuercher > 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 > > Sent: Monday, August 23, 2021 4:50 AM > > To: Enhanced Machine Controller (EMC) > > > > Subject: Re: [Emc-users] jerk control > > > > [EXTERNAL EMAIL] Be sure links are safe. > > > > On Mon, 23 Aug 2021 at 04:40, Chris Albertson > > > > 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-usersdata=04%7C01%7Cto > > ddz%40pgrahamdunn.com%7Cdd7544f442b14a481c5d08d9666dccd5%7C5758544c573 > > f47cebee96c3e0806fb43%7C0%7C0%7C63765382037937%7CUnknown%7CTWFpbGZ > > sb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3 > > D%7C3000sdata=2OcIVDtgOdrHp0UmetoWxlAJ3mdvi%2FoT5hRpOH3Oc4Q%3D > > 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-usersdata=04%7C01%7Cto > > ddz%40pgrahamdunn.com%7Cdd7544f442b14a481c5d08d9666dccd5%7C5758544c573 > > f47cebee96c3e0806fb43%7C0%7C0%7C63765382037937%7CUnknown%7CTWFpbGZ > > sb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3 > > D%7C3000sdata=2OcIVDtgOdrHp0UmetoWxlAJ3mdvi%2FoT5hRpOH3Oc4Q%3D > > p;reserved=0 > > > > > -- > > Chris Albertson > Redondo Beach, California > >
Re: [Emc-users] jerk control
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 Sent: Monday, August 23, 2021 3:39 PM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] jerk control [EXTERNAL EMAIL] Be sure links are safe. On Mon, Aug 23, 2021 at 7:16 AM Todd Zuercher 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 > Sent: Monday, August 23, 2021 4:50 AM > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] jerk control > > [EXTERNAL EMAIL] Be sure links are safe. > > On Mon, 23 Aug 2021 at 04:40, Chris Albertson > > 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-usersdata=04%7C01%7Cto > ddz%40pgrahamdunn.com%7Cdd7544f442b14a481c5d08d9666dccd5%7C5758544c573 > f47cebee96c3e0806fb43%7C0%7C0%7C63765382037937%7CUnknown%7CTWFpbGZ > sb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3 > D%7C3000sdata=2OcIVDtgOdrHp0UmetoWxlAJ3mdvi%2FoT5hRpOH3Oc4Q%3D > 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-usersdata=04%7C01%7Cto > ddz%40pgrahamdunn.com%7Cdd7544f442b14a481c5d08d9666dccd5%7C5758544c573 > f47cebee96c3e0806fb43%7C0%7C0%7C63765382037937%7CUnknown%7CTWFpbGZ > sb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3 > D%7C3000sdata=2OcIVDtgOdrHp0UmetoWxlAJ3mdvi%2FoT5hRpOH3Oc4Q%3D > 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-usersdata=04%7C01%7Ctoddz%40pgrahamdunn.com%7Cdd7544f442b14a481c5d08d9666dccd5%7C5758544c573f47cebee96c3e0806fb43%7C0%7C0%7C63765382037937%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=2OcIVDtgOdrHp0UmetoWxlAJ3mdvi%2FoT5hRpOH3Oc4Q%3Dreserved=0 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] jerk control
Just had a look at tiny g looks great. Hopefully we can adapt the code On Tue, Aug 24, 2021, 6:45 AM Rob C wrote: > how do they get it to work on the tiny g? > > https://github.com/synthetos/TinyG/wiki/Jerk-Controlled-Motion-Explained > > could we not adapt and improve on the code > > On Mon, 23 Aug 2021, 15:32 Feral Engineer, > wrote: > > > As someone who uses functions like g8p1, g5.1q1 and g5p1 on > mits/fanuc > > and cycle832 on Siemens, I can say that the need for high speed data > > processing functionality is pretty great. Although I don't know how > > Linuxcnc processes g code data, I do know that the aforementioned > functions > > will buffer hundreds of lines of code and smooth the transitions between > > points to a certain degree of accuracy, much like calculating down to a > > nurb or spline instead of worrying about acc/dec on a point to point > basis. > > Much like how lcnc has g64 with selectable accuracy, these functions > offer > > selectable acc/dec settings that will either rattle your fillings or > smooth > > out sharp corners to be razor perfect. I've not tried to run any of my > lcnc > > machines at speeds that would make me see an eminent need for this > > functionality, but I'm sure it would be a welcomed addition. > > > > Phil T. > > The Feral Engineer > > > > Check out my LinuxCNC tutorials, machine builds and other antics at > > www.youtube.com/c/theferalengineer > > > > Help support my channel efforts and coffee addiction: > > www.patreon.com/theferalengineer > > > > On Mon, Aug 23, 2021, 10:17 AM Todd Zuercher > > 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. > > > > > > 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 > > > Sent: Monday, August 23, 2021 4:50 AM > > > To: Enhanced Machine Controller (EMC) > > > > 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%2Flists.sourceforge.net%2Flists%2Flistinfo%2Femc-usersdata=04%7C01%7Ctoddz%40pgrahamdunn.com%7Caaabdbd2b59a4e0ad88708d966134695%7C5758544c573f47cebee96c3e0806fb43%7C0%7C0%7C637653055682515186%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=iD2Nxd21YC5aKx8hByW2ScEBuMjM9%2FXJCwo05FHb%2BLU%3Dreserved=0 > > > > > > > > > ___ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > ___ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
[Emc-users] jerk and a bit of humor
read all the way to the bottom for the humor. https://www.linearmotiontips.com/how-to-reduce-jerk-in-linear-motion-systems/ Dave ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] jerk control
On Mon, Aug 23, 2021 at 7:16 AM Todd Zuercher 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 > Sent: Monday, August 23, 2021 4:50 AM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] jerk control > > [EXTERNAL EMAIL] Be sure links are safe. > > On Mon, 23 Aug 2021 at 04:40, Chris Albertson > 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%2Flists.sourceforge.net%2Flists%2Flistinfo%2Femc-usersdata=04%7C01%7Ctoddz%40pgrahamdunn.com%7Caaabdbd2b59a4e0ad88708d966134695%7C5758544c573f47cebee96c3e0806fb43%7C0%7C0%7C637653055682515186%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=iD2Nxd21YC5aKx8hByW2ScEBuMjM9%2FXJCwo05FHb%2BLU%3Dreserved=0 > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] jerk control
how do they get it to work on the tiny g? https://github.com/synthetos/TinyG/wiki/Jerk-Controlled-Motion-Explained could we not adapt and improve on the code On Mon, 23 Aug 2021, 15:32 Feral Engineer, wrote: > As someone who uses functions like g8p1, g5.1q1 and g5p1 on mits/fanuc > and cycle832 on Siemens, I can say that the need for high speed data > processing functionality is pretty great. Although I don't know how > Linuxcnc processes g code data, I do know that the aforementioned functions > will buffer hundreds of lines of code and smooth the transitions between > points to a certain degree of accuracy, much like calculating down to a > nurb or spline instead of worrying about acc/dec on a point to point basis. > Much like how lcnc has g64 with selectable accuracy, these functions offer > selectable acc/dec settings that will either rattle your fillings or smooth > out sharp corners to be razor perfect. I've not tried to run any of my lcnc > machines at speeds that would make me see an eminent need for this > functionality, but I'm sure it would be a welcomed addition. > > Phil T. > The Feral Engineer > > Check out my LinuxCNC tutorials, machine builds and other antics at > www.youtube.com/c/theferalengineer > > Help support my channel efforts and coffee addiction: > www.patreon.com/theferalengineer > > On Mon, Aug 23, 2021, 10:17 AM Todd Zuercher > 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. > > > > 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 > > Sent: Monday, August 23, 2021 4:50 AM > > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] jerk control > > > > [EXTERNAL EMAIL] Be sure links are safe. > > > > On Mon, 23 Aug 2021 at 04:40, Chris Albertson > > > 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%2Flists.sourceforge.net%2Flists%2Flistinfo%2Femc-usersdata=04%7C01%7Ctoddz%40pgrahamdunn.com%7Caaabdbd2b59a4e0ad88708d966134695%7C5758544c573f47cebee96c3e0806fb43%7C0%7C0%7C637653055682515186%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=iD2Nxd21YC5aKx8hByW2ScEBuMjM9%2FXJCwo05FHb%2BLU%3Dreserved=0 > > > > > > ___ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] jerk control
As someone who uses functions like g8p1, g5.1q1 and g5p1 on mits/fanuc and cycle832 on Siemens, I can say that the need for high speed data processing functionality is pretty great. Although I don't know how Linuxcnc processes g code data, I do know that the aforementioned functions will buffer hundreds of lines of code and smooth the transitions between points to a certain degree of accuracy, much like calculating down to a nurb or spline instead of worrying about acc/dec on a point to point basis. Much like how lcnc has g64 with selectable accuracy, these functions offer selectable acc/dec settings that will either rattle your fillings or smooth out sharp corners to be razor perfect. I've not tried to run any of my lcnc machines at speeds that would make me see an eminent need for this functionality, but I'm sure it would be a welcomed addition. Phil T. The Feral Engineer Check out my LinuxCNC tutorials, machine builds and other antics at www.youtube.com/c/theferalengineer Help support my channel efforts and coffee addiction: www.patreon.com/theferalengineer On Mon, Aug 23, 2021, 10:17 AM Todd Zuercher 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. > > 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 > Sent: Monday, August 23, 2021 4:50 AM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] jerk control > > [EXTERNAL EMAIL] Be sure links are safe. > > On Mon, 23 Aug 2021 at 04:40, Chris Albertson > 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%2Flists.sourceforge.net%2Flists%2Flistinfo%2Femc-usersdata=04%7C01%7Ctoddz%40pgrahamdunn.com%7Caaabdbd2b59a4e0ad88708d966134695%7C5758544c573f47cebee96c3e0806fb43%7C0%7C0%7C637653055682515186%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=iD2Nxd21YC5aKx8hByW2ScEBuMjM9%2FXJCwo05FHb%2BLU%3Dreserved=0 > > > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] jerk control
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. 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 Sent: Monday, August 23, 2021 4:50 AM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] jerk control [EXTERNAL EMAIL] Be sure links are safe. On Mon, 23 Aug 2021 at 04:40, Chris Albertson 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%2Flists.sourceforge.net%2Flists%2Flistinfo%2Femc-usersdata=04%7C01%7Ctoddz%40pgrahamdunn.com%7Caaabdbd2b59a4e0ad88708d966134695%7C5758544c573f47cebee96c3e0806fb43%7C0%7C0%7C637653055682515186%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=iD2Nxd21YC5aKx8hByW2ScEBuMjM9%2FXJCwo05FHb%2BLU%3Dreserved=0 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] jerk control
On Mon, 23 Aug 2021 at 04:40, Chris Albertson 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://lists.sourceforge.net/lists/listinfo/emc-users
