On Tue, 01 May 2012 14:11:15 -0400 Kenneth Lerman <kenneth.ler...@se-ltd.com> wrote:
> My understanding of the goal is that it is to have a minimum time > subject to certain constraints. > > The current constraints in LinuxCNC are to have certain acceleration > and velocity limits. It has been suggested that it would also be > appropriate to limit the jerk. Doing so could only make the time > longer. For a variety of reasons (smaller error, less > vibration, ...), some commercial machines add such constraints. > > I suggest that if enhance LinuxCNC to add the jerk constraints, that > will be sufficient to "compete" with commercial solutions. > =============== > > I've noticed that most of the papers I've looked at seem to discuss > the problem of moving a single axis. Presumably, changing this to an > N-axis solution is straight forward. LinuxCNC, though, handles both > linear and circular interpolation. I've never looked closely enough > at the design to understand how circular interpolation would change > the problem. > > Regards, > > Ken > > On 5/1/2012 1:41 PM, Joachim Franek wrote: > > Look at > > http://www.roymech.co.uk/Useful_Tables/Maths/fourier/Maths_Fourier_transforms.html > > and compare the fourier transform of: > > 1. top hat (sinc) > > 2. triangle (sinc^2) > > 3. gauss (gauss) > > > > trapezoidal is inbetween top hat and triangle. > > > > for accaleration function > > 1. top hat: jerc is unboundet > > 2. triangle and trapezoidal: jerc is constant > > 3. gauss: jerc is gauss > > > > _Conclusion:_ > > gaussian accaleration gives the _lowest_ frequency components! > > > > Unfortunately gaussian jerk is impossible. You have to > > wait infinite time to start the motion. > > > > Which function looks like a gaussian? > > The sinusoidal type in > > STR_V8_N1_07_MCH.pdf: Fig.1 (a) > > or > > 4267.pdf: page 8, upper trace > > is a candidate! > > > > Joachim Ken, Joachim, et al My understanding is: decent acceleration within the mechanical constraints of the machine. gauss ( e^-k) in very simplified form as opposed to sine. I'm guessing that any smooth function will allow one to increase acceleration to achieve good performance without jerk, therefore it must be jerk limited. Smoothness is very desirable in trying to get good curves or surfaces. One takes their pick and pays their money. ;-) For many years now we've had the computing power to do control much more sophisticated than G1, G2 and G3. An italian group extended emc with nurbs several years ago and to my knowledge it doesn't get used much. With a really good 3D nurbs within emc there is the possibility of doing most surfacing in nurbs. However, this awaits an easy to understand in implement CAM. Sorry for the digression; just couldn't resist. Dave > > > > ------------------------------------------------------------------------------ > > Live Security Virtual Conference > > Exclusive live event will cover all the ways today's security and > > threat landscape has changed and how IT managers can respond. > > Discussions will include endpoint security, mobile security and the > > latest in malware threats. > > http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > > _______________________________________________ Emc-developers > > mailing list Emc-developers@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-developers > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. > Discussions will include endpoint security, mobile security and the > latest in malware threats. > http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ Emc-developers > mailing list Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
