> On 02 May 2017, at 08:18, Hedge Hog <hedgehogshia...@gmail.com> wrote: > > Thanks for taking the time to reply Alex, > > Re Q3 and using HAL to control the stepper motor. Is there some example you > know of that I could review?
Why don't you take the stepgen maxvel and maxaccel pins? You'll have to set them to a certain value anyway. http://www.machinekit.io/docs/man/man9/hal_pru_generic/ Will your use case include a user setting these pins in Hal? In not, then is this "privilege" enough? If the tp has bigger values then the stepgen has. The stepgen will not be able to keep up and will be limited to these values. So you won't violate your hardware specs, but get deviation from the path. If you don't want that you need to be sure that the limits on the tp are lower than your stepgen. > If not, does this approach employ some sort of Trajectory Planner API, or > would this approach require implementing a TP from scratch. > > If I understand correctly, that understanding comes mostly from reviewing > some of the issues in GRBL, a TP is a non-trivial undertaking. > > Best wishes > Hedge > >> On Monday, May 1, 2017 at 2:47:22 PM UTC+10, Alexander Rössler wrote: >> I can answer Q3: >> You can protect your stepper motor spec on the HAL level. To ensure the >> acceleration and maximum velocity values are never violated one could drive >> the stepper via PID loop tuned with the correct parameters. If you want to >> ensure the user cannot edit or override the values you can compile them into >> a HAL component. >> >> Am Samstag, 15. April 2017 07:49:33 UTC-5 schrieb Hedge Hog: >>> >>> Hi, >>> I am considering a 3D printing use case, which is likely different from >>> most CNC use cases in that the bed load/inertia is relatively >>> constant/stable. >>> That's a generalization, but probably reasonable to say that in 80% of >>> cases the mass and forces will be within a very narrow range. >>> Compared to say a CNC machine carving a cubic foot of wood then a cubic >>> foot of steel. >>> >>> I have read [1]-[8] and have three questions. >>> From [1]-[8] I can't see that the pull-in/pull-out envelope (or slew range) >>> is identified for a stepper motor. Nor does it appear that inputs are >>> sought that would allow them to be guesstimated. >>> >>> Q1) Am I wrong (and there is a set of approximations used to define the >>> slew range given the inputs sought)? >>> >>> AFAICT: >>> a) the trajectory planner might be working with a single point on the >>> pull-out curve of a motor, so you can expect the TP to try change direction >>> in the slew-range of a stepper motor. >>> b) The TP does not consider/use the stop-start range where direction can be >>> reversed without deceleration. >>> >>> Q2) Which of the above possibilities is applicable? >>> >>> Q3) Is there a way to ensure that an end user cannot get the trajectory >>> planner to violate a stepper motors specs? >>> I suppose these settings would have to be a compiled, or set by privileged >>> user access, and can't be overridden by a configure file settings. >>> >>> Thanks again for all the effort that has gone into MachineKit >>> >>> Best wishes >>> Hedgehog >>> >>> [1]: http://www.machinekit.io/docs/quickstart/stepper_quickstart/ >>> [2]: http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Stepper_Formulas >>> [3]: >>> http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Stepper_Motor_Speed_Limitations >>> [4]: http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Mechanical_Spreadsheet >>> [5]: http://www.soundproofingforum.co.uk/halitosis/ >>> [6]*: http://www.machinekit.io/docs/config/stepconf/ >>> [7]: http://www.machinekit.io/docs/common/Stepper_Diagnostics/ >>> [8]: http://www.machinekit.io/docs/motion/tweaking_steppers/ > > -- > website: http://www.machinekit.io blog: http://blog.machinekit.io github: > https://github.com/machinekit > --- > You received this message because you are subscribed to the Google Groups > "Machinekit" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to machinekit+unsubscr...@googlegroups.com. > Visit this group at https://groups.google.com/group/machinekit. > For more options, visit https://groups.google.com/d/optout. -- website: http://www.machinekit.io blog: http://blog.machinekit.io github: https://github.com/machinekit --- You received this message because you are subscribed to the Google Groups "Machinekit" group. To unsubscribe from this group and stop receiving emails from it, send an email to machinekit+unsubscr...@googlegroups.com. Visit this group at https://groups.google.com/group/machinekit. For more options, visit https://groups.google.com/d/optout.
