Help find an analogue.

[TomKerekes]

My only question is why would you do the trajectory planning outside of the Galil controller? Trajectory planning is what it is designed to do, and they do it very well. Just tell it where to go, give it speed and acceleration, and let it do its thing.

I think optimal Trajectory Planning is a more complex task than implied here. High speed motion through 3D paths can involve the analysis of hundreds of GCode blocks/segments, each involving multiple axes, and where each axis has multiple constraints to consider. Additionally there can be path filtering, smoothing, blending, and kinematic requirements. I'm not aware of any controller that handles this problem well internally.

Systems based on Mach3 (including our own plugin) rely on Mach3's Trajectory Planner which sometimes has issues as I believe relatively few segments are being collectively considered. Settings may either result in slow jerky motions, or fast motion, that may deviate from the specified path by an unconstrained amount.

For these reasons we run our GCode Interpreter, Trajectory Planner, and Kinematics on the PC in order to take advantage of the PC's vast resources. As long as a PC is available whether the GCode file is submitted to a PC Library, or directly to the Controller, is normally transparent to the User.

I think you will find Controllers that accept GCode directly, and do Trajectory Planning internally, to be very limited.

[joeavaerage]

Hi,

I think optimal Trajectory Planning is a more complex task than implied here

I personally am of the same opinion, its all very well having a controller which can natively interpolate multi axis movements but my
understanding is that trajectory planning is more than that.

In particular if you wish what I'd call CV (constant velocity) then successive moves must be chained together and a calculation done to blend
the moves together in some (optimal) fashion.

I used Mach3 for a year or so before upgrading to Mach4 about five years ago. Thus my experience is based on my memory of Mach3 but now many hundreds
if not thousands of hours 'hands on' with Mach4.

To the best of my knowledge the essential trajectory planner is very similar. For instance both Mach3 and Mach4 have a second order planner only. There was talk
at the time that Mach4 was developed that a third order planner could be used however it was not (as yet) adopted. Where the two differ is the means of blending moves,
and again to the best of my knowledge, Mach3 and Mach4 share similar look-ahead strategies however Mach4 has a considerably refined calculation to blend moves.
It is for instance possible to set a max deviation and other parameters that allow a user to make a trade off between tool path speed and tool path fidelity.

Not withstanding Mach4's better CV strategies my understanding is that Mach4's trajectory planner is adequate but 'entry level' by comparison to some of the established
but expensive industrial controllers.

There has been research done and code written for a more sophisticated Mach4 planner (Tempest Planner) and even some talk in recent months of introducing it. It is no
more than a module in Mach4 and so could be introduced at will without any modifications to the rest. We will wait and see.

Craig

[Jim Dawson]

I should note here that my software is more than a G code translator and UI. It does quite a bit of preprocessing on file load before compiling the DMC command code that is ultimately passed to the Galil controller. Without that preprocessing and deep look ahead it would not run a machine very well. Just directly translating the G code and feeding it to the controller line by line would make for a rather inefficient system, there are a number of things to be considered. I never thought of the preprocessing as trajectory planning, but maybe it could be defined that way.

[Alexiv]

Jim Dawson, do Galil controllers have the lookahead function or something like that? I mean the function that analyzes the motion program and recalculates this program to its code then puts this to buffer, something like that... It's necessary for soft movement, I am sure you understand what I mean.
You're right, we have a complete application for our CNC machines. I think to change the motion controller type not so large problem. Here is an example:
We generate G-code by artcam and fusion 360. I wrote the special cps (preprocessor) for fusion, while it works well.