Hi, thanks for all your comments so fare. >> 0. move to home position (0°) >> 1. wait for low frequency trigger, a hardware or a software signal >> 2. within say 10° accelerate and synchronises to the 50Hz trigger >> so that the 10° position is reached 20ms after the last trigger >> and at a given speed (specified in degree per trigger pulse, >> not in seconds as the pulse rate of the trigger may change slightly) >> 3. keep on moving at the give speed (in sync with the trigger) for 100° >> 4. decelerate an move to a safe position > > This sounds like fun. It might "just work" with a G33 or G33.1 > synchronised move, or it might need an elaborate system of PIDs and > PLLs.
I've been doing some research on rigid taping and I think is should work. As fare as I understood it rigid taping takes the information from the spindle encoder and moves Z accordingly. So in my case I take the ca. 50 Hz signal from the scanner and treat it like a spindle encoder signal (if necessary I can create A/B and an index pulse somehow, eg. using an external micro controller) and my rotary axis as a linear Z axis. OK. Now, how is acceleration and deceleration handled? I move to a specific starting location (G1 Z0 F100), start the synchronised motion (G33 Z90 K0.1). This should give me a total scan angel of 90° and 900 scan lines (not considering acceleration), total scan time is 18 seconds (+ acceleration/deceleration time). The LinuxCNC G-Code reference provides some information on acceleration [1] but I'm not sure if I really understand the paragraph. Lets say I takes about 2 seconds for the 'Z' axis to reach the necessary speed, this is equivalent to about 100 'spindle encoder' ticks (a=50 ticks/s). Where does my synchronised motion start? I guess at a 'Z' position of about 10 (z=1/2*t^2*a=100 ticks=10°). So I have to drop my first 100 scan lines and start collecting them at Z=10, or start at -10. What about the end of the synchronised motion? Using G33 the spindle is not revered and there will no return move. Where does Z stop? At the given Z value (90) or at the given Z value + 10 for deceleration? See you Flo [1] http://linuxcnc.org/docs/html/gcode/gcode.html#sec:G33-Spindle-Sync ------------------------------------------------------------------------------ Start Your Social Network Today - Download eXo Platform Build your Enterprise Intranet with eXo Platform Software Java Based Open Source Intranet - Social, Extensible, Cloud Ready Get Started Now And Turn Your Intranet Into A Collaboration Platform http://p.sf.net/sfu/ExoPlatform _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
