Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
On Friday 25 April 2014 11:08:55 Florian Rist did opine: Hi, thanks for all your comments so fare. 0. move to home position (0آ°) 1. wait for low frequency trigger, a hardware or a software signal 2. within say 10آ° accelerate and synchronises to the 50Hz trigger so that the 10آ° 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 100آ° 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 90آ° 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=10آ°). 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 And you have just stumbled over the conundrum that prevents one from changing the spindle speed in the middle of a G33.1 peck cycle you've just carved the gcode for. To do so ignores the accel delay in the z, and it will actually become synchronized at some point determined by the accel settings, but many tens of degrees after the index has passed. I am hoping that at some point that these synchronized motions will be made smart enough to spend an extra turn of the spindle while it calculates this delay based on those settings, and then issues the start synch command far enough ahead of the spindle index that it will be truly in sync at the index pulse. I have not experimented, but for Z in that case it might be helpful, since the Z speed when threading is not generally anywhere near as fast as a rapid move, to allow a larger much larger Ferror, and set MAX_VEL MAX_ACCEL that is much more brutal, based on the theory that it could play catch up and have lots less actual lag in terms of the rotational delay. If the start point for the sync is a couple turns of the spindle before the tool contacts, giving it time to truly get in step with minimal error, it might just work. If I get to the shop today, its set in to rain now, I might try playing with that. As long as it restores to the same starting position, we haven't lost any counts. This would apply to both the G33 stuffs and equally to the G76. It might also beat a 1 travel dial indicator into junk too. If nothing else, I can afford to throw away some rapid speed since my lathe can do at least 60 ipm for z, and close to 100 ipm for x. Way more than it needs. [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 Cheers, Gene -- There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order. -Ed Howdershelt (Author) Genes Web page http://geneslinuxbox.net:6309/gene US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS -- Start Your Social Network Today - Download eXo Platform Build your Enterprise Intranet with eXo Platform
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
Hi [Beaglebone black + BLDC contorller] Alternatively the Pico PWM brushless servo amp only needs a single channel of PWM: http://www.pico-systems.com/acservo.html A Gecodrive G320X [1] would be even easier to run from a Beaglebone as it does not require a PWM/Dir but a Step/Dir signal. This would be less challenging regarding timing and thread period, right? See you Flo [1] http://www.geckodrive.com/geckodrive-brush-dc-drives/g320x.html -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
On 24 April 2014 02:17, Jon Elson el...@pico-systems.com wrote: But, yes, a Mesa controller has a full sign/magnitude output available. I wasn't sure Florian was going to use a traditional controller and Hal for this. I think there is some confusion here still. The 7i39 needs three channels of PWM, one channel of PWM for each of the motor phases. It is a mainly-dumb drive with all commutation handled off-board in software. The Mesa three-phase-pwm is capable of providing 6 channels to drive every gate of the 3-phase bridge directly (with shoot-through prevention set by a parameter to the PWM generator) In the case of the 7i39 this is reduced to 3 channels to reduce pin usage and shoot-through inhibition is in hardware. I can't recall which scheme it uses to do this, whether it is 50%=0 or something else. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
Hi Jon http://www.pico-systems.com/acservo.html Ah, I see that would make thinks much easier. You COULD, in theory, run it with just the Direction signal in synchronous antiphase mode, but this may cause the filter inductors (and maybe the motor, too) to run hot. Our servo amp was designed to run in sign-magnitude mode. That only takes TWO signals, PWM and Direction. Hmm, by looking at the 'H-Bridge Secrets' [1] article by Andras Tantos I think I got an idea what the two different modes of operation are. (The article is on DC motors, but I seams to be more or less clear what it means on the phase BLDC drivers.) But I don't see how the mode of operation makes a difference regarding my synchronisation problem. What do I miss? See you Flo [1] http://www.modularcircuits.com/blog/articles/h-bridge-secrets/ -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
On Tue, 22 Apr 2014, Florian Rist wrote: Date: Tue, 22 Apr 2014 18:24:42 +0200 From: Florian Rist fr...@fs.tum.de Reply-To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net To: emc-users@lists.sourceforge.net Subject: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?) Hi, I'm facing a slightly unusual problem and before I head forward into the wrong direction I'd like to hear what you think about it: I have to pan a laser scanner (a single rotary axis), so I thought about using a BLDC (which I happen to have already), a MESA 7I39 BLDC controller and a BeagleBone Black. So, first question: Can I hook up the 7I39 to a BeagleBone Black. Well of course I can, but is this somehow supported already, so that it is simple to do? Any other driver suggestions? The bigger problem is that I need to synchronise the motion with a high 'frequency trigger' signal (about 50 Hz). The motion pattern needed is cyclic an has to look something like his: 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 5. goto 1. and repeat the process in reverse direction How could I use LiuxCNC/Machinekit to synchronise the motion to the external trigger signal and ensure a specific position is reached at a specific speed in sync with the trigger? The reason why I want this is to make sure the scanner captures lines at the same angular positions. The trigger comes from the scanner an indicates the start of a line capture. Unfortunately the scan process can not be trigger externally, this would be much easier, but I only get a signal each time a scan line starts. I suspect this can be done using the a stepgen in velocity mode in a feedback loop: first setup a stepgen in velocity mode, a pid component and a accumulator that generates the desired 20 ms scanner waypoints At every 20 ms trigger from the scanner, sample the stepgens position and increment the 20ms waypoint accumulator. Then use a pid component that uses the waypoint position as command input and sampled stepgen position as feedback and outputs the velocity command to the stepgen. (the PID loop will be mainly FF0 to set the rate and a small amount of P to phase lock the stepgen to the sample positions) The stepgen step/dir outputs could be used directly for step.dir drives or the stepgen FB pin could be used as a position setpoint for a servo of some sort Hmm, well. What do you think. Is LiuxCNC right for the job or not. See you Flo -- 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 Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your ()_() signature to help him gain world domination. -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
On 04/23/2014 09:07 AM, Florian Rist wrote: Hi Jon http://www.pico-systems.com/acservo.html Ah, I see that would make thinks much easier. You COULD, in theory, run it with just the Direction signal in synchronous antiphase mode, but this may cause the filter inductors (and maybe the motor, too) to run hot. Our servo amp was designed to run in sign-magnitude mode. That only takes TWO signals, PWM and Direction. Hmm, by looking at the 'H-Bridge Secrets' [1] article by Andras Tantos I think I got an idea what the two different modes of operation are. (The article is on DC motors, but I seams to be more or less clear what it means on the phase BLDC drivers.) But I don't see how the mode of operation makes a difference regarding my synchronisation problem. What do I miss? Andy Pugh suggested you could run my PWM servo amps with just ONE wire/output pin. That is what I was referring to, and that two wires would be better. With sign/magnitude control, there is no output until the PWM signal has pulses on it (ie. when power is needed to move the motor). With synchronous antiphase, both sides of the full-bridge are cycling at 50% duty cycle all the time, ramping triangle-wave currents through the motor windings. As for the synchronization part of your question, I didn't have any comment on that. But, I think it might be fairly simple to rig up suitable functions with standard HAL components that can do what you need. Probably there'd be the PID component, but I don't understand the rest of the requirement enough to say more. Jon -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
Hi Jon Andy Pugh suggested you could run my PWM servo amps with just ONE wire/output pin. That is what I was referring to, and that two wires would be better. Ah, OK. Got it. Thank for the clarification. With sign/magnitude control, there is no output until the PWM signal has pulses on it (ie. when power is needed to move the motor). With synchronous antiphase, both sides of the full-bridge are cycling at 50% duty cycle all the time, ramping triangle-wave currents through the motor windings. As for the synchronization part of your question, I didn't have any comment on that. But, I think it might be fairly simple to rig up suitable functions with standard HAL components that can do what you need. Probably there'd be the PID component, but I don't understand the rest of the requirement enough to say more. I'll try to wire something up on the weekend. We'll see how fare I get. A possible alternative would be to make LinuxCNC capture the current position when the trigger signal is received and send the position data via Ethernet to the scanner control computer. This is less elegant though and will rewire more post processing of the captured scan data. See you Flo -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
On 23 April 2014 16:57, Jon Elson el...@pico-systems.com wrote: Andy Pugh suggested you could run my PWM servo amps with just ONE wire/output pin What I was meaning was that it only needed one PWM channel, rather than the phase-locked 3-phase PWM that the 7i39 needs. I wasn't suggesting that it didn't also need direction, enable etc pins. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
Hi Andy Andy Pugh suggested you could run my PWM servo amps with just ONE wire/output pin What I was meaning was that it only needed one PWM channel, rather than the phase-locked 3-phase PWM that the 7i39 needs. I wasn't suggesting that it didn't also need direction, enable etc pins. That's how I understood your comment in the first place. Never the less the keywords sign-magnitude and synchronous anti-phase led me to some interesting insight in motor control. See you Flo -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
On 04/23/2014 12:06 PM, andy pugh wrote: On 23 April 2014 16:57, Jon Elson el...@pico-systems.com wrote: Andy Pugh suggested you could run my PWM servo amps with just ONE wire/output pin What I was meaning was that it only needed one PWM channel, rather than the phase-locked 3-phase PWM that the 7i39 needs. I wasn't suggesting that it didn't also need direction, enable etc pins. It COULD be run by feeding a single signal to direction, making it synchronous antiphase. But, after having a lot of heating with some of those drives, I went to a lot of trouble to figure out how to do sign/magnitude. But, yes, a Mesa controller has a full sign/magnitude output available. I wasn't sure Florian was going to use a traditional controller and Hal for this. Jon -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
On 22 April 2014 17:24, Florian Rist fr...@fs.tum.de wrote: So, first question: Can I hook up the 7I39 to a BeagleBone Black. Well of course I can, but is this somehow supported already, so that it is simple to do? Any other driver suggestions? The problem here is that the 7i39 expects a three-phase PWM signal, and I don't think that the BBB PWM code (if there even is any for the PRU) has a three-phase mode. You would have a simpler task either using something that drives Mesa cards (PCI or parallel) and a Mesa FPGA card, or using the BBB ethernet to drive a 7i90 (I am not sure this works). Alternatively the Pico PWM brushless servo amp only needs a single channel of PWM: http://www.pico-systems.com/acservo.html Any number of off-the-shelf drives from the likes of AMC are likely to be able to drive your motor Both the Pico and AMC drives are likely to need Hall sensors on the motor. If you need to you may be able to fake these with the bldc HAL component. 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. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
Hi Andy, thanks for you comments. Alternatively the Pico PWM brushless servo amp only needs a single channel of PWM: http://www.pico-systems.com/acservo.html Ah, I see that would make thinks much easier. And I'm not forced to use the Beaglbone I could was well you a micro/nanoATX board and a MESA FPGA card. I'm jut flowing the Beagelbone news with interest and one day I'd like to use it - this might not be the right project. Any number of off-the-shelf drives from the likes of AMC are likely to be able to drive your motor Both the Pico and AMC drives are likely to need Hall sensors on the motor. If you need to you may be able to fake these with the bldc HAL component. Oh, the motor has HAL sensors and 1000 CPR encoder and a 1:50 or so gearbox. 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. Hmm, not sure if its fun for me... :-) It might just work with a G33 or G33.1 synchronised move, Oh, good idea, instead of syncing to a spindle speed I use my scanner signal. I'll think about it and see if I understand the idea and can map my problem to rigid taping. or it might need an elaborate system of PIDs and PLLs. This is what I am afraid of and is even more complicated than a PLL as not only the phase (in this case speed) has to be correct but also a position. Is there something like a PLL component in LinuxCNC See you Flo -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
I think this could be done as a geared solution, if you could work from a phase locked (to 50hz) clock at some higher rate, and use that as the encoder signal, and the 50hz as a trigger to g76 with suitable parameters it would then be synchronised and have a flyback (gate the laser off then), or use g33 or play with the gearing that can be used with hobbing, see http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Hobbing (add any logic to suit). Dave Caroline On 22/04/2014, Florian Rist fr...@fs.tum.de wrote: Hi, I'm facing a slightly unusual problem and before I head forward into the wrong direction I'd like to hear what you think about it: I have to pan a laser scanner (a single rotary axis), so I thought about using a BLDC (which I happen to have already), a MESA 7I39 BLDC controller and a BeagleBone Black. So, first question: Can I hook up the 7I39 to a BeagleBone Black. Well of course I can, but is this somehow supported already, so that it is simple to do? Any other driver suggestions? The bigger problem is that I need to synchronise the motion with a high 'frequency trigger' signal (about 50 Hz). The motion pattern needed is cyclic an has to look something like his: 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 5. goto 1. and repeat the process in reverse direction How could I use LiuxCNC/Machinekit to synchronise the motion to the external trigger signal and ensure a specific position is reached at a specific speed in sync with the trigger? The reason why I want this is to make sure the scanner captures lines at the same angular positions. The trigger comes from the scanner an indicates the start of a line capture. Unfortunately the scan process can not be trigger externally, this would be much easier, but I only get a signal each time a scan line starts. Hmm, well. What do you think. Is LiuxCNC right for the job or not. See you Flo -- 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 -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
On 22 April 2014 18:20, Florian Rist fr...@fs.tum.de wrote: Is there something like a PLL component in LinuxCNC Not as far as I know. Or perhaps the better answer is not yet. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
Hi Dave I think this could be done as a geared solution, Of couse, I forgot to mention, there will be a reduction gear about 1:50 or 1:100, the motor is not very strong and the scanner ways about 5 kg and will be mounted eccentrically, so it will create quite some torque and inertial mass. if you could work from a phase locked (to 50hz) clock at some higher rate, I guess I could build a external PLL to generate more or less any frequency from the 50 Hz, yes. and use that as the encoder signal, and the 50hz as a trigger to g76 with suitable parameters it would then be synchronised and have a flyback (gate the laser off then), I'll look into G76 (I never worked on a CNC lathe, so I haven't used it yet), but I think I don't get the 'flyback' part. or use g33 By the way, can the starting angular position of the thread be specified in LinuxCNC? The machines here running LinuxCNC do not support rigid taping (no spindle feedback), so I never used G33.1. On Sinumeric controls it is possible to set the starting angle of the thread. or play with the gearing that can be used with hobbing, see http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Hobbing (add any logic to suit). The video link in the Wiki article is broken, I guess it refers to this video, if so I'll update the articel: https://www.youtube.com/watch?v=ZhICrb0Tbn4 See you Flo -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
On 22 April 2014 18:38, Florian Rist fr...@fs.tum.de wrote: By the way, can the starting angular position of the thread be specified in LinuxCNC? Not directly. For multi-start threads you offset the starting position. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
Hi Andy Not directly. For multi-start threads you offset the starting position. So two G33.1 calls at the same position and with the same parameters or a Z offset of an integer multiple of the pitch will cut the same thread. In a way the thread starts always at 0°. See you Flo -- 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
Re: [Emc-users] Motion Synchronization to ext. trigger? (BeagleBone Back + Mesa 7I39, Machinekit?)
On 04/22/2014 12:20 PM, Florian Rist wrote: Hi Andy, thanks for you comments. Alternatively the Pico PWM brushless servo amp only needs a single channel of PWM: http://www.pico-systems.com/acservo.html Ah, I see that would make thinks much easier. You COULD, in theory, run it with just the Direction signal in synchronous antiphase mode, but this may cause the filter inductors (and maybe the motor, too) to run hot. Our servo amp was designed to run in sign-magnitude mode. That only takes TWO signals, PWM and Direction. Jon -- 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
