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 New Dmoco 6 Axis Rig Driven by DMC16 
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Joined: Wed Feb 15, 2012 3:36 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Mike, thank you, that is a site to look at after drinking a few gallons of camomile. But lots of info there.

Due to time constrains, I like the idea of buying a complete (assembled) machine, and I won't go for the largest footprint either.


Edward


Sun Jun 19, 2016 4:25 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
So how well did it perform realtime multipass? Can we see it in motion?


Wed Jun 22, 2016 5:58 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hi SL. - It may be true - that "good things come to those who wait" - but equally "if you don't buy a ticket then you won't win" :)

Meantime - I am putting rebuilding a similar scale rig at present. It uses Leadshine nema 34 Easy Servos for lift and swing and a servo for track - but is aimed at faster speeds. I'll post some results soon..

Cheers G


Thu Jun 23, 2016 12:46 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Gerald, So you recommend adding closed loop steppers when swinging a long lever like a crane arm? For some reason, I can't reach the Leadshine site today so I can't immediately read up on their benefits. I am assuming that if a second pass drifts out of phase with the first (because of missed steps), the encoder would get the shot back on track quickly instead of leaving the offset continue through the rest of the frames in the run? Would you keep the shot with the one frame slightly off, or is the alarm from the feedback a convenient early sign you need to repeat the shot with slightly less aggressive movement?

Any BTS pictures of the rig you are reworking? Is it for realtime multipass or stopmotion? Somehow I am acquiring a great fascination with multipass as I contemplate what to do next in my life.


Fri Jun 24, 2016 9:13 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hi SL.

Regarding maintaining accuracy for multiple passes. A well setup conventional stepper is no more likely to loose steps than a closed loop system. The main advantage of closed loop is smoother and quieter operation and more power at higher rpm. If a closed loop motor is accelerated too quickly or strikes an obstacle it will simply cut out and stop responding, in which case you would reset it the same way you would need to do with a normal stepper.

In practice with either system you should first test the move at a slightly higher frame rate and confirm it still runs ok. Then you will know that you have a margin and can confidently shoot multiple passes. Running steppers too close to their limit means you might experience stalls as the motors begin to heat up.

If you are being cautious do mark the start and /or end of the move on all axes to confirm position has not been lost after each take.

Hope this is helpful... G

PS the main Leadshine site seems to be down but http://leadshineusa.com is working as well as http://www.americanmotiontech.com/


Fri Jun 24, 2016 6:11 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Ah we on repeat ability and multipass again :D . Must admit its a great way to test ya rig . However how you achieve it may be up for debate . Personally i am happy with my cheap and cheerful timing belts and pulleys . I always go on results and not discussion and pulleys not let me down yet .
Just realised another advantages of pulleys now i am tempted by the speed thing . Theirs very little mechanical resistance in the gear train so your stepper is likely to attain a higher speed before stalling out . Their have been discussions on homemade HD drives the mechanical resistance and initial driving force seems quite high i dont think you would get a decent speed out of them .
The big rig as been moved and initial testing is fine . Stopframe is spot on as expected and relatively slow realtime is also spot on . Not so expected with such a long boom :D

Back on cnc routers my new project when i have time . As you can see from above vid i have a great new workshop to play with so bit busy at mo . Anyways if any body interested this is a great build http://www.cnczone.com/forums/cnc-wood- ... ost1655360 Mine will be similar but not quite as chunky.

I even like the colour :D
D1


Sat Jun 25, 2016 1:12 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
That crane is looking great! Any wobbles?

The router is chunky but very large, there is not much to them, should be quite easy to build a smaller version. I notice he uses some sort of resin/concrete stuff as a filler for rigidity.

Edward


Sat Jun 25, 2016 2:31 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hi, D1, that is an impressive video, looks like the larger workshop came in handy with that boom and the music topical :D

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Sat Jun 25, 2016 11:20 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hi Edward yes a few wobbles at the end of boom but thats to be expected really . But is it a problem ? Depends of the shot i suppose . Slow real time multipass no i dont think its a problem as clip shows . I will try some quicker moves and see what happens . I have worked and lots of adverts with manually operated cranes and they wobble quite a bit and thats never really a problem . Of course they are not doing multiple passes but i do wonder it the wobbles are consistent in a MOCO rig .
Notice the wobbles on the end of the boom of this one manually operated one .



The resin is for leveling the square section steel box as its far from perfect and square rails require a much more precise set up than round . I had to to do a similar thing on my rig as the revolve bearing could easily be distorted and the steel chassis not so level :( .
Hi Mike new workshop been a great help gonna put new router their to . Its the fellas in the vids place a good friend we hope to do a lot of work from their .
D1


Sun Jun 26, 2016 1:14 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
D1,

When I made my crane, a lot shorter than yours, a metre from yoke to end of arm, I had some problems with wobble and vibrations at the beginning and end of a move. I solved those by using a smooth servo, connected by pulley to a harmonic drive. There was quite a lot of reduction involved, but servos are fast, so this helps. This was the answer for the sway move. Any vibrations in your motor will be severely amplified as they travel through the arm,

For the lift, that was more complicated, as the HD introduced some dancing of its own, at some frequencies, maybe due to the internal flexing of the HD, who knows. Also, as an example, just take a long pole and attach some weight at either end watch it oscillate:) My arm was 4mm aluminium box, so quite rigid.

Maybe I needed a bigger HD. But that was a lot of money to spend without being certain of the outcome, So I decided to go for a specially made mega large pulley, about 300mm in diameter with AT5 16mm wide red belt also driven by a servo. Our friends at BeltingOnLine made two of these for me, and it didn't cost too much, maybe around the £150 each I seem to remember. The efficiency of this was very good, i.e, the servo needed very little effort to move the arm. But I still got some oscillation, although it was a vast improvement.

Then, as an afterthought, I removed some tension from the belt, which BTW had no idlers, as idlers can increase the rhythmic wobble due to the changes in torque, for instance when changing direction of movement or when accelerating.This belt tension adjustment was mega critical, but I found a good setting and the wobbles disappeared. I guess by varying the tension I varied the frequency at which the arm resonated. But I am no engineer, I just try things until I stumble into a solution.


But your question is: does it matter? Well, if you edit out the beginning and end wobbles, then no problem. But what if you have to do a job where the creative director or some other pundit insists on finishing or starting a move from zero? There is no way you can correct these wobbles/vibration in post, no way. And they do show on the actual movie, well I can see them, maybe other people don't, but if I can see them and can be very frustrating. So as far as I am concerned, yes, for real time moves, it does matter. For stop motion, it doesn't.

Edward


Sun Jun 26, 2016 2:26 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Nice! Especially that wood! It really makes it. Are you sad now DMAN? No more DMC. So, in your opinion is it worth the money to have the realtime?


Sun Jun 26, 2016 6:25 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Glad ya like the wood actually mdf but close enough . Still got the DMC for a few more weeks and i do like it a lot if it could interface like Mantis it would be perfect.
So think i am going to have to get both if funds go well this year .
Just been watching Dan Gilbert vids great https://www.youtube.com/user/dgelbart/videos
D1


Sun Jun 26, 2016 6:35 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Thanks very much for the demo and the multipass. This will go a long way in helping me convince people here who say its impossible. The multipass of the triplets is very impressive, even if you don't know them. The rig itself is awesome. A work of art as well an an engineering masterpiece with incredible precision.

Yes, I do owe you a similar demo with the robot arm. Sorry, I have gotten really bogged down, taking on too many different projects all at the same time. The truth about the robot arm is sad. it sits in its crate in the hallway of my home where it has been since I finished the build. The grinding noise when the dolly ran in the demo was just the stepper losing steps because I had the jog speed too high. It runs smoothly at a more reasonable speed. I tried to interest the kids in doing some stopmotion with it, but they are too young to pay attention to anything long enough to accomplish anything. They got the crayola easy animation studio for Christmas and never got the app, so the puppet got thrown away when their mom cleaned up. I have high hopes of getting out the robot and shooting some miniature stopmotion sometime, but I am crazy. I now aspire to build a much larger, more expensive crane rig for no apparent reason. I should stop making and go out shooting with what I already have, which is more than most photographers could ever hope for. Instead, I go out to the garage and build. Don't ask why cause I don't know.


Mon Jun 27, 2016 10:29 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hello SL i am sure their is a use for the arm i still think they would be very good for plant timelaspe you could get some really nice moves with it.
More testing on PT head which i emphasize is geared by simple cheap timing pulleys and belts nothing exotic at all . Its not outrageously big either in fact its as big as it needs to be to accommodate a standard DSLR i could make it smaller and lighter if i wanted to . I am just trying to answer some discussion on the merits of timing pulleys . If somebody can offer something as quick and accurate for a simalar cost without expensive HD drives i would consider using it but as it stands pulleys work very well indeed . I can make it got faster by the way :D


Three passes overlaid and offset notice no ghosting at all
D1


Mon Jun 27, 2016 2:30 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hey - D1 you are being funny about the ghosting? Panning is fast for sure..

But in the first 5 seconds, before you go obviously out of registration, if you slow down the playback frame by frame (have to download and examine in an editor) - it's clear there is "displacement" of the passes, and the faster the pan the greater the offset.

This is most likely due to lack of camera sync ... as mentioned elsewhere... ;)

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Tue Jun 28, 2016 1:05 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Most def camera sync as start and ends dont have ghosting on the smiley (which is what i meant by way ) If their was ant play in the system or dropped frames the smiley would be offset. Theirs three passes their all stacked as i say no ghosting on static smiley . What goes on with video and shutter sync i will leave to you as i know nothing about it but i still stand by my statement its good for cheap timing pulleys ;) . This is all new to me as stop frame is my usual norm . Do like going fast though :D
D1


Tue Jun 28, 2016 10:59 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Although I haven't gotten far enough on the build for it to be an issue, now seems like the perfect time to ask. Gerald, can a Canon 6D or Sony A7s shutter synch with the Mantis box? If not, what feature should I look for in a camera that can shutter-synch with the rig at realtime speed? This is never a problem with stopmotion because the shutter is triggered directly by DF.


Wed Jun 29, 2016 7:30 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hi SL A good question... With Mantis you can use any camera, (with some gotcha's) from which you can extract either a standard definition video signal or a TTL shutter pulse. In the case of DSLR's shutter pulse is non-existant - only professional cine cameras have this.

So you are left with video sync. If the camera only has HDMI out then you can use a converter. But first the main gotcha. I have tested a few DSLR cameras but not the Sony. In general, each time you start and stop recording, the phase relationship between video out and camera shutter actually changes randomly. So this might appear to make these cameras useless? However there is a trick which is useful for testing purposes - if you leave the camera recording, and make your passes as part of a single take - then there will be consistent sync. Obviously for working on actual productions this is a bit impractical. In those case it will depend if you think you can get away with less than perfect, or else use a camera that can provide proper sync.

I haven't tested every camera in the world, but Red cameras certainly provide a shutter pulse. Ironically, old school analog composite video cameras will work fine too... :)


Wed Jun 29, 2016 5:16 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Going even farther off topic, I looked at ebay and found some Red One 4K cameras at prices I could afford. Then I started checking on shutter synch and found this first model of red apparently doesn't have a shutter synch. Red User Forum users suggest what sounds like the same video frame synch you mentioned.

So if i wanted to shoot some passes in one location, then take the rig somewhere else to shoot the background for example, I'd need one of the newer red cameras or something else with an actual shutter synch socket? Otherwise the video synch could be out of synch by a frame because of the DSLRs quirky behavior of resetting the video synch by up to a frame each time the camera is turned off and back on again, is that correct?

And the socket I want to find on this more-expensive camera, is that whats called genlock? And if so, does the camera generate the genlock signal for the rig to follow, or does Mantis supply the signal, or do I need a separate genlock clock to synch both the camera and rig? This is all so interesting! we hardly ever get to talk about realtime MOCO on the forum.


Thu Jun 30, 2016 8:53 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
How noticeable is this sync problem ? I cant think when ever i would pan and tilt at such high speeds as my last test unless i was doing slow mo work . That would prob need a camera like the Phantom and i have a hunch thats synced to hell .
My first test with full rig was shot at a reasonable speed i would imagine using most of the time . It looked ok to me and every other average bod would think the same i would imagine .
D1


Thu Jun 30, 2016 11:29 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
My black frame video was synced using the sound track (stepper motor start noise shape) , I know the sound can be a few frames out (5D2) but as long as it is out by the same amount on each pass does it present practical or just theoretical problems for the finished video.

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Thu Jun 30, 2016 1:29 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
I think Gerald is on about some sub frame level sync its easy enough to match frames but apparently their can be drift within a frame ? But as i say i know nothing As a matter of interest all my passes where recorded without stopping the camera so ya would think it would be synced shutter wise ?
D1


Thu Jun 30, 2016 1:39 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hi guys.

I think we have to first distinguish between camera shutter (phase) sync and basic lineup. In Mike's case he is talking about recording an audio track played back by Mantis, as a way to line up passes. This is similar using the bloop light in Mantis. It provides a flash which can be recorded visually by placing an led in the frame. In post it helps to line up passes more quickly.

Normally I would roll the camera first, then start the moco, and once the bloop has fired, quickly remove it from the frame if necessary. Mike's method has some advantage since nothing has to be removed from the frame. In practice it is not always necessary, since you can normally find the fastest part of the move and nudge one of the passes in the timeline using a mix or splitscreen to observe the correct alignment.

However - this type of reference is quite distinct from shutter phase sync and only gets you to the nearest frame. Shutter phase can be better understood if you consider how it was done in the days of Mitchell film cameras. The camera was fitted with a stepper drive motor controlled by the motion control program as an additional axis - but designed so it would only run in the forward direction! This made certain that for every pass, the point at which the shutter was open always corresponded to an exact sub-frame position in the move.

In the case of shooting 3D, phase sync is also an issue, since the two cameras need to be locked so that every frame is recorded at the exact same instant. The reason for this is when the camera shutter angle is say 180deg, then half the time the shutter is closed and the other half it is recording an image. So if the cameras are out of phase they will be recording images at slightly offset positions during movement of the subject or the camera. Professional cameras take this into account by running both cameras from a common sync generator, which might be timecode or a tri-level video sync signal or other proprietary system.

In Mantis I use a simple technique where the camera is a master and the moco a slave. Either the video output from the camera, or a TTL shutter pulse is used. The procedure is : when sync is enabled, you press play, then Mantis actually waits for a sync pulse before starting the move. Because this is done with very fine micro-second timing by the hardware controller, it is extremely accurate. Once the moco is rolling it relies on the timebase of the camera and the motion control to maintain this sync. (The camera and moco timebases are both locked by individual internal crystal generators.)

In Dragon Frame you don't have this hardware feature, so phase sync is not possible - even if you keep the camera rolling between takes... Though perhaps if you were using an old time film camera you could assign one channel as a camera axis and drive it like the old days.. :)

In terms of slow and fast moves, it is true that for slow moves, sync is less critical if the difference between frames is very small. However, even a slow moving camera can cause visible offset, if for example an object is close to the camera as it moves past. Really it depends on the speed of an object relative to the field of view - ie. how many pixels it moves between each frame...

Note that phase sync is independent of the repeatability and general accuracy of the rig. Hence when the camera stops moving, the lineup will be as good as the mechanics of the rig, as seen on D1's test.

Finally - a technique for testing sync is to run a small stepper motor with a disk mounted on the shaft. Mark the disk clearly with a bold line - using white on black for best contrast. Then program the motor to turn at constant speed, and at some interval of the camera frame rate. For example so the disk turns one half revolution for each frame of the camera. At 25fps this could be a speed of 12.5 revs per second. Then film the disk full frame with the camera locked off, using a narrow shutter angle to reduce motion blur. Looking at the playback, the mark on the disk should be frozen - as though you were using a strobe light to illuminate it. And for each pass, if sync is successful, it will always be in exactly the same position. Without sync you will find it is frozen in random positions. Every now and then you might get a pass that does match, but this will be a matter of chance...

I hope this clarifies sync?

BTW SL. For passes shot at different locations, sync is not necessary. It is only required for multiple passes of the same scene. What early model of Red were you looking at? They often have firmware updates and there may still be a way. Just email me the model and I'll check for you. G


Thu Jun 30, 2016 4:50 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Your are right D1I was off track ;) slightly.

Hi, Gerald ............ Gotcha :D Good clear explanation.
Without looking at the manual it looks like I may be able to use my Shogun Flame with Mantis instead of sound track as it has video out feed as well as Timecode and Genlock to get familiar with.

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Fri Jul 01, 2016 12:35 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Mike, I have been looking into genlock and found some of the nicer atomos units have it. I'm becoming tempted to get one for shooting 4K with my Sony A7s. That little camera has a lot going for it as a cinema camera. It has internal focus peaking and zebras which is way cool, and you can get a very reasonably priced 50mm f0.95 lens from Mitakon Zhongyi. With this lens, the camera can record 30 frames per second video by moonlight or with a real dark ND filter, shoot insanely shallow depth of field stuff in the daytime.

D1, thanks for the education on multipass. I'm amazed the composite looks so good without sub frame level synch. I would have knocked myself out trying to achieve finer and finer resolution of movement without realizing the bottom line is what works for the shot being done today. Movements done at a reasonable speed synched by a flash or sound to within a half frame of synch is so brilliantly simple.

Gerald, There are a whole bunch of red one mysterium-X cameras on ebay between 3 to 6 thousand US dollars. My brief look at the manual informed me that it can apparently be connected to an external tristate genlock signal so two cameras can record 3-D while having their shutter opening times synchronized. Is there some way to have the rig also synch its start of movement to the same genolock signal so multiple passes can be repeated with sub-frame-level accuracy? It sounds like the genlock is different from a TTL shutter pulse, which I got the impression the red one mysterium-X does not have. Is there a workaround using a separate genlock device? If so, it might let me use the little Sony camera with an Atomos 4K monitor/recorder. I guess thats two questions. Can I use the red one? and can I use the Sony A7s with the atomos shogun flame series recorder which claims to have a genlock socket?

And sure, a good composite can be made without synching the camera shutter to the rig, but I'm intrigued by the idea that it could be. All that precision may be useless if my mechanicals flop around when moved aggressively, but I'm in build mode and want to learn as much as I can from the experts here on the forum. The more inquisitive I get now, the smoother things go when I revert to shooting mode and try to actually use this stuff.


Fri Jul 01, 2016 2:18 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hi SL..

With the Red One there is no shutter pulse output. However you have two options

1. Use a tri-level sync generator as common source for Camera and Mantis. The cheapest genlock I can find is this :

http://www.digikey.gr/product-detail/en ... ND/1867888

At ~ $300 it will require some DIY electronics knowledge... otherwise a good commercial generator will cost $600 or more.

2. Alternately use an SDI to composite video converter such as a RedBack Decimator or this AJA converter at $250.

https://www.aja.com/en/products/mini-converters/d4e

Using this - Red One SDI output is converted to SD which Mantis can sync to.

Second method seems preferred to me, it is less convoluted, and as I recall the Red One might appear to lock up if the sync source is turned off... :(

Btw - RedOne is not ideal for motion control (heavy and bulky) and takes ages to reboot. But the pictures aren't bad... A7 is great for low light, and if you can get it in focus at 0.95 that will be a bonus! Also look out for the GH5 when it appears...


Fri Jul 01, 2016 7:21 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
James, for quoted 1.5hrs battery life read approximately 15mins per battery, makes no difference using quick charge or long charge via Sony video recorder, not tried my large capacity Sony batteries or external battery options to date. You will also need some serious storage solutions if using hi res options and hi spec. Mac /PC for video processing and/or plenty of patience ;)

D1, well and truly off subject but very interesting ;) How is your rig progressing since last update? Restarting machining arms and bearing for my "C-slider" after my old PC gave up the ghost, "new" replacement £50 from flee bay, will be a while before pictures as I will be working during showers ;)

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Fri Jul 01, 2016 11:49 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hi Mike rig sat in workshop at mo needs a bit of internal wiring sorting out which will be this weekends job . Will be sad to see it go but i have learned a lot . My only slight niggle is the ballscew on the boom. It works great adds a huge amount of strength and stability to boom but its slow compared to head . This wasn't a problem until i got bitten by the speed bug :D It also as the problem its not a standard angular rotation so been driven by a CGI model will be difficult :( So unless i resolve these issues i may have to approach it differently . This may give you a hint of the direction i am looking http://www.ebay.co.uk/itm/TRIUMPH-1300- ... SwrklVAx-2.
The video sync problem as been a good of topic will do more test and see how much of a issue its in the real world . I wonder if you like motion blur any lack of sink will get lost in the blur caused by a long exposer ?
GH5 camera looks interesting looking forward to next batch of full frame shutterless cameras . Really not enjoyed my Nikon will be glad to move onto something else wonder how much i can get on ebay for it .
D1


Sat Jul 02, 2016 1:19 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
DISPLACEMENT 1 wrote:
Hi Mike rig sat in workshop at mo needs a bit of internal wiring sorting out which will be this weekends job . Will be sad to see it go but i have learned a lot . My only slight niggle is the ballscew on the boom. It works great adds a huge amount of strength and stability to boom but its slow compared to head . This wasn't a problem until i got bitten by the speed bug :D It also as the problem its not a standard angular rotation so been driven by a CGI model will be difficult :( So unless i resolve these issues i may have to approach it differently . This may give you a hint of the direction i am looking http://www.ebay.co.uk/itm/TRIUMPH-1300- ... SwrklVAx-2.
The video sync problem as been a good of topic will do more test and see how much of a issue its in the real world . I wonder if you like motion blur any lack of sink will get lost in the blur caused by a long exposer ?
GH5 camera looks interesting looking forward to next batch of full frame shutterless cameras . Really not enjoyed my Nikon will be glad to move onto something else wonder how much i can get on ebay for it .
D1

Couple that ring to a starter motor and the rig should fly -(wheel) ;)
Plenty of interesting developments in new cameras now the the "pixel race" is not so important, global shutter will hopefully become more available as video starts to play a more important roll in "still camera" production. Lighter weight, lighter, more responsive rigs should also be a future trend. 8 axis rig in a backpack would be an interesting project :D
My Axiom should be with me sometime in the Autumn but I would realistically expect late 2016 early 2017. That's one reason for the purchase of the Atomos Shogun.
Back to the ring, I think Doug uses motor cycle gears for his rig so some useful tips from him maybe.
Off topic, picking and shelling broad beans for the freezer this morning before they get too old.

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Sat Jul 02, 2016 1:45 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hey DMAN,
I also got bit by realtime speed when I was using that linear slide for boom movement. Then I took a look at the little crane over at Pacific Motion Control, I forget the name, but it uses a semi circle of steel with a timing chain wrapped around it. With a couple of tensioners it seems to work great. The motor connects via a Sorenson drive so it is a worm gear in there but you could build a belt drive just as easily. I went with the direct apporoach but I'm not moving any significant weight. And you would save a lot of weight. Maybe worth a small redesign?


Cheers.


Sat Jul 02, 2016 8:12 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hi Doug yeah in two minds on what to do the ballscrew is def zero backlash which is very good and perfect for stopframe . I can also prob up the speed by introducing a 2 to 1 belt drive and uping the micro stepping from 16 to 32 to retain the same resolution .Theirs more than enough torque in the motor to cope with the up gearing . I am still left with the problem of translating the linear motion to a form i can use in a CGI interface . I know the ballscrew as a pitch of 5mm so with 32 microstepping / 6400 steps equals 5mm of travel on the ballscrew . With a bit of Pythagoras it should be possible to work out the angle i assume .
The theirs is the chain option as you say but i think i prefer the starting ring and pinion gear which is more or less what i have with the revolve on the crane at the mo . It offers a very direct drive with no play and can go fast .
I will by one and do some test when i have the big CNC built . I may even be able to machine my own we will see .
D1


Sat Jul 02, 2016 1:08 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Speeding up the ball-screw might work. I have run small linear drives at high speed using a servo motor, and they flew. But if the screw is not perfectly balanced it could vibrate.

For boom lift I am using a cycloidal gear as used in robots. Very fast speeds are possible, suspect I could match Bolt on a vertical move, but they are expensive.

Meantime - Chain drive seems like a good alternative, and driven by a worm gear as Doug suggests, it will be rigid like a ballscrew. Though a good planetary gear may work just as well... I have also seen a slew axis driven by a large synchroflex timing belt.

I think with any approach, the devil is in the detail...


Sat Jul 02, 2016 3:45 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Yes the devil is in the detail one of my favorite comments been a model maker . ;)
Had a rethink on ball screw you can get different pitches. I do happen to have a very large pitch one in shed taken off the rostrum camera. But was thinking a 20mm pitch would give me the speed i would need http://www.ebay.com/itm/Ball-Screw-and- ... 1319260088
I was worried about vibration too but on the new rig the ballscrew is isolated buy a openrails slider and theirs now play in the mounting points . Its that very rigid triangle again and i would like to stick with it if can solve the CGI thing . The ballscrew means more of the boom is supported at the rear where the weights are and i think this cuts down resonance etc .
I am finding most drive transmission can be felt in some way You can feel the teeth disengaging and re engaging on my rack and pinon track if you place your hand on the drive unit . It doesn't seem to be noticeable final image though . Likewise large teeth timing pulleys and belts can be felt engaging and disengaging .HTD 5 its quite noticeable but again it doesn't seem to effect final video .Edward as mentioned very fine resonance in some of his drives i do wonder if its the timing belt causing some of this ?
D1


Sun Jul 03, 2016 1:58 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Me again ! Well apparently you use the Law of Cosines SSS to solve for the angles given the length of 3 sides . Yes i didn't pay much attention at school :D
Found this handy calculator to make up for my inability to get my head round maths http://www.free-online-calculator-use.c ... lator.html. I was hoping their would be some automatic excel or open office thing for this but unfortunately not . I suppose it should be possible to create my own solver in a spread sheet :( and use this to convert length ram to angle of boom and vice versa . I still wonder how precise a match between moves you would get .
D1


Sun Jul 03, 2016 3:22 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
DISPLACEMENT 1 wrote:
Me again ! Well apparently you use the Law of Cosines SSS to solve for the angles given the length of 3 sides . Yes i didn't pay much attention at school :D
Found this handy calculator to make up for my inability to get my head round maths http://www.free-online-calculator-use.c ... lator.html. I was hoping their would be some automatic excel or open office thing for this but unfortunately not . I suppose it should be possible to create my own solver in a spread sheet :( and use this to convert length ram to angle of boom and vice versa . I still wonder how precise a match between moves you would get .
D1

Do you have a sketch of what you want to calculate?

Just finished two arms and 4 bearing blocks, the first two took 2 days with PC problems and the next two around 2 hours including turning the arms over because tool length was 38mm and the arm depth 50mm. One more set to go and then to design the plates to hold the arms, camera and counterbalance weights....... Oct..... Nov ;)

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Sun Jul 03, 2016 9:38 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hi Mike sounds like you putting those carbon fiber tubes to use :D What Pc ya using ? I use one of these tested a few and this gave best clock results
[flickr]Image2016-07-03 19.03.25 by D 1, on Flickr[/flickr]
Dell Optiplex i changed the bios settings running one core seems best . Been running for ages now and not a single glitch .
Havent got crane her so cant do exact measurements but basically two sides of a triangle stay the same length and one side the ram changes length changing the corner angles . The angle of the boom in other words . If i can create a spread sheet formula i could simple convert all key frames from mm to angle for the boom if that makes sense . I need to sort this for my model mover hows the motion sensor going by the way ?
Quick pick of the ballsrew i have in shed think its about 20mm pitch but a bit long for a crane boom :(
[flickr]Image2016-07-03 16.28.02 by D 1, on Flickr[/flickr]
D1


Sun Jul 03, 2016 10:44 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hi Mike just a quick screen shot of SSS triangle calculator . Lets say side C is the boom ram current length 120 i need to get all the maths into a spread sheet . I will have a go . The C length will change A and B will stay constant .
[flickr]ImageScreenshot (265) by D 1, on Flickr[/flickr]
D1


Sun Jul 03, 2016 11:49 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Well seem to have managed to duplicate the function of the Triangle calculator http://www.free-online-calculator-use.c ... lator.html over to OpenOffice
[flickr]ImageScreenshot (266) by D 1, on Flickr[/flickr]
My version
[flickr]ImageScreenshot (267) by D 1, on Flickr[/flickr]
Will load some key frames into Dragon and see if the angles are near enough
D1


Sun Jul 03, 2016 2:29 pm
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Dell Optiplex - Snap ;) 755. Got without operating system, my XP was Pro but SP2, so had to get SP3 update, that was no longer available from Microsoft, also no drivers for the LAN so could not connect to internet to find updates - Chicken and the egg syndrome, All ok now.
That looks a mean ball drive you have uploaded. Back to calculations, a bit thick here ;) These are to keyframe the "camera" position in DF, so you are taking the linear movement created by the ball screw or does it create a circular movement. That movement is then translated to a circular movement at the camera (end of boom). I did a linear to circular movement a long while ago using polar to Cartesian coordinates to plot the key frames. There is an online calculator :-) So would be interested in the results from your first trials.
Now back to my bit of hay making whilst the sun doth shine 8-)

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Mon Jul 04, 2016 12:54 am
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Post Re: New Dmoco 6 Axis Rig Driven by DMC16
Hi Mike dont mention Cartesian coordinates just got me head round how to determine a angle from the length of the sides of a triangle .But think what you are saying is a ram doesn't produce a constant sweep or shall we say rotation. Dont think it maters in my case as long as theirs a measurement for length of ram and angle for each frame both will have the same inconsistency's . I think ?
[flickr]ImageScreenshot (266) by D 1, on Flickr[/flickr]
In the illustration at the bottom imagine the 109.665 side of the triangle been the ram that moves the boom the 90 degree angle is the fulcrum of the boom . I can convert the length of the ram to a angle of rotation of the boom . Again i think ! so yes this could be put into my Blender model of my crane or Dragon or Mantis if i do SAS triangle solving . All this because i want to keep my ballscrew ram :)
D1


Mon Jul 04, 2016 11:45 am
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