It is currently Fri Oct 23, 2020 3:00 am




Post new topic Reply to topic  [ 647 posts ]  Go to page Previous  1 ... 13, 14, 15, 16, 17  Next
 New Project 7 Axis Arm Rig Controlled by Blender. 
Author Message
User avatar

Joined: Thu Mar 10, 2011 11:38 pm
Posts: 585
Location: Exmouth, Western Australia
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
I still think a microswitch connecting a pin to ground is the simplest option to implement. Whatever method you choose, repeatability is the key. This will be affected by how fast the system responds to the pulse and is the response time always the same? You would need to use an interrupt routine on the Arduino to ensure that.

I think it was in the LinuxCNC documentation that I came across a description of their zeroing process: The motor runs until it hits the microswitch. Then backs off a few mm and approaches again at low speed. This minimises the effects of inertia, vibration and any slight variations in system response time. You will need to consider these issues regardless of how the actual "I'm Here!" pulse is generated.

This process needs to take place after DF has started and settled down. You could do this with a manual button, but that risks you forgetting and requires yet another pin. The first serial data that DF sends to the Arduino is 'HI'. The Arduino then responds with it's software version number, confirming it really is running DFMoco software. This happens once, every time the USB connection is remade. You might try modifying the response to 'HI' to include the zeroing routine.

Brain-dump over :-)

Kit


Fri Sep 11, 2015 4:19 pm
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Hi Kit thanks for input you understand arduino and code better than me . Yes i have seen how CNC homes work with the back off and slow approach . This approach may give a reasonable result but i am not sure if it would be accurate enough.
I would like to mount what ever sensor it is on the stepper rather than the rig itself . If i am using 16 microstepping i get a 3200 step resolution on the motor shaft . I think a printer encoder may be able to cope with this but could be wrong . Not sure how i could mount a micro switch on the stepper which is going to do a lot of revolutions before it gets to home .
You may have noticed on may design the slot on the encoder on the final output shaft of the gearbox is larger than that of the stepper encoder . So in my simplistic system you run DF as normal it will have returned the motors to what it thinks is home when you last closed it down . So when you power up DF then you simply jog the motors to what is really home which shouldn't be to far off close down position if it hasn't slumped to much. The bigger slot will light first and at this point i will just jog incrementally until the second led corresponding to the much finer slot on the motor shaft is illuminated . When both leds a lit you are precisely at home in a similar way to how a CNC approaches it .
As i said it would be nice to integrate this into the DF sketch but i think i can get a working solution without it .Have you had to leave any shots over night yet ? I do worry about leaving rigs powered up for days on end shit happens :(
D1


Sat Sep 12, 2015 3:11 am
Profile
User avatar

Joined: Thu Mar 10, 2011 11:38 pm
Posts: 585
Location: Exmouth, Western Australia
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
D1,
I have left my rig powered up overnight. In the morning the camera had tilted down enough to show a small vertical jump in the sequence. I assume this was due to the change in temperature as all the motor drivers had been powered up all night as had the laptop with DF running. Either that or the mice in my shed/studio jumped up and down on the camera while I was asleep! My rig is much more loosely engineered than your own, however.

assuming a disc on your stepper of about 30mm diameter, you're looking at a movement of around 0.03mm per step at the outer edge. If your optical sensor can reliably detect the position within this resolution then I'm going to stick my neck out and suggest you will get more errors from changes in temperature, flexing of the belts and other mechanical inaccuracies than from errors in repositioning. Others on this forum will have more expertise with these sorts of issues than I have.

Kit

P.S. You've mentioned that this thread has got rather long now, but it has been, and continues to be, a great collection of wisdom and has inspired a lot of creative thinking and discussion among your regular readers.


Sat Sep 12, 2015 4:33 pm
Profile
User avatar

Joined: Tue Nov 24, 2009 7:55 am
Posts: 951
Location: UK
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Hi, D1, if the inaccuracy of your initialisation position is down to start up movement (alignment of the stepper poles) then a 0.9 degree motor should reduce the problem by half at the motor shaft ? Higher gearing if possible will proportionally reduce the movement at the output shaft. Making the rig inherently more accurate should then reduce the need for electronic sensing unless I have missed something very basic and that environmental changes are not coming into play as Kit proposed.
Nearly ready to carry out some metal machining, did a bit of MDF milling last week but put it down somewhere and lost it before I could photograph it :oops:

_________________
Smile, it gives your face something to do!

http://www.vimeo.com/user1214873/videos
http://www.youtube.com/user/MrReggub


Sun Sep 13, 2015 12:45 am
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
MikeA wrote:
Nearly ready to carry out some metal machining, did a bit of MDF milling last week but put it down somewhere and lost it before I could photograph it :oops:

Put my butter in the microwave the other day took me ages to find it .Well it sort of looks like a fridge its got a door :D .
Hi Kit odd if you had movement on your rig overnight if it was powered up . Are you on a wooden floor it could be your house moving . Are sink holes common in your area ? A fella and his bed disappeared overnight in the states i would suggest tying a rope to your ankle just in case .
Back on topic ;) The home thing is just not a over night thing . If the motors stall out for what ever reason during a take you are stuck so the higher resolution stepper wouldn't help in this case . Having a precise home means you can reset and continue take from ware the whoops happened . I know this is all very animation specific sorry timelapsers .
I have been doing some test with encoders scrounged from me bits box . Broke two before i got anyware :( for various reasons
[flickr]Image2015-09-12 16.39.55 by D 1, on Flickr[/flickr]
[flickr]Image2015-09-12 18.37.38 by D 1, on Flickr[/flickr]
It reads the slot i made and drives a Led without the need of a arduino easily and will attempt i much finer one today . The problem is its not a simple sees light its on no light its off . These are quadrature encoders not switches it sort of latches on the when theirs a change of state . Found these very nice the encoder with out disc is about £20

They have a 5000 resolution but not sure if this a combination of the three sensors. They are prob more complicated than i need you can just get optical switches http://uk.rs-online.com/web/p/slotted-o ... s/7884947/ but they don't seem as accurate as the quadrature sensors .
Will carry on Kit doesn't seem to mind my waffling . I have come across rigs that home perfectly with out any problems of temp change etc . In fact pro rigs just do unfortunately i don't have access to any at mo wish i had made notes when did .
As i side note i want all the sensors on the gearbox a) for greater accuracy and b) because its neater i wont have to run wires every ware
[flickr]ImageScreenshot (221) by D 1, on Flickr[/flickr]
This is the proposed arm drive set up
D1


Sun Sep 13, 2015 1:43 am
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Me again had a productive today :D Sorted out a quick fix with LED latching on prob i found combining the output from A and B phase caused the LED just to illuminate when the gap appears. This is a schematic of the sensor their is some sort of logic arrangement which i think caused may latching on prob . Can you tell i actually don't know what i am doing !
[flickr]Imageencoder_schematic by D 1, on Flickr[/flickr]
So made up a proper disc and increased the diameter to 80mm just to give me a better resolution with .25mm gap
[flickr]Image2015-09-13 18.27.42 by D 1, on Flickr[/flickr]
[flickr]Image2015-09-13 16.49.06 by D 1, on Flickr[/flickr]
The gap was made using a jewelers .25mm coping saw http://www.cooksongold.com/Jewellery-To ... de-972-060 . I can get these down to .18mm but i think i will mill the final thing . I can get a .1mm mill which is tiny their used for milling PCBs http://www.crownhill.co.uk/product.php?prod=2211
So i connected everything up to DF and got really good results .
[flickr]Image2015-09-13 18.48.29 by D 1, on Flickr[/flickr]
Set home to when LED was illuminated then jog back and forth a bit then hit home again . LED lit again when home was reached . I then tried to find home just by using the led every time it was spot on or .003 degrees out either way , but mainly spot on . The reading is not degrees of the stepper but that of the actual rotation after the gearbox . It would be great if it was a .003 drift of the stepper but even so i think i can live with a .003 degree at th final out put . If the camera is moving that amount of drift shouldn't be noticeable.
Found another sensor that may be suitable http://www.pepperl-fuchs.com/great_brit ... odid=38808 I cant believe their isn't anything out their that doesn't register a precise stop point on a rotating shaft using a slotted disc . Still not a expensive solution so far so think will go with it .
D1


Sun Sep 13, 2015 12:04 pm
Profile

Joined: Wed Feb 15, 2012 3:36 pm
Posts: 408
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Hi D1, I'm trying to understand what you are doing.I find this subject very interesting.

How do you hit home (i.e. LED on) from a completely random position? Is it simply by jogging to and fro until the LED stays on? Can you jog single frame by frame, or step by step?

If so, how do you know if you are on the correct turn of the shaft and not 360 degrees ahead, or 360 degrees behind, for instance.

Lets's say you have an articulated arm. You switch off the power and unfortunately the arm drops a bit due to the payload, etc. Two of the motors have shifted position. How do you reposition the arm to the previous position? Because of the gear ratio, it may be quite difficult to know the exact turn of the motor.

Edward


Sun Sep 13, 2015 2:44 pm
Profile
User avatar

Joined: Tue Nov 24, 2009 7:55 am
Posts: 951
Location: UK
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
An old trick for making "slit beams" was to create a slot using the edges of two razor blades brought close together. For experimenting and if they will pass through your sensor slot you might try positioning a couple of pieces of blade over your existing slit.
Also finding your work interesting and I expect many have spun many of your S. M. ideas into the realm of time-lapse.

Still looking for the gear, re-cutting with new G code starts today hopefully, added an extra through hole for piece of string ;) ;)

_________________
Smile, it gives your face something to do!

http://www.vimeo.com/user1214873/videos
http://www.youtube.com/user/MrReggub


Sun Sep 13, 2015 10:20 pm
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Hi Edward its possible to obtain absolute position because their are two slot sensors on different parts of the gearbox
[flickr]ImageScreenshot (215) by D 1, on Flickr[/flickr]
When both LEDs corresponding to the sensors are lit you are at home even if the sensor on the stepper may a have rotated many times the one on the output shaft hasn't . Hope that makes sense . It doesn't take long to home manually and i can live with it but it would be nice to automate it . For what is effectively about £20 per gearbox for absolute home its not bad .
I Mike i like the razor blade idea . Are you saying i decrease the slot on the sensor to that of the size of the slot on the wheel so when the two slots are aligned that's the only moment light will fall on the sensor .
Going to order a few of the cheaper slot sensors and see how i go . Still think their should be a off the shelf item that does this but looked everywhere and i cant find one . Any ideas people ?
D1
Ps with my very simple maths i have worked out if i had a sensor disc with a diamerter of 110mm and a slot of .1mm that should give me a step resolution of 3200 .Could be wrong though maths never my strong point :(


Mon Sep 14, 2015 12:04 am
Profile

Joined: Wed Feb 15, 2012 3:36 pm
Posts: 408
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Yes, I see what you mean using two sensors. There is only one chance when both sensors will light if placed on different ratios of rotation.

Good idea, even though it's a manual finding of the home spot.

Edward


Mon Sep 14, 2015 4:17 am
Profile
User avatar

Joined: Tue Nov 24, 2009 7:55 am
Posts: 951
Location: UK
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
DISPLACEMENT 1 wrote:
I Mike i like the razor blade idea . Are you saying i decrease the slot on the sensor to that of the size of the slot on the wheel so when the two slots are aligned that's the only moment light will fall on the sensor .
(


I guess you could do that, I was looking at a method of controlling the slot width and altering it without the need to machine it accurately.
Make a slot, width not critical, then glue part of the blade to cover the edge of the slot with another piece of the blade covering the other edge, place a shim in between the two blades to create the slot width and glue / tape the other blade in place.
The advantage of the blades is the very sharp edge definition the slot will have and the slot width will be governed by the shim thickness. Variable width slot can be produced with no additional machining required

_________________
Smile, it gives your face something to do!

http://www.vimeo.com/user1214873/videos
http://www.youtube.com/user/MrReggub


Mon Sep 14, 2015 7:51 am
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Hi Mike yes that makes sense but going to try and reduce the aperture width of the sensor to :D Just don't have any razor blades at mo me a beardy !
Slot and encoder making wont be to much trouble if i ever order a new tube for my laser cutter. I can cut incredibly fine slots with that and it will produce a nice clean edge in thin black acrylic .
Had another look for off the shelf rotary position sensors . It may be a hall effect device but i no idea how sensitive these things are http://www.allegromicro.com/en/Design-C ... Guide.aspx.
Think will stick with the optical option though if its good enough for almost every printer out their then its good enough for me .
Have you cut any ali in anger yet ?
D1


Mon Sep 14, 2015 8:17 am
Profile
User avatar

Joined: Thu Mar 10, 2011 11:38 pm
Posts: 585
Location: Exmouth, Western Australia
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
D1,
I'm surprised there isn't a simple OTS solution out there. You could always make your own with an LED and a phototransistor embedded in something suitable. Options are a nicely machined/cast bit of plastic or a gob of Knead It :-)
There are squillions of circuits available via Google for how to wire it all up.

For those of us without the laser cutter, a clear (or translucent) disc, painted black and then scratched with the previously mentioned razor blade may have to do.

The DIY solution may be more prone to stray ambient light but I'm sure you could work you way around that.

Kit


Mon Sep 14, 2015 4:38 pm
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Hi Kit i tried the clear acrylic painted black didn't work the scratch may cause to much defraction to the plastic surface , A glass disc may be a solution but that as its own problems . But to be honest the jewelers coping saw blade is fine . You know what size slot you have cut .18mm is the finest and the black pvc i made mine out of cuts like butter .
Its not the slot senor that's the problem their are loads of those OTS i just thought their would be a high resolution shaft location sensor you simply clip on much like the quadra encoders i have already mentioned .
Still i have a solution that works and the final gearboxes assembly will be boxed in so ambient light wont be a issue .
D1


Tue Sep 15, 2015 1:19 am
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Well think this will be the last post on this one yeah I here you say .
Rigged up the new higher torque motor which meant I could lift close to 3kg at a reasonable speed with a 500mm extension . So that's the good news now for the bad news . I fitted a laser pointer to the end of the 500mm extension to test accuracy . Not to good unfortunately well not good enough for multipasses anyways . It may be good enough for timelapse but I wouldn't recommend anybody building anything like this just for timelapse.
[flickr]Image2015-09-21 17.39.14 by D 1, on Flickr[/flickr]
Theirs just to much give in the long length of belts . This may have improved if I had bought some steel banded belts . Or maybe used chain drive but think that would have its own problems . So think its time to put this one to bed I have enjoyed the process and I have learnt a lot but I know when its time to give up .
So going to start a new project you will see the new thread title 'Mini Techno Crane' soon .This is going to included all I have learned from the arm, optical end stops better drivers, slew bearings etc .
I will also have to make a new light weight pan tilt head my old one is far to heavy and I cant fit the optical encoding in . So back to the drawing board well Designspark in my case.
Ps got optical encoders working perfectly so that's a good start to new project :D
D1


Mon Sep 21, 2015 11:47 am
Profile
User avatar

Joined: Tue Nov 24, 2009 7:55 am
Posts: 951
Location: UK
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Looks like I will have buy a book for bedtime reading until the new title is published on Timescapes ;) Pity the project did not work out but as you say, a lot has been learned by your efforts in this thread that can be applied to the new project. It has been most interesting following this from the start both on and off topic ;)

_________________
Smile, it gives your face something to do!

http://www.vimeo.com/user1214873/videos
http://www.youtube.com/user/MrReggub


Mon Sep 21, 2015 1:33 pm
Profile
User avatar

Joined: Thu Mar 10, 2011 11:38 pm
Posts: 585
Location: Exmouth, Western Australia
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
I'm sorry the arm hasn't worked out after all this effort. A lot learned for next time, as you say.

Maybe you should just start a thread called ' D1's shed'. Then it becomes a place where your mates gather to look at whatever you're making at the time and chat about anything vaguely related to it.

Kit


Mon Sep 21, 2015 4:01 pm
Profile
User avatar

Joined: Tue Nov 24, 2009 7:55 am
Posts: 951
Location: UK
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Kitwn wrote:
I'm sorry the arm hasn't worked out after all this effort. A lot learned for next time, as you say.

Maybe you should just start a thread called ' D1's shed'. Then it becomes a place where your mates gather to look at whatever you're making at the time and chat about anything vaguely related to it.

Kit


Or not - LOL

_________________
Smile, it gives your face something to do!

http://www.vimeo.com/user1214873/videos
http://www.youtube.com/user/MrReggub


Mon Sep 21, 2015 9:41 pm
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Cheers fellas sometimes the process is more enjoyable than the actual end product and i have enjoyed our little chats . I am sure Mike and is new mill will produce something to talk about on topic or off who cares .
Plus we are all waiting to see what Kits next cinematic offering is going to be . So i think the future is reasonably bright and winters on the way so less pottering in garden and more shedding me thinks . May get the aluminum smelter underway at least i can smelt down all the failed arm stuff :D
D1


Mon Sep 21, 2015 11:53 pm
Profile
User avatar

Joined: Wed Nov 11, 2009 10:45 am
Posts: 1685
Location: Merritt Island, Florida, Estates Unitas
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
WHAT??? wait...no This can't be happening!
Its like Lost all over again.

You're not going to try steel banded belts? Those industrial robots have pretty good accuracy and are throwing a lot of weight around. Even if it doesn't do super precise multipass, you could have a lot of fun moving the camera around during stopmotion.

Yeah. Making an arm-dolly just for timelapse. Crazy idea. Although I think one little rig that can dolly to something then orbit it, or follow serpentine paths is kind of interesting. There is a branch full of orchids in my forest which I always wanted a dolly shot of, but it twists up-down and left-right a lot while following a relatively straight line. With a longer dolly and an arm, it should be possible. Even a realtime shot like that would be cool. Once you have it, you'd find unique shots you could do with it. Stuff nobody else has done.

Coincidentally, there happens to be this arm for sale on Ebay. It says free shipping to continental US. I happen to know that the seller would make a special exception if you bought it and would pay shipping to the UK out of the sale price if the buyer was you. It would probably cost close to the sale price to ship, but its you. Here's the link in case you want to try that route.

http://www.ebay.com/itm/Scorbot-3-Robot ... 35f192486a

The Scorbot arms are slightly larger and a lot stronger (heavier metal structure) than the LabVolt one I already converted. I also have a second LabVolt robot in case you want to try that.

So, its your shed, but I'd love to see how a precision belt would work on what you've already built. Also, converting an existing robot is pretty darn easy. Will definitely be looking forward to the show when you decide what to do next.


Tue Sep 22, 2015 6:40 am
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Hi SL no i think the arm as had enough of my time . Like you say you can do some really interesting stuff with a arm. Shots that wouldn't be possibly with any other type of rig but if i cant get it to do the move over and over again exactly then its no good to me. I would really have liked one and i will keep looking for a scrap industrial one just out of curiosity . In the case of my arm it was not just steel belts the gearbox was actually flexing with the amount of strain on it and it wasn't a unsubstantial lump of ali :( It may have been a case of using push rods instead of belts but that limits the amount of rotation you can have .
I am afraid the baton is with you SL on the robot arm front . Iam just going for a re design on my pan tilt the have a look at a techno crane . Soz
D1


Tue Sep 22, 2015 10:36 am
Profile

Joined: Wed Feb 15, 2012 3:36 pm
Posts: 408
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Hi D1,

Sorry to hear that you were having problems with your arm experiment. I do understand when you have issues of sponginess with a long length of belt. Sponginess is to be expected, even with internally reinforced steel belts . But once you apply the 3kg payload, I don't quite understand your problems with repeatability.

I gather that bouncing may be the problem rather than just sponginess? I think there is a difference between sponginess and bounce, although they are both related. I'm saying this because at one time I had bounce problems with my arm, even when using the red AT5 belts and I solved the problem by trying different belt tensions. In my case, too tight a tension was making the arm less spongy, (which was great) but more bouncy (which wasn't great). So I thought I could live with some sponginess, provided that the bounce was gone.

Bouncing at some frequencies during a move will obviously result in mismatched repeat moves. And the bouncing may also affect the motor steps, i.e. you may be missing the odd step here and there without even realising. Since I use servo motors, this doesn't apply to me so much because of the inherent self correction, although they don't eliminate bounce per se.

Regarding the gearbox flexing, is this due to shafts that are too small in diameter for the applied torque? What part is flexing?

These are difficult problems to solve, so I do understand your frustration…


Edward


Tue Sep 22, 2015 2:04 pm
Profile
User avatar

Joined: Thu Mar 10, 2011 11:38 pm
Posts: 585
Location: Exmouth, Western Australia
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
DISPLACEMENT 1 wrote:
Plus we are all waiting to see what Kits next cinematic offering is going to be . So i think the future is reasonably bright and winters on the way so less pottering in garden and more shedding me thinks . May get the aluminum smelter underway at least i can smelt down all the failed arm stuff :D
D1


My wife Christie has already devised a brilliant plan for a series of short films and I've been experimenting with the meltability and adjusting the consistency of the readily available plasticine here in WA to avoid costly shipping charges from over East. Just need to confirm it's sulphur-free.
I just hope the first of these films comes out faster than the last one.

Summer's on the way so less pottering in the garden and more playing in the air-conditioned shed for me.
As for smelting, Aluminium is easy to melt but I'm going to be experimenting with making 'Aluminium Bronze' which is 90% Copper after we get back from a week in chilly Canberra. I need some of this cast into round bar to finish the CNC router.

Plenty to keep us all talking on D1's next thread, whatever he decides to call it :D

Kit


Tue Sep 22, 2015 5:21 pm
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Eek will this thread ever die !
Hi Edward belts are funny things . The main problem on the arm is at some points the top of the belt is under extreme tension while the lower part is under no tension at all ( tried to uload photo Flickr down at mo . This in some cases causes a tipping point as the load switches to the lower part of the belt and you get a noticeable jump. I tried tensioning the belt as much as possible but this when the gearbox started to flex . I think a much heavier construction would be need to get any ware near usable device and that is totally the opposite of what i wanted . I could carry on and the final thing would look like it worked but for animation my final use it wouldn't be accurate enough.
I have no regrets i like problem solving but i also know when to stop ;)
Hi Kit i to was supposed to be doing a little film in me shed was sort of put on the back burner when the arm came into my life . I have a very usable crane so think its time to settle down to a bit of animation over the winter months . Funny how you have to go indoors because its to hot and i have to go inside because its to cold.
Going to put optical encoders on the crane a build a new pan tilt with encoders so i don't have to worry about leaving shots over night . So this will prob mean i never get round to doing any animation :D
D1


Wed Sep 23, 2015 12:53 am
Profile
User avatar

Joined: Tue Nov 24, 2009 7:55 am
Posts: 951
Location: UK
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
D1, just a thought, would printable CD,s work for the encoder discs, if you have a suitable printer that could print the pattern?

Cut some metal again today, playing with feeds / speeds and step over to achieve a decent surface finish. The Cutwel HSS Ali cutters seem to work well, very smooth finish but too many "tool path" marks at present.

_________________
Smile, it gives your face something to do!

http://www.vimeo.com/user1214873/videos
http://www.youtube.com/user/MrReggub


Wed Sep 23, 2015 12:01 pm
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Hi Mike was wondering if printing onto acetate would be dense enough to effect a optical sensor . Not had a chance to check but suppose similar to printing CDs.
You have more choice on the speed front than me one thing that lets my mill down often think the spindle is not running fast enough . But it works so will stick with it until the motor burns out then i might put a spindle motor on it as a upgrade .
Will have a look at those cutters was thinking of going completely over to carbide but not sure . Just looking at cutting a HTD3 pulley so need a long 1.5mm cutter . Do you find the Cutwel search tool doesn't work or is it just me. I think you are always going to get surface marks . If you order precision machined ali stock it as quite noticeable surface marks
Hi Edward this is the photo i was trying to post before may explain things better
[flickr] Image2015-08-31 18.10.50 copy by D 1, on Flickr[/flickr]
Think the thread is in free fall now :D
D1


Wed Sep 23, 2015 12:49 pm
Profile
User avatar

Joined: Tue Nov 24, 2009 7:55 am
Posts: 951
Location: UK
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Here Ends: New Project 7 Axis Arm Rig Controlled by Blender.

********************************************************************************************************

Here Begins The Shed....................LOL.

I have a range of Carbide cutters, will maybe give one a try tomorrow if I have time and check out the Cutwel search or their catalogue for a 1.5mm end mill.

Edit: 1.5mm x 10 and 12mm length (Ball nose :( ) but you will not like the price:
http://www.cutwel.co.uk/milling/milling ... b85-series
Another source here:
http://www.shop-apt.co.uk/end-mills-for ... rbide.html

_________________
Smile, it gives your face something to do!

http://www.vimeo.com/user1214873/videos
http://www.youtube.com/user/MrReggub


Wed Sep 23, 2015 1:23 pm
Profile

Joined: Wed Feb 15, 2012 3:36 pm
Posts: 408
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
D1, Quick yes or no question:

do you have any idlers between the two pulleys for tensioning the long belt? It looks like you have.

Edward


Wed Sep 23, 2015 3:24 pm
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Hi Mike yes this is just general chatter now and would perhaps be better in the CNC thread hey oh . Does Cutwel provide a good old fashioned paper catalog ? I like catalogs i view them as bed time reading theirs always a selection on the bedside table :D
The link you sent to the long 1.5 mm leads to a 3mm instead is my browser playing tricks . In a perfect world i am looking for a 1.5mm that can cut a depth of 9mm . Think this will be pushing it but its only skimming the final profile.
Hi Edward no idlers their would be no room or access in the final design as the arm was going to be a 80mm carbon fiber tube . I was relying on sliding the entire gearbox to tension the belt.I all also considered introducing a turnbuckle into the belt for extra tension. Idlers close to the bigger pulley may have helped but i still think their would be issues and remember my test rig is only half the length of what the real arm would need to be .It wasn't a yes or no answer was it :D
Hows the anodizing going did you find a suitable solution .
D1


Wed Sep 23, 2015 11:31 pm
Profile

Joined: Wed Feb 15, 2012 3:36 pm
Posts: 408
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
I only asked about the tensioning idlers because I have had similar problems to yours in the past when I used idlers and as soon as I removed them and resorted to tension the belt by pulling from one pulley (in your case you are pulling from the gearbox instead) , the problem was gone.

What I was getting was a jolt as soon as I changed motor direction and the lose side of the belt then suddenly tensioned hard against the idler. With the idler gone, the jolt was gone too, as the belt had no obstacles in the way. Idlers are fine for other uses, but in this heavy load case, they seem to only work well in one direction.

The only difference is that in my set up, I had the shortest possible belt length (pulley centres were very close) , and one pulley was much bigger than the other to act as a reducer. But I think the symptoms were similar to yours. And tensioning too much will introduce bounce.

I did solve my problem, so I encourage you to solve yours, defeat is not an option :lol:

Edward


Thu Sep 24, 2015 12:09 am
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Hi Edward the jolt on change of direction is what i was getting, you just described it better than me. But that is without idlers i think it is just the shear length of belt you can actually seen the untensioned side go slack and hang in space . I am upgrading my old crane in a few ways moving track motor of carriage ( Doug seems to find it better) So when i do this i am going to use steel banned belt and see what its like . I haven't used it before i may do quick test on the arm rig before i fit it to the crane .
You may notice on the Gearbox i use twin idlers i find it better
[flickr]Image2015-08-31 17.12.46 by D 1, on Flickr[/flickr]
D1


Thu Sep 24, 2015 12:26 am
Profile
User avatar

Joined: Tue Nov 24, 2009 7:55 am
Posts: 951
Location: UK
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Back to CNC thread after this one ;) Sorry about link, just realised I was looking at ball radius :oops: and yes there is a catalogue available and good bedtime reading it is, especially if you have deep pockets. Took a cut HSS 0.1mm at 600mm/min and 6000rpm, much improved, smooth finish with a regular pattern, it was the pattern that was causing me concern before.

_________________
Smile, it gives your face something to do!

http://www.vimeo.com/user1214873/videos
http://www.youtube.com/user/MrReggub


Thu Sep 24, 2015 1:29 am
Profile

Joined: Wed Feb 15, 2012 3:36 pm
Posts: 408
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Mike,

How are you finding the noise as it cuts at 6000 rpm, is it something that would bother the neighbours if repeated too often?

My mill (same as D1) is slow revved and it has a belt from motor to spindle, so it is relatively quiet.

Edward


Thu Sep 24, 2015 2:28 am
Profile
User avatar

Joined: Tue Nov 24, 2009 7:55 am
Posts: 951
Location: UK
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
edward wrote:
Mike,

How are you finding the noise as it cuts at 6000 rpm, is it something that would bother the neighbours if repeated too often?

My mill (same as D1) is slow revved and it has a belt from motor to spindle, so it is relatively quiet.

Edward

Neighbors too far away but within walking distance of their cats ;)
Quite quiet, also belt drive, but having worked on sound testing for a couple of years I wear ear plugs as a matter of course, you would never believe how damaging a seeming "low" sound can be without measuring it with spectrum analyser.
The enclosure reduces the noise as well even though the side panels are thin window blind material for now.

_________________
Smile, it gives your face something to do!

http://www.vimeo.com/user1214873/videos
http://www.youtube.com/user/MrReggub


Thu Sep 24, 2015 5:41 am
Profile
User avatar

Joined: Wed Nov 11, 2009 10:45 am
Posts: 1685
Location: Merritt Island, Florida, Estates Unitas
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
D1, nice speed reducer. How do you tension the idlers? Are they mounted on eccentric spacers like openbuilds stuff?

This is the part where the mega-thread flops around like a caught fish before the end.


Fri Sep 25, 2015 9:07 am
Profile
User avatar

Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1294
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
It will die soon ! Got some proper work to do . Just a slot with a bolt going through never been able to source ready made eccentric other than the openbuilds ones and they not man enough.
D1


Fri Sep 25, 2015 9:51 am
Profile

Joined: Wed Feb 15, 2012 3:36 pm
Posts: 408
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Last gasp!

For those who have given up, defeated, despondent and impotent….take your medicine, revisit this video and start drooling again...


https://vimeo.com/82184563

I can imagine this arm shaking like mad under some speed with the 10Kg payload, but for slow speeds you have to admit that it looks so tempting:)

I count 5 harmonic drives in this set up.


Edward


Sun Oct 04, 2015 8:09 am
Profile

Joined: Sat May 12, 2012 1:14 pm
Posts: 4
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Anyone heard of https://modbot.com/? Not sure where they are in the development of this but it looks like it could be a relatively inexpensive option.....


Sun Oct 04, 2015 10:13 am
Profile

Joined: Wed Feb 15, 2012 3:36 pm
Posts: 408
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Well, the idea of integrating encoder, brushless motor driver and gear mechanism into a nice, neat and affordable package is great.

Unfortunately I haven't seen this realised yet, although you could build yourself a similar joint package but costing quite a lot more money.

For instance, a small size 11 harmonic drive can cost over £1000 each, although you could buy the component set and design yourself a bespoke joint, if you know what you are doing. Still very expensive anyway. You can integrate a ready made harmonic drive directly with a brushless servo carrying the encoder and use a miniature driver, it can be done, but on an individual basis it would cost rather more than the $800 they are thinking of.

For a payload of 10Kg, you would need bigger/ stronger gears, particularly in the case of an arm that is not counterbalanced, you need more torque.

What they dream of doing is mass producing this to make it cheaper and more accessible. This is immensely complicated, as many gearing mechanisms are patented, you can't just copy them, so my guess is that they would probably be sourcing some of the parts from other manufacturers.

Of course, the small motor/joint prototype they are currently showing around would not be able to withstand the weight of a person sitting on an articulated seat, like in their presentation, you would need a much bigger mechanism, but you gotta start somewhere:)

Best of luck to them, they seem very enthusiastic, I just can't imagine having to deal with a bunch of venture capitalists and doing a glib presentation in simple terms they can understand.


Edward


Sun Oct 04, 2015 12:22 pm
Profile
User avatar

Joined: Wed Nov 11, 2009 10:45 am
Posts: 1685
Location: Merritt Island, Florida, Estates Unitas
Post Re: New Project 7 Axis Arm Rig Controlled by Blender.
Edward, that is a nice video of the robot arm in the Vimeo link. It is also mentioned on page 13 of this mega-thread. It is a Universal Robotics UR-10 in case you want to look into getting one. Those french guys may have modified the user interface to make it more useful for photographers. I especially like the directed method of programming its movements. They move the arm by hand and it reads the movement with its encoders. During the actual shooting, it follows the same path you moved it by hand, or you can apply some smoothing of paths in the software. I don't normally go for smooth jazz, but the tune is pretty catchy as well.


Sun Oct 04, 2015 6:21 pm
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 647 posts ]  Go to page Previous  1 ... 13, 14, 15, 16, 17  Next


Who is online

Users browsing this forum: No registered users and 5 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB © phpBB Group.
Designed by Vjacheslav Trushkin for Free Forums/DivisionCore. pozycjonowanie