/robowaifu/ - DIY Robot Wives

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Actuators For Waifu Movement Part 2 Waifu Boogaloo Kiwi 09/02/2021 (Thu) 05:30:48 No.12810
(Original thread >>406) Kiwi back from the dead with a thread for the discussion of actuators that move your waifu! Part Two! Let's start with a quick refresher! 1. DC motors, these use a rotating magnetic field created through commutation to rotate a rotor! They're one of the cheapest options and are 30 to 70 percent efficient usually. The bigger they are, the more efficient they tend to be. 2. Brushless motors, these use a controller to induce a rotating magnetic field by turning electromagnets on and off in a sequence. They trend 60 to 95 percent efficiency 3. AC motors, Though there are many different type, they function similarly to brushless motors, they simply rely on the AC electricity to turn their electromagnets on and off to generate their field. Anywhere from 15 to 95 percent efficiency. 4. Stepper motors, brushless motors with ferrous teeth to focus magnetic flux. This allows for incredible control at the cost of greater mass and lower torque at higher speeds. Usually 50 to 80 percent efficient but, this depends on control algorithm/speed/and quality of the stepper. 5. Coiled Nylon Actuators! These things have an efficiency rating so low it's best to just say they aren't efficient. What they are though is dirt cheap and easy as heck to make! Don't even think about them, I did and it was awful. 6. Hydraulics! These rely on the distribution of pressure in a working liquid to move things like pistons. Though popular in large scale industry, their ability to be used in waifu's has yet to be proven. (Boston Dynamics Atlas runs on hydraulics but, it's a power guzzler and heavy) 7. Pneumatics, hydraulics lighter sister! This time the fluid is air! This has the advantage in weight. They aren't capable of the same power loads hydraulics are but, who wants their waifu to bench press a car? 8. Wax motors, hydraulic systems where the working fluid is expanding melted parafin wax! Cheap, low power, efficient, and produce incredible torque! Too bad they're slow and hard to control. 9. Explosion! Yes, you can move things through explosions! Gas engines work through explosions! Artificial muscles can be made by exploding a hydrogen and oxygen mixture in a piston, then using hydrolysis to turn the water back into hydrogen and oxygen. None of this is efficient or practical but, it's vital we keep our minds open. Though there are more actuators, most are derivatives or use these examples to work. Things like pulleys need an actuator to move them. Now, let's share, learn, and get our waifu moving! >--- < add'l, related links from Anon: >Soft muscles with origami-inspired skeletons: https://youtu.be/OJO4FP0DXgQ >Cavatappi artificial muscles: https://youtu.be/yXAJGH5s4cs https://youtu.be/MpCFumHFZvU https://www.designnews.com/automation/cavatappi-robot-muscles-have-5-times-strength-human-muscles >Nameless nanofiber muscle, probably Cavatappi: https://youtu.be/H19p43NFqp4 >Supercoiled polymer (SPC) muscles: https://youtu.be/QHiTJ_zgGME https://youtu.be/N4VMoYFrusg https://youtu.be/hFuzQ4ed-t0 https://youtu.be/2GXWIozM4oQ (bundled/braided) >TCP (the same?) https://youtu.be/S4-3_DnKE9E https://youtu.be/wltLEzQnznM >Twisted string actuators (TSA) <I had the idea that they should in some cases be build with a loop. Grippers would hold a part of it and twist that. For fast release they coul let it go and grab the next part of the loop. Designing the gripper will be a bit of a challenge, though. But I think this is doable. Can't image I'm the first having that idea. <Not sure if this here >>12589 is already something like it bc I didn't understand it. <Here's some passive returning mechanism, followed by other videos on TSAs: https://youtu.be/J26y1nn7JMM https://youtu.be/QBQMZsSQJQM (freaking loud) Effect of bending: https://youtu.be/zYrHGMiqC9A Life cycle test setup: https://youtu.be/PABVsuV7Y1M Frequency response ( I don't get it): https://youtu.be/YLWsh1P80Dc Mixed with fluid/gel tube: https://youtu.be/tP9B3aqc4CI Transmission ratio and speed switch: https://youtu.be/Y1uceDzhjKY https://youtu.be/5PtXTI1t3Po <I don't like it being used for fingers but it's a good technology. >Nylon fishing line muscles: https://youtu.be/Za0VeU9Ov7A https://youtu.be/2OuRX65xbKE <(Reminder: The do have a high life span >1M) <I plan to rather use water for heating and cooling. >Continuous ransmission (CVT) / torque converters https://youtu.be/kVPjhmTThPo https://youtu.be/cd2-vsTzd9E https://youtu.be/c9e2y-5DMNc https://youtu.be/PEq5_b4LWNY >Twisted string series elastic actuator (TsSEA) <This strikes me as particular interesting. https://youtu.be/VBXykAIBKtA >Printed pneumatics https://youtu.be/_X0rDW6NQ58 >Using sugar as soluble support material for printing silicone muscles: https://youtu.be/L0Z0-y3qpNk >=== -add add'l links
Edited last time by Chobitsu on 09/06/2021 (Mon) 10:07:57.
>>12810 Welcome back Kiwi, good to see you found us again.
>>12810 >Stepper motors, brushless motors with ferrous teeth to focus magnetic flux. Neat I had no idea that's how they worked. I figured it was some kind of gears tbh.
>>12810 >Artificial muscles can be made by exploding a hydrogen and oxygen mixture in a piston, then using hydrolysis to turn the water back into hydrogen and oxygen. could we miniaturize this and make artificial muscle cells? granted they'd be larger than actual cells but what if we could mass print them each the size of a grain of rice? Just a thought, as 3d printing increases precision and resolution there's no reason we could not fabricate some pretty interesting structures on the micro-scale
Great, so my comment >>12813 was the last in the old thread: >Cavatappi artificial muscles >Supercoiled polymer (SPC) muscles / TCP >Twisted string actuators (TSA) >Nylon fishing line muscles >Continuous ransmission (CVT) / torque converters >Mechanical multiplexer >3D printed pneumatics >>12810 >5. Coiled Nylon Actuators! These things have an efficiency rating so low it's best to just say they aren't efficient. What they are though is dirt cheap and easy as heck to make! Don't even think about them, I did and it was awful. I guess you mean by heating them from a battery source, but not with hot water which is already there.
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>>12815 >but what if we could mass print them each the size of a grain of rice? Just a thought Actually, that's not too far-fetched Anon. It's certainly tracking the trend of miniaturization in technology and machining. It would certainly be a breakthrough, as you suggest. One of the most important men in the history of computing (and certainly to us here) is Carver Mead. During a talk he gave to EE students at Cal Tech where he (still !) teaches, he pointed out the proper place of vacuum tubes in the historical march of chip technology to the MOSFETs of the modern era. During the close of the talk he briefly evaluated future directions. One of those were micro-vacuum tubes, which are actually being produced on micron scales now there at the school. >also: >no cute anime catgrils in OP's pics <let us correct this oversight
(related x-post) >>12736 >adaptive motion smoothing
>>12819 Yes another anon recommended "There's Plenty of Room at the Bottom" by Richard Feynman . I should dig into that this weekend
>>12816 Ths video explores TSAs (Twisted String Actuators) for exoskeletons, which might give indications to how it could be used in a artificial body: https://youtu.be/lf4qPyHNzQk --write-sub TSA-powered glove: https://youtu.be/ZdsFULAslV4 --write-sub
>>12858 Neat! Thanks Anon I saw this pdf streaming by on BUMP's terminal window and stopped to have a look. Cool AF, and kind of addresses indirectly some of the topics I'm working through for pulley placements in windlass-based thigh motions under load.
>>12864 I suppose I could be more explicit exactly what I'm talking about. >
Adding another actuator which I think has great promise from the last thread. Hydraulically amplified self-healing electrostatic actuators with muscle-like performance https://www.science.org/doi/abs/10.1126/science.aao6139 Also called "Dielectric Elastomers" Links to explanations and other links >>10620 >>10639 Rough calculation on cost, forces needed and the number of muscles needed for full human mimicry.(the micro-controller cost might be less) >>12014 Rough equivalence to the force Tesla gets out of their cars to human actual forces >>12140 Rough cost budget of actual existing transistor and micro-controller parts to get full human mimicry >>12172
One I believe of high importance, switched reluctance motors https://www.controleng.com/articles/resurgence-for-sr-motors-drives/ One last one https://en.wikipedia.org/wiki/Piezoelectric_motor The piezo are very fast and powerful. They are used in pick and place machines for electronics parts at high rates of speed. The problem with piezo is high voltages. I think some of the actuator strategies used for piezo at the link could be used with solenoids or other magnetic type devices and it would make for low cost actuators.
>>12929 >Dielectric elastomer actuators are electrically powered muscle mimetics that offer high actuation strain and high efficiency but are limited by failure caused by high electric fields and aging. Acome et al. used a liquid dielectric, rather than an elastomeric polymer, to solve a problem of catastrophic failure in dielectric elastomer actuators. The dielectric's liquid nature allowed it to self-heal—something that would not be possible with a solid dielectric. The approach allowed the authors to exploit electrostatic and hydraulic forces to achieve muscle-like contractions in a powerful but delicate gripper. This is exactly what we need
>>12930 >The problem with piezo is high voltages Not sure, there are these voltage boosters. Might lead to loss of efficiency, though. I have piezo on the radar since I read about Festo using them. I was mainly thinking of valves for air and water, which might last longer than magnetic ones. Also for small actuators. Since this doesn't need much energy int the first place, the loss for boosting up the voltage might not be a problem. >>12932 >dielectric liquid >This is exactly what we need Yes. I agree.
>>12929 >Also called "Dielectric Elastomers" >related crosspost (>>6563)
>>12936 >Not sure, there are these voltage boosters. I had to think about that for a minute then I remembered that there is such a thing as a voltage transformer made of piezos. Is that what you are referring to? I think they would be different from ones made for transducers, motors, etc. Did you know you can make piezos out of PVC. Like the water pipe stuff? You heat it up, apply a high voltage field across it then cool it down while keeping the field on til it cools. For a short while they were making speakers out of it. I screwed around and didn't get any to play with and now I don't think they are around any more. Piezos are really wondrous. A solid state thing you can put voltage on and they move. The problem is they are pain in the ass. They don't move far and it takes high voltage. To get a lot of movement you have to complicate them with levers and...they just suck to do real stuff with but..they are very cool. I think the Japanese putting them in cameras was in reality just a "look at the cool techno-wizardry we can do" move. Succumbing to techno lust is a real thing and needs to be avoided. Some super complex wizard crap that is so difficult to get to work it becomes THE reason you work on something instead of what you were trying to build in the first place. Don't ask how I know about this.
I just now had an epiphany. What we need for a rough prototype is something that has fast movement when it's not under load but some strength when it's under load. Much like a regular human muscle. Well I was thinking about strings and came up with this. I really like this. Cheap and not too complicated. Now this is just a drawing. It's certainly not fleshed out. There would have to be some thinking done to make it work. You have motor with a cone shaped pulley on top of it. The string wraps around the cone. When you turn on the motor the string is pulled goes through a ring(purple) through a pulley(white) around and then up to the end of the limb. The purple ring acts just like the ring on a fishing pole that turns the string on a fishing pole. Now let's say the limb has little resistance to it moving then the motor winds the string up on the large part of the cone because the spring has pulled it down. High speed, low force. If the limb gets resistance the pulley and the ring that guides the string stretches the spring, pulling the sled the pulley and ring are mounted on up. This in turn means the ring that guides the string is now farther up the cone to a smaller section. The motor turning the same speed is now taking up much less string for every revolution. Higher torque but less speed. The pulley and ring are mounted on a sled of sorts that has a guide way so it can only go up and down the (red) slot. You could adjust the force by picking the right cone size, length and the spring force.
You could get some accurate movement with the spring cone auto trans if you had opposing muscles and ran it with pulse width modulation. So you run one muscle one way and the other the other way both with high force but one of them a little bit less. So you are holding the limb tight but moving slowly depending on the opposing difference in force.
>>12941 I used to own a Yamaha CVT (Continuously-Variable Transmission) Scooter. It was only 149cc, but I could regularly get it to 60mph on a flat highway. The neat thing was it would just pull through the powerband then entire way until it reached maximum speed: no shifting or drop-offs. I became interested to figure out how Yamaha did it, and found out it was a heavy-duty rubber conical cylinder that a transfer wheel would back and forth across the surface of transferring that engine power into the driveshaft. Thus the 'continuously-variable' bit. A working geometric expression of integral calculus! I say all that to say that the motor/cone part of your diagram reminds me very directly of the transmission on my scooter. You might look into it Anon.
Since the string would be tied to the cone you wouldn't have to worry about slippage like belts in CVT's.
>>12944 I suppose some forms of the idea use belts, but not my scooter. It was a direct-drive rubber takeup wheel that would ride firmly against the rubber drive cone. The takeup is run along different 'sections' of the cone depending on the drive conditions, which would vary the torque accordingly just like in your idea AFAICT. Anyway, belt-or-not isn't the question, it's "can we use this idea inexpensively to our advantage in creating robowaifus?" I'm betting we can.
>>12940 >>Did you know you can make piezos out of PVC. Like the water pipe stuff? You heat it up, ... Aarrgh!!1! DO NOT HEAT UP PVC. >>5106 >>9043
>>12940 >>voltage transformer made of piezos I mean the regular electronics ones. Boost converters is another name for those, wich can be buyed as a board, or build: https://youtu.be/QnUhjnbZ0T8 --write-sub https://youtu.be/hDZsBeYbDa4 --write-sub (Just in case, if anyone tries to get the inductor the same way, don't damage the lightbulb bc mercury) Btw, we don't need to build everything from the scratch. It's good to be able to, but doing so might also complicate things. If you want too make even the chrystals yourself: https://youtu.be/IGbVGKJldd8 >>12941 >cone gear or cone torque converter Interesting, but I would like to see an experiment based on it. Also, space might be an issue.
>>12947 >Aarrgh!!1! DO NOT HEAT UP PVC. I hate to be so blunt but the fact is you have no idea what you are talking about at all. Plumbers, electricians bend PVC by heating it up all the time.Here's a search for PVC heater bender. https://duckduckgo.com/?q=pvc+heater+bender&t=ffcm&ia=web They make a tool just for this.
>>12948 >Boost converters is another name for those, wich can be buyed as a board, or build I see thirty of them here for $20 https://www.banggood.com/30pcs-DC-2V-24V-To-5V-28V-2A-Step-Up-Boost-Converter-Power-Supply-Module-Adjustable-Regulator-Board-p-1614240.html?cur_warehouse=CN&rmmds=search but...what will you drive with them? If it's a motor then you have to make a bigger motor which cost big time. Also these little cheap things I don't think are going to drive piezos which to really drive them require much higher voltage. I'm not trying to be totally negative. I just don't think this will work out. If you look back at what I've posted a lot of it really won't work or will be so tedious that it will be too much of a pain but I throw ideas out there anyways.
>>12983 Doesn't mean it's healthy, especially if you want to do it on abigger scale. >>12984 The topic wasn't motors but dielectric muscles and small piezoelectric valves or such. My point was, that these boosters exist and some might work. One goes up to 500V from 3V.
>>12987 >The topic wasn't motors but dielectric muscles Ok I didn't see that. It wasn't clear to me.
>>12988 >dielectric muscles and small piezoelectric valves Okay, no problem. Maybe I should have quoted better. I think high voltages could only be used for small moving parts anyways. Bigger motors or muscles would need more ampere, and I don't want to get a shock touching my girlfriend. Or think her of holding a baby...
>>12810 I will model that madokami mecha
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I feel like we're overcomplicating things. We should be thinking of this as a simple physics problem: What method gives the best power-to-weight ratio for a simple bicep curl? A 20 inch long blocks split half-way down the middle by a single hinge, pointing straight down with the upper "arm" fixed and a weight attached to the "forearm" and made to curl that weight 180° up using only electricity. The more torque out compared to weight of the arm of that length using an input of X watts DC for Y seconds is the winner. (I'm not sure how many watts or long would be considered reasonable for the experiment) Finding out the most energy efficient way to do this is the key to making knees, elbows, fingers, and probably any other joint we'd need. Because most robots would run on batteries instead of wall outlets, the weight of any inverters would have to be included as part of the arm, because even if it weren't really in the arm, you'd still have the weight in her somewhere. This will likely also make hydraulics and pneumatics impractical even if it were more practical with more limbs. I know this might seem like an oversimplification, but it seems like something that can actually be made into class experiments or a challenge just about anyone could compete in. And I didn't really know how to explain the rule, but no "C-3PO arms", so the blocks have to rest flat against each other, not having a linear motor or cables connecting the bicep to the forearm. If it were a leg that'd be like the back of the thigh connected to a calf, which would get in the way of sitting in a chair. It's not something you could easily hide inside of a human body or clothes and would really get in the way if they were used in prosthetic limbs.
>>13178 Mind explaining that a bit more in-depth Anon? >>13180 >because even if it weren't really in the arm, you'd still have the weight in her somewhere. True. That's one of the challenges a good engineer has to account for, and why the thrown-weight issue is pertinent in any wildly dynamical systems like a robowaifu with all it's limbs and lifelike motions. The Boston Dynamics robot 'dog' Spot is a great example of the design outcome necessary for success at this. All the actuators, batteries, inverters, etc., are kept inboard inside the robot's chassis, and the limbs themselves are kept as simple, rigid, and lightweight as possible. IMO we'll need to attempt something similar to Spot here if we're to succeed at this.
>>13203 The short version: I will literally model and break each and every part of that design down so it can be 3D printed into a model kit as a prototype design. Madokami and all. Now for the long version: I would use existing model kits like megami devices as a reference for part size but start from scratch with the techniques and workflow Ive been practicing since I first showed off a rough draft of Allie. Though that is only the shell of the design. modeling the insides of the thruster equipment would be where the real engineering occurs and would have to use rocket designs for that. schematics for reference. This isnt a sci fi board and i know its a gundam inspired drawing, but I wonder if magnets could be used in the wings to hold up the robo waifu in the air. since magnets that powerful do exist and those wings seem very flimsy with too many bendable parts. I have also 3D printed miniatures using small magnets for the joints before and that works perfectly. Though at the moment the only real problem is that you need another magnet underneath the model or it falls.
>>13205 Excellent. Well I'd say to have at it then Anon! Work hard and I'm sure you'll succeed. >This isnt a sci fi board... We actually had a few similar topics come up when trying to help Fairybot-Anon devise approaches for his literal-flying-mini-robowaifu from years ago. Personally, I consider the fact that drones are so widespread, that IRL flying-fairybot robowaifus will be inevitable eventually.
>>13203 >All the actuators, batteries, inverters, etc., are kept inboard inside the robot's chassis, and the limbs themselves are kept as simple, rigid, and lightweight as possible. I think the automotive term for this is "unsprung mass" >IMO we'll need to attempt something similar to Spot here if we're to succeed at this. I don't really think so. I don't think you can outperform them by aping them. We can't just assume that's the best way to do it just because it's the way the professionals are doing it. My life experience has been that the professionals don't always know best, but people rarely question them because they think there's that significant of a knowledge gap that might not really exist. This YouTube video refers to it as the "Smarter Monkey Fallacy" https://youtu.be/wkiL3Q7cq7A his videos are great even if his presentation is crap. The purpose of simplifying the idea to just bending a lever to lift a weight is so we can get a hundred monkeys at a hundred typewriters trying to solve the problem and anyone could provide a simple solution virtually nobody's thought of yet.
>>13210 >I think the automotive term for this is "unsprung mass" Indeed it is. Thrown-weight is a mechanic's term, which I am.
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>>13205 You model her, I'll print her. Honestly, it would be nice if we could work together. I've always wanted to work on a waifu with another Anon. Please make a thread for her, I would be happy to make one for us if you'd like to work together. I'm not good at modelling exteriors but, I am a robotics engineer.
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>>13180 >no "C-3PO arms", so the blocks have to rest flat against each other, not having a linear motor or cables connecting the bicep to the forearm I'm not buying that. It's not like normal arms work See here
>>13226 A normal, healthy-weight person can bend their leg to a squat where their heels to touch their ass, and can sit upright in a chair with their knees bent 90° and have the back of the knees touching the seat, instead of having a cable extending somewhere from the calf to the ass getting in between the knee and seat. It's better to have that range of motion available for all joints and not need it, than to need it and not have it.
>>13180 >>I feel like we're overcomplicating things. We should be thinking of this as a simple physics problem: What method gives the best power-to-weight ratio for a simple bicep curl? I can't imagine we can get any cheaper type motor that a switched reluctance motor. It's a couple coils and metal rotors. The only thing I can see as better is "Dielectric Elastomers" >>12929 Regular motors are really expensive. All of them cost more than switched reluctance BUT it's not like you can buy switched reluctance motors all over the place because they need micro=controllers and MOSFETs or transistors to drive them. The cost of these has plummeted so to get the exact precise control we need we will need micro-controllers anyways. What do we need for power to run these things? Notice that a average human can only produce about 200 Watts or so of power over a good bit of time with world class athletes at about 400 watts but you can get much higher brief spurts. Power = Force * Distance/Time Where: Power is measured in watt. Force is measured in Newton. Distance is measured in meter. Time is measured in seconds. 1 lbs force = 4.44822162 newtons We'll use 200lbs. force so someone can be picked up 200lb. = 889.64 newtons Call the arm 0.5 meter Time call it a second Power = Force * Distance/Time So 889.64 newtons*0.5meter/1= 444.82watts Now you can easily get a MOSFET that can be driven with 40volts and that gives us 11.12 Amps @ 40 volts. You can get MOSFET's that will do this for $0.50 USD all day long. You need two if you are running a switched reluctance motor and the micro-computer to drive 18 of these you can get for less than $10 USD. Link on force https://www.thecalculator.co/others/Horsepower-Calculator-490.html Link of force humans need to lift stuff. It's much less than the high 200lb. weight I used. https://www.quora.com/How-much-strength-would-you-need-to-lift-a-human-in-the-air?share=1 There's a problem here. 11 Amps is a lot. It takes a #12 wire to carry 20 amps. It takes a #18 AWG to carry 10 amps. https://i.stack.imgur.com/QqXFg.png You could probably cut that in half because it's going to be intermittent and the current carrying capacity depends on the wire heating up which it won't if this power is in brief spurts. So maybe you could use #22 gauge. Lot cheaper. So here's something cheap and a little bigger . "100-ft 20/2 Twisted Doorbell Wire (By-the-Roll)" https://mobileimages.lowes.com/product/converted/032886/032886856167.jpg Stranded would probably be better but not hard to find.
>>13205 >I will literally model and break each and every part of that design down so it can be 3D printed into a model kit as a prototype design. Madokami and all. NICE!
>>13229 >"Dielectric Elastomers" The problem with these is they are new and it's not like you can go out and buy one you have to make them. Of course the advantage of these is exactly the same. You can make them yourself and don't have to go out and buy them.
>>13231 >"Dielectric Elastomers" I forgot to add no one really knows how long these will last or how well they will do. "IF" they work then long term there really seems to be nothing so satisfactory as these for muscles. They seem perfectly ideal in all ways.
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>>13229 Maybe I should repost this in the Meta Thread, because nobody seems to understand what I'm saying. The whole point of the idea was to get people to actually test to prove it and compete to create the most efficient arm, instead of just sitting around discussing and debating methods of actually testing it. Just saying to use a switched reluctance motor and showing a bunch of energy math doesn't really mean anything if you don't even explain where and how the motor is mounted to make the arm move.
>>13236 Where can we get these? I would assume that a smaller scale piston design hidden by some casing might be more efficient but requiring the wiring for sensors like construction vehicles. Diggers specifically. As for the power source, the goal I believe was to make a recharable robowaifu, so either using rechargable drone tier batteries, or some kind of solar power would probably work. Since it probably takes far less energy to grasp an apple than to create lift and maintain flight for prolonged periods of time.
>>12409 In this comment earlier I figured the force directly from pound force, used it to get newtons with an online unit converter. Newtons can be directly substituted for watts. I wasn't sure if this was correct but now using the other formula >>13229 I see the calculations come out the same so it's a good short cut to finding the amps needed at a certain voltage. pound force>convert to newtons>use amount in newtons to directly substitute for number of watts need for force
>>13236 >nobody seems to understand what I'm saying. Your right. You asked what's the best power to weight ratio, what length and how many watts needed. So... There's also a lot of links further up that go to the last thread before this one that go over all this. >The whole point of the idea was to get people to actually test to prove it and compete to create the most efficient arm, instead of just sitting around discussing and debating methods of actually testing it. If you build stuff and have no idea at all what forces are involved, no idea what power(watts) is needed then you are going to do a shit load of work that is not necessary when you could spend 10 minutes getting a ball park figure on what you need. Every time you change any of the weights, forces, etc. you need different wires, strength limbs, etc.. >Just saying to use a switched reluctance motor and showing a bunch of energy math doesn't really mean anything if you don't even explain where and how the motor is mounted to make the arm move. Picture of arm from above. >>13226 Maybe you missed it, The calculations are what you asked for. As for efficiency there's a mass, a ton, a whole lot of literature on what efficiency you can get from different type motors, hydraulics, air pneumatics, etc. It's pointless to just start randomly building stuff without at least using the stuff that people have spent thousands of hours working on the facts of how they work and what the advantages and disadvantages of them are. So no I don't know what you are asking for. The stuff you explicitly asked for a lot of it was given. Even a picture of a normal arms attachments as an idea.
>>13216 Well I also have a 3D printer, anon. If you want to start a thread then go ahead. Getting through the superficial diversity hire barriers in HR has been the only thing stopping me from getting into the field myself.
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>>13257 >Your right. You asked what's the best power to weight ratio, what length and how many watts needed. So... I wasn't asking a question, as much as I was proposing standards for an experiment for people to do. I am terrible at writing and explaining things. I should have put the end of the post first: "it seems like something that can actually be made into class experiments or a challenge just about anyone could compete in." That's the point of what I said. Getting people to build and test out a different methods of flexing a single standardized limb, instead of just posting our thoughts here about what's the best way to do it. I guess what I'm trying to propose is a simple community-driven challenge/experiment where we actually try to outperform each other instead of just a bunch of ideas on paper. I wanted to make as many constants as possible to keep the math simple, both so more people will be able to compete and so you don't end up with limbs that are only more efficient because of the scale, and such. I said 20 inches because that was the first thing to come to mind and I couldn't think of any constants for time or wattage, so I just used X & Y. I'd love to hear some better suggestions.
>>13277 > I was proposing standards for an experiment for people to do. I am terrible at writing and explaining things. I should have put the end of the post first: "it seems like something that can actually be made into class experiments or a challenge just about anyone could compete in." That's the point of what I said. Getting people to build and test out a different methods of flexing a single standardized limb, instead of just posting our thoughts here about what's the best way to do it. Ok, you lay out some standards, show a design to test and then build it, "...instead of just posting our thoughts here about what's the best way to do it...". You first. Show us.
How to double the power of magnets with a Hallback Array: https://youtu.be/uQWHjj6ofwo
>>13236 You're right. Building something is better than dreaming up technology. However, there's not gonna be one answer and best method. Whatever, I'm going to work on some arm soon.
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While working on OSRM, I've come to realize that DC cored motors inefficiency is a problem but brushless are too expensive. Coreless motors are where it's at. They're efficient like brushless but cheaper and don't need special controllers that increase costs.
>>13285 >You first. Show us. I will. Sometime between that post and now, I've found I'm going to get fired for not taking the vax. Also I've been working nights, which makes it hard to get anything done without noise complaints. There's also the fact that I know as soon as I post it I'm going to be met with replies about ways to change the experiment. I've already had one comment about how a 180° bend isn't necessary, but expect asking for a standard material and how thick or wide the arm should be, then eventually devolve into why I used an imperial measurement when we should use metric, etc. I expected a major backlash against the idea by people who prefer to just sit around thinking and talking, will find any way they can to ruin this. >>13313 >However, there's not gonna be one answer and best method It's just a general-purpose limb, mostly for bending at the elbow and knee. Scaling down to the fingers probably won't work and it won't be good for flexing face muscles or anything like that, but the application largely depends on what the leading design is. There's not gonna be one answer and best method regardless if the experiment is done or not, so why not do it anyway? It's application isn't just limited to waifubots either.
>>13318 >>I've found I'm going to get fired for not taking the vax That's really sucks. F the vax, F the people trying to force it on people and F the people who engineered corona. What ever you do don't quit. They will try to make you quit. Don't do it. That way they will have no liability. They will really try hard to do this. Watch you'll see. It may very well be that they will some day have to pay you for firing you. Force them to fire you. Of topic but we now have many serious test that show Ivermectin knocks out corona. We even have a whole country of billions, India, that has shown that corona can be stopped fast and eliminated. If they want to stop corona it's as easy as giving everyone Ivermectin, vit. D, and vit. C and corona is done in a few months for a couple dollars per person.
>>13322 >Force them to fire you. That was the plan, if only so it makes it easier to get unemployment if I can't get a new job soon. But please, let's not turn this thread about actuators into a Covid thread. When I leave the job, I'll switch back to sleeping normal hours, and it'll be easier for me to assemble the little CNC machine I bought but never got around to building. I don't trust my hand-eye coordination enough to do cut things by hand.
>>13324 Good luck Anon.
I was about to give up on creating and humanoid robowaifu because I can't afford it but I think this mechanism could be my savior: https://makezine.com/projects/the-chinese-windlass/ I think using this we could create high torque actuators using cheap small motors.
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>>13489 I actually mentioned those in the OSRM thread, they are also known as the differential windlass and have incredible efficiency with potential for incredible strength. Using two connected to the motor can provide push and pull forces. https://makezine.com/2014/05/28/rise-robotics-cyclone-muscle/
>>12810 https://youtu.be/ENMZsPwCUcA Capstan Drive: nema stepper motor with no gears?
Anyone got a guide to which joints are safe to put your fingers and other fleshy bits near? Obviously it's not so important on low torque motors, but for life size waifubots you're getting into dangerous territory. I wouldn't want to use anything on a sexbot that might mangle my wangle. Imagine having to explain that one in the hospital.
Nylon actuators seem like a real bad idea also because you'll stress the thread way too much. I don't see why you would choose this method over a simple spool (which has been proven to be reliable and efficient since they use it on cranes) or pair of spools. >who wants their waifu to bench press a car? Patricians.
>>13671 Nylon is dumb as heck for an actuator in a batery and thermal constrained robot. >>13506 ...Why put your rooster near any mechanical joints? Just use an onahole integrated into her pelvis.
>>13671 >Nylon ... stress the thread way too much Which thread? I think I recall these actuators to be very reliable. The developers tested them a lot and made this claim, if I recall it correctly. >over a simple spool Because the spool implies a motor, and it might be slower and certainly louder. You could have both. The Nylon is only used if the weight is to high for the other ones. >>13674 >Nylon is dumb as heck for an actuator in a batery and thermal constrained robot We had this several times here on the site. You're thinking in terms of the option of heating the Nylon with electricity. But hot water can be used, which might already be there anyways. It depends on the design of the robot. Like it or not, some might use that approach. Even the method with electric heating might be interesting for some smaller movements, e.g. in the face. Though, dielectric elastomers might be better suited in that case. Nylon actuators are also quite slow, so it's for some special use cases, especially support for other actuators in case of heavy lifting, but not generally useless. Don't judge everything based on your approach.
>>13678 Okay I totally misunderstood the way these things work. From the OP picture it looks like they are motor-based like a simple spool, but the motor is perpendicular and contraction is provided by overtwisting. I am now aware that that is not the case and I'll concede that they actually are cool and potentially useful.
>>13687 What you thought of is a twisted string actuator. I just got my drone motors and want to try those out for that.
>>13678 >heating nylon as a wire and totally not causing a house fire. >Hot water? From where? The cooling system? How would it help movement?
>>13688 Good, that's a genuinely good actuator mechanism and I hope you share your findings. Just know that drone motors require cooling if they are used for more then a few seconds at a time.
>>13689 Please read through the existing information before making some bold posting. There are actuators with thin wires and Nylon. Also, yes, hot water comes from the cooling but could also be heated on purpose if necessary while being plugged in. Actuators help movements by actuating or so, I think.
Has anyone replicated some bldc-actuated limb projects on hackaday? https://hackaday.io/project/181799-redacted-the-first-fully-open-bipedal-robo There are several great open-source projects which are a good place to start to actually build a robot instead of theorizing about what would be the perfect actuator and never getting anywhere. I was on a tear with nitinol braided actuators being the perfect actuator, but the part manufacturing held me back to the point where all I could work with wasn't nearly good enough. We need to start with something at all in order to have a hands-on perspective of what works and why to build these robots at all. Even a perfect first design nearly always has something go wrong with it, which is why iterating versions is a superior method to getting stuck in theoryland and never making anything.
found this just now https://www.youtube.com/watch?v=guDIwspRGJ8 >We have achieved strong, fast, power-dense, high-efficiency, biomimetic, soft, safe, clean, organic and affordable robotic technology. Dumbbell weights 7 kg (15,6 lbs) , forearm with hand only 1 kg (2,2 lbs). >This artificial muscles robotic arm is operated by water and consumes 200W at peak. We invent and produce our electro-hydraulic mini valves to have complete controllability of speed contraction and compress the whole powering system (for a full body) inside humanlike robot torso. >At this moment our robotic arm is operated only by a half of artificial muscles when compared to a human body. Strongest finger-bending muscle still missing. Fingers are going to move from left to right but they don't have muscles yet. Metacarpal and left-to-right wrist movement are also blocked. This version has a position sensor in each joint but they are yet to be software-implemented. We are going to add everything mentioned above in the next prototype. >The movement sequence was written and sent by simple commands to a hand.
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>>13723 To my knowledge, no one has replicated a Hackaday project here. That project is ok as a concept but, is severely flawed. All of the mass is centralized high up in the hips which means it would lack any stability IRL. It also suffers from having brushless motors close enough for the magnetic fields to adversely affect each other. The flaws in the design continue but, this is not the thread to discuss why that design would not make sense IRL. As for this thread, it was made for the express purpose of discussing actually useful actuators. Anon's enjoy dreaming about super coiled actuators and other ultra low cost actuators that do not actually make sense to use for various reasons. My guess is they want their waifus to be cheap to produce. I will continue to tell everyone to use DC and brushless motors as they are the only sensible option currently available unless she's constantly plugged in. Steppers could also work and are very cheap for their strength, they're just heavy.
>>13724 That thread mentions him in the "Humanoid Robot Project Videos" thread: Automaton dev from Poland >>5136 >>10179 >>13304, but I don't post every video of his. Crosslink in the actuator thread also exists.
>>13724 If only we had power systems capable of delivering hundreds of watts over prolonged periods. If only water was not heavy. These actuators are such heart breakers. They seem almost fantastical until you realize how inefficient electrolysis is for a pneumatic system. There's also the major problem of making sure the hydrogen and oxygen do not escape the system and reconstitute into water at the right time. This Eastern European man explains how the system actually works. https://www.youtube.com/watch?v=gy-Cl8X6Itk
>>13725 >thread, it was made for the express purpose of discussing actually useful actua It's the official thread for actuators, so we'll discuss all of them here. Being strongly opinionated doesn't mean you're right. >continue to tell everyone to use DC and brushless motors as they are the only sensible option For her primary joint movements it might be the best approach, but can still be combined with other accuators in case of lifting something for example. >unless she's constantly plugged in She can be plugged in most of the time, while not moving from one place to another. While sitting she can be plugged in. Then doing some movements while laid down or standing somewhere won't need much energy.
>>13723 >the-first-fully-open-bipedal-robot I answered here, in the meta thread: >>13737
>>13735 Hm, it would my personal biases have poisoned my judgment. I forgot there were those among us that would want a plug in waifu. I only want a waifu that can follow me so I only think about robowaifus through the lens of one that must be self powered.
>>13724 That's very impressive. Having hydrogen and oxygen in the same tube is...risky if I understand it correctly. Maybe he has a way to separate them. Not sure. He is making a gas to drive pneumatic actuators which is a good idea. It happened to occur to me possibly a spark gap which can expand water, or other liquid, would work as well??? Not sure it may be even more inefficient than splitting water. Maybe you could use some other sort of element that spit into a gas although I can't thing of one off hand. I'm complaining about the shortcomings but don't think I'm not impressed mightily by what he has done. It's very excellent.
>>13755 >>13729 >the major problem of making sure the hydrogen and oxygen do not escape the system ... >Having hydrogen and oxygen in the same tube .. H and o2 aren't going to be at standard pressure, that's something to factor in. No need to worry so much about escape, since that's still an issue in pneumatic and hydraulic systems regardless (and more dangerous in the latter). What's really interesting here is the way the actuators are arranged like muscles - with apparently opposing muscle pairs for greater control rather than jerky one-way movements or rigid machinelike movements. However don't rule servos out entirely they, and solenoids as well can do a lot still. Consider the human body, it has smooth muscle, skeletal muscle (slow and fast twitch) and cardiac muscle. Similarly, we should expect to use a diversity of tactics to the actuator problem. 1 .Hydraulics or large pneumatics where the most power is needed (shoulders, bicep, legs), 2. Where some power but more control is needed: wrists, neck, feet/ankles: smaller pneumatics (they don't have to be micro, but an array of micro pneumatics shouldn't be ruled out), the hydraulic transformer that other anon had mentioned, and/or pulleys which sound low-tech but don't have to be: try to envision something like a metallic herringbone chain inside a lubricated graphene or nylon weave bladder. 3. Finally for fine dexterity: nitrile wire or something similar from the "soft robotics" school: fingertips, facial muscles (when we cross that bridge), etc. Anyway I wanted to respond to you both before sharing this too: https://www.youtube.com/watch?v=6JNq1COqB_s[Embed] https://spectrum.ieee.org/kenshiro-robot-gets-new-muscles-and-bones
>>13506 >...to put your fingers and other fleshy bits near? Redundant sensors are your friend. Also, having the system only use so much force as necessary for each movement. Also, there are the terms 'compliant' and 'backdriveable' waifusearch> backdriveable OR backdrivable THREAD SUBJECT POST LINK The Basement Lounge >>4807 backdriveable Robotics Hardware General >>12511 " Actuators for waifu movement! >>7086 backdrivable " >>8207 " " >>9198 backdriveable " >>11700 " " >>11855 backdrivable " >>11881 backdriveable Work on my Elfdroid Sophie >>7675 " " >>7693 backdrivable " >>7695 " " >>7701 " Actuators For Waifu Movement Par >>13761 backdriveable, backdrivable ' backdriveable | backdrivable ' = 13 results waifusearch> compliant OR compliance THREAD SUBJECT POST LINK C++ General >>1073 compliant Robotics Hardware General >>12511 " R&D General >>2048 " Wifu that gives you Hope. >>6823 compliance " >>6827 " General Robotics/A.I. news and c >>6229 " " >>6231 " " >>6381 compliant " >>6919 " " >>12586 " Actuators for waifu movement! >>8207 " " >>8221 compliance " >>11023 " " >>11028 " " >>11030 compliant, compliance Prototypes and failures >>12882 compliance Why consider alternative CPU arc >>4506 compliant, compliance Robowaifu Power and Control Syst >>11175 compliant Actuators For Waifu Movement Par >>13761 compliant, compliance Madoka.mi prototype thread & rob >>13511 compliant ' compliant | compliance ' = 20 results Cycloidal drives with a gear ratio of maximum 10:1 are backdriveable, along James Bruton. A soft outer shell might also help with your concerns. Doing such a search with waifusearch requires the option "-y false" when starting the program from the shell. >=== -I hope you don't mind Anon, but I cleaned up your waifusearches a bit. I suggest you post them on the board inside codeblocks, as I've done here for you. This will help ensure the browser rendering of contiguous spaces is monospaced. -Also, I'd suggest you upgrade your Waifusearch copy to the latest v0.2a (>>8678). As you can see here, among other improvements, basic Boolean OR is available for different (though related) search terms. -Also, there's a newer version of the all_jsons just posted; 211117 - https://files.catbox.moe/jgmdxs.7z Cheers. >t.Chobitsu -edit waifusearch results
Edited last time by Chobitsu on 11/17/2021 (Wed) 11:09:26.
>>13754 Yeah, I knew the links weren't working. But for some reason the option to remove the hyperlinks didn't work when I tried waifusearch the last time. It seems not to be a bug, but I don't know why it didn't work the last time. I reposted the article, and I will delete this posting here later. So you might delete yours, if you wish. The new posting is still messy, probably because he didn't use tabs, my copypasta didn't copy them or I don't know.
>>13724 >>13728 Reliability test of hydraulic actutors (literally working with water) by Automaton robotcs: https://youtu.be/iQhYXE6cAEY This does it for me, I might actually use something like that. Because it's easiely imaginable to reuse the water by catching it with onter tube around the muscle.
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Hasel actuators are something to keep an eye on. They might not be interesting for the face, because of high voltage, but maybe somewhere. >Reminder: Hasel actuators https://youtu.be/PGGQc5q2NGo >Use cases, advantages https://youtu.be/TjglKIkLFSI >Speedtest: https://youtu.be/Lsn-Z1wKaEo >General progress, more stroke https://youtu.be/ep0CV9PYtSo >Accumulation conveyor, efficiency https://youtu.be/bjDdUn39H7s >Fast repetitive movements https://youtu.be/2ggwTlWbkZI >Dev kits https://youtu.be/i1QmwOxGGFA https://youtu.be/LhQgKnkxXXA https://youtu.be/usvoiGBAflY
>>13966 This is similar to a concept I was thinking of, except my design only contracts like a muscle. Any idea what that "self-healing liquid dielectric" is?
>>13978 All liquids are self healing. Dielectric just means they're insulators. Many HASEL actuators have been made with castor oil and transformer oils because they can handle large voltages. The system works through hydraulics and large voltage differentials causing conductive plates to attract each other. Really, the oil is only a working fluid that needs to easily flow when the plates squeeze it and, withstand large voltages so that shorts don't happen.
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>>13989 >All liquids are self healing. Well, that's obvious, but I'm not the one who called it that. It just seemed like he was trying too hard to make it sound more sophisticated than it actually is. >Many HASEL actuators have been made with castor oil and transformer oils because they can handle large voltages. That's good to hear. The thing I was going to make was very similar, but uses electrostatic repulsion instead of attraction, so I wasn't sure what to use aside from the main electrode. I was thinking of a dielectric powder instead of oil, but I guess either or a mix of both could do. Here's a crude doodle, it's a loop of wire inside a plastic bag with the dielectric. A single HV AC power source charges the loop, so both sides are the same charge and repel. Alternatively I was thinking of just a single wire, half of the loop, with dielectric doing all the repulsion like putting sand or something on the top load of a Tesla coil and turning it on to blast them off, but 'catching' them with the bag to push perpendicular to the wire to create the force. But maybe it would be better to use a conductor instead of a dielectric, for an added induction-levitation-like force? Or go in the opposite direction entirely and rely on wires, for something that'd look more like the other pic.
>>13989 >HASEL Actuators This was educational: https://www.youtube.com/watch?v=Lsn-Z1wKaEo They are also for sale apparently. What does "self healing" even mean? It sounds like a marketing gimmick.
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>>14021 >What does "self healing" even mean? It sounds like a marketing gimmick. Yeah, I made that joke already. It just means that it's a capacitor with a liquid dielectric, so when the capacitor plates attract and the liquid is squeezed out, it'll "self-heal" by the liquid moving back in once the plates move apart.
>>14018 >It just seemed like he was trying too hard to make it sound more sophisticated than it actually is. That's a polite way of putting it. >Dielectric repulsion That's fascinating. I take it it'll maintain constant repulsion until a drain is triggered. I would always use a dielectric oil for any electric charge based actuator. As you are no doubt aware, they have many advantages over most other dielectric mediums. Incorporating a dielectric powder could be interesting for experiments. Air is an excellent dielectric but, it makes for very weak and inefficient dielectric actuator from my albeit, very limited experience.
>>14024 I hadn't heard of the Hasel method until this thread, my original idea was inspired years ago by the beginning and end of this video: https://www.youtube.com/watch?v=P5za9sa4-qk but I genuinely don't know enough about electricity to know what would be the best material to use. I've seen people put flakes of aluminum foil on the top load of a tesla coil and they fly off. I've also seen it done with bits of paper, and that video uses sand. I was thinking of eventually doing the same thing with a little tesla coil of my own and just figured I'd try a bunch of things to see what gets the most distance. A lot of my ideas rely on brute force trial and error, because I have no idea what I'm doing. It wasn't even until later that I realized I could probably just use a bunch of insulated wires in phase with each other, (instead of 180° out of phase like Hasel) hence that wire ball pic. >I take it it'll maintain constant repulsion until a drain is triggered. I was just going to use HV AC in an ISM band, and figured the strength of the contraction could just be controlled with amplitude modulation, or maybe pulse-density modulation like a real nervous system. I didn't think about maintaining the contraction by maintaining a DC charge, because you'd probably need to keep putting energy into it just to do any meaningful work.
>>14022 I'm quite sure they mean if there's a hole somewhere the oil coming out dries and closes it, so it might be flexible when dried, maybe has something like silicone rubber mixed into it.
>>14039 That would make sense, but I'm not getting that from the diagram.
>>14039 That was never brought up in several HASEL research papers I've read. It's a good idea if you could figure out the appropriate additive to seal holes when reacting with oxygen or nitrogen.
>>14061 Thanks, then it was just my imagination. Would have been nice, though.
>>12810 >hasel actuators Would a continuous coil of the circlar disk actuators work? Also, I think the preferred direction of actuators are those that work in tension (contraction) or both ways (bi-directional) instead of expanion. This way, the actuator or string does not collapse on itself in buckling, easier to connect the pulling string, ect. A real muscle works in tension and tendons / joints / bones all work like wires in bowden tubes. I am going to start printing CF Nylon cycloidal gears with PC Max enclosures to make servos in the style of the anti-backlash cycloidal gearbox on hackaday. The carbon fibers, nylon, polycarbonate mix, and maybe some PTFE powder should give me plenty of dry lubrication that doesn't need frequent servicing. I would like to try planetary gearboxes, but I feel that any amount of warping from 3d printing very finely detailed gear teeth would lead to noise and backlash. Cycloidal gearboxes seem to be better optimized for 3d printing BLDC gearboxes at home. PolyMax PC/PC Max, PolyMax CoPA nylon, and NylonX are all higher temperature plastics with anti-warping compositions, and strong as fuck for being printable on entry-level 3d printer machines (all metal hot-end extruders, heated bed, and non-heated enclosures). Machining delrin gears would probably be better strength (~60MPa printed part tensile strength vs 83 MPa delrin tensile strength) and friction-wise. I will have to see how bad cycloidal gear vibration is for low-speed applications like a robutt muscle. If cycloidal gearboxes turn out to be heavy pieces of garbage, I will report back here with results and forge on ahead with planetary print-in-place gearboxes like I planned to originally, before I found an existing model for cycloidal gearbox actuators on hackaday.
>>14513 >Coil of disk hasel actuators Should indeed work, would be complicated to build though. >Contraction is better then extension You are correct. It must be said that unless gravity or a spring is used to provide a return force, you will need to pull both ways. >Cycloidal gearbox Mind sharing the link to the Hackaday project? Cycloidal gears are notorious for vibration, make sure you carefully balance the gears. Most modern designs use out of phase gears to balance out the forces, that can help a lot. Did you design a print-in-place planetary gearbox or, is this design online? Either way, please share links and information. Good luck, cycloidal gears have low backlash and high ratio to area potential, would be good to have as an option for Anons.
>>14517 >Hackaday cycloidal gearbox project https://hackaday.io/project/167855-simple-cycloidal-robot-leg-for-quadruped Also, >stepped gear planetary gearbox >file related Making a stepped gear in a single stage planetary actuator would give a working gear ratio with high backdrivability and low vibration compared to a cycloidal gearbox.
I got ahold of a BLDC dev kit (moteus) and tried it out. It is indeed the motor most suitable for human x robot interaction since it is light, backdriveable, powerful, available, long-lasting, and has a large platform of hobbyists doing development work right now. These beat shape memory actuators in precision and ease of use by miles. There's no working fluid, no compressors, no pumps or tubes, and they are ready to have many types of controllers bolted on right from the factory. This is the fastest way to build a good strong motor that isn't a non-backdriveable geared DC motor. The main downsides I'm noticing are that they aren't very cheap at 30-70$ for just a small low torque motor, 60-80$ in controllers per actuator, up to 500$+ for a geared high torque actuator. Also, there's effects at play that make the motor/actuator system surely undesirable for some people: >cost >bulky circular shape >cogging (motor has intermittent torque when the magnets align with the poles) which feels like it has "cogs" as you turn the motor with your hand (not perfectly smooth rotation like you might want) >noise (quiet static and grinding noise from electronics) >rigidity by virtue of being solid >backlash if using a gearbox with small motor >high inertia if using a big direct-drive motor If you don't care about the trade-offs, I'd recommend a BLDC + Controller system. I have a gearbox in the works to bolt onto the motor to see if 3d printed planetary gearboxes will work. I'd also like to see if there's a coreless/ironless/slotless motor that would be able to direct-drive a large surface (thighs) smoothly.
>>14689 One last thing I forgot to mention is the potential that low KV gimbal brushless motors have. They are used for camera panning, and have significantly higher coil turns/resistance, so they cannot have position accurately measured in the same way as some BLDC controllers are set up. The potential benefit is that they are cheaper and run on lower current that can be pumped out by cheaper controllers and power supplies.
>>14689 Thanks for the nice breakdown Anon, it's appreciated. I'd say cost is the most obvious (and limiting) factor for the significant majority of us. I hope we can at the least find alternatives for pricey single-use controllers, and spread the costs out among fewer, general-purpose drivers. >coreless/ironless/slotless motor What does 'slotless' motor mean?
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>>14691 Please use "ctrl + f" to find information in the relevant thread. Slotless means coreless and that's been explained before in this thread. Picrel for more info
>>14694 Ahh, I see. My apologies for appearing lazy. I would guess the little micro motors in tiny drones are of this type. I know they get pretty hot, but the RPMs achievable are frankly, amazing. Again, thanks.
Anyone have any updates to building a robot actuator?
>>15126 I'm not really aware of anything new on that front Anon. I expect we'll have something before long though.
>>15174 I'm making a nylon gearbox for the best feasable actuator mentioned in >>14689. I have about one or two more weekends until it is prototyped. This same actuator could even be applied in any other system for cheap power and precision.
In >>1002, there's some links to some decent looking electromagnetic actuators that are fairly simple to build. They're limited in that they only switch between two states, and do so quickly, without a smooth transition. I'm hoping to adapt them for arm and neck mechanisms in a mini robowaifu, and the current plan is to use a small spring and variable current to try and produce a finer position control/state transition. That said, this seems like an over-complicated method, so would anyone here have some recommendations for alternative avenues of consideration?
>>15735 I think we'll probably find plenty of uses for fast-acting, linear actuators Anon. I hope to see work here along that line, thanks! >>15737 >DC motors are the easiest. Just get a gear motor that exceeds your torque requirements and add a potentiometer to control position or, just use a readily available servo. Good thinking, Kiwi. Can you sort of diagram that for us? I think I understand most of the general points there, but I probably lack understanding in some of the details.
>>15313 I've made a gearset prototype from 3d printed nylon, and it's garbage. However, I will be tweaking it and trying to make a wolfrom stage planetary gearbox the same way. Here is a paper which has some details (key points: human-safe, high backdrivabilty, high gear ratio, small size) https://ieeexplore.ieee.org/document/8867893
>>15878 Any chance you can post pics of your WIP Anon?
>>15891 Thanks!
My idea for an artificial muscle is to have a good stretchy material, which has a certain amount of liquid in it and no liquid will get added or removed, rather the stretchy container of the liquid will be squeezed in proper places to deform the container, thus changing the shape and causing it to contract so as to work like a muscle. Right now its just theoretical, I haven't tested anything. >>14018 I also kinda like this idea Maybe there could be special structures kinda like meshes that would contract when turned separate directions on each end and could do it really quick, I think I may have seen something like that before.. its kinda like how the lower arm bones go when the lower arm is turned
>>16629 I'd recommend HASEL actuators. This post has good information: >>13966
>>16631 The only issue I see with the HASEL actuators is that they require direct current (DC) high voltages (3,000 - 10,000 V). I'm thinking maybe one could do this a different way using low power maybe with a small motor which controls clamps or something. but I guess it might get kinda unnecessarily complex.. 2 sacks with fluid could be connected and while one be squeezed the other be full or similar, might work well for an arm, just throwing out ideas.. eventually I'll do some tests to see what works well and what doesn't
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>>16632 At 15cm scale, you'd be best off implementing a rotary prioritizing selective mechanical multiplexer. With a power motor and an index motor that decides the output. This allows for a very small mechanism to provide high power to many outputs. (Relative to individual actuators for each joint.) Picrel is a decent example made with lego which should help make it easy to understand. Here's a link with valuable information: https://hackaday.com/2021/05/04/prioritising-mechanical-multiplexer/
>>16636 https://www.youtube.com/watch?v=tCQ2I_rga0k Apparently the squeezing actuators can work.. for certain applications. But you may be right that I should explore alternatives..
>>15126 I downloaded this code for making a cycloidal drive in OpenSCAD, and looking into it. https://www.youtube.com/watch?v=FdTGeYKB5NM - Code is in the video description (--write-description). I hope it works this time. I already had some small drone motors for a while, but also five Nema 17 coming in soon. The reason why I didn't do this before was that I had some tutorial for Fusion 360, but I wasn't capable of transferring that into Solvespace. I also had a builder for Blender, but this was before I got my new PC.
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>>16692 There's a new video on eccentrically cycloidal drives, and generally a good video on cycloidal drives, by RoTechnic: https://youtu.be/qMDU5tlGUwU - I thought I posted about the eccentrically ones before, but can't find it right now. Whatever, I'm trying to finally figure out at least one way to make a more regular cycloidal drive that I can adjust to my needs and actually print and build. The online examples are all a bit different from each other and many require some very specific gearing, and the plastic parts are mostly only available as stl files, so I can't just adjust the files for another size or another gearing or another reduction. The eccentrically cycloidal version is highly interesting, but it's still under patent protection and making my own version in OpenSCAD would probably require math skills which I simply don't have (or didn't have, I think one video explains it very good). I'm gonna try it anyways. Maybe I can do it with his Python code: https://github.com/roTechnic/internalECGears Another video from the same guy: https://youtu.be/xv5cd7Bg7Uk and the one where he explains the design fundamentals of how to design a regular cycloidal gear: https://youtu.be/y9vLVXjz2c0 I'm also thinking about a bevel drive for the shoulder now, inspired by Dan Royer and his Sixi Robot: https://youtu.be/W6xzBVVuml8
>>16709 I think I found a finished model, which I can use to wrap my head around. Actually it's several versions in one file. Understanding the formula or not, I think I can print and use it, and probably also modify to my use case. https://3dmdb.com/en/3d-model/cycloidal-speed-reducer-in-openscad-by-mattmoses/9065832/ Same on Thingiverse: https://www.thingiverse.com/thing:8348/files > By request of Syvwlch ( http://www.thingiverse.com/syvwlch ) and WilliamAAdams ( http://www.thingiverse.com/WilliamAAdams ), here is a stand-alone public-domain OpenSCAD cycloidal speed reducer. As with the Wankel Engine and Roots Blower I recently posted, this is intended more as an example of an interesting mechanism than as a practical device. If you want a practical printable speed reducer, you might consider one of the other alternatives like > the worm drives on this Tank http://www.thingiverse.com/thing:8080 or > differential planetary gears http://www.thingiverse.com/thing:7390 or > cascaded spur gears http://www.thingiverse.com/thing:7379 > or this planetary gear reducer http://www.thingiverse.com/thing:8460 > There are several cycloidal-type mechanisms already on Thingiverse, such as http://www.thingiverse.com/thing:3617 and http://www.thingiverse.com/thing:3736 > There are also several interesting external sites like: http://www.zincland.com/hypocycloid/ > http://fabricationsofthemind.com/2010/07/09/extruder-design-1-printable-1001-hypocycloidal-gearbox/ > https://github.com/triffid/Differential_Hypocycloid > http://reprap.org/wiki/Differential_Hypocycloid > http://en.wikipedia.org/wiki/Gerotor > http://en.wikipedia.org/wiki/Gear_pump > and many many interesting youtube videos such as http://www.youtube.com/watch?v=bRn1K2XeWVE[Embed] > http://www.youtube.com/watch?v=3WvPF6uGCq4[Embed] > http://www.youtube.com/watch?v=CG2sPuqEXBg[Embed] > http://www.youtube.com/watch?v=AMtyFwMDL7w[Embed] > http://www.youtube.com/watch?v=h236SP86nnQ[Embed] > This present script is based on a design by M.F. Hill described in his 1928 patent "Internal Rotor", number 1,682,563: > http://www.google.com/patents/about?id=mdF5AAAAEBAJ&dq=1682563 > Note that this design is based on an offset hypocycloid, similar to Figure I in Hill's patent. Most of the contemporary designs appear to be based on an offset epicycloid, more closely resembling Figure V in the patent. > The motivated student can modify the code so it generates epicycloidal-based profiles. Hint: start by making a module ``epitrochoidBandFast(n, r, thickness, r_off)". The motivated student could also probably clean up my train-wreck of code and/or figure out how to do arrays in OpenSCAD. > Note also that these rotors can be used for pumps - see the gifs in the comments for an example.
Great material Anons, thanks.
>>16629 I like the idea. Maybe we can use it somewhere. It's simpler than pushing in more liquid and then using a valve to keep it, till it can come out again. But it might also make more noise with the motors for the squezzers, and I'm not sure how strong it would be. Whatever, I think it's good to throw around some ideas. >>16637 Okay, cool. (Didn't watch it yet)
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I'm surprised you're not building a smaller 140cm version of the actuated ball joint dolls yet. We have standalone models for ai conversation now you can download from yandex. Anyway, here's how to have a smooth servo. https://youtu.be/jsXolwJskKM I should mention that vrchat supports osc out now. If you could convince someone over the web to be your waifu with some speech synthesis, you could use the movement of them in vrchat full body to remotely control your robo bjd in your living room. Have fun.
>>16890 Thanks for your contribution. But which "actuated ball joint dolls" do you mean?
As with the other Anon, thanks for the contribution OP. But this support having it's own thread so I'll be merging it to one of the others. Not sure if its Actuators or TITS yet, since you touch on both. I'll think about it a bit. Cheers.
>>16890 >If you could convince someone over the web to be your waifu with some speech synthesis, you could use the movement of them in vrchat full body to remotely control your robo bjd in your living room. No, it's a way too risky and awkward. We would still need additional layers controlled by AI: >>9709
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I'm currently looking into some bldc motor calculations, or guestimations. I found this calculator: https://www.societyofrobots.com/robot_arm_calculator.shtml and used it to get some idea about what might be possible. It's still hard and complex, since I don't know how to calculate the maximum fringe case of lifting a water container of 8kg near to the body with two hands. Then again, I don't really need it, I could go with a small water container. Size and batteries will be more of a limiting factor, I guess. Interesting in that regard (the tutorial): https://www.societyofrobots.com/robot_arm_tutorial.shtml I won't buy anything big soon, but wanted to start learning more about it. Gimbal motors seem to be the most interesting, though high torque bldc motors have more RPM and could be reduced to have more torque, but are heavy: GM8112 motor by iPower weighs 400 grams,, has 6 kilogram-force centimeter (kgf·cm) = 0.5886 Newton meter (N·m) A high torque one from Ato has 0.8 Nm, but weights 3kg: https://www.ato.com/250w-bldc-motor - but it has 10x more RPM, so would still be faster after reduction if I'm not misguided. Hmm.
>"Dielectric Elastomers" I finally watched this video here on inflatable muscles: https://youtu.be/iiStyGqAG9Y - Here some search terms for further research: Fergal Coulter, hexachiral structures, Minimum Energy Structure - these might be useful for creating other kind of inflatable or deflateable muscles or structures like soft shells: https://youtu.be/IJ1dgxSZuAY The process for creating such variant of dielectric elastomer based muscles is quite complex: https://youtu.be/Qmuf_6h7Kl8 >Multiple layers of hard silicone (Shore A 73) are printed with a seamless hexachiral structure on an inflated silicone balloon. >When the layers are cured, the balloon is deflated, leaving a Minimum Energy Structure (MES) tube. http://fergalcoulter.eu/?p=73 Searching for hexachiral structures lead me to this: >The objective of this study is to improve these two mechanical properties, without significantly compromising the effective yield stress, in the regime with significant material and geometrical nonlinearity effects. https://www.researchgate.net/publication/323503727_Auxetic_hexachiral_structures_with_wavy_ligaments_for_large_elasto-plastic_deformation (PDF related)
> (>>16908, >>16913 : artificial-muscle related)
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>>16900 This is a simple static calculator, which boils down to computing the torque needed to statically lift the described geometry (a center of mass placed at a distance from the root motor). On one hand, the dynamical motor load will be larger than a static estimate, on the other hand motors often have higher peak torque available. I think there is no realistic robot actuator technology on the market or in the engineering lab rn except for electric (BLDC), pneumatic and hydraulic actuators. Pneumatic actuators could be usable in theory for actuating fingers and face (and they are indeed used in some high-end japanese humanoid robots) if you can find a way to print/mold/produce the required valves and pneumatic lines and the pump cheap enough for that to make sense. Precision hydraulics is mostly impossible for a hobbyist. What remains is designing (because you likely won't be able to buy one) a BLDC+reducer servo for the most loaded joint of your robot arm, you know which one... And the hardest part here is a reducer (which could be solved by buying a batch of higher-quality load-bearing gears from a sympathetic machinist, or you could borrow ideas from SEA actuators and use a long ball-screw rod as a component: [1][2], or you could borrow ideas from [3] ). Peak motor power could be improved by an order of magnitude with water cooling and good enough power electronics, and it has been done: https://spectrum.ieee.org/schaft-robot-company-bought-by-google-darpa-robotics-challenge-winner Research-grade actuators of artificial muscle are for now useless, and look like a waste of time. I hope to see an excellent BLDC-actuated lightweight robot arm being designed and validated in our group, and I very much respect the prototyping of such devices being built by fellow anons. If/when you are serious about the alpha-version of the arm design, we can start modeling it in mujoco. 1. https://iopscience.iop.org/article/10.1088/1742-6596/1633/1/012052/pdf 2. http://www.romela.org/wp-content/uploads/2015/05/2014_design_of_a_compact_lightweight_electromechanical_linear_series_elastic_actuator.pdf 3. https://citeseerx.ist.psu.edu/viewdoc/download?doi=
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Excellent servo design: https://www.sciencedirect.com/science/article/pii/S2095809921005282 If we could manufacture a similar one, a question of hip actuator would be solved. There is a lot of metallic machined parts and a lot of gears (some could be bought though as these are relatively common planetary reducer gears), so a sympathetic machinist or a hackspace with a good machine shop is required. I also have some background thoughts about the backlash introduced by the planetary reducer (as opposed to cycloidal). But this is a straight solution of the powerful leg servo problem.
>>17025 Do I understand this correctly, the gear has a second motor attached to it, so the second one can help in certain situations?
>>16996 Thanks for the PDFs >>17025 This is very similar to how planetary gear transmissions are used in automotive applications. https://youtu.be/9sPi7DEbyI0 https://youtu.be/xOiAfOH-fU8
>>17026 Yes, there are two motors, the second is much smaller and its only purpose is rotating the ring gear with set speed, to regulate the transmission ratio of the main reducer. This way the system can balance torque vs speed as is required by the current situation. >>17030 You are welcome! I think PCM in this system is a bit of a meme, and it would be better served by the usual watercooling. Would be cool to get some standard planetary reducers (they are used everywhere, even in electric screwdrivers) and try to use their gear assemblies for a prototype of such servo. You would need an encoder, there are now good magnetic encoders (austria microsystems has a lineup of these https://ams.com/en/as5040 ) and a controller. There are some open-source/open-hardware servo controllers but I haven't seen a very good one, though maybe it still exists somewhere. We would have to either take some pre-engineered solution and adapt it or design our own. I could help here, but in the end someone will have to manufacture a prototype and iterate on it until it works.
>>17036 >controller For BLDCs we have simpleFOC. If you want to move abway from BLDCs then that's maybe not an option. I understood it so, that for BLDCs you won't need a additional sensor to measure the motor position.
>>16996 I agree with everything, and I've been stuck on fixing my printer to be perfect for a few months before I want to print all the components to a nylon gear BLDC actuator that I posted to this board before. Remember that ball-screw actuators have a very high backdrive force and aren't suitable for safe human interaction without a connection in series to an elastic element or equivalent. Pneumatic devices are loud, need plumbing, and need pressure sources that make them not ideal for human interaction.
>>17063 >Pneumatic devices are loud, need plumbing, and need pressure sources that make them not ideal for human interaction. Yes, though that japanese humanoid https://en.wikipedia.org/wiki/Actroid managed to keep noise low somehow. Also I expect our planetary drive reducer to by very noisy, and I don't see non-arcane methods https://en.nanotec.com/products/9893-quiet-gearbox-first-stage-plastic-gears-helical-toothing of removing this noise. Hope the anons will solve this problem eventually. >I want to print all the components to a nylon gear BLDC actuator that I posted to this board before. Cool, hope you will keep us posted. Expect difficulties, but we'll likely route around them with out DIY engineering mindset.
>>17040 Sure, the BLDC driver can measure the rotor position by native EMF sensing, but some method of absolute reckoning will be necessary anyway and a reducer is a nontrivial mechanism that may break and even if it works it will introduce backlash. Absolute encoder attached to the real joint solves this problem.
Related: >>17086 >Paradox Drive prototype >>17072 >Which BLDC for MaidCom?
I'm never sure if gears belong in this thread for actuators, but I think so. This video here https://www.youtube.com/watch?v=TzJkD87eQNI made me understand why planetary gears are interesting for robowaifus. I thought most of us would go with cycloidal drives, and ignored the planetary gears. Maybe because I one read something negative about backdriveablity, idk. However, different gear ratios in one gear are of course very interesting. Still need to catch up on the "Paradox Drive", though.
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Drilled a hole in my 50$ 8318 and superglued in a magnet for the hall effect sensor. More progress to come on soldering to a moteus and printing the controller bracket before actuator is operational. If you guys put one of these in the hips, whoo boy, I can't remember the calculation result exactly but I think 80 amps or so and a 8318 bldc gives 4Nm torque without a gearbox. Going to assemble it and then test the torque with a cheap aluminum arduino force sensor.
>>17201 Thanks. Great to see some progress, I hope you succeed. I'm surprised you do this without a gearbox, and I'm curious about the results. (However, please try to size down your images, they don't loose detail while being 20% of that size, for Android 'Imagepipe' works quite well but it might be from F-Droid)
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>>17206 >pic related Not my best work, but the power is soldered together with 100 amp banana jacks. Once I re-print the bracket for the controller I will do a test to see if it works.

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