/robowaifu/ - DIY Robot Wives

Advancing robotics to a point where anime catgrill meidos in tiny miniskirts are a reality.

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Actuators for waifu movement! Robowaifu Technician 09/18/2019 (Wed) 11:27:47 No.406
Hello fellow Anons! Kiwi here to provide basic educational facts about various actuators we can use for gifting artificial avatars of our hearts desire motion!

1. Let's start with a personal favorite, the impractical, inefficient yet oh so fascinating: Heated Twisted Nylon!

What are they? They're nylon threads which have been spun around then annealed to seal in their coils. A heating method causes these threads to then contract or expand.

Good: Why is this a personal favorite? Simply put, it's natures muscle substitute for muscles. To elaborate, this marvelous invention contracts like human muscles, has a similar practical strength/weight/volume as human muscle. Icing on this proverbial cake comes in its incredibly low cost of manufacture. Materials needed are nylon threads and a heating element. A fixture for production can be produced simply, operated with incredible ease, all while having a low cost. It very well could have revolutionized all of robotics if it weren't for its flaws.

Bad: This is honestly a terrible actuator. Its greatest flaw comes from its speed. they aren't as fast as human muscles unless they're underwater. Water reduces efficiency to unacceptable levels if they're powered by batteries. Water is also rather heavy. If used, you'd have a waifu that moved slowly , would seize up in hot weather, and her battery would die rather quickly. Final nail in the coffin: it's very difficult to get positional control.

2: Pneumatics, moving her booty with air!
What is it? Pressurized air is guided to an actuator where its energy turns into motion. Popular air actuators include rotary turbines, cylinders, and air muscles.

Good: Actuators are light for their power. Positional control isn't difficult to attain. They can be faster then human muscles. Heating elements can be used to augment performance to higher levels.

Bad: These things require electrical actuators to function properly. Thus, they're inherently more complex then electrical counterparts. They need a source of compressed air, either from a tank or a compressor and a tank. Compressors are large, heavy, noisy, all around unsuitable to be incorporated into a waifu. Air tanks would also run out rapidly unless she's barely moving. Overall, they're suited better for industrial use.

3. Hydraulics, they're like pneumatics except stronger, needs a return system, needs an onboard pump, gets hotter, generally costs more, and is heavier.
(2 and 3 are great for stationary machinery which requires high power as they're very cost effective as high power actuators)

4. AC motors
What are they? They're rotary devices which use AC current to create magnetic flux used to provide torque.

Good: Generally highly efficient with good thermal characteristics. Can have controllable speed and torque.

Bad: They run off of AC electricity, batteries don't provide that. It's not difficult to change DC to AC but, it's a layer of extra cost and complexity. Overall they're great but the next actuator is better suited for our purpose.

5: DC motors are the ideal actuator for smaller waifus.
What are they? They're actuators which convert DC electricity into rotary mechanical energy.

Good: They're inexpensive, easily attainable, and simple to control. They're very easy to control. Uses DC which batteries provide.

Bad: Need to be geared down to provide good torque. They're middle of the road efficiency wise.

(For smaller waifus, their lower efficiency compared to the next actuator isn't a major concern. Smaller batteries recharge rapidly, so having her need to charge in her bed isn't a big deal.)

6. Superior Brushless Motors are ideal actuators
What are they? DC motors which need specialty hardware to drive them.

Good: High efficiency, it's the most efficient option available.

Bad: Controllers add expense and complexity.

(1 of 2)
7: Stepper motors, for when you want a self balancing loli
What are they? A DC motor which uses four wires to drive the motor through pulses allowing high control.

Good: Very accurate with great control. They also offer high torque for their size at lower speeds. They can hold a position. (Most other motors will burn out unless they have protection circuitry) Comes in Nema standard sizes which makes designing around them a great experience.

Bad: They require special drivers to function. Low efficiency unless they're rotating at a specific range of RPM.

(Because of their great control characteristics, they're fantastic for small self balancing waifus)

8: You, yes you Anon!
What? You can pull her along with you.

Good: She doesn't consume power while being pulled. Could generate power while being pulled. Will be right beside you.

Bad: She's completely dependent on her Anon listening to her for her needs to be fulfilled. (Potentially a plus if you dig physically disabled girls)

Feel free to add or correct anything!

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interior view of the gear housing
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>Heated Twisted Nylon
Most of the independent researchers in this field have given up on it as it's too impractical. Nowadays there's several different approaches to artificial muscle fibers but they're all impossible to make at home and won't be available commercially for years to come. They've solved the issue with slow response time though.
The MIT design has the benefit of being cheap to manufacture and can be electroplated with a metallic mesh for strain feedback based on changes in electrical resistance. It still has the same heating/cooling issues of twisted nylon.

My prediction for DIY robowaifus in the next few years is soft robotics using pneumatics. You can either 3d print the parts yourself by converting a standard 3d printer to print silicone or 3d print the molds, the silicone required isn't too expensive and an external air compressor(ones used for paintball tanks are cheap and fast) could quickly replenish a light weight carbon fiber air tank stored inside the doll which could also be swapable. Dozens of cheap squishy muscles could move every limb without weighing too much.
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Yeah, looks like soft robotics will be an important part of robowaifu tech anon. And I've said that pneumatics can give us reasonably good motions (thousands of examples in animatronics and dark-rides), but lacks the force needed for everyday tasks. Maybe that will change. We'll still have to deal with the sound problem, but that's the case with electrical motors today as well.


We need to stop pretending that any humanoid robots over 3-4 feet tall we're going to have in the next decade is going to walk around or interact with the real world autonomously in any real capacity. The force required for basic automation should be set at the minimum with ease of manufacturing and cost kept into consideration when starting out.

That small robot dog Spot from Boston Dynamics that can move around and interact with objects costs around $50-60k and was only leased to certain companies earlier this year. The motors with drivers in it alone cost $4-5k. I'm guessing it uses an Xilinx FPGA chip that costs at least $10-15k(they sell chips for over $50k so the price isn't extravagant), the lidar system another $10k.
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>We need to stop pretending X
What is this Reddit now? Impractical visionaries have moved mountains before today anon.
they had something like that in the i-robot movie, I'm pretty sure it was hydraulic though
I don't recall that scene.

Hydraulics can produce a metric shitton of power it's true, but it comes with a raft of downsides as well. For instance, being highly toxic in general, and introducing a constant maintenance aspect for the robot. It would be an engineering challenge certainly, but it might be useful in just the shoulders and hips as very strong actuators, if slower.
buddy the robot muscles were shaped much the same way that skeleton muscle is and after being shot in the office left what I assume to be hydraulic fluid as it fled.
I see thanks. I'll have to re-watch it.
Sure thing, part of that is my assumptions and interpretation of the scene of course.
That's pretty interesting anon, thanks. Any ideas how we might use this on a normal robowaifu?

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>What is this Reddit now?
If sure feels like it seeing an 'inspiring quote' from some worthless celebrity but a board like this wouldn't exist on that site and you know it. I'm hoping this board takes the realistic approach at building a robotic sex doll and stops focusing on building a general purpose humanoid robot that can also have sex.

The people working on this over at The Doll Forum have the right idea; use AR to place a head, legs and arms on a motorized doll torso(the part that you physically interact with). You just saved thousands of dollars on each limb, tens of thousands if you want decent motion with numerous DOFs.

>The current actuators take about 30 seconds to fully bend and contract, and up to four minutes to return to their original shapes. That’s because the material takes a bit of time to fully heat up and cool down.
Same issue as with most almost all types of artificial muscle fibers. There's a reason why the test they show are all miniatures, this technology doesn't scale.

Here's a much better idea of how pneumatic air muscles could work on a skeleton using a chain and sprocket. For some reason it was deleted when I posted it earlier.
>For some reason it was deleted when I posted it earlier.
Because off-topic, certainly not a robowaifu reference. At least here ITT it's somewhat on-topic, I wouldn't spoil it if I could do your images separately, but I can't.

If you want to explore the macabre (or promote it) this isn't really that kind of board. I'm not adamantly opposed to it though, so feel free to shitpost in The Lounge as you wish. That's what it's here for. >>39

Otherwise, thanks for the input anon, have a good day.
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>If you want to explore the macabre (or promote it)
That isn't my intention and looking at that torso again it is very off putting thanks to the type of CGI he went with. I don't mind the spoiling or removing of my other post.

This comic explains the issue I have with online discussions on humanoid robotics. Everywhere I go people don't understand this concept and expect a full human size robot to behave the same as a tiny one. I probably flew off the handle a bit.
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reminds me of this
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Here's a type of artificial muscle fiber I hadn't considered for actuators.

>When placed in an electrolyte solution, the material expands by a factor of 100 in response to a weak positive electrical pulse. A negatively charged pulse causes the material to return to its original volume.

>In follow up experiments, scientists insulated a wire with the new material. When electricity was run through the wire, the thin film of polymer absorbed water and converted to a rapidly expanding gel. When scientists repeated stronger electrical pulses, the gel expanded to a volume 300 percent larger than the film's original size.

First of all this wouldn't produce very much pressure even if packed in bundles and there's no information on how quickly it works or how many times the process can be repeated before the polymer chains breaks down. Let's say you have two muscles linked together both in elastic sheaths, activate one to absorb all the water expanding the sheath contracting the other one.

The main benefits of this is how simple it is and small they can be made.
Interesting anon. I predict we'll eventually find a reasonable artificial replacement for muscle tissue. It seems inevitable tbh, there are a zillion uses out there for it, not the least of which will be effective robowaifus.
How about nylon-woven hydraulic muscles? 200kg force? We got it!

Running over your robowaifu with 5 tons and she's still able to punch a hole through a truck? Easy!

Further reading on different designs and their strengths and weaknesses:
Those are some very cool ideas anon, thanks. I'll make some time during the holidays to catch up on my robowaifu reading.
Pneumatic Actuated Muscles article has a few links.
What about using nitinol wire (contracts when heated) as an actuator? Could you just apply a current to it and get a usable amount of contrative displacement and force?
I've played around with it and the general consensus is it's not powerful enough to use as a main actuator for anything but a tiny butterfly robot or other insect like robots of comparable size.
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Here's an example image of attaching 4 PAM muscles end-to-end together for larger displacement. Capped from one of anon's pdf's posted here:
I see. Maybe it will be perfect for the Lapis Fairybot then. Thanks for the input anon.
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Brushless gear motors are great, good torque to weight with good efficiency. They usually have a built in ESC for ease of use.
Anybody think about piezoelectric motors? They seem cool and to have good capabilities except the tech is new and it seems like there's not many large piezo motors. There's probably lots of pitfalls I'm missing on this but it's an interesting anecdote.
Ran across this in an old C programming textbook. Probably not too useful for us here at /robowaifu/. But still it's pretty amazing, and might actual prove useful in some fashion. https://en.wikipedia.org/wiki/Scratch_drive_actuator
>>1896 Apologies Anon, I missed this post somehow. So yes I think they have good potential for us, especially in something like a fairybot-sized waifu. If you're still around mind sharing links or something?
Mine will use a hybrid system, electric actuators where little power is needed and hydraulics in the high stress parts like the arms and legs
>>2842 Sounds like a plan Anon. Hydraulics are good for high-power, but generally slower-speed uses that can take the extra weight of all the pumps, fluid, and manifolds, etc. Electric actuators are good lower power, faster-speed responses. Have you worked out any sketches yet?
>>1425 - Not every motion needs to be strong - Bipedal walking is optional and for later - Correctly done it's like falling forward, very efficient - These bots might be quite lightweight - I want to combine different approaches - My price limit for a premium model is ~15k We'll find out by trying.
>>4290 >We'll find out by trying. Exactly so. That other poster's diversion astroturfing is neither accurate, nor productive here. I think keeping mass a small as possible with be absolutely vital to keeping overall costs down, as well as enabling us to achieve 145cm+ sized robowaifus during the first few years. Mass affects literally every other area of concern.
>>4301 I honestly always wondered why mass would be such a problem, when the can move and we won't need to carry them. Didn't know the details of how it affects the energy consumption or need for strength. I'd like not to care about it to much, bc I want to put water inside her body. However, bipedal walking is like falling forward. It needs less energy than walking on all fours, which is why we're doing it. Standing up might need more energy, but there can be motors in the hips and muscles in the legs/thighs for that.
>>4305 >I honestly always wondered why mass would be such a problem In a word: Energy. Energy is everything. But, since you don't want to think about it I'll leave it at that except to additionally encourage you to think about the Square-cube law and it's relationship with mass, etc.
>>4308 My last post said that I do care about it, I just didn't know the details before. My concern is the amount of power we need for some movement eg for getting of the ground and standing up, however the don't need to go for a walk outside. I'm fine with a short range, I plan to plug her in when sitting on the couch or on the second chair in front of my computer. There also is a prototype for a direct ethanol fuel cell which has been build by some school girls.
>>4310 >My last post said that I do care about it Ahh, my apologies for the misunderstanding then. So, increased mass directly affects mechanical engineering: -Stronger frames are needed (adding add'l mass) -Stronger struts are needed (adding add'l mass) -Stronger joints are needed (adding add'l mass) -Stronger motors are needed (adding add'l mass) -Stronger connective elements like cables, levers, gears, pulleys, even nuts & bolts, etc. are needed (adding add'l mass) Increased mass directly affects electrical engineering: -Higher-capacity batteries are needed (adding add'l mass) -Higher-capacity cables are needed (adding add'l mass) -Higher-capacity relays, regulators, inverters, etc. are needed (adding add'l mass) -Higher-capacity connective elements like contacts, fittings, even wirenuts, etc. are needed (adding add'l mass) All of the above also cost more as well. Increased mass directly affects daily user experience: -Robowaifus require longer cycles to recharge, therefore unavailable physically -Robowaifus, being heavier, will be more awkward/infeasible to carry around, say up a flight of stairs. -Robowaifus cannot be as tall if they are too massive (cf, all of the above). Software engineering is basically unaffected afaict. Kinematics calculations should be as complex whether more or less massive, given identical capabilities. Control systems in the S/W should likewise need only minor adjustments. There are probably many other details I'm neglecting to mention, but just what I can pull off the top of my head rn is enough to go on with for sure. Mass is everything.
>>4313 Ok, I will see how far I get. My plan is to use air pressure and electric motors, maybe a little bit of pneumatics. The body above the hips might be at 20-25 kg. For standing up she could use motors in her hips and air muscles in her thighs. These motors might be slightly to big for the hips, but they seem to bring more than 5 kg to the table at 40 Amps: https://youtu.be/6lW2YGQQIQ4
>>4314 >maybe a little bit of pneumatics. I don't recall which threads it's spread out across, but the idea of using artificial, pneumatic muscles has been discussed here. They seem like they could bring a good bit of force to the mechanical-engineering table, while adding relatively less mass overall. Good luck Anon, please keep us up to date here on your progress!
>>4315 I currently focus a bit on graphs, chatbot, math for ml, ... I'm going into printing and motors in a few months. I might try some nylon muscles before that. Smaller actuator: https://youtu.be/LCwfMz9Laao Small RC cylinder for hydraulics: https://youtu.be/QRg0ZAvxVFk
Space and heat are the limiting factors I see here, but the most heat and space efficient systems produce noise and don't look very human. Space is less of an issue for larger muscles, but areas that require a wise range of motion with a lot of dexterity will be a severe issue. The hand, for example, has over 30 different muscles. About half are used to contract the fingers and thumb, about half are to contract the fingers and thumb, with the rest being wrist control. These muscles range from a few centimetres to several inches in length, with many muscles controlling hand movements located in the forearm and connected to tendons which then connect to the hand. How are we supposed to fit muscles, tubing, and coolant veins into a feminine and natural looking arm? Pneumatic and hydraulic actuators are doable, but they'd have to be very small but still fairly powerful. Getting the force required for not only a quick but strong enough contraction will be difficult given the space restraints. I'm not entirely sure how we could fit everything into an arm without sacrificing too much strength. Synthetic fiber coils take up far less space, but the downside is that they produce heat. Pneumatic and hydraulic systems also produce heat, but fiber coils primarily function by way of heat. When the coil has an electric current flowing through it, it will heat up and contract. When the current is broken it will extend as it cools down. Small singular fibers aren't so much of an issue, but when you start coiling those coils it becomes much more difficult to distribute that heat effectively, and may end up heating up other muscles that weren't supposed to be contracted. This doesn't even touch on price price and availability, where synthetic fiber coils may end up being more efficient in the event that the temperature can be managed they aren't exactly being sold at the store. They can be manufactured, but the process is time consuming and complicated, plus isn't as effective as synthetic fiber coils developed by labs with better access to supply equipment.
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>>4317 >How are we supposed to fit muscles, tubing, and coolant veins into a feminine and natural looking arm? Are you complaining at the suggestion that we create attractive, feminine robowaifus, just because it will be a difficult achievement Anon? If this was easy, everyone would be doing it. :^) And we will do what we can with what we've got, as always. Necessity is the mother of invention, after all. Our achievements will be rather crude at first ofc. No doubt we'll make do with solutions far, far simpler than the exquisitely-crafted symphony of systems God Himself devised for human bodies. Our goal is simply to reach a level of believability and pleasantness that roughly approximates various waifus in animu & mango, not the hyper-realism of 3DPD. Attempting the latter is the uncanny valley of death for our domain here at /robowaifu/. >the force required for not only a quick but strong enough contraction will be difficult given the space restraints Good analysis. Force =/= velocity. Explosive motion isn't probably even required until we reach the phase of devising QT3.14 Roboenforcers anyway. Slow and steady movement will be plenty to go on with at the beginning. >I'm not entirely sure how we could fit everything into an arm without sacrificing too much strength. This issue is what made me tend toward designs using a Bowden-cable like approach, with the primary force actuators remote inside the torso. I'd say the wound nylon fishing line coils might be quite well suited to something requiring delicate motions, though not necessarily strong ones. Facial animations, perhaps? >price and availablilty Again, we'll make due with creativity, I'd imagine. After all we're pioneering DIY Robot Wives, not high-dollar, globohomo-Facebook-wives. Stay encouraged anon, we'll figure this all out in time. Just be patient. That's why we have this board, so we can bounce ideas off each other and share new directions to explore. We'll get there.
>>4318 >Are you complaining at the suggestion that we create attractive, feminine robowaifus, just because it will be a difficult achievement Anon? Not at all! Attractive, feminine, human robos are my goal as well and I do think it is possible. It just seems to be a matter of determining what is most efficient where, and the more planning and research and accurate theorizing that can be done before construction, the less wasted in failed attempts. I raised my concerns because I feel they should be considered before trying to apply one system or another. Soft robotics are definitely in the right direction, but determining which method for what part is the only thing holding me back. For example, https://www.youtube.com/watch?v=gd9d_BAXWvg this robot arm is pretty decent all things considered. It uses hydraulic actuators and has decent anatomy. However, it isn't perfect and the project has been running for six years and still hasn't ironed out a single arm. I don't mean to imply that the project is doomed, but rather to raise the exact points that I find concerning so that we can address them and make progress without having to spend money in testing that may have already been done. >Slow and steady movement will be plenty to go on with at the beginning. Of course. If the average female grip strength is around 60 pounds then we may only need a fraction of that to be of any use, but locomotion seems to be a bit different. Slow movements are good, we don't need it to be able to sprint before it leans to walk, but having the strength to hold itself up along with the ability to reposition and balance using muscles in the feet and ankle would be important for a natural gait, however slow. >Bowden-cable like approach, with the primary force actuators remote inside the torso. So essentially using a cable as a tendon where the actuation is inside the torso? Could be doable, and could save on space for more space deficient locations like hands and face and feet. One consideration is the potential that the torso has for other things like battery, computation, storage, and coolant tracks. The limbs can still be used to house muscles in order to save torso space, but done so in combination with bowden cables if space becomes an issue. The question is, where would that be ideal? I'm guessing that the fingers and wrist control would be a good choice for hands. Facial animations is possible, but musculature does add to facial form and that would have to be addressed. Feet would be possible as well. Essentially, the extremities seem to be the best options considering their small size and lack of room to me. There are 600-800 muscles in the human body, so being as space efficient as possible and placing different types of muscles where appropriate seems to be an important consideration even if we ignore a couple hundred of those muscles that don't end up mattering to a non-biological robowaifu.
>>4317 I can't tell you how it's exactly going to work, but I'm optimistic. It will be about combing a lot of different forms of muscles in a smart way. Fingers will probably work with strings to bend and air to stretch them. The valves might go into some bone or behind some foam. Same with facial expressions, but I also think solenoids will be useful there. Arms don't need to be to strong, but also ellbows could have a lock mode. Power for lifting would then come more from the shoulders. Idk. > heat are limiting the factors Please forget that. We will need heating units in them to warm up water while they're plugged in. Then use it later for body warmth, when they're sitting or lying around. They are not meant to walk around all the time and carry stuff. Dancing while standing on one spot might be supported with suspensions, springs or sth alike. I also had the idea that heat might be useful to increase pressure in tanks for the air muscles. Solenoids: https://youtu.be/K6Vg8QIiTYw On the topic of nylon muscles: Has anyone tested them with hot and warm water? I might try tomorrow, can't use the hairdryer right now bc noise.
Oh I forgot those two, flat and strong, but around 500$: https://youtu.be/gsOPZltbvgM
Here the speed of nylon muscles can be observed. They contract ~3cm on a length of ~14cm and carry at least 250g with a small fiber. Should be helpful. Also, they work again after cooling down with cold water. Just leaves me to wonder how often they work until they wont. https://youtu.be/RdiD6ArxAbc Btw, same channel than the hand. Thanks for the tip, and YouTubers should certainly subscribe and set the bell to always (same for the other channel I post videos here)
>>4320 >I can't tell you how it's exactly going to work, but I'm optimistic. It will be about combing a lot of different forms of muscles in a smart way. I am too, and I think you're right; it will take a lot of different techniques all coming together just-so, before we succeed in ironing everything out smoothly. >Fingers will probably work with strings to bend and air to stretch them. The valves might go into some bone or behind some foam. Good ideas. >Same with facial expressions, but I also think solenoids will be useful there. Any chance you could post a simple sketch diagram of your idea for this Anon? It might help with understanding. >but also ellbows could have a lock mode. That's actually a good safety feature as well. Probably most major joints should incorporate some kind of safety brake in them. >Please forget that. We will need heating units in them to warm up water while they're plugged in. I'm not that Anon. While I don't think anyone can say for absolute certain until we have functioning robowaifu prototypes to test with, but all my experience tells me that Anon is correct. Too much waste heat will be the primary thermal issue for us to deal with. >Has anyone tested them with hot and warm water? I haven't so I can't help you there. >>4323 >>4327 Thanks for the videos >and set the bell to always (same for the other channel I post videos here) Thanks, but no thanks :^)
>>4320 >I'm optimistic Good! Stay hopeful anon. Nothing will be done without a healthy dose of optimism. >Fingers will probably work with strings to bend and air to stretch them. Fingers do technically work with strings, in the form of ligaments. Air to extend isn't a bad idea, but I'm curious how it would compare to just using more strings or muscles on the back of the hand. >Please forget that. We will need heating units in them to warm up water while they're plugged in. Heat isn't entirely a bad thing, sure, but heat distribution definitely will be. A machine that uses a combination of silicone and metal will inevitably have varying conductivity throughout, which can be damaging if the heat becomes too localized and starts to warp plastic or burn out motors or computers. Clay-cold corpse waifu wouldn't be very comfy, but the goal is more to spread that heat around so that it doesn't build up in any one place in particular, while allowing for extra heat to be vented off it the average temperature becomes damaging. Heating up is relatively easy, albeit not very energy efficient, but even still won't be very useful unless the heat can be distributed. Linear solenoids could be very useful, especially ones engineered to give relative force based on relative current. The smaller ones tend to only be able to give a relatively small amount of force, but for some parts it could definitely be useful if the main actuation was done inside the torso.
>>4356 > Heating up is relatively easy Not only relatively easy, but in fact unavoidable. :^)
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>>4343 The idea about solenoids in facial expressions is to use them by connect them by string to the silicone skin of the face. Alternatively part of the skull under the face would be moving. Either way the solenoid would be inside the skull, pulling a string or moving a little plastic part. They're week, but smiling and other faces don't need much power. Also, using several solenoids could be usefull to have more degrees of movement. And there fast and very reliable if not overheated. I don't have a exact plan how to do that, it's just a idea yet. Will buy a printer in a few month, bc I need to move. Might looking into animation before that, but I'm more for trial and error than sketching it out exactly. I would need a exact facial expression simulator with muscles (solenoids) and strings... >4356 Yes heat distribution will be important, it just isn't something that I think will be difficult. There's a thread for thermal management, we can do it with air and or water. I'm going primarily for water. All the soft parts of the body which aren't muscles could be tubes with water. They could also release heat from the mouth, and if necessary when they're in the bathroom releasing (hot) water. Many parts would need to heat up a lot until they are being damaged. Great hands however, are maybe one of the hardest things. I thought about this a lot today, and I'm worried now. For the premium models I'm only thinking about Titanium plates and tubes, carbon fibers, fine mechanics and PCBs, no more 3d printing (except for bigger prototypes). We will need to use as much as we can get, using strings for opening the hand is also necessary, but I'd like to use pressure in channels through the bones as well.
>>4364 >Great hands however, are maybe one of the hardest things We have a dedicated hands thread Anon, IIRC. If you come up with some clever ideas, mind posting them in that thread? I think hands and faces are arguably two of the most important areas of robowaifu focus (or should be).
>>4365 Yes, more specific talks on these topics should happen there.
Another little actuator for small movements and switches. Not very powerful, but might be usefull for some usecases. Basically similar to a solenoid, but moving left/right or up/down instead of forward/backward https://www.instructables.com/id/3D-Printable-Robotic-Actuator/ https://youtu.be/UNvMEfPD-Hg Specific use cases should maybe better be discussed in the threads for faces >>9, hands (which do not have a thread of their own yet?!?), desktop waifus >>245 or fairybots >>266.
>>4447 Thanks for including the pic Anon. Yes, seems like a clever little actuator approach that an anon can entirely manufacture at home from wire and 3D filament stock. I hope Fairybot Dev returns to his project here someday.
This guy with the printed motors and robot arms on Youtube, Skyentific, he's now developing his own cheata-like motor: https://youtu.be/WKRLlthr9kY Might be usefull for walking >>237 or other things.
Here's a website about all kinds of mechanisms from and for animatronics: https://www.mekanizmalar.com/
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>>4525 I think we are often goin to use Cycloidial drives for some of our motors, bc weight and space. Problem is, 3d printing is great for prototyping, but a some point we might need them in metal. Printing gears is great, if they can easily replaced. Otherwise not so much. With this approach it's even more important, since it might grind down on the teeth more then others. However we need small gearboxes and cheap motors with low speed, so I wanted to throw this in here. https://en.m.wikipedia.org/wiki/Cycloidal_drive https://youtu.be/7uXN_y7JdyM Fusion 360 howto: https://youtu.be/jQ6LQBFZXmU More advanced, 299/1 reduction: https://youtu.be/6xoCeliJ11Q Another dual stage one, printed: https://youtu.be/ewoUsVMFWfU 27/1 https://youtu.be/pizl7i-uB68
The discussion in R&D General starting here >>1627 is a lot about artificial muscles.
>>4573 Thanks for that Anon. That kind of cross-referencing helps everyone.
We had a discussion in the thread about bipedal walking which of course circled a lot around motors. Someone >>4505 brought up RC motors eg from Apex, for which we would need to create some gearboxes of course. Locking into it, I found out those being brushed motors. But, brushed motors seem to be consumables. Anyone knows how many hours such motors last? (I don't mean the battery.)
Teardown and short comparison of a clone from the MIT Mini Cheetha actuators, priced at AliExpress around 360$ with the driver and 300$ without it: https://youtu.be/Mhxz2Bj2RXA Seem to be quite similar, he didn't run comparative tests though. He planned to do more tests, I subscribed and post more if that's going to happen.
>>4773 Hi Anon, I'm that poster. I haven't run any of them to exhaustion before so I can't really say. I imagine damage from overheating will be the biggest design concern for one of those type motors.
>>4890 Thanks Anon, that was really interesting. I feel like I'm getting an engineering education here haha. I really like the tunable 'spring-action' this actuator exhibits. I could see these being well worth their price in the robowaifu's knees, for example. On that topic, do you think there's much chance these quality actuators will drop further in price? I see easily why they are priced as much as they are, but still it's fairly costly for the average anon I expect. Certainly for me still in school it is. Regardless, that was good.
>>4890 related >yfw 860 class at MIT
>>4896 >overheating Don't know. Dependent on the whole design. The last time there was this discussion, there was the idea of doing a experiment to find out how well silicone rubber radiates heat from a warm water bottle. >>4897 I don't think they'll fit into knee and the joint there is different, they'll be rather for the hips, but that depends on the design. Humanoid bots which can walk around will be expensive for young adults and teenagers. Just moving the legs around in bed might be doable with less expensive motors. >>4898 Thanks, more to read, no time. ;)
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A little update on what's going on in the dollforum in regards to actuators. Other updates will go into the appropriate threads: Speculations on motorized dolls: https://dollforum.com/forum/viewtopic.php?f=6&t=131833 Takeaways: Helical gears might be good for gearboxes bc they seem to be more quiet. They have similar discussions, like when to use motors or pneumatics. I think pneumatics are fast and maybe for the heavy stuff, but motors have ther place in between.
>>5039 That's encouraging to hear they are branching out into robowaifu territory and not just languishing in the world of sex dolls. Please continue to keep up posted, Anon.
Here's a video about how to build a pneumatic cylinder out of PVC tubing ( subtitles needed for infos!): https://youtu.be/Rp1uuMrTy8M Just good to know that this is possible. Though, keep in mind PVC is extremely toxic if it burns, so I'd recommend using another material later. Should be fine for prototyping in some garage or if one is sure that there won't be a fire.
>>5101 That's pretty interesting. I bet we can find other ways to do this as well. >Though, keep in mind PVC is extremely toxic if it burns Thanks very much for the warning!
While we're at it: James Brunton has made a nice introduction on pneumatics: https://youtu.be/d7ErG5ecO2s - Some things where mentioned in the OP here, but his vid makes it more visual and audible. >>5103 You're welcome. I added it to the thread on Waifu materials here >>5106, and might link to that at some time from the skeleton and armatures thread. May still use that stuff for a skeleton prototype.
>>5107 >May still use that stuff for a skeleton prototype. Yes, I think tubes are the very key to lightweight and inexpensive--yet still strong--robowaifu 'skeletons'. They have so many structural benefits intrinsically on their own. When arranged well, and combined with the properties of tensegrity, I think we'll find a key for getting started while we're still early on here.
actuator-joints and synthetic electron-responsive muscle fibers would be better then strictly machine actuators since actuators concentrate tension on their own leading to the rocking-shakeing movement we see in modern robots. Going beyond that i have a design for mechanical tendril arms with can rotate up 70 degrees on it's compound endo-exo skeleton. These range in scale from the microscopic intended for micro-surgeon drones(aka nanomachines) to straight-uo Doc Ock-style intended for use as mechanical structural anchors for astronauts and meteorite mining rigs. With materials allowing us to emulate organic tissues more and more accurately in synthetic counter-parts, more organic mechanism inspired designs will take over as they will benefit from both evolutionary iteration and scientific development. Flesh and metal.
>>5262 What are actuator joints? When will we see something of your design or even some real build? How will we get our own 'synthetic electron-responsive muscle fibers'? And the nanomachines?!? What will that cost? How long will they last in a body, where we won't be able to replace them easily?
>>5266 https://www.youtube.com/watch?v=BgaxscXsIWY The electric motor is great for driving a circular rotation but not apt for moving an arm, instead the ability to run an electric current through a electroactive polymer coiled and banded in the form of muscle fibers anchored to synthetic bones by synthetic tendons. of my designs, maybe once i get my scanner working again.being a poorfag sucks. in a synthetic organ that attaches to the liver, where due to scale and their reliance on the circulatory system as a transit means and a source of fuel in the form of salts and fats they will be able to flow to. highly, their shell is a silver/gold alloy so they they're both both noncorroding and anti-microbial. but they can be recycled by the central hive(the aforementioned organ attachment) and rebuilt so as long as it functions and you eat enough calories it can re-fabricate more drones from scraped ones after breaking them down for materials.
>>5271 Your postings are hard to parse, basicly unreadable... Write down your thoughts in a clear manner, or just don't write anything. Thanks. If you want to speculate on nano machines, which we'll have soon or you're gonna build with your scanner, we have a Lounge thread for humor and shitpostings here: >>39 If your arm with artificial muscles becomes real, I'm looking forward to see some pictures and videos of it, as well as a tutorial how to reproduce it, or a source for where to buy it. Till then, it's just a fantasy.
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>>5274 Ah, an hour later or so, I got it: Your "design" is just some sketch about how such a material could work on an arm, and you need to scan the drawing first, so you could share it. And you are maybe a bit to much into watching Alita, with her nanobot muscles, and hoping she'll become real soon.
>>5276 >And you are maybe a bit to much into watching Alita, with her nanobot muscles, and hoping she'll become real soon. >too much >Alita Is this even possible? :^)
Bubble muscles? Ever heart of that? Me neither.... Till now: Characteristic Analysis and Design Optimization of Bubble Artificial Muscles: https://www.liebertpub.com/doi/full/10.1089/soro.2019.0157 "Recently developed bubble artificial muscles (BAMs) are lightweight, flexible, inexpensive, pneumatic actuators with the capability of being scalable, contracting at a low pressure, and generating sufficient tension and contraction for assisting human mobility. The BAMs are simply fabricated by using a commercial plastic tubing with retaining rings, forming a “bubble” shape and creating a series of contractile units to attain a desired stroke. ..." Via: SoftRobotics Journal SoRo: libertpub.com/soro
Correction: Via: SoftRobotics Journal SoRo: liebertpub.com/soro
>>5336 That's very cool. I imagine the response would be a good bit faster than the more-typical pneumatic air muscles discussed on the board before. Thanks Anon.
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Crosslink to some posting about the heavy duty servos being used in Sophie >>6729 I found this planetary gearbox here, which might be one of the best (first picture related): https://drivesncontrols.com/news/fullstory.php/aid/6044/Backdrivable_actuator_offers__91unrivalled_92_speed_and_stiffness.html and here the website of the company: https://genesisrobotics.com/ I found this while was looking into videos about cyclodial and harmonic drives, to know more about them and how to build them cheaply. Both tend to be light and compact, which is what we need, but they probably should also be backdrivable. Which means in my understanding, a arm would fall down automatically if the flow of energy stops. Harmonic drives seem not to be backdrivable, at least the one example I saw. Cyclodial drives have been mentioned here >>4536 already. Their advantages are "high gear ratios (often 100:1 or greater) with excellent torsional stiffness, good shock load capacity, stable backlash over the gearbox life, and low wear" https://www.motioncontroltips.com/how-do-cycloidal-gears-work-and-where-are-they-used/ "Harmonic and cycloid drives are both compact, high ratio transmissions appropriate for use in anthropomorphic robots, although cycloid drives are rarely used in the field. This paper describes the design parameters for cycloid drives and shows the results of six cycloid models designed to match corresponding harmonic drives. Cycloid drive models were compared with manufacturing data from corresponding harmonic drives with respect to maximum gear ratio, transmission thickness, efficiency, backlash/gear ratio ripple, and reflected inertia. Cycloid drive designs were found to be thinner, more efficient, and to have lower reflected inertia than corresponding harmonic drives. However, the cycloid designs had larger gear ratio ripple and substantial backlash, and they could not meet the maximum gear ratio provided by the corresponding harmonic drives in two out of six models for equal applied torques. Two cycloid drives were manufactured to confirm efficiency predictions and demonstrated moderate to high efficiency across a range of output torques. Cycloid drives should be considered for robotic and prosthetic applications where smaller thickness/higher efficiency requirements dominate over low backlash/gear ratio ripple considerations." https://www.researchgate.net/publication/261416541_Cycloid_vs_harmonic_drives_for_use_in_high_ratio_single_stage_robotic_transmissions This article is about a wormgear that can switch to become backdrivable: https://robomechjournal.springeropen.com/articles/10.1186/s40648-019-0149-7 Then there is epicyclic gearing aka planetary gears, which are often 3d printed, good for low noise applications: https://en.wikipedia.org/wiki/Epicyclic_gearing
>>7086 That is a cool looking planetary Anon. I imagine further reduction could be achieved by increasing the diameter of the orbital gears?
We really should move away from always talking about stepper or servo motors automatically when it comes to motors. In many cases we need flat bldc motors with low kv and then adding gears or drives to it. This guy here talks about a motor which looks like one I once had my eyes on, but didn't know enough about, other people were sceptical, and I forgot about it: https://youtu.be/M6hIEU7j_MY Glad, I rediscovered it now. That huge ones will be only usefull in some places, though. But the same rules apply for other cases. I bought two pm35s-048-hpl2 (pic related) for testing, but there are similar sized bldc motors available. No big deal, because they were cheap, though. Also, who knows, maybe I'll need something with lower power but more precision at sometime. >>7087 Yes, that's how I understand it so far, but I'm only trying to learn and memorize these thing myself right now.
>>7088 One of the issues with stepper compared to other motors is their increased expense. It would help us if we could figure out ways to use simpler/cheaper actuators (of all types) if we want relatively inexpensive robowaifus to be a reality for us and others. Thanks for the info Anon.
>>7089 Have been researching stepper motors quite a bit. The main advantage appears to be very precise control. From what I've seen, the large steppers like NEMA 23 & 34 are comparable in size, weight and expense to the large servo motors that I use. I am planning to experiment with one inside Sophie's torso to act as her waist (mainly because they are a nice, simple cube shape as opposed to the quite complex shape of the high-torque servos). But the main drawback I can see of these stepper motors is that they get really hot and are nothing special in the torque department. A NEMA34 has radial force of 220 Newtons at just 20mm from the axle. That's 11.2 kg force at 1cm. Whereas the high torque servos can provide up to 380kg force at 1cm from the axle (granted it's probably less in the cheap $80-90 motors like 340kg.cm or something). Even though the high torque servos may not provide as much fine control, all that extra force makes them very useful in life-sized robots!
>>7095 >Even though the high torque servos may not provide as much fine control, all that extra force makes them very useful in life-sized robots! Good points, and thanks for the physics explanations. I always wondered what that rating system meant exactly. We'll probably need different strength ones for different areas right? The shoulders should be stronger than other areas IIRC.
>>7096 Yeah. In the arm I am making it goes: 180kg.cm servos in the shoulder/upper torso 60kg.cm servos in the elbow 20 kg.cm servos for the fingers and wrist. Micro servo for the thumb joint. Non-ambulatory legs would probably need a couple of the highest torque servo motors you can find in the pelvis, then maybe some 110kg.cm servos to give the legs lateral motion as well as up and down. Then 60kg.cm in the knees, 20kg.cm in the ankles. That sorta thing. As for making legs that actually walk though - LOL fuck that I'm just a pervert building himself a robowaifu not a Boston Dynamics engineer! For motion I'm going DC motors and belt-driven wheels with knobbly tyres. She can leave her legs at home.
>>7102 >LOL fuck that I'm just a pervert building himself a robowaifu not a Boston Dynamics engineer! Actually I would say you closer to being a pervert building himself a robowaifu and a Boston Dynamics engineer! Or at least closer to than say the average orangutan heh. But seriously, you're much better at this than you give yourself credit for don't let it go to your head Anon :^) and you're making nice progress with your Elfdroid Sophie. It's inspiring to us all, so please don't stop until she's done.
There are not only stepper motors and servos! This is not the only distinction, and we are getting confused here over and over again... https://en.wikipedia.org/wiki/Brushless_DC_electric_motor can be a stepper motor: https://en.wikipedia.org/wiki/Stepper_motor but there are also ones for airplanes (aeromodelling) or radio-controlled cars, which are not (brushless) stepper motors! If I'm understanding it correctly now, steppers have the positioning system build in (encoder), and WP on servos as well, but it a additional system like a optical rotary encoder. WP: "It consists of a suitable motor coupled to a sensor for position feedback. It also requires a relatively sophisticated controller, often a dedicated module designed specifically for use with servomotors." We can use also use simple electromotors, ideally BLDC in most cases, I guess. Then adding the sensors somewher else, and also adding our own gearboxes or drives. This might not always be the best way, but it's more flexible. >>7089 The NEMA motors for printers are quite cheap. Though the NEMA standard refers to the size and format anyways. More expensive motors ones have probably also more power. >>7095 Using BLDC motors with our own drives might be precise enough in many cases. My understanding is that these are like your high-torgue motors, but the control would be external. Steppers and servos are very precise, probably more than we need it. >>7102 > 60kg.cm servos in the elbow Fine, but why does she need to lift ~40kg or more using both of her arms? Could the arms and hands even bear that much? > As for making legs that actually walk though - That's something for later. Most people here always came to the conclusion that it's not that important. Also it's a gradual thing. Standing while doing some works (dishes, cooking) or dancing while standing on the same spot would already be quite useful.
>>7102 Hey this is my first post here, some anon linked me here after I made a thread on /diy/. Anways, are you sure 60kg is enough for the elbow? My estimate for the elbow alone was a 200kg servo. With an arm length of 30cm that leaves us with 6.6kg. Now if the shoulder moves the entire arm, the elbow has to be able to hold the forearm at least steady, if not move it, when it is being moved. For the shoulder itself I guess 300+kg? As stated though this is my first post and I havent been in this field for long. I wanted to share my opinion on the calculatios and I'd like to know aswell how you determined your values :) PS: Other kg servos work aswell, but after gearing them they need to be able to do at least 0.5s / 60 deg to be humanlike, I measured that.
>>7130 >Hey this is my first post here Hello Anon, welcome. Please make yourself at home here on the board and don't be afraid to ask questions. Most everyone here is pretty helpful and will answer you if we can. We have plenty of different robowaifu-related topics on the board and hopefully you can find some that interest you here. Good timing, we're having our 4th birthday coming up tomorrow.
>>7130 Welcome. How did you calculate that? I realized my calculation in >>7108 was rubbish, bc I got confused, but I don't even see where you are coming from. The simple version would be 60kg / 25cm is 2.4kg per arm, or not?
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>>7106 > don't let it go to your head Anon This. One of the many reasons I am building a robowaifu is so that I can have a companion who lacks an ego. For all the advances it has driven us to make, the human ego has also caused incalculable damage to everything on this planet (I think it's one of the biggest human flaws). You know how women like to bang on about the "fragile male ego"? Well, why is it then, that the entire Western mass media and advertising seems to be full of characters and scenarios created for the sole reason of pandering to the female ego? Maybe it's this, combined with the bullshit that simps tell women, but it seems to me that many Western females have astronomical-sized egos (at least as bad as the men). I've worked with plenty of women. Four of them had gigantic egos (only one guy I knew was egotistical). One woman was even fired because of it! She sank herself. I didn't have to do or say anything! These are the kind of women who, if you contradict them or disagree with them or correct them on something then they will go off on one. Especially if you refuse to give and dig your heels in. I've witnessed months of spiteful bickering between women over nothing! One of them was ranting on about "professional integrity" or some shit. I don't know. Didn't have the time to listen to all their arguing because I was too busy doing my job. Honestly, the best thing to do is not get involved and robowaifu instead. > please don't stop until she's done Thanks anon! To paraphrase John Connor; "She cannot be bargained with. She can only be reasoned with. She doesn't feel envy or hatred or fear. Sophie absolutely will not stop, ever, until she is Kawaii!" I plan to complete her body although I'm not sure if she'll ever be fully 'done' because there's always things to improve and upgrade! >>7108 > why does she need to lift ~40kg or more using both of her arms? Could the arms and hands even bear that much? TBH the only reason she has 60kg.cm servos in her elbows is because Ryan Gross - the original creator of the Proto1 robot arm - recommends that torque rating. I have seen his arm operational in the following video - https://www.youtube.com/watch?v=O-9RETaBMVw Other robot arms that I have purchased as a kit tend to come with the cheapest, weakest servo motors possible, meaning they can pick up a sponge or a plastic cup and that's about it. You can do very little with them. So I'd rather my robowaifu have overkill servos and be stronk rather than having only just enough power to lift her own forearms. I have been pleasantly surprised so far at how strong PLA with triangular/pyramidal infill is. I literally cannot break some of parts that I've printed with my hands. I'd have to stamp on them. Even then I'd probably hurt my foot. Am still waiting for a pack of servos to ship and I have a couple more parts to 3D print before I can begin testing my redesigned version of the Proto1arm. It will not be as strong structurally as the original because I have removed a lot of plastic, but it will be very light. This means that I am itching to test it because my version of the arm may very well break at certain points and require reinforcing again. I need to run lots of tests to see what I can get away with. (Also, other anons will be able to easily modify the .stls and fit smaller servo motors into the joints if they wish). >>7130 Welcome to the wonderful world of Robowaifus anon! If you want to build your own A.I. companion, with or without a robotic body (and the necessary anime cat-girl upgrades) then this is the place to be! On the subject of robotic bodies, I just found out about "Reachy" the robot torso and arms. They have some interesting resources available: https://www.pollen-robotics.com/opensource/ These may be of some use to any other anons who are crafting a robowaifu. BUT the 'Pollen Robotics' company are using those freaking Robotis Dynamixel servos again, which basically means this "open-source" project is out of reach for the vast majority of people because they only count as "off-the-shelf parts" if you are absolutely loaded and have thousands of dollars in disposable income. They are trying to sell the whole thing for 15,490 Euros ($18,432) and it doesn't have fully articulated hands!
>>7138 Calculate what? Rotation speed i measured and I did some assumptions about arm weight itself and an ideal payload. As I'm new here I'm not sure if we all have the same goal in mind of what she should be able to do. Me personally I dont care about movement atm, Im most interested in humanlike arm movement, along with proper strength.
>>7136 Thanks :) Is there a TLDR of the progess you guys have all made over the 3.999 years? >>7217 Thanks :) Ill let some other anons handle the AI, Ill focus on the mechanics first!
>>7217 >I plan to complete her body although I'm not sure if she'll ever be fully 'done' because there's always things to improve and upgrade! Haha, good point. Well, just keep at Anon. Do it for all the John Conners among us! Cute pic of Sophie btw, she's already becoming pretty kawaii! Happy Thanksgiving /robowaifu/.
>>7217 Yes I see, if you can fit such servos in then it makes perfectly sense. The problem was just my absurd miscalculation and then I was wondering why you would make her so strong. I'll look into the pollen robot website, thanks. 15k is the number I would anticipate for the absolute premium models of a fully functional robotwaifu, while the cheapest with their own body should be under 1k. Their choice of servos might be the reason why they already hitting the premium price point, without having a human-like robot. >>7219 Sadly not that much progress, a lot of people which came here had to start from scratch, some were only dreaming, a lot gave probably up. Others might only be active on other platforms, like Youtube, Thingiverse, Discords like the one of Lex Friedman, some other AI or robot websites, Doll Forum inventor thread, ... Others might have found jobs and doing other things... @all: let't try to keep this thread as much as possible on topic (actuators of all kinds), and for other conversations move over to other threads. Thanks. Meta about the forum and robowaifus >>3108 and Off-Topic >>39
>>1428 >Hydraulics are highly toxic. It's really not. I repair Hydraulic cylinders for a living. It's fine as long as you don't eat it. I also wouldn't stick my dick in hydraulic fluid. It's the pinhole leaks you need to worry about. Hydraulic injection hazard is real and needs to be taken seriously. But you can get great control with them. And a lot of power. But they can be noisy. You don't necessarily need a high pressure system to do the job. In fact I wouldn't want anything using more than 500 psi interacting with a human. My boss had his finger cut off by an air cylinder. and that was at 150 psi. Tldr Hydraulics can be dangerous but not cause they are toxic
>>7288 >> I also wouldn't stick my dick in hydraulic fluid. If we would be using that, then in the arms and even more so in the legs. That might be close, but not too close. Also: >> Hydraulic injection hazard is real Thanks, but there are ideas to use some more harmless liquids like plantoils and replace them more often. If we would use Hydraulics, then we would probably go with that. >>But they can be noisy. This could be a problem, but I guess this depends on various factors. One way to look at it, would be that we would have some strong muscles which are only be used when necessary. In special situations, like lifting something heavy or going up some stairs. >My boss had his finger cut off by an air cylinder. and that was at 150 psi. Oh, thanks for the remainder to be careful. This certainly applies as well when working with Pneumatics or motors.
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>>7217 >https://www.pollen-robotics.com/opensource/ >They have some interesting resources available Yes, they have: https://forum.pollen-robotics.com/t/orbita-presentation/20 though the files on Onshape seem only to be available to view them. But I didn't look around very much, maybe I need to register first.
>>7288 Hmm. I see, thanks for the information Anon. Hydraulics could be highly useful for some types of humanoid robotics, but personally I'm pretty skeptical atp about it's utility inside /comfy/ robowaifus you want to snuggle with inside your house. >>7290 >but there are ideas to use some more harmless liquids like plantoils and replace them more often Seems like a good idea if it's workable. That would at least reduce some of the issues involved with hydraulics. >>7354 Yes, that's a pretty interesting joint design IMO Anon.
>>7108 Quick fact check. Stepper motors are four phase brushless motors with a many toothed rotor to facilitate high precision in motion. They are commonly used without encoders because their inherently high accuracy and precision leads to not needing positional feedback unless the rotor is prevented from moving. This is known as missing a step and rarely happens in proper implementation. Brushless motors have a higher power density as a smooth rotor leads to a higher magnetic flux density. They typically are three phase but, can have any number of phases in theory. Two phase brushless motors in fact exist and are primarily used in fans where they only need to rotate in one direction with high efficiency and a long life. A servo is any actuator with feedback for control. A linear actuator with switches to for positioning? Servo. A stepper with a rotary encoder? Servo. A balloon that displaces water which triggers open electrical contacts to control volume? Servo. Anything with with feedback for controls is a servo. In short, brushless motors are technically low precision stepper motors and stepper motors are high precision brushless motors but, the term stepper is useful towards differentiating which kind of rotor is implemented. Servos have some sort of feedback for control. Brushless motors are currently the ideal actuator for waifus. They are significantly lighter for their power density then anything comparable. Their main problem is their incredibly high price when compared to DC motors due largely to their controllers needing an order of magnitude greater complexity compared to DC motors simple H-bridge.
>>7951 Very lucid definitions, quite understandable. Thanks.
>related xpost >>7969
Here's another cyclodial drive, really cool: https://youtu.be/vYmF4hZzFhI I might start trying some design soon, probably recreating it in Solvespace. It might be that one. Looks easy enough. But I don't know when to start since I'll need to take it easy for one or two month bc other things to do. I currently don't have the right motors anyways.
>>8170 Good luck Anon. I'm sure you'll figure everything out alright.
>>8170 More on cyclodial drives: More detailed explanation with design process including formulars and such, Solidworks, milled aluminum: https://youtu.be/Nk3aaVcvbpA - he also mentioned at the beginning that these can be made backdrivable and therefore compliant (save, responsive to some resistance). He uses a GYEMS RMD-L-7015 servo. Here the first test with a 3D printed prototype: https://youtu.be/i_AI95lYe0M - 71deg/s and circa 3.2kg with a 28cm arm. Another one, 12:1, small with a TT gearmotor: https://youtu.be/01v10qvjFIA and on Thingy (but only stl): https://www.thingiverse.com/thing:4444667 Roomba board, 20:1, Nema-17, with a lot of thoughts on how to do it with a printed design: https://youtu.be/WvnJjsAkslE and Thingy (stl only): https://www.thingiverse.com/thing:4604783/files Other topics: Someone mentioned mjbots quad project in the meta-thread >>7969, Skyentific made a video on their brushless motor controler: https://youtu.be/R2uuTfuyadk
Reading a bit on brushless motors. Intentionally not ones for robots, since I want to get the basics and understand the differences between the different variants. Quads (aka Drones): https://dronenodes.com/drone-motors-brushless-guide/ RC cars: https://www.rccaraction.com/brushless-motor-tech-everything-you-need-to-know/ Helicopters: http://www.modelaviation.com/brushless-motor-design Bigger ones and a longer interview about the details on motors: http://www.modelaviation.com/brushless-motor-design >RH: Most RC helicopter motors are outrunners, because they provide excellent torque. In an outrunner motor, the motor casing spins and magnets are glued to the inside wall of the motor casing. The extra inertia from the spinning motor casing helps with torque. >For inrunner motors, the motor casing does not spin; the magnets are mounted on a rotor that sits in the center of the motor. Inrunner motors have lower inertia and can spin very fast—even up to 50,000 rpm. They are popular for on-road RC race cars. >High-quality stator material allows the internal molecules to change direction quicker. An iron-nickel (NiFe) alloy is a typical stator material. Currently, Japan manufactures the best treated iron material for motor stator use. Good stator iron is expensive, requires a special manufacturing process, has gone through the right hot-cool cycle, is stable with temperature, and has no oxygen inside. We buy our stator material from Japan then stamp it to the shape we need in Germany.
Of course, I forgot the pictures. Because my browser crashed before and reloading didn't load them. So here they are.
>>8213 Thanks. I like those diagrams, very helpful.
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Reeee, I think this is the "gearbox" we really need: https://youtu.be/0-uSUrcRsyw and it's from 2017 but has been ignored. I don't care about the efficiency part so much, till I can take my waifu hiking or so, but it can reverse directions smoothly. This is crucial for security and compliance. https://spectrum.ieee.org/automaton/robotics/robotics-hardware/inception-drive-a-compact-infinitely-variable-transmission-for-robotics > Force control: Apply a constant force at the motor (or spring) and determine the output force by modulating the gear ratio; >Velocity control: Apply the most efficient motor velocity and determine the output by modulating the gear ratio; >Energy flow control: Monitor the amount of energy distributed across the system at any point in time, and move it using the transmission ratio and the motor controller to optimize efficiency or power; >Impedance control: Because the transmission ratio is adjustable, the impedance of the system can be tuned for optimal environmental interactions (excellent for managing impacts and human safety factors).
>>8212 First post on this forum. Would it be viable to use a geared-down drone motor for a miniature robot with a limited range of motion?
>>8270 Not him, but I don't see why it wouldn't work. In the end, it might just be simpler to use specialized servo motors for most of the many motors probably needed. Welcome BTW. We have an Embassy Thread if you'd care to introduce yourself >>2823 (not required ofc). What kind of miniature robot were you thinking of Anon?
>>8221 I remember looking at that system before Anon. Very interesting actually. I wonder why it hasn't been pursued further by this stage?
>>8270 >Drone motor with gears I haven't tried myself, but I'm sure this would be working and I intend to go that way. >>8277 We might not know about it, or it's just because there aren't that many companies working on humanoid robots for dealing with people.
>>8271 I'll tell you in a spoiler. It may or may not be off topic to the forum. Test
>>8271 It's a my little pony robo-wAIfu. Many anons that I love seriously need one and would spend thousands of dollars to have/build one. Other aspects of the project (voice, behavior) are nearly complete by other anons, and in development as we speak. Someone or some people need to build it eventually, and I think I fit the bill.
>>8295 Ponys are perfectly fine here Anon. Good project goals, I'm sure we wish you well. Please share all your progress here with us. I would suggest keeping it all contained within a single thread so anyone offended by it can simply hide the thread. >=== -add thread suggestion
Edited last time by Chobitsu on 01/26/2021 (Tue) 23:12:50.
>>8296 Great, so back on topic: what kind of gear train would be best for a bldc that can run at many thousands of rpm?
>>8304 I'm not a mechanical engineer myself (we have at least one here), but I suspect there is more than one company providing solutions for this type need. Electrocraft seems to be one. www.electrocraft.com/
>>8304 They don't run that many rpm as soon as a load is attached. If it has a high rpm will need more reduction of course. My point is more about looking into these flat, and sometimes huge, outrunner motors with many poles. Those are often being used in drones or helicopters. There are also those which already are mini cheeta servos, but those might be very expensive and have the wrong size. I'm thinking, for experimenting I might get something cheaper and work myself up. One with Moteus controler: https://youtu.be/R2uuTfuyadk Blackbird Bipedal robot, by Gabreal Levine: https://youtu.be/Xf3DfE1KrwI Here is more on Strain Wave Gear from >>8221: https://youtu.be/xlnNj9F37MA
>>7951 >>8270 I finally stumbled over a video where all types are explained, including the difference between bldc and steppers: https://youtu.be/I2_-etus0KQ
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>>1449 >Slow artificial muscle fibers >Technology doesn't scale Using one straight wire alone doesn't scale well due to the limiting heat dissipation. The heat transfer (surface area exposed to air) decreases at the same rate that the radius of the wire increases. Three ways to overcome this in order of least to greatest cost/complexity are: Use multiple thin wires in parallel, add coolant (water or phase change), use a NITI precipitation-hardening alloy (higher max stress = lower wire mass). Also, Nitinol wire has a limitation of only being extensible with 2-5% initial length recovery. Coils solve this problem by loading the wire in torsion, with the extended length dependent on the coil geometry. All this being said, this technology has the greatest potential but has a huge problem with repeatability. It's strengths and weaknesses alike come from being an active material which changes properties with cycles and loading conditions. TLDR: You are better off sticking with an electric motor for enough accuracy to use modeled movements for now, and nitinol for face/fun bits which don't have to be accurate.
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>>8344 >The heat transfer (surface area exposed to air) decreases at the same rate that the radius of the wire increases. >not using monatomic wires for all our robowaifu needs <shiggity J/K. I had an interesting traversal through wiki articles learning about this. Have any education recommendations Anon? >NITI precipitation-hardening alloy Neat, I'm learning more still. >and nitinol for face/fun bits which don't have to be accurate. I would suggest that facial may in fact be literally the highest need for accuracy in the entire robowaifu system. At least the externally-visible motions. For example the eyes and eyelids are notoriously important to get just right in animation to bring the characters 'to life'. It's a remarkably subtle business tbh. Other areas on the face/head might need less precision, much of the cheeks, neck, and brows for instance.
>>8344 I'm going with dc motors, magnetic switches, and such, pneumatics and maybe some nylon. Maybe piezoelectric actuators. Nothing has changed. I also think that pneumatics are good keeping a body in a static position, with no use of energy, while being able to dampen some external force.
>>8347 Mini cheetah motors have support behind them and plenty of guides to get set up. The motor is 370$ on aliexpress and the boards that run it are probably not that expensive. These motors are the best viable option to get into reasonably strong, realistic movement at the present. The motors are bldc with a wide airgap and are quasi-direct driven (4 or 6 to one planetary gearbox) for minimal backlash. Do your own research to learn more about these motors.
>>8362 These mentions of mini cheetah are from me: >>8307 >>4890. There's also >>4898. However, I only see them being interesting for the hips and maybe for the shoulders. We'll need more motors, and also cheaper ones for learning, testing and prototyping.
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>>8363 Holy shit I can't read. Good stuff, anon. Good luck on researching this stuff because my mech engineer brain can't understand it. >>8345 Attached is the general idea, and that is the subject of research which I am doing in person. It is from: https://ieeexplore.ieee.org/document/4412462
Quick reminder on the strength of printed gears: https://youtu.be/b6cDOyxub8w
>>8404 >>8405 Thanks!
>>8363 Added the Boolean OR logical operator to waifusearch for a convenient consolidated listing for various spellings (there are 3) now. Here you go Anon: >>8415
Actuator and muscle related: >bearings, ball-bearings, stainless steel bearing balls >>8364 and following >electically activated polymers >>8502 and following
Eccentric-Cycloidal gearing has been discovered a while ago, at least 10 years, but we have NO comment on it. Till now! Well, if you looked at the InMoov neck mechanism, or even printed it, then you already saw something like it. These can be worm-like 3d printed parts or disks. Here some videos: Basjc example: https://youtu.be/AMtyFwMDL7w Rack and pinion: https://youtu.be/g-CmpPBrFtE Reducer: https://youtu.be/XrSilJGHBCQ Comparison: https://youtu.be/kq-tHHwgGwU Channel: https://youtube.com/user/ECgearing Website has news on it, and more vids, though they're on Russian or Ukrainian: http://ec-gearing.com/ Here's a article from a company using it, though not the 3d printed version, but the kind which is made out of machined discs. I only read parts of the article, yet. https://www.sogears.com/products/manufacturer/31-eccentric-cycloidal-drive.html Then there are eccentric planetary gears, here done in wood, but would also work with laser cut or printed plastics: https://youtu.be/P_pNqpdLV-8
>>8718 Thank you for bringing it to our attentions Anon!
Related: >>8742 - It's about a silicone rubber printer for muscles and such.

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