/robowaifu/ - DIY Robot Wives

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Actuators For Waifu Movement Part 3 Kiwi 12/06/2023 (Wed) 01:18:16 No.27021
(1stl thread >>406 2nd thread >>12810) Kiwi back again with a thread for discussing actuators to move your waifu! Part Three! Let's start with a quick introduction to common actuators! 1. DC motors, these use brushes to switch the ferrous core electromagnets on a rotor to rotate its magnetic field relative to surrounding magnets! They're one of the cheapest options with an average efficiency range of 30 to 90%. Larger DC motors and motors with higher turn counts are more efficient. 1.5 Coreless DC motors, by removing ferrous materials, losses from hysteresis are almost eliminated, dramatically increasing efficiency to nearly 90% even in small motors. Eliminating the ferrous materials reduces flux focusing, resulting in weaker fields and higher speeds. 2. Brushless DC motors (BLDC), these use a controller to switch the electromagnets on a stator to rotate the magnets of a rotor! Without brushes, they have the potential to be more efficient with higher power density compared to DC motors. Their efficiency and behavior vary depending on the algorithm and sensors used to control them. Coreless brushless motors exist but are rare and only used for very niche applications. 3. AC motors, a wide and incredibly varied category. They all rely on AC’s frequency to control them. With single phase AC motors relying on shaded poles, capacitors, or some other method to induce a rotating magnetic field. 3 phase AC motors naturally have a rotating field which usually gives them higher efficiency and power density. Notably, most AC motors are brushless. The most commonly used brushed AC motor is the universal motor, which is 4. Stepper motors, brushless motors with ferrous teeth to focus magnetic flux. This allows for incredible control (stepping) at the cost of greater mass, subsequently giving them higher rotary inertia. Usually 50 to 80% efficient depending on control algorithm/speed/and quality of the stepper. Due to their increasing mass production (& ubiquitous low cost controllers), they have appeal as a lower cost alternative to BLDC motors if one carefully designs around them. 5. Coiled Nylon Actuators! These things have an efficiency rating so low it's best to just say they aren't efficient. (0.01% typical, 2% achieved under extremely specific conditions in a lab.) Though they are exciting due to their incredible low cost of fabrication, they’re far too slow and the energy requirements are nonsensical. https://youtu.be/S4-3_DnKE9E https://youtu.be/wltLEzQnznM 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) Efficiency varies wildly depending on implementation. They would work great for a giantess! 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? (Too loud and inefficient for mobile robotics.) 8. Wax motors, hydraulic systems where the working fluid is expanding melted (commonly paraffin) wax! Cheap, low power, and produce incredible forces! 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! Servos! These use an actuator and sensor to control motion. DC, coreless DC, and BLDC motors are the most commonly used actuators for servos in mobile robotics. Potentiometers or hall effect sensors are the most commonly used sensors to detect rotary motion in servo systems. >Soft muscles (pneumatic system) with origami-inspired skeletons: https://youtu.be/OJO4FP0DXgQ[ >Printed pneumatics (TSA can also be used instead of pneumatics for actuation.) https://youtu.be/_X0rDW6NQ58 >Using sugar as soluble support material for printing silicone muscles: https://youtu.be/L0Z0-y3qpNk >Cavatappi artificial muscles (hydraulic coiled nylon hybrid): https://youtu.be/yXAJGH5s4cs https://youtu.be/MpCFumHFZvU https://www.designnews.com/automation/cavatappi-robot-muscles-have-5-times-strength-human-muscles >Twisted string actuators (TSA) Be extremely careful when choosing your strings. They will be put under extreme strain and must be durable. https://youtu.be/N4VMoYFrusg https://youtu.be/hFuzQ4ed-t0 https://youtu.be/J26y1nn7JMM https://youtu.be/zYrHGMiqC9A https://youtu.be/PABVsuV7Y1M https://youtu.be/tP9B3aqc4CI https://youtu.be/Y1uceDzhjKY >Continuous ransmission (CVT) / torque converters https://youtu.be/kVPjhmTThPo https://youtu.be/cd2-vsTzd9E https://youtu.be/c9e2y-5DMNc https://youtu.be/PEq5_b4LWNY >=== -edit subj
Edited last time by Chobitsu on 12/06/2023 (Wed) 03:06:55.
>>27021 Sauce on 2nd pic?
There was a question in the old thread. If a new one is made, it would be good to link that, since the thread doesn't come up: >>26973
>>26973 That's more of a software issue. Check official documentation (https://www.arduino.cc/reference/en/libraries/can/) then go to StackOverflow. I default to them if an issue is outside of documentation.
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>>27031 It was from a post on Twitter that is lost. Nothing of value to it aside from serving as a reminder that actuators can be hidden in a base with outputs being translated via string in tubes. Picrel is a Sukabi illustration of what a potential robot could look is using such a system. Everything in a box with cables going into her to communicate with whatever sensors are in the main body and transmit motion. It's good to remember that actuators can be used in many ways.
>>27021 Just found an interesting transmission system for servo motors that has what appears to be built-in compliance: >https://www.gobilda.com/3405-series-round-belt-5mm-cord-diameter-214mm-circumference/ >https://www.gobilda.com/3400-series-hub-mount-round-belt-pulley-14mm-bore-64mm-pd/ There's stretchy 5mm round belts available on the same site I got my GT2 hub pulleys. I had been thinking of a way to put in a compliant (stretchy) mechanism as a shock absorber cable for the pony leg/foot to match the biology, and this might be just the right thing. Black loctite works for rubber belts and o-rings, but not platinum cure silicone material. Some have reported Smooth On Sil-Poxy works for all of the above but I've not tried it yet. I might end up making a finger-like round belt mechanism that is fixed at the end of the hoof. This way, the belt drive would have built-in spring and damping for when the leg hits the ground vs regular inextensible toothed timing belts.
I have some vacuous ideas, not well formed, about ferrofluids. I found a good paper on these with good references also. It's worth saving if you are interested in that sort of thing. https://pubs.rsc.org/en/content/articlehtml/2022/nr/d1nr05841j
>>27081 Your description reminds me of this: https://youtu.be/rY7IGdIvOyY
I've been trying to figure out how to convert rotational motion into linear motion for animating my papercraft waifu and learned about the Scotch yoke. It's probably one of the most basic mechanisms but I didn't see it mentioned in any of the threads so I thought I'd share it. For the joints I'm going to try using elastic bands and strings attached to little pins glued onto bamboo sticks on the back, but maybe there's a better way? I know jack shit about mechanical engineering.
>>28104 Neat! What a smooth, organic motion envelope Anon. That animation that shows that variable-position central pin, demonstrates that you can adjust such a mechanism on the fly, tuning it's leverage-advantage/power tradeoff, kinda like a transmission might. >that scoldy, Class President-chan tho Lo. A cute! :D Thanks Anon, cheers.
>>28104 I saw this before but forgot about it. It's certainly a good idea to keep in mind.
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>>28104 This "Cyloidal Heringbone Rack and Pinion" could also be used for linear motion, but the motor would be in a different orientation. https://youtu.be/Cu5LvIYXbU0 While this Rigid Chain Mechanism here also does linear motion, but it's also similar to something I wanted to do. So it might come in extra handy. I was thinking of a loaded spring mechanism, where the spring would push the mechanism at the start so it would have some extra energy. This would have to go around the elbow, so it would need to be a chain. https://youtu.be/loCBrD4gRi4
>>28104 just have the output shaft of the motor reel in fishing line and you have your rotation converted to linear. can wind 2 fishing lines to same output shaft winding in different directions so that one reels in while the other extends to get opposing muscle groups assigned to each motor.
What motors could be used for the arms to achieve an A pose. Assume the arms are say 1kg and 2 feet long.
>>28143 See https://www.engineeringtoolbox.com/levers-d_1304.html Assuming you’re talking about the shoulder rotating from arms-by-side “up” to an A-pose (or even a T-pose) - You’re looking at either a class 1 or 3 lever depending on how you transfer the force. 1. Make a spreadsheet with those equations and your length/mass parameters. 2. Make another sheet that calculates torque (force required) at all theta between 0 -> 90 (or 180, or just 40 for an A-pose, as you please) 3. Decide how long it can take to go from arms-by-side to your pose’s angle. You now have X degrees over T seconds 4. Select the spreadsheet row with the highest required torque to move (worst case) in your range of angles. This is how much torque your motor (or mechanism, in general) needs to be capable of. 5. Convert degrees-over-seconds to rotations-per-minute. You now have RPM and torque requirements. Use that to calculate power (mechanical watts or HP) 6. Select a motor that can output that much mechanical power PROVIDED you have a way to reduce it to your required RPM (most motors are above 2k, you’ll probably want under 30 RPM) 7. Can’t find anything? Start thinking over alternative mechanisms— you already know your force requirements, after all. Extra: integrate force over angle (or time) to calculate total energy required. Just be sure to normalize for time with a dT(theta) or theta(T) function (depending on what you integrated over)
>>28141 Ah, you mean a Twisted String Actuator? I had to translate your text with ChatGPT. The statement is describing a mechanical arrangement using a motor and fishing lines to convert rotational motion into linear motion. Here's a breakdown of the concept: 1. Output Shaft of the Motor: - The motor has a rotating output shaft. 2. Reeling in Fishing Line: - The fishing line is wound around the output shaft of the motor. - As the motor turns the shaft, the fishing line is reeled in. 3. Conversion of Rotation to Linear Motion: - The winding of the fishing line around the output shaft converts the rotational motion of the motor into linear motion. 4. Dual Fishing Lines with Different Winding Directions: - Two fishing lines are used, and they are wound around the same output shaft but in different directions. - This means that when the motor turns in one direction, one fishing line will be reeled in (shortened), and the other will extend (lengthen). 5. Opposing Muscle Groups: - The idea is to use this mechanism to engage opposing muscle groups. - For example, if one fishing line is reeled in, it could simulate a movement that engages one set of muscles. Conversely, if the other fishing line extends, it could engage a different set of muscles. 6. Overall Function: - By having two fishing lines wound in opposite directions on the same output shaft, the system can provide both contraction and extension movements, potentially targeting different muscle groups. This concept could be utilized in various applications, such as in rehabilitation devices or exercise equipment. The use of fishing lines allows for a flexible and lightweight means of transmitting motion, and by controlling the motor's direction, you can control the type of muscle engagement.
>>28165 no, not twisted string actuator. the string reels and never twists. This video explains the concept https://youtu.be/0emPU0bIwwc?t=1135 Also, will cogley uses the concept I'm describing here: https://youtu.be/MxbX9iKGd6w
>>28130 >This "Cyloidal Heringbone Rack and Pinion" could also be used for linear motion What a cool idea Anon, thanks! Cheers. :^)
>>28181 Nice content, thanks Anon. Yes, I've planned to use silk ribbons and 2 normal 'bobbin-like' spools affixed together to provide that sort of remote, bi-directional linear actuation system before. And I'm pretty sure ol' Leo DaVinci had a similar idea too! :D
>>28196 here's a drawing by will cogly showing his version of the rotational to linear mechanism I'm talking about. In my case, I would use a brushless dc motor instead and a complex pulley system instead of a geared brushed motor servo like he's using. My method would be much more powerful but his is much simpler to implement if you have the room for it.
>>28202 Thanks! Yes Bowden-cable -like arrangements are a good way to transmit force at some distance. That's a pretty good sketch IMO. >My method would be much more powerful That sounds very interesting. I'd love to be able to actuate the robowaifu's knee & elbow joints (not to mention ankles/wrists) in this fashion, to keep the actuation motors located back inside the torso near to the pelvic volume Center of Mass. This will ofc require much more power than, say, a single finger's force to be effective. Any chance you can let us in on your designs related to this?
>>28202 heres a few images to demonstrate my design on this matter
>>28229 the pulley system here was described in this video and demonstrated: https://youtu.be/M2w3NZzPwOM?t=576
>>28229 Thanks for clarification, that's one more good idea to keep in mind. I'm highly interested in doing things with strings, so this might be useful.
>Rigid robots can be precise but struggle in environments where compliance, robustness to disturbances, or energy efficiency is crucial. This has led researchers to develop biomimetic robots incorporating soft artificial muscles. Electrohydraulic actuators are promising artificial muscles that perform comparably to mammalian muscles in speed and power density. However, their operation requires several thousand volts. The high voltage leads to bulky and inefficient driving electronics. Here, we present hydraulically amplified low-voltage electrostatic (HALVE) actuators that match mammalian skeletal muscles in average power density (50.5 watts per kilogram) and peak strain rate (971% per second) at a 4.9 times lower driving voltage (1100 volts) compared to the state of the art. HALVE actuators are safe to touch, are waterproof, and exhibit self-clearing properties. We characterize, model, and validate key performance metrics of our actuator. Last, we demonstrate the utility of HALVE actuators on a robotic gripper and a soft robotic swimmer. https://www.science.org/doi/10.1126/sciadv.adi9319 via Kiwi on Discord
>>28229 Great post. That Archimedes pulley system is something I really, really need. The video is good too. I have like four or five of these snatch blocks like he showed in the video. Harbor freight. I need to lift some really heavy stuff and have been trying to find a good way. I have some cable That Archimedes pulley is perfect.
>>28274 Wow that sounds really exciting NoidoDev, thanks. I'd love to see this tech incorporated into opensauce robowaifus! Cheers.
>>28274 hydraulically amplified low-voltage electrostatic (HALVE) actuator used to control a small tube which controls a shut off valve to a large flow tube to muscle. I've had this idea for a while but haven't talked about it because it's not completely fleshed out and people complain I write too much so... but I'll talk about it anyways. I show high pressure tube but in fact it could be the same pressure. The idea is a spring operated rigid cut off valve which pushes a small area of the mass flow tube closed. The control tube uses a large surface area flexible bladder to push the valve open. The pressure pressing open the flow tube would be large because of the large surface area of the control tube bladder. What's the point of this? If you had to control this large flow tube for each muscle it would be too big to go through the bones or thread through the limbs. But if you have one big flow tube with individual T's off of it to each muscle and then used the smaller control tube you could thread a lot of tiny control tubes down and around the body. Like nerves. The big flow tube would be like the blood stream. Since the control tube has little flow it could still act quickly and since the large flow tube has a large flow it could fill the muscles quickly. I didn't draw it but the tiny control tube could be on a pivot. If the control tube activated it would let in fluid to the muscle(flow). If it turned off a spring could pivot it to a bleed line that would bleed the muscle when it turned off.
>>28447 I forgot to add, I personally much prefer electrically operated motors but I have had a hell of a time thinking of how I could get either a micro-controller close to what it actuated or all the mass of wires needed if it were placed in the chest. It would take a lot of manual labor to place all this stuff and that's not good. It would drive up cost extensively. Though I HATE hydraulics it may very well be that if a cheap enough valve can be engineered, and I think it can, it would be better to have a central pump in the chest and a bunch of small control tubes that control the flow to the muscles as I show. The control tubes could be really small as the volume of fluid needed to open the valve would be small making everything compact and relatively fast, if much slower than electrically operated motors. If you tried to add an individual tube for each muscle that would flow enough for each muscle the whole waifu would be one big ass mass of huge tubes. So yes this is...hydraulics, the New Jersey approach. Sigh...
>>28447 >>28449 This will be really interesting if you solve this Anon!
Good overview over a lot of mechanical principles. I thought about putting that into >>24152 but it's closely related to the servos and gears.
>>28522 Super cool! Wow I wish I'd seen this as a kid, Noido Dev. :D BTW, any idea what that system he's using for all this is? Looks kinda like Legos, but probably isn't. Thanks!
>>28546 >Looks kinda like Legos, but probably isn't No, those are all definitely Lego. The motors too, they come in a small number of sets. I have the exact same motor as the first one shown in an AT/AT.
>>28522 That's very cool.
>>28546 Pretty sure this is Lego Technic. I had some of it as as child. I wasn't sure at first if it could be Fischer Technik, but no.
>>28567 Thanks!
Update on cheap motors from china: I now have 20 wife servomotors. I'll need 16 for 4 legs and a few to move the back and head. They're kind of vibraty, kind of grindy, not perfectly smooth, buuuut they only cost 100 each and I needed a lot. Also, they're weak, but I don't care for a proof of concept since it just has to move. I've got an idea for a relatively cheap diy actuator bldc+planetary that would be much more powerful if I have to upgrade and no other stock motor can do it. The motors will use CAN bus so I can get the skills for a robotics job, and I'll learn ROS, gazebo, mujoco, and isaac sim too. mujoco and isaac sim will be most useful for rapid simulation since it has elastic tendons and ROS/gazebo are useful for a robot job skill.
>>28738 Which project is this? Please post ongoing projects and updates in the prototype thread: >>21647 - This thread here should be used for general discussions on specific actuators.
for my tendon based actuator, i have PE fishing line and it is .63mm OD and I have a teflon tube that is 1mm ID that I want to thread with this fishing line. When I cut the line, the end is a bulge. How do I make the end pointed so I can thread the tube eye with it?
>>28859 Heat up the fishing line over a candle flame and stretch out the melted plastic until it breaks. With practice you can get the total stretch down to a few inches instead of a couple of feet, but either will work. This way the plastic will only taper without a bulge. For source idea, that's how we modelers make whip antennas for model military vehicles.
>>28738 what is mujoco and isaac sim?
>>28862 We have a whole thread on simulators >>155, at least mujoco is mentioned there.
>>27021 What do you guys think of these? Especially the second one where they made a model that mimics human walking efficiency? Both are from this week/last week. https://www.news-medical.net/news/20240127/Biohybrid-robot-makes-sharp-rotations-with-lab-grown-muscles.aspx https://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1011771
>>28860 thanks I'll try it should work I think
>>28867 Thanks, just some addition: >Summary: Researchers achieved a significant advancement in robotics by replicating human-like variable speed walking using a musculoskeletal model. This model, steered by a reflex control method akin to the human nervous system, enhances our understanding of human locomotion and sets new standards for robotic technology. >The study utilized an innovative algorithm to optimize energy efficiency across various walking speeds. This breakthrough paves the way for future innovations in bipedal robots, prosthetics, and powered exoskeletons. https://github.com/Shunsuke-KK/reflex_plos_revision
Turbines driven by air might be interesting in some edge cases or for long term for optimization. I had the idea watching a video on Tesla Turbines. These can work with air pressure, but have up and downsides: https://www.youtube.com/shorts/9XTEGrze920 I mainly think of turbines an additional booster for an electric motor, e.g. to make it start faster and reach some high torque faster under some load. Or the turbine (Tesla or other) kicks in when the motor is already at a high speed but needs some extra kick for a moment. This is of course more relevant for builds which would use some air muscles or stabilizers already. I don't want to start this whole general discussion again, I think pressurized air actuators can be useful if combined with other actuators. Problems with Tesla Turbines in particular, based on some comment on that video: - centrifugal forces warp the discs that results in touching from the discs under extreme high speed, this can cause failure but also abrasion over a longer period of time. - seems to need high speed and only works with high speed, would need a gearbox making it less efficient. - efficiency goes down to ~65% under load, similar to normal turbines - sensitive stall speed - higher rotational masses compared to other turbines
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>>28910 hate turbines, this is 12th century technology i always wondered why you cant just send a balloon up into the ionosphere with a magnet, like the earth is already just one big solar magnet how hard can it be to put it to good use ffs
>>28911 Even if this was the case, how would we use this in a Robowaifu?
>>28910 We might be able to use a micro-turbine for the micro-rotary-engine, randoseru power pack? (>>28697, ...) After all Mazda made an awesome twin-turbo RX7 that was a rather-lightweight, relatively-inexpensive beast of a machine.
>>28921 With a balloon attached going up into the ionosphere?!
I feel like 20k is to much for this robot https://hello-robot.com/ do you guys have any suggestion to duplicate this telescopic approach much cheaper?
>>28943 Well, look for telescope actuators: https://youtu.be/X28CxOnxZh0[Embed] https://youtu.be/WavBXfh1giE[Embed] https://www.youtube.com/shorts/jWxARpHUVrg I recently had another one in my recommendations, but don't find it.
>>28943 >6x speed My fuggin sides are in orbit.
>>28957 ikr this is why I am thinking if there is a way to replicate this (make it faster) using pulley systems.
>>28958 why re-invent the wheel? just use rack & pinion.
>>28959 the problem is , if it lost energy in the height axis will fall, so I think a pulley system can keep it
>>28976 Screw-drive linear actuators for the main stalk, then. I love these things and use them in my mech projects. They only consume power when they move: to get them to maintain position you stop giving them power.
>>29007 that takes up a massive form factor and space is a great concern ruling such an actuator out for a humanoid with human form factor if you are going for humanlike full body articulation which requires so many more actuators that all are competing for space
>>29014 Oh, so you just want the approach, not building the same robot. I misunderstood this before. Do you mean the arm or the mechanism for up- and down? And how to put this into a human-like robot anyways?
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>>29014 Not really...
you have your motor which acts as a muscle and gives the strength. look at the volume that takes up. then look at the volume taken by the gearing. if the gearing is taking up even close to as much space as the motor itself, then you are being very wasteful on space imo. that's why small pulleys to downgear like I posted earlier in this thread are WAY more efficient on space and get you your desired linear motion making them 100x superior to the type of linear actuators you all are posting now
also bonus points if the gearing can be relocated to another area than the motor and is not physically bound to a certain orientation with respect to the motor and required to be located at the same general location as the motor. this lack of flexibility in arranging motor and gearing gives you less options for negotiating fitting everything into your desired build volume of the robot. whereas pulley based downgearing gives you all the flexibility in the world and WAY smaller downgearing total volume taken up comparatively
>>29017 yes I'm building a different robot than any designs I've seen here but I am here to learn and share techniques. you say "Do you mean the arm or the mechanism for up- and down?" --- I am saying the bulky linear screw based actuator has too much hardware volume taken up by things that are not the motor itself and this volume is not something that should be given away so loosely as space is at a premium in value for a robot and must be guarded visciously if you want to fit enough stuff into the robot to do the things you want it to do (depending on how capable you want it to be of course). You say "And how to put this into a human-like robot anyways?" --- my concern is that fitting all the components one would like to fit to get the functionality one wants in the end is going to be a huge challenge we all face (unless we are creating like dumbed down super simple completely incapable robot toys that are laughably simple and incompetent in their capabilities.
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>>28866 >>28867 >>28873 Good find! Adjusting power to actuators based on what is actually needed is essential for waifu efficiency! >>28910 Excellent out of the box thinking! Could be helpful for budget systems that need sudden bursts of power. Though, a proper coupling system to deliver power when needed, without imposing significant friction. >>28911 Explain how a magnet on a balloon could affect the actuation of a waifu. If you fail to do so, your post will be deleted. >>28921 >Power Randoseru Just like in Prima Doll! Though, routing kinetic energy from turbines into your waifu to animate her, is beyond my imagination at this point. >>28943 See >>29007 and >>29020 For the objectively correct answer on how to actuate the telescoping arm. >>28976 >Pulley maintaining static position sans power Are you referencing differential pulley systems (also known as differential/Chinese windlass)? https://en.wikipedia.org/wiki/Differential_pulley https://makezine.com/projects/the-chinese-windlass// Otherwise, there is too much friction in your pulley system. Without input power, the system should allow for the load to fall until it is stopped. >>29014 >>29030 >>29032 >>29034 I understand you are learning and likely have familiarity with pulleys. This being said, every method of reduction and translation of energy has its place and use. Pulleys are not universally superior in all applications. For a linear actuator based telescoping robotic arm, the precision/load capacity/simplicity of implementation of a stepper driven lead screw relative to its cost is essentially unbeatable. A pulley system can be used to achieve the same results, it will be more expensive, more complex, and require the same volume per work area. If you wish to argue your point, do so with engineering. Prove me wrong by designing and implementing a pulley based robot arm. Furthermore, try to think and breathe while your post. You are speaking with others who going through similar challenges and want to see you succeed. Be kind, always.
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>>29061 >Just like in Prima Doll! Though, routing kinetic energy from turbines into your waifu to animate her, is beyond my imagination at this point. Haha, me too! :D Actually, I simply meant using the unified rotary/turbo engine coupled together with a smol electrical power generator as a means to keep her electrical systems functioning outdoors, beyond just the limits of her own batteries. > pic-related
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>>28923 Kek. AS LONG AS YOU GIVE ME FREE HYDROGEN GENERATORS, ANON!111 :^) > (>>28681, >>28692)
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>>29061 you say " A pulley system can be used to achieve the same results, it will be more expensive, more complex, and require the same volume per work area" --- a pulley system is not necessarily more expensive and absolutely would not require the same volume by a long shot. It would be SIGNIFICANTLY less volume taken and more importantly, the volume taken would be like a pen so long and skinny which is ideally suited for fitting into the limbs and torso of a humanoid form factor body. the screw is thick and the pulleys can be very flat so stackable. the full pulley system for a 64:1 downgear can be 4mm thick and 11cm long and less than 1cm wide and it is very easy to fit many of these in a stackable manner into any humanoid limb of one's design with the volume constraints of a human body. Attached is design imagery of a 3d model of the archimedes pulley system, then teal green boxes showing the total build volume of such a pulley system with measurements demonstrated with a metric ruler to scale all placed within a humanoid robot forearm to scale over the top of the bldc motors between the motors and where the skin will be. you can see how many you can stack easily. The pulleys themselves can be made using 1x3x1mm bearings or 2x5x2.5mm bearings for larger force areas if needed in some cases. each bearing costs $25/200 bearings on aliexpress for the smaller size I just listed. so around $0.13 so $0.91 for a full archimedes pulley 64:1 downgear system. The weight will be a MASSIVE decrease compared to a ball screw style. The outer containment flanges can be sewn on through the center of the bearing by way of needle and thread and can be made of very thin plastic. effectively free. the string/cable PE braided fishing line 70lb test or 130lb test. You say "Pulleys are not universally superior in all applications" --- I argue they are for all applications relating to humanoid robotics of substantial complexity and humanlike movement and capabilities and humanlike form factor due to their light weight, extremely low cost, and their not being needed to be physically located in the same vicinity of the motor which creates tremendous freedom for squeezing things into the human form factor with less limitations on space concerns. You say "For a linear actuator based telescoping robotic arm, the precision/load capacity/simplicity of implementation of a stepper driven lead screw relative to its cost is essentially unbeatable.' --- I disagree completely. Maybe for a 3d printer but not for a humanoid. You say "try to think and breathe while you post. You are speaking with others who going through similar challenges and want to see you succeed. Be kind, always." --- this infers I'm not being kind which is false. Prove I'm not. This also infers I neither think nor breath while I post. Both of these inferences are false and unkind and insulting making you a hypocrite.
also stepper motors have inferior power density as compared to bldc motors. a so you add weight and lose power by going that route instead of bldc. also steppers can tend to be loud-ish although I hear this can be solved in software. Also, the pulleys are essentially silent as are the bldc motors. a 2430 bldc motor pulls 200w and is $11 and the archimedes pulley system is $0.91 in parts for the bearings. it can downgear it 64:1 ratio. gears also are loud whereas this is silent way to downgear.
here's a drawing of a even more simplified version of the basic gearing pulley for such a system as I am talking about based on a small bearing.
for clarity here's a little zoomed out image showing where all these archimedes pulley systems are in the arm design
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i also developed an alternative pulley design based on a M1.7x4 PCB rivet as the center shaft and a copper butt connector (basically a hollow metal cylinder) of 1.5mm ID. they are a perfect fit. just have to cut the butt connector to length of around 3mm and then insert the hollow M1.7mmx4mm PCB rivet into it then flare the rivet and you now have your pulley. very easy to make. then run your string through. will need to be greased with white lithium grease. acts similar in principle to a door hinge. This setup should cost closer to $0.05 per pulley in the materials needed to make it. So it is cheaper than the bearing method above but might wear faster not sure. Chat gpt said it would wear faster.
I don't know why everyone acts like the physical robot is a solved problem. Inmoovs arm movement is limited, its face is expressionless, it has no legs, I haven't looked into it much but it probably doesn't have a mechanism for keeping its upper half balanced either. Poppy is better however those actuators are prohibitively expensive and even then it needs to be handholded into walking. Its also a small robot. I don't know if pulleys are a good idea but the way they usually work is by leverage rope length, a robot doesn't have space to work with, quiet the opposite.
>>29065 do you really need all those wires though
>>29071 I'll see if I can record a vid of SPUD's torso copying the angle of her GY-521 gyroscope. Should be a relatively safe demonstration since she is currently sitting on a support stand rather than her own legs right now.
downgearing by way of a worm screw: the finer the thread pitch the more it is downgearing right? but that is capped I'd assume. what is the higher end to downgearing ratio that can be achieved with this method of downgearing like 6:1? we'd want more like 64:1
>>29079 I'm assuming you are called the black lines in the main model wires when in fact they are just indicators connecting parts to labels and other parts like when you draw a picture and draw little lines pointing to objects in the picture and part of the line comes near the object it is pointing to and the other end of the line goes up to the text that labels what the part is. I noticed you did a picture of gears in your post. well I explained why those preferrably are to be avoided: noisy, physically located at top of motor so less flexibility in design as far as moving them around to other areas where you have more room, etc.
>>29065 Tad odd, I'm usually defending pulleys. In this case, I would be happy to make a linear robot arm with a lead screw if you'll make an arm with pulleys. Howabout a friendly competition to see which is best in practice? >>29088 There are many factors which affect functionality of lead screws. These resources provide good information for anyone learning about screw based actuators. https://en.wikipedia.org/wiki/Leadscrew https://www.youtube.com/watch?v=0jrcs8lS7-M https://www.youtube.com/watch?v=BstZUC4tcOA
based on those videos, it looks like we might be looking at lead screws giving us a ballpark of 5:1 or 6:1 downgearing on the high end. What we want for a typical 2430 bldc motor is 64:1 at least if not 128:1 which can be achieved easily in a very small volume by way of pulleys. It does not appear lead screws offer significant down gearing at all like this
chat gpt and I discussed this just now and I'm gettign this: 64:1 is the very least downgearing we'd need. can a single lead screw give us that extreme downgearing or not? ChatGPT Achieving a 64:1 downgear ratio with a single lead screw might be challenging. Lead screws are generally better suited for lower gear ratios, typically up to 6:1 or 8:1. As you increase the gear ratio, the mechanical efficiency and precision can be compromised. For very high downgear ratios like 64:1, a pulley system, as you initially mentioned, may be more suitable. Combining multiple pulleys in a system, as per Archimedes' principles, allows for efficient torque multiplication and can achieve the higher ratios you're aiming for. In summary, while a single lead screw might struggle to provide a 64:1 downgear ratio efficiently, a pulley system could be a more viable solution for your specific needs.
interestingly, the lead screw idea involves clearly metal rubbing on metal and no bearing surfaces it seams to me. just like a nut and bolt it looks like. perhaps some are more sophisticated but I digress. I was thinking we could make pulleys also by having a shaft inside another shaft and the outer shaft rotates over the inner shaft - like the rivet drawing I made earlier, but shaped more like a bearing pulley in overal shape like the drawing I showed of a bearing based pully. This would remove the balls and so have more of a metal on metal approach but could be more robust for handling higher forces put onto it without crushing the bearing balls or warping the bearings. I noticed the load capacity of tiny bearings is startlingly and alarmingly low. like the 1x3x1mm ones are like 10lb only and the 2x5x2.5mm ones are like 35lb. the complexity of their design and larger number of moving parts they have make them vulnerable at these tiny sizes. So going with a metal on metal 2 part non-ball door hinge-like design (basically like fusing all the balls together with the core as one mass of metal) can make it able to handle way more forces evne if it loses some of the extreme frictionlessness it has. thoughts?
also for reference as a side note: your typical hobby servo motor which employs a dc brushed motor has gears integrated into the box it comes in that downgear that motor 180:1. so when I say we need at least 64:1, now you can see why. Higher speed, small, lower torque motors like the 2430 bldc motor need a ton of downgearing just like these small brushless dc motors in order for them to convert all of their inherent speed down to big torque and more moderate speeds. that is the principle at hand. lead screws primarily convert rotation to linear motion but are not really intended to be big downgearing approaches as they only offer very minor downgearing
Can't nitinol be used?
>>29071 >I don't know why everyone acts like the physical robot is a solved problem. Literally nobody does so. >pulleys are a good idea but the way they usually work is by leverage rope length I'm coming more and more to the conclusion that some soft parts should internally be made out of rope. >>29102 >Can't nitinol be used? >>1747 and >>13723
>>29092 What is this whole discussion even about?! The initial posting >>28943 showed a non-human robot. That's how I answered it, though it's kind of OT, until we get a thread for helper bots for chores. I focused on the telescope arm part. Obviously a inline screw drive or any screw-drive linear actuator might make sense for the vertical movement, though it would be worth contemplating why the hello-robot team didn't use them. More importantly, why on earth would anyone use that for the arm?! Also, how and why would anyone use a telescope element in a humanoid waifu(!) robot at all?! Could anyone picture that and maybe draw it for those who can't, so that we can all see how weird this would be looking? I assume >>28911 and >>28943 are troll attempts, and it would be worth contemplating to delete or move these together with the responses.
>>28202 That looks very useful. I had something like this in mind for some use cases, but it's good to have a few references. Especially combining it with a pulley: >>28229 >>28447 >>28449 >HALVE Thanks, very useful explanation. I guess for a lot of small valves piezo electric ones might be the right ones. I was thinking a while ago about using water bags as some kind of holding torque and a valve in between. So for example the chest could tilt sideways, but if water is in the bag inside and the valve closed it won't. If the valve is open it might tilt, in case a muscle is pulling it then it would certainly.
>Cycloidal Hub Gearbox Might require a resin printer and work better with a laser cutter https://youtu.be/IKkw4d7jyu0 https://www.thingiverse.com/thing:5437152 https://www.printables.com/model/333438-3d-printed-planetary- https://drive.google.com/drive/folders/1apuReZyJan5Dxpbf_ou8xmFl2_huDlke >What makes cycloidal gearboxes so amazing? https://youtu.be/8GDMShY8vAU >I discovered something really interesting about cycloidal gear drives that I did not expect! In this video, I use a 3D printed gearbox to demonstrate just a few of the reasons why cycloidal gearboxes are so useful. Then a video on "CNC Machined vs 3D Printed Cycloidal Drive": https://youtu.be/mPwbDrXq50Q - with the result that the CNC one is much heavier but the 3D printed one broke under heavy load and didn't have as much torque. Down to 50% under strong load. This might mean a smaller CNC machined one would be better or that we need to use galvanization for the 3D printed parts. It might also be so that the motor can't be too strong, so with a relatively weak motor it doesn't matter.
>In this electronics basics episode we will have a closer look at motor encoders. Those can not only turn any motor into an awesome and satisfying input device for your projects; but can also turn any kind of motor into a kind of stepper motor. There are many different types of such encoders. So let me show you how they work, what they do and how you can use them. https://youtu.be/d3IH8zwUVYU https://www.solomotorcontrollers.com https://www.youtube.com/@SOLOMotorControllers
Thanks for your nice inputs here, Noido Dev. Cheers.
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>>25792 Hey Kiwi, > I have a new hoverboard which uses a cheap Chinese chip that no one has figured out how to hack yet. It looks like that chip is here, under the "Three Gate Driver Chips" picrel. Click on the MM32SPIN05/06 = 2 boards link. https://github.com/RoboDurden/Hoverboard-Firmware-Hack-Gen2.x/wiki I got there from here: https://github.com/RoboDurden/Hoverboard-Firmware-Hack-Gen2.x RoboDurden seems to be one of the masters at reflashing hoverboards. Hope this helps.
I found this guys video channel on YouTube where he covers an extraordinary amount of actuators and motors and damn near everything. It covers not only all types of electric motors, also, pneumatic, hydraulic and even covers all the math from the very basics to do detailed analysis of all of these. And all the parts needed plus programmable logic control and circuits to control all these things. A PILE! As I was scrolling through his set of instruction videos it blew me away the depth of material this guy covers. It would be well worth bookmarking this and when you have a question scroll through his videos as an answer, while maybe not easy, is likely there. https://www.youtube.com/@bigbadtech/videos?view=0&sort=dd&shelf_id=0
>>30048 Yeah, that looks like a goldmine, Grommet. Thanks very much! :^) yt-dlp -i https://www.youtube.com/@bigbadtech/videos Do it today, /robowaifu/ anons! :^)

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