I would like to point out another advantage of the beautiful system that you designed: The torque is equal over the entire travel of the joint. This can be hugely beneficial in robotics where knowledge of the force is required.
Your comment caught my attention because I've been playing around with robotic joint actuators, 3D-printing some of the examples representing different types (planetary, wave, cycloid, etc.) I think I understand what you mean, but can you explain briefly why other types may not deliver equal torque over the range? Are you speaking specifically about cable-driven types? So far, I have built planetary and cycloid for 4 axes, and now I have been looking various types of capstan/cable drive systems, (hoping) to select the "right" one...
@@mbunds hey bro I can tell you why. It is because this is a form of mechanical power transfer. Where you transfer power from one location (motor/actuator) to another location in the system. The reason why he said torque is equal over the entire travel of the joint is because with other methods of power transfer such as the 4bar/2bar mechanism, have an inherent disadvantage due to the effect of the lever arm on the output torque of the joint. the torque changes base on the angle of the lever arm causing you to have more torque at a lower degree angle and lower torque at a higher degree angle.
@@mbunds traditional chain pulley belt system you see in automotive are big huge assembly power transfering system. You basically getting the same advantage as a belt pulley which reduces the overall size profile of the system.
Sadly I don't think he does. There was a comment on last week's video about someone suggesting this, and his reply was a typical 'I'm not doing that because I don't need it' kind of reply. I like James and his content, but he comes off extremely arrogant in his own comments, sometimes even in his own videos. Maybe he'll look into it in the future if QDD doesn't work well for his compliant dog projects, though this kind of actuator is exactly what he's looking for with his search for a compliant leg mechanism. The lab that developed LIMS2 also developed a finger joint with a single wire and some springs, where the springs return the finger to a neutral position when the wire actuator is relaxed. Something like that mechanism could be adapted to be a passive compliant foot, with an encoder on the drum for positioning purposes, spring on the foot would keep the foot securely planted no matter what the terrain type is, and a simple torsion spring on the drum itself would always keep the wire in tension. Of course, the foot would need to be redesigned to have a cam profile, that way the passive system actuates while the foot is stepping, but that's nothing more than some additional math in the programming as your foot position changes slightly as the leg steps down. I also believe this system, a passive actuator with a way to sense positioning, is _exactly_ what James is looking for with a compliant leg, and could easily be fitted to add compliance to a rigid leg like what openDog currently has.
@@xaytana i have to say in defense of James Bruton your accusation of arrogance is plain wrong , the phrase '' we are all on the spectrum '' comes to mind and may be applicable , James like a huge number of makers likes to forge his own path but arrogance is not one of them .
I don't think the spool to large pulley size makes a mechanical advantage because the large pulleys aren't moving, they are just functioning as a smooth corner for the cable. So it is only the spool to small pulley that function as a block and tackle.
Not at all, look at how the design would compare to a system that would be used to lift something instead of rotate it. The large pulleys are only functioning as bearing to allow smooth rotation around the axis, but they aren't actually part of the "reduction" system. The function of the size of the large pulleys is only to allow the small pulleys to have a straight pull on the cable.
Basically, if you look at the very first drawing he did with trying to lift a weight with only one pulley, that is exactly what the large pulleys are doing. In a block and tackle, it's only the pulleys that "move" that actually create an advantage. The fixed pulleys only redirect the force to make the system take up less space. You could get the same advantage with less pulleys but it would be a much "longer" system. (Hint: compound pulley)
@@randomalleycat But the amount of cable in contact with the large pulleys reduces as the joint closes, so I think the small pulleys on the forearm do count as "moving". The opposing cable large pulley arc increases by an equal amount, but since you could exclude the opposing cable and still be able to contract the joint in one direction, I don't think that will cancel the "moving pulley" advantage.
I made my version of a 7m animatronic robot with Nema23 3Nm motors. This is one of the most useful channels I have found in this place. Thanks for the videos, man!
Hi, it is a good design. This is called tendon driven actuator or robot sometimes it is called as cable driven mechanism. One of the best example is davinci surgical robot instrument arms.
daVinci engineer checking in. Aravinth is correct - the robot arms on the daVinici Standard, S, and Si were largely cable-driven. The current Xi system does NOT use cables (though there are some flat metal belts on one axis) in the robot arms. However, nearly all daVinci surgical INSTRUMENTS do still use cables. In fact, the very first CAD Skyentific shows is very similar to the system used in the instrument wrists. link to a video that shows some of how that works: ruclips.net/video/KNHgeykDXFw/видео.html
bschena what is the advantage disadvantage of the cable/flat metal belts that caused the change? @skyentific mentions this being back-drivable, is there a way to prevent that in this system, if that is unwanted?? Thank you immensely for your input
@@cedricpod They worked very well, but were not terribly stiff and required a lot of periodic maintenance to maintain performance. The fleet in the field started getting so large that having to touch every arm on every system a few times per year was a growing headache for both ISI and the hospitals.
I'm not even a student. I'm just someone who finds this stuff neat. He explains it so well that it all just seems simple and intuitive. Like, I feel like I could have come up with it and built it based on how simple he makes everything sound.
This is very interesting... I've been looking for an actuator like this for a long time, but hadn't seen one before. I had planned most of the other parts of the system that I wanted to build, but was missing this piece. The basis of the robot I want to build is a central rotating shaft, and a system of clutch units that engage the shaft. These clutch units would be variable, and could either apply a controllable sliding torque, or lock to the shaft to produce a burst of force on the cable. The main advantage of this is that you only need one massive motor centrally located, and then every limb has access to the full power available from the motor. When not being moved by the motor, the clutch for each joint could lock in place and provide zero power holding torque. Multiple joints can be actuated at the same time, and pulsing the clutches quickly between engaged and immobile (with a small amount of spring based backlash) could allow relatively precise multi joint simultaneous control.
Hi. I have been working on a cable driven system for a while now that uses this principle. I have worked out how to do it without having the cable travel sideways on the drive pulley and also incorporate a high reduction system at the same time say 10:1 but can be configured from 2 to about 30 to 1. It has no backlash. This allows for a smaller higher speed motor to drive it.
Awesome, can you share any information of documents about this kind of mechanism? I'm a student in major of Mechatronics engineering, and I'm really interested in these kind of knowledge, especially in these days when the situation is damn hard, lol. Anw, take care and keep up the good works.
@@laiquocbao2565 Hi. There's an article about this type of arm here... www.cs.cmu.edu/~cga/c/0749.pdf I plan on doing a video on my adaption of this shortly
I like how the axial movement of the rolled cable in the driver shaft could be used to activate toggle switches on each end and keep these very close to a motor without an encoder
Wow, with this design, if it's got the kind of mechanical advantage you calculated, you could use a fairly small stepper motor to lift a massive amount of weight! That's awesome!
Sarcos and Raytheon do a joint very similar to this in their exoskeleton system. Very cool to see it more fleshed out! Very well thought out and designed!
Nice and smooth! You could get a much higher reduction ratio with less pulleys in the joint if you use differential pulleys, would need both ends of each cable to be anchored into the winding drum but that's easier than trying to fit more pulleys into the joint. I think there is a good chance this is one of the lightest joints for the strength that can be achieved!
Very cool! We use that exact same concept only with much larger hardware, to automate scenery movement in theaters. Wires are redirected from hanging or rolling scenery, (and through double purchase snatch blocks in some cases) and run around both sides of a cable drum and kept in tight tension to enable very fine movement. We're talking pieces that weigh hundreds of pounds being able to fly consistently and safely to within a mm of the mark, night after night.
First of all fantastic build! There is a reducer based on cables that could be awesome in you set up. The elbow should have a single wheel and two single cables terminated in blocks. Just like your first set up but terminate in the “bicep” with the fixed side of blocks. The motor shaft should have two small and two slightly bigger cylinders. A cable should be wound on the small via the block to the big. This system gives reduction based on the circumference of the cylinders. Equal cylinders gives infinite reduction.
Not sure if you mentioned this but you could produce variable levels of torque from the arm by treating the fixed point of both ropes nearest the joint as a wheel with a brake on it and both ends of the rope are joined together. Putting the brake on different wheels will allow many different amount of torque. Downside is that you would have probably have to place the brake at different wheels to achieve the same torque in both directions. Also, after some maths on the back of an envelope, there will probably be no slack the rope as long as only one brake is activated at any one time. Soz for the lack of technical terms
This is a very good design, most of mine only ever came out as a 1:1 redirect type system for loads or at most 2:1. Would love to see a test of this vs say a system with half as many pulleys. Maybe measuring how much force or loads each can move
Awesome job. Since I met you at maker's fair in Paris you amaze me by your simple ways to make great things work smoothly! You definately deserve more attention!
I think this joint would make a fantastic robot arm, just for the fact that you could string the joints all the way down to the base and have the motors there, making it lightweight.
i was playing around with a capstan actuator like this for a spider robot over a decade ago, but this is a good idea for mechanical advantage, at the time i was thinking offset horns :-( and reduction gearing as a stop gap. one BIG advantage of cable systems is you can remove the motor from the "limb" and bury it inside the body (think bonnet release on a car or bike brake cables) that lets you move the wight to the static components and patently lower the center of gravity with a smaller and thinner limb. oooh there is an idea , if you add some overrun clutches you use more than one system per limb, 1st fast low load and a 2nd high torque system for power.
Are you sure about the bike brake cables? Radius of the pulleys are so small can develope more bending stress result in fatigue? Can you offer another alternative to those cables?
You can also gain a torque advantage by shrinking the diameter of the winch spool. Your way adds strength to the joint as well. By splitting the forces over multiple cable lines. The winch won't add strength. But It will add mechanical advantage.
using a PE fishing line you only need like 4x the diamter of the fishing line as the diameter of the winch shaft I heard. Whereas with metal you need like 20x or something since a overly small diameter would stress the metal cable. PE fishing line is more willing to make the tighter turns without stressing it to failure and stress fracturing internally.
Hi, to answer your question, I think the name of your reduction system is a 'Hauling System', exactly the same as for boat sails. Normally this system is rectilinear, but with your system of large intermediate pulleys you allow to work curved. It's a very good tip and a great idea, I probably won't use this principle but it's always good to know it. Thanks a lot for your investigations. Enjoy to see your next video. Bye Matthieu
It's crazy how smooth it is. You did such a great job designing this! Edit: why not use this technique in the robot arm? pretty sure it's possible to improve your already impressive design to make it thinner and increase the angle.
Joannot this probably introduces a lot of friction due to the increased contact between the cable and the pulleys. Not sure how that will play out in actual applications but I'm assuming it will hinder the torque tracking ability.
Bump this (follow-up) question! Why did you decide not to use this style of mechanism for your ongoing project? Was it because of the friction like @Kenny Kim suggests? Does using a mechanism like this complicate the placement of motors and resulting weight distribution?
i'm super impressed and enamoured by this beautifully smooth design too, but one issue i can imagine are the loads applied to some of the small bearings and axles that hold them, further into the reduction.
@@DMonZ1988 The force is the same at every pulley. The cable tension is the same everywhere, so each small pulley gets 2x the cable tension shear load on the axle.
Your enthusiasm and amazingly thorough explanations make all of your videos a delight to watch. As much as I don't need another project right now, I feel like I should begin printing parts for my own robotic arm. Thank you for another amazing installment.
Nice. Scale that down and you have a knuckle with a potentially strong grip and a drive outside the joint... just like a finger. The motor(s) could be in the shoulder or even the base... nice.
I think it would be interesting to make a second cable system to avoiding a single cable failure under stress and over time as steel cable will tend to keep "memory" of being wrapped around a curve.
With precision CNC metal parts and thinner dyneema wires, there's actually significant room to miniturize this joint to less than 1/10 of its original size. I'm not sure about the zero backlash, if the wire isn't tensioned enough you might easily introduce backlash. And to keep the cable preloaded the wire needs certain degree of elasticity. But then rigidity may suffer from elasticity. Still a very impressive design. A huge advantage with cable driven joints is that the motor and reduction may be relocated closer to the chassis, this significantly reduces moment of inertia on the moving parts.
@@Skyentific You are welcome. But really... that is an AWESOME idea! By the way... I am the guy who made the MegaMotor6. Google it. Maybe we can do some joint collaboration on something.
Hi sky. This reminds me a lot of differential a pulley system. I built something very similar to this for a gearbox of a parasol, with a similar level of reduction (but substantially simpler). If you make the driver pulleys of different diameters but on the same axle you can make use of the difference in length in winding-unwinding them. The smaller the diameter difference, the bigger the reduction rate. Then you only need two idler pulleys. This makes the design super compact. Check out the wikipedia article on differential pulleys. What I'm talking about is basically a mix between your pulley system (where the idler pulleys are the ones that transmit the force to the other member) and a differential pulley system. Good job, this prototype looks really well built!
Nothing I'd want to show to anyone. i made it while I was still in college and it contained several mechanical mistakes. If I find some time this week I'll whip up one in cad to demo the concept.
Perhaps a very smooth rope can be produced, suitable to touch a roller chain for direct rope bearing. That allows a very compact construction of a pulley.
Love the concept! Especially because with proper tensioning, it's a very cheap zero-backlash system. But... The way I see it, you only have the mechanical advantage of 4. IMHO It doesn't matter how big the gray big pulleys are - they are simple rolling guides in this system. The block-and-tackle mechanism works the same no matter how big or small the gray pulleys are. The real multiplication comes from the diameter difference between the driver drum and the knob. Am I seeing this wrong?
Yes, the video is misleading. The main mechanical advantage comes from the driver drum; the pulleys are just rolling guides. You can increase the torque on the forearm by moving the contact points further up the forearm (which makes the grey pulleys bigger) but it's incorrect to call this mechanical advantage.
@ErosNicolau @alirezanejati9712 The torque applied at the joint is occurring at the joint pulleys which have a radius that is larger than the drive pulley radius. I think the OP is correct in his 20:1 torque multiplication calculation. If you look at the amount of cable that if transferred on the drive pulley it is about 10 turns for less than half a turn on the joint pulleys so the mechanical advantage seems correct.
I think this kind of mechanism was used early in airplanes without servos and stepper motors, well I dont know the name but its a great video and it would be very useful in many robotic projects, thank you very much
I like this idea. I was thinking about the idea of using a cable (steel, or carbon thread/braid, or heavy duty fishing line) with a block and tackle for a 3d printer.
Great job! You are solved the matter of mounting a motor directly in the joint, in my experience, the joint of elbow is one of the most difficult articulation in the human body, for causes like the reduced space and the position in the angles of charge, previously, i did make a robotic arm based in pulleys, but it only works partially, only works back an forward when the arm was set in vertical position; in horizontal, only work's in one way. I will try to replicate your work whith your permission, thank's and cogratulations!!!
Personally I like to call these tendon actuators, as the wire/cable is doing the job of a tendon in a muscular-skeletal system. These can also be driven by any form of actuator, both linear and rotational. Personally, I'm more interested in the 2dof wrist actuator used on the LIMS2 arms. I know there's a video on the mechanical design of it, and it shows the internal joint in decent detail, but sadly it doesn't show it's pulley system in as much detail; I just know there's various hinges and wire guides, but I'm clueless on how the cables are routed through the wrist pulley system, the pulley system at the base of the wrist, or how the cables are routed through the arm in general.
Автор, ты гений! У меня в голове тоже была мысль про нечто подобное, но я почему-то не додумался до блоков. Ну и задача была получить механизм раздвижной, а не поворотный. Я все думал, как уменьшить сопротивление, чтобы актуатор мог воспринимать обратное воздействие, и как раз додумался до тросового механизма с двумя плечами (как у вас на валу привода). Вот блоков то мне и не хватало! спасибо)
Hi. Love the design. I do have one suggestion though, switch the wire cable for multi-strand fishing line, wire will stretch, but the fishing line doesn't.
I would like to point out another advantage of the beautiful system that you designed: The torque is equal over the entire travel of the joint. This can be hugely beneficial in robotics where knowledge of the force is required.
Your comment caught my attention because I've been playing around with robotic joint actuators, 3D-printing some of the examples representing different types (planetary, wave, cycloid, etc.) I think I understand what you mean, but can you explain briefly why other types may not deliver equal torque over the range? Are you speaking specifically about cable-driven types? So far, I have built planetary and cycloid for 4 axes, and now I have been looking various types of capstan/cable drive systems, (hoping) to select the "right" one...
@@mbunds hey bro I can tell you why. It is because this is a form of mechanical power transfer. Where you transfer power from one location (motor/actuator) to another location in the system. The reason why he said torque is equal over the entire travel of the joint is because with other methods of power transfer such as the 4bar/2bar mechanism, have an inherent disadvantage due to the effect of the lever arm on the output torque of the joint. the torque changes base on the angle of the lever arm causing you to have more torque at a lower degree angle and lower torque at a higher degree angle.
@@mbunds traditional chain pulley belt system you see in automotive are big huge assembly power transfering system. You basically getting the same advantage as a belt pulley which reduces the overall size profile of the system.
Would be cool to see it in action with a motor and some weight lifting tests. as always, great work!
Before the video:
After the video: pulleh
hahaha XD I was reading the intro some comments , but with the first "Pulleh". I paid attention to the video
Dude .. not cool. You had me saying polleh after every time he does!
poleh
zeh pulleh!
I think James Bruton would be very interested in this joint!
Joints always elicit interest...lol
Single servo dog leg!
Sadly I don't think he does. There was a comment on last week's video about someone suggesting this, and his reply was a typical 'I'm not doing that because I don't need it' kind of reply. I like James and his content, but he comes off extremely arrogant in his own comments, sometimes even in his own videos. Maybe he'll look into it in the future if QDD doesn't work well for his compliant dog projects, though this kind of actuator is exactly what he's looking for with his search for a compliant leg mechanism.
The lab that developed LIMS2 also developed a finger joint with a single wire and some springs, where the springs return the finger to a neutral position when the wire actuator is relaxed. Something like that mechanism could be adapted to be a passive compliant foot, with an encoder on the drum for positioning purposes, spring on the foot would keep the foot securely planted no matter what the terrain type is, and a simple torsion spring on the drum itself would always keep the wire in tension. Of course, the foot would need to be redesigned to have a cam profile, that way the passive system actuates while the foot is stepping, but that's nothing more than some additional math in the programming as your foot position changes slightly as the leg steps down. I also believe this system, a passive actuator with a way to sense positioning, is _exactly_ what James is looking for with a compliant leg, and could easily be fitted to add compliance to a rigid leg like what openDog currently has.
@@xaytana absolutely agree, this mechanism would give him the torque he needs on opendog.
@@xaytana i have to say in defense of James Bruton your accusation of arrogance is plain wrong , the phrase '' we are all on the spectrum '' comes to mind and may be applicable , James like a huge number of makers likes to forge his own path but arrogance is not one of them .
the cad drawings of line 1 and line 2 were extremely useful to visualize how it works. Thanks for putting those together!
This guy needs to be seen by more people!
This guy agrees! :)
@@Skyentific I'll share as much as I can! Haha
Beautiful! Would like to see it motorized and driven with a controller!
Nice work. The walk though in cad was great.
Thank you!
I don't think the spool to large pulley size makes a mechanical advantage because the large pulleys aren't moving, they are just functioning as a smooth corner for the cable. So it is only the spool to small pulley that function as a block and tackle.
Alana Catherine ..... possibly you missed the point of the design .... i am still pondering it
Not at all, look at how the design would compare to a system that would be used to lift something instead of rotate it. The large pulleys are only functioning as bearing to allow smooth rotation around the axis, but they aren't actually part of the "reduction" system. The function of the size of the large pulleys is only to allow the small pulleys to have a straight pull on the cable.
Basically, if you look at the very first drawing he did with trying to lift a weight with only one pulley, that is exactly what the large pulleys are doing. In a block and tackle, it's only the pulleys that "move" that actually create an advantage. The fixed pulleys only redirect the force to make the system take up less space. You could get the same advantage with less pulleys but it would be a much "longer" system. (Hint: compound pulley)
@@randomalleycat Yes, precisely. The big pulleys allow it to maintain a more even pull on the cable when the arm is moving.
@@randomalleycat But the amount of cable in contact with the large pulleys reduces as the joint closes, so I think the small pulleys on the forearm do count as "moving". The opposing cable large pulley arc increases by an equal amount, but since you could exclude the opposing cable and still be able to contract the joint in one direction, I don't think that will cancel the "moving pulley" advantage.
I made my version of a 7m animatronic robot with Nema23 3Nm motors. This is one of the most useful channels I have found in this place. Thanks for the videos, man!
Thank you a lot! I really appreciate this!
Hi, it is a good design. This is called tendon driven actuator or robot sometimes it is called as cable driven mechanism. One of the best example is davinci surgical robot instrument arms.
daVinci engineer checking in. Aravinth is correct - the robot arms on the daVinici Standard, S, and Si were largely cable-driven. The current Xi system does NOT use cables (though there are some flat metal belts on one axis) in the robot arms. However, nearly all daVinci surgical INSTRUMENTS do still use cables. In fact, the very first CAD Skyentific shows is very similar to the system used in the instrument wrists. link to a video that shows some of how that works: ruclips.net/video/KNHgeykDXFw/видео.html
@@bschena Yes absolutely right
bschena .... why was cable drive abandoned ?
bschena what is the advantage disadvantage of the cable/flat metal belts that caused the change?
@skyentific mentions this being back-drivable, is there a way to prevent that in this system, if that is unwanted??
Thank you immensely for your input
@@cedricpod They worked very well, but were not terribly stiff and required a lot of periodic maintenance to maintain performance. The fleet in the field started getting so large that having to touch every arm on every system a few times per year was a growing headache for both ISI and the hospitals.
One of the best video I watched in this lockdown situation.
I wish to see some more about this in future...
I love your style of talking simply, which makes me really understand from you while I am still a student in mechanical engineering thanks alot
i love the way he says pulley , just love it hahahah
@@abhishekprasad2935 lol
I'm not even a student. I'm just someone who finds this stuff neat. He explains it so well that it all just seems simple and intuitive. Like, I feel like I could have come up with it and built it based on how simple he makes everything sound.
Sometimes the simple things work the best, you have nailed it. Thanks
This is very interesting...
I've been looking for an actuator like this for a long time, but hadn't seen one before. I had planned most of the other parts of the system that I wanted to build, but was missing this piece. The basis of the robot I want to build is a central rotating shaft, and a system of clutch units that engage the shaft. These clutch units would be variable, and could either apply a controllable sliding torque, or lock to the shaft to produce a burst of force on the cable.
The main advantage of this is that you only need one massive motor centrally located, and then every limb has access to the full power available from the motor. When not being moved by the motor, the clutch for each joint could lock in place and provide zero power holding torque.
Multiple joints can be actuated at the same time, and pulsing the clutches quickly between engaged and immobile (with a small amount of spring based backlash) could allow relatively precise multi joint simultaneous control.
Really cool mate! I LOVE IT!
How I missed comment from Ivan Miranda itself?!! :)
@Payton Lane It's a scam
@Matias Spencer instaportal has really bad backlash and puts you at a mechanical disadvantage
The very end is hilarious!! Nice piece of engineering
Thank you!
Hi.
I have been working on a cable driven system for a while now that uses this principle.
I have worked out how to do it without having the cable travel sideways on the drive pulley and also incorporate a high reduction system at the same time say 10:1 but can be configured from 2 to about 30 to 1.
It has no backlash. This allows for a smaller higher speed motor to drive it.
Awesome, can you share any information of documents about this kind of mechanism? I'm a student in major of Mechatronics engineering, and I'm really interested in these kind of knowledge, especially in these days when the situation is damn hard, lol. Anw, take care and keep up the good works.
I want to know more about this kind of joints Please
me too i am interested
Me too
@@laiquocbao2565 Hi.
There's an article about this type of arm here...
www.cs.cmu.edu/~cga/c/0749.pdf
I plan on doing a video on my adaption of this shortly
I like how the axial movement of the rolled cable in the driver shaft could be used to activate toggle switches on each end and keep these very close to a motor without an encoder
Wow, with this design, if it's got the kind of mechanical advantage you calculated, you could use a fairly small stepper motor to lift a massive amount of weight! That's awesome!
Sarcos and Raytheon do a joint very similar to this in their exoskeleton system. Very cool to see it more fleshed out! Very well thought out and designed!
I was looking for something about cable driven mechanisms, but this work expands my thoughts, thank you
Nice and smooth!
You could get a much higher reduction ratio with less pulleys in the joint if you use differential pulleys, would need both ends of each cable to be anchored into the winding drum but that's easier than trying to fit more pulleys into the joint.
I think there is a good chance this is one of the lightest joints for the strength that can be achieved!
Very cool! We use that exact same concept only with much larger hardware, to automate scenery movement in theaters. Wires are redirected from hanging or rolling scenery, (and through double purchase snatch blocks in some cases) and run around both sides of a cable drum and kept in tight tension to enable very fine movement. We're talking pieces that weigh hundreds of pounds being able to fly consistently and safely to within a mm of the mark, night after night.
And that is why us animals have tendons. Nice work!
Thank you!
very clever, and i like your honest style and clear delivery method
This is exactly what I've been looking for (even the reduction ratio).
Thank you Skyentifc !
First of all fantastic build!
There is a reducer based on cables that could be awesome in you set up.
The elbow should have a single wheel and two single cables terminated in blocks. Just like your first set up but terminate in the “bicep” with the fixed side of blocks.
The motor shaft should have two small and two slightly bigger cylinders. A cable should be wound on the small via the block to the big.
This system gives reduction based on the circumference of the cylinders. Equal cylinders gives infinite reduction.
That's a really cool mechanism. It really leverages the advantages of 3d printing. Props for designing it yourself. Very impressive.
Great idea . Amazing the way you take existing concept and leverage it.
Thank you a lot!
Not sure if you mentioned this but you could produce variable levels of torque from the arm by treating the fixed point of both ropes nearest the joint as a wheel with a brake on it and both ends of the rope are joined together. Putting the brake on different wheels will allow many different amount of torque. Downside is that you would have probably have to place the brake at different wheels to achieve the same torque in both directions. Also, after some maths on the back of an envelope, there will probably be no slack the rope as long as only one brake is activated at any one time.
Soz for the lack of technical terms
This is a very good design, most of mine only ever came out as a 1:1 redirect type system for loads or at most 2:1. Would love to see a test of this vs say a system with half as many pulleys. Maybe measuring how much force or loads each can move
Awesome job. Since I met you at maker's fair in Paris you amaze me by your simple ways to make great things work smoothly! You definately deserve more attention!
Thank you a lot! I really appreciate this. I really liked Paris Maker Faire. Very friendly place!
I think this joint would make a fantastic robot arm, just for the fact that you could string the joints all the way down to the base and have the motors there, making it lightweight.
I'm sure @SmarterEveryDay appreciates the shoutout! Great to see science youtube sharing knowledge.
Such an elegant (and quiet) design! Love it!
I studied wire driven robots' arms. Using Snatch blocks principe is interesting. I didn't remembered seeing that but yours is quite compact. Well done
Beautifully conceived and beautifully executed. Such a good explanation too. Subscribed.
This is a very interesting approach, especially for compliancy since this is so easily back-drivable.
This would be a nice joint for a quadruped.
I will definitely be using this type mechanism for my canoe loading system on my roof rack.
Cheers mate, thanks for sharing!
That's a VERY impressive mechanism.
Thank you brother I learn something today. This is really good video!
Thanks for teaching this kind of technology. Greetings from Sri Lanka
Wonderful example... Thanks!
Thank you!
i was playing around with a capstan actuator like this for a spider robot over a decade ago, but this is a good idea for mechanical advantage, at the time i was thinking offset horns :-( and reduction gearing as a stop gap.
one BIG advantage of cable systems is you can remove the motor from the "limb" and bury it inside the body (think bonnet release on a car or bike brake cables) that lets you move the wight to the static components and patently lower the center of gravity with a smaller and thinner limb.
oooh there is an idea , if you add some overrun clutches you use more than one system per limb, 1st fast low load and a 2nd high torque system for power.
This is really an excellent idea!!!
Are you sure about the bike brake cables? Radius of the pulleys are so small can develope more bending stress result in fatigue? Can you offer another alternative to those cables?
That is a great universal design for both robotic elbow and knee joints....as well as a few other uses.
this is a really good design
going to replace the gearboxes on my brushless robot dog design with these. Awesome idea skyentific!
You can also gain a torque advantage by shrinking the diameter of the winch spool. Your way adds strength to the joint as well. By splitting the forces over multiple cable lines. The winch won't add strength. But It will add mechanical advantage.
using a PE fishing line you only need like 4x the diamter of the fishing line as the diameter of the winch shaft I heard. Whereas with metal you need like 20x or something since a overly small diameter would stress the metal cable. PE fishing line is more willing to make the tighter turns without stressing it to failure and stress fracturing internally.
I have been wondering about cables for awhile! This is a very cool system, thank you for sharing!
Thank you for your comment! :)
Hi,
to answer your question, I think the name of your reduction system is a 'Hauling System', exactly the same as for boat sails.
Normally this system is rectilinear, but with your system of large intermediate pulleys you allow to work curved.
It's a very good tip and a great idea, I probably won't use this principle but it's always good to know it.
Thanks a lot for your investigations.
Enjoy to see your next video. Bye
Matthieu
Matthieu FAUVINET .... “ probably won’t use it “ ..... why not ?
@@cedricpod I have no application for that... But i like to see mecanical systems.
It's crazy how smooth it is.
You did such a great job designing this!
Edit: why not use this technique in the robot arm? pretty sure it's possible to improve your already impressive design to make it thinner and increase the angle.
Joannot this probably introduces a lot of friction due to the increased contact between the cable and the pulleys. Not sure how that will play out in actual applications but I'm assuming it will hinder the torque tracking ability.
Bump this (follow-up) question! Why did you decide not to use this style of mechanism for your ongoing project? Was it because of the friction like @Kenny Kim suggests? Does using a mechanism like this complicate the placement of motors and resulting weight distribution?
i'm super impressed and enamoured by this beautifully smooth design too, but one issue i can imagine are the loads applied to some of the small bearings and axles that hold them, further into the reduction.
@@DMonZ1988 The force is the same at every pulley. The cable tension is the same everywhere, so each small pulley gets 2x the cable tension shear load on the axle.
zero backlash gears are used in the Canadarm and Canadarm2, if that's what you are asking.
That was really really cool!
Never thought to use leverage like that!
Thank you!
Great job mate
Your enthusiasm and amazingly thorough explanations make all of your videos a delight to watch. As much as I don't need another project right now, I feel like I should begin printing parts for my own robotic arm.
Thank you for another amazing installment.
Very cool mechanical design.
Very nice. Thank you for sharing! Would be interested to see how this type of reducer would perform under load when powered with a motor.
Nice. Scale that down and you have a knuckle with a potentially strong grip and a drive outside the joint... just like a finger. The motor(s) could be in the shoulder or even the base... nice.
I think it would be interesting to make a second cable system to avoiding a single cable failure under stress and over time as steel cable will tend to keep "memory" of being wrapped around a curve.
Beautiful! Are the cad files available? I'd like to try build it.. Thanks for sharing this wonderful design!
@@MUCKFOOT399 not everybody can engineering this themselves
you live in my dream country, Switzerland
by the way, amazing channel and amazing content and explanation for a layman like me
... Very intelligent engineering!!!!!!!!!!!!!
With precision CNC metal parts and thinner dyneema wires, there's actually significant room to miniturize this joint to less than 1/10 of its original size. I'm not sure about the zero backlash, if the wire isn't tensioned enough you might easily introduce backlash. And to keep the cable preloaded the wire needs certain degree of elasticity. But then rigidity may suffer from elasticity. Still a very impressive design. A huge advantage with cable driven joints is that the motor and reduction may be relocated closer to the chassis, this significantly reduces moment of inertia on the moving parts.
BEST video so far! AWEsome concept!
Thank you a lot!
@@Skyentific
You are welcome. But really... that is an AWESOME idea!
By the way... I am the guy who made the MegaMotor6. Google it. Maybe we can do some joint collaboration on something.
Love the result - would really enjoy watching a testing video
Excellent concept, well engineered! Love your videos, please keep them coming!
this was the first ever video i had seen in your channel subbed to your channel :)
Thank you! :)
Really awesome video, mechanical design, build execution, explanation, and I enjoy your speaking voice. New subscriber!
Thank you a lot!
this is actually genius reducer....
Hi sky. This reminds me a lot of differential a pulley system. I built something very similar to this for a gearbox of a parasol, with a similar level of reduction (but substantially simpler).
If you make the driver pulleys of different diameters but on the same axle you can make use of the difference in length in winding-unwinding them. The smaller the diameter difference, the bigger the reduction rate. Then you only need two idler pulleys. This makes the design super compact. Check out the wikipedia article on differential pulleys. What I'm talking about is basically a mix between your pulley system (where the idler pulleys are the ones that transmit the force to the other member) and a differential pulley system.
Good job, this prototype looks really well built!
free spirit 1 Do you have any pictures of the gearbox you built?
Nothing I'd want to show to anyone. i made it while I was still in college and it contained several mechanical mistakes. If I find some time this week I'll whip up one in cad to demo the concept.
Dont understand it from the description. Is it something like the WAM Arm drive? Have found a patent from Bill Townsend US5,207,114
Super cool design!
Perhaps a very smooth rope can be produced, suitable to touch a roller chain for direct rope bearing. That allows a very compact construction of a pulley.
I love this guys channel. Totally wanna use this technique for my life sized Johnny-5 robot one day. If i can ever muster the effort!
Awesome design
Beautiful, simple , elegant and nicely explained. Keep up the good work.
That really look interesting, great study.
this is exactly what i needed for my design
very cool design
Love the concept! Especially because with proper tensioning, it's a very cheap zero-backlash system.
But... The way I see it, you only have the mechanical advantage of 4. IMHO It doesn't matter how big the gray big pulleys are - they are simple rolling guides in this system. The block-and-tackle mechanism works the same no matter how big or small the gray pulleys are. The real multiplication comes from the diameter difference between the driver drum and the knob. Am I seeing this wrong?
Yes, the video is misleading. The main mechanical advantage comes from the driver drum; the pulleys are just rolling guides. You can increase the torque on the forearm by moving the contact points further up the forearm (which makes the grey pulleys bigger) but it's incorrect to call this mechanical advantage.
@ErosNicolau @alirezanejati9712 The torque applied at the joint is occurring at the joint pulleys which have a radius that is larger than the drive pulley radius. I think the OP is correct in his 20:1 torque multiplication calculation. If you look at the amount of cable that if transferred on the drive pulley it is about 10 turns for less than half a turn on the joint pulleys so the mechanical advantage seems correct.
I think this kind of mechanism was used early in airplanes without servos and stepper motors, well I dont know the name but its a great video and it would be very useful in many robotic projects, thank you very much
Very well designed ! Thanks a lot for sharing this build !
I don't know how you will ever get anything else done. I would play with that thing all day.
Very interesting joint. Thanks for sharing.
it is very much the same principle as for elevators, as you showed at the beginning, elevators workthe same
Or several comments! 😂
Like your work. You encourage me to want to design and print my own robotic arm.
I like this idea. I was thinking about the idea of using a cable (steel, or carbon thread/braid, or heavy duty fishing line) with a block and tackle for a 3d printer.
After recently studying some of Leonardo da Vinci‘s inventions, I noticed that his automaton used pulleys and it seems that he had the right idea.
Absolutely amazing. Super underrated channel!!
*Mentions smarter everyday*
Me: instant subscription
Awesome mechanism! I hope it makes the world a better place.
Great job! You are solved the matter of mounting a motor directly in the joint, in my experience, the joint of elbow is one of the most difficult articulation in the human body, for causes like the reduced space and the position in the angles of charge, previously, i did make a robotic arm based in pulleys, but it only works partially, only works back an forward when the arm was set in vertical position; in horizontal, only work's in one way.
I will try to replicate your work whith your permission, thank's and cogratulations!!!
11:00 hahhahahaahha !!! xD
oh.. i get it!! its a joke from star lord
That was a Thumb, right?
I've seen the original video and always wondered what the mechanism is thanks for sharing!
@smartereveryday this is the coolest application of a snatch block I’ve ever seen.
Yes! :)
you are one of those channels that i feel like subscribing is not enough
Great design
Personally I like to call these tendon actuators, as the wire/cable is doing the job of a tendon in a muscular-skeletal system. These can also be driven by any form of actuator, both linear and rotational.
Personally, I'm more interested in the 2dof wrist actuator used on the LIMS2 arms. I know there's a video on the mechanical design of it, and it shows the internal joint in decent detail, but sadly it doesn't show it's pulley system in as much detail; I just know there's various hinges and wire guides, but I'm clueless on how the cables are routed through the wrist pulley system, the pulley system at the base of the wrist, or how the cables are routed through the arm in general.
Автор, ты гений! У меня в голове тоже была мысль про нечто подобное, но я почему-то не додумался до блоков. Ну и задача была получить механизм раздвижной, а не поворотный. Я все думал, как уменьшить сопротивление, чтобы актуатор мог воспринимать обратное воздействие, и как раз додумался до тросового механизма с двумя плечами (как у вас на валу привода). Вот блоков то мне и не хватало! спасибо)
Very good alternative design!
Maybe no backlash but I think there will be some cable stretching.
Hi. Love the design. I do have one suggestion though, switch the wire cable for multi-strand fishing line, wire will stretch, but the fishing line doesn't.