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I'll bet hoverboard bldc motors would make a good servo

I dont get why it needs flex spline? Why not just two gears instead of bearings at 6:50?

Fantastic, thank you!

so uh Why not use two gears freewheeling where the lobes would be on the internal cam instead of a flexspine? you would still have the wedge-driving action, but it wouldn't require whatever process is needed to make a flex spline. I bet you could even install the inner gear bearings into slots axial to the "lobes" of the "cam" and spring load the gears to push away from the center so that you compensate for wear overtime and don't develop backlash. It'd be kind of like a planetary gear set, so I'm calling this a binary sun gear set until someone tells me it already exists xD

This is the most amazing and useful video i have seen in a long time. Thank you for explaining this. I was really struggling to understand exactly how it works. You are an awesome teacher.

Fantastic explanation and the hardware was really good. I now know 'Harmonic Drive' has nothing, at all, to do with music.

Great video! Thanks!

Easist tutoial that I 've ever got.

this explanation is wrong. just check the direction of the rotor and stator on a real harmonic drive, their direction is reversed.

Having read wikipedia article first, I had a hard time understanding this video, as you use 3 gears instead of just 2.

Best explanation I've ever seen!

It's so excellently explained! God Job!

Great teaching! I have learnt a lot. Thank you.

Need volume, can't hear you

Is there really no backlash at all?? Surely youd get some between the mesh teeth?

Hello Sir, I hope you are doing well. Please let me know if you are using FOC and PVM for control? Of it is a different control technique? Are you using back emf for sensing?

Sir, you are a life saver.

Wow, you're a great teacher, your video is terrific and I now know something completely new about gear drives. Years ago I got a fanuc welding robot arm and was amazed at the zero backlash on the joints but never knew why it was possible until now. As for how to get 2 more teeth with the same pitch, it's hits me now that the outer ring is naturally LONGER than the inner one, hence can have 2 more teeth in its' path. However, sizing up the tooth depth to accomodate the mating, etc is a challenge.Thanks for this explanation and I'll look at more of your videos in the future.

At the 1 minute mark , lunar rover, notice the pilot doesn't move, at all, he is utterly frozen in position, head does not swivel to look left into the turn, arms and hand positions utterly frozen in place over all bumps, rooster tail dust from wheels in a vacuum seems very out of place, rate of wheel dust collapse to the ground seems incredibly fast for 1/6 gravity conditions and rover cart seems to have no suspension give at any wheel - maybe a tad but not much if at all, and the antenna doesn't wiggle except at the end of the clip at the strongest bump ... just my observations ... anyway eager here to learn about harmonic drives!

Super great explanation. One would think that the flex spline gear would fatigue over a short time, but they're so widely used in so many applications that it must not be an issue. Thanks for the great video demonstration!

Thanks for the concise explanation. I can see that these drives have multiple applications beyond the world of robotics. As an astrophotographer who deals with backlash on a seasonal basis (ambient temperature variations) this technology would be exceptionally well suited to telescope drives. My impression is that this type of mechanism would be less prone to backlash due to temperature variation. Chhers!

I must subscribe to the channel. Immediately and deeply attracted by the awesome demonstration and teaching. Thank you!

Fascinating. Great explanation. Harmonic drives are showing up in telescope mounts and I wanted to see how they worked.

Really well done!

Thank you! Wonderful demostration!

I finally understand harmonic drives. In 12 minutes. Man that's stellar.

This is not a harmonic drive; It is a differential gear system, related to the split-ring planetary drive. In a true harmonic drive, the 2 high-torque members are the outer internal gear, & the flexspline, which is coupled to a cylinder terminated at its far end with a "bottom", forming a cup structure. There is no second internal gear. The bottom of the cup is the output & the outer gear is the stationary frame. The input is the wave driver. The outer gear & flexspline can be interchanged (output & stationary parts switched).

Great video, man.

“Harmonic Drives” piqued my interest, but the differential drive ( e.g; windlass, boat hoist… ) is at least centuries old. I have one for heavy moving, mostly engine swapping, and probably older than me. The only confusing parts are your use of “complicated”, the new name, and the addition of poor engineering to this time-proven device.

Best harmonic drive mechanical explanation I've seen (out of at least a dozen I've come across)

Awesome lesson, many thanks 👏👏👏

I do wish you had explained how all three models you demonstrated were not the same concept and functioned differently

Great demo!

Clear explaination and great video. Thank you

Now I got it, thank you

I 3d printed a barn door tracker for astrophotography and has huge limitations, I’ve been looking into a different way to make one that has less wobble and more load capabilities, I think I’ll give this a shot!

Had one fail on Cincinnati centre-less grinder in feed never got it fixed to expensive😮

I have heard of this but had never had an explanation. You provided a very good explanation.

Could you please provide me your WhatsApp number

Outstanding it is Crystal clear now

Thank you for sharing

You Sir defogged my mind in 12 minutes on harmonic drives, THANK YOU.

So here's a quick question: does the harmonic drive create an increase in torque, as what one would expect through a standard gear drive? More efficient? Less efficient? What are the benefits of a harmonic drive over a standard geared drive/transmission system?

I work for Harmonic Drive and it really doesn't surprise me that these things last. Much care an precision goes into making these.

Nice video! Looking at these drives I thought that instead of having the flexible gear to wedge the stator and output gears, why not have a plantetary/harmonic hybrid? It would be like a normal planetary setup, but instead of the drive going through the planet gears, the planet gears would only do the job of the flexible gear in a harmonic drive setup, becoming the wedging force to do the reduction, while transmitting the force/torque. There would no longer be a need for the traditional sun gear as in a plantetary setup, so it could be omitted. The difference in gear teeth needed for this to work as a harmonic drive could be achieved by making the outer part of the planetary drive (is it called the ring gear?), in two pieces with a different number of teeth. These two ring gears would act as the stator and the output respectively, connected by the aforementioned planet gears (which may need to be slightly elongated to allow for adequate meshing contact between the two ring gears). By using planet gears to do the job of the flexible gear, it negates the need for it to be flexible, removing the weak link. Also, if you adjust the teeth size to outer ring gear diameter ratio, you could have more than two spots where the teeth "harmonize" allowing for greater force transfer, while dispersing the load for better longevity. Just a thought...🤔

You can make a harmonic drive without the flex spline, which is nice for 3d printing them: th-cam.com/video/8Nd_RlZqcik/w-d-xo.html

Is there a more reliable gear reduction device that can last decades? Anyone?

Love it!!! I need to make some of these but specialized use.

This guy is a great explainer. Thanks for the video.

Thank you very much for a very simple explanation of strain wave drives. One of the newer places that these drives are starting to be used is in astronomy, more specifically astrophotography. Astrophotographers are always looking for lighter weight, more powerful, more reliable and less power consumption in their gear, since often time hobbyist astrophotographers are out in the middle of some open field, far away from any power. For the most part, telescope mounts fall into two categories, Alt/Az, or Altitude Azimunth and EQ, German EQ which means German Equatorial mounts For astrophotography, EQ mounts are much more common, albeit much more expensive. You can align one axis to the North Star, Polaris, and the mount will rotate around that point in the sky, and since all the stars and things in space also rotate around it, once you've selected your target, the mount tracks around the North Star, keeping the object in the center of the scope. Strain Wave drives are now offered by two companies, ZWO and iOptron. Usually, a normal EQ mount requires a counterweight and shaft to balance the load on the 'Right Ascension axis, which is the axis pointed at the North Star. Having the system balanced keeps down tracking errors. The Strain Wave drive eliminates the need for the counterweight (up to a certain payload), thereby reducing the entire weight of the mount. It also tracks better and has zero backlash, which is something astrophotographers also are interested in. So, yeah, Strain Wave mounts are coming, and they are going to be the future of hobbyist astrophotography. Because of you, I know a lot more about strain wave drives now than I did 45 minutes ago!