Harmonic drive as a speed increaser 1

[sanjidam]

I am working on Harmonic drive. I am confused about its working principle as a inceraser. It looks it will not lock but how it will give such a gear ratio? Where I can find them? Any helpful topic, link or book recommendation is appreciated I have gone through the handout from different company. But no good book or literature.

Anyone here work with harmonic drive as a speed increaser? Is the gear ratio same as a reducer?

Anyone have any prototype? or can give a low cost model for online shipping?

 

[MikeHalloran]

Sorry, "low cost" and "harmonic drive" do not go together.
Sorry, "speed increaser" and "harmonic drive" do not go together.

Since you haven't given us a clue about the ratio you need, or the speed, or the torque you need to transmit, we can't tell you how badly you are screwed if you don't have some other alternative.





Mike Halloran
Pembroke Pines, FL, USA

 

[sanjidam]

Thanks a lot MikeHalloran

In journal article they are saying that if felxspline is input and wave generator is output then it will act as a speed increaser. So speed increaser and harmonic gear must go together. There are also another two configuration for speed increaser as per articles.

Low cost just for a prototype... I saw harmonic drive with logo ... even anyone have something like that it will work...

Gear ratio is 1:100 required

Torque not decided yet

I can't go for other alternative

Any help?

 

[MikeHalloran]

Well, that's _one_ number.

Anyone else want to play Twenty Or More Questions to drag out some info?

I give up at "low cost" and "prototype" in the same line.



Mike Halloran
Pembroke Pines, FL, USA

 

[tygerdawg]

I think it is dangerously unwise to consider a harmonic drive as a "speed increaser". Same for epicyclic reducers.
Here is some reference material

http://www.harmonicdrive.net/reference/operatingprinciples/

The design philosophy was to make a zero-backlash speed reducer with a very high gear ratio capability (on the order of 1:50 or higher). One usually does not want to backdrive anything with such high ratios because the mechanical stress on the mating faces of the transmission components would probably be too high. Besides, if you performed your input vs output torque/RPM calculation, you would see that one must provide a very large motor.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[mfgenggear]

http://www.hds.co.jp/HDS_hp_english/english/principle/index.html

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[zekeman]

Well, kinematically at least, if you invert a low GR drive , then it becomes a high GR drive.
Maybe that is what the OP saw in his search.
IN most cases you can't.

 

[drawoh]

sanjidam,

I was told by their technical support that Harmonic drive worked perfectly well as a speed increaser. I was told this because I was under the impression that it was self locking, like a high ratio worm drive.

I have used harmonic drive in a design, and it can be back driven.

I don't see any problems with a harmonic drive speed increaser that would not be true of any other speed increaser of the same ratio and efficiency. I did not analyse the harmonic drive for this, but I have done it for some miniature gear-motors like those from MicroMo. You can turn the output shaft and impose some very high accelerations on the motor armature. It could be very easy to exceed the maximum torque of the output shaft of the motor itself. You need to analyse for this.

My problems with the mini-motor came because it was rotating a moderate size laser optic scanner. You can grab the output shaft of the gear-motor, and it would be too stiff to rotate. When everything was installed, you could grab a ten inch wide frame, and rotate that easily, along with the gearhead, and the tiny, fragile motor.



--
JHG

 

[sanjidam]

Thanks everyone for their reply.

drawoh,
Is the gear ratio same as the reducer? do you have any article or book reference for that? i have confusion about its working principle. my thinking is the working principle will be slightly different from the reducer. do you have any prototype?

thanks

 

[sanjidam]

http://www.eng-tips.com/viewthread.cfm?qid=261933

In this thread "spigor" said he had one. Its long time before. but anyone like him can help?

 

[drawoh]

sanjidam,

Note my reply to the earlier thread. The basic harmonic drive mechanism is back-drivable, and it can be used as a speed increaser. Just turn the thing around.

A speed increaser has an effect opposite to that of a speed reducer. Torque is increased. It is difficult to turn the input shaft of a speed increaser.

The load inertia is multiplied by the square of the drive ratio, not divided as with a speed reducer. With harmonic drive, that is a big number, resulting in more torque, and the shaft stresses I noted above.

Many years ago, I attached a thumb-wheel to the rear shaft of a Micro Mo gear-motor. It was a small motor with a 22:1 ratio. The wheel was aluminium, about half an inch in diameter. I was amazed at the resistance when I turned the gear-head's output shaft with the thumb-wheel in place.

--
JHG

 

[hydtools]

sanjidam, the gear ratio is inverted. 100:1 becomes 1:100 100 revolutions input to 1 revolution output becomes 1 revolution input to 100 revolutions output when reversing output to input.

Ted