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didip parent
I think those problems can be solved with further research in material science, no? Combined that with very responsive but low torque servos, I think this is a solvable problem.
michaelt
It's a simple matter of the number of motors you have. [1]

Assume every motor has a 1% failure rate per year.

A boring wheeled roomba has 3 motors. That's a 2.9% failure rate per year, and 8.6% failures over 3 years.

Assume a humanoid robot has 43 motors. That gives you a 35% failure rate per year, and 73% over 3 years. That ain't good.

And not only is the humanoid robot less reliable, it's also 14.3x the price - because it's got 14.3x as many motors in it.

[1] And bearings and encoders and gearboxes and control boards and stuff... but they're largely proportional to the number of motors.

mewpmewp2
Would it be possible to reduce the failure rates?
chrsw
Yes but like almost everything it comes down to cost. Most consumer devices are extremely cost constrained. Industrial robots can justify higher costs that come with higher reliability.
ac29
The 1%/year failure rate appears to just be made up. There are plenty of electric motors that dont have anywhere near that failure rate (at least during the expected service life, failure rates certainly will probably hit 1%/year or higher eventually).

For example, do the motors in hard drives fail anywhere close to 1% a year in the first ~5 years? Backblaze data gives a total drive failure rate around 1% and I imagine most of those are not due to failure of motors.

michaelt
Yes, obviously that 1% figure is a simplification. Of course not all motors are created equal, and neither are all operating conditions!

But the neat thing about my argument is it holds true regardless of the underlying failure rate!

So long as your per-motor annual failure rate is >0, 43x it will be bigger than 3x it.

mrheosuper
your calculation is true, but the absolute number is needed here.

43x of 1% failure rate is tragic, but 43x of 0.1% is acceptable in my book.

michaelt
To an extent, yes.

For example, an industrial robot arm with 6 motors achieves much higher reliability than a consumer roomba with 3 motors. They do this with more metal parts, more precision machining, much more generous design tolerances, and suchlike. Which they can afford by charging 100x as much per unit.

bamboozled
Also factory robots arms are probably operating in highly sterile, dry environments? How would working in a muddy / dusty / wet environment change this?
michaelt
Some are, some aren't.

For example, MIG welding robots tend to life a hard life. And if you look at photos of industrial painting robots, you'll find they're often fitted with plastic smocks.

If you look up photos online you'll only get marketing images from robot makers, where everything is shiny and brand new - I can assure you, it's not like that after they've been operating for a decade or two :)

Robelius
When designing hardware, you usually define what the expected operating environments are. Some typical environmental considerations are the min/max temperature, debris ingress, shock & vibration. If you know your product is going to operate in an area where material is likely to enter the product, then you can either try to keep that material out (sealing the product up), or make sure that dust entering the product won't cause failures (i.e. electrical shorts won't happen on a board by covering exposed areas with glue or making sure a mechanism can crush/clear particles). It's not necessarily more complexity in the product to navigate these constrains, but it is another thing to consider in the design.

For example, if you're making a phone that is going to be sold around the world, then you're going to worry about arctic/equator temps (will some of your components melt or ICs fail), salty sea air (will the product begin to corrode for people living by a beach), or fast moving elevators (will the speakers pop from a sudden change in pressure).

You can check out this manufacturers robot arms as some examples of existing products. They list some data sheets for their robot arms, including some arms that are IPxx rated. I don't think looking at robot arms is a 1to1 comparison for what you could expect from a humanoid robot since the considerations in the design process are going to be different.

website is kuka dot com/en-at/products/robotics-systems/industrial-robots/kr-agilus

ta988
Search for CNC videos, those machines work in oily, soapy, dusty and full of metal shavings environments and do fine.
bamboozled
It's still a fairly controlled environment with splash guards, liquid based dusts suppression and or dust collection, even then my friend has a factory and the CNC is a reliable machine but things screw up.

If the dust collection was disabled, the workshop and the machine would be caked in debris.

It doesn't move, it doesn't fall over or have anything falling on top of it either (like a robot could).

elcritch
With more motors and joints also comes some degree of redundancy however. Having multiple fingers means one finger dying won't be as big of an impedement. It'd require feedback and the ability for the motion planner / AI to account for it.

Plus they'll likely be modular and able to be replaced.

IMHO, the bigger design issue for humanistic is lowering the need for mechanical precision which requires lots more metals and instead using adaptive feedback and sensors to obtain accuracy similar to how humans and animals do it. AIs should be really good at that, eventually. I think the compute will need to be about 10x what it is now though.

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