Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Marine Corps Shelves Futuristic Robo-Mule Due to Noise Concerns

military.com

Post reply on HN
Print view View original

91–100 of 117 posts

Re: Marine Corps Shelves Futuristic Robo-Mule Due to Noise Concerns

#91

Post by Animats »

gene-h wrote: post #45
jarmitage wrote: post #14

Can anyone in robotics weigh in on whether new approaches like pneubotics / otherlab [0, 1] make Boston Dynamics' super heavy/noisy/expensive robots irrelevant or not? That's what Saul Griffith has been saying at least [2], I'd like to hear an impartial take on it [0] http://www.pneubotics.com/ [1] https://otherlab.com/projects [2] "[...] we're the only game in town." 21:00 onwards https://youtu.be/gyMowPAJwqo?t=1263

In my opinion, I don't think inflatable robots are very practical.(except for niche applications) One of the most important things in robotics is reliability, the more work your robot does before breaking down or needing maintenance the more money it makes you. In industrial robot arms the gold standard for this is a Mean Time Between Failures of more than 100,000 hours. That's more than 10 years of continuous operat…

(http://www.phriends.eu/URAI_08.pdf)

That's a very good paper. There are many advantages to using two opposed springs driven by actuators to simulate muscles. You get muscle-like properties. You get energy storage and recovery. (Humans recover about 70% of energy from muscle springiness when running. Cheetahs, 90%. BigDog, 0%.)

As that paper points out, there are several ways to do this. The cleanest is a double-ended pneumatic cylinder with proportional spool valves at each end able to connect to pressure or exhaust. That was tried on a legged robot at CWRU some years ago. There are schemes with linear springs, string, two motors, and linkages, which tend to be bulky and complex.[1][2] Those work, but are more of a research design than a production mechanism. Somebody will do a better design, probably with rotational springs and no strings.

I once considered a design with two motors, rotational springs, and a differential. One motor controls impedance, the other controls position. If you don't need to change impedance rapidly, which you usually don't, the impedance motor can be much smaller and geared down.

[1] http://mech.vub.ac.be/multibody/topics/maccepa.htm [2] http://www.inacomm2013.ammindia.org/Papers/106-inacomm2013_s...

Re: Marine Corps Shelves Futuristic Robo-Mule Due to Noise Concerns

#92

Post by grogenaut »

jonmrodriguez wrote: post #46
grogenaut wrote: post #44

Earlier quoted context omitted.

One big drawback not called out to electric is you have to power it to have it hold still. Hydraulic can just leave a valve closed which may or may not require power. Then again just have it "sit". This may not be the best tactically though in small group engagements as "sit" is movement and freeze is dead stop. I'll let people who know more about that debate it though.

> you have to power it to have it hold still Is it common to work around this by supplementing the electric motor with a disc brake? Depending where you want to be on the tradeoff between complexity vs energy-efficiency, you could use a hydraulically-powered disc brake in order for the brake to not need power except during state transitions.

Thought about this for a bit. I'm betting it's used. The deal with brakes is the ratio of the friction applicable by the brake and the lever distance of the compared to the lever arm it's stopping. I'm watching a movie so I'm not going to do the math right now but I think the size of disc rotor you could get on say a mule's knee joint versus the lever arm length of say a lower leg might cause problems either with the size of the rotor.

My thinking is mountain bike discs are 120mm/4.8"-203mm/8" diameter compared to a 29" wheel.

These are meant to stop a 160lb person who is going down a hill. Well Slow to a stop not lock dead in place as the wheel would break free so it's not the full stopping power of a real.

Anyway my gut reaction is it might be difficult in this use case. I think a 8" rotor on a similar lever arm might have trouble fully locking down that joint and would be very large and flimsy (8" thin sheet of metal) for rugged use. Plausible though.

But hey I failed out of mechanical engineering into computer science for a reason so maybe I shouldn't be trusted :)

Re: Marine Corps Shelves Futuristic Robo-Mule Due to Noise Concerns

#93

Post by njharman »

wehadfun wrote: post #7

why do they need this. What are they carrying? Are marines supposed to go without resupplies for weeks/months where they would need an additional robot mule to carry everything?

> resupplies

Telling your robot to carry this shit over there is great way to resupply. Compared to having soldiers (or contractors) get blown up driving trucks around.

Re: Marine Corps Shelves Futuristic Robo-Mule Due to Noise Concerns

#94

Post by njharman »

thinkcontext wrote: post #27

I wonder at what price point the civilian market could support these? There must be a fair number of applications for resupply where humans (sherpas), actual animal mules or helicopters are required, ie, forestry, National Park rangers, science, recreation, etc.

I would buy one, if $10-16k, and it went 40-50mph and was street legal. I'd ride it to work. Hell I'd ride it everywhere.

Re: Marine Corps Shelves Futuristic Robo-Mule Due to Noise Concerns

#96

Post by jkldotio »

tdy721 wrote: post #84

I call B.S. A nuclear powered one would probably be pretty quiet.

Are Rat Things[0] really viable?

"MMRTG contains a total of 10.6 pounds (4.8 kilograms) of plutonium dioxide (including Pu-238) that initially provides approximately 2,000 watts of thermal power and 110 watts of electrical power when exposed to deep space environments."[1]

Even if ~110 watts per ~4.8 kilograms is good for legs in agile situations, as opposed to wheels in a slow-and-steady rover, losing one in combat means you've just given the enemy a few kilos of radioactive material.

[0]https://en.wikipedia.org/wiki/Snow_Crash#Rat_Things [1]http://mars.nasa.gov/msl/files/mep/MMRTG_FactSheet_update_10...

Re: Marine Corps Shelves Futuristic Robo-Mule Due to Noise Concerns

#97

Post by dredmorbius »

kiba wrote: post #57
JabavuAdams wrote: post #42

Earlier quoted context omitted.

Much easier than the logistics of keeping a robot operational in the field. You don't care whether the Taliban captures your flesh and blood mule, but you really don't want them capturing your world's-most-advanced robotic mule.

The Taliban are not going to have the capability to reverse engineer and produce their own copy, let along having the logistic capability of keeping it in the field.

But the parties they sell it to, for substantial combat-enabling cash, will.

Re: Marine Corps Shelves Futuristic Robo-Mule Due to Noise Concerns

#98

Post by dredmorbius »

eliteraspberrie wrote: post #38
homerowilson wrote: post #2

There are these things called "mules." They're quiet, can carry about 200lbs., and can refuel themselves as they go by eating grass and drinking water...

Yaks and camels too, depending on the environment.

And if you ever run out of things to do, you can shave your yak.

Re: Marine Corps Shelves Futuristic Robo-Mule Due to Noise Concerns

#99

Post by Animats »

grogenaut wrote: post #92
jonmrodriguez wrote: post #46

Earlier quoted context omitted.

> you have to power it to have it hold still Is it common to work around this by supplementing the electric motor with a disc brake? Depending where you want to be on the tradeoff between complexity vs energy-efficiency, you could use a hydraulically-powered disc brake in order for the brake to not need power except during state transitions.

Thought about this for a bit. I'm betting it's used. The deal with brakes is the ratio of the friction applicable by the brake and the lever distance of the compared to the lever arm it's stopping. I'm watching a movie so I'm not going to do the math right now but I think the size of disc rotor you could get on say a mule's knee joint versus the lever arm length of say a lower leg might cause problems either with the…

Think smaller. Most of the mechanism has to fit inside the dimensions of an arm or elbow.

Re: Marine Corps Shelves Futuristic Robo-Mule Due to Noise Concerns

#100

Post by grogenaut »

Animats wrote: post #99
grogenaut wrote: post #92

Earlier quoted context omitted.

Thought about this for a bit. I'm betting it's used. The deal with brakes is the ratio of the friction applicable by the brake and the lever distance of the compared to the lever arm it's stopping. I'm watching a movie so I'm not going to do the math right now but I think the size of disc rotor you could get on say a mule's knee joint versus the lever arm length of say a lower leg might cause problems either with the…

Think smaller. Most of the mechanism has to fit inside the dimensions of an arm or elbow.

I think you're missing that this is EXACTLY my point. I'm really doubting a disc that could fit inside an elbow would be able to stop the torque of a few hundred (900/4) lbs on it. Actually one inside the elbow would have a very minimal surface area on the disc in the first place.
Post reply on HN