Throwable Robot Car Always Lands on Four Wheels | Hacker News Reader

Throwable Robot Car Always Lands on Four Wheels

spectrum.ieee.org

21 pointsheadalgorithm11 comments

Boston Dynamics tackled this problem with the SandFlea robot ca. 2010, albeit in a single axis while exploiting the intermediate axis theorem. You can see it in action @ 0:17 in their sole released video[1], where the robot snaps flat during the ascent phase.

This was done primarily to increase the likelihood that the vehicle would land on all four wheels, in order to maximize energy dissipation by the wheels on landing and thus minimize shock seen by the body. As a secondary benefit, footage from the onboard camera stood a chance to be usable during a hop, instead of being a blurry mess. Lots of great details in their patent filing for the robot[2].

Source: I helped design this robot

[1]: https://www.youtube.com/watch?v=6b4ZZQkcNEo [2]: https://patents.google.com/patent/US8849451B2/

I'd be pretty curious to know how well this scales. Nifty work for small bots, but the article mentions things like attempting this with Humvees during airdrops.

Seems like in this prototype, the wheels make up a non-trivial chunk of the total mass of the bot. Does this realistically work if the wheels are only a very small portion of the mass of the robot?

Not to mention that the design constraints of a reaction wheel and a drive wheel are almost polar opposites: a reaction wheel needs to have the largest possible moment of inertia, to maximize the change in angular momentum for a given mass and torque; meanwhile, a drive wheel should have the smallest possible moment of inertia, to maximize the change in angular speed for a given mass and torque, particularly since you typically want to minimize unsprung mass (in fairness, the demoed robot didn't have any suspension to worry about).

Big off-road tires are in the 100 lbs weight range, though. It might work for a special forces dune buggy. https://en.wikipedia.org/wiki/Light_Strike_Vehicle

They might even want that actuated tail, to have a camera/IR sensor at the end of..

I can see the markers for a motion capture system in the video.

Measuring or accurately calculating the orientation at a rate high enough for this is a challenge in itself.

Having ridden a lot of motocross in my younger stupider years I can attest to the fact that controlling the rotation of your wheels while airborne is a very important consideration when jumping a motorcycle. If you know what you are doing you can use the rotation or braking of your wheels to control your attitude (and subsequent landing) in the air.

At least from RC car to small motorcycle it seems to scale, no idea about the physics in flipping a humvee and whether the wheels have enough leverage to do that.

A fun fact about monster trucks is that they do exactly that: spin they massive wheels while in the air to control their angle during jumps.

Someday this will probably be used in some cheap plastic cat toy you can buy for a couple dollars at a $5 store.

Or an automated weapon, rolling down your street

You mean falling onto my street.

The funny thing is the researchers always talk about search and rescue applications. They've been inventing search and rescue robots for decades. Flying ones, walking ones, wheeled ones, jumping ones, self-assembling ones, object detection, all sorts of robotics are supposed to be for search and rescue. But in real life, they're for toys, and maybe weapons.

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