Soccerbots Learn How To Fall Gracefully

wjousts writes "Up until now, most work with humanoid robotics has focused on keeping them upright and balanced, but in the real world, falling down is inevitable. So now researcher in Chile are looking at teaching their Soccerbots how to fall down gracefully to minimize damage and allow for a quick recovery. According to a New Scientist article, 'They found that one of the main ways to minimise damage is for the robot to fold its legs underneath it. Among other things, that means the robot is much less likely to hit its head on the ground. Another good strategy is to use a fall sequence consisting of several movements, so the falling body has several points of contact with the ground, spreading the energy of the impact over a large number of joints, rather than taking it all in one disastrous crunch.'"

The essense of Judo

[diskofish]

As a Judo practitioner, I can tell you that learning how to fall correctly is the key to not getting hurt. The article describes exactly what a breakfall is. In Judo, you collapse your legs and roll. It would make sense that they program a robot to do the same thing.

Re:The essense of Judo

[cailith1970]

He means what is known as a break fall [wikipedia.org] where you do exactly what he says. It's one method of preventing injury from a throw or a fall in martial arts.

Re:*Ahem*

[Anonymous Coward]

Actually the American game isn't really football [eatliver.com]

Re:The essense of Judo

[DMUTPeregrine]

As a martial artist experienced in Hap Ki Do, I'd like to point out that even in a break fall you roll. Just slapping the ground won't prevent injury, and just rolling well likely have you roll over. Slapping the ground stops the roll, in addition to taking the impact & spreading it. You tuck your head to keep it from hitting at all, not slap the ground to reduce that impact.
The roll decreases the rate at which the impact energy enters your body, the slap distributes the energy & helps prevent harm caused by rolling onto your neck.

Re:This is great

[gadget junkie]

Every Chelsea player knows that the most important skill is knowing when and how to fall.

There, that should cover just about every nationality besides English.

That's nothing. Here in Italy, Inter played whole swathes of the season with exactly one (1) Italian player in the field.

In japanese martial arts, ...

[getuid()]

...people often hit against the floor with their arms and legs in the very moment of ground impact.

The reasoning behind this is "momentum conservation". Basically, the momentum of the whole body is split in the momentum of the torso+head (i.e. most vital parts) and the momentum of the extremities. While during the fall all parts of the body move downwards with approximately the same speed, in the moment of impact the falling person hits his arms/legs against the ground, this way giving them extra momentum downwards. By the laws of physics (specifically momentum conservation), this momentum has to come from somewhere. And that "somewhere" is torso+head, i.e. vital parts of the body get slower -- the slower, the harder one hits his arms/legs against the ground.

This basically saves from internal organ injuries at the expense of the outer extremities, which, in general, are more robust and less critical to survival.

There are three problems that should be solved with robots, if something similar is to be tried:

1) The extremities. Robots need outer extremities, and they should be rather massive -- the more massive, the more momentum they can generate.

2) The joints. Joints to outer extremities should unlock immediately in the moment of inpact in order not to transfer the vibrations of impact from the extremites through the joints to the rest.

3) Useful energy dissipation mechanisms in the extremities. The whole idea is not only that the robot "survives", but that it actually can continue playing after falling. Therefore the extremity is to be built in such a way, that it has some kind of soft, massive buffer, that can get deformed repeatedly on impact without braking (think of "sand sack", for example).

The more I think about it: why not anchor 3-4 sand weights to the robot's outer shell, and "shoot" them against the ground during the impact? Also make them automatically retractable at some point (maybe version 2.0? :-) by having strings attached to them, so that the robot can reuse them minutes later...

Nao's are fragile

[CAPSLOCK2000]

I've worked with NAO robots, and while they are very sophisticated, they are also very fragile. Especially the fingers will break at the slightest provocation.

When working with these robots you constantly have to hold them to prevent them from falling. As the robots are rather heavy and have quite powerfull engines you arms tend to get tired from working with them. Fortunately there is a decent simulator.

We've considered to buy some inflatable swimming armbands and put them on our robots to protect them from falling.