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'Hedgehog' Robot Could Hop & Tumble on the Surface of a Comet or Asteroid

Hopping, tumbling, and flipping over are not typical maneuvers to be expected from a spacecraft exploring other planets. Traditional Mars rovers roll around on wheels and they can't operate upside-down. But on a small body like an asteroid or a comet, the low-gravity conditions and rough surfaces make traditional driving all the more hazardous. Hedgehog is a new concept for a robot that is specifically designed to overcome the challenges of traversing small bodies. The project is being developed by researchers at NASA's Jet Propulsion Laboratory, Stanford University, and MIT. The basic concept is a cube with spikes that moves by spinning and braking internal flywheels. The spikes protect the robot's body from the terrain and act as feet while hopping and tumbling. There are two Hedgehog prototypes - one from Stanford and one from JPL - and both maneuver by spinning and stopping three internal flywheels using motors and brakes. The braking mechanisms differ between the two prototypes. JPL's version uses disc brakes, and Stanford's prototype uses friction belts to stop the flywheels abruptly.

Topics:
Aerospace Automation Motion Control Motors & Drives Robotics

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    Transcript

    00:00:00 (Music) Comets and asteroids are very fascinating places. They may contain building blocks or the remnants of the building blocks of the solar system. However, to explore they present a unique set of challenges. There's the low gravity environment, or microgravity, as we call it. For example, a person here on Earth would weigh as little as a paperclip on the surface of a comet. So a rover, like Curiosity, which is currently exploring Mars would actually only weigh a couple of kilograms. It wouldn't be able to generate much traction. And in fact, as it turns its wheels it would probably just push itself away from the surface. It's actually quite likely to end up rotating and landing upside down,

    00:00:40 at which point it's end of the mission for the rover. So instead, together JPL and Stanford University have been working on a totally different rover concept that is well suited to these environments called Hedgehog. Instead of rolling around on wheels, the Hedgehog design actually puts three flywheels on the inside of a cube. By spinning these flywheels up very slowly and then very quickly applying the brake, which transfers all the momentum from the fly wheels, we're able to cause Hedgehog to either hop, or tumble, or perform small adjustments. We've done many tests here on Earth in gravity off-loading test beds. Recently, we have flown two hedgehog prototypes on a Zero-G aircraft.

    00:01:16 In these tests we demonstrated that we would be able to perform on a comet or an asteroid. Hedgehog doesn't have a right way up. Instead, it can tumble over the surface and come to rest on any one of its faces and still work perfectly. The Rosetta mission has sent back lots of very fascinating images from the surface of comet 67P and these images show us some incredibly rugged terrain, including large sinkholes where a traditional rover would get terribly stuck. So we've even tested Hedgehog performing a type of escape maneuver where it spins itself up and does this tornado-like maneuver, where it can actually launch itself vertically out of a sandpit. In our future work we're looking at increasing the level of autonomy, giving the Hedgehog rovers' the ability to think for himself and navigate from one point to another.

    00:02:00 The Hedgehog rovers' ability to move around on the surface of comets and asteroids can enable a wide range of applications in science in the future