Hedgehog Robots will Hop, Tumble in Microgravity

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Hedgehog Robots – Hopping & Tumbling on Surface

Researchers have developed models of Hedgehog Robots which would be exploring small bodies like an asteroid or a comet by hopping and tumbling on the surface rather than on wheels. Hedgehog is considered to be a new concept as a robot which has been designed specially to overcome challenges faced with regards to navigating small bodies.

The said project is developed together by researchers at NASA’s Jet Propulsion Laboratory –JPL in Pasadena, California, Stanford University in Stanford, California and the Massachusetts Institute of Technology in Cambridge. The leader of the JPL team, Issa Nesnas informs that `Hedgehog is a different type of a robot which can hop and tumble on the surface instead of rolling on wheels and is shaped like a cube and operates irrespective on which side it tends to land.


The simple concept is a cube having spikes which moves by spinning and braking internal flywheels and the spikes tend to protect the robot’s body from terrain, acting as feet in the course of hopping and tumbling. Nesnas alleged that the spikes also house instruments like the thermal probes to take the temperature of the surface as the robot tumbles.

`Yaw’ & `Tornado’ Manoeuvre

In June 2-15, two Hedgehog Robots models were tested aboard NASA’s C-9 aircraft for microgravity research, one from Stanford and one from JPL. Over the course of four flights, at the time of 180 parabolas, these robots portrayed numerous kinds of manoeuvres which could be useful in getting around on small bodies having reduced gravity. These manoeuvres were tested by the researchers, on various materials which imitate a wide range of surface like sandy, rough and rocky, slippery and icy and soft and crumbling.


The simplest manoeuver of Hedgehog is a `yaw’ or a turn in place wherein after pointing itself in the appropriate direction, it either hops long distances with the use of one or two spikes or tumble short distances by rotating from one face to another. It usually takes large hops in the direction of a target of interest followed by smaller tumbles as it tends to get closer.


During an experiment on the parabolic flights, the researcher had confirmed that Hedgehog could also perform a `tornado’ manoeuvre where the robot tends to spin violentlyto launch itself from the surface. This movement could be used in order to escape from sandy sinkhole or any other situation which would get the robot stuck in it.

Cube Provides Best Hopping Performance

Lead engineer on the project at JPL, Robert Reid informed that for the first time, they demonstrated the Hedgehog Robots prototypes performing controlled hopping and tumbling in comet like environments.


JPL Hedgehog Robots model is said to have eight spikes with three flywheels weighing around 5 kg alone, however the researchers envisage that it could weigh more than 9 kg together with instruments like the camera and spectrometers. The Stanford model is somewhat smaller and lighter with shorter spikes. Both the models tend to move by spinning and stopping three internal flywheels with the use of motors and brakes.


The mechanism of the brakes differ between the two models wherein JPL version had disc brakes while Stanford’s model used friction belts in order to stop the flywheels suddenly. Marco Pavone, leader of the Stanford team who initially had proposed Hedgehog Robots with Nesnas in 2011 has commented that `by controlling how you apply brake to the flywheels, you can adjust Hedgehog’s hopping angle.


The idea was to test the two braking systems and understand the advantages as well as disadvantages’. Benjamin Hockman, lead engineer on the project at Stanford has commented that the geometry of the Hedgehog spikes seems to have a great impact on its hopping course and they had experimented with numerous spike configurations and have found that a cube shape provide the best hopping performance.

Hedgehog Robots in Phase II Stage

The structure of the cube also seems to be easy to manufacture and pack within a spacecraft.Researchers are presently working on the autonomy of Hedgehog in an attempt to increase how much the robots could do by themselves without instructions from Earth. Their notion is that an orbiting mother-ship would transmit signals to and from the robot just the way NASA’s Mars rovers Curiosity and Opportunity communicates though satellites orbiting Mars. The robot would also get support from mother-ship in navigating and determining their position.

Construction of a Hedgehog Robots is comparatively low cost when compared to a traditional rover and numerous can be packed jointly for flight, according to the researchers. Mother-ship could release several robots either at once or in stages enabling them to spread out in making discoveries on a world which have never been navigated before.

The Hedgehog Robots is presently in Phase II stage through the NASA Innovative Advanced Concepts – NIAC Program, led by Pavone. Flight development and testing are supported by NASA’s Centre Innovation Fund – CIF and NASA’s flight Opportunities Program – FOP, led by Nesnas. NIAC, CIF and FOP are the programs in NASA’s Space Technology Mission Directorate, situation at the agency’s headquarters in Washington. California Institute of Technology for NASA Stanford University manages JPL and MIT and JPL collaborate on the subject.


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