Robot arm to help catch space debris

A new rapidly moving robotic arm could be used to catch space debris, according to its creators in Switzerland.


The 1.5m-long arm, built as an attachment for a satellite, can catch various irregularly shaped projectiles in less than five hundredths of a second.

The project is part of the Clean- mE project at the Swiss Space Center, which aims to develop technologies for recovering and disposing of space debris orbiting around Earth, which poses an increasing danger to satellites and other space infrastructure.

In order to enable the arm to react fast enough to anticipate the trajectory of approaching objects and catch them mid-flight, the researchers had to program it with the ability to learn from being operated manually.

‘Today’s machines are often pre-programmed and cannot quickly assimilate data changes,’ said Prof Aude Billard, one of the researchers from the Swiss Federal Institute of Technology in Lausanne (EPFL).

‘Consequently, their only choice is to recalculate the trajectories, which requires too much time from them in situations in which every fraction of a second can be decisive.’

To obtain the desired speed and adaptability, LASA researchers were inspired by the way humans themselves learn: by imitation and trial and error.

This technique, called “programming by demonstration”, does not give specific directions to the robot. Instead, it shows examples of possible trajectories to it by manually guiding the arm to the projected target and repeating this exercise several times.

The research was conducted with a ball, an empty bottle, a half full bottle, a hammer and a tennis racket, a selection of objects that offered a varied range of situations in which the part of the object that the robot has to catch (the handle of the racket, for example) does not correspond to its centre of gravity.

Once it had undergone sufficient training, the robot was able to use a series of cameras to create a model for the objects’ kinetics based on their trajectories, speeds and rotational movement. It can then calculate how to position itself very quickly in the right direction in order to catch the object.

During the few milliseconds of the approach, the machine refines and corrects the trajectory for a real-time and high precision capture. This efficiency is further enhanced by the development of controllers that couple and synchronize the movements of the hand and fingers.