The latest Mars rover prototype developed by Astrium UK engineers demonstrated its autonomous navigation capability in front of an audience of journalists in a specially constructed mock-up of a Martian landscape – a ‘Mars yard’ – at the company’s Stevenage site on 1 September.
With work on the robot’s Guidance, Navigation and Control (GNC) system now finalised, this was the first public test of a technology that truly puts this rover – nicknamed Bruno – in a class of its own. While previous planetary rovers have had to sit idle for considerable periods of time awaiting control instructions to be beamed up from the operators back on Earth, Bruno will be able to decide on his own course across the Red Planet’s uneven, boulder-strewn and gully-pitted surface, identifying hazards such as rocks, slopes and drops, and plotting out the most appropriate route to a given destination. The human controllers simply provide the coordinates of a target location; Bruno works out how best to get there, and trundles off.
Less waiting about means that Bruno will be able to spend more time usefully getting on with his mission – exploring our neighbouring planet for signs of past or even present life. As Dr Jim Clemmet, Astrium’s rover vehicle engineering manager, puts it, “if we have more autonomy on board, we can do more science in the same timescale and hopefully also travel larger distances within the same timeframe.”
Bruno’s GNC system converts images of his surroundings captured by stereo cameras atop his two-metre mast into a 3D terrain model and then applies algorithms to create a ‘navigation map’ plotting out a path which avoids areas classified as non-navigable (impassable obstacles and unsafe zones) to take it to its designated destination.
In the Mars yard tests, Bruno proved that he could recognise an insurmountable obstacle blocking the direct route to the target location (in this case a large pile of rocks), devised and followed a path to circumnavigate it step by step, and arrived successfully at his appointed destination.
He also showed that he can make real-time locomotion adjustments to correct for disturbances as he goes – steering himself to the right, for example, to compensate for being slightly deflected to the left while traversing a biggish rock. This constitutes a significant advance over his robotic predecessors, which could not make on-the-move path corrections like this. “If you cannot correct your errors as you drive,” explains Richard Lancaster, Astrium’s lead guidance and control analyst, “you have to put greater margins into your chosen path to allow for the fact that you will slip off track. By reducing those margins with this system, we can travel through more complex terrains with greater confidence.”
The rover prototype has been developed under the European Space agency’s ExoMars programme, a collaborative undertaking with NASA for Mars exploration. The original mission envisaged two rovers, one European and one American, travelling together and descending to the same spot on the surface of the Red Planet. Lately, however, budget restrictions and programme revisions have led to a new focus on sending a single rover to investigate our neighbouring planet, with a launch slated for 2018.
Astrium is at the forefront of promoting the ExoMars mission, particularly the rover, and is continuing to develop technologies as part of risk-mitigation activities. The superiority of the UK-designed autonomous navigation system, demonstrated with such aplomb by Bruno on 1 September at Stevenage, makes a strong case for its inclusion in the eventual rover which will fly to Mars in 2018. Confirmation of the mission is expected shortly.
Copyright 2011 Astrium