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NASA tells Curiosity: Quit showing off, no 'wheelies' please

Software update adds traction control to protect rover's wheels

By Richard Chirgwin, 30 Jun 2017

After 18 months of testing, NASA's pushed a patch to the Mars Curiosity Rover – to extend its wheels' life, and eliminate over-exuberant climbs causing “wheelies”.

Written by NASA Jet Propulsion Laboratory's Jeff Biesiadecki and Olivier Toupet, the software update went live earlier this month, having been uploaded to the famous robot in March.

The space agency has exercised its engineering hive-mind for years about the best way to deal with the dents the wheels have accumulated over the years: such considerations, for example, were a major consideration about the best way to reach Mount Sharp back in 2014.

As NASA writes, the first signs of wear appeared in 2013, and the biggest problem is tackling inclines, when some of the wheels lose grip and start slipping.

“This change in traction is especially problematic when going over pointed, embedded rocks. When this happens, the wheels in front pull the trailing wheels into rocks; the wheels behind push the leading wheels into rocks,” NASA explains.

“In either case, the climbing wheel can end up experiencing higher forces, leading to cracks and punctures. The treads on each of Curiosity's six wheels, called grousers, are designed for climbing rocks. But the spaces between them are more at risk.”

Hence the upgrade: a traction control algorithm that takes realtime data and adjusts each wheel's speed to cut down pressure from rocks.

A wheel's contact points are worked out by measuring changes to the suspension, and the software calculates the right speed to avoid slippage.

The traction control also helps manage unwanted “wheelies”, when “a climbing wheel will keep rising, lifting off the actual surface of a rock until it's free-spinning”. That puts too much load on the remaining wheels, so instead if there's a wheelie, each wheel's speed is adjusted until everything's back on the ground. ®

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