NASA scientists create robotic cliffhanger

NASA researchers are developing new prototype robots that can drive up steep hills and descend almost-vertical cliffs. Working alone or as a team, these autonomous robotic explorers may be used to traverse the cliffs of Mars.

Recent Mars Global Surveyor images suggest water outflows near cliff edges and the possibility of rich water-borne mineral deposits that extend all the way to the cliff base.

‘We know that some of the most exciting Mars science and history will be in very rough, currently inaccessible terrain. Getting to those hard-to-reach spots – navigating and exploring them – will require altogether new types of robotic vehicles,’ said Dr. Paul Schenker, supervisor of the Mechanical and Robotics Technologies Group at NASA’s Jet Propulsion Laboratory, and principal investigator for the All-Terrain Explorer.

‘These include rover systems that can surmount the hilly base of cliffs, even descend from cliff edges to study cliff stratigraphy. Some years from now, rovers may literally be hanging out on Mars,’ he said.

In a demonstration near JPL, a new mobility system navigated a cliff face. Two ‘tether-bot’ rovers stationed themselves at the cliff’s edge, assisting a third steerable ‘cliff-bot’ as it actively descended and ascended the steep terrain.

‘They’re a true team, tightly co-ordinating their behaviours, sharing what they sense,’ Schenker said. ‘They communicate instantaneously, make mutually informed decisions and jointly implement their control actions. We can think of them as a climber with two good friends. We’re not yet at the point of human competence, where one robot can go it all alone.’

The rovers can reportedly co-operate in a number of ways: controlling tension to avoid slackness in the tethers, matching velocity of tether payouts to cliff-bot navigation, maintaining stability to prevent cliff-bot tip-over and hauling actions to initiate the ‘climber’s’ uphill driving when the going gets really rough.

Over the past year, the JPL researchers also successfully developed and demonstrated a single rover that can traverse sandy natural terrain on slopes of 40 to 50 degrees.

Similar to an agile animal, this mechanically reconfigurable All-Terrain Explorer behaviourally adapts its stance and balance, reacting to visually perceived changes in the terrain ahead and motion cues from onboard accelerometers.

‘These technology advances should enable broader robotic exploration of planetary surfaces, letting rovers truly follow the water, thus giving us a better look at possibilities of past or present life on Mars,’ Schenker said. ‘Similarly, there are potentially important terrestrial applications, including urban and rural search-and-rescue operations.’

Basic research on the All-Terrain Explorer rovers continues, and engineers envision that their work may well be part of a future Mars mission to explore the steep hills and gullies, nooks and crannies of the red planet.