Fancy locomotion for rovers

Question

For its upcoming ExoMars mission, ESA's rover "Rosalind Franklin" can use its wheels like legs in an insect-like gait, to walk out of deep sand that it can't drive out of.

A brief video shows that the rover can brake each wheel and independently command motion of each leg's "hip" and "knee." Here's an animated GIF excerpt of the video.

How close do already launched rovers approach this? Independent braking of wheels? Some kind of active suspension? Some other unorthodox independent use of wheels and legs that would be pointless on smooth terrain? If some rover can't do such things, could a software update enable them?

different (forward-looking) but related: Does new technology make it advantageous to have walking rovers? — uhoh, Dec 10 '21 at 22:15
I'd imagine all leg joints would need to have a motor in the joints or a motor & an actuator associated with each joint, to get each joint "flexibility", for such movement to be possible. A rigid or semi rigid frame for the wheels won't be able to walk, irrespective of software. — Fred, Dec 11 '21 at 02:26
All rovers to date have had independent braking of wheels. Simply because all wheeled rovers have had all-wheel drive systems, which can do independent braking and so much more. — CuteKItty_pleaseStopBArking, Dec 11 '21 at 11:17
That's exactly what I seek evidence of. Even when each wheel has its own geared-down motor, how much does the control software exploit that? — Camille Goudeseune, Dec 11 '21 at 16:18
Here is an interesting robotic locomotion design from McGill University that seems to have no problem with sand… or surf, either ! https://www.youtube.com/watch?v=H8lxBfQ5jqg — Woody, Dec 12 '21 at 01:43

score 7 · Answer 1 · answered Dec 10 '21 at 22:27

7

The question is exploratory in nature and seems to allow for some degree of flexibility, so I will pick and choose words and address:

fancy locomotion for rovers

and

How close do already launched rovers approach this? Some other unorthodox... use of... legs...

in order to remind us of the two launched Prop-M rovers that are on Mars.

From this answer to Which rover(s) didn't have wheels?

above: GIF of how the Prop-M rover uses it's "skis" to walk. Linked here, from Giphy.

above: Mars Prop-M rover from here.

answered Dec 10 '21 at 22:27

uhoh

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Such motion would require all equipment on rovers that moved that way to be robust to the shaking up they'd get during motion. – Fred Dec 11 '21 at 02:28
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For large scale application usage of such walking techniques people might want to look at walking draglines - digging machines as big a houses that can walk smallish distances to position themselves so they can dig, spin & dump. See the animation in the link. – Fred Dec 11 '21 at 02:34
The "related" questions that our website offers explain why, for usual terrain, wheels are more energy efficient than legs or treads or these delightful snowshoes, and why (even with an RTG) that's what the engineers must optimize for. – Camille Goudeseune Dec 11 '21 at 04:41
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Here is an interesting robotic locomotion design from McGill University that seems to have no problem with sand… or surf, either ! youtube.com/watch?v=H8lxBfQ5jqg . The drive mechanism has the advantage that it is rotational on hard surfaces, has no external "knees" and the motors are enclosed in the chassis. – Woody Dec 12 '21 at 02:42

Camille Goudeseune · Answer 2 · 2022-04-08T20:11:44.050

According to its obituary(!) in The Economist, 2019 Feb 23, p. 86, Opportunity could brake wheels independently. It

dug a trench by spinning one wheel while it kept the others locked

Also, JPL reports control of individual wheel speeds and sensing of suspension state on Curiosity:

The traction control algorithm uses real-time data to adjust each wheel's speed, reducing pressure from the rocks. The software measures changes to the suspension system to figure out the contact points of each wheel. Then, it calculates the correct speed to avoid slippage, improving the rover's traction.
During testing at JPL, the wheels were driven over a six-inch (15-centimeter) force torque sensor on flat terrain. Leading wheels experienced a 20 percent load reduction, while middle wheels experienced an 11 percent load reduction, Rankin said.
Traction control also addresses the problem of wheelies. Occasionally, a climbing wheel will keep rising, lifting off the actual surface of a rock until it's free-spinning. That increases the forces on the wheels that are still in contact with terrain. When the algorithm detects a wheelie, it adjusts the speeds of the other wheels until the rising wheel is back into contact with the ground.

There must be better sources with more details. I challenge others to find them!

The best way for your challenge to get noticed and perhaps met is to ask it as a new question! — uhoh, Jan 23 '22 at 22:02

Fancy locomotion for rovers

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