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ROVER WHEELS: Monitoring changes over time, NOTE: Read back through the thread to avoid repeating misconceptions
elakdawalla
post May 2 2015, 03:51 AM
Post #271


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Here's a look at the left-middle wheel over time, which is the one I'm most concerned about. Although there have been changes between sol 708 and 962, they're only incremental -- I'm actually pretty pleased with how they look after the Pahrump campaign and a whole lot of driving besides. There are no broken grousers. The grousers to watch closely are the ones between fields 11 and 12 and 13 -- those areas have a lot of tears running a substantial width of the wheel, leaving the grousers with little support except at their ends. So those are the ones that will probably break first, eventually. Hopefully continued careful driving will prevent that from happening for a while.

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elakdawalla
post Jun 8 2015, 04:27 PM
Post #272


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Moved a couple of posts about Mars 2020 wheel design to a new thread in the new Mars 2020 subforum.


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peter.neaum
post Oct 10 2015, 05:56 AM
Post #273


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The latest series of images from MSL / Mars Hand Lens Imager / MAHLI camera has several views of the wheels.

From Sol 1127 (40 img): http://mars.jpl.nasa.gov/msl/multimedia/ra...mp;camera=MAHLI

One of the images shows a nasty looking spike of metal jutting into the wheel space. I presume the axle shaft will knock it away / back, before it becomes an issue for the wire bundle.
I was unable to find a better image of the metal spike, but here's a ghastly, tweaked & cropped version (I presume it's a spike and not an optical illusion).

From here:
http://mars.jpl.nasa.gov/msl-raw-images/ms...794E01_DXXX.jpg
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elakdawalla
post Oct 12 2015, 03:44 PM
Post #274


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That one has been developing for a while, but it does have quite the inward point. Engineers are justifiably concerned about the possibility of these sharp edges abrading the wire bundles. I actually am having trouble figuring out a scenario in which this one, ripping further, would then straighten in the right way and place to actually scrape a wire bundle; I think it gets to be a more serious problem if (when) grousers start breaking.


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peter.neaum
post Oct 13 2015, 10:29 AM
Post #275


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Yes, you're right - when it (or any others) get long enough, they will hit and be bent in/out/forward/aft - but certainly away from the centre of the wheel - which is a very good thing.


QUOTE (elakdawalla @ Oct 12 2015, 03:44 PM) *
That one has been developing for a while, but it does have quite the inward point. Engineers are justifiably concerned about the possibility of these sharp edges abrading the wire bundles. I actually am having trouble figuring out a scenario in which this one, ripping further, would then straighten in the right way and place to actually scrape a wire bundle; I think it gets to be a more serious problem if (when) grousers start breaking.
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DeanM
post Jun 30 2016, 06:01 AM
Post #276


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Been pretty quiet on here: any developments in 'Wheel World'?!

Dean
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Gerald
post Jun 30 2016, 11:49 AM
Post #277


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The driving software update appears to have slowed down the wheel degradation. There has been less driving and more science activity. And there haven't been again these sharp and strongly embedded rocks, which caused much of the damage.
I'm not really disappointed about Curiosity being fit for the trip uphill Mt. Sharp.
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atomoid
post Jun 30 2016, 09:27 PM
Post #278


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As wheels continue to tatter and shred, lets hope the grousers survive or well soon end up dead!
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elakdawalla
post Jul 1 2016, 04:45 PM
Post #279


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I included this comparison in my most recent update. Degradation has progressed, but only slowly, and there was no acceleration as they went across the Naukluft plateau, as I'd feared. As long as drive distances are relatively short (less than 50 m or so), the rover drivers can prevent a lot of damage by driving around hazards they can see. Not sure how much longer the grousers on the right middle wheel are going to last, but they're hanging on for now.

Full wheel survey sol 1315:



LM wheel over time:



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fredk
post Nov 7 2016, 09:58 PM
Post #280


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I thought something looked a bit odd about the LM wheel on the latest survey, from 1512. Comparing it to an earlier view, from 708, you can pretty clearly see that the grousers near the top have been bent inwards:
Attached Image

They've bent where the skin in between is quite heavily damaged, so I guess it makes sense that this is a weaker point.

I haven't checked carefully to see how far back this bending occured, but judging from Emily's LM compilation it seems to show up at around sol 1315.

(Mods - oops, sorry, I forgot about the pinned wheel thread.) [MOVED - MOD.]
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elakdawalla
post Nov 7 2016, 10:20 PM
Post #281


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Oof. Well spotted. I won't have time to look back in time for a bit, but if people want to hunt for where/when this happened, there have been full wheel surveys on 1046, 1127, 1179, 1260/9, 1315, 1434, and 1471. There have also been partial (one position only) surveys on 1182, 1214, 1245, 1287, 1313, 1355, 1380, 1403, 1416, 1435, 1444, 1459, and 1482.


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peter.neaum
post Nov 13 2016, 11:17 AM
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With thanks to Post #278 from atomoid, above, I found their mentioned link to the site http://www.midnightplanets.com/web/MSL/sols.html
I've always found the MSL Raw image site to be quite cumbersome to use - one has to open each day, from each camera, to see what imagery was taken, and then open each thumbnail to get the final image. The midnightplanets site is a much better interface and shows all images in a neat grid array (though I'm sure, bandwidth heavy). I presume it's a bit of clever coding - a front end image scraper for the main msl site. It's very good, and, after all these years, I've only just stumbled across it.

Here are the links to the useful MAHLI (and others) images for full wheel surveys days (thanks to E Lakdawalla for pointing them out).

1046 1127 1179 1260 1269 1315
1434 1471

The partial surveys are here:

1182 1214 1245
1287 1313 1355
1380 1403 1416
1435 1444 1459
1482

The area dented inwards appears to be section 12/13/14.
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peter.neaum
post Mar 21 2017, 10:16 PM
Post #283


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And now the first broken grouser, seems to be between 12-13 (as predicted in Post #271!)

https://mars.nasa.gov/news/2017/breaks-obse...er-wheel-treads
https://mars.jpl.nasa.gov/multimedia/images...curiosity-wheel

Images here.
https://mars.nasa.gov/msl/multimedia/raw/?s...mp;camera=MAHLI

This is a very interesting event.
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atomoid
post Mar 22 2017, 01:59 AM
Post #284


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A different view of the two broken grousers: one looks somewhat pushed into the wheel and is slightly severed just outside the hole to the right. Below it a second grouser is severed and displaced quite a bit and is probably the one sticking up in the original image. These are also visible lower down in the next wheel roll image and looks about right to put the lower one in the right place to peek up over the top in the original linked image. its sort of grimly funny how the middle wheels take the brunt of the damage, more load-bearing perhaps..
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alan
post Jun 30 2017, 08:08 PM
Post #285


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An Algorithm Helps Protect Mars Curiosity's Wheels

QUOTE
There are no mechanics on Mars, so the next best thing for NASA's Curiosity rover is careful driving. A new algorithm is helping the rover do just that. The software, referred to as traction control, adjusts the speed of Curiosity's wheels depending on the rocks it's climbing.

On level ground, all of the rover's wheels turn at the same speed. But when a wheel goes over uneven terrain, the incline causes the wheels behind or in front of it to 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. 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.

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. 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.


https://www.jpl.nasa.gov/news/news.php?feature=6887
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