Wheel Trouble, ...down to 5 good wheels? |
Wheel Trouble, ...down to 5 good wheels? |
Mar 18 2006, 10:29 PM
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#106
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Junior Member Group: Members Posts: 90 Joined: 13-January 05 Member No.: 143 |
Sorry for the flood of pictures, but here's one more corrected view that makes it easy to see how much they pivoted around the RF wheel:
About 45 degree yaw. I take back what I said... the situation doesn't seem too bad; they can probably just back straight up with no problem. I guess I'm not as adept at understanding the 'language' of the wheels as you are. Can you explain how to interpret the haz photos? I would say that the left-rear wheel (facing front) has run into the 'popcorn mesa' and been unable to climb it (or else we just stopped at this point by programming). As a result the other wheels churned a bit and the forward wheels (facing aft) slid a little to the left before we stopped. Can we carry on and run over the popcorn, or do we need to skirt it to the left? Or is that what we are about to find out? I'm just guessing like everyone else. Looks to me like one of two things happened. Either they lost traction on the right middle/rear wheels (the ones leading the stuck wheel as they drive backwards), and the other 3 wheels pivoted them around the dragging wheel. Or the stuck wheel snagged a stubborn subsurface rock. Either way, you need to back up, change direction a bit, and move along. Presumably this kind of occurrence will be common from now on. I would think JPL is working on algorithm enhancements to prevent and/or automatically recover from situations like this so they don't lose driving opportunities. |
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Mar 19 2006, 12:20 AM
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#107
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Senior Member Group: Moderator Posts: 3431 Joined: 11-August 04 From: USA Member No.: 98 |
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Mar 19 2006, 07:12 AM
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#108
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Member Group: Members Posts: 477 Joined: 2-March 05 Member No.: 180 |
Sorry for the flood of pictures, but here's one more corrected view that makes it easy to see how much they pivoted around the RF wheel: About 45 degree yaw. I take back what I said... the situation doesn't seem too bad; they can probably just back straight up with no problem. I'm just guessing like everyone else. Looks to me like one of two things happened. Either they lost traction on the right middle/rear wheels (the ones leading the stuck wheel as they drive backwards), and the other 3 wheels pivoted them around the dragging wheel. Or the stuck wheel snagged a stubborn subsurface rock. Either way, you need to back up, change direction a bit, and move along. Presumably this kind of occurrence will be common from now on. I would think JPL is working on algorithm enhancements to prevent and/or automatically recover from situations like this so they don't lose driving opportunities. I don't know - look at the hazcam pics in the drive direction. It looks like they might have made an intentional end-of-drive turn. And look at the tracks - they are fairly straight despite the draggin wheel. It seems like they're compensating reasonably well, possibly with a modification of the previous 5-wheel mode. |
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Guest_Bobby_* |
Mar 19 2006, 08:54 AM
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#109
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Guests |
With the wheel now turned completely sideways. How much stress can the wheel take? Is there a chance that driving with the wheel turned sideways like this rip the wheel off?
http://qt.exploratorium.edu/mars/spirit/fo...74P1209R0M1.JPG And if Spirit did lose the wheel. Can it drive ok with 5 wheels??? Hope for a Dust Devil soon also |
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Mar 19 2006, 09:10 AM
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#110
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
I can't believe I'm saying this again....there is no evidence that a dust devil ever cleaned Spirit. Some of the cleaning events happened overnight. You don't get DD's at night. Further more - the fact that there was a clear lack of cleaning 'downwind' from the HGA shows that it wasnt a spiralling whirlwind, but simply strong local winds in a constant direction that cleaned Spirit.
What we need is a big hill - the sort of place that has strong winds - not a DD - not to mention the fact that the DD season is long finished. Doug |
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Mar 19 2006, 01:27 PM
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#111
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Newbie Group: Members Posts: 3 Joined: 19-March 06 Member No.: 716 |
I can't believe I'm saying this again....there is no evidence that a dust devil ever cleaned Spirit. Some of the cleaning events happened overnight. You don't get DD's at night. Further more - the fact that there was a clear lack of cleaning 'downwind' from the HGA shows that it wasnt a spiralling whirlwind, but simply strong local winds in a constant direction that cleaned Spirit. What we need is a big hill - the sort of place that has strong winds - not a DD - not to mention the fact that the DD season is long finished. Doug Doug, Your comments sound interesting. I have never heard about strong winds other than DDs? Do you have any info on this? |
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Mar 19 2006, 01:42 PM
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#112
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
Listen to or read the Steve Squyres Q'n'A I did .
http://www.unmannedspaceflight.com/index.php?showtopic=1683 Doug |
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Mar 19 2006, 04:12 PM
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#113
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Newbie Group: Members Posts: 17 Joined: 25-April 05 From: Pilsen, CZ, EU Member No.: 363 |
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Mar 19 2006, 06:11 PM
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#114
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Senior Member Group: Moderator Posts: 3431 Joined: 11-August 04 From: USA Member No.: 98 |
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Mar 19 2006, 10:58 PM
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#115
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Newbie Group: Members Posts: 4 Joined: 20-April 05 From: UK Member No.: 282 |
With the wheel now turned completely sideways. How much stress can the wheel take? Is there a chance that driving with the wheel turned sideways like this rip the wheel off? I don't think the wheel has turned sideways. What has happened is that the Rover has slewed around so that it is sideways on. |
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Mar 19 2006, 11:15 PM
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#116
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Newbie Group: Members Posts: 3 Joined: 19-March 06 Member No.: 716 |
delete
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Mar 20 2006, 10:16 AM
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#117
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Member Group: Members Posts: 593 Joined: 20-April 05 Member No.: 279 |
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Mar 20 2006, 03:01 PM
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#118
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Senior Member Group: Members Posts: 1636 Joined: 9-May 05 From: Lima, Peru Member No.: 385 |
I have a pair comments about Spirit's new situation.
First, I am thinking a possible better solution to minimize the dragging of the front right wheel is that the rover don't go straight in comparision to the troubled wheel but try to go in the same line as the troubled wheel. That is in order to minimize the width of friction. That is only a tought. The other comment, the dragging wheel would provide a good chance to know better the different types of land: dark and light color which is the indication of the different degrees of sulfate process. Meanwhile, I hope that at any moment the friction force will turn on again the troubled wheel during its struggling dragging. Rodolfo |
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Mar 20 2006, 03:18 PM
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#119
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
First, I am thinking a possible better solution to minimize the dragging of the front right wheel is that the rover don't go straight in comparision to the troubled wheel but try to go in the same line as the troubled wheel. That is in order to minimize the width of friction. That is an only a tought. I think you might be missing the problem. The problem is driving the wheel, not turning it. They can turn the wheel left and right, i.e. have it in the direction it would normally be for driving. What they can't do is DRIVE the wheel. For comparison, Opportunity has a wheel that is steering-locked just off centre, but still driveable - and they're doing quite well with it. Doug |
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Mar 20 2006, 03:29 PM
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#120
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Senior Member Group: Members Posts: 1636 Joined: 9-May 05 From: Lima, Peru Member No.: 385 |
Good for the clarification. Thanks
Then why the wheel was not aligned to the direction. Let suppose that unaligned wheel was leading greater friction on the surface. From this view, I am re-thinking that the diagonal position (45 degree to the motion direction) is the best position that minimizes the friction because the wheel surface has small "carets"? that is perpendicular to the direction. Rodolfo |
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