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Unread 06-14-2017, 07:22 AM
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pic: Mars Game 2018 (Work in Progress)

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Unread 06-14-2017, 07:25 AM
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Re: pic: Mars Game 2018 (Work in Progress)

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Originally Posted by Kaorin View Post
Anyways, although it's not really a serious design, tell me what you think![/cdm-description]
Looks totally serious to me.

Assuming 2018 rules include something like R1, R22, R23, R24 from this year, you'll need to think about how to get a legal set of bumpers on it. The MER designers had many challenges, but bumper rules were not among them.
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Unread 06-14-2017, 07:28 AM
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Re: pic: Mars Game 2018 (Work in Progress)

This is very cool!
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Unread 06-14-2017, 07:31 AM
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Re: pic: Mars Game 2018 (Work in Progress)

What do you have the drive geared for?
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Unread 06-14-2017, 07:52 AM
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Re: pic: Mars Game 2018 (Work in Progress)

Any reason you have the drive motors vertical instead of parallel to the wheel axle? Would probably eliminate some inefficiency and allow the modules to turn 360*.

Also why 775pros for drive motors over CIMs? 6 775pros (with voltage/current limits) is barely enough power to drive a full weight robot and not burn up. 6 CIMs is still legal, requires less reduction (smaller gearbox), and is a lot more resistant to high torques, which is likely in a rocker-bogie suspension system. If you think 6 CIMs is too much power, you can use 6 miniCIMs, which is about the same amount of power as 4 CIMs.

FYI, there are 16 slots in the PDP (8 40A max, 8 30A max). Your system uses 12 of those (assuming 6x 30A and 6x 40A), so you would have 2x 30A slots and 2x 40A slots left for manipulators. That combined with pneumatics and servos is enough to have a decent manipulator for pretty much any game since at least 2010.
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Unread 06-14-2017, 08:59 AM
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Re: pic: Mars Game 2018 (Work in Progress)

This is absolutely nuts. *Please* build this, at least a small one, simply to say you did. I mean, how many people can say "I used a rover drivetrain design for a robotics competition... and it worked."

Legal... who knows with bumpers. Awesome? Well, that's a given.
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Unread 06-14-2017, 10:13 AM
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Re: pic: Mars Game 2018 (Work in Progress)

I love it. Crazy enough, there is actually more gearing required in this to make it work. You have to have a differential gear box set in between the left and right side on the front pivot so that as one side goes up the other goes down to compensate on rough terrain. I had to build one of these with banebots gearboxes for a lunar mining competition. It does get heavy quick and there are some other things you have to do to keep the chassis level but it worked swell at Kennedy Space Center.
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Unread 06-14-2017, 10:40 AM
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Re: pic: Mars Game 2018 (Work in Progress)

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Originally Posted by Richard Wallace View Post
you'll need to think about how to get a legal set of bumpers on it.
Challenge accepted.
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Unread 06-14-2017, 01:05 PM
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Re: pic: Mars Game 2018 (Work in Progress)

We seriously considered building something similar in 2016. A rocker-bogie suspension at least, not one that slapped swerve drive on top of it.

As to making bumpers work... in 2016 we did build an actuating drive train to help us clear defenses. One drive rail was an integral part of the frame. Then the frame was lifted a couple inches on opposite side. The second drive rail was mounted on a pivot underneath the frame. The bumpers were mounted to the frame and the frame was deemed by inspectors to be non-articulating (the drive rail articulated) as such the bumpers were non actuating as well.

I expect you could design a similar system for the bogie suspension. You mount both suspensions to a solid frame and mount bumpers to it. The question becomes, if both halves of the drive train articulate does the frame articulate?
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Unread 06-14-2017, 05:19 PM
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Re: pic: Mars Game 2018 (Work in Progress)

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Originally Posted by Richard Wallace View Post
Looks totally serious to me.

Assuming 2018 rules include something like R1, R22, R23, R24 from this year, you'll need to think about how to get a legal set of bumpers on it. The MER designers had many challenges, but bumper rules were not among them.
Yeah... I haven't really figured out what to do about bumpers. Mounting them at normal height would also make the suspension pretty useless, so I have no clue what to do.
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Unread 06-14-2017, 05:20 PM
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Re: pic: Mars Game 2018 (Work in Progress)

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Originally Posted by FrisbeeFunTime View Post
What do you have the drive geared for?
I haven't selected a gearing ratio yet, but the drive motors have 2-stage VP's on them, allowing for a range of different ratios.
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Unread 06-14-2017, 05:22 PM
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Re: pic: Mars Game 2018 (Work in Progress)

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Originally Posted by Thayer McCollum View Post
We seriously considered building something similar in 2016. A rocker-bogie suspension at least, not one that slapped swerve drive on top of it.

As to making bumpers work... in 2016 we did build an actuating drive train to help us clear defenses. One drive rail was an integral part of the frame. Then the frame was lifted a couple inches on opposite side. The second drive rail was mounted on a pivot underneath the frame. The bumpers were mounted to the frame and the frame was deemed by inspectors to be non-articulating (the drive rail articulated) as such the bumpers were non actuating as well.

I expect you could design a similar system for the bogie suspension. You mount both suspensions to a solid frame and mount bumpers to it. The question becomes, if both halves of the drive train articulate does the frame articulate?
My plan for getting the frame to stay put is to have a differential bar running across it. This way, when the left side goes down it rotates the bar, causing the right side to go up and cancel out its motion. Because of this opposite reaction, the frame will be able to hold itself up mechanically and without the use of motors or weights.
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Unread 06-14-2017, 05:23 PM
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Re: pic: Mars Game 2018 (Work in Progress)

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Originally Posted by OccamzRazor View Post
I love it. Crazy enough, there is actually more gearing required in this to make it work. You have to have a differential gear box set in between the left and right side on the front pivot so that as one side goes up the other goes down to compensate on rough terrain. I had to build one of these with banebots gearboxes for a lunar mining competition. It does get heavy quick and there are some other things you have to do to keep the chassis level but it worked swell at Kennedy Space Center.
Yeah, the amount of gearing on this thing is insane. Instead of using a gearbox for the differential, though, I plan on using a bar that will act as a differential. This way, when the left rotates down, the right will rotate up proportionally and cancel out any tilt, allowing the bot to stay upright without the use of motors or weights.
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Unread 06-14-2017, 05:26 PM
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Re: pic: Mars Game 2018 (Work in Progress)

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Originally Posted by tjf View Post
This is absolutely nuts. *Please* build this, at least a small one, simply to say you did. I mean, how many people can say "I used a rover drivetrain design for a robotics competition... and it worked."

Legal... who knows with bumpers. Awesome? Well, that's a given.
I'd really love to build this, but... it costs like $2000 just for the drivetrain, and I'm not even sure if it would work. I'm prototyping a swerve drive using a 3D printer, but even that requires a lot of components. I think it would be cool to 3D print a little model of this for my desk, though...
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Unread 06-14-2017, 05:28 PM
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Re: pic: Mars Game 2018 (Work in Progress)

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Originally Posted by Ari423 View Post
Any reason you have the drive motors vertical instead of parallel to the wheel axle? Would probably eliminate some inefficiency and allow the modules to turn 360*.

Also why 775pros for drive motors over CIMs? 6 775pros (with voltage/current limits) is barely enough power to drive a full weight robot and not burn up. 6 CIMs is still legal, requires less reduction (smaller gearbox), and is a lot more resistant to high torques, which is likely in a rocker-bogie suspension system. If you think 6 CIMs is too much power, you can use 6 miniCIMs, which is about the same amount of power as 4 CIMs.

FYI, there are 16 slots in the PDP (8 40A max, 8 30A max). Your system uses 12 of those (assuming 6x 30A and 6x 40A), so you would have 2x 30A slots and 2x 40A slots left for manipulators. That combined with pneumatics and servos is enough to have a decent manipulator for pretty much any game since at least 2010.
I chose to put the 775's vertical mostly just for the aesthetics, to be honest. Curiosity has some kind of hubbed (or very small and hard to see) motor for its wheels, so I wanted to try to imitate that. Also, I heard that my team had a really bad experience in the past using VP's horizontally directly to the wheels.

Also, how would you recommend utilizing CIM's for drive in this design? As far as I'm aware of, CIM's can't be mounted to VP's and creating a custom gearbox for this would be either too big or an absolute nightmare.
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