Cars, trucks, tanks and more.
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ahalekelly

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Sun Aug 09, 2015 10:47 pm

Differential Drive Invertable Robot

by ahalekelly » Sun Aug 09, 2015 10:55 pm

Hello, I have an application that's going to be a little strange for this forum, but the hardware is exactly what I need, and hopefully I can get the software to work. I make combat robots (think of tiny Battlebots) that use differential drive, and they don't always drive straight. Some people use helicopter gyros to correct for things like wheel slip and keep them driving in a straight line, but they don't work when upside down. With the accelerometer on the flight controller, you can tell when you're upside down and reverse the steering so that everything works again. I have a fair amount of C and Arduino programming knowledge, and am not afraid of getting my hands dirty if I need to in order to accomplish this.

I downloaded the GCS software and there seems to be a ground vehicle mode that supports differential drive, but it won't let me look through the menus without a board attached. Does this mode use the gyro to stabilize yaw rotation?

I need to be able to enable and disable the gyro stabilization from the RC transmitter, in case something on the robot breaks and I need manual control. Can I have two different mixes that I switch between using the transmitter?

I assume there is no built in way to operate upside down (reverse both motor positions and directions), but is there a way to implement it in the custom configuration? It would be preferable to switch between modes on its own based on accelerometer data, but it would also be fine to have to flip a switch on the transmitter.

I'm planning on using the CC3D Atom, because it's small and low cost. Why is this platform not recommended for new designs?

If I have to delve into the code, how accessible and readable is it? Is there a document somewhere describing the general structure of the codebase?

Thank you!
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ernieift

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Re: Differential Drive Invertable Robot

by ernieift » Mon Aug 10, 2015 7:07 am

CC3D is F1-based. For your setup i suggest a user firmware or have a look at picoC. For picoC you need a F4-board like Sparky2, Quanton, Revomini. It is easy to write a script for this problem. Just read the z-accel and calculate the motor direction.
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ahalekelly

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Re: Differential Drive Invertable Robot

by ahalekelly » Wed Aug 19, 2015 4:05 am

PicoC looks great, but the Sparky2 and Quanton are too big and I wouldn't use the radio on the Sparky2 anyway, and the RevoMini and Revo Nano seem to be continually out of stock :(

What do you mean by a user firmware?
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ernieift

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Re: Differential Drive Invertable Robot

by ernieift » Thu Aug 20, 2015 6:29 am

Ground vehicles uses no sensors yet. A differential drive (you mean tank?) has only two motors. You want to steer the vehicle upside down. Do you know what the rotation axis was? This changes the influence of the steering. Maybe you have to watch on the compass too.
Sure it is possible to change the firmware but picoc were my first try.

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