Skid Steer/ Tank Drive Vehicle

Hi Everyone,

I am wanting to make a skid steer/tank drive vehicle large enough for one person. I was thinking of using a skateboard motor on each side. I am not too sure how to make the controls work though. I am wanting it to be controlled by a single joystick and found this article that does a pretty good job of explaining the logic. https://home.kendra.com/mauser/joystick.html

I thought I could use separate motor controllers for each side, connected to an arduino to translate the joystick position to speed commands for each side. Does that make sense?

I am wondering if there is anything out there like this already? I can manage to tweak existing code, but I am not great at creating from scratch. Any tips or guidance would be greatly appreciated.

Thanks,
JD

How fast does this need to go? What kind of torque requirements? (hills, accleration rate?)

If it doesn't need speed and doesn't have to accelrate quickly or climb much of a hill, there are numerous powerchairs out there that already do what you want. If you don't want to have the motors be the wheel axles or directly drive the wheel, you can use a chain or belt drive from the motors to the wheels (or tracks).


An MCU of whatever type can certainly take a joystick or other input and create a split throttle signal to drive separate controllers, and I'll bet someone already has a project out there to do this for robotic stuff that you can borrow the code from to start your project off, rather than doing it from scratch. I'm in a similar boat to you about creating from scratch, and am much better at hacking together / repurposing other things to my uses. I have a project thread here:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=110497&p=1618943#p1618938
where at some point I'll be making a Nano-based thing to take a steering input and use that to split a throttle to drive wheels equally when straight, or increase the outboard wheel and decrease the inboard wheel in a turn, based on the amount of steering input and speed of vehicle. Right now the thread is focused on the first more important Nano device for a different part of the trike.


More project specifics may help us help you find the simplest solution(s) to create it (and it's always much more interesting and engaging to know what you're helping with...more people will help with something the more they know about it, than a mysterious something).

@amberwolf - I had thought about the electric wheelchair option, but used ones in my area are still around $600 and I wanted to be able to use the batteries from this project in other ones as well, which is why I was trying to find a solution using eskate parts.

As far as performance goes, speed and acceleration are not the goal of this project. I will probably limit the speed to 10mph to start with.

If you have an idea where I could find an out of the box MCU with this capability, please send me a link.

Check out this place to see if anything can help
https://www.surpluscenter.com/Electric-Motors/

mrjoedave said:

If you have an idea where I could find an out of the box MCU with this capability, please send me a link.

Click to expand...

I don't know of any, but if you are already thinking about Arduino, etc., your best first bet is to look at places with repositories of projects using that MCU, to see if any use two non-tandem motors for something, and if they use the motors for steering. If they do, you may be able to repurpose some of their code (and possibly hardware) for yours. Places that do little robotic projects are more likley to have usable things, robot wars type of stuff, etc., but you could find one almost anywhere.

THere might even be usable projects in this very basic google:
https://www.google.com/search?q=arduino+motor+steering
but I have not visited any of the links from it.

Use reversible wheelchair motors or something similar.

My first choice is to use a purely mechanical linkage to allow one stick to operate fwd/rev/operate one side only for turning.

This way, you are using two off-the-shelf throttles

The single stick would pass through a plate with an opening that has a curved slot in the center.

When the center stock is moved forward or backwards, both throttles underneath are moved forward or backwards an equal amount.

If the stick is moved side to side, the plate is rotated clockwise or counter-clockwise in order to move the two throttles in opposing directions.

It's a creative solution @spinningmagnets but I would prefer it stay as a single joystick control. If I go with separate joysticks the simplest solution would be a true tank style control and I wouldn't need to mix inputs. That could be all off the shelf and pretty easy to do, however it would require other changes to the vehicle that compromise the real intent.

I am really looking for feedback specifically on using a single joystick to control two separate motors. I agree that the wheelchair parts may be the best option in the end, but there are some advantages for me if I can get Eskate parts to work, so I am taking a swing at that first. Plus, they are a lot cheaper.

I've been thinking about this for a while. More from the perspective of taming tank style controls.

Best I came up with was:

2x pwm input controllers (VESC, anything with forwards and reverse basically... Can experiment with torque and speed controls)
1x arduino with 20 lines of custom code to convert your joystick to 2xpwm out, you can then easily mess around with mappings etc.
Few fuses and some kind of kill switch.

There's probably joystick:arduino interface libraries, and the rcpwm is supported easily.

Skateboard motors (6374 kind of thing) unlikely to cut it for a tracked vehicle. The next size up, 80100 kind of thing better but still going to be mediocre.

Re. Joystick... I just had a look and the internet is swamped with 2$arduino joystick modules which aren't what you want... But I'll bet if you ripped a few joysticks apart you'd quickly find the outputs of some potentiometers that you could just analog read with your arduino (or stm32, harder to use but ultimately will have better results)