Let's Make Robots!

Homemade Unmanned Ground Vehicle (UGV, Work In Progress)


This project is based around a Little Tikes H2 ride-on toy; it's a work-in-progress to ultimately result in a beta-testing UGV (unmanned ground vehicle) platform. I intend to use it to develop various control software, sensors, artificial intelligence, machine learning, and machine vision experiments.

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K120189's picture

i found one of those in the trash and painted it up and re wired it for my daughter. if you have any questions about the motors or anything i might be able to help.

 

junkbotix's picture

I read somewhere that the rear drive motors are 550 size; at some point, I would like to change them out for brushless motors. This may or may not happen, as this platform is a complete beta device. My intent in the future (far future, at the rate I am going!) is to make a larger platform - either using something like a quad bike or Polaris ORV machine (if I can afford it), or by building a 6WD buggy kind of machine (like the old CMU Terragator machine). Over the weekend, I bought a nice pair of mobility chair motors and wheels that may end up in this future machine.

K120189's picture
Yes they are 550 but these are very weak gearboxes brushless would not end well
junkbotix's picture

Thanks for confirming the size; I guess I'll just stick with what exists currently, and move on to another platform when ready.

MnGeeky's picture

That looks like a cool platform to start with. What are you going to use to control the steering?

 

junkbotix's picture

If you read my other articles in the series, you'll see that over time (over a loooong time) I have tried a few different methods.

My first shot was to use a gear motor with a custom control "horn" connected via a linkage to the steering (I removed the steering wheel and shaft - those aren't needed). That made for an expensive lesson into why limit switches are important (and also why a spur-gear drive system isn't the best for this kind of application).

I then tried a cable/winch type system, using a similar motor, but that ultimately didn't sit right with me. It just didn't feel right...

So I picked up a used and fairly inexpensive linear actuator off of Ebay - but that proved to be too large for the area I needed to put it in, and it was very heavy as well. Plus, it moved really slow (about an inch per second). I needed something powerful, but a bit faster...

I stared and stared some more at the problem, thinking and mulling it over - and I came up with what I thought was a solution: I would implement a linear actuator myself, using a "gearmotor" from a cordless drill driving a piece of all-thread, along with a homemade follower nut. Plus a bunch of linkages to get it where it needed to go...

But even that didn't satisfy me - it seemed way too complex, and overthought. So - I thought about it some more...

I ended up thinking really far outside the box - I said to myself "What if instead of mounting the homemade linear actuator on the body, I mounted it on the moving bar instead?" - when I did that, I figured out the solution:

I ended up mounting the whole thing on the metal bracing bar that the wheels mount to; then a simple two-point linkage to the moving bar that actuates the wheels. I am also changing the feedback potentiometer to fit it with gears salvaged from some junk (this will make the motion of the potentiometer linear - before it was logarithmic in motion, which I didn't want); I also had to relocate my limit switches...

The end results seem much better; I am still working out some minor problems, and I kick myself for how long it took me to come up with the solution. Oh well; better long than never, right? Anyhow - I have a bunch of pictures that I hope to add to my site at some point, and put up a good writeup. That should make it more clear what I am doing...

 

Salvage's picture

Good meeting you at the Hamfest today. Good luck with your project, stop & say hi at Yuma, Scottsdale, DeVry, & Tucson.