Let's Make Robots!

Homemade Unmanned Ground Vehicle (UGV, Work In Progress)

Intended as an unmanned ground vehicle (UGV) beta-testing platform for other technology development

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

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

 

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...