Let's Make Robots!

Why Tri

Tries to turn by matching front wheel steering angle to rear wheel PWM differential steering.
WhyTri0.5.pde12.4 KB

This is a robot built mostly to explore how you can steer with a combination of differential rear steering and a single servo controlled front wheel. This is a stupid way to steer. Why try it? I expect I'll learn a few things. Maybe you will too.

There's more pictures, videos and information on my blog Why Tri? A stupid way to build a robot.

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this looks like auto rickshaws in India :D 3 wheelers

Love it!  Not a stupid way to steer, just more "natural".  It looks like an excellent base for something more.  I'd love to see this in a reverse trike configuartion, sort of like the T-Rex motorcycle we've seen on youtube. 

Maybe after I've fully explored this configuration, I'll mount a servo on the back and place the Sharp sensor there for some backwards driving.

I've just implemented the basic obstacle avoidance (seen everywhere on this site), but using a 1/3 rate turn on one wheel, instead of spinning. I must say it does look nice. ; j

Still a lot to do! I want to create a circular_navigation function that takes parameters like turn rate, turn direction, forward/backward. Right now each mode of turning is a separate function to call.

Nooooooo! You can't put the single wheel at the back... I was going to do that. :'-( Lol, go ahead if you want, and good luck with it. Here's my prototype, TR1KE; http://letsmakerobots.com/node/27553

Hey, with the limited time I have and the number of projects I spit my attention over, you will beat me to it by a long shot! I'm taking a look at your TR1KE project blog and will comment there.

interesting experiments, well executed.

would you get the same results if the front wheel had no servo, and was on a simple pivot / caster, being dragged whichever way the back 2 wheels called for?

If you check out the second video under the associated blog, you can see I did a drive test with a ball caster. The caster offers no resistance in any direction, of course, so that simplifies everything.

That's why I call the blog "a stupid way to steer". You can get the same results more easily with a caster.. Granted, a wheel works better for crossing some obstacles, etc.

However, I will next be integrating the obstacle avoidance with the steering more elegantly. It should make for some very nice smooth turns. Even though you may not want to go with the front steerable wheel, the code I eventually produce may be helpful to others. I'll post it when it's ready.

I used to make a three whells car just like this.