Why Tri

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.

Tries to turn by matching front wheel steering angle to rear wheel PWM differential steering.

  • Actuators / output devices: Two 3V DAGU gearmotors, GWS S03 servo
  • CPU: Arduino uBotino
  • Power source: 4xAA alkaline batteries
  • Programming language: Arduino C++
  • Sensors / input devices: Sharp GP2Y0A21YK0F IR sensor (coming soon)
  • Target environment: indoor flat surfaces

This is a companion discussion topic for the original entry at https://community.robotshop.com/robots/show/why-tri

Moves very nicely, IG

But my question is, why would you want 2 steering methods on the same bot? Will they be used at the same time?

Very slick test ‘bot you got goin’ there.

I will be interested to see how things play out with it.

An excellent question. If

An excellent question. If you read the linked blog Why Tri. A stuid way to steer a robot, it explains. It’s an experiment that I know is not very practical, but it will teach me some things about precise control with pwm, programming, etc.

I like it! Can’t wait to see

I like it! Can’t wait to see the finished product…

I made some updates, but the

I made some updates, but the post didn’t bump.


Very nice math experiment

Very nice math experiment you got right there.

Exactly right. I had to pull
Exactly right. I had to pull out my protractor to work out some angles too. Math is more fun when it involves robots.

Nah, maths is always fun.

Nah, maths is always fun. But I have to admit it’s easy to say for me as I am a mathematician :stuck_out_tongue:

Looks like it controls

Looks like it controls well.

I have been looking into the same concept before I saw your robot. I am glad that I saw your robot, it provides a proof of concept!

Looking really good so far!

this looks like auto

this looks like auto rickshaws in India :smiley: 3 wheelers

Love it! Not a stupid way

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

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.

It doesn’t look fun when you

It doesn’t look fun when you PLAY math with explosion.

interesting experiments,

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

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.

Nooooooo! You can’t put the
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; https://www.robotshop.com/letsmakerobots/node/27553

Hey, with the limited time I

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.

I used to make a three

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