Let's Make Robots!

Brabenec

follow wall/avoid obstacles

 

 

Overview

We are building this robot with my friend. It is (when finalized) supposed to be able to detect metal objects and interact with them (move them, ideally...). So far it has only two IR sensors for obstacle detection, so no metal detection.

  The front - two IR sensor modules

Current state

It uses the Tamyia gears and Pololu motors with Tamyia tracks. The brain is an Arduino Uno.

The tracks. You can see the ratnest on the Arduino (before the PCB).


I have made (after three attempts and failures) my own PCB, that is used similarly as the Arduino shields - it plugs completely into the Arduino and distributes the needed signals, powers and grounds so that everything can be plugged nicely, easily and quickly.

The PCB to Arduino connection.

It features the 7805-STM 5V stabilizer and a TB6612FNG dual motor driver as well.

The motor driver and 5V stabilizer on the PCB.

Asides from this, I made some plastic parts to fit the strangely placed screw holes on the Arduino into the Merkur base (Merkur is a great construction kit for kids!).
The batteries are some 7,2V 1500mAh LiPol packs from electro RC helicopters - they work really nice! I made a little reduction to the 9V battery connector to easily plug and unplug the batteries with the ability to switch to 9V battery without any problems (with the stabilizer in Arduino taking from 6 to 12 V and the 7805-STM up to something about 36V it's just fine...).

This is how it looks now:

The whole robot.

The FUTURE!

Well and that's about it for now! I am gonna work on both the tracks moving the same speed, so that the robot does go straight (probably some oil or PWM at worst will do the trick) and my friend is (hopefully) going to work on the programming (so far it just barely avoids some simple obstacles).

Thanks for checking this out, hope you like it!


Update 17.9.2012:

OK, so I wrote this very simple wall-following program, making use of the two IR sensors the robot possesses (a nice word, btw.).
Sadly, the IR sensors are quite inaccurate and as I said before, the program is really very simple, so it does not work very precisely... It tends to bump with its tracks into the wall and therefore turn and it has some other mistakes, but - see for yourselves - here is a video!

Anyway... I fixed the tracks-not-going-the-same-speed problem - first I used some grease on the gears and than used PWM to get rid of the rest of the problem. Now it's working all right.
I have ordered an accelerometer (an ADXL345), so I'm looking forward to receiving it and using it! Maybe I'll design a new PCB for the Arduino to hold the sensor's board - I started to like making my own PCBs!

 

Update  17.11.2012:

 After two months of fiddling with the Parallax PING)), the accelerometer and other stuff, I finally got to make some encoders for the robot. I ordered four ball mice and used one of them to create the encoders. I also had to make a part of plexi-glass to hold the axis of the wheels (I was lucky, that there were two more geared wheels and a hexagonal axis in the Tamyia chassis), so I had some fun with our CNC milling machine!

 

 View from above

 

Here you can see the encoders (the geared wheels behind the motors):

 View from the back

More pics:

 

From the front

From the front 2another pic

 

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Oh! Homemade PCB!

I love them, I do not use a lot of ready platforms for my bots, because with homemade PCBs I can customise it for my needs.
But cool bot!  Keep on doing like this!

Nice bot, you should present it at Robot Revue forum too ;-)

That's a nice idea! I guess you mean the czech "Robot Revue" magazine? I thought it was not printed anymore... But if it has a live community, I'll be glad to contribute! Nice to see other robot fans from Czechia around here as well! :D

Not bad on the DIY shield either. :)

Re: moving straight. Does it move in a constant arc, or, does it just not move straight ahead?

If it is a constant arc, some PWM will work nicely. If it wanders instead of being consistent, you may have some mechanical slippage issues to work through rather than just programming issues.

Thanks!

Yes, it does turn left constantly. I think I'll first try to do some mechanical adjustements, like checking if all the wheels are moving as they are supposed to, and then I'll use PWM.