Monday, September 7, 2009

Hobby built car-like robot

Article from http://www.aforgenet.com/articles/qwerk_robot_car/

Introduction

It has passed a while since the time I got interested in robotics and started building some stuff. Initially, as many other novice hobbyists do, I started with something simple and tried different Lego Mindstorms Robotics kits, like RCX and NXT. These kits are really easy to start with and allow building many different things, like car-bots, pan-tilt cameras, etc. But eventually you may want trying something more sophisticated, which could result in a robot with wider range of features. To get most flexibility and also enjoy building robots on your own, it is much more preferred to switch from kits like Lego, to some more specialized hardware, like different motors, servos, sensors, controllers, robotics boards, etc. Of course it will not be that easy as with plug-n-play Lego kits, but it may allow us designing our own robot putting the hardware we want for tasks we need. Going this road we need to be a bit prepared and get some simple tools like screwdrivers, soldering tools, wire-cutters, maybe a small saw, files, etc. It may end up in real building, which is real fun!

One of the easy things to use for building your custom robots is a range of different controllers and interface boards provided by Phidgets. These are very nice things which can be plugged into computer's USB port and programmed very easily with SDK provided by the company. Last time I've tried Phidgets for building pan-tilt module for a simple stereo vision setup. This worked really nice and I definitely consider building more on their base. But this time I was interested in building mobile robot and I did not want making PC (even a tiny notebook like EeePC) part of my robot. Instead of this I wanted to get something, which is not so big in size and could be controlled over Wi-Fi. In order to achieve this goal, I made my choice in using Qwerk.

I was already writing about Qwerk board in the past and the way to control it remotely. This is really nice peace of manufacturing, which allows building quite sophisticated robots carrying bunch of sensors, servos, motors, etc. This time it will be used for building mobile robot controlled remotely over Wi-Fi.

What are we going to build ?

This time we are going to build a remotely controlled car robot, with the next list of features:

  • 3 wheels - 2 in the front and 1 one rear. The two wheels in the front will be motorized and will direct robot's movement. Setting equal speed to both motors will result in straight forward/backward movement, but setting different speeds will lead to going left or right.
  • On board camera, which will give a view to the person controlling the robot. In the future the camera may be used also for automated robot's controlling with the help of developed computer vision algorithm.
  • To mimic real cars, the car robot will have some lights - stop lights, turn lights and dimension lights.
  • It will carry some sensors on board, which may be used as for fun, as for future tasks targeted to autonomous movement.
  • And finally to make it wireless, it will have its own battery on board and a Wi-Fi communication module.

It should be really nice, when all the above is done and works!

Let's start building

The base

One of the fun things in building something as a hobby is building everything on your own using all sort of stuff you can find around and can make use of. For example, building a robot you may find that different stuff left after flat repairing will work fine, as well as old broken child's toys, electronics, etc. Sometimes it may be hard to find a specialized part for the robot you build or it may be not that cheap buying dedicated stuff out of a set. So, building a robot I always take a look around the flat for something, which may become useful.

This time it happened with robot's base. I was looking for something, which could be used to attach wheels to and carry all the robot's stuff. And I found that a small cutting board looks so nice as a robot's base ... Yes, sounds crazy - cutting board used in robotics. But I could not resist when I found that accidentally in a regular shop and imagined my robot with it.

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