Classy Chassis 2.0

At last!  A hellish semester is now over and I have some time to update this blog with all the things I've accomplished in the past few months.  I'll start off by describing how I've upgraded the chassis for differential steering and end with the power wiring I've done.  Plus I'll try and add a video of it actually working!

So when I last left off I had decided to go with differential steering and buy an extra set of Power Wheels motors to give it four wheel drive.

Motor Pictures with shoddy wiring

The new motors I bought are slightly different from the original ones I bought and set me back roughly $70.  However from the tests I've done so far the two sets of motors are compatible enough.  It's also hard to see in this picture, but this motor came without the stock leads so I had to make some pretty poor quality ones by attempting to solder wires inside of the motor casing.

Here's a better picture of the bad motor leads.  The other ones are also a bit fragile so I'll have to be careful they don't get jerked around too much.

These are the wheels I got along with the new motors.  Pretty and purple!

The existing support for the original wheels didn't work for the new ones so I had to build an all new support system out of angle aluminum from Home Depot and Lowes.  It's essentially an aluminum H, closes at the bottom with the wheel axle and closed at the top with a flat piece of aluminum.  Some more pictures are below.

Here's on of the axle caps to keep the wheels attached.

The mounting panel all taped and glued together.

Here's an overview of the total chassis.  I decided to put the new wheels in the back since they're larger,  but it looks a little weird since the front wheels are wider.

The axle width also makes it difficult to fit through doors, which is a little disappointing since I was hoping the robot could be used indoors and outdoors.  But it looks like it's going to turn out being just an outdoors robot which will still be pretty cool.

I also got around to upgrading the electronics system a bit to make it a little less of a rats nest, though I'm not really sure it works.

I finally got the chance to take the breadboarded motor controller and solder it onto a PCB.  The wires are a little fragile and occasionally need resoldering but overall it works well.  For my next iteration of motor controller I'm hoping to upgrade to a custom PCB with MOSFETs, speed control, and temperature detection.

I also bought some power distribution blocks from Radioshack to help regulate the power better.  The white block on the bottom is for the 12V from the batteries and the motor outputs and the black block on the top is for the logic from the Arduino below.

I'm still trying to figure out the logic and control for the robot, but I do know that the first revision will have an Arduino in control of the sensors and movement.  For those of you who don't know anything about the Arduino or microcontrollers I'll try and put up a write up about them soon.

Here's a servo that will eventually be used to sweep the distance sensors back and forth.  This sort of radar/sonar system will use distance sensors to map out any obstacles in the path of the robot.

And lastly for the electronics, I got a fancy new charger for the batteries!  The crappy charger that comes with the power wheels provides a steady current the batteries and doesn't protect against overcharging the batteries if you leave them plugged in too long.  Leaving the battery in the charger for too long could result in hydrogen building up inside the battery and eventually an explosion.  This charger, however, optimizes the charging of the battery and turns it off when the battery is full.  Considering the fact that the batteries were really expensive, it was well worth the $30 for the charger to help elongate the life of the batteries.

And I got a fancy new laptop!  The Lenovo X220 is supposed to be a highly mobile laptop that you can squeeze 10 hours of battery out of!  If I manage to get the system advanced enough to warrant it, I hope to at some point use this laptop as the main brain of the robot and have it do a bunch of cool image processing stuff.

I've also heard that Lenovo laptops are built like tanks so it should be plenty capable to survive the rough ride the robot will give, though to be safe I'll try and add some shock absorption.

So that's what I've accomplished in the past six months or so with the robot.  In the two weeks before school starts again I'll try and get it up and running and put a video up on here.  This semester will probably be far less stressful and busy than the last one so hopefully I'll have more time to work on this!

Basic Robot Rundown

So for this robot, I've broken the entire thing into four separate, but complementary systems.  I'll start at the bottom level and work my way up.

1. The first level of the robot, and in my opinion the simplest (sorry MechE's!), is the mechanical level. It's comprised of the wheels, chassis, motors, etc.  Essentially I was lucky enough to get this level as one complete set, as the Power Wheels Jeep supports my every need.  The motors, while mainly mechanical, bridge us over to the next level.
2. The electronics are the blood and guts of the robot.  They bring power throughout the entire thing, giving it life and movement.  Batteries pump power through the entire system, sending energy to the brains, motors, cameras, and any other electronics in the robotic system.
3. Firmware is the third level and is right in between pure software and the electronics.  It's the set of commands that tell the hardware what to do, usually by passing a command given to it by the software.  The firmware usually resides, as it does in this 'bot, in a microcontroller.  A microcontroller/MCU/uC is essentially a very small computer.  The basic controller can be purchased for under $5, or an augmented one, which is easier to work with, will cost between $20-$100.
4. Lastly is the pure software.  This is generally a nonexistent level on most amateur robots.  However, since I have no little voice in my head that tells me I'm biting off more than I can chew, I've decided to dream big, and will be installing an old laptop inside of the 'bot which will run the whole show.  While a microcontroller is fully capable of controlling the robot's lower functions, such as movement, tracking, and obstacle avoidance, the laptop will provide the robot with the potential of even greater possibilities!  I'm talking about grand things such as computer vision to keep track of particular people, environment mapping so the robot knows where it is, and voice recognition so it can here my commands of world domination (cue evil laughter).

So that's a basic rundown of how most robots tend to work, although level 4 can certainly be omitted.  However, I do understand that I'm terrible at explaining things, so if you have any questions, either ask in the comments or take a look at this fantastic website, where I learned most of what I know.

http://societyofrobots.com/

Laying Down the Data

So just the other day, I was fortunate enough to receive a Power Wheels Jeep from my good friend, Ian.  Being the avid robotics fan that I am, I have since decided that I am going to use this Jeep as a robotics platform that I can build upon to form a fully functioning, autonomous vehicle.  I have named this project rUD2, a play off of R2D2, and after the University of Delaware which I am currently attending as a Computer Engineering and Computer Science sophomore.  I plan on using the robot to represent the ECE Department in the hope that I might get some funding from them.

My goals for this project include the following:

1. To write this blog as a helpful tutorial for beginner through advanced roboticists interested in medium scale mobile robotics
2. Use this robot as a platform for experimental technologies including non-lethal self defense, computer vision, gps tracking, self charging, artificial intelligence, full automation, and general bad-assery
3. Develop the project to the point where it becomes a University backed robotics project that students who have a passion for robotics can participate in