Sparkfun AVC 2012: Enter the T1.

Even though I have not posted these last 6 months, I haven’t been inactive. What has happened is that I didn’t like where the blog was going. While I think the Rover 5 platform is a fine platform for what it is, a small radio controlled robot… that’s not where I want to go. The other problem is that my house in Virginia simply doesn’t have the zoning for what I really need to do… which is set up a real machine shop so I can build real robots.

So I sold the house in Virginia, and moved to the wide open spaces of the Missouri Ozarks where I can literally build whatever I want. Then I founded a company, Tesla Robotics. The goal of Tesla Robotics is to research and develop Open Source robotics using the Linux and Arduino systems.

Yup, the icon of my vision, my inspiration, is Nikola Tesla. A man I consider to be one of the greatest engineering minds ever. There’s no way I can ever fill those shoes, but that doesn’t mean I can’t have fun trying! If Nikola Tesla had the tools we have today? Wow.

Here’s what’s going to happen: Both of my current projects, the Tron robot and the Eyeborg are dropped. Both used the Rover 5 platform, and that’s not doing it for me. It’s time to reach a LOT higher.

The new project is called the T1. Yeah, that means “Tesla One”. Ok, I know that’s not original. In my mind, it’s the first in a series of autonomous, fully Open Source robots that will explore just how deep this rabbit hole really goes.

What is the T1?

The T1 is an autonomous robot equipped with an array of positioning systems and powered by 4 brushless DC motors, one at each wheel. It will also have 4 wheel steering, GPS, IMU, 4 wheel optical encoders for Odometrics, and a Magnetometer for compass direction. It’s goal is to win the 2012 Sparkfun AVC held in Colorado on June 16, 2012. Here’s a rundown of some of the components I plan to use:

Control computer: It’s the same as in This post. I’m currently using a Giada Cube with integrated WiFi. I’ve pimped it out with 4 gigs of RAM and a 50 gig SS Hard Drive. Hmm. I can’t find a link to it on NewEgg to link it. Anyway, I’m running Fedora 14 on it, and the integrated WiFi is running in Master Mode using the hostapd daemon so it’s it’s own WiFi Access Point. This computer is overkill, but it’s the easiest way to drop a Linux control system into a robot. Eventually I may investigate things like the Beagle Board for it’s replacement. But for the T1, this is the computer I plan to use. In future posts, I’ll delve into it’s configuration and how to set up your OWN Linux computer for embedded robotic applications.

Motors: Originally, I specced some wimpy 1/11 and 1/7 horsepower 12 volt motors for the T1. Those didn’t cut it. They were just too big and heavy to practically use in a 4 wheel drive, one motor per wheel robot. My plan originally was to power the robot with 12 volt lead-acid motorcycle batteries. Heh. That didn’t roll very far. This is my current thinking: This thing is a beast: Neodymium magnetics, 3 phase DC brushless, and it’s reasonably priced at only 33 bucks each! This motor is an “Outrunner” type, meaning the magnets are on the outside and the stationary coils are on the inside. There are also more magnets than coils, so the motor is constantly “out of phase” with one of the coils and the controller has to keep up by switching the current to the in phase coils. We’ll go into that when we research the motor better. Expect a motor to be taken apart and fully explored in a future post.

Batteries: What was I thinking? Motorcycle Batteries? I’m turning to Turnigy again on this one. The electronics package (Consisting of the Giada Cube computer and all the Arduinos controlling the motors, sensors, etc.) is powered by this battery The 25C part is overkill as the Giada requires 1.8 to 2.2 amps at 12 volts. The Arduinos… MUCH less. In testing, the Giada runs with as little as 11.25 volts, giving a 1 hour life on a single charge. That will work fine. The motors are more power hungry and I plan to use these. I expect I can use 2 of these total, running 2 motors on each one. Total weight of batteries? 4 pounds.

Motor Controllers: Arduinos networked to the Linux computer. I’m working on the third prototype now. The first prototype is in the first link above, and the second was a custom Arduino board with two SPI UARTS on it. The third prototype, which is the T1 candidate, will be documented in a future post. The actual motor driver will be a shield attached to that board. I’ll design it when I fully understand the brushless motors.

GPS: Watching the last AVC, and reading blog posts about the one before, two things were clear: First, don’t scrimp on the GPS. Second, don’t rely on it as your sole position indicator.

IMU: I’m not convinced I need an IMU, but I’ll add one as insurance. The need (Or otherwise) will come out in testing.

Magnetometer: This is a critical component. In conjunction with the optical encoders at each wheel, this forms the most accurate millisecond to millisecond position measurement in the robot.

Last year, Team Tobor won the AVC. They won the year before that, too. So I studied scott’s blog and went to school on it. I’ll be using the enhanced Kalman filter as he did, integrating all my positioning data into one “Best Guess” result to run the robot.  Unlike Tobor, T1 will have a Linux Computer to do the heavy lifting, enabling the servo solution for all 4 wheels to be computed independently with no CPU overhead problems. It will also have a similar power to weight ratio to his Tamia Grasshopper, but greater stability due to the 4 wheel drive and much bigger contact patch for the tires. My thinking is that my heavier, more powerful robot will be more stable at speed, giving it an advantage.

It’s on! The 2012 AVC awaits.