The Intelligent Ground Vehicle Competition (IGVC) is the precursor to the DARPA Grand Challenge, and in many ways it is just as difficult. We have the pleasure of being at the competition this year with the Tennessee Technological University Autonomous Robotics Team. The teams at the competition pull off some amazing home-brew robotics, so we’ve decided to do a short section on some exemplary robotic hacking each day of the competition.
Today’s robot comes from the York College of Pennsylvania. The robot, dubbed “Green Lightning”, features an impressive set of custom made hardware.
We interviewed the team, and got a pretty thorough rundown of their robot with pictures after the jump.
The spinal cord of the robot is this custom built beauty.
It consists of six layers, each with a specific function. The boards were designed by the team and fabricated by Sunstone Circuits. Each layer except for the top has its own teensy++ unit, programmed in C, providing an SPI interface to the hardware it’s designed to connect to. The first layer has an Arduino Mega programmed in C on it. The layers communicate with the Mega through an SPI bus running at 500Kbaud. The Mega processes the information and then communicates to a computer through a 1Mbaud usb serial connection.
The remaining five layers are each designed to interface with a specific section of the robot’s hardware. The second layer communicates with a Wheel Commander from Nubotics, simplifying the robot’s motion controls.The third layer is the interface to the robot’s emergency stop. The rules require that there be a visible hardware e-stop on the back of the robot and a wireless remote e-stop. They solved their wireless e-stop problem with a zig-bee module that connects to the robot through this layer.
The fourth, fifth, and sixth layers all connect to the robot’s sensor groups. The fourth layer is the interface to their gps, mounted at the top of the robot. Most gps units communicate with simple serial and it’s pretty elegant that they managed to save a usb port by adding a board. The robot has nine Sharp 2Y0A710 distance sensors acting as a short-range bumper for obstacle avoidance which all connect to the fifth layer. The final layer is the interface for 10 long range sonar sensors located at compass points around the robot.
The robot also has two USB Web Cams for line and object detection mounted on the mast. The AI and computer side hardware interface is programmed in a mix of C and Java. The AI follows a reactive model instead of a mapping/planning one which has been proven to be very effective in this competition for many teams.
The frame, track, and drive train were custom built by the team as well.
Here you can see the back of the robot where the drive train, Wheel Commander, and two SaberTooth motor drivers are.
A side shot shows their track system. They modeled it in SolidWorks first and then fabricated everything including the belt in house.
In the end the robot cost them around $5,200 after discounts which is pretty impressive considering its capabilities and that some of the robots at this competition easily break $50,000 dollars. It’s a prime example of what good engineering and home-brew magic can accomplish. We’ll finish with a shot of their manual control system.