Short Stuff

Short Stuff will be small enough to be entered in most competitions, while still be large enough to easily work on. Additionally, it is designed to traverse many obstacles and be able to run in many different types of environments. The max size of the robot will be 9.5" in diameter and 12" tall. The design consists of two decks, the top one 6.5" in diameter, and the bottom one slightly more than 9" in diameter. The decks are spaced 6" apart, as dictated by the height of the card rack. The rotating head assembly will be mounted on a neck above the upper deck. A set of skins are designed to fully enclose the central body.

The drive train is designed to be robust and powerful. The robot will be powered by two 7.2VDC gear motors with encoders. These motors will be attached to 3.5" diameter by 1.75" wide off-road wheels with 6mm hubs. This provides a drive train that provides excellent grip and that can work both off-road and on. There will be two 4cm omni-wheel casters which will have full spring suspension systems allowing travel over obstacles up to 2" high (must be width of robot).

Short Stuff will be powered by several AVR microcontrollers. These microcontrollers will each be on their own 100mm x 100mm card, and will be connected through the back plane via an IIC bus. The entire electrical system, as well as the motor drivers, will be powered by a single 9.6V NiMH battery. The computing systems will be isolated from the motors by a high-efficiency DC-DC converter.

The AVR architecture was picked for several reasons. First, the GCC compiler is available for the AVR, but not for architectures like the PIC. Second, the AVR has 32 general purpose registers, and all setup is done through control registers, making the architecture very easily adapted to the object-oriented paradigm. Finally, the AVRs have high pin-counts, and clock rates up to 16 MHz. The ATmega32 was chosen because it is the most powerful AVR available in a non-surface mount package.

The back plane and card architecture is essential to meeting a key goal of the Short Stuff robot, expandability. The master card on the bus will be a card with a single ATmega32 AVR, a 1Msps 8-channel 8-bit ADC, a level-shifted serial port, and an ISP header. This card can be programmed through AVR-GCC and will command all the other cards on the bus. The ISP header will only be used to update the bootloader. Once the bootloader is working the chip can be reprogrammed through the serial port. The motor card will carry an ATmega32 chip running an intensive program that will control up to four DC motors with encoders and 12 servos. The board can be setup through IIC or through a level shifted serial port. Additional cards will include an RF communications card and Sensor Card for added expandability.

The software for the robot will be written in C++ using the AVR-GCC compiler.

So far I have almost finished desiging the robot. I am currently making the PVC parts. I have purchased almost everything else, except the PC Boards.