Network Robots – Netbots

The Netbot (Network Robot) vehicle was designed and built to test distributed cooperative control algorithms being developed for DARPA ITO’s Software for Distributed Robotics program. In order to test the algorithms, twenty or more vehicles that could communicate and localize with respect to one another were needed. Looking at commercially available platforms, we found two extremes in capabilities and price. On one extreme are the inexpensive ($30-$100) remote control cars by Tyco and others. These vehicles are remotely driven with radio controlled joysticks, but they were not designed for autonomous navigation. On the other extreme are the expensive ($20,000) robotic vehicles from Real World Incorporated (RWI). These vehicles can be controlled remotely via a joystick or can be programmed to perform autonomous navigation. The cost of 20 vehicles of this caliber was beyond the budget of this project; therefore, we decided to build upon the less expensive platform. The mechanical design of commercial RC cars is fairly advanced. What is missing from commercial RC cars are the "brains", sensing, and communication to perform autonomous navigation and cooperative motion.

Our Netbot electronics kit provides the necessary "brains", sensing, and communication. The first implementation of the Netbot vehicle is built upon a commercially available remote control (RC) car called "Super Rebound" from Tyco. The printed circuit board from the RC car was removed and replaced it with two printed circuit boards of our own design. The first printed circuit board contains power conditioning electronics and two full bridge PWM amplifiers for controlling the motors. The second printed circuit board contains a microcontroller and interface electronics to a 915MHz radio transceiver, a wheel encoder, electronic compass, 4 infrared proximity sensors, and an omni directional ultrasound range sensor. In addition, this board contains a dual port memory interface to a commercially available 33MHz 386EX computer board. A CMOS camera module has recently been added. If the printed circuit boards were mass-produced, the price of this kit could drop an order of magnitude to the $150 or less range.

In addition to the vehicle hardware, we have also designed a base station controller that plugs into the serial port of a Palm Pilot. From the Palm Pilot’s user interface, it is possible to control each Netbot vehicle individually or to control a "swarm" of Netbots in a coordinated fashion, and to display images seen by the vehicle cameras. A network protocol allows the vehicles to pass messages and camera images to other vehicles that are out of line of sight. The radio and acoustic sensor are used to determine the range between vehicles, and an advanced localization algorithm is used to determine the x,y position of each vehicle.