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Hardware Test Platform
To test the algorithms and software developed in this project, we have built 20 low-cost robotic vehicle platforms that contain the necessary processing and sensing to navigate and traverse a building. The platforms are built on top of a $60 commercial radio control car called Super Rebound from Tyco. We have removed the external housing and replaced the radio control and motor amplifier electronics with our own custom circuit boards. A smaller circuit board in the back of the vehicle contains the power conditioning and two motor amplifier H-bridges. The larger circuit board on top of the vehicle contains a 4MHz 8-bit microcontroller, 900MHz radio, 4 infrared sensors, wheel encoder interface electronics, ultrasound interface electronics, and an electromagnetic compass. This board also has 16 kilobytes of dual port SRAM which allows it to interface to a commercially available embedded processing board with a 66MHz 386EX processor. This processor will be used for computationally intensive tasks such as computing the location of the vehicles from the ultrasound ranging information. On top of the vehicle is an omni-direction ultrasound transceiver. Using the RF radio to indicate the start of a ultrasound chirp, the ultrasound transceivers can be used to measure the distance (via time of flight) between vehicles. With three or more vehicles, we can triangulate to determine their x,y position in a plane. Currently, the system has a positioning accuracy of 25-50 mm.
Figure 8: Netbot (Network robot) vehicle used in hardware tests. |
