The Loon Project

The above robot is named Loon. It was built to compete in the "Schedule a Meeting" competition that was held at the 1996 AAAI conference in Portland, Oregon. The students who worked on this project were: Paul Rybski, Brian Schmalz, Dirk Edmonds, and Margaret Hsieh (a student from Stanford University who visited us for the summer). This robot is actually a pair of robots, the smaller one (Baby Loon) riding upon the back of the larger one (Mama Loon). Since Loons in the wild carry their young on their backs, we thought the name fitting. The Loon is also Minnesota's state bird.

The Mama Loon is constructed from a high-speed remote controlled off-road racer chassis. The electric motor on it is capable of speeds upwards of 20 mph or so. Fortunately, we determined a way of slowing it down to managable speeds. The Baby Loon is built on a toy car chassis which had the steering motor removed and replaced with a Futaba RC servo motor. The bodies of the robots were built out of LEGOs since it was an extremely robust and efficient prototyping and construction material.

The Baby Loon

Both robots have nearly identical sensor configurations. In the front, there is a ring of five Polaroid ultrasonic sensors as well as a single polaroid sensor on a 360 degree freedom turret. There are also four close-range IR detectors placed on front, back, and on both sides of each robot. Each robot is equipped with a shaft encoder on one of its wheels for PWM calculations and dead-reckoning capabilities. The Mama Loon has an infrared/motion proximity sensor mounted just below its turret sonar.

Each robot is equipped with a two Motorola 68HC11-based microcontrollers, a Handyboard and a Miniboard. The two boards are hooked together via the SPI synchronous serial port in a master-slave configuration where the Handyboard serves as the master to the slave Miniboard. The Handyboard is equipped with 32K of RAM and runs Newton Lab's Interactive-C, while the Miniboard has only 2K of code space and 256 bytes of RAM and is programmed in assembly. The Handyboard also has a peizo-electric buzzer with which it could sing songs to communicate with the outside world. It also has a small LCD display on the front with which it can display messages. All high-level processing (planning, scheduling, and robot control) is handled by the Handyboard. The Miniboard is in charge of driving all of the physical actuators and sensors. It handles all of the sensor value averaging and keeps current values of the sensor readings at all times so the Handyboard does not have to wait before receiving a value back.

Communications between the robots works across the RS232 asynchronous serial lines of the robot's respective Handyboards. When the Mama determines that it is time to launch the robot, she downloads the relevant information to the Baby and then gives the launch command. The Mama extends the back of the trailer and the Baby rolls backwards and down the ramp. After launch, the communications cord pulls out from the Baby's serial port and the two robots are completely isolated from one another until they are manually reset.

In the "Schedule a Meeting" competition, the Mama robot (with the Baby on her back) was to be given a map of an office complex. She would start out in the "Director's" office and then have to calculate the shortest path to a conference room. Once she reached the conference room (while avoiding walls and pedestrians), she would use her proximity sensor to see whether the conference room was open. If there was someone in the conference room, she would have to determine the shortest path to the next conference room and see if it was open. If neither conference rooms were free, then the robot could schedule the meeting in the Director's office. Once the Mama knew where the meeting was, it could calculate just how long it would take to reach two of the professor's offices as well as the Director's office (also allowing for the problem of running into pedestrians). She would give this information to the Baby robot, launch the Baby robot, and then proceed to inform one of the professors at what time the meeting would be held. The Baby would inform the other professor and then whichever robot happened to be closer to the Director's office would then tell the Director at what time the meeting would be.

MPEG movie showing Mama loon deploying the Baby loon

 Look at our other Mini-Robots.

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