Micromouse - IEEE79-4
robotsystems.net
Back to - Micromouse - The early years 1978-9 22 November 2004

IEEE spectrum 1979
Page-1Page-2Page-3Page-4
The battle of the wall huggers

It was at the third time trial in Los Angeles last year that the Battelle team of Art Boland. Ron Dilbeck, and Phil Stover (Mr Stover is now with WED Enterprises), decided to build a wall hugger They had designed the Moonlight Special, the smartest micromouse observed, but at the time trial the team of Gary Gordon, Gary Sasaki, and Ken MacLeod of Hewlett-Packard, Santa Clara. Calif., Introduced Harvey Wallbanger (below). This right-wall-hugging mouse, with no electronic intelligence, made up with speed what it lacked in brains. It traversed the Spectrum maze in the third time trial In 41 s on its first run.
     Thus was born the Moonlight Flash, (right) an optical right-wall-hugging micromouse entered by the Battelle team. Moonlight Flash won the grand prize of $1000 with a first run of 30.04 s, beating out Harvey Wallbanger, whose first run was clocked at 41.68 s.
     Although the Moonlight Flash was not considered "intelligent," compared with the Moonlight Special and Moonlight Express -- two other mlcromice designed by the same team -- It did incorporate an 8748 microprocessor and memory that gave it just enough Intelligence for the winning margin For example, three forward optical sensors mounted on extended arms were used to provide "look ahead" capability to cut corners where possible. The microprocessor and optical sensors optimized the Moonlight Flash's turns at cor-


ners to cut down on running time. Whereas an ordinary wall hugger would make a turn at a corner, often slowing in the process and sometimes bouncing off walls, the Moonlight Flash did not require contact with the walls while rounding the corners and did not slow down.
     Another feature of the winner that was not used at the finals (insufficient time prevented the incorporation of this feature) was dead-end blocking. With it, the mouse would have been able to sense ahead dead ends and mousetraps and avoid them. Moonlight Flash was designed to operate from two small dc motors to achieve a top speed of 63.5 cm/s Power was provided by three sub-C Ni-Cd rechargeable and four AA batteries.
     Harvey Wallbanger operated on four wheels two main ones driven by two small dc hobby motors, one on the left and one on the right; a swivel wheel in front;and a horizontal wheel mounted on the frontright and driven by a third small hobby dc motor to hug the right wall. Two contact switches, one in front and one on the right side, made up the rest of the main components.
     Shortly before the finals, it was discovered that the horizontal wheel's motor was burned out. A search for a replacement was fruitless, and it was decided to do without it. To compensate for its loss, its designers slightly rearranged Harvey Wallbanger's switches and added another switch. This was a supplement to the right-hand switch in place, to keep the right-hand motor turning during left turns. Harvey Wallbanger was designed for a maximum speed of 100 cm/s. Power was provided by six AA alkaline batteries.

To negotiate the maze perfectly -- that is, to solve the maze in the shortest run -- a mouse would have had to travel but 8 m from entrance to exit. Right-wall huggers would have had to travel 15.83 m while left-wall huggers would have had to endure a more punishing distance of 30.05 m.
     In practice, only the Moonlight Express and Special made perfect runs (on their second and third trials). The $1000 grand-prize winner, the Moonlight Flash, solved the mazc in 30.04 s on the first run, 30.62 s on the second run and 29.78 s the third time around.
     "It's been quite an experience," said one of the three designers of the Flash, Art Boland. "As designers of wall

followers, dead-end blockers and shortest-path computers, we know the difficulties encountered in making a transition from one level of intelligence to the next. The number of entrants with plans for intelligence that didn't succeed is evidence that these transitions are more difficult than some people realise. The problem essentially boils down to one of control. For a mouse to be truly capable of learning a maze and making smart decisions about solving the maze, physical control ol the mouse must be both accurate and repeatible. No attempt was made by us to implement our learning algorithms for our micromice until our control software was good enough to accept the learning algorithms."
Allan - The amazing micromice see how they won 65