Micro Mouse--A Brief Description

Jeff Weisberg (portions by: Peter Newcomb, Joe Rosato, Otten, Kassakian, Bodmer, etal...)

Synopsis

A Micro Mouse is a clever little gadget with a silicon brain that finds its way through an arbitrary maze. It competes against other members of its species, racing as fast as it can.

In a Micro Mouse contest the contestants design and build a small, self-contained, autonomous robot to negotiate and solve an unknown maze in the shortest time.

Overview

A Micro Mouse is an electro-mechanical device, typically consisting of three main subsystems. The drive system, an array of sensors, and the control system.

The drive system consists of a mechanical chassis, a set of motors, gears and wheels. The chassis is usually designed to operate like a wheel-chair, with two large drive wheels on either side of a lightweight aluminum frame. The chassis is built to house the motors, gear system, batteries, and circuitry, and must also be small enough to manuever within the constraints of the maze.

The control system is series of circuit boards functioning as the brain of the critter. The control system runs a maze solving algorithm based on the information recived by the CPU from the sensors. Typically the first several runs through the maze will be a search sequence, in which the mouse learns the maze and stores it in memory. It must then calculate the fastest possible path, which it will repeatedly run trying to achieve successively faster times.

The final sub-system is the sensors. They report to the CPU the current state of the suroundings--where the walls and paths are. These are usually either infrared sensors which pick up light reflected off of the tops of the walls, or a sonar system which recieve reflected sound waves off of the walls.

Each mouse must be fully autonomous, they may not have any form of control link to an external source.

In an official Micro Mouse contest, the main objective is to achieve the fastest maze running time. However, another important objective may be the use of a Micro Mouse as a student project at engineering colleges. Because it integrates several different disciplines of engineering, ranging from electrical to mechanical to computer science, it can offer a valuble learning experience.

History

In the spring of 1991, a student from the Rochester Institute of Technology came to the University of Rochester to round up support for their Micro Mouse team.

Their motive was simple. With only two people in their group, they needed more man power. However, due to the large turnout at the first meeting, we decided that joining a two man team from RIT seemed foolish if the vast majority of the effort came from the UofR. In the excitement, we decided to set out on our own, and started work on the UR-MM1, the University of Rochester's first attempt at building a Micro Mouse.

Over the next several months we were hard at work planning out our design. By the time winter-break rolled around, we had gone through many design revisions, and were ready to start construction. In February, we were just about finished (but not quite) when we headed off to Boston, for the IEEE APEC Micro Mouse competition. It was the first real test of our device. But alas, technical difficulties abound, we were unable to actually run the maze (but it looked good sitting there). With a race behind us and a fresh set of new ideas, we set to fixing and revising our mouse. In April, we set off for an IEEE contest in West- Point. Our hard work finally paid off. Victory was ours! We came in first place (there were no other entries, but that's irrelevant).

In April of 1993, we packed up our equiptment and headed upto Toronto for the 2nd annual BEAM robot olympics, where we met up with our past rivals who trounced us in Boston (Dave and Louis). As expected, Dave cleaned up with his Mitee Mice, followed closely by the Mouse-Mobiles, but much to everyone's surprise the UR-MM1.2a, performed rather well, (it moved, beeped, and flashed its lights) beating out several other non-functional mice, although there were still small problems with the turning algorithm.

The following year, we took our updated mouse (now the UR-MM 1.3141578A) to the following BEAM competition, in March 1994. Apperantly Dave had heard of our progress, and was too scared to show up. Louis took first (after some technical problems with the mazes were corrected), and a suprise entry from Queen's University took second over our third place, by judges desicion. Our performance was quite a sight to be seen, we wandered around the maze for the full 15 minutes, covering roughly 3/4 of the total maze area, without ever crossing into the finish cell. With thanks going to Tom Rickey of the University public relations office, we received much media attention, including: WHAM, WXXI, UR Currents, UR Campus Times, Rochester Review, New York Times, Toronto Globe and Mail, Mechanical Engineering, San Fransico Examiner, etc.

Present Status

Currently, the team consists of a moderate number of students, both graduate and undergraduate, from several departments, such as Mechanical Engineering, Electrical Engineering, Computer Science, Optics, and Physics.

Using experience gleaned from the current mouse design, we have been putting together a design for a new and improved micro mouse, that we will be refining over the upcoming months, and will hopefully have constructed before the end of the academic year. We will of course also continue with work on the current mouse.

When not working on the robot itself, we are usually trying to solicit financial support to further our progress. Currently we are recieving contributions from the departments of Electrical Engineering, Mechanical Engineering, Computer Science, the College of Engineering and Applied Science, and are always looking for other sources. 

Please send contributions to:
The University of Rochester Micro Mouse team c/o
Jeff Weisberg
Dept. of Electrical Engineering
University of Rochester
Rochester, NY 14627

Thank you for your support!

UR-MM1 Implentation details

The UR-MM1's drive system consists of two DC motors, two sets of gears, and two wheels mounted one on each side wheelchair style. Small castors keep each end of the mouse from dragging on the floor. Mounted within the chassis are optical shaft encoders on each of the two drive wheels. These tell how far the wheels move.

For wall detection, we have experimented with a number of different techniques, including: electrostatic sonar elements, arrays of IR emitter/detectors mounted on "wings" over the tops of the walls, linear arrays of charge coupled devices (CCDs), and several other methods. Currently we are using sets of IR emiter/detector pairs mounted on the sides of the mouse pointing horizontally at the sides of the walls.

The heart of the UR-MM1 is the intel 80C196KC microcontroller. It contains many useful features on-chip, including the analog to digital converter used for the sensors, and a serial port enabling the transfer of data and code with a host computer.

Future Objectives

Our objectives of this project are severalfold:
  1. To continue work on the UR-MM1.2a
  2. To compete in several competitions each year.
  3. To continually come up with new ideas and implementations, modifying and improving on the previous design, year after year.
  4. Design and build the UR-MM2 using the knowledge gleaned from the experiments and experiences with the UR-MM1, while continuing the use of the UR-MM1 for competition and experimental use.
  5. To expand our practical experiences and learn valuable knowledge about microprocessor and control circuitry, efficient algorithm design, motor control, drive systems, organizational skills, how to work with a group towards a common goal, and many other skills that will undoubtedly come in handy later in life.
  6. To have FUN!!!

Contest Rules

Jeff Weisberg (adapted from IEEE/APEC Rules)

I. Specifications for the maze

  1. The maze shall comprise 16 x 16 multiples of an 18 cm x 18 cm unit square. The walls constituting the maze shall be 5 cm high and 1.2 cm thick. Passageways between the walls shall be 16.8 cm wide. The outside wall shall enclose the entire maze.
  2. The sides of the maze shall be white, and the top of the walls shall be red. The floor of the maze shall be made of wood and finished with a non-gloss black paint. The coating on the top and sides of the walls shall be selected to reflect infred-red light and the coating on the floor shall absorb it.
  3. The start of the maze shall be located at one of the four corners. The starting square shall have walls on three sides. The starting square orientation shall be such that when the open wall is to the "north", outside maze walls are on the "west" and "south". At the center of the maze shall be a large opening which is composed of 4 unit squares. This central square shall be the destination. A red post, 20 cm high, and 2.5 cm on each side, may be placed at the center of the large destination square if requested by the handler.
  4. Small square posts, each 1.2 cm x 1.2 cm x 5 cm high, at the four corners of each unit are called latice points. The maze shall be constituted such that there is at least one wall touching each lattice point, except for the destination square.
  5. The dimensions of the maze shall be accurate to within 5% or 2 cm, whichever is less. Assembly joints on the maze floor shall not incolve steps greater than 0.5 mm. The change of slope at an assembly joint shall not be greater than 4. Gaps between the walls of adjacent squares shal not be greater than 1 mm.

II. Specifications for the Micro Mouse

  1. A Micro Mouse shall be self contained. It shall not use an energy source employing a combustion process.
  2. The length and width of a Micro Mouse shall be restricted to a square region of 25 cm x 25 cm. The dimensions of a Micro Mouse which changes its geometry during a run shall never be greater than 25 cm x 25 cm. The height of a Micro Mouse is unrestricted.
  3. A Micro Mouse shall not leave anything behind while negotiating the maze.
  4. A Micro Mouse shall not jump over, climb, scratch, damage, or destroy the walls of the maze.

III. Rules for the Contest

The basic function of a Micro Mouse is to travel from the start square to the destination square. This is called a run. The time it takes is called the run time. Traveling from the destination square back to the start square is not considered a run. The total time from the first activation of the Micro Mouse until the start of each run is also mesured. This is called the maze time. If a mouse requires manual assistance at any time during the contest it is considered touched. By using these three parameters the scoring of the contest is designed to reward speed, efficiency of maze solving, and self-reliance of the Micro Mouse.
  1. The scoring of a Micro Mouse shall be done by computing a handicapped time for each run. This shall be calculated by adding the time for each run to 30 of the maze time associated with that run and subtracting a 10 second bonus if the Micro Mouse has not been touched yet1. 1 For example assume a Micro Mouse, after being on the maze for 4 minutes without being touched, starts a run which takes 20 seconds; the run will have a handicapped time of: 20+4300-10=18seconds The run with the fastest handicapped time for each Micro Mouse shall be the offical time of that Micro Mouse.
  2. Each contesting Micro Mouse shall be subject to a time limit of 15 minutes on the maze. Within this time limit, the Micro Mouse may make as many runs as possible.
  3. When the Micro Mouse reaches the maze center it may be manually lifted out and restarted or it may make its own way back to the start square. Manually lifting it out shall be considered touching the Micro Mouse and will cause it to loose the 10 second bonus on all further runs.
  4. The time for each run shall be measured from the moment the Micro Mouse leaves the start square until it enters the finish square. The total time on the maze shall be measured from the time the Micro Mouse is first activated. The mouse does not have to move when it is first activated but it must be positioned in the start square ready to run.
  5. The time taken to negotiate the maze shall be measured either manually by the contest officials or by infra-red sensors set at the start and destination. If infra-red sensors are used, the start sensor shall be positioned at the boundary between the start square and the next unit square. The destination sensor shall be placed at the entrance to the destination square. The infra-red beam of each sensor shall be horizontal and positioned approximately 1 cm above the floor.
  6. The starting procedure of the Micro Mouse shall not offer a choice of strategies to the handler.
  7. Once the maze configuration for the contest is disclosed, the operator shall not feed the Micro Mouse with any maze information.
  8. The illumination, temperature, and humidity of the room in which the maze is located shall be those of an ambient enviornment. Requests to adjust the illumination may be accepted at the discretion of the contest officials.
  9. If a Micro Mouse appears to be malfunctioning, the handlers may ask the judges for permission to abandon the run and restart the Micro Mouse at the beginning. A Micro Mouse shall not be re-started merely because it has taken a wrong turn.
  10. If a Micro Mouse team elects to stop because of technical problems, the judges may, at their discretion, permit the team to run again later in the contest with a 3 minute maze time penalty1. 1 For example, assume a Micro Mouse is stopped after 4 minutes; it must be restarted as if it had already run for 7 minutes, and will have only 8 more minutes to run.
  11. If any part of a Micro Mouse is replaced during its performance, such as batteries or EPROMS, or if any significant adjustment is made, the memory of the maze within the Micro Mouse shall be erased before restarting. Slight adjustments, such as to the sensors may be allowed at the discretion of the judges, but operation of speed or strategy controls is expressly forbidden without a memory erasure.
  12. No part of the Micro Mouse (with the possible excpetion of batteries) shall be transferred to another Micro Mouse. For example if one chassis is used with two alternative controllers, then they are the same Micro Mouse and must perform within a single 15 minute allocation. The memory must be cleared with the change of a controller.
  13. The contest officials shall reserve the right to stop a run, or disqualify a Micro Mouse, if they believe its continued operation is endangering the condition of the maze.