Ohio Northern University Micromouse
Spencer Cupp, Kiel Wood, advisor Dr. Khalid Al- Olimat
ECCS Senior Design 2012-2013
IEEE Micromouse Competition Rules
Motors
Infrared sensor readings do not change linearly with distance to object, and
do not function when objects are extremely close
IR Sensor Output Voltage vs. Distance to Object
3.5
3
Flooding Algorithm
Discrepancies in both the production of the motors and their mounting
make them behave differently. Given the same input voltage, each of the
motors on the mouse will rotate at a different speed. The difference
between the motors is compensated for in the motor control code, passing
different voltages to each motor to achieve equal rotation speed, moving
the mouse in a straight line. Sensor feedback was also incorporated to
direct the mouse back to the center of the path as it veers off course.
2.5
The algorithm begins by assuming that there are no walls, calculating the
distance (in number of cells) from each cell in the maze to the center.
Right and Left Motor Speeds vs. Input Voltage
2
140
1.5
120
1
100
0.5
0
0
5
10
15
20
Distance to Object (cm)
25
30
35
Motor Speed (RPM)
Sensor Output (V)
•A Micromouse must be a self-contained robot that can find the shortest
path to the center of a maze autonomously within ten minutes
•The Maze is a 16 x 16 grid of cells, each 18cm x 18cm, separated by 5cm
tall walls which are 1.2 cm thick
•Information cannot be fed to the mouse by the user, and the mouse must
not damage or alter the maze in any way
•Winners will be selected based on the amount of time it takes a mouse to
move from the starting cell to the center of the maze.
•A mouse may travel from the starting cell to the center as many times as
desired within the ten minute timeframe, with the fastest run achieved
being its official time
Sensors
Right
Motor
RPM
80
60
40
To avoid this cutoff region, sensors were strategically placed such that
walls would never be close enough to the sensors to give these readings.
Left
Motor
RPM
20
0
0
1
2
3
4
5
Motor Input Voltage (V)
6
7
As the mouse moves through the maze and learns the locations of walls, it
updates the distance calculated for each cell, always moving in a direction
it assumes will move it towards the center.
8
Prototype
System Overview
The mouse consists of:
•1 Arduino Uno Microcontroller
•1 Arduino Motorshield
•2 DC Motors with Encoders
•2 Wheels with independent shafts and gear trains
•1 Caster
•4 Infrared Sensors
•1 Lithium Ion Battery and Power Switch
Infrared sensors transmit infrared light from one side and receive reflected
infrared light on the other, therefore sensors mounted in different
orientations will return different readings
Mounted Side Sensor Readings: Normal vs Inverted
Block Diagram
3
Sensor Voltage (V)
2.5
2
1.5
Normal Sensor
Inverted Sensor
1
0.5
0
0
5
10
15
20
Perpendicular Distance from Mouse to Wall (cm)
25
These differences can lead to difficulties in wall-detection, therefore
sideways facing sensors were mounted in matching orientation
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After finding the center of the maze, the mouse will continue to look for
alternate, possibly shorter, routes between the starting cell and center. Once
the mapping is complete, the mouse can simply follow the cell distances in
descending order (As traced by the red line below) to reach the center of
the maze via the shortest possible route.