Micromouse Team
Fall 2008

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Engineering Design Constraints for an Autonomous Maze Solving Robot

Ambrose McJunkin, Tim Montague, and Chris Gibson
Advisor: Mr. Randy Larimer
Department of Electrical and Computer Engineering

Abstract�The design and building of an autonomous robot to solve a maze. The robot is able to rotate and move with the aid of Ultrasonic range sensors. A microcontroller executes the path finding algorithm that will allow it to complete the maze. The following engineering design constraints will be considered: economic, environment, sustainability, manufacturability, ethical, health and safety, social, political, and time.

I. INTRODUCTION

There are many considerations in any design project, perhaps the foremost being the constraints of the project. The constraints dictate how, and to what extent, the item (or items) being designed needs to work and the resources available to accomplish this task. These constraints fall into many categories, including but not limited to: economic, environmental, sustainability, manufacturability, ethical, health and safety, social, political, and time. It is best to consider each constraint individually in determining the feasibility of a project. What follows is a consideration of each constraint with regard to an autonomous maze solving robot.

II. DESIGN IMPACT

A. Economic

It is often the case that financial support is needed to see a project through. Unless the project lives solely in the brain of the individuals, funds must be acquired in order to purchase the necessary parts and equipment for the project. To help in this regard, the robot will be based on the pre-existing design of the ECEBOT which is the robot used in the electrical fundamentals class at Montana State University. Specifically, the PCB (with HCS12 microcontroller) and frame will be used as a starting point. Costs will come from the Ultrasonic range sensors, new DC motors, an H-bridge, and a gyroscope. These additional parts will be used to effectively navigate the robot through the maze and are therefore essential. When selecting these additional parts, price beat out performance. Inaccuracy of the parts can be compensated by feedback mechanisms in the firmware to correct errant behaviors in the robots moving parts.

B. Environmental

The chief environment for the robot will be the IEEE Micromouse maze it must traverse. For this reason, perhaps the biggest constraint is on the size of the robot. The robot must be able to fit and move freely within the walls of the maze. It also must be able to detect side paths so that it may move intelligently. Uneven ground or bumps in the maze may cause slight deviations in the robot�s course. To combat this, the gyroscope will be used to keep the robot aligned and making consistent 90 degree turns. Temperature, while not a huge concern, could also be a factor. Specifically, if the temperature of the room is high enough, it could cause the electrical components in the robot to overheat, possibly damaging them. This could be addressed, if need be, by providing a mechanism for cooling the components, such as a fan or heatsink.

C. Sustainability

Sustainability refers to the ability of a system to perform for a period of time after it has been made, as well as offer some guarantee about the performance of future systems made from the same design. Because the integral parts, such as the body of the robot and the microcontroller, are being borrowed from the ECEBOT, which is manufactured every year for the EE101 course at Montana State University, there should be no trouble in coming by these parts in the near future. The Ultrasonic range sensor selected should not matter too much with regard to how the robot performs. Another sensor could take its place, for instance, and perform the same function, although this would probably require a change in the firmware. It is the goal of this project to keep the firmware for the robot encapsulated, meaning the algorithm or behavior of the robot is blind to the actual implementation (the motor, the sensors, etc). In this way, different sensors or different motors could be used with minimal change to the firmware.

D. Manufacturability

The ability of a system to be constructed efficiently and cheaply is referred to as its manufacturability. Because the ECEBOT materials are being used for the integral parts of the robot, which have been proven to have high manufacturability by the fact that they have been used by Montana State University for many years, and that the peripheral devices such as the sensors and motor can be swapped out, it should not be a problem to manufacture this robot now or in the future.

E. Ethical

Ethical considerations should be a factor in every decision made during a design project. There are a few that specifically relate to a Micromouse design. The IEEE competition has a well defined set of rules for any robot entered. In actuality it would be possible to create a robot whose components/ abilities reside outside of these rules, but it would be ethically irresponsible to do so. One must be honest and prudent about citing all parts, algorithms, and writings not of his or her personal design.

F. Health and Safety

The safety of anyone who handles the robot needs to taken into account. The robot needs to be properly grounded and wires need to be covered to prevent any shock hazards. The robot will run on batteries, which need to be checked often to prevent any damage or leaking.

G. Social

There are always social constraints that accompany any design project. The social goal of this project is to make a positive impact within the EE/ECE department; it has the ability to stimulate interest of current and future students. The robot may participate in the IEEE maze competition next April, where it would represent Montana State University. Hopefully with this public exposure, the project will bring positive attention to the University.

H. Political

The political ramifications of the Micromouse robot need to be taken into account for the entire lifecycle of the design process. When choosing components, it is important to know where each component is coming from and know if the political climate in that country is favorable to US national security. When publishing information about the robot, it is also important to keep in mind the regulations imposed by ITAR (International Traffic in Arms Regulations). While unlikely, it is possible that some of the technologies present on the robot are export controlled. For example, some types of analog to digital converters are covered under ITAR.

I. Time

This project is restricted to a single semester, or 15 weeks, from conception to delivery. This is one of the most important constraints of the entire project. To mitigate this constraint as much as possible, milestones were developed to help keep the project on schedule. The milestones were scheduled such that there is extra time to allow for unforeseen obstacles. In addition, the robot is being constructed with a frame, PCB, and microcontroller borrowed from the ECEBOT. This plus the addition of sensors which are designed to be easily integrated, make for a rapid development cycle.

III. CONCLUSION

In summary, many factors contribute to the design of the Micromouse robot. These factors include economic, environmental, sustainability, manufacturability, ethical, health and safety, social, political, and time constraints. All the constraints must be taken into account for the project to be completed satisfactorily.

ACKNOWLEDGMENTS

The design team would like to thank the Electrical and Computer Engineering Department at Montana State University, the IEEE Montana Chapter, Dr. Hongwei Gao and our advisor, Mr. Randy Larimer.


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