EECS for Speed

EECS373 Winter 2009 - Final Project

Team members and tasks performed:

Introduction

We have created a ‘Need for Speed’ type game, where one vehicle is in pursuit of another vehicle.  In our case we had a vehicle that is remotely controlled by a user (the runner) and a vehicle that is controlled by a MPC 555 mobile microprocessor (the chaser). 

 

The objective of this game for you as a player is to run away from the AI vehicle which will follow a beacon that is attached to your RC-controlled vehicle.  You are scored based on how well you dodge the pursuer.  While the game is running, we have programmed and integrated our 4-line character LCD display to display the game status.  The game has been configured to run for 3 minutes, which can be adjusted.  The software will keep track of your score while the game is running and when the game over condition is reached (3 minutes elapsed), proper game over message will appear and will display 3 highest top scores.  The game scoring system will be discussed in detail below under Software Component Section.

 

The major functions:

 

1)      Upload software to flash memory in MPC555.

2)      AI vehicle running on MPC555 will take inputs from an IR sensor beacon system and 3 ultrasonic sensors in order to chase the user-controlled vehicle

3)      The game software in the AI vehicle will keep track of how well you are evading the pursuer to calculate your final at the end of the game.

4)      When the game ends after a certain time, display a message on an LCD display attached to the AI-vehicle to notify the user that the game has finished.

High Level Design

Hardware Design

Due to the fact that the MPC555 does not involve a FPGA, the hardware design was focused primarily on building the AI vehicle.  We have mounted our MPC555 on the flat surface located in the middle of our vehicle as shown in the picture below.  Then, we have mounted our 3 sensors in front, left, and right side of our vehicle.  Our beacon system consisted of a receiver and transmitter, where the receiver was mounted on our vehicle and the transmitter was mounted on our human controlled RC vehicle.  In addition, we have mounted our character display LCD screen on the back of our AI vehicle to display the status of the game while the game is in session as well as its score when the game over condition is reached. 

All the above-mentioned hardware components were wired to the corresponding pins in the MPC555.  As for the servo and the motor, we have created a power supply circuit using a breadboard.  Furthermore, we have created two separate breadboards specially dedicated to powering and controlling the 4 LEDs which were mounted on the vehicle to provide the feel of a police vehicle in pursuit.

As for our beacon system, we have implemented an IR beacon system developed by a company named Pololu.  The Pololu IR Beacon System consists of a pair of identical IR beacons.  Each IR beacon consists of 4 IR sensors that detect high intensity IR produced by the other IR beacon and outputs its direction in North, South, East, and West.

Software Design

Most of our work in this project was dedicated in designing the software.  The major components of our software design are as follows:

1. PWM for 3 ultrasonic sensors, a servo, and a DC motor.

2. Vehicle control algorithm

3. Game status output to LCD display

When the MPC 555 is powered on, our software will be loaded from the flash memory, automatically initiating the game sequence.  At the start-up of the game, the program will be in a wait state while constantly polling to see if a push button is pressed.  The player will be prompted to press the push button to begin the game via LCD display.

Our vehicle control algorithm was based on the input values from the 3 ultrasonic sensors and the beacon system.  The software first checks to see which direction the human controlled RC vehicle is located with respect to the current position of the MPC555 controlled vehicle.  Once it has determined which direction the vehicle is located, it will then look at the sensor values to see how fast it should rotate the motor (motor speed) and how much it should turn the wheel (servo angle).  Instead of measuring the exact distance of the human controlled vehicle, we have used the time values generated by the ultrasonic sensors as references to determining the distance.  The measurements and their corresponding approximate distance are summarized in the table shown below.

When the beacon system is turned off or the vehicles are out of the detectable range of the IR sensors on the beacons, the vehicle software will enter ‘recovery mode’ where the vehicle will propel on its own while dodging the obstacles on its way until it senses the beacon values again to start pursuing the human controlled vehicle again.

While the game is running, the 4-line character LCD display will show the current score and the time remaining.  We have created global variables to store and display the score and the time remaining in real-time on the LCD display.  Once the game is finished, the software will determine how well you have been dodging away from the AI-controlled vehicle based on the score and display corresponding messages on the LCD display.  The list of possible messages is as follows.

1. If score is less than 5000 points

            “YOU NEED MORE PRACTICE”

2. If score is greater than 5000 points

            “YOU ARE PRETTY GOOD”

3. If score is larger than one of the three high scores

            “NEW EECS FOR SPEED MASTER”

                        “WE ARE PROUD”

After displaying the appropriate message, the LCD display will show the 3 high scores which will be updated accordingly. 

Conclusions

Due to the fact that our vehicles depended on the beacon system to operate properly, it required sufficiently large space with low IR noise.  Under such environment, our vehicle operated well.

Given more time, we would have improved our motor control by implementing a H-bridge to allow backward movement.  The backward movement would have allowed our MPC555 controlled vehicle to be able to dodge its obstacles better and even allow the vehicle to escape from corner conditions (when the vehicle is stuck in a corner).

Media

Under construction