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-1- Boe-Bot Final Project Final Report Mechanical Engineering 224 Professor Espinosa Thursday December 8, 2005 Ashley Nidiffer Tom Cohlmia Eric Yim Scott Moffat-2- Table of Contents I. Introduction II. Boe-Bot Assembly and Servo Adjustment III. Gyroscope Calibration IV. Communication a. Serial b. Wireless V. Programming a. Basic Stamp b. Labview VI. Conclusions Appendices: Appendix A: Gyroscope Calibration Program (BASIC Stamp) Appendix B: HyperTerminal Program (BASIC Stamp) Appendix C: Labview Program to establish Bluetooth Connection with while loops. Appendix D: Labview Program to establish Bluetooth Connection with for loops Appendix E: Calibrated Labview program to establish Bluetooth connection and create a final user interface.-3- Introduction: The goal of this project was to communicate with the Boe-Bot robot such that we could get it to travel along a pre-determined path, such as that seen in figure 1. To do this Figure 1 requires many distinct disciplines (electronics, mechanics, computer programming and wireless communication) working together side by side. The goal is to communicate from the computer to the robot wirelessly in order to inform the robot what path it needs to take. Further, the gyroscope on board the Boe-Bot will communicate, using a closed-loop feedback system, in order to keep the Boe-Bot on a straight path.-4- Boe-Bot Assembly and Servo Adjustment: Fortunately the Boe-Bot came mostly pre-assembled. The main components such as the chassis and board of education had already been connected with four support posts. However, during the process of the project, it was necessary to uninstall and install a new board of education as well as fully secure the servomotors after they had been centered. Centering the servomotors was really the first task for the group. Using the attached BASIC stamp program, we ran each servomotor and adjusted the internal potentiometer so that the motors stopped turning. This provided that PULSOUT 12, 750 would be the center position. The 12 refers to which motor (R or L) and 750 refers the angular velocity. A number higher than 750 would turn the motor one way, while a number below 750 would turn the motor the other way. We next secured the servomotors to the chassis with four screws and attached the wheels to those motors. Now our Boe-Bot was ready to move.-5- Gyroscope Calibration: The gyroscope on board the Boe-Bot outputs a voltage between 0 and 5 volts depending on the angular velocity of the Boe-Bot. The gyroscope outputs a voltage of 2.5 volts at rest and increases this voltage output if the Boe-Bot rotates one way, while decreasing the output with rotation occurs in the opposite direction. In order to make this voltage output useful, we needed to calibrate the gyroscope so that we would know what each voltage value meant in terms of an angular velocity. We first used BASIC stamp to run the program seen in Appendix A to rotate the Boe-Bot at increasing angular velocities. As the Bot rotated, we used Labview to record the voltage outputs of the gyroscope in real-time and write them to an excel file. We rotated the Boe-Bot from the digital velocity values of 700 up to 800 for 20 seconds each. During each trial we recorded the number of Bot rotations such that we could calculate an angular velocity in terms of degrees/second. A sample of the plot obtained from one of Sample Gyroscope Response (Figure 3)020040060080010001200140016001E+091E+091E+091E+091E+091E+091E+091E+091E+091E+091E+091E+091E+091E+091E+091E+091E+091E+091E+09Time (Digital)Digital VoltageSeries2-6- these trials can be seen in Figure 3. We took the average of the voltage readings taken in each trial and plotted them versus the observed Bot angular velocity. This plot, seen in Figure 4, gave a linear relationship between gyroscope voltage output and Boe-Bot-Bot angular velocity. It can easily be seen that this linear relationship is fairly accurate, with an R^2 value of .9889. This information will be needed in using the voltage reading from the gyroscope to predict the actual angular velocity of the Boe-Bot. Gyroscope Calibration (Figure 4)y = 0.451x - 0.3005R2 = 0.988900.511.522.533.544.55-208 -174 -158 -122 -63 0 27 87 116 158 176Angular Velocity (deg/s)Gyroscope Voltage (Volts)Volt vs wLinear (Volt vs w) Communication: Serial Before going on too much further, it is important to document the evolution of communication methods we employed in order to control the Boe-Bot. First, we communicated with the Boe-Bot using the serial cable that came with it. This was mainly used in the beginning of the process in order to load BASIC stamp programming onto the board of education. This form of communication was used in the centering of the servomotors and the gyroscope calibration.-7- Communication: Wireless One of the main challenges of this project was to communicate wirelessly with the Boe-Bot. Today’s society has truly begun to embrace and depend on wireless technology and it is important to understand its format, advantages, as well as shortcomings. Since our group was very unfamiliar with how wireless technology worked, we had to research Bluetooth software and hardware. Bluetooth is the wireless format we are using with our Boe-Bot. After familiarizing ourselves with the software, our first task was to establish a connection with the wireless communication card on the Boe-Bot, the eb500. We were able to do this fairly easily using the USB Bluetooth device and the software that accompanied it. Once a connection was established, we found it quite easy to transmit text wirelessly in “data mode.” Practically speaking, this accomplishment served no purpose other than confirming that a connection had been made and information could in fact be transmitted. The next steps in establishing useful communication with the Boe-Bot will be discussed in the “Programming” section of this document. Programming: Programming was an extremely big part of getting the Boe-Bot to perform the desired tasks involved in the project. The initial programming was done in BASIC Stamp. We discussed these programs earlier, as we used BASIC Stamp in order to center the servomotors. Next, we tackled the problem of actually getting the Boe-Bot to respond to our wireless commands. Using the BASIC stamp program in Appendix B, we-8- were able to get the Boe-Bot to respond to commands we would input in


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