2.1.3.4 Motors and Wheels 2.1.3.4.1 Introduction The motors and wheels are necessary in order to have MrC follow the user. As previously covered, the motors and wheels are controlled by the tracking subsystem on the main microcontroller. The microcontroller turns and moves forward by a set of relays and by using the 24 V and 12 V power supplies. The maximum speed of this platform needs to be around average human walking speed which is approximately 3 MPH in this case. In order to achieve this speed, a host of calculations needed to be done in order to figure out exactly what wheel size and speed is necessary. Next a motor with a proper amount torque needed to be found. Again, a host of calculations needed to be done to figure out the minimum amount of torque needed for this application. 2.1.3.4.2 Implementation The first and foremost calculation was to determine the speed at which the wheel had to turn in order to move at the designated 3 MPH. First, the wheels that come with the motors are 8 inches in diameter, so using this as the basis for calculations was a good measurement to use initially. Using this, the circumference of the wheel was calculated as: Using this equation, the circumference of the wheel was 25.13 inches. From here the distance that needed to be traveled per second can be found using the following equation: After doing this calculation the distance that needed to be traversed in a second was 4.4 ft/sec. Since the wheel itself was 25.13 in, this meant that the conversion to 2.01 ft. After figuring this conversion, the rotation rate of the motor needed to be calculated. This calculation is calculated as follows: * 60 sec After doing this calculation the rotation rate was found to be 131 RPM. Next the torque of the motor that was necessary to drive MrC was determined. First, a weight for propulsion needed to be decided on. For the purposes of this project 100 lbs was assumed for the weight of the total project. Using this as a basis the calculation of the torque was as follows:
Microchip Corporation, “PIC18F87J10 Data Sheet”. [Online]. http://ww1.microchip.com/downloads/en/DeviceDoc/39663D.pdf Microchip Corporation, “PIC18F4515 Data Sheet”. [Online]. http://ww1.microchip.com/downloads/en/DeviceDoc/39636d.pdf Microchip Corporation, “PIC18F45K20 Data Sheet”. [Online]. http://ww1.microchip.com/downloads/en/DeviceDoc/41303G.pdf Microchip Corporation, “MCP23S17 Data Sheet”. [Online]. http://ww1.microchip.com/downloads/en/DeviceDoc/21952b.pdf 7.2.2 Voice-Control Components Knowles Acoustics, “Digital SiSonic Microphone Specification”. [Online]. Hualon Microelectronic Corporation, “HM2007 Speech Recognition”. [Online]. http://www.sunrom.com/files/HM2007.pdf 7.2.3 Musical Subsystem Components Crystalfontz America, Incorporated, “Serial LCD Module Specifications”. [Online]. Crystalfontz America, Incorporated, “Specification For LCD Module CFAF320240F-T-TS”. [Online]. Sanyo Semiconductors, “LV4230LP-A Bi-CMOS LSI Compact Portable Equipment 1-Chip FM Tuner IC”. [Online]. TyMPHany, “TyMPHany LAT 250 Subwoofer” [Online]. http://www.tyMPHany.com/datasheet/pdf/LAT250-001.pdf HiVi Incorporated, “DMN Dome Midrange”. [Online]. TyMPHany, “BC/OC 1” Tweeter”. [Online]. http://www.tyMPHany.com/datasheet/pdf/BC25SC55-04.pdf