Transcript Slide 1
TEAM SOLBOT CRITICAL DESIGN REVIEW Martin Carbajal Curtis Porter Mike Mellman Erik Zurinskas Project Description Review Solar Operated Lawnmower Bot Our project is a battery powered automatic lawn mower The user will be able to wirelessly control the mower along a desired path The mower will record the path and be able to autonomously replicate the user’s mowing process High Level View Microcontroller Design Microcontroller MSP430F2418 • Low power for a wireless/remote system Zigbee/RF optimized AD converter for input/output control Code Composer development environment Compass 3-Axis Compass HMC6343 Mounted on microcontroller PCB I2C communication to microcontroller at pins 30 and 31 Outputs 3 bytes of data: heading, pitch, and roll Typical 2° Heading Accuracy with 1° Pitch and Roll Accuracy On breakout board due to size of chip Compass Functionality Wireless Communications The Xbee will provide communications between our computer and the lawn mower Initiation of lawn mower via computer Send a ‘*’ if tilt data exceeds a predetermined safety value, which will shut off all power to mower and, when received at computer, will display warning message Sending to microcontroller through RS232 ASCII characters at a baud rate of 9600bps The Xbee module will be hooked up on pins 32 and 33 of the microcontroller For testing with the USB to Xbee we are using X-CTU software that came with the Xbee XBee UART Data Flow Microcontroller UART code Demo of Microcontroller and Xbee Communication Software Code Composer will be the development environment Computer will be used to load code to microcontroller on mower through JTAG connection Software receives characters and based on which character it will perform the various functions (speed, brake, direction, and blade motor) Currently working on the path recording Error correction with compass and velocity records Motor Control Circuit Schematic Prototype Motor Control Board LMD18200 H-Bridge Rated to 55V & 3A, which will allow control of different sized motors Our project will use 20V supply and ~0.3A per motor Input from microcontroller is PWM signal (PWM square wave) & direction/brake (high/low logic signals) Change in duty cycle will vary motor speed Optoisolators PS2501 Photocoupler (16 pin DIP) has 4 separate optoisolators Used to electrically isolate the control signals from motor control board, which prevents noise from motors getting onto microcontroller board To Motor Board From Microcontroller Board Demo of Motor Control Board Chassis Constructed small prototype with small DC motors to test and debug motor control circuit Will scale up to full sized lawn mower chassis with larger motors Drive Motors Prototype uses small DC motors Final version will be Pittman GM9236S018 DC motors Peak Torque = 6.1 N-m No-Load Current 0.33 A Mower Motor We will use a single DC motor that will spin faster than the drive motors Motor is controlled (on/off signal) from microcontroller using two MOSFETS Will also run on 20V supply and use ~0.3A Power Supply Microcontroller board will be run off of a 12V (7.5 AH) battery which is regulated at 3.3V using an LM317 voltage regulator Motor control board will be run off of a 24V (12 AH) battery which will have two regulated supplies: 3.3V for optoisolator control voltage and 20V for motor supply voltages Solar Power System (tentative) Small solar (RV) panel continuously charges 24V battery at charging station When mower returns to charging station, the on-board batteries are recharged Updated Project Cost Part Vendor Price (USD) Microcontroller TI samples Free Xbee Sparkfun.com $100 Compass Sparkfun.com $150 Chassis Retrofit existing model Free Wheels TBD $50 Wheel Encoders Sparkfun.com $30 Drive Motors Pittman $100 Mower Motor Pittman $50 Mower Batteries Donation Free Base Station Battery Donation Free Solar Panel Siliconsolar.com $130 Misc. Components EE store / Sparkfun.com $100 PC Boards TBD ~$100 TOTAL $810 Updated Division of Labor TASK CURTIS ERIK MARTIN MIKE Hardware Frame retrofit X X Motor Control X X Power system design X X RF Communication design X X PCB Layout X X X X Electronics mounting/soldering X X X X Microcontroller path control X X Communication coding X X Memory management X X System testing X X X X Preliminary User’s Manual X X X X Final Technical Manual X X X X Final User’s Manual X X X X Software Documentation Updated Schedule Critical Dates Milestone 1 Complete control of mower from computer Milestone 2 Record a given path and be able to reasonably reproduce path Expo Fully completed mower with all hardware mounted and functional path reproduction Any possible additional features that time permits Questions?