December 2, 2004Aaron Ard and Jeremy Skipper1 Competitive Inhibition by Aaron M. Ard and Jeremy W. Skipper

December 2, 2004Aaron Ard and Jeremy Skipper2 Introduction Three Main Topics Design Goals and Requirements Electrical Design Mechanical Design

December 2, 2004Aaron Ard and Jeremy Skipper3 Goals and Requirements Goals: Win Tiger Scramble Receive an “A” Provide a basis and example for future participants in EE 4701 Requirements: Build a working robot Remain within allocated budget of $ Ensure that our robot is the fastest, “smartest”, most efficient, and most reliable

December 2, 2004Aaron Ard and Jeremy Skipper4 Preliminary Design Primary Systems Electrical –Boards, Microcontroller, Power, AI, Controls, RF, Sensors Mechanical –Motors, Gearing, Wheels, Platform, Ball Manipulator, Actuator

December 2, 2004Aaron Ard and Jeremy Skipper5 Electrical Overview

December 2, 2004Aaron Ard and Jeremy Skipper6 Microcontrollers Requirement: The microcontroller(s) must provide enough I/O, speed, memory, etc. Solution: Microchip’s 18F452 for the main microcontroller and two 18F2431’s for motor control

December 2, 2004Aaron Ard and Jeremy Skipper7 Microcontrollers Features Microchip 18F452Microchip 18F2431 Max. Clock Frequency (MHz) 40 Flash Memory (Bytes) PWM YES A/D 8/10-Bit5/10-Bit Encoder Interface NOYES Serial Interfaces USART, I2C, SPI I/O Pins 3422 Package 44-Pin PLCC28-Pin DIP The main features of each MCU

December 2, 2004Aaron Ard and Jeremy Skipper8 Motors Requirement: The entry must move a minimum of.12 meters per second. Solution: COPAL 30:1 DC Gearmotor 6-12 volts in-oz max torque max rpm 1.3A stall current.78 m/s (w/ chosen tires) Image from

December 2, 2004Aaron Ard and Jeremy Skipper9 Motor Control Low level motor control performed by two independent 18F2431’s –Quadrature input from encoders –Receive required speed from main MCU –Transmit distance traveled to main MCU High level motor control performed by the 18F452 –Calculate required speed and direction of each motor to arrive at target –Implements “dead reckoning” with distance data from the 18F2431’s

December 2, 2004Aaron Ard and Jeremy Skipper10 Encoders Requirement: The entry must provide feedback on motor performance. Solution: US-Digital S4 optical rotary quadrature encoder Image from

December 2, 2004Aaron Ard and Jeremy Skipper11 Motor Drivers Requirement: The entry must have the ability to drive two DC motors simultaneously. Solution: Texas Instruments TPIC0107B PWM controlled intelligent H-Bridge 0-33V supply voltage 5A internal current shutdown Direction input

December 2, 2004Aaron Ard and Jeremy Skipper12 RF Communication Requirement: The entry must receive data from the vision system on ball and robot locations. Solution: MHz RF receiver from Parallax provided to each team Image from

December 2, 2004Aaron Ard and Jeremy Skipper13 Local Sensors Requirement: The entry must eliminate vision system error, if present. Solution: Sharp GP2D120 IR sensor Analog voltage corresponding to distance 4-30cm (~12 in) range Image from

December 2, 2004Aaron Ard and Jeremy Skipper14 Local Sensors (cont.) Requirement: The entry must know when the tennis ball is within the capture mechanism. Solution: Two crossing bend (flex) sensors 4 1/2” x 1/4” in 0° 90° Image from

December 2, 2004Aaron Ard and Jeremy Skipper15 PCB Board Requirement: The entry must reliably and efficiently connect components together. Solution: 4-Layer PCB board Designed in Cadence Capture and Layout Parts securely soldered in place 4-Layer board reduces long and unnecessary traces

December 2, 2004Aaron Ard and Jeremy Skipper16 Power Requirements: The entry must operate continuously for 15 minutes. Copal motor requires 6V-12V for operation. Solution: 9.6V 1600 mAh Ni-MH rechargeable RC car battery. As shown below, this battery will operate the robot continuously for over an hour. DeviceCurrent DC Motors250mA Servo250mA PCB Board100mA IR sensor50mA Encoders20mA TOTAL:670mA

December 2, 2004Aaron Ard and Jeremy Skipper17 Power (cont.) Requirement: The entry must provide a regulated 5V supply for the MCU board and servo. Solution: National Instruments LM2676 switching regulator 3A current output 94% efficiency ON/OFF pin Available in common TO-220 package

December 2, 2004Aaron Ard and Jeremy Skipper18 Locomotion Requirement: The entry must have the ability to take the shortest path possible between any two points. Solution: Differential steering will enable the entry to move forward and backward as well as turn in place.

December 2, 2004Aaron Ard and Jeremy Skipper19 Wheels Requirement: The entry must have wheels with a diameter to complement the gearing of the motor and allow only minimal slip. Solution: Solid rubber wheels with rib pattern 1 1/2” diameter 1/16” axle.65 oz Image from

December 2, 2004Aaron Ard and Jeremy Skipper20 Casters Requirement: The entry must stay balanced while moving freely in any direction dictated by the motor-driven wheels. Solution: Omni-directional caster Omni-directional rotation 2” diameter 8mm axle Image from

December 2, 2004Aaron Ard and Jeremy Skipper21 Base Requirement: The entry must have a base that protects the wheels and allows for the mounting of other hardware. Solution: Custom made aluminum base

December 2, 2004Aaron Ard and Jeremy Skipper22 Platter Requirement: The entry must have a platter that provides extra space for mounting electronic hardware without the risk of unwanted conduction. Solution: Custom made Plexiglas ® platter

December 2, 2004Aaron Ard and Jeremy Skipper23 Ball Manipulation Requirement: The entry must capture a tennis ball, but continue to allow it to roll freely. Solution: Custom made gripper with actuator

December 2, 2004Aaron Ard and Jeremy Skipper24 Actuator Requirement: The entry must have an actuator that consumes minimal power in the standby state, operates in under 3 seconds, and takes up minimal space. Solution: Hitec HS-85BB+ servo.16 sec/60° at no load 240mA max current drain 29 x 13 x 30mm 42 oz-in torque Image from

December 2, 2004Aaron Ard and Jeremy Skipper25 General Operation

December 2, 2004Aaron Ard and Jeremy Skipper26 Preliminary Budget ItemQuantityCost (Each)Total 4” x 6” PCB Board1$92.40 Copal Gearmotors2$21.99$43.98 Optical Rotary Shaft Quadrature Encoders2$39.99$79.98 Microcontroller1$0.00 TPIC0107B H-Bridge2$0.00 Wheels, Tires, Gears, and Misc. Drive-train PartsN/A$65.00 Misc. Electronics (Caps, Diodes, Regulators, Resistors)N/A$75.00 Servo1$25$25.00 Bend Sensors2$0.00 Infrared Distance Sensors1$12.50 Body made of 1/8” AluminumN/A$0$0.00 TOTAL:$393.86

December 2, 2004Aaron Ard and Jeremy Skipper27 Feedback Questions? Comments? Suggestions? Thank you for your time and attentiveness!