december 2, 2004aaron ard and jeremy skipper1 competitive inhibition by aaron m. ard and jeremy w....

December 2, 2004 Aaron Ard and Jeremy Skipper 1

Competitive Inhibition

byAaron M. Ard

andJeremy W. Skipper


Introduction

Three Main Topics

• Design Goals and Requirements

• Electrical Design

• Mechanical Design


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 $500.00• Ensure that our robot is the fastest, “smartest”, most efficient, and

most reliable


Preliminary Design

Primary Systems

• Electrical– Boards, Microcontroller, Power, AI, Controls, RF, Sensors

• Mechanical– Motors, Gearing, Wheels, Platform, Ball Manipulator, Actuator


Electrical Overview


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


Microcontrollers

Features Microchip 18F452 Microchip 18F2431

Max. Clock Frequency (MHz) 40 40

Flash Memory (Bytes) 32768 16384

PWM YES YES

A/D 8/10-Bit 5/10-Bit

Encoder Interface NO YES

Serial Interfaces USART, I2C, SPI USART, I2C, SPI

I/O Pins 34 22

Package 44-Pin PLCC 28-Pin DIP

The main features of each MCU


Motors

Requirement: The entry must move a minimum of .12 meters per second.

Solution: COPAL 30:1 DC Gearmotor

• 6-12 volts• 29-52 in-oz max torque• 390-770 max rpm• 1.3A stall current• .78 m/s (w/ chosen tires)

Image from www.robotcombat.com


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


Encoders

Requirement: The entry must provide feedback on motor performance.

Solution: US-Digital S4 optical rotary quadrature encoder

Image from www.usdigital.com


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


RF Communication

Requirement: The entry must receive data from the vision system on ball and robot locations.

Solution: 433.92 MHz RF receiver from Parallax provided to each team

Image from www.parallax.com


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 fromwww.acroname.com


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• 75k-80kΩ @ 0°• 150k-200kΩ @ 90°

Image from www.imagesco.com


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


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.

Device Current

DC Motors 250mA

Servo 250mA

PCB Board 100mA

IR sensor 50mA

Encoders 20mA

TOTAL: 670mA


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


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.


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

www.robotcombat.com


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 www.imagesco.com


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


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


Ball Manipulation

Requirement: The entry must capture a tennis ball, but continue to allow it to roll freely.

Solution: Custom made gripper with actuator


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

www.servocity.com


General Operation


Preliminary Budget

Item Quantity Cost (Each) Total

4” x 6” PCB Board 1 $92.40 $92.40

Copal Gearmotors 2 $21.99 $43.98

Optical Rotary Shaft Quadrature Encoders 2 $39.99 $79.98

Microcontroller 1 $0.00 $0.00

TPIC0107B H-Bridge 2 $0.00 $0.00

Wheels, Tires, Gears, and Misc. Drive-train Parts N/A $65.00 $65.00

Misc. Electronics (Caps, Diodes, Regulators, Resistors) N/A $75.00 $75.00

Servo 1 $25 $25.00

Bend Sensors 2 $0.00 $0.00

Infrared Distance Sensors 1 $12.50 $12.50

Body made of 1/8” Aluminum N/A $0 $0.00

TOTAL: $393.86


Feedback

• Questions?

• Comments?

• Suggestions?

Thank you for your time and attentiveness!

december 2, 2004aaron ard and jeremy skipper1 competitive inhibition by aaron m. ard and jeremy w....

Documents

aaron ard

motor control slide

mcu slide

18f2431s slide

actuator slide

skipper slide

reliable slide

jeremy skipper3 goals