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EE4701 Preliminary Design
Presentation
Ben Maderazo
Justin Smith
Presentation Goals
Present our own requirements analysis
and design decisions for critique
Defend our decisions and explain why
our design will perform better than
others
Prove that we are ready to begin
assembling and testing our robot for
competition
Team Goals
Apply KISS principle in hardware
implementation to save time
Spend more time on algorithm
development and application than
hardware
Win competition
Competition Rules
Each robot must fit within a twelve inch cube
Each match will be the best of three rounds with
each round lasting no longer than fifteen minutes
The ball may be captured, pushed, or kicked into
the goal
Robot and ball position will be monitored by an
overhead camera
To enter into the competition, each robot must
pass preliminary qualification tests
Preliminary Qualifications
Robot must travel from one goal to other and
back in less than two minutes
The robot must capture a ball and return it to
the home goal in under five minutes
The robot must retrieve three balls, one at a
time, and return them to its home goal in
fifteen minutes while avoiding an immobile
obstruction
Robot Subsystems
Information processing
Obstacle detection
Locomotion
RF reception
Ball capture
Power
Information Processing
Subsystem
Must take data from other subsystems,
process it, and issue commands.
Analysis
Speed
Function
# of Times
Instructions
Calculate relative distance
5
10
Check current score
1
15
Check if target ball has moved
1
10
Check if robot is at destination
1
2
Misc.
1
65
Total

~150
Must be done 10x per second
Mathematical Computation


Addition, subtraction, and absolute value
Arc tangent
Requirements
3 input ports for switches
2 A/D converter ports for IR sensors.
2 PWM output ports for H-Bridge.
Ability to send and receive 4 serial
transmissions.
Ability to compute basic math and binary
operations.
Ability to compute the arc tan function.
Ability to use interrupts.
OOPIC
Advantages





Virtual Circuits
Interrupts
Object Oriented Programming
Predefined objects
Unlimited serial ports
Disadvantages

Slower than the PIC
Math Coprocessor
PAK-II

Features
 Communicates Serially
 20Mhz
 Performs sin, cos, tan, inverse functions,
square roots, powers, and many other
functions
Schematics
Obstacle Detection Subsystem
The robot will need to detect objects in
its path to pass the second round of
qualifying.
It is not certain if this will be used
during the contest.
Analysis
Distance Requirements



Robot travels at max 2 ft/s
Estimate .5s for robot to stop after
detection
.5s x 2 ft/s = .5 ft
IR Detector
Advantages

Long Distance
 ~4” to 3’
Disadvantages

Higher power
 Ability to test at set times to save power
RF Reception
RF Reception will be used to receive
data and instructions from the Vision
System.
The part will be supplied by Bryan
Audiffred and there will be little room
for design in this subsystem.
Ball Capture
The robot will be required to capture a
ball, know if the capture was successful,
and secure it.
Requirements
Can only control one ball at a time
Must be able to effectively capture and
release balls
Must be able to provide feedback of
success or failure
Hardware choice
Construct a housing on the robot
chassis that will encase the ball
Use a generic servomotor to close a
gate at the entrance of the housing
Interior is lined with material to reduce
inertia of the tennis ball
IR emitter, receiver pair on sides of the
housing to determine if ball captured
Locomotion Subsystem
Fetching a ball and returning that ball
to a goal requires some type of
locomotion.
Locomotion involves steering, a
propagation system, equipment to drive
the propagation, and control circuitry to
operate the equipment.
Minimum Requirements
Speed of at least 0.14 feet per second.
Ability to alter the heading and direction
of travel.
Ability to stop.
Locomotion: Introduction to
Steering
To compete well in the 6’ x 8’ area,
robots will need a tight turning radius.
The chassis configuration must also be
taken into account when analyzing the
problem of steering.
Locomotion: Steering Analysis
Robot must be able to rotate 360°
without changing its position
Robot must be able to rotate a
minimum of 3° at a time
Locomotion: Steering Hardware
Differential steering system
2 Wheels driven by two separate
motors and 2 casters for support
Use formula Vi / Rt = Vo / (Rt+D) and
derivations to calculate velocities and
turning radii
Steering Hardware Continued
Tires: ‘Lite Flite’ Foam tires have a 3”
diameter and are made of a foam
rubber compound
Chassis Schematics
Locomotion: Introduction to
Motor
Drives the propagation and steering
systems
A good balance of power and precision
is desired
Efficiency considerations must be taken
into account
Locomotion: Motor Requirements
To be competitive with other robots, we
want our robot to travel an average of 1
foot/second.
To achieve this speed with our 3”
wheels, only around 100 rpms are
needed. However, to account for
friction, the motor can be geared down
to increase the torque.
Locomotion: Motor Hardware
2 Mabuchi FA-130RA-2270 motors with
Tamiya 70097 Dual Motor Gear box
The gear box has ratios of 58:1 and
203:1
The motor has an operating range of
1.5-3.0 volts
The stall current is 2 amps
Motor Hardware Continued
At max efficiency, the speed is 6990
rpms. Using the 58:1 gear setting and
3” wheels, the projected speed is 1.6
feet per second. Our goal of 1 foot per
second is easily accomplished with this
motor and gearbox combo.
Motor Schematic
Locomotion: Introduction to
Motor Driver
External circuitry is needed to interface
the motors with the mcu
This circuitry helps the motors run
efficiently and safely
Allows motor to operate at various
RPMs as well as forward and reverse
Locomotion: Motor Drive
Requirements
Drive two motors simultaneously
Must be able to output from 1.5 to 3
volts
Must be able to output up to 2 amps
per motor at stall torque
Locomotion: Motor Driver
Hardware
Lynxmotion Dual H-bridge
All that is needed is to hook up mcu
input lines, motor output lines, motor
power supply, and 5V Vcc
Power: Introduction
Power efficiency much more crucial in
battery powered devices
Batteries can add significant weight
Robot will need adequate voltage and
amp output
Need batteries to power MCU and
motor
Power: Requirements
H-bridge we chose requires 6 volts to drive
the motor and max of 4 amps if both motors
stall
MCU must have voltage regulated to 5 volts
Robot must compete in an undetermined
number of matches so rechargeable or extra
batteries may be needed
Power: Hardware
2 prepackaged Rechargeable Nickel
Metal Hydride battery packs
Smart charger
9V battery with a voltage regulator for
MCU
Power: Hardware continued
Maximum 30 amp discharge rate.
As high as 3000mah capacity nickel
metal hydride.All cells are matched. No
cell memory, you can recharge the pack
without fully discharging
Voltage: 9.6 volts
Power: Hardware continued
2000ma constant output current for any voltage
battery pack
Charging current will reduce to trickle charging at
50mah when battery pack close to full, then green
LED will be on
For 3000 mAh battery pack, charging time is about
90 minutes
Battery Packs and Smart Charger
Budget
OOPIC IC
$26.00
Pak-II
$30.00
IR transmitter
$1.00
IR receiver
$1.00
GP2D12 IR Ranging Module
$18.95
Twin Motor Gearbox Kit
$15.95
Standard Futaba Servo
$15.00
Ball Casters
$8.95
3" Lite Flite Wheels
$4.75
Chassis
$30.00
Lynxmotion H-Bridge
$25.00
Battery Pack
$30.00
PCB Board
$100.00
________________________________________________________________
Total Price
$307.00
Main Process