Team GPS Rover
Critical Design Review
Alex Waskiewicz
Andrew Bousky
Baird McKevitt
Dan Regelson
Zach Hornback
Overview

Project Description
 Hardware Implementation
 Software Implementation
 Milestones
 Risks and Contingencies
PROJECT DESCRIPTION
Project Goals

The human user will be able to remotely control the rover from a
laptop computer
– Direct driving control
– Issue location commands







Rover will calculate its current bearing
Rover will calculate desired bearing to user specified location
Rover will autonomously maneuver to its assigned destination
Rover will transmit telemetry to the user
Rover will sense and avoid obstacles
Rover could have onboard camera(s) providing visual feedback to user.
Rover could carry and deploy instrumentation packages
– Examples:



Rocket launch platform
Environmental sensors
Mechanical Manipulator
HARDWARE IMPLEMENTATION
VEHICLE


Traxxas Rustler
– 445x311x178 mm
– 1.69 kg
– Top Speed 35 mph
– $203 with batteries
– High Load Capacity
– Replaceable parts
Electronics Platform
– Attaches to the chassis
– Carries electronics, sensors, and batteries
– Interfaces directly with car controls
– Weight and Size are constraints
Test: Steering and Driving

The steering and speed of the vehicle can be controlled
using the PWMs of the microcontroller.
 Both are controlled by altering the duty cycle of the
input square wave.
– The wave (for both steering and speed) has an amplitude of
4.2 Volts and a frequency of 49.75Hz
•The duty cycles for steering are:
•Straight – 7.72%
•Full Left – 10.21%
•Full Right – 5.37%
•The duty cycles for driving are:
•Idle – 7.46%
•Full Forward – 9.95%
•Full Reverse – 4.71 %
Hardware Block Diagram
Digital
Compass
GPS
Module
User PC
SCI
SCI
Module Module
I2C
Microcontroller
Module
Proximity
Sensors
PWM PWM
Module Module
Drive Steering
Motor Motor
Test: GPS Parts




Serial communication
OOB
Acquired outside signal
Impressive spatial
resolution (probably to
WAAS enable)
1 Hz update rate
– Documentation says
modifiable and/or queryable but currently having
technical difficulties
Digital Compass

$60
 ½ degree resolution
 I2C interface
 Testing will be
imminent once I2C
communication on the
development board is
established
Sensors

Two-forward facing sensors to allow obstacle
avoidance
 Ultrasonic: 2 x Devantech SRF08 Ranger ($62)



6m range
I2C interface
Testing will be imminent once I2C communication
on the development board is established
Development Board

Serial Ports
 LCD
 DIP Switches
 LEDs
 Shaft Encoder
 Mini-Breadboard
 Great for testing!
Power Subsystem

3.3V, 5V systems
 Need to pick battery
 Use of 2 voltage regulators
– Need to pick type

Will be implemented upon completion of
PCB fabrication
– Due to development board usefulness
Microcontroller: Freescale
HCS08

60K of low-speed Flash
 4K of internal ram – Requires no external
routing
 Internal A/D
 Internal PWM
 3.3V
Microcontroller: Freescale HCS08
Memory Map
Internal
module
status/comm
registers
Preliminary PCB Layout:
PCB:
US1
US2
GPS
4
4
6
•Microcontroller
•RF link
•Voltage Regulators: Power Bus
•Caps/Resistors
V/R
Power
Altium Schematic
SOFTWARE IMPLEMENTATION
User Interface
Data Flow Diagram
HCS08 Hardware Interfaces
Application Functions
MILESTONES
Milestone #1
(Implementation Cycle 1)

User control with
Arrow Keys
– Serial
Communication
(tethered)
– Independent PWM
Control
– Windows-based GUI

Why?
– Tests many
subsystems that are
required for GPS
Control (i.e.
Milestone #2)
Milestone #2
(Implementation Cycle 2)

GPS Feedback
– GPS
communication
– Digital
Compass
communication
(IIC)
– Bearing
calculation
Implementation Cycle 3

Obstacle Avoidance
– Left and Right
Sensors with
minimal common
FOV
– Left and Right
allows for an easy
avoidance algorithm



Left sensor = high
 go Right
Right sensor =
high  go Left
Both = high 
requires long
range detection to
avoid
DIVISION OF LABOR AND
RESPONSIBILITIES
ALEX
•Windows XP
GUI
•Development
board testing
•Implement
control
software
•GPS Module
ANDREW
BAIRD
DAN
ZACH
•Schematic
& PCB
layout
•Digital
compass
•Schematic
and PCB
layout
•GPS
module
•Chassis
Fabrication
•Power
Sub-system
•Ultrasonic
Sensors
•Documenta
tion
•Chassis
Fabrication
•PWM
interface
•Power
sub-system
•Implement
control
software
•Developm
ent board
testing
SCHEDULE
RISKS AND CONTINGENCY
PLAN
Updated Risks and Contingency



•
•
•
•
•
Parts availability and shipping times
We have purchased many of our discrete
components
The car interface is electrically simple
Interfacing I2C components
Microcontroller RAM/Storage limitations
RF Link
Learning curve on design software (CodeWarrior
& Altium)
Power Consumption
Questions?