Filip Maksimovic
Viliam Klein
Peter Zhang
Corrina Gibson
Brandon Benjamin
Vicki Hsu
Elliott Richerson
Tyson Wolach
John Jakes
Aerospace Advisor:
Scott Palo
Critical Design Review
February 2, 2011
XROVER CDR
Introduction
• JPL funded project with the
Aerospace department
• Goals are to explore feasibility of
using multi-rover configurations for
extraterrestrial exploration
• Our system architecture has one
mother rover and two deployable
child rovers
• Continuation of a project started
two years ago
Objectives
Objective
The system maintains former capabilities
from REMUS and R3
Description
• CRs can deploy and dock from MR.
• CRs can drive to LOI and capture
images that are transmitted back to
the GS.
Relaying between MR and CRs for data
transfer
• Mission CR will explore behind
locations where maintaining
communication with MR will be
through relay.
MR and CR can traverse defined terrain
• CRs will maintain communication with
MR at various orientations and
altitudes.
• CRs will deploy and dock on flat
terrain.
Terrain Definition
• 20 degree slopes (CR only)
• 1 inch rises/discontinuities
• 2 inch depth pea gravel surface
(slipping assumed)
Concept of Operations
Location of Interest
(LOI) Identified
Relay Ability
Confirmed
Rover Mission Sent
to MR
MR to deployment location
CR Status and Data
Evaluated
Relay CR
Commands Sent to
CRs
dock
&
undock
Mother Rover (MR)
Ground Station
Mother Rover
C&DH
Child Rovers
Relay Area
Terrain
Location of Interest
Concept of Operations
Location of Interest
(LOI) Identified
Relay Ability
Confirmed
Rover Mission Sent
to MR
C&DH
Relay
Waypoint
Relay CR and MR
Communication
CR Status and Data
Evaluated
Relay CR
Commands Sent to
CRs
dock
&
undock
Mother Rover (MR)
Ground Station
Mother Rover
C&DH
Child Rovers
Relay Area
Terrain
Location of Interest
Concept of Operations
Location of Interest
(LOI) Identified
Relay Ability
Confirmed
Rover Mission Sent
to MR
C&DH
Relay
Waypoint
Relay CR and MR
Communication
CR Status and Data
Evaluated
Relay CR
Commands Sent to
CRs
dock
&
undock
Mission CR
Mother Rover (MR)
Ground Station
Mother Rover
C&DH
Child Rovers
Relay Area
Terrain
Location of Interest
Concept of Operations
boundary of communication
Location of Interest
(LOI) Identified
LOI
C&DH
Image Obtained by
Mission CR
Relay Ability
Confirmed
Mission CR Position
Evaluated
Rover Mission Sent
to MR
Terrain
isolated
travel
Mission CR and
Relay CR Comm.
Relay
Waypoint
Relay CR and MR
Communication
CR Status and Data
Evaluated
Relay CR
Commands Sent to
CRs
dock
&
undock
Mission CR
Mother Rover (MR)
Ground Station
Mother Rover
C&DH
Child Rovers
Relay Area
Terrain
Location of Interest
Electronics Functional Block Diagram
Ground Station
Mother Rover
GUI
Computer
User inputs ‘waypoints’ to control
child rovers
Child Rover
Motor Control,
Interrupt
Desired
Location
CDH
Wireless
Router
Power
Position
Navigation
Power
Wireless
Router
CR
Drive
MR
Drive
CDH
Wireless
Router
USB
RS232
Wireless
Network
Wireless
Router
Motor Control,
Interrupt
User Input
Power
Child Rover
Desired
Location
CDH
Power
Position
Navigation
CR
Drive
Child Rover Functional Block Diagram
Child Rover
5V
Wireless
Router
Power
Interrupt, Request Data
Desired Location
Data
5V
CDH
Navigation Data
Sensors
Power
5V/12V
CR Drive
RS232
Motor Drive
Child Rover Drive Subsystem
Functional Decomposition
Module
Child Rover Drive
Inputs
• 5V @ 50mA from power system
• 12V @ 2A max from power system
• OneRS232 drive signal from CDH board
Outputs
• Child Rover movement
Functionality
This drive subsystem receives an RS232
motor control command. The motor
controllers have convert the serial
command to rotate the 12V motors.
Child Rover Drive Subsystem Block Diagram
RS232
5V/12V
Motor voltages
Child Rover Drive Subsystem
Further Functional Decomposition
Module
Motor Controller (Pololu qik2s9v1)
Inputs
• 5V @ 50mA from power system
• 12V @ 2A max from power system
• One RS232 drive signal from CDH board
Outputs
• Motor Voltages @ 1A max each
Functionality
Two controllers can control two motors each. They
can be daisy-chained along the same RS232 line
and commands are issued to each motor
individually. The motor voltages determine speed.
Module
DC Motor (Pololu 19:1 Metal Gearmotor)
Inputs
• Motor Voltages @ 1A each
Outputs
• Child Rover movement
Functionality
The DC motor receives a voltage and spins. The
stall current is 5A, but the controller has a current
limiter to prevent excessive draw.
Sensors Functional Decomposition
Module
Child Rover Navigation Sensors
Inputs
• 5V from battery
• The world
Outputs
• 4x quadrature from encoders
• 2x indexed quadrature from encoders
• 3-axis accelerometer ±18g (IMU)
• Triaxial digital gyroscope ±75 o/sec (IMU)
• 3-axis magnetometer (cheating)
• Range from 2 ultrasonic crickets
Functionality
The child rover sensors provide data to
the CDH for processing to determine the
CR’s position and orientation.
Further Sensor Functional Decomposition
Module
Inputs
Outputs
Functionality
Module
Inputs
Outputs
Functionality
Module
Inputs
Outputs
Functionality
Analog Devices IMU
• 5V from Power system
• Configuration settings from CDH
• 3-axis accelerometer, gyro, and magnetometer (unused)
• All available on an SPI line (depending on configuration settings)
The IMU provides highly accurate angular and linear acceleration experienced by
the child rover. Downsides are thermal noise and (usually) linear gyro drift
US Digital 100CPR Free Wheel Encoder
• 5V from Power system
• Indexed quadrature related to the distance that one of the two free wheels has
travelled
These optical encoders spin when the wheels move. Based on this movement, the
output is a quadrature line that can easily be converted to a count. These encoders
also include an index line which goes high for one cycle when the encoder detects
one revolution.
Pololu 64CPR 19:1 Encoder (comes with motor)
• 5V from Power system
• Quadrature related to the distance that one of the corner wheels has travelled
These encoders spin when the wheels move. Based on this movement, the output
is a quadrature line that can easily be converted to a count. Because of the gear
ratio, these encoders spin 19 times faster that the motor shafts.
A
o
em
D
n
Ge
Ge
n
D
em
o
1
e
Tim
TimeGen Demo
Tim
eG
en
De
mo
Quadrature
2
e
Tim
TimeGen Demo
Tim
eG
en
De
mo
mo
De
en
eG
Tim
TimeGen Demo
Tim
e
mo
De
en
eG
Tim
TimeGen Demo
Tim
e
Index
4
mo
De
n
Ge
o
m
e
en D
Ge
n
De
mo
G
e
m
i
T
B
3
5
6
7
8
9
10
o
m
e
en D
G
e
m
i
T
TimeGen Lite
• Quadrature encoders have an A line and a B line 90o out of phase
• Phase lead/lag is used to determine whether shaft is rotating
clockwise or counter-clockwise
• Frequency of signals can be used to determine rotation rate
• If encoder spins too quickly, sometimes counter will miss a count
resulting in erroneous reading
• Index line signals whenever one revolution has completed and
can be used to “zero out” the encoder count to remedy the missedcounts problem
Rangefinding Crickets
Power System Functional Decomposition
Module
Child Rover Power
Inputs
• 14.4V from Li-ion battery
• 4x1.5V from AAA batteries
Outputs
• 5V to motor controllers
• 5V to logic, sensors (separate)
• 12V to motors
Functionality
The power system must provide regulated
voltages to all of the electronic
components on the child rover. It must
also keep the motor lines voltages
separate from the logic and sensor
voltages
Power System Block Diagram
5V
14.4V Li-ion
Motor
Controllers
Pico PSU
12V
5V
5V
Gumstix
Crickets,
Webcam
Electronic Isolation
6V AAA
Linear
Regulator
5V
5V
I/O Expander
Sensors
Onboard
Optoisolator
CDH Functional Decomposition
Module
Child Rover CDH
Inputs
• Desired waypoint from user (via wifi)
• IMU, encoder, and cricket data
• Webcam picture
• 5V from power system
Outputs
• RS232 motor commands to controllers
• Webcam picture to GS via wifi
• CR position measurement
Functionality
The CDH acts as the brain of the child
rover. It closes the navigation loop by
providing a PID controller that moves the
CR based on user input.
CDH Block Diagram
Crickets
Range
Image
Camera
Request
Picture
Interrupt
CR Position,
Image
Gumstix
Computer
Interrupt, Motor
Command
Sensor Data
I/O
Expander
IMU Data
Encoder Data
Requested
Position,
Mission Info
Mesh
Router
USB
SPI Bus
I/O Expander Schematic (rev.1)
I/O Expander Block Diagram
Encoder
Counter
5V Regulator
Aux PSU
Encoder
Counter
Encoder
Counter
SPI
Atmega128
Encoder
Counter
RS232 Motor
Control
Encoder
Counter
USB
IMU
RS232
Encoder
Counter
To
Gumstix
I/O Expander PCB Layout
Revision 2 plans:
• Fix reset pin circuit
• Add VCC, GND pins for all
encoder and motor headers
• Wire the USB properly
• Change LED circuit so that
they are off when line is high
• Move USB and IMU
connectors to same side of
board
mo
De
n
Ge
4
5
6
7
o
em
nD
e
G
8
e
Tim
TimeGen Demo
Tim
eG
en
De
mo
mo
De
en
eG
Tim
TimeGen Demo
Tim
e
o
m
e
en D
mo
De
en
eG
Tim
TimeGen Demo
Tim
e
SS_IMU
3
G
e
nD
em
o
SS_Encoder
2
G
e
nD
em
o
1
Clock
e
Tim
TimeGen Demo
Tim
eG
en
De
mo
SPI Timing Diagram
G
e
m
i
T
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
o
m
e
en D
G
e
m
i
T
MISO
TimeGen Lite
• Both encoders and IMU have continuous data modes
where they will release data while the SS line is held low
• Each encoder has 4 bytes of data, and the IMU can
provide 39 bytes of status registers and data
Additional IMU Timing Information
• Maximum SPI clock is 1MHz
• Minimum stall time is 9
clock cycles (9 µs)
• 600 µs delay between sync
timer and data ready when
specific data is requested
Encoder Counter Circuit
ATMega128
Free/Powered
Wheel Encoder
SPI Protocol
Encoder to Counter
Converter
LS366R 32bit Counter
Each component is
powered by
regulated 5V from
the AUX battery
Aux
Battery
PID Control Simulation
• PID simulation run
in Mathematica to
determine
effectiveness of
controller in
following waypoints
• Input to
simulation is actual
CR position
GUI
Software – Finite State Machine Logic
Docked
mission started
yes
Conn?
no
Wait
Conn?
yes
Rotate to Next
Waypoint
no
Safe
no
Undock
waypoint
?
Calibrate
Switch
COMM
Interface
DEFCON1
no
yes
Relay
rover?
yes
Wait for
Mission CR
Drive
Waypoint
Reached
Returning
?
no
Reverse
Waypoints
yes
no
Returning
?
yes
File
Update
Final
waypoint
returning = true
yes
Rotate to Next
Waypoint
no
Imaging
Rotate to
LOI
no
Returning
?
yes
Mission
Complete
Software – How to determine position
x’’, y’’, z’’
θ‘, ψ’, φ’
r (crickets)
V, r (encoders)
The Black Box
x, y, z, θ, ψ, φ
Wireless Communication
• Must provide communication
between GS, MR, and CRs
• Also must provide relay
communication to a hidden CR
• Solution is an ad-hoc mesh
network to maximize throughput
and minimize packet loss
• These from Alfa Corporation are
wireless mesh routers
• They also come with nice
software showing packet transfer
and were free
Budget
Source
JPL Funding
EEF
Confirmed? [Y/N]
Y
N
Item Name / Description
ASUS Eee PC 1015T-MU17-BK
Black AMD V Series V105
(1.20GHz)
MR Body Materials (aluminum,
screws, nuts, bolts, bearings, etc.)
CR Body Materials (aluminum,
wheels, tires, screws, etc.)
S5 Optical Shaft Encoders
Polulu Qik 2s9v1 Dual Serial Motor
Controller
LFLS7366R-S 32-bit Quadrature
Counter with Serial Interface
100:1 Metal Gear Motor
37Dx57Lmm with 64 CPR Encoder
Atmega128A-AU-ND
PCB
Analog Devices IMU ADIS16360
Cabling and Miscellaneous
Adapters
Test Bed Materials (wood, gravel,
screws, etc.)
Shipping Costs
Printing (fall and spring final reports)
Margin
Total Amount
$5000
$2000
Unit Price
Quantity
Total Amount
$350
1
$350
$800
1
$800
$800
2
$1600
$85
4
$340
$25
3
$75
$6
6
$36
$40
8
$320
$10
$80
$750
2
2
1
$20
$160
$750
$200
1
$200
$300
1
$300
$250
30%
2
Total $
$200
$500
$1670
$7321
Manufacturing Schedule
Milestone 1 Milestone 2
Verification and Testing Schedule
Milestone 1 Milestone 2
Milestone Goals
Milestone 1
Milestone 2
• 2nd revision of board
ordered and populated
• Display functional
interrupt-driven
communication between
Gumstix and I/O expander
• Drive (not navigate) a child
rover
• Confirm reception of data
by Gumstix from IMU,
encoders, and crickets
• Demonstrate wireless
packet transfer over mesh
network through
intermediary node
• Drive child rover with use
input through GUI
• Determination of absolute
position within 10cm with
sensor data and navigation
algorithm
• Complete all physical
construction of electronics
and mechanical hardware