RAppelling Cave Exploration Rover
Advisor:
James Nabity
Customer:
Barbara Streiffert
Critical Design Review
PREVIOUS WORK
2008-2009
• 1st generation
Mother Rover
(MR)
• Optical
navigation
system
• 2 COTS Child
Rover (CR)
a
Overview
2009-2010
2010-2011
• 1st generation CR • 3rd generation MR
• 2nd generation MR • Deployable MR
• 2D ultrasonic
ramp
“cricket”
• Enhanced relay
navigation system COM system
• CR imaging
• 2nd generation CR
system
• CR rocker-bogie
suspension
a
Design
Rappelling
Comm
2011-2012
• 3rd generation CR
• Sample
identification
based on color
• CR sample
collection and
retrieval
Software
2012-2013
2013-2014
• 4th generation MR
• Sample storage
• Multiple CR storage
• Retractable ramp
• LED-based automated
docking system for STARR
Power
V&V
Risks
a
• 4th generation CR
• Ascend/descend
slopes between
30° and 70° using
suction fan
• Dock with
TREADS
Logistics &
Summary
2
PROJECT STATEMENT
• This
project encompasses designing, building, and verifying a
rappelling child rover that can deploy from the legacy TREADS
MR. The mission is to:
• Rappel a 90° surface down 5m into cave/pipe
• Explore up to 5m out from the rappel touchdown point
• Surface has scattered rocks ≤ 3cm diameter
• A GS operator will control CR motion and imaging
• Know its distance travelled and depth within ±10cm
• Return to and re-dock with the MR
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
3
CONOPS
GROUND STATION
COMMANDS
DATA
TETHER
0) Arrival
- CR on MR
1) Deployment (5 min)
- CR undocks
- CR enters cave/pipe
2) Rappelling (15 min)
- CR rappels 5m
- Transitions from
vertical  horizontal
TREADS MR
5
1
3) Exploration (120 min)
- CR traverses 5m
- CR takes/stores
image of POI
NOTE: If comm is dropped
during exploration, the CR will
be retracted by the MR winch
system until comm is restored
2
RACER Mission Timeline:
5
Overview
4
4) Return (15 min)
- CR is retracted by
MR winch system
10cm diameter
POI
3
Margin
RACER Mission Duration: 160 min
15
Margin: 20 min
TOTAL: 180 min
15
120
Design
5) Re-docking (5 min)
- CR re-enters MR bay
Rappelling
Comm
Software
Power
V&V
5
Risks
20
Logistics &
Summary
4
FINAL DESIGN SUMMARY
MR Comm System
2 x 2mW 2.4GHz XBee Radios
Serves as relay between GS&CR
GS Comm System
2mW 2.4GHz XBee Radio
Transmits commands from user
Fixed Rappelling
Attachment Point
Zinc-plated steel U-bolt
Rappelling Tether
7x19 Braided Steel
Imaging System
720p Raspberry Pi Cam
Pan/tilt servos and LED light panel
CR Comm System
2mW 2.4GHz XBee Radio
5dBi dipole antenna
Driving Motors
0.53Nm Faulhaber DC Motors
134:1 internal gear-box
Driving Wheels
18cm diam., Nitrile rubber treads
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
5
FINAL DESIGN SUMMARY
CR Power System
81Wh 14.8V LiPo Battery
Custom power distribution PCB
- With passive thermal management
CR Software System
Raspberry Pi Model B+ SBC
- For CD&H and imaging
Arduino Mega Microcontroller
- For motor/sensor interfacing
CR Positioning System
XL MaxSonar Ultrasonic Range-finder
- For CR depth determination
HEDM 1024P/R Optical Encoder
- For CR odometry
CR Mass: 6.1 kg
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
6
FINAL DESIGN SUMMARY – MR ADDITIONS
Winch Motor
23.5 Nm Stepper Motor
Spool Drum
L=12cm, D=7.6cm
• Winch system (left) is attached
L
•
D
at back end of TREADS CR bay
NOT SHOWN:
• MR Auxiliary Battery
•
44Wh 14.8V LiPo
• MR Comm and Software
Existing MR
Structure
Existing MR
Structure
Systems
•
•
2x2mW 2.4GHz XBee radios
Arduino Mega microcontroller
MR Addition Mass: 6.67 kg
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
7
FUNCTIONAL BLOCK DIAGRAM
MR
CR
Controller
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
8
CRITICAL PROJECT ELEMENTS
• 4 out of 8 subsystems
have been determined
to be critical
• Design requirement
•
•
Overview
satisfaction was not
immediately clear
Feasibility was not proven
by PDR
These subsystems are vital
for minimum level of
success
Design
Rappelling
Comm
PROJECT ELEMENT
Reasoning for Critical Status
Rappelling System
Minimum success requires rappelling
Communications System
Comm feasibility was not proven at
PDR
Software
With comm system overhaul, software
must be written from scratch
Power System
CR system must supply its own power
otherwise mission will fail
Driving System
4-wheel fixed chassis design is proven technology
and terrain is relatively benign
CR System Mass
CR has 9.8kg and an additional 10kg can safely be
added to the MR
Positioning System
Accuracy requirements can be met using proven
COTS technology
Imaging System
Resolution requirements are relatively low and
proven COTS parts can be utilized.
Software
Power
V&V
Risks
Logistics &
Summary
9
RAPPELLING
• Functional Requirement and Critical Design Driving Requirements
FR.3
The CR shall explore a cave/pipe
DR.3.1
The CR shall be able to rappel slopes of 900
inclination
The CR shall be able to rappel to a maximum depth
of 5m
The MR software shall have a feedback control loop
between the rangefinder and the winch motor to
rappel a commanded distance
DR.3.1.1
DR.7.5
Rappel Tether
to MR
CR
5m
Vertical
Descent
Ultrasonic
range-finder
signal to
measure
depth
• Experiments, Models and Analysis
•
•
Overview
Spooling test
Software feedback control loop analysis
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
10
RAPPELLING SYSTEM – SPOOLING TEST
• Tested winch drum spooling for effects of improper spooling
• Spooled and unspooled 10m of braided steel cable under tension
• Also tested effect of repeated loss of tension
• When not in tension wire loosens around the drum
•
•
•
Requires high walls on the spool drum to keep wire properly contained
Wire weight kept the wire wrapped on the spool
Drum diameter = 7.62 cm
• Improper spooling had no adverse effects during the ascent and
descent
Proper
spooling while
in tension
Loose wire
with weight of
5m of cable
D = 7.62 cm
Loose wire
due to loss of
tension
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
11
RAPPELLING SYSTEM - SOFTWARE
Rappel
tether to
MR
Command constant
stepping rate when
above 1m from
cave/pipe floor
CR
Use proportional control
to slow CR when
approaching bottom
5m
Measured
depth from
rangefinder
Software on MR
• Time to Rappel:
220s
• Time for Control:
140s
• Time Constant:
60s
• No Overshoot
MR Rappelling Mechanism
Commanded
Depth
Measured
Depth (from
range-finder)
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
12
RAPPELLING SYSTEM SUMMARY
• Rappel requires 11.3 Nm of holding torque 9.8kg CR
•
Design uses 23.5 Nm stepper motor
• Spooling Test showed that improper spooling will not affect the CR rappelling
•
into or out of the cave/pipe
Simulink model analysis demonstrates software feedback loop effectiveness
Rappel
tether to MR
DR.3.1
The CR shall be able to rappel slopes of 900
inclination
DR.3.1.1 The CR shall be able to rappel to a maximum
depth of 5m
DR.7.5
Overview
The MR software shall have a feedback control
loop between the rangefinder and the winch
motor to rappel a commanded distance
Design
Rappelling
Comm
Software


CR
5m
Vertical
Descent
Ultrasonic
range-finder
signal to
measure
depth

Power
V&V
Risks
Logistics &
Summary
13
COMMUNICATION
• Functional Requirement and Critical Design Driving Requirements
FR.2
DR.2.1
The CR shall communicate with GS via MR
The CR shall receive commands from the
GS via the MR relay system
DR.2.1.1
DR.2.1.2
DR.2.1.2.1
DR.2.2
DR.2.2.1
DR.2.3
The CR shall receive motion commands to move
forward and backward specific distances
The CR shall receive commands to take a picture
and store the image
The GS shall be able to command imaging system to
specific position
The CR shall be able to transmit images to
the GS via the MR
Transmission will have a minimum of 0.1
bits/sec for each pixel/image
The CR shall be able to transmit position
information to the GS via the MR
5m
Comm System
2mW 2.4GHz XBee
Radios
Must work without direct
LOS
CR
• Experiments, Models and Analysis
•
•
Overview
Data flow diagram
Communication propagation testing
Design
Rappelling
Comm
5m
Software
Power
V&V
Risks
Logistics &
Summary
14
COMMUNICATION DATA FLOW DIAGRAM
GS
• Real-time data transmission at 250 kbps
• UART Serial
• 8-O-1 (10 bit packets)
• For transmitting:
GS Laptop
UART/USB
GS XBee
MR XBee 1
UART/RS232
Relay time on MR
is negligible to
read & then
retransmit packet
MR
MR: 𝜇C
16MHz
• Commands, Acknowledgements, Positioning
Data: ~200-300𝝁s (4-6 packets)
• Images: ~29s* (92.2×103 packets)
• Mission timeline requires under 112s
*Raw 720p JPEG image w/ no compression
UART/RS232
UART
MR XBee 2
Positioning calculations are
done onboard CR. Values are
transmitted in millimeters
Overview
Design
Rappelling
Comm
Software
Power
CR XBee
CR
V&V
CR: CD&H
UART/USB
700MHz
UART/USB
CR: 𝜇C
16MHz
Risks
Logistics &
Summary
15
COMMUNICATION PROPAGATION TESTING
•
•
Purpose: validate the communication system
• LOS will be lost during the CR’s mission so it must be shown that
wireless communication is feasible in this lossy environment
Equipment: Test was performed with two 1mW 2.4GHz XBee radios
• Design will use 2mW 2.4GHz XBee radios with a 5dBi antenna
• Less power consumption and same price
Test Overview:
• Measured signal attenuation with LOS
over 10m
• Measured signal attenuation without
LOS using “L” shaped hallway
Top-Down View of “L” Shaped Hallway
Top-Down View of Line of Sight Setup
HALLWAY
CONCRETE
WALLS
MR
XBee
MR
XBee
HALLWAY
10m
5m
CONCRETE
WALLS
CR
XBee
CR
XBee
Overview
Design
5m
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
16
COMMUNICATION PROPAGATION TESTING
•
•
CR Rounds Corner
Effect of hardware
changes
Overview
Design
Rappelling
Comm
Software
Power
•
Tested comm propagation with 1mW
2.4 GHz radios with wire antennas
• With and without line of sight
Radios in design:
• Dipole antenna: 5dBi gain
• Doubled transmission power:
2mW up from 1mW
• Predicted attenuation reduction:
-63dBm up from
-75dBm at max distance
Hardware changes are predicted
to decrease attenuation above
threshold where packet loss
occurred and reduce power
consumption
V&V
Risks
Logistics &
Summary
17
COMMUNICATION SYSTEM SUMMARY
• Transmitters will wait for confirmation after each packet is sent
•
If the packet was not received, the packet will be sent again for up to 30
seconds. At this point a comm drop-out is declared.
• Maximum transmission rate of 250kbps
•
•
Raspberry Pi Camera for imaging captures 720p color pictures
Based on DR.2.2.1 transmitting 720p images requires 92.2 kbps
DR.2.1
The CR shall receive commands from the
GS via the MR relay system
DR.2.2
The CR shall be able to transmit images to
the GS via the MR
DR.2.2.1 Transmission will have a minimum of 0.1
bits/sec for each pixel/image
DR.2.3
The CR shall be able to transmit position
information to the GS via the MR




5m
Comm System
2mW 2.4GHz XBee
Radios
Must work without direct
LOS
CR
5m
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
18
SOFTWARE
• Functional Requirement and Critical Design Driving Requirements
FR.7
DR.7.1
DR.7.2
DR.7.2.1
The CR, MR, and GS systems shall be controlled with software
The CR shall have software to interpret commands received.
The CR shall receive “transmission received” acknowledgements from MR
The CR software shall acknowledge if transmissions were not received by MR, switch to front
wheel encoders and then wait for communication to be reestablished
DR.7.4
The MR software shall be able to interpret commands from UART data
received by MR communication system
DR.7.5
The MR software shall have a feedback control loop between the range-finder and
the winch motor to rappel a commanded distance
DR.7.6
MR software shall enable winch motor to deploy/retract tether proportional to CR’s motion
DR.7.7
The GS software shall allow the user to input commands that will be sent
to GS communication system
• Experiments, Models, and Analysis
•
•
Software flowcharts along with mission timeline from CONOPS
GS, MR, and CR Firmware
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
19
SOFTWARE: DEPLOYMENT
1) Deployment (5 min)
- CR undocks
- CR enters cave/pipe
Deploy Tether
Deployment
•
•
•
•
Power Up and
Run Initialize
Routines
Drive To End of
Ramp and Into
Cave/Pipe
Acknowledge
Reel out tether before driving (incrementally)
No slack in tether at top corner
Drive with PID control
𝑑𝐸𝑟𝑟𝑜𝑟
𝐷𝑟𝑖𝑣𝑒 = 𝐾𝑃 ∗ 𝐸𝑟𝑟𝑜𝑟 + 𝐾𝐼 ∗ 𝐸𝑟𝑟𝑜𝑟 + 𝐾𝐷 ∗
𝑑𝑡
Rappel
RACER
Timeline
(minutes)
5
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
20
SOFTWARE: RAPPELLING
1) Deployment (5 min)
- CR undocks
- CR enters cave/pipe
2) Rappelling (15 min)
- CR rappels 5m
- Transitions from
vertical  horizontal
RAPPELLING LOOP
TRANSITION
5
Overview
RACER
Timeline
(minutes)
15
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
21
SOFTWARE: EXPLORATION
DRIVING LOOP
1) Deployment (5 min)
- CR undocks
- CR enters cave/pipe
2) Rappelling (15 min)
- CR rappels 5m
- Transitions from
vertical  horizontal
3) Exploration (120 min)
- CR traverses 5m
- CR takes/stores
image of POI
IMAGING
5
Overview
15
RACER
Timeline
(minutes)
120
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
22
SOFTWARE: RETURN
1) Deployment (5 min)
- CR undocks
- CR enters cave/pipe
2) Rappelling (15 min)
- CR rappels 5m
- Transitions from
vertical  horizontal
3) Exploration (120 min)
- CR traverses 5m
- CR takes/stores
image of POI
• Front wheel encoders maintain
position when rear wheels leave the
ground
• Must keep track of tether deployed
5
Overview
15
4) Return (15 min)
- CR is retracted by
MR winch system
15
120
Design
Rappelling
Comm
RACER
Timeline
(minutes)
Software
Power
V&V
Risks
Logistics &
Summary
23
SOFTWARE: RE-DOCKING
1) Deployment (5 min)
- CR undocks
- CR enters cave/pipe
2) Rappelling (15 min)
- CR rappels 5m
- Transitions from
vertical  horizontal
3) Exploration (120 min)
- CR traverses 5m
- CR takes/stores
image of POI
• A target will be placed on the inside
of the MR bay
• The user will line up the camera with
the target for a successful docking
5
Overview
15
4) Return (15 min)
- CR is retracted by
MR winch system
5) Re-docking (5 min)
- CR re-enters MR bay
15
120
Design
Rappelling
Comm
Software
Power
V&V
5
Risks
RACER
Timeline
(minutes)
Logistics &
Summary
24
SOFTWARE: COMMS DROPOUT
1) Deployment (5 min)
- CR undocks
- CR enters cave/pipe
2) Rappelling (15 min)
- CR rappels 5m
- Transitions from
vertical  horizontal
3) Exploration (120 min)
- CR traverses 5m
- CR takes/stores
image of POI
4) Return (15 min)
- CR is retracted by
MR winch system
5) Re-docking (5 min)
- CR re-enters MR bay
• A comm drop-out is declared if no “acknowledgements” are received for more than 30 seconds
• Assume communication is never lost between GS and MR due to direct line of sight and close
proximity
RACER
5
Overview
15
15
120
Design
Rappelling
Comm
Software
Power
V&V
5
Risks
20
Timeline
(minutes)
Logistics &
Summary
25
SOFTWARE: GS GUI
Images will be displayed to
the user as they are received
by the MR
The depth and horizontal
distance of the CR can be
seen graphically
Mission status is
continuously updated and
then displayed to the user
Easy to use command
interface. Actual commands
are then constructed behind
the scenes
11:06 – RAPPELLING COMPLETE
11:08 – CAPTURE IMAGE COMMAND TRANSMITTED
11:08 – IMAGE RECEIVED
Overview
Design
Rappelling
The mission log will keep track of
commands and acknowledgements.
This information will also be saved to
the physical GS
Comm
Software
Power
V&V
Risks
Logistics &
Summary
26
FIRMWARE: MR
GS
XBEE
Serial
RS232
Serial
RS232
MR Arduino Mega
Transceiver
XBEE
CR
Transceiver
mrconstants.h
mrmain.cpp (C++)
controller.cpp
• Reference header
containing all constants
for the MR
•
• Will provide the
functionality to control
the stepper motor
during rappel and drive
commands
serial.h
• Existing Arduino library
that provides serial port
functionality
Overview
Design
Rappelling
Parses commands and
relays them to CR
init()
loop(){
readCommand()
Switch Statement:
Rappel -> Controller
Drive -> Controller
Capture Image
Move Camera
relayCommand()
}
Comm
Software
Power
• Will use range-finder
data as feedback for
the rappelling process.
V&V
Risks
Logistics &
Summary
27
FIRMWARE: CR
MR
XBEE
USB
USB
CR Raspberry Pi
Transceiver
crmain.py (PYTHON)
CD&H:
-Parse commands
-Determine action
System Commands:
-Take image
-Read image
Comm Dropout
Protocol:
- Tell CR Arduino to
switch encoders
Overview
Design
crconstants.h
•
Reference
header
serial.h
•
CR Arduino Mega
crmain.cpp (C++)
Class Files
• Parse commands
• Drive motors
• Encoder Interrupt
Routines
• Read range-finder
• Drive Servos
• Collect power data
- Battery capacity
• MotorControl
serial port
functionality
Rappelling
Comm
Software
Power
V&V
• ServoControl
• EncoderControl
• RangeFinder
• ControlLoop
Risks
Logistics &
Summary
28
SOFTWARE: SUMMARY
• Driving Requirements:
FR. 7
The CR, MR, and GS systems shall be controlled with software
DR.7.1
The CR shall have software to interpret commands received.
DR.7.4
The MR software shall be able to interpret commands from UART data received
by MR communication system


DR.7.5
The MR software shall have a feedback control loop between the rangefinder and
the winch motor to rappel a commanded distance

DR.7.7
The GS software shall allow the user to input commands that will be sent to GS
communication system

Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
29
POWER
• Functional Requirement and Critical Design Driving Requirements
FR. 6
DR.6.1
The CR and MR systems shall contain their own electrical power sources
The CR power system shall provide power for the CR to complete its mission
DR.6.1.1
The CR power subsystem shall be able to supply 4.6 A of power at 12V+/-1V for up to 45 minutes
DR.6.1.2
The CR power subsystem shall be able to supply 700 mA of power at 5V+/-0.25V for up to 180 minutes
DR.6.1.3
The CR power subsystem shall be able to supply 600 mA of power at 3.3V+/-0.5V for up to 180 minutes
DR.6.1.4
The CR power subsystem shall be able to supply 2.2A of power at 12V +/-2V for up to 5 minutes
DR.6.2
The auxiliary MR power system shall provide power for the communication relay
system as well as the rappelling system to complete the mission
DR.6.2.1
The MR power subsystem shall be able to supply 2.8A of power at 12V+/-1V for up to 30 minutes
DR.6.2.2
The MR power subsystem shall be able to supply 2.8A of power at 3.3V+/-0.5V for up to 180
minutes
• Experiments, Models, and Analysis
•
•
•
Energy budgets
Power distribution board design
Electrical load analysis
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
30
ENERGY BUDGETS
•
•
•
Child Rover
•
64.9 Wh of total required energy
•
5.5 Wh of dissipated energy
•
•
Battery: MaxAmps LiPo 5450mAh 14.8V
81 Wh allocated (20% Margin)
Mother Rover
30.6 Wh of total required energy
•
2.4 Wh of dissipated energy
Battery: MaxAmps LiPo 3000mAh 14.8V
44 Wh allocated (30% Margin)
CR Energy Budget (Wh)
MR Energy Budget (Wh)
4Wh
2Wh
MARGIN
16Wh
41Wh
6Wh
3Wh
MARGIN
Rappelling
Rappelling
Communication
C&DH
Margin
Dissipated Power
10Wh
2Wh
Design
17Wh
13Wh
Margin
Lighting
11Wh
Overview
Driving
Imaging/C&DH
Communication/Sensing
Dissipated Power
Comm
Software
Power
V&V
Risks
Logistics &
Summary
31
POWER SYSTEM DESIGN
• System designed to reliably provide high currents at 3 voltage levels
• Includes global and regulator-level protection circuitry
• Battery → Global Protection → Measurement → Regulation → Rail protection → Devices
• Includes passive thermal management (heat sinks, not shown)
14.8V
LiPo
Battery
Fuse
Global
Protection
Battery
Overview
Reverse
Polarity
Protection
Design
Rappelling
Power
Measurement
Measurement
(voltage and
current)
Comm
Back-EMF
Protection
12V
Devices
12V
Regulation
Overcurrent
Protection
5V
Regulation
Overcurrent
Protection
5V Devices
3.3V
Regulation
Overcurrent
Protection
3.3V
Devices
Voltage
Regulation
Software
Current
Regulation
Power
V&V
Devices
Risks
Logistics &
Summary
32
ELECTRICAL LOAD ANALYSIS
• Need to verify:
• Operating points, tolerances, and duration
• Simulations done with Texas Instruments Power Architect:
• Simulations also provide power dissipation estimates and efficiency calculations
• 12V voltage regulation
• Steady state
• Input transient (in backup slides)
• Output transient
• Startup conditions (in backup slides)
• 5V voltage regulation (in backup slides)
• 3.3V voltage regulation (in backup slides)
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
33
ELECTRICAL LOAD ANALYSIS
Case Study: 12V Regulation - Steady State Operation
• Maximum fluctuation of 0.178 V is within +/- 1V tolerance
• Able to supply the full 6.8A required
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
34
ELECTRICAL LOAD ANALYSIS
Case Study: 12V Regulation – Output Transient
• Output transient is modelled by a suddenly disconnected load
• Maximum fluctuation of 0.28 V is within +/- 1V tolerance
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
35
POWER: SUMMARY
• Verification of power system requirements met by simulation
• Operating points and tolerance results are summarized in table below
Power
Source
Maximum
Allowed Voltage
Fluctuation
Maximum
Simulated Voltage
Fluctuation –
Steady State
Maximum
Simulated Voltage
Fluctuation Transient
Design
Requirement
CR – 12V
1V
0.02 V
0.28 V
6.1.1
CR – 5V
0.25 V
0.03 V
0.15 V
6.1.2
CR – 3.3V
0.5 V
0.009 V
0.021 V
6.1.3
MR – 12V
0.5 V
0.02 V
0.27 V
6.2.1
MR – 3.3V
0.5 V
0.009 V
0.021 V
6.2.2
Design Satisfies
Requirements?





• All level, tolerance, and duration requirements have been met with this design.
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
36
VERIFICATION & VALIDATION
PHASE 1
Power
Positioning
Imaging
Communication
Rappelling
Software
Driving
Components and
Sub-systems
Dynamic
Loading
Timeline
• Test how startup of dynamic
loads affect voltage/current
• How do transients on the
input/output affect output
voltage/current
• Verify power supply can act at
max draw for the entirety of a
mission
Overview
Design
Duplicated
Radio-to-Radio
packet
transmission
• Duplicate earlier test
using more powerful
XBee radios and high
gain antennas
Rappelling
Comm
Motor to
spool drum
connection
Spooling
Test
Individual
Functions
• Testing individual functions for
different sub-systems
• Functions will include:
• Reading encoder data
• Taking a picture
• Reading range finder data
• Transmitting data
• Controlling drive motors
with PWM
• Etc.
• Verify wire spooling performs as
well as previous testing
• Verify stepper motor supplies
required torque throughout
required range of operation
Software
Power
V&V
Risks
Logistics &
Summary
37
VERIFICATION & VALIDATION
PHASE 1
Power
Components and
Sub-systems
Positioning
PHASE 2
Imaging
Communication
Rappelling
Software
Transmit Data
and Images
from CR to GS
via MR
GS Commands
to MR for
Rappelling
Feedback
control loop
for Rappelling
Driving
commands
from GS to CR
Sub-system
Integration
Complete
Rappelling
Test
• Phase 1 and Phase 2 verify components and
sub-systems based off of requirements
• Phase 3 validates the system
PHASE 3
Complete
Driving Test
ITLL Patio Required
•
Have permission for
use from Victoria
Lanaghan @ ITLL
Full Systems
Test
Full System
Overview
Design
Rappelling
Comm
Driving
Software
Power
V&V
Risks
Logistics &
Summary
38
V&V: PHASE 3 – TEST A
Test Purpose: The purpose of this test is to validate the
Driving, Imaging, Positioning, and Rappelling systems. The
communication system will be in use but will not be validated
by this test due to the environment not being a cave or pipe.
Test Overview:
•
•
•
•
•
•
MR placed on platform where CR will un-dock and begin rappelling
CR will rappel wall and transition to horizontal surface
CR will travel 5m straight out where an object is located inside a
plywood box
The CR will enter the box and the box will be closed off
The CR will take and transmit a photo back to the GS of the object
The CR will then return and re-dock with the MR
Required Materials/Facilities:
• TREADS MR
• CR
• GS
• Platform
• Plywood box
• ITLL Facility (have permission)
MR Location
EXPLORATION
Location
Rappelling
Location
5m
Exploration
Location
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
39
V&V: PHASE 3 – TEST B
Test Purpose: The purpose of this test is to validate the
communication system. The Driving, Imaging, and
Positioning systems will all be a part of this test but will not
be verified by this test. To simulate a cave/pipe with ideal
conditions, an “L” shaped concrete hallway will be used.
Top-Down View of “L” Shaped Hallway
HALLWAY
MR
Test Overview:
•
5m
•
•
(1) The CR will start 5m down the hallway from the MR at the
bend of the “L”
(2) The CR will travel 5m straight and take an image of an object
(3)(4)The CR will transmit an image back to the GS and then
return to the starting point
CONCRETE
WALLS
3
4
Required Materials/Facilities:
• TREADS MR
• CR
• GS
• AES basement hallway
Overview
Design
Rappelling
CR
CR
1
CR
2
5m
Comm
Software
Power
V&V
Risks
Logistics &
Summary
40
PROJECT RISKS
Risk Management Matrix
• Complete winch
system power loss
Severe
(2)
Risk
• Light source not
bright enough
Intolerable
Minor
(8)
(4)
• Software
schedule slips
(9)
• Driving/rappelling more
or less than commanded
• Power consumption is
higher than expected
• Missing pulses from
encoders
Moderate
Tolerable
• Comm does not
propagate
(1)
Significant
Acceptable
• Inadequate thermal
management
• Back-EMF from motors
• Imperfect spooling
leads to jumps in depth
(7)
(3)
(5)
Negligible
(6)
Very Unlikely
Unlikely
Possible
Likely
Very Likely
Likelihood
Mitigations
(1) MR battery margin & safety tether during testing
(2) Design uses radios with double the transmission power of
what was tested
(3) Feedback control loop between range-finder and rappelling
stepper motor
(4) Use feedback control loops for driving/rappelling
(5) Allocate large battery capacity margins
(6) Design power distribution circuitry with over-current protection
(7) Off-ramp to increase size of heat-sinks or add active cooling
(8) Have enough battery margin to increase the number of LEDs
used in parallel
(9) Software version control & internal code reviews.
Large schedule uncertainty allocated
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
41
ORGANIZATIONAL CHART
RACER
Advisor: Dr. Nabity
Customer: Barbara
Streiffert, JPL
CU TEAM
LEADERSHIP
Financial:
Michael Hanson
Safety:
John Russo
PM:
Thomas Green
Systems:
Nicole Harris
Manufacturing:
Dustin Larsen
TECHNICAL
Mechanical:
Drew
Penrod
Materials:
Nicole
Harris
GNC:
John Russo
Power:
Greg
McQuie
CAD:
Dustin
Larsen
C&DH:
Casey
Zahorik
Rappelling:
Hunter
Hoopes
Testing:
Michael
Hanson
Imaging:
Thomas
Green
Software Sub-group
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
42
WORK BREAKDOWN STRUCTURE
RACER
Electronics
Subsystem
Software Subsystem
Power
Distribution
Circuit Diagram
Drivetrain/Rappelling
Software
Architecture
System CAD
Model
Integration and
Testing
Fall Class
Deliverables
Full System
Test Plan
Project
Definition
Document
Risk Analysis
Matrix
Conceptual
Design
Document
CR&MR
I/O Schematics
GS: MATLAB
for comm &
command
CR&MR
Arduinos
CR Chassis
Spring Class
Deliverables
Manufacturing
Status Review
Test Readiness
Review
AIAA Report
CR
Raspberry Pi
Encoders for
Odometry
Arduinos: C++
for MR&CR
control
MR Winch
System
Project Budget
and Timeline
Preliminary
Design Review
Spring Final
Review
Raspberry Pi:
Python for CR
CD&H
Full Integration
Critical Design
Review
Range Finder
Power
Distribution PCB
Overview
Design
Test Results
Complete --Incomplete ---
Rappelling
Comm
Software
Power
Fall Final
Report
V&V
Spring Design
Symposium
Spring Final
Report
Risks
Logistics &
Summary
43
WORK PLAN
CDR
Week 1
Week 15
Week 10
Week 5
PHASE 1
• Ordering Parts (as early as post-CDR)
• Begin software – individual functions
• Component-level testing
• Basic integration
Legend
= Procurement
= Integration
= Testing
= Software
PHASE 2
• Complete
software
• Subsystem-level
testing
• Full integration
PHASE 3
• Full system
validation
= Uncertainty
= Class Milestone
= Internal Milestone
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
44
WORK PLAN
CDR
Week 1
Week 15
Week 10
Week 5
Purchasing Components
Hardware/Software Component
Manufacturing/Testing/Integration
CRITICAL PATH
Hardware/Software Subassembly Testing/Integration
Legend
= Procurement
= Integration
= Testing
Testing Entire
Functionality
= Software
= Uncertainty
= Class Milestone
= Internal Milestone
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
45
TEST PLAN
CDR
Week 1
Week 15
Week 10
Week 5
PHASE 1 Testing: Hardware
and software component tests
PHASE 2 Testing: Hardware and
software subassembly tests
Legend
ITLL Patio
Required
(can only use
Saturdays)
= Procurement
= Integration
= Testing
= Software
= Uncertainty
PHASE 3 Testing: Full-system validation
= Class Milestone
= Internal Milestone
Overview
Design
Rappelling
Comm
Software
Power
V&V
Risks
Logistics &
Summary
46
COST PLAN
MARGIN: 10% TOTAL PROJECT COST
Rappelling
15%
7%
CPU/Comms
Imaging
19%
8%
Positioning
Driving
12%
Power
29%
Margin
Total Cost - $4483.94
Margin - $516.06
Overview
Design
Rappelling
Comm
*All sub-systems are
planned for 2 iterations
MR- $1079.46
CR - $3404.48
Software
Power
V&V
Risks
Logistics &
Summary
47
SUMMARY
• All critical project elements
meet their design driving
requirements
•
Non-critical subsystems are
shown in backup slides
• Steps forward:
• Purchase parts prior to
•
Winter Break so
manufacturing can
begin at start of spring
semester
Start software over
Winter Break so that
component tests can
begin early next
semester
Overview
Design
Rappelling
Comm
PROJECT
ELEMENT
Reasoning for Critical Status
Rappelling
System
Minimum success requires rappelling

Communications
System
Comm feasibility was not proven at
PDR

Software
With comm system overhaul, software
must be written from scratch

Power System
CR system must supply its own power
otherwise mission will fail

Driving System
4-wheel fixed chassis design is proven technology
and terrain is relatively benign
CR System Mass
CR has 9.8kg and an additional 10kg can safely be
added to the MR
Positioning System
Accuracy requirements are high (10cm over ~10m
travelled)
Imaging System
Resolution requirements are relatively low and proven
COTS parts can be utilized.




Software
Power
V&V
Risks
Logistics &
Summary
48
QUESTIONS?
49
ACKNOWLEDGEMENTS
• RACER would like to thank
•
•
•
•
•
•
Barbara Streiffert
Professor James Nabity
Trudy Schwartz
Matt Rhode
Bobby Hodgkinson
Professor Jelliffe Jackson
50
BACKUP SLIDES
51
POSITIONING
• Functional Requirement and Critical Design Driving Requirements
FR. 4
The CR shall contain a positioning system
DR.4.1
The CR shall know its depth and distance travelled from the MR
DR.4.1.1
DR.4.1.1.1
DR.4.1.2
•
•
The CR shall know its depth within ± 10cm
Range-finder must be parallel to a vertical surface
The CR shall know its distance travelled within ± 10cm
Range-finder and Encoder details
Encoder IC schematic
52
POSITIONING: RANGE-FINDER
• XL-MaxSonar-WRM1
• Comes equip with filtering firmware
•
•
that detects the object with the largest
acoustic presence
Narrow beam directs signal directly to
cave/pipe floor
Resolution is well within the
positioning requirement (10cm)
Specs
Value
Max Range
765 cm
Min Range
20 cm
Resolution
1 cm
Beam Width
Narrow
Filtering
Firmware
Yes
DR.4.1.1 The CR shall know its depth
within ± 10cm

53
POSITIONING: ENCODERS
• HEDM-5505 Optical Encoder
• 𝐸𝑟𝑟𝑜𝑟 = 𝑁𝑢𝑚𝑅𝑒𝑣𝑠
∗ 𝐸𝑟𝑟𝑜𝑟 𝑝𝑒𝑟 𝑅𝑒𝑣
• 𝐸𝑟𝑟𝑜𝑟 =
𝑇𝑜𝑡𝑎𝑙 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒
𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑝𝑒𝑟 𝑅𝑒𝑣
• 𝐸𝑟𝑟𝑜𝑟 =
1000𝑐𝑚
2𝜋∗17.78 𝑐𝑚/𝑟𝑒𝑣
• 𝐸𝑟𝑟𝑜𝑟 =
∗ 𝐸𝑟𝑟𝑜𝑟 𝑝𝑒𝑟 𝑅𝑒𝑣
∗
±0.05𝑐𝑚
Value
Pulse/Revolution
1024
Type
Optical
Output
Quadrature
𝑟𝑒𝑣
±0.44 𝑐𝑚
• Still need a decoder/buffer IC (next slide)
DR.4.1.2
Specs
Angular Error per 10 min of arc
Rev
Or ± 1/6 deg
Horizontal Error
per Rev
The CR shall know its distance
travelled within 10cm
0.05 cm
(7in wheels)

54
POSITIONING: ENCODER IC
• LS7184 Quadrature Decoder
• Setting MODE to x4 yields a resolution of
4096 PPR
CR Microcontroller
• Decoder yields the direction of the shaft
55
POSITIONING: SUMMARY
• Depth: XL-MaxSonar-WRM1
•
Resolution: 1 cm
• Distance Traveled: HEDM-5505 Optical Encoder
•
•
Resolution: 1024 PPR and 4096 PPR with LM7184
Total Error: 0.44 cm
• Driving Requirements:
FR. 4
The CR shall contain a positioning system 
DR.4.1.1
The CR shall know its depth within ± 10cm

DR.4.1.2
The CR shall know its distance travelled within ± 10cm

56
MASS
• Functional Requirement and Critical Design Driving Requirements
FR.1
The CR shall use TREADS as the MR
DR.1.1.2
The CR system shall have a mass of no more than 9.8 kg
DR.1.3.1
Additions to the MR structure will not exceed 10 kg
• Experiments, Models and Analysis
•
Weight testing on MR bay
57
MASS
FR.1
The CR shall use TREADS as the MR
DR.1.1.2
The CR system shall have a mass of no more than 9.8 kg

DR.1.3.1
Additions to the MR structure will not exceed 10 kg

CR Mass: 6.1 kg
MR Addition Mass: 6.67 kg
CR Mass Budget
MR Mass Budget
4%
Rappelling
45%
34%
16%
1%
Imaging
Driving
Power
Communication
Positioning
Margin
33%
67%
0.1%
(comm)
Communication
Margin
0.1%
(comm)
58
DRIVING
• Functional Requirement and Critical Design Driving Requirements
FR.3
The CR shall explore a cave/pipe
DR.3.3
The CR shall be able to traverse a distance of up to 5m horizontally from the rappel
touchdown point
DR.3.3.1
The CR will be able to move forward and backward
DR.3.3.2
The CR shall be able to traverse a floor with small rocks no larger than 3cm in
diameter
• Experiments, Models and Analysis
•
•
•
Corner Analysis
Chassis Structural analysis
Moment analysis at transition point
59
MOTOR SELECTION
Motor
Mass
Cost
Lead Time
Score
Himax HC5018-530
0.28kg
$115.99
1 week
3.3
Faulhaber
3242G012BX4
0.18kg
$300.42
8 weeks
3.0
Faulhaber
3257G012CR
0.24kg
$0
DARE’s motors
8 weeks
3.4
Pittman 1312S103SP
0.21kg
$328.15
1 week
2.9
Pittman 3442S100SP
0.23kg
$305.52
1 week
2.9
A0421046NCNAXX-SP
0.36kg
$232.52
3 weeks
3.0
Conclusion: Use DARE’s Faulhaber motors
60
MOTOR SCORING CRITERIA
• Mass most important. Weighting = 0.5
• Cost and Availability (determined by lead time) also considered. Weighting: Cost =
•
•
•
•
0.3 and Availability = 0.2
For each category, 1 is bad and 5 is good
Mass on a scale from 0-.1 kg (5) to >.5 kg (1)
Cost on a scale from $0-100 (5) to > $350 (1)
Availability on a scale from <1 week (5) to >8 weeks (1)
61
TORQUE – SPEED PLOT
PWM
The motor and gearbox supply much more power than
required for any driving regime (blue line)
Worst-case torque required is 0.2189 N-m (red dot)
Motor stall-torque is 73.7N-m
At design speed, motor supplies 18.2 N-m (83.2 FOS)
All 3 driving regimes well within motor capability
PWM control required to prevent over torqueing motor
PWM
62
TOP CORNER ANALYSIS
• Geometric Proof of top corner clearance + graphic
Acceptable above
black line
Design Point
𝑐=𝑙−
2+1 𝑅
R = 3.5”, so c > 0.55”
Current design: c = 1.00” will allow chassis to completely clear corner
63
RAPPELLING ALONG WALL ANALYSIS
• CR must be vertical during rappel for proper range finder operation
𝛉
𝛕
𝐝𝐲 𝐝
𝐗
N
𝐖𝐖
𝐝𝐂𝐆
W
𝐖𝐖
T
Σ𝐹𝑥 = 𝑁 − 𝑇𝑐𝑜𝑠𝜃 = 0
Σ𝐹𝑦 = 𝑇𝑠𝑖𝑛𝜃 − 𝑊 = 0
Σ𝑀𝑂 = 𝑇𝑠𝑖𝑛𝜃𝑑𝑥 + 𝑇𝑐𝑜𝑠𝜃𝑑𝑦 − 𝑊𝑑𝐶𝐺 = 0
If these conditions are met, the CR will rappel down the wall
and will remain vertical at all times for the Range Finder
Solve for dy and dx on the next slide
64
BOTTOM CORNER ANALYSIS
• Front wheels apply torque to rotate chassis 90º
• Torque on wheels applies opposite torque on chassis
𝜃
𝐝𝐲 𝐝
𝐗
𝐍𝟏
T
Σ𝐹𝑥 = 𝑁1 + 𝜇𝑁2 − 𝑇𝑐𝑜𝑠𝜃 = 0
Σ𝐹𝑦 = 𝑇𝑠𝑖𝑛𝜃 + 𝑁2 − 𝑊 = 0
𝐖𝐖
Σ𝑀𝑂 = 𝜏 + 𝜇𝑁2 𝑅 + 𝑇2 𝑠𝑖𝑛𝜃𝑑𝑥 − 𝑊𝑑𝐶𝐺 + 𝑇2 𝑐𝑜𝑠𝜃 𝑙 + 𝑑𝑦 − 𝑁1 𝑙 > 0
𝐝𝐂𝐆
l
𝐖
𝛕
𝐖𝐖
𝐍𝟐
𝑡𝑎𝑛𝜃 =
5 − 𝑙 − 𝑑𝑦
𝑅 + 𝑑𝑥
Solve Rappelling Along Wall equations and
Bottom Corner equations for tether attachment
point (dy and dx)
All other variables known
Results on next slide
65
TETHER ATTACHMENT POINT
From Bottom Corner Analysis:
𝜏 + 𝑊𝐶 + 4𝑊𝑊 𝑑𝑋 − 𝑊𝐶 𝑑𝐶𝐺
𝑑𝑦 <
tan(𝜃)
𝑊𝐶 + 4𝑊𝑊
Known Values:
l = .3184m
R = .0889m
dCG = .01842m
Ww = 2.496N
Wc = 49.775N
𝜃 = 86.7°
𝜏 = .063𝑁𝑚
From Along Wall Analysis:
𝑊𝐶 𝑑𝐶𝐺 − 𝑊𝐶 + 4𝑊𝑊 𝑑𝑋
𝑑𝑦 =
tan(𝜃)
𝑊𝐶 + 4𝑊𝑊
Thus:
2𝑊𝐶 𝑑𝐶𝐺 − 𝜏
𝑑𝑋 >
2(𝑊𝐶 + 4𝑊𝑊 )
𝑑𝑦 𝑅
𝑊𝐶 𝑑𝐶𝐺
−
𝑊𝐶 + 4𝑊𝑊 5 − 𝑙 − 𝑑𝑦
𝑑𝑋 =
𝑑𝑦
1+
5 − 𝑙 − 𝑑𝑦
Choose dx such that dy lies within size restrictions, dy<5.15”: dx>0.49”
If dy = 0”, dx = .60”
.49”<dx<.60”, 0”<dy<5.15”
Current design: dy = 1.81” -> dx = 0.57” are both within this requirement
66
WHEEL MATERIAL STRENGTH
Failure Stress of ABS Plastic: 40 MPa
Maximum Stress on Wheel: 0.2014 MPa
FOS = 198.6
Tolerable Wheel Deformation: 1 cm
Maximum Wheel Deformation:0.056 cm
FOS = 17.9
Wheel can support weight of CR
67
AXLE LOADING
• Motor axle can support 50 N loaded radially
F1 is maximum when M = (W/4)l2
F1 = W/4
W/4 = 12.44 N
Factor of Safety of 4.02
68
DRIVING VERIFICATION & TEST PLAN
Phase 1
Phase 2
Apply expected
force to wheels
Send power
to motors
Integrate with full
CR, confirm axial
loading on drive
shaft
Send power
to motors
through PWM
Phase 3
While rappelling,
confirm constant
vertical alignment
Verify chassis
clearance over
top corner
transition
Full System Test
Apply torque to
motors to test
vertical-horizontal
transition. Verify CR
does not flip
Verify expected
power consumption
while driving 5m
forward/backward
Drive off MR
Transition corner and rappel 5m to ground
Transition to horizontal
Drive 5m forward/backward over 3cm obstacles
Verify clearance
while starting
from rest at 3cm
obstacle
69
SUMMARY
FR.3
The CR shall explore a cave/pipe
DR.3.2
DR.3.3
The CR shall be able to transition from rappelling to horizontal and
vice versa

The CR shall be able to traverse a distance of up to 5m horizontally from
the rappel touchdown point
DR.3.3.1
The CR will be able to move forward and backward

DR.3.3.2
The CR shall be able to traverse a floor with small rocks no larger
than 3cm in diameter

• Motor + Gearbox can supply 18N-m of torque
•
Only .2N-m required
•
Only 29.9N applied
• PWM controller to adjust speed as required
• Wheels can support 12900N of weight
• Tether attachment point 1.81” behind and 0.57” above wheel center
70
SHOCK LOADING OF WINCH WIRE
Variables:
• Pf = Stress at impact = SOLVING FOR
• P = Static Load = 13.448 lbs.
• A = Area of wire = .00418 in2
• E = Modulus of elasticity = 1.5 x 107 psi
• h = Slack = 39.37 in
• L = length of wire = 98.4252 in
• ∆L = Elastic Stretch of wire
Slack
L
CR
h
CR
∆L
CR
𝑃𝑓 = 𝑃 ∗ 𝑘
2ℎ
𝑘 = 1 + 1 + ∆𝐿  1 + 1 +
𝑃𝑓 = 𝑃 ∗ [1 + 1 +
2ℎ𝐴𝐸
]
𝑃𝐿
2ℎ𝐴𝐸
𝑃𝐿
Conclusion:
𝑃𝑓 = 834.6862 lbs.
3/32” 7x19 braided steel wire is rated for 1000 lbs.
𝑃𝑓 is less than 1000 lbs. and can therefor handle a 1m drop
while rappelling
71
VERIFICATION & TEST PLAN
• Test sending signals to motors through PWM controller
•
Verify output speed and torque are expected values
•
Verify chassis clearance
•
Verify CR does not flip
•
Verify CR can drive over 3cm obstacle after starting from rest
•
Verify power consumption is expected value
• Test top corner transition
• Test vertical alignment during descent
• Test transition from vertical to horizontal
• Test starting at an obstacle
• Test driving forward and backward 5m
72
IMAGING
• Functional Requirement and Critical Design Driving Requirements
FR. 5
The CR shall capture photographic images
DR.5.1
DR.5.3
The imagine system shall have a minimum resolution of 3.7 pixels per degree of field
of view in a single image
The CR shall be able to take photos within an azimuthal angular FOV of 180°
DR.5.4
The CR shall be able to take photos with an elevation angular FOV of 90°
DR.5.5
The imaging system light source shall provide adequate lighting to determine POI
from background.
• Experiments, Models and Analysis
•
Low-light imaging test
73
LOW-LIGHT IMAGING TEST
•
•
Tested 16MP camera with two brightness levels of a light
(25 and 50 lumens)
Attempted to resolve a 10-cm diameter pile of rocks and a
10-cm diameter yellow cup
•
•
25 lumen test
•
Both objects 5-m from the camera
25 lumens (top) can barely resolve pile of rocks
50 lumens (bottom) can clearly resolve both pile of
rocks and yellow cup from image background
• Design will output 500 lumens
DR. The imaging system light source
5.5 shall provide adequate lighting to
determine POI from background.

50 lumen test
74
IMAGING SYSTEM SUMMARY
• Raspberry Pi camera
•
2592x1944 resolution with 54°x41° FOV
•
48x47 pixels/° in a single image
• Hitec HS-485HB servo
•
•
0.6 Nm of torque
Two rotation options
•
•
600usec-2400usec for 180° range of motion
1050usec-1950usec for 90° range of motion
FR. 5
The CR shall capture photographic images
DR.5.1
The imagine system shall have a minimum resolution of 3.7 pixels per
degree of field of view in a single image
DR.5.3
The CR shall be able to take photos within an azimuthal angular FOV of
180°
DR.5.4
The CR shall be able to take photos with an elevation angular FOV of 90°
DR.5.5
The imaging system light source shall provide adequate lighting to
determine POI from background.
‡




‡ https://www.sparkfun.com/products/11868
* https://www.servocity.com/html/hs-485hb_servo.html#.VGrSE_nF-5B
*
75
IMAGING SYSTEM V&V
PHASE 1
Take picture
with RPi
Camera
Store Images
taken by
camera
Command servos to
angles using PWM
from CR Arduino
Make sure
LEDs work with
external power
source
Components
PHYSICAL INTEGRATION
PHASE 2
Sub-systems
Power on LEDs with
CR power
distribution circuitry
Pan and tilt
while taking
pictures via GS
Low-light
imaging
testing
• Required equipment: Raspberry Pi, Arduino Mega, GS Laptop, CR battery
and power distribution board
• Required facilities: Room that can be blacked out and is at least 5-m long
(Lockheed Martin Room would suffice)
76
RAPPELLING FEM ANALYSIS
• Analyzed CR chassis
under rappelling loads
•
𝑇𝑒𝑛𝑠𝑖𝑜𝑛 = 60𝑁
Fixed Rappelling
Attachment Point
Zinc-plated steel U-bolt
CR
CR
Chassis
5m
Vertical
Descent
𝑊𝐶𝑅
•
60N applied at tether
attachment point
Found a maximum of 15
MPa concentrated at
attachment point
• F.S. of 40 to
yield strength
60N applied at tether
attachment point
Yield strength:
630 MPa
Max Stress:
15.4 MPa
77
RAPPELLING SYSTEM – DRIVE SHAFT
• Tension force from rappel will cause a bending in the drive shaft. This
bend must be very minimal to ensure no issues arise during the rappel
Drive Shaft will be steel
•
2𝐹𝑇 𝑥 3 𝐿−𝑥 2
• ∆𝑏𝑒𝑛𝑑 = 3𝐸𝐼 2𝑥+𝐿 2 , 𝐼 = .78𝑟 4 , 𝐸 = 200𝐸 9 𝑚𝑁2
• For a maximum of 0.00001 m bend the minimum radius is 0.718 cm
• Chosen radius of 1.27 cm to ensure minimum FoS = 1.6
End Cap
End Cap
Drive Shaft
Fixed
(Bearing)
3.81
cm
19.685 cm
𝐹𝑇
𝐹𝑇
3.81
cm
Fixed
(Bearing)
Motor
Connection
78
RAPPELLING SYSTEM – SPOOL DRUM
• Thickness of the Spool Drum is Dependent on the required screw size
for the end caps. The shear stress based on max tension will find
screw radius
𝐹
𝜏=
2 , 𝐹 = 287.9092 𝑁, n: number of screws
•
𝑛𝜋𝑟
𝑁
• If 𝜏 = 55𝑒6 𝑚2 and n = 5 then 𝑟𝑚𝑖𝑛 = 0.06 𝑐𝑚
• Screws chosen were 8-32 which have a .42672 cm diameter
• Spool drum thickness was chosen to be 1.27 cm
𝐹𝑇
Spool
Drum
End Cap
𝜏
79
RAPPELLING SYSTEM – DRUM CAP
• Thickness of the spool cap is based on the required screw size to
ensure tension force doesn’t pull the cap away from the screw
For calculation one screw will feel entire tension force
𝐹𝑇
𝜎 = , where 𝐹𝑇 = 287.9092 𝑁 and 𝜎 = 240 𝑀𝑃𝑎
•
•
𝑡𝑑
𝑆𝑡𝑟𝑒𝑛𝑔𝑡ℎ 𝑆𝑐𝑟𝑒𝑤
• Must account for material differences 𝐽 = 𝑇𝑒𝑛𝑠𝑖𝑙𝑒
= 2.146
𝑇𝑒𝑛𝑠𝑖𝑙𝑒 𝑆𝑡𝑟𝑒𝑛𝑔𝑡ℎ 𝐶𝑎𝑝
• 𝑡𝑚𝑖𝑛 = 0.0618 cm
• Chose a cap thickness of .3175 cm
𝑑
𝑡
𝐹𝑇
80
MR STABILITY
• Addition of rappelling system to MR must not cause instability
•
MR cannot slip and cannot rotate over edge of cave/pipe
•
•
Coefficient of Friction = 0.54 to ensure max tension will not cause MR to slip
Testing found MR wheel material has Coefficient of Friction of 1.22 ± 0.04
• MR Slippage
• MR Moment
•
•
Maximum Tension will create a moment on front wheel of MR
Tension creates minimum moment of 165.84 Nm Clockwise opposite of flipping into the
cave/pipe
Winch
𝑇𝑥
𝑇𝑦
h= .33 m
MR
𝑀𝑀𝑅
𝑜
𝑦
𝑙 = 0.6 m
𝑊𝑀𝑅
𝑥
81
MR NON-SLIP
• From maximum tension force the minimum coefficient of friction required is
•
•
0.534
The MR wheels used Nitrile Rubber Treads
From testing the nitrile rubber treads provide a coefficient of friction of 1.219
•
This is between the nitrile rubber and concrete, which is what the MR will be on during
testing
• The rubber was placed on a wood block and then pulled to find the force to
move the block
82
RAPPELLING – MOTOR SELECTION
• Metric Weights
•
•
•
•
•
Cost – 20%: Total project has $5,000 maximum budget. Rappelling system is one of 9 critical systems and
cannot use a large budget portion
Mechanical Complexity – 25%: Must be easy to construct and integrate on the existing MR system
Mass – 25%: From testing, 10kg can be safely added to MR system. This mass includes battery, structure,
motor, and electronics. Motor cannot use large portion of the additional mass so entire system will fit in mass
budget
Power – 20%: The larger power consumption would require more battery power. Extra batteries use more
mass, which is limited.
Size – 10%: Spool drum must be at center of the CR bay. The length of the motor will affect the spool drum
placement. Additional length will also require additional structure, which affects the mass of the system.
Score
1 (Worst)
2
3
4
5 (Best)
Cost
> $400
$300-$400
$200-$299
$100-$199
<$100
Mass
> 8 kg
5.5-8 kg
3-5.5 kg
1.5-3 kg
< 1.5 kg
Power
> 120 J/s
100-120 J/s
80-99 J/s
60-79 J/s
< 60 J/s
Mechanical
Complexity
Motor and Gearbox
require high tolerance
machining
Required Gearbox
not COTS
Separate Gearbox and
Motor different
companies
Separate Gearbox and
Motor same company
Geared Stepper
Motor
Size
> 20 cm
17.5 – 20 cm
15-17.5 cm
12.5 – 15 cm
< 12.5 cm
83
RAPPELLING – MOTOR SELECTION
• Chosen Motor: 3334_057STH56 Nema 23 77:1gearbox stepper motor
•
•
•
Holding Torque: 23.5 Nm
Mass: 1.5 kg
Cost: $74.00
• Chosen for large margin in holding torque.
Metric
Weight
PG15
Nema 23
Pg47
Nema 23
Phi-266
Nema 23
AEN5
Nema 23
S18GM01
8
3333_0
Nema 23
3334_0
Nema 23
Cost
20%
5
5
5
1
2
5
5
Mass
25%
5
4
5
3
5
5
5
Power
20%
4
4
5
5
2
5
5
Mechanical
Complexity
25%
4
3
3
3
4
4
3
Size
10%
5
5
5
5
5
5
5
4.7
4.35
4.8
3.5
3.7
4.9
4.8
Final Score
84
POWER DISTRIBUTION SCHEMATIC
Fuse
0.7 V
5V
22 uF
511 kOhm
100 nF
5.6 uH
25 V
100 Amp
12 V
0.1 uF
14.8 V Battery
Vcc
Vin
Vin
VREF
AD7327
0.7 V
Vin
HG
Ron
Vcc
SS
BST
2.2 uF
VIOUT
ACS712
12 V
FILTER
1K
Gnd
Gnd
VMeas
Gnd
340 KOhm
1 nF
EN
330 pF
SW
191 kOhm
470 nF
Red LED
lim
SGND
SGND
PGND
System Protection
Measurement
LG
Back EMF
Protection
MOV
3.3 nF
LM3150
15 nF
180 uF
30 V
80 Amp
866 Ohm
10.0 KOhm
FB
12V Regulation
10 KOhm
3.3 V
5V
SD
BST
27 uH
45.3 KOhm
22 nF
SW
VIN
3.3 uH
SS
PRE
0.32 V
2 Amp
LM5005
100 nF
10 KOhm
FB
GND
8.2 nF
LMR10510Y
OUT
RAMP
SW
Vin
IS
VCC
SYNC
1 uF
FB
4.7 uF
EN
GND
3.09 KOhm
COMP
100 uF
4.7 uF
0.6 V
3 Amp
470 pF
19.1 KOhm
2.7 nF
1 KOhm
20.5 KOhm
820 pF
5V Regulation
3.3V Regulation
85
ELECTRICAL LOAD ANALYSIS
Case Study: 12V Regulation – Startup Conditions
• Reaches steady state in 0.002 sec
86
ELECTRICAL LOAD ANALYSIS
Case Study: 12V Regulation – Input Transient
• Input transient is modelled by a increasing source voltage
• Maximum fluctuation of 0.27 V is within +/- 1V tolerance
87
ELECTRICAL LOAD ANALYSIS
Case Study: 5V Regulation – Steady State
• Maximum fluctuation of 0.02 V is within +/- 0.03 V tolerance
88
ELECTRICAL LOAD ANALYSIS
Case Study: 5V Regulation – Output Transient
• Maximum fluctuation of 0.13 V is within +/- 0.03 V tolerance
89
ELECTRICAL LOAD ANALYSIS
Case Study: 3.3V Regulation – Steady State
• Maximum fluctuation of 0.001 V is within +/- 0.009 V tolerance
90
ELECTRICAL LOAD ANALYSIS
Case Study: 5V Regulation – Output Transient
• Maximum fluctuation of V is within +/- 0.03 V tolerance
91
GS & MR EMBEDDED SYSTEMS
Ground Station
Mother Rover
• All connections were considered to verify power inputs
as well as component I/O on the MR and CR (following
slide)
92
CHILD ROVER EMBEDDED SYSTEMS
93
SOFTWARE: Child Rover V&V
Reading the
encoder inputs
via interrupt
service routines
Switch between
the front and
rear encoders
for position data
Controlling the
drive wheels via
PWM to the drive
motor controllers
Controlling the
camera servos via
PWM
Send commands
to the Arduino
using the
Raspberry Pi
Take a picture
with the
Raspberry Pi
camera
Receive and
interpret
commands using
the Raspberry Pi
Save an image to
the Raspberry Pi
Transmit images
PHASE 1
Use the encoder
data to compute
distance traveled
Full Raspberry Pi
System Test
Languages
C++
Full Driving
Software Test
PHASE 2
Full CR
Software Test
Full CR Imaging
Software Test
Python
SOFTWARE: Communication V&V
Transmit
images and
other data
PHASE 1
Read data
from the
ultrasonic
rangefinder
Receive and
transmit commands
and data using the
MR Arduino
Control the MR
rappelling winch
stepper motor via
the MR Arduino
Languages
Send and receive
data between the
MR Arduino and
CR Arduino
Matlab
Python
PHASE 2
Successfully
transmit an
image to the MR
Test the rappelling
control loop
Receive and
interpret
commands from the
Ground Station
Full CR/MR
Communications
Software Test
Full MR Software
Test
Full GS/MR
Communications
Software Test
C++
SOFTWARE: Ground Station V&V
Receive and
interpret
commands from
the Ground Station
Read commands
from a command
line
Display images to
the user
Ground Station
GUI Test
Display position
and other
information to the
user
Language
Matlab
Full Ground
Station Software
Test
PHASE 2
POWER: Verification & Validation
PHASE 1
Static
Load
No-Load
• Do the 12/5/3.3V
rails supply
12/5/3.3V in a
no-load situation
• Noise Threshold
on 12/5/3.3V rail
• Can the
12/5/3.3V rails
supply enough
current under
static load
conditions
Testing Purposes
Dynamic
Load
Thermal
Test
• How does the
12/5/3.3V rail
voltage/current
change during
startup of a
dynamic load
• How do transients
on the outputs
(motor torques)
affect the output
voltage/current
• How do input
transients affect
output
voltage/current
• How do varying
5V loads affect the
3.3V output
• What is the max
temperature of the
regulation
circuitry under
max draw
• How long under
max draw until
temperature
exceeds max
allowable
Protection
• Test reverse
polarity
protection
• Does constant
current protection
circuitry limit
12/5/3.3V rail to
6/1/1 A
Measurability
• Input
voltage/current
accuracy testing
• Output
voltage/current
accuracy testing
Timeline
• Can the power
supply act at a
max draw for the
entre mission
duration
* Power will encompass
all Phase 2 and 3 testing
but does not have any
specific tests
RAPPELLING: Verification & Validation
PHASE 1
Motor to
spool drum
connection
Spooling
Test
MR
Moment
No-slip
PHASE 2
Software
feedback
control loop
Winch Test
STATUS
Analysis
Completed /
Testing
Needed
Testing &
Analysis
Needed
Structure
Stress
Analysis
MR
Integration
Full
Rappelling
System Test
Winch motor
control via
MR Arduino
Rappelling
Software Test
COMMUNICATION: Verification & Validation
PHASE 1
Using borrowed
radios and no high
gain antennas
Using more
powerful radios and
using high gain
antennas
PHASE 2
* These tests are a high level
overview of what Comm. Tests
need to be done. Much of the
Comm. Testing will be done handin-hand with the Software Comm.
Testing portion as seen later.
Verify link
between GS
and MR
Radio-toRadio packet
transmission
STATUS
Completed
Test/Analysis
Duplicated
Radio-to-Radio
packet
transmission
Needs
Testing/Analysis
Verify link
between MR
and CR
Full
Communication
Test
Test Matlab
command assembly
from GUI for
transmission
VERIFICATION & VALIDATION: Phase 3
Testing
Full Systems Test
Test A: Full Systems
test minus comm.
conditions
Test B: Difficult
comm. conditions
• Test A: Full systems test minus the difficult communication conditions for an ideal test. This test
validates the Rappelling system, Driving system, Positioning system, and the Imaging system.
• Test B: Test the system in difficult communication conditions. This test will validate the
communication system while also testing the Driving, Positioning, and Imaging systems in these
communication conditions
THIS IS A TEST SLIDE
• This is literally only here so that we have more than 100 slides.
101