VITL Preliminary Design Review (PDR)

1
VITLPreliminary Design Review (PDR)

• Wednesday, July 08, 2015

Team Members Ryan Hickman, Chris Homolac, Jen
Krupp, Kyle Ligon,
Heather Love, Alex
Paulson, Kathryn Rash, Veronica Vertucci
2
Overview

• Project Objectives Overview
• System Design Alternatives
• System Design-To Specifications
• Subsystem Design Alternatives Feasibility
• Drive System
• Sensors Software
• Command Data Handling (CDH)
• Structure
• Power
• Thermal
• Testing Analysis
• Risk Assessment
• Project Management Plan

3
Overview

• Project Objectives Overview
• System Design Alternatives
• System Design-To Specifications
• Subsystem Design Alternatives Feasibility
• Drive System
• Sensors Software
• Command Data Handling (CDH)
• Structure
• Power
• Thermal
• Testing Analysis
• Risk Assessment
• Project Management Plan

4
Objectives Goals Overview

• Design and build a prototype for the locomotion
  system of a vehicle exploring Europa
• Capable of traversing 1 km of icy terrain in 7
  days
• Capable of traversing obstacles characteristic of
  Europa
• Maximize traversable incline
• Maximize range
• Minimize power draw and mass

5
Objectives Overview

• Why Europa?
• One of the best candidates for life
• beyond earth
• Under Europas surface (100m)
• is the most likely location for
• liquid water outside of Earth
• Technological Challenges
• Europas surface temperature is about 100K
• Power
• Radiation
• Traction
• 1/6 Earth gravity

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Overview

• Project Objectives Overview
• System Design Alternatives
• System Design-To Specifications
• Subsystem Design Alternatives
• Drive System
• Sensors Software
• Command Data Handling (CDH)
• Structure
• Power
• Thermal
• Testing Analysis
• Risk Assessment
• Project Management Plan

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System Design Alternatives

• Wheeled
• Spider
• UAV

• Snake
• Roller
• Tracked

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System Design Alternatives

• Performance Variables
• Experience
• Power
• Thermal
• Traction
• Speed
• Stability
• Complexity
• Agility
• Mass
• Structure
• Payload

• Initial Calculations
• Trade Study Weighting
• Top Level Feasibility

• Wheeled Architecture
• 3, 4 and 6 Wheeled designs
• Additional Trades
• 6 Wheeled Design

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Overview

• Project Objectives Overview
• System Design Alternatives
• System Design-To Specifications
• Subsystem Design Alternatives Feasibility
• Drive System
• Sensors Software
• Command Data Handling (CDH)
• Structure
• Power
• Thermal
• Testing Analysis
• Risk Assessment
• Project Management Plan

10
System Design To Specifications
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Design To Specifications

• Traction and Maneuverability
• Six wheels to grip icy terrain
• Sufficient traction for accurate navigation
• Autonomy
• Sensors to detect hazardous terrain
• Navigate unpredictable terrain
• Survivability
• Substantially built
• Insulated to survive at cryogenic temperatures
• Last seven days
• Travel one kilometer
• Payload attachment

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Overview

• Project Objectives Overview
• System Design Alternatives
• System Design-To Specifications
• Subsystem Design Alternatives Feasibility
• Drive System
• Sensors Software
• Command Data Handling (CDH)
• Structure
• Power
• Thermal
• Testing Analysis
• Risk Assessment
• Project Management Plan

13
Drive System
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Drive Design To Specifications

• Geometry
• Maximum Size of vehicle 1 m3
• Terrain Crossing
• Ice at 100 K
• Ruts Ridges 1 m x 8 cm x 3 cm (L x W x H)
• Inclination 20
• Capabilities
• Zero turning radius
• Range 1 km in 7 Earth days

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Drive Design Components
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Drive Drivetrain Alternatives

Chain or Belt Drive Shaft Drive Direct Drive
Pros Moderate Mass Low No. Motors Moderate Complexity Adequate Wheel Speed Control High Efficiency (94) Low No. Motors High Reliability Good Wheel Speed Control High Efficiency (99) High Reliability Low Complexity Low Mass
Cons Low Efficiency (75-97) Low Reliability Chains Belts High Mass High Complexity High No. Motors Poor Wheel Speed Control
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Drive Wheel Alternatives

• Location Number

Design A B C D
Stability 2 1 4 4
Complexity 4 3 2 1
Reliability 2 1 4 3
Feasibility 4 4 4 4
Overall 12 9 14 12
1 Poor/Unsatisfactory 2 Good/Average 3 Better/Exceptional 4 Best/Excellent
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Wheel Design Alternatives

• Size

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Drive Motor Alternatives

• Type

Brush D.C. Motor Brushless D.C. Motor A.C. Induction Motor Stepper Motor
Pros High Torque _at_ Low RPM Low cost Simple High Torque _at_ High RPM Long Life High Efficiency Good Vacuum Qualities Large Speed Range High Torque _at_ High RPM High Reliability High Precision Actuation
Cons Limited Life Limited Speed Range Poor Vacuum Qualities Low Efficiency EMF High cost High Complexity Limited Life Limited Speed Range Poor Vacuum Qualities Low Efficiency Low Torque Limited Speed Range High Complexity EMF

• NASA Report Selection of Electric Motors for
  Aerospace Applications

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Drive Suspension Alternatives

• Type

Fixed Rocker-Bogie
Complexity 2 1
Obstacle Clearance 1 2
Efficiency 1 2
Mass 2 2
Feasibility 2 2
Overall 8 9
1 Poor/Unsatisfactory 2 Best/Excellent
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Suspension Design Alternatives

• Turning

Design A B C
Maneuverability 1 3 3
Complexity 2 1 3
Efficiency 2 3 1
Speed 1 3 2
Feasibility 3 3 3
Overall 9 13 12
1 Poor/Unsatisfactory 2 Good/Average 3 Best/Excellent
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Sensors

• Design-to-Specifications
• Slope
• Vehicle shall not exceed a slope of 20
• Obstacles
• Vehicle shall detect obstacles that are larger
  than 1 as defined by customer
• Cliff
• Vehicle must be able to detect if a cliff, wall,
  or slope larger 20 is in its current path
• Distance
• Vehicle shall travel 100 m and be accurate to
  that distance within one vehicle body length

23
Sensors
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CDH/Comm Design Alternatives
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CDH CPU Alternatives

• Criteria
• Easily programmable
• Fair price
• Must be able to afford back up CPUs
• Supports enough ADC for all analog inputs
• If not, ability to add external ADCs or have two
  controllers working together

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Structures

• Overview
• Primary requirements
• Volume less than 1 m3
• Survival at 100 K
• Payload Considerations (lt10 kg)
• Flowdown requirements
• Structural stability
• Structure/drivetrain interactions
• Support for subsystems (structural and wiring)
• Maximum load sustained

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Structures

• Fundamental Design Alternatives
• Primary structure layout
• Box
• Circular
• Subsystem boxes
• Shell
• Wire frame
• Drivetrain interface
• Integration into design
• Modular
• Wiring support
• Common bus
• Distributed network

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Structures

• Primary Structure Layout Alternatives
• Circular Box
• -Minimize stress points -Conventional Design
• -Complex drivetrain interaction, stability
  -Straightforward drivetrain
• -Good for agility, common data/power
  -Strength may be an issue

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Structural Feasibility
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Power

• Design To Specifications
• Wattage/Voltage
• Provide enough wattage and voltage to run all
  components needed for testing
• Capacity
• Provide a long enough run-time to verify the
  requirements for the tests

31
Power

• Not a requirement for prototype but is still
  considered
• Needed for testing purposes
• Actual Rover
• RTGs - but these may cause contamination
• Future technological advancements
• Prototype
• Batteries Lithium Ion
• Wide range of operating temperatures
• High capacity
• Rechargeable

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Thermal

• Design To Specifications
• Thermal Vac
• Provide the system with enough heat where needed
  to function properly at 100K
• Other tests
• Keep the ambient temperature of each of the
  components within operating temperatures

33
Thermal

• Need to keep all internal components -20C or
  above for prototype
• Due to operating temperatures of most components
• Actual Rover
• Need heaters on all servos
• Due to the specifications of the material used
• Can use RHUs
• Aerogel Insulation
• Prototype
• Fiberglass insulation
• Aerogel for thermal vacuum testing

34
Overview

• Project Objectives Overview
• System Design Alternatives
• System Design-To Specifications
• Subsystem Design Alternatives Feasibility
• Drive System
• Sensors Software
• Command Data Handling (CDH)
• Structure
• Power
• Thermal
• Testing Analysis
• Risk Assessment
• Project Management Plan

35
Testing Verification of Requirements
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Testing Needs
37
Testing Terrain Course
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Testing Out of Prototype Scope

• Design
• Power Source
• Testing
• Europa Environment
• Radiation
• Pressure
• Total vehicle at 100 K

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Overview

• Project Objectives Overview
• System Design Alternatives
• System Design-To Specifications
• Subsystem Design Alternatives Feasibility
• Drive System
• Sensors Software
• Command Data Handling (CDH)
• Structure
• Power
• Thermal
• Testing Analysis
• Risk Assessment
• Project Management Plan

40
Top Risks Assessment
(1) Motor/Electronics Failure at 100K ?Use
cryogenic motors/electronics ?Add heaters (2)
Localized Stress Concentrations ?Design with
large stress margins (3) Schedule Delays
?Overestimate time by at least 2x (4) Cost
Overruns ?Apply for UROP/EEF ?Maximize
existing facilities and resources (5)
Availability of Testing Facilities ?Backup
thermal tests at lower temp.
2 1 4
5
3


Consequence
Probability
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Risk Assessment Prototyping

• Component boxes to represent subsystem loads and
  distributions
• Motor testing in thermal vacuum (if available)
• Possible materials testing in thermal vacuum (if
  available)

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Overview

• Project Objectives Overview
• System Design Alternatives
• System Design-To Specifications
• Subsystem Design Alternatives Feasibility
• Drive System
• Sensors Software
• Command Data Handling (CDH)
• Structure
• Power
• Thermal
• Testing Analysis
• Risk Assessment
• Project Management Plan

43
Organizational Responsibilities
44
Work Breakdown Structure (WBS)
45
PDR-CDR Schedule
46
Spring Semester Schedule
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Cost Estimates
  Number Cost
Drive Subsystem   1,040
Drive Train 0 0
Wheels 6 175
Motors 7 840
Suspension 1 25
Sensors Software   417
Accelerometer 1 12
Odometer 4 75
Rate Gyro 1 30
Radar/IR/Laser 2 300
Autonomy Algorithm 1 0
Locomotion Algorithm 1 0
CDH/COMM   290
CPU 1 50
Data Storage 1 10
Motor Control/Misc 1 150
Remote Controller 1 50
RF TX 1 15
RF RX 1 15
  Number Cost
Structures   670
Frame 1 500
Connecters 20 50
Cables 10 20
Component boxes 4 100
Power   84
Battery 3 34
Battery Charger 1 50
Thermal   177
Heater for 100K 1 40
Insulation 1 7
Insulation for testing100K 1 130
Testing   1,205
100 K   910
Structure 1 30
Torquemeter 1 800
Voltmeter 1 0
Ammeter 1 0
Rotary sensor (optional) 1 80
  Number Cost
Thermal Vacuum 1 0
Terrain Course   255
Obstacles - Boxes 3 5
Surface Material - Wood 4 160
Structure - Wood 10 90
Observation 1 0
Timer - Stop Watch 1 0
Straight/Level Course   40
Distance Sensor 1 40
Shipping   300
Management Costs   250
Subtotal   4,433
35 Margin   1,551
Total   5,985

• Will require additional funding from EEF/UROP
  grants

48
Limited Budget
  Cost
Drive Subsystem 1,000
Sensors Software 400
CDH/COMM 290
Structures 500
Power 84
Thermal 150
Testing 800
Shipping 250
Management Costs 150
Subtotal 3,624
10 Margin 362.40
Total 3,986

• Still possible without EEF/UROP funding
• Requires substantial decrease in Testing and
  Structures and minor cuts in the remaining
  subsystems

49
Specialized Facilities and Resources

• Ball Thermal Vacuum
• University of Colorado Ice Rink
• Lake

50
Acronym List

• ADC Analog to Digital Converter
• CDH Command and Data Handling
• COTS Commercial Off The Shelf
• CPU Central Processing Unit
• RF Radio Frequency
• RHU Radioisotope Heater Unit
• RTG Radioisotope Thermoelectric Generator
• RX Receiver
• TX Transmitter
• WBS Work Breakdown Structure

51
References

• Trudy Schwartz
• SolidWorks 2005
• Vable, Madhukar. Mechanics of Materials.
• www.onlinemetals.com
• www.matweb.com
• www.analog.com
• www.pcb.com
• www.thomasnet.com
• www.globalspec.com
• www.servosystems.com
• www.sensotech.com
• www.omega.com
• www.powerelectrics.co.uk
• www.quadratureencoders.com
• www.panasonic.com
• www.powerstream.com
• www.all-battery.com
• www.media.popularmechanics.com
• www.maxon.com

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• Additional Slides

53
1.1 Geometry Requirement
54
1.2 Payload Considerations
55
Drive System Demonstration
56
Drive Motor Alternatives
57
Drive Wheel Alternatives

• Moment of Inertia Calculations

58
Drive Wheel Alternatives

• Material

304 Stainless Steel INVAR 32-5 Titanium Aluminum 7075 T6
Density (g/cm3) 8 8.14 4.5 2.81
Yield Strength (MPa) 215 276 140 503
Tensile Strength (MPa) 505 483 220 572
CTE (µm/m-C) 17.3 0.63 8.9 23.6
Rockwell B Hardness 70 90 40 87
Cost (/cm3) 0.15 0.34 4.33 0.10
59
Drive Motor Alternatives

• Torque

• EC Brushless DC Motors
• COTS operational temps
• -35C to 100C
• Heritage operational temps
• -120C to 25C

60
Drive Suspension Alternatives

• Material

304 Stainless Steel INVAR 32-5 Titanium Aluminum 7075 T6
Density (g/cm3) 8 8.14 4.5 2.81
Yield Strength (MPa) 215 276 140 503
Tensile Strength (MPa) 505 483 220 572
CTE (µm/m-C) 17.3 0.63 8.9 23.6
Rockwell B Hardness 70 90 40 87
Cost (/cm3) 0.15 0.34 4.33 0.10
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Drive Mass and Cost Budgets
Mass Margin Mass Margin Cost Margin Cost Margin
Drivetrain 0.00 0.00 0.00 0.00
Motor 1.50 kg 50 720.00 50
Wheels 1.38 kg 25 175.00 25
Suspension 0.60 kg 200 25.00 25
Total 7.43 7.43 920.00 920.00
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Design System Calculations

• Coefficient of Friction

• µs 0.36397

63
Drive System Calculations

• Equivalent Earth Inclination

? finclination,Earth 2.62

• Rollover Angle

64
Typical Sensor Specifications
65
Sensors Range

• Odometry
• Straight
• Incremental
• Phase
• Turning
• Rate Gyro
• Accelerometer

66
Autonomy
Matlab C/C
Pros More Experience More Powerful Simple Light weight Easy Integration
Cons Processor Intensive Not as powerful Not as experienced
67
CDH Control Alternatives

• Criteria
• Creates easy testing environment
• Maintains simple design (not overly complex to
  implement)

• Control Methods
• Radio Frequency (RF)
• Requires Comm subsystem with receiver/transmitter
  equipment
• Remote Control
• Programmable
• Pre-programmed software modules
• Programs must be quickly and easily changeable
  for testing (Might require laptop)

68
CDH Data Storage Alternatives

• Onboard Memory
• Memory embedded within CPU
• Might lower resolution of data
• External Memory modules connected to CPU
• More complex to integrate
• Offers large data storage

• Telemetered Data
• Requires Comm subsystem
• Requires high baud rate to telemeter data back to
  external memory
• Requires external memory not a part of main
  system (Might require laptop)

69
CDH Motor Control Alternatives

• Criteria
• Easy to implement
• Fair price
• Must be able to reproduce easily or buy spares

• H-Bridge
• Tailored to specific designs
• Might not be compatible with type of rover design
• Self-Constructed
• Requires more electronic configuration
• Adaptable to any rover design

70
Structures
71
Structures

• Initial Material Assessment
• Rough comparisons of materials commonly used in
  cryogenic applications
• Steps
• Cost is of that of
• 12x12x.1 inch or
• similar sized plate

Material ksi lb/in3 Specific Strength ( / ) Amin (in2) X10-4 m/L lb/in (x10-4) Cost ()
AISI 304 steel 39 0.289 134.94 28 8.1 36
Ti 5-Al 2.5-Sn 115 0.162 709.8 9.6 1.5 1,021
INVAR 40 0.291 137.45 28 8.0 80
Aluminum 7075 21 0.097 215.38 50 5.1 23
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Structures

• Initial Feasibility Assessment
• SolidWorks with dimensions of available materials
• 50 kg load at center, edges fixed, determine if
  any points exceed yield strength of material
• Shows that some Aluminum configurations would not
  be feasible, though most would, as would most
  configurations of other materials

73
Power

• Component Trade Study

Component Cost Accessibility Added Mass to Vehicle Usability
RTG High Poor Low Medium
Power Supply Medium Good None High
Batteries Low Good High High
Electrical Outlet Very Low Good None Low
74
Power

• Battery Trade Study

Battery Mass (g) Operating Temperature Capacity (mAh) Primary/ Secondary Cost
Lithium Thionyl Chloride Multi-Cell 40 -40C to 60C 1000 Primary 5.40
Manganese Dioxide Lithium 35 -40C to 60C 1300 Primary 5.95
Lithium Thionyl Chloride 40 -40C to 60C 1000 Primary 5.95
Primary Lithium Thionyl Chloride 190 -55C to 85C 36000 Primary 34.95
Lithium Ion 47 -60C to 40C 2350 Secondary 7.85
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Thermal

• Component Trade Study

Component Cost Accessibility Added Mass to Vehicle Usability
Aerogel Insulation High Low Low Medium
Other Insulation (Fiberglass etc.) Low High Medium High
Heaters Medium Medium High Medium
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Testing 100K Thermal Vacuum

• Facility Resources
• Ball Aerospace
• Advanced Product Testing
• Sensors to measure
• Torque
• Voltage
• Current
• Wheel and Axle Rotation
• Supporting Apparatus
• Same material as suspension

77
Testing Terrain Course Characteristics

• Odometers to measure distance traveled
• Defined box/grid to measure direction change
• Camera to document success or failure to maneuver
  as expected
• Timer to record test duration

• Potential surface materials
• Wood
• Plastic
• Metals
• Dangerous Obstacles
• Cardboard boxes
• Variable Inclines
• Notched vertical supports
• Vertical supports of varying height

78
Testing Straight and Level Course

• Potential surface materials
• Wood
• Plastic
• Metals
• Ice
• Arena
• Lake
• On-board sensors to measure distance traveled

• Timer to record test duration
• Location Measurement
• GPS
• Surveying equipment
• Reel Tape Measure
• Accuracy need depends on length of course