VITL April 21, 2023
VITLCritical Design
Review (Sec 2.1)
Friday, April 21, 2023
Team Members: Ryan Hickman, Chris Homolac, Jen Krupp, Kyle Ligon,
Heather Love, Alex Paulson, Kathryn Rash, Veronica Vertucci
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Objectives Overview
Design and build a prototype for the locomotion system of a vehicle exploring a Europa-like surface capable of traversing 1 km of icy terrain in 7 days with characteristic obstacles.
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Characteristic Mission Profile
Aerial View
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Characteristic Mission Profile
Side View
Not to Scale
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Theoretical Europa Mission (TEM)• What makes a Europa mission?
– Surface Characteristics• Ice
– Friction (µ~0.55) and Hardness (~6 mohs)• Obstacles
– Inclines, Bumps and Ruts
– Environment• Low Temperature (100K)• Reduced Gravity (1/6 g)• Power Supply challenges-Solar power not viable• Radiation (1MRad)• Low Pressure (10-6 Pa)
– Scientific Objectives• One of the best candidates for liquid water and life beyond Earth• 3 proposed instruments (camera, magnetometer and radiation
sensor)
• A Theoretical Europa Mission (TEM) would accommodate all of these.
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TEM Simplification• The VITL locomotion will concentrate on:
– Surface Characteristics (previously shown)– Simplified Environment
• Low Temperature– 100K manufacturing and testing is infeasible due to resources and
experience.– Instead vehicle will be designed for 0°C operation
» Entire vehicle can be tested on a “cold” Earth day on frozen lake» Design methods can be extended for TEM using materials for 100K
operation• Reduced Gravity• Accommodate mass of a traditional power supply • NOT worrying about pressure or radiation on Europa (out of scope)
– Simplified Scientific Objectives• Accommodate mass of 10kg payload
– Additional locomotion and sensing requirements• These form the design requirements of the Engineering
Design and Manufactured Unit (EDMU) for Senior Projects
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Top Level System Requirements
VITL
Structural 1.0 Electronics 2.0 Performance 3.0
Geometry 1.1
Payload Considerations 1.2
Terrain Crossing 3.1
Inclination 3.2
Direction Change 3.3
Obstacle Detection 2.1
Control 2.2
Mission Life 2.3
Temperature 3.4
Range 3.5
Efficiency/Accuracy 3.6
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1.1 Geometry Fit within one cubic meter
Fit within one cubic meter
1.2 Payload Power, heat and facilitate the use of any possible science sent to Europa.
Use a 10 kg dummy payload to simulate the mass
Requirement Flow-down from TEM to EDMU
TEM EDMU
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2.1 Obstacle Detection
Sense obstacles specified in PDD, cease movement and wait for further command
Sense obstacles specified in PDD and cease movement
2.2 Controller Some form of odometry coupled with visual data sent to earth to navigate
Use of a COTS controller to manually navigate terrain for testing and verification purposes
2.3 Mission Life
System must operate for 7 days and components must be rad-hard to survive intense radiation environment
All systems must be capable of operation at least 7 days
TEM EDMU
Requirement Flow-down from TEM to EDMU
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3.1 Terrain Crossing
Traverse obstacles outlined in PDD on Europa’s surface
Traverse obstacles outlined in PDD on lake ice
3.2 Inclination Stop or go on in any direction on a 20 degree slope
Equating torques yields an Earth slope of 2.62 degrees
3.3 Direction Change
Yaw 180 degrees to allow removal from a dangerous situation
Yaw 180 degrees to allow removal from a dangerous situation
3.4 Temperature Entire vehicle must operate in 90-110K
No 100K testing. Design for 0°C. Some Drive components may be tested
Requirement Flow-down from TEM to EDMU
TEM EDMU
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Requirement Flow-down from TEM to EDMU
TEM EDMU
3.5 Range The vehicle must travel a distance of no less than 1 kilometer in 7 days
Must show repeatability to prove that EDMU can travel 1 kilometer
3.6 Efficiency/Accuracy
Destination coordinates accurate to one body length of TEM
Using odometry, a scale of one body length to every 100 meters traveled accuracy must be obtained
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EDMU System BreakdownVITL
Drive Electronics Structure Testing
Sensors
C&DH/COMM
Software
Power/Thermal
Sensors
Structures
Facilities
Suspension
Wheels
Motors
Frame
Component boxes
Material Selection
Thermal
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EDMU Preliminary Layout
Science Payload
TEM Power (dummy mass)
BatteriesSonar and
Proximity
SensorLaser Range
Thermal Strip
Suspension
and Drive train
Attachments
Motor Controller
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Structures EDMU Layout
Accelerometer and
Rate Gyro
Receiver, C&DH
Board, and Motor Controller
ThermalStrip
For Analysis, assume Aluminum alloy
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Structures EDMU Layout
Science Payload
TEM Power (dummy mass)
BatteriesSonar and
Proximity
SensorLaser Range
Thermal Strip
and Motor ControllerSuspension
and Drive train
Attachments
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Electrical Interconnects Block Diagram
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Friction Analysis
• Required Coefficient of FrictionEuropatotalw gmF
)cos()cos( inclineEuropatotalinclinewN gmFF
)sin()sin( inclineEuropatotalinclinewslide gmFF
slideinclineEuropatotalsNsf FgmFF )cos(
)tan()cos(
)sin(incline
inclineEuropatotal
inclineEuropatotal
N
slides gm
gm
F
F
)tan( inclines
φincline
Fslip
FfFw
FN
• μs = 0.36397– Difficult to design to
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Penetration Analysis• Spike Penetration
– Easy to design to
– Fspike > Fslide
– mrover = 70 kg
– 20° Inclination– α < 70°
φincline
αFslide
F Fspike
FN
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Design System Calculations
• Equivalent Earth Inclination
h
wroll 2
tan 1
θroll
w
h
)sin( ,inclineEuropatotalwheelfwheelEuropa gmrFr
EarthEuropa
)sin()sin( ,, EarthinclineEarthtotalwheelEuropainclineEuropatotalwheel gmrgmr
)sin(sin ,
1, Europaincline
Earth
EuropaEarthincline g
g
• Rollover Angle
φinclination,Earth = 2.62°
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Structures Load Analysis – Load Distribution
Science Payload
TEM Power (dummy mass)
Min FOS = 22
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CDR Prototyping
• Traction tests– Surface hardness– Spike penetration– Slippage
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Acronym List
• ADC: Analog to Digital Converter• C&DH: Command and Data Handling• COTS: Commercial Off The Shelf• CPU: Central Processing Unit• EDMU: Engineering Design and Manufactured Unit• RF: Radio Frequency• RHU: Radioisotope Heater Unit• RTG: Radioisotope Thermoelectric Generator• RX: Receiver• TEM: Theoretical Europa Mission• TX: Transmitter• WBS: Work Breakdown Structure
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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• www.nasa.gov
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Quick Links
• Objectives Overview• Theoretical Europa Mission (TEM)• Top Level System Requirements• EDMU Preliminary Layout• Electrical Interconnects Block Diagram• CDR Prototyping
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