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