camcube critical design review - colorado.edu file– mechanical – software • integration plan...

Brian Roberts (PM)Jennifer Uchida (CFO)Brian MadgeTom FreestoneSteve PfauSam Baker

CamCubeCritical Design Review

CamCube CDR Presentation ASEN 4018 – Fall 2003 2

Presentation Outline

• Status of RFA’s• System Architecture• Design Elements

– Electrical– Mechanical– Software

• Integration Plan• Verification and Test Plan• Project Management Plan


Request For Action

• Issue: Check optical analysis via geometric optics text (Peterson)– Resolution: Descope of CamCube project to

multi-year. This year will encompass a single axis attitude system, which removes the need for an in depth optical analysis

• Issue: Analyze stability requirements – Ensure jitter and drift level required is feasible (Peterson)– Resolution: Reduce ability of CamCube from

detection of ¼ in crack to entire missing tile.

System Architecture



Overall Multi-year Objective

• Eliminate the need for the shuttle to dock at the ISS and allow for additional scientific experiments and maintenance tasks to be performed.

• ACS must create a stable platform for a camera to take images of the shuttle in order to access the condition of the tiles on the space shuttle in flight.


Current Year Objective

• Conceive, Design, Fabricate, Integrate, Test and Verify a viable attitude control system (ACS) for a picosatellitewhich adheres to the overall objective.

• Maintain attitude within one axis


Requirements Overview

• Maintain 15º pointing in 1-axis for 60 minutes• Rate gyro must sense angular change as small

as 0.0167 deg/s• System must be integrated in a 10 cm cube• Center of gravity must be within 2 cm of the

geometric center of cube• Must stay within 1 kg mass requirement


Orbital Analysis

• Clohessy – Wiltshire (Hill’s) Equations– ? V = 0.27 m/s– ? = -113.9º– Range = 100m– ~7 min to prepare for a ? V to

align with Shuttle orbit

• GEODYN II– ? = -115º– t = 6.5213 min = 6:31– Range ~104m

• ? V = 0.27716 m/s• Stays within 110m• With shuttle ~63 min

– Operation time ~57 min

• Lifetime ~16 days


Flight Plan


CAMCube

System Design: Flow Chart

MotorMotion Controller

Encoder ReactionWheel

RateGyro

Power

Rigid BodyDyn

? c

Software User Input

ExternalForce

ITLLLab station

Testing


System Design

• Fabricated Cube (Structure)– Aluminum 5052– 10cm x 10cm x 10 cm (1/16 in thick =.16 cm)– Weight 215 grams

• Rate Gyro (ADXRS150)– 0.7 cm x 0.7 cm x 0.3 cm– Weight is ~0.3 grams


System Design

• Reaction Wheel– Motor w/ encoder (MicroMo Series 2224 006SR)

• Mass = 1.62 oz (43.93 grams)

– Motion controller (MicroMo MCDC2805) • Mass = 3.88 oz (110 grams)

– Fabricated Wheel• Aluminum 5052• Disk radius =.75 in (1.9 cm) thickness 0.136 in (.345 cm)• Mass: 1.1 grams (0.039 oz)


System Design

• Power– Li-ion has best kW/kg ratio and a flat voltage

discharge profile– 4 Li-ion cells (3.6 V each, min of 1050 mAh) – 2 in series and 2 in parallel – Each cell will weigh ~24 g total = 96 g

• Software– LabView


Solid Model


Mass Budget

488.4Total mass20Mountings

2Wiring

1.1Fabricated Wheel

110Motion controller

44Motor

157.1Reaction Wheel96Power (4 Cells)0.3Rate Gyro215StructureMass (g)

Electrical Design Elements



Power Analysis

• Total Amp hours is 2 Ah for battery design (capable of handling 2 motors)• Voltage usage is 5 V for battery design• 4 Li-ion cells with 3.6 V each and a minimum of 1050 mAh each

connected with 2 in series an 2 in parallel will satisfy requirements• Each cell will weigh ~24 g to have a total weight of 6 g

Amp hoursPowerCurrentVoltageComponent

550 mAh2.75 W (max)550 mA (max)70 mA (run)

1 – 24 VMotor

5 mAh0.025 W5 mA5 V (±0.5)A/D Converter

6 mAh0.03 W6 mA5 V (±0.5)Rate Gyro


Electronic Block Diagram

BatteryVoltage Regulator

Reaction Wheel Rate Gyro

External Computer

Filter

Amplifier

A/D Converter


Noise Analysis

• Nominal Lab Station Noise– 1 mV

• Minimum Signal Strength– 0.15 mV

• Correction Plan– Shielded Wire– Soldering Expertise– Low Pass Filter and Amplifier Implementation– Minimize Cable Lengths

Mechanical Design Elements



Attitude Sensing

• Drift Requirement– Provide platform for

picture taking– Prevent “blurring” of

pictures – Primary design drivers

• Pixel allocation• FOV

• Pointing Requirement– Based on typical camera

FOV– Provide nadir pointing

for tile observation– Primary design drivers

• Nadir pointing cone• Time duration


Rate Gyro Requirements

• Driving factor for sensing => pointing req.– Drift rate will require sensing 0.352 deg/s– Pointing req. will require sensing 0.0167 deg/s

• Mass => Must be as light and small as possible• Output => Must be able to communicate with

a computer


Rate Gyro Selected:

Analog Devices: ADXRS150

• Has resolution of 0.015 deg/s• Operates from +/- 5 DC @ 6 mA• Small size!!

– 0.7 cm x 0.7 cm x 0.3 cm– Weight is ~0.3 grams

• Output is analog voltage => will need an A/D converter for computer interface


Risk Assessment

• Device is hermetic– Filled at one atmosphere– If puncture occurs performance is drastically

affected• Lid is made of Kovar, a magnetic alloy that provides

expansion match for ceramic package• Unit is unaffected by any magnetic fields

• Need to minimize/eliminate tethered wires


A/D Converter Requirements

• In order to provide resolution of 0.015 deg/s…– Gyro Sensitivity = 12.5 mV/(deg/s)– V(resolution needed) = 0.1875 mV

• 16 bit converter with no gain– V(resolution obtained) = 0.1526 mV

• Need serial interface to communicate with computer


A/D Converter Selected:Analog Devices: AD977A

• 16 bit, 5 V DC power supply, Int/Ext ref.• Has four input channels

– Allows for output of multiple gyros to be sent to the computer on one serial interface

• 10 µs throughput speed for a complete cycle• Same manufacturer as rate gyro simplifying

the integration process• Low cost ~ $30/unit


Filtering

• Data will be at a frequency of 40 Hz• Can use either a first or second order active LPF• Easy to fabricate and integrate


Amplification

• Non-Inverting feedback amplifier• May be required in order to get desired resolution out

of A/D converter• Simple to fabricate and integrate


Design To Specs: Motor

• Find a DC servo motor that meets the criteria of the following different categories:– Torque: 2.3 oz-in.– Mass: 200 g– Volume: 200 cm3

– Power: feasibility with integration– Cost

• Servo amplifier


Motor & Servo Amp Selected:

MicroMo Electronics

• MicroMo Electronics– FAULHABER (Brush Type Coreless DC-Micromotors

Series 2224 006SR w/ int 12 line encoder)• Skew wound, basket formed, low inductance, ironless

rotor coil • Elimination of hysteresis and core (iron) losses• Rotors are extremely light (low inertia)• Complete absence of cogging

– MCDC2805 motion controller• Velocity, Position, and Torque Control modes• Temperature, voltage and current protection


Risk Assessment

• Torques beyond projected maximums– Software– Manufacturing safety mechanisms

• Easily replaceable– Low cost (1/100 of allotted budget) – Fast Delivery (approx 1 week)


Attitude Control

• Induced Spin Rate– Need to counter induced

spins– Induced spins are from

the spring launcher or the environment

– Spring launcher• K = 1.24 N/m• X = 0.3429 m

• Field of View (FOV)– Ensure shuttle will be in

the camera’s FOV– 15º cone


Induced Spin Rate Requirements

• Inertias– 1 cube: 1.67 g m2

– Wheel: 2 mg m2

• Maximum spin rate of the cube:– Launch spring: 0.024 rpm– Propulsion system: 0.433 rpm


Attitude Control Solution:

Reaction Wheel Fabrication

• Mass: 0.039 oz• Radius: 0.75 in• Thickness: 0.136 in• Material: Aluminum 5052• Hole diameter: 0.079 in


Risk Assessment

• The wheel and shaft of the motor could be misaligned causing a wobble from the wheel.

• The motor could fail at the end of the mission due to over exhaustion and exposure to unplanned speeds.

• When placing the wheel on the motor the pin could get bent.

• The wheel could not be inline with the center of gravity causing an induced spin on the cube.

• Vibrations can come from the motor screwed into the cube.


Attitude Control System Design

• Fly-wheel• DC Motor• Mounting

Software



System Model


Root Locus & Bode Plot


Software Fault Analysis

• Requirements:– Small torques applied over a long interval can

create error in estimated-pointed direction.• Spinning the reaction wheels constantly should prevent

this from happening.

– Lack of error handling in the code– Initial states will be off from the assumed zero

states.


Latency and Throughput Analysis

• The 40 Hz 3 db bandwidth of the rate gyro and 16 bit serial port of the A/D converter limits the system data rate to 640 bits/s

• The latency is the time that it will take a 16 bit signal to go through the lab station at 40 Hz is 0.025 s

Integration Plan



Drawing Tree


Assembly Timeline

CUBE3-1-04

SubcomponentMounting Hardware and Wiring

2-25-04

RateGyros

1-21-04

Driveshaft2-4-04

Motor1-21-04

ReactionWheels1-21-04

Battery HousingCasing2-11-04

PCU2-11-04

Battery2-11-04


Assembly/Integration Timeline

02468

10121416182022242628303234363840

January February March April

Reaction WheelTest ApparatusCubeMotor IntegrationGyro IntegrationSoftwareBattery


Functional Test Plan

• Aluminum Cube– Cross-referenced with Cal Poly design requirements and specifications

• Reaction Wheel– Twin disk testing apparatus/further testing

• Rate Gyro– Twin disk testing apparatus/further testing

• Motor– Apply known voltages to determine if measured rpm values correspond to theoretical

values– Measure motor Speed (no)

• HP HEDS-5505 A06– Measure motor current (Io)

• Current probe• Battery/PCU

– Check outputs to insure actual output is sufficient and/or consistent with theoretical• Voltmeter

• Software– Multiple redundancy parameters


Critical Path Elements

• Driveshaft Fabrication– Mechanically delivering power from the motor to the

reaction wheels• Center of Mass Distribution

– Setting the center of mass within 2 cm of the geometric center

• Data Transfer– Issuing control signals between computer and reaction

wheels• Servo Control

– Varying the current between the motor and the reaction wheels to induce the necessary torque


Purchased Items

System Member Item Company Purchase Date Received PriceAtt Control Tom 1.5-3.0 V DC Motor Radio Shack 11/12/03 11/12/03 $1.99 $4,000.00 CUStructures Sam 5052 H32 Aluminum 11/18/03 11/19/03 $9.04 $4,200.00 UROPAtt Determ Madge Rate Gyros $0.00Testing Tom 3-Axis Gimbal Small Pts 11/25/03 12/3/03 $27.95

Spent $38.98 $8,161.02 Remain

Available Funds

Verification and Test Plan: Four Methods



Testing Details

DisplacementTimeApplied TorqueConnection to LC

MovementPerturbations1 axisApplied ForceCurrentLever Arm

MeasurementsVariablesConstantsMeasurementsVariablesConstants

Test 2Test 1

Drift rate

Time of slewStarting angleResponse time

Accuracy of slewSlew Angle1 axisCorrection accuracyTorque1 axis

MeasurementsVariablesConstantsMeasurementsVariablesConstants

Test 4Test 3


Test 1: Dual Disk Apparatus

• Explanation: RW attached to freely rotating plate mounted on a stationary flat plate– Lever arm connected to

rotating plate exerts a force on a load cell producing a measurable torque

• Hypothesis: This test will verify the transfer function and constraints of the motor/reaction wheel system


Procedures

1. Place reaction wheel on top flat plate2. Connect lever arm to the load cell3. Input a known current4. Measure force from load cell5. Repeat for different current values


Data Analysis

• Response Predictions– Establish a relationship between input current and output

force/torque => transfer function

• Analysis of Data– Bode diagram: System identification

• Poles => Roots of denominator • Zeros => Roots of numerator

– Transfer function for motor system can be verified


3-Axis Gimbal

• Allows rotation about 3 axes

• Two axes will be fixed to isolate the rotation about one axis


Movement Tracking System

• Laser – Mounted on CamCube• Grid – Placed on wall• Video Camera – Tracks real time movement of

laser on the grid– Digital Cannon A-70 Power Shot (USB interface)– Can be loaded into MATLAB one frame at a time

• Digital clock – Filmed along with movement of laser for use in later analysis


Test 2: Stability Test

• Explanation: Beginning at rest, slight environmental perturbations will cause CamCube to deviate from an initial point– These deviations will be measured while the RW

tries to correct itself

• Hypothesis: CamCube will maintain stability within a 15º pointing over 15 minutes in a single axis


Procedures

1. Mount CamCube on 3-axis gimbal with laser pointer directed at origin of grid

2. Hold CamCube stationary while turning on reaction wheels

3. Let go of CamCube and allow reaction wheels to compensate for gravitational perturbations

4. Let CamCube run for 60 minutes5. Track movement of laser pointer with video camera

and digital clock


Data Analysis

• Position points will be taken from the video at TBD time increments– Plot position vs. time

• Centroiding– Frame by frame


Test 3: Applied Torque

• Explanation: Apply a known torque to CamCube and allow the RW to correct itself– The response time will be measured as well as

accuracy of correction

• Hypothesis: With an impulse torque applied, CamCube can maintain the max drift rate of less than 0.352 deg/sec and a pointing accuracy of 0.01667 deg/sec


Procedures

1. Mount CamCube on 3-axis gimbal2. Turn on reaction wheels3. Apply a known torque4. Measure movements of laser pointer with

video camera and digital clock5. Repeat for varying values of torque


Data Analysis

• Position points will be taken from the video at TBD time increments– Plot position vs. time

• Plot measured ? vs. predicted ?• Plot applied torque vs. response time


Test 4: Slewing Test

• Explanation: With CamCube initially at origin of grid, allow the RW to slew CamCube to a desired angle– The accuracy at which CamCube slews to the

desired angle will be measured as well as the time

• Hypothesis: With a commanded degree of slew CamCube will stop within 15º of projected end point


Procedure

1. Mount CamCube on 3-axis gimbal2. Turn on reaction wheels3. Command CamCube to rotate a specified

angle between 0º-180º4. Measure movement of laser pointer with

video camera and digital clock5. Repeat for varying slew angles


Data Analysis

• Determine the response time of slew– Plot ? vs. time (for each test)

• Determine accuracy of slew– Plot ?measured

- ?desired vs. time (for each test)

• Analyze step response– Overshoot– Settling time


Sensors List

• Laser Pointer• Video Camera• Digital Clock• Load Cell• Rate Gyros

Project Management Plan



Organizational Chart

Project ManagerBrian Roberts

Chief Financial OfficerJen Uchida

Orbital MechanicsJen Uchida

SoftwareTom Freestone

Project Advisory BoardProf Steve Nerem

Prof Scott Palo Chris Koehler

MotorSteve Pfau

Attitude ControlTom Freestone

Attitude DeterminationBrian Madge

TestingJen Uchida

StructuresSam Baker

ElectronicsBrian Roberts


Work Breakdown Structure

TF3-Axis Gimble8.2

JUTwin disk testing aparatus8.1

JUTesting8

TFSoftware7.3

SBMounting7.2

BMSpace Allocation7.1

BMIntegration7

TFControl Law6.3

TFReaction Wheel6.2

BMRate Gyro6.1

TFData Acquisition and Control6

SBFabrication5.2

SBDesign5.1

SBStructure5

BMFabrication4.2

BMDesign4.1

BMRate Gyro4

SPMotor3.2

TFWheel3.1

JUReaction Wheel3

SBTest Plan2.5

JUFlight Plan2.4

JUOrbital Analysis2.3

BMRequirements and Specification Definition2.2

BMGoals, Objectives, and Needs Documentation2.1

BMSystem Engineering2

TFExternal Interface1.4

BRTask Management1.3

JUFinancial Management1.2

BRPlanning and Scheduling1.1

BRProject Management1

ResponsibilityActivity NameControl Number


ScheduleID Task Name Duration Start Finish

1 CDR 1 day Wed 11/26/03 Wed 11/26/03

2 Project Management 100 days Mon 10/20/03 Thu 4/1/04

3 Project Management Plan 10 days Mon 10/20/03 Fri 10/31/034 Budjet Projections 7 days Mon 10/20/03 Tue 10/28/03

5 Financial Report 97 days Thu 10/23/03 Thu 4/1/04

30 Work Breakdown Structure 10 days Mon 10/20/03 Fri 10/31/03

31 Meeting Agendas 97 days Thu 10/23/03 Thu 4/1/0456 System Engineering 23 days Mon 10/20/03 Wed 11/19/03

57 Goals, Objectives and Needs Documentation 10 days Mon 10/20/03 Fri 10/31/03

58 Requirements and Specification definition 23 days Mon 10/20/03 Wed 11/19/03

59 Technical Specifications 11 days Mon 10/20/03 Mon 11/3/0360 Power Requirements 5 days Mon 11/3/03 Fri 11/7/03

61 Weight Requirements 5 days Mon 11/3/03 Fri 11/7/03

62 Drawing Tree 3 days Mon 11/17/03 Wed 11/19/0363 Structural Specifications and Requirements 5 days Mon 10/20/03 Fri 10/24/03

64 Orbital Analysis 12 days Mon 10/20/03 Tue 11/4/03

65 Shuttle Divergence 5 days Mon 10/20/03 Fri 10/24/03

66 Shuttle Avoidence Plan 5 days Mon 10/20/03 Fri 10/24/0367 De-orbit Plan 5 days Mon 10/20/03 Fri 10/24/03

68 Flight Plan 7 days Mon 10/20/03 Tue 10/28/03

69 Spring Mass analysis 7 days Mon 10/27/03 Tue 11/4/03

70 Test Plan 5 days Fri 10/31/03 Thu 11/6/0371 Testing Requirements 5 days Fri 10/31/03 Thu 11/6/03

72 Reaction Wheel 57 days Thu 10/30/03 Thu 2/12/04

73 Wheel 57 days Thu 10/30/03 Thu 2/12/04

74 Design 17 days Thu 10/30/03 Fri 11/21/0375 Calculation of Size 5 days Thu 10/30/03 Wed 11/5/03

76 Solidworks Drawings 5 days Thu 11/6/03 Wed 11/12/03

77 Prototype Construction 7 days Thu 11/13/03 Fri 11/21/03

78 Fabrication 40 days Mon 11/24/03 Thu 2/12/0479 Adjustments to Drawings 10 days Mon 11/24/03 Fri 12/5/03

80 Machining 25 days Mon 12/8/03 Thu 2/5/04

81 Tolerancing 30 days Mon 12/8/03 Thu 2/12/04

82 Motor 12 days Thu 11/6/03 Fri 11/21/0383 Calculations and Requirements 5 days Thu 11/6/03 Wed 11/12/03

84 Trade Study 7 days Thu 11/13/03 Fri 11/21/03

85 Rate Gyro 15 days Mon 11/3/03 Fri 11/21/03

86 Calculation of Requirements 5 days Mon 11/3/03 Fri 11/7/0387 Trade Study 10 days Mon 11/10/03 Fri 11/21/03

88 Structure 77 days Mon 10/20/03 Mon 3/1/04

89 Design 20 days Mon 10/20/03 Fri 11/14/03

90 Material 5 days Mon 10/20/03 Fri 10/24/0391 Dementions 20 days Mon 10/20/03 Fri 11/14/03

92 Frame 5 days Mon 10/20/03 Fri 10/24/03

93 Mounting Brackets 10 days Mon 10/27/03 Fri 11/7/03

94 Drawings 20 days Mon 10/20/03 Fri 11/14/0395 Fabrication 57 days Mon 11/17/03 Mon 3/1/04

96 Adjustments to Drawings 10 days Mon 11/17/03 Fri 11/28/03

97 Machining 15 days Fri 2/6/04 Thu 2/26/04

98 Tolerancing 2 days Fri 2/27/04 Mon 3/1/0499 Electronics 20 days Mon 10/20/03 Fri 11/14/03

100 Battery 17 days Mon 10/20/03 Tue 11/11/03

101 Type 5 days Mon 10/20/03 Fri 10/24/03

102 Size 2 days Mon 11/10/03 Tue 11/11/03103 Wiring Diagrams 3 days Wed 11/12/03 Fri 11/14/03

104 Software 65 days Mon 10/20/03 Thu 2/12/04

105 Block Diagram 25 days Mon 10/20/03 Fri 11/21/03

106 Write code 30 days Mon 11/24/03 Thu 1/29/04107 Debug 10 days Fri 1/30/04 Thu 2/12/04

108 Systems Integration 15 days Tue 3/2/04 Mon 3/22/04

109 Structure 5 days Tue 3/2/04 Mon 3/8/04

110 Electronics 5 days Tue 3/9/04 Mon 3/15/04111 Software 5 days Tue 3/16/04 Mon 3/22/04

112 Testing 105 days Fri 11/7/03 Wed 4/28/04

113 Test Matrix 2 days Fri 11/7/03 Mon 11/10/03

114 Sensor List 4 days Fri 11/7/03 Wed 11/12/03115 Reaction Wheel and Rate Gyro Calibration 57 days Thu 11/13/03 Thu 2/26/04

116 Test Stand 21 days Thu 11/13/03 Wed 1/7/04

117 Design 3 days Thu 11/13/03 Mon 11/17/03

118 Solidworks Drawings 3 days Thu 11/13/03 Mon 11/17/03119 Fabrication 15 days Tue 11/18/03 Mon 12/8/03

120 Tolerancing 3 days Tue 12/9/03 Wed 1/7/04

121 Testing Operations 5 days Fri 2/13/04 Thu 2/19/04

122 Data Analysis 5 days Fri 2/20/04 Thu 2/26/04123 3-Axis Gimble 105 days Fri 11/7/03 Wed 4/28/04

124 Drawings 2 days Fri 11/7/03 Mon 11/10/03

125 Attachment to CamCube 2 days Tue 3/23/04 Wed 3/24/04

126 Testing operations 15 days Thu 3/25/04 Wed 4/14/04127 Data Analysis 10 days Thu 4/15/04 Wed 4/28/04

11/26M T W T F S S M T W T F S S M T W T F S S M T W T F S S M T W T F S S M T W T F

Oct 19, '03 Oct 26, '03 Nov 2, '03 Nov 9, '03 Nov 16, '03 Nov 23, '03


Cost Estimates

General Requirement Specific Device Best Cost EstimateAttitude Determination Rate Gyros $640Battery Lithium Ion $500Motor Amplifier $1,395Attitude Control Reaction Wheels $200Structures Aluminum $10Electronics Voltage Regulator $30Testing 3-axis Gimbal $30

$2,805Total


Conclusion

• System Architecture– Overview of Objectives and Requirements– System design– Overall expected performance

• Design Elements– Mechanical Design Elements– Electrical Design Elements– Software Design Elements

• Integration Plan• Verification and Test Plan• Project Management Plan

Any Questions?


Thank you

•Blair Thompson

•Walt Lund

•Trudy Schwartz

•Prof Peterson

•Prof Palo

•Prof Nerem


Ideal Orbital Analysis

• Clohessy – Wiltshire (Hill’s) Equations

– ? V = 0.27 m/s– ? = -113.9º– Range = 100m– ~7 min to prepare for a ? V to

align with Shuttle orbit


Orbital Analysis

• GEODYN II– ? = -115º

• RShuttle = RCamCube– t = 6.5213 min = 6:31– Range ~104m

• From ephemeris– VShuttle at t = 6:30 ? 6:31– VCamCube at t = 6:31


Mission Profile

• ? V = 0.27716 m/s• Stays within 110m• With shuttle ~63 min

– Operation time ~57 min

• Lifetime ~16 days


CamCube Velocity Relative to Shuttle


CamCube Position Relative to Shuttle


Position Vector Magnitude


Rate Gyro Trade Study

Weight and size unknownOnly 1-axis measurement

Con reason 3

Price unkownPrice is unknownPrice is unknownPrice is unknownCon reason 2

Flight units are listed for 2003, release unsure

Higher power required

Limited Availability

Resolution is unknown

Resolution is unknown

Con reason 1

Resolution is low: 0.015 deg/s

Interface is RS-485

Pro reason 3

Low drift and noiseResolution is low: 0.02 deg/s

Power requirements +/-5 DC

Power requirements +/-5 DC

Int. circuit digitizes output (RS 448)

Pro reason 2

Extremely high accuracyMedium size and weight

Small size: volume and weight

Fiber optic: may yield desired res.

3-axis measurement in one whole unit

Pro reason 1

Honeywell Fiber-Optic IRS

Honeywell GG440

Analog ADXRS150

FibersenseFOG1

FibersenseTRF-90


Drift Requirement-Field of View

• Based on average tile size (15.2 cm x 15.2 cm)• Pixels per tile are in 1-dim only (2-dim = x2)• Pixel allocation leads to max drift rate

4.962.98343.56307.444.4722920

14.888.94114.5210Pixels per tile: 4 M-PixelPixels per tile: 2 M-Pixel Tiles in FOV (1 dim)FOV (°)


Drift Requirement-Shutter Speed

• Shutter Speeds are very conservative• Design based on 30º field of view (FOV) and

conservative shutter speeds• Slowest drift rate is yielded from 4 M-Pixel camera

0.3520.5821/208.814.551/500

Omega: 4 M-Pixel (deg/s)Omega: 2 M-Pixel (deg/s)Shutter speed (s)


Pointing Requirement

• Best option is 15º cone for 15 minutes– Will reach the perimeter of original nadir cone– Will hold for slightly more than 25% of total mission

0.0166715150.004176015

0.0111115100.002776010

Omega (deg/s)Time Frame (min)Pointing Cone (º)


Steve supplemental slide

• I_wheel = 2.831e-4 oz-in-s2

• I_motor = 1.3e-4 oz-in-s2

• I_total = 4.13e-4 oz-in-s2

• Max_torque = 2.55 oz-in• Alpha = 6172.8


Motor Design-To Specs: Torques

• Torques– Max impulse Torque of 2.3 oz-in (.016 Nm)

• From Propulsion System (1.12 oz-in)• Safety Factor of 2• Frictional Torque of .033 oz-in (1.9e-4 Nm) • Motor chosen has a Stall Torque = 3.0 oz-in• Less then 0.1 s (impulse)

– Constant Torque of .5 oz-in (.0035 Nm)• Motor’s Rec. Torque .708 oz-in (.0049 Nm)


Motor Design-To Specs: Mass &Volume

• Less then 20% of total mass– Total mass = 1kg = 35 oz– Allotted mass = 200 g = 7 oz– Motor mass = 1.62 oz ; Motion Cont. mass = 3.88 oz– Total (motor/controller) mass = 5.5 oz = 157 g

• Less then 20% of total volume– Total volume = 1000 cc = 61 in3– Allotted volume = 200 cc = 12.2 in3– Motor volume = 8.6 cc ; Motion Cont. volume = 105 cc– Total (motor/controller) volume = 114 cc = 6.93 in3


Motor Design-To Specs: Power

• Current– Motor

• Torque sensitivity (Kt) = 0.980 oz-in/amp• Max Current needed = 2.35 Amps• No Load Current = 0.029 Amps (friction)

– Motion Controller • Max Peak Output Current =10 A• Max Continuous Output Current = 5 A


Motor Thermal Analysis

• Assume Ambient Temp = 25°C• Maximum permissible winding temperature =

100°C• Temperature increase needs to be < 75°C

– Tinc = I2R (Rth1+Rth2)– Rth1/Rth2 : 5/20– R =1.94 Ohms – Imax = 2.3 Amps– Icont = 0.722 Amps


Motor Thermal Analysis

• Maximum Tinc = 256°C !!!– Too high– Temperature control

• Lowering of Rth2 (case-to-ambient thermal resistance)• Heat Sinks• Rth2 = 2.0

– Operating time < 1 minute• MicroMo technical support

• Continuous Tinc = 25°C


Supplemental Slides: MC


Supplemental Slides: Motor


References

• http://www.micromo.com/library/docs%5Cproducts%5CMCDC_2805.PDF

• http://www.micromo.com/library/docs/products/2224_SR.PDF• http://www.micromo.com/library/docs/products/1628_B.PDF• http://www.a-m-c.com/download/z12a.pdf• http://www.micromo.com/library/docs/notes&tutorials/Motor

%20Calculations.pdf• http://www.pidc.gov.tw/Research/Remote/Yamsat/tokyo-u-

cdr.pdf• http://msowww.anu.edu.au/nifs/cdr/index.shtml

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