mav design case study - indian institute of technology bombay · iit bombay 02 miniature aerial...

IIT Bombay

MIT 2002

MiniatureAerial

Vehicle

DesignBuild

& Fly

Lecture 3: MAV Design - Case Study

MAV DesignCase Study

Lecture 3

IIT Bombay

MIT 2002

MiniatureAerial

Vehicle

DesignBuild

& Fly

Lecture 3: MAV Design - Case Study

� The Problem

¾ Design the smallest AV to fly and photograph a 1.5 msize object located 600 m away from the launch site.

� The Objective

¾ To encourage use of MDO in a rational design processinstead of trial and error.

¾ The designers must be able to predict the effect ofdesign changes on the AV’s performance.

ISSMO Design Competition

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

Tools Required

� Aerodynamics analysis package

¾ Low Re analysis

¾ Lift, Drag, Pitching Moment

� Structural analysis package

¾ Weight and c.g.

� Powerplant data

¾ Thrust

� Optimizer

IIT Bombay

MIT 2002

MiniatureAerial

Vehicle

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Lecture 3: MAV Design - Case Study

Tools Available

� A panel code (based on vortex lattice method)for aerodynamic analysis

� Insufficient design literature for MAV design

IIT Bombay

MIT 2002

MiniatureAerial

Vehicle

DesignBuild

& Fly

Lecture 3: MAV Design - Case Study

� Design and build an aerial vehicle capable ofcarrying a video camera and transmitter.

� Vehicle is to fly upto a distance of 500m andrelay video images of a ground target to aground station.

� The vehicle is to return to the launch site at theend of the mission.

Requirements Capture

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

Distance 500m

TargetLaunch

Other requirements

� The targets will be a circle of 0.7m diameterand rectangle of 1.7m x 0.7m

� Max dimension of vehicle ≤ 24”

� Max All-Up-Weight ≤ 1 kg

� Easy to dismantle

� Two man crew

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

Limitations

� Some hardware was already available atCASDE (imported)

¾ R/C unit

¾ Engine

¾ Miniature camera & transmitter

� Time bound

¾ No new hardware search & procurement

¾ Conservative design philosophy

IIT Bombay

MIT 2002

MiniatureAerial

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Lecture 3: MAV Design - Case Study

� Multidisciplinary Optimization Report for Universityof Florida Observer by J Bostjancic, et al

� Multidisciplinary Design, Construction and FlightTesting of a Remotely-Piloted “Micro”Reconnaissance Airplane by George Hicks, et al

� UIUC low speed airfoil databank.

� “Basics of RC Model Aircraft Design” - Andy Lennon

� “Model Aircraft Aerodynamics” - Martin Simons

Literature Survey

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

� Role of the vehicle is photo reconnaissance

¾ High inherent stability for better picture quality

¾ Large tail volume, wings with adequate dihedral andlarge fin

� Rudder is rarely used during flying

¾ Dispensed with the rudder

¾ Weight savings in the order of 30-35 gm (i.e. weight ofservo, linkages and rudder hinging)

Airframe

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

� Low speed airfoil

¾ Takeoff and landing speed were crucial

¾ Wing of 6” chord flying at 36 kmph will operate at a Renumber of 105,300 (desired landing speed)

� The Selig S 3021-095-84 airfoil was chosen

¾ Specially developed for model aircraft

¾ Good CL Vs alpha characteristics at low Re numbers(CLmax of 1.2 at Re as low as 100,000)

Airfoil Selection

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

� Miniature IC engine (OS Max 15 FP )

¾ weight 142 grams

¾ displacement of 0.15 cubic inch (2.46 cc)

� No data on engine thrust was available

Propulsion System

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

� Model RC aircraft with small wing spanexhibit poor roll stability

� Gyro based flight stabilization system toaugment the roll stability

� Standard aeromodelling 6-channel controlsystem used.

¾ Receiver weight =40g

¾ Servo weight = 17.3g (per unit)

Control System

IIT Bombay

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Lecture 3: MAV Design - Case Study

� A forward looking camera was consideredpreferable

¾ depression angle ≈ 45 deg

� Easy for second crew member monitoring thevideo images to pick up ground targetssufficiently in advance to enable him to giveappropriate navigation cue to the pilot.

Video System

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

Video Transmitter& Receiver

Camera

Video System

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

VideoCameraPC87XS

VideoTransmitterAVX900MINI

Video ReceiverAVX-900-R2

Size 0.86”x0.86”x1.02” 1.07”x0.7”x0.21” 5.1”x5.5”x1”

Weight 9.5 g 10 g

Voltage

Current

5 Volts DC

160 mA

9 volts DC

Not Known

12 volts DC

300 mA

Field of View 45 deg NA NA

Resolution 350 lines NA NA

Frequency NA 900 MHz Band 900 MHz band

Range NA NA 1200 feet (std antenna)

3500 feet (Yagi antenna)

Video System - specs

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

� Dimensions

¾ Sensor-30 mm x 30 mm x 31 mm

¾ Amp-61 mm x 38 mm x 13.5 mm

� Weight - 52 grams

� Power supply - 4.8 to 6 V (DC)

� Current Drain - 18 mA at 4.8 V

Piezoelectric Rate gyro

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

� Mission time (7 min); fuel (60 ml)

� Onboard power supply (100 gm)

� Fixed Weights of engine, control system, videosystem, fuel and batteries (≈ 580 gm)

� Airframe weight based on experience (300 gm)

� Max AUW of the vehicle (≈ 900 gm)

� Required wing area (2 sq. ft) for typical wingloading data for such platforms (16 oz/sq. ft or4.89 kg/m2)

Planform Synthesis

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

� Wing

¾ Area = 2 sq. ft area

¾ Span = 24” span

¾ Chord =12”.

¾ Aspect Ratio = 2

¾ Poor lift and high induced drag characteristics

� Examine Monoplane Vs Biplane configuration

� Analysis based on panel code developed at IIT,Bombay.

Configuration

IIT Bombay

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Lecture 3: MAV Design - Case Study

CL Vs. Alpha

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

CD Vs. CL

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

� Biplane configuration was selected

¾ better CL Vs Alpha and drag characteristics.

¾ a longer tail moment arm and so a smaller tailplane

¾ better trim characteristics

� Tailplane and fin were sized based on empiricalrules

2.5 * mac * 20% of WA HTA = TMA

VFA = 8% of WA

Configuration

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

� Spreadsheet based

� Input

¾ Weights of equipment (measured physically)

¾ linear and area density of standard sections

¾ wing and fuselage geometry

� Result

¾ Estimated weight = 860 gm

¾ Actual weight = 840 gm

� CG calculations useful in placement ofequipment onboard.

Tool for Weight & c.g

IIT Bombay

MIT 2002

MiniatureAerial

Vehicle

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Lecture 3: MAV Design - Case Study

� Wing Airfoil - Selig 3021 - 095 -84

� Wing Span - 24” (both wings)

� Wing Chord - 6”

� Wing Gap - 4.25”

� Wing Area - 288 sq. in (2 sq. ft)

� Fuselage Length - 23.5”

� Tailplane span - 14”

� Tailplane Chord - 4.5”

� Tail Moment Arm - 12.25”

� Max AUW - 860 gm (30.27 oz)

� Wing loading - 15.14 oz/sq. ft

Final Aircraft Specifications

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

Aircraft Wings

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

Final Aircraft

IIT Bombay

MIT 2002

MiniatureAerial

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Lecture 3: MAV Design - Case Study

Final Aircraft

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

� Ground steering problem

� Too much power

� Reasonable ground handling after tailwheel installation

� Improved in-flight handling after gyrocut in

Flight test observations

IIT Bombay

MIT 2002

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Lecture 3: MAV Design - Case Study

Captured Images

IIT Bombay

MIT 2002

MiniatureAerial

Vehicle

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Lecture 3: MAV Design - Case Study

Captured Images

IIT Bombay

MIT 2002

MiniatureAerial

Vehicle

DesignBuild

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Lecture 3: MAV Design - Case Study

Captured Images

IIT Bombay

MIT 2002

MiniatureAerial

Vehicle

DesignBuild

& Fly

Lecture 3: MAV Design - Case Study

Captured Images

IIT Bombay

MIT 2002

MiniatureAerial

Vehicle

DesignBuild

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Lecture 3: MAV Design - Case Study

� Difficult to fly visually beyond 300m

� Needs additional forward looking camera to flydesired mission profile

� Flying skills need to be developed for this modeof flying

� Hand launch of vehicle is highly desirable

� Better ground antenna system needed forimproved and reliable reception.

Conclusions

IIT Bombay

MIT 2002

MiniatureAerial

Vehicle

DesignBuild

& Fly

Lecture 3: MAV Design - Case Study

� Design of an aerial vehicle capable ofindoor flight (highly challenging task)

� Design of a vehicle of lower weight, with asmaller engine (perhaps electric powered)

� MDO based design of the vehicle

Future Work

IIT Bombay

MIT 2002

MiniatureAerial

Vehicle

DesignBuild

& Fly

Lecture 3: MAV Design - Case Study

MAV DesignCase Study

Lecture 3