Development of

Guidance and Control System for

Parafoil-Payload System

VVR Subbarao, Sc ‘C’Flight Mechanics & Control Engineering

ADE

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Parafoil-Payload System

• Control Surfaces – 1 pair at the Trailing Edge

• Symmetrical Deflection

• Changes flight path angle and rate of descent

• Asymmetrical Deflection

• Generates turn

Cell`

Leading Edge

Payload

Steering Lines

Suspension Lines

Stabilizer Panels

Differences with Aircraft

• Flexible lifting surface

• Centre of mass is suspended below canopy

• Control is achieved by changing parafoil shape

• No external power to push forward

Advantages• Sufficient glide and wind penetration• Low potential damage to payload• Fly aircraft at safe stand-off distance• Greater offset distance for given altitude

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CADS

Name Controlled Aerial Delivery SystemObjective To demonstrate the technology for precise delivery of a payload of 500 kg using a Ram Air Parafaoil

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Airborne Guidance &Control System`

TaskTo develop Airborne Guidance and Control System to meet

required CEP of 100m

Followed Strategy• Phase I

– Developing path control in 2-D plane on 80kg p/p system• To assess the control effectiveness of parafoil• To arrive the suitable guidance and control scheme

• Phase II– Development of guidance and control scheme to make touch down

within 100m CEP• Design of Energy Management Maneuvers• Extension of these CLAW for 300kg parafoil

Phase I

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Issues• Simulation Model

– Conventional 6 DOF equations do not hold– Multi-body dynamics

• 4, 6, 9, 12 Degree-of-Freedom– Lifting surface is not rigid

• Flexible canopy

• Aerodynamic Data– Not available at the beginning– Data was generated semi-rigid canopy– Later data available only for 500kg parafoil

• Stability and control derivatives• No rate derivatives

• Data Generation Trials– Controlled from ground– Planned data generation trials– Developed 4 DOF model

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Ground based Guidance and Control System Architecture

Analog

RS 232On-Board Sub-Systems

PFCC BL 2120

Actuators

GPS Receiver

Alt. Sensor

Heading

DRUNMEA

Tx,Rx

Tx, RxPt & SB Lanyard Commands

Ground Sub-Systems

JoyStick

Issues

•Vehicle state information

•Sensors Mounting

•Sensors selection

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4 DOF Mathematical Model

• Assumption– parafoil-payload (p/p) load system as a single rigid body.

• Simulates – the forward and downward translations

– roll and yaw (turn) motions of the para-foil.

– Does not required much aero data

• Used– to finalize the implementation of control laws

– In Hardware-In-Loop Simulation to close control loop

– To design failure logics

– Train ground pilot

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Guidance and Control Scheme

Autonomous Mode•Two loop

•Outer loop•Cross-track error minimization

•Inner loop•Heading error minimization

Sensors•Main

•GPS•Monitoring

•Static Pressure•Compass

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AG&CS Architecture

ParaFlight Control

Computer

On-board DRU

HeadingSensor

GPS Antenna

IAS Transducer

Altitude Transducer

Proximity Sensor

Port Lanyard Actuator

StarboardLanyardActuator

HandheldTerminal

TX/RX CBL 2120

Parachute Power Supply

RS 232

RS 422

Analog

Analog

RS 232

Target Point

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Phase II

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Energy Management Maneuver

• Objective– To ensure the touchdown within CEP– Selected Fig-of-Eight Maneuver for altitude management– Length of leg is fixed considering turn time

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300kg p/p system

• Sluggishness response– No turn rate response up to 20% of differential command

• No aerodynamic rate derivative data• Model derived from flight data

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Challenges

• Design of Guidance and Control Scheme– catering to high wind– Payload mass variations

• Terminal Guidance for Soft Landing– Flight path can be influenced only with symmetrical deflection above 50% of

total deflection– Turn and altitude control cannot simultaneously done

• Sluggish Response– No Turn rate for command less than 20% of total command– Non-linear turn rate response against differential command

• Gain Scheduling– Measuring wind magnitude and direction– Air speed measurement