1 1 The Laddermill - Design, Building & Testing Bas Lansdorp Richard Ruiterkamp Background Kite...

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1

The Laddermill

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Design, Building & Testing

Bas LansdorpRichard Ruiterkamp

Background Kite control mechanism Groundstation Electronics Testing

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Agenda

Background

Kite control mechanism

Groundstation

Electronics

Test plans


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Laddermill principle


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Types of wings

Surfkites

Rigid/inflatable kites

Cloth kites


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Early concepts

Drag flap control Wingtip AoA control

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Tow point control

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Lightweight

Sand proof

Strong

Successful?

What can go wrong, will go wrong

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Laddermill 2 kW groundstation


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Slipping occurs


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•Cable is on the drum under low tension, low stretch

•Cable is pulled off under high tension, high stretch

•This means that a larger length of cable leaves the drum, than is actually on the drum!

•Slip occurs over a certain angle, about 1 revolution


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New laddermill 4 kW groundstation

•Rotating platform: cable always straight

•Traversing train: cable always in the middle of the platform

•Very large drum: only a single layer of cable during energy generation (Drum 1 m wide)


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Who will help us?

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Instead of the rotating platform, the rotation can be placed on top of the traversing drum.


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Testing:

•4 kW groundstation not tested yet

•Force of the kite: ~1500 N


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Electronics

Main computer GUIManual Input

Flight Computer Servo controlFlight sensors

Manual override


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Electronics

Manual Input

• Main computer program• Allows manual input from joystick/keyboard• Control input directly send to flight computer• Logfile created for all input/output• GUI allows graphical representation of kite in flight data such as apparent wind speed, position, altitude, heading

Main computer GUI


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Electronics

Flight Computer Servo controlFlight sensors

• Flight computer receives servo commands from ground computer• Sensor package: - altitude (abs. pressure)

- apparent wind speed (diff. pressure + pitot tube) - Servo current consumption - XYZ acceleration (accelerometers) - Gravity vector direction (accelerometers) - Position/heading (GPS module) - Visual data (web-cam)


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Electronics

Flight Computer Servo control

• Servo signal (PWM) generated by slave u-processor• Pilot take over switch allows overruling flight electronics in case of failure• Flight sensor data is polled and compressed before sending package• max. 20 km range (current version 5 km range)

Manual override

Flight sensors


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Electronics

Transceiver unit

Ethernet and USB ports

Embedded PCRunning Linux

Altimeter and pitot diff.pressure sensors

XYZ accelerometer


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Testing

Load cell assembly for measuring line tension vector

Low stiffness beam

Load cell


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Testing

Setup for kite testing:•Line connected to load cell sensor•2 lines to the kite, connected to control mechanism

Interesting tests:•cl and cd vs. AoA and wind speed•Static and dynamic stability•Response of the kite control mechanism•Flying patterns


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Testing

cl and cd vs. AoA and wind speed•Put kite at the zenith position•Keep kite steady by computer•Test various AoA at different wind speeds•Measure L and D to determine cl and cd


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Testing

Static and Dynamic stability•Put kite at the zenith position•Keep kite steady by computer•Give various types of input and look at the response•Measure position by the load cell


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Testing

Response of the kite control mechanism•Put kite at the zenith position•Keep kite steady by computer•Give various steering inputs and measure accelerations


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Testing

Check what happens during pattern flying•Put control at certain location•Measure the tension in the line•Compare with same tow point position and same wind speed at zenith

Tension the same, AoA the same?


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Questions?


1 1 The Laddermill - Design, Building & Testing Bas Lansdorp Richard Ruiterkamp Background Kite...

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