1 1 The Laddermill - Design, Building & Testing Bas Lansdorp Richard Ruiterkamp Background Kite control mechanism Groundstation Electronics Testing

2 2 Agenda Background Kite control mechanism Groundstation Electronics Test plans Background Kite control mechanism Groundstation Electronics Testing

3 3 Laddermill principle Background Kite control mechanism Groundstation Electronics Testing

4 4 Laddermill principle Background Kite control mechanism Groundstation Electronics Testing

5 5 Laddermill principle Background Kite control mechanism Groundstation Electronics Testing

6 6 Kite control mechanism Types of wings Surfkites Rigid/inflatable kites Cloth kites Background Kite control mechanism Groundstation Electronics Testing

7 7 Kite control mechanism Background Kite control mechanism Groundstation Electronics Testing Early concepts Drag flap controlWingtip AoA control

8 8 Kite control mechanism Background Kite control mechanism Groundstation Electronics Testing Tow point control

9 9 Kite control mechanism Background Kite control mechanism Groundstation Electronics Testing

10 10 Kite control mechanism Background Kite control mechanism Groundstation Electronics Testing

11 11 Kite control mechanism Background Kite control mechanism Groundstation Electronics Testing

12 12 Kite control mechanism Background Kite control mechanism Groundstation Electronics Testing Lightweight Sand proof Strong Successful? What can go wrong, will go wrong

13 13 Laddermill 2 kW groundstation Background Kite control mechanism Groundstation Electronics Testing

14 14 Laddermill 2 kW groundstation Slipping occurs Background Kite control mechanism Groundstation Electronics Testing

15 15 Laddermill 2 kW groundstation 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 Background Kite control mechanism Groundstation Electronics Testing

16 16 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) Background Kite control mechanism Groundstation Electronics Testing

17 17 New laddermill 4 kW groundstation Background Kite control mechanism Groundstation Electronics Testing Who will help us?

18 18 New laddermill 4 kW groundstation Background Kite control mechanism Groundstation Electronics Testing

19 19 New laddermill 4 kW groundstation Instead of the rotating platform, the rotation can be placed on top of the traversing drum. Background Kite control mechanism Groundstation Electronics Testing

20 20 New laddermill 4 kW groundstation Testing: 4 kW groundstation not tested yet Force of the kite: ~1500 N Background Kite control mechanism Groundstation Electronics Testing

21 21 New laddermill 4 kW groundstation Background Kite control mechanism Groundstation Electronics Testing

22 22 Electronics Main computerGUIManual Input Flight ComputerServo controlFlight sensors Manual override Background Kite control mechanism Groundstation Electronics Testing

23 23 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 computerGUI Background Kite control mechanism Groundstation Electronics Testing

24 24 Electronics Flight ComputerServo 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) Background Kite control mechanism Groundstation Electronics Testing

25 25 Electronics Flight ComputerServo 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 Background Kite control mechanism Groundstation Electronics Testing

26 26 Electronics Transceiver unit Ethernet and USB ports Embedded PC Running Linux Altimeter and pitot diff. pressure sensors XYZ accelerometer Background Kite control mechanism Groundstation Electronics Testing

27 27 Testing Load cell assembly for measuring line tension vector Low stiffness beam Load cell Background Kite control mechanism Groundstation Electronics Testing

28 28 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 Background Kite control mechanism Groundstation Electronics Testing

29 29 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 Background Kite control mechanism Groundstation Electronics Testing

30 30 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 Background Kite control mechanism Groundstation Electronics Testing

31 31 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 Background Kite control mechanism Groundstation Electronics Testing

32 32 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? Background Kite control mechanism Groundstation Electronics Testing

33 33 Questions? Background Kite control mechanism Groundstation Electronics Testing