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SkySails Tethered Kites for Ship Propulsion and Power Generation: Modeling and System Identification Michael Erhard, SkySails GmbH, Hamburg, Germany Contents • Introduction SkySails Marine and Power • Simple Model • Sensors and Navigation • Validation of Model and Parameter Estimation • Control System • Further Challenges of the Real-World System Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Business Segments KITE PROPULSION aux. propulsion system up to 2000 kW engine equivalent power pilot customer operation since 2008 PERFORMANCE MANAGER SKYSAILS POWER improved communication ship to shore small scale model for airborne wind energy automatic fuel and condition monitoring installed in a trailer in operation on 35+ ships autopilot controlled autopilot controlled Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 kites up to 30 m² SkySails Marine – Towing Kite System Control Systems Airborne Control Pod Kite sizes up to 320m2 Launch and Recovery System Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Substitute 1-2 MW of main engine power System Overview Guiding line Towing kite Telescopic mast Control pod Towing line Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Kite – Reefing Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Machine Supported Ground Handling Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Production and Installation Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Impressions (Marine Video) See http://youtu.be/ckyHeizCAdk Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 SKYSAILS POWER Development Functional prototype: • Design load • Kite size • installed generator power • maximum winch speed • installed tether length http://www.skysails.info/english/power/ Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 20 kN typ. 30 m2 55 kW 5 m/s 450 m SkySails Power • Pumping Cycle M. Erhard, H. Strauch, Flight control of tehered kites in autonomous pumping cycles for airborne wind energy, to appear in Control Engineering Practice (2015) Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 SkySails Power Economic energy generation Fully automated AWE plants Reliability of control system crucial Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Impressions (Power Video) Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Simple Model Simple Model Coordinate System • Position , • Orientation , Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Simple Model Model Assumptions 1.) Forces huge compared to masses Neglect Accelerations & Masses 2.) Airflow in Roll Direction 3.) Glide Ratio Condition Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Aerodynamics of Tethered Kites Paraglider (Free flight) : vtot = 10m/s Tethered Kite: v 0 cos vges . vhor. vtot = 1..E v0 Ftot = 1..E2 F0 Wind v0 = 10m/s with E=5 yields vtot = 10..50m/s ! Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Simple Model • Equations of motion for , and (3d kite position) • orientation • winch speed Parameters • glide ratio • wind speed Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Kinematic Equations of Motion Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Model of Tethered Kites Angle is the central control variable: - Determines force - Keep static zenith position (=const) Periodic signal on yields pattern: +0 --0 Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Control of Orientation Steering Steering by means of canopy (and force vector) rotation Side Force Aerodynamic force vector Passive section Actively steered section F1 F2 Control pod Towing rope Turn Rate Law Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Sensors and Navigation Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Control Pod Sensors Barometer IMU -3Gyro -3Acc. Impeller-Anemometer Flight Control Computer Line Force Sensor (Strain Gauge) Servo Control Energy Buffer Cable: Data/Energy Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Motor Sensor Overview Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Inertial Navigation • Quaternion integration… • Problem: drift of turn rate sensors ? Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Inertial Navigation Reference to ‚Down‘-Direction Average Accelerations Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Yaw Angle Estimator M. Erhard, H. Strauch, Sensors and Navigation Algorithms for Flight Control of Tethered Kites, Proc. European Control Conf., 2013 Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Experimental Results IMU Angles Tether Tow Point Angles Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Wind Referencing IMU Winddirection Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Merging of Algorithms Complementary Filter M. Erhard, H. Strauch, Sensors and Navigation Algorithms for Flight Control of Tethered Kites, Proc. European Control Conf., 2013 Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Validation of kinematics Validation of Kinematics Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Validation of Kinematics Flight Direction Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Validation of Turn Rate Law Turn Rate Law Turn rate Parameter Air path speed Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Steering deflection System Identification ? G(s) „kite“ ? Challenges: • How to fly open loop and not crash ? • Flight pattern ? • Operational point ? (Flight speed, wind window position, …) Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 System Identification Test Turn Rate Law? Bang-Bang-Experiment +0 --0 Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Extended Turn Rate Law 2 Fit Parameter Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Gravitation Online Parameter Estimation ˆt arg min (t , k )y (k ) T (k ) t Weighted least-square 2 k 1 ˆt R 1 (t ) f (t ) t R (t ) (t , k ) ( k ) T ( k ) k 1 t f (t ) (t , k ) ( k ) y ( k ) k 1 Example: turn rate law m g va y (k ) ˆt (k ) result Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 See e.g.: Ljung, System identification Online Parameter Estimation Weight (t, k ) e ( t k ) ( t k ) Time ‚now‘ Recursive algorithm: ˆt R 1 (t ) f (t ) R (t ) R (t 1) (t ) T (t ) f (t ) f (t 1) (t ) y (t ) Applications: System monitoring (degrading, damage, …) Adaption of controller Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Online Parameter Estimation Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Control System Flight control Human Control Strategy? Use Angle w.r.t. horizon (or wind) Orientation determines flight direction Controlled System (Plant) Steering Input Turn Rate Law Kinematic Orientation Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Flight Direction Control System • Cascaded control setup kinematics Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Turn rate law Controller Performance Turn rate control loop (FBK << FF) ‚Indirect‘ system identification Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Limits and challenges Challenges and limits Wind is challenging: Profile ? ? ? ? ? Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 How to model the wind field? Profile? Boundary layer? ... Challenges and limits Soft Materials Free Flight Modelling Accuracy is limited Limited Sensor `Accuracy´ Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Tether Slack Line Angle Sensors Free flight Due to gusts or wave induced motion: temporarily untethered system Angle w.r.t. Horizon `undefined´ Line Angle Sensor Michael Erhard, SkySails GmbH, Talk at IMTEK, University of Freiburg, January 20, 2015 Thank you for your Attention! Questions?
