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1 st International Workshop on Modelling and Optimization of Power Generating Kites KITE-OPT 07. Moritz Diehl Optimization in Engineering Center (OPTEC), K.U. Leuven and Boris Houska, Andreas Ilzhoefer IWR, University of Heidelberg Co-sponsored by OPTEC, ICCoS.
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1st International Workshop on Modelling and Optimization of Power Generating KitesKITE-OPT 07 Moritz Diehl Optimization in Engineering Center (OPTEC), K.U. Leuven and Boris Houska, Andreas Ilzhoefer IWR, University of Heidelberg Co-sponsored by OPTEC, ICCoS Moritz Diehl ESAT 00.62, January 30, 2007
Overview • What is OPTEC ? • Motivation and Today‘s Program Moritz Diehl
What is OPTEC? Founded as “Center of Excellence: Optimization in Engineering“ (12 centers of this type at K.U. Leuven) Five year project with 500.000 Euro per year, from 2005 to 2010 Promoted by four engineering departments, in order to connect OPTIMIZATION METHODS AND APPLICATIONS: • CHEM - Chemical Engineering • CS - Computer Science • ESAT - Electrical Engineering • MECH - Mechanical Engineering New positions: • 4-6 PhD, 2-4 Postdoc • new professorship (at ESAT) for „Principal Investigator“ (M.D.) Moritz Diehl
Quarterly and Weekly OPTEC Lecture Series • Quarterly „Simon Stevin Lecture on Optimization in Engineering“: • Dec. 6: Larry Biegler, CMU Pittsburgh (past) • Mar. XX: Julio Banga, Varga, Spain (tentative) • July XX: Steven Wright, Wisconsin • Oct 26: Manfred Morari, ETH Zurich • Dec XX: David Mayne, Imperial, London (tentative) Simon Stevin, 1548-1620) • „K.U. Leuven Seminar on Optimization in Engineering“ : • Jan. 31: Mario Milanese (Torino): MPC of semi-active damping • Feb. 8: Philippe Toint (Namur): large scale optimization methods • Feb. 22: Peter Kuehl (Heidelberg): Robust optimal feedback control • March 1: Yurii Nesterov (UCL)/ Florian Jarre (Duesseldorf): new optimization algorithms Moritz Diehl
OPTEC Aim Become a center where • mathematical optimization is driven and inspired by engineering demands, and • engineering innovation profits from the use of modern optimization techniques. Kite Wind Power project excellent example for symbiosis of methods and applications Moritz Diehl
Overview • What is OPTEC ? • Motivation and Today‘s Program Moritz Diehl
Conventional Wind Turbines • Due to high speed, wing tips are most efficient part of wing • High torques at wings and mast limit size and height of wind turbines • But best winds are in high altitudes! Could we construct a wind turbine with only wing tips and generator? Moritz Diehl
Conventional Wind Turbines • Due to high speed, wing tips are most efficient part of wing • High torques at wings and mast limit size and height of wind turbines • But best winds are in high altitudes! Could we construct a wind turbine with only wing tips and generator? Moritz Diehl
Kite Wind Power [Loyd 1980, Ockels 1996, Ippolito/Milanese 2004, D. 2006,...] • use kites with high lift-to-drag-ratio • use strong lines, but no mast and basement • automatic control keeps kites flying • Allows to exploit the strong winds in high altitudes But how could a generator be driven? Three teams give different answers... Moritz Diehl
Today‘s Schedule (ESAT, 00.62) • 9:00 Welcome (M. Diehl) • 9:10 Keynote W. Ockels: The Laddermill Project • 10:00 Coffee Break • 10:30 Delft Presentation (B. Lansdorp, A. Podgaets, J. Breukels, R. Ruiterkamp) • 11:10 Keynote M. Milanese: The KiteGen Project • 12:00 Lunch (The Lodge) • 14:00 M. Diehl: Optimal Control of Kites • 14:45 B. Houska: Robustly Stable Orbits • 15:15 A. Ilzhoefer: Predictive Control of Kites • 15:45 Coffee Break • 16:15 K. Lindholm; A System Perspective • 16:45 Discussion on Future Plans • 18:00 End Moritz Diehl
The Leuven-Heidelberg Approach to Optimization of Power Generating Kites Moritz Diehl Optimization in Engineering Center (OPTEC) K.U. Leuven, Belgium joint work with Boris Houska, Andreas Ilzhoefer, Karin Lindholm Moritz Diehl KITE-OPT 07, January 30, 2007
Organisation of the Talk • Basic Idea • Kite Modelling • Periodic Optimization Problem Formulation • Numerical Methods for Optimal Control • Nonlinear Model Predictive Control • Five Provocative Claims Moritz Diehl
Conventional Wind Turbines • Wing tips move 8-10 times faster than true wind • Due to high speed, wing tips are most efficient part of wing • High torques at wings and mast limit size and height of wind turbines Could we construct a wind turbine with only wing tips and generator? Moritz Diehl
Conventional Wind Turbines • Wing tips move 8-10 times faster than true wind • Due to high speed, wing tips are most efficient part of wing • High torques at wings and mast limit size and height of wind turbines Could we construct a wind turbine with only wing tips and generator? Moritz Diehl
Crosswind Kite Power (Loyd 1980) • use kite with high lift-to-drag-ratio • use strong line, but no mast and basement • automatic control keeps kites looping But where could a generator be driven? Moritz Diehl
New Power Generating Cycle New cycle consists of two phases: • Power generation phase: • add slow downwind motion by prolonging line (1/3 of wind speed) • generator at ground produces power due to large pulling force • Retraction phase: • change kite‘s angle of attack to reduce pulling force • pull back line Cycle produces same power as (hypothetical) turbine of same size! Moritz Diehl
New Power Generating Cycle New cycle consists of two phases: • Power generation phase: • add slow downwind motion by prolonging line (1/3 of wind speed) • generator at ground produces power due to large pulling force • Retraction phase: • change kite‘s angle of attack to reduce pulling force • pull back line Cycle produces same average power as wind turbine of same wing size, but much larger units possible (independently patented by Ockels, Ippolito/Milanese, D.) Moritz Diehl
Can stack kites, can use on sea Moritz Diehl
Organisation of the Talk • Basic Idea • Kite Modelling • Periodic Optimization Problem Formulation • Numerical Methods for Optimal Control • Nonlinear Model Predictive Control • Five Provocative Claims Moritz Diehl
Kite Model: State Variables Kite position in polar coordinates: Cable elasticity: distinguish true and nominal cable lengths and Velocities are also states, changed by forces at kite and cable Control roll angle and lift: Power = cable force x velocity: forces at kite Moritz Diehl
Kite Model Summarize in form ODE Model with 12 states and 3 controls Control inputs: • line length (2nd derivative) • roll angle (1st der.) • lift coefficient (1st der.) Moritz Diehl
Periodic Optimization Problem Maximize mean power production: by varying line thickness, period duration, controls, subject to periodicity and other constraints: Moritz Diehl
Generic Periodic Optimal Control Problem Moritz Diehl
Organisation of the Talk • Basic Idea • Kite Modelling • Periodic Optimization Problem Formulation • Numerical Methods for Optimal Control • Nonlinear Model Predictive Control • Five Provocative Claims Moritz Diehl
Simplified Problem for Illustration of Algorithms Moritz Diehl
First Approach: Single Shooting Moritz Diehl
Nonlinear Program (NLP) in Single Shooting • After control discretization, obtain NLP: • Solve with NLP solver, e.g. Sequential Quadratic Programming (SQP) Moritz Diehl
Sequential Quadratic Programming (SQP) Moritz Diehl
Toy Problem with One ODE for Illustration Mildly nonlinear and unstable system. Moritz Diehl
Single Shooting Moritz Diehl
Single Shooting: First Iteration Moritz Diehl
Single Shooting: Second Iteration Moritz Diehl
Single Shooting: Third Iteration Moritz Diehl
Single Shooting: 4th Iteration Moritz Diehl
Single Shooting: 5th Iteration Moritz Diehl
Single Shooting: 6th Iteration Moritz Diehl
Single Shooting: 7th Iteration (Solution) Moritz Diehl
Single Shooting: Pros and Cons Moritz Diehl
2nd Approach: Direct Multiple Shooting [Bock, Plitt 1981] Moritz Diehl
Nonlinear Program in Multiple Shooting Moritz Diehl
SQP for Multiple Shooting Summarize NLP: Moritz Diehl
Toy Example: Multiple Shooting Initialization Moritz Diehl
Multiple Shooting: First Iteration Moritz Diehl
Multiple Shooting: Second Iteration Moritz Diehl
Multiple Shooting: 3rd Iteration (already solution!) Moritz Diehl
Multiple Shooting: 3rd Iteration (already solution!) Single shooting converged much slower! Moritz Diehl
Multiple Shooting: Pros and Cons Optimal control package MUSCOD-II (C/C++/Fortran) for large ODE/DAE models continuously developed in Heidelberg and Leuven (Leineweber, Schäfer, Diehl, Sager, Albersmeyer, Potschka, ..., 1999 - ) Moritz Diehl
The MUSCOD Team in Heidelberg Crucial Algorithmic Features for Fast NMPC Moritz Diehl
Periodic Problem in Multiple Shooting Moritz Diehl
Kite Periodicity and Boundary Conditions Moritz Diehl