Jochem De Schutter PhD Researcher University of Freiburg Department of Microsystems Engineering
Systems Control and Optimization Laboratory Georges-Köhler-Allee 102 79110 Freiburg im Breisgau Germany jochem.de.schutter@imtek.de www.syscop.de
OpenOCL - The Open Optimal Control Library
Jonas Koenemann1, Jochem De Schutter1, Rachel Leuthold1, Giovanni Licitra2, Moritz Diehl1
1Systems Control and Optimization Laboratory, University of Freiburg 2Neurocast B.V.
With OpenOCL, we aim to develop an optimal control modeling framework that allows to define optimal con-trol problems in a user friendly way. Domain specific models for airborne wind energy can be implemented in Matlab or using the optimal control modeling language (.ocml). A library of power optimization models for the Ampyx Power AP2 system is available at the OpenAWE project [1]. Results are shown in the figure on the right. The two main applications of optimal control are trajec-tory optimizationand model predictive control. Open-OCL is designed to be used for both. While trajectory opti-mization can be used to study, analyze, and simulate the behavior of the system, model predictive control can be used to control the actual physical system in a real-time loop.
For trajectory optimization, OpenOCL implements a direct collocation method that transcribes the continuous time optimal control problem into a non-linear program. The non-linear program is then solved using ipopt [2]. For real-time model predictive control there is an interface to acadosthat allows to generate efficient code that can run on embedded systems [3]. Derivatives for the models are automatically generated using CasADi [4].
OpenOCL is available online as a Matlab package at https://openocl.org/
An optimal flight path for an airborne wind energy system to gener-ate maximal power calculgener-ated by OpenOCL using CasADi and Ipopt, flight models from OpenAWE. The system generates power when the winch releases tether (indicated by the orange lines).
References:
[1] J. Koenemann, S. Sieberling, M. Diehl, łOpenAWE: An Open Source Toolbox for the Optimization of AWE Flight Trajectories,ž Air-borne Wind Energy Conference 2017, 2017.
[2] A. Waechter, L. T. Biegler, łOn the Implementation of an Interior-point Filter Line-search Algorithm for Large-scale Nonlinear Pro-gramming,ž Mathematical Programming, vol. 106, no. 1, pp. 25ś57, 2006.
[3] R. Verschueren, G. Frison, D. Kouzoupis, N. van Duijkeren, A. Zanelli, R. Quirynen, M. Diehl, łTowards a Modular Software Pack-age for Embedded Optimization,ž in Proceedings of the IFAC Con-ference on Nonlinear Model Predictive Control, 2018.
[4] J. A. Andersson, J. Gillis, G. Horn, J. B. Rawlings, M. Diehl, łCasADi: A Software Framework for Nonlinear Optimization and Optimal Control,ž Mathematical Programming Computation, 2019.
