# Prof. Sina Ober-Blöbaum

Since October 2015 I have been an Associate Professor of Control Engineering at the Department of Engineering Science in the University of Oxford. I am also a Tutorial Fellow in Engineering at Harris Manchester College. My research is situated in the fields of Nonlinear Dynamical Systems, Numerical Integration and Optimal Control. My research focus lies in the development and analysis of structure-preserving simulation and optimal control methods for mechanical, electrical and hybrid systems, with a wide range of application areas including astrodynamics, drive technology and robotics.

**Contact:**

- Department of Engineering Science
- University of Oxford
- Parks Road
- Oxford, OX1 3PJ

- Fellow of Harris Manchester College
- OX1 3TD

- Tel: (+44 or 0) 1865 273153
- Email: sina.ober-blobaum@eng.ox.ac.uk

**Short curriculum vitae**

2004 | Dipl. Math., Diploma in Technomathematics, University of Paderborn | |

2008 | Dr. rer. nat, PhD in Applied Mathematics, University of Paderborn | |

2008 - 2009 | Postdoctorial Scholar, Control and Dynamical Systems, California Institute of Technology | |

2009 - 2015 | Junior Professor, Computational Dynamics and Optimal Control, Department of Mathematics, University of Paderborn | |

Oct 2011 - Mar 2012 | Deputy Professor (W2) for Applied Mathematics, Zentrum Mathematik, Technische Universität München | |

Oct 2013 - Mar 2014 | Eleonore-Trefftz Visiting Professor, Institute of Mathematics, Technische Universität Dresden | |

Oct 2014 - Mar 2015 | Visiting Professor for Scientific Computing, Institute of Mathematics, Free University Berlin | |

since Oct 2015 | Associate Professor for Control Systems and Tutorial Fellow for Engineering Department of Engineering Science, Harris Manchester College, University of Oxford, UK |

## Research interests

**Structure-preserving integration**
Simulations of dynamical systems are intended to reproduce the dynamic behavior in a realistic way. Using structure-preserving integration schemes for the simulation of mechanical systems, certain properties of the real system are conserved in the numerical solution. Examples are the conservation of energy or momentum induced by symmetries in the system (e. g. conservation of the angular momentum in case of rotational symmetry). A special class of structure-preserving integrators are variational integrators that are derived based on discrete variational mechanics. Using the concept of discrete variational mechanics,
variational multirate integrators as well as adaptive step size strategies are developed for an efficient treatment of systems with different time scales. Moreover, the integrators are extended for the application to new system classes such as electric circuits well as for Lie-group simulations of flexible beams.

**Optimal control methods**
Optimal control aims to prescribe the motion of a dynamical system in such a way that a certain optimality criterion is achieved. The research focus lies in the development of efficient numerical schemes for the solution of optimal control problems that are based on structure-preserving integration. In particular, optimal control methods are designed for the treatment of multi-body systems as well as for complex systems with certain substructures for which hierarchical approaches are developed. Further aspects of research interest are the development of numerical methods using inherent properties of the dynamical system such as symmetries or invariant objects, multiobjective optimization approaches for optimal control problems and the optimal control of hybrid systems. Besides the investigation of theoretical aspects regarding accuracy and convergence of the numerical schemes, their performance is validated by means of problems from different fields of applications, e.g. mechatronic systems, biomechanics and astrodynamics.

## Completed research projects

2012 - 2015 | Leading-Edge Cluster it’s OWL – Intelligent Technical Systems OstWestfalenLippe, crosssectional project Self-optimization (link) | |

2009 - 2013 | German Research Foundation (DFG) research project CRC 614, A1 Self-optimizing systems in mechanical engineering: model-oriented self-optimization (link) |

## Publications

### Journal publications

S. Peitz, S. Ober-Blöbaum and M. Dellnitz.

Multiobjective Optimal Control Methods for Fluid Flow Using Reduced Order Modeling.

Submitted.

J.C. Mergel, R.A. Sauer, and S. Ober-Blöbaum.

C1-continuous space-time discretization based on Hamilton's law of varying action.

Accepted for publication in ZAMM, 2016.

M. Ringkamp, S. Ober-Blöbaum, and S. Leyendecker.

On the time transformation of mixed integer optimal control problems using a consistent mixed integer control function.

Accepted for publication in Mathematical Programming, 2016.

S. Ober-Blöbaum.

Galerkin variational integrators and modified symplectic Runge-Kutta methods.

IMA Journal of Numerical Analysis, 1-32, 2016.
doi:10.1093/imanum/drv062
(link)

K. Flaßkamp, S. Hage-Packhäuser, and S. Ober-Blöbaum.

Symmetry exploiting control of hybrid mechanical systems.

Journal of Computational Dynamics, 2(1):25-50, 2015.
(link)

C.M. Campos, S. Ober-Blöbaum, and E. Trélat.

High order variational integrators in the optimal control of mechanical systems.

Discrete and Continuous Dynamical Systems A, 35(9):4193-4223, 2015
(link)

S. Ober-Blöbaum and Nils Saake.

Construction and analysis of higher order Galerkin variational integrators.

Advances in Computational Mathematics, 41(6): 955–986, 2015.
(link)

F. Demoures, F. Gay-Balmaz , S. Leyendecker, S. Ober-Blöbaum , T. S. Ratiu , Y. Weinand.

Discrete variational Lie group formulation of geometrically exact beam dynamics.

Numerische Mathematik, 130(1): 73-123, 2015.
(link)

K. Flaßkamp, J. Timmermann, S. Ober-Blöbaum, and A. Trächtler.

Control strategies on stable manifolds for energy-efficient swing-ups of double pendula.

International Journal of Control, 78(9), pages 1886-1905, 2014.
(link)

S. Ober-Blöbaum, M. Tao, M. Cheng, H. Owhadi, and J. E. Marsden.

Variational integrators for electric circuits.

Journal of Computational Physics, 242(C), pages 498-530, 2013. (link)

K. Witting, S. Ober-Blöbaum, and M. Dellnitz.

A variational approach to define robustness for parametric multiobjective optimization problems

Journal of Global Optimization, 57(2), pages 331-345, 2013. (link)

K. Flaßkamp, S. Ober-Blöbaum, and M. Kobilarov.

Solving optimal control problems by exploiting inherent dynamical systems structures.

Journal of Nonlinear Science, 22(4), pages 599-629, 2012. (link)

A. Moore, S. Ober-Blöbaum, and J. E. Marsden.

Trajectory design combining invariant manifolds with discrete mechanics and optimal control.

Journal of Guidance, Control, and Dynamics, 35(5), pages 1507-1525, 2012. (link)

M. Ringkamp, S. Ober-Blöbaum, M. Dellnitz, and O. Schütze.

Handling high dimensional problems with multi-objective continuation methods via successive approximation of the tangent space.

Engineering Optimization, 44(6), pages 1117-1146, 2012. (link)

S. Leyendecker, S. Ober-Blöbaum, J.E. Marsden, and M. Ortiz.

Discrete mechanics and optimal control for constrained systems.

Optimal Control, Applications and Methods, 31(6), pages 505-528, 2010. (link)

M. Dellnitz, S. Ober-Blöbaum, M. Post, O. Schütze, and B. Thiere.

A multi-objective approach to the design of low thrust space trajectories using optimal control.

Celestial Mechanics and Dynamical Astronomy, 105(1), pages 33-59, 2009. (link)

S. Ober-Blöbaum, O. Junge, and J.E. Marsden.

Discrete mechanics and optimal control: an analysis.

ESAIM: Control, Optimisation and Calculus of Variations, 17(2), pages 322--352, 2011.(link)

### Book chapter

T. Leitz, S. Ober-Blöbaum, and S. Leyendecker.

Variational Lie group formulation of geometrically exact beam dynamics - synchronous and asynchronous integration.

In Zdravko Terze, editor, Multibody Dynamics, volume 35 of Computational Methods in Applied Sciences, pages 175–203. Springer International Publishing, 2014.

H. Anacker, M. Dellnitz, K. Flaßkamp, S. Groesbrink, P. Hartmann, C. Heinzemann, C. Horenkamp, B. Kleinjohann, L. Kleinjohann, S. Korf, M. Krüger, W. Müller, S. Ober-Blöbaum, S. Oberthür, M. Porrmann, C. Priesterjahn, R. Radkowski, C. Rasche, J. Rieke, M. Ringkamp, K. Stahl, D. Steenken, J. Stöcklein, R. Timmermann, A. Trächtler, K. Witting, T. Xie, and S. Ziegert.

Methods for the design and development.

In Jürgen Gausemeier, Franz Josef Rammig, and Wilhelm Schäfer, editors, Design Methodology for Intelligent Technical Systems, Lecture Notes in Mechanical Engineering, pages 183-350. Springer Berlin Heidelberg, 2014.

M. Dellnitz, R. Dumitrescu, K. Flaßkamp, J. Gausemeier, P. Hartmann, P. Iwanek, S. Korf, M. Krüger, S. Ober-Blöbaum, M. Porrmann, C. Priesterjahn, K. Stahl, A. Trächtler, and M. Vaßholz.

The paradigm of self-optimization.

In Jürgen Gausemeier, Franz Josef Rammig, and Wilhelm Schäfer, editors, Design Methodology for Intelligent Technical Systems, Lecture Notes in Mechanical Engineering, pages 1-25. Springer Berlin Heidelberg, 2014.

W. Dangelmaier, M. Dellnitz, R. Dorociak, K. Flaßkamp, J. Gausemeier, S. Groesbrink, P. Hartmann, C. Heinzemann, C. Hölscher, P. Iwanek, J.H. Keßler, B. Kleinjohann, L. Kleinjohann, S. Korf, M. Krüger, T. Meyer, W. Müller, S. Ober-Blöbaum, M. Porrmann, C. Priesterjahn, F.J. Rammig, C. Rasche, P. Reinold, W. Schäfer, A. Seifried, W. Sextro, C. Sondermann-Woelke, K. Stahl, D. Steenken, R. Timmermann, A. Trächtler, M. Vaßholz, H. Wehrheim, K. Witting, T. Xie, Y. Zhao, S. Ziegert, and D. Zimmer.

Dependability of Self-optimizing Mechatronic Systems.

Lecture Notes in Mechanical Engineering. Springer, Heidelberg New York Dordrecht London, 2014.

S. Leyendecker and S. Ober-Blöbaum.

A variational approach to multirate integration for constrained systems.

In Paul Fisette and Jean-Claude Samin (editors), Multibody Dynamics: Computational Methods and Applications. Springer, volume 28, pages 97-121, Springer, Netherlands, 2013.

O. Schütze, K. Witting, S. Ober-Blöbaum, and M.Dellnitz.

Set oriented methods for the numerical treatment of multi-objective optimization problems.

In Emilia Tantar et al. (editors), EVOLVE -- A Bridge Between Probability, Set Oriented Numerics, and Evolutionary Computation, volume 447, pages 187-219, Springer, Berlin Heidelberg, 2013.

M. Dellnitz, O. Junge, A. Krishnamurthy, S. Ober-Blöbaum, K. Padberg, and R. Preis.

Efficient control of formation flying spacecraft.

In Friedhelm Meyer auf der Heide and Burkhard Monien (editors), New Trends in Parallel & Distributed Computing, volume 181, pages 235-247, Heinz Nixdorf Institut Verlagsschriftreihe, 2006. (pdf)

### Reviewed conference proceedings

T. Leitz, S. Ober-Blöbaum, and S. Leyendecker.

Variational integrators for dynamical systems with rotational degrees of freedom.

In 11th World Congress on Computational Mechanics, 20-25 July 2014.

T. Gail, S. Leyendecker, and S. Ober-Blöbaum.

On the role of quadrature rules and system dimensions in variational multirate integrators.

In 3rd Joint International Conference on Multibody System Dynamics, 30 June - 3 July 2014.

M. Dellnitz, J. Eckstein, K. Flaßkamp, P. Friedel, C. Horenkamp, U. Köhler, S. Ober-Blöbaum, S. Peitz, and S. Tiemeyer.

Multiobjective Optimal Control Methods for the Development of an Intelligent Cruise Control.

In ECMI 2014 Proceedings, Taormina, Italy, 2014.

M. Dellnitz, J. Eckstein, K. Flaßkamp, P. Friedel, C. Horenkamp, U. Köhler, S. Ober-Blöbaum, S. Peitz, and S. Tiemeyer.

Development of an intelligent cruise control using optimal control methods.

In SysInt 2014 Proceedings, Bremen, Germany, 2014.

S. Ober-Blöbaum and H. Lindhorst.

Variational formulation and structure-preserving discretization of nonlinear electric circuits.

In 21st International Symposium on Mathematical Theory of Networks and Systems, Groningen, The Netherlands, 7-11 July 2014.

K. Flaßkamp, S. Ober-Blöbaum, T. Schneider, and J. Böcker.

Optimal control of a switched reluctance drive by a direct method using a discrete variational principle.

In 52nd IEEE International Conference on Decision and Control, pages 7467--7472, Florence, Italy, 10-13 December 2013.

F. Demoures, F. Gay-Balmaz, T. Leitz, S. Leyendecker, S. Ober-Blöbaum, and T. S. Ratiu.

Asynchronous variational Lie group integration for geometrically exact beam dynamics.

In Proceedings of Applied Mathematics and Mechanics, 13(1), pages 45-46, 2013.

K. Flaßkamp, T. Murphey, and S. Ober-Blöbaum.

Optimization for discretized switched systems.

In Proceedings of Applied Mathematics and Mechanics, 13(1), pages 401-402, 2013.

T. Gail, S. Leyendecker, and S. Ober-Blöbaum.

Computing time investigations for variational multirate integration.

In Proceedings of Applied Mathematics and Mechanics, 13(1), pages 43-44, 2013.

M. Ringkamp, S. Leyendecker, and S. Ober-Blöbaum.

Multiobjective optimal control of a four-body kinematic chain.

In Proceedings of Applied Mathematics and Mechanics, 13(1), pages 27-28, 2013.

K. Flaßkamp, T. Murphey, and S. Ober-Blöbaum.

Discretized Switching Time Optimization Problems.

In Proceedings of the European Control Conference, pages 3179-3184, Zurich, Switzerland, 17-19 July 2013.

S. Ober-Blöbaum and A. Seifried.

A multiobjective optimization approach for the optimal control of technical systems with uncertainties.

In Proceedings of the European Control Conference, pages 204-209, Zurich, Switzerland, 17-19 July 2013.

F. Demoures, F. Gay-Balmaz, T. Leitz, S. Leyendecker, S. Ober-Blöbaum, and T. S. Ratiu.

Asynchronous variational Lie group integration for geometrically exact beam dynamics.

In ECCOMAS Thematic Conference on Multibody Dynamics, Zagreb, Kroatien, 1-4 July 2013.

T. Gail, S. Leyendecker, and S. Ober-Blöbaum.

Computing time investigations of variational multirate systems.

In ECCOMAS Thematic Conference on Multibody Dynamics, Zagreb, Kroatien, 1-4 July 2013.

M. Ringkamp, S. Ober-Blöbaum, and S. Leyendecker.

A numerical approach to multiobjective optimal control of multibody dynamics.

In ECCOMAS Thematic Conference on Multibody Dynamics, Zagreb, Kroatien, 1-4 July 2013.

A. Specht, S. Ober-Blöbaum, O. Wallscheid, C. Romaus, and J. Böcker.

Discrete-time model of an IPMSM based on variational integrators.

In IEEE International Electric Machines & Drives Conference (IEMDC), pages 1411-1417, Chicago, IL, USA, 12-15 May 2013.

K. Flaßkamp and S. Ober-Blöbaum.

Optimale Steuerungsstrategien für selbstoptimierende mechatronische Systeme mit mehreren Zielkriterien.

In 9. Paderborner Workshop Entwurf mechatronischer Systeme, pages 65-78, Paderborn, Germany, 18-19 April 2013.

K. Flaßkamp, C. Heinzemann, M. Krüger, S. Ober-Blöbaum, W. Schäfer, D. Steenken, A. Trächtler, and H. Wehrheim.

Verifikation der Konvoibildung von RailCabs mittels optimaler Bremsprofile.

In 9. Paderborner Workshop Entwurf mechatronischer Systeme, pages 177-190, Paderborn, Germany, 18-19 April 2013.

S. Ober-Blöbaum, M. Ringkamp, and G. zum Felde.

Solving Multiobjective Optimal Control Problems in Space Mission Design using Discrete Mechanics and Reference Point Techniques.

In Proceedings of the 51th IEEE Conference on Decision and Control, pages 5711-5716, Maui, HI, USA, 10-13 December, 2012. (pdf)

K. Flaßkamp, T. Murphey, and S. Ober-Blöbaum.

Switching time optimization in discretized hybrid dynamical systems.

In Proceedings of the 51th IEEE Conference on Decision and Control, pages 707-712, Maui, HI, USA, 10-13 December, 2012. (pdf)

C. M. Campos, O. Junge, and S. Ober-Blöbaum.

Higher order variational time discretization of optimal control problems.

In 20th International Symposium on Mathematical Theory of Networks and Systems, Melbourne, Australia, 9-13 July 2012. (pdf)

K. Flaßkamp and S. Ober-Blöbaum.

Energy efficient control for mechanical systems based on inherent dynamical structures.

In Proceedings of American Control Conference, pages 2609-2614, Montréal, Canada, 27-29 June 2012. (pdf)

J. Timmermann, S.Khatab, S.Ober-Blöbaum, A. Trächtler.

Discrete mechanics and optimal control and its application to a double pendulum on a cart.

In 18th International Federation of Automatic Control World Congress (IFAC), Milano, Italy, 28 August - 2 September, 2011. (pdf)

S. Leyendecker and S. Ober-Blöbaum.

A variational approach to multirate integration for constrained systems.

In Proceedings of Multibody Dynamics, ECCOMAS Thematic Conference, Brussels, Belgium, 4-7 July 2011. (pdf)

S. Leyendecker and S. Ober-Blöbaum.

Variational multirate integration of constrained dynamics.

In Proceedings of Applied Mathematics and Mechanics, 11(1), pages 53-54, 2011. (pdf)

S. Ober-Blöbaum, M. Tao, and H. Owhadi.

Variational integrators for electric circuits.

In Proceedings of Applied Mathematics and Mechanics, 11(1), pages 783-784, 2011. (pdf)

K. Flaßkamp, S. Ober-Blöbaum, M. Ringkamp, T. Schneider, C. Schulte and J. Böcker.

Berechnung optimaler Stromprofile für einen 6-phasigen, geschalteten Reluktanzantrieb.

In Proceedings of 8. Paderborner Workshop Entwurf mechatronischer Systeme, 19-20 May, 2011. (pdf)

K. Flaßkamp and S. Ober-Blöbaum.

Variational formulation and optimal control of hybrid Lagrangian systems.

In Proceedings of the Conference on Hybrid Systems: Computation and Control, Chicago, Illinois, 12-14 April, 2011. (pdf)

A. Moore, S. Ober-Blöbaum and J.E. Marsden.

Mesh refinement strategies for spacecraft trajectory optimization using discrete mechanics and optimal control.

In Proceedings of the 21st AAS/AIAA Space Flight Mechanics Meeting, New Orleans, Lousiana, USA, 13-17 February, 2011. (pdf)

B. Thiere, S. Ober-Blöbaum and P. Pergola.

Detecting initial guesses for trajectories in the (P)CRTBP.

In Proceedings of the AIAA/AAS Astrodynamics Specialist Conference, Toronto, Canada, 2-5 August, 2010.

S. Ober-Blöbaum and A. Walther.

Computation of derivatives for structure preserving optimal control using automatic differentiation.

In Proceedings of Applied Mathematics and Mechanics, 10(1), pages 585-586, 2010.

DOI: 10.1002/pamm.201010285. (pdf)

K. Flaßkamp, S. Ober-Blöbaum and M.Kobilarov.

Solving optimal control problems by using inherent dynamical properties.

In Proceedings of Applied Mathematics and Mechanics,10(1), pages 577-578, 2010.

DOI: 10.1002/pamm.201010281 (pdf)

A. Moore, S. Ober-Blöbaum and J.E. Marsden.

The effect of mesh reﬁnement on spacecraft trajectory design using discrete mechanics and optimal control.

In Proceedings of the 4th European Conference on Computational Mechanics, Paris, France, 16-21 May, 2010. (pdf)

S. Ober-Blöbaum and S. Leyendecker.

A variational approach to multirate integration.

In Proceedings of the 4th European Conference on Computational Mechanics, Paris, France, 16-21 May 2010. (pdf)

M. Gehler, S. Ober-Blöbaum, and Bernd Dachwald.

Application of discrete mechanics and optimal control in non-keplerian motion around small solar systems.

In Proceedings of 60th International Astronautical Congress, Daejeon, Republic of Korea, 12-16 October, 2009. (pdf)

S. Nair, S. Ober-Blöbaum, and J.E. Marsden.

The Jacobi-Maupertuis principle in variational integrators.

In Proceedings of the 7th International Conference of Numerical Analysis and Applied Mathematics, Rethymno, Crete, Greece, 18-22 September 2009. (pdf)

S. Ober-Blöbaum and J. Timmermann.

Optimal control for a pitcher's motion modeled as constrained mechanical system.

In Proceedings of the 7th International Confenrence on Multibody Systems, Nonlinear Dynamics, and Control, ASME International Design Engineering Technical Conferences, San Diego, 29 August - 2 September 2009. (pdf)

M. Gehler, S. Ober-Blöbaum, Bernd Dachwald, and J.E. Marsden.

Optimal control of gravity tractor spacecraft near arbitrarily shaped asteroids.

In Proceedings of 1st IAA Planetary Defense Conference: Protecting Earth from Asteroids, Granada, Spain, 27-30 April, 2009. (pdf)

A. Moore and S. Ober-Blöbaum, and J.E. Marsden.

Optimization of spacecraft trajectories: a method combining invariant manifold techniques and discrete mechanics and optimal control.

In Proceedings of 19th AAS/AIAA Space Flight Mechanics Meeting, Savannah, Georgia, USA, 2009. (pdf)

W. Zhang, T. Inanc, S. Ober-Blöbaum, and J.E. Marsden.

Optimal trajectory generation for a dynamic glider in ocean flows modeled by 3D B-Spline Functions.

In Proceedings of the IEEE International Conference on Robotics and Automation, Pasadena, California, USA, 19-23 May 2008. (pdf)

S. Leyendecker, S. Ober-Blöbaum, J.E. Marsden, and M. Ortiz.

Discrete mechanics and optimal control for constrained multibody dynamics.

In Proceedings of the 6th International Conference on Multibody Systems, Nonlinear Dynamics, and Control, ASME International Design Engineering Technical Conferences, Las Vegas, Nevada, USA, 4-7 September 2007. (pdf)

O. Junge, J.E. Marsden, and S. Ober-Blöbaum.

Optimal reconfiguration of formation flying spacecraft - a decentralized approach.

In Proceedings of the 45th IEEE Conference on Decision and Control and European Control Conference ECC, San Diego, USA, pages 5210-5215, 13-15 December 2006. (pdf)

O. Junge and S. Ober-Blöbaum.

Optimal reconfiguration of formation flying satellites.

In Proceedings of the 44th IEEE Conference on Decision and Control and European Control Conference ECC, Seville, Spain, 12-15 December 2005. (pdf)

O. Junge, J.E. Marsden, and S. Ober-Blöbaum.

Discrete mechanics and optimal control.

In Proceedings of the 16th IFAC World Congress, Prague, Czech Republic, 3-8 July 2005. (pdf)

### Theses

S. Ober-Blöbaum.

Discrete mechanics and optimal control.

Phd thesis, University of Paderborn, Germany, 2008. (pdf)

S. Ober-Blöbaum.

Zur optimalen Kontrolle von Verbunden starrer Körper.

Diploma thesis, University of Paderborn, Germany, 2004