@article{UffmannAbichtGroteetal.2002, author = {Uffmann, Kai and Abicht, Claus and Grote, Wolfgang and Quick, Harald H. and Ladd, Mark E.}, title = {Design of an MR-compatible piezoelectric actuator for MR elastography}, series = {Concepts in Magnetic Resonance Part A: Bridging Education and Research}, volume = {15}, journal = {Concepts in Magnetic Resonance Part A: Bridging Education and Research}, number = {4}, publisher = {Wiley}, doi = {https://doi.org/10.1002/cmr.10045}, pages = {239 -- 254}, year = {2002}, abstract = {Magnetic Resonance (MR) elastography is a method for measuring tissue elasticity via phase images acquired with an MR scanner. The propagation of periodic mechanical waves through the tissue can be captured by means of a modified phase contrast sequence. These waves are generated with a mechanical oscillator (actuator) and coupled into the tissue through the skin. The actuator must be capable of generating a sinusoidal excitation with excellent phase and amplitude stability, while not disturbing the MR imaging process. In this work, an actuator based on a piezoelectric principle was developed. Based on the imaging evaluation of several material samples, the housing for the piezoelectric ceramic was constructed of aluminum. Smaller parts of the housing were manufactured from brass and titanium to fulfill the mechanical constraints. A lever was used to transfer the oscillation generated by the piezoelectric ceramic to the point of excitation. The lever amplifies the piezoelectric motion, allowing for a more compact design. Three different lever designs were characterized by an acceleration sensor both outside and inside the magnet. It was shown that the rigidity of the lever, as determined by its material and form, was decisive in determining the resonant frequency of the system and therefore the maximum practical frequency of operation. It was also shown that the motion of the oscillator is unaffected by the electromagnetic fields of the MR imager. The final design can be placed directly in the magnet bore within a few centimeters of the tissue volume to be imaged without generating significant artifacts. An amplitude range of 0-1 mm in the frequency range from 0 to over 300 Hz was achieved, sufficient for performing most MR elastography applications. © 2002 Wiley Periodicals, Inc. Concepts in Magnetic Resonance (Magn Reson Engineering) 15: 239-254, 2002}, language = {en} } @article{GalbanMaderwaldHerrmannetal.2005, author = {Galban, Craig and Maderwald, Stefan and Herrmann, Burkhard and Brauck, K. and Grote, Wolfgang and de Greiff, A. and Uffmann, K. and Ladd, M.}, title = {Measuring Skeletal Muscle Elasticity in Patients with Hypogonadism by MR Elastography}, series = {Proc. Intl. Soc. Mag. Reson. Med.}, volume = {13}, journal = {Proc. Intl. Soc. Mag. Reson. Med.}, pages = {2016}, year = {2005}, abstract = {Men afflicted with hypogonadism have reduced fat-free mass and in some cases a loss in muscle strength. We hypothesize that muscle elasticity of the lower extremities differs between patients with hypogonadism and healthy controls. The shear modulus of the soleus muscle was measured non-invasively using MR elastography (MRE) at 0\%, 5\%, 10\%, 15\%, and 20\% of the subject's maximum applied force. The results from this study showed statistical differences between the patients and controls, even though there were no statistical differences in applied force.}, language = {en} } @article{GalbanMaderwaldEggebrechtetal.2005, author = {Galban, Craig and Maderwald, Stefan and Eggebrecht, Holger and Grote, Wolfgang and de Greiff, A. and Uffmann, K. and Ladd, M. E.}, title = {Monitoring the Effects of Chronic Obstructive Pulmonary Disease on Muscle Elasticity by MR Elastography}, series = {Proc. Intl. Soc. Mag. Reson. Med.}, volume = {13}, journal = {Proc. Intl. Soc. Mag. Reson. Med.}, pages = {2015}, year = {2005}, abstract = {Men afflicted with chronic obstructive pulmonary disease (COPD) show signs of muscle dysfunction, such as increased muscle fatigue and acidosis during exercise. We hypothesize that muscle elasticity of the lower extremities differs between patients with COPD and age-related controls. The shear modulus of the soleus muscle was measured non-invasively using MR elastography (MRE) at 0\%, 5\%, 10\%, 15\%, and 20\% of the subject's maximum applied force. The results from this study showed statistical differences between the patients and controls, even though there were no statistical differences in the maximum applied force.}, language = {en} } @article{BeyerGroteReinig2008, author = {Beyer, Marc-Andr{\´e} and Grote, Wolfgang and Reinig, Gunter}, title = {Adaptive exact linearization control of batch polymerization reactors using a Sigma-Point Kalman Filter}, series = {Journal of Process Control}, volume = {18}, journal = {Journal of Process Control}, number = {7-8}, publisher = {Elsevier}, doi = {10.1016/j.jprocont.2007.12.002}, pages = {663 -- 675}, year = {2008}, abstract = {The Chylla-Haase polymerization reactor is widely accepted as a benchmark process for the evaluation of control strategies for batch reactors. In this contribution a control concept based on Exact I/O-Linearization is proposed and compared to a conventional cascade control structure. In order to adapt the exact linearization control strategy to various polymerization products and batch conditions, an advanced probabilistic inference algorithm (Sigma-Point Kalman Filter) is applied and investigated. Sigma-Point Kalman Filters have the major improvement of simplified implementation compared to local linearization methods (i.e. Extended Kalman Filter) because no analytical Jacobians are required. Stochastic simulation studies are introduced and show the effectiveness, accuracy and benefit of the control concept. Within several scenarios a satisfying robustness against structural errors in the underlying model equations for the nonlinear control law and the inference algorithm is demonstrated. Furthermore it is pointed out, that with little effort in reassembling the plant design, control performance can be improved significantly.}, language = {en} } @phdthesis{Grote2009, author = {Grote, Wolfgang}, title = {Ein Beitrag zur modellbasierten Regelung von Entnahmedampfturbinen}, publisher = {Bochum}, organization = {Ruhr-Universit{\"a}t Bochum}, pages = {244}, year = {2009}, subject = {Dynamische Modellierung}, language = {de} } @inproceedings{GroteSchulzeDarupReinig2009, author = {Grote, Wolfgang and Schulze Darup, M. and Reinig, G.}, title = {Modellpr{\"a}diktive Regelung von Entnahmeturbinen und Dampfnetzen (Poster)}, series = {Chemie Ingenieur Technik}, volume = {2009}, booktitle = {Chemie Ingenieur Technik}, number = {8}, publisher = {Wiley}, address = {Weinheim}, doi = {10.1002/cite.200950184}, pages = {1113 -- 1114}, year = {2009}, language = {de} } @inproceedings{GroteReinig2009, author = {Grote, Wolfgang and Reinig, Gunter}, title = {Modellbasierte Regelung von Entnahmedampfturbinen (eingeladener Vortrag)}, series = {43. Regelungstechnisches Kolloquium in Boppard vom 25.-27. Februar 2009}, booktitle = {43. Regelungstechnisches Kolloquium in Boppard vom 25.-27. Februar 2009}, year = {2009}, language = {de} } @inproceedings{GroteKastsianMoennigmann2011, author = {Grote, Wolfgang and Kastsian, Darya and M{\"o}nnigmann, Martin}, title = {Optimal power system unit commitment with guaranteed local stability}, series = {Proceedings of the 2011 American Control Conference}, booktitle = {Proceedings of the 2011 American Control Conference}, publisher = {IEEE}, issn = {2378-5861}, doi = {10.1109/ACC.2011.5991058}, pages = {4526 -- 4531}, year = {2011}, abstract = {This article deals with the cost optimal commitment of power systems. System stability is often only considered after solving the commitment problem. We show by example that a cost optimization may result in a mode of operation that, while economically optimal, is unstable or has otherwise unacceptable dynamics. As a remedy, we propose to use the so-called normal vector method, which has been developed for the optimization of nonlinear dynamical systems with stability boundaries and uncertain parameters. We apply the method to a small sample power grid, where the optimization goal is to minimize the energy production costs for a given power consumption.}, language = {en} } @article{GroteKastsianMoennigmann2013, author = {Grote, Wolfgang and Kastsian, Darya and M{\"o}nnigmann, Martin}, title = {Guaranteed stability in optimal power generation dispatching under uncertainty}, series = {IEEE Transactions on Power Systems}, volume = {28}, journal = {IEEE Transactions on Power Systems}, number = {2}, publisher = {IEEE}, issn = {1558-0679}, doi = {10.1109/TPWRS.2012.2207970}, pages = {1103 -- 1112}, year = {2013}, abstract = {Stability and cost optimality of power generation and supply systems must not be considered independently from one another. Simple examples show that optimizing cost without considering stability may result in modes of operation that, while economically optimal, are unstable. We demonstrate that stability, robustness, and optimality can be considered systematically and simultaneously by combining bifurcation theory and nonlinear optimization. Essentially, the proposed method enforces a backoff distance between the optimal point of operation and operational or stability boundaries in the space of the optimization variables, where bifurcation theory is used to describe nonlinear stability boundaries.}, language = {en} } @article{JostGroteMoellenbrucketal.2014, author = {Jost, Michael and Grote, Wolfgang and M{\"o}llenbruck, Florian and M{\"o}nnigmann, Martin}, title = {Plant-wide control of a parabolic trough power plant with thermal energy storage}, series = {IFAC Proceedings Volumes}, volume = {47}, journal = {IFAC Proceedings Volumes}, number = {3}, publisher = {Elsevier}, issn = {2589-3653}, doi = {10.3182/20140824-6-ZA-1003.00879}, pages = {419 -- 425}, year = {2014}, abstract = {We present a control scheme for a parabolic trough power plant that is equipped with a molten salt thermal energy storage system. We show that the multivariable control problem for the solar field can be decoupled by controlling the three way valve that splits the heat transfer fluid between the storage system and the steam generator. The steam generation cycle is regulated with inlet pressure control. The subsystems of the plant are modeled based on first principles, where we focus on the steam generation cycle. A multi-group extraction turbine with pre- and reheater is considered, which is suitable for solar power plants. We demonstrate the benefits of the proposed control scheme with a day-to-day simulation.}, language = {en} }