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204 results on '"BEHRENS, MICHAEL"'

4. Smart Magnetic Microrobots Learn to Swim with Deep Reinforcement Learning

Author

Behrens, Michael R. and Ruder, Warren C.

Subjects
Computer Science - Robotics, Computer Science - Artificial Intelligence, Electrical Engineering and Systems Science - Systems and Control, I.2.9
Abstract

Swimming microrobots are increasingly developed with complex materials and dynamic shapes and are expected to operate in complex environments in which the system dynamics are difficult to model and positional control of the microrobot is not straightforward to achieve. Deep reinforcement learning is a promising method of autonomously developing robust controllers for creating smart microrobots, which can adapt their behavior to operate in uncharacterized environments without the need to model the system dynamics. Here, we report the development of a smart helical magnetic hydrogel microrobot that used the soft actor critic reinforcement learning algorithm to autonomously derive a control policy which allowed the microrobot to swim through an uncharacterized biomimetic fluidic environment under control of a time varying magnetic field generated from a three-axis array of electromagnets. The reinforcement learning agent learned successful control policies with fewer than 100,000 training steps, demonstrating sample efficiency for fast learning. We also demonstrate that we can fine tune the control policies learned by the reinforcement learning agent by fitting mathematical functions to the learned policy's action distribution via regression. Deep reinforcement learning applied to microrobot control is likely to significantly expand the capabilities of the next generation of microrobots., Comment: 23 pages, 5 figures

Published
2022

9. SPATIAL AND TEMPORAL DISTRIBUTION OF THE EARLY LIFE HISTORY STAGES OF THE NATIVE OLYMPIA OYSTER OSTREA LURID A (CARPENTER, 1864) IN A RESTORATION SITE IN NORTHERN PUGET SOUND, WA

Author

Becker, Bonnie J., Behrens, Michael D., Allen, Brian, Hintz, Megan, Parker, Hannah, McCartha, Michelle M., and White, Sarah M.

Subjects
Puget Sound -- Natural resources, Ostreidae -- Distribution -- Protection and preservation -- Natural history -- Methods, Habitat conservation -- Methods -- Protection and preservation, Company distribution practices, Biological sciences, Zoology and wildlife conservation
Abstract

ABSTRACT For effective long-term restoration of depleted marine species, it is critical that populations are able to replenish themselves through reproduction. The Olympia oyster Ostrea lurida (Carpenter, 1864), the only [...]

Published
2020
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10. Towards Automatic Robotic NDT Dense Mapping for Pipeline Integrity Inspection

Author

Miro, Jaime Valls, Hunt, Dave, Ulapane, Nalika, Behrens, Michael, Siciliano, Bruno, Series editor, Khatib, Oussama, Series editor, Antonelli, Gianluca, Advisory editor, Fox, Dieter, Advisory editor, Harada, Kensuke, Advisory editor, Hsieh, M. Ani, Advisory editor, Kröger, Torsten, Advisory editor, Kulic, Dana, Advisory editor, Hutter, Marco, editor, and Siegwart, Roland, editor

Published
2018
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15. The Role of Temperature in the Latitudinal Diversity Gradient in Herbivorous Fishes: Implications of Global Climate Change

Author

Behrens, Michael

Abstract

In temperate latitudes, algae often dominate shallow-water marine habitats which can lead to net primary productivity as high as anywhere on earth, including tropical rain forests. Climate change has been shown to shift the geographic ranges of species towards higher latitudes and cause declines in algal productivity. Herbivorous fishes as a group tend to be distributed in the tropics. However climate change would be expected to shift their geographical ranges towards higher latitudes in a similar manner. Increased levels of herbivory at higher latitudes due to climate change may drastically change the structure of these communities which are dominated by algae.The reasons why herbivorous fishes have distributions skewed towards the tropics have been debated for decades. The hypotheses include limited time for evolution of herbivory, a lack of consistent food, and a physiological constraint related to latitude. I hypothesize that temperature constrains the ability of herbivorous fishes to digest algae, therefore limiting their ability to survive and reproduce in cold waters. To test this hypothesis, I will investigate the sources of nutrition for an herbivorous fish, the opaleye Girella nigricans, throughout a latitude and temperature gradient with the use of stable carbon and nitrogen isotope analyses. I will also study how temperature affects microbial digestion in the gut of opaleye by culturing cellulose degrading intestinal bacteria from G. nigricans at various temperatures. Additionally, I will investigate the role temperature plays in affecting the ability of opaleye to control algal abundance with the use of field cages to enclose herbivorous fish in different thermal regimes in the vicinity of a power plant discharge. The results of these studies will help me determine (1) what factors limit herbivorous fishes to the tropics and (2) the effect herbivorous fishes may have on benthic algal assemblages in response to global climate change.

Published
2004

19. Fingerbilderkennung

Author

Behrens, Michael, Heumann, Björn, Pfitzmann, Andreas, editor, Reimer, Helmut, editor, Rihaczek, Karl, editor, Roßnagel, Alexander, editor, Behrens, Michael, editor, and Roth, Richard, editor

Published
2001
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22. Roberto Gonzalez Echevarria. Cervantes' Don Quixote

Author

Behrens, Michael

Subjects
Cervantes Don Quixote (Obra de ficción), Literature/writing
Abstract

Roberto González Echevarría. Cervantes Don Quixote. New Haven: Yale UP, 2015. 384 pp. ISBN: 978-0-300-19864-5. Near the end of Cervantes Don Quixote, Roberto González Echevarría urges his readers to pay [...]

Published
2018

23. Engineering Automated Microrobotic Systems with Machine Learning-Based Control for Biomedical Applications

Author

Behrens, Michael R. and Behrens, Michael R.

Abstract

For many diseases and injuries, the pathological effects are local to particular areas of the body. In such cases, systemic drug delivery is nonideal treatment because drugs used to treat the pathological condition may have a deleterious effect on the remaining healthy tissue and cause damaging side effects. A similar kind of harm is done in many surgical scenarios when healthy tissue must be cut in order to give the surgeon physical access to the damaged tissue underneath. There exists an unmet clinical need to be able to deliver minimally invasive therapeutic interventions precisely within the body, while minimizing harm to healthy tissue. Towards this end, we are developing swimming microrobotic systems to traverse the fluidic pathways within the body, in order to deliver locally targeted therapeutic payloads noninvasively, and with precision, to areas which are difficult to access noninvasively using current methods. In this dissertation, I present a control approach which uses machine learning in order to develop robust control policies for magnetically actuated microrobots navigating within small scale fluidic environments. We have developed a controller for a helical magnetic hydrogel microrobot that uses the soft actor critic reinforcement learning algorithm to autonomously derive control policies which allow the microrobot to swim through an uncharacterized biomimetic fluidic environment, actuated by time varying magnetic fields generated from a three-axis array of electromagnets. Our results show that this model-free control approach can learn and adapt to the dynamic features of the microrobot, the fluidic environment, and the electromagnetic actuator in order to successfully accomplish navigation tasks. Additionally, we demonstrate that the control policies learned by the reinforcement learning algorithm repeatedly converge to recapitulate the behavior of rationally designed controllers based on physical models of helical swimming microrobots. We also pr

Published
2022

31. Determining distribution and size of larval pacific geoduck clams (Panopea generosa Gould 1850) in quartermaster harbor (Washington, USA) using a novel sampling approach

Author

Becker, Bonnie J., Behrens, Michael D., Shevalier, Yvonne R.A., Henzler, Christine M., Hoaglund, Elizabeth A., and Lemay, Brenda K.

Subjects
Clams -- Distribution, Home range -- Research, Company distribution practices, Biological sciences, Zoology and wildlife conservation
Abstract

ABSTRACT Realistic species-specific information about larval life history is necessary for effective management of shellfish and parameterization of larval connectivity models. The patchiness of dispersing larvae, and the resources needed [...]

Published
2012
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34. Temperature and diet effects on omnivorous fish performance: implications for the latitudinal diversity gradient in herbivorous fishes

Author

Behrens, Michael D. and Lafferty, Kevin D.

Subjects
Fishes -- Comparative analysis, Fishes -- Observations, Temperature -- Influence, Perciformes -- Observations, Animal feeding behavior, Earth sciences
Abstract

Abstract: Herbivorous fishes show a clear latitudinal diversity gradient, making up a larger proportion of the fish species in a community in tropical waters than in temperate waters. One proposed [...]

Published
2007

35. Disease dynamics and the potential role of thermal stress in the sea urchin, Strongylocentrotus purpuratus

Author

Lester, Sarah E., Tobin, Elizabeth D., and Behrens, Michael D.

Subjects
Sea urchins -- Diseases, Sea urchins -- Environmental aspects, Earth sciences
Abstract

Abstract: Evidence from field and laboratory data indicates that warmer ocean temperatures likely play a critical role in the disease dynamics of intertidal populations of the sea urchin, Strongylocentrotus purpuratus. [...]

Published
2007

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