Coordination of Multirobot Systems Under Temporal Constraints

Multirobot systems have great potential to change our lives by increasing efficiency or decreasing costs in many applications, ranging from warehouse logistics to construction. They can also replace humans in dangerous scenarios, for example in a nuclear disaster cleanup mission. However, teleoperating robots in these scenarios would severely limit their capabilities due to communication and reaction delays. Furthermore, ensuring that the overall behavior of the system is safe and correct for a large number of robots is challenging without a principled solution approach. Ideally, multirobot systems should be able to plan and execute autonomously. Moreover, these systems should be robust to certain external factors, such as failing robots and synchronization errors and be able to scale to large numbers, as the effectiveness of particular tasks might depend directly on these criteria. This thesis introduces methods to achieve safe and correct autonomous behavior for multirobot systems. Firstly, we introduce a novel logic family, called counting logics, to describe the high-level behavior of multirobot systems. Counting logics capture constraints that arise naturally in many applications where the identity of the robot is not important for the task to be completed. We further introduce a notion of robust satisfaction to analyze the effects of synchronization errors on the overall behavior and provide complexity analysis for a fragment of this logic. Secondly, we propose an optimization-based algorithm to generate a collection of robot paths to satisfy the specifications given in counting logics. We assume that the robots are perfectly synchronized and use a mixed-integer linear programming formulation to take advantage of the recent advances in this field. We show that this approach is complete under the perfect synchronization assumption. Furthermore, we propose alternative encodings that render more efficient solutions under certain conditions. We also provide numerical results that showcase the scalability of our approach, showing that it scales to hundreds of robots. Thirdly, we relax the perfect synchronization assumption and show how to generate paths that are robust to bounded synchronization errors, without requiring run-time communication. However, the complexity of such an approach is shown to depend on the error bound, which might be limiting. To overcome this issue, we propose a hierarchical method whose complexity does not depend on this bound. We show that, under mild conditions, solutions generated by the hierarchical method can be executed safely, even if such a bound is not known. Finally, we propose a distributed algorithm to execute multirobot paths while avoiding collisions and deadlocks that might occur due to synchronization errors. We recast this problem as a conflict resolution problem and characterize conditions under which existing solutions to the well-known drinking philosophers problem can be used to design control policies that prevents collisions and deadlocks. We further provide improvements to this naive approach to increase the amount of concurrency in the system. We demonstrate the effectiveness of our approach by comparing it to the naive approach and to the state-of-the-art.PHDElectrical Engineering: SystemsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/162921/1/ysahin_1.pd

From Drinking Philosophers to Wandering Robots

In this paper, we consider the multi-robot path execution problem where a group of robots move on predefined paths from their initial to target positions while avoiding collisions and deadlocks in the face of asynchrony. We first show that this problem can be reformulated as a distributed resource allocation problem and, in particular, as an instance of the well-known Drinking Philosophers Problem (DrPP). By careful construction of the drinking sessions capturing shared resources, we show that any existing solutions to DrPP can be used to design robot control policies that are collectively collision and deadlock-free. We then propose modifications to an existing DrPP algorithm to allow more concurrent behavior, and provide conditions under which our method is deadlock-free. Our method do not require robots to know or to estimate the speed profiles of other robots, and results in distributed control policies. We demonstrate the efficacy of our method on simulation examples, which show competitive performance against the state-of-the-art.Comment: 13 pages, 7 figures. Under submission for a journa

Wczesne versus opóźnione odżywianie po cięciu cesarskim z różnymi metodami znieczulenia – badanie randomizowane

Objective: The aim of the study was to evaluate the safety and efficacy of early feeding after cesarean delivery under different anesthetic methods. Study design: Two hundred women with elective cesarean delivery were randomly assigned to early oral feeding (EOF) or routine oral feeding (ROF) groups. EOF patients were informed that they could begin taking fluids orally (regime I) as soon as 2 hours after the delivery and then gradually progress to solid foods (regime III), if tolerated. ROF patients were informed that they could start regime I right after bowel sounds were heard on examination and then gradually move on to regime III. Hospitalization time and total time to ambulation (primary outcomes), gasstool discharge time and onset of bowel sounds (secondary outcomes) were compared in groups A [EOF patients after regional anesthesia (n=49)], B [EOF patients after general anesthesia (n=48)], C [ROF patients after regionalanesthesia (n=47)] and D [ROF patients after general anesthesia (n=48)]. Results: There were significant differences in primary and secondary outcomes between group A and the remaining groups, especially group D. The status of patients from group B was not better than group C. In fact, the latter were discharged home sooner and passage of gas, as well as initiation of regime I occurred earlier as compared to the former. Conclusions: Cesarean section under regional anesthesia and encouragement of oral feeding 2 hours after the operation should be recommended in order to achieve postoperative recovery and early hospital discharge. Routine oral feeding (right after bowel sounds are heard on examination) after cesarean section under general anesthesia should be the last choice.Cel: Celem badania była ocena bezpieczeństwa i skuteczności wczesnego włączenia odżywiania po cesarskim wykonanym przy różnych metodach znieczulenia. Do badania włączono 200 kobiet po elektywnym cięciu cesarskim. Po randomizacji pacjentki przydzielano do grupy wczesnego odżywiania dojelitowego (EOF) lub grupy zwykłego włączania jedzenia (ROF). Pacjentkom z grupy EOF pozwolono pić płyny już 2 godziny po porodzie (reżim I) a następnie stopniowo przechodzić do pokarmów stałych (reżim III). Pacjentki z grupy ROF mogły rozpocząć odżywianie wg reżimu I gdy w badaniu osłuchiwaniem obecna była perystaltyka a następnie stopniowo przechodzić do reżimu III. Czas hospitalizacji, całkowity czas do uruchomienia (pierwotny punkt końcowy), czas do oddania gazów i stolca i czas do rozpoczęcia perystaltyki (wtórny punkt końcowy) porównano pomiędzy grupami A [pacjentki EOF ze znieczuleniem przewodowym, n=49], B [EOF ze znieczuleniem ogólnym, n=48], C [ROF ze znieczuleniem przewodowym, n=47] i D [ROF ze znieczuleniem ogólnym, n=48]. Wyniki: Zaobserwowano istotne różnice pomiędzy grupą A a pozostałymi grupami, zwłaszcza grupą D, w odniesieniu do pierwotnego i wtórnego punktu końcowego. Status pacjentek z grupy B nie był lepszy niż z grupy C. W rzeczywistości pacjentki z grupy C były zwalniane do domu wcześniej, również pasaż gazów i włączenie diety wg reżimu I następowały wcześniej niż w grupie B. Wnioski: Cięcie cesarskie ze znieczuleniem przewodowym i włączeniem odżywiania 2 godziny po operacji powinno być zalecane ze względu na szybszą rekonwalescencję oraz wczesny wypis ze szpitala. Jako ostatnie powinno się wybierać cięcie cesarskie ze znieczuleniem ogólnym i rutynowym włączeniem odżywiania po usłyszeniu perystaltyki jelit

The Relations between the Organizational Happiness and the Organizational Socialization Perceptions of Teachers: The Sample of Physical Education and Sport

The main purpose of this research is to examine the relationship between levels of organizational happiness and organizational socialization of physical education and sport teachers. The research is quantitative and correlational model. The population of the research is composed of 257 physical education and sports teachers working in Siirt province. The entire universe was tried to be reached and 244 physical education and sports teachers were reached at the target stage. Within the scope of the research, 2 measurement tools were used. The Organizational Happiness Scale was developed by Bulut. The ''Organizational Socialization Scale'' was developed by Erdogan. Some of the research results are as follows: Arithmetic mean, standard deviation, correlation and simple regression tests were used in the analysis of the research data. Teachers' organizational happiness levels are high and organizational socialization levels are very high. There is a high level of positive correlation (r =, 67) between the levels of organizational happiness and organizational socialization of teachers. Teachers' organizational happiness is predicting organizational socialization. The model explains organizational socialization by 55%