On Using Wind Speed Preview to Reduce Wind Turbine Tower Oscillations

We investigate the potential of using previewed wind speed measurements for damping wind turbine fore-aft tower oscillations. Using recent results on continuous-time H2 preview control, we develop a numerically efficient framework for the feedforward controller synthesis. One of the major benefits of the proposed framework is that it allows us to account for measurement distortion. This results in a controller that is tailored to the quality of the previewed data. A simple yet meaningful parametric model of the measurement distortion is proposed and used to analyze the effects of distortion characteristics on the achievable performance and on the required length of preview. We demonstrate the importance of accounting for the distortion in the controller synthesis and quantify the potential benefits of using previewed information by means of simulations based on real-world turbine data

Decentralized feedforward control of wind farms: Prospects and open problems

The problem of load mitigation in wind turbines located in wind farms is addressed. The benefits of letting turbines communicate with and account for their neighbors are explored. First, the idea of exploiting previewed wind speed measurements is examined. The problem is formulated as an H 2 model matching optimization. The influence of preview length on the performance is analyzed and simulation results are presented. Then, the possibility of cooperation between turbines is studied within a distributed feedforward control scheme. The problem is formulated as a decentralized model matching optimization and several theoretical challenges associated with it are outlined. An approximate frequency domain solution and preliminary simulation results are presented

H2/H∞ controller design for input-delay and preview systems based on state decomposition approach

This thesis concentrates on the efficient solution methods of H2/H∞ optimal control problems for input-delay and preview systems. Although the problems can be reformulated to the ones for delay-free systems by augmenting the state space of the controlled systems, the numerical solution of the Riccati/KYP (Kalman-Yakubovich-Popov) equations for the augmented systems requires special efforts, and complicates controller tuning. On the other hand, it is known that the optimal control laws for certain classes of time-delay systems can be constructed without solving the augmented Riccati/KYP equations. Such design problems are called reduced-order construction problems in this thesis. The solutions of the reducedorder construction problems are still limited in theoretical and practical perspectives. The main purpose of the thesis is to propose a new approach for the reduced-order construction problems, which enables to derive the optimal output feedback controllers for input-delayed and preview systems in a unified manner. We focus on the internal dynamics of the overall systems, and decompose it toward the H^2 and H^∞ performance objectives. The fundamental idea of our approach is first introduced for the discrete-time inputdelayed H^2/H^∞ control problems. The state decomposition enables to solve the output feedback problem through the simpler ones, namely, the full information and output estimation problems. The discrete-time optimal controllers are obtained in the Smith predictor form. They are constructed from the Riccati/KYP equations for the delay-free systems. The solution procedure is further extended to the continuous-time preview H^2/H^∞ control problems in an output feedback setting. The optimal utilization of the preview information is exploited at the full information and output estimation problems. The clear structures of the optimal controllers are revealed as the combination of the finite-dimensional observers and preview-feedforward compensation. In the H^∞ control problems for the input-delayed and preview systems, the J-spectral factorization techniques in the literature are employed. Their interconnection to the augmented Riccati/KYP equations is clarified by reviewing the techniques from a view point of the internal state dynamics.首都大学東京, 2014-03-25, 博士(工学), 甲第440号首都大学東

航空宇宙機への実装を考慮した制御則設計手法

電気通信大学201

Learning and Type Compatibility in Signaling Games

Which equilibria will arise in signaling games depends on how the receiver interprets deviations from the path of play. We develop a micro-foundation for these off-path beliefs, and an associated equilibrium refinement, in a model where equilibrium arises through non-equilibrium learning by populations of patient and long-lived senders and receivers. In our model, young senders are uncertain about the prevailing distribution of play, so they rationally send out-of-equilibrium signals as experiments to learn about the behavior of the population of receivers. Differences in the payoff functions of the types of senders generate different incentives for these experiments. Using the Gittins index (Gittins, 1979), we characterize which sender types use each signal more often, leading to a constraint on the receiver's off-path beliefs based on "type compatibility" and hence a learning-based equilibrium selection

A Survey of Models of Network Formation: Stability and Efficiency

I survey the recent literature on the formation of networks. I provide definitions of network games, a number of examples of models from the literature, and discuss some of what is known about the (in)compatibility of overall societal welfare with individual incentives to form and sever links

A synbiotic-containing amino acid-based formula improves gut microbiota in non-IgE-mediated allergic infants

BACKGROUND: Prebiotics and probiotics (synbiotics) can modify gut microbiota and have potential in allergy management when combined with amino acid-based formula (AAF) for infants with cow's milk allergy (CMA). METHODS: This multicenter, double-blind, randomized controlled trial investigated the effects of an AAF including synbiotic blend on percentages of bifidobacteria and Eubacterium rectale/Clostridium coccoides group (ER/CC) in feces from infants with suspected non-IgE-mediated CMA. Feces from age matched healthy breastfed infants were used as reference (HBR) for primary outcomes. CMA subjects were randomized and received test or control formula for 8 weeks. Test formula was a hypoallergenic, nutritionally complete AAF including a prebiotic blend of fructo-oligosaccharides and the probiotic strain Bifidobacterium breve M-16V. Control formula was AAF without synbiotics. RESULTS: Thirty-five (test) and 36 (control) subjects were randomized; HBR included 51 infants. At week 8, median percentage of bifidobacteria was higher in test group vs control group (35.4 vs. 9.7%, respectively P<0.001), whereas ER/CC was lower (9.5 vs. 24.2%, respectively; P<0.001). HBR levels of bifidobacteria and ER/CC were 55 and 6.5%, respectively. CONCLUSION: AAF including specific synbiotics, which results in levels of bifidobacteria and ER/CC approximating levels in HBR group, improves the fecal microbiota of infants with suspected non-IgE-mediated CMA

Demonstration of magnetic field tomography with starlight polarization towards a diffuse sightline of the ISM

The availability of large datasets with stellar distance and polarization information will enable a tomographic reconstruction of the (plane-of-the-sky-projected) interstellar magnetic field in the near future. We demonstrate the feasibility of such a decomposition within a small region of the diffuse ISM. We combine measurements of starlight (R-band) linear polarization obtained using the RoboPol polarimeter with stellar distances from the second Gaia data release. The stellar sample is brighter than 17 mag in the R band and reaches out to several kpc from the Sun. HI emission spectra reveal the existence of two distinct clouds along the line of sight. We decompose the line-of-sight-integrated stellar polarizations to obtain the mean polarization properties of the two clouds. The two clouds exhibit significant differences in terms of column density and polarization properties. Their mean plane-of-the-sky magnetic field orientation differs by 60 degrees. We show how our tomographic decomposition can be used to constrain our estimates of the polarizing efficiency of the clouds as well as the frequency dependence of the polarization angle of polarized dust emission. We also demonstrate a new method to constrain cloud distances based on this decomposition. Our results represent a preview of the wealth of information that can be obtained from a tomographic map of the ISM magnetic field.Comment: 25 pages, 14 figures, published in ApJ, data appear in journa

Features of Optimally Motivating College Classrooms: Perspectives of Preservice Teachers

The primary objective of this mixed methods study was to explore the parameters of college students\u27 perspectives on classroom learning environments. Specifically, the investigation sought to identify and describe the relevant features of the college classroom context that undergraduate students distinguished as promoting and supporting academic motivation at one four-year postsecondary institution. Secondarily, the study sought to examine the extent to which there was an association between the achievement goals students endorsed and their perspectives concerning the motivating features of the classroom learning environment. The nonprobability purposeful sample of undergraduate students consisted of 122 preservice teachers who were attending a small, private four­ year East Coast university. A questionnaire containing 12 likert-type items and two open-ended questions was administered during the tenth and eleventh weeks of the Fall 2006 semester. Respondents\u27 personally endorsed achievement goals were computed by scoring their responses to the likert-type items. Reponses to the open-ended questions were coded and categorized to reveal the features of the classroom learning environment that preservice teachers viewed as having the greatest positive and negative influence on their level of academic motivation. A total of eleven thematic categories emerged from the inductive analysis of preservice teachers\u27 responses to the two open-ended survey questions. Analysis of responses to the achievement goals measures revealed that preservice teachers pursued mastery-approach goals the most, followed by performance­ approach goals, then followed by mastery-avoidance goals. Preservice teachers reported pursuing performance-avoidance goals the least. The series of Pearson chi-square analyses undertaken to examine the association between preservice teachers\u27 adopted achievement goals and their perspectives on the motivating features of the college classroom revealed that, with two exceptions, there were no significant relationships among these variables

Resource-aware motion control:feedforward, learning, and feedback

Controllers with new sampling schemes improve motion systems’ performanc