In order to meet higher performance demands on brushless motor controllers, motor feedback signals must meet correspondingly higher standards. Brushless motor controllers require angular feedback for motor commutation, and generally for one or more of the following: torque, velocity or position regulation. These feedback categories impose different requirements on the control system. In many brushless motor applications, sinusoidal encoders have significant advantages over square-wave encoders. Signal processing techniques for sinusoidal encoder feedback signals are considered in the context of a brushless motor positioning system. In particular, a method is presented for correcting gain and offset measurement errors based on ellipse-fitting techniques. / Master of Science

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第21294号 / 医博第4383号 / 新制||医||1030(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 佐藤 俊哉, 教授 今中 雄一, 教授 増永 慎一郎 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

The actor-observer effect suggests that actors attribute to the situation while observers attribute to the actor's disposition. This effect has come under scrutiny because of an alternative perspective that accounts for anomalous finding. This alternative, called the contextual perspective, suggests that actors and observers foreground different aspects of the context because of a relationship with the context, and has roots in Gestalt psychology and phenomenology. I manipulated a researcher's prompt and the presence of a distressed confederate as the context for attributions, and hypothesized that actors and observers would differ on attributions to choice, situation, and disposition because of presence of a distressed confederate. Actors were presented with either a distressed or non-distressed confederate and either a prompt to leave, a prompt to stay, or no prompt. For example, some actors experienced a distressed confederate and were asked to leave while others experienced a non-distressed confederate and were asked to stay. Actors then made a decision to either stay and help the confederate or leave. Observers watched one of ten videos, each of one actor condition in which the actor either stayed or left (five actor conditions by 2 options of stay or leave). Actors' and observers' choice, situational, and dispositional attributions were analyzed using factorial MANOVAs. Actors and observers foregrounded the distressed confederate when making attributions to choice, situation, and disposition. Furthermore, observers' attributions to choice were also influenced by the actor's behavior. These findings support the contextual perspective since context does influence actors' and observers' attributions.

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An observer rat that interacts with a conspecific, a demonstrator that has eaten a flavoured food, is subsequently more likely to eat that food than an alternative, novel food (Galef & Wigmore, 1983). In the first part of this thesis, four experiments were undertaken to determine the influence of unreliable demonstrators on observer food preference. In the first three experiments, observers were poisoned after interaction with demonstrators; a demonstrator that demonstrated a food that led to poisoning was considered an unreliable demonstrator. The first experiment compared the influence of an unreliable demonstrator and an unfamiliar demonstrator on observers' food preferences. Experiment 2 compared the influence of demonstration from an unreliable conspecific and a familiar conspecific that had only provided irrelevant information. The third experiment compared the influence of an unreliable and a reliable demonstrator. Experiment 4 compared the influence for protein-deficient observers of a demonstrator that had previously demonstrated a protein-deficient diet and a demonstrator that was unfamiliar. None of the first four experiments showed a significant difference in effectiveness of social transmission due to demonstrator quality. In the second part of the thesis I investigated the influence of familiarity on demonstrator effectiveness. In Experiment 5, the influence of local sisters was compared with that of unfamiliar non-relatives as demonstrators. Sisters were not better demonstrators than unfamiliar non-relatives. / Thesis / Master of Science (MSc)

Control and diagnosis of complex systems demand accurate knowledge of certain quantities to be able to control the system efficiently and also to detect small errors. Physical sensors are expensive and some quantities are hard or even impossible to measure with physical sensors. This has made model-based estimation an attractive alternative. Model-based estimators are sensitive to errors in the model and since the model complexity needs to be kept low, the accuracy of the models becomes limited. Further, modeling is hard and time consuming and it is desirable to design robust estimators based on existing models. An experimental investigation shows that the model deficiencies in engine applications often are stationary errors while the dynamics of the engine is well described by the model equations. This together with fairly frequent appearance of sensor offsets have led to a demand for systematic ways of handling stationary errors, also called bias, in both models and sensors. In the thesis systematic design methods for reducing bias in estimators are developed. The methods utilize a default model and measurement data. In the first method, a low order description of the model deficiencies is estimated from the default model and measurement data, resulting in an automatic model augmentation. The idea is then to use the augmented model for estimator design, yielding reduced stationary estimation errors compared to an estimator based on the default model. Three main results are: a characterization of possible model augmentations from observability perspectives, an analysis of what augmentations that are possible to estimate from measurement data, and a robustness analysis with respect to noise and model uncertainty. An important step is how the bias is modeled, and two ways of describing the bias are introduced. The first is a random walk and the second is a parameterization of the bias. The latter can be viewed as an extension of the first and utilizes a parameterized function that describes the bias as a function of the operating point of the system. The parameters, rather than the bias, are now modeled as random walks, which eliminates the trade-off between noise suppression in the parameter convergence and rapid change of the offset in transients. This is achieved by storing information about the bias in different operating points. A direct application for the parameterized bias is the adaptation algorithms that are commonly used in engine control systems. The methods are applied to measurement data from a heavy duty diesel engine. A first order model augmentation is found for a third order model and by modeling the bias as a random walk, an estimation error reduction of 50 % is achieved for a European transient cycle. By instead letting a parameterized function describe the bias, simulation results indicate similar, or better, improvements and increased robustness.

Synchronization and estimation of unknown constant parameters for Lorenz-type transmitter are studied under the assumption that one of the three state variables is not transmitted and that transmitter parameters are not known apriori. An adaptive algorithm is proposed to estimate both the state and system parameters. Since Lorenz system shows the property of sensitivity to initial conditions and evolves in different mode with parameter variation, an equivalent system is introduced. The adaptive observer is designed based on this equivalent system without any requirement on initial conditions of the observer. It is shown by Lyapunov arguments and persistent excitation analysis that exponential stability of state and parameter estimation is guaranteed. Simulation results are included to demonstrate properties of the algorithm. In a practical communication system, the received signals presented at the receiver part differ from those which were transmitted due to the effects of noise. The proposed synchronization scheme is robust with regard to external bounded disturbance. When an additive white gaussian noise (AWGN) channel model is considered, estimates of state and parameter converge except for small errors. The results show promise in either coherent detection or the message decoding in telecommunication systems.

Assessment of image interpretation competency is commonly undertaken through review of a defined image test bank. Content of these image banks has been criticised for the high percentage of abnormal examinations which contrasts with lower reported incidences of abnormal radiographs in clinical practice. As a result, questions have been raised regarding the influence of prevalence bias on the accuracy of interpretive decision making. This article describes a new and novel approach to the design of musculoskeletal image test banks. Three manufactured image banks were compiled following a standard academic menu in keeping with previous studies. Three further image test banks were constructed to reflect local clinical workload within a single NHS Trust. Eighteen radiographers, blinded to the method of test bank composition, were randomly assigned 2 test banks to review (1 manufactured, 1 clinical workload). Comparison of interpretive accuracy was undertaken. Inter-rater agreement was moderate to good for all image banks (manufactured: range k = 0.45–0.68; clinical workload: k = 0.49–0.62). A significant difference in mean radiographer sensitivity was noted between test bank designs (manufactured 87.1%; clinical workload 78.5%; p = 0.040, 95% CI = 0.4–16.8; t = 2.223). Relative parity in radiographer specificity and overall accuracy was observed. This study confirms the findings of previous research that high abnormality prevalence image banks over-estimate the ability of observers to identify abnormalities. Assessment of interpretive competency using an image bank that reflects local clinical practice is a better approach to accurately establish interpretive competency and the learning development needs of individual practitioners.

yes / Introduction: Reducing tube voltage is an effective dose saving method in computed tomography (CT) assuming tube current is not concurrently increased. Recent innovations in scanner technology now enable CT tube voltage reduction to 70 kV thereby increasing opportunities for dose reduction in paediatric patients, but it is unclear if the increased image noise associated with 70 kV impacts on ability to visualise renal stones accurately. The purpose was to assess detectability of nephrolithiasis using a bespoke paediatric phantom and low kV, non-contrast CT and to assess inter-observer agreement. Methods: Forty-two renal stones of different size and chemical composition were inserted into porcine kidneys and positioned in a bespoke, water-filled phantom mimicking a 9-year-old child weighing approximately 33kg. The phantom was scanned using 120 and 70 kV CT protocols, and the detectability of the stones was assessed by three radiologists. Absolute agreement and Fleiss’ kappa regarding detectability were assessed. Results: The mean diameter of renal stones as measured physically was 4.24 mm ranging from 1 to 11 mm. Four stones were missed by at least one observer. One observer had a sensitivity of 93 and 95% at 70 and 120 kV, respectively, while the sensitivity for observers 2 and 3 was 98% at both kV levels. Specificity was 100% across readers and kV levels. Absolute agreement between the readers at 70 kV was 92% (kappa = 0.86) and 98% (kappa = 0.96) at 120 kV indicating a strong agreement at both kV levels. Conclusions: The results suggest that lowering the kV does not affect the detection rate of renal stones and may be a useful dose reduction strategy for assessment of nephrolithiasis in children.