Learning and Reacting with Inaccurate Prediction: Applications to Autonomous Excavation

Motivated by autonomous excavation, this work investigates solutions to a class of problem where disturbance prediction is critical to overcoming poor performance of a feedback controller, but where the disturbance prediction is intrinsically inaccurate. Poor feedback controller performance is related to a fundamental control problem: there is only a limited amount of disturbance rejection that feedback compensation can provide. It is known, however, that predictive action can improve the disturbance rejection of a control system beyond the limitations of feedback. While prediction is desirable, the problem in excavation is that disturbance predictions are prone to error due to the variability and complexity of soil-tool interaction forces. This work proposes the use of iterative learning control to map the repetitive components of excavation forces into feedforward commands. Although feedforward action shows useful to improve excavation performance, the non-repetitive nature of soil-tool interaction forces is a source of inaccurate predictions. To explicitly address the use of imperfect predictive compensation, a disturbance observer is used to estimate the prediction error. To quantify inaccuracy in prediction, a feedforward model of excavation disturbances is interpreted as a communication channel that transmits corrupted disturbance previews, for which metrics based on the sensitivity function exist. During field trials the proposed method demonstrated the ability to iteratively achieve a desired dig geometry, independent of the initial feasibility of the excavation passes in relation to actuator saturation. Predictive commands adapted to different soil conditions and passes were repeated autonomously until a pre-specified finish quality of the trench was achieved. Evidence of improvement in disturbance rejection is presented as a comparison of sensitivity functions of systems with and without the use of predictive disturbance compensation

Interface Circuits for Microsensor Integrated Systems

ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. [Recent advances in sensing technologies, especially those for Microsensor Integrated Systems, have led to several new commercial applications. Among these, low voltage and low power circuit architectures have gained growing attention, being suitable for portable long battery life devices. The aim is to improve the performances of actual interface circuits and systems, both in terms of voltage mode and current mode, in order to overcome the potential problems due to technology scaling and different technology integrations. Related problems, especially those concerning parasitics, lead to a severe interface design attention, especially concerning the analog front-end and novel and smart architecture must be explored and tested, both at simulation and prototype level. Moreover, the growing demand for autonomous systems gets even harder the interface design due to the need of energy-aware cost-effective circuit interfaces integrating, where possible, energy harvesting solutions. The objective of this Special Issue is to explore the potential solutions to overcome actual limitations in sensor interface circuits and systems, especially those for low voltage and low power Microsensor Integrated Systems. The present Special Issue aims to present and highlight the advances and the latest novel and emergent results on this topic, showing best practices, implementations and applications. The Guest Editors invite to submit original research contributions dealing with sensor interfacing related to this specific topic. Additionally, application oriented and review papers are encouraged.

Numerical and experimental methods for the comparison of radiated immunity tests in EMC sites

Electromagnetic compatibility plays a central role in today's manufacturing of electronic products. Unintended radiation by one device could produce various effects on other devices, ranging from innocuous to very dangerous. On the other hand, insufficient immunity to RF energy can cause malfunctions and interruptions in device operation. For these reasons in the past decades lots of regulatory directives were compiled to help manufacturers in producing better-performing devices in terms of electromagnetic compatibility. The ''compatibility'' of a product is verified in specific laboratories, where testing is divided in radiated immunity, radiated emissions, conducted immunity and conducted emissions. The first two kinds of tests are about disturbances propagating ''in air'', while the last two kinds are about disturbances propagating via connecting cables. Despite being of fundamental importance, neither regulations nor testing provide perfect receipts to build compatible devices; moreover testing needs to be done by means of carefully prepared experiments performed in sites whose performance is well known. Being composed by an anechoic chamber, cables, antennas, receivers and other instrumentation, a site is usually quite complex and it can be difficult to control all the involved variables. This thesis, which is focused on the radiated part of testing, proposes a novel numerical method useful to predict the performance of electrically large anechoic chambers, a topic currently subject of significant research. The method is based on the concept of \emph{equivalent models}, which allow to substitute complex objects with simpler ones. The subjects of the equivalent modeling are the antennas and the walls of the anechoic chamber, which are the most complex objects from the point of view of the geometry in this kind of simulation and which could heavily impact on its computational requirements. The aim of the proposed technique is to be a complement to the measurements usually made to evaluate the performance of anechoic sites. Since this kind of measurements is very tricky and a misplaced cable could be source of problems, using simulations measurements can be cross-checked against a numerical model, so a laboratory can be more confident about its procedures and its results. The developed theory and models would be useless without a confirmation of their functionality and applicability, so the thesis includes also an experimental part carried out at Emilab in Amaro. An extensive set of measurements was made in their anechoic chambers to compare with the predictions of the numerical models and to confirm the plausibility of the results. Finally, the numerical scheme is part of a purpose-built software that allows to simulate quite big sites on rather modest hardwar

Mass-radius relationships for exoplanets

For planets other than Earth, interpretation of the composition and structure depends largely on comparing the mass and radius with the composition expected given their distance from the parent star. The composition implies a mass-radius relation which relies heavily on equations of state calculated from electronic structure theory and measured experimentally on Earth. We lay out a method for deriving and testing equations of state, and deduce mass-radius and mass-pressure relations for key materials whose equation of state is reasonably well established, and for differentiated Fe/rock. We find that variations in the equation of state, such as may arise when extrapolating from low pressure data, can have significant effects on predicted mass- radius relations, and on planetary pressure profiles. The relations are compared with the observed masses and radii of planets and exoplanets. Kepler-10b is apparently 'Earth- like,' likely with a proportionately larger core than Earth's, nominally 2/3 of the mass of the planet. CoRoT-7b is consistent with a rocky mantle over an Fe-based core which is likely to be proportionately smaller than Earth's. GJ 1214b lies between the mass-radius curves for H2O and CH4, suggesting an 'icy' composition with a relatively large core or a relatively large proportion of H2O. CoRoT-2b is less dense than the hydrogen relation, which could be explained by an anomalously high degree of heating or by higher than assumed atmospheric opacity. HAT-P-2b is slightly denser than the mass-radius relation for hydrogen, suggesting the presence of a significant amount of matter of higher atomic number. CoRoT-3b lies close to the hydrogen relation. The pressure at the center of Kepler-10b is 1.5+1.2-1.0 TPa. The central pressure in CoRoT-7b is probably close to 0.8TPa, though may be up to 2TPa.Comment: Added more recent exoplanets. Tidied text and references. Added extra "rock" compositions. Responded to referee comment

Vibration from underground railways: considering piled foundations and twin tunnels

Accurate predictions of ground-borne vibration levels in the vicinity of an underground railway are greatly sought after in modern urban centers. Yet the complexity involved in simulating the underground environment means that it is necessary to make simplifying assumptions about this system. One such commonly made assumption is to ignore the effects of nearby embedded structures such as piled foundations and neighbouring tunnels. Through the formulation of computationally efficient mathematical models, this dissertation examines the dynamic behaviour of these two particular types of structures. The effect of the dynamic behaviour of these structures on the ground-borne vibration generated by an underground railway is considered. The modelling of piled foundations begins with consideration of a single pile embedded in a linear, viscoelastic halfspace. Two approaches are pursued: the modification of an existing plane-strain pile model; and the development of a fully three-dimensional model formulated in the wavenumber domain. Methods for adapting models of infinite structures to simulate finite systems using mirror-imaging techniques are described. The interaction between two neighbouring piles is considered using the method of joining subsystems, and these results are extended to formulate models for pile groups. The mathematical model is validated against existing numerical solutions and is found to be both accurate and efficient. A building model and a model for the pile cap are developed, and are attached to the piled foundation. A case study is used to illustrate a procedure for assessing the vibration performance of pile groups subject to vibration generated by an underground railway. The two-tunnel model uses the superposition of displacement fields to produce a fully coupled model of two infinitely long tunnels embedded in a homogeneous, viscoelastic fullspace. The significance of the interactions occurring between the two tunnels is quantified by calculating the insertion gains that result from the existence of a second tunnel. The results show that a high degree of inaccuracy exists in any underground-railway vibration prediction model that includes only one of the two tunnels present

A measurement based comparison of full-wave and quasi-static methods for baseband modeling of plated through hole via structures

As signaling rates increase, the usable bandwidth of modern telecommunication and storage systems is bounded by parasitic elements within the signal path. To improve data throughput, system designers use cascaded combinations of equivalent circuit models obtained through component level simulation and measurement to evaluate the communications channel. The analytical methods used to create these models have frequency dependent limitations and restrict applications. To this end, a measurement based comparison of quasi-static and full-wave simulation methodologies was performed on plated through hole via structures in a printed circuit board over a frequency range of 0.1GHz to 20GHz. Test fixtures and calibration standards, which isolate the behavior of the component under test from the measurement set-up, are required to establish performance metrics used for the evaluation. In this study, a printed circuit board was designed and fabricated to contrast two different calibration methodologies as applied to plated through hole via structures. The results of this study will describe the usable bandwidth associated with equivalent circuit models derived from quasi-static electromagnetic simulations while demonstrating strong correlation between the full-wave electromagnetic models and measured scattering parameters of a plated through hole via structure

Radio emission from extensive air showers

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