Design and optimal springs stiffness estimation of a Modular OmniCrawler in-pipe climbing Robot

This paper discusses the design of a novel compliant in-pipe climbing modular robot for small diameter pipes. The robot consists of a kinematic chain of 3 OmniCrawler modules with a link connected in between 2 adjacent modules via compliant joints. While the tank-like crawler mechanism provides good traction on low friction surfaces, its circular cross-section makes it holonomic. The holonomic motion assists it to re-align in a direction to avoid obstacles during motion as well as overcome turns with a minimal energy posture. Additionally, the modularity enables it to negotiate T-junction without motion singularity. The compliance is realized using 4 torsion springs incorporated in joints joining 3 modules with 2 links. For a desirable pipe diameter (\text{\O} 75mm), the springs' stiffness values are obtained by formulating a constraint optimization problem which has been simulated in ADAMS MSC and further validated on a real robot prototype. In order to negotiate smooth vertical bends and friction coefficient variations in pipes, the design was later modified by replacing springs with series elastic actuators (SEA) at 2 of the 4 joints.Comment: arXiv admin note: text overlap with arXiv:1704.0681

Design, Modelling, and Control of a Reconfigurable Rotary Series Elastic Actuator with Nonlinear Stiffness for Assistive Robots

In assistive robots, compliant actuator is a key component in establishing safe and satisfactory physical human-robot interaction (pHRI). The performance of compliant actuators largely depends on the stiffness of the elastic element. Generally, low stiffness is desirable to achieve low impedance, high fidelity of force control and safe pHRI, while high stiffness is required to ensure sufficient force bandwidth and output force. These requirements, however, are contradictory and often vary according to different tasks and conditions. In order to address the contradiction of stiffness selection and improve adaptability to different applications, we develop a reconfigurable rotary series elastic actuator with nonlinear stiffness (RRSEAns) for assistive robots. In this paper, an accurate model of the reconfigurable rotary series elastic element (RSEE) is presented and the adjusting principles are investigated, followed by detailed analysis and experimental validation. The RRSEAns can provide a wide range of stiffness from 0.095 Nm/deg to 2.33 Nm/deg, and different stiffness profiles can be yielded with respect to different configuration of the reconfigurable RSEE. The overall performance of the RRSEAns is verified by experiments on frequency response, torque control and pHRI, which is adequate for most applications in assistive robots. Specifically, the root-mean-square (RMS) error of the interaction torque results as low as 0.07 Nm in transparent/human-in-charge mode, demonstrating the advantages of the RRSEAns in pHRI

Nitrogen flows from European watersheds to coastal marine waters

Nitrogen flows from European watersheds to coastal marine waters Executive summary Nature of the problem • Most regional watersheds in Europe constitute managed human territories importing large amounts of new reactive nitrogen. • As a consequence, groundwater, surface freshwater and coastal seawater are undergoing severe nitrogen contamination and/or eutrophication problems. Approaches • A comprehensive evaluation of net anthropogenic inputs of reactive nitrogen (NANI) through atmospheric deposition, crop N fixation,fertiliser use and import of food and feed has been carried out for all European watersheds. A database on N, P and Si fluxes delivered at the basin outlets has been assembled. • A number of modelling approaches based on either statistical regression analysis or mechanistic description of the processes involved in nitrogen transfer and transformations have been developed for relating N inputs to watersheds to outputs into coastal marine ecosystems. Key findings/state of knowledge • Throughout Europe, NANI represents 3700 kgN/km2/yr (range, 0–8400 depending on the watershed), i.e. five times the background rate of natural N2 fixation. • A mean of approximately 78% of NANI does not reach the basin outlet, but instead is stored (in soils, sediments or ground water) or eliminated to the atmosphere as reactive N forms or as N2. • N delivery to the European marine coastal zone totals 810 kgN/km2/yr (range, 200–4000 depending on the watershed), about four times the natural background. In areas of limited availability of silica, these inputs cause harmful algal blooms. Major uncertainties/challenges • The exact dimension of anthropogenic N inputs to watersheds is still imperfectly known and requires pursuing monitoring programmes and data integration at the international level. • The exact nature of ‘retention’ processes, which potentially represent a major management lever for reducing N contamination of water resources, is still poorly understood. • Coastal marine eutrophication depends to a large degree on local morphological and hydrographic conditions as well as on estuarine processes, which are also imperfectly known. Recommendations • Better control and management of the nitrogen cascade at the watershed scale is required to reduce N contamination of ground- and surface water, as well as coastal eutrophication. • In spite of the potential of these management measures, there is no choice at the European scale but to reduce the primary inputs of reactive nitrogen to watersheds, through changes in agriculture, human diet and other N flows related to human activity

Cascade solar thermal power system modeling and research of the key features.

El objetivo de esta tesis es investigar sistemas de generación eléctrica termosolar para proponer, desa-rrollar y optimizar un sistema de energía solar térmica en cascada para conseguir un mejor rendimiento de las tecnologías de generación eléctrica termosolar y explorar una nueva tecnología viable generación a gran escala. Los contenidos y conclusiones principales de la tesis son los siguientes.Se han propuesto múltiples y novedosas estructuras topológicas para diseños de cascada termosolar, combinando ciclo Stirling como ciclo de cabecera y ciclo rankine como ciclo de cola, incluso con chimenea solar. Como colectores se integran el colector cilindro parabólico, el disco parabólico y la torre central con campo de heliostatos. La topología seleccionada para el estudio consiste en un campo solar de alta tempera-tura de colectores de disco parabólico para calentar aire a alta temperatura que se utiliza como foco caliente de un motor sterling. El foco frío de dicho motor es, a su vez, y utilización en cascada de la energía termosolar un ciclo rankine que se alimenta de vapor generado con un campo solar de colectores cilindro parabólicos (media temperatura).Se establecen modelos mecanicistas para los componentes del sistema de generación solar, usando he-rramientas informáticas de cálculo matemático y desarrollo de sistemas. El proceso de modelado usa una aproximación orientada al objeto, para asegurar la independencia y relevancia de cada componente. El mo-delo del sistema tiene la ventaja de una organización pertinente, una estructura clara y fácil capacidad de mejora. Para el modelado del motor Stirling, se consideran varias irreversibilidades y pérdidas, lo que permite ve-rificar una predicción más precisa que la del modelo clásico. Se ha estudiado el efecto de diferentes disposi-ciones de motores Stirling sobre el rendimiento del sistema en cascada. De acuerdo a las características de funcionamiento del motor, se proponen 5 disposiciones básicas de una matriz de motores Stirling y se imple-mentan los correspondientes modelos de simulación. Se analizan las diferencias de funcionamiento entre los distintos conjuntos para diferentes temperaturas y capacidades térmicas de fluido de entrada y diferentes parámetros del motor Stirling. Se concluye que la conexión en serie es la mejor disposición en términos de robustez y rendimiento de la matriz de motores Stirling. Se propone un sistema de calentamiento multietapa que puede reducir efectivamente la pérdida de exer-gía del proceso de generación de vapor de agua. Durante el proceso completo de intercambio de calor en un generador de vapor de agua convencional, no hay cambio de fase en el fluido calefactor y sí en el fluido cale-factado. En los intercambiadores de calor, existen amplias diferencias de temperaturas entre ambos, lo que amplía la pérdida de exergía durante el proceso. En esta tesis, se propone un método de calentamiento por etapas, en el que los caudales másicos del fluido calefactor en diferentes intercambiadores se controlan para reducir la diferencia de temperatura y las pérdidas de exergía. Este método puede incrementar efectivamente el rendimiento térmico de campos solares.Se propone un método para evaluar el funcionamiento de sistemas de generación eléctrica termosolar en cascada. Se escogen para comparación los sistemas independientes que componen la cascada y se esta-blecen los modelos de evaluación de su funcionamiento. Los resultados de la simulación y su análisis revelan que el sistema en cascada tiene un rendimiento de conversión solar-eléctrico mayor para altas irradiaciones solares si se compara con los correspondientes sistemas independientes.Se ha construido una plataforma de ensayo de generación eléctrica termosolar y se han efectuado ensa-yos experimentales con los colectores. Los experimentos determinan la influencia de la irradiación solar nor-mal directa, caudal y temperatura de entrada del fluido de transferencia de calor. Los resultados experimen-tales validan lo establecido mediante los modelos de los colectores y de los discos<br /

Salmon action plan. River Ribble - June 2000

In February 1996 A Strategy for the Management of Salmon in England and Wales was launched by the National Rivers Authority. The strategy concentrates on four main objectives for the management of salmon fisheries in England and Wales: (i) Optimise the number of salmon returning to home water fisheries, (ii) Maintain and improve the fitness and diversity of salmon stocks, (iii) Optimise the total economic value of surplus stocks, (iv) Ensure necessary costs are met by beneficiaries. These four objectives will be addressed through local Salmon Action Plans (SAPs) which will be produced for each of the principle salmon rivers in England and Wales by the year 2001. A consultation report was produced for the River Ribble and released publicly in October 1999. This document determined an egg deposition figure of 8.5 million eggs for the Ribble, that would allow maximum gain from the net and rod fisheries; raised a number of issues which are thought to currently limit salmon production; identified actions which may be undertaken by the Environment Agency and other bodies to improve stocks. This action plan re-addresses the issues raised in the consultation document, taking into account the comments received, and also identifies areas of possible improvement in data gathering that would allow more accurate estimation of the spawning target and compliance in future years. The progress of this plan will be monitored and reported annually

DFB Quantum Cascade Laser Arrays

DFB quantum cascade laser (DFB-QCL) arrays operating between 8.7 and 9.4 mum are investigated for their performance characteristics-single-mode selection of the DFB grating, and variability in threshold, slope efficiency, and output power of different lasers in the array. Single-mode selection refers to the ability to choose a desired mode/frequency of laser emission with a DFB grating. We apply a theoretical framework developed for general DFB gratings to analyze DFB-QCL arrays. We calculate how the performance characteristics of DFB-QCLs are affected by the coupling strength kappaL of the grating, and the relative position of the mirror facets at the ends of the laser cavity with respect to the grating. We discuss how single-mode selection can be improved by design. Several DFB-QCL arrays are fabricated and their performance examined. We achieve desired improvements in single-mode selection, and we observe the predicted variability in the threshold, slope efficiency, and output power of the DFB-QCLs. As a demonstration of potential applications, the DFB-QCL arrays are used to perform infrared absorption spectroscopy with fluids.Engineering and Applied Science

Salmon action plan. River Lune - February 1998

In February 1996 A Strategy for the Management of Salmon in England and Wales was launched by the National Rivers Authority. The strategy concentrates on four main objectives for the management of salmon fisheries in England and Wales: (i) Optimise the number of salmon returning to home water fisheries, (ii) Maintain and improve the fitness and diversity of salmon stocks, (iii) Optimise the total economic value of surplus stocks, (iv) Ensure necessary costs are met by beneficiaries. These four objectives will be addressed through local Salmon Action Plans (SAPs) which will be produced for each of the principle salmon rivers in England and Wales by the year 2001. This Salmon Action Plan for the River Lune reviews the status of the stock and the fisheries, seeks to identify the main factors limiting performance, to draw up and cost a list of options to address these, and to consult with local interest groups

Report of the 2005 Workshop on Ocean Ecodynamics Comparison in the Subarctic Pacific

I. Scientific Issues Posed by OECOS II. Participant Contributions to the OECOS Workshop A. ASPECTS OF PHYTOPLANKTON ECOLOGY IN THE SUBARCTIC PACIFIC Microbial community compositions by Karen E. Selph Subarctic Pacific lower trophic interactions: Production-based grazing rates and grazing-corrected production rates by Nicholas Welschmeyer Phytoplankton bloom dynamics and their physiological status in the western subarctic Pacific by Ken Furuya Temporal and spatial variability of phytoplankton biomass and productivity in the northwestern Pacific by Sei-ichi Saitoh, Suguru Okamoto, Hiroki Takemura and Kosei Sasaoka The use of molecular indicators of phytoplankton iron limitation by Deana Erdner B. IRON CONCENTRATION AND CHEMICAL SPECIATION Iron measurements during OECOS by Zanna Chase and Jay Cullen 25 The measurement of iron, nutrients and other chemical components in the northwestern North Pacific Ocean by Kenshi Kuma The measurement of iron, nutrients and other chemical components in the northwestern North Pacific Ocean by Kenshi Kuma C. PHYSICAL OCEANOGRAPHY, FINE-SCALE DISTRIBUTION PATTERNS AND AUTONOMOUS DRIFTERS The use of drifters in Lagrangian experiments: Positives, negatives and what can really be measured by Peter Strutton The interaction between plankton distribution patterns and vertical and horizontal physical processes in the eastern subarctic North Pacific by Timothy J. Cowles D. MICROZOOPLANKTON Microzooplankton processes in oceanic waters of the eastern subarctic Pacific: Project OECOS by Suzanne Strom Functional role of microzooplankton in the pelagic marine ecosystem during phytoplankton blooms in the western subarctic Pacific by Takashi Ota and Akiyoshi Shinada E. MESOZOOPLANKTON Vertical zonation of mesozooplankton, and its variability in response to food availability, density stratification, and turbulence by David L. Mackas and Moira Galbraith Marine ecosystem characteristics and seasonal abundance of dominant calanoid copepods in the Oyashio region by Atsushi Yamaguchi, Tsutomu Ikeda and Naonobu Shiga OECOS: Proposed mesozooplankton research in the Oyashio region, western subarctic Pacific by Tsutomu Ikeda Some background on Neocalanus feeding by Michael Dagg Size and growth of interzonally migrating copepods by Charles B. Miller Growth of large interzonal migrating copepods by Toru Kobari F. MODELING Ecosystem and population dynamics modeling by Harold P. Batchelder III. Reports from Workshop Breakout Groups A. PHYSICAL AND CHEMICAL ASPECTS WITH EMPHASIS ON IRON AND IRON SPECIATION B. PHYTOPLANKTON/MICROZOOPLANKTON STUDIES C. MESOZOOPLANKTON STUDIES IV. Issues arising during the workshop A. PHYTOPLANKTON STOCK VARIATIONS IN HNLC SYSTEMS AND TROPHIC CASCADES IN THE NANO AND MICRO REGIMES B. DIFFERENCES BETWEEN EAST AND WEST IN SITE SELECTION FOR OECOS TIME SERIES C. TIMING OF OECOS EXPEDITIONS D. CHARACTERIZATION OF PHYSICAL OCEANOGRAPHY V. Concluding Remarks VI. References (109 page document

Combining series elastic actuation and magneto-rheological damping for the control of agile locomotion

All-terrain robot locomotion is an active topic of research. Search and rescue maneuvers and exploratory missions could benefit from robots with the abilities of real animals. However, technological barriers exist to ultimately achieving the actuation system, which is able to meet the exigent requirements of these robots. This paper describes the locomotioncontrol of a leg prototype, designed and developed to make a quadruped walk dynamically while exhibiting compliant interaction with the environment. The actuation system of the leg is based on the hybrid use of series elasticity and magneto-rheological dampers, which provide variable compliance for natural-looking motion and improved interaction with the ground. The locomotioncontrol architecture has been proposed to exploit natural leg dynamics in order to improve energy efficiency. Results show that the controller achieves a significant reduction in energy consumption during the leg swing phase thanks to the exploitation of inherent leg dynamics. Added to this, experiments with the real leg prototype show that the combined use of series elasticity and magneto-rheologicaldamping at the knee provide a 20 % reduction in the energy wasted in braking the knee during its extension in the leg stance phase

A Sliding Mode Force and Position Controller Synthesis for Series Elastic Actuators

This paper deals with the robust force and position control problems of Series Elastic Actuators. It is shown that a Series Elastic Actuator's force control problem can be described by a second-order dynamic model which suffers from only matched disturbances. However, the position control dynamics of a Series Elastic Actuator is of fourth-order and includes matched and mismatched disturbances. In other words, a Series Elastic Actuator's position control is more complicated than its force control, particularly when disturbances are considered. A novel robust motion controller is proposed for Series Elastic Actuators by using Disturbance Observer and Sliding Mode Control. When the proposed robust motion controller is implemented, a Series Elastic Actuator can precisely track desired trajectories and safely contact with an unknown and dynamic environment. The proposed motion controller does not require precise dynamic models of the actuator and environment. Therefore, it can be applied to many different advanced robotic systems such as compliant humanoids and exoskeletons. The validity of the motion controller is experimentally verified.Comment: Accepted by Robotica in 201