Magnetic Actuators and Suspension for Space Vibration Control

The research on microgravity vibration isolation performed at the University of Virginia is summarized. This research on microgravity vibration isolation was focused in three areas: (1) the development of new actuators for use in microgravity isolation; (2) the design of controllers for multiple-degree-of-freedom active isolation; and (3) the construction of a single-degree-of-freedom test rig with umbilicals. Described are the design and testing of a large stroke linear actuator; the conceptual design and analysis of a redundant coarse-fine six-degree-of-freedom actuator; an investigation of the control issues of active microgravity isolation; a methodology for the design of multiple-degree-of-freedom isolation control systems using modern control theory; and the design and testing of a single-degree-of-freedom test rig with umbilicals

Simulation-based determination of systematic errors of flow meters due to uncertain inflow conditions

Computational fluid dynamics (CFD) provides well-established tools for the prediction of the velocity profiles in turbulent pipe flows. As far as industrial pipe and district heating systems are concerned, combinations of elbows are the most common pipe assemblies. Among the different pipe combinations, double elbows out-of-plane are of special interest, since they introduce strong disturbances into the flow profile and have a strong influence on many common types of flow meters. In front of a double elbow there is often another flow-disturbing installation. As a result the upstream conditions are unknown and an investigation of the resulting systematic bias on the measurement of the flow rate and the associated contribution to its measurement uncertainty is necessary. We demonstrate here that this can be achieved by a variation of the inlet profile in terms of swirls and asymmetry components. In particular, an ultrasonic and an electromagnetic flow meter are modeled in order to quantify the systematic errors stemming from uncertain inflow conditions. For this purpose, a generalized non-intrusive polynomial chaos method has been used in conjunction with a commercial CFD code. As the most influential parameters on the measured volume flow, the distance between the double elbow and the flow meter as well as the orientation of the flow meter are considered as random variables in the polynomial chaos approach. This approach allowed us to obtain accurate prediction of the systematic error for the ultrasonic and electromagnetic meter as functions of the distance to the double elbow. The resulting bias in the flow rate has been found to be in the range of 1.5–4.5% (0.1–0.5%) with a systematic uncertainty contribution of 2–2.4% (0.6–0.7%) for the ultrasonic (electromagnetic) flow meter if the distance to the double elbow is smaller than 40 pipe diameters. Moreover, it is demonstrated that placing the flow meters in a Venturi constriction leads to substantial decrease of the bias and the contribution to the measurement uncertainty stemming from the uncertain inflow condition

From raw measurements to human pose - a dataset with low-cost and high-end inertial-magnetic sensor data

This database is accompanied by a folder with all the scripts used to process and handle the data described. It is openly hosted in Zenodo: https://doi.org/10.5281/zenodo.5801927Additionally, an extended code repository is available on Github (https://github.com/ManuelPalermo/HumanInertialPose.git) with updated code to not only process the data described, but also calculate kinematics, visualize and evaluate the resulting motions and offers extended support for general inertial pose estimation pipelines. All scripts are based on the Python programming language and, thus, open source. The code contains a permissive MIT license for unrestricted usage.Wearable technology is expanding for motion monitoring. However, open challenges still limit its widespread use, especially in low-cost systems. Most solutions are either expensive commercial products or lower performance ad-hoc systems. Moreover, few datasets are available for the development of complete and general solutions. This work presents 2 datasets, with low-cost and high-end Magnetic, Angular Rate, and Gravity(MARG) sensor data. Provides data for the complete inertial pose pipeline analysis, starting from raw data, sensor-to-segment calibration, multi-sensor fusion, skeleton-kinematics, to complete Human pose. Contains data from 21 and 10 participants, respectively, performing 6 types of sequences, presenting high variability and complex dynamics with almost complete range-of-motion. Amounts to 3.5 M samples, synchronized with a ground-truth inertial motion capture system. Presents a method to evaluate data quality. This database may contribute to develop novel algorithms for each pipeline's processing steps, with applications in inertial pose estimation algorithms, human movement forecasting, and motion assessment in industrial or rehabilitation settings. All data and code to process and analyze the complete pipeline is freely available.This work is supported by: European Structural and Investment Funds in the FEDER component, through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project n° 39479; Funding Reference: POCI-01-0247-FEDER-39479]. Sara Cerqueira was supported by the doctoral Grant SFRH/BD/151382/2021, financed by the Portuguese Foundation for Science and Technology (FCT), under MIT Portugal Program

Current methods for characterising mixing and flow in microchannels

This article reviews existing methods for the characterisation of mixing and flow in microchannels, micromixers and microreactors. In particular, it analyses the current experimental techniques and methods available for characterising mixing and the associated phenomena in single and multiphase flow. The review shows that the majority of the experimental techniques used for characterising mixing and two-phase flow in microchannels employ optical methods, which require optical access to the flow, or off-line measurements. Indeed visual measurements are very important for the fundamental understanding of the physics of these flows and the rapid advances in optical measurement techniques, like confocal scanning laser microscopy and high resolution stereo micro particle image velocimetry, are now making full field data retrieval possible. However, integration of microchannel devices in industrial processes will require on-line measurements for process control that do not necessarily rely on optical techniques. Developments are being made in the areas of non-intrusive sensors, magnetic resonance techniques, ultrasonic spectroscopy and on-line flow through measurement cells. The advances made in these areas will certainly be of increasing interest in the future as microchannels are more frequently employed in continuous flow equipment for industrial applications

Energy disaggregation using a single voltage sensor

Continuous and detailed energy monitoring is essential to ensure the energy efficient operation of complex systems, for instance, buildings. Energy efficiency is becoming a relevant topic in the last years because of the growing concerns on sustainability and the will of reducing the energetic costs. The idea behind this Master’s thesis is a novel energy monitoring solution that with a single sensor enables the monitoring of energy consumption per each single device in an electrical group.The proposed method enables an extremely simple energy monitoring since it does not require monitoring the overall current. All other existing methods need to have access to the electrical current to estimate correctly the power consumption of the different devices. The current meter has to be clamped around a wire inside the electrical cabinet and its installation is a non-trivial task. The main advantage of this novel method is that the unit of sensing can be installed by any user in any socket. Our method monitors only the voltage signal and maps the voltage variations to the power jumps caused by the different device

Local liquid velocity measurement of trickle bed reactor using digitial industrial X-ray radiography

Trickle Bed Reactors (TBRs) are fixed beds of particles in which both liquid and gas flow concurrently downward. They are widely used to produce not only fuels but also lubrication products. The measurement and the knowledge of local liquid velocities (VLL) in TBRs is less which is essential for advancing the understanding of its hydrodynamics and for validation computational fluid dynamics (CFD). Therefore, this work focused on developing a new, non-invasive, statistically reliable technique that can be used to measure local liquid velocity (VLL) in two-dimensions (2-D). This is performed by combining Digital Industrial X-ray Radiography (DIR) and Particle Tracking Velocimetry (PTV) techniques. This work also make possible the development of three-dimensional (3-D) VLL measurements that can be taken in TBRs. Measurements taken through both the combined and the novel technique, once validated, were found to be comparable to another technique (a two-point fiber optical probe) currently being developed at Missouri University of Science and Technology. The results from this study indicate that, for a gas-liquid-solid type bed, the measured VLL can have a maximum range that is between 35 and 51 times that of its superficial liquid velocity (VSL). Without the existence of gas, the measured VLL can have a maximum range that is between 4 and 4.7 times that of its VSL. At a higher VSL, the particle tracer was greatly distributed and became carried away by a high liquid flow rate. Neither the variance nor the range of measured VLL varied for any of the replications, confirming the reproducibility of the experimental measurements used, regardless of the VSL. The liquid\u27s movement inside the pore was consistent with findings from previous studies that used various techniques --Abstract, page iii

Robust Control and Estimation for Unmanned Aerial Vehicles

In recent years, unmanned aerial vehicles (UAVs) have found applications in many diverse fields encompassing commercial, civil, and military sectors. These applications include surveillance, search and rescue operations, aerial photography, mapping of geographical areas, aerial cargo delivery, to name a few. This research addresses how to develop next-generation UAV systems, namely, effective modeling of UAVs, robust control techniques, and non-linear/robust state estimation. The first part addresses modeling and control of a six-degree-of-freedom unmanned aerial vehicle capable of vertical take-off and landing in the presence of wind disturbances. We design a hybrid vehicle that combines the benefits of both fixed-wing and rotary-wing UAVs. A non-linear model for the hybrid vehicle is built, combining rigid body dynamics, the aerodynamics of the wing, and the dynamics of the motor and propeller. Further, we design an H2 optimal controller to make the UAV robust to wind disturbances. It is easy to achieve robustness in this design framework with respect to wind gusts. The controller is determined by solving a convex optimization problem involving linear matrix inequalities and simulated with a non-linear hybrid UAV model developed in the first section, with a wind gust environment. Further, we compare its results against that of PID and LQR-based control. Our proposed controller results in better performance in terms of root mean squared errors and time responses during two scenarios: hover and level-flight. In the second part of the research, we discuss robust Proportional-Integral-Derivative (PID) control techniques for the quadcopters. PID control is the most commonly used algorithm for designing controllers for unmanned aerial vehicles (UAVs). However, tuning PID gains is a non-trivial task. A number of methods have been developed for tuning PID gains but these methods do not handle wind disturbances, which is a major concern for small UAVs. In this paper, we propose a new method for determining optimized PID gains in the H2 optimal control framework, which achieves improved wind disturbance rejection. The proposed method compares the classical PID control law with the H2 optimal controller to determine the H2 optimal PID gains and involves solving a convex optimization problem. The proposed controller is tested in two scenarios, namely, vertical velocity control, and vertical position control. The results are compared with the existing LQR based PID tuning method. A good performance of the controller requires an accurate estimation of states from noisy measurements. Therefore, the third part of the research concentrates on the accurate attitude estimation of UAVs. Most UAV systems use a combination of a gyroscope, an accelerometer, and a magnetometer to obtain measurements and estimate attitude. Under this paradigm of sensor fusion, the Extended Kalman Filter (EKF) is the most popular algorithm for attitude estimation in UAVs. In this work, we propose a novel estimation technique called extended H2 filter that can overcome the limitations of the EKF, specifically with respect to computational speed, memory usage, and root mean squared error. We formulate our attitude-estimation algorithm using two distinct coordinate representations for the vehicle's orientation: Euler angles and unit quaternions, each with its own sets of benefits and challenges. The H2 optimal filter gain is designed offline about a nominal operating point by solving a convex optimization problem, and the filter dynamics is implemented using the nonlinear system dynamics. This implementation of this H2 optimal estimator is referred as the extended H2 estimator. The proposed technique is tested on four cases corresponding to long time-scale motion, fast time-scale motion, transition from hover to forward flight for VTOL aircrafts and an entire flight cycle (from take-off to landing). Its results are compared against that of the EKF in terms of the aforementioned performance metrics

Ergowear: desenvolvimento de um vestuário inteligente para monitorização postural e biofeedback

Dissertação de mestrado em Engenharia Biomédica (especialização em Eletrónica Médica)Atualmente, as Lesões Musculoesqueléticas Relacionadas com o Trabalho (LMERT) são considera das o ”problema relacionado com o trabalho mais prevalente”na União Europeia, levando a um custo estimado de cerca de 240 biliões de euros. Em casos mais severos, estes distúrbios podem causar danos vitalícios à saúde do trabalhador, reduzindo a sua qualidade de vida. De facto, LMERTs são con sideradas a principal causa da reforma precoce dos trabalhadores. Foi reportado que os segmentos da parte superior do corpo são mais suceptíveis ao desenvolvimento de LMERTs. Para mitigar a prevalência de LMERTs, ergonomistas maioritariamente aplicam métodos de avaliação observacionais, que são alta mente dependentes da experiência do analista, e apresentam baixa objetividade e repetibilidade. Desta maneira, esforços têm sido feitos para desenvolver ferramentas de avaliação ergonómica baseadas na instrumentação, para compensar essas limitações. Além disso, com a ascensão do conceito da indústria 5.0, o trabalhador humano volta a ser o foco principal na indústria, juntamente com o robô colaborativo. No entanto, para alcançar uma relação verdadeiramente colaborativa e simbiótica entre o trabalhador e o robô, este último precisa de reconhecer as intenções do trabalhador. Para superar este obstáculo, sis temas de captura de movimento podem ser integrados nesta estrutura, fornecendo dados de movimento ao robô colaborativo. Esta dissertação visa a melhoria de um sistema de captura de movimento autónomo, da parte supe rior do corpo, de abordagem inercial que servirá, não apenas para monitorizar a postura do trabalhador, mas também avaliar a ergonomia do usuário e fornecer consciencialização postural ao usuário, por meio de motores de biofeedback. Além disso, o sistema foi já idealizado tendo em mente a sua integração numa estrutura colaborativa humano-robô. Para atingir estes objetivos, foi aplicada uma metodologia de design centrado no utilizador, começando pela análise do Estado da Arte, a avaliação das limitações do sistema anterior, a definição dos requisitos do sistema, o desenvolvimento da peça de vestuário, arquite tura do hardware e arquitetura do software do sistema. Por fim, o sistema foi validado para verificar se estava em conformidade com os requisitos especificados. O sistema é composto por 9 Unidades de Medição Inercial (UMI), posicionados na parte inferior e superior das costas, cabeça, braços, antebraços e mãos. Também foi integrado um sistema de atuação, para biofeedback postural, composto por 6 motores vibrotáteis, localizados na região lombar e próximo do pescoço, cotovelos e pulsos. O sistema é alimentado por uma powerbank e todos os dados adquiridos são enviados para uma estação de processamento, via WiFi (User Datagram Protocol (UDP)), garantindo autonomia. O sistema tem integrado um filtro de fusão Complementar Extendido e uma sequência de calibração Sensor-para-Segmento estática, de maneira a aumentar a precisão da estimativa dos ângulos das articulações. Além disso, o sistema é capaz de amostrar os dados angulares a 240 Hz, enquanto que o sistema anterior era capaz de amostrar no máximo a 100 Hz, melhorando a resolução da aquisição dos dados. O sistema foi validado em termos de hardware e usabilidade. Os testes de hardware abordaram a caracterização da autonomia, frequência de amostragem, robustez mecânica e desempenho da comuni cação sem fio do sistema, em diversos contextos, e também para verificar se estes estão em conformidade com os requisitos técnicos previamente definidos, que foi o caso. Adicionalmente, as especificações da nova versão do sistema foram comparadas com a anterior, onde se observou uma melhoria direta signifi cativa, como por exemplo, maior frequência de amostragem, menor perda de pacote, menor consumo de corrente, entre outras, e com sistemas comerciais de referência (XSens Link). Testes de usabilidade foram realizados com 9 participantes que realizaram vários movimentos uniarticulares e complexos. Após os testes, os usuários responderam a um questionário baseado na Escala de Usabilidade do Sistema (EUS). O sistema foi bem aceite pelos os usuários, em termos de estética e conforto, em geral, comprovando um elevado nível de vestibilidade.Nowadays, Work-Related Musculoskeletal Disorders (WRMSDs) are considered the ”most prevalent work-related problem” in the European Union (EU), leading to an estimated cost of about 240 billion EUR. In more severe cases, these disorders can cause life-long impairments to the workers’ health, reducing their quality of life. In fact, WRMSDs are the main cause for the workers’ early retirement. It was reported that the upper body segments of the worker are more susceptible to the development of WRMSDs. To mitigate the prevalence of WRMSD, ergonomists mostly apply observational assessment methods, which are highly dependant on the analyst’s expertise, have low objectivity and repeatability. Therefore, efforts have been made to develop instrumented-based ergonomic assessment tools, to compensate for these limitations. Moreover, with the rise of the 5.0 industry concept, the human worker is once again the main focus in the industry, along with the Collaborative Robot (cobot). However, to achieve a truly collaborative relation between the worker and the cobot, the latter needs to know the worker’s intentions. To surpass this obstacle, Motion Capture (MoCap) systems can be integrated in this framework, providing motion data to the cobot. This dissertation aims at the improvement of a stand-alone, upper-body, inertial, MoCap system, that will serve to not only monitor the worker’s posture, but also to assess the user’s ergonomics and provide posture awareness to the user, through biofeedback motors. Furthermore, it was also designed to integrate a human-robot collaborative framework. To achieve this, a user-centred design methodology was applied, starting with analyzing the State of Art (SOA), assessing the limitations of the previous system, defining the system’s requirements, developing the garment, hardware architecture and software architecture of the system. Lastly, the system was validated to ascertain if it is in conformity with the specified requirements. The developed system is composed of 9 Inertial Measurement Units (IMUs), placed on the lower and upper back, head, upper arms, forearms and hands. An actuation system was also integrated, for postural biofeedback, and it is comprised of 6 vibrotactile motors, located in the lower back, and in close proximity to the neck, elbows and wrists. The system is powered by a powerbank and all of the acquired data is sent to a main station, via WiFi (UDP), granting a standalone characteristic. The system integrates an Extended Complementary Filter (ECF) and a static Sensor-to-Segment (STS) calibration sequence to increase the joint angle estimation accuracy. Furthermore, the system is able to sample the angular data at 240 Hz, while the previous system was able to sample it at a maximum 100 Hz, improving the resolution of the data acquisition. The system was validated in terms of hardware and usability. The hardware tests addressed the char acterization of the system’s autonomy, sampling frequency, mechanical robustness and wireless commu nication performance in different contexts, and ascertain if they comply with the technical requirements, which was the case. Moreover, the specifications of the new version were compared with the previous one, where a significant direct improvement was observed, such as, higher sampling frequency, lower packet loss, lower current consumption, among others, and with a commercial system of reference (XSens Link). Usability tests were carried out with 9 participants who performed several uni-joint and complex motions. After testing, users answered a questionnaire based on the System Usability Scale (SUS). The system was very well accepted by the participants, regarding aesthetics and overall comfort, proving to have a high level of wearability

Uncertainty Quantification of the Responses of Transient Electromagnetic Disturbance Coupling to Transmission Lines Based on Stochastic Models

L'abstract è presente nell'allegato / the abstract is in the attachmen