The electrical activity of skeletal muscle¡ªthe electromyogram (EMG)¡ªis of value to many different application areas, including ergonomics, clinical biomechanics and prosthesis control. For many applications the EMG is related to muscular tension, joint torque and/or applied forces. In these cases, a goal is for an EMG-torque model to emulate the natural relationship between the central nervous system and peripheral joints and muscles. This thesis mainly describes an experimental study which relates the simultaneous biceps/triceps surface EMG of 12 subjects to elbow torque at seven joint angles (ranging from 45¡ÃƒÂ£to 135¡ÃƒÂ£) during constant-posture, quasi-constant-torque contractions. The contractions ranged between 50% maximum voluntary contractions (MVC) extension and 50% MVC flexion. Advanced EMG amplitude (EMG¦Ãƒâ€™) estimation processors were investigated, and three nonlinear EMG¦Ãƒâ€™-torque models were evaluated. Results show that advanced (i.e., whitened, multiple-channel) EMG¦Ãƒâ€™ processors lead to improved joint torque estimation, compared to unwhitened, single-channel EMG¦Ãƒâ€™ processors. Depending on the joint angle, use of the multiple-channel whitened EMG¦Ãƒâ€™ processor with higher polynomial degrees produced a median error that was 50%-66% that found when using the single-channel, unwhitened EMG¦Ãƒâ€™ processor with a polynomial degree of 1. The best angle-specific model achieved a minimum error of 3.39% MVCF90 (i.e., error referenced to MVC at 90¢X flexion), yet it does not allow interpolation across angles. The best model which parameterizes the angle dependence achieved an error of 3.55% MVCF90. This thesis also summarizes other collaborative research contributions performed as part of this thesis. (1) Decomposition of needle EMG data was performed as part of a study to characterize motor unit behavior in patients with amyotrophic lateral sclerosis (ALS) [with Spaulding Rehabilitation Hospital, Boston, MA]. (2) EMG-force modeling of force produced at the finger tips was studied with the purpose of assessing the ability to determine two or more independent, continuous degrees of freedom of control from the muscles of the forearm [with WPI and Sherbrooke University]. (3) Identification of a nonlinear, dynamic EMG-torque relationship about the elbow was studied [WPI]. (4) Signal whitening preprocessing for improved classification accuracies in myoelectric control of a prosthesis was studied [with WPI and the University of New Brunswick].

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Submitted by Renata Lopes (renatasil82@gmail.com) on 2015-12-16T11:40:36Z No. of bitstreams: 1 thiagoribeirofurtadodemendonca.pdf: 2671419 bytes, checksum: 9751de9437139252fdb339ca32b4f21d (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2015-12-16T11:57:40Z (GMT) No. of bitstreams: 1 thiagoribeirofurtadodemendonca.pdf: 2671419 bytes, checksum: 9751de9437139252fdb339ca32b4f21d (MD5) / Made available in DSpace on 2015-12-16T11:57:41Z (GMT). No. of bitstreams: 1 thiagoribeirofurtadodemendonca.pdf: 2671419 bytes, checksum: 9751de9437139252fdb339ca32b4f21d (MD5) Previous issue date: 2015-07-13 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Em face ao aumento da demanda por energia elétrica e maior confiabilidade em seu fornecimento, diversas metodologias de controle e proteção da rede elétrica estão sendo desenvolvidas. Para isso é de fundamental importância a utilização de técnicas de processamento de sinais que permitam a extração de forma precisa e rápida dos parâmetros da rede elétrica. O advento de novas tecnologias permitiu a modernização dos sistemas de geração, transmissão e distribuição de energia elétrica, melhorando a eficiência energética e confiabilidade. Por outro lado, observou-se a proliferação na indústria de novas cargas, em sua maioria de natureza não linear, responsáveis pela geração de componentes harmônicos e inter-harmônicos que distorcem o sinal do sistema elétrico (tensão e corrente), dificultando a estimação de parâmetros importantes. Com o intuito de continuar provendo energia de forma segura e confiável, alguns pré-requisitos devem ser atendidos, tais como a baixa distorção harmônica, amplitude estável, baixa oscilação da frequência fundamental, entre outros. Hoje em dia, devido ao maior nível de cargas e equipamentos não lineares conectados a rede, rastrear estes parâmetros de qualidade de energia não é uma tarefa fácil. Para isso, novas técnicas de processamento de sinais devem ser combinadas às teorias de sistemas de potência como forma de estimar e acompanhar as mudanças destes parâmetros. Nesse contexto, diversos algoritmos vêm sendo implementados, cada um com suas especificidades e desempenho. O presente trabalho propõe o desenvolvimento de um novo filtro baseado no filtro Hanning, que é capaz de eliminar harmônicos e atenuar inter-harmônicos com maior eficiência além de ser mais estável quando se considera a implementação em ponto fixo. Este filtro foi combinado com um algoritmo capaz de ajustar seus coeficientes de acordo com a estimação da frequência fundamental de forma a garantir amostragem síncrona, ou seja, a frequência de amostragem será sempre múltipla inteira da frequência atual. Dessa forma, a estimação de amplitude e reconstrução de componentes são feitas com maior precisão mesmo quando se considera a natureza variante da frequência fundamental do sinal bem como a maior quantidade de harmônicos e inter-harmônicos presentes, retratando com maior fidelidade o sinal real do sistema de potência. Os resultados mostram-se superiores às técnicas já existentes, considerando sinais com frequências fora da nominal bem como com grande quantidade de componentes harmônicos e inter-harmônicos, atingindo uma melhoria de 74% em relação ao MAF e de quase 90% em relação ao Hanning convencional. / Due to the growing demand for energy provided in a more reliable way, several control, protection and monitoring methodologies are been developed. For this reason it is of great importance the utilization of appropriate signal processing techniques that allow a precise and fast extraction of parameters from the electrical grid. The advent of new technologies has enabled the modernization of the electric energy generation, transmission and distribution systems, improving its efficiency and service reliability. On the other hand, it was noted a widespread in the application of non-linear loads, responsible for generating harmonics and inter-harmonics components that distorts the electrical signal (voltage and current), hindering the estimation process of useful parameters. With the aim to keep providing energy in a safe and reliable way, some prerequisites must be taken into account, such as the low harmonic distortion, stable amplitude, low oscillation of the fundamental frequency among others. Nowadays, due to the widespread use of nonlinear loads and equipment coupled to the grid, tracking these power quality parameters is not an easy task. That is why novel approaches and techniques of signal processing must be combined with knowledge of power systems theory as a form to estimate and keep track of these measurements. Within this context several algorithms are been developed, each one with its specificity and performance. The present work proposes the development of a new filter, based on the Hanning filter, capable of eliminating harmonics and attenuate with more efficiency the inter-harmonic components besides being more stable for fixed point implementation. This filter is combined with an algorithm that enable the adjustment of its coefficients according to the frequency estimation, assuring a synchronous sampling process, that is, the sampling rate will always be an integer multiple of the actual system frequency. In this way, the amplitude estimation and component reconstruction are performed with better accuracy even when considering the time-varying nature of the fundamental frequency of the signal and the high amount of distortion due to harmonics and inter-harmonics, depicting with greater fidelity the true signal of power system. Results have shown better performance than the already known techniques, considering signal with off-nominal frequency as well as high level of harmonic and inter-harmonic distortion, reaching 74% of improvement in relation with MAF and almost 90% in relation of conventional Hanning.

Recently, a lot of research work has been dedicated toward enhancing performance, reliability and integrity of distributed energy resources that are integrated into distribution networks. The problem of islanding detection and islanding prevention (i.e. anti-islanding) has stimulated a lot of research due to its role in severely compromising the safety of working personnel and resulting in equipment damages. Various Islanding Detection Methods (IDMs) have been developed within the last ten years in anticipation of the tremendous increase in the penetration of Distributed Generation (DG) in distribution system. This work proposes new IDMs that rely on transient and distributed behaviors to improve integrity and performance of DGs while maintaining multi-DG islanding detection capability. In this thesis, the following questions have been addressed: How to utilize the transient behavior arising from an islanding condition to improve detectability and robust performance of IDMs in a distributive manner? How to reduce the negative stability impact of the well-known Sandia Frequency Shift (SFS) IDM while maintaining its islanding detection capability? How to incorporate the perturbations provided by each of DGs in such a way that the negative interference of different IDMs is minimized without the need of any type of communication among the different DGs? It is shown that the proposed techniques are local, scalable and robust against different loading conditions and topology changes. Also, the proposed techniques can successfully distinguish an islanding condition from other disturbances that may occur in power system networks. This work improves the efficiency, reliability and safety of integrated DGs, which presents a necessary advance toward making electric power grids a smart grid.