7,688 research outputs found
Wave-based sensor, actuator and optimizer
Programa doutoral em Sistemas Avançados de Engenharia para a Indústria (AESI)A presente tese explora a utilização de ondas para abordar dois desafios significativos na indústria automóvel.
O primeiro desafio consiste no desenvolvimento de um sistema de cancelamento ativo de ruído
(ANC) que possa reduzir os ruídos não estacionários no compartimento de passageiros de um veículo. O
segundo desafio é criar uma metodologia de conceção ótima para sensores de posição indutivos capazes
de medir deslocamentos lineares, rotacionais e angulares.
Para abordar o primeiro desafio, foi desenvolvido de um sistema ANC onde wavelets foram combinadas
com um banco de filtros adaptativos. O sistema foi implementado em uma FPGA, e testes demonstraram
que o sistema pode reduzir o ruído não estacionário em um ambiente acústico aberto e não controlado em
9 dB. O segundo desafio foi abordado através de uma metodologia que combina um algoritmo genético
com um método numérico rápido para otimizar um sensor de posição indutivo. O método numérico foi
usado para simular o campo eletromagnético associado à geometria do sensor, permitindo a maximização
da corrente induzida nas bobinas recetoras e a minimização da não-linearidade no sensor. A minimização
da não-linearidade foi conseguida através do desenho (layout) das bobinas que compõem o sensor. Sendo
este otimizado no espaço de Fourier através da adição de harmónicos apropriados na geometria. As
melhores geometrias otimizadas apresentaram uma não-linearidade inferior a 0,01% e a 0,25% da escala
total para os sensores de posição angular e linear, respetivamente, sem calibração por software.
O sistema ANC proposto tem o potencial de melhorar o conforto dos ocupantes do veículo, reduzindo o
ruído indesejado dentro do compartimento de passageiros. Isso poderia reduzir o uso de materiais de
isolamento acústico no veículo, levando a um veículo mais leve e, em última análise, a uma redução
no consumo de energia. A metodologia desenvolvida para sensores de posição indutivos contribui para
o estado da arte de sensores de posição eficientes e económicos, o que é crucial para os requisitos
complexos da indústria automóvel. Essas contribuições têm implicações para o desenho de sistemas
automotivos, com requisitos de desempenho e considerações ambientais e económicas.This thesis explores the use of waves to tackle two major engineering challenges in the automotive industry.
The first challenge is the development of an Active Noise Cancelling (ANC) system that can effectively
reduce non-stationary noise inside a vehicle’s passenger compartment. The second challenge is the
optimization of an inductive position sensor design methodology capable of measuring linear, rotational,
and angular displacements.
To address the first challenge, this work designs an ANC system that employs wavelets combined with a
bank of adaptive filters. The system was implemented in an FPGA, and field tests demonstrate its ability
to reduce non-stationary noise in an open and uncontrolled acoustic environment by 9 dB. The second
challenge was tackled by proposing a new approach that combines a genetic algorithm with a fast and
lightweight numerical method to optimize the geometry of an inductive position sensor. The numerical
method is used to simulate the sensor’s electromagnetic field, allowing for the maximization of induced
current on the receiver coils while minimizing the sensor’s non-linearity. The non-linearity minimization was
achieved through its unique sensor’s coils design optimized in the Fourier space by adding the appropriate
harmonics to the coils’ geometry. The best optimized geometries exhibited a non-linearity of less than
0.01% and 0.25% of the full scale for the angular and linear position sensors, respectively. Both results
were achieved without the need for signal calibration or post-processing manipulation.
The proposed ANC system has the potential to enhance the comfort of vehicle occupants by reducing
unwanted noise inside the passenger compartment. Moreover, it has the potential to reduce the use of
acoustic insulation materials in the vehicle, leading to a lighter vehicle and ultimately reducing energy
consumption. The developed methodology for inductive position sensors represents a state-of-the-art
contribution to efficient and cost-effective position sensor design, which is crucial for meeting the complex
requirements of the automotive industry.I would like to thank the Fundação para a Ciência e Tecnologia (FCT) and Bosch Car Multimedia for funding
my PhD (grant PD/BDE/142901/2018)
Large pseudoscalar Yukawa couplings in the complex 2HDM
We start by presenting the current status of a complex flavour conserving
two-Higgs doublet model. We will focus on some very interesting scenarios where
unexpectedly the light Higgs couplings to leptons and to b-quarks can have a
large pseudoscalar component with a vanishing scalar component. Predictions for
the allowed parameter space at end of the next run with a total collected
luminosity of and are also discussed. These
scenarios are not excluded by present data and most probably will survive the
next LHC run. However, a measurement of the mixing angle , between
the scalar and pseudoscalar component of the 125 GeV Higgs, in the decay will be able to probe many of these scenarios, even with low
luminosity. Similarly, a measurement of in the vertex
could help to constrain the low region in the Type I model.Comment: 21 pages, 10 figure
LGMD based neural network for automatic collision detection
Real-time collision detection in dynamic scenarios is a hard task if the algorithms used are based on conventional techniques of computer vision, since these are computationally complex and, consequently, time-consuming. On the other hand, bio-inspired visual sensors are suitable candidates for mobile robot navigation in unknown environments, due to their computational simplicity. The Lobula Giant Movement Detector (LGMD) neuron, located in the locust optic lobe, responds selectively to approaching objects. This neuron has been used to develop bio-inspired neural networks for collision avoidance. In this work, we propose a new LGMD model based on two previous models, in order to improve over them by incorporating other algorithms. To assess the real-time properties of the proposed model, it was applied to a real robot. Results shown that the LGMD neuron model can robustly support collision avoidance in complex visual scenarios.(undefined
Timed trajectory generation combined with an Extended Kalman Filter for a vision-based autonomous mobile robot
Series : Advances in intelligent systems and computing, vol. 193, ISSN 2194-5357Planning collision-free trajectories requires the combination of generation and modulation techniques. This is especially important if temporal stabilization of the generated trajectories is considered. Temporal stabilization means to conform to the planned movement time, in spite of environmental conditions or perturbations. This timing problem has not been addressed in most current robotic systems, and it is critical in several robotic tasks such as sequentially structured actions or human-robot interaction. This work focuses on generating trajectories for a mobile robot, whose goal is to reach a target within a constant time, independently of the world complexity. Trajectories are generated by nonlinear dynamical systems. Herein, we extend our previous work by including an Extended Kalman Filter (EKF) to estimate the target location relative to the robot. A simulated hospital environment and a Pioneer 3-AT robot are used to demonstrate the robustness and reliability of the proposed approach in cluttered, dynamic and uncontrolled scenarios. Multiple experiments confirm that the inclusion of the EKF preserves the timing properties of the overall architecture.Work supported by the Portuguese Science Foundation (grant PTDC/EEA-CRO/100655/2008), and by project FCT PEst-OE/EEI/LA0009/2011. Jorge B. Silva is supported by PhD Grant SFRH/BD/68805/2010, granted by the Portuguese Science Foundation
Developing a timed navigation architecture for hospital delivery robots
In hospitals, typical tasks of delivering goods between
different locations are usually done by auxiliary staff.
With the development of robotic technologies, such tasks can
be performed by mobile robots releasing the staff effort to other
tasks. In order to successfully complete the tasks of delivering
goods inside hospitals, mobile robots should be able to generate
trajectories free of collisions. In addition, including timing
constraints to the generated trajectories has not been addressed
in most current robotic systems, and it is critical in robotic
tasks as human-robot interaction. Including timing constraints
means to obey to the planned movement time, despite diversified
environmental conditions or perturbations. In this paper we aim
to develop a navigation architecture with timing constraints based
on a mesh of nonlinear dynamical systems and feedthrough maps
for wheeled mobile robots. A simulated hospital environment
and a wheeled robot pioneer 3-DX are used to demonstrate
the robustness and reliability of the proposed architecture in
cluttered, dynamic and uncontrolled hospital scenarios
Generating trajectories with temporal constraints for an autonomous robot
Trajectory modulation and generation are two fundamental
issues in the path planning problem in autonomous robotics,
specially considering temporal stabilization of the generated movements.
This is a very critical issue in several robotic tasks including:
catching, hitting, and human-robot scenarios.
In this work, we address these problems and focus on generating
movement for a mobile robot, whose goal is to reach a target within
a constant time. We use an Hopf oscillator whose solution controls
velocity, adapted according to temporal feedback. We have also
proposed an adaptive mechanism for frequency modulation of the
velocity profile that enables setting different times for acceleration
and deceleration.
This approach is demonstrated on a DRK8000 mobile robot in
order to confirm the system’s reliability with low-level sensors.(undefined
Timed trajectory generation for a toy-like wheeled robot
In this work, we address temporal stabilization
of generated movements in autonomous robotics. We focus on
generating movement for a mobile robot, that must reach a
target location within a constant time. Target location is online
calculated by using the robot visual system, such that action is
steered by the sensory information. This is a very critical issue
in several robotic tasks including: catching, hitting, and humanrobot
scenarios.
Robot velocity is controlled through an Hopf oscillator,
adapted according to temporal feedback. Timing of the velocity
profile is modulated according to an adaptive mechanism that
enables setting different times for acceleration and deceleration.
Results on a DRK8000 mobile robot confirm the system’s
reliability with low-level sensors
Evaluation of Pozzolanic Reactivity of Artificial Pozzolans
Materials Science Forum Vols. 730-732 (2013) pp 433-438Pozzolanicity is a very interesting issue regarding building materials, as a way to enhance mortars
and concrete durability. This property results from the reaction between calcium hydroxide and
silica and alumina based materials. Different types of natural and artificial pozzolans show
pozzolanic activities that differ depending on the materials characteristics. Therefore, the study of
this property, namely its reactivity with calcium hydroxide, reveals itself to be important in the
selection of the type and content of these materials.
This paper presents the results of several pozzolanic reactivity methods, applied to different
pozzolanic materials. The selected pozzolanic methods include Chapelle method, Fratinni method
and Strength Activity Index. Those tests have been applied to evaluate the reactivity of various
kinds of artificial pozzolans. The correlation between the test methods are presented and discussed
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