10,329 research outputs found
Visual Sensor with Resolution Enhancement by Mechanical Vibrations
The resolution limit of visual sensors due to finite pixel spacing can be overcome by applying continuous low-amplitude vibrations to the image—or taking advantage of existing vibrations in the environment. Thereby, spatial intensity gradients turn into temporal intensity fluctuations which can be detected and processed by every pixel independently from the others. This approach enhances resolution and virtually eliminates fixed-pattern noise. A visual sensing microsystem taking advantage of this principle is described. It incorporates a custom analog integrated circuit implementing an array of 32 by 32 pixels with local temporal signal processing. Another key component is a resonant mechanical device producing low-amplitude image scanning movements powered by environmental vibrations
Image enhancement from a stabilised video sequence
The aim of video stabilisation is to create a new video sequence where the motions (i.e. rotations, translations) and scale differences between frames (or parts of a frame) have effectively been removed. These stabilisation effects can be obtained via digital video processing techniques which use the information extracted from the video sequence itself, with no need for additional hardware or knowledge about camera physical motion.
A video sequence usually contains a large overlap between successive frames, and regions of the same scene are sampled at different positions. In this paper, this multiple sampling is combined to achieve images with a higher spatial resolution. Higher resolution imagery play an important role in assisting in the identification of people, vehicles, structures or objects of interest captured by surveillance cameras or by video cameras used in face recognition, traffic monitoring, traffic law reinforcement, driver assistance and automatic vehicle guidance systems
The role of fingerprints in the coding of tactile information probed with a biomimetic sensor
In humans, the tactile perception of fine textures (spatial scale <200
micrometers) is mediated by skin vibrations generated as the finger scans the
surface. To establish the relationship between texture characteristics and
subcutaneous vibrations, a biomimetic tactile sensor has been designed whose
dimensions match those of the fingertip. When the sensor surface is patterned
with parallel ridges mimicking the fingerprints, the spectrum of vibrations
elicited by randomly textured substrates is dominated by one frequency set by
the ratio of the scanning speed to the interridge distance. For human touch,
this frequency falls within the optimal range of sensitivity of Pacinian
afferents, which mediate the coding of fine textures. Thus, fingerprints may
perform spectral selection and amplification of tactile information that
facilitate its processing by specific mechanoreceptors.Comment: 25 pages, 11 figures, article + supporting materia
A Review of Smart Materials in Tactile Actuators for Information Delivery
As the largest organ in the human body, the skin provides the important
sensory channel for humans to receive external stimulations based on touch. By
the information perceived through touch, people can feel and guess the
properties of objects, like weight, temperature, textures, and motion, etc. In
fact, those properties are nerve stimuli to our brain received by different
kinds of receptors in the skin. Mechanical, electrical, and thermal stimuli can
stimulate these receptors and cause different information to be conveyed
through the nerves. Technologies for actuators to provide mechanical,
electrical or thermal stimuli have been developed. These include static or
vibrational actuation, electrostatic stimulation, focused ultrasound, and more.
Smart materials, such as piezoelectric materials, carbon nanotubes, and shape
memory alloys, play important roles in providing actuation for tactile
sensation. This paper aims to review the background biological knowledge of
human tactile sensing, to give an understanding of how we sense and interact
with the world through the sense of touch, as well as the conventional and
state-of-the-art technologies of tactile actuators for tactile feedback
delivery
Sensor-based optimized control of the full load instability in large hydraulic turbines
Hydropower plants are of paramount importance for the integration of intermittent renewable energy sources in the power grid. In order to match the energy generated and consumed, Large hydraulic turbines have to work under off-design conditions, which may lead to dangerous unstable operating points involving the hydraulic, mechanical and electrical system. Under these conditions, the stability of the grid and the safety of the power plant itself can be compromised. For many Francis Turbines one of these critical points, that usually limits the maximum output power, is the full load instability. Therefore, these machines usually work far away from this unstable point, reducing the effective operating range of the unit. In order to extend the operating range of the machine, working closer to this point with a reasonable safety margin, it is of paramount importance to monitor and to control relevant parameters of the unit, which have to be obtained with an accurate sensor acquisition strategy. Within the framework of a large EU project, field tests in a large Francis Turbine located in Canada (rated power of 444 MW) have been performed. Many different sensors were used to monitor several working parameters of the unit for all its operating range. Particularly for these tests, more than 80 signals, including ten type of different sensors and several operating signals that define the operating point of the unit, were simultaneously acquired. The present study, focuses on the optimization of the acquisition strategy, which includes type, number, location, acquisition frequency of the sensors and corresponding signal analysis to detect the full load instability and to prevent the unit from reaching this point. A systematic approach to determine this strategy has been followed. It has been found that some indicators obtained with different types of sensors are linearly correlated with the oscillating power. The optimized strategy has been determined based on the correlation characteristics (linearity, sensitivity and reactivity), the simplicity of the installation and the acquisition frequency necessary. Finally, an economic and easy implementable protection system based on the resulting optimized acquisition strategy is proposed. This system, which can be used in a generic Francis turbine with a similar full load instability, permits one to extend the operating range of the unit by working close to the instability with a reasonable safety margin.Postprint (published version
Analog VLSI circuits for inertial sensory systems
Supervised by Rahul Sarpeshkar.Also isssued as Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (leaves 67-68).by Maziar Tavakoli Dastjerdi
Piezoelectric Sensors for Real-time Monitoring and Quality Control in Additive Manufacturing
Within the ever-evolving landscape of engineering, particularly in the
dynamic domain of additive In manufacturing, a pursuit of precision and
excellence in production processes takes centre stage. This research , This
paper serves to give a comprehensive understanding of piezoelectric sensors, a
topic that is both academically engaging and of practical significance,
catering to both seasoned experts and those newly venturing into the field.
Additive manufacturing, lauded for its groundbreaking potential, underscores
the imperative of rigorous quality control. This introduces piezoelectric
sensors, devices that may be unfamiliar to many but possess considerable
potential. This paper embarks on a methodical journey, commencing with an
introductory elucidation of the piezoelectric effect. It then advances to the
vital role of piezoelectric sensors in real-time monitoring and quality
control, unveiling their potential and relevance for newcomers and seasoned
professionals alike. This research, structured systematically from fundamental
principles to pragmatic applications, presents findings that are not only
academically informative but also represent a substantial stride towards
achieving precision and high-quality manufacturing processes in the engineering
field.Comment: 14 Pages, encompassing electrical element (piezoelectric sensor) and
its use in advanced manufacturing technolog
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