45,985 research outputs found
Encoderless position estimation and error correction techniques for miniature mobile robots
This paper presents an encoderless position estimation technique for miniature-sized mobile robots. Odometry techniques, which are based on the hardware components, are commonly used for calculating the geometric location of mobile robots. Therefore, the robot must be equipped with an appropriate sensor to measure the motion. However, due to the hardware limitations of some robots, employing extra hardware is impossible. On the other hand, in swarm robotic research, which uses a large number of mobile robots, equipping the robots with motion sensors might be costly. In this study, the trajectory of the robot is divided into several small displacements over short spans of time. Therefore, the position of the robot is calculated within a short period, using the speed equations of the robot's wheel. In addition, an error correction function is proposed that estimates the errors of the motion using a current monitoring technique. The experiments illustrate the feasibility of the proposed position estimation and error correction techniques to be used in miniature-sized mobile robots without requiring an additional sensor
Contactless measurement of electric current using magnetic sensors
We review recent advances in magnetic sensors for DC/AC current transducers, especially novel AMR sensors and integrated fluxgates, and we make critical comparison of their properties. Most contactless electric current transducers use magnetic cores to concentrate the flux generated by the measured current and to shield the sensor against external magnetic fields. In order to achieve this, the magnetic core should be massive. We present coreless current transducers which are lightweight, linear and free of hysteresis and remanence. We also show how to suppress their weak point: crosstalk from external currents and magnetic fields
A High Stability Optical Shadow Sensor with Applications for Precision Accelerometers
Gravimeters are devices which measure changes in the value of the
gravitational acceleration, \textit{g}. This information is used to infer
changes in density under the ground allowing the detection of subsurface voids;
mineral, oil and gas reserves; and even the detection of the precursors of
volcanic eruptions. A micro-electro mechanical system (MEMS) gravimeter has
been fabricated completely in silicon allowing the possibility of cost
e-effective, lightweight and small gravimeters. To obtain a measurement of
gravity, a highly stable displacement measurement of the MEMS is required. This
requires the development of a portable electronics system that has a
displacement sensitivity of nm over a period of a day or more. The
portable electronics system presented here has a displacement sensitivity nm ( nm at s). The battery power
system used a modulated LED for measurements and required temperature control
of the system to 2 mK, monitoring of the tilt to 2 radians,
the storage of measured data and the transmission of the data to an external
server.Comment: 8 Pages, 12 figures, 5 equations, currently submitted and under
review at IEEE Sensors SIE
A comparative study of calibration methods for low-cost ozone sensors in IoT platforms
Š 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper shows the result of the calibration process of an Internet of Things platform for the measurement of tropospheric ozone (O 3 ). This platform, formed by 60 nodes, deployed in Italy, Spain, and Austria, consisted of 140 metalâoxide O 3 sensors, 25 electro-chemical O 3 sensors, 25 electro-chemical NO 2 sensors, and 60 temperature and relative humidity sensors. As ozone is a seasonal pollutant, which appears in summer in Europe, the biggest challenge is to calibrate the sensors in a short period of time. In this paper, we compare four calibration methods in the presence of a large dataset for model training and we also study the impact of a limited training dataset on the long-range predictions. We show that the difficulty in calibrating these sensor technologies in a real deployment is mainly due to the bias produced by the different environmental conditions found in the prediction with respect to those found in the data training phase.Peer ReviewedPostprint (author's final draft
ARAS: an automated radioactivity aliquoting system for dispensing solutions containing positron-emitting radioisotopes.
BackgroundAutomated protocols for measuring and dispensing solutions containing radioisotopes are essential not only for providing a safe environment for radiation workers but also to ensure accuracy of dispensed radioactivity and an efficient workflow. For this purpose, we have designed ARAS, an automated radioactivity aliquoting system for dispensing solutions containing positron-emitting radioisotopes with particular focus on fluorine-18 ((18)F).MethodsThe key to the system is the combination of a radiation detector measuring radioactivity concentration, in line with a peristaltic pump dispensing known volumes.ResultsThe combined system demonstrates volume variation to be within 5 % for dispensing volumes of 20 ÎźL or greater. When considering volumes of 20 ÎźL or greater, the delivered radioactivity is in agreement with the requested amount as measured independently with a dose calibrator to within 2 % on average.ConclusionsThe integration of the detector and pump in an in-line system leads to a flexible and compact approach that can accurately dispense solutions containing radioactivity concentrations ranging from the high values typical of [(18)F]fluoride directly produced from a cyclotron (~0.1-1 mCi ÎźL(-1)) to the low values typical of batches of [(18)F]fluoride-labeled radiotracers intended for preclinical mouse scans (~1-10 ÎźCi ÎźL(-1))
inTrack: High Precision Tracking of Mobile Sensor Nodes
Radio-interferometric ranging is a novel technique that allows
for fine-grained node localization in networks of inexpensive COTS
nodes. In this paper, we show that the approach can also be applied
to precision tracking of mobile sensor nodes. We introduce inTrack, a
cooperative tracking system based on radio-interferometry that features
high accuracy, long range and low-power operation. The system utilizes
a set of nodes placed at known locations to track a mobile sensor. We
analyze how target speed and measurement errors affect the accuracy of
the computed locations. To demonstrate the feasibility of our approach,
we describe our prototype implementation using Berkeley motes. We
evaluate the system using data from both simulations and field tests
A handheld high-sensitivity micro-NMR CMOS platform with B-field stabilization for multi-type biological/chemical assays
We report a micro-nuclear magnetic resonance (NMR) system compatible with multi-type biological/chemical lab-on-a-chip assays. Unified in a handheld scale (dimension: 14 x 6 x 11 cmÂł, weight: 1.4 kg), the system is capable to detect<100 pM of Enterococcus faecalis derived DNA from a 2.5 ÎźL sample. The key components are a portable magnet (0.46 T, 1.25 kg) for nucleus magnetization, a system PCB for I/O interface, an FPGA for system control, a current driver for trimming the magnetic (B) field, and a silicon chip fabricated in 0.18 Îźm CMOS. The latter, integrated with a current-mode vertical Hall sensor and a low-noise readout circuit, facilitates closed-loop B-field stabilization (2 mT â 0.15 mT), which otherwise fluctuates with temperature or sample displacement. Together with a dynamic-B-field transceiver with a planar coil for micro-NMR assay and thermal control, the system demonstrates: 1) selective biological target pinpointing; 2) protein state analysis; and 3) solvent-polymer dynamics, suitable for healthcare, food and colloidal applications, respectively. Compared to a commercial NMR-assay product (Bruker mq-20), this platform greatly reduces the sample consumption (120x), hardware volume (175x), and weight (96x)
Performance characterisation of a new photo-microsensor based sensing head for displacement measurement
This paper presents a robust displacement sensor with nanometre-scale resolution over a micrometre range. It is composed of low cost commercially available slotted photo-microsensors (SPMs). The displacement sensor is designed with a particular arrangement of a compact array of SPMs with specially designed shutter assembly and signal processing to significantly reduce sensitivity to ambient light, input voltage variation, circuit electronics drift, etc. The sensor principle and the characterisation results are described in this paper. The proposed prototype sensor has a linear measurement range of 20 Îźm and resolution of 21 nm. This kind of sensor has several potential applications, including mechanical structural deformation monitoring system
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