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Publikācijas
729 publikācijas
- 2020
Testing Pulse Timing Devices Using Arbitrary Function Generators(atveras jaunā logā)
V. Bespalko, I. Burak, A. Rybakov
Automatic Control and Computer Sciences, Sēj. 54 (5), lpp. 466 - 473, Pleiades Publishing
Kopsavilkums
Arbitrary function generators in the mode of generating time intervals are used to test pulse timing devices (PTDs). It is shown that the generators have a specific amplitude-dependent error when variations of the amplitude of pulses that specify the time intervals cause distortions in the duration of the generated intervals. At the same time, the results of the PTD testing have a characteristic step component, which allows one to reduce the mathematical processing of the test results to the separation into the components: smooth (actually the PTD characteristic) and step (determined by the amplitude-dependent error of the generator). To identify the break points of the derivative corresponding to the transitions between the amplitude subbands, a discrete differentiation is performed based on the calculation of finite differences of the first or second order. The step function is formed in the process of discrete integration of finite differences. The efficiency of accounting for the amplitude-dependent error of generators of special form is demonstrated by the example of testing the PTD with constant and tracking thresholds. It is shown that a picosecond testing accuracy is achievable. © 2020, Allerton Press, Inc.
Indeksēts Scopus / WoS · SNIP: 0.676
- 2020
Bluetooth Low Energy Wireless Sensor Network Library in MATLAB Simulink(atveras jaunā logā)
Shavelis, R., Ozols, K.
Shavelis, R., Ozols, K., Sēj. 9 (3), lpp. 38, Journal of Sensor and Actuator Network
Kopsavilkums
The paper describes the elements of the developed MATLAB Simulink library for building the models of Bluetooth Low Energy (BLE) wireless sensor networks to simulate the communication between BLE devices in the presence of interference and channel noise. Various parameters can be configured for the devices including their 2D positions to take into account the distances between them for calculating the attenuation coefficients of the transmitted signals. Two simulation examples are provided, one of which demonstrates the data exchange between one master device and one slave at high data packet transmission rate (2 kHz), while the other example shows the data exchange between one master and multiple slaves simultaneously, in which case the data packet transmission rate can be no larger than 133 Hz. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Q1/Q2 žurnāls · SNIP: 1.329
- 2020
Towards Body Coupled Communication for eHealth: Experimental Study of Human Body Frequency Response Institute of Electronics and Computer Science(atveras jaunā logā)
J. Ormanis, A. Elsts
2020 IEEE International Conference on Communications Workshops, IEEE
Kopsavilkums
The Internet of Things promises to enable numerous future applications spanning many domains, including healthcare. Currently, most health care devices communicate either by using wires or by using a Radio Frequency technology such as Bluetooth or WiFi. In this paper, we describe an alternative communication method: Body Coupled Communication, where the signal is transmitted using an electrical field that propagates through the human body. We perform experimental measurements using a wrist-to-wrist setup to determine the human body frequency response in the 10 kHz to 30 MHz frequency range and find that the 3.25 MHz frequency has the lowest attenuation in this range. We also show that the frequency response patterns remain the same when a number of common chemical substances are applied between the electrode and the skin, and that electrically conductive substances such as sweat enhance the received signal strength.
- 2020
Dataset of annotated food crops and weed images for robotic computer vision control(atveras jaunā logā)
K. Sudars, J. Jasko, I. Namatevs, L. Ozola, N. Badaukis
Data in Brief, Sēj. 31, lpp. 105833, Elsevier Inc.
Kopsavilkums
Weed management technologies that can identify weeds and distinguish them from crops are in need of artificial intelligence solutions based on a computer vision approach, to enable the development of precisely targeted and autonomous robotic weed management systems. A prerequisite of such systems is to create robust and reliable object detection that can unambiguously distinguish weed from food crops. One of the essential steps towards precision agriculture is using annotated images to train convolutional neural networks to distinguish weed from food crops, which can be later followed using mechanical weed removal or selected spraying of herbicides. In this data paper, we propose an open-access dataset with manually annotated images for weed detection. The dataset is composed of 1118 images in which 6 food crops and 8 weed species are identified, altogether 7853 annotations were made in total. Three RGB digital cameras were used for image capturing: Intel RealSense D435, Canon EOS 800D, and Sony W800. The images were taken on food crops and weeds grown in controlled environment and field conditions at different growth stages © 2020 The Author(s)
Indeksēts Scopus / WoS · Q1/Q2 žurnāls · SNIP: 2
- 2020
On the origin of finger enslaving: Control with referent coordinates and effects of visual feedback(atveras jaunā logā)
V. Abolins, A. Stremoukhov, C. Walter, M. L. Latash
Journal of Neurophysiology, Sēj. 124 (6), lpp. 1625 - 1636, American Physiological Society
Kopsavilkums
When a person tries to press with a finger, other fingers of the hand produce force unintentionally. We explored this phenomenon of enslaving during unintentional force drifts in the course of continuous force production by pairs of fingers of a hand. Healthy subjects performed accurate force production tasks by finger pairs Index-Middle, Middle-Ring, and Ring-Little with continuous visual feedback on the combined force of the instructed (master) fingers or of the noninstructed (enslaved) fingers. The feedback scale was adjusted to ensure that the subjects did not know the difference between these two, randomly presented, conditions. Across all finger pairs, enslaved force showed a drift upward under feedback on the master finger force, and master force showed a drift downward under feedback on the enslaved finger force. The subjects were unaware of the force drifts, which could reach over 50% of the initial force magnitude over 15 s. Across all conditions, the index of enslaving increased by ~50% over the trial duration. The initial moment of force magnitude in pronation-supination was not a consistent predictor of the force drift magnitude. These results falsify the hypothesis that the counter-directional force drifts reflected drifts in the moment of force. They suggest that during continuous force production, enslaving increases with time, possibly due to the spread of excitation over cortical finger representations or other mechanisms, such as increased synchronization of firing of a-motoneurons innervating different compartments of extrinsic flexors. These changes in enslaving, interpreted at the level of control with referent coordinates for the fingers, can contribute to a variety of phenomena, including unintentional force drifts. Copyright © 2020 the American Physiological Society
Indeksēts Scopus / WoS · Q1/Q2 žurnāls · SNIP: 0.953
- 2020
Wearable Devices for Digital Health: The SPHERE Wearable 3(atveras jaunā logā)
A. Vafeas, X. Fafoutis, A. Elsts, I. Craddock, R. Piechocki, G. Oikonomou
International Conference on Embedded Wireless Systems and Networks, Junction Publishing
Kopsavilkums
This paper presents a novel wearable device: the SPHERE Wearable 3. The Wearable 3 is a wrist-worn sensor node tailored for low maintenance residential health and behaviour monitoring. It features multiple inertial measurement sensors, as well as a heart-rate sensor, capacitive button, and OLED screen. The Wearable 3 builds on our experience with previous generations of wearable sensing nodes while adding novel features, including interactive elements. We present a novel two-way communication based on a customized implementation of the Bluetooth Low Energy (BLE) protocol to connect the Wearable 3 with a gateway device, and describe various optimizations of energy consumption. The Wearable 3 is currently being deployed in residential homes in Bristol, UK, as part of a project aiming to collect diagnostic data from early-stage Alzheimer’s patients. © 2020 the authors
Indeksēts Scopus / WoS
- 2020
What do people match when they try to match force? Analysis at the level of hypothetical control variables(atveras jaunā logā)
V. Abolins, C. Cuadra, J.Ricotta, M. L. Latash
Experimental Brain Research, Sēj. 238 (9), lpp. 1885 - 1901, Springer Science and Business Media Deutschland GmbH
Kopsavilkums
We used the theory of control with spatial referent coordinates (RC) to explore how young, healthy persons modify finger pressing force and match forces between the two hands. Three specific hypotheses were tested related to patterns of RC and apparent stiffness (defined as the slope of force-coordinate relation) used in the presence of visual feedback on the force and in its absence. The subjects used the right hand to produce accurate force under visual feedback; further the force could be increased or decreased, intentionally or unintentionally (induced by controlled lifting or lowering of the fingertips). The left hand was used to match force without visual feedback before and after the force change; the match hand consistently underestimated the actual force change in the task hand. The “inverse piano” device was used to compute RC and apparent stiffness. We found very high coefficients of determination for the inter-trial hyperbolic regressions between RC and apparent stiffness in the presence of visual feedback; the coefficients of determination dropped significantly without visual feedback. There were consistent preferred sharing patterns in the space of RC and apparent stiffness between the task and match hands across subjects. In contrast, there was much less consistency between the task and match hands in the magnitudes of RC and apparent stiffness observed in individual trials. Compared to the task hand, the match hand showed consistently lower magnitudes of apparent stiffness and, correspondingly, larger absolute magnitudes of RC. Involuntary force changes produced by lifting and lowering the force sensors led to significantly lower force changes compared to what could be expected based on the computed values of apparent stiffness and sensor movement amplitude. The results confirm the importance of visual feedback for stabilization of force in the space of hypothetical control variables. They suggest the existence of personal traits reflected in preferred ranges of RC and apparent stiffness across the two hands. They also show that subjects react to external perturbations, even when instructed “not to interfere”: Such perturbations cause unintentional and unperceived drifts in both RC and apparent stiffness. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
Indeksēts Scopus / WoS · SNIP: 0.925
- 2020
Implementation of IoT Concept for Early Diagnostic of Subacute Rumen Acidosis in Cows(atveras jaunā logā)
A. Zabasta, N. Kunicina, U. Grunde, J. Judvaitis, I. Sematovica
2020 9th Mediterranean Conference on Embedded Computing,, IEEE
Kopsavilkums
Highly productive dairy cow' ration under intensive production conditions causes the development of subacute rumen acidosis (SARA). In this paper we discuss a reticulo-ruminal long-acting cyber-physical diagnostic system' prototype, which applies Internet of Things (IoT) for monitoring rumen parameters of cows. The new diagnostic system architecture includes, reticulo-ruminal bolus with pH and temperature sensors, a microcontroller, a radio transmitter and a power supply module. The system includes gateways for data collection from boluses, an MQTT (Message Queuing Telemetry Transport) broker, a web server and a database. The diagnostic system' prototype provides timely data on cow health status to the users, so they can evaluate the cow' health status and implement further actions. Therefore, the use of diagnostic system provides opportunity to increase cow productivity, longevity and to save maintenance cost of milk farms. The results of the first stage of the research are discussed in this paper. © 2020 IEEE.
Indeksēts Scopus / WoS
- 2020
Research of Indirect Method of Measuring the Pulse Generator Output Resistance by the Step Recovery Diode(atveras jaunā logā)
V. Aristov
Proceedings of the 2020 24th International Conference Electronics, IEEE
Kopsavilkums
Paper describes the research on the output resistance of the nanosecond pulse generator built on a Step Recovery Diode. Such generators are used as sources of short (tenths of a nanosecond) pulses. The latter are the basis for: measuring instruments, impact excitation of ultra-wideband antennas of radar sensors, radar of underground sounding and other purposes. To enable a comprehensive analysis of elements the system of differential algebraic equations is solved. The Equations are written for Kirchhoff's laws, describing the 'behavior' of currents and voltages of discrete circuit elements, and the parasitic inductors and capacitors also. This is caused by strong influence of parasitic components on transients in the circuit, operating in the time range of less than a nanosecond, which is equivalent to the gigahertz frequencies and higher. The obtained solutions made it possible to reveal the influence of the nominal values of the generator circuit elements on its output resistance. Adjusting the output resistance of the generator to a value close to the characteristic resistance of the line, through which the pulses of the generator are transmitted to the load, maximize the transmission of power to the load and eliminate masking of the useful signal by pulses of re-reflections in the line. © 2020 IEEE.
Indeksēts Scopus / WoS
- 2020
Mathematical Analysis of the Nanosecond Pulse Generator on Two SRD Diodes Used in UWB Radars(atveras jaunā logā)
V. Aristov
Automatic Control and Computer Sciences, Sēj. 54 (3), lpp. 271 - 278, Pleiades Publishing
Kopsavilkums
This paper describes mathematically an expanded circuit additionally containing parasitic capacitors and inductors for the pulser circuit on two SRDs, which allows a relatively wide range to vary the output pulse duration with a rise time and fall time of less than a nanosecond. Resolving a system of differential equations, we acquire a possibility of analyzing the influence of the circuit elements on the output pulse parameters and to select the optimum value. The calculation results are compared with experimental data. © 2020, Allerton Press, Inc.
Indeksēts Scopus / WoS · SNIP: 0.676
- 2020
Edge pre-processing of traffic surveillance video for bandwidth and privacy optimization in smart cities(atveras jaunā logā)
A. Skadins, R. Rava, M. Ivanovs, K. Nesenbergs
Proceedings of the Biennial Baltic Electronics Conference, IEEE Computer Society
Kopsavilkums
Traffic surveillance is essential for regulating traffic and reducing congestion. Nonetheless, the video data generated is non-structured, high-volume, bandwidth intensive and also raises privacy concerns. Edge computing solves these issues by preprocessing the data locally. In this paper we propose a fast, realtime vehicle detection and tracking method running on an edge device. The device sends only a single high resolution image of each detected vehicle accompanied with its trajectory. Allowing not only lower bandwidth requirements for smart city cameras, but also improved privacy, as only minimum required data is sent for post-processing. We implement object detection and tracking on an edge device, validate it in a real city environment and compare it to a state-of-The-Art deep learning method using a publicly available benchmark data set where our method shows speed increase of up to 24 times. © 2020 IEEE.
Indeksēts Scopus / WoS
- 2020
Classification of actual sensor network deployments in research studies from 2013 to 2017(atveras jaunā logā)
Judvaitis, J., Mednis, A., Abolins, V., Skadins, A., Lapsa, D., Rava, R., Ivanovs, M. and Nesenbergs, K.
Classification of Actual Sensor Network Deployments in Research Studies from 2013 to 2017, Sēj. 5 (4), lpp. 1 - 19, MDPI AG
Kopsavilkums
Technologies, such as Wireless Sensor Networks (WSN) and Internet of Things (IoT), have captured the imagination of researchers, businesses, and general public, due to breakthroughs in embedded system development, sensing technologies, and ubiquitous connectivity in recent years. That resulted in the emergence of an enormous, difficult-to-navigate body of work related to WSN and IoT. In an ongoing research effort to highlight trends and developments in these technologies and to see whether they are actually deployed rather than subjects of theoretical research with presumed potential use cases, we gathered and codified a dataset of scientific publications from a five-year period from 2013 to 2017 involving actual sensor network deployments, which will serve as a basis for future in-depth analysis of the field. In the first iteration, 15,010 potentially relevant articles were identified in SCOPUS and Web of Science databases; after two iterations, 3059 actual sensor network deployments were extracted from those articles and classified in a consistent way according to different categories, such as type of nodes, field of application, communication types, etc. We publish the resulting dataset with the intent that its further analysis may identify prospective research fields and future trends in WSN and IoT. Dataset: https://doi.org/10.5281/zenodo.4048214 Dataset License: CC0. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Q1/Q2 žurnāls · SNIP: 1.086
- 2020
Energy-efficient activity recognition framework using wearable accelerometers(atveras jaunā logā)
A. Elsts, I. Craddock, R. McConville, N. Twomey,
Journal of Network and Computer Applications, Sēj. 168, lpp. 102770, Academic Press
Kopsavilkums
Acceleration data for activity recognition typically are collected on battery-powered devices, leading to a trade-off between high-accuracy recognition and energy-efficient operation. We investigate this trade-off from a feature selection perspective, and propose an energy-efficient activity recognition framework with two key components: a detailed energy consumption model and a number of feature selection algorithms. We evaluate the model and the algorithms using Random Forest classifiers to quantify the recognition accuracy, and find that the multi-objective Particle Swarm Optimization algorithm achieves the best results for the task. The results show that by selecting appropriate groups of features, energy consumption for computation and data transmission is reduced by an order of magnitude compared with the raw-data approach, and that the framework presents a flexible selection of feature groups that allow the designer to choose an appropriate accuracy-energy trade-off for a specific target application. © 2020 Elsevier Ltd
Indeksēts Scopus / WoS · Q1/Q2 žurnāls · SNIP: 2.637
- 2020
An empirical survey of autonomous scheduling methods for TSCH(atveras jaunā logā)
A. Elsts, S. Kim, H. S. Kim, C. Kim
IEEE Access, Sēj. 8, lpp. 67147 - 67165, IEEE
Kopsavilkums
Time Slotted Channel Hopping (TSCH) is a link layer protocol defined in the IEEE 802.15.4 standard. Although it is designed to provide highly reliable and efficient service targeting industrial automation systems, scheduling TSCH transmissions in the time and frequency dimensions is left to the implementers. We evaluate the performance of existing autonomous scheduling approaches for TSCH on various traffic patterns and network configurations. We thoroughly investigate the pros and cons of each scheme; moreover, we propose the use of node based channel allocation to improve the performance of the best scheme, and demonstrate its practicality and reliability, with up to 6 percentage points better packet delivery ratio than the second best option while retaining a similar radio duty cycle. Finally, based on our extensive performance evaluation, we provide some guidelines on how to select a scheduler for a given network. © 2013 IEEE.
Indeksēts Scopus / WoS · Q1/Q2 žurnāls · SNIP: 1.421
- 2020
From bits of data to bits of knowledge—an on-board classification framework for wearable sensing systems(atveras jaunā logā)
Zalewski, P., Marchegiani, L., Elsts, A., Piechocki, R., Craddock, I. Fafoutis
From bits of data to bits of knowledge—an on-board classification framework for wearable sensing systems, Sēj. 20 (6), lpp. 1655, MDPI AG
Kopsavilkums
Wearable systems constitute a promising solution to the emerging challenges of healthcare provision, feeding machine learning frameworks with necessary data. In practice, however, raw data collection is expensive in terms of energy, and therefore imposes a significant maintenance burden to the user, which in turn results in poor user experience, as well as significant data loss due to improper battery maintenance. In this paper, we propose a framework for on-board activity classification targeting severely energy-constrained wearable systems. The proposed framework leverages embedded classifiers to activate power-hungry sensing elements only when they are useful, and to distil the raw data into knowledge that is eventually transmitted over the air. We implement the proposed framework on a prototype wearable system and demonstrate that it can decrease the energy requirements by one order of magnitude, yielding high classification accuracy that is reduced by approximately 5%, as compared to a cloud-based reference system. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Q1/Q2 žurnāls · SNIP: 1.555
- 2020
TSCH Networks for Health IoT: Design, Evaluation, and Trials in the Wild(atveras jaunā logā)
X. Fafoutis, A. Elsts, I. Craddock, R. Piechocki, G. Oikonomou
ACM Transactions on Internet of Things, Sēj. 1 (2), lpp. 1–27, Association for Computing Machinery
Kopsavilkums
The emerging Internet of Things has the potential to solve major societal challenges associated with healthcare provision. Low-power wireless protocols for residential Health Internet of Things applications are characterized by high reliability requirements, the need for energy-efficient operation, and the need to operate robustly in diverse environments in the presence of external interference. We enhance and experimentally evaluate the Time-Slotted Channel Hopping protocol from the IEEE 802.15.4 standard to address these challenges. Our contributions are a new schedule and an adaptive channel selection mechanism to increase the performance of time-slotted channel hopping in this domain. Evaluation in a test house shows that the enhanced system is suitable for our e-Health application and compares favorably with state-of-the-art options. The schedule provides higher reliability compared with the minimal scheduling function from the IETF 6TiSCH Working Group and has a better energy-efficiency/reliability tradeoff than the Orchestra scheduler. Results from 29 long-term residential deployments confirm the suitability for the application and show that the system is able to adapt and avoid channels used by WiFi. In these uncontrolled environments, the system achieves 99.96% average reliability for networks that generate 7.5 packets per second on average.
- 2020
TSCH-Sim: Scaling Up Simulations of TSCH and 6TiSCH Networks(atveras jaunā logā)
A. Elsts
Sensors, Sēj. 20 (19), lpp. 1 - 17, MDPI AG
Kopsavilkums
TSCH (Time-Slotted Channel Hopping) and 6TiSCH (IPv6 over the TSCH mode of IEEE 802.15.4e) low-power wireless networks are becoming prominent in the industrial Internet of Things (IoT) and other areas where high reliability is needed in conjunction with energy efficiency. Due to the complexity of IoT deployments, network simulations are typically used for pre-deployment design and validation. However, it is currently difficult and time-consuming to simulate large-scale IoT networks with thousands of nodes. This paper proposes TSCH-Sim: a new discrete event simulator for IEEE 802.15.4-2015 TSCH and 6TiSCH networks. The evaluation shows that simulation results obtained with TSCH-Sim show a good match with results from other simulators that are commonly used to investigate TSCH networks. At the same time, TSCH-Sim is faster than these alternatives at least by an order of magnitude, making it more practical to carry out simulations of large networks. © 2020 by the author. Licensee MDPI, Basel, Switzerland.
Indeksēts Scopus / WoS · Q1/Q2 žurnāls · SNIP: 1.555
- 2020
Programmable Systems for Intelligence in Automobiles (PRYSTINE): Technical Progress after Year 2(atveras jaunā logā)
N. Druml, B. Debaillie, A. Anghel, N. Ristea, J. Fuchs, A. Dubey, T. Reisland, M. Hartstem, V. Rack, A. Ryabokon, K. Ozols, R. Novickis
Proceedings - Euromicro Conference on Digital System Design, IEEE
Kopsavilkums
Autonomous driving has the potential to disruptively change the automotive industry as we know it today. For this, fail-operational behavior is essential in the sense, plan, and act stages of the automation chain in order to handle safety-critical situations by its own, which currently is not reached with state-of-The-Art approaches.The European ECSEL research project PRYSTINE realizes Fail-operational Urban Surround perceptION (FUSION) based on robust Radar and LiDAR sensor fusion and control functions in order to enable safe automated driving in urban and rural environments. This paper showcases some of the key results (e.g., novel Radar sensors, innovative embedded control and E/E architectures, pioneering sensor fusion approaches, AI controlled vehicle demonstrators) achieved until year 2. © 2020 IEEE.
Indeksēts Scopus / WoS
- 2020
An Approach of Feed-Forward Neural Network Throughput-Optimized Implementation in FPGA(atveras jaunā logā)
Rihards Novickis, Daniels Jānis Justs, Kaspars Ozols and Modris Greitāns
Electronics journal, Sēj. 9 (12), lpp. 1 - 16, MDPI AG
Kopsavilkums
Artificial Neural Networks (ANNs) have become an accepted approach for a wide range of challenges. Meanwhile, the advancement of chip manufacturing processes is approaching saturation which calls for new computing solutions. This work presents a novel approach of an FPGA-based accelerator development for fully connected feed-forward neural networks (FFNNs). A specialized tool was developed to facilitate different implementations, which splits FFNN into elementary layers, allocates computational resources and generates high-level C++ description for high-level synthesis (HLS) tools. Various topologies are implemented and benchmarked, and a comparison with related work is provided. The proposed methodology is applied for the implementation of high-throughput virtual sensor. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Q1/Q2 žurnāls · SNIP: 0.985
- 2020
World Coordinate Virtual Traffic Cameras: Edge-Based Transformation and Merging of Multiple Surveillance Video Sources(atveras jaunā logā)
R. Rava, M. Ivanovs, A. Skadiņš, K. Nesenbergs
2020 7th International Conference on Soft Computing & Machine Intelligence (ISCMI), lpp. 233-236, IEEE
Kopsavilkums
Video cameras are an important high-fidelity source of surveillance information. They are especially useful in traffic monitoring scenarios in smart cities to reduce congestion, regulate traffic and enforce regulations. Unfortunately, increasing the number of cameras at a specific location makes it harder to keep quality attention on the scene due to high amount of unstructured data mixed with privacy breaching non-essential data, like faces of pedestrians etc. In this paper, we propose a method for real-time merging of multiple surveillance video sources to extract the required information in a single, world coordinate-based, virtual traffic camera view. Such a composite view allows for future improvements in quality of critical details using techniques as super resolution, while at the same time removing unnecessary private information. The implementation is validated on real world traffic data using NVIDIA Jetson TX2 as an edge device and consists of perspective transformation, image merging and object detection/tracking using YOLOv4 machine learning model for the extraction of significant objects only.
Indeksēts Scopus / WoS