Design and Implementation of a Narrow-Band Intersatellite Network with Limited Onboard Resources for IoT

Satellite networks are inevitable for the ubiquitous connectivity of M2M (machine to machine) and IoT (internet of things) devices. Advances in the miniaturization of satellite technology make networks in LEO (Low Earth Orbit) predestined to serve as a backhaul for narrow-band M2M communication. To reduce latency and increase network responsivity, intersatellite link capability among nodes is a key component in satellite design. The miniaturization of nodes to enable the economical deployment of large networks is also crucial. Thus, this article addresses these key issues and presents a design methodology and implementation of an adaptive network architecture considering highly limited resources, as is the case in a nanosatellite (≈10 kg) network. Potentially applicable multiple access techniques are evaluated. The results show that a time division duplex scheme with session-oriented P2P (point to point) protocols in the data link layer is more suitable for limited resources. Furthermore, an applicable layer model is defined and a protocol implementation is outlined. To demonstrate the technical feasibility of a nanosatellite-based communication network, the S-NET (S band network with nanosatellites) mission has been developed, which consists of four nanosatellites, to demonstrate multi-point crosslink with 100 kbps data rates over distances up to 400 km and optimized communication protocols, pushing the technological boundaries of nanosatellites. The flight results of S-NET prove the feasibility of these nanosatellites as a space-based M2M backhaul.BMWi, 50YB1225, S-Band Netzwerk für kooperierende SatellitenBMWi, 50YB1009, SLink - S-Band Transceiver zur Intersatelliten-Kommunikation von NanosatellitenDFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

Hemispherical Net-structure Proximity Sensor Detecting Azimuth and Elevation for Guide Dog Robot

Abstract-We have developed a net-structure proximity sensor that detects the azimuth and elevation to a nearby object. This information can be used by robots to avoid obstacles or to respond to human behavior. We propose detection principles where the azimuth is detected by arranging two onedimensional net-structure proximity sensors along orthogonal axes, and the elevation is detected by arranging two onedimensional net-structure proximity sensors in a stacked ring. We also experimentally demonstrate the feasibility of these detection principles. The experimental result shows the sensor can detect azimuth at all peripheral angles and elevation from side to top up

Airborne Directional Networking: Topology Control Protocol Design

This research identifies and evaluates the impact of several architectural design choices in relation to airborne networking in contested environments related to autonomous topology control. Using simulation, we evaluate topology reconfiguration effectiveness using classical performance metrics for different point-to-point communication architectures. Our attention is focused on the design choices which have the greatest impact on reliability, scalability, and performance. In this work, we discuss the impact of several practical considerations of airborne networking in contested environments related to autonomous topology control modeling. Using simulation, we derive multiple classical performance metrics to evaluate topology reconfiguration effectiveness for different point-to-point communication architecture attributes for the purpose of qualifying protocol design elements

Antennas for wireless sensor network applications

The objective of this thesis is to present an analysis of antennas, which are applicable to wireless sensor networks and, in particular, to the requirements of the Speckled Computing Network Consortium. This was done through a review of the scientific literature on the subject, and the design, computer simulation, and experimental verification, of various suitable designs of antenna The first part of this thesis outlines what an antenna is and how it radiates. An insight is also given to the fundamental limitations of antennas. As antennas investigated in this thesis are planar-printed designs, an insight into the types of feed lines applicable, such as microstrip, CPW and slotline, is given. To help characterise the antennas investigated, the fundamental antenna analysis parameters, such as impedance bandwidth, S-parameters, radiation pattern, directivity, antenna efficiency, gain and polarisation are discussed. Also discussed is the 3D electromagnetic simulation software, HFSS, which was used to simulate the antennas in this thesis. To help illustrate the use of HFSS, a proximity-coupled patch antenna, operating at 5.8 GHz, was used as an example. A range of antennas were designed, manufactured and tested. These used conventional printed circuit boards (PCBs) and Gallium Arsenide (GaAs) substrates, operating at a range of frequencies from 2.4 GHz to 12 GHz. A review was conducted into relevant, suitable radio architectures such as, conventional narrowband systems, Ultra-Wide Band (UWB), and simplified radio architectures such as those based on the diode rectifier method, and Super Regenerative Receivers (SRR). There were several UWB antennas designed, which operate over a 3.1 – 10.16 GHz operational band with a VSWR ≤ 2. All the UWB antennas were required to transmit a UWB pulse with minimal distortion, which placed a requirement of linear phase and low values of group delay to minimise distortion on the pulse. UWB antennas investigated included a Vivaldi antenna, which was large, directional and gave excellent pulse transmission characteristics. A CPW-fed monopole was also investigated, which was small, omni-directional and had poor pulse transmission characteristics. A UWB dipole was designed for use in a UWB channel modelling experiment in collaboration with Strathclyde University. The initial UWB dipole investigated was a microstrip-fed structure that had unpredictable behaviour due to the feed, which excited leakage current down the feed cable and, as a result, distorted both the radiation pattern and the pulse. To minimise the leakage current, three other UWB dipoles were investigated. These were a CPW-fed UWB dipole with slots, a hybrid-feed UWB dipole, and a tapered-feed UWB dipole. Presented for these UWB dipoles are S-parameter results, obtained using a vector network analyser, and radiation pattern results obtained using an anechoic chamber. There were several antennas investigated in this thesis directly related to the Speckled Computing Consortiums objective of designing a 5mm3 ‘Speck’. These antennas were conventional narrowband antenna designs operating at either 2.45 GHz or 5.8 GHz. A Rectaxial antenna was designed at 2.45 GHz, which had excellent matching (S11 = -20dB) at the frequency of operation, and an omni-directional radiation pattern with a maximum gain of 2.69 dBi as measured in a far-field anechoic chamber. Attempts were made to increase the frequency of operation but this proved unsuccessful. Also investigated were antennas that were designed to be integrated with a 5.8 GHz MMIC transceiver. The first antenna investigated was a compact-folded dipole, which provided an insight into miniaturisation of antennas and the effect on antenna efficiency. The second antenna investigated was a ‘patch’ antenna. The ‘patch’ antenna utilised the entire geometry of the transceiver as a radiation mechanism and, as a result, had a much improved gain compared to the compact-folded dipole antenna. As the entire transceiver was an antenna, an investigation was carried into the amount of power flow through the transceiver with respect to the input power

An Enhanced Fuselage Ultrasound Inspection Approach for ISHM Purposes

This effort constitutes a systems engineering approach in which the materials science, ultrasound structural health monitoring, flight and maintenance operations, and relevant aeronautical policies and programs are involved to explore the evolution and characterization of structural cracks in aircraft fuselage structures in which the loads are varying. During flight, an aircraft fuselage skin and structure are subjected to varied cyclic loads, which can cause embedded cracks and other damage features to change their characteristics due to loading effects. The current research is based in the application of finite element modeling techniques using COMSOL and PZFLEX software to characterize the behavior of a crack under static loads as well as experimental techniques to observe the behavior of cracks under different static loads, with the goal of understanding the interaction of ultrasonic energy with opening-closing crack features. Specimen testing under tensile loads were considered, where crack detection and crack characterization were studied for bonded piezoelectric sensing and guided ultrasonic waves useful in structural health monitoring applications. The results suggest that crack detection and crack sizing accuracy can be impacted by load-induced, crack opening-closure effects, where linear elastic loading of the structure resulted in linear changes in the ultrasonic signal response

A general architecture for robotic swarms

Swarms are large groups of simplistic individuals that collectively solve disproportionately complex tasks. Individual swarm agents are limited in perception, mechanically simple, have no global knowledge and are cheap, disposable and fallible. They rely exclusively on local observations and local communications. A swarm has no centralised control. These features are typifed by eusocial insects such as ants and termites, who construct nests, forage and build complex societies comprised of primitive agents. This project created the basis of a general swarm architecture for the control of insect-like robots. The Swarm Architecture is inspired by threshold models of insect behaviour and attempts to capture the salient features of the hive in a closely defined computer program that is hardware agnostic, swarm size indifferent and intended to be applicable to a wide range of swarm tasks. This was achieved by exploiting the inherent limitations of swarm agents. Individual insects were modelled as a machine capable only of perception, locomotion and manipulation. This approximation reduced behaviour primitives to a fixed tractable number and abstracted sensor interpretation. Cooperation was achieved through stigmergy and decisions made via a behaviour threshold model. The Architecture represents an advance on previous robotic swarms in its generality - swarm control software has often been tied to one task and robot configuration. The Architecture's exclusive focus on swarms, sets it apart from existing general cooperative systems, which are not usually explicitly swarm orientated. The Architecture was implemented successfully on both simulated and real-world swarms

Mobile Robots Navigation

Mobile robots navigation includes different interrelated activities: (i) perception, as obtaining and interpreting sensory information; (ii) exploration, as the strategy that guides the robot to select the next direction to go; (iii) mapping, involving the construction of a spatial representation by using the sensory information perceived; (iv) localization, as the strategy to estimate the robot position within the spatial map; (v) path planning, as the strategy to find a path towards a goal location being optimal or not; and (vi) path execution, where motor actions are determined and adapted to environmental changes. The book addresses those activities by integrating results from the research work of several authors all over the world. Research cases are documented in 32 chapters organized within 7 categories next described