The purpose of this paper is to provide a comprehensive presentation and interpretation of the Ensemble Kalman Filter (EnKF) and its numerical implementation. The EnKF has a large user group, and numerous publications have discussed applications and theoretical aspects of it. This paper reviews the important results from these studies and also presents new ideas and alternative interpretations which further explain the success of the EnKF. In addition to providing the theoretical framework needed for using the EnKF, there is also a focus on the algorithmic formulation and optimal numerical implementation. A program listing is given for some of the key subroutines. The paper also touches upon specific issues such as the use of nonlinear measurements, in situ profiles of temperature and salinity, and data which are available with high frequency in time. An ensemble based optimal interpolation (EnOI) scheme is presented as a cost-effective approach which may serve as an alternative to the EnKF in some applications. A fairly extensive discussion is devoted to the use of time correlated model errors and the estimation of model bias.

The Ensemble Kalman Filter: Theoretical formulation and practical implementation

Theory of Equations. By J. V. Uspensky. Pp. vii, 353. 27s. 1948. (McGraw-Hill)

Path planning techniques for unmanned aerial vehicles: A review, solutions, and challenges

Visual inspection has traditionally been used for structural health monitoring. However, assessments conducted by trained inspectors or using contact sensors on structures for monitoring a...

Autonomous UAVs for Structural Health Monitoring Using Deep Learning and an Ultrasonic Beacon System with Geo‐Tagging

Technology has become ubiquitous, it is all around us and is becoming part of us. Togetherwith the rise of the Internet of Things (IoT) paradigm and enabling technologies (e.g., Augmented Reality (AR), Cyber-Physical Systems, Artificial Intelligence (AI), blockchain or edge computing), smart wearables and IoT-based garments can potentially have a lot of influence by harmonizing functionality and the delight created by fashion. Thus, smart clothes look for a balance among fashion, engineering, interaction, user experience, cybersecurity, design and science to reinvent technologies that can anticipate needs and desires. Nowadays, the rapid convergence of textile and electronics is enabling the seamless and massive integration of sensors into textiles and the development of conductive yarn. The potential of smart fabrics, which can communicate with smartphones to process biometric information such as heart rate, temperature, breathing, stress, movement, acceleration, or even hormone levels, promises a new era for retail. This article reviews the main requirements for developing smart IoT-enabled garments and shows smart clothing potential impact on business models in the medium-term. Specifically, a global IoT architecture is proposed, the main types and components of smart IoT wearables and garments are presented, their main requirements are analyzed and some of the most recent smart clothing applications are studied. In this way, this article reviews the past and present of smart garments in order to provide guidelines for the future developers of a network where garments will be connected like other IoT objects: the Internet of Smart Clothing.

https://www.mdpi.com/2079-9292/7/12/405/pdf

Towards The Internet of Smart Clothing: A Review on IoT Wearables and Garments for Creating Intelligent Connected E-Textiles

This work proposes the use of a hybrid acoustic and optical indoor positioning system for the accurate 3D positioning of Unmanned Aerial Vehicles (UAVs). The acoustic module of this system is based on a Time-Code Division Multiple Access (T-CDMA) scheme, where the sequential emission of five spread spectrum ultrasonic codes is performed to compute the horizontal vehicle position following a 2D multilateration procedure. The optical module is based on a Time-Of-Flight (TOF) camera that provides an initial estimation for the vehicle height. A recursive algorithm programmed on an external computer is then proposed to refine the estimated position. Experimental results show that the proposed system can increase the accuracy of a solely acoustic system by 70–80% in terms of positioning mean square error.

3D Indoor Positioning of UAVs with Spread Spectrum Ultrasound and Time-of-Flight Cameras.

Advanced sensorial system for an acoustic LPS

Acoustic local positioning systems (ALPSs) are an interesting alternative for indoor positioning due to certain advantages over other approaches, including their relatively high accuracy, low cost, and room-level signal propagation. Centimeter-level or fine-grained indoor positioning can be an asset for robot navigation, guiding a person to, for instance, a particular piece in a museum or to a specific product in a shop, targeted advertising, or augmented reality. In airborne system applications, acoustic positioning can be based on using opportunistic signals or sounds produced by the person or object to be located (e.g., noise from appliances or the speech from a speaker) or from encoded emission beacons (or anchors) specifically designed for this purpose. This work presents a review of the different challenges that designers of systems based on encoded emission beacons must address in order to achieve suitable performance. At low-level processing, the waveform design (coding and modulation) and the processing of the received signal are key factors to address such drawbacks as multipath propagation, multiple-access interference, near–far effect, or Doppler shifting. With regards to high-level system design, the issues to be addressed are related to the distribution of beacons, ease of deployment, and calibration and positioning algorithms, including the possible fusion of information obtained from maps and onboard sensors. Apart from theoretical discussions, this work also includes the description of an ALPS that was implemented, installed in a large area and tested for mobile robot navigation. In addition to practical interest for real applications, airborne ALPSs can also be used as an excellent platform to test complex algorithms (taking advantage of the low sampling frequency required), which can be subsequently adapted for other positioning systems, such as underwater acoustic systems or ultrawideband radio-frequency (UWB RF) systems.

Acoustic Local Positioning With Encoded Emission Beacons

The present work shows a local positioning system (LPS) for mobile robots (MR) using simultaneous emissions in the ultrasonic beacons. In order to solve the problem of the simultaneous emission of the ultrasonic beacons, the well-known technique called direct sequence code division multiple access (DS-CDMA) is used. This technique modulates the ultrasonic signal (50 kHz) with a 127-bit Gold code for even beacon. In this way, it is possible to detect the arrival time of the code, by earning out the simultaneous correlations with the assigned codes to each beacon. For determining the absolute position, the triangulation technique uses the time difference-of-arrival (TDOA) obtained between a reference beacon and the others. Using this method, certain errors, derived from the delay in the firing of the beacons and the response times of the ultrasonic transducers, are avoided. The existence of a synchronism in the emission of the beacons, that guarantees a periodic and simultaneous emission in all of them, is required, not being necessary to know the emission instant in the mobile robot. This is particularly useful in environments where several robots can coexist

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Iimprovement of ultrasonic beacon-based local position system using multi-access techniques

This work describes the design of a ultrasonic local positioning system (ULPS) with large covered area. The beacons have been designed with a cylindrical PVDF transducer (piezofilm transducer) to which a conical reflector has been connected to enlarge the covered area and to guarantee 3D indoor positioning. The proposed ULPS for mobile robots (MR) uses simultaneous emissions from ultrasonic beacons. In order to solve the problem of simultaneous emissions from ultrasonic beacons, the well-known technique, direct sequence code multiple division access (DS-CDMA), is used. This technique encodes the ultrasonic signal with a 255-bit Kasami code for every beacon. It implies the emitted signal by every beacon to have a wide bandwidth. PVDF-based transducers suitably guarantee this requirement. Their cylindrical or semi-cylindrical shape makes the emission pattern not suitable when using them as ultrasonic beacons, often located in the ceiling of an indoor room. To adapt the emission pattern and to increase the covered area in the ground, the design process of a conical reflector is described.

J.M. Villadangos

Papers

3D Indoor Positioning of UAVs with Spread Spectrum Ultrasound and Time-of-Flight Cameras.

Advanced sensorial system for an acoustic LPS

Acoustic Local Positioning With Encoded Emission Beacons

Iimprovement of ultrasonic beacon-based local position system using multi-access techniques

Ultrasonic Local Positioning System with Large Covered Area