Examinando por Autor "Gualda, David"

Mostrando 1 - 7 de 7

Acoustic Local Positioning With Encoded Emission Beacons
(IEEE, 2018-05-07) Ureña, Jesús; Hernández, Álvaro; García, Juan Jesús; Villadangos, José Manuel; Pérez, María del Carmen; Gualda, David; Álvarez, Fernando; Aguilera, Teodoro
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, nearfar 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 radiofrequency (UWB RF) systems.
Calibration of Beacons for Indoor Environments based on a Digital Map and Heuristic Information
(MDPI, 2019-02-06) Gualda, David; Ureña, Jesús; Alcalá, José; Santos, Carlos
This paper proposes an algorithm for calibrating the position of beacons which are placed on the ceiling of an indoor environment. In this context, the term calibration is used to estimate the position coordinates of a beacon related to a known reference system in a map. The positions of a set of beacons are used for indoor positioning purposes. The operation of the beacons can be based on different technologies such as radiofrequency (RF), infrared (IR) or ultrasound (US), among others. In this case we are interested in the positions of several beacons that compose an Ultrasonic Local Positioning System (ULPS) placed on different strategic points of the building. The calibration proposal uses several distances from a beacon to the neighbor walls measured by a laser meter. These measured distances, the map of the building in a vector format and other heuristic data (such as the region in which the beacon is located, the approximate orientation of the distance measurements to the walls and the equations in the map coordinate system of the line defining these walls) are the inputs of the proposed algorithm. The output is the best estimation of the position of the beacon. The process is repeated for all the beacons. To find the best estimation of the position of the beacons we have implemented a numerical minimization based on the use of a Genetic Algorithm (GA) and a Harmony Search (HS) methods. The proposal has been validated with simulations and real experiments, obtaining the positions of the beacons and an estimation of the error associated that depends on which walls (and the angle of incidence of the laser) are selected to make the distance measurements.
Design of a complete simulator for underwater acoustic localization systems based on spread-spectrum signals
(Elsevier, 2022-10) Murano, Santiago; Pérez, María del Carmen; Aparicio, Joaquín; Gualda, David; de Vicente, Jorge; Hernández, Álvaro
Deploying prototype positioning systems in underwater environments is expensive and an especially challenging task, so a first common approach is to carry out simulated studies to evaluate the requirements and restrictions imposed by the environment. In this regard, it is helpful to have simulation models that allow the generation of a wide range of tests as a previous step to any experimental prototype implementation. For that purpose, this work focuses on the design of a simulation tool that facilitates research on underwater positioning systems by considering several parameters and features, such as the design of the signals emitted by the acoustic transducers (encoding techniques, modulation schemes, etc.), the frequency response and location of emitters and hydrophones, the bathymetry of the seabed, and the channel effects on the ultrasonic signal propagation, implemented in a model based on ray tracing for the propagation of acoustic signals. The simulation tool has been validated through a complete set of tests for different configurations and situations, analyzing the signals involved at different processing stages: baseband, modulated signals, received signals, and final estimated positions. This simulation tool is a valuable asset to research different positioning system configurations or to illustrate several concepts in a pedagogical context.
Evaluation of Zadoff-Chu, Kasami and Chirp based encoding schemes for Acoustic Local Positioning Systems
(IEEE, 2019-12-13) Murano, Santiago; Pérez, María del Carmen; Gualda, David; Álvarez, Fernando
The task of determining the physical coordinates of a target in indoor environments is still a key factor for many applications including people and robot navigation, user tracking, location-based advertising, augmented reality, gaming, emergency response or ambient assisted living environments. Among the different possibilities for indoor positioning, Acoustic Local Positioning Systems (ALPS) have the potential for centimeter level positioning accuracy with coverage distances up to tens of meters. In addition, acoustic transducers are small, low cost and reliable thanks to the room constrained propagation of these mechanical waves. Waveform design (coding and modulation) is usually incorporated into these systems to facilitate the detection of the transmitted signals at the receiver. The aperiodic correlation properties of the emitted signals have a large impact on how the ALPS cope with common impairment factors such as multipath propagation, multiple access interference, Doppler shifting, near-far effect or ambient noise. This work analyzes three of the most promising families of codes found in the literature for ALPS: Kasami codes, Zadoff-Chu and Orthogonal Chirp signals. The performance of these codes is evaluated in terms of time of arrival accuracy and characterized by means of model simulation under realistic conditions and by means of experimental tests in controlled environments. The results derived from this study can be of interest for other applications based on spreading sequences, such as underwater acoustic systems, ultrasonic imaging or even Code Division Multiple Access (CDMA) communications systems.
LOCATE‐US: Indoor Positioning for Mobile Devices Using Encoded Ultrasonic Signals, Inertial Sensors and Graph‐Matching
(MDPI, 2021-03-10) Gualda, David; Pérez, María del Carmen; Ureña, Jesús; Pérez, Sergio; Villadangos, José Manuel; Hernández, Álvaro; García, Juan Jesús; Jiménez, Ana
Indoor positioning remains a challenge and, despite much research and development carried out in the last decade, there is still no standard as with the Global Navigation Satellite Systems (GNSS) outdoors. This paper presents an indoor positioning system called LOCATE-US with adjustable granularity for use with commercial mobile devices, such as smartphones or tablets. LOCATE-US is privacy-oriented and allows every device to compute its own position by fusing ultrasonic, inertial sensor measurements and map information. Ultrasonic Local Positioning Systems (U-LPS) based on encoded signals are placed in critical zones that require an accuracy below a few decimeters to correct the accumulated drift errors of the inertial measurements. These systems are well suited to work at room level as walls confine acoustic waves inside. To avoid audible artifacts, the U-LPS emission is set at 41.67 kHz, and an ultrasonic acquisition module with reduced dimensions is attached to the mobile device through the USB port to capture signals. Processing in the mobile device involves an improved Time Differences of Arrival (TDOA) estimation that is fused with the measurements from an external inertial sensor to obtain real-time location and trajectory display at a 10 Hz rate. Graph-matching has also been included, considering available prior knowledge about the navigation scenario. This kind of device is an adequate platform for Location-Based Services (LBS), enabling applications such as augmented reality, guiding applications, or people monitoring and assistance. The system architecture can easily incorporate new sensors in the future, such as UWB, RFiD or others.
Multipath Compensation Algorithm for TDMA-Based Ultrasonic Local Positioning Systems
(IEEE, 2018-02-19) Aguilera, Teodoro; Álvarez, Fernando; Gualda, David; Villadangos, José Manuel; Hernández, Álvaro; Ureña, Jesús
This paper proposes a multipath compensation algorithm (MCA) to enhance the performance of an ultrasonic local positioning system under adverse multipath conditions. The proposed algorithm is based on the accurate estimation of the environment impulse response from which the corresponding line of sight for each channel is obtained. Experimental results in two different environments and with different conditions have been conducted in order to evaluate the performance of this proposal. In both environments, results confirm the expected improvements, even under severe multipath conditions where positioning errors have been reduced from 44 to 9 cm for the 95% of the measurements.
Simultaneous calibration and navigation (SCAN) of multiple ultrasonic local positioning systems
(Elsevier, 2018-01-06) Gualda, David; Ureña, Jesús; García, Juan Carlos; Alcalá, José
This paper proposes a Simultaneous Calibration and Navigation (SCAN) algorithm of a multiple Ultrasonic Local Positioning Systems (ULPSs) that cover an extensive indoor area. The idea is the development of the same concept than SLAM (Simultaneous Localization and Mapping), in which a Mobile Robot (MR) estimates the map while it is navigating. In our approach, the MR calibrates the beacons of several ULPSs while it is moving inside the localization area. The concept of calibration is the estimation of the position of the beacons referenced to a known map. The scenario is composed of some calibrated ULPSs that we denote as Globally Referenced Ultrasonic Local Positioning Systems (GRULPSs) that are located in strategic points like entrances covering the start and the end of a possible trajectory in the environment. Additionally, there are several non-calibrated ULPSs named Locally Referenced Ultrasonic Local Positioning Systems (LRULPSs) that are placed around the localization area. The proposal uses a MR with odometer for calibrating the beacons of the LRULPSs while it is navigating on their coverage area and go from one GRULPS to another. The algorithm is based on multiple filters running in parallel (one filter for each LRULPS and another one for the GRULPSs) that estimate the global and local trajectories of the MR (one trajectory for each local reference system of the LRULPSs) fusing the information related to the Ultrasound Signals (US) and the odometer of the MR. The position of the beacons of the LRULPSs are obtained by a transformation vector for each LRULPS that converts the local coordinates to the global reference system. This transformation vector is calculated using several points of a local trajectory and the corresponding points of the global one. The method is independent of the type of filter, provided that it works properly with non-linear systems and possibly non-Gaussian noise. Extended Kalman Filter (EKF), Unscented Kalman Filter (UKF) and H-∞ Filter have been tested, in simulations and real experiments, in order to compare their performance in this case.