Visible light positioning system based on a quadrant photodiode and encoding techniques

Visible light positioning systems (VLPSs) are a feasible alternative to local positioning systems due to the technology improvement and massive use of light-emitting diodes (LEDs). Compared to other technologies, VLPSs can provide significant advantages, such as the achieved accuracy, although they still present some issues, mainly related to the reduced coverage area or the high computational load. This article proposes the design of a VLPS based on four LED lamps as transmitters and a quadrant photodiode angular diversity aperture (QADA) as a receiver. As the shape of the QADA is circular and the aperture to be installed over it is square, we derive the corresponding general equations to obtain the currents through the different pads of the QADA, regarding the angle of incidence of the light (and, inversely, how to estimate the angle of incidence from the measured currents). An encoding scheme based on 1023-bit Kasami sequences is proposed for every transmission from the LED lamps, thus providing multiple access capability and robustness against low signal-to-noise ratios and harsh conditions, such as multipath and near-far effect. A triangulation technique has been applied to estimate the receiver's position, by means of the least-squares estimator (LSE), together with some geometrical considerations. The proposal has been validated by simulation and by experimental tests, obtaining 3-D positioning average errors below 13 and 5.5 cm for separations between the transmitters' plane and the receiver of 2 and 1 m, respectively

Combined infrared-ultrasonic positioning system to improve the data availability

Many indoor positioning applications related to accurate monitoring and tracking targets require centimeter precision. Infrared (IR)- and ultrasound (US)-based systems represent a feasible approach providing high robustness against interference. Furthermore, their combination may achieve better performance by mitigating their complementary drawbacks, covering larger areas, and improving the availability of positioning measurements. In this context, this work presents the proposal and experimental evaluation of a tightly coupled fusion method that uses an extended Kalman filter (EKF) to merge an IR- and a US-based positioning system. An outlier detection method is considered to select measurements with an adequate performance. Experimental results reveal that the IR and US systems are unable to position in 4.08% and 26.06% of locations, whereas the combined IR -US system has 100% of availability. In addition, the merged solution achieves less than 4 cm of positioning error in 90% of cases, outperforming the IR and US systems when they work independently

3D indoor positioning of UAVs with spread spectrum ultrasound and time-of-flight cameras

Este trabajo propone el uso de un sistema híbrido de posicionamiento acústico y óptico en interiores para el posicionamiento 3D preciso de los vehículos aéreos no tripulados (UAV). El módulo acústico de este sistema se basa en un esquema de Acceso Múltiple por División de Código de Tiempo (T-CDMA), en el que la emisión secuencial de cinco códigos ultrasónicos de espectro amplio se realiza para calcular la posición horizontal del vehículo siguiendo un procedimiento de multilateración 2D. El módulo óptico se basa en una cámara de Tiempo de Vuelo (TOF) que proporciona una estimación inicial de la altura del vehículo. A continuación se propone un algoritmo recursivo programado en un ordenador externo para refinar la posición estimada. Los resultados experimentales muestran que el sistema propuesto puede aumentar la precisión de un sistema exclusivamente acústico en un 70-80% en términos de error cuadrático medio de posicionamiento.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.• Gobierno de España y Fondos para el Desarrollo Regional Europeo. Proyectos TARSIUS (TIN2015-71564-C4-4-R) (I+D+i), REPNIN (TEC2015-71426-REDT) y SOC-PLC (TEC2015-64835-C3-2-R) (I+D+i) • Junta de Extremadura, Fondos FEDER y Fondo Social Europeo. Proyecto GR15167 y beca predoctoral 45/2016 Exp. PD16030peerReviewe

Evaluation of Multi-Sensor Fusion Methods for Ultrasonic Indoor Positioning

Indoor positioning systems have become a feasible solution for the current development of multiple location-based services and applications. They often consist of deploying a certain set of beacons in the environment to create a coverage volume, wherein some receivers, such as robots, drones or smart devices, can move while estimating their own position. Their final accuracy and performance mainly depend on several factors: the workspace size and its nature, the technologies involved (Wi-Fi, ultrasound, light, RF), etc. This work evaluates a 3D ultrasonic local positioning system (3D-ULPS) based on three independent ULPSs installed at specific positions to cover almost all the workspace and position mobile ultrasonic receivers in the environment. Because the proposal deals with numerous ultrasonic emitters, it is possible to determine different time differences of arrival (TDOA) between them and the receiver. In that context, the selection of a suitable fusion method to merge all this information into a final position estimate is a key aspect of the proposal. A linear Kalman filter (LKF) and an adaptive Kalman filter (AKF) are proposed in that regard for a loosely coupled approach, where the positions obtained from each ULPS are merged together. On the other hand, as a tightly coupled method, an extended Kalman filter (EKF) is also applied to merge the raw measurements from all the ULPSs into a final position estimate. Simulations and experimental tests were carried out and validated both approaches, thus providing average errors in the centimetre range for the EKF version, in contrast to errors up to the meter range from the independent (not merged) ULPSs.Agencia Estatal de InvestigaciónUniversidad de Alcal

Estimation of the polar angle in a 3D infrared indoor positioning system based on a QADA receiver

2019 International Conference on Indoor Positioning and Indoor Navigation (IPIN), 30 September 2019 - 03 October 2019, Pisa, Italy.Three-dimension infrared positioning systems are a must on indoor local positioning systems, where those based on photodetectors are the most typically used in order not to have complex processing algorithms but a fast positioning computation. Most optical positioning systems are characterized by their low cost, low lifetime, and easy integration on the workplace. This work proposes an infrared positioning system based on four infrared LEDs and a QADA receiver. By applying encoding techniques to the infrared transmissions, the points of incidence from those transmitters on the QADA receiver are simultaneously obtained and the polar angle compensated, in order to finally estimate the receiver?s position. The geometrical considerations of the system have been derived, including the polar angle and its behaviour with regard to the receiver?s position, the angle of incidence and the aperture height. The proposal has been successfully validated by simulation and experimental tests, obtaining positioning errors below 10 cm.Ministerio de Economía y CompetitividadAgencia Estatal de Investigació

Implementation of a High Measurement Rate VLP System

redOptical positioning systems have raised interest in recent years, due to the centimeter accuracy in three-dimension environments they are able to provide, thanks to the use of light emitting diodes (LED) and diode photoreceptors. This work is based on the design and implementation of the signal processing algorithms for an optical indoor positioning system. It is configured using some LED beacons placed at known positions and the corresponding receivers to be positioned moving in the coverage area. The definition and design of the hardware architecture for the processing associated to the receiver, for the case of a Quadrant Photodiode Angular Diversity Aperture (QADA) detector is proposed, analyzing different aspects involved in the final performance, such as the fixed-point notation used in the hardware definition. Furthermore, the implementation of the proposal includes an analog conditioning stage, an acquisition system, as well as a FPGA-based (Field-Programmable Gate Array) System-on-Chip (SoC) for implementing the necessary hardware and software elements, required to estimate the final position coordinates of the QADA receiver. In addition to the description of the positioning system and all its stages, some preliminary experimental tests are also shown, including position estimation for two specific locations, achieving the validation of a processing system associated with indoor positioning systems capable of handling high data rates (in the range of Msps)

Review of UAV positioning in indoor environments and new proposal based on US measurements

Este documento se considera que es una ponencia de congresos en lugar de un capítulo de libro.10th International Conference on Indoor Positioning and Indoor Navigation (IPIN 2019) Pisa, Italy, September 30th - October 3rd, 2019The use of unmanned aerial vehicles (UAVs) has increased dramatically in recent years because of their huge potential in both civil and military applications and the decrease in prize of UAVs products. Location detection can be implemented through GNSS technology in outdoor environments, nevertheless its accuracy could be insufficient for some applications. Usability of GNSS in indoor environments is limited due to the signal attenuation as it cross through walls or the absence of line of sight. Considering the big market opportunity of indoor UAVs many researchers are devoting their efforts in the exploration of solutions for their positioning. Indoor UAV applications include location based services (LBS), advertisement, ambient assisted living environments or emergency response. This work is an update survey in UAV indoor localization, so it can provide a guide and technical comparison perspective of different technologies with their main advantages and drawbacks. Finally, we propose an approach based on an ultrasonic local positioning system.Universidad de AlcaláJunta de Comunidades de Castilla-La ManchaMinisterio de Economía, Industria y Competitivida

High-rate acquisition system for an infrared LPS

2023 38th Conference on Design of Circuits and Integrated Systems (DCIS), 15-17 November 2023, Málaga, Spain.In the last years, the demand for positioning systems based on visible light, infrared light or, in general, optical signals has increased considerably due to their high accuracy and low cost compared to positioning systems based on other technologies, as well as their ease of integration due to their wide presence in domestic and industrial environments. The main constraint of these solutions is that the high speed of light makes the acquisition process complex. This work proposes a complete acquisition architecture for the twelve signals coming from four QADA (Quadrature Angular Diversity Aperture) photoreceptors, based on an analog front-end for signal conditioning at the input, an analog-to-digital converter, and a final digital stage using an FPGA for the acquisition of the data coming from the converter with high data rates up to 16.25 Msps. To verify the system performance, LS (Loosely Synchronized) sequences, often used in positioning systems, are emitted by a LED, and, later, they are acquired and digitally processed successfully by the proposed architecture in some preliminary experimental tests.Agencia Estatal de InvestigaciónUniversidad de AlcaláJunta de Comunidades de Castilla-La ManchaEuropean Science Foundatio

Detecting relative amplitude of IR signals with active sensors and its application to a positioning system

Nowadays, there is an increasing interest in smart systems, e.g., smart metering or smart spaces, for which active sensing plays an important role. In such systems, the sample or environment to be measured is irradiated with a signal (acoustic, infrared, radio‐frequency…) and some of their features are determined from the transmitted or reflected part of the original signal. In this work, infrared (IR) signals are emitted from different sources (four in this case) and received by a unique quadrature angular diversity aperture (QADA) sensor. A code division multiple access (CDMA) technique is used to deal with the simultaneous transmission of all the signals and their separation (depending on the source) at the receiver’s processing stage. Furthermore, the use of correlation techniques allows the receiver to determine the amount of energy received from each transmitter, by quantifying the main correlation peaks. This technique can be used in any system requiring active sensing; in the particular case of the IR positioning system presented here, the relative amplitudes of those peaks are used to determine the central incidence point of the light from each emitter on the QADA. The proposal tackles the typical phenomena, such as distortions caused by the transducer impulse response, the near‐far effect in CDMA‐based systems, multipath transmissions, the correlation degradation from non‐coherent demodulations, etc. Finally, for each emitter, the angle of incidence on the QADA receiveris estimated, assuming that it is on a horizontal plane, although with any rotation on the vertical axis Z. With the estimated angles and the known positions of the LED emitters, the position (x, y, z) of the receiver is determined. The system is validated at different positions in a volume of 3 × 3 × 3.4 m3 obtaining average errors of 7.1, 5.4, and 47.3 cm in the X, Y and Z axes, respectively.Agencia Estatal de InvestigaciónUniversidad de AlcaláJunta de Comunidades de Castilla-La Manch

Evaluating Human Activity and Usage Patterns of Appliances with Smart Meters

2022 IEEE International Symposium on Medical Measurements and Applications (MeMeA), 22-24 June 2022, Messina, Italy.Population ageing is becoming a key issue for most western countries, due to the challenges that it poses to the sustainability of future healthcare systems. In this context, many proposals and development are emerging trying to enhance the independent living of elderly and cognitive impaired people at their own homes. For that purpose, the massive deployment of smart meter at houses and buildings, initially focused on improving the energy management, has become a useful tool to provide the society with a variety of services and applications that can be employed for independent living. This work proposes the use of a commercial smart meter that delivers the disaggregated consumption per appliance every hour. This device has been installed on a test house during a training period of two months, in order to infer the behavior routines in the usage of the microwave. After the training, every new day can be compared to the obtained usage pattern of that appliance, in order to launch a notification when the day routine significantly differs. Similarly, since the use of the microwave is related to cooking, activities such as breakfast, lunch or dinner, may also be monitored and/or compared to a trained pattern. The proposal has been validated preliminary with experimental data coming from the aforementioned household.Agencia Estatal de InvestigaciónUniversidad de Alcal