Teodoro Aguilera

Electronic Nose Based on Independent Component Analysis Combined with Partial Least Squares and Artificial Neural Networks for Wine Prediction

The aim of this work is to propose an alternative way for wine classification and prediction based on an electronic nose (e-nose) combined with Independent Component Analysis (ICA) as a dimensionality reduction technique, Partial Least Squares (PLS) to predict sensorial descriptors and Artificial Neural Networks (ANNs) for classification purpose. A total of 26 wines from different regions, varieties and elaboration processes have been analyzed with an e-nose and tasted by a sensory panel. Successful results have been obtained in most cases for prediction and classification.

Acoustic local positioning system using an iOS device

This work benefits from the capability of the iPhones or iPads microphone to acquire high-frequency sound for accurate acoustic code identification. Although the maximum theoretical value for the frequency response of the built-in iOS device microphone is 20 kHz, emissions with frequencies close to 22 kHz have been experimentally detected. The frequencies used in this work are in the range from 18 to 22 kHz, which are high enough to be inaudible for almost every people but low enough to be generated by standard sound hardware. The aim of this work is to develop an inexpensive indoor positioning system where the user gets its location by using an iOS devices microphone. For this purpose a third-generation iPad is used for high-frequency sound data acquisition and neither external acquisition system nor ultrasonic microphone are required. The capability of iOS devices to acquire acoustic signals in the vicinity of 20 kHz has been successfully demonstrated. This fact allows the use of this kind of device for acoustic code detection and accurate positioning by means of multilateration.

Analysis of Doppler Effect on the Pulse Compression of Different Codes Emitted by an Ultrasonic LPS

This work analyses the effect of the receiver movement on the detection by pulse compression of different families of codes characterizing the emissions of an Ultrasonic Local Positioning System. Three families of codes have been compared: Kasami, Complementary Sets of Sequences and Loosely Synchronous, considering in all cases three different lengths close to 64, 256 and 1,024 bits. This comparison is first carried out by using a system model in order to obtain a set of results that are then experimentally validated with the help of an electric slider that provides radial speeds up to 2 m/s. The performance of the codes under analysis has been characterized by means of the auto-correlation and cross-correlation bounds. The results derived from this study should be of interest to anyone performing matched filtering of ultrasonic signals with a moving emitter/receiver.

Analysis of the performance of an Ultrasonic Local Positioning System based on the emission of Kasami codes

This work presents the performance analysis of an Ultrasonic Local Positioning System (ULPS). The system is composed of four beacons, forming a square structure in the ceiling of a rectangular room, that emit orthogonal Kasami codes BPSK modulated with a carrier frequency of 50 kHz. These emissions are detected by the receiver by pulse compression, giving the system high precision and robustness to noise. A complete model of the system has been built to conduct this study, considering effects such as the ultrasonic transducers response, signal attenuation in air, multipath propagation, reflection coefficient of walls and floor and receiver response. This model helps to identify critical zones where the self-induced noise generated in the cross-correlations masks the main peaks of the auto-correlations, making it difficult to obtain reliable Time-of-Flights from which the receivers position is determined. Also, the dependence of these critical zones with different parameters integrated in the model is investigated.

CDMA-based acoustic local positioning system for portable devices with multipath cancellation

Abstract This paper presents an acoustic local positioning system (ALPS) suitable for indoor positioning of portable devices such as smartphones or tablets, based on the transmission of high frequency CDMA-coded signals from a fixed network of beacons. The main novelty of the proposed ALPS is its capability to mitigate the effects of multipath propagation by performing an accurate estimation of the Line-of-Sight Time-of-Flights (LOS-TOF) through the Matching Pursuit algorithm. Signal detection, multipath cancellation and positioning estimation all take place within the portable device, which provides a graphical representation of the updated position in less than a second. The performance of the Matching Pursuit algorithm is analyzed in a real scenario and the results show that the proposed method is capable to retrieve the multipath-free System Availability under strong multipath conditions with SNR levels as low as 0 dB.

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

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.

Characterization of the Near-Far problem in a CDMA-based acoustic localization system

In this work the Near-Far problem is characterized in the context of an acoustic local positioning system (ALPS). First, a simple energy normalization algorithm is presented to identify the Near-Far situation and also to resolve the signal detection in the case of non-overlapping receptions. Then, an improved signal interference cancellation (ISIC) algorithm is proposed to remove from the received signal most of the energy of the most powerful reception in case of overlapping receptions, thus allowing the detection of weaker signals. The performance of these algorithms has been first studied by simulating the behaviour of an ALPS with four beacons emitting BPSK-modulated Kasami codes installed in a rectangular anechoic chamber. The same study has been later conducted with signals acquired in a real scenario, using a third-generation iPad as the mobile node of the ALPS.

New pseudo-orthogonal family of polyphase codes to improve Doppler resilience

Ultrasonic positioning systems presents performance problems when the object to be localized is in movement. The reasons are the degradation suffered by emitted sequences because of Doppler shifts, and the low level of orthogonality of the set of codes when they are being identified in different beacons. In this work, a search of a set of four 256-element polyphase sequences has been carried out, in order to improve the resilience to velocity possessed by other well-known codes, maintaining good orthogonality properties. As result, the obtained set can be used in an ultrasonic Local Positioning System (LPS), where the codes can be detected up to 1.5 m/s.

Acoustic Local Positioning With Encoded Emission Beacons

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.

Performance improvement of an ultrasonic LPS by applying a multipath compensation algorithm

This work presents an algorithm to improve the estimation of the position in indoor environments when using an Ultrasonic Local Positioning System (ULPS). This system is composed of several beacons, with an encoded transmission based on 255-bits Kasami sequences and a BPSK modulation. The received ultrasonic signals are processed to determine the time of arrival (ToA) for every beacon. The differences in times of arrival allow the estimation of the receiver position by means of an hyperbolic positioning algorithm. Nevertheless, in some environments, the determination of ToAs is strongly affected by non-desired effects, such as multipath. This multipath effect often implies a degradation in the correlation properties, thus providing a loss of accuracy in the final position estimation. The proposed algorithm tries to determine the ToA related to the direct path of the ultrasonic transmissions, in order to reduce the corresponding error in the later position estimation of the receiver. Experimental results have shown the feasibility of the approach.