Jesús Ureña

Integral system for assisted mobility

Abstract This paper presents the results of a research work carried out in the Electronics Department of the University of Alcala in the field of electronic systems for the guidance of wheelchairs for the disabled and/or the elderly. These electronic systems have been designed to meet a wide range of needs experienced by users of this type of wheelchair. One of their most important features is their modularity, thereby making them adaptable to the particular needs of each user according to the type and degree of handicap involved. The overall system includes a complete user–machine interface, motor control modules and safety and autonomous guidance systems. The project is called: “Sistema Integral de Ayuda a la Movilidad (SIAMO)” (integral system for assisted mobility).

Ultrasonic ranging sensor using simultaneous emissions from different transducers

In recent applications based on ultrasound, several ultrasonic transducers have been geometrically and electronically associated to constitute a global sensor. There are several different methods used to process the ultrasonic signals obtained from these transducers. In this work, multimode techniques using Golay complementary sequences are proposed for processing the ultrasonic signal. The system increases scan rate, precision, and reliability. It is also capable of echo discrimination, allowing simultaneous measurements to be made and detection of the same obstacle by different transducers without cross-talk problems. The real-time implementation of the algorithm is presented on a field-programmable gate array (FPGA) device.

Modular Architecture for Efficient Generation and Correlation of Complementary Set of Sequences

Golay sequences and complementary sets of sequences have been long studied for their application in multisensor and communication systems. The feasibility of these systems strongly depends on the design of an efficient generator and correlator with the aim of reducing the computational load and hardware complexity. Recursive algorithms, which allow efficient architectures, are available in the case of complementary pairs of sequences and complementary sets of four sequences. This work presents a generalization of these algorithms with the purpose of obtaining complementary sets of M sequences with length L, the number of sequences M being a power of two (M=2m), and the length L a power of M (L=2mN) with m,Nisin N-{0}. This fact allows an ideal Kroumlnecker delta function of weight MmiddotL in the addition of the autocorrelation functions of the M sequences of the set. Furthermore, the generation of M different mutually orthogonal sets can be obtained. This fact makes their application suitable in simultaneous multiemission systems. With the proposed algorithm, an effective reduction in the number of operations necessary to implement the correlator can be obtained, if it is compared with the straightforward implementation. Also, a regular structure is provided that allows implementation of the generator and/or the correlator for complementary sets of M sequences, based on the structure for complementary sets of M/2 sequences The sequence length can also be easily extended to any multiple of M. Finally, the generation and correlation of M different mutually orthogonal complementary sets of M sequences can be immediately derived

Wheelchair for physically disabled people with voice, ultrasonic and infrared sensor control

This paper describes a wheelchair for physically disabled people developed within the UMIDAM Project. A dependent-user recognition voice system and ultrasonic and infrared sensor systems has been integrated in this wheelchair. In this way we have obtained a wheelchair which can be driven with using voice commands and with the possibility of avoiding obstacles and downstairs or hole detection. The wheelchair has also been developed to allow autonomous driving (for example, following walls). The project, in which two prototypes have been produced, has been carried out totally in the Electronics Department of the University of Alcalá (Spain). It has been financed by the ONCE. Electronic system configuration, a sensor system, a mechanical model, control (low level control, control by voice commands), voice recognition and autonomous control are considered. The results of the experiments carried out on the two prototypes are also given.

Correlation detector based on a FPGA for ultrasonic sensors

In the field of mobile robots ever more frequent use is being made of ultrasonic sensors composed of several transducers carrying out readings simultaneously and in a coordinated way. These sensors can read not only the distances but also listening angles, and they can also determine the reflector type (i.e. edge, plane or corner). To this end it is especially important that, after each emission of a pulse of ultrasound, each transducer can accurately detect the arrival of the echoes (providing accurate time-of-flight (TOF) readings). Another desirable feature is that the transducers be capable of discriminating between the echoes of simultaneous emissions (avoiding problems of crosstalk). This article describes the design and development of a correlation detector (implemented on a low-cost electronic system) allowing for both functions. q 1999 Elsevier Science B.V. All rights reserved.

Using Golay complementary sequences for multi-mode ultrasonic operation

In many of the recent array ultrasonic applications, acquisition rate is a crucial issue. Many of those applications are even impractical due to the sequential nature of ultrasound systems scanning. Obviously, one way of increasing this rate is the use of multi-mode operation. This paper introduces the basic aspects of multi-mode ultrasonic operation based on pulse compression techniques by means of binary sequences in a BPSK modulation scheme, and the advantages of Golay sequences, in multi-mode operation with respect to m-sequences, mostly used in recent works. Finally, some results of simulations using four modes simultaneously and a hardware architecture for testing these results are shown.

Electronic control of a wheelchair guided by voice commands

Abstract This paper describes the control of an electric wheel chair with voice commands. This chair has been developed and built at the U.A.H. Electronic Department and financed by the ONCE Foundation (Spain). The first prototype consists of voice recognition, motor control, user interface and central processor modules. The electronic system allows the chair user a safe, easy ride, and guarantees the concordance between user commands and actual trajectories. Furthermore, the system has been designed to allow the addition of future features, like obstacle and stair detection and the tele-commanding of electrical household appliances from the chair.

Using PCA in time-of-flight vectors for reflector recognition and 3-D localization

This paper presents a reflector recognition and localization technique in three-dimensional (3-D) environments, using only times-of-flight (TOFs) data obtained from ultrasonic transducers. The recognition and localization technique is based on the principal component analysis applied to the TOF vectors originating from a sensor that contains two emitting transducers and several receivers. The two emitters simultaneously transmit two coded pulses that are detected later on and discriminated by the receivers, after being reflected in the environment. The proposed technique allows for the possibility of not only recognizing the reflectors, but also estimating approximately its localization referred to the sensor. This technique has been tested with three types of reflectors in 3-D environments: planes, edges, and corners. The achieved results are very satisfactory for reflectors located in the range 50-350 cm.

Real-time implementation of an efficient Golay correlator (EGC) applied to ultrasonic sensorial systems

Abstract Multi-mode techniques reduce scanning times in ultrasonic systems, as they allow transducers in a sensor to simultaneously emit and receive without interference. In order to implement these techniques, it is necessary to encode each transducers emission. The use of orthogonal pairs of Golay sequences associated with different emitters avoids crosstalk among them. However, these sequences imply an increase in the computational complexity required in the receiver. This paper presents the practical implementation of a system, with two emitters and four receivers, using a low-cost hardware architecture based on a FPGA. The ultrasonic signal processing is performed in real time.

Classification of reflectors with an ultrasonic sensor for mobile robot applications

Abstract This paper describes a sensor model made up of four ultrasonic transducers able to classify reflectors (wall, edge or corner) in specular environments. The main goal has been to effect the classification from a single reading cycle: emission of ultrasounds and reception of echoes (measuring only times of flight—TOFs). Working from the four TOFs obtained after a single emission of ultrasounds (thereby facilitating its practical implementation in a mobile robot, when readings are taken while the robot is moving), an algorithm has been proposed for discriminating between edge and plane type reflectors. The configuration of the four transducers enabled dependent discriminating functions to be determined directly from the quadratic terms of the TOFs, without the need for previous geometric transformations. Special attention was given to the effect of the separation between the sensor transducers and the reading-associated noise. Finally, some considerations have been pointed out about the possibility of two transducers emitting, so allowing discrimination between walls and corners.