1,720,969 research outputs found
Noise-tolerant ultrasonic distance sensor based on a multiple driving approach
No full textUltrasonic sensors are a cost-effective solution to the problem of distance measurement when contactless operation is required. They are robust, intrinsically safe, and capable of noticeable accuracy when used in quiet environments, but suffer from acoustic noise that can greatly reduce their performance. In this paper an ultrasonic distance sensor that is able to provide good performance in different conditions is presented. The good performance is obtained by automatically changing the signal that drives the transmitter according to the environmental noise level. Such an approach allows accuracies of up to 1 mm to be obtained in distance measurements up to a few meters, even in the presence of acoustic noise levels which would otherwise impair the sensor performance. The proposed sensor is cheap and easy to be implemented, therefore enabling the design of low-cost, high-performance device
Enhancing the ultrasonic sensor performance by the optimisation of the driving signal
No full textThe issue arising from limitations in sensor performance is crucial in most measuring systems, so it is a matter of high interest to define strategies able to optimize a sensor's behaviour. This paper describes a method for determining a sensor driving signal that enhances the sensor capabilities in stimulation-and-response-based measuring systems. The method is based on a signal theory approach and is quite general, enabling the best performance for different kinds of sensors to be obtained, provided that they can be described in terms of transgfer functiions and that the required performance can be represented by suitable functionals. The method's capabilities are shown in an application involving the measurement of the time-of-flight of ultrasonic pulses. A resolution improvement of more than one order of magnitude is achieved with respect to the standard approaches, still employing low-cost low-damping devices
Ultrasonic distance sensor improvement using a two-level neural network
Full text linkThis paper discusses the performance improvement that a neural network can provide to a contactless distance sensor based on the measurement of the time of flight (TOF) of an ultrasonic (US) pulse. The sensor, which embeds a correction system for the temperature effect, achieves a distance uncertainty (rms) of less than 0.5 mm over 0.5 m by using a two-level neural network to process the US echo and determine the TOF in the presence of environmental acoustic noise. The network embeds a "guard" neuron that guards against gross measurement errors, which would be possible in the presence of high environmental noise
Procedure for effortless in-field calibration of three-axial rate gyro and accelerometers
No full textThe contemporaneous use of three-axis rate gyro and accelerometer is required in industrial applications such as strap-down platforms. The use of low-cost sesnors ofter requires a calibration immediately before the sensor use. This paper describes a procedure which does not require either angular velocity standards or standard accelerometers. The procedure makes use of the local gravity and of a set of rotations returning to the original position
A neural network for fast-response ultrasonic distance sensors
No full textUltrasonic techniques can provide a cost effective solution for distance measurements, but frequently suffer from poor resolution and acoustic noise. In this paper a new approach based on neural networks to process the echo signal is described, it permits the improvement of the resolution of the distance measuring systems by employing ultrasonic techniques and requires a negligible computing time, even though the network, is implemented without special purpose hardware. The results obtained with less-than-one-dollar piezoelectric transducers and a neural network are described. The neural network performance is compared with that of traditional techniques. A sub-millimeter resolution is obtained even in the presence of some acoustic noise, which could prevent other simple detection strategies
Comparison among photovoltaic technologies: an experimental case study
No full textThis paper deals with the experimental comparison among the performance indexes of different photovoltaic technologies, which are obtained by means of a specifically designed monitoring system. A description of the monitoring system is provided by focusing attention towards its metrological management, which allows traceable results to be obtained that are qualified in terms of measurement uncertainty. Preliminary results are also described for a photovoltaic plant that includes ten sub-plants based on different technologies. Reported results refer to a time interval of nine month
Calibration of three-axial rate gyros without angular velocity standards
No full textGyro calibration is a complex taskm, mainly because of the difficulty of managing angular velocity standards. This is especially true 'in field' and therefore low-cost sensors cannot to be used in high-accuracy applications. This paper presents a calibration process that does not require rotating tables or other velocity standards. The calibration is carried out making reference only to geometrical quantities and using the A/D conversion system and the computing system normally connected to the gyro. The calibration can be completed in a few minutes, and results in a noticeable improvement in accuracy
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