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In this paper, the authors present a new strategy for accurately reconstructing an L-shaped obstacle such as some wooden panels opportunely connected so as to form a right angle. The mechatronics scanning system consists of four inexpensive ultrasonic sensors moved in three-dimensional (3-D) space by means of a digital motor. The motor rotation is controlled in order to point the sensor array at the target and to obtain distance measurements for each shaft position. Ultrasonic distance sensors propagate large beams and feel the significant effect of multiple reflections. For the sake of excluding all misrepresented distance values at the intersection of the planes, the proposed approach uses powerful mathematical tools together with a physical indicator based on the reflected signal energy. The Fuzzy C-Means (FCM) classification allows partitioning a data set, and the introduced physical indicator is able to select the specific cluster corresponding to the spurious distances. Each remaining cluster permits to calculate the equation of a plane because it is referred to the distance values deriving from a direct reflection. These distances are then transformed considering the sensors directivity and the direction of reflection so as to obtain two sets of 3-D points. Finally, the reconstruction of each plane is achieved by the RANdom SAmple Consensus (RANSAC) in such a way as to better fit these points. The details of this strategy and the experimental tests are shown, demonstrating the applicability and the good results. [ABSTRACT FROM PUBLISHER]

A new vector field smoothing algorithm for direction-of-arrival (DOA) estimation of multiple coherent, underwater acoustic signals is proposed based on the array with vector hydrophones, which is located at or near a reflecting boundary. The performance of the proposed algorithm is examined in two practical applications: hull-mounted and seabed array. The advantage of the vector field smoothing scheme is no reduction in the overall array's spatial aperture. [ABSTRACT FROM PUBLISHER]

A biomimetic sonar is configured using two conventional sensors that generate point processes related to echo waveform intensity, resembling biological action potential spikes. The sensors point slightly outward from the sonar axis, similar to pinnae in some bats, to acquire slightly different views of the environment during a rotational scan. Artifacts in sonar maps are points that do not relate to actual object locations. Physical criteria identify artifacts by applying echo strength, azimuthal extent, and binaural coincidence criteria. Neuromorphic processing implements these criteria with thresholding, delays, and short-term memories. Artifacts are deleted to produce robust sonar maps. Multiple resolution maps, generated by using two thresholds, illustrate improvements over conventional sonar maps and tradeoffs between resolution and stability [ABSTRACT FROM PUBLISHER]

This paper presents a novel ultrasonic sensing system for autonomous mobile systems. We describe how wide-angled ultrasonic transducers can be used to obtain substantial information from the environment. This can be achieved by exploiting the overlapping of detection cones from neighbor sensors and by receiving cross echoes between them. The ultrasonic sensing system also allows the detection of multiple echoes from different echo paths for each sensor. In this way, a significantly higher number of echoes can be obtained in comparison to conventional ultrasonic sensing systems for mobile robots. In order to benefit from the increased sensor information, algorithms for adequate data post-processing are required. In this context, we describe how an environment model can be created from ultrasonic sensor data. [ABSTRACT FROM PUBLISHER]

Many applications require the sensing of plants. When an ultrasonic sensor insonifies a plant, the resultant echo is the superposition of the echoes from the leaves. As a result, the echo contains information about the geometric structure of the foliage. In this paper, we present a model of sensing that facilitates the extraction of geometric features from the echo for plant classification, recognition and discrimination. We model the echo from a CTFM ultrasonic sensor with the acoustic density profile model. Then, we identify a set of features that represent plant geometric characteristics and use these to perform an inverse transform from echo features to plant geometry [ABSTRACT FROM PUBLISHER]

A new processing technique of sonar echoes is introduced to estimate the inclination angle of a planar reflector. Correlation with normalized echo amplitude model and its derivatives has improved estimation accuracy. Experimental results show how a single transducer placed on a step motor can be used for estimating the reflector's orientation on a sensor coordinate system. [ABSTRACT FROM PUBLISHER]