Object Classification and Localization with an Airborne Ultrasound Imaging System

An airborne ultrasound imaging system (ABUS) was developed at KIT for reflection tomography. The prototype system consists of sixteen ultrasonic transducers surrounding a region of interest (ROI) of defined shape with a diameter of 50 cm. The transducers have a center frequency of 200 kHz and a bandwidth of 20 kHz. The prototype aims to demonstrate possible industrial applications for object classification and localization with airborne ultrasound. This paper is a detailed version of the previous publication in IEEE Ultrasonics Symposium (IUS) 2017 [1]

Rendering volumetric haptic shapes in mid-air using ultrasound

We present a method for creating three-dimensional haptic shapes in mid-air using focused ultrasound. This approach applies the principles of acoustic radiation force, whereby the non-linear effects of sound produce forces on the skin which are strong enough to generate tactile sensations. This mid-air haptic feedback eliminates the need for any attachment of actuators or contact with physical devices. The user perceives a discernible haptic shape when the corresponding acoustic interference pattern is generated above a precisely controlled two-dimensional phased array of ultrasound transducers. In this paper, we outline our algorithm for controlling the volumetric distribution of the acoustic radiation force field in the form of a three-dimensional shape. We demonstrate how we create this acoustic radiation force field and how we interact with it. We then describe our implementation of the system and provide evidence from both visual and technical evaluations of its ability to render different shapes. We conclude with a subjective user evaluation to examine users’ performance for different shapes

Current status and future trends of mechanized fruit thinning devices and sensor technology

This paper reviews the different concepts that have been investigated concerning the mechanization of fruit thinning as well as multiple working principles and solutions that have been developed for feature extraction of horticultural products, both in the field and industrial environments. The research should be committed towards selective methods, which inevitably need to incorporate some kinds of sensor technology. Computer vision often comes out as an obvious solution for unstructured detection problems, although leaves despite the chosen point of view frequently occlude fruits. Further research on non-traditional sensors that are capable of object differentiation is needed. Ultrasonic and Near Infrared (NIR) technologies have been investigated for applications related to horticultural produce and show a potential to satisfy this need while simultaneously providing spatial information as time of flight sensors. Light Detection and Ranging (LIDAR) technology also shows a huge potential but it implies much greater costs and the related equipment is usually much larger, making it less suitable for portable devices, which may serve a purpose on smaller unstructured orchards. Portable devices may serve a purpose on these types of orchards. In what concerns sensor methods, on-tree fruit detection, major challenge is to overcome the problem of fruits’ occlusion by leaves and branches. Hence, nontraditional sensors capable of providing some type of differentiation should be investigated.This work was developed as part of +Pêssego project which purpose is to promote the innovation and development of peach tree culture in the region of Beira Interior, Portugal. This project was financed by a national rural development and support program, PRODER.info:eu-repo/semantics/publishedVersio

Mid-air haptic rendering of 2D geometric shapes with a dynamic tactile pointer

An important challenge that affects ultrasonic midair haptics, in contrast to physical touch, is that we lose certain exploratory procedures such as contour following. This makes the task of perceiving geometric properties and shape identification more difficult. Meanwhile, the growing interest in mid-air haptics and their application to various new areas requires an improved understanding of how we perceive specific haptic stimuli, such as icons and control dials in mid-air. We address this challenge by investigating static and dynamic methods of displaying 2D geometric shapes in mid-air. We display a circle, a square, and a triangle, in either a static or dynamic condition, using ultrasonic mid-air haptics. In the static condition, the shapes are presented as a full outline in mid-air, while in the dynamic condition, a tactile pointer is moved around the perimeter of the shapes. We measure participants’ accuracy and confidence of identifying shapes in two controlled experiments (n1 = 34, n2 = 25). Results reveal that in the dynamic condition people recognise shapes significantly more accurately, and with higher confidence. We also find that representing polygons as a set of individually drawn haptic strokes, with a short pause at the corners, drastically enhances shape recognition accuracy. Our research supports the design of mid-air haptic user interfaces in application scenarios such as in-car interactions or assistive technology in education

Application and Challenges of Signal Processing Techniques for Lamb Waves Structural Integrity Evaluation: Part B-Defects Imaging and Recognition Techniques

The wavefield of Lamb waves is yielded by the feature of plate-like structures. And many defects imaging techniques and intelligent recognition algorithms have been developed for defects location, sizing and recognition through analyzing the parameters of received Lamb waves signals including the arrival time, attenuation, amplitude and phase, etc. In this chapter, we give a briefly review about the defects imaging techniques and the intelligent recognition algorithms. Considering the available parameters of Lamb waves signals and the setting of detection/monitoring systems, we roughly divide the defect location and sizing techniques into four categories, including the sparse array imaging techniques, the tomography techniques, the compact array techniques, and full wavefield imaging techniques. The principle of them is introduced. Meanwhile, the intelligent recognition techniques based on various of intelligent recognition algorithms that have been widely used to analyze Lamb waves signals in the research of defect recognition are reviewed, including the support vector machine, Bayesian methodology, and the neural networks

A kalman filter for validate points and areas of constant depth in the acquisition of the profiles surfaces

This paper presents multisensor fusion techniques for the acquisition of the profile of surfaces with minimum error using low cost ultrasonic sensors. These surfaces are composed by areas with different depths, corners and specular surfaces. To minimize the constraints of sonar sensors, it was developed dedicated software and hardware, as well as an empirical model was obtained from real data. This model is based in two proposed concepts: Points of Constant Depth (PCD) and Areas of Constant Depth (ACD). Having this sonar model in mind, four sensor fusion techniques are used separately to validate the PCDs and decide the ACDs: average and variance, a simplified kalman filter and heuristic method based in rules. In this work a PUMA 560 manipulator was equipped with a CCD video camera and four ultrasonic sensors on the wrist, to acquire data for internally representation of the geometry of the part’s surface, exploiting the mobility of the robot. The CCD camera defines the working area while the ultrasonic sensors enable the acquisition of the surface profile

Real-time digital signal processing system for normal probe diffraction technique

Ultrasonic systems are widely used in many fields of non-destructive testing. The increasing requirement for high quality steel product stirs the improvement of both ultrasonic instruments and testing methods. The thesis indicates the basics of ultrasonic testing and Digital Signal Processing (DSP) technology for the development of an ultrasonic system. The aim of this project was to apply a new ultrasonic testing method - the Normal Probe Diffraction method to course grained steel in real-time and investigate whether the potential of probability of detection (POD) has been improved. The theories and corresponding experiment set-up of pulse-echo method, TOFD and NPD method are explained and demonstrated separately. A comparison of these methods shows different contributions made by these methods using different types of algorithms and signals. Non-real-time experiments were carried out on a VI calibration block using an USPC 3100 ultrasonic testing card to implement pulse-echo and NPD method respectively. The experiments and algorithm were simulated and demonstrated in Matlab. A low frequency Single-transmitter-multi-receiver ultrasonic system was designed and built with a digital development board and an analogue daughter card to transmit or receive signals asynchronously. A high frequency high voltage amplifier was designed to drive the ultrasonic probes. A Matlab simulation system built with Simulink indicates that the Signal to Noise Ratio (SNR) can be improved with an increment of up to 3dB theoretically based on the simulation results using DSP techniques. The DSP system hardware and software was investigated and a real-time DSP hardware system was supposed to be built to implement the high frequency system using a rapid code generated system based on Matlab Simulink model and the method was presented. However, extra effort needs to be taken to program the hardware using a low-level computer language to make the system work stably and efficiently

Refraction-corrected ray-based inversion for three-dimensional ultrasound tomography of the breast

Ultrasound Tomography has seen a revival of interest in the past decade, especially for breast imaging, due to improvements in both ultrasound and computing hardware. In particular, three-dimensional ultrasound tomography, a fully tomographic method in which the medium to be imaged is surrounded by ultrasound transducers, has become feasible. In this paper, a comprehensive derivation and study of a robust framework for large-scale bent-ray ultrasound tomography in 3D for a hemispherical detector array is presented. Two ray-tracing approaches are derived and compared. More significantly, the problem of linking the rays between emitters and receivers, which is challenging in 3D due to the high number of degrees of freedom for the trajectory of rays, is analysed both as a minimisation and as a root-finding problem. The ray-linking problem is parameterised for a convex detection surface and three robust, accurate, and efficient ray-linking algorithms are formulated and demonstrated. To stabilise these methods, novel adaptive-smoothing approaches are proposed that control the conditioning of the update matrices to ensure accurate linking. The nonlinear UST problem of estimating the sound speed was recast as a series of linearised subproblems, each solved using the above algorithms and within a steepest descent scheme. The whole imaging algorithm was demonstrated to be robust and accurate on realistic data simulated using a full-wave acoustic model and an anatomical breast phantom, and incorporating the errors due to time-of-flight picking that would be present with measured data. This method can used to provide a low-artefact, quantitatively accurate, 3D sound speed maps. In addition to being useful in their own right, such 3D sound speed maps can be used to initialise full-wave inversion methods, or as an input to photoacoustic tomography reconstructions

Development of a real-time ultrasonic sensing system for automated and robotic welding

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The implementation of robotic technology into welding processes is made difficult by the inherent process variables of part location, fit up, orientation and repeatability. Considering these aspects, to ensure weld reproducibility consistency and quality, advanced adaptive control techniques are essential. These involve not only the development of adequate sensors for seam tracking and joint recognition but also developments of overall machines with a level of artificial intelligence sufficient for automated welding. The development of such a prototype system which utilizes a manipulator arm, ultrasonic sensors and a transistorised welding power source is outlined. This system incorporates three essential aspects. It locates and tracks the welding seam ensuring correct positioning of the welding head relatively to the joint preparation. Additionally, it monitors the joint profile of the molten weld pool and modifies the relevant heat input parameters ensuring consistent penetration, joint filling and acceptable weld bead shape. Finally, it makes use of both the above information to reconstruct three-dimensional images of the weld pool silhouettes providing in-process inspection capabilities of the welded joints. Welding process control strategies have been incorporated into the system based on quantitative relationships between input parameters and weld bead shape configuration allowing real-time decisions to be made during the process of welding, without the need for operation intervention.British Technology Group (BTG