The detection of gear noise computed by integrating the Fourier and Wavelet methods

This paper presents a new gearbox noise detection algorithm based on analyzing specific points of vibration signals using the Wavelet Transform. The proposed algorithm is compared with a previouslydeveloped algorithm associated with the Fourier decomposition using Hanning windowing. Simulation carried on real data demonstrate that the WT algorithm achieves a comparable accuracy while having a lower computational cost. This makes the WT algorithm an appropriate candidate for fast processing of noise gear box

A problem of emphasizing features of a surface roughness by means the Discrete Wavelet Transform

When we are interested to the detection of the roughness features by means of the 3D reconstruction, based on photometric stereo techniques, an important problem is the elimination of the brightness variation due to different light conditions which can alter the response. This paper will concentrate on presenting results of a new method for eliminating this problem. Every pixel of a picture gives only one number: the brightness of the corresponding point on the object, whereas the surface orientation is described by a normal vector that has two degrees of freedom. The level of brightness depends on many factors as well as the homogeneity of reflection properties of the material or its physical continuity and the surface smoothness or roughness. In this work we will show how the application of the Discrete Wavelet Transform (DWT) to the processing of some images, captured on different light conditions, permits to solve the problem of emphasizing roughness features of a metallic surface. Wavelet transforms can model irregular data patterns such as sharp changes, better than the Fourier transforms and standard statistical procedures (e.g., parametric and non-parametric regressions) and provide a multiresolution approximation to the data. Here we propose, also, a non-parametric method, based on the wavelet theory, for the estimation of the threshold level of a gray levels distribution, obtained from the intensity image matrix

A New Real Time Shape Acquisition with a Laser Scanner: First Test Results

Abstract The first results of a new method for real-time shape acquisition with a laser scanner are presented. The new method is essentially based on the use of a laser beam and a web-cam. A digital filter parameters identification was studied for the laser line detection in the image. After this, a model for the reconstruction in real-time of the laser line in the space was developed. The firsttest rig was just conceived to validate the method; hence, no high resolution cameras were adopted. Nevertheless, the tests have showed encouraging results. Tests were made on both plane and non-plane surfaces. First of all, it was confirmed that it is possible to calibrate the intrinsic parameters of the video system, the position of the image plane and the laser plane in a given frame, all in the same time. Moreover the surface shapes were recognized and recorded with an appreciable accuracy. The tests also showed that the proposed method can be used for robotic applications, such as robotic kinematic calibration and 3D surfaces recognition and recording. For this last purpose, the test rig is fitted on a robot arm that permits to the scanner device to ‘observe’ the 3D object from different and known positions

Robot assisted 3D shape acquisition by optical systems

In this chapter, a short description of the basic concepts about optical methods for the acquisition of three-dimensional shapes is first presented. Then two applications of the surface reconstruction are presented: the passive technique Shape from Silhouettes and the active technique Laser Triangolation. With both these techniques the sensors (telecameras and laser beam) were moved and oriented by means of a robot arm. In fact, for complex objects, it is important that the measuring device can move along arbitrary paths and make its measurements from suitable directions. This chapter shows how a standard industrial robot with a laser profile scanner can be used to achieve the desired d-o-f. Finally some experimental results of shape acquisition by means of the Laser Triangolation technique are reported

Robot Assisted 3D Shape Acquisition Optical Systems

In this chapter, a short description of the basic concepts about optical methods for the acquisition of three-dimensional shapes is first presented. Then two applications of the surface reconstruction are presented: the passive technique Shape from Silhouettes and the active technique Laser Triangolation. With both these techniques the sensors (telecameras and laser beam) were moved and oriented by means of a robot arm. In fact, for complex objects, it is important that the measuring device can move along arbitrary paths and make its measurements from suitable directions. This chapter shows how a standard industrial robot with a laser profile scanner can be used to achieve the desired d-o-f. Finally some experimental results of shape acquisition by means of the Laser Triangolation technique are reported

AN UNDERACTUATED MECHANICAL HAND PROSTHESYS BY IFToMM ITALY

This paper describes a mechanical underactuated hand, whose design is under patenting. The proposed hand can be used as robot grasping end-effector and, mainly, as a human prosthesis. The proposed underactuated mechanism is based on an adaptive scheme, hence it permits to move five fingers with only one actuator. The actuator is connected to a set of pulleys that operate five tendons. Each tendon will move the phalanxes of a finger. The proposed mechanism permits each finger to adapt its configuration to almost any object shape so that each of the fingers will grasp the object independently on the configuration of the finger itself and independently on the configuration of the other fingers. The tendons are un-extendible so that each finger will grasp an object always with the same force, regardless of object shape. The overall grasping force will be controlled just by adjusting the input actuator torque. This paper also reports preliminary kinematic and dynamic studies aiming to a validation of the feasibility of the proposed design solution. Finally an early experimental prototype is shown

Technical Feasibility of Laser Dissimilar Welding of Superalloys on Casted Nozzle Guide Vanes

Abstract An increasing degree of automation is required both in the automotive and aircraft industry in order to allow scrap reduction and flexibility. In this frame, the shift from arc welding to laser beam welding is being investigated for a number of applications on metals in aerospace engineering, where strict standards apply. In comparison with conventional welding methods, a number of advantages are benefited; nevertheless, when moving to a new technology, some issues must be addressed. Hence this study is aimed to investigate laser dissimilar welding of real metal components, in order to assess the technical feasibility as well as to discuss set-up and operating issues in view of the implementation of the process for actual industrial application. A second-stage stator of low-pressure turbine is considered: lightening of the airfoils of the nozzle guide vane is achieved thanks to inner hollows which are drained from wax upon casting; afterward, the core exits on the outer side of the nozzle must be conveniently closed off by means of metal plates. Joining of the plates to the nozzle is performed by fusion welding along the edge of each plate and a condition of dissimilar welding is in place, being the nozzle and the plates made of C1023 and Nimonic 75, respectively. A mixed factorial plan has been arranged, laser power, welding speed and focus position being the leading processing parameters; a convenient welding set-up is proposed. Reasons are given for the implementation of laser beam welding as an alternative to conventional arc welding

Autoptic findings of sudden cardiac death (SCD) in patients with arrhythmogenic ventricular cardiomiopathy (AVC) from left ventricle and biventricular involvement.

Objectives: To evaluate autoptic histopathological findings of arrhythmogenic ventricular cardiomyopathy (AVC) as major cause of sudden cardiac death (SCD) in young adults. Background: According to Heart Rhythm Society (HRS)'s international consensus, histological criteria for AVC diagnosis include a progressive myocardial atrophy of the right ventricle characterized by a transmural fatty or fibrofatty replacement in a segmental or diffuse pattern (residual myocytes <60 % vs 60–75 % by morphometric analysis) explaining the electrical instability with increased risk of SCD. However, there is increasing evidence for atypical patterns of localizations and percentage of fibrofatty replacement suggesting the need to update histopathological features of AVC. Methods: Histology examination of ventricles, atria, and septum was performed on 10 autopsy of SCD due to AVC. Staining with hematoxylin-eosin and PicroSirius Red/Fast Green were performed on the heart samples to identify specific fibrofatty patterns. Results: Our analysis showed that: 1) myocardial replacement by a diffuse segmental fatty or fibro-fatty tissue characterized right and left ventricles as well as atrial walls; 2) the degree of fibrofatty tissue replacement was less than 40 % both in left ventricle (n = 4, 40 %) and biventricular (n = 6, 60 %) localization; 3) perivascular fibrosis, inflammatory infiltrate, areas of hypertrophy and/or areas of coagulative necrosis as signs of hypoxic damage in the first stage. Conclusions: We confirmed prior evidence for fibrofatty replacement both in biventricular and septal localizations. Importantly, we observed a less degree (<40 %) of fibrofatty replacement as compared to current guidelines. This supports the need to further explore the histological patterns of fibrofatty infiltration in a larger study population to improve the histological diagnostic criteria of AVC