Diseño completo de un mecanismo de palancas articuladas mediante software SOLIDWORKS/COSMOS

Proyecto de un mecanismo divisor sinusoidal. Project of a senoidal dividerIngeniería Técnica en Mecánic

Crack detection in rotating shafts based on 3x energy: analytical and experimental analyses

Maintenance is essential to prevent catastrophic failures in rotating machinery. A crack can cause a failure with costly processes of reparation, especially in a rotating shaft. In this study, the wavelet transform theory was applied to vibration signals to detect cracks in a rotating shaft. Data were obtained from an analytical Jeffcott rotor model with a breathing function to simulate cracks. Large changes in energy when a crack appears were discovered at 1 ×, 2 × and 3 ×. Thereafter, vibration signals were obtained from a rotating machine at different steady-state rotational speeds using an accelerometer mounted on the bearing housing. Nine defect conditions were induced in the shaft (with depths from 4% to 50% of the shaft diameter). By matching the theoretical results with the experimental data, it was found that only the 3 × component of the rotational speed is a clear indicator of the presence of a crack in this case. The energy level at this harmonic can be used for the inverse process of crack detection. Moreover, “probability of detection” curves were calculated. They showed very good results.The authors would like to thank the Spanish Government for financing through the CDTI project RANKINE21 IDI-20101560.Publicad

Review of recent advances in the application of the wavelet transform to diagnose cracked rotors

Wavelet transform (WT) has been used in the diagnosis of cracked rotors since the 1990s. At present, WT is one of the most commonly used tools to treat signals in several fields. Understandably, this has been an area of extensive scientific research, which is why this paper aims to summarize briefly the major advances in the field since 2008. The present review considers advances in the use and application of WT, the selection of the parameters used, and the key achievements in using WT for crack diagnosis.The authors would like to thank the Spanish government for financing through the CDTI project RANKINE21 IDI-20101560

Automatic condition monitoring system for crack detection in rotating machinery

Maintenance is essential to prevent catastrophic failures in rotating machinery. A crack can cause a failure with costly processes of reparation, especially in a rotating shaft. In this study, the Wavelet Packets transform energy combined with Artificial Neural Networks with Radial Basis Function architecture (RBF-ANN) are applied to vibration signals to detect cracks in a rotating shaft. Data were obtained from a rig where the shaft rotates under its own weight, at steady state at different crack conditions. Nine defect conditions were induced in the shaft (with depths from 4% to 50% of the shaft diameter). The parameters for Wavelet Packets transform and RBF-ANN are selected to optimize its success rates results. Moreover, ‘Probability of Detection’ curves were calculated showing probabilities of detection close to 100% of the cases tested from the smallest crack size with a 1.77% of false alarms.The authors would like to thank the Spanish Government for financing through the CDTI project RANKINE21 IDI-20101560

Métodos de Diagnóstico de Averías para Transformadores con Cambiadores de Tomas en Carga

There is a great variety of diagnosis techniques for on load tap changer (OLTC), some of them can be used only in power transformers off-line and other techniques in power transformers online. This paper describes the different failure diagnosis method on OLTC, and gives a report of the implementation of the diagnosis method of vibration measurement into the transformer tank.Existen una gran variedad de técnicas de diagnostico en Cambiadores de Tomas en Carga (CTC), algunas de ellas pueden usarse solo con el transformador fuera de línea y otras técnicas con el transformador en línea. Este artículo describe los diferentes métodos de diagnóstico de fallos en CTC y reporta la implementación del método de diagnostico de la medida de la vibración en la cuba del transformador

Wild boar battues reduce crop damages in a protected area

Agricultural damages caused by wild boar Sus scrofa have given farmers a negative impression of protected areas and their management. To mitigate those damages and the social conflicts that they create, hunting battues involving experienced local hunters were used as a lethal population control method in a protected Iberian wetland. In the Ebro Sotos and Galachos Nature Reserve, Spain, between 1994 and 2011, 259 wild boars were culled during 476 battues. On average, battues involved six hunters and ten dogs, and culling efficiency (number of animals killed per animals seen during battues) was 39 %. The number of battues per year and the area of crop damages caused by wild boar were significantly negatively correlated, demonstrating battue efficiency to decrease damages. Moreover, intermittent population control through culling led to a substantial increase in the wild boar population, with an increase in crop damages. This underlines the importance of constant control. The numbers of hunters and dogs and the number of wild boar seen during battues were strongly correlated. To minimize the conflicts between farmers and the management of protected areas, we suggest that the inexpensive, volunteer-based population control program could be enhanced by incorporating stalking and mobile electric fences

Methodology for the navigation optimization of a terrain-adaptive unmanned ground vehicle

The goal of this article is to design a navigation algorithm to improve the capabilities of an all-terrain unmanned ground vehicle by optimizing its configuration (the angles between its legs and its body) for a given track profile function. The track profile function can be defined either by numerical equations or by points. The angles between the body and the legs can be varied in order to improve the adaptation to the ground profiles. A new dynamic model of an all-terrain vehicle for unstructured environments has been presented. The model is based on a half-vehicle and a quasi-static approach and relates the dynamic variables of interest for navigation with the topology of the mechanism. The algorithm has been created using a simple equation system. This is an advantage over other algorithms with more complex equations which need more time to be calculated. Additionally, it is possible to optimize to any ground-track-profile of any terrain. In order to prove the soundness of the algorithm developed, some results of different applications have been presented.The authors wish to thank the Spanish Government for financing provided through the MCYT project "RETOS2015: sistema de monitorización integral de conjuntos mecánicos críticos para la mejora del mantenimiento en el transporte-maqstatus" and also thank the anonymous reviewers for their insightful comments and suggestions on an earlier draft of this article

Analysis of the influence of crack location for diagnosis in rotating shafts based on 3 x energy

The aim of condition monitoring is to detect faults before a catastrophic failure occurs. Cracks in rotating shafts are especially critical. The present work studies vibration signals obtained from a rotating shaft under different crack depths and locations. Tests were performed in a rig called Rotokit at a steady state at different rotation speeds. Signals obtained are analyzed by means of energy using the Wavelet theory, specifically the Wavelet Packets Transform. Nine crack depths in the shafts were tested, from 4% to 50% of the shaft diameter. Previous related work showed good reliability for crack diagnosis using 3 x energy for cracks in the middle section. In the present work, previous results are compared to the obtained for a crack in a change of section at one side. In both crack locations, large changes in energy are observed at 3 x at high speeds. Energy levels at this harmonic were used for the inverse process of crack detection, and probability of detection curves were calculated by thresholding. Cracks with depths above 12% can be detected with reliability in the locations tested using this method.The authors would like to thankthe Spanish Government for financing through the projects RANKINE21 IDI-20101560 and MAQ-STATUS DPI2015-69325-C2-1-R

The Quasi-Passive Quadruped Robot walking: PASIQUAD

The design of the four legged walking robot "PASIQUAD" is presented in this article. It was designed in the university Carlos III of Madrid. It is a quadruped quasi-passive robot (with only one motor/actuator). The manuscript is focused on how the PASIQUAD walks and the kinematics and dynamics of the movement. In the manuscript the position, velocity and acceleration of each of its parts, as well as all the forces and torques on each of them, motor torque included, will be explain. The PASIQUAD robot copy the movement of animals and it is almost passive. That is a big advantage in energy cost

Railway Axle Condition Monitoring Technique Based on Wavelet Packet Transform Features and Support Vector Machines

Railway axles are critical to the safety of railway vehicles. However, railway axle maintenance is currently based on scheduled preventive maintenance using Nondestructive Testing. The use of condition monitoring techniques would provide information about the status of the axle between periodical inspections, and it would be very valuable in the prevention of catastrophic failures. Nevertheless, in the literature, there are not many studies focusing on this area and there is a lack of experimental data. In this work, a reliable real-time condition-monitoring technique for railway axles is proposed. The technique was validated using vibration measurements obtained at the axle boxes of a full bogie installed on a rig, where four different cracked railway axles were tested. The technique is based on vibration analysis by means of the Wavelet Packet Transform (WPT) energy, combined with a Support Vector Machine (SVM) diagnosis model. In all cases, it was observed that the WPT energy of the vibration signals at the first natural frequency of the axle when the wheelset is first installed (the healthy condition) increases when a crack is artificially created. An SVM diagnosis model based on the WPT energy at this frequency demonstrates good reliability, with a false alarm rate of lower than 10% and defect detection for damage occurring in more than 6.5% of the section in more than 90% of the cases. The minimum number of wheelsets required to build a general model to avoid mounting effects, among others things, is also discussed.This research was funded by the Spanish Government through the project MAQSTATUS with grantnumber DPI2015-69325-C2-1-R