Analysis of Vibroacoustic Modulations for Crack Detection: A Time-Frequency Approach Based on Zhao-Atlas-Marks Distribution

The vibro-acoustic modulation (VAM) technique is probably the most widely used nonlinear method for crack detection. The VAM method is based on the effect of modulation of high-frequency acoustic waves by a low-frequency vibration. The intensity of the modulation is related to the severity of the damage and has been used so far as a damage index. The damage index simply based on the amplitude of the first side bands in the spectral domain often leads to controversial results about the severity of the damage. In this work, the nonlinear characteristics of the vibro-modulation were systematically investigated by employing time-frequency analysis based on the Zhao-Atlas-Marks (ZAM) distribution. The results of the analysis show that the amplitude of the sideband components is modulated by the low frequency vibration and the modulation amplitude depends on the size of the crack. Based on the obtained results, a new damage index was defined in relation to the strength of the modulation. The new damage index is more sensitive and robust and correlates better with crack size compared to the index based on the amplitude of the sidebands

RAPP System Architecture

International audience— Robots are fast becoming a part of everyday life. This rise can be evidenced both through the public news and announcements, as well as in recent literature in the robotics scientific communities. This expanding development requires new paradigms in producing the necessary software to allow for the users' particular needs. In this paper we present a novel architectural design of the RAPP framework that attempts to address this issue, developed within the context of the EU funded project RAPP "Robotic Applications for Delivering Smart User Empowering Application". The proposed framework has been designed aiming towards a cloud-based approach to integrating robotic devices and their respective applications. This goal was defined going beyond the up-coming trends in infrastructures, and focusing on alternative approaches to conventional robotic controllers, while at the same time expanding the capabilities of the RAPP framework in a seamless and scaling manner

Variable structure robot control systems: The RAPP approach

International audienceThis paper presents a method of designing variable structure control systems for robots. As the on-board robot computational resources are limited, but in some cases the demands imposed on the robot by the user are virtually limitless, the solution is to produce a variable structure system. The task dependent part has to be exchanged, however the task governs the activities of the robot. Thus not only exchange of some task-dependent modules is required, but also supervisory responsibilities have to be switched. Such control systems are necessary in the case of robot companions, where the owner of the robot may demand from it to provide many services.

Analysis of Vibroacoustic Modulations for Crack Detection: A Time-Frequency Approach Based on Zhao-Atlas-Marks Distribution

The vibro-acoustic modulation (VAM) technique is probably the most widely used nonlinear method for crack detection. The VAM method is based on the effect of modulation of high-frequency acoustic waves by a low-frequency vibration. The intensity of the modulation is related to the severity of the damage and has been used so far as a damage index. The damage index simply based on the amplitude of the first side bands in the spectral domain often leads to controversial results about the severity of the damage. In this work, the nonlinear characteristics of the vibro-modulation were systematically investigated by employing time-frequency analysis based on the Zhao-Atlas-Marks (ZAM) distribution. The results of the analysis show that the amplitude of the sideband components is modulated by the low frequency vibration and the modulation amplitude depends on the size of the crack. Based on the obtained results, a new damage index was defined in relation to the strength of the modulation. The new damage index is more sensitive and robust and correlates better with crack size compared to the index based on the amplitude of the sidebands

BlogForever D4.8: Final BlogForever Platform

This report presents the integration of the two components, the nal weblog Spider and the final webblog digital Repository, fully functional and communicating optimally with each other, resulting in the Final BlogForever Platform. The implementation activities carried out during the last period as well as a detailed documentation of both components are provided

BlogForever D4.5: Initial Weblog Digital Repository Prototype

This report presents the implementation activities carried out for the BlogForever digital repository component. In this respect, it provides detailed implementation descriptions as well as the testing activities of the implemented features according to their feature specifi cations. Furthermore, this report outlines the adopted collaboration workflow together with the technologies utilised