A Sensor Classification Strategy for Robotic Manipulators

In practice the robotic manipulators present some degree of unwanted vibrations. The advent of lightweight arm manipulators, mainly in the aerospace industry, where weight is an important issue, leads to the problem of intense vibrations. On the other hand, robots interacting with the environment often generate impacts that propagate through the mechanical structure and produce also vibrations. In order to analyze these phenomena a robot signal acquisition system was developed. The manipulator motion produces vibrations, either from the structural modes or from endeffector impacts. The instrumentation system acquires signals from several sensors that capture the joint positions, mass accelerations, forces and moments, and electrical currents in the motors. Afterwards, an analysis package, running off-line, reads the data recorded by the acquisition system and extracts the signal characteristics. Due to the multiplicity of sensors, the data obtained can be redundant because the same type of information may be seen by two or more sensors. Because of the price of the sensors, this aspect can be considered in order to reduce the cost of the system. On the other hand, the placement of the sensors is an important issue in order to obtain the suitable signals of the vibration phenomenon. Moreover, the study of these issues can help in the design optimization of the acquisition system. In this line of thought a sensor classification scheme is presented. Several authors have addressed the subject of the sensor classification scheme. White (White, 1987) presents a flexible and comprehensive categorizing scheme that is useful for describing and comparing sensors. The author organizes the sensors according to several aspects: measurands, technological aspects, detection means, conversion phenomena, sensor materials and fields of application. Michahelles and Schiele (Michahelles & Schiele, 2003) systematize the use of sensor technology. They identified several dimensions of sensing that represent the sensing goals for physical interaction. A conceptual framework is introduced that allows categorizing existing sensors and evaluates their utility in various applications. This framework not only guides application designers for choosing meaningful sensor subsets, but also can inspire new systems and leads to the evaluation of existing applications. Today’s technology offers a wide variety of sensors. In order to use all the data from the diversity of sensors a framework of integration is needed. Sensor fusion, fuzzy logic, and neural networks are often mentioned when dealing with problem of combing information from several sensors to get a more general picture of a given situation. The study of data fusion has been receiving considerable attention (Esteban et al., 2005; Luo & Kay, 1990). A survey of the state of the art in sensor fusion for robotics can be found in (Hackett & Shah, 1990). Henderson and Shilcrat (Henderson & Shilcrat, 1984) introduced the concept of logic sensor that defines an abstract specification of the sensors to integrate in a multisensor system. The recent developments of micro electro mechanical sensors (MEMS) with unwired communication capabilities allow a sensor network with interesting capacity. This technology was applied in several applications (Arampatzis & Manesis, 2005), including robotics. Cheekiralla and Engels (Cheekiralla & Engels, 2005) propose a classification of the unwired sensor networks according to its functionalities and properties. This paper presents a development of a sensor classification scheme based on the frequency spectrum of the signals and on a statistical metrics. Bearing these ideas in mind, this paper is organized as follows. Section 2 describes briefly the robotic system enhanced with the instrumentation setup. Section 3 presents the experimental results. Finally, section 4 draws the main conclusions and points out future work

Fractional order fourier spectra in robotic manipulators with vibrations

This paper presents a fractional system perspective in the study of signals captured during impacts and vibrations of mechanical manipulators. In order to acquire and study the signals an experimental setup was developed. The system acquires data from the sensors, in real time, and, in a second phase, processes it through an analysis package. The experimental study provides useful information that can assist in the design of a control system to be used in eliminating or reducing the effect of vibrations.N/

Experimental Apparatus for Vibration Analysis in Robotics

Robotic systems use different types of sensors both in control and in environment perception. Those sensors can be digital encoders, tachometers, accelerometers, force sensors,current sensors and many others. In this paper an experimental setup is presented to study vibrations and impacts. The system acquires data from the sensors, in real time, and, in a second phase, processes it through an analysis package. Several examples with experimental results are carried out showing the functionalities of the developed apparatus.N/

Multidimensional Scaling Analysis of Robotic Signals

This paper analyzes the signals captured during impacts and vibrations of a mechanical manipulator. To test the impacts, a flexible beam is clamped to the end-effector of a manipulator that is programmed in a way such that the rod moves against a rigid surface. Eighteen signals are captured and several metrics are calculated between them, such as the correlation, the mutual information and the entropy. A sensor classification scheme based on the multidimensional scaling technique is presented.N/

Tuning the Windowed Fourier Transform of Robotic Signals in the Perspective of Information Theory

In many applications we are interested in the frequency content of a signal at a given period of time. The windowed Fourier transform is one of the most widely used timefrequency representations. To use this technique several parameters must be defined according to the signal analyzed. A new method based on the mutual information between frequency and time is proposed. The tests developed with robotic signal show the capability of the presented method.N/

A Statistical Approach for Tuning the Windowed Fourier Transform

The windowed Fourier transform is one of the most widely used time-frequency representations. In order to use this technique several parameters must be defined according to the signal analyzed. In this paper are studied the effects of the type, the shape, the length and the overlap of the windows, and new method for tuning the window parameters is presented. The study method is based on the information theory and is applied to signals captured during the movement of a robotic manipulator. The experimental results demonstrate the applicability and the effectiveness of the proposed approach.N/

A sensor classification scheme of robotic manipulators using multidimensional scaling technique

This paper analyzes the signals captured during impacts and vibra-tions of a mechanical manipulator. To test the impacts, a flexible beam is clamped to the end-effector of a manipulator that is programmed in a way such that the rod moves against a rigid surface. Eighteen signals are captured and theirs correlation are calculated. A sensor classification scheme based on the multidimensional scal-ing technique is presented.N/

The Power Law Applied to the Windowed Fourier Transform

The windowed Fourier transform is one of the most widely used time-frequency representations. In order to use this technique several parameters must be defined according to the signal analyzed. In this paper are studied the effects of the type, the shape, the length and the overlap of the windows. A power law/fractional window that we call fractional is defined and a new method for tuning the window parameters is presented. The study is based on the information theory and is applied to signals captured during the movement of a robotic manipulator. The experimental results demonstrate the applicability and the effectiveness of the proposed approach.N/

Prevalent Leadership Profile: A Research on Management of Innovation in the Military Organization

In this work we investigate prevailing leadership in a military organization. Our study has a multi-disciplinarily nature as it focuses on Organizational Innovation and the profile of a leader as well as a little investigation on history of the development of a military organization Our main objective is to identify the profile of a strategic prevalent leadership at the Firemen Corporation in Porto Velho, Rondonia – Northern Brazil. We propose to describe the process of nomination for someone to exercise the role of a leader used in the military structure. In this context, we make a survey of the prevalent elements considering the profile of leadership in the face of organizational innovation having in mind the expectation of the people involved in the process of research. At the end we conduct a critical analysis comparing the prevalent elements identified in our study with the expectation of innovation revealed by the military structure investigated. We apply the method of content analysis through convenient procedures. As a result, we present the elements which show prevalence for the definition of the leadership profile of the investigated military structure. We hope our research can contribute to the studies in the field of leadership, as we still have few references in the area of knowledge

Potencial nutricional de macroalgas marinhas dos Açores. Determinação do teor de proteína.

IV Congresso da Ordem dos Biólogos e II Congresso dos Biólogos dos Açores (Painel Biologia Marinha e Oceanografia). Ponta Delgada, Açores, 13-15 de Outubro de 2011