1,312 research outputs found
Fractional dynamics in liquid manipulation
This paper presents a fractional calculus perspective in the study of signals captured during the movement of a mechanical
manipulator carrying a liquid container. In order to study the signals an experimental setup is implemented. The system acquires data from
the sensors, in real time, and, in a second phase, processes them through an analysis package. The analysis package runs off-line and handles
the recorded data. The results show that the Fourier spectrum of several signals presents a fractional behavior. The experimental study
provides useful information that can assist in the design of a control system and the trajectory planning to be used in reducing or eliminating
the effect of vibrations
Experimental backlash study in mechanical manipulators
The behavior of mechanical manipulators with backlash is analyzed. In order to acquire and study the signals an experimental setup is implemented. The signal processing capabilities of the wavelets are used for de-noising the experimental signals and the energy of the obtained components is analyzed. To evaluate the backlash effect upon the robotic system, it is proposed an index based on the pseudo phase plane representation. Several tests are developed that demonstrate the coherence of the results
Filtering method in backlash phenomena analysis
The behavior of robotic manipulators with backlash is analyzed. Based on the pseudo-phase plane two indices are proposed to evaluate the backlash effect upon the robotic system: the root mean square error and the fractal dimension. For the dynamical analysis the noisy signals captured from the system are filtered through wavelets. Several tests are developed that demonstrate the coherence of the results
Chemical characterization and biological properties of royal jelly samples from the mediterranean area
Royal jelly (RJ) is a bee product that has high nutritional value and is beneficial for the human health, earning importance as a functional food. Thus, the characterization of its main biological properties is with high importance. In this work, 6 RJ samples obtained in Morocco, Portugal, and Spain were evaluated in terms of total phenol and flavone/flavonol contents; total protein; 10-hydroxy-2-decenoic acid (10-HDA); volatiles composition; antioxidant and anti-inflammatory properties; and inhibition of tyrosinase, xanthine oxidase (XO), and acetylcholinesterase (AChE) activities. Total phenolic content ranged from 3 to 9 mg gallic acid equivalent/g RJ, and flavone/flavonol content from 0.1 to 0.5 mg quercetin equivalent/g RJ. 10-Hydroxy-2-decenoic acid content varied from 0.9% to 1.2% and total protein from 5.5% to 29.7%. Gas chromatography-flame ionization detector and gas chromatography-mass spectrometry analysis showed RJ volatiles dominated by linolenic acid, 2-decenoic acid, and octanoic acid in variable amounts. The antioxidant activity was monitored through nitric oxide (NO) scavenging activity and hydrogen peroxide (H2O2) scavenging capacity, where the IC50 ranged from 2.3 to 3.4 and 0.2 to 1.5 mg/mL, respectively. Anti-AChE activity IC50 ranged from 0.7 to 4.6 mg/mL, while XO inhibition IC50 ranged from 3.3 to 11.9 mg/mL. The results showed that phenols and flavonoids highly contributed to the RJ biological properties in contrast to 10-HDA and proteins.UID/AMB/50017/2019
UIDB/05183/2020info:eu-repo/semantics/publishedVersio
A multidimensional scaling analysis of musical sounds based on pseudo phase plane
This paper studies musical opus from the point of view of three mathematical tools: entropy, pseudo phase plane (PPP), and multidimensional scaling (MDS). The experiments analyze ten sets of different musical styles. First, for each musical composition, the PPP is produced using the time series lags captured by the average mutual information. Second, to unravel hidden relationships between the musical styles the MDS technique is used. The MDS is calculated based on two alternative metrics obtained from the PPP, namely, the average mutual information and the fractal dimension. The results reveal significant differences in the musical styles, demonstrating the feasibility of the proposed strategy and motivating further developments towards a dynamical analysis of musical sounds
Architecture based on keyword driven testing with domain specific language for a testing system
For Cyber-physical systems (CPSs), whose task is to test industrial products, to carry out these tests, highly qualified engineers are always needed to design the tests, since the computational part of the tests is programmed in low-level languages. To optimize this process, it is necessary to create an abstraction of current methods so that tests can be created and executed more efficiently. Although this problem has arisen within the CPS, the architecture we propose will be generic enough to solve the problem in any testing system. We intend to do this by automating some of the current processes to minimize human error. In this paper, we present a novel architecture for a testing system that abstracts single low-level programming and coding of tests, based on two main concepts: the use of Keyword Driven Testing (KDT) that will abstract tests to the person responsible for the machine; the creation of a Domain Specific Language (DSL) to help configure and design new tests without requiring the experience of a highly qualified engineer.This paper is a result of the project POCI-01-0247-FEDER-040130, supported by Operational Program for Competitiveness and Internationalization (COMPETE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF)
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/
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/
Application of fractional algorithms in the control of a robotic bird
In this paper, it is studied the dynamics of the robotic bird in terms of time response and robustness. It is analyzed the wing angle of attack and the velocity of the bird, the tail influence, the gliding flight and the flapping flight. The results are positive for the construction of flying robots. The development of computational simulation based on the dynamic of the robotic bird should allow testing strategies and different algorithms of control such as integer and fractional controllers
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