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Estrada Q.,Autonomous University of Ciudad Juarez | Szwedowicz D.,National Center for Research and Technological Development | Majewski T.,Universidad de Las Americas Puebla | Martinez E.,National Center for Research and Technological Development | Rodriguez-Mendez A.,University of California at Berkeley
Eksploatacja i Niezawodnosc

In this paper the effect of discontinuity size on energy absorption performance of steel square profiles is reported. The analysis consists of finite element simulations and experimental results of the compression strength of steel profiles with discontinuities. The discontinuities were placed at the mid span of the profiles in two walls opposite to each other. Square, rectangular and diamond initiators were evaluated at different scales. The numerical results determined the size intervals that present a good energy absorption performance in each case. Energy absorption capabilities were increased up to 12.54% with respect to a structure without discontinuities. Additionally, the peak load value (Pmax) was decreased 25.97% with the implementation of a diamond initiator. For structures with discontinuities with major axis close to the profile width, a buckling effect was observed. Finally, it was observed that the size of the initiators contributes to reduce the peak load (Pmax) value. © 2016, Polish Academy of Sciences Branch Lublin. All rights reserved. Source

Blanco A.,National Center for Research and Technological Development | Gomez F.A.,Higher Technological Institute of Puerto Vallarta | Olivares V.H.,National Center for Research and Technological Development | Abundez A.,National Center for Research and Technological Development | Colin J.,National Center for Research and Technological Development
International Journal of Automation and Control

The continuous passive motion (CPM) machines are used in the rehabilitation of members that have been injured to recover their range of motion and prevent stiffness. Nowadays, some CPM machines for knee, ankle, arm and elbow are available commercially. In this paper, a novel design of a parallel robot based on an XY table for ankle rehabilitation, that provides dorsiflexion-plantarflexion and abduction-adduction movements, is presented. Some results are presented in order to show the performance of the parallel robot for ankle rehabilitation. Proportional-derivative (PD), proportional-integral-derivative (PID) and generalised proportional integral (GPI) controllers for trajectory tracking are implemented in the virtual and physical prototype. Copyright © 2015 Inderscience Enterprises Ltd. Source

Estrada Q.,National Center for Research and Technological Development | Szwedowicz D.,National Center for Research and Technological Development | Baltazar M.,National Center for Research and Technological Development | Cortes C.,National Center for Research and Technological Development | And 2 more authors.
International Journal of Advanced Manufacturing Technology

A numerical study of the energy absorption characteristics of structural steel is presented, by implementing geometric imperfections. The geometric discontinuities were placed at half height of the structures in two opposite walls. In this case, different curved shapes discontinuities and quadrilaterals were evaluated. The shape and aspect ratio of the discontinuity modify the behavior of the structure even though the analyzed shapes have the same area value. The best performance in energy absorption of 12.54 % compared to a shape with no discontinuities was obtained with the implementation of a curved form initiator. Finally, and with the same comparison pattern, the value of the peak load was reduced up to 22.13 % by using the diamond-shaped discontinuities. © 2015 Springer-Verlag London Source

Szwedowicz D.,National Center for Research and Technological Development | Estrada Q.,National Center for Research and Technological Development | Cortes C.,National Center for Research and Technological Development | Bedolla J.,Apizaco Technological Institute | And 2 more authors.
Latin American Journal of Solids and Structures

This article details the experimental and numerical results on the energy absorption performance of square tubular profile with circular discontinuities drilled at lengthwise in the structure. A straight profile pattern was utilized to compare the absorption of energy between the ones with discontinuities under quasi-static loads. The collapse mode and energy absorption conditions were modified by circular holes. The holes were drilled symmetrically in two walls and located in three different positions along of profile length. The results showed a better performance on energy absorption for the circular discontinuities located in middle height. With respect to a profile without holes, a maximum increase of 7% in energy absorption capacity was obtained experimentally. Also, the numerical simulation confirmed that the implementation of circular discontinuities can reduce the peak load (Pmax) by 10%. A present analysis has been conducted to compare numerical results obtained by means of the finite element method with the experimental data captured by using the testing machine. Finally the discrete model of the tube with and without geometrical discontinuities presents very good agreements with the experimental results. Source

Martinez-Solis F.,National Center for Research and Technological Development | Claudio-Sanchez A.,National Center for Research and Technological Development | Rodriguez-Lelis J.M.,National Center for Research and Technological Development | Vergara-Limon S.,Autonomous University of Puebla | And 2 more authors.
BioMedical Engineering Online

Background: Gait analysis and research have been developed to obtain characteristics of movement patterns of people while walking. However, traditional measuring systems present different drawbacks that reduce their use and application. Among those drawbacks one can find: high price, low sampling frequency and limiting number of steps to be analyzed. Traditional measuring gait systems carry out their measurement at frequencies oscillating between 60 to 100 Hz. It can be argued about the need of higher sampling rates for gait measurements. However small displacements of the knee or hip for example, cannot be seen with low frequencies required a more detailed sampling and higher frequency sampling. Bearing this in mind, in this paper is presented a 250 Hz system based on accelerometers for gait measurement, and the particularities of knee and hip angles during gait are highlighted.Methods: The system was designed with a PCI data acquisition card instrumented with an FPGA to achieve a rate sample of 250 Hz. The accelerometers were placed in thighs and legs to calculate the joint angles of hip and knee in the sagittal plane. The angles were estimated using the acceleration polygon method without integrating the acceleration and without filters.Results: The gait of thirty healthy people of Mexican phenotype was analyzed over a flat floor free of obstacles. The results showed the gait phases and particularities associated with the walking style and people's laterality; the movement patterns were similar in the thirty persons. Based on the results, the particularities as the maximum amplitude in the angles and the shape in the movement patterns were related to the anthropometry and people phenotype.Conclusions: The sampling frequency was essential to record 340 samples in single gait cycle and so registering the gait cycle with its particularities. In this work were recorded an average of 8 to 10 gait cycles, and the results showed variation regarding works carried out in biomechanics laboratories; this variation was related to the method and reference frame used to obtain the joint angles and the accuracy of measurement system. © 2014 Martínez-Solís et al.; licensee BioMed Central Ltd. Source

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