Ingeniería Mecánica (Mag.)
URI permanente para esta colecciónhttp://54.81.141.168/handle/123456789/9096
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Ítem Texto completo enlazado Developing of a device for measuring the areal distribution of the forces in the contact zone of foot and underground for the use in leg prostheses(Pontificia Universidad Católica del Perú, 2020-09-18) Kubisch, Jörg; Fröhlich, Thomas; Elías Giordano, Dante ÁngelThe presented work demonstrates the process of designing a cheap, low cost three axis force sensor. Further it describes its integration in an array of multiple sensors to measure the distribution of forces acting on the sole of a prosthetic foot. The focus will be on easy manufacturing and common materials since the sensor will be integrated in a low cost prosthesis for lower limp amputees. Using the knowledge from bio mechanics and some basic assumptions for the later use, requirements for the project are derived. After a presentation of some state of the art sensor principles, suitable concepts are collected. Than, the concepts are compared using a comparison table to find the one the fits the requirements the best. A very compelling concept using barometers casted in silicone rubber is tested using a simple prototype to try out whether it is a good candidate or not. The tests show that the concept is capable of measuring forces but due to its disadvantageous susceptibility for temperature changes it is rejected for the further development process. The concepts are reevaluated and a new concept is chosen. Afterwards the design process is described. Beginning with the mechanical design explaining the working principle. The calculation of the dimensions is presented. After that a circuit to work with a capacitive measurement as well as a version for resitive measurement is developed and a layout for a prototype board using capacitive measurement is proposed. To prove the functionality, the capacitive system is built up as a prototype. To try the measurement behavior and to measure its repeatability a test stand is designed. It uses commercial available load cells to conduct a reference measurement. The output of the sensor is compared to the reference measurement. With various different test procedures the curves mapping the measured values to the force for normal and shear force measurement are determined. During the tests, different aspects of performance like creep behavior or hysteresis are investigated. Also the repeatability is measured various times under different loads to make reliable estimations of the precision of the measurement. Further on, a resistive force sensor which could be used instead of the capacitive sensing elements is tested regarding its curve and performance to have a comparison of the advantages and disadvantages of either designing the future sensor with resistive or capacitive sensing elements. With both concepts a repeatability of a few percent uncertainty can be achieved. Further on ways to improve future versions of the sensor are described based on the experiences made during the work with the prototype. Finally a possible way to integrate multiple sensors into a sensing array is proposed. The design as well as possible electrics to acquire the data are discussed. This way a solid basis for further developments of a sensing array measuring the force distribution is given.Ítem Texto completo enlazado Hybrid electromagnetic actuator design for an AMB prototype(Pontificia Universidad Católica del Perú, 2019-07-31) Betz, Björn Arnold Heinrich; Calderón Chavarri, Jesús Alan; Barriga Gamarra, Eliseo Benjamín; Ströhla, TomIn Peru, mining is one of the main drivers behind most developments in engineering, an area of high dynamic forces and high pollution. As an illustration, shovel excavators transport tons of sediment each day while cylinder screens sort the stones by size. Typically, ball or cylindrical bearings support these screens and companies, such as SKF, replace the bearings in regular intervals. Thus, the idea is to implement a system, which can dynamically adapt to loads and dynamical load changes to reduce maintenance intervals and vibrations. Ultimately, for a prototype this thesis presents two design proposals of a homopolar, hybrid active magnetic bearing. Moreover, the selection of an inductive type sensor should represent an adequate solution for determining the shaft position.Ítem Texto completo enlazado Theoretical and numerical investigations of the parametric resonance of the mechanical vibrissa(Pontificia Universidad Católica del Perú, 2019-02-25) Perez Tineo, Cesar Augusto; Alencastre Miranda, Jorge HernánIn nature, vibrissae are tactile hairs of mammals used as sensor elements for the exploring the surrounding area. These hairs, also known as whiskers, can be found in different locations on an animals body. Mystacial vibrissae are distributed over a whiskerpad on a muzzle. Carpal vibrissae are located on the downside aspect of the forelimbs of mammals. The vibrissal hair has a conical shape and grows from a special heavily innervated hair follicle incorporating a capsule of blood. As the hair itself has no receptors along its length, the vibrissa may be considered as a system for transmitting forces and torques that arise from the contact between the hair and an object to sensory receptors inside the follicle. The present thesis deals with the vibrational motion of vibrissae dur- ing natural exploratory behaviour from the mechanical point of view. The phenomenon of the parametric resonance of the vibrissa is investigated the- oretically and numerically. In the first part of this thesis, two mechanical models of an elastic beam are presented based on findings in the literature. The first model considers a straight beam with the linearly decreasing radius of the circular cross-section. The second model takes into account the circu- lar natural configuration of the cylindrical beam. Within these models, the small transverse vibration of the beam under a periodic following force at the tip are analysed using the Euler-Bernoulli beam theory and asymptotic methods of mechanics. In the second part of the thesis, the numerical analysis of the problems is performed based on the finite element method using ANSYS 16.2 software. For each model, the dynamical response of the system on the parametric excitation is simulated for different frequency values. It is shown theoretically and numerically that at specific ranges of the excitation frequency the phenomenon of the parametric resonance of the beam takes place. That means that the amplitude of vibrations of the beam increases exponentially with time, when it is stimulated within one of the frequency ranges of the parametric resonance. These ranges depend on the geometrical and material parameters of the beam model, as well as the am- plitude of the periodic excitation.