Tesis y Trabajos de Investigación PUCP

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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 Ángel
The 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.
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Modelación y simulación dinámica en el desarrollo de un sistema actuado para tobillo que asista al movimiento del pie en la marcha
(Pontificia Universidad Católica del Perú, 2018-06-19) Luis Peña, Abraham Israel; Elías Giordano, Dante Ángel
En el presente estudio se realizó la modelación y simulación dinámica de un novedoso sistema actuado para tobillo para la asistencia del movimiento de flexión plantar durante la caminata. Es así que, en la primera parte, se describe la anatomía funcional y biomecánica del sistema pierna-pie, y además se detalla el comportamiento de los principales elementos del sistema músculo esquelético. Posteriormente, se realiza el estado del arte sobre tecnologías portátiles asistenciales de tobillo, y se presentan los principales métodos de modelación y simulación computacional para la evaluación del desempeño de dichos dispositivos. En base al marco teórico presentado, se desarrollan los requerimientos y la conceptualización del diseño preliminar de un sistema actuado cuasi pasivo que contiene un accionamiento controlable capaz de almacenar y liberar energía elástica y así asistir a la marcha. Luego se realiza la modelación del cuerpo humano empleando el modelamiento “linksegmento”, ampliamente usado para análisis biomecánico del movimiento, y se implementa virtualmente el dispositivo propuesto a fin de analizar el comportamiento de su interacción durante la caminata a través de simulaciones dinámicas. El cálculo de la simulación se realiza de manera computacional empleando el software MATLAB a través de la técnica de dinámica inversa. Finalmente, estos resultados permiten entender el comportamiento dinámico del sistema actuado propuesto, así como los parámetros del accionamiento controlable para un desempeño óptimo en la asistencia de la marcha. Este conocimiento aporta al entendimiento de la interacción biomecánica de dispositivos asistenciales y además sienta las bases para el futuro diseño e implementación del dispositivo.

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