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 Non-linear beam theory in context of bio-inspired sensing of flows(Pontificia Universidad Católica del Perú, 2017-03-31) Lavayen Farfán, Daniel; Behn, Carsten; Elías Giordano, Dante ÁngelThe thesis at hand is part of a research project that attempts to study and develop vibrissa inspired tactile sensors for object and fluid flow detection. The main focus of the thesis is on the development of a model for a vibrissa-like sensor for obstacle contour recognition under fluid loads. To this end, a mechanical model – based on the non-linear Euler-Bernoulli beam theory – is established. The model includes the main characteristics found in a natural vibrissa, such as elasticity of the base, that acts as the vibrissa follicle; the intrinsic curvature; and conicity. The characteristics are represented as parameters of the model. The model is subjected to a contact load and a fluid flow load, represented by a concentrated load and a distributed load, respectively. Then, the model is transformed into a dimensionless representation for further studies to achieve more general assertions. A variation of the magnitude of these loads, as well as the vibrissa parameters is also analyzed. A direct numerical approximation using the finite difference method, along with the shooting method, is used to obtain a solution of the model. Subsequently, the model is used to simulate an ideal contact between an obstacle and the vibrissa. This simulation considers a quasi-static sweep of the artificial vibrissa with the contour of a profile, while measuring and recording the forces and moment at the base. This procedure is then repeated in combination of a distributed force acting on the vibrissa, simulating the effect of a fluid flow. Two types of contact phases are identified and the conditions for each one are set. Finally, the measured quantities, which represent the observables an animal solely relies on, are used to obtain the magnitude of the fluid load and to reconstruct the profile contour of the obstacle. The developed model is used again for the reconstruction, an analysis of the observables is performed to identify and predict which contact phase the vibrissa is in. The results successfully show identification of the fluid flow load as well as reconstruction of the profile, the difference between the reconstructed profile and the original profile is then calculated as a measure of reconstruction quality.Ítem Texto completo enlazado Tracking controller design for a nonlinear model of a gantry crane based on dynamic extension and robustification(Pontificia Universidad Católica del Perú, 2015-11-19) Zárate Moya, José Luis; Reger, Johann; Elías Giordano, Dante ÁngelOverhead cranes are widely used in industry for transportation of heavy loads and are common industrial structures used in building construction, factories, and harbors, traditionally operated by experienced crane operators. The underlyng system consists of three main components: trolley, bridge, and gantry. Basically, the system is a trolley with pendulum. In normal operation, the natural sway of crane payloads is detrimental to the safe and efficient action. Other external disturbances parameters, wind for example, also affect the controller performance. Basically, a crane system is an underactuated system. This makes the design of its controllers complicated. Usually, this is done via the crane acceleration required for motion. The most important issues in crane motion are high positioning accuracy, short transportation time, small sway angle, and high safety. The main goal of this thesis is to achieve a robust controller design procedure, based on H∞ control theory, for a nonlinear model of a 3-D gantry crane system. The approach shall be compared with classic controllers in terms of attenuating the perturbation on the payload transportation. The model describes the position of the load, as well as the time derivatives of the position. In vew of this, flatness-based feedforward control has to be devised, accompanied by the design of an optimal linear and nonlinear feedback controller. The nomnal states can be used as optimization parameters and restrictions on stability, overshoot, position regulation, and oscillation angle, being independent of the load mass and depending on the rope length. The procedure is as follows. First, a dynamic nonlinear model of the system is obtained using the Lagrange equations of motion which describe the simultaneous travelling, crossing, lifting motions and the resultant load swing of the crane. Then, the system is exactly linearised by a dynamic extension. Next the closed-loop system, based on the linear quadratic regulator scheme, is probed and compared with the H∞ robust control system for compensating modeling errors and/or internal and external perturbation. Finally, simulation results are presented showing the efficiency of the proposed controller design scheme. Results are provided to illustrate the improved performance of the nonlinear controllers over classic pole placement and linear quadratic regulator approaches, testing its fast input tracking capability, precise payload positioning and minimal sway motion.