Aportació a l'estudi de la reducció de vibracions residuals en transitoris de moviment generats mitjançant accionaments de cinemàtica no lineal
- Autores: Eduard Lores Garcia
- Directores de la Tesis: Lluisa Jordi Nebot (dir. tes.), Joaquim Maria Veciana Fontanet (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2017
- Idioma: español
- Tribunal Calificador de la Tesis: Jordi Romeu Garbi (presid.), Guillermo Reyes Pozo (secret.), Joan Roca (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería Mecánica, Fluidos y Aeronáutica por la Universidad Politécnica de Catalunya
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Machines and mechanisms can usually exhibit a vibratory behavior during operation since they are formed by deformable solids of non-negligible mass and non-rigid joints. This oscillatory behavior can be shown for transient excitations caused by both external forces and internal inertia movements. Normally, this kind of vibrations are still present even after the end of the transient, and can negatively influence the correct operation of the system. Remaining oscillations in the system once the transient excitement has finished are called residual vibrations. On the other hand, the drive that moves a machine generally requires a non-unitary transmission ratio in order to adjust the torque -or force- and the speed of the drive with the movement of the load. With the objective of achieving the desired ratio, one may think about using elements with lineal kinematics -or roughly linear- such as, for example, gears, belts or chains. However, gears and chains introduce plays in the system that may hinderits control and its correct operation. In addition, this fact may produce the uncontrolled excitation of some of its own vibration modes, which makes it difficult to reduce residual vibrations. Regarding belts, they add an additional stiffness low enough to introduce a relevant vibration mode as regards the control of residual vibrations. Another possible solution is to use one degree of freedom bar mechanisms with non-linear kinematics and planar motion that works around a dead point configuration. This optionallows to notably reduce the plays introduced in the system and achieve high transmission ratios, but implies the study in detail of the inverse kinematics around these configurations. In this dissertation the generation of excitation or control signals in mechanical systems in order to minimize the appearance of residual vibrations is proposed. The transmission of the motion is carried out through one degree of freedom non-linear kinematic drives with planar motion. In general, in linear kinematic transmission mechanisms -or roughly linear-, the desired motion law at the output of the drive is nearly the same than the inputsignal to the corresponding control. In the proposed development, however, as non-lineal kinematics transmissions are used near dead point configurations, the control signal of the drive and the resulting motion law differ considerably. On the other hand, the feasibility of control signal design of the drive depends to a great extend on the conditions of continuity of the motion law at the beginning, ending and passing through these singular configurations. The development performed is based on the resolution of the resultant indeterminacies of the inverse kinematic analysis through the use of L'Hôpital's rule to obtain the continuity relations between the control signal and the resulting law of motion. For the reduction of residual vibrations, currently knownmethods are used imposing the restrictions that entails the existence of dead points in the operating range of the mechanism. Finally, the validity of the method is verified based on experimental tests. The test bench consists of a drive formed by a direct current servomotor (DC), a transmission mechanism of a piston-slider-crank mechanism and a pendulum as an oscillating system, whose rotation axis moves in conjunction with the piston. The goodness in the results validates the analytical study proposed.
