Ciencias Exactas y Ciencias de la Salud

Permanent URI for this collectionhttps://hdl.handle.net/11285/551014

Pertenecen a esta colección Tesis y Trabajos de grado de los Doctorados correspondientes a las Escuelas de Ingeniería y Ciencias así como a Medicina y Ciencias de la Salud.

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A new methodology for inverse kinematics and trajectory planning of humanoid biped robots
(Instituto Tecnológico y de Estudios Superiores de Monterrey) Rodriguez, Alejandro; Soto Rodríguez, Rogelio; School of Engineering and Sciences; Campus Monterrey
This dissertation presents a new methodology for Inverse Kinematics and Trajectory Planning for small-sized humanoid biped robots. Regarding the Inverse Kinematics, this study presents an explicit, omnidirectional, analytical, and decoupled closed-form solution for the lower limb kinematics of the humanoid robot NAO. It starts by decoupling the position and orientation analysis from the concatenation of Denavit-Hartenberg (DH) transformation ma- trices. Here, the joint activation sequence for the DH matrices is mathematically constrained to follow the geometry of a triangle. Furthermore, the implementation of a forward and a reversed kinematic analysis for the support and swing phase equations is developed to avoid the complexity of matrix inversion. The allocation of constant transformations allows the position and orientation end-coordinate systems to be aligned with each other. Also, the re- definition of the DH transformations and the use of constraints allows for the decoupling the shared Degree of Freedom (DOF) located between the legs and the torso; and which activates the torso and both of the legs when a single actuator (the hip-yaw joint) is activated. Further- more, a three dimensional geometric analysis is carried out to avoid the singularities during the walking process. Numerical data is presented along with experimental implementations to prove the validity of the analytical results. In relation to the trajectory planning, a method taken from manipulator robot theory is applied to humanoid walking. Fifth and seventh order polynomials are proposed to define the trajectories of the Center of Gravity (CoG) and the swing foot. The polynomials are designed so that the acceleration and jerk are constrained to be zero particularly at two moments: at the single support phase (when the robot is standing on a single foot), and at the foot landing (to prevent foot-to-ground impacts); thus, minimizing internal disturbance forces. Computer simulations are performed to compare the effects of the acceleration and jerk constraints. In addition, the basics of the future work is given by providing a control model for robot equilibrium. First, the analysis of this model starts with a static equilibrium model which reacts to an ankle perturbation by using a hip actuation. Second, a dynamic model is proposed which incorporates the ground perturbations into the robot model by representing the ground tilt as an additional, passive, and redundant DOF located at the ankle. This procedure allows for two separate models (the one corresponding to the humanoid and the one corresponding to the ground) to be accounted into a single model, thus, minimizing complexity.
Study on the convective heat transfer behaviour of laminar nanofluids flow
(Instituto Tecnológico y de Estudios Superiores de Monterrey) Ramirez Tijerina, Ramon; 0000-0002-4132-6301; Rivera Solorio, Carlos Iván; García Cuellar, Alejandro Javier; López Salinas, Jose Luis; Gijón Rivera, Miguel Ángel; Jogender, Singh; School of Engineering and Sciences; School of Engineering and Sciences; Campus Monterrey
Nanofluids are engineered colloids of nanoparticles dispersed homogenously within base fluids. The term nanofluids refers to a mixture composed of a continuous phase, usually a saturated liquid, and a dispersed phase constituted of extremely fine metallic particles of size below 100 nm called nanoparticles. Due to the presence of nanoparticles, the thermophysical and transport properties of base fluids are subject to change. The nanofluids are considered the next-generation heat transfer fluids because of the new possibilities compared to pure fluids. Existing technologies for industrial applications, such as: microelectronics, vehicle thermal management (engine cooling) and heat exchangers seem to be insufficient and nanofluids, as reported in several studies, might offer a better alternative for proper heat transfer. The main purpose of this study is to investigate numerically the potential for replacing nanofluids in a single-phase flow for a conventional straight tube and a straight microtube under the constant temperature and constant heat flux conditions, separately. Nanofluids with a wide range of process parameters had been studied by varying three different types of base fluids including water, ethylene glycol and oil with five different type of nanoparticles viz. Al2O3, TiO2, CuO, SiO2 and ZnO. During the present investigation, six different combinations of the geometries, based fluids and nanoparticle concentrations were considered. The thermophysical properties of the nanofluids were obtained from the literature. The mathematical modeling was done using single-phase approach (SPH) were the flow was assumed as a steady incompressible flow and the continuity, momentum and energy equations are solved using the effective properties of the nanofluids. In addition to the single-phase model (SPH), the single-phase dispersion model (SPD) was also used for effectiveness of the computed results. The governing equations of mass, momentum and energy were solved using finite volume approach/method. To ensure the accuracy and consistency of computational results, various uniform grids were tested. An extensive number of numerical simulations were performed to determine the Nusselt number (Nu) of laminar nanofluids. For validation purposes, the present results of the Nusselt number were compared with the literature computational and experimental results. The results showed that the Nusselt number increases with increase in Reynolds number (Re) for all the nanofluids considered. In the case of the straight tube with 𝝓𝒃=𝟒%, the Nu increases 16% for Al2O3-water as comparted to water, 12% for Al2O3-EG as compared to EG and 8% for Al2O3-oil as compared to oil. The investigation concludes with the proposition of heat transfer correlations for the flow of nanofluids in conventional straight tube and straight microtube over a wide range of process conditions: 25