UN ACERCAMIENTO A LA PRODUCCIÓN CERÁMICA EN YAXCHILÁN DURANTE EL CLÁSICO TARDÍO A TRAVÉS DE DOS ESTUDIOS DE CASO

En el presente trabajo se aborda el tema de la producción alfarera en las Tierras Bajas Mayas durante el Clásico Tardío (600-900 d.C.), desde la perspectiva de Yaxchilán. A partir de una muestra de vasijas completas procedentes de contextos funerarios elitistas del sitio, se evalúa si las vasijas que abastecían a la élite gobernante se producían en talleres especializados adscritos al palacio o en los de artesanos independientes que laboraban a tiempo parcial. Teniendo en consideración estudios previos tanto tipológicos como de pastas para determinar cuál es el material que acusa una producción local, se llevaron a cabo análisis modales de formas, medidas y motivos decorativos presentes en las vasijas con la intención de determinar el nivel de estandarización y así evaluar el grado de especialización en la producción; aunado a lo anterior el estudio también atendió a un atributo adicional, el grado de desgaste por uso que muestra cada ejemplar, pues dicho aspecto permite obtener información sobre su costo de reemplazo. El material ha permitido obtener datos que sugieren que la cerámica que consumió la élite del sitio durante dicho periodo fue manufacturada en talleres de artesanos de tiempo parcial.This paper addresses the issue of pottery production in the Maya Lowlands during the Late Classic (600-900 AD) from the perspective of Yaxchilán. A sample of complete vessels from the site's elitist funerary contexts evaluated whether the vessels that supplied the ruling elite were produced in specialized workshops attached to the palace or in those of independent artisans who worked part-time. Considering previous typological and paste studies to determine the material that shows a local production, modal analyses of shapes, measurements, and decorative motifs present in the vessels were carried out to determine the level of standardization and thus evaluate the degree of specialization in production. In addition to the above, the study also addressed an additional attribute, the degree of use-wear that each specimen shows since this aspect allows obtaining information on its replacement cost. The material has yielded data suggesting that the pottery consumed by the site's elite during that period was manufactured in part-time artisan workshops

On Controlling Aircraft Formations

We describe a framework for controlling a group of unmanned aerial vehicles (UAVs) flying in close formation. We first present a nonlinear dynamical model which includes the induced rolling moment by the lead aircraft on the wing of the following aircraft. Then, we outline two methods for trajectory generation of the leading aircraft, based on interpolation techniques on the Euclidean group, SE(3). Two formation controllers that allow each aircraft to maintain its position and orientation with respect to neighboring UAVs are derived using input-output feedback linearization. Numerical simulations illustrate the application of these ideas and demonstrate the validity of the proposed framework

A Framework for Scalable Cooperative Navigation of Autonomous Vehicles

We describe a general framework for controlling and coordinating a group of non-holonomic mobile robots equipped with range sensors, with applications ranging from scouting and reconnaissance, to search and rescue and manipulation tasks. We first describe a set of control laws that allows each robot to control its position and orientation with respect to neighboring robots or obstacles in the environment. We then develop a coordination protocol that allows the robots to automatically switch between the control laws to follow a specified trajectory. Finally, we describe two simple trajectory generators that are derived from potential field theory. The first allows each robot to plan its reference trajectory based on the information available to it. The second scheme requires sharing of information and results in a trajectory for the designated leader. Numerical simulations illustrate the application of these ideas and demonstrate the scalability of the proposed framework for a large group of robots

Hybrid Control of Formations of Robots

We describe a framework for controlling a group of nonholonomic mobile robots equipped with range sensors. The vehicles are required to follow a prescribed trajectory while maintaining a desired formation. By using the leader-following approach, we formulate the formation control problem as a hybrid (mode switching) control system. We then develop a decision module that allows the robots to automatically switch between continuous-state control laws to achieve a desired formation shape. The stability properties of the closed-loop hybrid system are studied using Lyapunov theory. We do not use explicit communication between robots; instead we integrate optimal estimation techniques with nonlinear controllers. Simulation and experimental results verify the validity of our approach