No abstract

Optical encoders are sensors based on grating interference patterns. Tolerances inherent to the manufacturing process can induce errors in the position accuracy as the measurement signals stand apart from the ideal conditions. In case the encoder is working under vibrations, the oscillating movement of the scanning head is registered by the encoder system as a displacement, introducing an error into the counter to be added up to graduation, system and installation errors. Behavior improvement can be based on different techniques trying to compensate the error from measurement signals processing. In this work a new “ad hoc” methodology is presented to compensate the error of the encoder when is working under the influence of vibration. The methodology is based on fitting techniques to the Lissajous figure of the deteriorated measurement signals and the use of a look up table, giving as a result a compensation procedure in which a higher accuracy of the sensor is obtained.

In this paper, an intelligent scheme for detecting incipient defects in spur gears is presented. In fact, the study has been undertaken to determine these defects in a single propeller system of a small-sized unmanned helicopter. It is important to remark that although the study focused on this particular system, the obtained results could be extended to other systems known as AUVs (Autonomous Unmanned Vehicles), where the usage of polymer gears in the vehicle transmission is frequent. Few studies have been carried out on these kinds of gears. In this paper, an experimental platform has been adapted for the study and several samples have been prepared. Moreover, several vibration signals have been measured and their time-frequency characteristics have been taken as inputs to the diagnostic system. In fact, a diagnostic system based on an artificial intelligence strategy has been devised. Furthermore, techniques based on several paradigms of the Artificial Intelligence (Neural Networks, Fuzzy systems and Genetic Algorithms) have been applied altogether in order to design an efficient fault diagnostic system. A hybrid Genetic Neuro-Fuzzy system has been developed, where it is possible, at the final stage of the learning process, to express the fault diagnostic system as a set of fuzzy rules. Several trials have been carried out and satisfactory results have been achieved.

Optical linear encoders are high‐precision positioning sensors based on the interference patterns produced by the relative movement between two gratings. One of the gratings is impressed on a scale and the other is located in what is known as the scanning head. The rest of the main components are a light source, collimating lens, and a set of photodetectors. The arrangement of these components is mainly conditioned by the scanning method chosen, resulting in a different encoder mechanical design and therefore in dissimilar dynamic behavior if transmission or reflection is selected. In these methods, sealed single field scanning encoders represent the ultimate state‐of‐the‐art becoming the most widespread solution nowadays, but it has to be said that there is a lack of information concerning their dynamic behavior under vibrations in relation to conventional transmission or reflection reading heads. A novel methodology that allows identifying both the frequency and the error due to vibrations, which can be used in compensation procedures to correct the sensor's displacement measurement, is proposed in this work. Additionally, a comparison study based on the simulation results obtained by finite element models of transmission and reflection type encoders is presented. In the second part of the work, experimental performance comparison under vibration of the above‐mentioned scanning methods used in optical linear encoders is done. Using the new methodology that includes an experimental technique with an improved mathematical approach that allows not only to assess the loss of accuracy of the sensor due to vibration, but also the error committed by the encoder in a range of excitation frequencies is characterized.

En la actualidad estamos sumergidos en un cambio de paradigma comunicacional, con lo cual asistimos al despliegue, en palabras de McLuhan, de un entorno que lleva como consecuencia un cambio antropológico. Estas transformaciones a través de las tecnologías están provocando la aparición de nuevas prácticas en relación al amor, hecho que encuentra un desarrollo vertiginoso en las redes sociales. En este artículo analizaremos el amor el partir de las definiciones de eros, philia y ágape. Lo abordaremos poniendo en juego el tétrade de McLuhan con sus cuatro interrogantes, de tal forma que emerja una visión sobre las tecnologías de la información y la comunicación para los cambios de prácticas afectivas. Encontraremos que estamos sumergidos en un entorno que dibuja unos modos de relación mediatizados por las redes sociales.