Diseño de un BMS modular para EV enfocado a MotoStudent

The project is based on the design of a Modular Battery Management System for a battery pack that will be in the Eupla Racing Team prototype racing in Alcañiz during the MotoStudent IV event. The present memory explains the development of such design. It starts presenting a state of the art and a theoretical framework to give the reader some background and understanding before starting with the technical work. Knowledge of the existing technologies is a must to be able to design a reliable BMS. The next section explains the development of the prototype. It is divided into several sections. MotoStudent regulations and the battery pack for which we are designing the BMS will be introduced to be able to start with the design. We will first carry out a market study of the available monitoring chips and search for one with the optimal features for our application. Once the chip is selected the electronic design will start taking into account the suggestions given by the manufacturer in the datasheet. Also the extra features needed for our application will be added. For instance, the conditioning circuit for the chosen temperature sensors; in our case, NTCs. For the hardware development we will have to choose an appropriate balancing current for a competition application and make the corresponding calculations such as trace width to withstand the current applied. A meticulous component selection will be elaborated to ensure we have a reliable prototype. Finally, software will be divided into two stages: software development and the interface. The former will be based on the chip libraries offered by the manufacturer and adapted to our application, the latter will be developed with LabVIEW. The LabVIEW interface will be a key feature to ensure a testing procedure and a quick way to check the battery pack state during the competition

Factory Oriented Technique for Thermal Drift Compensation in MEMS Capacitive Accelerometers

Capacitive MEMS accelerometers have a high thermal sensitivity that drifts the output when subjected to changes in temperature. To improve their performance in applications with thermal variations, it is necessary to compensate for these effects. These drifts can be compensated using a lightweight algorithm by knowing the characteristic thermal parameters of the accelerometer (Temperature Drift of Bias and Temperature Drift of Scale Factor). These parameters vary in each accelerometer and axis, making an individual calibration necessary. In this work, a simple and fast calibration method that allows the characteristic parameters of the three axes to be obtained simultaneously through a single test is proposed. This method is based on the study of two specific orientations, each at two temperatures. By means of the suitable selection of the orientations and the temperature points, the data obtained can be extrapolated to the entire working range of the accelerometer. Only a mechanical anchor and a heat source are required to perform the calibration. This technique can be scaled to calibrate multiple accelerometers simultaneously. A lightweight algorithm is used to analyze the test data and obtain the compensation parameters. This algorithm stores only the most relevant data, reducing memory and computing power requirements. This allows it to be run in real time on a low-cost microcontroller during testing to obtain compensation parameters immediately. This method is aimed at mass factory calibration, where individual calibration with traditional methods may not be an adequate option. The proposed method has been compared with a traditional calibration using a six-sided orthogonal die and a thermal camera. The average difference between the compensations according to both techniques is 0.32 mg/°C, calculated on an acceleration of 1 G; the maximum deviation being 0.6 mg/°C

Lightweight thermal compensation technique for MEMS capacitive accelerometer oriented to quasi-static measurements

The application of MEMS capacitive accelerometers is limited by its thermal dependence, and each accelerometer must be individually calibrated to improve its performance. In this work, a light calibration method based on theoretical studies is proposed to obtain two characteristic parameters of the sensor’s operation: the temperature drift of bias and the temperature drift of scale factor. This method requires less data to obtain the characteristic parameters, allowing a faster calibration. Furthermore, using an equation with fewer parameters reduces the computational cost of compensation. After studying six accelerometers, model LIS3DSH, their characteristic parameters are obtained in a temperature range between 15 °C and 55 °C. It is observed that the Temperature Drift of Bias (TDB) is the parameter with the greatest influence on thermal drift, reaching 1.3 mg/°C. The Temperature Drift of Scale Factor (TDSF) is always negative and ranges between 0 and −400 ppm/°C. With these parameters, the thermal drifts are compensated in tests with 20 °C of thermal variation. An average improvement of 47% was observed. In the axes where the thermal drift was greater than 1 mg/°C, the improvement was greater than 80%. Other sensor behaviors have also been analyzed, such as temporal drift (up to 1 mg/h for three hours) and self-heating (2–3 °C in the first hours with the corresponding drift). Thermal compensation has been found to reduce the effect of the latter in the first hours after power-up of the sensor by 43%

Using ages and kinematic traceback: the origin of young local associations

Over the last decade, several groups of young (mainly low-mass) stars have been discovered in the solar neighbourhood (closer than ~100 pc), thanks to cross-correlation between X-ray, optical spectroscopy and kinematic data. These young local associations offer insights into the star formation process in low-density environments, shed light on the substellar domain, and could have played an important role in the recent history of the local interstellar medium. Ages estimates for these associations have been derived in the literature by several ways. In this work we have studied the kinematic evolution of young local associations and their relation to other young stellar groups and structures in the local interstellar medium, thus casting new light on recent star formation processes in the solar neighbourhood. We compiled the data published in the literature for young local associations, including the astrometric data from the new Hipparcos reduction. Using a realistic Galactic potential we integrated the orbits for these associations and the Sco-Cen complex back in time. Combining these data with the spatial structure of the Local Bubble and the spiral structure of the Galaxy, we propose a recent history of star formation in the solar neighbourhood. We suggest that both the Sco-Cen complex and young local associations originated as a result of the impact of the inner spiral arm shock wave against a giant molecular cloud. The core of the giant molecular cloud formed the Sco-Cen complex, and some small cloudlets in a halo around the giant molecular cloud formed young local associations several million years later. We also propose a supernova in young local associations a few million years ago as the most likely candidate to have reheated the Local Bubble to its present temperature.Comment: 9 pages, 5 figures. Invited talk, to appear in "The Ages of Stars", Proceedings of the IAU Symposium 258, Baltimore USA 13-17 Oct 2008, eds D. Soderblom et al., CUP in pres

Self-Calibration Technique with Lightweight Algorithm for Thermal Drift Compensation in MEMS Accelerometers

Capacitive MEMS accelerometers have a high thermal sensitivity that drifts the output when subjected to changes in temperature. To improve their performance in applications with thermal variations, it is necessary to compensate for these effects. These drifts can be compensated using a lightweight algorithm by knowing the characteristic thermal parameters of the accelerometer (Temperature Drift of Bias and Temperature Drift of Scale Factor). These parameters vary in each accelerometer and axis, making an individual calibration necessary. In this work, a simple and fast calibration method that allows the characteristic parameters of the three axes to be obtained simultaneously through a single test is proposed. This method is based on the study of two specific orientations, each at two temperatures. By means of the suitable selection of the orientations and the temperature points, the data obtained can be extrapolated to the entire working range of the accelerometer. Only a mechanical anchor and a heat source are required to perform the calibration. This technique can be scaled to calibrate multiple accelerometers simultaneously. A lightweight algorithm is used to analyze the test data and obtain the compensation parameters. This algorithm stores only the most relevant data, reducing memory and computing power requirements. This allows it to be run in real time on a low-cost microcontroller during testing to obtain compensation parameters immediately. This method is aimed at mass factory calibration, where individual calibration with traditional methods may not be an adequate option. The proposed method has been compared with a traditional calibration using a six tests in orthogonal directions and a thermal chamber with a relative error difference of 0.3%

Impact of Thermal Variations and Soldering Process on Performance and Behavior of MEMS Capacitive Accelerometers

This work presents an analysis of performance and multiple parameters of microelectromechanical system (MEMS) capacitive accelerometers in applications with large thermal variations and the effects of the soldering process on them. The proposed test consists of a thermal characterization phase performed between two mechanical calibrations. The test is performed on multiple units before and after the soldering process. Mechanical, thermal, and performance parameters are analyzed and compared among all tests. The ranges and relative variations of these characteristics, both during the soldering process and the tests, have been identified and characterized individually. Mechanical bias shows greater variability than other parameters in both the soldering process and thermal tests. On the contrary, the thermal characteristic parameters show great stability in all cases. The thermal drifts, which are the main source of error in environments with large thermal variations, are successfully compensated for using a model with only two characteristic parameters. According to the observed behaviors, negative thermal variations (toward cooler temperatures) might be more suitable for thermal calibration due to other effects, such as creep, taking place primarily at hotter temperatures. The creep effect at constant temperature is analyzed according to the Kelvin–Voigt model with promising results, and a possible link between thermal drift and creep effects is presented. Performance results are calculated in multiple compensation scenarios. Using the proposed compensation techniques, the average maximum error is reduced from over 70 to 7 mg and the uncertainty is also reduced to a third of the initial value

Banco de ensayos multipropósito para caracterizar baterías de LiPo

1.RESUMENEl presente trabajo final de grado (TFG) tiene como finalidad desarrollar el diseño y la fabricación de dos bancos de prueba; un banco de pruebas para validar contactos eléctricos y un banco de pruebas para caracterizar un acumulador. Se comienza por realizar un estudio completo de los sistemas existentes en el mercado y se plantean las soluciones adoptadas para resolver cada una de las cuestiones.En primer lugar, se diseña un banco de pruebas con el objetivo de validar el comportamiento de un contacto eléctrico, y analizar e interpretar su comportamiento en un ensayo de 5 minutos. En este trabajo se ponen a prueba dos diseños, el primero consiste en una pieza de cobre rectangular atornillada sobre las pletinas del acumulador para aumentar la superficie conductora. En el segundo diseño se añaden a la pieza anterior unos refuerzos de cobre y acero, además de una grasa para contactos que mejora la conductividad eléctrica.Analizando los resultados, se obtienen mejores datos en el segundo caso, puesto que la presión ejercida en todos los puntos de la unión es uniforme. La termografía refleja que la transmisión del calor en este segundo contacto es más homogénea y la temperatura al finalizar el ensayo tiende a estabilizarse.En segundo lugar, se diseña un banco de ensayos para caracterizar celdas de Litio-Polímero. El objetivo de este banco es someter al acumulador a un ensayo de carga y descarga profunda, pudiendo analizar así su comportamiento e interpretar los resultados obtenidos.Se realizan dos ensayos, el primero de ellos utilizando una carga resistiva, por lo que la corriente no es constante, sino que depende de la tensión. En el segundo, se utiliza una carga electrónica programable, pudiendo realizar el ensayo de descarga a corriente constante. En ambos casos, la fase de carga se realiza utilizando una fuente de alimentación modificada con el objetivo de poder limitar y variar la tensión vía software durante el ensayo. Para ambos bancos de ensayo se diseña una interfaz de usuario mediante el software LabView, que permite el guardado de datos y la automatización del sistema. Estos resultados se comparan con los datos obtenidos mediante una instrumentación de precisión en el centro de investigación Tecnalia.Finalmente obteniendo que el error absoluto máximo del sistema desarrollado en el presente trabajo, no supera el 0,5%, se concluye que, utilizando equipos de menor coste económico, se pueden conseguir resultados eficientes y válidos. Y que el uso de estas herramientas es de vital importancia para el desarrollo de vehículos eléctricos.<br /

Simplificación de la calibración térmica para acelerómetros MEMS

The thermal drifts of MEMS inertial sensors limit their use, due to the cost of their calibration. Simplifying thermal calibration and compensation methods can reduce the cost and equipment required. In this work, a light compensation algorithm with its corresponding rapid calibration technique is proposed.Las derivas térmicas de los sensores inerciales MEMS limitan su uso, debido al coste de su calibración. Simplificando los métodos de compensación y calibración térmica se puede reducir el coste y equipamiento necesario. En este trabajo se propone un algoritmo ligero de compensación con su correspondiente técnica rápida de calibración