Metodología mecánica pasiva de aislación de vibraciones aplicada a la cámara a bordo de un RPA.
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Date
2024
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Publisher
Universidad de Concepción
Abstract
Actualmente, una gran variedad de aplicaciones en áreas científico-tecnológicas de alto impacto social y ambiental requieren del uso de cámaras en RPA (Remotely Piloted Aircraft). Tales aplicaciones incluyen: búsqueda de personas, monitoreo de recursos geológicos, hídricos y forestales, vigilancia y seguridad, entre otras. No obstante, los RPAs experimentan naturalmente vibraciones debido a las condiciones de vuelo y partes mecánicas móviles. Cuando las vibraciones son transmitidas a la cámara se producen borrosidades del tipo motion blur y desencuadre de escena en las imágenes, alterando su definición y utilidad. Por esto, es sumamente importante estudiar estas vibraciones para desarrollar formas de mitigarlas. En este trabajo se desarrolla una metodología de aislación de vibraciones para una cámara a bordo de un RPA de pequeño tamaño a través de un sistema de aislación mecánico pasivo. Para ello, se caracterizaron empíricamente las vibraciones experimentadas por el RPA para dos fases de vuelo: estático y horizontal, utilizando un sistema de medición de vibraciones a bordo especialmente desarrollado para operar de forma remota. Se realizaron pruebas experimentales en condiciones de laboratorio con un excitador mecánico para determinar la respuesta vibratoria de un sistema de aislación mecánico pasivo ajustable con aisladores instalados en diferentes configuraciones espaciales. Esto con el propósito de determinar el efecto de la disposición en el aislamiento de las vibraciones, y seleccionar los aisladores y su disposición más adecuada para ser implementados en el sistema de aislación. Se determinaron las curvas de transmisibilidad del sistema de aislación para cuatro configuraciones con cuatros aisladores del tipo bola de suspensión para un barrido frecuencial entre 5 y 220 [Hz]. En este rango se producen las mayores excitaciones dinámicas en un RPA comercial de pequeño tamaño, como es el caso del RPA seleccionado. Se seleccionó un sistema de aislación para implementar en el RPA, y se realizaron pruebas de vuelo con captura de imagen. El deterioro observado en la calidad de las imágenes se cuantificó mediante una métrica de grado de enfoque de imagen. De los resultados obtenidos se concluye que la disposición de los aisladores mecánicos puede afectar significativamente la efectividad en el aislamiento de las vibraciones, por lo tanto, deben ser correctamente seleccionados y dispuestos en base al rango de la frecuencia operacional. Finalmente, a partir del estudio realizado, se propuso un sistema de aislación mecánico pasivo que, al ser implementado en el RPA, logró una reducción de las vibraciones experimentadas por la cámara a bordo de aproximadamente un 95%.
Currently, there is a wide range of applications in scientific and technological fields with significant social and environmental impact that rely on the use of RPA (Remotely Piloted Aircraft) cameras. These applications include searching for people, monitoring geological, water, and forest resources, as well as surveillance and security, among others. However, RPA naturally experiences vibrations due to flight conditions and its mechanical moving components. These vibrations can cause motion blur and misframing in captured images, affecting their clarity and usability. It is crucial to study these vibrations to develop effective mitigation methods. This study focuses on developing a vibration isolation method for a camera mounted on a small commercial RPA using a mechanical passive isolation system. To this end, the vibrations experienced by the RPA during flight were empirically characterized for two flight phases: static and horizontal, using an onboard vibration measurement system specially developed to operate remotely. Experimental tests were conducted under laboratory conditions using a mechanical shaker to determine the vibration response of an adjustable mechanical passive isolation system with isolators installed in various spatial configurations. This is to determine how spatial arrangement affects vibration isolation and to select the isolators and their most appropriate arrangement to be implemented in the isolation system. The isolation system's transmissibility curves were determined for four configurations using four suspension ball-type isolators for a frequency sweep ranging from 5 to 220 [Hz]. For this frequency range, the most significant dynamic excitations occur in small commercial RPAs such as the selected one. An isolation system was chosen for implementation in the RPA, and flight tests with image capture were conducted. The degradation observed in the image quality was quantified using an image focus metric. The findings from this study conclude that the arrangement of mechanical isolators can greatly impact the effectiveness of vibration isolation, and it is crucial to select and arrange them properly based on the operational frequency range. Based on these results, a mechanical passive isolation system was proposed and tested in the RPA, resulting in a 95% reduction of vibrations experienced by the on-board camera.
Currently, there is a wide range of applications in scientific and technological fields with significant social and environmental impact that rely on the use of RPA (Remotely Piloted Aircraft) cameras. These applications include searching for people, monitoring geological, water, and forest resources, as well as surveillance and security, among others. However, RPA naturally experiences vibrations due to flight conditions and its mechanical moving components. These vibrations can cause motion blur and misframing in captured images, affecting their clarity and usability. It is crucial to study these vibrations to develop effective mitigation methods. This study focuses on developing a vibration isolation method for a camera mounted on a small commercial RPA using a mechanical passive isolation system. To this end, the vibrations experienced by the RPA during flight were empirically characterized for two flight phases: static and horizontal, using an onboard vibration measurement system specially developed to operate remotely. Experimental tests were conducted under laboratory conditions using a mechanical shaker to determine the vibration response of an adjustable mechanical passive isolation system with isolators installed in various spatial configurations. This is to determine how spatial arrangement affects vibration isolation and to select the isolators and their most appropriate arrangement to be implemented in the isolation system. The isolation system's transmissibility curves were determined for four configurations using four suspension ball-type isolators for a frequency sweep ranging from 5 to 220 [Hz]. For this frequency range, the most significant dynamic excitations occur in small commercial RPAs such as the selected one. An isolation system was chosen for implementation in the RPA, and flight tests with image capture were conducted. The degradation observed in the image quality was quantified using an image focus metric. The findings from this study conclude that the arrangement of mechanical isolators can greatly impact the effectiveness of vibration isolation, and it is crucial to select and arrange them properly based on the operational frequency range. Based on these results, a mechanical passive isolation system was proposed and tested in the RPA, resulting in a 95% reduction of vibrations experienced by the on-board camera.
Description
Tesis presentada para optar al grado de Magíster en Ciencias de la Ingeniería con mención en Ingeniería Mecánica
Keywords
Drones, Vibración Mediciones, Imágenes