Abstract
Small autonomous unmanned aerial systems (UAS) could be used for indoor inspection in emergency missions, such as damage assessment or the search for survivors in dangerous environments, e.g., power plants, underground railways, mines and industrial warehouses. Two basic functions are required to carry out these tasks, that is autonomous GPS-denied navigation with obstacle detection and high-resolution 3D mapping with moving target detection. State-of-the-art sensors for UAS are very sensitive to environmental conditions and often fail in the case of poor visibility caused by dust, fog, smoke, flames or other factors that are met as nominal mission scenarios when operating indoors. This paper is a preliminary study concerning an innovative radar sensor based on the interferometric Synthetic Aperture Radar (SAR) principle, which has the potential to satisfy stringent requirements set by indoor autonomous operation. An architectural solution based on a frequency-modulated continuous wave (FMCW) scheme is proposed after a detailed analysis of existing compact and lightweight SAR. A preliminary system design is obtained, and the main imaging peculiarities of the novel sensor are discussed, demonstrating that high-resolution, high-quality observation of an assigned control volume can be achieved.
Highlights
Unmanned aerial systems (UAS) are commonly defined as medium-small scale uninhabited aerial vehicles able to attain stable flight operation thanks to a control system that can be programmed to follow a certain flight path or can be remotely controlled from a ground station
After the state-of-the-art analysis of existing small Synthetic Aperture Radar (SAR) sensors, frequency-modulated continuous wave (FMCW) has been individuated as a suitable scheme to be exploited in combination with InSAR technology for applications requiring both high-resolution performance and compact and lightweight systems
Based on the FMCW features, a system design procedure has been achieved, outlining guidelines to trade-off the design choices based on the specific mission requirements and operative environments
Summary
Unmanned aerial systems (UAS) are commonly defined as medium-small scale uninhabited aerial vehicles able to attain stable flight operation thanks to a control system that can be programmed to follow a certain flight path or can be remotely controlled from a ground station. Use of very compact sized and extreme lightweight small UAS or micro aerial vehicles (MAV), different from outdoor applications, represents an additional strong constraint when indoor flight operations must be performed. In theory, accurate geometric models of the operational environment combined with thematic information and the description of all of the present objects could reduce the need for continuous and real-time sensing Those data are often neither updated nor available at the required spatial resolution and accuracy. It should be noted that for matching with the considered operational scenarios, the sensor must be compact, lightweight and characterized by low power consumption It has to guarantee very high 3D resolution and accuracy, as well as the capability to perform real-time onboard processing in order to support autonomous navigation, exploration and mapping in completely unknown and unstructured environments
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