Navigation with UAVs - Assessment of ultra-tight GNSS/INS integration for small UAVs

Research output: ResearchPh.D. thesis – Annual report year: 2018

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This thesis is focusing on improving navigation for UAVs in degraded and harsh GNSS reception environments. Applications with UAVs has encountered anenormous growth in recent years and UAV missions are destined to become completely autonomous without any need for human interaction. Autonomous operation emphasizes the need for a robust navigation system as failures could cause damage of equipment and personal injuries.
The direction taken in this thesis, has been to explore potential benefits of aultra-tightly coupled GNSS/INS system on small UAVs. This processing strategy has shown clear improvement in GNSS signal tracking and positional accuracyin other types of applications, but has until now not been assessed forsmall UAVs.
Ultra-tightly coupled systems require direct access to the baseband processing algorithms within a GNSS receiver. This is generally not possible with commercial GNSS receivers, but requires a software-based GNSS receiver implementation. Furthermore, Intermediate Frequency (IF) samples need to be collectedand provided as input to the software receiver. Commercial systems for IF data recording do exists, but the available options are generally too large and heavy to be used on small UAVs. To overcome this limitation, a small, low-cost and lightweight system was designed to provide IF data for subsequent experiments.The IF data-recorder was hereafter combined with a MEMS-based IMU and survey-grade GNSS receiver to collect data for the developed ultra-tightly coupled system.
Data was initially recorded and processed from a static test for initial assessment. Hereafter, two kinematic missions were performed. The first mission was completed on a 4-wheeled trolley and featured a passage under dense foliage. Finally, the system was mounted on a small UAV while a mission in harsh GNSS reception conditions was conducted. The processed data was compared with atightly-coupled GNSS/INS solution and a survey-grade GNSS receiver. The benefits of the ultra-tightly coupled system could clearly be recognized in terms of the sustainment of GNSS signals tracked and magnitude of position errors.
Original languageEnglish
Place of PublicationKgs. Lyngby
PublisherTechnical University of Denmark (DTU)
Number of pages135
ISBN (Electronic)978-87-91694-36-3
StatePublished - 2017

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