We describe a waterproof, lightweight (1.3 kg) low power (∼1.1 W average power) fluorometer operating on 5 VDC deployed on a small Uncrewed Aircraft System (sUAS) to measure chlorophyll and used for triggering environmental water sampling by the sUAS. The fluorometer uses a 450 nm laser modulated at 10 Hz for excitation and a standard photodiode and transimpedance amplifier for the detection of fluorescence. Additional detectors are available for measuring laser intensity and light scattering. Control of the fluorometer and communication between the fluorometer and the Raspberry Pi 4B computer controlling the sampler were provided by an Arduino microcontroller using the Robot Operating System (ROS). Calibrations were based on standards of dissolved chlorophyll extracted from Chlorella powder (a widely available dietary supplement). The detection limit for chlorophyll from these calibrations was found to be 0.2 micrograms per liter of water for a single 0.1 sec differential measurement. The detection limit decreases with the square root of the integration time as expected. Detection limits increase by a factor of 2 to 3 when mounted in the sUAS due to electrical noise; sUAS acoustic noise and vibration do not appear to contribute significantly.
A plethora of state estimation techniques have appeared in the last decade using visual data, and more recently with added inertial data. Datasets typically used for evaluation include indoor and urban environments, where supporting videos have shown impressive performance. However, such techniques have not been fully evaluated in challenging conditions, such as the marine domain. In this paper, we compare ten recent open-source packages to provide insights on their performance and guidelines on addressing current challenges. Specifically, we selected direct methods and tightly-coupled optimization techniques that fuse camera and Inertial Measurement Unit (IMU) data together. Experiments are conducted by testing all packages on datasets collected over the years with underwater robots in our laboratory. All the datasets are made available online.
Unmanned Aircraft Systems (UAS) have seen unprecedented levels of growth during the last two decades. Although many challenges still exist, one of the main UAS focus research areas is in navigation and control. This paper provides a comprehensive overview of helicopter navigation and control, focusing specifically on small-scale traditional main/tail rotor configuration helicopters. Unique to this paper, is the emphasis placed on navigation/control methods, modeling techniques, loop architectures and structures, and implementations. A 'reference template' is presented and used to provide a basis for comparative studies and determine the capabilities and limitations of algorithms for unmanned/autonomous flight, as well as for navigation, and control. A detailed listing of related research is provided, which includes model structure, helicopter platform, control method and loop architecture, flight maneuvers and results for each. The results of this study was driven by and has led to the development of a 'one-fits-all' comprehensive and modular navigation controller and timing architecture applicable to any rotorcraft platform.
Standard quadcopters are popular largely because of their mechanical simplicity relative to other hovering aircraft, low cost and minimum operator involvement. However, this simplicity imposes fundamental limits on the types of maneuvers possible due to its under-actuation. The dexterity and fault tolerance required for flying in limited spaces like forests and industrial infrastructures dictate the use of a bespoke dual-tilting quadcopter that can launch vertically, performs autonomous flight between adjacent obstacles and is even capable of flying in the event of the failure of one or two motors. This paper proposes an actuation concept to enhance the performance characteristics of the conventional under-actuated quadcopter. The practical formation of this concept is followed by the design, modeling, simulation and prototyping of a dual-axis tilting quadcopter. Outdoor flight tests using tilting rotors, to follow a trajectory containing adjacent obstacles, were conducted in order to compare the flight of conventional quadcopter with the proposed over-actuated vehicle. The results show that the quadcopter with tilting rotors provides more agility and mobility to the vehicle especially in narrow indoor and outdoor infrastructures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.