• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.6
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• pp.555-562
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• 2021

Recently, in the field of geospatial information construction, unmanned aerial vehicles have been increasingly used because they enable rapid data acquisition and utilization. In this study, photogrammetry was performed using fixed-wing, rotary-wing, and VTOL (Vertical Take-Off and Landing) unmanned aerial vehicles, and geospatial information was constructed using two types of unmanned aerial vehicle LiDAR (Light Detection And Ranging) sensors. In addition, the accuracy was evaluated to present the utility of spatial information constructed through unmanned aerial photogrammetry and LiDAR. As a result of the accuracy evaluation, the orthographic image constructed through unmanned aerial photogrammetry showed accuracy within 2 cm. Considering that the GSD (Ground Sample Distance) of the constructed orthographic image is about 2 cm, the accuracy of the unmanned aerial photogrammetry results is judged to be within the GSD. The spatial information constructed through the unmanned aerial vehicle LiDAR showed accuracy within 6 cm in the height direction, and data on the ground was obtained in the vegetation area. DEM (Digital Elevation Model) using LiDAR data will be able to be used in various ways, such as construction work, urban planning, disaster prevention, and topographic analysis.

• Journal of Platform Technology
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• v.11 no.3
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• pp.24-31
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• 2023

Recently, interest in UAM (Urban Air Mobility, UAM), which can take off and land vertically in the operation of urban air transportation systems, has been increasing. Therefore, various start-up companies are developing related technologies as eco-friendly future transportation with advanced technology. However, studies on ways to increase safety in the operation of UAM are still insignificant. In particular, efforts are more urgent to improve the safety of risks generated in the process of attempting to land in the city center by UAM equipped with autonomous driving. Accordingly, this study proposes a plan to safely land by avoiding dangerous region that interfere when autonomous UAM attempts to land in the city center. To this end, first, the latitude and longitude coordinate values of dangerous objects observed by the sense of the UAM are calculated. Based on this, we proposed to convert the coordinates of the distorted planar image from the 3D image to latitude and longitude and then use the calculated latitude and longitude to compare the pre-learned feature descriptor with the HOG (Histogram of Oriented Gradients, HOG) feature descriptor to extract the dangerous Region. Although the dangerous region could not be completely extracted, generally satisfactory results were obtained. Accordingly, the proposed research method reduces the enormous cost of selecting a take-off and landing site for UAM equipped with autonomous driving technology and contribute to basic measures to reduce risk increase safety when attempting to land in complex environments such as urban areas.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.4
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• pp.343-352
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• 2016

A multi-rotor vehicle is an unmanned vehicle consisting of multiple rotors. A multi-rotor vehicle can be categorized as tri-, quad-, hexa-, and octo-rotor depending on the number of the rotors. Multi-rotor vehicles have many advantages due to their agile flight capabilities such as the ability for vertical take-off, landing and hovering. Thus, they can be widely used for various applications including surveillance and monitoring in urban areas. Since multi-rotors are subject to uncertain environments and disturbances, it is required to implement robust attitude stabilization and flight control techniques to compensate for this uncertainty. In this research, an advanced nonlinear control algorithm, i.e. sliding mode control, was implemented. Flight experiments were carried out using an onboard flight control computer and various real-time autonomous attitude adjustments. The feasibility and robustness for flying in uncertain environments were also verified through real-time tests based on disturbances to the multi-rotor vehicle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.10
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• pp.845-855
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• 2018

Cross section design of a prop-blade is carried out for VTOL(Vertical Takeoff and Landing) Quad Tilt Prop-rotor UAV with a maximum takeoff weight of 55 kg and a maximum cruising speed of 180 km/h. Design procedure for cross section design is established and design requirements for prop-blade are identified. Through the procedure, cross section design is carried out to meet the identified requirements. Main design factors including stiffness, weight per unit length, and elastic axis are obtained by using a finite element section analysis program, and the design weight of the prop-blade is predicted. The obtained design factors are used along with the rotor system analysis program CAMRAD II to evaluate the dynamic stability of prop-blade in operating environment. In addition, the prop-blade load is obtained by CAMRAD II software, and it is used to verify the safety of the prop-blade structure. If the design results are not satisfactory, design changes are made in an iterative manner until the results satisfy the design requirements.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.1
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• pp.37-46
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• 2014

This paper describes the conceptual design and development test procedure of a unmanned scaled-down personal air vehicle(PAV) with drive and flight dual mode capability. Trade studies on operational requirements led to the suggestion of a quad tilt prop platform which has nacelle tilt capability with multi rotor configuration. Motors for propeller propulsion and driving mechanism were integrated into a single nacelle, then they were implemented by nacelle tilt mechanism for conversion between the drive and the flight modes. Primary design parameters and initial specifications were confirmed through conceptual design, then functional tests were performed with the test platforms for the drive and the flight modes.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.1-9
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• 2009

The ground integration test of Smart UAV has been performed according to the flight test plan. The flight test of full scaled model will be performed followed by 4 DOF ground rig test and a tethered hover test. Smart UAV is the first indigenous tiltrotor aircraft which can fly with fast cruise speed and take off or land vertically. In order to prove the flight control law of Smart UAV, the 40% scaled airplane was developed and have been tested. During flight test of small scaled model, many unique and unexpected problems occurred. After clearing these problems, fully automatic flight test was performed successfully. The experiences about many trouble shooting and resolving the problems would be basic material to avoid the unexpected but similar flight test problems hidden behind of the full scaled Smart UAV. This paper presents the detailed procedures of trouble shootings to solve the unique problems which occurred during the flight test of small scaled tiltrotor UAV.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.9
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• pp.1019-1025
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• 2014

Recently, the studies of the Unmanned Aerial Vehicle(UAV) has been studied a variety from military aircraft to civilian aircraft and for general hobby activity aircraft. In particular, for small unmanned aircraft research for the ease of turning and hovering and Vertical-Off Take Landing(VTOL), have been studied mainly quadrotor unmanned aircraft is a type suitable for this study of small unmanned aircraft. The studies of these unmanned aircraft is the kinetic analysis requires complex processes, because these support by the aerodynamic forces on the unmanned aircraft study, and the controller design based on these dynamical analysis and experimental model analysis. In this paper, after the implementation of the basic attitude control based on a general PID controller, we propose concept design of the attitude control method on quadrotor attitude control by using the reinforcement learning algorithm of neural networks for non-linear elements not considered in the controller design.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.9
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• pp.711-723
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• 2017

This paper proposes a flight control system for an organic flight array(OFA) which has a new configuration to consist of multi modularized ducted-fan unmanned aerial vehicles (UAVs). The OFA is able to apply to various missions such as indoor reconnaissance, communication relay, and radar jamming by using capability of hover flight. The OFA has a distinguished advantage due to reconfigurable structure to assemble or separate with respect to its missions or operational conditions. A dynamic modelling of the OFA is derived based on equations of motion of the single ducted-fan modules. In order to apply nonlinear control method, an affine system of attitude dynamics is derived. Moreover, the control system is composed of a back-stepping controller for attitude control and a PID controller for position control. Then the performance of the proposed controller is verified via a numerical simulation under wind disturbance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.8
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• pp.56-64
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• 2005

It is prerequisite that we have to fomulate the nonlinear mathematical modeling to design the guidance and control system of rotorcraft-based unmanned aerial vehicle using a small-scaled commercial helicopter. The small-scaled helicopters are very different from the full-scale helicopters in dynamic behavior such as high rotation speed and high frequency dynamic characteristics. In this paper, the formulation of the mathematical model of the small-scaled helicopter to minimize the complexity is presented by component and source build-up approach. It is linearized at the trim condition of hovering and forward flight and analyzed the flight modes. The results of this approach have general trends but a little difference. To verify this approach, it is necessary to compare this theoretical model with experimental results by system identification using flight test as a next research topic.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.64-71
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• 2006

For SUAV is required to have the capacity of VTOL and fast forward flight, the SUAV development program has decided to adopt the tiltrotor mechanism which includes helicopter and turboprop mechanisms. From the engine point of view, the key engine parameters such as engine operating mechanism, engine control scheme, the dynamics characteristic of power train, engine intake/exhaust concept, and engine installation requirements should fulfill the requirements of the two different mechanisms, helicopter and turboprop. And for the maximum efficiency of the rotor, rotational speed for the two modes are 20% different, the power train shall find a way to make it so. Meeting these specific requirements for the tiltrotor mechanism, this research begins with a conventional OTS(off-the-shelf) turboshaft engine survey and minimizes engine modification to develop an economical propulsion system. The engine technical review has been performed on the basis of those requirements and capabilities.