• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.6
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• pp.465-472
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• 2013

In this paper, we suggest how to determine the parachute deploy position for accurate landing of a UAV at a desired position. The 9-DOF dynamic modeling of UAV-parachute system is required to construct the proposed algorithm based on neural network nonlinear function approximation technique. The input and output data sets to train the neural network are obtained from simulation results using UAV-parachute 9-DOF model. The input data consist of the deploy position, UAV's velocity, and wind velocity. The output data consist of the cross range and down range of landing positions. So we predict the relative landing position from the current UAV position. The deploy position is then determined through distance compensations for the relative landing positions from the desired landing position. The deploy position is consistently calculated and updated.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.1
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• pp.19-26
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• 2010

To expand the application area of global navigation satellite systems, precision landing is one of the most critical area to be solved. For the development and validation of the precision landing system, many aspects need to be analyzed including the system architecture, signal characteristics, atmospheric delay, communication delay, accuracy, integrity, and availability. Among them, the signal characteristics analysis requires the processing of measurements collected by real-flight experiments. This paper presents the processing results of the real measurements collected by a flight and landing experiment. To process and analyze the data, double differencing position-domain hatch filter is utilized. Accuracy of the proposed filter is evaluated utilizing reference trajectory generated by commercial software. Finally, by comparing with conventional range domain characteristics of position domain filter is analyzed.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.363-366
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• 1996

A Reclaimer is used to dig raw material from a pile and transfer it to the blast furnaces. In this paper, we propose the method for trajectory landing position of bucket of reclaimer to fully automate the reclaimer. We use 3-dimensional range finder to detect the shape of a pile. From the image which was detected by 3-dimensional range finder, we extract the outline paths which has same height, and then determine digging height. Finally, we compute the landing point from the outline path. We can prevent overload which can occur on the bucket wheel and guarantee maximum production rate by using the algorithm for determining the landing position on the piles.

• Journal of Advanced Navigation Technology
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• v.25 no.6
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• pp.485-492
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• 2021

Vision-based autonomous precision landing technology for UAVs requires precise position estimation and landing guidance technology. Also, for safe landing, it must be designed to determine the safety of the landing point against ground obstacles and to guide the landing only when the safety is ensured. In this paper, we proposes vision-based navigation, and algorithms for determining the safety of landing point to perform autonomous precision landings. To perform vision-based navigation, CNN technology is used to detect landing pad and the detection information is used to derive an integrated navigation solution. In addition, design and apply Kalman filters to improve position estimation performance. In order to determine the safety of the landing point, we perform the obstacle detection and position estimation in the same manner, and estimate the speed of the obstacle using LSM. The collision or not with the obstacle is determined based on the CPA calculated by using the estimated state of the obstacle. Finally, we perform flight test to verify the proposed algorithm.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.8
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• pp.647-661
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• 2017

This paper presents a robust method for autonomously landing on small bodies. Autonomous landing is accomplished by generating and following reference position and attitude profiles. The position and attitude tracking controllers are based on discrete sliding mode control, which explicitly treats the discrete and impulsive natures of thruster operation. Vision-based inertial navigation is used for autonomous navigation for landing. Numerical simulation is carried out to evaluate the performance of the proposed method in a realistic situation with environmental uncertainties.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.1
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• pp.54-60
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• 2009

In this paper, a precision landing approach is implemented based on real-time image processing. A full-scale landmark for automatic landing is used. canny edge detection method is applied to identify the outside quadrilateral while circular hough transform is used for the recognition of inside circle. Position information on the ground landmark is uplinked to the unmanned helicopter via ground control computer in real time so that the unmanned helicopter control the air vehicle for accurate landing approach. Ground test and a couple of flight tests for autonomous landing approach show that the image processing and automatic landing operation system have good performance for the landing approach phase at the altitude of $20m{\sim}1m$ above ground level.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.1
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• pp.77-84
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• 2013

Most research on the inkjet printing technology has focused on the development of inkjet head itself, and of process, not on the landing accuracy of the droplets to a target. Thus, this paper presents the modeling and experimental verification on the static landing accuracy and precision of the droplets from the magnetostrictive inkjet head. A simple model based on the angle deviation of a nozzle tip and on a distance to a substrate is considered, assuming that there is no ambient effect. The angle deviation of the nozzle tip is determined by using its digital image with the aid of a pixel calculation program, and the distance to the substrate is set to 1 mm. Three experiments have planned and preformed. The first experiment is to collect the initial data for the landing distribution of the droplets. The second experiment is to collect the repeatability data of the stage used. Then, these data are used to rederive the equation for the final landing position of the droplet. The final experiment is to verify the equation and to show the calibration results. The respective landing accuracy of the droplet after calibration on the x-axis and on y axis has improved from $338.51{\mu}m$ and $-133.63{\mu}m$ to $7.06{\mu}m$ and $13.11{\mu}m$. The respective percent improvement on the x-axis and on y axis reaches about 98 and about 90. The respective landing precision of the droplet after calibration on the x-axis and on y axis has improved from ${\pm}182.6{\mu}m$ and ${\pm}182.88{\mu}m$ to ${\pm}24.64{\mu}m$ and ${\pm}42.76{\mu}m$. The respective percent improvement on the x-axis and on y axis reaches about 87 and about 77.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.2
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• pp.164-173
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• 2012

Landing ship tank with well dock has the important mission transferring troops or landing equipments from sea to shore. Such transfers are usually carried out using landing crafts, which are loaded or unloaded in flooded well dock. In this situation, as relative motions are occur between well dock and landing craft, safety verifications are demanded. In this paper, seakeeping and safety performances are investigated through model test. First of all, well dock dimensions are reviewed and model tests are performed with sea state 3&4 in 180degree wave direction. Model tests are conducted for three relative positions and seakeeping performances are investigated each position.

• The Journal of Korea Robotics Society
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• v.17 no.1
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• pp.48-57
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• 2022

In this paper, we propose a legged landing platform for the quadcopter taking off and landing in the ship environment. In the ship environment with waves and winds, the aircraft has risks being overturned by contact impact and excessive inclination during landing on the ship. This landing platform has four landing legs under the quadcopter for balancing and shock relief. In order to make the quadcopter balanced on ships, the position of each end effector was controlled by PID control. And shocks have mainly happened when quadcopter contacts the ship's surface as well as legs move fast. Hence, impedance control was used to cope with the shocks. The performance of the landing platform was demonstrated by a simulation and a prototype in three sea states based on a specific size of a ship. During landing and tracking the slope of the ship's surface, oscillations of rotation and translation from the shock were mitigated by the controller. As a result, it was verified that transient response and stability got better by adding impedance control in simulation models and prototype experiments.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.339-341
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• 2006

This paper proposes a method of container position measurement using automatic landing system that is estimated by a laser range finder. In the most of container position measurement methods, CCD cameras or laser scanners have been used to get the source data. However those sensors are not only weak for disturbances, for examples, the light, fog, and rain, but also the system cost is high. When the spreader arrives the goal position, it is still swung by inertia or by wind effect. In this paper, the spreader swung data have been used to find the container position. The laser range finder is equipped in the front side of spreader. It can measure distance and relative position between spreader and container. This laser range finder can be rotated as desired by a motor. And a tilt sensor is equipped on the spreader to measure spreader sway. We estimate the relative position information between the spreader and a container using the laser range finder and tilt sensor through the geometrical analysis.