• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.576-584
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• 2022

AIS is widely utilized in vessel traffic services for marine traffic safety. In 2021, Korea deployed the high-speed maritime wireless communication system (LTE-Maritime) on the sea following IMO's proposal for the introduction of e-Navigation. In this paper, vessel trajectory data from AIS and LTE-Maritime were used for vessel trajectory prediction to compare and analyze the two systems. The results show that the trajectory prediction error of LTE-Maritime was smaller than that of AIS due to the granular and uniform data provided by LTE-Maritime. Additionally, it was revealed that time interval is the most important factor influencing the errors in trajectory prediction, with the prediction error of LTE-Maritime growing at a slower rate of 17% than AIS. This research contributes to the literature by quantitatively comparing AIS and LTE-Maritime systems for the first time.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1867-1870
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• 1997

Waypoint guidance is a technique used to steer an autonomous vehicle along a desired trajectory. In this paper, a waypoint guidance algorithm for horizontal plane is derived by combining a line following guidance law and a turning guidance law. The line following guidance is derived based on LQR while the turning guidance is designed using rendzvous problem. Through simulation, the proposed method shows a good performance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.7
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• pp.1032-1040
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• 2012

This paper proposes controller of leader robot considering following robot with input constraints based on leader-following approach. In the previous formation control researches, it was assumed that leader and follower is same object. If leader robot drives as maximum speed that the initial position errors still remain even if following robot have same velocity as a leader. In the situation that velocity of following robot is lower than its leader robot, following robot cannot follow leader robot. Furthermore, the following robot will not be able to made formation with leader robot and keep proximity communication or sensing range. Therefore, multiple mobile robot system using leader-following method should be guaranteed range to get information each other. In this paper, Leader robot is driving to goal position using linear controller and following robot is following trajectory to be made from leader robot. We assume that following robot has input constraints to realize different performance between leader robot and following robot. We design controller of leader robot for desired goal position including the errors between formation and following robot. Thus, we propose leader robot controller considering input constraints of following robot. Finally, we were able to confirm the validity of the proposed method based on simulation results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.252-261
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• 1991

A particle trajectory model to simulate two-phase particle-laden crossjets into two-dimensional horizontal free stream has been developed to study the variations of the jet trajectories and velocity variations of the gaseous and the particulate phases. The following conclusions may be drawn from the predicted results, which are in agreement with experimental observations. The penetration of the two-phase jet in a crossflow is greater than that of the single-phase jet. The penetration of particles into the free stream increases with increasing particle size, solids-gas loading ratio and carrier gas to free stream velocity ratio at the jet exit. When the particle size is large, the solid particles separate from the carrier gas , while the particles are completely suspended in the carrier gas for the case of small size particles. As the particle to carrier gas velocity ratio at the jet exit is less than unity, the particles in the vicinity of the jet exit are accelerated by the carrier gas. As the injection angle is increased, the difference of the particle trajectory from that of the pure gas becomes larger. Therefore, it can be concluded that the velocities and trajectories of the particle-laden jets in a crossflow change depending on the solids-gas loading ratio, particle size, carrier gas to free stream velocity ratio and particle to gas velocity ratio at the jet exit.

• Journal of Korean Society of Transportation
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• v.26 no.5
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• pp.51-62
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• 2008

An innovative feature of this study is to propose a methodology for evaluating safety performance in real time based on vehicle trajectory data extracted from video images. The essence of evaluating safety performance is to capture unsafe car-following and lane-changing events generated by individual vehicles traveling within video surveillance area. The proposed methodology derived three indices including real-time safety index(RSI) based on the concept of safe stopping distance, time-to-collision(TTC), and the collision energy based on the conservation of momentum. It is believed that outcomes would be greatly utilized in developing a new generation of video images processing(VIP) based traffic detection systems capable of producing safety performance measurements. Relevant technical challenges for such detection systems are also discussed.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.6
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• pp.7-14
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• 1989

A trajectory control method being capable of singularity avoidance is proposed for a robot and positoner (R-P) system. In the proposed method, the damping factor of the Damped Least Square (DLS) method is adjusted by gradients of trajectory following errors so that the singularity avoidance can be achieved while mimimizing the errors. Two numerical examples are given by employing a Rhino robot with five degrees-of-freedom (d.o.f.) and two d.o.f's, where the method of maximizing the manipulagility the DLS method with a fixd damping factor and the proposed method are compared in terms of trajectory following errors, manipulabilities and joint velocities.

• Journal of the Korean Society of Industry Convergence
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• v.17 no.4
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• pp.245-254
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• 2014

In this paper, stable and robust dynamic walking for a biped motion is proposed. To success this objective, the following structures are processed. In this paper, the proposed control method is one that adjusts actual zero moment position to move to the closest possible point in the stable area instead of following desired zero moment position. This minimizes energy consumption with the smallest joint movements. The proposed control method makes mechanical energy that drives lower limb of the bipedal robot efficient. In this paper, walking experiment is carried out with the three control structures mentioned above. The trajectory generated by off-line is illustrated by performing to walking on flat ground. experiment with an obstacle whose height is lower than that of trajectory is executed to validate dynamic motion.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.6
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• pp.915-923
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• 2008

This paper focuses on optimal tuning of nonlinear parameters of a dual-input power system stabilizer(dual-input PSS), which can improve the system damping performance immediately following a large disturbance. Until recently, various PSS models have developed to bring stability and reliability to power systems, and some of these models are used in industry applications. However, due to non-smooth nonlinearities from the interaction between linear parameters(gains and time constants of linear controllers) and nonlinear parameters(saturation output limits), the output limit parameters cannot be determined by the conventional tuning methods based on linear analysis. Only ad hoc tuning procedures('trial and error' approach) have been used. Therefore, the steepest descent method is applied to implement the optimal tuning of the nonlinear parameters of the dual-input PSS. The gradient required in this optimization technique can be computed from trajectory sensitivities in hybrid system modeling with the differential-algebraic-impulsive-switched(DAIS) structure. The optimal output limits of the dual-input PSS are evaluated by time-domain simulation in both a single machine infinite bus(SMIB) system and a multi-machine power system in comparison with those of a single-input PSS.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.11
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• pp.1137-1145
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• 2007

Palletizing tasks are necessary to promote efficient storage and shipping of boxed products. These tasks, however, involve some of the most monotonous and physically demanding labor in the factory. Thus, many types of robot palletizing systems have been developed, although many robot motion commands still depend on the teach pendant. That is, the operator inputs the motion command lines one by one. This is very troublesome and, most importantly, the user must know how to type the code. We propose a new GUI(Graphic User Interface) for the palletizing system that is more convenient. To do this, we used the PLP "Fast Algorithm" and 3-D auto-patterning visualization. The 3-D patterning process includes the following steps. First, an operator can identify the results of the task and edit them. Second, the operator passes the position values of objects to a robot simulator. Using those positions, a palletizing operation can be simulated. We chose a widely used industrial model and analyzed the kinematics and dynamics to create a robot simulator. In this paper we propose a 3-D patterning algorithm, 3-D robot-palletizing simulator, and modified trajectory generation algorithm, an "overlapped method" to reduce the computing load.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1527-1533
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• 2011

The reaction of gas-phase atomic hydrogen with oxygen atoms chemisorbed on a silicon surface is studied by use of the classical trajectory approach. We have calculated the probability of the OH formation and energy deposit of the reaction exothermicity in the newly formed OH in the gas-surface reaction H(g) + O(ad)/Si${\rightarrow}$ OH(g) + Si. All reactive events occur in a single impact collision on a subpicosecond scale, following the Eley-Rideal mechanism. These events occur in a localized region around the adatom site on the surface. The reaction probability is dependent upon the gas temperature and shows the maximum near 1000 K, but it is essentially independent of the surface temperature. The reaction probability is also independent upon the initial excitation of the O-Si vibration. The reaction energy available for the product state is carried away by the desorbing OH in its translational and vibrational motions. When the initial excitation of the O-Si vibration increases, translational and vibrational energies of OH rise accordingly, while the energy shared by rotational motion varies only slightly. Flow of energy between the reaction zone and the solid has been incorporated in trajectory calculations, but the amount of energy propagated into the solid is only a few percent of the available energy released in the OH formation.