Numerical Study on Bouncing and Separation Collision Between Two Droplets Considering the Collision-Induced Breakup

Ko, Gwon-Hyun,Ryou, Hong-Sun,Hur, Nahm-Keon,Ko, Seung-Woo,Youn, Myoung-O 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.4

The main purpose of the present study is to perform numerical study on bouncing and separation collision between two droplets considering the collision-induced breakup. In this study, the collision model proposed in our previous study is used for simulation of collision-induced breakup, and we modify this model to consider the effect of liquid property on the behavior of droplet-droplet collision. This collision model is based on the conservation laws for mass, momentum, and energy between before and after collision and provides several formulae for post-collision characteristics of colliding droplets and satellite droplets. Improving the accuracy of the model, in this study, appreciate criterion for bouncing collision is added and dissipation energy during collision process is newly modeled. To validate the new model, numerical calculations are performed and their results are compared with experimental data published earlier for binary collisions of water, propanol, and tetradecane droplets. It is found from the results that the new model shows good agreement with experimental data for the number of satellite droplets. It can be also shown that the predicted mean diameter by the new model decrease with increasing the Weber number because of the collision-induced breakup, whereas the O'Rourke model fails to predict the size reduction via the binary droplet collision.

9축센서 기반의 도로시설물 충돌감지 알고리즘

홍기현,이병문 한국멀티미디어학회 2022 멀티미디어학회논문지 Vol.25 No.2

Road facilities such as CCTV poles have potential risk of collision accidents with a car. A collision detection algorithm installed in the facility allows the collision accident to be known remotely. Most collision detection algorithms are operated by simply focusing on whether a collision have occurred, because these methods are used to measure only acceleration data from a 3-axis sensor to detect collision. However, it is difficult to detect other detailed information such as malfunction of the sensor, collision direction and collision strength, because it is not known without witness the accident. Therefore, we proposed enhanced detection algorithm to get the collision direction, and the collision strength from the tilt of the facility after accident using a 9-axis sensor in this paper. In order to confirm the performance of the algorithm, an accuracy evaluation experiment was conducted according to the data measurement cycle and the invocation cycle to an detection algorithm. As a result, the proposed enhanced algorithm confirmed 100% accuracy for 50 weak collisions and 50 strong collisions at the 9-axis data measurement cycle of 10ms and the invocation cycle of 1,000ms. In conclusion, the algorithm proposed is expected to provide more reliable and detailed information than existing algorithm.

A New Analytical Representation to Robot Path Generation with Collision Avoidance through the Use of the Collision Map

Seung-Hwan Park,Beom-Hee Lee 대한전기학회 2006 International Journal of Control, Automation, and Vol.4 No.1

A new method in robot path generation is presented using an analysis of the characteristics of multi-robot collision avoidance. The research is based on the concept of the collision map, where the collision between two robots is presented by a collision region and a crossing curve TLVSTC (traveled length versus servo time curve). Analytic collision avoidance is considered by translating the collision region in the collision map. The 4 different translations of collision regions correspond to the 4 parallel movements of the actual original robot path in the real world. This analysis is applied to path modifications where the analysis of collision characteristics is crucial and the resultant path for collision avoidance is generated. Also, the correlations between the translations of the collision region and robot paths are clarified by analyzing the collision/non-collision areas. The influence of the changes of robot velocity is investigated analytically in view of collision avoidance as an example.

A Study of the Collision Detection of Robot Manipulator without Torque Sensor

Hwan-Wook Je,Jun-Young Baek,Min-Cheol Lee 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8

In this study, we proposed the collision observer for real-time detection of collisions between service robot and unknown obstacle. In case of a mobile equipped extra manipulator such as a service robot the safety of the systemin service field is very important because a collision between the manipulator and a person may damages against the one. Therefore it is required to detect the collision against the unknown obstacle and to make them safe. This paper proposes current based method to detect unexpected collision without using extra sensor such as the force/torque(F/T), tactile sensor or the visual sensor. Instead of these sensors, the collision is detected by the observer for collision. To detect the collision of the manipulator without force/torque sensor, two parameters are only required for calculation of collision observer. One is current value, the other is control input value. Because the current from the servo amplifier is generated to follow the controller command input, the current can be used for detecting the collision.After detecting the collision of robot manipulator, we can control the robot to make them safe or reduce damage. The proposed collision detection method is implemented in a light weight robot manipulator. It is confirmed that the proposed method is valid by experimental results.

증강현실 바둑알 충돌게임에서의 연속적인 충돌감지를 방지하기 위한 오토마타 기반 충돌 시나리오 설계

이도희,권혁윤 한국정보과학회 2022 정보과학회 컴퓨팅의 실제 논문지 Vol.28 No.8

증강현실 바둑알 충돌 게임은 사용자의 손 모션을 인식하여 바둑알의 움직임을 구현하기 때문에, 자연스러운 바둑알의 충돌을 구현하기 위해 정교한 바둑알 충돌 시나리오의 설계가 필요하다. 이때, 증강현실 기반의 손 모션 인식은 주기적인 이미지 처리에 의해 수행되기 때문에 인식 주기에 따라 바둑알의 충돌 여부가 감지된다. 하지만, 이 방식은 최초 충돌 이후에도 손 모션 인식 주기에 의해 연속적인 충돌의 감지를 야기하기 때문에 구현을 통해 충돌 지점을 정확히 선정하는 데 어려움이 있다. 본 연구에서는 게임에서 연속적인 충돌감지를 방지하기 위하여 오토마타 기반의 충돌 시나리오를 설계한다. 이를 위해 푸시다운 오토마타를 적용한 손가락 모션에 따른 상태 전이와 비결정적 유한 상태 오토마타를 적용한 바둑알의 상태 전이를 설계한 후, 이들을 통합한 전체 충돌 시나리오를 설계한다. 실험에서 제안한 충돌 시나리오 설계를 도입한 실제 바둑알 충돌 게임과 기존의 라이브러리의 동작 주기에 따라 동작하는 바둑알 충돌 게임을 비교하여, 오토마타 기반의 충돌 시나리오가 연속적인 충돌감지 문제를 효과적으로 해결할 수 있음을 보인다. In the augmented reality-based Go stone collision game, designing the sophisticated Go stone collision scenario for implementing natural collision between stones is important because it implements the movement of the stone based on the recognition of the user’s hand motion. Since the augmented reality-based hand motion recognition is performed by periodic image processing, the detection of collision is performed by the library operation cycle. However, this makes it difficult to calculate the accurate collision position because the continuous collision is detected even after the initial collision. In this paper, to prevent continuous collision detection, we design the collision scenario of the game based on automata. The entire scenario is designed based on two-state transitions: 1) the state transition according to the finger motion with push-down automata and 2) the state transition of the Go stone with non-deterministic finite automata. Through the experiment, the proposed automata-based collision scenario solved the problem of continuous collision detection by comparing it with the game working based on the library operation cycle.

선박충돌 위기상황에서 선박운항자가 지각한 충돌위험도 분석

김대식,임정빈,Kim, Dae Sik,Yim, Jeong Bin 대한인간공학회 2017 大韓人間工學會誌 Vol.36 No.5

Objective: The purpose of this study is to present the basic guidelines for preventing human error by measuring and analyzing the risk of collision perceived by the ship operator in the collision risk situation by using Korea Coast Guard patrol ships. Background: In the last 5 years, 97.5% of the causes of ship collision occurred at the sea was caused by human factors. However, the rate of marine accidents due to human error has not been reduced yet. Experiments and researches on the ship operators using the ships in actual operation are rarely performed. Method: Using two K.C.G Ships on the sea, the ship measured by 30 persons who are the subject of the ship (ship operator) when both ships approach and the relative distance gradually decreases in four encounter situations, perceived ship collision risk (PSCR) data were analyzed by statistical analysis. Results: The age and boarding career of the ship operator in the situation of ship collision risks encountered a negative impact on perceived collision risk in all four opposing encounter situations S1 ($000^{\circ}$), S2 ($045^{\circ}$), S3 ($090^{\circ}$) and S4 ($135^{\circ}$) respectively. That is, the higher the age of the ship operator, the lower the perceived risk of collision and the lower the age, the higher the risk of collision. Also, there was a difference between the average of group A (20~30 years) and group B (40~50 years) according to age of the ship operators at $000^{\circ}$, $045^{\circ}$ and $090^{\circ}$ and there was no difference at $135^{\circ}$. The mean difference of the experience of boarding career was also significantly different between group A (less than 4 years) and group B (more than 5 years), but there was no significant difference at $135^{\circ}$. Conclusion: The results showed that age and boarding career of the ship operators had negative impact on perceived collision risk and there was a difference in perceived risk of collision according to age and abundance of boarding career. As a result, by focusing on the ship operators who are in the age group of 20~30 years old and have less than 4 years of experience in boarding the ship. It is expected that the effect of prevention of marine accidents can be expected by avoiding collision avoidance. Application: The results of this study can be used as policy data of related organizations to prevent human error of ship operators and as training data of training institutes.

LNG외조를 구성하는 샌드위치 콘크리트 패널의 충돌거동해석

이계희 한국전산구조공학회 2017 한국전산구조공학회논문집 Vol.30 No.6

본 연구에서는 LNG 저장시설의 외조를 구성하는 SCP(sandwich concrete panel)에 대한 충돌해석을 수행하고 그 거동을 분석하였다. 설계기준 중 하나인 BS7777에서 제시하는 충돌에너지와 동일한 값을 갖도록 두 종류의 충돌체와 다양한 충돌 속도를 이용하여 충돌조건을 구성하고 이에 대한 비선형동적 해석모델을 구성하여 설정된 충돌조건에 대하여 수치해석을 수행하였다. 또한 1차 충돌 후에 동일한 지점에 같은 충돌에너지를 가진 2차 충돌이 일어나는 것을 가정하여 충돌거동을 분석하였다. 해석결과 동일한 충돌에너지를 갖는 충돌에서 충돌체의 크기가 작고, 충돌속도가 작을수록 큰 변형이 발생하는 것 으로 나타났다. 충돌에너지는 외측강판과 내부 충진콘트리트가 6:4정도의 비율로 소산시키는 것으로 나타났다. 중복충돌해석 에서는 2차 충돌체의 크기에 따라 최종충돌변형이 지배되는 것으로 나타났고 2차 충돌에 의한 변형량은 1차 충돌에 비하여 적은 값을 나타냈는데 이는 강판의 막거동 때문인 것으로 분석되었다. 이격된 중복충돌에서는 이격위치와 관계없이 2차 충 돌점에서 가장 큰 변형이 발생하는 것으로 나타났다. In this study, the collision analysis of SCP(Sandwich Concrete Panel) composing the outer tank of LNG storage was performed and its collision behavior was analyzed. For the same collision energy value proposed in BS7777 code, the collision conditions are composed by using two types of missiles and various collision speeds. Nonlinear dynamic analysis models were constructed to perform numerical analysis on the various collision conditions. Also, the collision behavior was analyzed assuming that the second collision with the same collision energy occurs at the same point after the first collision. As a result of the analysis, it was found that with smaller missile and low collision speed had caused larger deformation. The collision energy dissipated in ratio of about 6: 4 in the outer steel plate and the inner filling concrete. In the results of double collision analysis, the final collisional deformation was dominated by the size of the second missile, and the amount of deformation due to the second collision was smaller than that of the first collision because of the membrane behavior of the steel plates.. In the offset double collision cases, the largest deformation occurs at the secondary collision point regardless of the offset distance.

퍼지종합평가에 의한 연안해역의 선박충돌위험성 평가

박진완,정중식 한국지능시스템학회 2020 한국지능시스템학회논문지 Vol.30 No.4

국제해상충돌예방규칙에 따라 선박은 충돌위험의 존재 여부를 판단하여 충돌위험이 있을 시 조기에충돌회피동작을 취하여야 하나, 지난 5년간 충돌사고 원인 분석결과 96%가 인적오류에 의한 사고로밝혀졌다. 본 연구는 연안해역에서 선박충돌의 위험성을 평가하여 항해사들에게 충돌회피를 위한정보를 제공하는데 있다. 국내 연안해역에서 항해하는 선박 간 조우상황 중 충돌위험이 존재하는 상황을 Lenart의 알고리즘을 적용하여 분류하고, 분류된 상황별로 퍼지종합평가 방법을 통하여 충돌위험을 정량적으로 평가하였다. 입력 데이터는 선박자동식별장치 데이터를 전처리하여 확보하였다. 제안된 방법으로 대상 해역을 평가한 결과 인천항 부근의 연안해역의 충돌위험성이 가장 높은 것으로 나타났다. 연안해역에서 선박교통특성을 분석하고 충돌위험성을 평가함으로써 선박에서 인적오류의 감소에 기여할 것으로 기대된다. According to the COLREGs, every ship should determine the existence of a collision risk and take an action to avoid collision in ample time if there is a collision risk. However, the results of analysis on the maritime collision accidents over the past five years revealed that 96% of all accidents were caused by the human errors. This article aims to assess the collision risk between ships in coastal waters and provide the information on the collision avoidance to navigator. Among the encounter situations between ships in the coastal waters of Korea, the situations where collision risk exists were classified by the Lenart's algorithm, and the collision risk was quantitatively evaluated by the FCE(Fuzzy Comprehensive Evaluation) method for each classified situation. The input data was obtained from the AIS(Automatic Identification System) of the ships. As a result of evaluating the target waters using the proposed method, it was found that the coastal waters near Incheon Port had the highest risk of collision. By analyzing the ship traffic characteristics in the coastal waters and assessing the ship collision risk, it is expected that the proposed method contributes to reduce human errors in the ship.

COLREGs-compliant multiship collision avoidance based on deep reinforcement learning

Zhao, Luman,Roh, Myung-Il Elsevier 2019 Ocean engineering Vol.191 No.-

<P><B>Abstract</B></P> <P>Developing a high-level autonomous collision avoidance system for ships that can operate in an unstructured and unpredictable environment is challenging. Particularly in congested sea areas, each ship should make decisions continuously to avoid collisions with other ships in a busy and complex waterway. Furthermore, recent reports indicate that a large number of marine collision accidents are caused by or are related to human decision failures concerning a lack of situational awareness and failure to comply with the Convention on the International Regulations for Preventing Collisions at Sea (COLREGs). In this study, we propose an efficient method to overcome multiship collision avoidance problems based on the Deep Reinforcement Learning (DRL) algorithm by expanding our previous study (Zhao et al., 2019). The proposed method directly maps the states of encountered ships to an ownship's steering commands in terms of rudder angle using the Deep Neural Network (DNN). This DNN is trained over multiple ships in rich encountering situations using the policy-gradient based DRL algorithm. To address multiple encountered ships, we classify them into four regions based on COLREGs, and consider only the nearest ship in each region. We validate the proposed collision avoidance method in a variety of simulated scenarios with thorough performance evaluations, and demonstrate that the final DRL controller can obtain time efficient and collision-free paths for multiple ships. Simulation results indicate that multiple ships can avoid collisions with each other while following their own predefined paths simultaneously. In addition, the proposed approach demonstrates its excellent adaptability to unknown complex environments with various encountered ships.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study deals with a multiship collision avoidance problem in congested sea areas. </LI> <LI> A COLREGs-compliant method for multiship collision avoidance is proposed based on deep reinforcement learning. </LI> <LI> A novel strategy is used to solve the problem by categorizing target ships into four regions defined by COLREGs. </LI> <LI> The proposed method is applied to a wide range of problems, from single collision avoidance to multiple collision avoidance. </LI> </UL> </P>

Analysis of vehicle collision accidents based on qualitative mechanics

Elsevier 2018 Forensic science international Vol.291 No.-

<P><B>Abstract</B></P> <P>In this paper, a method for vehicle collision analysis based on qualitative mechanics is presented. In collisions where accurate quantitative information is difficult to gather, this analytic method can act as a useful complement. Based on qualitative dynamic theories, reasonings of various factors including qualitative vector, collision behavior, translational and rotational motion are suggested. Using the law of momentum conservation within the frame of rigid-body dynamics, vehicle collision analyses based on this qualitative reasoning were developed into an accident analysis tool. This newly developed qualitative collision analysis tool was verified using 45 cases of vehicle-to-vehicle collision test data, and its practicality was proved by performing analyses of various vehicle collision accidents.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Artificial intelligence method using qualitative data for collision accident analysis. </LI> <LI> Reasoning method to estimate the changes in movements caused by the collision. </LI> <LI> Verification using vehicle crash tests and various collision accident cases. </LI> <LI> Prediction and avoidance of collision accidents for autonomous driving. </LI> </UL> </P>