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NODEIK: Solving Inverse Kinematics with Neural Ordinary Differential Equations for Path Planning
Suhan Park,Mathew Schwartz,Jaeheung Park 제어로봇시스템학회 2022 제어로봇시스템학회 국제학술대회 논문집 Vol.2022 No.11
This paper proposes a novel inverse kinematics (IK) solver of articulated robotic systems for path planning. IK is a traditional but essential problem for robot manipulation. Recently, data-driven methods have been proposed to quickly solve IK for path planning. These machine learning-based models can handle a large amount of IK requests at once by leveraging the GPU. However, such methods suffer from reduced accuracy and considerable training time. We propose an IK solver that improves accuracy and memory efficiency with continuous normalizing flows by utilizing the continuous hidden dynamics of a Neural ODE network. The performance is compared using multiple robots, and our method is shown to be highly performant on complex (including dual end effector) manipulators.
Comparison of Injection and Spray Characteristics of Water and n-heptane in a PFI Injector
( Jeonghyun Park ),( Kyung-hwan Lee ),( Suhan Park ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-
The improvement of engine performance and fuel economy is very important. Therefore, many engineers and researchers have tried the development and application of various new combustion strategies, such as gasoline compression ignition, waste heat recovery, 6-stroke combustion, and water-injection. Among them, it is reported that the water injection technologies have effects on the improvement of fuel economy and the reduction of knock intensity. For a deep understanding on the effect of water injection on the combustion and emissions characteristics, it needs to investigate the injection and spray characteristics when the water injected into the intake port. Therefore, the study on the injection and spray characteristics of water using port fuel injection (PFI) injector was conducted. The results for water injection were compared with those for n-heptane injection. The test injector has a twelve-hole, 138 ㎛ diameter. The tap-water and n-heptane were used as fuel. The test fuels were compressed by a nitrogen gas, the pressurized test fuels were injected through the PFI injector, which was controlled using Compact RIO and Lab view. A visualization experiment was carried out using a high-speed camera and light-source in a constant-volume chamber. The droplet size (Sauter mean diameter, SMD) was measured using phase Doppler anemometry (PDA) system. The injection pressure was 3 bar to 9 bar with 2 bar of interval, and the test was carried out with the energizing duration of 1 ms to 4 ms with 1 ms of interval. From experimental results, it revealed that the injection quantity of water was higher than that of n-heptane as about 21 %. As the energizing duration and the injection pressure increased, the injected quantity of both fuel also increased. The spray tip penetration was increased with increasing injection pressure, and the energizing duration have a little effect. The spray tip penetration of water was longer than n-heptane due its higher density. As the injection pressure increased, the SMD of both fuels decreased and the droplet size of water was larger than that of n-heptane. The size distribution of the spray droplet of water is spread evenly compared to n-heptane, and the size distribution of the droplet was concentrated as the injection pressure was increased.
분사압력 변화에 따른 가솔린 직접분사 인젝터의 거시적 분무와 분무패턴 특성에 관한 연구
박정현 ( Jeonghyun Park ),박수한 ( Suhan Park ) 한국액체미립화학회 2018 한국액체미립화학회지 Vol.23 No.1
The purpose of this study is to investigate the macroscopic spray characteristics and spray pattern of a gasoline direct injection (GDI) injector according to the increase of injection pressure. The macroscopic spray characteristics, such as a spray tip penetration and spray angle, were measured and analyzed from the frozen spray images, which are obtained from the spray visualization system including the high-speed camera, light-source, long-distance microscope (LDM). The spray pattern was analyzed through the deviation of the center of the spray plum and images were acquired using Nd: YAG Laser and ICCD(Intensified charge coupled device) camera. From the experiment and analysis, it revealed that the injection pressure have a significant influence on the spray tip penetration and spray pattern. However, the injection pressure have little influence on the spray angle. The increase of injection pressure induced the reduction of a closing delay. In addition, the deviation of spray center increase with the increase of injection pressure and the distance from a nozzle tip.