• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.3
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• pp.137-142
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• 2021

In recent years, permanent magnets such as IPM (Interior Permanent Magnet) motors or SPM (Surface Permanent Magnet) motors that can obtain high efficiency and power density by inserting rare earth permanent magnets into the rotor are used. Research on the used electric motor is being actively conducted. Since it uses a permanent magnet, it has the advantage of high efficiency and high power density compared to reluctance motors and induction motors, but by inserting a permanent magnet into the rotor, it operates at high speeds and decreases reliability due to demagnetization of the permanent magnets, and increases the cost of rare earth metals. In this paper, in accordance with the development of future technology that can replace rare-earth permanent magnet motors and technological preoccupation of rare-earth reduction type motors and de-rare-earth motors, switched reluctance motors that do not require permanent magnets (Switched Reluvtance Motors) Motor, SRM) to drive driving control. Using the 3-phase SRM library provided by the PSIM simulation program, we will study the driving and control system modeling of SRM using the rotor position information sensor.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.3
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• pp.214-221
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• 2021

SiC MOSFETs require a faster and more reliable short-circuit protection circuit than conventional methods due to narrow short-circuit withstand times. Therefore, this research proposes a short-circuit protection circuit using a current-sensing circuit based on Rogowski coil. The method of designing the current-sensing circuit, which is a component of the proposed circuit, is presented first. The integrator and input/output filter that compose the current-sensing circuit are designed to have a wide bandwidth for accurately measuring short-circuit currents with high di/dt. The precision of the designed sensing circuit is verified on a double pulse test (DPT). In addition, the sensing accuracy according to the bandwidth of the filters and the number of turns of the Rogowski coil is analyzed. Next, the entire short-circuit protection circuit with the current-sensing circuit is designed in consideration of the fast short-circuit shutdown time. To verify the performance of this circuit, a short-circuit test is conducted for two cases of short-circuit conditions that can occur in the half-bridge structure. Finally, the short-circuit shutdown time is measured to confirm the suitability of the proposed protection circuit for the SiC MOSFET short-circuit protection.

• Design & Manufacturing
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• v.14 no.4
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• pp.65-70
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• 2020

Partial reinforcement of sheet metal parts with CFRP patch is a technology that can realize ultra-lightweight body parts while overcoming the high material cost of carbon fiber. Performing these patchworks with highly productive press equipment solves another issue of CFRP: high process costs. The A-pillar is the main body part and has an undercut shape for fastening with other parts such as roof panels and doors. Therefore, it is difficult to bond CFRP patches to the A-pillar with a general press forming tool. In this paper, a flexible system that applies uniform pressure to complex shapes using ceramic particles and silicone rubber is proposed. By benchmarking various A-pillars, a reference model with an undercut shape was designed, and the system was configured to realize a uniform pressure distribution in the model. The ceramic spherical particles failed to realize the uniform distribution of high pressure due to their high hardness and point contact characteristics, which caused damage to the CFRP patch. Compression equipment made of silicone rubber was able to achieve the required pressure level for curing the epoxy. Non-adhesion defects between the metal and the CFRP patch were confirmed in the area where the bending deformation occurred. This defect could be eliminated by optimizing the process conditions suitable for the newly developed flexible system.

• Journal of the Korea Convergence Society
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• v.12 no.2
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• pp.215-219
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• 2021

The flow analyses around the wing of airplane installed with winglet or sharkelt were carried out in this study. At the model without winglet, it can be seen that the air flows beside the wing and the flow is concentrated at the end of wing. At the model of winglet or sharklet, the pressure on the bottom of the wing happens to be lower in the wide area than for model without winglet. At the analysis result, the air flowing next to the wing can be seen to go over and rotates over the main wing. The model with the sharklet shows that the flow rate is the fastest. In case of model with sharklet, it is thought that the maximum total pressure of flow is distributed at the bottom of the wing, which can further improve the lift force of the wing. It is thought that the analysis results in this study on the air flow due to the configuration of aircraft edge wing can be helped at its convergent research.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.6
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• pp.768-777
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• 2020

In this paper, we describe recent research results on AODV routing protocol, which is widely deployed at mobile ad hoc networks, and AODV related routing protocols with multi-path routing schemes. We suggest the critical problems which minimum hop routing schemes have, such as AODV routing protocol, and then, propose a new C-AODV routing protocol with two routing metrics: the primary metric is the hop count, the secondary metric is the sum of link delay times. We implemented C-AODV protocol by modifying AODV at the NS-3, and thus, elaborate on how we change the original AODV source code of NS-3 in order to implement the C-AODV scheme. We show numerical comparison of C-AODV scheme with the original AODV scheme and then, discuss how much the C-AODV enhances routing performance over AODV protocol. In conclusion, we present future research items.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.3
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• pp.40-46
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• 2021

An automatic transmission of automobiles enables comfortable driving experience with lower transmission shifting jerks. However, the assembly structure is more complicated and requires additional components with lower efficiency than the manual transmission system. Extensive research has been conducted to improve the overall transmission efficiency by optimizing each component of the automatic transmission assembly. This study focuses on enhancing the friction torque of double angular contact ball bearings used in automatic transmission. The friction torque of the bearing varies with the operating conditions such as the operational load and rotating speed. Since reducing the friction torque of the bearing tends to deteriorate the durability of the bearing, it is necessary to design the bearing having a minimum required friction torque by determining the durability life of an automatic transmission assembly, In this study, the theoretical life and friction torque of conventional and newly-developed bearings are calculated. The difference in the friction torque between the new and existing bearings are also evaluated.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.295-299
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• 2022

In this paper, paint-free metallic plastic material, polypropylene (PP) and acrylonitrile styrene acrylate (ASA) materials were investigated on the applications for bumper skid plate and outside mirror housing parts. In order to maximize metallic effect, type, size and content of aluminum pigment were optimized based on flop index. Hybrid aluminum pigments with different aspect ratios were used to conceal weld lines. By controlling the fluidity of the material, the flow mark problem, generated on the surface of the part, was resolved. We also investigated the surface defects of flow and weld lines by using the developed modeling and simulation.

• Journal of IKEEE
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• v.25 no.4
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• pp.762-765
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• 2021

In this paper, an automotive ECU (electronic control unit) with Kalman filter accelerator is designed and implemented. RISC-V is exploited as a processor core. Accelerator for Kalman filter matrix operation, CAN (controller area network) controller for in-vehicle network, and LIN (local interconnect network) controller are designed and embedded. Kalman filter operation consists of time update process and measurement update process. Current state variable and its error covariance are estimated in time update process. Final values are corrected from input measurement data and Kalman gain in measurement update process. Usually floating-point multiplication is exploited in software implementation, but fixed-point multiplier considering accuracy analysis is exploited in this paper to reduce hardware area. In 28nm silicon fabrication, its operating frequency, area, and gate counts are 100MHz, 0.37mm², and 760k gates, respectively.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1311-1316
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• 2021

In this paper, we present a bifocal stereo camera system combining two cameras with different focal length cameras to generate stereoscopic image and their corresponding depth map. In order to obtain the depth data using the bifocal stereo camera system, we perform camera calibration to extract internal and external camera parameters for each camera. We calculate a common image plane and perform a image rectification for generating the depth map using camera parameters of bifocal stereo camera. Finally we use a SGM(Semi-global matching) algorithm to generate the depth map in this paper. The proposed bifocal stereo camera system can performs not only their own functions but also generates distance information about vehicles, pedestrians, and obstacles in the current driving environment. This made it possible to design safer autonomous vehicles.

• Journal of Korea Trade
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• v.24 no.3
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• pp.37-54
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• 2020

Purpose - This study is to investigate the determinants of suppliers' dependence on buyers in the home country by developing a theoretical model of innovative activities. The high dependence of auto parts suppliers on a single local buyer in South Korea due to firm ownership issues and incremental innovation is examined using data from a set of organizations that supply intermediate goods to this automotive manufacturer. Furthermore, we tested the moderating effect of FDI and global knowledge sourcing on the relationship between firm ownership and suppliers' dependence on the local buyer. Design/methodology - To test the hypotheses, we examined a sample of 101 suppliers over 10 years in the Korean automobile parts industry. In this empirical analysis, we utilized a fixed-effects generalized least squares model using panel data. Findings - In this study, domestic firms (automobile parts suppliers) were more dependent on a single local buyer (automobile assembler) than foreign-owned suppliers operating in Korea. In addition, incremental innovation was the mediating mechanism between domestic firms and dependence on the local buyer. To reduce this dependence on the buyer, we suggest two different international strategies: geographical diversification through FDI and global knowledge sourcing. Originality/value - Previous studies showed that asymmetric dependence between firms has many adverse effects. This study proved that domestic and foreign-owned suppliers have different levels of dependence on local buyers due to their heterogeneous characteristics and business strategies. We distinguish two different types of innovation - radical innovation and incremental innovation - that previous studies have often treated as equal when it comes to firm autonomy. Finally, we propose that both FDI and international knowledge sourcing as global strategies to weaken suppliers' asymmetric dependence on a single buyer.