This study presents a vertically deployable rotor-sail structure utilizing multi-layer Sarrus linkages. The structure fully extends during sailing to maximize Magnus lift and compresses to less than half its length for docking. An analytical beam model integrates link thickness, mid part spacing, and centrifugal loading to predict deflection and mass. Parametric comparisons of two-layer, six-layer, and twelve-layer configurations reveal that the twelve-layer design reduces structural mass by 90% while meeting an L/1000 deflection limit. Dynamic simulations using RecurDyn confirm that mid part segmentation decreases damping time and reduces peak stress, thus enhancing deployability and mechanical reliability. The findings offer quantitative design guidance for high-speed rotating deployable structures.
Recently, as UAM has been in the spotlight worldwide, the issue of aerodynamic noise generated from propellers has emerged. Therefore, changes in thrust and aerodynamic noise were compared while changing the propeller lay-out distance. The designed propeller model was analyzed using ANSYS Fluent, a CFD software. Based on steady-state analysis, transient analysis was performed, and SPL was calculated using the FW-H noise model. Based on the standard propeller lay-out distance of 0.1 R (0.12 mm), 5 cases from 0.2 R to 0.6 R were compared with the reference model at equal intervals of 0.1 R. The thrust increased by up to 3.5% as the propeller distance increased. In most listeners positioned to measure SPL, noise was reduced by 0.07-0.7% in the improved model compared to the reference model due to reduction in local vorticity. However, because pressure fluctuation due to the increase in thrust and high SPL in the low-frequency region were measured, noise increased by 0.6% to 3.5% in some listeners. Increasing the propeller distance enhances thrust performance, but inevitably increases noise due to pressure fluctuations and SPL in the low-frequency region. Therefore, strict analysis of noise prediction according to a specific frequency and various design shapes are needed.
The aim of this research was to investigate the torque performance of the motor in an electric vehicle depending on the rotor shape and air gap. The research focused on numerical comparison of torque performance of new rotors based on the average torque and torque ripple rate, which appeared according to the number and placement of permanent magnets. This research was numerically analyzed by MAXWELL V21.1. Average torque values in cases 1, 2, and 3 were increased, but vibration and noise in cases 1 and 3 were increased as the torque ripple rate increased. Considering the average torque and torque ripple rate, the torque performance of case 2 was the most optimal. Compared with Model N, the average torque of case 2 was increased by 9.1% and the torque ripple rate was reduced by 1.5%. The torque performance according to the size of air gap was compared with the basic model of case 2, which showed the best performance. An air gap of 0.7 mm applied to Model N showed the best torque performance. An additional magnet on case 2 and air gap of 0.7 mm provided the best torque performance and improved the driving motor performance for motor durability.
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Vehicle-motion-based Front Wheel Steer Angle Estimation for Steer-by-Wire System Fault Tolerance Seungyong Choi, Wanki Cho, Seung-Han You Journal of the Korean Society for Precision Engineering.2024; 41(5): 347. CrossRef
Numerical Analysis of Outer-Rotor Synchronous Motors for In-Wheel E-Bikes: Impact of Number of Windings, Slot, and Permanent Magnet Shapes Jaewoong Han, Chanyoung Jin, Insu Cho, Jinwook Lee Applied Sciences.2024; 14(10): 4167. CrossRef
The large gas turbine rotor used for power generation has a structural characteristic comprising a shaft, disk, and blade assembled to the disk. Because the start/stop is repeated, the tightening force may be reduced in the process of repeating the tightening force between the tie rod and the disk. When the tightening force falls below the threshold, changing the critical speed, increasing the vibration, or in extreme cases, the rotor may loosen and cause a major accident. Also, it is imperative to continuously maintain the proper tightening force because the thread of the tie rod is damaged when the tightening force exceeds the yield stress condition of the tie rod. In this paper, the gas turbine rotor system is modeled and simplified to identify the control variable of the tightening force of the tie rod bolts of the rotor. For verification, a simplified model of the gas turbine rotor was designed, manufactured, and verification tests were conducted to confirm the adequacy of the calculation method. As a result, the tightening force decreased as the stiffness of the pressing disk decreased, so the stiffness of the pressing disk should have a stiffness range similar to that of the tie rod.
This paper addresses the design of an integrated high torque DC motor. In this paper, a method to improve the torque according to the shape of the stator magnet and the rotor teeth of the DC motor is studied. During the course of design, the rotor and stator are designed to satisfy the required performance through FEM analysis by reflecting similar materials in design. As a result of satisfying the design result and requirements, the motor that is imported and operated in the future can be applied as a domestic developed product.
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Smart Design of Rotor and Permanent Magnet considering Torque and Torque Ripple of Interior Permanent Magnet Synchronous Motor of Electric Vehicle Seong-Hwan Bang, Si-Mok Park, Min-Gi Chu, Ji-Hun Song, Dong-Ryul Lee Journal of the Korean Society for Precision Engineering.2021; 38(8): 605. CrossRef
Effect of Thermal Conductivity of Coil Insulator Material on the Temperature Variation of High Voltage Motor Jaehyun Park, Seung Ho Paek, Hyun Woo Lee, Heesung Park Journal of the Korean Society for Precision Engineering.2020; 37(5): 355. CrossRef
The importance of environmentally-friendly energy production has been growing globally, and studies on energy storage technologies are underway, to supply produced energy to consumers. Flywheel Energy Storage System (FESS) is physical energy storage technology, that stores generated electric energy into kinetic energy in the rotor. To design the FESS with a high-strength steel rotor, that is inexpensive, recyclable and easy to manufacture, mechanical and electrical components such as a rotor, bearings, etc. are required. Among these, safety of rotor and bearings is critical, because the rotor with high rotating speed may cause axis failure or fracture of the rotating body. Proper size of a rotor for required energy storage and radial, axial forces generated by the spinning rotor was calculated, considering gyroscopic forces acting on the rotating body. Based on the calculation, adequately sustainable angular ball bearings were selected. As a result, by conducting structural, modal and critical speed analysis, safety verification is presented pursuant to the American Petroleum Institute (API) publication 684.
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An Analytical Study on the Design of Housing Components for 10 kWh Flywheel Energy Storage System Deuk Kyu Lee, Beom Soo Kang Journal of the Korean Society for Precision Engineering.2020; 37(1): 59. CrossRef
The vibration analysis of flexible rotor systems supported by angular contact ball bearings is presented. Vibration analysis of rotor-ball bearing systems has often been performed via simplification of supporting bearings as linear springs with constant stiffness. In this study, an improved model of rotor-ball bearing systems was proposed. It utilizes a general bearing model based on response and time-dependent bearing characteristics. The system equations of motion were established using the finite-element method and numerically solved using the Newmark-β method. The method was used to recalculate the bearing stiffness matrices at every interval of numerical integration as a function of the instantaneous bearing displacements using a separated five-degrees-of-freedom bearing model. The method was verified via comparison with experimental data available in the literature. The extended simulations were conducted to investigate the unbalanced responses of a rotor-ball bearing system using the proposed and conventional methods. Numerical results showed a meaningful discrepancy between the vibrational responses obtained by the proposed model using the response and timedependent bearing stiffness model and the traditional constant-stiffness model.
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Study on Thermo-mechanical Modeling and Analysis of High-speed Angular Contact Ball Bearings Under Oil-jet Lubrication Gilbert Rivera, Shinhyang Park, Chan-sik Kang, Dongjoo Kim, Seong-Wook Hong Journal of the Korean Society for Precision Engineering.2024; 41(7): 569. CrossRef
The differential gear distributes the power from the transmission shaft to both wheel axles and automatically ensures rotational difference to maintain the speed difference between the two axles. However, when the vehicle travels on a slippery road surface, a slip in the wheel induces improper transmission of the driving force. Therefore, the limited slip differential limits the function of the differential gear by transmitting the driving force to the normal wheel without the slip. The hydraulic differential limiting device is based on the principle that the fluid between the inner and the outer rotors is compressed by the rotation of the trochoidal gear, and the compressed fluid moves to the cylinder to generate sufficient pressure in the side pinion gear to limit the differential. In this study, the pressure is predicted by variation in viscosity and rotational speed through flow analysis.
Gerotor oil pumps are widely used for the lubrication oil of an engine and the hydraulic source of an automatic transmission. Recently, improvements for the purposes of fuel efficiency and noise reduction have come to the forefront of the automobile industry, and it has become necessary to study the design of gerotors and ports. In this study, an expanded cardioid curve was developed, and an equation for a tooth profile with an expanded cardioid lobe shape has been suggested to reduce pump noise. The design was created using an automatic program; the program generated inner and outer rotor profiles and calculated performance parameters. Also, in order to decrease irregularity, CFD analyses were performed according to groove shapes in the exhaust port. Results showed the noise of the improved oil pump (the suggested gerotor [expanded cardioid] + the proposed port) was 5.44% lower than the existing oil pump (the existing gerotor [2-ellipse] + basic port).
The role of dynamic behavior of operating rotor system in rotor design may or may not be evaluated under the impact of an external force such as earthquake. This article reports the result of an experimental study to resolve the dilemma. First, a sine weep test was performed to determine the first natural frequency of a Jeffcott rotor and compared with the ANSYS mode analysis demonstrating the reliability of experimental tests. The operating rotor vibrations were measured under the impact of sinusoidal forces at several frequencies, generated by the MTS vibration exciter. The experimental data suggest the need for a rotor design considering the dynamic behavior of the operating rotor under exciting external forces.
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