• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.4
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• pp.96-103
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• 2005

We designed the compound CVT(Continuously Variable Transmissions) by combining power circulation mode and power split mode, which have been proposed for connecting 2K-H I differential gear to the V- belt type CVU(Continuously Variable Unit), as an input coupled type. With the designed compound CVT, we carried out theoretical analysis and performance experiments for efficiency, speed ratio, power flow, and power transmission ratio. We proved that the compound CVT had a better performance than either of the power circulation mode or power split mode.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.670-673
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• 2005

We designed the compound CVT (Continuously Variable Transmissions) by combining power circulation mode CVT and power split mode CVT, which have been proposed for connecting 2K-H II differential gear to the V- belt type CVU (Continuously Variable Unit), as an input coupled type. With the designed compound CVT, we carried out theoretical analysis and performance experiments. We proved that the compound CVT had a better performance than either of the power circulation mode or power split mode.

• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.19-28
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• 2007

In this study, a nonlinear 2 degree of freedom mathematical model has been developed for impact analysis of the nose landing gear of a light aircraft which is composed of an wheel & tire, an Oleo-pneumatic shock strut and the castering wheel fork for the differential braking steering, and then the response of impact is computed using a numerical method. The mathematical model of a nose landing gear contains nonlinear characteristics which are an impact load - deflection property of a tire and internally frictional forces between an inner surface of an upper cylinder and a bearing of a lower rod due to side forces like the declined angle of strut, the moment due to an wheel fork, the side drag due to a steering and it is computed using the 4th-order Runge-Kutta method. The comparison process between analytical results and experimental results of the other proven nose landing gear is carried out to verify the mathematical model.

• Structural Engineering and Mechanics
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• v.88 no.4
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• pp.389-403
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• 2023

In order to explore the influence of tooth root cracks on the dynamic characteristics of multi-stage planetary gear transmission systems, a concentrated parameter method was used to construct a nonlinear dynamic model of the system with 30-DOF in bending and torsion, taking into account factors such as crack depth, length, angle, error, time-varying meshing stiffness (TVMS), and damping. In the model, the energy method was used to establish a TVMS model with cracks, and the influence of cracks on the TVMS of the system was studied. By using the Runge- Kutta method to calculate the differential equations of system dynamics, a series of system vibration diagrams containing cracks were obtained, and the influence of different crack parameters on the vibration of the system was analyzed. And vibration testing experiments were conducted on the system with planetary gear cracks. The results show that when the gear contains cracks, the TVMS of the system will decrease, and as the cracks intensify, the TVMS will decrease. When cracks appear on the II-stage planetary gear, the system will experience impact effects with intervals of rotation cycles of the II-stage planetary gear. There will be obvious sidebands near the meshing frequency doubling, and the vibration trajectory of the gear will also become disordered. These situations will become more and more obvious as the degree of cracks intensifies. Through experiments, the theoretical results are in good agreement with experimental results, verifying the correctness of the theoretical model. This provides a theoretical basis for fault diagnosis and reliability research of the system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.433-434
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• 2006

The limited slip differential(LSD) is a device which enables the driving force to be transmitted from one slipping wheel to another wheel in such case that the car is stuck in clay or snow. When the unwanted slipping occurs on one wheel, the LSD temporarily restraints the differential motion to transmit the driving force in the other wheel. So far, many types of LSD were developed such as mechanical lock type, disk clutch type, viscous coupling type, torsion type and multiple clutch type. we designed a new type of the hydraulic LSD which uses the principle of trochoid gear pump.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.7
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• pp.938-947
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• 2003

In this paper, we derived the formula for estimating the power of the electric motors needed to operate the Decanter-type centrifuge. In the derivation of the formula the sludge-removal torque is to be supplied from the formula derived in the first paper. The intricate nature of the transmission mechanism in the planetary gear trains of the sludge-removal power and torque has been clarified in this second paper. In particular we considered two-motor system, where the main motor drives the machine while the differential-speed control motor plays the role of braking in adjusting the differential speed. Sample calculation for the specific design treated in the first paper showed that the selection criterion for the main motor depends on the lower limit of the differential speed; when the lower limit is set low, it should be selected based on the steadily operating power, while it should be selected based on the starting power when the lower limit is set high. The total power required by both the main motor and the differential-speed control motor increases as the differential speed is decreased. It is suggested that the power loss in the differential-speed control motor could be minimized by attaching an electric generator to it.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1495-1505
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• 2002

As combining the functions of a 2K-H B type differential gear unit and a V-belt type continuously variable unit(CVU), 16 different mechanisms are presented. Some useful theoretical formula related to speed ratio, power flow and efficiency are derived and analyzed. Continuously variable transmission(CVT) mechanisms are proposed, which can of ffr a backward mode, a geared neutral, an underdrive mode and an overdrive mode. They are not required of a starting device as a torque converter. CVT mechanisms developed here present two distinct operating modes which are a power circulation mode and a power split mode. The transition of two modes takes place at the particular CVU speed ratio. For these CVT mechanisms, performance analysis related to speed ratio, power ratio and theoretical efficiency are executed.

• Journal of Computational Design and Engineering
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• v.1 no.1
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• pp.27-36
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• 2014

Similar to the essential components of many mechanical systems, the geometrical properties of the teeth of spiral bevel gears greatly influence the kinematic and dynamic behaviors of mechanical systems. Logarithmic spiral bevel gears show a unique advantage in transmission due to their constant spiral angle property. However, a mathematical model suitable for accurate digital modeling, differential geometrical characteristics, and related contact analysis methods for tooth surfaces have not been deeply investigated, since such gears are not convenient in traditional cutting manufacturing in the gear industry. Accurate mathematical modeling of the tooth surface geometry for logarithmic spiral bevel gears is developed in this study, based on the basic gearing kinematics and spherical involute geometry along with the tangent planes geometry; actually, the tooth surface is a parametric surface defined on a parallelogrammic domain. Equivalence proof of the tooth surface geometry is then given in order to greatly simplify the mathematical model. As major factors affecting the lubrication, surface fatigue, contact stress, wear, and manufacturability of gear teeth, the differential geometrical characteristics of the tooth surface are summarized using classical fundamental forms. By using the geometrical properties mentioned, manufacturability (and its limitation in logarithmic spiral bevel gears) is analyzed using precision forging and multiaxis freeform milling, rather than classical cradle-type machine tool based milling or hobbing. Geometry and manufacturability analysis results show that logarithmic spiral gears have many application advantages, but many urgent issues such as contact tooth analysis for precision plastic forming and multiaxis freeform milling also need to be solved in a further study.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.6
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• pp.115-121
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• 2016

The aircraft flight control system controls an aircraft's direction and flying attitude, and actuators are key components of control systems. Actuators can be classified as Geared Rotary Actuator (GRA) and Ball Screw Actuator (BSA). GRA is used in mid-sized aircraft, and BSA is used in larger aircraft. A two-stage differential GRA model was suggested in this paper, and structural analysis and performance tests were performed. According to the analysis and experiment, the stiffness of the two-stage differential GRA was 17.57% higher than that of the conventional GRA, and the structural safety was improved.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.13-22
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• 1997

Power flow characteristics of a hydro-mechanical transmission system(HMT) are investigated for tracked vehicle in steering. A HMT consisting of two hydrostatic pump motors(HST), several planetary gear trains and steer differential gear is considered. In order to obtain the direction and magnitude of the power flow of the HMT, network theory for the general power transmission is used. Network model for the HMT in steering is developed, which consists of shafts, nodes and transmission elements such as clutch, gear, etc. Power flow analysis procedure consists of two stages : (1) traction force analysis in steering, (2) power flow analysis in HMT. Torque and speed of every transmission element of the HMT is determined from the network analysis. Also, efficiency, mechanical and hydraulic power loss including HST, are obtained. In addition, the regenerative power flow resulting from steering can be studied in graphic display. The power flow analysis program(PCSTEER) developed in this work can be used as a useful design tool for the tracked vehicle with HMT.