• Proceedings of the KSR Conference
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• 2004.10a
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• pp.728-732
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• 2004

The purpose of this study is to examine wheel load variations on the bridge. It had been reported that wheel load variations involved un-sprung mass, sprung mass and train running speed, but there are no examples that measured in the running speed actuality track. In this experiment, Attach measurement sensor to equal distance on the track and measured wheel loads by using a dynamic shear strain technique.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.10
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• pp.1099-1107
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• 2009

Numerical simulation and experimental study to evaluate the critical speed of the railway bogie according to the tread inclination of wheel profile were conducted using 1/5 scale model. It has been shown that the results of the critical speed analysis for the scale bogie model is very close to the test results using scale bogie model and the critical speed is decreased in proportion to the increase of equivalent conicity of wheel profile. Results of this study show that the scale model could be applied to research area relating to vehicle stability as an alternative to overcome the experimental problems caused by full scale test on the roller rig.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.507-512
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• 2003

The railroad is a means of large transportation which has many latents such as a safety and a regularity. That is a results from various confidential performance tests and evaluations of the system. The railroad system consist of various subsystems - vehicle, power supply, signal, communications, track structures, operations, etc. Among them, as an item of safety evaluation there is a measurement of wheel/rail force, so called a measurement of derailment coefficient. This is a very important item because a derailment of a train will bring about a big accident. Especially it is more important in high speed rail of which operation speed is over two times as fast as existing rail. In this paper, it is introduced to preprocess the wheelset for measuring wheel/rail force of high speed rail, such as to treat a measuring wheelset, its finite element analysis, adhesion of strain gauges and static toad test, running test result of main line.

• Journal of Biosystems Engineering
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• v.21 no.4
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• pp.399-405
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• 1996

In order to maintain a constant speed ratio between the tractor and attached seed planter, a feedback control unit to rotate the feed shaft of the planter in proportional to the ground speed of the tractor was designed. The fifth wheel was used as a ground speed sensor for the unit. Using this control unit a feed shaft driving system was developed and tested to estimate its performance both in laboratory and fields. The test results showed that the system rotates the feed shaft proportionally to the ground speed in the range of the normal planting speed of 0.5-0.8m/s with errors less than 5%.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.1000-1004
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• 1995

In the case of the external cylindrical grinding machine, the grinding mechanism can cause a wheel to vibrate due to a wheel cutter. This phenomena will bring about the unsymmetric wear up to high frequency without any relation of rotational speed. So far, when the grinding spindle is analyzed, it is assumed that a wheel is considered as lumped mass at the endof a beam. Nowadays, there is a tendency to use the wheel with a lsrge diameter or CBN wheel to achieve the high speed and accuracy grinding performance. Therefore, this kind of assumption is no longer valid. At the analysis of the grinding spindle, the parameter which dapends on the dynamic characteristics is a combination force between each part. For example, there is the tightness torque of a bolt and taper element in the grindle. In addition, the material property of the wheel can contribute the dynamic characteristics. This paper shows the mode participation of the shell mode of the wheel in the grindle and the dynamic characteristics according to the parameters which are the configuration of the flange and tightness torque of a bolt and taper. Modal parameter of the wheel, flange and the spindle can be extracted through frequency response function obtained by modal test. After that, by changing the tightness torque and kinds of wheel, we could accomplish the test in the whole combined grinding spindle. To perform modal analysis of vibration characteristics in the grinding spindle, we could develop the model of finite element method.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.12
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• pp.1340-1345
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• 2012

Industrial products developed in recent years have focused on usability and stability. Especially, for the products used in daily life, steady efforts have been made to secure the safety. Among them, the products equipped with wheels such as strollers, shopping carts, and carriers can occur the safety accidents by unintended over speed at a ramp. Therefore, development of speed limit device is required to prevent such accidents. However, the existing speed limit devices are very expensive and have a complex drive principle, so it's generally difficult to apply them. In this study, a simple speed limit wheel is suggested which can replace the previous complex and inconvenient speed limit devices. The developed speed limit wheel can be simply applied to existing products by changing the wheels. In addition, it has an advantage to operate only by mechanical mechanism without power supply. Thus it can minimize the cost and waste of resources. For this purpose, the operating condition of the target products was analyzed, and trochoid gear mechanisms were selected for the speed limit. Based on this, finite element analysis was conducted to estimate the operating mechanism. After the prototype of the wheel was produced, the performance under various conditions was tested and has been improved.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1387-1395
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• 2013

When the center of mass of a railway wheel is not aligned with the geometrical center of the wheel axis, wheel unbalance occurs. If a railway vehicle runs without removing the wheel unbalance, vibrations will be produced. This will also cause wear and damage of the axle bearing. In this study, dynamic analysis of a railway vehicle with wheel unbalance was conducted to examine the reduction in critical speed and the resonance of the car-body and the effect on the magnitude of wheel unbalance was examined. In addition, the calculation of the car-body vibration owing to static and dynamic unbalance in the railway wheel shows that two-plane balancing is necessary.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.179-186
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• 2001

As the freight traffic becomes heavier, the high speed of existing freight cars is essential instead of the construction of a new railway. The high speed can be achieved by the design modifications of the freight bogie. In this paper, an analytical model of freight bogie including the lateral force between rail and the flange of wheel is developed to decide the critical speed, which activates a hunting motion and tells the running safety of freight bogie. The dynamic responses of the analytical model were compared with an experimental data from a running test of a freight bogie and showed good agreements between them. The analytical model is used to find the design modifications of the freight bogie by parameter studies. The results show that the reduction of wheelset mass ratio and the increase of the axle distance of the freight bogie can increase the critical speed, but the primary lateral stiffness has little effects on the critical speed. And this also study shows that smaller wheel conicity deteriorates the running safety of the freight car, which means the overhauling of the wheel of freight bogie should be done regularly.

• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.530-543
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• 2013

This paper describes a control scheme of speed sensorless fuzzy direct torque control (FDTC) of permanent magnet synchronous motor for electric vehicle (EV). Electric vehicle requires fast torque response and high efficiency of the drive. Speed sensorless FDTC In-wheel PMSM drives without mechanical speed sensors at the motor shaft have the attractions of low cost, quick response and high reliability in electric vehicle application. This paper presents a new approach to estimate the speed of in-wheel electrical vehicles based on Model Reference Adaptive System (MRAS). The direct torque control suffers in low speeds due to the effect of changes in stator resistance on the flux measurements. To improve the system performance at low speeds, a PI-fuzzy resistance estimator is proposed to eliminate the error due to changes in stator resistance. High performance sensorless drive of the in-wheel motor based on MRAS with on line stator resistance tuning is established for four motorized wheels electric vehicle and the whole system is simulated by matalb/simulink. The simulation results show the effectiveness of the new control strategy. This proposed control strategy is extensively used in electric vehicle application.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.5
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• pp.101-109
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• 1994

Recently, four-wheel steering systems have been developed and studied as one of the latest automotive technologies for improving the handling characteristics of a vehicle. In much of the proposed four-wheel steering systems, the side slip angle at the vehicle's center of gravity is maintained at zero. This approach allows the greater maneuverability at low speed by means of counter-phase rear steering and the improved stability at high speed through same-phase rear steering. In this paper, the effects of several four-wheel steering systems are studied and discussed on the responsiveness and stability of the vehicle by using the linear analysis. Especially, the effects of the cornering stiffnesses of both front and rear wheels are investigated on the yaw velocity gain and critical speed of the vehicle.