• Journal of the Korean Society for Precision Engineering
• /
• v.24 no.7 s.196
• /
• pp.106-111
• /
• 2007

In this paper, the transient brake time was studied on the van type vehicle with accelerometer. Experiments were carried out on the asphalt(new and polished), unpacked road(earth and gravel) and on wet or dry road conditions. The transient brake time is not effected bzy the vehicle speed. The transient brake time is about 0.41$\sim$0.43second on the asphalt road surface and the error range is within 0.1$\sim$0.16second. For the asphalt road condition, the transient brake time is not effected by both new asphalt road surface and the polished asphalt road surface. With compared by dry and wet road surface condition, the transient brake time of wet condition is longer than dry road condition and compared with unpacked road condition and packed road condition, unpacked road condition is shorter than packed road condition. It is considered that the transient brake time is effected by the road surface fraction coefficient. In other words, the transients brake time increases as friction coefficient decreases.

• Journal of Mechanical Science and Technology
• /
• v.16 no.6
• /
• pp.776-784
• /
• 2002

We have performed experimental studies for the improvements of pneumatic brake systems of freight trains. Currently, most of the freight trains operated by the Korean National Railroad have either empty-load or diaphragm type brake systems. In this study, appropriate methods that the air pressure characteristics in both type of brake systems are in accordance with each other have been investigated. We have also performed running tests using a 30 car-train set to design optimum capacity of a quick release valve. The test results show that the quick release valve is considerably effective in shortening the release time of the diaphragm type brake system. In the case of a normal brake application, the diaphragm type brake system with the quick release valve reduces the release time to 34% of that of the system without the quick release valve. This release time is almost equivalent to that of the empty-load type brake system. Accordance of braking performance in different types of brake systems in a train set is expected to prevent wheel flats and to reduce maintenance costs.

• The Journal of Korean Physical Therapy
• /
• v.21 no.3
• /
• pp.81-86
• /
• 2009

Purpose: This study compared the characteristics of the brake response time during the driving task between elderly and younger drivers. Methods: The participants consisted of an elderly group (n=12) and a younger group (n=12). The brake response time (BRT), which consisted of the reaction time (RT) and movement time (MT), was assessed in an actual driving car. The BRT was measured at the initiation and termination of the brake response for the driving task Results: The elderly group showed a significantly longer delay in the initiation and termination of the brake response than the younger group. The BRT correlated significantly with both the RT and MT. However, the RT showed a more significant correlation. Conclusion: A delay in the initiation and termination of the brake response may have clinical implications. A further study will be needed to determine the different factors contributing to the driving performance of elderly drivers.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.261-264
• /
• 1997

A contactless eddy current type braking system is developed to take advantages of the recent brake system which uses hydraulic force can show high efficiency in a certain velocity region, but not in a high velocity region, and has initial response delay time and pressure build-up time which make stopping distance longer. These are the limits of mechanical brake system of a contact type, which makes a concept brake system required. So, in this paper, the contactless brake system .of a inductive current type is chosen instead of hydraulic brake system. This brake system can be used almost forever for being no wear and contributed to lightening weight of a vehicle. Besides, the contactless brake system can be used as that of electric or solar car with anti-lock brake system. The analysis of induced electromotive force and braking torque obtained with theoretical approximate model, the design of a braking system and a nonlinear controller, and the results of simulation of the ABS, experiment are included.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.12
• /
• pp.1739-1747
• /
• 2001

Experimental study has been conducted to clarify the pneumatic characteristics of brake system for freight train and enhance the performance of diaphragm valve. Empty-load and diaphragm valves are installed in pneumatic brake system for freight trains of KNR (Korean National Railroad). Experiments are conducted by using freight train and diesel locomotive in operation. From the experimental results. new quick release valve shortens release time after brake application. In case of normal brake application, the release time is shortened to 34% of the original diaphragm valve. Reducing the release time of pneumatic brake system will be helpful to assure brake-release application and save maintenance efforts like wheel grinding.

• Journal of the Korean Society of Safety
• /
• v.10 no.3
• /
• pp.106-109
• /
• 1995

Optimum relocation of the brake relative to the accelerator can reduce stopping diatance and may mean the difference between an accident and a near-accident. A driving simulator was used to examine effiency of brake time. Brake time was measured for 30 participants in six conditions. Brake times were shown to improve as a result of moving the brake pedal from its typical heights above the accelerator to positions below the accelerator.

• Journal of the Korean Society for Precision Engineering
• /
• v.33 no.7
• /
• pp.535-540
• /
• 2016

The braking device in railway vehicles decelerates or stops the train by dissipating the thermal energy converted from kinetic energy into the air. Therefore, the brake system is crucial for safety. In this paper, we performed a study on an electromechanical brake actuator using an electrical motor as an alternative to pneumatic air cylinders to reduce the idle running time in braking, which subsequently increases braking distance, and to ensure reliable response characteristics. Especially, to analyze the response characteristics of the electromechanical brake actuator, we measure the delay time, response time and power consumption compared to the air cylinder. It is confirmed that the electromechanical brake actuator can reduce reaction time by 0.1 seconds (Braking Action) and 0.46 seconds (Brake Release) compared to the air cylinder.

• Tribology and Lubricants
• /
• v.22 no.2
• /
• pp.87-92
• /
• 2006

In tread brake of freight cars, brake force is produced by the friction between the wheel and the brake shoe. Friction coefficients associated with the brake power, weight variation and brake shoe types should be sensitively treated as the design parameters. The conditions of the car, empty and loaded, should also be taken into consideration in brake force design and the control of brake force has some limitations in terms of the brake system design so that the brake friction materials selection should be considered as important measures to solve that difficulties. Friction characteristics of brake friction materials should remain within the range of maximum and minimum value and the friction performance should remain stable regardless of brake time and temperature. This study presented an experimental evaluation method to secure optimum brake performance by keeping safe brake effect and brake distance by the friction coefficient of the brake shoe of the freight cars.

• Journal of Mechanical Science and Technology
• /
• v.15 no.5
• /
• pp.569-579
• /
• 2001

This study investigates the effects of operating conditions on the chattering of an automotive disk brake by experimental and computational methods. Design factors, which cause chattering in automobiles, have attracted great attentions for long time; but they are not well understood yet. For this study, we construct a brake dynamometer for measuring the disk surface temperature during chattering, and propose an efficient hybrid algorithm (combining FFT-FEA and traditional FEA program) for analyzing the thermo-elastic behavior of three-dimensional brake system. We successfully measure the judder in a brake system via the dynamometer and efficiently simulate the contact pressure variation by the hybrid algorithm. The three-dimensional simulation of thermo-mechanical interactions on the automotive brake, showing the transient thermo-elastic instability phenomenon, is presented for the first time in this academic community. We also find from the experimental study that the disk bulk temperature strongly influences the brake chattering in the automotive disk brakes.

• Proceedings of the KIPE Conference
• /
• 1998.10a
• /
• pp.560-563
• /
• 1998

For the next generation railway brake system, a disc brake which can be operated directly and electrically is strongly expected. This paper deals with newly developed disc brake actuator using giant magnetostrictive materials(GMM) which can be integrated with disc brake. Regarding the brake system performance, a better delay time was also attained which can be integrated with disc brake. Regarding the brake system performance, a better delay time was also attained which will contribute to shorten a stopping distance.