• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.474-479
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• 1998

In this paper, we present a mathematical model of the piezoelectric pump and its application to the automobile brake system. The piezoelectric pump consists of a multi-layered piezoelectric element a diaphragm, pumping values, resonant pipes and accumulators, and the maximum pumping power of 62W nab obtained in the previous experiments by using the piezoelectric element of 22mm diameter and 55.5mm length. A detailed mathematical model of the pump is derived here by considering the compressibility of the working oil, nonlinear characteristics of piezoelectric element, the time delay of pumping values' action and be on. The validity of the model is illustrated by comparing the experimental data and the simulation results. Using the mathematical model of the piezoelectric pump, a brake system for automobile disk brake is also simulated in this paper. The brake system consists of a piezoelectric pump as a power source, calipers and its piston to generate brake force, and a three position solenoid value to change the brake situation. It is shown that 15mm/sec of piston speed and 20kN of piston force are obtained by using the piezoelectric element of 33mm diameter and 55.5mm length.

• Journal of Power System Engineering
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• v.16 no.2
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• pp.5-10
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• 2012

The parking brake is one of the essential units embedded in track driving motor for forward and backward motion of an excavator. It is composed of multi-friction discs. When the hydraulic motor stops, the multi-friction discs closely stick to the facing discs by acting of multi-spring forces. So, the friction forces generate the braking force by compressing the cylinder barrel of hydraulic motor. In this study, we combined the multi-friction discs to two kinds of spring which have different spring force, and the maximum torque measured at the rotational starting point of hydraulic motor through gradually increasing the rotational torque of load side hydraulic motor by use of 1 and 2 sheets of friction plates. And, under this experimental condition, the maximum coefficient of static friction and the characteristics of paper friction sheet were analyzed. The obtained experimental results will be applied to the design of parking brake system for producing large size excavator in the 85-ton weight class.

• Journal of Magnetics
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• v.18 no.3
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• pp.276-282
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• 2013

In this paper, magnetic flux distributions of several permanent magnet arrays, including Halbach array, are analyzed and compared. Also, braking force characteristics on a moving solid conductor in the eddy current brake systems with such magnet arrays are analyzed. Then, a new performance index taking into account the maximum braking force and the volume of the magnet is introduced for the comparison and case study of permanent magnet arrays. By changing the lengths, magnetization directions and the height of the permanent magnet arrays, a higher braking force per volume of the magnet can be achieved.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.1
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• pp.17-22
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• 2013

Design of braking system is one of the most critical subjects in vehicle stability. In this paper, optimal scheme for brake force proportioning of all-wheel-drive vehicle is proposed to guarantee the vehicle dynamic stability under plausible drive circumstances. A brake force distribution of generic $8{\times}4$ vehicle is calculated according to proposed scheme and braking stability of this vehicle is verified by using a commercial vehicle software, Trucksim.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.211-215
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• 2010

Continuous contraction and expansion of disk brake can be due to friction and temperature difference at repeated sudden braking. As serious vibration at disk is produced, the braking force will be changed ununiformly and braking system can not be stabilized. Temperature and heat flux at disk brake are investigated by structural and thermal analysis in this study. The maximum equivalent stress and displacement are shown respectively at the ventilated hole and the lower part of disk plate. At thermal analysis of initial state, temperature on disk plate is distributed from $95.9^{\circ}C$ to $100^{\circ}C$. The maximum heat flux of $0.0168W/mm^2$ is shown at the inner friction part between disk plate and pad. At thermal analysis of transient state, temperature on disk plate is distributed from $95^{\circ}C$ to $96.5^{\circ}C$ after 100 second. The maximum heat flux of $0.0024W/mm^2$ is also shown at the inner friction part between disk plate and pad. By comparing with initial state, the temperature on disk plate is more uniformly distributed and heat flux is more decreased by 7 times at transient state.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.4
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• pp.525-533
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• 1998

A conventional contact type brake system which uses a hydraulic system has mny Problems such as time delay response due to pressure build-up, brake pad wear due to contact movement, bulky size, and low braking performance in high speed region. As vehicle speed increases, a more powerful brake system is required to ensure vehicle safety and reliability. In this work, a contactless brake system of an eddy current type is proposed to overcome problems. Optimal torque control which minimizes a braking distance is investigated with a scaled-down model of an eddy current type brake. It is possible to realize optimal torque control when a maximum friction coefficient (or desired slip ratio) corresponding to road condition is maintained. Braking force analysis for a scaled-down model is done theoretically and experimentally compensated. To accomplish optimal torque control of an eddy current type brake system, a sliding mode control technique which is, one of the robust nonlinear control technique is developed. Robustness of the sliding mode controller is verified by investigating the braking performance when friction coefficient is varied. Simulation and experimental results will be presented to show that it has superior performance compared to the conventional method.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.1
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• pp.130-137
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• 2018

In long freight trains, there is a brake time delay in the neighboring freight cars that causes damage and fractures of couplers, especially the knuckle of them. If there is a problem for couplers in the cars, this could cause a derailment and lead to damage of human life and property damage. In this study, maximum forces on the couplers are studied when a long freight car brakes, with brake delay time and coupler gap. We have made a dynamic model of 50 freight cars and couplers, applying contact between couplers and a characteristic curve for expressing force and displacement of buffers with SIMPACK, a multi-body dynamics program. We use EN 14531-2 from the British Standards Institution, a standard of freight car brakes for the verification of the dynamic model. We also use a simplified method to analyze the dynamic model of 50 freight cars. With changing coupler gap and brake delay time, we do comparative analysis with AAR M-201 from the Association of American Railroads, a standard of AAR couplers. From this result, we find that the standard on fatigue limit is satisfied, such that the brake delay time is within 0.06 second if the coupler gap of the AAR coupler is within 20 millimeters.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.1
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• pp.78-85
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• 2013

This paper presents the sliding mode control methods for anti-lock brake system (ABS) with the friction force observer. Using a simplified quarter car model, the sliding mode controller for ABS is designed to track the desired wheel slip ratio. Here, new method to find the desired wheel slip ratio which produces the maximum friction force between road and tire is suggested. The desired wheel slip ratio is varying according road and tire conditions to produce maximum friction force. In order to find optimum desired wheel slip ratio, the sliding mode observer for friction force is used. The proposed sliding mode controller with observer is evaluated in simulation, and the control design is shown to have high performance on roads with constant and varying adhesion coefficients.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.3 s.246
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• pp.295-301
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• 2006

The wheel slip control systems are able to control the braking force more accurately and can be adapted to different vehicles more easily than conventional ABS systems. In order to achieve the superior braking performance through the wheel-slip control, real-time information such as the tire braking force at each wheel is required. In addition, the optimal target slip values need to be determined depending on the braking objectives such as minimum braking distance, stability enhancement, etc. In this paper, a robust wheel slip controller is developed based on the adaptive sliding mode control method and an optimal target slip assignment algorithm. An adaptive law is formulated to estimate the longitudinal braking force in real-time. The wheel slip controller is designed using the Lyapunov stability theory and considering the error bounds in estimating the braking force and the brake disk-pad friction coefficient. The target slip assignment algorithm is developed for the maximum braking force and searches the optimal target slip value based on the estimated braking force. The performance of the proposed wheel-slip control system is verified In simulations and demonstrates the effectiveness of the wheel slip control in various road conditions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.2
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• pp.65-72
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• 2019

In long freight trains, there is a brake time delay in neighboring freight cars, which causes damage and fractures in the couplers, especially at their knuckle. A problem in the couplers of the cars can cause derailment and damages of human life and property. In this study, maximum forces on the couplers are studied when a long freight car brakes with the brake delay time and coupler gap. We make a dynamic model of 50 freight cars and couplers, applying contact between the couplers and a characteristic curve to express the force and displacement of the buffers using SIMPACK, which is a multi-body dynamics program. We use EN 14531-2, which is a standard of freight car brakes, to verify the dynamic model. Then, we compare the analyzed impact force with the coupler knuckle standard after applying the two carriages of a locomotive in the model based on the dispersed double head control system. The result shows that all coupler gap conditions satisfy the infinite lifetime of the material when the brake delay time is 0.1 second.