• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.142-153
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• 2005

The brake judder is a phenomenon that the steering wheel is abnormally vibrating when the car is braked at a high speed. It is classified by the cold and the hot judder. The former is generated due to the initial uneven disk surface and the latter is resulted from the uneven heat spots on disc surface by repeatedly braking. There are two ways to reduce the judder. One is to control vibration by modification of the disk shapes and pad ingredients. The other is to improve modal characteristics of the suspension system. The latter approach is used in this research. In this paper, the real vehicle test and computer simulation are considered to systematically understand the judder phenomenon of the vehicle. The Macpherson strut suspension is employed. Especially, the judder sensitivity is calculated based on design sensitivity analysis. A bush stiffness was reworked and braking test was done to verify the sensitivity result. The judder reduction by the mode control was verified.

• Journal of KSNVE
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• v.9 no.3
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• pp.613-620
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• 1999

Brake judder{or cold judder) caused by the disc thickness variation(DTV) is investigated experimentally, This cold judder is often perceived by steering wheel vibration, brake pedal pulsation, and vehicle body vibration. In this paper, how the DTV profile affects the vibration characteristics of vehicle body is shown by order tracking analysis(OTA) and operational vibration analysis(OVA) The tri-axial vibrations are measured at the knuckle, lower rm, and the body side of the lower arm. Also, measured are the wheel speed and the detail DTV profile. The interpretations of OTA results in three directions of tested vehicle indicate the relative importance in the contribution of the run-out and the DTV to the judder vibration. Also, the OVA results show the prominent vibration amplitude of the lower arm in the direction of the vehicle movement. in which the second order of wheel speed is dominant. These results could be used to diagnose the judder problem and to establish the correction methods.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.764-769
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• 2001

Brake-induced vibrations of a vehicle such as brake judder are determined by the excitation of brake torque variations and by their transfer to the driver's contact points via suspension, body and steering system. The formation of brake torque variation is mainly determined by static and dynamic disk thickness variations. The vibration transfer from the excitation by brake torque variation to the perception by the driver depends on the kinematic and dynamic behaviour of the components in the transfer path. Optimization of the judder performance can be achieved either by minimizing the excitation or by reduction of the judder sensitivity of the vehicle. In this paper, the optimization process of a front rotor is suggested to reduce brake judder considering the cooling performance of the rotor, the judder sensitivity of the vehicle and durability of the rotor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.432-439
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• 2020

Brake judder has been identified in some operating military units of Korean Light Tactical Vehicles(KLTV) with In-board brake systems to improve braking performance. Severe vibration generated while driving the vehicle may reduce the KLTV's driving stability and further lead to accidents. For the prevention of this, this study analyzes the root cause through the failure analysis on the vehicles with the brake judder identified. Furthermore, the improvement factor was derived by identifying a vibration transmission path by analyzing the vibration transmission mechanism. The study analysis confirmed that the vibration of the frame during braking in the tactical vehicle is a cold judder phenomenon, which is caused by an increase in disk thickness variation due to rust and foreign substances under excessive brake disc's run-out. In addition, it was confirmed that such vibration can be reduced by improving the mounting structure. So, an improvement method for each factor was suggested and its effectiveness was verified by comparison test. Finally, it is expected that the improvement plans derived through this study can be used in the development of a next military vehicle.