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Adaptive Cruise Control (ACC) technology is presently emerging in the automotive market as a convenience function intended to reduce driver workload. It allows the host vehicle to maintain a set speed and distance from preceding vehicles by a forward object detection sensor. The forward object detection sensor is the focal point of the ACC control system, which determines and regulates vehicle acceleration and deceleration through a powertrain torque control system and an automatic brake control system. This paper presents a design of an automatic braking system that utilizes a microprocessor-controlled brake hydraulic modulator. The alternatively qualified automatic braking means is reviewed first. The product level requirements of the performance, robustness, and durability for an automatic brake system are addressed. A brief overview of the presented system architecture is described.

The severe thermal distortion of a brake rotor can affect important brake system characteristics such as the system response and brake judder propensity. This paper will propose a technique to determine the thermal distortion under transient or steady state conditions. The technique involves utilizing a PC-based computer program to calculate the necessary thermal parameters and apply the results as input to a finite element-based thermal stress analysis. This unique approach provides a reliable methodology to determine the heat input and cooling characteristics of a given brake system in addition to resultant distortion and stress components within the brake rotor. Analysis results are also compared to measured temperature and distortion data.

Long repetitive braking, such as one which occurs during a mountain descent, will result in a brake fluid temperature rise and may cause brake fluid vaporization. This may be a concern particularly for passenger cars equipped with aluminum calipers and with a limited air flow to the wheel brake systems. This paper describes the computer modeling techniques to predict the brake fluid temperature rise as well as other brake component temperatures during braking and heat soaking. Numerical results are compared to the measured vehicle data and the effects of relevant brake system parameters on the fluid temperature are investigated. The techniques developed in this study will help brake engineers to build a safer brake system and reduce the extensive vehicle tests currently required.

In automotive disk brake systems, frictional heat is not uniformly distributed due to various reasons such as thermal expansion and imperfections in geometry. It is well known that thermoelastic distortion due to frictional heating affects the contact pressure distribution and can lead to thermoelastic instability or TEI, where the contact load is concentrated in one or more small regions on the brake disk surface. These regions then reach very high temperatures and the passage of these hot spots moving under the brake pads can cause low frequency vibration called brake judder. Disk thickness variation (DTV) will further promote the localized contact. Nonuniform contact can also be generated by disk lateral runout (LRO). This study investigated the effects of various contact conditions on the heating patterns and judder characteristics of a disk brake by using a state of the art infrared camera technology and vibration measurements.