畢業(yè)設(shè)計(jì)外文翻譯---汽車的轉(zhuǎn)向控制-汽車設(shè)計(jì)(參考版)
2025-01-23 04:17本頁(yè)面
【正文】 another pair, which is displaced by 90 degrees, stabilizes the vibration. At both element pairs in between, socalled vibration nodes shift slightly depending on the rotation of the car about its vertical axis. If there is no yaw input, the vibration forms a standing wave. With a rate input, the positions of the nodes and antinodes move around the cylinder wall in the opposite direction to the direction of rotation (Coriolis acceleration). This slight shift serves as a measure for the yaw rate (angular velocity) of the car. Several drivers who have had handson experience with the new systems in slippery cornering conditions speak of their cars being suddenly nudged back onto the right track just before it seems that their back ends might break away. Some observers warn that stability controls might lure some drivers into overconfidence in lowfriction driving situations, though they are in the minority. It may, however, be necessary to instruct drivers as to how to use the new capability properly. Recall that drivers had to learn not to pump antilock brake systems. Although little detail has been reported regarding nextgeneration active safety systems for future cars (beyond various types of costly radar proximity scanners and other similar systems), it is clear that accidentavoidance is the theme for automotive safety engineers. The most survivable accident is the one that never happens, said ITT39。s Graber explained, causes the car to fishtail, throwing the vehicle even further out of control. ASMS sensors, he said, can quickly detect the beginning of a skid and momentarily activate the brakes at individual wheels to help return the vehicle to a stable line. It is important that stability control systems be userfriendly at the limit of adhesion that is, to act predictably in a way similar to normal driving. The biggest advantage of stability control is its speed it can respond immediately not only to skids but also to shifting vehicle conditions (such as changes in weight or tire wear) and road quality. Thus, the systems achieve optimum driving stability by changing the lateral stabilizing forces. For a stability control system to recognize the difference between what the driver wants (desired course) and the actual movement of the vehicle (actual course), current cars require an efficient set of sensors and a greater puter capacity for processing information. The Bosch VDC/ESP electronic control unit contains a conventional circuit board with two partly redundant microcontrollers using 48 kilobytes of ROM each. The 48kB memory capacity is representative of the large amount of intelligence required to perform the design task, van Zanten said. ABS alone, he wrote in the SAE paper, would require onequarter of this capacity, while ABS and traction control together require only one half of this software capacity. In addition to ABS and traction control systems and related sensors, VDC/ESP uses sensors for yaw rate, lateral acceleration, steering angle, and braking pressure as well as information on whether the car is accelerating, freely rolling, or braking. It obtains the necessary information on the current load condition of the engine from the engine controller. The steeringwheel angle sensor is based on a set of LED and photodiodes mounted in the steering wheel. A siliconmicromachine pressure sensor indicates the master cylinder39。t aware of the coefficient of friction between the tires and the road and have no idea of their vehicle39。s lateral movement cannot be calculated from its wheel speeds. SPIN HANDLERS The new systems measure any tendency toward understeer (when a car responds slowly to steering changes), or oversteer (when the rear wheels try to swing around). If a car understeers and swerves off course when driven in a curve, the stability control system will correct the error by braking the inner (with respect to the curve) rear wheel. This enables the driver, as in the case of ABS, to approach the locking limit of the roadtire interface without losing control of the vehicle. The stability control system may reduce the vehicle39。s actions even when the car is freerolling. Depending on the particular driving
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