【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 (Carioles 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 14 ITT39。t aware of the coefficient of friction between the tires and the road and have no idea of their vehicle39。s actions even when the car is freerolling. Depending on the particular driving situation, the system may activate an individual wheel brake or any bination of the four and adjust engine torque, stabilizing the car and severely reducing the danger of an uncontrolled skid. The new systems control the motion not only during full braking but also during partial braking, coasting, acceleration, and engine drag on the driven wheels, circumstances well beyond what ABS and traction control can handle. The idea behind the three active safety systems is the same: One wheel locking or slipping significantly decreases directional stability or makes steering a vehicle more difficult. If a car must brake on a lowfriction surface, locking its wheels should be avoided to maintain stability and steer ability. Whereas ABS and traction control prevent undesired longitudinal slip, stability control reduces loss of lateral stability. If the lateral forces of a moving vehicle are no longer adequate at one or more wheels, the vehicle may lose stability, particularly in curves. What the drive “fishtailing is primarily a turning or spinning around the vehicle39。s group and a team of engineers from MercedesBenz, led by project manager Armin Muller, developed the first fully effective stability control system, which regulates engine torque and wheel brake pressures using 8 traction control ponents to minimize the difference between the desired and actual motion. Automotive safety experts believe that stability control systems will reduce the number of accidents, or at least the severity of damage. Safety statistics say that most of the deadly accidents in which a single car spins out (accounting for four percent of all deadly collisions) could be avoided using the new technology. The additional cost of the new systems is on the order of the increasingly popular antilock brake/traction control units now available for cars. The debut of stability control technology took place in Europe on the MercedesBenz S600 coupe this spring. Developed jointly during the past few years by Robert Bosch GmbH and MercedesBenz AG, both of Stuttgart, Germany, Vehicle Dynamics Control (VDC). in Bosch terminology, or the Electronic Stability Program (ESP), as Mercedes calls it, maintains vehicle stability in most driving situations. Bosch developed the system, and MercedesBenz integrated it into the vehicle. Mercedes engineers used the stateoftheart DaimlerBenz virtualreality driving simulator in Berlin to evaluate the system under extreme conditions, such as strong crosswinds. They then put the system through its paces on the slick ice of Lake Hornavan near Arjeplog, Sweden. Work is currently under way to adap