动力转向系统的演变

动力转向系统的演变(中文3300字,英文1800字)
动力转向系统的简单介绍
动力转向帮助司机通过补充方向盘转向力度来操纵汽车。液压或电动执行器向转向机构增加控制的能量，因此不管在什么条件下，驾驶员只需要提供适度的力。当车辆停止或缓慢移动，动力转向的帮助很大。另外，动力转向系统提供了一些作用在前轮上力的反馈，得到车轮与路面如何相互作用的持续感，这通常称为“路感”。
代表汽车的动力转向系统通过一个致动器---液压缸来增大转向力，这液压缸是伺服系统的一部分。这些系统在方向盘和联动之间有一个直接的机械连接来操纵车轮。这意味着，动力转向系统发生故障时，仍然允许车辆转向时单独使用手动力来操作。

The Evolution of Power Steering
Brief introduction for power steering
   Power steering helps drivers steer vehicles by augmenting steering effort of the steering wheel. Hydraulic or electric actuators add controlled energy to the steering mechanism, so the driver needs to provide only modest effort regardless of conditions. Power steering helps considerably when a vehicle is stopped or moving slowly. Also, power steering provides some feedback of forces acting on the front wheels to give an ongoing sense of how the wheels are interacting with the road; this is typically called "rοad feel".
   Representative power steering systems for cars augment steering effort via an actuator, a hydraulic cylinder, which is part of a servo system. These systems have a direct mechanical connection between the steering wheel and the linkage that steers the wheels. This means that power-steering system failure still permits the vehicle to be steered using manual effort alone.
  In other power steering systems, electric motors provide the assistance instead of hydraulic systems. As with hydraulic types, power to the actuator  is controlled by the rest of the power-steering system.