机械设计制造及其自动化专业外语15单元.ppt

; (1)Numerically controlled machines often weigh up to 100 tons and yet are required to position a cutting tool with an accuracy of the order of 0.002mm. The control system must move the tool at federates as high as 8cm/sec while encountering loads which may vary dramatically on a given path. The NC machine must have dynamic response characteristics that enable it to follow intricate contours with a minimum of path error. Clearly, these requirements dictate a control system that is matched to the mechanical characteristics of the machine it drives. ; (2) A control system is a combination of devices that regulate an operation by administering the flow of energy and other resources to and from that operation . Essentially, a control system is made up of interrelated subsystems that perform tasks which in orthodox machining processes are managed by an intelligent human operator.; （1）数控机械通常重达100吨，可是却要求安装一个精度高达0.002mm数量级的切削刀具。在遇到预定路径下载荷变化较大的情况时，控制系统仍要以高达8厘米/秒的进给速度下移动刀具。数控机床必须具有动态响应特性，使它能够复制较复杂的轮廓线，并具有最小的路径误差。显然，这些条件要求控制系统必须与它所驱动的机器机械特征相匹配。 （2）控制系统是一组设备的组合，他通过管理能量流和与该操作有关的其它资源来控制操作。从本质上说，控制系统由相互关联的子系统组成，并有它们执行传统上通常由只能人工操作员控制的机械加工过程。;; (4) In summary, a machine control system is a combination of electronic circuitry, sensing devices, and mechanical components which guide the cutting tool along a predefined path. (5) In the sections that follow, the reader is introduced to the theory of machine control.;（3）因此，数控机床的控制系统用于代替人工机器操作员并可显著地改进即使最好的人工操作。可从以下几个方面对数字控制系统和它们代替的人工操作员直接进行类比： 检测机器的现状； 做出完成任务所需的逻辑决策； 通过操纵机械设备向机器传送决策信息； 具有储存指令、数据、与逻辑决策结果等各种信息的能力。 （4）总之，机械控制系统是电路系统、检测装置以及机器零件的结合体，并指导切削刀具沿着预定路径实现进给动作。 （5） 以下的内容，将给读者介绍机械控制的原理。 ; (6) We have attributed four major characteristics to any control system: the ability to sense data; make logical decisions; communicate and actuate; and store information in a memory. If a system performs these functions without the aid of a human operator, by definition it automatically controls a given task. Let us consider one such simple