外文翻译-PID控制器的设计.doc

英 文 翻 译 系 别 专 业 班 级 学生姓名 学 号 指导教师 Introduction The PID controller has several important functions: it provides feedback; it has the ability to eliminate steady state offsets through integral action; it can anticipate the future through derivative action. PID controllers are sufficient for many control problems, particularly. when process dynamics are benign and the performance requirements are modest. PID controllers are found in large numbers in all industries. The controllers come in many different forms. There are standalone systems in boxes for one or a few loops, which are manufactured by the hundred thousands yearly. PID control is an important ingredient of a distributed control system. The controllers are also embedded in many special-purpose control systems. In process control, more than 95% of the control loops are of PID type, most loops are actually PI control. Many useful features of PID control have not been widely disseminated because they have been considered trade secrets. Typical examples are techniques for mode switches and antiwind up. PID control is often combined with logic, sequential machines, selectors, and simple function blocks to build the complicated automation systems used for energy production, transportation, and manufacturing. Many sophisticated control strategies, such as model predictive control, are also organized hierarchically. PID control is used at the lowest level; the multivariable controller gives the setpoints to the controllers at the lower level. The PID controller can thus be said to be the bread and butter of control engineering. It is an important component in every control engineers toolbox. PID controllers have survived many changes in technology ranging from pneumatics to microprocessors via electronic tubes, transistors, integrated circuits. The microprocessor has had a dramatic 2 Chapter 1 Introduction influence on the PID controller. Practically all PID controllers made today are based on micropro