In the motion control system,the control of electromotor's rotate speed is of great importance,there
are a lot of speed control arithmetics and methods ,the analog PID control is one of the earliest
developed control policies which has formed typical structure ,its parametric setting is convenient and
it's easy to meet normal control's demand,but as the whole control process is fixed once the parameter
has been set while practically the changes of those conditions like the system parameters and
temperature of the environment prohibit the system from reaching its best control effect,so the analog
PID controller barely has satisfied effect.With the development of computer technology and intelligent
control theory ,the digital PID technology is thriving which can achieve the analog PID's control tasks
and consists of many advantages like flexible control arithmetics and high reliability,it is widely used
now.
This design is based on the digital PID mentioned above as basic control arithmetic and AT89S51
SCM as control core,the system produces PWM impulse whose duty ratio is controlled by digital PID
arithmetic to make sure the running of direct current machine's rotate speed.Meanwhile,the design uses
photoelectric sensor to transduce the electromotor speed into impulse frequency and feed it back to
SCM,this process implements rotate speed's closed loop control to attain the purpose of rotate speed's
astatic modulation.In this system, the 128×64LCD is used as display unit , the 4×4 keyboard
sets those four parameters P、I、D、V and obverse and reverse control,after starting up,the display unit
shows the electromotor's current rotate speed and runtime.The system has great control precision and
anti-jamming capability.
Keywords： digital PID；PWM impulse；dutyfactor；astatic modulation
前言
21 世纪，科学技术日新月异，科技的进步带动了控制技术的发展，现代控制设备的性能和结
构发生了翻天覆地的变化。我们已进入高速发展的信息时代，控制技术成为当今科技的主流之一，
广泛深入到研究和应用工程等各个领域。
控制理论的发展经历了古典控制理论、现代控制理论和智能控制理论三个阶段。其控制系统
包括控制器﹑传感器﹑变送器﹑执行机构﹑输入输出接口。控制器的输出经过输出接口﹑执行机
构、加到被控系统上；控制系统的被控量、经过传感器、变送器、通过输入接口送到控制器。不
同的控制系统、传感器﹑变送器﹑执行机构是不一样的。比如压力控制系统要采用压力传感器。
