【摘要】：随着时代发展，进入21世纪崭新工业控制领域。PLC仍然能够引导自动化行业的发展，而长期以来PLC始终处于工业自动化控制领域主战场，为各种各样的自动化设备提供了非常可靠的控制应用，随着电子事业的飞速发展，PLC已经可以在各个领域去适应不同的客户要求。

　　　本课题是应用PLC的可变参数PI控制来实现单容水箱的快速、精确、稳定控制。因为单容水箱惯性系数小，所以无需采用微分控制。通过实验寻找一组可以迅速减小误差的PI参数和一组在误差小时超调小，状态稳定的参数。然后在可变参数控制中结合两组参数的优点，达到理想效果。

　　　本文的主要内容包括：水箱的特性确定与实验曲线分析， S7-200可编程控制器的硬件掌握，PID参数的整定及各个参数的控制性能的比较，应用PID控制算法所得到的实验曲线分析，整个系统各个部分的介绍和应用PLC语句编程来控制水箱水位。 

【关键词】：S7-200西门子PLC、控制对象特性、PID控制算法、PID指令。 

【Abstract】: With the development of the computer technology, PLC automation is able to guide the development of the industry. While the PLC is always used in the field of industrial automation, it controls the main battlefield for a wide business. PLC has been able to adapt in various fields and different customer requirements.

　　　The graduation project topic is the PLC Variable parameter PI control to achieve the single-capacity water tank’s fast, accurate and stable control. Due to the inertia coefficient of the single-tank water level control was small, differential control was not adopted. A set of PI parameters that can quickly reduce the error and a set of parameters in the error-hour steady state control were found by experiment.Then the variable parameters control in combination with a two set of parameters advantages can achieve the desired effect.

　　　In article, it mainly includes: water tank characteristic determination and experimental curve analysis; the S7-200 programmable controller hardware grasps; PID parameter installation and each parameter control performance comparison; experimental curve analysis obtains which using the PID control algorithm and overall system each part of introduction and programs using the PLC sentence controls the water tank water level. 

【Key words】: SIMATIC S7-200 PLC, the controlled member characteristic, the PID control algorithm。