Figure 4. Internal structure of PID controller

Figure 5. The dialog box after mask PID controller

In order to avoid changing the content of system model and simplify model, make subsystem for the model that don’t change constantly. After make subsystem the Simulink model is shown as Fig.6.

Figure 6.  The Simulink model after make subsystem

VI. ANALYSIS THE SIMULATION RESULTS

Because the tracking precision and the positioning accuracy are two most important index of electro-hydraulic position servo control system, so need to examine the variation of these two indexes. The unit step signal is selected as Simulation test signal to check localization accuracy of the system. The PID parameters after optimizing are as follows, proportional coefficient P is 3.5, Integral coefficient I is 2.5, differential coefficient D is 0.01,the simulation result show as Fig.7. The result  shows that the adjust time is 0.08s, the overshoots is 2% and the error at steady-state is  f0.02. It can better meet the system needs.  The ramp signal, which slope rate is 1, is selected as simulation test signal to compare tracking precision of the system. The PID parameters after optimizing are as follows, proportional coefficient P is 14.5, Integral coefficient I is 76, differential coefficient D is 0.01, the simulation result show as Fig.8. The result shows that it can better meet the system needs.

摘要：本文建立的数学模型,是基于控制理论的对转台电液位置伺服系统,并且利用Simulink对系统模型进行简化系统仿真过程。这转台电液位置采用PID控制器。 PID控制是缩写的比例、积分及微分控制,它广泛适用于大多数的控制系统,特别是当数学模型的控制对象是已知的,PID控制就显得特别有用。本文通过调整PID参数，应用数字PID来得到理想的系统的动态性能。另外，本文也提供了一种能在其它控制系统分析设计时候运用的方法。

关键词：数学模型；系统仿真；建模

I.介绍

电液伺服系统是将电液两种控制方式结合起来的控制系统.利用电、电对信号进行检测、传输和处理电子部件，通过液压伺服控制系统中的液压传动来驱动负载。

因此，它可以充分利用电气系统的方便和能力，充分发挥作用采用液压系统具有响应速度快、负载刚度大、定位准确等特点，使整个系统更具适应性。PID控制是比例的缩写。，积分和微分控制，它的价值取决于它广泛适用于大多数控制系统，特别是当被控对象的数学模型已知时，PID控制共。特别有用。SIMULINK是一个交互式的动态系统建模、仿真和分析的图形环境[1]。利用SIMULINK环境，可以建立复杂的系统仿真模型，利用掩码函数对模型进行简化，用M文件对模块变量进行初始化，为f提供了很大的方便。或PID参数设置和更改各个模块的变量值[2-3]。本文建立了阀控非对称液压缸位置伺服系统的数学模型和仿真模型，并对系统动态性能进行了优化。