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一、比例积分(PI)控制前面讲过,单比例控制存在静差、手动重定不能适应实际工况的变化,所以若要精确控制被调量,必须采用比例积分控制方式。比例积分方式是工业过程中使用最为广泛的控制方式,它实际上是比例控制与积分控制两种作用的迭加。 1.积分控制作用积分控制实现的输出-输入关系为:调节器的输出为给定值与测量值之偏差对时间的积分;换言之,调节器输出的变化率正比于偏差输入。积分作用的数学表达式为 Y=1/T_i ∫edt+Y_0式中Y为输出,Y_0为输出初值,T_i为积分时间,e为偏差,t为时间。如果偏差e为恒值,则输出Y为等速上升(下降)的直线,如图1所示,其斜率tga与偏差e成正比。比例tga/e称作积分作用系数,其倒数e/tga称为积分时间,记作T_i,则积分作用系数为1/T_i。只要存在偏差,输出就要变化;只有当偏差为零
Proportional Integral (PI) Control As mentioned above, there is static difference between single proportional control and manual re-adjustment. Therefore, if precise control is to be adjusted, proportional integral control method must be adopted. Proportional integral method is the most widely used control method in industrial process. It is actually superposition of two functions of proportional control and integral control. 1. Integral Control Function The output of the integral control-input relationship is: The output of the regulator is the integral of the deviation of the given value from the measured value over time. In other words, the rate of change of the regulator output is proportional to the deviation input. Integral function of the mathematical expression Y = 1 / T_i ∫edt + Y_0 Where Y is the output, Y_0 for the initial output, T_i for the integration time, e is the deviation, t is the time. If the deviation e is a constant value, the output Y is a straight line of equal speed rising (falling), as shown in FIG. 1, the slope tga is proportional to the deviation e. Ratio tga / e is called the integral action coefficient, the reciprocal e / tga is called the integral time, denoted as T_i, then the integral action coefficient is 1 / T_i. As long as there is deviation, the output will change; only if the deviation is zero