一篇关于比例-积分-微分控制器的文章的一部分
Therefore,the PID controller has three parameters,that must be tuned to obtain satisfactory control.Notice that there is only one derivative tuning parameter.It has same units,minutes,for all manufactures.
As just mentioned,the derivative action gives the controller the capability to anticipate where the process is heading,that is,to "look ahead",by calculating the derivative of the error.The amount of "anticipation"is decided by the value of tuning parameter.
Let us consider the heat exchanger shown in Fig.40-1 and use it to clarify what is meant by "anticipating where the process is heading." Assume that the inlet process temperature decreases by some amount and the outlet temperature starts to decrease correspondingly as shown in Fig. 40-1. At time the amount of the error is positive and may be small.Consequently, the amount of control correction provided by the PI mode is small,However,the derivative of this error,the slope of the error curve,is large and positive,making the control correction provide by the derivative mode large,By looking at the derivative of the error ,the controlled konws that the controlled variable is heading away from the set point rather fast and,consequently,it uses this fact to help in controlling.At time the error is still positive and larger than before. The amount of control correction provide by the proportional and integral modes is also large than before and is still adding to the output of the controller to further open the steam value.However,the derivative of the error at this time is negative,signifying that the error is decreasing;that is ,the controlled variable has started to come down to set point.Again,using this fact,the derivative mode starts to subtract from the other two modes since it recognizes that the error is decreasing,By doing this it takes longer for the process to return to set point, howver,the overshoot and oscillations around set point are reduced.
PID controllers are used in processes with long time constants.Typical examples are temperature and concentration loops.Processes with short time constants are fast and susceptive to process noise.Typical of there processes are flow loops and loops controlling the pressure of liquid streams.
Therefore,the PID controller has three parameters,that must be tuned to obtain satisfactory control.
因此，PID控制器要达到预期的控制结果，其三个参数必须是已被调谐的。
Notice that there is only one derivative tuning parameter.
要注意的是这里只有一个导数调谐参数
It has same units（单位，机组，单元，装置）,minutes,for all manufactures（制造，生产，研制）.
并且同样有为所有生产所具有的单元和测定时侍圆间。
As just mentioned,the derivative action（微分作用） gives the controller the capability（能力，性能，容量） to anticipate（预期） where the process（过程，工艺，进程，流程） is heading（航向，磁头）,that is,to "look ahead"（前景）,by calculating（计算） the derivative of the error.
如上所述，微分作用给予了控制器在进程航向上前瞻的能力以预期导数的计算错误。
The amount of "anticipation"is decided by the value of tuning parameter.
预期的总量决定于其调谐参数的值。
Let us consider the heat exchanger（换热器） shown in Fig.40-1 and use it to clarify（明确，阐明） what is meant by "anticipating（预测，未知的） where the process（过程，工艺，进程） is heading（航向，标题）."
接下来考虑图40-1中所示的换热器，以及使用他来阐明老腊塌何为“目标进程中的预测”。
Assume（设想，承担，假定） that the inlet（进口，入口，进气道） process temperature decreases（温度下降，温度减少，温度逐渐下降） by some amount（量，用量，数量） and the outlet temperature（出口温度，终点温度，出风温度） starts to decrease correspondingly（相应的，相对的） as shown in Fig. 40-1.
假设进气道的工程温度逐渐有所下降，并且出口温度也开始相应的下降，就如图40-1所示。
At time（时刻，在时间） the amount of the error is positive（阳性，正，积极） and may be small.
在一定时间内错误数量为正且可以很小。
Consequently（因此，从而）, the amount of control correction（控制校正） provided（提供）by the PI mode is small.
因此，PI模型提供的控制校正是很小的一部分。
However,the derivative（导数，衍
生物，局搭） of this error,the slope（斜率） of the error curve（误差曲线）,is large and positive,making the control correction（控制校正） provide by the derivative mode（导数模式） large.
然而，错误的导数和误差曲线的斜率较大且为正，导数模式提供了很大一部分的控制校正。
By looking at the derivative of the error ,the controlled（控制，对照） konws that the controlled variable（受控变量） is heading（航向，标题） away from（远离） the set point（调定点，设定值，设定点） rather fast（比较快） and,consequently（因此）,it uses this fact to help in controlling.
与错误导数对照后可知受控变量是比较快的远离设定点的标题。
At time the error is still positive and larger than before.
一段时间内错误比之以前仍然是较大且为正。
The amount of control correction provide by the proportional（比例） and integral（积分） modes is also large than before and is still adding to the output（输出，产量，产出） of the controller（控制器） to further open（进一步开放） the steam（蒸汽） value.
由比例和积分模式提供的数量控制校正的含量比之前大了，而且为了进一步开发蒸汽的价值增加了控制器的输出
However,the derivative of the error at this time is negative（负的，阴）,signifying（表示，表明，意味着） that the error is decreasing;that is ,the controlled variable（受控变量） has started to come down（衰落） to set point（设定点）.
然而，错误导数在这时是负的，这就表明错误开始减少；即受控变量已经开始在设定点回落。
Again,using this fact,the derivative mode starts to subtract（去掉，减去） from the other two modes since it recognizes that the error is decreasing.
再次使用，导数模式自从意识到错误正在减少，就开始把自己从另两个模式中去掉。
By doing this it takes longer for the process to return to set point, howver,the overshoot and oscillations around set point are reduced.
这样会使进程花更多的时间返回设定点，然而，设定点周围的过冲和震荡减少了。
PID controllers are used in processes with long time constants.
PID控制器曾被使用在长流程进程中。
Typical examples are temperature and concentration loops.
温度和浓度的循环就是典型的例子。
Processes with short time constants are fast and susceptive to process noise.
流程短在噪音进程中是快速和敏感的。
Typical of there processes are flow loops and loops controlling the pressure of liquid streams.
典型的有过程的循环流动和循环控制的压力，液体流。
所以， PID控制器有三个参量，必须调整获得令人满意的控制。注意只有一个衍生物调整的参量。它有同样单位，分钟，全部的制造。 被提及的As，微分作用给控制器能力期望过程哪里朝向，是， “通过计算错误的衍生物朝前看”。相当数量“预期"由调整的参量的价值决定。
Let我们考虑在Fig.40-1显示的热转换器并且使用它澄清“期望过程哪里是什么意思朝向”。 假设，入口过程温度减少由某一数量如图40-1所显示，并且出口温度开始相应地减少。 在时间相当数量错误是正面的，并且也许是小的。结果， PI方式控制更正提供的相当数量是小的，然而，这个错误，错误曲线的倾斜衍生物，是大和正面，做控制更正由衍生物方式提供大，通过看错误的衍生耐销拍物，受控知道受控变量朝向远离调整点宁可斋戒，并且，因而，它在控制使用这个事实帮助。在时间错误大于以前是正面的和。 相当数量控制更正由比例提昌羡供，并且缺一不可的方式比以前也大和仍然增加到控制器的产品进一步打开蒸汽价值。然而，错误的斗斗衍生物此时的是阴性，符号化错误是越来越少的; 那是，受控变量开始下来到调整点。再次，使用这个事实，衍生物方式开始从另外两个方式减去，因为它认为错误是越来越少的，它通过该执行花费很多时间为了过程能返回到调整点，然而，减少在调整点附近的调整量和动摆。
PID控制器用于与长的时间常数的过程。典型的例子是温度和集中圈。与短的时间常数的过程是快速和susceptive处理噪声。特点过程有控制液体小河的压力流程圈和圈。