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1、外文翻译PID CONTROL SYSTEMIndustrial automation has become an important indicator to measure the level of modernization of all walks of life. Meanwhile, the development has also experienced a classical control theory and control theory, the modern control theory and theory of intelligent control in thre
2、e stages. Intelligent control is a classic example of fuzzy automatic washing machines. Control systems can be divided into open loop control system and closed-loop control system. Control system includes a controller, sensor, transmitter, the executing agency, I accept input and output. After the o
3、utput controller output interface enforcement agency charged with a war system; Charged with volume control system, through sensors. Transmitter by input interface to the controller. Different control systems, sensor, transmitter, and the executing agency is not the same. For example, pressure contr
4、ol system using pressure sensors. Heating the sensor is a temperature sensor control system. At present, or PID control and intelligent controller PID controller (meters) have many, engineering products have been widely used in a wide variety of PID controller products. major companies have develope
5、d an intelligent self-tuning PID regulator (intelligent Ampre gulator), which automatically adjust the parameters of a PID controller is intelligent self-tuning or adjustment, adaptive algorithm is to be achieved. PID control is achieved using pressure, temperature, flow, liquid level control device
6、. PID control function can be realized in the programmable logic controller (PLC). There PID control of the PC, etc. can be realized. Programmable Logic Controller (PLC) is used to achieve its PID control loop control module. and programmable logic controller (PLC) can be connected directly with Con
7、trolNet. Rockwell such as the PLC-5. PID controller can also control function, such as Rockwells Logix product lines. ControlNet it can be linked directly with the use of the network to achieve its remote control function.1, The open-loop control systemsOpen-loop control system is the object of the
8、output ( control volume) of the controller (controller), the output will not be affected. In this control system, not dependent on the volume will be charged and sent back to form against any closed-loop. 2,The closed-loop control system Closed-loop control system (loop control system) features of t
9、he accused The output (volume control) and the output affected by anti sent back to form a loop or more. And the positive feedback loop feedback control system, if the feedback signal and the signal systems to setting the contrary, call negative feedback (Negative Feedback), and if the same polarity
10、, as positive feedback, closed-loop control system is used generally negative feedback, or negative feedback control system. Many examples of closed-loop control system. For example, people in a negative feedback loop control systems, sensor is the eyes, as feedback keep the human system through var
11、ious amendments to finally make the right moves. If there are no eyes, no feedback loop, it became an open-loop control system. Another, when a real clothing consecutive automatic washing machine will have to wash it. Wash and can automatically after 7659, it is a closed loop control system. 3, step
12、 response Step response is a step input added to the system, the system output. Responded to enter the steady-state error is steady, the difference between the desired output and actual output. Can be used to control the performance of the system stability, prospective, quick word to describe. Syste
13、m stability is the stability, a system to work normally must first be stable, Step response is from the point of view of convergence; access control system is the accuracy and precision control. Usually steady-state error (Steady error) description It said output steady-state value and margin expect
14、ations; Express refers to the control of the rapid response system, Usually time to quantify the increase.4, PID control elements and features In practical projects, the most widespread application of the law to the regulator to control the ratio, integral, differential, called PID control, called P
15、ID. PID controller has been developed nearly 70-year history, with its simple structure, stability, reliability, easy to adjust and become one of the key technologies in industrial control. When the object is not fully grasp the structure and parameters, or any precise mathematical model, Other tech
16、nology difficult to control, The controller structure and parameters have to rely on experience and on-the-spot tests to determine. Then use the most convenient PID control. When a system that we do not fully understand and object, or can not be an effective means to measure system parameters, PID c
17、ontrol with the most suitable technology. PID control, and reality have PI PD control. PID controller is based on the error, using a proportional, integral and differential control of the calculated volume control.Proportional (P) control Proportional control is a simple control method. And the cont
18、roller output signal proportional to input error. When there is only a proportion of output steady-state error control system (Steady error). Integral (I) Control Integral in control, the controller output and input error signal proportional to the integral relationship. For a control system, if the
19、re after entering the stable steady-state error. she claimed that the control system is referred to a steady-state error or poor system (System with Steady- Error state). To eliminate static error, the controller must introduce the integral. Integration depends on the time integral of the error, wit
20、h the increase in time, integral increases. Thus, even if the error is very small, sub-plot will increase with the increase of time. Output increased to enable it to promote the steady-state error controller further reduced, until zero. Therefore, the ratio of plus integral (PI) controller, the syst
21、em can be no stability in the state into steady-state error Differential (D) control Differential control, the controller output and input error differential signal (that is, the rate of change of error) in proportion. Automatic control system to overcome the error in the adjustment process may occu
22、r even oscillatory instability. The reason is because there is a greater inertial measurement unit (link) or backward (delay) components. inhibit the role of error, the changes are always behind the changes in error. The solution is to change the role of inhibition error get ahead in error close to
23、zero. inhibit the role of error should be zero. This means that the introduction of the controller only proportional items often is not enough. only items of the ratio of the amplitude error is enlarged, and now need to increase the differential item. it forecasts changes in the trend, with the prop
24、ortion of + differential controller early enough so error control will be able to curb the role of zero, or even negative, in order to avoid the amount charged with a serious overshoot. Therefore, a greater inertia of the object or delay. + ratio differential (PD) controller can improve the dynamic
25、characteristics in the process of adjustment.5, the parameter tuning PID controller Tuning PID control system design parameters of the core. It was based on PID control the process of determining the ratio coefficient, the size of the time differential and integral time. PID tuning parameters are ma
26、ny ways to sum up, there are two major categories : theoretical calculations tuning. It is mainly based on the mathematical model, the parameters of the controller Through theoretical calculations. This method has been used in the calculations may not be directly, it is also necessary to adjust and
27、engineering. Second tuning method, which mainly rely on engineering experience, the control system directly for the test, and simple method easy to master, which are widely used in engineering practice. PID tuning parameters, the main critical ratio, response and attenuation curves. Three methods ha
28、ve their own characteristics, through their common test Then in accordance with the empirical formula of the controller tuning parameters. But no matter what kind of methods used by the controller, it was necessary to make a final adjustment and improvement of the actual operation. Now is the critic
29、al proportion of the general law. PID controller using this method for setting the parameters of the following steps :(1) First, a pre-selection of the sampling period short enough to allow the system (2) adding proportional control only link until the step response of critical system for the import
30、ation of oscillation Then note the ratio magnification factor and critical oscillations (3) In a certain formula to be adopted under the control parameters of the PID controllerPID parameter setting process is based on experience, and familiarity with the reference measurement tracking and setpoint
31、curve. PID thereby adjusting the size.PID tuning parameters, all parameters of empirical data P.I.D conditioning system following reference :TemperaturePressure P : P=3070%, T=24180s,Level L : P=2080%. T=60300s,Flow L : P=40100% flow, T=660s.Now a PID controller for example, specify experience in th
32、e law setting steps ：(1)Let regulator parameters appropri S0=0 integral factor, the actual differential coefficient 0, closed-loop control system is put into operation. S1 headed change the ratio coefficient, disturbance signals step change control process of observation, Until satisfactory control
33、of the process so far.(2)S1 proportional to the current value multiplied by the coefficient of 0.83, an increase over the integral factor S0. Let disturbance signal changes for the same step up the process to achieve satisfactory control.(3) remain unchanged integral factor S0, S1 change the ratio c
34、oefficient observed any improvement in process control. If improvement is to continue to adjust until satisfied. Otherwise, the original ratio coefficient increased number of S1, adjusted integral factor S0, and strive to improve process control. And try the case again, until they found a satisfacto
35、ry score coefficient ratio coefficient S1 and S0 far.(4)The actual differential coefficient k introducing appropriate differential and the actual time TD. S1 coefficient ratio increases at this time would be appropriate and integral factor S0. And the aforementioned steps the same time setting diffe
36、rential also need repeated adjustments to control the process until satisfied.Simulation of the system : PID controller with PID controller is different from the traditional industries, Isolation between various parameters, separating thus observe its laws regulating very convenient. 译文：PID控制系统目前工业自
37、动化水平已成为衡量各行各业现代化水平的一个重要标志。同时，控制理论的发展也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。智能 控制的典型实例是模糊全自动洗衣机等。自动控制系统可分为开环控制系统和闭环控制系统。一个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，其传感器、 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。电加热控制系统的传感器是温度传感器。目前，PID控制及其控制器或智能PID控制器 （仪表）已经很多，产品已在工程
38、实际中得到了广泛的应用，有各种各样的PID控制器产品，各大公司均开发了具有PID参数自整定功能的智能调节器 (intelligent regulator)，其中PID控制器参数的自动调整是通过智能化调整或自校正、自适应算法来实现。有利用PID控制实现的压力、温度、流量、液位控制 器，能实现PID控制功能的可编程控制器(PLC)，还有可实现PID控制的PC系统等等。 可编程控制器(PLC) 是利用其闭环控制模块来实现PID控制，而可编程控制器(PLC)可以直接与ControlNet相连，如Rockwell的PLC-5等。还有可以实现 PID控制功能的控制器，如Rockwell 的Logix产品系
39、列，它可以直接与ControlNet相连，利用网络来实现其远程控制功能。 1、开环控制系统 开环控制系统(open-loop control system)是指被控对象的输出(被控制量)对控制器(controller)的输出没有影响。在这种控制系统中，不依赖将被控量反送回来以形成任何闭环回路。 2、闭环控制系统 闭环控制系统(closed-loop control system)的特点是系统被控对象的输出(被控制量)会反送回来影响控制器的输出，形成一个或多个闭环。闭环控制系统有正反馈和负反馈，若反馈信号与系 统给定值信号相反，则称为负反馈( Negative Feedback)，若极性相同，则
40、称为正反馈，一般闭环控制系统均采用负反馈，又称负反馈控制系统。闭环控制系统的例子很多。比如人就是一个具有负反馈 的闭环控制系统，眼睛便是传感器，充当反馈，人体系统能通过不断的修正最后作出各种正确的动作。如果没有眼睛，就没有了反馈回路，也就成了一个开环控制系 统。另例，当一台真正的全自动洗衣机具有能连续检查衣物是否洗净，并在洗净之后能自动切断电源，它就是一个闭环控制系统。 3、阶跃响应 阶跃响应是指将一个阶跃输入（step function）加到系统上时，系统的输出。稳态误差是指系统的响应进入稳态后，系统的期望输出与实际输出之差。控制系统的性能可以用稳、准、快三个字 来描述。稳是指系统的稳定性(
41、stability)，一个系统要能正常工作，首先必须是稳定的，从阶跃响应上看应该是收敛的；准是指控制系统的准确性、控 制精度，通常用稳态误差来(Steady-state error)描述，它表示系统输出稳态值与期望值之差；快是指控制系统响应的快速性，通常用上升时间来定量描述。 4、PID控制的原理和特点 在工程实际中，应用最为广泛的调节器控制规律为比例、积分、微分控制，简称PID控制，又称PID调节。PID控制器问世至今已有近70年历史，它 以其结构简单、稳定性好、工作可靠、调整方便而成为工业控制的主要技术之一。当被控对象的结构和参数不能完全掌握，或得不到精确的数学模型时，控制理论的 其它技术
42、难以采用时，系统控制器的结构和参数必须依靠经验和现场调试来确定，这时应用PID控制技术最为方便。即当我们不完全了解一个系统和被控对象，或 不能通过有效的测量手段来获得系统参数时，最适合用PID控制技术。PID控制，实际中也有PI和PD控制。PID控制器就是根据系统的误差，利用比例、 积分、微分计算出控制量进行控制的。 比例（P）控制 比例控制是一种最简单的控制方式。其控制器的输出与输入误差信号成比例关系。当仅有比例控制时系统输出存在稳态误差（Steady-state error）。 积分（I）控制 在积分控制中，控制器的输出与输入误差信号的积分成正比关系。对一个自动控制系统，如果在进入稳态后存
43、在稳态误差，则称这个控制系统是有稳态误差的 或简称有差系统（System with Steady-state Error）。为了消除稳态误差，在控制器中必须引入“积分项”。积分项对误差取决于时间的积分，随着时间的增加，积分项会增大。这样，即便误差很小，积 分项也会随着时间的增加而加大，它推动控制器的输出增大使稳态误差进一步减小，直到等于零。因此，比例+积分(PI)控制器，可以使系统在进入稳态后无稳 态误差。 微分（D）控制 在微分控制中，控制器的输出与输入误差信号的微分（即误差的变化率）成正比关系。 自动控制系统在克服误差的调节过程中可能会出现振荡甚至失稳。其原因是由于存在有较大惯性组件（环节
44、）或有滞后(delay)组件，具有抑制误差的作用， 其变化总是落后于误差的变化。解决的办法是使抑制误差的作用的变化“超前”，即在误差接近零时，抑制误差的作用就应该是零。这就是说，在控制器中仅引入 “比例”项往往是不够的，比例项的作用仅是放大误差的幅值，而目前需要增加的是“微分项”，它能预测误差变化的趋势，这样，具有比例+微分的控制器，就能 够提前使抑制误差的控制作用等于零，甚至为负值，从而避免了被控量的严重超调。所以对有较大惯性或滞后的被控对象，比例+微分(PD)控制器能改善系统在 调节过程中的动态特性。 5、PID控制器的参数整定 PID控制器的参数整定是控制系统设计的核心内容。它是根据被
45、控过程的特性确定PID控制器的比例系数、积分时间和微分时间的大小。PID控制器参数整定的方法很多，概括起来有两大类：一是理论计算整定法。它主要是 依据系统的数学模型，经过理论计算确定控制器参数。这种方法所得到的计算数据未必可以直接用，还必须通过工程实际进行调整和修改。二是工程整定方法，它主 要依赖工程经验，直接在控制系统的试验中进行，且方法简单、易于掌握，在工程实际中被广泛采用。PID控制器参数的工程整定方法，主要有临界比例法、反应 曲线法和衰减法。三种方法各有其特点，其共同点都是通过试验，然后按照工程经验公式对控制器参数进行整定。但无论采用哪一种方法所得到的控制器参数，都需 要在实际运行中进
46、行最后调整与完善。现在一般采用的是临界比例法。利用该方法进行 PID控制器参数的整定步骤如下：(1)首先预选择一个足够短的采样周期让系统工作；(2)仅加入比例控制环节，直到系统对输入的阶跃响应出现临界振荡， 记下这时的比例放大系数和临界振荡周期；(3)在一定的控制度下通过公式计算得到PID控制器的参数。PID参数的设定：是靠经验及工艺的熟悉，参考测量值跟踪与设定值曲线，从而调整PID的大小。PID控制器参数的工程整定,各种调节系统中P.I.D参数经验数据以下可参照：温度T: P=2060%,T=180600s,D=3-180s压力P: P=3070%,T=24180s,液位L: P=2080%
47、,T=60300s,流量L: P=40100%,T=660s。 下面以PID调节器为例，具体说明经验法的整定步骤： 让调节器参数积分系数S0=0，实际微分系数k=0，控制系统投入闭环运行，由小到大改变比例系数S1，让扰动信号作阶跃变化，观察控制过程，直到获得满意的控制过程为止。 取比例系数S1为当前的值乘以0.83，由小到大增加积分系数S0，同样让扰动信号作阶跃变化，直至求得满意的控制过程。 (3)积分系数S0保持不变，改变比例系数S1，观察控制过程有无改善，如有改善则继续调整，直到满意为止。否则，将原比例系数S1增大一些，再调整积分系数S0，力求改善控制过程。如此反复试凑，直到找到满意的比例系数S1和积分系数S0为止。 引入适当的实际微分系数k和实际微分时间TD，此时可适当增大比例系数S1和积分系数S0。和前述步骤相同，微分时间的整定也需反复调整，直到控制过程满意为止。 注意：仿真系统所采用的PID调节器与传统的工业 PID调节器有所不同，各个参数之间相互隔离，互不影响，因而用其观察调节规律十分方便。- 6 -