【導(dǎo)讀】比例積分微分控制器是一個(gè)控制環(huán)，廣泛地應(yīng)用于工業(yè)控制系統(tǒng)里的反饋機(jī)制。PID控制器通過調(diào)節(jié)給定值與測(cè)量值之間的偏差，給出正確的調(diào)整，從而有規(guī)律地糾正控制過程。比例控制是對(duì)當(dāng)前偏差的反應(yīng)，積分控。制是基于新近錯(cuò)誤總數(shù)的反應(yīng)，而微分控制則是基于錯(cuò)誤變化率的反應(yīng)。這三種控制的結(jié)合可用來。調(diào)節(jié)過程系統(tǒng)，例如調(diào)節(jié)閥的位置，或者加熱系統(tǒng)的電源調(diào)節(jié)。根據(jù)具體的工藝要求，通過PID控。制器的參數(shù)整定，從而提供調(diào)節(jié)作用?？刂破鞯捻憫?yīng)可以被認(rèn)為是對(duì)系統(tǒng)偏差的響應(yīng)。是，PID算法不一定就是系統(tǒng)或系統(tǒng)穩(wěn)定性的最佳控制。一些應(yīng)用可能只需要運(yùn)用一到兩種方法來提供適當(dāng)?shù)南到y(tǒng)控制。這是通過把不想要的控制輸出。PI調(diào)節(jié)器很普遍，因?yàn)槲⒎挚刂茖?duì)測(cè)量噪音非。節(jié)熱水流直到溫度處于期望的穩(wěn)定值。的輸入對(duì)象稱為控制參數(shù)。即是PID控制器的比例度的確定。PID控制器沒有學(xué)習(xí)能力，必須正確的設(shè)定。間常數(shù)Kd引起的變化的速率。

　　

【正文】 actual output will proportional and derivative terms can produce excessive movement in the output when a system is subjected to an instantaneous step increase in the error, such as a large setpoint change. In the case of the derivative term, this is due to taking the derivative of the error, which is very large in the case of an instantaneous step change. 5. Limitations of PID control While PID controllers are applicable to many control problems, they can perform poorly in some controllers, when used alone, can give poor performance when the PID loop gains must be reduced so that the control system does not overshoot, oscillate or hunt about the control setpoint value. The control system performance can be improved by bining the feedback (or closedloop) control of a PID controller with feedforward (or openloop) control. Knowledge about the system (such as the desired acceleration and inertia) can be fed forward and bined with the PID output to improve the overall system performance. The feedforward value alone can often provide the major portion of the controller output. The PID controller can then be used primarily to respond to whatever difference or error remains between the setpoint (SP) and the actual value of the process variable (PV). Since the feedforward output is not affected by the process feedback, it can never cause the control system to oscillate, thus improving the system response and stability. For example, in most motion control systems, in order to accelerate a mechanical load under control, more force or torque is required from the prime mover, motor, or actuator. If a velocity loop PID controller is being used to control the speed of the load and mand the force or torque being applied by the prime mover, then it is beneficial to take the instantaneous acceleration desired for the load, scale that value appropriately and add it to the output of the PID velocity loop controller. This means that whenever the load is being accelerated or decelerated, a proportional amount of force is manded from the prime mover regardless of the feedback value. The PID loop in this situation uses the feedback information to effect any increase or decrease of the bined output in order to reduce the remaining difference between the process setpoint and the feedback value. Working together, the bined openloop feedforward controller and closedloop PID controller can provide a more responsive, stable and reliable control system. Another problem faced with PID controllers is that they are linear. Thus, performance of PID controllers in nonlinear systems (such as HVAC systems) is variable. Often PID controllers are enhanced through methods such as PID gain scheduling or fuzzy logic. Further practical application issues can arise from instrumentation connected to the controller. A high enough sampling rate, measurement precision, and measurement accuracy are required to achieve adequate control performance. A problem with the Derivative term is that small amounts of measurement or process noise can cause large amounts of change in the output. It is often helpful to filter the measurements with a lowpass filter in order to remove higherfrequency noise ponents. However, lowpass filtering and derivative control can cancel each other out, so reducing noise by instrumentation means is a much better choice. Alternatively, the differential band can be turned off in many systems with little loss of control. This is equivalent to using the PID controller as a PI controller. 6. Cascade control One distinctive advantage of PID controllers is that two PID controllers can be used together to yield better dynamic performance. This is called cascaded PID control. In cascade control there are two PIDs arranged with one PID controlling the set point of another. A PID controller acts as outer loop controller, which controls the primary physical parameter, such as fluid level or velocity. The other controller acts as inner loop controller, which reads the output of outer loop controller as set point, usually controlling a more rapid changing parameter, flowrate or accelleration. It can be mathematically proved that the working frequency of the controller is increased and the time constant of the object is reduced by using cascaded PID controller.[vague] 7. Physical implementation of PID control In the early history of automatic process control the PID controller was implemented as a mechanical device. These mechanical controllers used a lever, spring and a mass and were often energized by pressed air. These pneumatic controllers were once the industry analog controllers can be made from a solidstate or tube amplifier, a capacitor and a resistance. Electronic analog PID control loops were often found within more plex electronic systems, for example, the head positioning of a disk drive, the power conditioning of a power supply, or even the movementdetection circuit of a modern seismometer. Nowadays, electronic controllers have largely been replaced by digital controllers implemented with microcontrollers or FPGAs. Most modern PID controllers in industry are implemented in software in programmable logic controllers (PLCs) or as a panelmounted digital controller. Software implementations have the advantages that they are relatively cheap and are flexible with respect to the implementation of the PID algorithm. 指導(dǎo)教師意見： 指導(dǎo)教師簽名： 年 月 日