The sig nifica nee of PID con trol
The curre nt level of in dustrial automati on in dustries to measure the level of modernization has become an important symbol. Meanwhile, the control also experieneed the development of the theory of classical control theory, modern control theory and intelligent control theory of three stages. Intelligent control is a typical example of fuzzy automatic wash ing mach ine. Open-loop con trol system can be divided into con trol systems and closed-loop con trol system. A con trol system in clud ing con troller, sen sors, tran smitters, actuators, in put and output in terfaces. Con troller's output through the output in terface, the impleme nting age ncy, added to the charged system; control system, the amount charged, through sensors, tran smitters, sent to the con troller through the in put in terface. Differe nt con trol systems, sensors, transmitters, actuators are not the same. Such as pressure con trol system pressure sen sor to be used. Electric heat ing con trol system sen sor is a temperature sensor. At present, PID control and controller or intelligent PID con troller (in strume nt) has a lot of products have bee n in the engin eeri ng practice has been widely applied, there is a wide range of PID controllers, the major companies have developed PID parameter self-tuning capabilities of intelligent controller (intelligent regulator), which automatically adjusts the PID controller parameters are adjusted through the in tellige nt or self-correct ion, adaptive algorithms to achieve. PID control are achieved using pressure, temperature, flow, liquid level con troller, PID con trol can achieve programmable con troller (PLC), also allows PID con trol of PC systems, etc.. Programmable Logic Con troller (PLC) is to use the closed-loop PID control module to achieve control, programmable logic controller (PLC) can be connected directly with ControlNet, such as Rockwell's PLC-5 and so on. PID control function also allows the controller, such as Rockwell's Logix product line, which can be connected directly with ControlNet, use the n etwork to achieve its remote con trol fun cti ons.
1, the ope n-loop con trol system
Open-loop control system (open-loop control system) is charged with the object output (controlled variables) on the controller (controller) did not affect the output. In
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this control system, not dependent on the amount will be charged aga inst sending it back to form any closed loops.
2, closed loop con trol system
Closed loop con trol system (closed-loop con trol system) is characterized by the system con trol object output (con trolled variables) will affect the con troller aga inst the output sent back to form one or more closed loop. Closed-loop con trol system has positive feedback and n egative feedback, if the feedback sig nal and system for a give n value of sig nal con trast, is known as n egative feedback (Negative Feedback), if the same polarity is called positive feedback, the general closed-loop negative feedback control systems are used , also known as negative feedback control system. Many examples of closed loop con trol system. Such pers on is a n egative feedback loop con trol system, the eye is the sen sor, as feedback, the huma n system through constant correction to all the right moves last. If there are no eyes, no feedback loop, will become an ope n-loop con trol system. Other cases, whe n a truly automatic wash ing mach ines have to continu ously check whether clothes washed, and cut off the power automatically after cleaning, it is a closed loop control system.
3, step resp onse
Step resp onse is a step in put (step fun cti on) added to the system, the system outputs. Steady-state error is the response of the system into steady state, the system's expected output and actual output of the differenee. Control system performa nee can be stable, accurate, fast and three words to describe. Stability is the stability of the system (stability), a system to work properly, first of all must be stable, from the step resp onse appears to be that con verge nee; quasi-c on trol system refers to the accuracy, control precision, usually stable state error to (Steady-state error)
description, it said the system output and the expected steady-state value of the differe nee; faster con trol system resp onse is fast, usually the rise time to qua ntify.
4, PID con trol prin ciples and characteristics
In engineering practice, the most widely used regulator control law is proporti on al, i ntegral, differe ntial con trol, referred to as PID con trol, also known as PID regulator. PID controller has been developed for nearly 70 years, it is its simple
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structure, stable, reliable, easy to adjust and become one of the main techniques of in dustrial con trol. When the structure and parameters of the object and can not fully grasp, or lack of accurate mathematical models, control theory is difficult to use other tech no logies, the system con troller structure and parameters must rely on experie nee and on-site commissi oning to determ ine, whe n applied PID con trol technique is more convenient. That is, when we do not fully understand a system and the con trolled object, or can not be an effective means of measureme nt to obtai n system parameters, the most suitable PID con trol tech no logy. PID con trol, i n practice there are PI and PD control. PID controller is the error according to the system, using proporti on al, in tegral, differe ntial calculati on of the volume con trol to con trol.
Proporti on (P) con trol
Proportional control is the most simple control method. The controller's output and the in put error sig nal proporti on al. When only a proporti onal con trol system output whe n there is steady-state error (Steady-state error).
In tegral (I) con trol
In in tegral con trol, the con troller's output and the in put error sig nal proportional to the integral. An automatic control system into the steady state if there is steady-state error, claimed that this con trol system is called a steady-state error or poor system (System with Steady-state Error). In order to elim in ate steady state error, the controller must introduce the \time in tegral, as time in creases, in tegral term will in crease. Thus, eve n if the error is very small, i ntegral term will in crease over time to in crease its promoti on of the con troller output in creases to further reduce the steady-state error, un til zero. Therefore, the ratio of + in tegral (PI) con troller allows the system to en ter steady state of no steady state error.
Differe ntial (D) con trol
In the differe ntial con trol, the con troller output and differe ntial in put error sig nal (ie, rate of cha nge of error) is proporti onal to. Automatic con trol system to overcome the errors in the adjustme nt process of oscillati on or eve n in stability may occur. The reason is because of greater inertia components (links), or a lag (delay)
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PID控制的意义中英文翻译资料
