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The Application of the Intelligent Control Technology on Complicated Engineering Machine

Author: ZhangLiPeng
Tutor: LiuMingShan
School: Jilin University
Course: Signal and Information Processing
Keywords: fuzzy control on-line tuning PID control robustness Digital Filter intelligent control
CLC: TP273.5
Type: Master's thesis
Year: 2006
Downloads: 178
Quote: 2
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Abstract


The modern industry control is developing towards the direction of highprecision,high speed and more intelligent to adapt the production. Theleather belt steelyard control system is the system that based on the errorcontrol generally. The traditional method is to adopt the PID control. Thiskind of control function is constitute by the P-Proportional part,the I-Integralpart and the D-Derivative part, it carries out the error control towards theexact model system by lines combining these three kinds of control function.The principle of traditional PID is in brief and easy to realize, without anyerror in steady state. So it is applied to the process control in the industryextensively for a long time, and obtains good results. However, the traditional PID control is to process the linear system, whichwith the exact model. But actually, the circumstance of the industrial spot iscomplicated, and the parameters are time variant and the model isundetermined, the electrical engineering of leather belt steelyard is again ancontrol object of multi-variable,non-linear and strong coupling. Therefore, itcan’t always obtain good parameters. So it needs to tune the parameters ofthe PID control. The tuning methods for the parameters of the traditional PID controlinclude: The Ziegler-Nichols method, the Cohn-Coon method, theattenuation curve method and tests the parameters by experience method.Among them, the parameters by experience method is to adjust theparameters of PID control directly to obtain the experience value k p, k i andk d, and then find out a set of suitable parameters off-line, make the systemnear to the best work condition. It can obtain ideal control results when thesystem is under the condition of time invariant. But when a PID controllerwith good adjustment applies to the system whose model parameterschange with the time, the function of the system will become bad, evenunsteady. And in the tuning of the parameters, the PID parameters arevalues which have certain field optimization, but not whole field optimization,and the PID controller also exists the confliction of overshoot,the quicknessand the steady state precision. So it can’t solve this kind of confliction ofdynamic state and steady state precision completely.Therefore, under the situation that keeping steady state precision of thePID control system, adopts advanced control technology, improves thedynamic state and anti-interference and the adaptability to the parametertuning is an inevitable trend.The intelligent control is a kind of control technology which springs uprecent years, it has been applied in extensively field. Usually, the neuralnetwork, the fuzzy control and the expert system are called the modernintelligent control technology. Among them, the expert system is the expert’sknowledge and experience that obtained from a certain realm, then expressthem to be a kind of language which can be accepted by the computer, andthen the computer imitates the mankind’s experts to reason logically withjudgment, and makes a decision to resolve some complicated problems thatcan be resolved by expert. In another word, it is a kind of computer programwith a lot of exclusively knowledge and experience. The neural network is akind of emulation living creature nerve cell and connect among each other, ithas the ability of self-studying, self-organizing and approaches with thefunction. It has the infinite potential to be applied in the intelligence control.The method to realize these two kinds of control technology are still not verymature, especially the expert’s knowledge is difficult to obtain, so they stillhasn’t been applied extensively.Compare with them, the theories of the fuzzy control is more mature. Asearly as in 80’s end,it has been used in Japan in extensively field. It has theadvantage of no need to depend on the exact mathematics model. Bymeans of fuzzy mathematics and fuzzy logic, it changes the mankind’sexperience and intuition to be a series of concepts and rules, then changesthem to be a kind of arithmetic language which can be accepted by thecomputer. But because of having no integral part, the fuzzy control also hasa weakness to have steady state error. Using the fuzzy control to tune thePID control will make full use of the advantages of both. It not only canassure the high steady state precision, but also can improve the dynamicstate performance;it still has strong robustness to the parameter of theobject which is controlled.This text makes a simple description about the structure and controlfunction, surrounding the stable soil facility which belongs to a kind ofengineering machines. And then make a systemic description to the controlmodel of the tuning speed system of leather belt steelyard. Then designed akind of fuzzy control on-line tuning the PID control arithmetic. Combining themodel of tuning speed system, the writer made the design of the collectionsystem of data and adopts a kind of software filter to let down the hardwarecost. According to the characteristic of PID control, the text makes particularrules to the three parameters k p, k i and k d, then takes the MATLAB as ansimulation tool to make the simulation and analysis in detail. And then inducta jamming to the system to test the characteristic of this control arithmetic.Both the theory and the simulation indicate that the control technology offuzzy control on-line tuning PID control is more superior than the traditionaltuning methods.1.There is no need to tune the parameters off-line, the controller can adjustitself by the status of system. It can alleviate the laboring force for a lot.2.It shortened the tuning time of the system effectively, let down theovershoot and make it more stable.3.Compare with the traditional PID control, its anti-interference abilities ismuch stronger.4.Take it as the theories foundation, we can study a fuzzy-neural network,expert-fuzzy system and other more intelligent control arithmetic.Therefore, we can say that it is a kind of control arithmetic that has thetheories instruction function.This text puts forwards a speculation finally, aimed at a technical furtherimprovement. Such as increase the grades of the measure. And make theerror smaller to the best of itself. Lead into the calculation arithmetic, andmake the fuzzy measure is more approximate to the actual. In addition, wecan use the mixed method to tune the traditional PID control, such as fuzzycontrol and expert control, the fuzzy control and neural network and etc. Allof these are the directions that the writer will study in the future.

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CLC: > Industrial Technology > Automation technology,computer technology > Automation technology and equipment > Automation systems > Automatic control,automatic control system > Computer control, computer control system
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