Design Of The Pressure System For Aluminum Cylinder Block Based On Fuzzy Control

Since professor L.A.ZaDeh who worked for University of California at Berkeley presented Fuzzy problem and gave a measurable descriptive method in the Fuzzy Sets in 1965,fuzzy maths has been developed quickly in recent 30 years, it was been applied widely in the theory and application fields .The application fields of fuzzy maths is involved in auto control, identifying image and word, artificial intelligence, geology and earthquake, diagnosing medical treatment, analyzing weather, aviation and spaceflight, train and automobile driving, management of traffic, appraising decision-making, managing corporation and society economy .It needn't the precise mathematical model of the controlled object when we design the fuzzy controller. The Fuzzy controller has the following merit: simple design, flexible application, good robustness. If the fuzzy controller is used to the uncertain model of system, we can get the better effect. The basic idea of the fuzzy control is that people's control experience is realized by computer .we can not only describe the process variables and their relationship by the fuzzy maths method, but also get the control magnitude through fuzzy reasoning when we check the value of the process variables (need changing the fuzzy value) in one time and their relationship.There is being disturbed in the process of low pressure die casting, so liquid surface pressure control system hardly acquire accurate maths model. Because liquid surface pressure control system is the key that affect casting quality, many scholars at home and abroad research the liquid surface pressure control system of low die casting. In this paper, the author firstly introduces the four component part of the fuzzy control system, and then introduces the design method of fuzzy controller. We can gain the rule base of fuzzy controller by summarizing experience and knowledge of operator, expert and control engineer, we can acquire them throng establishing process fuzzy model which can give birth to a group of rules,we can also build Self-Organization Fuzzy Controller to gaining the rules. We can fuzzy the determine through the following tow ways ,one is single fuzzy aggregate, the other is transforming one exact point into a fuzzy aggregate .There is three ways to fuzzy reasoning in the fuzzy controller, Mamdani fuzzy reasoning, Larsen fuzzy reasoning, Takagi-Sugeno fuzzy reasoning. The ways of Defuzzification have five ways,area center, max-max subjection , max-min subjection , average max subjection, area deuce.The arithmetic of fuzzy control mostly has four steps: transition from the input to fuzzy, that is to say, fuzzification; Establishing control rule; fuzzy reasoning; transition from fuzzy to output, that is to say, defuzzification. The author also introduces how to confirm the quantification factor in the fuzzification and proportion factor in the defuzzification. It is very important that we reasonable choose quantification factor and proportion factor of the fuzzy controller. Magnitudes of the quantification factor and proportion factor, the Magnitude's relatively relationship of the different quantification factor, have the important effect on dynamic control of fuzzy controller.The pressure control for the low pressure casting include the following process, rising Aluminum liquid ,filling model, adding pressure ,keeping pressure and removing pressure. The system can adjust the parameter to gain the different slope curve.According to the theory of process control, the system is the program control system if the set value of the control system varies with the time. In the low pressure casting, we can measure the change of the pressure value. We take the pressure value as a measured interference, so the better compensated way is feed forward control. The feed forward control adjusts the reason of parameter windage. The system control compensates the parameter according to the character and value of the interference, keep the parameter steadiness.The last phase of the technique curve is keep pressure, we chose the PI adjust rule because the fuzzy controller can not eliminate the steady state error. To gain better dynamic performance and upper precision, we adopt fuzzy control when the error exceeds the set valve value; we adopt PI control when the error falls into the set valve value.According to the theory of the fuzzy control and the character of the aluminum cylinder block, the author designed the aluminum cylinder block's liquid surface pressure control system。The author adopt fuzzy control arithmetic to realize pressure tracking of the low pressure casting aluminum cylinder block, adopt PI control to realize steady performance during the cast. The affect of the control is very good in the practice.Take the pressure's error and the rate of change of error as input in this paper, and then use step 7 software realizing fuzzy control. The system is mainly made of 3 modules, one is interrupt module, another is fuzzy control module, another is control valve perform module. The transposition subprogram of domain transform input domain, that is to say, transform the exact analog which is been gained by sensor to dispersed value, and then inquire the corresponding value. Subprograms of defuzzification transform the corresponding value in the form to the opening of the control valve. The valve's opening adjust the group valve by the I/O of PLC, dry gas was supplied the crucible.