| In order to overcome the present disadvantages of instruments such as narrow universality and the need to specially design and manufacture, a new kind of intelligent instrument has been developed, which can receive several common sensor signals and then generate control signals according to the requirements of industrial spot. The invented intelligent measurement & control instrument adopts the advanced control strategy of Fuzzy PID which makes use of fuzzy deduction mechanism to realize on-line tuning of parameters including K_p,K_I and K_D in terms of the error and its change ratio of the measured object. This not only maintenances traditional PID advantages such as simple principle, convenient application and strong robustness but also has greater flexibility, adaptability and better control accuracy. The system also owns the ability of automatic replacement of range and elimination of excursion caused by temperature and time. In addition, to meet with demands of modern industry on measurement & control systems, RS-485 interface has been applied in the mutual connection between a number of instruments and the real-time communication with computer, by which a stronger DCS can be formed.During the development of this instrument, hardware and software have been divided into several functional parts to design and debug conveniently, which can make them used more universally. Consequently the substitution of one part for another can lead to the change of system function. |
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