A PRACTICAL TEST SYSTEM WITH A FUZZY-LOGIC CONTROLLER

A test system with a fuzzy logic controller is proposed to assure stab le outgoing quality as well as to raise throughput. The test system co ntrols the number of items under test in accordance with fuzzy informa tion as well as statistical information about incoming quality and out going quality. First, an algorithm, minimum-minimum-the center of grav ity-weighted mean method, is studied with both fuzzy reasoning rules a nd membership functions which are used for the control. Second, charac teristics of the test system are verified and examined with computer s imulations so that the fuzzy logic control rules are determined to rea lize sufficient sensitivity to process changes. Third, the control rul es are installed in the test management processor which commands test equipment for testing very large scale integrated circuits, with progr amming language C. The authors have obtained satisfactory results thro ugh a trial run using a series of lots of 16 bit micro controller unit s in an IC manufacturing factory. Finally, they study the stability co ndition of the fuzzy test system.