Apparatus for controlling lock-up clutch in vehicle automatic transmission according to fuzzy set theory

Claim 3

An apparatus according to claim 1, wherein said determining means provisionally selects one of said released and engaged positions of said lock-up clutch as a provisional position Lu* according to said predetermined clutch control pattern, and said at least one basic fuzzy set theory rule consists of a basic fuzzy set theory rule whose satisfaction degree corresponding to the selected one position of the lock-up clutch is higher than that corresponding to the other position.

Claim 4

An apparatus according to claim 1, wherein said fuzzy set control rules whose degrees of satisfaction are calculated by said first calculating means consist of a first control rule R ON for selecting the engaged position of the lock-up clutch, and a second control rule R OFF for selecting the released position of the lock-up clutch, said first and second control rules R ON and R OFF are expressed by the following formulas: R.sub.ON= A and [{(B or C) and D} or E] and F R OFF= G or {(B or C) and H}or I where, "A"represents a sub-rule A for determining a probability degree in which a speed of said engine falls within a stable range if said lock-up clutch is operated in said engaged position, "B" represents a sub-rule B for determining a probability degree inn which an accelerator pedal of the vehicle is in the process of being depressed, "C" represents a sub-rule C for determining a probability degree in which said accelerator pedal is in the process of being released, "D" represents a sub-rule D for determining a probability degree in which vibrations of the vehicle are not likely to be generated by the lock-up clutch if said lock-up clutch is operated to said engaged position, "E" represents a sub-rule E for determining a probability degree in which said accelerator pedal is held at a constant position, "F" represents a sub-rule F for determining a probability degree in which said speed changing mechanism is placed in a second-speed position or an overdrive position, "G" represents a sub-rule G for determining a probability degree in which said speed of said engine falls within an unstable range if said lock-up clutch is operated to said engaged position, "H" represents a sub-rule H for determining a probability degree in which vibrations of the vehicle are likely to be generated by said lock-up clutch if said lock-up clutch is operated too said engaged position, and "I" represents a sub-rule I for determining a probability degree in which said speed changing mechanism is not placed in said second-speed position or said overdrive position.

Claim 5

An apparatus according to claim 1, wherein said second calculating means calculates said overall degrees of adequacy of for said released and engaged positions of the lock-up clutch, respectively, each by obtaining an algebraic product of a corresponding one of the degrees of satisfaction of said at least one basic fuzzy set theory rule for said released and engaged positions which are determined by said determining means, and a corresponding one of the degrees of satisfaction of said fuzzy set control rules for said released and engaged positions which are calculated by said first calculating means.

Claim 6

An apparatus according too claim 1, wherein said fuzzy set control rules and said at least one basic fuzzy set theory rule are selectively combined to provide a plurality of complex control rules whose degrees of satisfaction provide said overall degrees of adequacy for selecting said released and engaged positions of said lock-up clutch.

Claim 7

An apparatus according to claim 5, wherein said determining means provisionally selects one of said released and engaged positions of said lock-up clutch as a provisional position Lu* according to said predetermined clutch control pattern, and said at least one basic fuzzy set theory rule consists of a basic fuzzy set theory rule Q whose degree of satisfaction corresponding to the selected one position of the lock-up clutch is higher than that corresponding to the other position, said plurality of complex control rules consist of a first complex control rule R ON' for selecting said engaged position of the lock-up clutch, and a second complex control rule R OFF' for selecting said released position of the lock-up clutch, said first and second complex control rules R ON' and R OFF' being expressed by the following formulas: R.sub.ON' =Q and J R OFF' =Q or K where, "J" represents a sub-rule j for determining a probability degree in which a time elapse after a last releasing action of said lock-up clutch is longer than a predetermined value, and "K" represents a sub-rule K for determining a probability degree in which said time elapse is shorter than said predetermined value.