Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Patent
1996-02-28
1999-07-06
Cuchlinski, Jr., William A.
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
701 65, 477138, G06F 300
Patent
active
059192445
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a control system for changing the ratio of an automatic transmission. It specially concerns a control by use of fuzzy logic methods for determining the gearshifting point. Means (sensors, switches, etc.) exist for detecting input variables derived from a driver-vehicle system. Related functions, that is, fuzzy sets, are produced for the input variables; means likewise exist for this. Means such as hydraulically actuatable shift clutches and valves are also provided for changing transmission ratios. The means for detecting the input variables, the means for producing related functions and the means for changing the transmission ratio interact in a certain manner: according to fuzzy generating rules, output variables are found with which a transmission ratio is determined.
Automatic transmissions serve basically for the adaptation of the torque delivered by an input engine of a vehicle to the traction need thereof. Such automatic transmissions have an electronic-hydraulic control. To the electronic control a central significance must be conceded for the whole driving characteristics, since the gearshifting operations are detected and carried out by means of loadspeed characteristic fields.
Whether and which gear to engage depends on the load adjustment, that is, the actual state of the throttle valve and of the output speed of the transmission. The individual speed levels are shifted according to shift characteristic lines which are formed from said two parameters. The shift characteristic lines of an automatic transmission consist of upshift and downshift straight lines for the individual gears which, in a shift diagram, extend in such a manner that a hysteresis generates between the individual gear ranges. Despite said hysteresis, it is precise, invariant decision thresholds which determine whether and what gear to engage. The use of such exact decision thresholds means, on one hand, that only discrete, invariant states can lead to the start of a shifting operation and on the other that here systematically exists an adulteration of the logical information content of the decision. The shift characteristics of an automatic transmission can be changed by activating adaptive shift characteristic lines, that is, shift characteristic lines which according to the driving performance are oriented to the consumption or special driving modes.
Despite a multiplicity of possibilities already used for automated determination of the shifting point, the objective of approximating the automatic gear selection to the behavior of a human driver, specially of a certain type of driver, has been only imperfectly achieved.
A possibility of better representing human decision finding than is possible by threshold values or characteristic fields, is the use of fuzzy logic methods. A fuzzy inference system makes possible a decision in which a multiplicity of parameters are taken into consideration and includes features of human decision finding. A great advantage of this method consists in that it allows a direct processing of verbally formulated problem descriptions. Contrary to the conventional control strategies, judgment criteria which cannot be comprised in mathematical description forms but play an essential part in the finding of a decision can be used.
An example of a control system for shifting an automatic transmission using fuzzy logic methods is to be understood from U.S. Pat. No. 4,841,815. The vehicle speed or change thereof, the engine load or change thereof and the driving resistance are processed as input variables in such a manner that fuzzy references are assembled for each gear to be shifted. This control system is based on a complex matrix consisting of parallel fuzzy references interlinked in series. Compared to a transmission control where the speed level is determined only by the vehicle speed and the opening of the throttle valve, the fuzzy control thus disclosed represents an improvement, since the aforementioned exact decision thresholds do not exist.
However, the known control has
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Danz Wolfgang
Eschrich Gerhard
Gillich Udo
Runge Wolfgang
Cuchlinski Jr. William A.
Pipala Ed
ZF Friedrichshafen AG
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