Method and system for controlling a drive train of a motor vehicle

#The invention relates to a method for controlling a drive train of a motor vehicle and to a drive train control system.

#In conventional transmission control systems for motor vehicles, the transmission ratio of the transmission is set automatically as a function of the position of the accelerator pedal and of the speed of travel by using stored maps. Instead of using the position of the accelerator pedal as such, it is also possible to use a signal of a so-called electronic accelerator pedal (E-Gas for short) or some other variable derived from the engine torque demanded by the driver. In this case, various driving parameters and operating states of the motor vehicle are taken into account as is described in International Publication WO 97/01051. The respective gear to be selected or—in the case of continuously variable transmissions—the transmission ratio to be set is selected by control circuits operating by fuzzy logic methods. This logic describes expert knowledge gained from experience in the form of what is referred to as a basic set of rules. These rules are then used for regulating operations or control operations of the motor-vehicle transmission. The fuzzy logic circuit produces control signals, which, among other things, define the transmission ratio of the transmission and, in the case of automatic step-change transmissions, the gear to be selected.

#Published, Non-Prosecuted German Patent Application DE 196 37 210 A1 discloses a conventional integrated drive train control system for a motor vehicle. The drive train control system interprets the position of the accelerator pedal and of the brake pedal as a wheel torque desired by the driver. It has a calculating device which receives the positions of the accelerator pedal and the brake pedal and which produces central control parameters for the drive unit and for those units of the drive train that exert a decelerating effect.

#FIG. 1 is a block diagram of a motor vehicle controlled in accordance with the method according to the invention and provided with a drive train control system according to the invention;

#FIG. 2 is a structogram illustrating the method according to the invention;

#FIG. 3 is a graph illustrating a temporal course of measured braking times;

#Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is shown a schematically illustrated motor vehicle 1 which has an engine 2, which is controlled by an engine control system 3. An engine output shaft 4 is connected through the use of a torque converter or hydrodynamic coupling to an automatic transmission 5, which is controlled by an electronic drive train or transmission control system 6 according to the invention—also referred to below simply as a control system. In the exemplary embodiment, the transmission 5 is embodied as a step-change transmission or multi-step transmission, but a control system 6 according to the invention could equally well be used for a continuously variable transmission or to control the other devices in a motor vehicle. A control system of this kind may for example be used in a motor vehicle to control not only an automatic transmission but also a rear-wheel steering system, a traction control system or a cruise control system. The crucial component of the control system 6 is a fuzzy logic circuit 7. A transmission output shaft 8 is connected to the driven wheels of the motor vehicle, here symbolized by a driven wheel 9.

#The driver of the motor vehicle communicates his or her commands or, more precisely, his or her intentions to the engine control system 3 through the use of an accelerator pedal 10.

#When a brake pedal 11 is actuated, the brakes of the motor vehicle, which are here indicated schematically by a brake system 22, are actuated. The motor vehicle is furthermore provided with a wheel-slip or traction control system (ASR) 12 and an anti-lock brake system (ABS) 13, which are connected by signal lines or a bus 15 to one another and to the engine control system 3 and transmission control system 6 for the purpose of exchanging signals. Via a signal line 16, the engine control system 3 sends the engine 2 signals that control the ignition, the injection and the throttle valve (the latter only if there is a corresponding control device).