Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
2001-01-02
2001-10-30
Camby, Richard M. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C477S078000
Reexamination Certificate
active
06311115
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
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.
There are driving situations in which it would be expedient if actuation of the brakes by the driver were assisted by the drive train of the motor vehicle, when traveling downhill for example. This can, for example, be accomplished by the suppression of upshifts specified by a map, i.e. by retaining the existing transmission ratio.
European Patent Application EP 0 531 154 A2 discloses a transmission control system, with which the transmission ratio, which is determined as a function of the position of the accelerator pedal and of the speed of travel by using stored maps, can be corrected. For this purpose, a correction factor is determined by a fuzzy unit as a function of the driver's desire for braking, of the tractive resistance and of the current transmission ratio, and is added to the corresponding map value.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for controlling a drive train of a motor vehicle and a drive train control system which overcome the above-mentioned disadvantages of the heretofore-known methods and systems of this general type and which detect a driver's desire or intention for braking and which assist the desired braking action sensitively and in an effective manner by controlling the transmission ratio of the automatic transmission.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for controlling a drive train of a motor vehicle, the method including the steps of:
automatically setting, by using stored maps, a transmission ratio of an automatic transmission at least as a function of a speed of a motor vehicle and as a function of one of a position of an accelerator pedal and a substitute variable for the position of the accelerator pedal;
evaluating, with a fuzzy logic circuit, signals characterizing a driving state of the motor vehicle and subsequently producing, with the fuzzy logic circuit, control signals for setting the transmission ratio;
assessing, with the fuzzy logic circuit, a braking torque desire of a driver of the motor vehicle only after a brake pedal has been actuated for a given period of time and controlling the transmission ratio for assisting a braking torque of a brake system, for example by changing or maintaining a transmission ratio; and
assessing, with the fuzzy logic circuit, the braking torque desire of the driver again after changing the transmission ratio, and, if appropriate, adapting the transmission ratio again to the braking torque desire in accordance with an assessment result.
The invention has in particular the advantage that it requires only little additional expenditure or outlay. The basic circuit components and sensor signals required are already available in the control system known for example from the above-mentioned patent applications.
Moreover, no additional sensors are required. Essentially only a few different or additional fuzzy algorithms are required. Adaptation to the driver's desire or intention for braking can be carried out very sensitively since it takes place in several stages if required. Once the driver's desire for braking has been evaluated and the transmission ratio has been changed accordingly, the driver's desire for braking is in each case reassessed if the brake is still being activated, and the transmission ratio is adapted if necessary, and so forth.
According to another mode of the invention, after adapting the transmission ratio, the braking torque desire of the driver again is assessed again and the transmission ratio is changed in steps until a demanded braking torque is achieved.
According to yet another mode of the invention, the transmission ratio for assisting the braking torque is determined with the fuzzy logic circuit in parallel with a map-based calculation of the transmission ratio, and a change in the transmission ratio is calculated, with the fuzzy logic circuit, by using an actual transmission ratio present in the automatic transmission.
According to a further mode of the invention, the transmission ratio for assisting the braking torque is determined with the fuzzy logic circuit in parallel with a map-based calculation of the transmission ratio, and the transmission ratio is set to a statically determined transmission ratio if the statically determined transmission ratio results in an increase of the transmission ratio.
According to yet a further mode of the invention, driving state variables of the motor vehicle are derived, and the fuzzy logic circuit calculates the braking torque desire of the driver from the driving state variables.
According to another mode of the invention, a control signal is generated with the fuzzy logic circuit, the control signal is used as a rotational speed threshold for a comparison with a rotational speed of a turbine of the automatic transmission, and a change in the transmission ratio for assisting the brake torque is induced, if the rotational speed of the turbine falls below the rotational speed threshold.
According to yet another mode of the invention, a control signal is generated with the fuzzy logic circuit, the control signal is used as a rotational speed threshold for a comparison with an output rotational speed of the automatic transmission, and a change in the transmission ratio is induced for assisting the brake torque, if the output rotational speed of the automatic transmission falls below the rotational speed threshold.
According to a further mode of the invention, the transmission ratio for assisting the braking torque is maintained until given exit conditions are met.
With the objects of the invention in view there is also provided, a drive train control system, including:
a drive train controller for setting, based on stored map data, a transmission ratio as a function of at least a motor vehicle speed and as a function of one of an accelerator pedal position and a substitute variable for the accelerator pedal position;
the drive train controller including a fuzzy logic circuit,
a signal line connecting the fuzzy logic circuit to a brake system;
the fuzzy logi
Camby Richard M.
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
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