Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
1999-09-07
2001-08-07
Zanelli, Michael J. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
Reexamination Certificate
active
06272421
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
This invention lies in the automotive arts. Specifically, the invention pertains to an antilock braking system, in which an actuator in a braking system is controlled using a number of speed values and pressure values, with the aid of a fuzzy controller.
New requirements in the braking functions, and the requirement to reduce the assembly and maintenance costs, lead to new braking systems in which the force is no longer produced by a braking-torque requirement which originates from the driver and is transmitted directly as a force via a hydraulic system. Instead, an electromechanical brake actuator is controlled with the aid of an electric signal and produces a frictional force on a brake by means of an electrical power supply. This recent advance is generally referred to as a brake-by-wire braking system. Even in such an electromechanical braking system, a device is expedient which prevents the locking of a braked wheel and thus maintains the driving stability of the braked wheel. For this purpose, wheel-speed sensor devices for each wheel or for each group of wheels, and electric, continuously setting braking-pressure or braking-force actuators, which can set an independent braking pressure or an independent braking force for each wheel or for each wheel group, are needed.
Each wheel has an associated wheel-speed sensor which transmits a wheel-speed signal to the computing unit and the control unit. These wheel speeds are used in a conventional computation of the wheel slip in that, for example, a vehicle reference speed is determined from the quickest, non-driven wheel, taking into account steering lock. The slip of a wheel is calculated from the ratio between the measured wheel speed and the vehicle reference speed. If the reference brake pressure requested by the driver exceeds a specific value, which depends on the roadway surface, the affected wheel would lock. This is undesirable, for obvious reasons. It is therefore necessary for the reference pressure to be reduced such that locking of the wheel no longer takes place.
U.S. Pat. No. 4,842,342 to Takahashi et al. discloses an ABS system based on a fuzzy controller, in which the braking force of a hydraulic braking system is controlled from wheel speed values and vehicle acceleration values, with the aid of a fuzzy controller.
U.S. Pat. No. 5,001,640 to Matsumoto et al. discloses an antilock braking system based on a fuzzy controller in which, in addition to speed values, the hydraulic pressure required by an electronic control unit is used to control the braking pressure.
The prior art systems of this generic type are generally complicated and require considerable outlay in computing power and electromechanical control systems.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a fuzzy-logic controlled antilock braking system for an electromechanical braking system, which overcomes the abovementioned disadvantages of the heretofore-known devices and methods of this general type and which achieves largely optimal ABS regulation with the lowest possible outlay and with a relatively simple rule base.
With the foregoing and other objects in view there is provided, in accordance with the invention, a fuzzy-logic controlled antilock system for an electromechanical vehicle braking system, comprising:
a fuzzy controller adapted to form a braking-pressure rate of change; and
a unit with integral behavior connected to the fuzzy controller, the unit with integral behavior utilizing the braking-pressure rate of change to output a nominal braking pressure as input variable for the vehicle braking system, and a signal connection between the vehicle braking system and an input upstream of the fuzzy controller whereby the vehicle braking system supplies an actual braking pressure as a comparative variable.
In accordance with an added feature of the invention, the fuzzy controller is adapted to form the braking-pressure rate of change as a function of a wheel slip, a wheel acceleration, a locking pressure and a pressure ratio between the actual a braking pressure or a nominal pressure and the locking pressure.
In accordance with an additional feature of the invention, there is provided a unit for calculating the locking pressure, whereby the actual pressure is in each case stored as the locking pressure when the wheel slip exceeds a specific threshold value.
In accordance with another feature of the invention, the fuzzy controller has a rule base defining the positive pressure rate of change to be lower the closer the pressure ratio is to one.
In accordance with a further feature of the invention, the fuzzy controller has a rule base defining the braking-pressure rate of change to depend only on the wheel acceleration and the pressure ratio, on the proviso that the wheel slip is judged to be in order.
In accordance with a concomitant feature of the invention, the rule base of the fuzzy controller is based on:
definitions for the wheel slip consisting only of the linguistic values “ok,” “too small,” “too large,” and “much too large”;
definitions for the wheel acceleration consisting only of the linguistic values “normal,” “too negative” and “too positive”;
definitions for the pressure ratio consisting only of the linguistic values “one,” “greater than one,” “small,” “large,” and “very large”; and
definitions for the locking pressure consisting only of the linguistic values “small” and “large”.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an antilock braking system, based on a fuzzy controller, for an electromechanical vehicle braking system, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing FIGURE.
REFERENCES:
patent: 4842342 (1989-06-01), Takahashi et al.
patent: 5001640 (1991-03-01), Matsumoto et al.
patent: 5409302 (1995-04-01), Chabbert
patent: 5416709 (1995-05-01), Yeh et al.
patent: 0 585 134 A2 (1994-03-01), None
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
Zanelli Michael J.
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