Method and system for determining a vehicle mass

Data processing: measuring – calibrating – or testing – Measurement system – Weight

Reexamination Certificate

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Details

C073S865000

Reexamination Certificate

active

06314383

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method and a system for determining a mass value representing a mass of a vehicle.
BACKGROUND INFORMATION
Systems for the open-loop and closed-loop control, respectively, of the driving dynamics of automobiles are known. The control of the braking system is the priority here. In such systems, the most precise information possible about the vehicle mass is of major significance.
If the motor vehicle is a commercial vehicle having a towing vehicle and a trailer/semi-trailer, an optimal coordination of the braking forces with regard to economic efficiency, safety and driving comfort can be attained if the masses of the towing vehicle and the trailer/semi-trailer are known as accurately as possible. If the mass of the entire truck with trailer is known, then, given the known mass of the towing vehicle, the mass of the trailer/semi-trailer can be determined. Since, however, according to its intended purpose, large differences can occur in the payload of commercial vehicles and thus in the total mass of the vehicle, the total mass and the distribution of the mass between the towing vehicle and the trailer/semi-trailer must continually be redetermined. Thus, the driving stability can be increased by suitably distributing the braking torque on the individual wheel brakes.
German Patent Application No. 42 28 413 describes a determination of the total mass of a vehicle, in which the longitudinal acceleration of the vehicle and the appertaining driving and propulsive forces are measured at two different points of time in brief succession during an acceleration process of the vehicle. The vehicle mass can then be determined as a function of these measured variables. It is assumed here that the driving resistance while determining the mass does not change significantly, for example due to a change in the roadway slope.
An object of the present invention is to determine mass as simply as possible and with greatest possible precision in view of a possibly sloped roadway.
SUMMARY OF THE INVENTION
The present invention relates to a method and a system for determining a mass value of a motor vehicle representing the vehicle mass, particularly of a commercial vehicle, having a drive unit. For this, provision is made for acquisition of at least a first and a second acceleration value. These acceleration values represent the vehicle acceleration at a first and a second point of time. Furthermore, at least a first and a second drive value are detected. These drive values represent the drive force or the drive torque of the drive unit at a first and at a second point of time. At least as a function of the acquired acceleration values and the acquired drive values, at least a first and a second driving resistance or mass estimated value is then determined. According to the present invention, the determination of the mass value occurs at least as a function of a comparison of at least the determined first driving-resistance or mass estimated value with the determined second driving-resistance or mass estimated value.
A roadway slope is detected using the comparison in accordance with the present invention, whereby an erroneous determination of mass due to a roadway slope is avoided without necessitating an additional sensor for determining the mass and/or for determining the roadway slope. The mass can be determined during a single acceleration process, the method according to the present invention being simple to apply. In so doing, the result of the mass estimation achieved according to the present invention is sufficiently precise for a practical use.
In another embodiment of the present invention, the points of time are selected such that the acquired drive values vary from one another in a predeterminable manner. In particular, the difference or differences between the acquired drive values exceed(s) or fall(s) below a predeterminable first threshold value. The background for this embodiment is that a roadway descending gradient or roadway incline is having a particularly significant affect on the acceleration values of the vehicle if highly variable drive values exist.
In addition, or particularly as an alternative to the last cited variation, it can be provided that a signal representing the gear ratio of the vehicle transmission is generated. The points of time at which the acceleration and drive values are acquired can then be selected as a function of the generated signal. In so doing, different transmission ratios exist at these points of time. In this way, it can be ensured in a simple manner that the drive forces, which are drawn upon to determine the driving resistance or mass estimated values, are sufficiently different. The differing drive forces, which are necessary to recognize the slope, are realized in this embodiment by using “gear-speed tracking”. This has a basis in that, during the start-up (e.g., drive off), the transmission ratio becomes smaller, and thus smaller forces act on the drive axle as the vehicle speed increases.
For the comparison according to the present invention, it is ascertained whether the determined driving resistance or mass estimated values are within a predeterminable range. In particular, it can be ascertained whether the difference or differences between the determined driving resistance or mass estimated values exceeds or falls below or exceed or fall below a predeterminable second threshold value. In this manner, it can be determined whether the vehicle is currently located on a sloped roadway, because in this case, the driving-resistance or mass estimated values, which were ascertained for different drive values, vary significantly.
To compensate for short-term fluctuations, the determined driving-resistance or mass estimated values are low-pass filtered.
In particular, the mass value is ascertained only if the determined driving-resistance or mass estimated values are within a predeterminable range, thus if there is no or only a slight roadway slope. This ensures the reliable determination of a mass value.
In a further embodiment of the present invention, to ascertain the mass value, at least one of the determined driving-resistance or mass estimated values is also drawn upon, provision being made in particular that the average value from at least two of the determined driving-resistance or mass estimated values is ascertained as the mass value. This increases the quality of the mass value determined according to the present invention.
If a value representing the vehicle speed and/or a value representing the rotational speed of the vehicle wheels is (are) also drawn upon to determine the driving-resistance or mass estimated values, the influences of the aerodynamic drag and/or moments of inertia of the vehicle wheels can be considered in the mass determination according to the present invention.


REFERENCES:
patent: 4548079 (1985-10-01), Klatt
patent: 4656876 (1987-04-01), Fremd
patent: 4941365 (1990-07-01), Reiner et al.
patent: 5187977 (1993-02-01), Koschorek et al.
patent: 5402345 (1995-03-01), Kost
patent: 38 43 818 (1990-05-01), None
patent: 42 28 413 (1994-03-01), None
patent: WO 93 18375 (1993-09-01), None
patent: WO93/18375 (1993-09-01), None

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