Method for the avoidance of rollover phenomena in semitrailers

This application claims the priority of German Application No. 101 30 407.2, filed Jun. 23, 2001, the disclosure of which is expressly incorporated by reference herein.

The invention relates to a method for the avoidance of rollover phenomena in semitrailers, with the emission of warning signals for the driver of the vehicle when driving inappropriately.

Known rollover protection methods on semitrailers are based on the principle of performing brief test brakings—so-called “test-brake inshots”—on the wheels on both sides of the semitrailer continuously while in motion, and measuring the accelerations of the wheels during these test brakings. With the wheels lifted, excessively high wheel accelerations are measured by the test brakings—in much the same way as in known ABS brake control—from which a rollover condition of the semitrailer is inferred, resulting in an automatic warning to the driver of the vehicle.

These methods have the disadvantage, however, that they detect whether the wheels have already lifted. It is then often already too late to initiate rollover protection measures. The fact that a large amount of wear occurs in the brake system due to the test brakings that continuously have to be performed is to be seen as a further disadvantage.

The object of the invention is to create a rollover protection method which predicts the onset of rollover in semitrailers before lifting of the wheels occurs and which can be performed without test brakings.

According to the invention, this object is achieved by the emission of warning signals for the driver of the vehicle when driving inappropriately. For this purpose, the center of gravity of the load of the semitrailer is calculated in an on-board computer, and is used, together with the known weight of the loaded semitrailer, to calculate a rollover limit as a function of instantaneous driving parameters in the on-board computer. When the vehicle exceeds this limit, a warning is issued to the driver. Developments of the invention are specified herein.

The method according to the invention is based on the principle that the position of the center of gravity of the semitrailer is determined for an existing load, and used together with the measured, instantaneous lateral acceleration of the trailer—or alternatively with the measured road speed and the measured lock angle of the front wheels—to calculate a limit for the lateral acceleration of the trailer or alternatively for the road speed at a given lock angle, up to which any onset of rollover is safely avoided. If this rollover limit is exceeded, the driver is warned and/or automatic intervention in the control of the vehicle is undertaken.

The solution according to the invention advantageously allows the rollover to be predicted and reduces the brake system wear, since no test brakings have to be performed.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

FIG. 1 shows a loaded semitrailer with an uneven but secure weight distribution of the load.

FIG. 2 shows a loaded semitrailer with center of gravity of a moveable load varying as a function of the instantaneous lateral acceleration of the trailer.

According to the invention, the position of the center of gravity 2 of the loaded semitrailer 1 shown in FIG. 1 is calculated from the estimated weight of the load in the trailer, assuming an uneven weight distribution. In the case of uneven weight distributions—as indicated, for example, in FIG. 1 —a more precise determination of the position of the center of gravity may alternatively be undertaken, if information on the weight distribution is available. It may be possible to infer such information from electronic waybills, for example.

The determination of the center of gravity may be based on a stowage plan and known density of the cargo and may be calculated by hand or by any suitable manual or automated method. The type of cargo and its form may be determined from a chip card or the like.

The position of the center of gravity of the loaded semitrailer—such as the semitrailer of a tanker vehicle, for example—shown in FIG. 2, varies with the instantaneous lateral acceleration of the trailer.

The method according to the invention for determining the rollover limit must therefore take account of the instantaneous position of the center of gravity. At the same time, the calculation either takes additional account of the measured instantaneous lateral acceleration of the trailer, or, alternatively, of the measured road speed and the measured steering angle. A method for calculating the shift of the center of gravity is disclosed in U.S. Pat. No. 6,324,447, to Schramm et al., the disclosure of which is incorporated by reference.

The calculation of the rollover limit may be performed, for example, by means of a suitable characteristics curve method, into which the data obtained on the load center of gravity and the lateral acceleration of the trailer—or the road speed and the steering angle—are introduced as input variables. Suitable characteristic curves may be determined by way of experiments or by use of algorithms.

The rollover limit may be calculated as a maximum admissible lateral acceleration of the trailer or as a maximum admissible road speed for a given wheel lock angle.

These driving parameters are continuously registered by corresponding sensors on the vehicle, and the driver is warned if the determined rollover limit is exceeded.

Alternatively, should the limits be exceeded, the method according to the invention may intervene automatically in the kinematics of the vehicle and, for example, reduce the road speed for a given steering angle, so that the rollover limit is not exceeded.

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.