Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication
Reexamination Certificate
1999-04-16
2001-04-10
Zanelli, Michael J. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
C701S072000
Reexamination Certificate
active
06216061
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for determining a reference magnitude, and more particularly, a reference magnitude which indicates the state of a vehicle traveling in reverse and which is determined based on a comparison of at least two measured variable magnitudes.
A method of this type, referred to generally as “situation recognition,” is disclosed, for example, in German patent document DE 195 15 051 A1 (U.S. Pat. No. 5,774,821). In accordance with the known method, such situation recognition permits the distinguishing of various travel states, for example, straight forward travel, turning, reverse travel and stopping of a vehicle. Such distinction is required in applications involving a situation-dependent determination of control algorithms for a system which regulates vehicle stability.
The situation recognition method disclosed in the above referred patent document determines the state of reverse travel as a reference magnitude by comparing, for example, the angular yawing speed measured by a sensor with an angular yawing speed calculated from a steering angle measured by another sensor. When the measured angular yawing speed and the calculated angular yawing speed have different signs, and when the derivatives of these magnitudes with respect to time also have different signs, the state of reverse travel is recognized.
In order to convert the magnitudes measured by the sensors in the above example into a usable reference magnitude, several computing steps are necessary. In particular, the known method requires a conversion of the measured steering angle into an angular yawing speed, followed by a differentiation of measured and calculated angular yawing speed with respect to time. In order to ensure reliable recognition of reverse travel and/or good reproducibility of the comparison results, these computing steps, which are normally carried out by a microprocessor, must be carried out with a high degree of computing precision. In addition, a high degree of signal resolution is generally required, i.e., requiring small quantized steps from the sensors and from any downstream analog/digital converters which may be present.
Execution of the computing steps with the required level of computing precision, for example, by implementation of floating-point arithmetic, requires a microprocessor providing high computing capability, or may further require an additional floating-point processor, resulting in increased cost. High-resolution sensors and analog/digital converters are also expensive.
The utilization of simpler calculation methods for implementing the known method, such as integer arithmetic in which the computing steps involve only integer magnitudes, and which would otherwise be desirable because of a lower computing capability requirement, would however lead to computing errors, for example, when the remainder in a division of two magnitudes into each other is simply ignored. Particularly where several computing steps of this kind are used, such computing errors, which would then occur in a cumulative manner, would lead to unsatisfactory results in the determination of a reference magnitude, for example, one indicative of reverse travel.
It is therefore the object of the present invention to provide a method for the determination of a reference magnitude based on a comparison of at least two variable magnitudes, and in which the reference magnitude can be determined with relative reliability using simple computing steps and which may be implemented with inexpensive circuitry.
SUMMARY OF THE INVENTION
In accordance with these and other objects of the invention, there is provided a method for determining a reference magnitude by comparison of at least two variable magnitudes. A first variable magnitude with a first representation and a second variable magnitude with a second representation are obtained. A relationship exists between the first and second representations of the first and second variable magnitudes, permitting conversion thereof one to the other. The first and the second variable magnitudes are then compared with one another in a first comparison criterion on the level of the first representation. Subsequently, the first and the second variable magnitudes are again compared with one another in a second comparison criterion on the level of the second representation, thereby providing support for the first comparison result.
Hereinafter, a “comparison criterion” is understood to be a simple identity or similarity comparison between two magnitudes, as well as utilization of several individual criteria in a comparison process, as described in the example which follows.
The invention provides the advantage that by using simple sensing means, conversion means and computing means, and only slightly greater computing effort, i.e., by twice comparing the same magnitudes, once in the representation of the first magnitude and a second time in the representation of the second magnitude while using, for example, integer arithmetic, it is possible to achieve a significant improvement in the comparison results. In addition, by using a second comparison criterion for the second comparison, certain fixed magnitudes inherent to the comparison criterion, such as recognition thresholds, can be determined independently on the level of the second representation, thereby providing further advantage. It is also possible to convert the thresholds used with the first comparison criterion in the first representation simply by using the same rules which serve to convert the variable magnitudes, or the magnitudes measured by the sensors, into the second representation. Alternatively, however, the thresholds for the second comparison criterion can be set separately on a case by case basis. The method according to the invention can thereby be readily adapted to the most different of applications and can thus be used in an extremely flexible manner.
In an advantageous further development of the invention, the method for the recognition of reverse travel is used in a vehicle. In this regard, sensors are provided on the vehicle for the sensing of an angular yawing speed, a steering angle and a longitudinal vehicle speed. The additional or alternative utilization of sensors for transversal acceleration of the vehicle and for sensing the wheel speeds of individual wheels is also deemed advantageous.
To recognize reverse travel, the effect in the state of the art method mentioned above is used, in accordance with which the angular yawing speed obtained from the signal of the angular yawing speed sensor changes its sign between forward and reverse travel, while the normally used sensors for the determination of the longitudinal vehicle speed always reflects the actual vehicle speed in forward as well as in reverse travel. As a result, the angular yawing speed measured from the steering angle and the longitudinal vehicle speed by definition corresponds to the measured angular yawing speed, insofar as no unstable travel conditions exist, while conversely, in reverse travel, the calculated angular yawing speed evolves as an exact mirror image of the measured angular yawing speed.
In order to recognize the behavior described above, the state of the art method mentioned above proposes, inter alia, a differentiation between the magnitudes to be compared. In practice, in particular where microprocessor-controlled devices are used, this creates significant difficulties due to the potential quantizing errors noted earlier herein, because a differentiation in such time-discrete as well as value-discrete systems is effected by difference quotients. A highly precise calculation of such difference quotients requires costly computing and storage capabilities, and is advantageously avoided.
In an advantageous further development of the invention, the disadvantages resulting from the differentiation of the signals are avoided by using other comparison criteria which use only the non-differentiated signals as input magnitudes. Thus, a verification is first made in the
Franke Torsten
Gläbe Klaus
Koschorek Ralf
Reich Thomas
Proskauer Rose LLP
WABCO GmbH
Zanelli Michael J.
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