Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle diagnosis or maintenance indication
Reexamination Certificate
1999-12-17
2001-10-09
Chin, Gary (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle diagnosis or maintenance indication
C701S096000, C701S301000, C702S104000
Reexamination Certificate
active
06301532
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for correcting a signal of at least one sensor, on the basis of which a path curve can be determined, on which the vehicle is moving.
Systems are known in which the environment of a vehicle is evaluated—for example by means of radar beams—in order to control the speed of the vehicle. A further possible aim may also be for automatically steering the vehicle without any action by the vehicle driver. The orientation process involves sensing both objects which are identified as being stationary in the environment and, other vehicles. In this case, it is important to identify whether other vehicles are travelling in the same lane as one's own vehicle, or in an adjacent lane. If the lane is incorrectly assigned, it is possible for the driver to be given an unnecessary warning or for the vehicle to be braked unnecessarily when a slower-moving vehicle on an adjacent lane is identified as driving in the same lane. On the other hand, the vehicle driver may be warned, or the vehicle may be braked, too late or not at all if a vehicle travelling more slowly in front in the same lane is identified as driving in the adjacent lane. It is thus important to assign a vehicle's own direction of travel correctly with respect to other objects. To this end, it is necessary to identify with as little error as possible the path curve on which the vehicle is moving.
The object of the present invention is to carry out a correction of a signal on the basis of which a path curve can be determined on which the vehicle is moving.
SUMMARY OF THE INVENTION
This object is achieved according to the invention in that the vehicle has a sensing device by means of which the environment of the vehicle can be identified, and in that the correction of sensor signal is carried out such that, at at least one point in time, the object location expected at at least one further point in time of an object which is identified as being stationary is determined on the basis of the vehicle speed and of the signal of the sensor, and in that, at the one further point in time, the object location of the object which is identified as being stationary is recorded, with a correction of the signal of the one sensor being carried out on the basis of the discrepancy between the expected object location and the recorded object location.
This method advantageously allows compensating for static errors such as those arising from displacement of the vehicle's lane. Since the expected object location at a further point in time is determined, starting from a first point in time, by means of the vehicle speed and the signal of the at least one sensor, this object location can be compared with the object location measured, that is to say recorded, at the further point in time.
In one embodiment of this invention, the device identifies the environment by means of radar beams.
Such devices are known and are already being tested. Such devices allow the environment in terms of moving and stationary objects to be identified well. Furthermore, such devices are preferably used in the systems described initially, in which vehicle speed control and/or steering control are intended to be carried out without any action by the vehicle driver. The device can then be used not only for control purposes, but also for adjusting of the sensor or sensors which determine the path curve of the vehicle.
Also, at least one parameter of a path curve can be determined for the discrepancy between the curve of the expected object locations and the recorded object locations. An offset for the signal of the sensor can be determined on the basis of this parameter.
The use of a plurality of object locations makes it possible to compensate for statistical fluctuations, which express themselves as incorrect measurement results. If, for example, the path curve is described by an n-th order polynomial, an overdefined equation system is obtained if the number of, object locations used to calculate the parameters is greater than n+1. It has been found to be advantageous to assume a 2nd order polynomial for the path curve. In this case, only the parameters for the second-order term need be determined by suitable selection of the coordinate system. The overdefined equation system may be evaluated, for example, using least-square error methods.
This parameter can be determined for a set of expected and recorded object locations. Furthermore, specific parameters can be averaged for a plurality of sets of expected and recorded object locations.
This allows statistical fluctuations in the determination of the parameters to be compensated for.
The parameter for a set of expected and recorded object locations can be determined with a weighting in the averaging, at least if a certain limit value is exceeded by the parameter.
This weighting makes it possible to analyse the reliability of the parameter determined for a set of expected and recorded object locations. If the value of the specific parameter would result in a correspondingly large correction, this parameter can be taken into account, for example, with a low weighting, in order to wait until it is clear whether this parameter value is confirmed by further sets of expected and recorded object locations. This allows errors to be compensated for in an advantageous manner if object locations identified from successive measurements in time are assigned to a specific object for which object locations have already been determined. In this case, however, there may be a plurality of objects which are located comparatively close to one another and may be concealed for individual measurements, so that the associated object locations did not actually correspond to the same object.
The weighting can also be carried out, such that the parameter is taken into account with reduced weighting in the averaging if the parameter exceeds a certain limit value. The parameter may even be ignored if it exceeds limit value. It is likewise also possible to provide a factor in the weighting whose profile can be differentiated continuously, in which case this factor reduces as a function of the value of the parameter in relation to a certain limit value.
When a limit is exceeded by an error (&Dgr;y) which results from a discrepancy between the path curve of the expected and/or recorded object locations and the path curve calculated by means of the parameter, the parameter can be taken into account with a weighting for the averaging.
This advantageously allows account to be taken of the extent to which discrepancies occur between the mean value, which is obtained on the path curve on the basis of the one calculated parameter, and the expected and/or recorded object locations. If the error is excessive, the parameter may be given, for example, a correspondingly lower weighting.
The weighting may be applied, for example, by taking account of the parameter in the averaging with a reducing weighting if the error &Dgr;y exceeds the limit. The parameter may even be ignored if the error &Dgr;y exceeds the limit. It is likewise also possible to provide a factor in the weighting whose profile can be differentiated continuously, in which case this factor reduces as a function of the value of the error &Dgr;y in relation to a limit.
A statistical error analysis could also be carried out in the averaging process, with the correction value becoming invalid and/or a warning signal being output if the error exceeds a limit value.
In this way, it is advantageously possible to identify whether the values of the parameter determined for individual sets of expected and recorded object locations differ excessively from one another, so that uncertainties may exist with regard to the reliability of the resultant correction value.
The parameter within a set may also be determined only when the maximum magnitude of the change in the signal of a sensor during this set is less than a specific threshold value.
If the signal of the sensor changes to be above a threshold value during the period of t
Kull Wolfgang
Lauer Wolfgang
Reichmann Thomas
Chin Gary
Crowell & Moring LLP
Daimler-Chrysler AG
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