Communications – electrical: acoustic wave systems and devices – Echo systems – Returned signal used for control
Reexamination Certificate
1999-07-01
2001-05-01
Pihulic, Daniel T. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Echo systems
Returned signal used for control
Reexamination Certificate
active
06226226
ABSTRACT:
The invention pertains to a method for range measurement of obstacles from a vehicle with the aid of an echo method, preferably, an ultrasonic method. In this method, a transmitted signal is reflected to the vehicle from the illuminated object in the form of an echo and, in the vehicle, a warning signal is triggered during a temporal listening window, as a function of the threshold value of a receiver. In connection with this type of method, it is known to blank out certain echoes that do not represent a danger to the vehicle in order to avoid false warnings. These may be, for example, pavement echoes from certain pavement structures. In addition, it is known to evaluate only those echoes that appear during a certain time period. While, on one hand, a certain amount of settling time of the transmitted signal must pass before echoes can be evaluated, on the other hand, it makes little sense to evaluate echoes with a very large travel time, since the latter come from objects at a great distance, which do not represent a danger to the vehicle. Consequently, this so-called listening window can monitor a comparatively large spatial depth in time. However, the listening window also can be very restricted in time so that a spatial segment of only little depth is monitored. Other ways of changing the monitoring behavior of said type of monitoring system are shortening or lengthening the transmission period and/or increasing the transmitter power. As a rule, a greater transmitter power also requires a greater transmission period, since settling times and decay times must be observed.
References to the described method may be obtained, e.g., from DE-OS 3,937,585. Also, it is known to change the sensitivity threshold of the receiver during the chronological progression of the listening window. In principle, this method proceeds in such a way that the threshold is increasingly lowered for echoes with a longer travel time until, finally, the listening window is closed. One reason for this is because pavement echo appears at a relatively limited distance from the vehicle. This comparatively simple curved path of the timing progression of the listening window as a function of time achieves a pavement echo that does not lead to a warning signal with range measurement. Nevertheless, it is a disadvantage because the sensitivity of the range measurement always should be as great as possible, even in the near range located between the transmitter and pavement echo. Nonetheless, within this region, projections of the vehicle, such as a trailer coupling, may still cause a warning signal.
A similar consideration relates to the fact that triggered warning signals are of different significance for the driver. If an obstacle is detected behind the tail of a car, this is of relatively limited significance if the driver is traveling forward. The reaction is similar if the driver is traversing a curve Here, among other things, warning signals are triggered that relate to obstacles that, based on the steering angle of the vehicle, the driver will never reach. In addition, indications of far distant obstacles are comparatively insignificant if the driver is driving particularly slowly, while, for more rapid travel, such warnings may be entirely meaningful. Conversely, even weak echoes may be significant to the driver if they come from an area of the surroundings of the vehicle into which it is traveling based on its steering angle, but which it would never reach if it was traveling straight ahead.
Therefore, the invention starts from a method of the class obtained from the preamble of claim
1
. The purpose of the invention is to adapt the procedure of range measurement to the parameters of the vehicle. The problem is solved by means of the combination of features obtained from the characterizing clause of claim
1
. A suitable way can then be following according to the indicated teaching. With respect to spatial data (parameters) of the vehicle, one may proceed, e.g., such that although the listening window remains open in the very near range, the threshold is adapted for an echo coming from near range. Then it is no longer true that the threshold rises steadily as the distance to the vehicle decreases; the threshold also may decrease again or reverse its direction several times. Thus, e.g., it can be that raising the threshold within a certain time domain of the listening window blanks out ground return, then upon further nearing the vehicle, the threshold is again lowered and then finally, at a close proximity to the vehicle (trailer coupling) the threshold is once again raised within a short range. In this way, the threshold progression in the measuring system can remain in a fixed setting; it can, however, also change as a function of spatial data of the vehicle. Thus, e.g., a change in reflected echoes is to be expected if the tail of the vehicle is lowered due to a great load or raised due to an unloaded state. Since the speed of sound changes with temperature, changes in echo behavior also may appear. With the use of several transmitters, receivers, or transducers arranged next to each other on the bumper, one may proceed, in an advantageous refinement of the invention, in such a way that the position and duration of the listening window changes or the measured length of at least some of the transducers decreases. If, for example, the front wheels are set at a certain angle, it is not necessary to measure the far range on the side of the vehicle that will not reach this far range based on the relative position of the steering wheels. Here, for example, the listening window may end earlier. Conversely, it can be recommended to enlarge the listening window on the opposite, endangered, side and/or to increase the transmitter power. In addition, other data relating to the dynamics of vehicle movement may be used in order to change the measuring parameters of the range measurement. This data may be, e.g., acceleration of the vehicle, velocity, change of the steering angle or the like. This applies, more specifically, to an echo measuring device that measures the distance to the vehicle traveling in front.
In addition, the invention indicates different range measurement devices that are particularly suited for carrying out the method of the invention. In this connection, especially the range measures are emphasized, which operate as measuring devices using an ultrasonic method. However, the principle of the invention also may be applied analogously to other echo methods, operating, e.g., with infrared, radar or laser irradiation. In this respect, claims that are oriented to range measurement devices are to be understood as examples only and shall not represent a restriction of the invention to ultrasound. The characteristics cited in the claims also may be combined with each other in a suitable way as a function of the respective application. In this connection one must keep in mind the fact that individual measures mutually support each other. In this connection, a threshold, e.g., which has been raised to a very large value, acts as an interruption of the listening window. On the other hand, it does not make sense to increase the transmitter power in order to detect echoes with a larger travel time if the listening window is not correspondingly expanded. It also is possible, instead of increasing the input threshold to an extreme level, to briefly interrupt the listening window. This measure comes into question if it is easier to control the listening window than to control the threshold.
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Kiemes Jochen
Lill Anton
Mathes Joachim
ITT Manufacturing Enterprises Inc.
Lewis J. Gordon
Pihulic Daniel T.
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