Communications: electrical – Vehicle parking indicators
Reexamination Certificate
1999-09-02
2001-04-10
Hofsass, Jeffery A. (Department: 2736)
Communications: electrical
Vehicle parking indicators
C340S435000, C340S436000, C340S539230, C250S349000
Reexamination Certificate
active
06215415
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a parking aid for a motor vehicle, which measures the distance between an object and the motor vehicle in a contactless manner and has a plurality of sensors which are arranged on the motor vehicle, each sensor emitting a signal and receiving the signal reflected from an object located in the direction of the beam, an evaluation device connected to the sensors determining the distance between the object and the motor vehicle from the signals received.
BACKGROUND OF THE INVENTION
To make the motor vehicle easier to drive and avoid collisions with cars or other objects in the way, it is known to provide sensors at the front and/or rear of the motor vehicle, these sensors transmitting ultrasonic or radar signals, for example, and receiving the signals reflected from the obstacle. In this arrangement, the distance between the sensor arranged on the motor vehicle and the obstacle is determined from the propagation time of the signal from the sensor to the obstacle and back again.
A collision warning system of the same generic type is known from the as yet unpublished patent application DE 197 11 467.9, in which contactless distance measurement between an obstacle and a motor vehicle is carried out with a plurality of sensors. In this arrangement, one sensor transmits a sensor signal in all cases, and this signal is reflected by an object situated in the sensor beam. The reflected signal is received by all the sensors. To enable imaginary objects reliably to be excluded, all possible positions of the object relative to the motor vehicle are determined from the propagation times of three sensors. Only those positions of the object are recognized as real which are detected by all three sensors.
Particularly for propagation-time measurement, referred to as indirect, in which the signal is transmitted by one sensor and the reflected signal is received by another sensor, it is necessary that the sensors should be synchronized with the aid of an evaluation device, ensuring that each sensor is ready to receive when the signal reflected by the obstacle reaches it. Here, the evaluation device controls the time sequence in such a way that one sensor transmits a signal and all the sensors are then simultaneously switched to the receptive condition.
Particularly when using radar sensors, the electrical synchronization of the sensors is very complex, if not impossible, due to the rapid signal propagation times of the transmitted and reflected sensor signal, since the propagation times of the control signals on the connecting lines between the evaluation device and the sensor are always slower than the sensor signals, which propagate approximately at the speed of light.
Thus, there is a need to specify an arrangement for contactless measurement of the distance between an object and a motor vehicle, in which the outlay for electrically synchronizing the sensors is reduced and which nevertheless allows reliable detection of the actual object for accurate measurement of the distance.
Other needs will become apparent upon a further reading of the following detailed description taken in conjunction with the drawings.
SUMMARY OF THE INVENTION
In one form of the invention, the aforementioned needs are fulfilled by three sensors arranged directly next to one another to provide approximate coverage of the same detection area, the main beam of each sensor having approximately the same beam angle.
The invention has the advantage that the arrangement of the sensors at approximately the same location makes it possible to dispense completely with indirect propagation time measurements. This eliminates complex electronic synchronization in relation to the propagation times. The actual object is determined solely by direct measurements of the propagation time from the sensor to the object and back to the same sensor.
To increase reliability in the detection of stationary objects when using radar sensors, the evaluation device activates all sensors simultaneously to transmit the sensor signal and to receive the reflected signal, it being possible for each sensor to be activated with a different frequency for the transmission of the sensor signal. It is not necessary to select the sensor with regard to the measurement task. The signal received is differentiated in terms of the carrier frequency.
In a development in which it is possible to reduce the outlay for distinguishing between the signals received, the evaluation unit activates all the sensors in succession to transmit the sensor signal. Here, each sensor is activated with the same frequency.
A variant of simple construction is achieved if the sensors are arranged at a distance from the outer contour of the motor vehicle, with the result that the detection range of each sensor covers the entire outer contour extending in the direction of the beam of the sensor and the adjoining space. Setting the sensors back behind the bumper avoids gaps in measurement in the area close to the sensor since the measuring range of the sensors is fully effective, even in the area close to the bumper. The arrangement proposed makes it possible to achieve a greater degree of redundancy in the detection ranges of the individual transducers in the particularly critical close-up zone, thereby allowing better quality in the calculation of the distance of the object.
In one configuration, the evaluation device determines the propagation time between the transmission of the sensor signal of a sensor and the reception of the reflected sensor signal by the same sensor and from the propagation times of the three sensors determined in this way, determines the position and distance of the motor vehicle from the object.
A compact device is achieved if the evaluation device forms a structural unit with one sensor. However, the evaluation unit can also be an electronic system that would be present in the motor vehicle in any case.
The device according to the invention is particularly suitable for radar sensors, where the problems with propagation-time synchronization are particularly severe.
REFERENCES:
patent: 4467313 (1984-08-01), Yohsino et al.
patent: 4490716 (1984-12-01), Tsuda et al.
patent: 4528563 (1985-07-01), Takeuchi
patent: 5396070 (1995-03-01), Lee
patent: 5574426 (1996-11-01), Shisgal et al.
patent: 5754123 (1998-05-01), Nashif et al.
patent: 5940011 (1999-08-01), Agravante et al.
patent: 5999092 (1998-08-01), Smith et al.
patent: 3244358 (1984-06-01), None
patent: 3420004 (1985-12-01), None
patent: 4023538 (1992-01-01), None
patent: 197 11 467 (1997-10-01), None
Hofsass Jeffery A.
Mannesmann VDO AG
Mayer Brown & Platt
Nguyen Phung
LandOfFree
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