Communications – electrical: acoustic wave systems and devices – Receiver circuitry
Reexamination Certificate
2000-09-29
2001-10-23
Lobo, Ian J. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Receiver circuitry
C367S137000, C340S870030
Reexamination Certificate
active
06307811
ABSTRACT:
FIELD OF AND BACKGROUND OF THE INVENTION
The invention relates to a method for the operation of several adjacent ultrasonic sensors which are synchronized. A first ultrasonic sensor emits first transmission pulses, a second ultrasonic sensor emits second transmission pulses, and a third ultrasonic sensor emits third transmission pulses.
A method of this type is described in European Patent Application EP 0 519 090 B1. In the operation of adjacent ultrasonic sensors, mutual influence can occur as a result of unfavorable reflections of the ultrasound in the area of the ultrasonic sensors. If the ultrasonic sensors do not transmit synchronously, the run-time measurement of an ultrasonic sensor is disturbed by the echo signal of the adjacent ultrasonic sensors. It is then possible that the echo signals will not be correctly assigned to the ultrasonic sensors which have emitted the corresponding transmission pulses. Therefore, errors occur in the run-time evaluation because the switching output is undefined. To solve this problem, it has been known in the past to operate the ultrasonic sensors serially so that the supply voltages of the ultrasonic sensors are cyclically switched on or off. The response time of the ultrasonic sensors in this technique is correspondingly lengthy. Additionally, the response time is further delayed through internal reset times. Another possibility for avoiding mutual influence, in the past, has included complying with mounting instructions, i.e., by specifying minimum distances for the installation of the ultrasonic sensors. The minimum distances, however, are very dependent on the respective application. For many potential applications, this method is not suitable, if a high degree of reliability is required. An additional solution for avoiding mutual influence includes connecting the adjacently operated ultrasonic sensors to each other through a common conductor via their release output. Through this arrangement, a parallel synchronization takes place. In this case, transmission pulses are emitted by all proximity switches at the same point in time so that the problem of correct temporal assignment of the echo signals to the appropriate ultrasonic sensors is avoided. Parallel synchronization of this type, however, has the drawback that the run-time evaluation does not contain a systematic evaluation algorithm. European Patent Application EP 0 519 090 B1 describes the connection of several ultrasonic sensors via their release outputs through a common conductor with automatic parallel or serial synchronization.
However, the sampling of rapid events, as is required, for example, for counting automobiles in the entrance to a parking garage, represents a problem which has not yet been solved.
OBJECTS OF THE INVENTION
Therefore, it is one object of the invention to provide an improved method for operating several adjacent ultrasonic sensors, such that the run-time measurement of an ultrasonic sensor can be reliably performed without disturbance of echo signals of adjacent ultrasonic sensors.
SUMMARY OF THE INVENTION
According to one formulation of the invention, this and other objects are achieved by a method for operating a plurality of adjacent ultrasonic sensors. The adjacent ultrasonic sensors are synchronized via a common conductor and the transmission pulses are emitted with changing time offset. The offset of the transmission pulses of the individual ultrasonic sensors is significantly smaller than the measuring cycle, i.e., smaller than the duration between two successive transmission pulses. As a result, a significantly higher measuring rate can be achieved than is possible with, for example, the known serial synchronization. Through the changing transmission pulse offset, the echo signals of adjacent ultrasonic sensors can be masked out through their constantly changing run-time.
The method is advantageously further developed with various added refinements. Accordingly, echo signals of several measurement cycles received by ultrasonic sensors, i.e., both their own echo signals as well as echo signals of others, are compared with each other and evaluated with respect to their position.
An especially advantageous further development of the method according to the invention is achieved by using the position of a single echo signal as a stability criterion to determine each ultrasonic sensor's sought echo signal. Therein, in successive measurement cycles, the position of the single echo signal always occurs within the same time window.
With respect to size and position, the echo signal is applied to the transmission pulse which precedes it. Only the transmission pulse's own echo signal always approximately retains the position, while as a result of the transmission pulse offset, which changes from measurement cycle to measurement cycle, the position of extrinsic echo signals changes. Thus, a simple and reliable criterion for the determination of the echo signal sought is given.
BRIEF DESCRIPTION OF THE DRAWING
The invention and further advantageous refinements of the invention according to the features of the dependent claims are explained in more detail below with the aid of a single drawing, which shows the clock signal, the transmission pulses and the received echo signals associated with the operation of three ultrasonic sensors.
REFERENCES:
patent: 4779240 (1988-10-01), Dorr
patent: 4974072 (1990-11-01), Hasegawa
patent: 5355130 (1994-10-01), Luber
patent: 3701521 A1 (1988-08-01), None
patent: 4003775 A1 (1991-08-01), None
patent: 0519090 A1 (1992-12-01), None
Patent Abstract of Japan, vol. 010, No. 080, Komatsu KK, Oct. 31, 1985, P-441 (JP 60 218087).
Lobo Ian J.
Siemens AG
Sughrue Mion Zinn Macpeak & Seas, PLLC
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