DE3620783A1 - Apparatus and method for suppressing interference signals in ultrasound pulse-echo apparatuses - Google Patents

Abstract

The invention describes an apparatus and a method for suppressing interference signals. In this case, the invention makes use of the knowledge that interference signals are always randomly distributed while target echoes, in contrast, always occur at the same position on the time axis. An evaluation method evaluates the received pulses on the basis of the frequency of occurrence on the time axis. The invention uses a microprocessor in the preferred embodiment.

Description

It is known that pulse-echo devices by evaluation the time between sending and receiving an Ultra sound signal, conclusions about the distance between Allow sensor and object.

It is also known to use such ultrasound devices as an approximation insert switch. Especially in the field of industry, security technology and surveillance technology, however Sensors required that are without prejudice to the highest environmental pollution work reliably.

In particular, harmonics led to the device operating frequency very often to disturbances, especially with noises, their Frequency spectrum contains extremely harmonics. (Key and Clinking tools, pneumatic hissing etc.).

P 36 07 336.9 describes a process for suppressing these disruptive influences. This invention takes advantage of the fact that interference pulses very rarely occur so regularly and so frequently that they occur in every measurement sequence. In this respect, a suitable circuit technology ensured that the sensor only responds when the pulse occurs in direct succession from n measurements.

With this measure, the interference immunity could be significantly increased be increased. Nevertheless, cases have occasionally been observed where there was interference.

While only the presence of a pulse within the measuring gate ( Fig. 2) and its regular presence was checked in the above invention, the invention described below goes much further.

According to the invention, the time axis is divided into sections, that of any period, i.e. any route correspond. Downstream to the receiver is fiction according to a preferably uP-controlled storage unit, the when a received pulse occurs, time it on organizes and stores accordingly.

Interference impulses will be distributed statistically on the time axis. Such sections are indicated in Fig. 1 (1, 5,). By contrast, useful echoes ( Fig. 1; 3) will always appear at approximately the same point on the time axis and thus result in an accumulation. By walking on the timeline, represented as Fig. 1; 2 u. 5, the direction of movement of objects can be detected.

Such as the immunity to interference and the ability to exercise Being able to increase directions is a multitude of evaluations algorithms conceivable. However, they are all classified according to statistics Work procedures such that the relative clustering in one Section is recognized. In this respect, there is a closeness to the invention P 36 07 336.9 probably always exist.

In the preferred solution, the pulses received by the receiver are assigned in time and counted as an event in the corresponding storage unit. After a sequence comprising n measurements, it is checked whether n pulses could be counted in one of the memory cells. If this is the case, the presence of an object is recognized and a corresponding process is triggered (alarm, for example). The relative increase can be detected in further variants. The program can change the useful pulses on the time axis by simply comparing them as a change in position of the object detect. In this respect, another very advantageous application of the invention can be seen in the fact that it is possible to distinguish moving from static targets. In this respect, technical connections are proposed according to the invention, which emit a switching impulse when the program simultaneously detects an object and determines that this object is in motion. Since it can be seen whether the object is approaching the sensor or is moving away, two switching pulses are possible. In this respect, the sensor can be used advantageously for securing vehicles and objects, furthermore, for example, as an automatic door opener.

Of course, a variety of shapes possible, whose commonality is that the incoming Impulses are assigned on the timeline and in their Frequency counted and statistically evaluated.

Claims (6)

1. Apparatus and method for the purpose of contactless object detection using the echo evaluation of short ultrasonic pulses according to the transit time method, characterized in that the incoming pulses are assigned to the transit time and stored so that the temporal distribution of the incoming pulses on the time axis is recognizable. 2. Apparatus and method according to claim 1, characterized in that the incoming impulses define any one assignable sector, its temporal extension corresponds to a corresponding route. 3. Apparatus and method according to at least one of the preceding Claims, characterized in that the evaluation in evaluation logic or a microprocessor, that individually occurring impulses are disregarded, In contrast, impulses that occur more frequently in one sector than Object can be recognized, with the necessary number of Measurement sequences can be freely selected. 4. Apparatus and method according to claim 3, characterized in that pulses are detected in a directly adjacent segment are taken into account in the evaluation. 5. Apparatus and method according to claims 1-4, characterized in that the change in the pulse accumulation on the time axis as Movement is recognized, this information being differentiable is in "approach" and "remove", taking any shortcuts possible are. 6. Apparatus and method according to at least one of the preceding Claims, characterized in that one or more If these are static and immobile, aim them from the evaluation circuit can be tolerated, but it is too a switching impulse comes when a change occurs.