DE3739597A1 - Apparatus for protecting vehicles by means of ultrasound sensors - Google Patents

Abstract

The invention relates to an apparatus, in the case of which a vehicle can be protected with the aid of ultrasound sensors which operate on the pulse-echo principle. A solution is advantageously described which ignores parts located on the vehicle to the extent that it is possible to distinguish between static and dynamic targets. The invention achieves this object using special evaluation logic.

Description

In the automotive industry in particular, this is often the case have gone without rigid conveyor belts or assembly lines. Rather, z. B. the body shells by conveyor vehicles transported, which are usually guided, for example drive on an induction loop.

To these driverless transport systems (AGVs) against Un to secure cases and / or collisions, it is state of the art, to attach a shock-sensitive bar around the vehicles, which emits an impulse when it comes into contact with an object the vehicle is stopped. It is also common to use mirrors systems a rotating beam of light around the vehicle lead, also when the light beam is interrupted Hold command is triggered.

There are also various suggestions with help from ultrasonic pulse echo sensors to the AGV vehicle watch.

In German patent application P 37 01 521.4 from 1986 there is one Arrangement described in which the vehicle by a variety is secured by ultrasonic sensors, whereby ver Different measures are achieved that several vehicles are the same can be operated in time and in parallel.

Since it is common today that the AGV vehicles are consistently smaller are as the body-in-white transported on the vehicles the following problem arises:

The sensors are mandatory attached to the AGV vehicle. The bottom of the body basically creates an echo that must of course be ignored. On the sides of the drive This would be possible by adding echoes as objects  be identified if this is a certain minimum distance from the sensor. If it falls below this, the echo is not accepted. Because the echoes thrown back by the body consistently from close range, this would be a conceivable one Path.

Fig. 1 shows in principle how the problem presents itself. The AGV vehicle ( 2 ) drives on the generally very smooth and level floor ( 1 ). The body ( 3 ) is on the AGV vehicle.

The Fig. 2 schematically shows the plan view. It can be seen that the AGV vehicle ( 4 ) is significantly smaller than the raw body ( 5 ). The fork-shaped mounting recess on the bow of the vehicle is remarkable. A motor-driven axle etc. is installed in this recess from the front.

Here there is a need to recognize a worker who is in this zone, for example. Here it is itself understandably not allowed to hide targets at close range, because the location of a person can be in this close range can.

Here the invention described below shows a solution way that ignores the existing goals on the one hand, others on the other hand, the penetration of effective and reliable People and / or objects sensed in the shelter.

Fig. 3 shows the schematic course of a typical echo curve. At the beginning, the transmission pulse is clearly recognizable. Some echoes are also registered in the immediate vicinity. In the middle area, however, only isolated echoes are registered.

This echo train is according to the invention with a fast Digital / analog converter digitized and in the main memory Microcomputers filed.

Each new echo train is ver with the existing echo train like.

If there is no significant deviation, the ak current echo train and the existing echo train each a means value, which in turn is the new reference value is saved. Put simply, the sensor "learns" its surroundings know.

Deviations that lie outside a tolerance band are added by the program. Put simply, the route to be monitored, e.g. B. a distance of 2.5 m accordingly, divided into any number of individual sectors. In FIG. 3, 18 sectors are for example shown. The current echo amplitude is compared with the pre-stored value in each sector. If a difference occurs, the difference value is converted into an absolute number, ie it does not matter whether the deviation is positive or negative. A shadowed echo is therefore evaluated and recognized in exactly the same way as a new echo.

The program continues to add the absolute values in its own Register. The program checks the register after each operation. About if the value increases a certain, freely definable limit, Alarm triggered.

In order to have some protection against false alarms, it is itself understandably possible to only activate this alarm if it has appeared in a certain number in a row, for example 5 times.  

A possible circuit design is described in FIG. 4. 3 transducers ( 10 ) are attached at different angles so that they cover the widest possible area.

In the embodiment described, the sound transducers are connected both as transmitters and receivers. Of course it is possible to use separate transmitters and receivers. The transmitter ( 18 ) is excited by a short pulse, which usually consists of several vibrations. The transmit pulse reaches the transmitter capsule via a resistor and two anti-parallel diodes, which at the same time is the receiver capsule.

Any echoes pass through an amplifier ( 11 ) and a narrow-band filter together with a logarithmic amplifier and demodulator ( 12 ) to an RC combination ( 13 ), where the individual echo signals are added. A controlled A / D converter ( 14 ) detects the respective echo amplitude and transports this value via a microprocessor ( 16 ) to the main memory ( 17 ) of the microprocessor.

The processing of the data in the microprocessor takes place via the computing instruction which is stored in the ROM ( 15 ) of the microprocessor.

In a further embodiment of the invention, the learning event triggered when another detector reports that a Body has been placed on the AGV vehicle.

The "learning process" that begins immediately afterwards must be completed before the start of the AGV vehicle can be released. Various signal lines ( 18, 19, 20 ) are used for this purpose, which enable the sensor to communicate with the vehicle.

Claims (6)

1. Sensor for monitoring vehicles, robots and machines in the sense of a safety device, an ultrasound pulse being emitted with the aid of a sound transducer, impulses reflected by people being received again as an echo, characterized in that immediately or for a short time after the start of the transmission of the transmission pulse continuously and in a freely defined sequence, e.g. B. corresponding to a sound propagation time of 1 cm, the respective echo amplitude is queried by a fast A / D converter. The determined value is temporarily stored with the aid of a microprocessor, with the aim of comparing the stored values with the respective current values in the subsequent work cycle, with each deviation (positive or negative difference amount) being converted into an absolute value, this individual deviation is added in the course of the echo train, with the result that an alarm is triggered when a certain freely specified sum of deviations is exceeded, this only taking place when requested by a contact provided for this purpose. 2. Sensor according to claim 1, characterized in that the echo curve does not result from a single echo train, but rather as the mean of a large number of echo trains from Microprocessor is calculated and in a separate work memory is stored. 3. Sensor according to at least one of the preceding claims, characterized in that deviations only then make a report-relevant contribution to an alarm sum if them arithmetically from one of the previous measurements determined tolerance band fall out (min / max curve).   4. Sensor according to at least one of the preceding claims, characterized in that deviations from the target echo curve can only be added when the difference is one certain, freely defined size exceeds. 5. Sensor according to at least one of the preceding claims, characterized in that the redefinition of the comparison curve controlled from the outside whenever, for example, by Assembly steps a change in the curve is required. 6. Sensor according to at least one of the preceding claims, characterized in that the transmission rate is not constant The time grid is discontinuous and programmatic controlled with the aim of achieving a certain coding.