DE102021115198B4 - security scanner - Google Patents

Abstract

Use of a security scanner (10) for protecting the surroundings of a vehicle of a driverless transport system, with- a light transmitter (14) for emitting transmitted light beams (16) in the form of light pulses, - a light deflection unit (18) for periodically deflecting the transmitted light beams, (16) which cover a protective field (22) to be monitored, - a receiver (30) for providing received signals depending on the light reflected from objects (24, 36) present in the field of view (23) of the scanner (10), - an evaluation unit (32) for evaluating the received signals, the location of the reflection being able to be determined via the propagation time of the reflected light pulses and an angle at which a reflected light pulse was emitted, and the evaluation unit (32) being further developed to provide a safety signal if an object (24 ) In the protected area (22) is detected, characterized in that the protective field (22), at least one Angle section area has the shape of a right circular cone and that an opening angle (φ) of the circular cone (50) is in the range from 176° to 179°, with an axis of rotation (17) of the light deflection unit being aligned vertically and the tip of the circular cone (50) facing the ground (60) and at least part of the angular section area is in the direction of travel and the security scanner (10) is mounted close to the ground at a height of between 10 cm and less than 20 cm.

Description

The invention relates to a safety scanner for protecting the surroundings of a vehicle of a driverless transport system, with a light transmitter for emitting transmitted light beams in the form of light pulses, a light deflection unit for periodically deflecting the transmitted light beams, which cover a protective field to be monitored, a receiver for providing received signals as a function of light reflected from objects present in the field of vision of the scanner and an evaluation unit for evaluating the received signals, the location of the reflection being able to be determined via the propagation time of the reflected light pulses and an angle at which a reflected light pulse was emitted, and the evaluation unit being further developed to provide a safety signal when an object is detected in the protected area.

Such a security scanner scans a flat surface running parallel to the roadway with its light beam, so that objects within a defined protection area can be detected with spatial resolution within the field of vision. The flat scanning surface is generated by a deflection mirror at exactly 45° in order to deflect the transmitted light beams by exactly 90°. Deviations from this would lead to a scan cone and thus to transmitted light beams that are not in one plane, but would be directed downwards towards the ground or upwards towards the sky.

When using such security scanners on the vehicle of a driverless transport system, when used horizontally, the task is usually to be able to detect a person lying on the ground. This means that the scanner must be mounted low in order to be able to measure just above the ground in the entire protective field. This 'near' is normatively defined in such a way that an object (e.g. a person lying down) with a height of 200 mm must be detected in the protective field. There is also an additional function that is used a lot in this application. The scan data is also used for vehicle navigation. Spatial contours or so-called reflector marks should also be detected at a much greater distance than the protective field range, i.e. beyond the protective field (typical values are: 20 m to 40 m navigation range versus 3 m to 5 m protective field range). Here, too, it must be ensured that the scanner does not hit the ground in any scanning direction, but measures parallel to it or at least the 'viewing direction' is only slightly inclined upwards.

Furthermore, an exact alignment of the scanning plane parallel to the roadway is important, otherwise if the plane tilts, e.g. due to pitching movements of the vehicle while driving, either the roadway would be detected, which could result in unnecessary shutdown, or the transmitted light beams are directed "into the sky". , so that objects could be missed.

For these reasons, the applicant specifies a so-called 'scan field flatness' in its data sheets for such security scanners, which states how good 'or 'even' the scan field plane is. The deviations from the ideal, horizontal scan plane can also be described with the following parameters: opening angle/height of a scan cone (an ideal plane would have an opening angle of 180° or a height of the scan cone of 0 mm, i.e. it would not be a cone at all) and tilting of the Scan plane/scan cone to the front or to the side.

The scan plane can also be tilted due to adjustment tolerances, which causes the same problems. It is therefore necessary to operate a high adjustment effort. The demands on the opto-mechanics are very high in order to achieve an optimal scan level. This is particularly problematic in mobile applications in which the scanner performs the tilting and tipping movements of the vehicle. For example, in order to still look over the ground at a distance of 20 m at a mounting height of 200 mm (for the detection of navigation marks), an accuracy of 0.03° is required for the inclination angle of the scanning mirror. However, the same requirement must also be placed on the alignment when mounting the device in the receptacle on the driverless vehicle.

From Choi, H., Kim, W.C.: Optical system design for light detection and ranging sensor with an ultra-wide field-of-view using a micro actuator. Microsystems Technologies. 2020. Vol. 26, no. 11, pp. 3561-3567. DOI: 10.1007/300542-020-04997-1 discloses a lidar scanner in which a so-called fish-eye optic is used, but the scanning area continues to lie in a known manner in a horizontal plane.

From the DE 10 2019 125 684 A1 a lidar scanner is known in which the transmitter and receiver and the entire optics rotate and the light beam can also be deflected transversely to the scanning direction in the transmission path by means of a micromechanical element.

Proceeding from this state of the art, it is the object of the invention to provide an improved possibility of using a security scanner with which the problems mentioned are solved or at least reduced.

This object is achieved by using a security scanner with the features of claim 1.

• - einen Lichtsender zur Aussendung von Sendelichtstrahlen in Form von Lichtimpulsen,
• - eine Lichtablenkeinheit zur periodischen Ablenkung der Sendelichtstrahlen, die ein zu überwachendes Schutzfeld überstreichen,
• - einen Empfänger zur Bereitstellung von Empfangssignalen in Abhängigkeit von an im Sichtbereich des Scanners vorhandenen Objekten remittiertem Licht und
• - eine Auswerteeinheit zur Auswertung der Empfangssignale, wobei über die Laufzeit der reflektierten Lichtimpulse und einem Winkel, in den ein reflektierter Lichtimpuls ausgesandt wurde, der Ort der Reflexion bestimmbar ist und wobei die Auswerteeinheit weiter ausgebildet ist zur Bereitstellung eines Sicherheitssignals, wenn ein Objekt im Schutzbereich detektiert wird.

In the use according to the invention, the safety scanner includes for securing the surroundings of a vehicle of a driverless transport system

• - a light transmitter for emitting transmitted light beams in the form of light pulses,
• - a light deflection unit for the periodic deflection of the transmitted light beams that sweep over a protective field to be monitored,
• - A receiver for providing received signals as a function of light remitted to objects present in the field of view of the scanner and
• - an evaluation unit for evaluating the received signals, the location of the reflection being determinable via the propagation time of the reflected light pulses and an angle at which a reflected light pulse was emitted, and the evaluation unit being further developed to provide a safety signal when an object is in the protected area is detected.

Provision is made for the protective field to have the envelope shape of a right circular cone, at least over a section of an angle, and for the opening angle of the circular cone to be in the range from 176° to 179°. In this case, an axis of rotation of the light deflection unit is aligned vertically and the tip of the circular cone points to the ground. At least part of the angular section area is in the direction of travel and the safety scanner (10) is mounted close to the ground at a height of between 10 cm and less than 20 cm.

The invention therefore breaks with the previous view that a scanning area should be as flat as possible, ie the opening angle should be 180° as much as possible and tilting of the plane should be avoided as far as possible. This breaks with the dogma that security scanners open up a scanning plane that is as perfect as possible. According to the invention, a real scan cone with an opening angle of less than 180° is now deliberately provided.

Such a safety scanner should be mounted relatively low and the scanning cone should open upwards so that the transmitted light beams of the safety scanner look slightly obliquely upwards in all directions. In this way, low objects, such as people lying down, are still recognized, but measurement data at a greater distance (to the navigation) are also guaranteed. In addition, the user has it easier during assembly. The scanner does not have to be aligned to fractions of a degree in terms of tilt in order to look as parallel as possible to the ground.

For example, if the devices are mounted low with a transmitted light beam exiting approx. 100 mm above the floor, the aperture cone pointing upwards ensures that measurements are taken at a greater distance from the floor as the distance increases. With a cone height of 50 mm (related to the maximum protective field range) and a 100 mm height of the beam exit, there is still a 'safe' detection height of max. 150 mm within the protective field range. There is even a safety margin of 50 mm to compensate for tilting. Therefore, no exceptionally small tolerances have to be observed during assembly. Tilting is tolerable to a certain degree. There are a total of three degrees of freedom with which a deviation from the ideal scan plane can be described: tilting to the horizontal in the x and y directions, and the height or opening angle of the scan cone.

With these measures, which in retrospect appear quite simple, a very old problem in the field of security scanners is solved.

In this way, lying people are still detected, but measurement data is also guaranteed at a greater distance. In addition, the user has it easier during assembly, because the scanner does not have to be aligned to a fraction of a degree with regard to tilting in order to look as parallel as possible to the ground.

wobei Smax die maximale Schutzfeldreichweite ist.In a development of the invention, the opening angle is determined by the protective field range in such a way that the cone height is 50 mm in relation to the maximum protective field range. The opening angle ϕ then satisfies the equation $\phi =180°-2\ast \text{arctan}\left(\frac{0.05m}{Smax\left[m\right]}\right)$

where Smax is the maximum protective field range.

The angular section range is advantageously at least 270°.

In a known and thus proven manner, the light deflection unit is formed by a rotating mirror, the flat mirror surface of which is arranged at a different angle than 45° to the axis of rotation.

Alternatively, it is also possible for the light deflection unit to be formed by a rotating measuring unit that carries the light emitter and the receiver.

• 1 einen schematischen Aufbau eines erfindungsgemäßen Sicherheitsscanners;
• 2 eine schematische Darstellung eines Sicherheitsscanners nach dem Stand der Technik mit einem schematisch dargestellten Schutzfeld;
• 3 eine schematische Darstellung wie in 2 eines erfindungsgemäßen Sicherheitsscanners;
• 4 eine schematische Darstellung ähnlich wie 3 mit einer Ausführungsform des erfindungsgemäßen Sicherheitsscanners mit Verkippung;
• 5 eine schematische Darstellung wie 4 in der Anwendung mit zu detektierendem Objekt.

The invention is explained in detail below using an exemplary embodiment with reference to the drawing. Show in the drawing:

• 1 a schematic structure of a security scanner according to the invention;
• 2 a schematic representation of a security scanner according to the prior art with a protective field shown schematically;
• 3 a schematic representation as in 2 a security scanner according to the invention;
• 4 a schematic representation similar to 3 with an embodiment of the security scanner according to the invention with tilting;
• 5 a schematic representation of how 4 in the application with an object to be detected.

In 1 an exemplary embodiment of an optoelectronic security scanner 10 according to the invention is shown. This works according to the known light scanner operation, in which a light transmitter 14 transmits light beams 16 in the form of light pulses. The transmitted light beams 16 are emitted via a deflection unit 18 rotating about an axis of rotation 17 by means of a mirror 20 .

If an object 24 is in a field of view 23 of the safety laser scanner 12 , the transmitted light beams 16 are reflected on this object 24 . The reflections of the transmitted light beams 16 are fed as received light beams 26 on the same path via the deflection unit 18 and receiving optics 28 to a light receiver 30 and converted there into received signals.

The received signals are fed to an evaluation unit 32 for evaluating the received signals and for outputting a safety signal at a safety output 34-1 and possible other signals, which are used for example for navigation, at a second output 34-2. The pulse propagation time of the transmitted light pulses is recorded in the evaluation unit 32, which also controls the light transmitter 14, and the distance between the safety laser scanner 12 and the object 24 is determined therefrom. In addition, the rotary position of the deflection unit 18 at the point in time at which the light is emitted is detected via an encoder 19, so that overall the location of the object 24 is known from the knowledge of the deflection angle and the distance from the object 24. In this way it can be checked whether the object 24 is located in a specific protected area 22 defined within the field of view 23 . The protective area 22 with a protective field range Smax is also called a protective field. By scanning the transmitted light beams 16 over the protected area 22, the protected area 22 is monitored to determine whether objects 24 are located in the protected area 22 or not. Depending on whether an object 24 is located in the protection area 22, the safety signal can be output at the safety output 34-1. In the same way, other reflections from the field of view 23, for example from stationary reflectors 36, are detected in a spatially resolved manner and evaluated, for example, for navigation. Signals from such reflections are output at the second output 34-2.

The safety scanner according to the invention is used to protect the surroundings of a vehicle 40 of a driverless transport system. Such a vehicle 40 is in 2 shown, but there with a security scanner 100 according to the prior art. This is because it has a protective field 122 , which is essentially flat and is formed by the transmitted light beams 116 circulating periodically in a horizontal line to the floor 60 about an axis of rotation 117 .

According to the invention, it is now provided that the transmitted light beams 16 do not run exactly horizontally, but are deflected in the deflection unit, for example by an angle that is not equal to 90°, so that a scanning cone 50 is formed with a jacket shape in the form of a right circular cone, such as this in 3 is shown. Since a scanner generally has a scanning area that covers less than 360°, such a scanning cone 50 is formed at least over an angular section area that is preferably at least 270°. According to the invention, the protective field 22 therefore has the shape of a section of a scan cone 50. According to the invention, the opening angle of the scan cone 50 is in the range of 176° to 179°. The tip of the scan cone 50 points to the bottom 60, as is shown, for example, in 3 and 4 is shown, whereby the deflection of the transmitted light beams 16 by the deflection unit 18 must be adapted depending on how the safety scanner 10 is mounted on the vehicle 40, so that the scanning cone 50 is open away from the floor 60, i.e. its cone tip points to the floor 60 and thus the opening angle away from floor 60. The 3 and 4 show two exemplary embodiments in which the method of attachment to the vehicle 40 is rotated by 180°.

The security scanner 10 according to the invention should be mounted relatively low, because the transmitted light beams of the security scanner 10 look slightly obliquely upwards in all directions. Since there is a safety norm that stipulates that objects with a height of 20 mm above the floor 60 must be recognized, it has been found that, for example, mounting on the vehicle 40 in which the tip of the scan cone is approximately 100 mm above the floor 60 is advantageous. Such minimal objects will then still be detected even at a greater distance. In particular, it has been found that it is particularly preferred if the opening angle is determined by the protective field range Smax, specifically in such a way that the cone height h is 50 mm in relation to the maximum protective field range. The opening angle ϕ then satisfies the equation $\phi =180°-2\ast \text{arctan}\left(\frac{0.05m}{Smax\left[m\right]}\right).$

When mounted with the tip of the scanning cone 100 mm above the floor, there is still a 'safe' detection height of max. 150 mm within the protective field range. There is even a safety margin of 50 mm to compensate for tilting. this is in 5 clarifies, in which a tilting of the safety scanner 10 and thus of the scanning cone 50 is shown and it becomes clear that on the one hand objects 24 can still be detected and on the other hand objects located outside of the protective area 22, i.e. objects that are further away than the protective field range Smax, such as Navigation markers in the form of reflectors 36 can also be recognized because the transmitted light beams 16 do not end in the ground 60.

Claims (5)

Use of a security scanner (10) for protecting the surroundings of a vehicle of a driverless transport system, with - a light transmitter (14) for emitting transmitted light beams (16) in the form of light pulses, - a light deflection unit (18) for periodically deflecting the transmitted light beams, (16) which sweep over a protective field (22) to be monitored, - a receiver (30) for providing received signals depending on light reflected from objects (24, 36) present in the field of view (23) of the scanner (10), - an evaluation unit (32) for evaluating the received signals, the location of the reflection being able to be determined via the propagation time of the reflected light pulses and an angle at which a reflected light pulse was emitted, and the evaluation unit (32) being further developed to provide a safety signal if an object (24 ) In the protected area (22) is detected, characterized in that the protective field (22), at least over an angular section area has the envelope shape of a right circular cone and that an opening angle (φ) of the circular cone (50) is in the range from 176° to 179°, with an axis of rotation (17) of the light deflection unit being oriented vertically and the tip of the circular cone (50) at the Ground (60) and at least part of the angular section area is in the direction of travel and wherein the security scanner (10) is mounted close to the ground at a height of between 10 cm and less than 20 cm. using a security scanner claim 1 , characterized in that the aperture angle φ satisfies the equation φ = 180° - 2 ∗ arctan $\left(\frac{0.05}{Smax\left[m\right]}\right),$

where Smax is the maximum protective field range. using a security scanner claim 1 or 2 , characterized in that the angular section range is at least 270°. Use of a security scanner according to one of the preceding claims, characterized in that the light deflection unit is formed by a rotating mirror, the flat mirror surface of which is arranged at a different angle than 45° to the axis of rotation. Use of a security scanner according to any of the preceding Claims 1 or 2 , characterized in that the light deflection unit is formed by a rotating measuring unit which carries the light transmitter and the receiver.

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