TRANSPORT SYSTEM FOR TRANSPORTING WORKPIECES AND METHOD FOR OPERATING A TRANSPORT SYSTEM OF THIS TYPE

Abstract

A transport system for transporting workpieces includes a plurality of objects disposed along a path of travel and a driverless transport vehicle having a workpiece holder and a personal protection sensor such as a laser scanner. The sensor has a transmitter for generating detection radiation and a receiver adapted to receive detection radiation generated by the transmitter and reflected from persons or objects located in a monitoring area that is monitored by the detection radiation. A control device steers the transport vehicle along the travel path so that it does not collide with the objects and triggers a safety measure if the personal protection sensor has detected a person in the monitoring area. The objects support a coating or cladding that absorbs detection radiation impinging thereon or reflects it in such a direction that it cannot reach the receiver. As a result, the objects become invisible to the personal protection sensor and cannot trigger any safety measures.

Claims

1. A transport system for transporting workpieces, comprising: a travel path, several objects arranged along the travel path, an unmanned transport vehicle comprising a workpiece holder and a personal protection sensor, wherein the personal protection sensor comprises a transmitter for generating detection radiation and a receiver configured to receive detection radiation generated by the transmitter and reflected from persons or objects located in a monitoring area monitored by the detection radiation, a control device configured to steer the transport vehicle along the travel path in such a way that it does not collide with the objects and to trigger a safety measure if the personal protection sensor has detected a person in the monitoring area, wherein at least one of the objects supports a coating or cladding that absorbs detection radiation impinging thereon or reflects it in such a direction that it cannot reach the receiver.

2. The transport system of claim 1, wherein the personal protection sensor is a laser scanner.

3. The transport system of claim 1, wherein the detection radiation generated by the personal protection sensor propagates in a plane arranged at least approximately parallel to a ground surface on which the transport vehicle moves, and wherein the objects support the coating or the cladding only in a height portion which is traversed by said plane.

4. The transport system of claim 1, wherein the cladding comprises a mirror-coated support.

5. The transport system of claim 4, wherein the support is selected from the group consisting of a plastic film, a cardboard, a metal plate and a glass plate.

6. The transport system of claim 5, wherein the support is oriented such that a plane of incidence of the detection radiation is oriented vertically.

7. The transport system of claim 6, wherein the support has a conical shape at least in sections.

8. A method for operating a transport system for transporting workpieces, wherein the method comprises the following steps: a) providing a transport system comprising a driverless transport vehicle having a workpiece holder and a personal protection sensor that comprises a transmitter configured to generate detection radiation and a receiver, wherein the receiver is configured to receive detection radiation generated by the transmitter and reflected from persons or objects located in a monitoring area that is monitored by the detection radiation, b) applying a coating or a cladding to objects disposed along a path of travel for the transport vehicle, wherein the coating or cladding absorb detection radiation incident thereon or reflecting it in such a direction that it cannot reach the receiver; c) steering the transport vehicle along the travel path so that it does not collide with the objects.

9. The method of claim 8, wherein the personal protection sensor is a laser scanner.

10. The method of claim 8, wherein the detection radiation generated by the personal protection sensor propagates in a plane arranged at least approximately parallel to a ground surface on which the transport vehicle moves, and wherein the objects support the coating or the cladding only in a height portion which is traversed by said plane.

11. The method of claim 8, wherein the cladding comprises a mirror-coated support.

12. The method of claim 11, wherein the support is selected from the group consisting of a plastic film, a cardboard, a metal plate and a glass plate.

13. The method of claim 12, wherein the support is oriented such that a plane of incidence of the detection radiation is oriented vertically.

14. The method of claim 13, wherein the support has a conical shape at least in sections.

15. A transport system for transporting workpieces, comprising: a travel path, several objects arranged along the travel path, an unmanned transport vehicle comprising a laser scanner, wherein the laser scanner comprises a transmitter for generating detection radiation and a receiver configured to receive detection radiation generated by the transmitter and reflected from persons or objects located in a monitoring area that is monitored by the detection radiation, a control device configured to trigger a safety measure if the laser sensor has detected a person in the monitoring area, wherein at least one of the objects supports a coating or cladding that absorbs detection radiation impinging thereon or reflects it in such a direction that it cannot reach the receiver.

16. The transport system of claim 51, wherein the detection radiation generated by the laser scanner propagates in a plane arranged at least approximately parallel to a ground surface on which the transport vehicle moves, and wherein the objects support the coating or the cladding only in a height portion which is traversed by said plane.

17. The transport system of claim 15, wherein the cladding comprises a mirror-coated support.

18. The transport system of claim 17, wherein the support is selected from the group consisting of a plastic film, a cardboard, a metal plate and a glass plate.

19. The transport system of claim 17, wherein the support is oriented such that a plane of incidence of the detection radiation is oriented vertically.

20. The transport system of claim 19, wherein the support has a conical shape at least in sections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Various features and advantages of the present invention may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings in which:

[0033] FIG. 1 a schematic top view of a transport vehicle according to the invention;

[0034] FIG. 2 a schematic side view of a personal protection sensor arranged in the transport vehicle according to FIG. 1;

[0035] FIG. 3 the transport vehicle shown in FIG. 1 approaching stationary objects;

[0036] FIG. 4 a top view, corresponding to FIG. 3, of a transport vehicle known from the prior art, in which the monitoring area is reduced in size as the vehicle approaches in order to avoid interference from objects;

[0037] FIGS. 5a and 5b representations corresponding to FIG. 1 of a transport vehicle approaching objects disguised according to the invention before and after the objects enter the monitoring area;

[0038] FIG. 6 a schematic side view of a front section of the transport vehicle and a clad object;

[0039] FIG. 7 a perspective view of a pillar-shaped object carrying a cladding according to the invention;

[0040] FIG. 8 a schematic cross-section through a paint booth in which a transport vehicle according to the invention conveys a vehicle body while being protected by a tunnel;

[0041] FIG. 9 a schematic cross-section through a dryer in which a transport vehicle according to the invention conveys a vehicle body while being protected by a tunnel;

[0042] FIG. 10 a schematic cross-section through a support structure on which a transport vehicle according to the invention deposits a vehicle body; and

[0043] FIG. 11 a schematic longitudinal section through an assembly section of a production line in which several transport vehicles according to the invention move under-neath an assembly platform which is elevated by means of covered supports.

DETAILED DESCRIPTION OF EMBODIMENTS

[0044] While the present invention is susceptible to embodiments in many different forms, there is described in detail herein, preferred embodiments of the invention with the understanding that the present disclosures are to be considered as exemplifications of the principles of the invention and are not intended to limit the broad aspects of the invention to the embodiments illustrated.

[0045] FIG. 1 shows a schematic top view of a transport vehicle according to the invention, which is designated 10. The contour of a vehicle body 12, which is supported by a workpiece holder 14 of the transport vehicle 10, is indicated by dashed lines. Two personal protection sensors 16 are arranged at the front end of the transport vehicle 10, the task of which is to detect persons located in a monitoring area 18 ahead and indicated by hatching in FIG. 1. For the sake of simplicity, it is assumed that the monitoring area 18 does not comprise a warning field, but consists only of a protective field. If one of the two personal protection sensors 16 detects a person in the monitoring area 18, a control device 20 of the transport vehicle 10 triggers a safety measure, which can be, for example, an emergency stop of the transport vehicle 10.

[0046] FIG. 2 shows an exemplary design of one of the personal protection sensors 16. The personal protection sensor 16 comprises a foot part 21 in which an evaluation unit 22 is arranged. The foot part 21 is connected to a housing 26 via a rotary bearing 24, which can be set in rotation about an axis of rotation 28 by means of a drive which is not shown. A transmitter 30 and a receiver 32 are arranged in the housing 26, which rotate along with the housing 26. The transmitter 30, which may be in the form of a laser diode, emits a light beam 34 during operation of the personal protection sensor 16, which eventually strikes an object 36. In the illustrated embodiment, infrared light with a wavelength of 905 nm is generated by the transmitter 30.

[0047] The light beam 34 is diffusely reflected at the surface of the object 36. A small portion of the reflected light returns to the receiver 32, where it is detected by a photodiode or other light-sensitive electronic component. In order to be able to locate the object 36, the travel time of the light beam 34 to the object 36 is determined, from which the distance to the object 36 can be derived. At the same time, the current rotational position of the housing 26 is detected. In this way, a distance profile of the environment is obtained within the plane swept by the light beam 34 during rotation about the axis of rotation 28.

[0048] In order to define the lateral limits of the monitoring area 18, only those distance data are taken into account where the housing 26 is in a certain angular range. In order to determine the length of the monitoring range 18, only those distances are considered which are smaller than the desired length. Thus, by combining the angular position and the distances considered, the shape and size of the monitoring area 18 can be freely determined within certain limits.

[0049] If the vehicle 10 approaches two objects 36, as illustrated in FIG. 3, they will eventually enter the monitoring area 18. Since the personal protection sensors 16 cannot detect whether the objects 36 are objects that are in their intended location and do not pose a danger to the transport vehicle 10 or people who happen to be in that location, the control device 20 must initiate an emergency stop or other safety measure as soon as the transport vehicle 10 has approached the objects 36 to the point that they enter the monitoring area 18.

[0050] In order to avoid such undesirable interruptions or delays in the travel of the transport vehicle 10, in conventional transport systems the monitoring area 18 is modified when the transport vehicle 10 approaches the objects 36, as illustrated in FIG. 4. To do this, the transport vehicle 10 first passes between the two objects 36 along the predetermined path of travel by way of a teach-in process not shown. When the personal protection sensors 16 detect the objects 36, the monitoring area 18 is automatically reduced so that the objects 36 are outside the monitoring area 18. In this way, the transport vehicle 10 can pass between the objects 36 without the personal protection sensors 16 triggering safety measures.

[0051] Thus, in the known transport systems, the objects 36 are visually detected by the personal protection sensors 16, but are computationally ignored because it is known after the teach-in process that stationary objects 36 are located at the depicted positions. Since the distance data to the objects 36 is available, it can also be used by the control device 20 for navigation to enable safe passage of the transport vehicle 10 between the objects 36.

[0052] However, the teach-in process described above is complex and often requires the involvement of software specialists. Furthermore, this approach only works if the transport vehicle 10 approaches the objects 36 exactly along the travel path on which the teach-in process was based. If, for example, the transport vehicle 10 approaches the objects 36 in a curved path, they may enter the monitoring area 18 and trigger a safety measure. A further disadvantage is that, at least temporarily, the monitoring area 18 must be reduced in size, as shown in the bottom right of FIG. 4. No persons can be detected in this area, which can lead to safety risks.

[0053] FIGS. 5a and 5b show a transport system according to the invention in representations based on FIGS. 3 and 4. The transport vehicle 10 with the personal protection sensors 16 is structurally exactly the same as in the prior art. However, the control device 20 need not have the capability to modify the monitoring area 18 by way of a teach-in process.

[0054] Modification of the monitoring area 18 is not required in the transport system according to the invention because the objects 36 wear coverings 38 that make the objects 36 invisible to the personal protection sensors 16.

[0055] FIG. 6 shows this principle in a schematic side view. Attached to the object 36 is a support 40 which carries a directionally reflective coating 42. The support 40 may, for example, be made of plastic, cardboard, metal or glass and carries a thin metal layer applied, for example, by vapor deposition. The substantially planar support 40 is attached to the object 36 such that the surface normal is not horizontal, but at an angle thereto. The plane of incidence, which is spanned by the direction of incidence of the incident light beam 34 and the surface normal, is thus vertically oriented and extends in the plane of the paper. A light beam 34 of a personal protection sensor 16 impinging on the coating 42 is therefore not reflected back into itself, but deflected upwards, whereby it can no longer reach the receiver 32 of the personal protection sensor 16.

[0056] Thus, due to the shroud 38, the object 36 is invisible to the personal protection scanner 16. Since the receiver 32 of the personal protection sensor 16 does not receive any reflected light when the light beam 34 is in the position shown, the personal protection sensor 16 assumes that the light beam 34 has never encountered an obstacle.

[0057] If an object 36 disguised in this way enters the monitoring range 18 of the personal protection sensors 16, as shown in FIG. 5b, this merely means that persons behind the objects 36 cannot be detected. This is no different in the prior art and does not pose a problem, since in such a case the person is protected by the object 36. In contrast to the prior art, however, the monitoring area 18 remains completely unchanged in its size and thus does not have to be computationally modified in its dimensions. The previously necessary time-consuming learning processes, which can usually only be mastered with the help of software experts, can be omitted. All that is required is to provide the objects 36 that are located in the vicinity of the possible travel paths of the transport vehicle with suitable coverings 38.

[0058] Preferably, the lateral vertical edges of the support 40 are rounded so that interference effects at the edges do not lead to detection of the support 40.

[0059] In many cases, the objects 36 are vertically extending legs, pillars or columns. FIG. 7 shows such an object 36 with a cladding 38 supported thereby in a schematic perspective view. Here, the cladding 38 comprises a cardboard support 40 coated with an aluminum foil and having the shape of a conical shell section. The cladding 38 is provided as a curved band and is simply wrapped around the object 36, joined at the ends and secured at the desired height. In this manner, the entire object 36 has been rendered invisible to the personal security scanners by simple mechanical means.

[0060] FIGS. 8 to 11 show possible application examples for the transport system according to the invention.

[0061] FIG. 8 shows a cross-section of a paint booth 43. In this application, the transport vehicle 10 with a personal protection sensor 16 arranged at the front is located in a tunnel 44 which protects the transport vehicle 10 from overspray. Overspray is defined as paint particles that are created by atomization and have not settled on the surface to be coated.

[0062] In the illustrated embodiment example, rotary atomizers are used for atomization, which are guided by painting robots 46 over the vehicle bodies 12 conveyed by the transport vehicle 10.

[0063] The interior surfaces of the tunnel 44 have reflective coatings or wear reflective facings to make them invisible to the personal protection sensor 16.

[0064] FIG. 9 shows a schematic cross-section of a transport vehicle 10 which is also guided in a tunnel 44. However, the tunnel 44 is not located in a paint booth 43 here, but in a dryer 46. The tunnel 44 protects the transport vehicle 10 from the heat prevailing in the dryer 46. In this embodiment, the personal protection sensor 16 emits microwaves. The inner wall of the tunnel 44 is coated with a Dallenbach absorber 47, which reflects the incident microwaves in a phase-shifted manner, resulting in suppression of the reflection due to destructive interference.

[0065] FIG. 10 shows a transport vehicle 10 transferring a vehicle body 12 to a support structure 48 on which the vehicle body 12 is placed. The legs of the support structure 48, between which the transport vehicle 10 must pass, also represent objects which can be made invisible to the personal protection sensor 16 in the manner according to the invention.

[0066] In this embodiment, the personal protection sensor 16 of the transport vehicle 16 emits radar radiation. The legs of the support structure 48 carry cylindrical claddings 38 designed as foam absorbers, which absorb the incident radar radiation, making the legs invisible to the personal protection sensor 16.

[0067] FIG. 11 shows several transport vehicles 10 moving through an assembly section 50 of a production line. The robots 52 used for assembly are located on a raised assembly platform 54, which is elevated with respect to a moving floor for the vehicles 10 by means of supports 56. The supports 56 represent objects which, in the manner according to the invention, must be made invisible to the personal protection sensors 16, since they are located in the monitoring area 18 of the personal protection sensors 16 indicated by a dashed line. For this purpose, the supports carry directionally reflective coverings 38, as shown in FIG. 7.

[0068] While in the foregoing there has been set forth preferred embodiments of the invention, it is to be understood that the present invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. While specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the characteristics of the invention and the scope of protection is only limited by the scope of the accompanying claims.