A DEVICE AND A METHOD FOR DETERMINING ROTATIONAL POSITION OF A ROTATING SHAFT

Abstract

The invention relates to a position sensing device (10) for determining a rotational position of a rotating shaft (12) of a remotely operated vehicle of a system (1) for storing and retrieving goods holders, said rotating shaft (12) being a wheel axle of the remotely operated vehicle. The device comprises a reflector (14) attached to the rotating shaft so as to rotate simultaneously with said shaft (12), a distance measuring unit (16) arranged to emit a beam (18) of radiation towards a portion of the reflector (14), wherein the emitted beam is parallel to the rotating shaft, as the shaft (12) and the reflector (14) are rotated with respect to the distance measuring unit (16), and to receive a return beam (20) generated when the emitted beam (18) is reflected by the portion of the reflector (14). The distance measuring unit (16) is configured to output a signal based on a distance of said beam to said portion of the reflector (14), wherein a rotational position of the rotating shaft (12) is determined based on the output signal of measured distance from said distance measuring unit (16). The invention further relates to a method for determining rotational position of a rotating shaft (12).

Claims

1. A position sensing device (10) for determining a rotational position of a rotating shaft (12) of a remotely operated vehicle of a system (1) for storing and retrieving goods holders, said rotating shaft (12) being a wheel axle of the remotely operated vehicle, wherein said position sensing device (10) comprises: a reflector (14) attached to the rotating shaft (12) so as to rotate simultaneously with said shaft (12), a distance measuring unit (16) arranged to emit a beam (18) of radiation towards a portion of the reflector (14), as the shaft (12) and reflector (14) are rotated with respect to the distance measuring unit (16), wherein the emitted beam (18) is parallel to the rotating shaft (12), and to receive a return beam (20) generated when the emitted beam (18) is reflected by the portion of the reflector (14), the distance measuring unit (16) being configured to output a signal based on a distance of said beam (18) to said portion of the reflector (14), a rotational position of the rotating shaft (12) is determined based on the output signal of measured distance from said distance measuring unit (16), wherein said portion of the reflector (14) has an irregular surface, and wherein reflector (14) is integrally formed with the rotating shaft (12) and arranged at an end of the rotating shaft (12) and said reflector (14) is substantially cylindrically-shaped and doesn't radially extend beyond outer surface of the rotating shaft (12).

2. The position sensing device (10) of claim 1, wherein said portion of the reflector (14) has a wavy and/or a stepped surface.

3. The position sensing device (10) of claim 1, wherein a surface of said reflector (14) faces the distance measuring unit (16).

4. The position sensing device (10) of claim 1, wherein the distance measuring unit (16) is at least partially enclosed by a housing (22).

5. The position sensing device (10) of claim 4, wherein the reflector (14) is at least partially enclosed by the housing (22).

6. The position sensing device (10) of claim 1, wherein the reflector (14) projects from the circumferential surface of the rotating shaft (12) and extends around the circumferential surface of the rotating shaft (12) so as to rotate simultaneously with the shaft (12).

7. The position sensing device (10) of claim 1, wherein the emitted beam (18) is a light beam.

8. The position sensing device (10) of claim 7, wherein said light beam is an IR light beam.

9. The position sensing device (10) of claim 1, wherein the emitted beam is an ultrasonic beam.

10. The position sensing device (10) of claim 1, wherein the reflector (14) is disc-shaped and comprises a radially and/or a circumferentially extending cut-out (25).

11. The position sensing device (10) of claim 1, wherein the reflector (14) is helix-shaped.

12. The position sensing device (10) of claim 11, wherein the helix of the helix-shaped reflector (14) is circular.

13. The position sensing device (10) of claim 11, wherein the helix is right-handed.

14. The position sensing device (10) of claim 1, wherein the distance measuring unit (16) is arranged to emit a further beam of radiation towards a portion of the reflector (14), as the shaft (12) and reflector (14) are rotated with respect to the distance measuring unit (16), and to receive a further return beam (20) generated when the emitted further beam (18) is reflected by the portion of the reflector (14).

15. A method for determining rotational position of a rotating shaft (12) of a remotely operated vehicle of a system (1) for storing and retrieving goods holders, wherein a reflector (14) is attached to the rotating shaft (12), the reflector (14) rotating simultaneously with said shaft (12) and said rotating shaft (12) being a wheel axle of the remotely operated vehicle, said method comprising: providing a distance measuring unit (16) for measuring a distance to said reflector (14) by emitting a beam (18) of radiation towards a portion of the reflector (14) as the shaft (12) and reflector (14) are rotated with respect to the distance measuring unit (16), the emitted beam being parallel to the rotating shaft, wherein said portion of the reflector (14) has an irregular surface, and wherein the reflector (14) is integrally formed with the rotating shaft (12) and arranged at an end of the rotating shaft (12) and said reflector (14) is substantially cylindrically-shaped and doesn't radially extend beyond outer surface of the rotating shaft (12) and by receiving a return beam (20) generated when the emitted beam (18) is reflected by the portion of the reflector (14), the distance measuring unit (16) being configured to output a signal based on a distance of said beam to said portion of the reflector (14), and determining a rotational position of the rotating shaft (12) based on the output signal of measured distance of said distance measuring unit (16).

16-19. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Following drawings are appended to facilitate the understanding of the invention. The drawings show embodiments of the invention, which will now be described by way of example only, where:

[0043] FIG. 1 is a perspective view of a framework structure of a prior art automated storage and retrieval system.

[0044] FIG. 2 is a perspective view of a prior art container handling vehicle/remotely operated vehicle having a centrally arranged cavity for carrying storage containers therein.

[0045] FIG. 3a is a perspective view of a prior art container handling vehicle/remotely operated vehicle having a cantilever for carrying storage containers underneath.

[0046] FIG. 3b is a perspective view, seen from below, of a prior art container handling vehicle/remotely operated vehicle having an internally arranged cavity for carrying storage containers therein.

[0047] FIG. 4a is a perspective view of a first embodiment of a position sensing device for determining a rotational position of a rotating shaft when fixedly attached to said shaft.

[0048] FIG. 4b is a perspective view of the arrangement of FIG. 4a, where the position sensing device and the shaft have rotated 180 degrees relative to the position shown in FIG. 4a.

[0049] FIG. 5 is a perspective view of a second embodiment of a position sensing device for determining rotational position of a rotating shaft.

[0050] FIG. 6 is a cross-sectional view a third embodiment of a position sensing device for determining rotational position of a rotating shaft.

DETAILED DESCRIPTION OF THE INVENTION

[0051] In the following, embodiments of the invention will be discussed in more detail with reference to the appended drawings. It should be understood, however, that the drawings are not intended to limit the invention to the subject-matter depicted in the drawings.

[0052] The framework structure 100 of the automated storage and retrieval system 1 is constructed in accordance with the prior art framework structure 100 described above in connection with FIGS. 1-3b, i.e. a number of upright members 102, wherein the framework structure 100 also comprises a first, upper rail system 108 in the X direction and Y direction.

[0053] The framework structure 100 further comprises storage compartments in the form of storage columns 105 provided between the members 102 where storage containers 106 are stackable in stacks 107 within the storage columns 105.

[0054] The framework structure 100 can be of any size. In particular, it is understood that the framework structure can be considerably wider and/or longer and/or deeper than disclosed in FIG. 1. For example, the framework structure 100 may have a horizontal extent of more than 700700 columns and a storage depth of more than twelve containers.

[0055] Various aspects of the present invention will now be discussed in more detail with reference to FIGS. 4a-5.

[0056] FIG. 4a is a perspective view of a first embodiment of a position sensing device 10 for determining a rotational position of a rotating shaft 12 when fixedly attached to said shaft 12. The position sensing device 10 is for determining a rotational position of a rotating shaft 12 of a vehicle of a system 1 for storing and retrieving goods holders. Typically, said vehicle is a remotely operated vehicle of the type shown in FIGS. 1-3b and the rotating shaft 12 is a wheel axle of such a remotely operated vehicle. A section of the wheel 25 is also shown.

[0057] The position sensing device 10 of FIG. 4a comprises a reflector 14 projecting from a circumferential surface of the rotating shaft 12 and extending around the circumferential surface of the rotating shaft 12 so as to rotate simultaneously with said shaft 12. The device 10 further comprises a distance measuring unit 16 that emits a beam of radiation 18 towards a portion of the reflector 14, as the shaft 12 and the reflector 14 are rotated with respect to the distance measuring unit 16 and receives a return beam 20 generated when the emitted beam 18 is reflected by the portion of the reflector 14.

[0058] The reflector 14 shown in FIG. 4a is helix-shaped with a circular, right-handed helix. In the shown embodiment, number of turns of the helix is a decimal numeral between 1 and 2. The sensor device 10 has the advantage that the sensor fitter need not be overly thorough when fitting the reflector 14a strong, consistent signal will be received regardless of the relative position of the reflector 14 when fitted to the shaft 12.

[0059] In an embodiment, said portion of the reflector 14 has an irregular surface facing the distance measuring unit 16. By way of example, said surface could be wavy and/or stepped surface. In one embodiment, the wavy and the stepped surfaces are superposed. This could improve resolution of the device 10 or, alternatively, generate two different return signals.

[0060] In the shown embodiment, the distance measuring unit 16 is at least partially enclosed by a housing 22. In a related embodiment (not shown), the housing could also enclose the reflector and a section of the shaft. Hereby, total light contamination of the position sensing device 10 could be kept at a minimum.

[0061] Still with reference to FIG. 4a, the emitted beam 18 is substantially parallel to the rotating shaft 12. In this arrangement, the reflector 14 will not scatter the emitted beam 18 too wide and direct it back, substantially along the path it came on.

[0062] The distance measuring unit 16 of FIG. 4a is further configured to output a signal based on a distance of said beam 18 to said portion of the reflector 14, wherein a rotational position of the rotating shaft 12 is determined based on the output signal of measured distance from said distance measuring unit 10. Thus obtained information may subsequently be used to determine speed and/or acceleration of the wheel axle 24 and the previously-mentioned vehicle.

[0063] The above-discussed position sensing device 10 is structurally simple and robust as its performance is not negatively affected by presence of dust and/or debris. The device is capable to perform high resolution measurements.

[0064] The distance measuring unit 16 can be part of a central computer system of the remotely operated vehicle or it can be a separate, standalone unit (as shown in FIG. 4a).

[0065] FIG. 4b is a perspective view of the arrangement of FIG. 4a, where the position sensing device 10 and the shaft 12 have rotated 180 degrees relative to the position shown in FIG. 4a. For the sake of brevity, components described in connection with FIG. 4a are not further discussed. A rotational position of the rotating shaft in FIG. 4b is determined as discussed in connection with FIG. 4a. Thus obtained shaft position information of FIGS. 4a and 4b may be used to determine speed and/or acceleration of the axle.

[0066] In one embodiment of the invention, the beam emitter emits a light beam, preferably an IR light beam. One suitable beam emitter is part of a Vishay VCNL4000 sensor with a wavelength detection peak at around 900 nm. In an alternative embodiment, the beam emitter emits an ultrasonic beam.

[0067] FIG. 5 is a perspective view of a second embodiment of a position sensing device 10 for determining rotational position of a rotating shaft 12. In the shown embodiment, the reflector 14 is disc-shaped and comprises a radially extending cut-out 25. In another embodiment (not shown), the cut-out made in the disc-shaped reflector extends circumferentially. Many of the features discussed above are equally applicable in the context of the disc-shaped reflector. By way of example, reflector's 14 surface may be wavy and/or stepped, a light/ultrasound beam 18 may be used. The purpose of the cut-out 25 is to reset the position sensing device 10. For the sake of brevity, components described in connection with FIG. 4a, and provided with reference numeral in FIG. 5, are not further discussed.

[0068] In another embodiment (not shown), a distance measuring unit is arranged to emit a further beam of radiation towards a portion of the reflector, as the shaft and reflector are rotated with respect to the distance measuring unit, and to receive a further return beam generated when the emitted further beam is reflected by the portion of the reflector. Hereby, resolution/accuracy may be even further improved.

[0069] FIG. 6 is a cross-sectional view a third embodiment of a position sensing device 10 for determining rotational position of a rotating shaft (wheel axle) 12. More specifically, it is shown a section of the wheel axle 12, a wheel 24 itself and a reflector 14 that is integrally formed, i.e. in one piece, with the axle 12. In this embodiment, the reflector 14 is arranged at a very end of the axle 12. The reflector 14 in accordance with this embodiment is substantially cylindrically-shaped and doesn't radially extend beyond outer surface of the axle 12. In addition to achieving space savings, this embodiment confers a more robust axle design as well as easier part manufacturing and mounting. Furthermore, the assembly becomes less prone to breakage. Analogously to previously discussed embodiments, a distance measuring unit 16 is arranged to emit a beam 18 of radiation towards a portion of the reflector 14 that faces said unit 16. The emitted beam 18 is parallel to the rotating shaft 12. The distance measuring unit 16 further receives a return beam 20 generated when the emitted beam 18 is reflected by the portion of the reflector 14. As seen, said portion of the reflector 14 has an irregular surface. The emitted beam 18 is off-center 3 with respect to the wheel axle 12.

[0070] On a general level, the above-discussed position sensing device could also be employed to detect wear and tear of the axle and its components. More specifically, if an axle bearing is failing for example, its vibrations would be transferred to the axle and, in turn, make it vibrate. Hereby, external noise information would be added to the return beam reflected by the portion of the reflector. Subsequently, the distance measuring unit would separate the distance-related information from the external noise-information. Based on the external noise-information, it could be determined whether a mechanical failure of the axle is imminent.

[0071] In the preceding description, various aspects of the position sensing device 10 for determining rotational position of a rotating shaft 12 according to the invention have been described with reference to the illustrative embodiment. For purposes of explanation, specific numbers, systems and configurations were set forth in order to provide a thorough understanding of the device and its workings. However, this description is not intended to be construed in a limiting sense. Various modifications and variations of the illustrative embodiment, as well as other embodiments of the system, which are apparent to persons skilled in the art to which the disclosed subject matter pertains, are deemed to lie within the scope of the present invention.

LIST OF REFERENCE NUMBERS

[0072] 1 Storage and retrieval system [0073] 10 Position sensing device [0074] 12 Rotating shaft [0075] 14 Reflector [0076] 16 Distance measuring unit [0077] 18 Emitted beam [0078] 20 Reflected beam [0079] 22 Housing of the distance measuring unit [0080] 24 Wheel [0081] 25 Cut-out [0082] 100 Framework structure [0083] 102 Upright members of framework structure [0084] 104 Storage grid [0085] 105 Storage column [0086] 106 Storage container/goods holder [0087] 106 Particular position of storage container [0088] 107 Stack of storage containers [0089] 108 Rail system [0090] 110 Parallel rails in first direction (X) [0091] 111 Parallel rails in second direction (Y) [0092] 112 Access opening [0093] 119 First port column [0094] 201 Container handling vehicle belonging to prior art [0095] 201a Vehicle body of the container handling vehicle 201 [0096] 201b Drive means/wheel arrangement, first direction (X) [0097] 201c Drive means/wheel arrangement, second direction (Y) [0098] 301 Cantilever-based container handling vehicle belonging to prior art [0099] 301a Vehicle body of the container handling vehicle 301 [0100] 301b Drive means in first direction (X) [0101] 301c Drive means in second direction (Y) [0102] 401 Container handling vehicle belonging to prior art [0103] 401a Vehicle body of the container handling vehicle 401 [0104] 401b Drive means in first direction (X) [0105] 401c Drive means in second direction (Y) [0106] X First direction [0107] Y Second direction [0108] Z Third direction