EP0849608A2 - Device for determining the position of the edge of a moving belt - Google Patents

Abstract

The sensor (3) has a rotary mirror (18) which deflects a beam (15) from a radiation source (5) across the direction of the belt's (1) travel, and scans an observation field. A retro-reflex beam (24) reflected on the retro-reflector is detected by a receiver (28). A second beam (21) hits the rotary mirror at a second impact point (R2) spaced apart from the first impact point (R1) of the first beam. The second retro-reflex beam (29) reflected from the impact point of the second beam on the retro-reflector (4) is detected by a second (33) or by the same receiver. The signals of the second retro-reflex beam in the evaluation circuit for determining a second position date of the edge of the belt, together with the first position date, serve to determine the spatial position.

Description

The present invention relates to tracking the position of a running belt through monitoring the location of one or both edges of this tape. The Invention is based on a device according to the preamble of claim 1, which is known from U.S. Patent 4,788,441. In this known training determined a position date from each band edge, namely the angle at which the scanning beam from the retroreflector to the tape material or from Tape material passes to the retroreflector. Out of this essentially results in the lateral offset of the current Band.

A clear connection between the page offset the current tape and the position date mentioned above is only given with the same Height of the band edge or distance from it Scanning device. This is not always to be expected especially not when using a rotating frame Direction control of the belt because of its swiveling movements typically corresponding cross bank inclinations have as a consequence. In these cases, it is for the Quality of the tape guiding is important, the location, i.e. the side and altitude of the monitored Track band edge.

US Pat. No. 5,354,992 relates to a device the signals from the band edge detectors, e.g. Cameras, in case of inclination of the Band be corrected, however, for identification This inclination requires another measuring device is.

The object of the present invention is to create a device that allows, in proportion simple construction and operation of both the side and the altitude, i.e. the spatial location of at least one Track band edge.

The solution to the problem is in the claim 1 specified. The two obtained from a band edge Position data are angular coordinates of two of different ones Place outgoing beacons in their Intersection is the band edge and the light if necessary in Cartesian coordinates or in any other system suitable for controlling the belt can be implemented.

In itself is from the above-mentioned US Pat. No. 4,788,441 Determining the spatial position of an object using two beacons originating from different places known; however, this is not about persecution of a running tape, but about the determination of Position or dimension of the object in a surrounding the object Box, with two rotating mirror arrangements necessary are. This training is apparatus and related the adjustment of the components and the signal evaluation quite complex. Because the object of the present invention, only a rotating mirror for generation a plurality of direction finding beams are used, the arrangement is also more tolerant of errors Fluctuations in the mirror speed.

Further features of the invention are in the subclaims specified. The decoupling proposed in claim 2 of the retroreflected beam and exposure to the associated receiver by means of a radiation splitter is known per se from US Pat. No. 4,523,093. Here too but it’s just about getting one-dimensional data, when reading barcodes.

The expansion of the laser beam proposed according to claim 4 to a fan beam using a cylindrical lens causes inhomogeneities to be averaged the width of the retroreflector, so that it was narrowly limited local fluctuations in the reflective properties are not impact. Local inhomogeneities are e.g. given there where the triple reflectors collide.

Fig. 1

die Gesamtansicht einer Bandlaufsteuervorrichtung mit einer Abtastvorrichtung zur Bestimmung der räumlichen Lage eines Bandrandes;

Fig. 2

eine schematische Darstellung der Abtastvorrichtung in einer ersten Ausbildungsform;

Fig. 3

eine schematische Darstellung der Abtastvorrichtung in einer zweiten Ausbildungsform;

Fig. 4

eine schematische Darstellung der Abtastvorrichtung in einer dritten Ausbildungsform;

Fig. 5

eine schematische Darstellung der Abtastvorrichtung in einer vierten Ausbildungsform;

Fig. 6

eine schematische Darstellung der Abtastvorrichtung in einer fünften Ausbildungsform;

Fig. 7

schematisch eine Abtastvorrichtung und die von ihr erhaltenen Signalimpulse bei einer bestimmten Auswanderung des überwachten Bandrandes;

Fig. 8

die Darstellung gemäß Fig. 7 bei einer anderen Auswanderung des Bandrandes;

Fig. 9

die Darstellung gemäß Fig. 7 bei noch einer anderen Auswanderung des Bandrandes;

Fig. 10

die Darstellung gemäß Fig. 7 bei einem nicht vollständig undurchsichtigem Bandmaterial;

Fig. 11

schematisch eine Abtastvorrichtung mit einem Spiegelrad, dessen Spiegelfacetten Abstände voneinander aufweisen, und die von dieser erhaltenen Signalimpulse;

Fig. 12

die Gesamtansicht einer Bandlaufsteuervorrichtung gemäß Fig. 1 mit einem Zusatzbauteil zur Bestimmung der Winkelstellung des steuernden Drehrahmens.

The invention is further explained below by the description of exemplary embodiments with reference to the accompanying drawings. It shows:

Fig. 1

the overall view of a tape travel control device with a scanning device for determining the spatial position of a tape edge;

Fig. 2

a schematic representation of the scanning device in a first embodiment;

Fig. 3

a schematic representation of the scanning device in a second embodiment;

Fig. 4

a schematic representation of the scanning device in a third embodiment;

Fig. 5

a schematic representation of the scanning device in a fourth embodiment;

Fig. 6

a schematic representation of the scanning device in a fifth embodiment;

Fig. 7

schematically a scanning device and the signal pulses received by it during a certain migration of the monitored band edge;

Fig. 8

the representation of Figure 7 in another emigration of the band edge.

Fig. 9

the representation of Figure 7 with yet another emigration of the tape edge.

Fig. 10

the representation of Figure 7 with a not completely opaque tape material.

Fig. 11

schematically a scanning device with a mirror wheel, the mirror facets of which are spaced from one another, and the signal pulses obtained therefrom;

Fig. 12

the overall view of a tape control device according to FIG. 1 with an additional component for determining the angular position of the controlling rotating frame.

A tape 1 is drawn off from a roll A in order to Processing station B, e.g. a printing unit, a processing or to be subjected to treatment before it is rewound on a reel C. For precise Regulation of the lateral position of the volume is before Processing station B provided a rotating frame 2, the represents the actuator of the control loop and its Control the direction of rotation. To obtain the Control signal for the swivel drive of the rotating frame the spatial location of one of the band edges and thus the deviation from the nominal position of the belt a scanning device 3 is detected. In their scanning area a retroreflector 4 is arranged behind the running belt.

2 consists of a scanning device 3 Housing 3 'with a window 36 through which the scanning Boresight the observation field with the retroreflector 4 and coat the tape edge in front of this. The running direction of the belt, not shown here runs at right angles to the drawing plane, i.e. in these in or out of it. In the center is a constant Speed rotating polygon mirror wheel 18 stored with eight flat mirror facets.

A laser diode 5 generates a beam 6, e.g. one Beam of light in the visible range from a cylindrical lens 7 is expanded into a fan beam 8, where the plane intersects the drawing plane at right angles, that is, the running direction of the belt. This Fan beam 8 is emitted by a radiation splitter 9 (50% mirror) split into two partial beams 10 and 11.

The partial beam 11 is split again by a radiation splitter 13, one part being unnecessary for the function as a residual beam 14 and swallowed by an absorber 35, and the other part falling onto the mirror wheel 18 via a mirror 16 as a first beam. The point where it strikes the mirror wheel and is thrown back is referred to as the throw-back point R ₁ , which dances slightly back and forth along the incoming direction finding beam when the mirror is rotating.

With the direction of rotation of the mirror wheel 18 drawn in, the reflected beam begins at the transition of the discard point R ₁ from one mirror facet to the next, a new scanning swivel from right to left. In doing so, shortly before falling out of the window 36, it hits a scan start detector 17.

As soon as the sighting beam 15 falls on the retroreflector 4 after reaching the window, it is reflected back by it as the first retroreflective beam 24 in the same direction and, in view of the high speed of light and the negligible scanning speed of the mirror wheel 18, falls on the discarding point R ₁ and the mirror 16 the underside of the radiation divider 13, through which a part 25 passes and has no meaning and another part as a reflex part 26 acts on a first receiver 28 via a filter 27 which only allows the wavelength of the laser radiation used.

The partial beam 10 is reflected downward by a mirror 12 and similarly passes through a second radiation splitter 19 as a second directional beam 21, the residual beam 20 arising here being swallowed by an absorber 34. The second directional beam acts on the rotating mirror 18 at a second discard point R ₂ , which is at a distance from the first discard point R ₁ , via a mirror 22 and sweeps the observation field, the second retroreflecting beam 29 which is produced when the retroreflector 4 is acted upon, practically without delay via the Discarding point R ₂ , the mirror 22 and the radiation splitter 19 acted on a second receiver 33 as a reflex part 31 by a filter 32. The passage part 30 has no meaning.

In a second embodiment of the scanning device 3 are two similar or different Radiation sources 5, 37 for generating the two bearing beams 15, 21 provided, the second directional beam 21 from its own cylindrical lens 39 to a fan beam 40 is expanded. Otherwise makes a difference this training only through the spatial arrangement of the components, while the function and mode of operation is the same and same components same Have reference numerals as in Fig. 2. In this second Form of training can have higher radiation intensities be realized and there will be different mirrors and radiation splitter saved. In addition, there is Possibility by choosing different wavelengths of the two laser sources is from the two directional beams clearly separate generated impulses.

The third embodiment shown in Fig. 4 differs differs from that according to FIG. 2 in that it only has a receiver 28 with an upstream filter 27. In itself it is possible to change the geometry of the arrangement, especially the angles at which the rotating mirror is struck by the direction-finding beams 15, 21 shape that the retroreflective beams 24 and 29 temporally successive and thus separable the band edge scan. However, if this is difficult, you can light modulators 41, 42 are provided in the beam path, which represent controllable LCD elements that at Applying a control voltage become translucent. These are controlled alternately, so clearly it is determined whether the signals of the receiver 28 from come from the first or from the second beam.

The fourth embodiment shown in FIG. 5 differs differs from that of FIG. 4 in that also the light modulators and the rotating mirror are still missing 18 'with flat mirror facets, between which non-reflective distances remain. The facets in bold are supposed to be those that are mirrored while the others do not reflect. This also creates gaps in time between the scanning strokes of the observation field by a bearing beam and the scans of the two Beacons are intermittent at different times.

Another possibility, not shown in the drawing is to have one with two laser radiation sources Device to alternately key them out, so that the signal pulses are clearly separated in this way and can be assigned.

The following with reference to FIGS. 7 to 11 in detail described signal pulse sequences generated by the receivers are idealized with vertical front and Trailing edge and shown at a constant level. are such conditions are not sufficient, known techniques for processing the signals be used up to the storage of out Test runs without a band of comparison pulse sequences, with which the pulse sequences occurring during operation are compared, the times of occurrence of the flanks result from the comparison.

If the latter technique is used, the Comparison of the pulse trains over a complete turn of the rotating mirror the currently active mirror facet, i.e. the angular position of the rotating mirror can be identified. The training according to FIG. 6 can be used for this purpose a mirror wheel 18 with three mirror facets two equal sized larger non-reflective distances and has a smaller non-reflective distance. The short characteristic of this distance The beam is interrupted only once per revolution and indicates the rotational position of the rotating mirror, so that it is used as a synchronization signal for pulse train comparison can serve.

7 to 11 are now to illustrate how different Layers of the band edge on the received pulse signals impact, so that from these about appropriate Arithmetic operations or look-up tables the spatial Position of the band edge can be tracked. Here is in the scanning device 3 to simplify the radiation source (s) omitted and are only the gradients the direction finder or retroreflective beams shown.

In Fig. 7 is a radiation-opaque tape 1 in two positions Pos.a and Pos.b shown.

Each time the scanning start detector 17 is crossed (the times t _o and t _{1 are designated} ), the first directional beam 15 produces signals S ₁₇ which serve as reference pulses for the time interval measurements of the scanning process. The period between the scanning processes has the duration t _o → t ₁ , however, the remaining signal curves are only shown for one process in order not to overload the figure.

When the first sighting beam comes into the layer 43 shown in narrow dotted lines, it emerges from the housing window and falls onto the retroreflector. This happens at time t ₃ and its retroreflective beam acts on the first receiver 28 and this generates the signal S ₂₈ . At time t ₄ , the first directional beam reaches position 47, drawn as a two-dot line, in which it reaches the edge of band 1, both in its position a and in position b. As a result, the first sighting beam no longer reaches the retroreflector and the signal S ₂₈ disappears at time t ₄ .

If band 1 were not present, the first direction finding beam would be retroreflected until the left window edge was reached in the narrowly dotted position 44 at time t ₈ and the signal S ₂₈ would continue until this time, which is indicated in dashed lines in the diagrams.

The second direction finding beam 21 falls out of the housing window for the first time in the wide-dotted position 45 at the time t ₅ and reaches the edge of the band 1 in its position a at the time t ₆ . His retroreflective beam 29 thus generates the signal S ₃₃ Pos.a. If the band were not present, the signal would be generated up to time t ₉ , at which the second sighting beam reaches the left window edge in the position 46 shown in a dotted line.

When the band 1 is in the position b, it only shadows the retroreflector 4 from the second directional beam in its position 49 shown in broken lines, which is reached at time t ₇ . In this case, the signal S _{33 continues} until this time.

It can be seen that with a scan only by the first direction finding the positions a and b of the band edge indistinguishable, but adding it of the second directional beam not only the distinction succeeds, but also the determination of the spatial location of the band edge, namely from the intersection points of the Beam positions 47 and 48 for position a and the beam positions 47 and 49 for position b. It is still too see that the field of view of the device between the beam positions 43 and 46 is because only this area is swept by both beacons.

In Fig. 8 it is shown how two different band edge positions affect the pulse sequences if the band 1 with its edge at the same height (distance from the retroreflector 4) more (Pos.b) or less (Pos.a) in the field of observation Scanning device protrudes. The leading edges of the signals S ₂₈ and S ₃₃ occur again at the same times t ₃ and t ₅ . In position a of the band edge, this is reached by the first direction finding beam in position 47 at time t ₄ and by the second direction finding beam in position 48 at time t ₆ , the crossing point of these positions defining the spatial position of the band edge and the spatial position of the band edge in whose position b is defined by the angular positions 50 and 51 of the first and second direction finding beam, which in turn clearly follow from the times t ₁₀ and t ₁₁ .

The same considerations can be made with regard to FIG. 9, where the two edge positions a and b are both at different heights and at different lateral immersion depths in the observation field. The spatial position of the edge in position b is defined by the beam positions 52 and 53, which in turn clearly result from the times t ₁₂ and t ₁₃ .

Fig. 10 still shows the waveforms that result when the tape edges are in the positions shown in Fig. 7 and the tape material is not completely opaque is. The transition of the beam to the The belt surface then does not lead to complete elimination of the retroreflective beam and drop in the signal level to zero, but only to darken the retroreflective beam and a drop in the signal to one corresponding darkening value. In one If this is the case, setting the response threshold is recommended the evaluation circuit connected to the receivers 28, 33 to a midpoint between the full Signal lift and the darkening level, which means known Techniques can happen automatically.

If the difference between full signal level and darkening level is only slight, so right translucent tape material, e.g. temperature-related Fluctuations in the power of the radiation source 5, 37 or changes caused by pollution the detection power of the received radiation power impair and must be compensated will. One option is to replace the absorber 34, 35 (FIG. 2) to arrange control receivers and their Use the signal to adjust the response threshold.

FIG. 11 shows the signal curves in the configuration of the scanning device according to FIG. 5, that is to say with spaced mirror facets of the mirror wheel 18 ′, which manages with only one receiver 28 because of the temporal separation of the first and second retroreflective beams. It can be seen how the one receiver 28 delivers the signals of the first retroreflective beam t ₃ → t ₄ (beam positions 43 → 47) and the signals of the second retroreflective beam t ₅ → t ₆ (corresponding to the second position data of the band edge position a) the beam positions 45 → 48, which are hidden in the rotating mirror position shown, but can be seen in FIG. 7), or the signals t ₅ → t ₇ (beam positions 45 → 49 in FIG. 7) providing the second position data of the band edge position b, so that the clear assignment during further processing is possible.

In all cases it applies that the time spans between the scanning start pulse t _o serving as reference impulse and the leading edges of the retroreflective beams at times t ₃ and t _{5 are} a device constant and the position data are obtained from the time spans t _o → t ₄ and t _o → t ₆ (item a) or t _o → t ₇ (item b).

It should also be pointed out that it is possible to use the leading edge, for example of the first retroreflective pulse, at time t ₃ as the reference signal for the start of the scan, so that a scan start detector 17 is not necessary. Another possibility is given if the geometry of the scanning device is such that the scanning pivoting of the first directional beam 15 begins so far to the right that the mirror 16 is already hit, ie in a rotating position of the rotating mirror 18 that arrives at the discard point R ₁ Direction-finding beam 15 strikes a mirror facet located at right angles to it, so that it is thrown back into itself and generates a marking pulse from the first receiver 28. This too can then be used as a reference pulse for the start of the scan and makes a special detector 17 unnecessary.

Fig. 12 shows an embodiment in which in addition to 1 according to the arrangement with the rotating frame 2 via a boom 54 rigidly connected in the scanning direction short rotating frame retroreflector 55 in front of band 1 is present, at a point where it is certain always tape 1 will run and none Time can be reached from a band edge that however still in the observation area of the scanning device 3 lies. Then from the rotating frame retroreflector 55 received a retroreflective pulse that the rotational position of the Rotating frame 2 defined. The rotating frame is the actuator of the control loop of the strip guiding system and such Rotation position pulse can be used to align the rotating frame be used in its centering position, in which rolls parallel to the other rolls of the station and the coils A and B are oriented.

It is understood that with an appropriate interpretation of the Scanning device this is not just an edge of the running Band, but pursue both edges of the same can and so continuous monitoring of bandwidth and Faults are possible. The one in the scanning panning direction the beam is the front edge of the band as described, characterized by the rear Flanks the pulses while the other band edge is defined by the leading edges of second retroreflective pulses, that are generated when the beacon again towards the end of its scan Band hits the retroreflector behind.

Finally, a possibility should be pointed out a constant scanning speed of the bearing beam via the retroreflector 4 or the band 1 in the area of To achieve observation field. When using a Rotary mirror with flat mirror facets results in one constant angular velocity of the scanning bearing beam and thus a migration speed of Application point in the middle of the observation field is the smallest because here the distance at the smallest and the angle of incidence is a right one. To both sides, i.e. at the beginning and end of the scanning process is the rate of migration because of the larger one Distance and the more acute angle of impact there biggest. If this is not desired, there is the possibility to profile the mirror facets in such a way that they compensate for this effect and a constant rate of progress the sampling point.

Claims (12)

Device for determining the position of the edge of a band (1) which runs between a retroreflector (4) and a scanning device (3),
wherein the scanning device has a rotating mirror (18) which deflects the beam (15) of a radiation source (5) transversely to the direction of travel of the strip and sweeps the observation field, the one reflected by the point of action (R ₁ ) of the directional beam (15) on the retroreflector Retroreflective beam (24) is detected by a receiver (28) to which an evaluation circuit for determining a position date of the band edge is connected,
characterized in that a second sighting beam (21) strikes the rotating mirror (18) at a second throw-back point (R ₂ ) which is spaced from the throw-back point (R ₁ ) of the first sighting beam (15),
wherein the second retroreflective beam (29) which is thrown back on the retroreflector (4) by the point of application of the second directional beam (21) from a second receiver (33) or from the same receiver (28, Fig. 4, 5, 6) separated in time from receipt of the first retroreflective beam is detected, and the signals of the second retroreflective beam (29) are used in the evaluation circuit for determining a second position data of the band edge and together with the first position data for determining the spatial position of the same. Device according to claim 1, characterized in that the directional beams by a beam splitter (13, 19) are thrown onto the rotating mirror (18) and the retroreflected rays (24, 29) from the respective Radiation divider (13, 19) to the respective receiver (28, 33) can be reflected. Device according to claim 1 or 2, characterized in that that the rotating mirror (18) is a polygon mirror with flat mirror facets. Device according to one or more of the preceding Claims, characterized in that the beacons (15, 21) from a laser radiation source (5, 37), preferably a laser diode are generated and on their way to the rotating mirror (18) through a cylindrical lens (7, 39) expanded into a radiation fan (8, 40) in whose plane the running direction vector of the tape lies. Device according to one or more of the preceding Claims, characterized by two radiation sources (5, 37), each of which has one of the directional beams (15, 21) generated (Fig. 3). Device according to one or more of claims 1 to 4, characterized by a radiation source (5), whose beam (6) after expansion through a cylindrical lens (7) as a fan beam (8) from a radiation splitter (9) is divided into two partial beams (10, 11), which after passing through radiation splitters assigned to them (13, 19) as directional beams (15, 21) via the rotating mirror (18) sweep the observation field (Fig. 2). Device according to one or more of the preceding Claims, characterized by a the device elements housing with one to the monitoring field directed window (36), near the a scan start detector (17) is arranged at a window edge is. Device according to one or more of the preceding Claims, characterized in that the Passage of the bearing beam through the associated radiation splitter (13, 19) resulting partial beam (14, 20) an absorber (34, 35) falls. Device according to one or more of claims 1 to 7, characterized in that the passage of the bearing beam through the associated radiation splitter (13, 19) partial beam (14, 20) arising on a control receiver falls, whose signal to adjust the Receiver response thresholds to fluctuations in radiation power and serves the receiver sensitivity. Device according to one or more of the preceding Claims, characterized in that the polygon mirror (18 ') has flat mirror facets, between which there are non-reflective sections. Device according to one or more of claims 1 to 9, characterized by two alternately controllable Light modulators (41, 42; Fig. 4) in the way of the two Beacons. Device according to one or more of the preceding Claims, characterized by a rotating frame fixed Retroreflector (55) in front of the running belt 1 (Fig. 12).

Images