Conveyor belt with magnetic linear encoder readable magnetic indicia

Abstract

A conveyor (1) comprises a conveyor belt (2) having a magnetic mark (3) and comprises at least three, preferably 3 to 16, position sensing units (51, 52, 52, 5N) deriving position information from the magnetic mark (3) and a control unit (6) generating position information from sinusoidal and cosine signals generated by the position sensing units (51, 52, 52, 5N). The conveyor belt (2) has an end joining region (4) in which the magnetic marking (3) is absent or unreadable. Each position sensing unit preferably further comprises Hall sensors (511, 512) that generate a blank area entry signal indicative of entry of the position sensing unit in question into the end junction area when the maximum intensity of the magnetic field of the marker falls to or below a threshold intensity lower than a default maximum intensity, and generate a clear space exit signal indicating that the position sensing unit in question exits the end junction region when the maximum intensity of the magnetic field rises to or above the threshold intensity. The control unit neglects the position information from any position sensing unit in question from the time it generates the white space entry signal, and re-considers the position information from that position sensing unit from the time it generates the white space exit signal. Methods for calculating error corrections and applying error corrections to position information of position sensing units (51, 52, 52, 5N) are also disclosed. One-pass and multi-pass inkjet printers comprising the conveyor (1) of the invention are also disclosed.

Description

Technical Field

[0001] The present invention relates to a conveyor belt comprising a periodic pattern of magnetic marks embedded in the belt, the periodic pattern being arranged in rows extending parallel to the direction of travel of the belt. The present invention also relates to a conveyor device comprising such a belt. In particular, it also relates to a single-pass or multi-pass inkjet printer comprising such a belt. Background Art

[0002] In any conveyor device that is integrated with other machine components or equipment and where the speed and position of the substrate on the conveyor belt must be synchronized with other devices (for pick and place, filling or printing applications), accurate conveyor belt position control is required. The conventional way to determine the position of the conveyor belt during operation is to use a rotatable wheel in non-sliding contact with the conveying surface of the belt, where the moving belt causes the wheel to rotate, and the rotation of the wheel is converted into belt travel distance.

[0003] A single-pass inkjet printer is a special type of conveying device that can print images onto conveyed goods at the same time. The basic colors (black, yellow, magenta and cyan in the simplest CMYK model, optionally more colors (such as light magenta and light cyan) in more complex models, in some cases up to nine basic colors) are ejected as small ink dots from the nozzles of individual print heads, which are spaced apart from each other by some offset in the longitudinal direction. The print heads with color nozzles extend over the entire lateral width of the substrate, so that no lateral movement of the print heads is required. With this arrangement, all basic colors can be printed sequentially onto the substrate in a single pass, whereby the substrate is transported from one print head to the next print head to obtain a fully printed image with all colors. Non-basic colors are formed by mixing two or more of the basic colors, which is done by superimposing ink drops of different basic colors. Therefore, an inkjet printer must be able to print ink drops of different basic colors from different print heads spaced apart by some offset in the longitudinal direction onto the same position of the substrate. For example, consider that a printing resolution of 600 dpi (dots per inch) means a positioning tolerance of ±21 μm for each drop of color. This tolerance should be maintained along the entire length of the printing process area, and it will increase as the distance between the printheads increases and the number of basic colors increases. This requires the print driver to synchronize the ink ejection of the printheads and know exactly the position of the substrate at any time when the substrate is transported from one printhead to the next, with the lowest possible tolerance and in any case not exceeding the printing resolution.

[0004] Conveyor belts comprising magnetic marks which allow the position of the belt to be determined by appropriate magnetic detectors, and conveying devices using such belts, have been known for a long time. Magnetic marks are magnets with a north pole to a south pole which extend from one side of the belt to the other along the thickness of the belt. Typical detection devices are magnetic linear encoders which are conventional in themselves and are sold on the market. The earliest publication in this field known to the applicant is JPS55-123806. This publication, which is apparently already in the field of printing presses, discloses the use of magnetic marks on the belt and the use of two magnetic heads (presumably just to generate a "quadrature signal" (see below)) for belt position determination. Other publications disclosing belts with magnetic marks and their use in printing presses are JP 2001 / 125333A1, US2008 / 049054A1 and US2008 / 0192076A1.

[0005] The four publications mentioned above clearly relate to endless belts, i.e. belts that do not require end joining. However, the vast majority of belts on the market are of open form, such as to allow, after the belt has been installed on the conveyor, to be cut to the necessary length on site and pre-tensioned to the desired tension. Only after these steps have been carried out, the installed open belt and its open ends, which are maintained under the required pre-tension, are made into annular form. Such end joining is usually carried out using heat and pressure, optionally in conjunction with the use of hot-melt adhesives. For belts containing magnetic markings, such end joining can lead to a degradation or even destruction of the magnetic markings, so that in the end joining area the magnetic markings can no longer be read by the magnetic linear encoder.

[0006] The non-prepublished EP 4 060 291 A1 discloses a device for position determination on a support having a periodic pattern of magnetic marks, the device having two linear encoders, a "downstream" linear encoder and an "upstream" linear encoder. By making the "reading window" (the distance between the two linear encoders) larger than the "transition region", the device is able to handle "transition regions" in which the magnetic signal is unreliable or absent. EP 4 060 291 A1 relies on the calculated displacement to handle a unique "transition region"; however, the publication does not explain how this should work when there are several "transition regions" of different sizes.

[0007] Although the maximum flux density of the marked sinusoidal magnetic signal does not drop sharply to zero when entering the end joint area, but gradually drops to zero, the magnetic linear encoder "can read" or "cannot read" the mark is a "yes / no" decision. When the linear encoder enters the end joint area and the strength of the sinusoidal signal decreases and therefore its output position information becomes unreliable, the belt position determination system must at some stage decide to completely ignore the output of the encoder. Similarly, when the linear encoder leaves the end joint area and the strength of the sinusoidal signal increases sufficiently again, such as to make the encoder's output position information reliable again, the system must at some stage decide to start reconsidering the output of the encoder.

[0008] The end connection zone containing marks that cannot be read by the magnetic linear encoder typically has a length of 80 mm to 120 mm. Nevertheless, it must still be possible to use the magnetic marks for position determination at any time and in any belt position. The usual initial solution is to use two linear encoders spaced apart from each other by a longitudinal distance that is greater than the longitudinal length of the end connection zone. In this way, it can be ensured that there is always at least one linear encoder that is not in the end connection zone and that can provide position information based on the readable magnetic marks. The applicant is aware of some prior art that aims to solve the above-mentioned problems.

[0009] JP 2006 / 096429A1 discloses belt position determination using optical (transparent / opaque) marks on the belt, where the belt has a "knot 141x" (an area wider than one mark and clearly transparent), using two detectors and an "home label" to be detected by an "origin detection machine". The signal is processed by a CPU.

[0010] US2012 / 124848 A1 relates to position detection using at least two sensors using a code containing absolute position values, the code containing at least one discontinuity. The publication therefore does not rely on marks to be counted by the sensors, but on position values ​​to be read directly and corrected if necessary for missing position values ​​in discontinuities.

[0011] US2012 / 124849 A1 relates to the use of magnetic markers for angular position determination of a rotating shaft. There the magnetic markers are applied as an open strip around the shaft, the ends of the strip being subsequently mechanically joined. The end joints form a zone without magnetic markers. To detect this zone, the markers are arranged near the border of the end joints at a spatial frequency (called the "position frequency" there) that is different from the spatial frequency of the markers along the rest of the strip, such as twice the latter's spatial frequency. This allows the linear encoder to detect the proximity of the end joint zone.

[0012] WO 2016 / 146463 A1 relates to the problem of position determination in a tape with magnetic marks using two linear encoders, wherein the end joining zone of the tape contains unreadable magnetic marks. For this purpose, the publication uses a reference mark and two associated reference mark detectors which should allow switching from a first linear encoder to a second linear encoder and vice versa, depending on which of the two linear encoders is located in the end joining zone. The publication also discloses a single-pass inkjet printer using such a tape.

[0013] The object of the present invention is to provide an improved position determination in tapes which contain magnetic markings and in which the tapes have end attachment areas in which the magnetic markings are not readable for a position determination system. Summary of the invention

[0014] Therefore, the present invention provides a conveyor, the conveyor comprising:

[0015] a) an endless conveyor belt having a belt periphery, an outer conveying surface, an inner surface facing the pulleys, magnetic marks along the entire belt periphery except for one or more blank areas, each blank area having a length Lj, where j is the index of the blank area, the magnetic marks being arranged in the belt travel direction such that the north pole or the south pole of the magnetic marks points to the outer conveying surface in an alternating manner, adjacent such north and south poles being spaced apart from each other by a pole pitch DP, thereby generating a periodic magnetic field of a default maximum strength; wherein in each of said blank area(s), the magnetic marks are absent or the maximum strength of the generated magnetic field is lower than said default maximum strength;

[0016] b) at least 2 position sensing units arranged along the belt periphery and in close spatial proximity of the magnetic marks, each position sensing unit is capable of detecting the magnetic field of the magnetic marks not in the blank zone(s) when the conveyor belt is running in the direction of travel, thereby generating 1) a sinusoidal voltage signal with respect to the orientation of the magnetic flux density B sensed from the magnetic marks and thus corresponding to the angular position of the position sensing unit relative to the pattern; and 2) a corresponding cosine voltage signal corresponding to the angular position of the position sensing unit relative to the pattern; wherein among the at least 2 position sensing units, there are at least 2 spaced apart position sensing units, each of the at least 2 spaced apart position sensing units is spaced apart from any of the remaining spaced apart position sensing units by a circumferential distance in the belt travel direction that is greater than any length Lj of any blank zone;

[0017] c) means capable of generating a blank zone entry signal when the maximum intensity of the magnetic field detected by the position sensing unit drops or is about to drop to or drops below a threshold intensity lower than said default maximum intensity and means capable of generating a blank zone exit signal for the same position sensing unit when the maximum intensity of the magnetic field detected by the position sensing unit rises or has risen to or has risen above said threshold intensity;

[0018] d) a control unit which derives belt position information from the sinusoidal voltage signals and cosine voltage signals of all position sensing units when the conveyor belt runs in the direction of travel, except that the control unit disregards the sinusoidal voltage signals and cosine voltage signals from any position sensing unit from the point in time when it receives the blank zone entry signal for the position sensing unit, and reconsiders the sinusoidal voltage signals and cosine voltage signals of the position sensing unit from the point in time when it receives the blank zone exit signal for the position sensing unit.

[0019] Preferred embodiments of the conveyor of the invention are according to the dependent claims.

[0020] The invention also provides a single-pass or multi-pass inkjet printer comprising the conveyor of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A preferred embodiment of the position sensing unit used in the present invention is shown;

[0022] Figure 2 , Figure 3 and Figure 4 Two embodiments of the conveyor of the present invention are shown;

[0023] Figure 5 Schematically shows the construction of a preferred embodiment of a control unit used in the present invention;

[0024] Figure 6 shows a schematic diagram of a printing press including the conveyor of the present invention;

[0025] Figure 7 shows the results of synchronization tests using a conveyor of the present invention relative to a prior art conveyor, wherein position determination was performed using a commercial linear encoder; and

[0026] Figure 8 The result of performing phase error correction on a cosine input signal and a sine input signal including a phase error between the cosine input signal and the sine input signal is shown. DETAILED DESCRIPTION

[0027] For the purposes of this invention, the following definitions apply:

[0028] The "periphery" of an endless belt corresponds essentially to the longitudinal length of an open belt or strip from which the endless belt is made by end joining. The periphery of an endless belt typically extends along the "mid-diameter" or "neutral line" of the endless belt, i.e., a line located inside the endless belt that does not change in length when the endless belt is in use and bent over a pulley. According to the practice of the art, the term "periphery" should refer to both the physical peripheral lateral edge of the endless belt and the associated length L of such peripheral lateral edge. The end joining that makes the belt or strip endless is typically done as a last step and is customary per se using a heat press and optionally a hot melt adhesive.

[0029] The "magnetic mark" suitable for use in the present invention forms a pattern of alternating north / south poles when viewed from one side of the strip. From the other side of the strip, the pattern of magnetic poles is reversed, since for every north pole on one side there is a south pole on the other side. The distance between the magnetic flux density maxima of adjacent north / south poles is half the length of the period of the magnetic mark pattern and is usually named "pole pitch". If a magnetic detection device is moved along the path of alternating north and south poles and detects their magnetic field from a certain distance, the detected signal does not have a nearly rectangular shape, but a sinusoidal shape.

[0030] For purposes of the present invention, this pole pitch is designated as DP. Although for purposes of the present invention, DP may be any value, it is preferred that DP is in the range of about 0.5 mm to about 10 mm; and more preferably, DP is about 0.5 mm, about 1 mm, about 2 mm, about 2.5 mm, about 5 mm, or about 10 mm. The term "about" does not imply variability in the nominal value of DP itself, but rather reflects variability due to elongation or contraction of the conveyor belt included in the conveyor of the present invention during operation. DP may therefore deviate by up to +2% above its respective nominal value due to elongation of the conveyor belt, and may therefore deviate by up to -2% below its respective nominal value due to contraction of the conveyor belt; these deviations are suitable as the definition of the term "approximately" as used herein.

[0031] The pattern of magnetic marks is preferably substantially periodic in the direction of tape travel. "Substantially periodic" preferably means that the standard deviation of the geometrical dimensions of the magnetic marks (such as their length in the tape direction, their width transverse to the tape travel direction, and / or their thickness in the tape thickness direction) and / or the standard deviation of the magnetic flux density B they produce at a given constant distance from the tape surface in the tape thickness direction does not exceed 50% of the average value of the geometrical dimension in question or of said average magnetic flux density, respectively. More preferably, "substantially periodic" means that (several) said standard deviations do not exceed 10% of the respective average values. Most preferably, "substantially periodic" is periodic.

[0032] A "blank zone" is a zone on a conveyor belt in which magnetic markings are absent, destroyed, erased, or have a lower magnetic flux density B than the default maximum magnetic flux density B produced by magnetic markings outside any such blank zone by default. A typical example of a blank zone in the aforementioned sense is an end joining zone of a conveyor belt in which the magnetic markings have been damaged or destroyed by the action of heat and pressure during the end joining process. Another example of a blank zone is a zone in which magnetic markings have been identified as defective and in which all such defective markings have been deliberately erased to indicate to a position sensing unit that no position information can be derived therefrom. The conveyor belt used in the present invention may include one or more such blank zones; typically it may include exactly one such blank zone in the form of said end joining zone.

[0033] A "Hall sensor" detects magnetic flux density B through the Hall effect and produces an output voltage that is typically proportional to B.

[0034] A "magnetoresistive sensor" detects the direction (inclination) of the magnetic flux density B relative to the pattern of magnetic marks in the conveyor belt and thus to the direction of travel of the conveyor belt by means of anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR) or tunnel magnetoresistance (TMR) (preferably by means of AMR for the purposes of the present invention). For an AMR sensor, the resistivity ρ (α) of the magnetoresistive material depends on the angle α between the direction of the current I in the magnetoresistive material (which remains constant within the AMR sensor) and the direction of the magnetic flux density B (which varies depending on the position of the AMR sensor relative to the pattern of magnetic marks) and is preferably given by the formula

[0035] ρ(α)=ρ o +(ρ p -ρ o )cos 2 (α)

[0036] where ρ o is the resistivity when B is perpendicular to I, ρ p is the resistivity when B is parallel to I, and is typically ρ o Greater than ρ p For GMR or TMR sensors, clamped with a fixed reference magnetic field B ref The resistance ρ(α) of the thin insulating material between the magnetized reference layer and the free layer, which can be magnetized in any direction by an external magnetic field B (which varies depending on the position of the GMR or TMR sensor relative to the magnetic marker pattern), depends on B. ref The angle α between B and is preferably given by

[0037] ρ(α)=ρ p+(ρ p -ρ ap )cos(α)

[0038] where ρ p It's B and B ref Resistivity when parallel, ρ ap It's B and B ref The resistivity when antiparallel and typically ρ p Minimum, ρ ap Magnetoresistive materials for any of AMR, GMR and TMR sensors are known per se in the art.

[0039] The "position sensing unit" detects the angular position within a pattern of magnetic marks, which pattern of magnetic marks is preferably substantially periodic in the aforementioned sense. Thus, when the belt is running in the direction of travel, a typical output of a position sensing unit arranged in the vicinity of the magnetic marks is: 1) a sinusoidal voltage signal corresponding to the orientation of the magnetic flux density B sensed from the magnetic marks and therefore to the angular position of the position sensing unit relative to the pattern; and 2) a corresponding cosine voltage signal corresponding to the angular position of the position sensing unit relative to the pattern. The position sensing unit in the aforementioned sense preferably comprises: a first Wheatstone bridge, the first Wheatstone bridge comprising two half-bridges, each half-bridge being formed by an upper leg and a lower leg made of resistors, which are magnetoresistive sensors in the aforementioned sense, the first Wheatstone bridge being capable of generating said sinusoidal signal; and a second Wheatstone bridge of identical construction being capable of generating said cosine signal. The two Wheatstone bridges may comprise an upper leg and a lower leg, each consisting of several magnetoresistive sensors in the above sense, which can be switched electrically in series and / or in parallel with each other, but with spatial orientations different from each other, to allow correction of errors in the magnetic signal B from the magnetic mark, as is known in the art; for example, when the magnetoresistive sensors are AMR sensors, see US2017 / 322052A1. If the magnetoresistive sensors constituting the Wheatstone bridge are AMR sensors, the angular position (in radians) is within a full period of 2π, which corresponds to the pole pitch DP, and therefore to half the distance between two adjacent north poles (or two adjacent south poles) of the magnetic mark pattern. If the magnetoresistive sensors constituting the Wheatstone bridge are GMR or TMR sensors, the angular position (in radians) is within a full period of 2π, which corresponds to 2DP, and therefore to the full distance between adjacent north poles (or adjacent south poles) of the magnetic mark pattern. For the first Wheatstone bridge generating a sine signal and the second Wheatstone bridge generating a cosine signal, the following features are preferred:

[0040] a) If the magnetoresistive sensor included in the Wheatstone bridge is an AMR sensor:

[0041] a1) the upper legs of the first half-bridge and the second half-bridge of the first Wheatstone bridge are spaced apart from each other by a full pole pitch, thus by a distance DP, and the lower legs of the first half-bridge and the second half-bridge are spaced apart from each other by the same distance DP, wherein these distances are measured from the geometric center of the magnetoresistive sensor constituting the leg in question. The same distances apply to the upper legs of the first half-bridge and the second half-bridge of the second Wheatstone bridge and to the lower legs of the first half-bridge and the second half-bridge of the second Wheatstone bridge;

[0042] a2) The first Wheatstone bridge and the second Wheatstone bridge are spaced apart from each other by a spacing distance of one quarter of the pole pitch of the magnetic marks in the strip, thus DP / 4, wherein the spacing distance is measured from the geometric center of the magnetoresistive sensor of the lower leg of the first half-bridge of the first Wheatstone bridge to the geometric center of the magnetoresistive sensor of the lower leg of the first half-bridge of the second Wheatstone bridge.

[0043] b) If the magnetoresistive sensor included in the Wheatstone bridge is a GMR or TMR sensor:

[0044] b1) Same as a1) above;

[0045] b2) As a2) above, except that the separation distance between the first Wheatstone bridge and the second Wheatstone bridge is half the pole pitch of the magnetic marks in the tape, thus DP / 2.

[0046] If these characteristics are met, when the position sensing unit is arranged near or in close spatial proximity to the magnetic mark pattern in the belt so that the direction of the magnetic mark pattern and therefore the belt travel direction are parallel to the spacing distance, and the conveyor belt runs in the travel direction, the first Wheatstone bridge generates a sinusoidal voltage signal with a given amplitude as a difference voltage between its midpoints, and the second Wheatstone bridge generates a corresponding cosine voltage signal with the same amplitude within the experimental error range as a difference voltage between its midpoints.

[0047] However, such a position sensing unit preferably comprises a first pair of Wheatstone bridges as described above and spaced apart from each other by said spacing distance so as to generate therefrom a sine signal and a corresponding cosine signal, and such a position sensing unit preferably further comprises a second pair of Wheatstone bridges as described above and spaced apart from each other by said spacing distance so as to again generate therefrom a pattern of alternating south and north magnetic poles a sine signal and a corresponding cosine signal. The two pairs of Wheatstone bridges are again spaced apart from each other by a full DP, wherein the spacing is measured from the geometric center of the magnetoresistive sensor of the lower leg of the first half-bridge of the first Wheatstone bridge of the first pair of Wheatstone bridges to the geometric center of the magnetoresistive sensor of the lower leg of the first half-bridge of the first Wheatstone bridge of the second pair of Wheatstone bridges. Furthermore, the polarity of the power supply of one pair of Wheatstone bridges is opposite to the polarity of the power supply of the other pair of Wheatstone bridges. The result of the combination of the spacing of exactly DP between the two pairs of Wheatstone bridges and the reverse polarity of their power supplies is that the magnetoresistive sensors of the second pair of Wheatstone bridges detect the so-called magnetic north pole when the magnetoresistive sensors of the second pair of Wheatstone bridges are actually on the magnetic south pole and at the same time when the magnetoresistive sensors of the first pair of Wheatstone bridges are on the actual magnetic north pole and detect the actual magnetic north pole, and vice versa. Similarly, the magnetoresistive sensors of the second pair of Wheatstone bridges detect the so-called magnetic south pole when the magnetoresistive sensors of the second pair of Wheatstone bridges are actually on the magnetic north pole and at the same time when the magnetoresistive sensors of the first pair are on the actual magnetic south pole and detect the actual magnetic south pole, and vice versa. Similar considerations can be made for the magnetoresistive sensors of the first pair and the magnetoresistive sensors of the second pair. Summing and optionally averaging the signal from the first Wheatstone bridge of the first pair of Wheatstone bridges and the signal from the first Wheatstone bridge of the second pair of Wheatstone bridges may remove systematic differences in the magnetic flux density B and / or the spatial dimension between the magnetic north pole and the magnetic south pole to give a total or averaged sine (respectively cosine) signal. Similarly, summing and optionally averaging the signal from the second Wheatstone bridge of the first pair of Wheatstone bridges and the signal from the second Wheatstone bridge of the second pair of Wheatstone bridges may again remove systematic differences in the magnetic flux density B and / or the spatial dimension between the magnetic north pole and the magnetic south pole to give a total or averaged corresponding cosine (respectively corresponding sine) signal.

[0048] For the purposes of this invention, a "sinusoidal signal" refers to an analog signal S (before conversion to a digital signal in an ADC) typically in volts or amperes, which can be represented as a discrete Fourier spectrum in time as follows:

[0049] Among them, C, A1 and A i (where i = 2, 3, ... N) is a constant with the same unit as S, is in 1 / s and is the fundamental angular velocity of the Fourier spectrum, γ1 and γ i(where i = 2, 3, ... N) is in radians and is the angular displacement, N being the largest integer which in theory could be up to infinity but in practice is typically in the range of 10 to 100, and more precisely 10, 20, 50 or 100, for example. In this definition, the magnitude of A1 is the coefficient A i at least 2 times, preferably at least 10 times, and more preferably at least 20 times the magnitude of any one of γ1 and γ i (where i = 2, 3, ... N) are all equal within the experimental error range. Most preferably, within the experimental error range, S = C + A1sin(ωt + γ1). The corresponding "cosine signal" should be understood as an analog signal that also conforms to the above formula, explanation and definition, but the premise is that for any γ1 and γ i (i=2, 3, ... N), an additional offset is added. In theory, this additional offset is exactly +π / 2 to represent the exact transition from sine to cosine, in practice, the additional offset may have a further small offset of ±α from +π / 2. This is one reason why error correction is needed (see below).

[0050] The conveyor of the present invention also includes a device capable of generating a blank area entry signal when the maximum intensity of the magnetic field detected by the position sensing unit drops or is about to drop to or drops below a threshold intensity, thereby informing the control unit to start ignoring the position signal of the position sensing unit, and the threshold intensity is lower than the default maximum intensity.

[0051] Once the position sensing unit enters the clear zone, the clear zone entry signal can be derived from the falling strength of the magnetic signal detected by the position sensing unit itself. This is an example of a device capable of generating a clear zone entry signal when the maximum strength of the magnetic field detected by the position sensing unit drops to or below a threshold strength.

[0052] However, in view of position accuracy, it is preferred that there are additional devices that are capable of generating such a blank zone entry signal and are arranged upstream relative to the corresponding downstream position sensing unit, so that the upstream additional device generates the blank zone entry signal before the corresponding downstream position sensing unit itself enters the blank zone. This is an example of a device that is capable of generating a blank zone entry signal when the maximum strength of the magnetic field detected by the position sensing unit is about to drop to or drop below the threshold strength.

[0053] For such additional devices capable of generating a blank zone entry signal upon entering a blank zone, the term “start signaling device” is also used herein. These additional devices capable of generating a blank zone entry signal upon entering a blank zone, or start signaling devices, are typically Hall sensors in the aforementioned sense.

[0054] The conveying device of the present invention may also include a corresponding timer in addition to each starting point signaling device, for allowing a time period to pass, after which a blank zone exit signal is generated, after which the control unit reconsiders the position signal of the position sensing unit (embodiment A). If the blank zone entry signal is generated by the position sensing unit itself (embodiment A1), then the time period t satisfies the following inequality

[0055]

[0056] where L is a length greater than the maximum length of any blank space present on the tape; and D u is the distance from the end point of the blank zone in question to the start point of the next blank zone upstream (relative to the direction of travel of the belt) of the blank zone in question. If there is only one blank zone, the "blank zone in question" and the "next blank zone upstream" refer to the same blank zone, and D u refers to the entire belt circumference excluding the length of the only blank zone that exists. It is recalled that the belt in the conveyor of the present invention is endless and the distance is actually the circumferential distance around the belt loop. Alternatively, if the blank zone entry signal is generated by the upstream starting point signaling device (embodiment A2), then the timer period satisfies the following inequality

[0057]

[0058] Where D m is the distance between the upstream origin signaling device and the associated downstream position sensing unit, and all other symbols have the same meanings as in the above inequality.

[0059] Alternatively, the conveyor of the present invention may include, in addition to the various devices capable of generating a blank zone entry signal, corresponding additional devices capable of generating a blank zone exit signal when leaving the blank zone (embodiment B). These devices capable of generating a blank zone exit signal may be the position sensing units themselves, in which case they are examples of devices capable of generating a blank zone exit signal when the maximum intensity of the magnetic field detected by the position sensing unit rises to the threshold intensity or rises to above the threshold intensity. Alternatively, there may be additional devices capable of generating a blank zone exit signal when leaving the blank zone, each of which is arranged downstream relative to the corresponding upstream position sensing unit, so that the downstream additional device generates a blank zone exit signal after the corresponding upstream position sensing unit has left the blank zone. This is an example of a device capable of generating a blank zone exit signal when the maximum intensity of the magnetic field detected by the position sensing unit rises to the threshold intensity or rises to above the threshold intensity. The additional device capable of generating a blank zone exit signal when leaving the blank zone is referred to herein as an "end signaling device". The control unit begins to reconsider the position information from a given position sensing unit from the time it receives the blank zone exit signal from the corresponding end signaling device.

[0060] If the blank zone entry signal is generated by the position sensing unit itself, then preferably the blank zone exit signal is also generated by the position sensing unit itself (embodiment B1). Then, these position sensing units are also examples of means capable of generating a blank zone exit signal when the maximum intensity of the magnetic field detected by the same position sensing unit rises to or above the threshold intensity.

[0061] However, if the blank area entry signal is generated by a start point signaling device (such as a Hall sensor), preferably the blank area exit signal is also generated by an end point signaling device (such as a Hall sensor) (embodiment B2), or the additional device is capable of generating both the blank area entry signal and the blank area exit signal (embodiment B3). The additional device capable of generating a blank area entry signal when entering a blank area and capable of generating a blank area exit signal when leaving a blank area is referred to herein as a "start point / end point signaling device".

[0062] It is preferred that the conveyor of the present invention is able to detect both the start and end of the blank zone (such as in embodiments B, B1, B2, B3). More preferably, the conveyor of the present invention comprises a start signaling device and an end signaling device for this purpose, in particular wherein both the start signaling device and the end signaling device are Hall sensors (such as in embodiment B2).

[0063] If the detection of the start and end points of the blank area is performed by the position sensing unit itself (embodiment B1 above), each position sensing unit will generate its own blank area entry signal when it enters the blank area (as can be detected by a weakened or disappeared magnetic signal), and will generate its own blank area exit signal when it leaves the blank area (as can be detected by the reappearance or increase of the magnetic signal). The control unit will ignore the position signal from any position sensing unit during the time period between the receipt of the blank area entry signal of any position sensing unit and the receipt of the blank area exit signal of any position sensing unit. Here, among all the position sensing units present, there are typically at least two position sensing units, preferably at least three position sensing units (not necessarily but preferably adjacent to each other), wherein any two position sensing units are spaced apart from each other in pairs by a distance greater than the maximum length of any blank area present on the belt. Position sensing units that meet this condition are referred to as "separated position sensing units" in this application.

[0064] If the conveyor of the present invention comprises a start signaling device and an end signaling device, in particular wherein these start signaling devices and end signaling devices are Hall sensors (above embodiment B2), each position sensing unit has one such start signaling device and one such end signaling device, wherein each start signaling device is located upstream of a corresponding position sensing unit, and each end signaling device is located downstream thereof, so that the start signaling device and the end signaling device sandwich the corresponding position sensing unit between them. For at least two mandatory separated position sensing units, each position sensing unit is separated from any of the remaining separated position sensing units by more than any length L of any blank area in the belt travel direction. j Each of these spaced apart position sensing units also has associated start signalling means and end signalling means, any pair of two (not necessarily but preferably adjacent to each other) upstream and downstream spaced apart position sensing units preferably has the end signalling means of the upstream position sensing unit of the pair spaced apart from the start signalling means of the downstream position sensing unit of the pair spaced apart by more than the maximum length L of any blank space present on the belt jA greater distance L ensures that at least one of the pair of position sensing units is always outside any blank area present on the conveyor belt. The distance between the paired upstream and downstream position sensing units themselves is then even greater than said distance L. The control unit disregards the position information from a given position sensing unit from the time it receives a blank area entry signal from the corresponding start signalling device (when the corresponding first additional device enters the blank area) and starts to reconsider the position information of this position sensing unit from the time it receives a blank area exit signal from the associated end signalling device (when the corresponding end signalling device leaves the blank area). This embodiment B2 is considered to be the most preferred.

[0065] If the conveyor of the present invention includes a start / end signaling device, in particular, wherein the start / end signaling device is a Hall sensor (embodiment B3 described above), each position sensing unit may have exactly one start / end signaling device, wherein the position sensing units and the start / end signaling devices are arranged in an alternating manner along the belt periphery in the longitudinal direction of the conveyor belt or the belt travel direction, and each position sensing unit is sandwiched between two adjacent start / end signaling devices. In addition, there are at least two spaced apart position sensing units, preferably at least three spaced apart position sensing units, wherein any two (not necessarily but preferably mutually adjacent) pairs of upstream and downstream position sensing units are spaced apart from each other by a distance L1 greater than the maximum length of any blank area present on the belt. In this embodiment B3, each start / end signaling device (when the start / end signaling device enters a blank area) generates a blank area entry signal for a position sensing unit located downstream of the start / end signaling device (and not necessarily but preferably adjacent to the start / end signaling device), and the start / end signaling device generates a blank area exit signal for the same position sensing unit when the start / end signaling device leaves the blank area.

[0066] In embodiment B3, as in embodiment B31, the control unit disregards the position information from a given position sensing unit from the time it receives a blank zone entry signal from the corresponding upstream start / end signaling device (when the corresponding start / end signaling device enters the blank zone), and begins to reconsider the position information of the position sensing unit from the time it receives a blank zone exit signal from the corresponding downstream start / end signaling device (when the corresponding start / end signaling device exits the blank zone). This embodiment B31 is similar to the above-described embodiment B2, except that there are start / end signaling devices rather than separate start signaling devices and end signaling devices.

[0067] Alternatively, within embodiment B3, in embodiment B32, there are: a first starting point signaling device, which is located upstream of all position sensing units and is capable of generating a blank area entry signal for a downstream (not necessarily but preferably adjacent) position sensing unit when entering a blank area; a second starting point signaling device, which is located downstream of all position sensing units, and the blank area entry signal generated by the starting point signaling device when entering the blank area is used as (interpreted as) a blank area exit signal for the upstream (not necessarily but preferably adjacent) position sensing unit; and additional starting point signaling devices, the number of which is one less than the number of position sensing units, and each such additional starting point signaling device is sandwiched between an upstream (not necessarily but preferably adjacent) position sensing unit and a downstream (not necessarily but preferably adjacent) position sensing unit; and the blank area entry signal generated by each such additional starting point signaling device is used as (interpreted as) a blank area entry signal for the downstream (not necessarily but preferably adjacent) position sensing unit, and is used as (interpreted as) a blank area exit signal for the upstream (not necessarily but preferably adjacent) position sensing unit. In this embodiment B32, any of the additional start signaling devices is separated from the corresponding upstream position sensing unit for which it generates the blank zone entry signal (the blank zone exit signal used / interpreted) by a distance L m is greater than the maximum length of any blank area present on the conveyor belt. In addition, the second start signaling device is separated from the adjacent upstream position sensing unit for which it generates the blank area entry (blank area exit used / interpreted) signal by a distance L n is also greater than the maximum length of any blank area present on the conveyor belt. In this embodiment B32, the control unit disregards the position information from the most upstream position sensing unit from the time when it receives the blank area entry signal from the first starting point signaling device when the first starting point signaling device enters the blank area, disregards the position information from the position sensing unit from the time when it receives the blank area entry signal from another starting point signaling device located upstream of any one of the other position sensing units (and not necessarily but preferably adjacent to the position sensing unit) when the position sensing unit enters the blank area, reconsiders the signal of the most downstream position sensing unit from the time when it receives the blank area entry (blank area exit using / interpretation) signal from the second starting point signaling device, and reconsiders the position information from the position sensing unit from the time when it receives the blank area entry (blank area exit using / interpretation) signal from another starting point signaling device located downstream of any one of the other position sensing units (and not necessarily but preferably adjacent to the position sensing unit).

[0068] In any embodiment of the conveyor of the present invention, in the case where the generation of the blank zone entry signal and / or the blank zone exit signal is done by the position sensing unit itself (such as in the above-mentioned embodiments A1 and B1), the blank zone entry signal and / or the blank zone exit signal can also be derived from the phasor (= square sum) of the sine signal and the cosine signal of the position sensing unit or from the square root of the sum. The square sum is also within the experimental error constant, and its square root is equal to the default maximum intensity of the sine signal and the cosine signal within the experimental error. However, in the case where one of the two magnetoresistive sensors of the position sensing unit enters the blank zone of the belt and thus generates a signal with reduced amplitude, the square sum of the two signals or its square root drops significantly below the default intensity. If such a significant intensity drop occurs, such as a typical drop to 0.4 to 0.9 times the default intensity, this indicates that the position sensing unit enters the blank zone and triggers the generation of the blank zone entry signal. On the other hand, if the intensity of the square sum or its square root of the two signals rises again to more than 0.9 times or substantially 1.0 times the default intensity, this indicates that the two magnetoresistive sensors of the position sensing unit are again outside the clear zone and this triggers the generation of the clear zone exit signal.

[0069] Similarly, in any embodiment of the conveyor of the present invention, in the case where the generation of the blank area entry signal and the blank area exit signal is accomplished by an additional device (such as a Hall sensor) and each position sensing unit is sandwiched between two such additional devices (such as in the above-mentioned embodiments B2, B3, B31 and B32), the above-mentioned phasors can also be obtained from the signals of the two additional devices that sandwich the position sensing unit between them. The blank area entry signal and the blank area exit signal are evaluated from the decrease and re-increase of the phasors respectively as described above. The sandwiching start signaling device and the end signaling device (embodiment B2), the sandwiching start / end signaling device (embodiment B31), or the sandwiching start signaling device (embodiment B32) are spaced apart from each other by a distance LH, which is given by the following formula:

[0070] LH=(2N+0.5)×DP

[0071] wherein N is a positive integer of at least 0, and DP is as defined above, provided that N is large enough to accommodate the sandwiched position sensing unit. Taking into account the spacing LH defined above, the signal strengths of the clamping start and end signaling devices (embodiment B2), the clamping start / end signaling devices (embodiment B31), or the clamping start signaling devices (embodiment B32) are again the sine signal and the corresponding cosine signal, respectively, which allow the formation of the phasor (the sum of the squares of their strengths) therefrom. For any such phasor-derived blank area entry signal and blank area exit signal, the control unit disregards the position information of the position unit from the time it receives the phasor-derived blank area entry signal from the phasor generating additional device that clamps any position sensing unit, and reconsiders the position information of the position unit from the time it receives the phasor-derived blank area exit signal from the phasor generating additional device that clamps the position sensing unit.

[0072] In all embodiments of the conveyor of the present invention, all position sensing units and, if present, all additional devices capable of generating a blank zone entry signal or capable of generating a blank zone exit signal are preferably arranged near, on top of or below the portion of the periphery of the conveyor belt that is not bent over the pulley or is not in contact with the pulley.

[0073] The position sensing unit applicable to the above-mentioned most preferred embodiment B2 (regardless of whether the phasor-derived blank zone entry signal and blank zone exit signal are used) may include the start signaling device and the end signaling device as a combined unit, which may optionally even be located in the same housing, such as Figure 1 shown on the left or right side of the display. Figure 1The combined unit shown in the left part of comprises a start signaling device 511 and an end signaling device 512 (such as in the form of two Hall sensors) and two Wheatstone bridges 513, 514 (in which the legs are composed of resistors which are AMR sensors) of the position sensing unit 51, which are spatially arranged so that the start signaling device 511 (such as a Hall sensor) is located on the outer side of the first Wheatstone bridge 513, and the end signaling device 512 (such as a Hall sensor) is located on the outer side of the second Wheatstone bridge 514, so that the start signaling device 511 and the end signaling device 512 sandwich the Wheatstone bridges 513, 514 between them and form a row arrangement of the start signaling device 511 (such as a Hall sensor) / first Wheatstone bridge 513 / second Wheatstone bridge 514 / end signaling device 512 (such as a Hall sensor). The two Wheatstone bridges 513, 514 are shown in a vertically staggered arrangement to allow for proper illustration of the proportional spacing of DP / 4 to allow for the generation of sine and cosine signals therefrom by this spacing. This staggering also symbolically represents the spatial interweaving of the legs of the first Wheatstone bridge 513 with the legs of the second Wheatstone bridge, which also facilitates the generation of sine and cosine signals therefrom. When such a combined unit with the row arrangement is aligned so that the rows are parallel to the belt travel direction, the belt travels in its travel direction, and the start signaling device is located upstream relative to the belt travel direction, then the start signaling device 511 will be the first of the four sensors to detect the start of the end connection area of ​​the belt and will therefore generate the blank area entry signal before any of the two Wheatstone bridges 513, 514 enters the blank area, while the end signaling device 512 located downstream relative to the belt travel direction will be the last of the four sensors to detect the end of the blank area of ​​the belt and will therefore generate the blank area exit signal only after each of the two Wheatstone bridges 513, 514 has left the blank area. The blank area entry signal is formed directly from the reduced signal of the start signaling device entering the blank area, or from a phasor formed by the sum of the squares of the signal strengths of the start signaling device 511 and the end signaling device 512 or the square root of this sum, if Figure 1 The distance LH between the start signaling device 511 and the end signaling device 512 shown in the left part of is calculated according to the above formula, and the phasor is also sine and cosine. Similarly, the blank area departure signal is directly formed by the added signal of the end signaling device 512 leaving the blank area, or by the added phasor formed by the signals of the start signaling device 511 and the end signaling device 512. If Figure 1The distance LH between the start signaling device 511 and the end signaling device 512 shown in the left part of is calculated according to the above formula, then the added phasor is also sine and cosine. In any way, whether directly or by phasor formation, it is ensured that the sine and cosine signals from the two magnetoresistive sensors 513, 514 forming the position sensing unit are only considered by the control unit when they represent useful position information.

[0074] Figure 1 The right part of shows a further position sensing unit suitable for the above-described most preferred embodiment B2 (regardless of whether phasor-derived blank zone entry and blank zone exit signals are used), which further position sensing unit also comprises the start signaling device and the end signaling device as a combined unit, which combined unit is optionally even located in the same housing. However, the combined unit of this embodiment comprises in its position sensing unit 51 a first pair of Wheatstone bridges 513, 514 and a second pair of Wheatstone bridges 515, 516 (wherein the legs here consist of resistors for AMR sensors), wherein the two Wheatstone bridges of each pair are again shown in a vertically staggered arrangement (see Figure 1 The first pair of Wheatstone bridges and the second pair of Wheatstone bridges are spaced full DP from each other, wherein the polarity of the power supply (VCC to GND) of one pair of Wheatstone bridges (513, 514) is opposite to the polarity of the power supply (GND to VCC) of the other pair of Wheatstone bridges (515, 516). The purpose of this full DP spacing between the Wheatstone bridge pairs and the reverse power supply polarity is as described above in the general definition of the position sensing unit. The purpose and meaning of the spacing LH between the start signaling device 511 and the end signaling device 512 (such as a Hall sensor) and the rest of the explanation are as described above for Figure 1 as described on the left side of the .

[0075] To generate said phasor, the conveyor of the unit then preferably also comprises analog or digital circuitry. In analog circuitry, the two squares may typically be formed using two conventional analog multipliers; the sum of the two squares may typically use a conventional summing operational amplifier. To compare said sum of squares or its square root with a threshold voltage which again may typically be 0.4 to 0.9 times said constant intensity, and to decide whether to generate said blank zone entry signal or said blank zone exit signal, the analog circuitry may typically also comprise a comparator. Digital circuitry for performing the phasor calculation and making the comparison with said threshold value may typically form part of the control unit and may be programmed by software.

[0076] The conveyor of the present invention preferably comprises at least 3 position sensing units, more preferably 3 to 16 position sensing units, or still more preferably 4 to 8 or 4 to 16 position sensing units, and error correction is then preferably based on position information derived from at least two position sensing units. In this case, at any time during the travel of the belt, there are at least two such position sensing units that are not in a blank area of ​​the belt. To ensure this, there are at least 3 spaced apart position sensing units, each of which is spaced apart from any of the remaining position sensing units in the direction of belt travel by more than the maximum L of any blank area present in the conveyor belt. j That is, if any one of the at least three position sensing units is labeled with an index i, and any one of the remaining position sensing units is labeled with an index k (i and k are from 1 to N, and i and k are different from each other), then the distance between them is labeled as L. ik and is measured as the associated peripheral distance of the following magnitude

[0077] L ik =|(t i -t k )×V|

[0078] (where t i and t j The time at which the i-th position sensing unit and the j-th position sensing unit (or the associated i-th start signaling device and the j-th start signaling device) generate a blank zone entry signal, respectively, and v is defined as above) is greater than the maximum L j ; where L j The measurements were performed as described above.

[0079] Figure 2The implementation of the above-mentioned embodiment A1 or B1 of the conveyor 1 of the present invention is shown. It comprises an endless conveyor belt 2, the periphery of which consists of a portion 21 bent on the pulley and a portion 22 thereof which is not bent on the pulley and which may be straight (as shown) or may be convexly bent, for example, by using a suitably curved support. In this example, the direction of travel (looping motion) of the belt is clockwise. This embodiment does not use any additional means to detect the entry of the blank area 4; it instead uses the signal information provided by the position sensing units 51, 52, 53 themselves as a means for generating a blank area entry signal. In order to generate a corresponding blank area exit signal, it may include a suitable timer (see the explanation of the above-mentioned embodiment A1), or it may generate a corresponding blank area exit signal from the position sensing units 51, 52, 53 themselves (see the explanation of the above-mentioned embodiment B1), in the latter case, such as by the above-mentioned phasor calculation from its sine and cosine signals. The alternating, preferably substantially periodic pattern of magnetic marks 3 extends along the entire periphery of the belt 2 (the portion 21 of the belt 2 that is bent on the pulley and the portion 22 of the belt 2 that is not bent on the pulley), except for the blank area 4, which can be the end connection area of ​​the conveyor belt 2. In this blank area, the mark produces a magnetic field of less than the default maximum strength (as the magnetic mark 3 outside the blank area will produce), or as shown in the figure, the mark is completely eliminated. The three position sensing units are marked with numbers 51, 52, and 53. The pairwise spacing distance L between any two of these three spacing units 12 , L 13 , L 23 are greater than the length L of the only blank area j . By meeting this requirement, it does not matter which of the three position sensing units is located in the blank area 4 and therefore cannot generate a useful position signal: the other two position sensing units are not located in the blank area 4, so the control unit 6 can always rely on the position information received from at least two of the position sensing units.

[0080] For the purposes of the present invention, the "length L" of any blank area of ​​the tape as it moves in the direction of travel of the tape is j ” is defined as

[0081] Li=(t2-t1)×V

[0082] wherein t1-t2 is the time period between a blank area entry signal and a corresponding blank area exit signal, wherein, where applicable, the blank area entry signal and the corresponding blank area exit signal are both generated by the same position sensing unit as defined above; or, the blank area entry signal is generated by a starting point signaling device as defined above, and the corresponding blank area exit signal is generated by an end point signaling device as defined above; or, the blank area entry signal is generated by an upstream starting point signaling device, and the corresponding blank area exit signal is a blank area entry signal generated by an adjacent downstream starting point signaling device but used as (interpreted as) a blank area exit signal, wherein "upstream" and "downstream" are related to the direction of belt travel; or, the blank area entry signal and the blank area exit signal are derived from phasors as described above, and v is the belt speed.

[0083] Figure 3 A further embodiment of the conveyor 1 of the invention according to the most preferred embodiment B2 is shown, which has only 2 position sensing units 54, 55, and has a start signaling device 511 and an end signaling device 512 (such as a Hall sensor) for detecting the first position sensing unit 54 entering and leaving the blank area 4, and has a start signaling device 521 and an end signaling device 522 (such as a Hall sensor) for detecting the second position sensing unit 55 entering and leaving the blank area 4. In this example, the direction of travel (looping movement) of the belt is again clockwise. The start signaling devices 511, 521 can generate a blank area entry signal for the first position sensing unit 54 and the second position sensing unit 55 respectively when entering the blank area 4, and the end signaling devices 512, 522 can generate a blank area exit signal for the first position sensing unit 54 and the second position sensing unit 55 respectively when leaving the blank area 4. Alternatively, the start signaling device 511 and the end signaling device 512 can use the phasor calculation explained above to generate such a blank area entry signal and blank area exit signal for the first position sensing unit 54 together, and the start signaling device 521 and the end signaling device 522 can use the phasor calculation explained above to generate such a blank area entry signal and blank area exit signal for the second position sensing unit 55 together. For this phasor calculation alternative, the spacing LH between the start signaling device 511 and the end signaling device 512 and between the start signaling device 521 and the end signaling device 522 is again such that it satisfies the above equation for LH calculation. The end signaling device 512 of the upstream position sensing unit 54 is spaced apart from the start signaling device 521 of the downstream position sensing unit 55 by a length L greater than the only blank area 4 present on the conveyor belt 2. j The upstream position sensing unit 54 and the downstream position sensing unit 55 are themselves spaced apart from each other by a distance then even greater than said distance L. The remaining parts and the associated numbers are as follows Figure 2 Shown and described. Figure 4 A further embodiment of the conveyor 1 of the invention according to the above-mentioned embodiment B32 is shown. In this example, the direction of travel (looping) of the conveyor belt is again clockwise. There is: a first starting point signaling device 531 (such as a Hall sensor) which is located upstream of all position sensing units and can enter the length L j The invention relates to a first embodiment of the present invention, wherein the first and second start-point signaling devices 532 and 533 are configured to generate a blank zone entry signal for the downstream (not necessarily but preferably adjacent) position sensing unit 56 when entering the blank zone 4; a second start-point signaling device 534 (such as a Hall sensor) which is located downstream of all the position sensing units and is capable of generating a blank zone entry (blank zone exit used / interpreted) signal for the upstream (not necessarily but preferably adjacent) position sensing unit 57 when entering the blank zone 4; and two additional start-point signaling devices 532 and 533 (such as Hall sensors) which are capable of generating a blank zone entry signal for the corresponding downstream and adjacent position sensing units 57 and 58 when entering the blank zone 4, and the blank zone entry signal is also used (interpreted) as a blank zone exit signal for the corresponding upstream and adjacent position sensing units 56 and 57. Therefore, the number of such additional start-point signaling devices 532 and 533 is two, which is one less than the number of the position sensing units 56, 57, and 58. Each of the additional start signaling devices 532 and 533 is sandwiched between the corresponding upstream (and adjacent) position sensing units 56 and 57 and the corresponding downstream (and adjacent) position sensing units 57 and 58. Any of the additional start signaling devices 531, 532 is separated from the corresponding upstream position sensing unit 56 or 57 by a distance L m Than the length L of the only blank area 4 on the conveyor belt 2 j In addition, the distance L between the second starting point signaling device 534 and the adjacent upstream position sensing unit 58 is n Also greater than the L j. The control unit 6 disregards the position information from the most upstream position sensing unit 56 from the time it receives the blank area entry signal from the first additional device 531 when the first starting point signaling device 531 enters the blank area; disregards the position information from the other position sensing units 57 or 58 from the time it receives the blank area entry signal from the corresponding and adjacent upstream starting point signaling device 532 or 533; reconsiders the signal of the most downstream position sensing unit 57 from the time it receives the blank area entry (blank area exit used / interpreted) signal from the second starting point signaling device 534; and reconsiders the position information from any one of the other position sensing units 56 or 57 from the time it receives the blank area entry (blank area exit used / interpreted) signal from the corresponding downstream and adjacent additional starting point signaling device 532 or 533. The remaining parts and associated numbers are as follows Figure 2 and Figure 3 Shown and described.

[0084] For the purposes of the present invention, the length involving the additional device as one of its end points is measured starting from the geometric center of the additional device, in particular, in the case where such additional device is a Hall sensor, the geometric center of the semiconductor layer contained therein. Similarly, the length involving the magnetoresistive sensor as one of its end points is measured starting from the center of the bridge within the Wheatstone bridge contained therein.

[0085] As described above, the conveyor of the present invention comprises at least two, preferably at least three, more preferably a plurality of position sensing units. The output voltage of any position sensing unit is preferably converted into digital information of typically 8 to 16 bits depth using a conventional analog-to-digital converter (ADC). This conversion is performed regardless of whether the position sensing unit in question generates a sine / cosine voltage signal with a default strength (as long as the position sensing unit is in the vicinity of a readable magnetic mark) or whether it generates a sine / cosine voltage signal of less than the default strength (when the position sensing unit is located in one of the blank zones of the belt). The task of the control unit is to decide whether to take into account the digital information thus generated based on the blank zone entry signal and the blank zone exit signal it receives from each of the position sensing units.

[0086] The position sensing unit, the optional start and end signaling means, and the optional start / end signaling means may be arranged so that they are closer to the conveying surface of the conveyor belt than to its pulley-facing surface, or they may be arranged so that they are closer to the pulley-facing surface of the conveyor belt than to its conveying surface. In either of these two variants, the magnetic mark may be located at the conveying surface (not covered by any covering layer), near the conveying surface (e.g., when covered by a top covering layer), embedded in the belt, at the pulley-facing surface (not covered by any bottom layer), or near the pulley-facing surface (e.g., when covered by a bottom covering layer).

[0087] The output signal of the position sensing unit may be optionally filtered by a low-pass filter to remove high-frequency noise therein, and then converted into a digital signal using an ADC.

[0088] The output of each ADC is typically an unsigned byte (if the ADC has an 8-bit depth). In this case, the positive maximum value of the sine and cosine signals (if they are assumed to be ideal) will be close to 255, such as 238; the zero point will be at 128; the negative minimum value of the sine and cosine signals will be close to zero, such as 18. In this case, the amplitude of the digitized cosine and sine signals will be 110. If the ADC has a 16-bit depth, its output is typically an unsigned short integer, and the positive maximum value of the sine and cosine signals (if they are assumed to be ideal) will be close to 65535, such as 62768; the zero point will be at 32768; the negative minimum value of the sine and cosine signals will be close to zero, such as 2768. In this case, the amplitude of the digitized cosine and sine signals will be 30000. The amplitudes of the analog input sine signal and the analog input cosine signal are conveniently appropriately scaled before being fed into the ADC, for example by using two operational amplifier instrumentation amplifiers, so that the operating range of the ADC of 256 (8-bit depth) or 65538 (16-bit depth) is utilized as much as possible, but their outputs are not saturated. This optimized digital output amplitude of the ADC (such as 110 for an 8-bit depth ADC and 30000 for a 16-bit depth ADC) is hereinafter referred to as the "nominal amplitude A" of the ADC digital signal output.

[0089] The control unit performs substantially all subsequent tasks using the digital signals it receives from the ADCs of all position sensing units. The control unit may be software-implemented (thus implemented by a suitably programmed computer) or hardware-implemented (e.g. by a field programmable gate array FPGA, optionally in combination with a microcontroller).

[0090] The mandatory and optional functions of the control unit are described below. In this description, any reference to "ωt" is the product of the angular velocity multiplied by the time, and therefore the position angle (in radians). If the position sensing unit comprises an AMR sensor, the position angle lies within a full period of 2π, which corresponds to the pole pitch DP and therefore to half the distance between two adjacent north poles (or two adjacent south poles) of the magnetic marker pattern. Alternatively, if the position sensing unit comprises a GMR or TMR sensor, the angular position (in radians) lies within a full period of 2π, which corresponds to 2DP and therefore to the full distance between two adjacent north poles (or two adjacent south poles) of the magnetic marker pattern. The same assumptions apply to the calculated position angle And the phase shifts α and αα which will be used in the following discussion are also valid.

[0091] The first mandatory task of the control unit is to ignore the digital signal from any position sensing unit within the time range between the white space entry signal and the white space exit signal it receives from the position sensing unit. To this end, the control unit may include a corresponding flag for each position sensing unit, which the control unit sets to a value indicating "don't consider" (such as "zero") when the control unit receives a white space entry signal from the position sensing unit in question, and which the control unit sets to a value indicating "consider" (such as "one") when the control unit receives a white space exit signal from the position sensing unit in question.

[0092] A second optional but preferred task of the control unit is, based on the first task described above, to process the digital signals from any ADC it considers (and hence from any associated position sensing unit) to remove phase, offset and amplitude (POA) errors from the digital sine and cosine signals from any considered ADC. The two error-laden input signals cos input and sin input Even when digitized it can be written within experimental error as follows:

[0093]

[0094] Where C and S (dimensionless) represent the offset, ΔA C and ΔA S (an integer in ADC units) represents the amplitude deviation from the above nominal amplitude A, α (in radians) represents a further phase shift beyond the normal phase shift of -π / 2 of the sine signal relative to the cosine signal, and Z (an integer in ADC units) represents the zero point of the ADC. When the output of the ADC is an unsigned integer, the zero point Z is typically located at half the resolution of the ADC, i.e., for an 8-bit ADC, it is located at 2 7= 128, while for a 16-bit ADC it is located at 2 15 =32768; when the output of the ADC is a signed integer, Z is typically zero.

[0095] The purpose of this second optional but preferred task is to generate a digital error-corrected cosine signal cos from the above input signal corr and the sinusoidal signal sin corr In the present invention, these digital error-corrected signals are assumed and defined as follows within experimental error:

[0096]

[0097] Among them G C and G S (dimensionless) is the scaling gain relative to the nominal amplitude A; ΔC and ΔS (dimensionless) are the digital correction offsets, and Δα (radians) is the correction phase shift. After applying these corrections, and should each be as close as possible to the nominal amplitude A above; and C-ΔC and S-ΔS should each be as close to zero as possible.

[0098] In (3b) and (4b), Δα is also assumed to be small, and α / 2 is also assumed to be small, and taking into account the latter (from the first term of the corresponding Taylor series),

[0099]

[0100] Using (3c) and for small Δα and α / 2, the above (3b) is further modified to:

[0101]

[0102] Assume 1-α 2 and Each is essentially one, then (3d) can be further simplified to:

[0103]

[0104] Still further, optionally assuming that approximately (A+ΔA C )=(A+ΔA S )Equation (3e) can still be simplified to:

[0105]

[0106] Even still more alternatively, αΔαC can be assumed to be zero, 1-α is essentially equal to one, so (3f) can be further simplified to:

[0107]

[0108] In the simplest embodiment, (A+ΔA C ) can be assumed to be A, so (3g) gives:

[0109]

[0110] Similarly, using (4c) and for small Δα and α / 2, the above (4b) is further modified to:

[0111]

[0112] Again, assuming 1-α 2 and Each is essentially one, then (4d) can be further simplified to:

[0113]

[0114] Still further, again optionally assuming the approximation (A+ΔA C )=(A+ΔA S )Equation (4e) can still be simplified to:

[0115]

[0116] Even still alternatively, αΔαS can be assumed to be zero, 1-α again being essentially equal to one, so (4f) can be further simplified to:

[0117]

[0118] In the simplest embodiment, (A+ΔA S ) can be assumed to be A, so (4g) gives:

[0119]

[0120] Equations (3f), (3g) or (3h) and (4f), (4g) or (4h) are the equations for calculating sin corr and cos corr A simple optimization equation for .

[0121] For this second optional but preferred task, three exemplary variations are illustrated below, assuming that the sine input signal sininput and the cosine input signal cosinput meet their most preferred definitions above.

[0122] In a first exemplary modification, the control unit stores the position angles within a period of 2π. cos input and sin inputThe value of cos input value to obtain its maximum value (assuming that ) and the minimum value (assuming that ), and take them as C max and C min , and using them in (1) above, this gives:

[0123]

[0124] All symbols are as above.

[0125] Similarly, the storage unit scans the stored sin input The value of to obtain its maximum value (assuming that ) and the minimum value (assuming that ), and take them as S max and S min , and using them in (2) above, this gives:

[0126]

[0127] Again all symbols are as above.

[0128] The control unit increases the gain G C and G S Use as:

[0129]

[0130] According to the above requirement, C-ΔC=0, use the above (6)

[0131] Given

[0132] Similarly, according to the above requirement S-ΔS=0, use the above (8)

[0133] Given

[0134] In addition, the control unit scans the stored cos input and sin input value pairs to obtain the sin input1 -Z=cos input1 The first instance of -Z takes the value as CS eq1 , and to obtain the sin input2 -Z=-cos input2 The second instance of -Z takes the value as CS eq2 If sin input and cos input Without any further phase shift betweeneq1 Will be in At, and CS eq2 Will be in Sin input and cos input A further phase shift α between the two is due to sin input The sine term in the equation is relative to cos input The cosine term in is further phase shifted by α (see (1) and (2)). It is also cos input The cosine term in is relative to cos input The opposite phase shift of the sine term α in CS eq1 :

[0135]

[0136] Using (7) and (8) gives:

[0137]

[0138] For CS eq2 :

[0139]

[0140] Using (5) and (6) gives:

[0141]

[0142] According to (13) and (14), the sought phase shift α / 2 is obtained and therefore the correction phase Δα which must be equal to it according to (3) and (4) above is

[0143]

[0144] To perform this first exemplary variant of error correction, the control unit stores the cosine from a given period. input and sin input Value pairs, and calculate ΔA according to formulas (5), (7), (9), (10), (11), (12), and (15) respectively C , ΔA S , G C , G S , ΔC, ΔS, and Δα, and use the stored cos input and sin input The control unit then uses the ΔA obtained in this way to C , ΔA S , G C , G S, ΔC, ΔS, and Δα, using the above formulas (3d), (3e) or (3f), and (4d), (4e) or (4f), for one or more subsequent cycles, while correcting any input signal value from the considered ADC for cos input / sin input In this first exemplary variant of error correction, a single iteration is required to obtain the error correction signal cos corr and sin corr The control unit preferably replaces the stored cos from a given cycle with a corresponding updated value from a subsequent cycle after typically having observed one or two subsequent cycles. input and sin input Value pair.

[0145] This first exemplary variant does not use analog position angles and / or any feedback for error correction in conjunction with the measured position angles. Omitting such feedback can avoid potential stability problems associated with high frequency noise in the measured input position angles. Such noise can cause the calculated position angle to be fed back to be phase shifted relative to the original measured position angle, thereby switching from negative feedback to positive feedback, causing possible oscillations. This problem can also occur when the feedback is digital, when the calculation rate of the analog position angle is comparable to the sampling rate of the digital measured position angle.

[0146] The second exemplary variation for error correction uses the correction value pair (sin corr |cos corr ), where the ADC zero point Z has been removed by subtraction and assumed to be zero. In this second exemplary variant, from each value pair (sin corr |cos corr ) to obtain the amplitude M and phase between the two signals

[0147]

[0148] This can be evaluated using equation (17) or using the known CORDIC algorithm in "vectorized" mode. An exemplary overview of this "vectorized" CORDIC algorithm is as follows i)-v):

[0149] i) Assumed phase Negative value of (so ) The initial value of is zero; it is assumed that the incremental correction angle , where i is an integer from -2 to a maximum value N, is chosen such that atn(2 -N ) is not greater than The acceptable residual error of , and the value of the i-th tangent is given as Assuming a symbolic variable σ, if the initial sin corr value ≥ 0, the symbol variable takes the value +1. If the initial sin corr If the value is <0, the symbol variable takes the value -1;

[0150] ii) Calculate sin as follows corr and cos corr The new iteration value of :

[0151] If i = 0, then the above cos corr and sin corr The initial value of is inserted into the right side (including its first factor This multiplication matrix is ​​orthogonal; it only performs a rotation of the right-hand side vector without changing its magnitude);

[0152] iii) If the (sin corr ) i+1 and (sin corr ) i have the same sign, then

[0153] The value σ×atn(2 -i ) added to

[0154] Set(sincorr) i =(sincorr) i+1 and

[0155] Setting (coscorr) i =(coscorr) i+1 ;

[0156] iv) increase i by 1; and

[0157] v) Repeat steps ii)-iv) until (sin corr ) i+1 is equal to zero, or until i reaches N (whichever occurs first);

[0158] v) The amplitude M sought is taken as the (cos corr ) i , and the phase sought Take as the value obtained in the last iteration of ii)+iii)

[0159] atn(2 -i )and The array of is typically stored in a corresponding look-up table, for example in the control unit.

[0160] The value pair thus obtained from one or two cycles of the input signal is required To obtain ΔC, ΔS, Δα, G C , and G S , which is explained below (for the phase angle The amplitude M at For example, for the magnitude M at zero radians, write "M0"). Assume that each value with the cos from which it was obtained input Value and sin input The values ​​of ωt±α / 2 in the values ​​are approximately the same.

[0161] Then according to equation (3g), for the correction gain G C and the difference (C-ΔC), set Z to zero (which has been taken from cos input and sin input subtracted from , see above):

[0162]

[0163]

[0164] and ignore the rightmost minor term:

[0165]

[0166] If we collect two cycles of value pairs Then for the correction gain G C Sum difference (C-ΔC):

[0167] And again ignore the rightmost minor term:

[0168]

[0169] Similarly, according to equation (4d), for the correction gain G S Sum difference (S-ΔS):

[0170]

[0171]

[0172] and ignore the rightmost minor term:

[0173]

[0174] If we collect two cycles of value pairs but

[0175] And again ignore the rightmost minor term:

[0176]

[0177] For the correction additional phase shift Δα:

[0178]

[0179] This gives for Δα

[0180]

[0181] For the correction gain G C , the above formula (18a) can be used.

[0182] If two cycles of value pairs have been collected but

[0183]

[0184] For the correction gain G C , the above formula (18b) can be used.

[0185] In order to carry out this second exemplary variant of the error correction, the control unit therefore proceeds as follows:

[0186] a) It uses equations (16) and (17) for one or two cycles of cos input and sin input For each input value pair, the magnitude M and phase are calculated. The values ​​of ΔC, ΔS and Δα are taken as zero, G C and G S The value of is taken as one here; therefore cos input and sin input Each input value pair and the corresponding correction value pair cos corr and sin corr is the same as can be obtained using equations (4c) and (4d); therefore equations (16) and (17) here can also be used for cos input and sin input The control unit stores all the amplitudes M and phases obtained in this way. The control unit preferably evaluates equations (16) and (17) using the CORDIC algorithm in the "vectorized" mode described above.

[0187] b) It stores the value of Using the above equation (18a) (assuming (A + ΔA C ) is equal to A) calculate G C and the value of C-ΔC calculated using equation (19a) above (if one cycle is stored), or the stored value of Using the above equation (18b) (again assuming (A + ΔA C )Calculate G C The value and the value of C-ΔC calculated using equation (19b) above (if two cycles are stored); it is based on the stored value Using the above equation (20a) (assuming (A + ΔA S ) is equal to A) calculate G S and the value of S-ΔS calculated using equation (21a) above (if one cycle is stored), or the stored value Using the above equation (20b) (again assuming (A + ΔA S ) is equal to A) calculate G S The value of and the value of S-ΔS calculated using the above equation (21b) (if two cycles are stored); and the value of Δα calculated using the above equation (22a) (if one cycle is stored) or the above equation (22b) (if two cycles are stored).

[0188] c) It adds the value of C-ΔC obtained by step b) or d1) (if applicable) to the value of ΔC and adds the value of S-ΔS obtained by step b) or d1) (if applicable) to the value of ΔS.

[0189] d) For at least one additional period of cos input and sin input For any value pair of

[0190] d1) Using equations (3d) and (4d) (assuming Z is zero and (A+ΔA C ) and (A+ΔA S ) is equal to A) and G obtained by step b) or d1) C , G S and Δα (if applicable) and the values ​​of ΔC and ΔS obtained by the above step b) or step d1) (if applicable) and the corresponding cos corr and sin corr The value pair of coscorr and sin corr Using equations (16) and (17), again preferably using the CORDIC algorithm in the “vectorized” mode described above, the magnitude M and phase The value of; and according to the amplitude M and phase obtained in this way The value pair of G is calculated by the procedure described in step b). C , C-ΔC, G S , S-ΔS, and new values ​​of Δα;

[0191] d2) If G obtained in step d1) C and / or G S If the deviation from one exceeds the acceptable difference, and / or the deviation from zero of C-ΔC, S-ΔS and / or Δα obtained by step d1) exceeds the acceptable difference, it goes to step c) and subsequent steps to reprocess the same cos input and sin input otherwise, it will obtain the amplitude M and phase The value pair is taken as the final amplitude M and the final phase and processing the next cos of the at least one next cycle by executing step d1) and subsequent steps input and sin input .

[0192] e) controlling the control unit to process the cos input and sin input After one to ten, preferably four further cycles of the value pairs of , steps a) and b) are performed again.

[0193] A third exemplary variant for error correction can be used when the sign and preferably also the approximate magnitude of α / 2 is known. This third exemplary variant again uses the correction value pair (sin corr |cos corr ), where the ADC zero Z has been removed by subtraction if necessary and assumed to be zero, and the identity The above formulas (3e) and (4e) can be converted into the following formulas (3i) and (4i):

[0194]

[0195] Assume (A+ΔA C ) and (A+ΔA S ) is equal to the magnitude M (where appropriate), which in turn gives (3j) and (4j):

[0196]

[0197] On the other hand, using equations (3a) and (4a) above in equation (16a) above, assuming that Z is zero:

[0198] In the above equation, ωt can be assumed to be approximately equal to And Δα and α / 2 can be assumed to be close to zero. Therefore:

[0199] Similarly, using equations (3a) and (4a) above in equation (16b) above, and assuming that Z is zero:

[0200]

[0201] In the above equation, ωt can again be assumed to be approximately equal to And Δα and α / 2 can again be assumed to be close to zero. Therefore:

[0202]

[0203] because and are independent of each other, so equation (23a) uses the above identities to yield the following:

[0204]

[0205] Similarly, because and are independent of each other, so equation (23b) also uses the above identity to obtain the following equation:

[0206]

[0207] Based on (24a) and (24b), (A+ΔA S ) / G S and (A+ΔA C ) / G C The values ​​of are always the same. They must actually all converge to the nominal amplitude A.

[0208] The third exemplary variant is recursive and forms an independent subject of the present invention. It is based on sin input Value and cos input The value is calculated using the above formulas (3j) and (4j) to calculate sin corr and cos corr value, and then use the sin obtained in this way corr Value and cos corrThe values ​​are calculated using formulas (16) and (17) or by the CORDIC algorithm. and and using formulas (16a) and (16b) respectively and Then use the obtained and In (24b), (24a), (25b), and (25a), we obtain (A+ΔA S ) / G S , (A+ΔA C ) / G C , (S-ΔS), and (C-ΔC), and then reuse the latter in equations (3j) and (4j). In these equations, the term is an adjustable parameter that changes with each iteration. It is derived from the power σ2 -k , where k is an integer from an initial value up to a suitable maximum index that is greater than or equal to the initial value (such as in the range of 10 to 64, e.g. 10, 15 or 31) and increases with each iteration, where the initial value of k may be assumed to be in the range of 4 to 8, preferably 6, but, if the magnitude of α / 2 is known, is more preferably selected such that

[0209]

[0210] And if α / 2 is positive or zero, then σ is +1, and if α / 2 is negative, then σ is -1.

[0211] According to the third exemplary variation, given an input signal cos input and sin input The iterative phase adjustment of the value pair is as follows:

[0212] a) For the start of the iteration, assume that the initial values ​​of Δα, ΔC and ΔS (as defined in equations (3a) and (4a) above) are zero, assume that the initial values ​​of k and σ are chosen as described above, and assume that the amplitude To reasonably approach the value of the nominal amplitude A (such as in the range of 0.5 to 2 times, for example 1.25 times, the nominal amplitude A), and assuming is equal to the input signal cos input and sin input The value of ωt in the pair is given by and , where ω in ωt is the nominal angular velocity which can be derived as πv / DP', where v is the nominal belt travel speed and DP' is the pole pitch as defined above, representing the nominal (unextended and unshortened pole pitch), or ω in ωt is the position angle from the previously determined is derived and its first derivative with time is formed; and t in ωt is derived from a timer or clock;

[0213] b) Use σ from step a, k from step a) or step g) (as applicable) to set and using it and the step a) or step d) and (If applicable) Calculate the values ​​of S-ΔS and C-ΔC using equations (25b) and (25a) above, respectively, and use the values ​​in step a) or step d) (A+ΔA) (if applicable) and Δα in step a) or step f2) (if applicable) are calculated using the above equations (24b) and (24a), respectively. S ) / G S and (A+ΔA C ) / G C 's value (so these values ​​are the same);

[0214] c) using Δα, ΔC and ΔS in step a) or step f2) (if applicable) and (A+ΔA) in step b) S ) / G S＝ (A+ΔA C ) / G C , C-ΔC, and S-ΔS, using equations (3j) and (4j) to calculate cos corr and sin corr ;

[0215] d) Using the cosine in step c) corr and sin corr The new associated magnitude is calculated using equations (16) and (17) or preferably using the CORDIC algorithm in the "vectorized" mode described above Related to the new and use equations (16a) and (16b) to calculate the new associated Value and value, and optionally if digital calculations by equation (17) or the CORDIC algorithm provide values ​​limited between -π / 2 and +π / 2 Then in addition i) if sin corr <0 and cos corr > 0, then add 2π to the restricted or ii) if sin corr >0 and cos corr < 0, then add π to the restricted or iii) if sin corr <0 and cos corr< 0, then add π to the restricted

[0216] e) using the obtained in step d) the value of , the value of Δα in step (a) or step f2) (if applicable), and the value of The values ​​of (A+ΔA) are calculated using the above equations (24b) and (24a) respectively. S ) / G S and (A+ΔA C ) / G C the new value of (so they are the same);

[0217] f) If (A+ΔA S ) / G S =(A+ΔA C ) / G C The new value is greater than that in step b) (A+ΔA S ) / G S =(A+ΔA C ) / G C The corresponding previous value of is closer to A), then:

[0218] f1) Reverse the (A+ΔA) in step e) S ) / G S =(A+ΔA C ) / G C The new value of is set to (A+ΔA S ) / G S =(A+ΔA C ) / G C The corresponding previous value of ;

[0219] f2) Replacing the The values ​​of C-ΔC and S-ΔS are added to the values ​​of Δα, ΔC, and ΔS, respectively;

[0220] g) Increase k by 1;

[0221] h) repeating steps b) to g) until k is the other maximum index; and

[0222] i) Take the value obtained in step d) of the last iteration performed and and / or eventually and finally Used for location determination.

[0223] Computer simulations of this third exemplary variation for error correction show that it is able to remove the cos input and sin inputA further phase shift between α may account for most or even almost all of it, but it is less suitable for removing the amplitude deviation ΔA C and ΔA S As well as offsets C and S. Therefore, this third exemplary variation is particularly suitable for substantially no offsets C and S and amplitude deviation ΔA C and ΔA S sin input Signal and cos input signal, or the offset C and S and the amplitude deviation ΔA C and ΔA S has been pre-averaged, for example by using Figure 1 The right side of the embodiment and the associated position sensing unit are described. For this third exemplary variant, the above phase error α is preferably positive, such as in the range of 0 to +0.06 radians, more preferably in the range of 0 to +0.03 radians. Computer simulations also show that when sin input Signal and cos input A further phase shift α can also be mostly or almost completely removed when the signal is loaded with a small amount of random noise.

[0224] Figure 8 a. Figure 8 b shows the result of phase error correction according to the third exemplary variant of the above invention. The above formulas (1) and (2) contain the terms -α / 2 and +α / 2 as phase errors, respectively. If α / 2 itself is greater than zero, then according to formula (1), cos input will lag behind (move to the right in time or angle), and according to formula (2), sin input will be advanced (moved to the left in time or angle). The final result is sin input Closer to cos by phase shifting α input , that is, from cos input to sin input The phase shift is π / 2-α instead of the normal π / 2. This typically occurs when the tape with the magnetic marker is stretched during use (the pole pitch therefore increases from the normal, unstretched DP' to the stretched DP) without a corresponding increase in the distance between the sensor generating the sine signal and the sensor generating the cosine signal in the position sensing unit. Figure 8 a shows an exemplary α / 2 of +0.03 radians over the entire period in radians. This corresponds to a ribbon stretch factor, and therefore to an increase factor of DP to DP', of 1+0.06 / 2π=1.0095 or nearly 1% ribbon stretch. sin input and cos input The nominal digitized amplitude (ADC units) is 55000. The cosinput The signal is shown as a dotted line, with sin leading in time or angle input The signal is shown as a dotted line. An initial amplitude of 1.25 times the nominal amplitude A is used. After iterations from an initial value of k=6 up to a maximum value of 31, the phase error corrected cosine corr Value and sin corr Value, corresponding to the phase error correction angle is plotted and shown as a solid line. cos corr Now basically shows that relative to sin corr The normal phase shift of π / 2 is negligible. The corresponding corrected Δα, ΔC and ΔS values ​​obtained after the last iteration are Figure 8 The corresponding corrected phase angle in b for the entire period in radians are drawn and shown as solid lines, dashed lines and dotted lines respectively.

[0225] Figure 5 An exemplary schematic diagram of a control unit 6 suitable for executing the above second exemplary variant using equations (3f) and (4f) and executing the above third exemplary variant using equations (3j) and (4j) is depicted in FIG. The control unit comprises an FPGA 7, for example a Cyclone 5 (Intel). The FPGA 7 firstly calculates for each considered ADC signal pair A(cos input ) and B(sin input ) performs the calculations of equations (3f) and (4f) above, typically using two consecutive Altera lpt_mult macro functions for each of the two equations. The first macro function for equations (3f) and (3j) has reference numeral 71 and performs sin input The first macro function for equations (4f) and (4j) has reference numeral 72 and performs cos input The second macro function for equations (3f) and (3j) has reference numeral 73 and performs the multiplication with (A+ΔA C ) / G C The second macro function for equations (4f) and (4j) has reference numeral 74 and performs the multiplication with (A+ΔA S ) / G SThe final scaled multiplication. Further logic gates 75, 76, 77, 78 implement the addition / subtraction appearing in formulas (3f), (3j), (4f), and (4j). FPGA7 may also include two AND gates 81, 82 for determining whether to consider the input signal pair A / B based on the signal state of signal line E. The state of the signal line E can be directly derived from the corresponding position sensing unit as a result of its Hall sensor, which can be the blank area entry signal and the blank area exit signal. Alternatively, the state of the signal can be derived from the state of the above-mentioned "consider / do not consider" flag, which in turn is set by the blank area entry signal and the blank area exit signal. FPGA7 also includes a suitable architecture 9 for correcting the error-corrected output signal A' (cos corr ) and B'(sin corr )Execution amplitude Calculation and phase angle The control unit 6 further comprises a microcontroller 10 for performing calculations on the error correction value G using formulas (18a) / (18b), (20a) / (20b), (19a) / (19b), (21a) / (21b), and (22a) / (22b) respectively. C , G S , (C-ΔC), (S-ΔS), and Δα (second exemplary variation), or for performing the initialization using formulas (24b), (24a), (25a), and (25b), respectively. Value and Value and error correction value (A+ΔA S ) / G S , (A+ΔA C ) / G C , (C-ΔC), and (S-ΔS), and for summing the (α / 2-Δα) increments to Δα (third exemplary variant). If the control unit 6 is used in the second exemplary variant for error correction, it also includes a read / write memory space 11 for storing the value pairs of amplitude M and phase for one or two cycles. Alternatively, if it is used in the third exemplary variation, such a read / write storage space 11 is not required. The output of the microcontroller 10 is used as the input of the FPGA 7. On the other hand, and The final output value of will be used for further processing as will be explained below.

[0226] Figure 5The operation paths shown in are for a single considered ADC input signal pair A / B and a signal E; in practice, FPGA 7 will include corresponding operation paths for each ADC input signal received from a position sensing unit (whether considered or not).

[0227] The control unit performs the incremental position angle The calculation of is the third mandatory task. This can be done by simply dividing each sin received directly from any of the ADCs considered input and cos input The value and the inverse tangent of the quotient thus obtained are obtained (if the second but preferred error correction described above is not performed), or it may be the final phase obtained after performing one of the second but preferred error corrections described above.

[0228] The control unit performs the incremental position angle The calculation of the time first derivative of is performed as a fourth optional task (simultaneously or sequentially with or after the third task) to obtain ω defined above, which is independent of the original sin obtained from the different considered ADCs input Signal and cos input Any (unknown) phase shift β between the signals. If the fourth task is performed simultaneously with the third task, then directly:

[0229]

[0230] This unknown phase shift β may be due to, for example, the distance L between the two position sensing units to be considered. ik is a non-integer multiple of 2*DP (DP is as defined above) and / or the length L of the terminal connection region j The control unit can only approximately calculate ω at discrete time points, each of which is separated from the next by a finite constant time interval Δt, as shown in the following formula:

[0231]

[0232] where Δt is small enough, such as to constitute a reasonable approximation to the above formula.

[0233] The control unit may assume that ω is constant over time, or that it varies over time. In particular, in the case of the above approximate calculation, the approximate ω thus obtained may be considered as a series of discrete value pairs t n / ω(t n ), where t n is the nth time point, and ω(t n) is the value of ω at that point in time. The control unit may store this series in an internal memory to calculate an approximate angular acceleration or deceleration value therefrom.

[0234] The control unit performs incremental position determination as a fifth mandatory task. On the one hand, this can be done by counting at a frequency proportional to said ω (whether constant or variable) while completing the fourth optional task mentioned above. An "increment" is an arbitrarily chosen increment length ΔL, which is chosen to be small enough to allow the position determination to the required finesse. ΔL can typically be in the range of 1 mm to 1 nm, depending on the required finesse. This spatial increment length ΔL can be stored in the control unit in an erasable / rewritable form or in a read-only form. For counting such ΔL increments, the control unit typically includes an integer register that can be incremented in steps of 1. Each such increment of 1 added to the integer register corresponds to a spatial increment of length ΔL to the absolute position. The control unit increases the count in the integer register with a frequency f, which is

[0235]

[0236] where all symbols are as defined above. Alternatively, if the optional fourth task above is not completed, the incremental position angle obtained in the third mandatory task above is directly calculated. Incremental position determination is accomplished by the methods and calculations disclosed in WO 2016 / 146463 A1.

[0237] The control unit may perform, as a sixth optional but preferred task, resetting to zero each of the aforementioned integer registers for which it receives a blank zone entry signal from the corresponding magnetic position sensing unit, or for which it receives a blank zone exit signal from the position sensing unit. The result is that the integer registers then contain the integer p i , which integer represents the absolute position P of each i-th position sensing unit relative to the starting point of the end connection area as a reference point (if the control unit uses the blank area entry signal to reset) or relative to the end point of the end connection area (if the control unit uses the blank area exit signal to reset) i . Therefore, there exists a definition relation P i ≡ΔL×p i .

[0238] The control unit utilizes the position information contained in its integer registers to perform one or more of the evaluations outlined below as a seventh optional but preferred task.

[0239] The first type of evaluation is that for each p in the i-th integer register corresponding to the i-th position sensing unit being considered (and therefore having its associated “consider / not consider” flag set to “consider”) i At any time there may be some deviation from the theoretically correct integer value representing the absolute position of each position sensing unit at that time along the outer edge of the belt relative to the end point of the end connection zone as a reference. To correct this first type of error, the control unit typically adjusts the p contained in the integer register associated with the position sensing unit having generated a blank zone exit signal and having associated it with a given fixed index (usually index 0). i When reset to zero (see above), the content of any integer register in which the flag is set to "take into account" is compared with the corresponding comparison value stored in the look-up table and the content of each integer register deviating from the comparison value is replaced by the corresponding comparison value. Alternatively, the control unit may generate a white space leaving signal at a position sensing unit with a given fixed index (typically index 0) and has replaced the p contained in its associated integer register. i When reset to zero (see above), the contents of all other integer registers are simply replaced by the corresponding comparison values ​​in the lookup table. The comparison value stored in the lookup table of each position sensing unit is the quotient obtained by dividing its absolute position along the belt perimeter relative to the end point of the end connection zone of the belt by the ΔL defined above (integer division); it is assumed that the belt is in such a position that the position sensing unit with said given fixed index (such as 0) is exactly at the end point of the end connection zone of the belt and therefore has a comparison value of 0 obtained by said integer division.

[0240] A second type of evaluation that the control unit can correct is the positional deformation of the belt due to its uneven acceleration / deceleration. Note that in the case of a multi-pass inkjet printer, which is one of the preferred applications of the conveyor of the invention, when the belt should move from a line already printed to the next line to be printed, the belt is typically subjected to an acceleration step / deceleration step by a servomotor, while during the printing of this next line the belt does not move at all. To correct this second type of error, the control unit can make the comparison after fixed time periods, which can be integer multiples of the ones mentioned.

[0241] The control unit may publish its final position information in one or more channels, for example as conventional quadrature signals using channels A and B. If the conveyor of the invention is used in a single-pass or multi-pass inkjet printer, in particular for printing on textiles, the final position information may be fed into a conventional printer head drive to control printing.

[0242] Therefore, a preferred conveyor of the present invention suitable for implementing the phase error correction (third exemplary variation) of the above-mentioned invention preferably comprises:

[0243] (a) An endless conveyor belt having a belt periphery, an outer conveying surface, an inner surface facing a pulley, and magnetic marks arranged periodically in the belt travel direction so that the north pole or the south pole of the magnetic marks points to the outer conveying surface in an alternating manner, and adjacent such north poles and south poles are spaced apart from each other by an elongated pole pitch DP, thereby generating an alternating magnetic field, the elongated pole pitch DP being greater than, equal to or shorter than the un-elongated and un-shortened pole pitch DP';

[0244] (b) at least one position sensing unit arranged along the belt periphery and in close spatial proximity to the magnetic markers, when the conveyor belt is running in the direction of travel and DP is greater than or less than said DP', the at least one position sensing unit is capable of detecting from the magnetic field of the magnetic markers 1) a cosine voltage signal; and 2) a corresponding phase-shifted sinusoidal voltage signal, which is offset by a phase angle α-π / 2 relative to the cosine signal 1), αα being greater than zero; and when the conveyor belt is running in the direction of travel and DP is equal to DP', the at least one position sensing unit is also capable of detecting from the magnetic field of the magnetic markers 3) a cosine voltage signal corresponding to the angular position of the position sensing unit relative to the magnetic marker pattern; and 4) a corresponding sinusoidal voltage signal, which is offset by a phase angle -π / 2 relative to the cosine signal 3) and corresponds to the same angular position of the position sensing unit relative to the magnetic marker pattern;

[0245] (d) a control unit that derives position information from a digitized sinusoidal voltage signal and a digitized cosine voltage signal of at least one position sensing unit, the digitized signals having a nominal amplitude A, wherein the control unit is further configured to use the third exemplary variation described above using equations (3j) and (4j) to digitize the digitized sinusoidal voltage signal as follows: input ) and cosine (cos input ) voltage values ​​to perform iterative phase error correction:

[0246] a) For the start of the iterations, the initial values ​​of Δα, ΔC, and ΔS are assumed as shown in equations (3j) and (4j) above, and as defined for equations (3a) and (4a) above to be zero; the value σ is assumed to be +1 if α / 2 is positive or zero, and -1 if α / 2 is negative; the initial integer value of k is assumed to be in the range of 4 to 8, preferably 6, or if the magnitude of α / 2 is known, the initial value of k is assumed to be such that Assumed Amplitude reasonably close to the nominal amplitude A, preferably within the range of 0.5 to 2 times the nominal amplitude A, and assuming that the initial position angle (where v is the nominal belt travel speed, t can be derived from a timer or clock included in the control unit, and DP' is the above-mentioned unstretched and unshortened pole pitch) and from the initial Value Generation and The initial value of

[0247] b) Set the value using σ from step a) and k from step a) or step g) (as applicable). and use this value and the and (If applicable) Calculate the values ​​of S-ΔS and C-ΔC using equations (25b) and (25a) above, respectively, and use the values ​​in step a) or step d) (A+ΔA) (if applicable) and Δα in step a) or step f2) (if applicable) are calculated using the above equations (24b) and (24a), respectively. S ) / G S and (A+ΔA C ) / G C 's value (so these values ​​are the same);

[0248] c) using the Δα, ΔC and ΔS from step a) or step f2) (if applicable) and the (A+ΔA S ) / G S＝ (A+ΔA C ) / G C , C-ΔC and S-ΔS, respectively, using equations (3j) and (4j) to calculate cos corr Value and sin corr value;

[0249] d) Using the cos obtained in step c) corr Value and sin corr The new associated magnitudes are calculated using equations (16) and (17), respectively, or preferably using the CORDIC algorithm in the "vectorized" mode described above. Related to the new value, and using equations (16a) and (16b), calculate the new associated Value and value, and optionally, if provided by equation (17) or by calculation by the CORDIC algorithm, a value limited between -π / 2 and +π / 2 but

[0250] i) If sin corr <0 and cos corr > 0, then add 2π to the restricted or

[0251] ii) If sin corr >0 and cos corr< 0, then add π to the restricted or

[0252] iii) If sin corr <0 and cos corr < 0, then add π to the restricted

[0253] e) using the obtained in step d) the value of , the value of Δα in step (a) or step f2) (if applicable), and the value of value, and use the above equation (24b) or (24a) to calculate the new value (A+ΔA S ) / G S =(A+ΔA C ) / G C (thus they are identical);

[0254] f) Check (A+ΔA S ) / G S =(A+ΔA C ) / G C Is the new value greater than (A+ΔA in step b)? S ) / G S =(A+ΔA C ) / G C The corresponding previous value of is closer to A, and if so, then:

[0255] f1) Reverse the (A+ΔA) in step e) S ) / G S =(A+ΔA C ) / G C The new value of is set to (A+ΔA S ) / G S =(A+ΔA C ) / G C The corresponding previous value of ;

[0256] f2) Replacing the The values ​​of C-ΔC and S-ΔS are added to the values ​​of Δα, ΔC, and ΔS, respectively;

[0257] as well as

[0258] g) Increase k by 1;

[0259] h) repeating steps b) to g) until k is a maximum index greater than or equal to the initial value, such as in the range of 10 to 64, for example 10, 15 or 31); and

[0260] i) Take the value obtained in step d) of the last iteration performed and and / or and finally For location determination;

[0261] Thereby, the control unit is configured for not using the read / write memory device containing the stored digitized sinusoidal voltage signal and / or the digitized cosine voltage signal when performing the above iterations.

[0262] For the conveyor of the present invention, the above-mentioned phase error α is preferably in the range of 0 radians to +0.06 radians, corresponding to a ratio of DP / DP', and therefore to a belt elongation in the range of 1 to 1.00955. More preferably, the above-mentioned phase error α is in the range of 0 radians to +0.03 radians, corresponding to a ratio of DP / DP', and therefore to a belt elongation in the range of 1 to 1.00477.

[0263] It is still more preferred for the conveyor of the present invention that the cosine of the loading phase error in the above formulas (1) and (2) is input and sin input The signal offsets C and S appearing in are both zero, and the ADC zero point Z appearing in the above formulas (1) and (2) is also zero or has been corrected to zero.

[0264] Preferably, for the conveyor of the present invention, the control unit comprises an FPGA and / or a microcontroller.

[0265] The sensors generating the sine voltage signal and the cosine voltage signal in the conveyor of the present invention may be Hall sensors generating signals according to the intensity of the magnetic flux density B as described above, or may be (multiple) Wheatstone bridges generating signals according to the direction of the magnetic flux density B, as described above. In the latter case, each sensor may comprise one or two Wheatstone bridges, and further reference embodiments of such a conveyor are hereby described as in claim 3 (one Wheatstone bridge per sensor) and claim 4 (two Wheatstone bridges per sensor).

[0266] For the purposes of the present invention, any absolute position of a position sensing unit is understood to be the absolute position of a point located in the middle of the spacing between two magnetoresistive sensors contained therein, relative to the end point (or starting point) of the end connection area of ​​the belt and along the periphery of the belt, wherein the length of the spacing involving the two magnetoresistive sensors as end points is calculated as defined above.

[0267] The magnetic label can be typically in the form of an elastomeric material, a thermoplastic elastomer material or a matrix of a thermoplastic material comprising particles of a ferromagnetic material. The ferromagnetic material used for the magnetic label is not particularly limited, as long as it meets the aforementioned magnetic parameters. It can preferably be selected from the group consisting of the following: alkaline earth ferrites (e.g., barium ferrites, strontium ferrites), aluminum nickel cobalt types, and ferromagnetic chromium oxide (IV) and iron oxide types. Preferably, the ferromagnetic material is anisotropic.

[0268] The material of the matrix in which the particles of ferromagnetic material are embedded is an elastomer, a thermoplastic elastomer, or a thermoplastic. The most preferred material of the matrix is ​​an elastomer, in particular NBR or EPDM, or a thermoplastic elastomer, in particular TPU.

[0269] The filling degree of the ferromagnetic material particles in the matrix is ​​typically 60 to 90%, preferably 60 to 80% by volume, more preferably 65 to 75% by volume, based on the matrix in which the ferromagnetic particles are embedded.

[0270] The geometric thickness of the marking thus introduced is preferably between 30% and 70%, more preferably between 30% and 60%, of the total thickness of the tape.

[0271] The magnetic markers thus introduced generate a raw magnetic signal which can be detected by a magnetoresistive sensor if arranged at a certain distance A or air gap between the surface of the magnetic marker and the center of a Wheatstone bridge contained in the magnetoresistive sensor (see Figure 1 ). The air gap A typically depends on the pole pitch DP, and is preferably approximately proportional to the pole pitch DP. For example, the air gap A may typically be 0.2 to 1.0 times the pole pitch DP.

[0272] The periodic pattern of magnetic markings may be provided in the form of a preformed strip of markings of ferromagnetic particles embedded in a matrix of an elastomeric material, optionally provided with a suitable backing material. Preformed strips of this type are commercially available in open (linear) form for use in static (non-conveyor belt) applications. Examples thereof are available at the time of filing of this application from Arnold Magnetic Technologies of Newark, Norfolk, USA. and Max Baermann Holding AG of Bergisch Gladbach, Germany Strip. Preferably, the strip(s) of matrix of elastomer or thermoplastic elastomer material comprising particles of ferromagnetic material are incorporated into the cover layer of the belt. In particular, it can be embedded into a matching shaped groove that has been milled into the cover layer, which groove extends in the longitudinal direction of the belt. The strip can be welded after being incorporated with the belt by adhesive or thermoplastic bonding. Preferably, the cover layer and the strip of matrix material in which the ferromagnetic material is embedded are also coated with a top layer to protect the strip from environmental dust or dirt.

[0273] The belt included in the conveyor of the present invention is conventional. It can be any type of integral or single or multi-layer fabric-reinforced or cord-reinforced belt, as long as it is suitable for inserting a periodic pattern of magnetic marks therein and suitable for joining the ends of the belt into an endless form from the two ends. To make the belt endless, the joining of the ends of the belt can preferably use the so-called "finger end" method, in which the two ends of the open belt are cut into a zigzag shape so that each tooth of one end can seamlessly abut the corresponding recess between the two teeth of the other end, and vice versa. Once the teeth of one end of the belt are seamlessly engaged with the teeth of the other end, the two ends of the belt are welded together using heat and pressure, and optionally a hot melt adhesive is used together. The result is an extended zigzag belt joint over the entire lateral width of the now endless belt.

[0274] The conveyor of the present invention does not use any additional reference marks to detect any blank zone(s), it only relies on the magnetic marks themselves to detect the blank zone(s).

[0275] The conveyor of the invention can be used in any field where it is necessary to position the belt, in particular to position it with high precision. It can then be configured and used, for example, as a timing belt, a positive drive belt, a flat belt, a positive drive belt, or a power transmission belt. However, a preferred application of the conveyor of the invention with alternating markings, in particular with a periodic marking pattern, is a single-pass or multi-pass inkjet printer, in particular for printing of textiles. Such a printer is in fact a conveying device, which typically has at least a drive pulley and an idler pulley and an endless conveyor belt around these pulleys, but in addition has the ability to print on the conveyed substrate at the same time.

[0276] Figure 5An exemplary embodiment of an inkjet printer incorporating a conveyor of the present invention is shown. The printer (which may be a single-pass or multi-pass inkjet printer) includes four inkjet print heads 101, 102, 103, 204 that may correspond to the C color, the M color, the Y color, and the K color. There is again a control unit 6 that will evaluate the angle information received from the position sensing units 51, 52, 53...5N (a total of 8 position sensing units). In this embodiment, for each inkjet print head, two position sensing units are associated within the control unit 6, for example, two position sensing units 101, 102 (which may be considered to have indexes 1 and 2) are associated with the first print head 101 (which may be considered to have index 1) in the control unit 6; two position sensing units 53, 54 (which may be considered to have indexes 3 and 4) are associated with the second print head 102 (which may be considered to have index 2) in the control unit 6, and so on. The figure also illustrates what the absolute position Pm of the mth print head (here: m=4) means relative to the end of the end joining zone if the belt is assumed to travel in a clockwise rotation around the pulley. The control unit 6 generates position information of each print head from two position sensing units associated with the print head, which is transmitted to the print head containing the printer drive for timing the print heads 101, 102. Generating such timing based on the position information of the belt and the image to be printed is conventional and well known in the field of inkjet printers, in particular in the field of textile printing.

[0277] The present invention will now be further described by way of examples.

[0278] Example 1: Synchronous error test of the conveyor of the present invention

[0279] Set up with Figure 4 The periodic pattern of magnetic marks 3 is in the form of a commercially available magnetic strip, but without magnetic marks, which corresponds to 200 m of magnetic marks. -1 The spatial frequency ξ m The belt was made into a loop to obtain a length of 4 m, with an end connection (blank) area of ​​length L j The magnetic strip is an endless belt of about 100 mm and is installed on the conveyor 1. The magnetic strip is then provided with a magnetic mark with a pole pitch of 5 mm, which corresponds to 200 mm of the magnetic mark. -1 The spatial frequency ξ m The magnetic mark is applied to the entire periphery of the endless belt, except for a blank area of ​​about 100 mm, which is the end connection area of ​​the belt to which no magnetic mark is applied. Then, a set of periodically repeated identical small test images of approximately rectangular shape are burned by laser into the entire longitudinal periphery of the conveying surface 23 of the belt 2. The number of test images N iis 800, and they are spaced 5 mm apart from each other in the direction of belt travel. Therefore, their spatial frequency ξ i 200m -1 , which is consistent with the above ξ m same.

[0280] On top of the portion of the circumference of the belt 2 that is not bent onto the pulley 22, two position sensing units are mounted, which are arranged according to Figure 1 The preferred embodiment shown in the right part of and in the associated description (AL780AMA, Sensitec), one is located upstream and one is located downstream in the direction of travel (circular motion) of the belt and are spaced apart from each other by a precisely known distance L 12 , the distance is 1 / ξ m is an integer multiple of , and is therefore 1 / ξ i The same integer multiple of .

[0281] In order to detect the end connection (blank) area of ​​the conveyor belt 2, four Hall sensors (EQ-731L, AsahiKasei Microdevices) are placed on top of the portion of the periphery of the belt 2 that is not bent on the pulley 22, so that each of the two position sensing units is sandwiched between two Hall sensors. The inner two Hall sensors, (corresponding to the end signaling device for the upstream position sensing unit and the start signaling device for the downstream position sensing unit) are spaced apart by a distance greater than the length of the blank area, and accordingly the above-mentioned length L12 is even greater than the length of the blank area. This corresponds to the above-mentioned most preferred embodiment B2.

[0282] The raw sine and cosine outputs of the two position sensing units are low-pass filtered, scaled by a dual op-amp instrumentation amplifier, and converted to digital signals by two 18-bit ADCs to give a digitized sine output signal and a digitized cosine output signal with a nominal amplitude A of 50,000 ADC units in the form of signed integers (Z=0). These are connected by Figure 4 The control unit 6, which is similar to the control unit schematically shown in the related description, uses the error correction according to the second exemplary variant of the above general description and the end connection (blank) area detection also described in the general description for processing. The control unit 6 defaults to a spatial resolution of 400000 m generated from the signal of the upstream position sensing unit. -1 The square wave signal is a square wave signal, unless its output is ignored (see above), in which case the control unit 6 generates the square wave signal from the signal of the downstream position sensing unit. Therefore, the spatial resolution of the square wave signal is the above-mentioned spatial resolution 1 / ξ m and 1 / ξ i2000 times of the spatial resolution, and therefore an integer multiple of the two spatial resolutions. In addition, a photographic camera is mounted near each of the two position sensing units, which is focused on the conveying surface 23 of the belt 2, wherein the two cameras are spaced apart by the same distance L as the position sensing units. 12 , and each camera is capable of taking a picture of the small test image on the conveying surface of the belt. Each of the cameras is controlled by a separate synchronization station so that for every 2000 pulses of the square wave signal, therefore, given its 400000m -1 At said spatial frequency, the camera takes one picture of the surface of the belt for every 5 mm of belt travel. Thus, each camera so synchronized takes exactly one picture for each small test image that passes by the camera.

[0283] As soon as the starting point of the pattern of the small test image passes the first upstream position sensing unit and the camera, the relevant LEONI synchronization station starts generating trigger signals for the upstream camera every 2000 pulses of the square wave signal. The pictures produced by the upstream camera are vignetted and brightness corrected and stored on the computer. After the pattern of the small test image has completely passed the upstream camera and the position sensing unit, the photographic acquisition process of the upstream camera stops.

[0284] However, the synchronization station of the upstream camera also transmits the first trigger signal to the synchronization station of the downstream camera. After receiving the trigger signal, the synchronization station of the downstream camera waits for a predefined integer number of pulses of the square wave signal from the control unit 6, which predefined number is higher than L 12 Multiply by 400000m -1 , and after reaching the predefined number of pulses, the synchronization station of the downstream camera starts to create a trigger signal for the downstream camera every 2000 pulses of the square wave signal from the control unit 6. The photos produced by the downstream camera are also vignetted and brightness corrected and stored on the computer. After the pattern of the small test image has completely passed the downstream synchronization station, the photography acquisition process of the downstream camera is also stopped.

[0285] Therefore, in theory, each picture of a given nth small test image taken by the upstream camera at a count of n×2000 pulses of the square wave signal should produce a picture of the downstream camera at a count of (n+L 12 ×400000m -1 )×2000 pulse counts.

[0286] The conveyor belt 1 of the present invention prepared and arranged in this way has a speed of 0.25 ms. -1 The nominal belt travel speed is determined only by the maximum number of photos that the camera can take, which is 60 photos per second. -1. Take a picture every 5mm of tape travel distance (see above) with 0.25ms -1 50 pictures per second are given. A series of 3 belt rotations is completed. The corresponding pictures of the upstream and downstream cameras of a given small test image indexed n are compared by a computer (as described in the preceding paragraph) to find out whether the centers of the test images appearing on the two corresponding pictures deviate from each other by some distance Δx in the horizontal direction of the pictures (which corresponds to the direction of travel of the belt during transport). This distance Δx, typically in the order of micrometers, is considered as the synchronization error in the longitudinal (travel) direction of the belt of the nth test image. All the synchronization errors thus obtained are classified into groups of 2 micrometer width, ranging from -40 micrometers to +40 micrometers (thus, a first group containing the number of synchronization errors observed in the range of -40 micrometers to -38 micrometers, a second group containing the number of synchronization errors in the range of -38 micrometers to -36 micrometers, up to a last group containing the number of synchronization errors in the range of +38 micrometers to +40 micrometers), and the number of synchronization errors observed in each group is divided by the total number of synchronization errors to give the probability of a synchronization error in a given group. The probability group thus obtained is best fitted by a first Gaussian curve. The groups thus obtained are in Figure 7 Shown as shaded bars in , the first Gaussian curve of the best fit lies on top of them. Figure 7 The x-axis of the graph is the synchronization error in microns, and the y-axis of the graph is in probability units (so between 0 and 1). The mean of the first best fit Gaussian curve is -5.33 microns and the standard deviation is 6.28 microns.

[0287] Comparative Example 2: Synchronous Error Testing of a Conveyor Using a Prior Art Linear Encoder

[0288] The setup of Example 1 was repeated except that a commercial linear encoder (Lika) was used instead of the two position sensing units and the control unit 6 to generate a linear encoder with a linear amplitude of 400,000 m. -1 The commercial linear encoder can also pass through the conveyor belt with a length of L j The end connection area of ​​​​the comparison setting is not lost without losing position information. However, the exact construction and working principle of this commercial linear encoder is unknown. This comparison setting produces the same synchronization errors as the inventive setting of Example 1, and they are again classified into the probability groups described in Example 1. The resulting probability groups are also Figure 7 The second best-fitting Gaussian curve is also located on top of them. The mean of the second best-fitting Gaussian curve is +9.27 microns and the standard deviation is 10.96 microns, which shows that the synchronization errors are larger on average and more unevenly distributed than in the present invention.

Claims

1. A conveyor (1), comprising: a) an endless conveyor belt (2) having a belt periphery (21, 22), an outer conveying surface (23), an inner surface facing the pulley (24), and a magnetic mark (3) along the entire belt periphery (21, 22) except for one or more blank areas (4), each of which has a length L j , wherein j is the index of the blank area, the magnetic mark (3) is arranged in the belt travel direction so that the north pole (31) or the south pole (32) of the magnetic mark (3) points to the outer conveying surface (23) in an alternating manner, and adjacent north poles and south poles of this type are spaced apart from each other by a pole pitch DP, thereby generating an alternating magnetic field of a default maximum intensity; wherein in each of the blank areas (4), the magnetic mark does not exist or the maximum intensity of the generated magnetic field is lower than the default maximum intensity; b) at least two position sensing units (51, 52, 53, 54, 55, 56, 57, 58), said at least two position sensing units being arranged along the belt periphery (21, 22) and in spatial proximity to said magnetic marks (3), each position sensing unit being capable of detecting the magnetic field of a magnetic mark (3) not in said blank area (4) when said conveyor belt (2) is running in the direction of travel, thereby generating 1) a sinusoidal voltage signal, said sinusoidal voltage signal being related to the orientation of the magnetic flux density B sensed from said magnetic marks and therefore corresponding to the angular position of said position sensing unit relative to the pattern, when said conveyor belt (2) is running in the direction of travel; and 2) a corresponding cosine voltage signal, wherein the corresponding cosine voltage signal corresponds to the angular position of the position sensing unit relative to the pattern; wherein among the at least two position sensing units (51, 52, 53, 54, 55, 56, 57, 58), there are at least two separated position sensing units (51, 52, 53, 54, 55, 56, 57, 58), and each of the at least two separated position sensing units is separated from any one of the remaining separated position sensing units by a length L greater than any blank area (4) in the direction of belt travel. j Greater peripheral distance; c) means (51, 52, 53, 511, 521, 531, 532, 533, 534) capable of generating a blank zone entry signal when the maximum intensity of the magnetic field detected by the position sensing unit drops or is about to drop to or drops below a threshold intensity lower than said default maximum intensity, and means (512, 522) capable of generating a blank zone exit signal for the same position sensing unit when the maximum intensity of the magnetic field detected by the position sensing unit rises or has risen to or has risen above said threshold intensity; as well as d) a control unit (6) which derives belt position information from the sinusoidal voltage signals and cosine voltage signals of all position sensing units (51, 52, 53, 54, 55, 56, 57, 58) when the conveyor belt (2) is running in the direction of travel, provided that the control unit (6) ignores the sinusoidal voltage signal and cosine voltage signal from any position sensing unit from the time point when the control unit receives the blank area entry signal for the position sensing unit, and reconsiders the sinusoidal voltage signal and cosine voltage signal of the position sensing unit from the time point when the control unit receives the blank area exit signal for the position sensing unit.

2. The conveyor (1) according to claim 1, wherein there are at least 3 position sensing units (51, 52, 53, 54, 55, 56, 57, 58); among the at least 3 position sensing units, there are at least 3 separated position sensing units (51, 52, 53, 54, 55, 56, 57, 58), and each of the at least 3 separated position sensing units is separated from any one of the remaining separated position sensing units by a distance greater than the L in the belt travel direction. j The surrounding distance.

3. The conveyor (1) according to claim 1 or 2, wherein each position sensing unit (51, 52, 53, 54, 55, 56, 57, 58) comprises: i) two Wheatstone bridges (513, 514), each comprising an upper leg and a lower leg of a magnetoresistive sensor operating by anisotropic magnetoresistance (AMR), the Wheatstone bridges (513, 514) being spaced apart from each other by a spacing distance DP / 4, DP being as defined in claim 1, such that when the position sensing unit (51, 52, 53, 54, 55, 56, 57, 58) is arranged in the spatial proximity of the magnetic mark (3) so that the direction of the magnetic mark pattern and thus the travel direction of the conveyor belt (2) are parallel to the spacing distance and the conveyor belt (2) runs in the travel direction, one of the two Wheatstone bridges (513 or 514) generates the sinusoidal voltage signal depending on the angle between the orientation of the magnetic flux density B and the direction of the magnetic mark pattern, while the other Wheatstone bridge (514 or 513) generates the corresponding cosine voltage signal.

4. A conveyor (1) according to claim 1 or 2, wherein each position sensing unit (51, 52, 53, 54, 55, 56, 57, 58) comprises a first pair of Wheatstone bridges (513, 514) which are spaced DP / 4 from each other, DP as defined in claim 1, so as to generate a sine signal and a corresponding cosine signal from a pattern of alternating north and south magnetic poles, and each position sensing unit further comprises a second pair of Wheatstone bridges (515, 516) which are again spaced DP / 4 from each other, so as to generate a sine signal and a corresponding cosine signal from a pattern of alternating north and south magnetic poles. The pattern of the north pole and the south pole again generates a sine signal and a corresponding cosine signal, and the two pairs of Wheatstone bridges are separated from each other by the DP, and further, the polarity of the power supply of one pair of Wheatstone bridges (513, 514 or 515, 516) in the two pairs of Wheatstone bridges is opposite to the polarity of the power supply of the other pair of Wheatstone bridges (515, 516 or 513, 514), so that when the first Wheatstone bridge (515) of the second pair of Wheatstone bridges (515, 516) is on the magnetic south pole (32), at the same time, when the first Wheatstone bridge (513, 514) of the first pair of Wheatstone bridges (513, 514) When the first Wheatstone bridge (513) of the second pair of Wheatstone bridges (515, 516) is located on the magnetic north pole (31) and detects the magnetic north pole (31), the first Wheatstone bridge (515) of the second pair of Wheatstone bridges (515, 516) detects the magnetic north pole, and vice versa; and when the first Wheatstone bridge (515) of the second pair of Wheatstone bridges (515, 516) is located on the magnetic north pole (31) and when the first Wheatstone bridge (513) of the first pair of Wheatstone bridges (513, 514) is located on the magnetic south pole (32) and detects the magnetic south pole (32), the first Wheatstone bridge (515) of the second pair of Wheatstone bridges (515, 516) detects the magnetic north pole A bridge (515) detects a magnetic south pole and vice versa; and summing and optionally averaging a signal from a first Wheatstone bridge (513) of the first pair of Wheatstone bridges (513, 514) and a signal from a first Wheatstone bridge (515) of the second pair of Wheatstone bridges (515, 516); and summing and optionally averaging a signal from a second Wheatstone bridge (514) of the first pair of Wheatstone bridges (513, 514) and a signal from a second Wheatstone bridge (516) of the second pair of Wheatstone bridges (515, 516).

5. A conveyor according to any one of the preceding claims, wherein each position sensing unit (51, 52, 53, 54, 55, 56, 57, 58) itself generates a blank area entry signal when the maximum intensity of the magnetic field detected by the position sensing unit drops to or drops below a threshold intensity lower than the default maximum intensity, and generates a blank area exit signal when the maximum intensity of the magnetic field detected by the position sensing unit rises to the threshold intensity or rises to above the threshold intensity.

6. The conveyor according to claim 5 is capable of forming the sum of the squares of the sine signal and cosine signal strengths detected by each position sensing unit (51, 52, 53, 54, 55, 56, 57, 58) or the square root of such sum, and is capable of generating the blank area entry signal for the position sensing unit when the sum of the squares of the signal strengths from the position sensing unit or the square root of the square sum significantly drops below the default strength, and is capable of generating the blank area exit signal for the position sensing unit when the sum of the squares of the signal strengths or the square root of the square sum rises to the threshold strength or rises above the threshold strength.

7. The conveyor (1) according to any one of claims 1 to 4, wherein for each position sensing unit (54, 55), there is a starting signaling device (511, 521) and an end signaling device (512, 522), wherein the starting signaling device is capable of generating a blank area entry signal when the maximum intensity of the magnetic field detected by the starting signaling device (511, 521) drops to or drops below a threshold intensity lower than the default maximum intensity, and the end signaling device is capable of generating a blank area exit signal when the maximum intensity of the magnetic field detected by the end signaling device (512, 522) rises to the threshold intensity or rises above the threshold intensity, wherein each starting signaling device (511 or 521) is located at a corresponding position sensing unit. The conveyor belt (2) is a conveyor belt comprising a plurality of end signaling devices (512 and 522) arranged upstream of a position sensing unit (54 or 55), and each end signaling device (512 or 522) is arranged downstream of the corresponding position sensing unit (54 or 55), so that the start signaling device and the end signaling device sandwich the corresponding position sensing unit between the start signaling device and the end signaling device; and wherein for the at least two separated position sensing units (54, 55), any pair of two upstream and downstream separated position sensing units (54, 55) also has an end signaling device (512) of the paired upstream position sensing unit (54) spaced apart from the start signaling device (521) of the paired downstream position sensing unit (55) by a distance L, wherein the distance L is greater than the maximum length L of any blank area (4) present on the conveyor belt (2). j and any references to "upstream" and "downstream" are relative to the direction of travel of the belt.

8. The conveyor according to claim 7, wherein each start signaling device (511 or 521) corresponding to a position sensing unit (54 or 55) and each end signaling device (512 or 522) corresponding to the same position sensing unit (54 or 55) are spaced apart from each other by a distance LH given by the following formula: LH=(2N+0.5)×DP wherein N is a positive integer of at least 0, and DP is defined as above, as long as N is large enough to accommodate the position sensing unit (54 or 55) in question to be sandwiched between the starting signaling device (511 or 521) and the end signaling device (512 or 522), and the conveyor (1) is capable of forming the sum of the squares of the intensities of the signals detected by a pair of such spaced-apart starting signaling devices and end signaling devices (511, 512 or 521, 522), and generating the blank area entry signal for the sandwiched position sensing unit (54 or 55) when the sum of the squares of the signal intensities drops below the default intensity, and is capable of generating the blank area exit signal for the sandwiched position sensing unit (54 or 55) when the sum of the squares of the signal intensities rises to the threshold intensity or rises above the threshold intensity.

9. The conveyor according to any one of claims 1 to 4, wherein there are: a first starting point signaling device (531), which is located upstream of all position sensing units (56, 57, 58) and is capable of generating a blank area entry signal for the most upstream (not necessarily but preferably adjacent) position sensing unit (56) when entering the blank area (4); a second starting point signaling device (534), which is located downstream of all position sensing units (56, 57, 58) and is capable of generating a blank area entry signal used or interpreted as a blank area exit signal by the most downstream (not necessarily but preferably adjacent) position sensing unit (58) when entering the blank area (4); and additional starting point signaling devices (532, 533), the number of which is greater than the number of position sensing units (56, 57, 58). , 58) is one less, and any such position units are paired (56, 57 or 57, 58) with one such additional device (532 or 533) sandwiched between them, and each additional starting signaling device (532 or 533) is capable of generating a blank area entry signal for a clamping position sensing unit (57 or 58) located downstream of the starting signaling device (and not necessarily but preferably adjacent to the starting signaling device) when entering the blank area (4), which signal is also used or interpreted as a blank area exit signal for a clamping position sensing unit (56 or 57) located upstream of the additional starting signaling device (and not necessarily but preferably adjacent to the additional starting signaling device), wherein any additional starting signaling device (532 or 533) is separated from the corresponding upstream clamping position sensing unit (56 or 57) by a distance L m than the maximum length L of any blank area (4) present on the conveyor belt (2) j and the distance L between the second starting point signaling device (534) and the most downstream position sensing unit (58) is large. n than the maximum length L of any blank area (4) present on the conveyor belt (2) j and any references to "upstream" and "downstream" are relative to the direction of travel of the belt.

10. The conveyor according to claim 9, wherein a) the first start point signaling device (531) and an additional start point signaling device (532) sandwich the most upstream position sensing unit (56) and are spaced apart from each other by a distance LH; as well as b) the second start point signaling device (534) and an additional start point signaling device (533) sandwich the most downstream position sensing unit (58) and are spaced apart from each other by a distance LH; as well as c) in any other pair of additional start point signalling devices (532, 533), another position sensing unit (57) is sandwiched therebetween, these additional start point signalling devices being spaced apart from each other by a distance LH; where any such distance LH is given by LH=(2N+0.5)×DP wherein N is a positive integer of at least 0, and DP is as defined in claim 1, provided that N is large enough to accommodate the sandwiched position sensing unit, and the conveyor (1): i) capable of forming a square sum of the intensities of the signals detected by the first start-point signaling device (531) and the one further start-point signaling device (532) so spaced apart or a square root of the square sum, and capable of generating a blank zone entry signal for the sandwiched most upstream position sensing unit (56) when the square sum of the intensities of the signals detected by the first start-point signaling device (531) and the one further start-point signaling device (532) so spaced apart or the square root of the square sum significantly drops below the default intensity, and capable of generating the blank zone exit signal for the sandwiched most upstream position sensing unit (56) when the square sum of the signal intensities rises to the threshold intensity or rises above the threshold intensity; ii) capable of forming a square sum of the intensities of the signals detected by the second start-point signaling device (534) and the one further start-point signaling device (533) so spaced apart or a square root of the sum, and capable of generating a blank zone entry signal for the sandwiched most downstream position sensing unit (58) when the square sum of the intensities of the signals detected by the second start-point signaling device (534) and the one further start-point signaling device (533) so spaced apart or the square root of the sum significantly drops below the default intensity, and capable of generating the blank zone exit signal for the sandwiched most downstream position sensing unit (58) when the sum of the signal intensities or the square root of the sum rises to the threshold intensity or rises above the threshold intensity; as well as iii) capable of forming a sum of squares of the intensities of the signals detected by any pair of further start signalling devices (532, 533) or the square root of said sum, and capable of generating a blank zone entry signal for a position sensing unit (57) sandwiched between said pair of further start signalling devices (532, 533) when said sum of squares of the intensities of the signals detected by said pair of further start signalling devices (532, 533) so spaced apart significantly drops below said default intensity, and capable of generating said blank zone exit signal for said position sensing unit (57) sandwiched between said pair of further start signalling devices when said sum of squares of the intensities of the signals or said square root of said sum rises to said threshold intensity or rises above said threshold intensity; And any references to "upstream" and "downstream" are relative to the direction of travel of the belt.

11. The conveyor (1) according to claim 7 or 8, wherein the first start point signaling device (531) and / or the second start point signaling device (534) are Hall sensors.

12. The conveyor (1) according to claim 9 or 10, wherein the first start point signaling device (531), the second start point signaling device (534), and / or the further start point signaling device (532, 533) are Hall sensors.

13. Conveyor (1) according to any of the preceding claims, without any other markings for detecting the clear areas (4) besides the magnetic markings (3).

14. The conveyor (1) according to any one of the preceding claims, comprising 3 to 16 position sensing units (51, 52, 53, 54, 55, 56, 57, 58).

15. The conveyor (1) according to any one of the preceding claims, wherein the position sensing unit (51, 52, 53, 55, 56, 57, 58) is arranged near, on top of or below the portion (22) of the conveyor belt (2) that is not bent over the pulley.

16. The conveyor (1) according to any of the preceding claims, wherein the DP is in the range of about 0.5 mm to about 10 mm, and is preferably about 0.5 mm, about 1 mm, about 2 mm, about 2.5 mm, about 5 mm, or about 10 mm.

17. A conveyor (1) according to any one of the preceding claims, wherein the magnetic markings form an essentially periodic pattern in the belt travel direction.

18. A single-pass or multi-pass inkjet printer comprising a conveyor (1) according to any one of the preceding claims.

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