EP0110821A2 - Method and apparatus for automatic traversing using servo control - Google Patents

Abstract

During the various phases of fabrication of cables, tubes or similar products, it is necessary to load them onto spools. In certain cases, the winding must be particularly carefully done and have only close-packed windings, without overlap. The process and the device described bring a solution to the problem in the form of a feedback-control of the position of the winding guide. This control is realized such as to maintain the tightening-angle constant, that is the angle formed by the product at its loading-point referred to the preceeding turn, taking in consideration the irregularities of the real helix angle and the effect of the flanges of the loading spool.

Description

During the numerous operations relating to the manufacture and / or marketing of cables, ropes and other products manufactured in great length, it is necessary or desirable to store them by winding on reels of suitable dimensions. These coils, which will be called drums in the rest of the text, consist of an at least approximately cylindrical barrel bounded by two approximately planar and parallel surfaces, perpendicular to the axis of the cylinder and designated by the usual term of cheeks.

The loading operation, that is to say winding of a cable, a tube or other product on the reel consists in rotating the latter on itself around its axis and, in the case which we interested in guiding the product in its external part to the drum so that the winding is carried out regularly in turns as contiguous as possible. This is called trancannage.

In the case of systems for industrial use, the reel is driven by a motor. The guidance of the product to be wound up, which we will designate by the term cable in the rest of the text, is carried out either manually by an operator, or by a mechanical guidance device. Currently known automatic trenching systems can be divided into two groups: fixed winders with mobile guide, mobile winders (self-cutting) with fixed guide.

In both cases, the relative translational movement is ensured by a device comprising at least one adjustable speed variator which makes correspond to the rotation of the winding reel a predetermined (programmed) displacement of the guide, proportional to the fixed pitch. A device for reversing the direction of movement generally using α- stops assumes the function of reversing the guide when the cable reaches a cheek.

In practice, the operator tries to obtain a winding as precise as possible, that is to say without spacing of the turns and without overlapping, by manually correcting the position of the guide and / or the pitch, the goal being to lay the cable against the previous turn by forcing it slightly against it.

• - les tourets de chargement ne sont pas parfaits géométriquement - (irrégularités à l'usinage ou acquise par suite de chocs) : le corps cylindrique n'est pas parfaitement centré par rapport à l'axe de rotation, les joues ne sont qu'imparfaitement perpendiculaires à cet axe.
• - l'introduction du câble (amorce du bobinage) crée une perturbation qui se répercute de proche en proche sur les spires suivantes.
• - le changement de couche contre les joues constitue lui aussi un point singulier.
• - les défauts de serrage se répercutent souvent d'une couche à la suivante.

If we examine in detail the parameters of the problem, we are led to make the following remarks;

• - the loading reels are not geometrically perfect - (irregularities during machining or acquired as a result of impacts): the cylindrical body is not perfectly centered relative to the axis of rotation, the cheeks are only imperfectly perpendicular to this axis.
• - the introduction of the cable (initiation of the winding) creates a disturbance which is passed on step by step on the following turns.
• - the change of layer against the cheeks is also a singular point.
• - tightening faults are often passed on from one layer to the next.

It follows from the first 3 remarks above that the helix angle of a perfectly executed winding is not constant. A perfectly wound cable does not exactly have the shape of a regular helix.

Consequently, the programmed advance slicing does not (in many cases) make it possible to obtain a perfectly regular winding as desired by the cable manufacturer.

Fig. 1 schematically shows for understanding a partial developed view of a cable during winding.

• α = angle de chargement, c'est-à-dire angle que forme le câble, dans sa partie approximativement rectiligne située juste avant le point de tangence au touret avec un plan perpendiculaire à l'axe de rotation du touret
• β = angle d'hélice, c'est-à-dire angle que forme la tangente au câble, en un point quelconque de sa partie déjà enroulée, avec un plan perpendiculaire à l'axe de rotation du touret, cet angle étant à considérer pour chaque point particulier.
• γ=β-α = angle de serrage, c'est-à-dire angle que forme approximativement la portion de câble en cours de pose en son point de tangence avec la spire précédente.

The following parameters will be designated in the following text:

• α = loading angle, that is to say the angle formed by the cable, in its approximately rectilinear part situated just before the point of tangency to the drum with a plane perpendicular to the axis of rotation of the drum
• β = helix angle, that is to say the angle formed by the tangent to the cable, at any point on its already wound part, with a plane perpendicular to the axis of rotation of the reel, this angle being to be considered for each particular point.
• γ = β-α = clamping angle, that is to say the angle that approximately forms the portion of cable being laid at its point of tangency with the previous turn.

This clamping angle conditions the installation of the cable: if it is too strong the whorl in formation risks overlapping the previous one, if it is too weak or negative, the whorl deviates from the previous one.

The helix angle is not constant for the various reasons stated above, it follows that the loading angle must be constantly adapted, in order to keep as constant as possible the value of the clamping angle.

The object of the present invention is to provide a solution to this problem, namely to maintain the clamping angle by a constant value.

From the point of view of automatic adjustment, the problem is apparently simple: it suffices to control the relative position of the drum guide.

The difficulty, however, consists in defining the set value of this position, since its aim is to achieve a very specific condition for a quantity (the clamping angle) which cannot be measured directly.

As defined in fig. 1, this angle is the difference between the helix angle and the loading angle. These two angles must therefore be determined.

It should be noted that the helix angle β as shown in FIG. l is, for the purposes of drawing, significantly larger than life. Experience shows that the desired tightening angle γ is normally larger than the helix angle β. It follows that the loading angle α = β -γ is actually negative, that is to say that the cable is in fact retained behind, the guidance being late as will be seen below at About fig. 4.

Fig. 2 schematically shows by way of example for understanding an embodiment of the device according to the present invention,

• Un touret 20 tourne autour de son axe, entraîné par un dispositif motorisé non représenté.

plan view:

• A reel 20 rotates about its axis, driven by a motorized device not shown.

This drive device is provided with a first not shown sensor (absolute or incremental) of the usual type, potentiometer or optical encoder for example, supplying in electrical form a signal enabling the angular position Ω of the reel to be known. This same sensor will supply the rotation speed information if necessary: value derived from the position in the case of a potentiometer measurement, pulse frequency in the case of an incremental sensor.

A guide 21, made up here of two cylindrical rollers with a vertical axis, performs the function of guiding the cable during winding. This guide is movable along the axis X` X ", this axis being parallel to the axis of rotation of the reel: A conventional motorized drive device of known type (lead screw or chain for example) ensures its movement. This device (not shown) is additionally provided with a second sensor (potentiometer or optical encoder for example) intended to supply an analog or digital signal corresponding to the displacement of the guide along its axis of translation X 'X ", in absolute or incremental value.

A third sensor, secured to an arm 23 carrying an oscillating roller 22, makes it possible to know the loading angle α, that is to say the angle formed by the cable 24 relative to the perpendicular to the axis of rotation of the drum 20: The arm supporting this roller 22 has for example as point of rotation that of the two guides 21 which precedes it. It is recalled by a spring or even for example by a pneumatic cylinder, in order to keep it in contact with the cable.

In the case of a pneumatic cylinder, the roller can thus be automatically released to the left during the operation of placing the cable leader, then pressed into the measurement position in a timely manner.

The sensor defining the loading angle α can be a coaxial potentiometer at the point of oscillation of the arm, but it can just as easily be of the inductive, capacitive type or consist of a binary encoder. It may possibly be of the linear type, coupled to the spring or to the pneumatic return piston.

The roller 22 can finally be provided with a fourth rotation sensor (for example of the incremental type) in order to know the speed of travel of the cable and incidentally the loaded length, by counting or integration of the pulses.

These sensors being usual models known in the trade, there will be no more detailed description here.

The scroll measurement sensor can also just as easily be independent of the roller 22, the corresponding signal being able to be supplied by the device existing on the production machine.

In the frequent case where the configuration of the fixed guide winder with axial translation of the reel is preferred, it is obvious that the longitudinal position sensor of the guide 21 along the axis X 'X "is purely and simply replaced by an equivalent sensor secured to the translation of said reel. The drive motor of the reel will act as actuator for the position control. The other sensors mentioned keep their respective functions: the system must be included in a relative space whose reference frame is simply changed.

Note: This last configuration, although more expensive given the mass of material to be moved, has the substantial advantage of a fixed position and direction of the cable as it enters the guide, this position being in the axis d '' a production machine, such as a corder or an extruder.

• - un touret de trancannage motorisé avec capteur de sa position angulaire Ω
• - un guide d'entrée du câble
• - un mécanisme d'asservissement assurant la translation relative du guide par rapport au touret (ou inversement) et un capteur définissant cette position relative x selon l'axe X' X"
• - un galet oscillant muni d'un capteur destiné à définir l'angle de chargement α que forme le câble par rapport au plan perpendiculaire à l'axe de rotation du touret
• - un capteur accessoire de rotation fournissant l'information Δℓ du défilement du câble.

In summary, the system described above so far comprises:

• - a motorized cutting drum with sensor of its angular position Ω
• - cable entry guide
• - a servo mechanism ensuring the relative translation of the guide relative to the reel (or vice versa) and a sensor defining this relative position x along the axis X 'X "
• - an oscillating roller fitted with a sensor intended to define the loading angle α formed by the cable relative to the plane perpendicular to the axis of rotation of the reel
• - an accessory rotation sensor providing the information Δℓ of the cable travel.

• - Pour ne pas risquer un écrasement du câble par suite de légères variations de son diamètre, les galets 21 doivent présenter un certain jeu par rapport au diamètre moyen du câble
• - Le câble n'étant pas infiniment flexible, l'angle α de chargement tel que défini à la fig. 1 n'est pas exactement identique à celui mesuré par le capteur, le câble présentant une certaine courbure au voisinage des galets 21.

A closer look at all of the rollers reveals a certain simplification in the above explanations:

• - In order not to risk crushing the cable due to slight variations in its diameter, the rollers 21 must have a certain clearance with respect to the average diameter of the cable
• - Since the cable is not infinitely flexible, the loading angle α as defined in fig. 1 is not exactly identical to that measured by the sensor, the cable having a certain curvature in the vicinity of the rollers 21.

In addition, it must be considered that the optimum clamping angle (determined experimentally) is a function of the type of cable, that is to say of its diameter, its rigidity and the coefficient of friction of its surface.

In practice, it can be seen that this angle can be understood, for a given cable, between two extreme values, one corresponding to the risk of overlapping, the other to the risk of non-juxtaposition of the turns. This therefore results in a certain margin of tolerance.

In most cases, the approximations mentioned above will therefore be without disadvantage.

• - L'un des galets de guidage 21 est mobile transversalement, sa position et/ou sa force d'appui étant asservies.

It is however possible, in certain severe applications, to improve the device by the following measures, described here in the case of an installation with fixed guide and mobile reel:

• - One of the guide rollers 21 is movable transversely, its position and / or its bearing force being controlled.

• - Palpeurs situés en amont des galets de guidage et ayant pour fonction de commander le rapprochement ou l'éloignement du galet mobile en fonction de leur position.
• - Capteur de force lié au galet non mobile et commandant le rapprochement du galet mobile sitôt une valeur minimum atteinte, son éloignement sitôt une valeur maximum dépassée.
• - Capteur de rotation solidaire du galet non mobile commandant le rapprochement du galet mobile sitôt détecté un arrêt de rotation
• - De manièére plus simple, sans faire appel à un dispositif d'asservissement, il suffit de munir chacun des 2 galets d'un détecteur de rotation : selon que le câble s'appuye sur l'un ou l'autre des 2 galets, l'un tourne, l'autre pas. L'information ainsi obtenue peut être utilisée pour corriger l'information du capteur d'angle de chargement, l'écartement des galets étant connus.

Several possibilities are then offered, let us quote for example the following simple solutions:

• - Sensors located upstream of the guide rollers and having the function of controlling the approximation or the distance of the movable roller according to their position.
• - Force sensor linked to the non-mobile roller and controlling the approach of the mobile roller as soon as a minimum value is reached, its distance as soon as a maximum value is exceeded.
• - Rotation sensor integral with the non-movable roller controlling the approach of the movable roller as soon as a rotation stop is detected
• - In a simpler way, without using a servo device, it suffices to provide each of the 2 rollers with a rotation detector: depending on whether the cable is supported on one or the other of the 2 rollers, one turns, the other does not. The information thus obtained can be used to correct the information from the loading angle sensor, the spacing of the rollers being known.

In the case of particularly rigid cables and / or of large diameter, the error on the measurement of the angle of loading α can not be negligible, even if the oscillating lever is relatively long, the cable being unable to change suddenly orientation as soon as you exit guide 21.

• - 2 galets 31 et 32 montés sur un bras oscillant 33 s'appuyent contre le câble 34. Le capteur angulaire non représenté sur 1a figure et destiné à la mesure de l'angle de chargement α est alors monté au point de pivotement 35 du bras par rapport au support coulissant 36. Le dispositif est encore muni du ressort rappel 37 qui prend appui sur le guide fixe 38.

The swing arm system is then replaced by the device shown by way of example in FIG. 3:

• - 2 rollers 31 and 32 mounted on an oscillating arm 33 bear against the cable 34. The angular sensor not shown in the figure and intended for measuring the loading angle α is then mounted at the pivot point 35 of the arm relative to the sliding support 36. The device is also provided with the return spring 37 which bears on the fixed guide 38.

As indicated above, this spring can be replaced by a pneumatic cylinder or any other conventional device capable of ensuring a longitudinal displacement parallel to the axis X 'X "of translation of the drum.

The device is applied to a portion considered to be reasonably straight of the cable lying between the guides 21 and the point of tangency to the drum 25, the distance between the guides 21 and the drum being able to be increased without disadvantage to a sufficient value.

Being thus demonstrated that it is easy to measure the angle of loading α, it is necessary to explain how to obtain the value of the angle of helix / 3 of the preceding turn and this more particularly at the point of tangency of the cable with the reel loading.

• - le tronçon de câble compris entre le guide avec son abscisse x₂ sur l'axe X' X" et le touret à son point de contact d'abscisse x₁ sur la génératrice g du cylindre
• - la distance h entre l'axe X' X" et la génératrice g
• - l'angle de chargement α défini par rapport au plan perpendiculaire à l'axe de rotation du touret.

Fig. 4 shows schematically for understanding:

• - the section of cable between the guide with its abscissa x ₂ on the axis X 'X "and the reel at its abscissa contact point x ₁ on the generator g of the cylinder
• - the distance h between the axis X 'X "and the generator g
• - the loading angle α defined with respect to the plane perpendicular to the axis of rotation of the reel.

By examining this fig. 4, we see that an immediate reasoning using elementary geometry makes it possible to understand that a simple trigometric relationship links the abscissa x ₁ of the point of tangency of the cable to the abscissa x ₂ measured from the guide as a function of l 'measured loading angle α,
we have indeed:
x ₁ = ^x ₂ - h.tg α

The relative abscissa x ₂ reel guide being measured by the translation sensor, that of the point of tangency can thus be determined by calculation at each instant, by means of a microprocessor for example.

It is then enough to memorize these successive values in correlation with those of the rotation Ω of the reel to know, by call successive in memory, the position of the previous turn.

As mentioned above, the cable loading angle during cutting is generally negative. Thus, unlike the representation in FIG. 4, we have ₁ > x2.

Note also that the distance h varies somewhat depending on the filling state and the diameter of the drum. Since this variation is small, it is generally not necessary to take it into account, although the corrective trigonometric calculation could be carried out by the microprocessor if necessary, the winding diameter being able to be determined as described below.

si l'on admet de remplacer les accroissements différentiels par des accroissements limités.In addition, the microprocessor can give, by simple calculation, the value of the helix angle at the point considered according to the relationship:

if one accepts to replace the differential increases by limited increases.

Δx is the difference between 2 successive values x _n and x _{n + 1} calculated for the abscissa of the point of tangency corresponding to 2 successive values Ωn and Ω _{n + 1} of the angular position of the reel stored, Δl corresponding to the length of cable having passed in contact with the roller 22 during the same interval, namely:

In the case of reels of known diameter, the microprocessor can calculate the length of the wound cable itself without using an ad-hoc sensor. For the first layer, we have ₁ = π.n ₁ .D where n and the number of turns (determined from Ω), D the diameter of the drum. For the second layer: l ₂ = π.n ₂ (D + d), where d is the cable diameter, a value that the microprocessor can easily determine from the average displacement (step) for each turn of the reel. And so on.

s'obtient de la même manière, individuellement pour chaque couche, le microprocesseur mémorisant le nombre de couches bobinées, c'est-à-dire le nombre de renversements de sens de l'hélice.The value

is obtained in the same way, individually for each layer, the microprocessor memorizing the number of coiled layers, that is to say the number of reversals of the direction of the helix.

A trigonometric calculation of the same kind then makes it possible to define the set value to be imposed for the relative position of the drum-guide in order ensure the correct value of the desired loading angle α, a value which must satisfy, as described above, the relationship α = β-γ where γ is the clamping angle whose value, constant for a given cable, is experimentally chosen. This value can be entered as setpoint tô by manual insertion at the control panel. It can also be memorized for the various types and diameters of cables and automatically recalled by the processor.

Note: the servo could also take α as the reference value, the measured value being that given by the corresponding sensor. A quick examination of the algorithms however makes it possible to realize that the function is identical, the bases of computation being in fact the same.

It is preferable to control the position x ₂ along the axis X'X ", the input quantity corresponding to the measurement x being more practical.

In another embodiment of the servo device, the helix angle β is obtained by analysis of the image observed by a TV camera arranged perpendicular to the axis of rotation of the reel.

The system as described up to this point performs the function of correctly winding the cable with respect to the previous turn during a layer. It therefore remains to examine the solutions to be provided to the transistors which constitute the beginning of the winding and the reversal of the direction of the helix against the cheeks.

Hanging the cable leader is a manual operation. Similarly, the winding of the first turn is to be considered as an operation which is not a servo, but rather a programming, the cable simply having to be wound against the cheek, circularly in its first part. The winding will then be carried out at a pitch fixed by the supposedly known diameter of the cable or by manual control of the movement. The enslavement, that is to say its engagement, will be either decided by the operator, or automatic, for example after a rotation of a fraction of a turn of the reel. The memorization of the parameters x, α and Ω being carried out from the start of the rotation, the system will be able to intervene immediately, taking into account in particular the anomaly of propeller caused by the birth of the first turn since knows its position.

The arrival of the cable against a cheek also represents an anomaly that the system must interpret:

The last free turn of the layer having been placed in a cylindrical helix, the servo-control will at first sight continue the relative movement of the guide-reel as a function of the position of this last turn. However, the cable abuts on the cheek, the effective step will be zero (apart from cheek irregularities). The effective loading angle measured oC. will therefore gradually change. A comparison with the successive values stored in memory corresponding to the preceding turn will make it possible to decide after exceeding a predetermined threshold the reversal of the propeller pitch. In order to avoid overlapping, this reversal will take place for example after a little less than one turn, thus initiating by automatic programming the first complete turn of the new layer.

Note that the diameter of the cable is necessarily known to the microprocessor at that time, either because this value was manually entered by the operator, or because a sensor was provided for the purposes of positioning the spacing of the guides 21, either because the microprocessor itself calculated it from the average of the differences of the successive values of the translation at each turn of the reel: no mean propeller.

Fig. 5 shows by way of example for understanding a simplified diagram of the device.

We note that in addition to the organs mentioned in fig. 2, the device is also at least provided with a control unit 51 consisting of at least the interfaces necessary for the reception of the signals coming from the angle and position sensors, including the analog-digital converters for reading the potentiometers corresponding to the angle and to the abscissa x, of a device making it possible to introduce and / or correct the set value of the clamping angle, of a microprocessor and / or of an arithmetic unit for the processing of this data and its storage in memory according to an adequate program (software), of a digital-analog converter providing the set value of the relative abscissa x of the displacement by guide-reel translation and of a servo amplifier 52 for controlling the motor 53 ensuring said displacement.

Note that the processor can be equipped, if necessary, with a device 54 allowing the display and / or recording of the various values that it receives and / or calculates: helix angle, loading angle, clamping angle, diameter of the product, loading speed, loaded length, number of turns and / or layers, speed of rotation of the drum, etc.

Generally, only one switchable display on the various values will be used, for the needs of the service for example.

Experience showing that the precision required for the translation of the guide is not very severe, the servo amplifier may, if a low-cost economic solution is desired, be replaced by two comparators having as signals enter the setpoint. from the computer and the value of the actual position measured by the sensor. The output signals of these comparators, whose switching thresholds will be slightly offset, will serve as a control order with two relays, each ensuring a direction of operation of a simple three-phase motor, this intermittently, that is to say say by small successive displacements.

The solution is obviously significantly less expensive than that consisting of a regulator and a DC motor, especially when it is an already existing installation to be transformed.

Claims (5)

1. Automatic method of cutting a cable, a tube or similar product, on a motorized reel fitted with a guide, characterized by the measurement and control of the relative guide-reel position, the set value of this position being calculated successively step by step from the measurement of the loading angle, the angle of rotation of the reel and directly or indirectly from the length of wound product, so as to keep as constant as possible the tightening angle of the winding, this tightening angle being defined at all times by the difference between the helix angle of the previous turn at the point where the product is tangent to it and the loading angle formed by the rectilinear part of the product relative to the plane perpendicular to the axis of rotation of the reel, the set value of the clamping angle being chosen beforehand by the operator or automatically pre-determined according to the measured diameter of the product. 2. Motorized winding device provided with a guide and relative displacement for the implementation of the method according to revendicaticn 1 characterized by the presence of at least one angular sensor intended for the measurement of the loading angle formed by the rectilinear part of the product with the plane perpendicular to the axis of rotation of the reel, an angular sensor for measuring the rotation of the reel, a sensor for the relative displacement of the guide-reel translation, an electronic device for capturing, storing and processing said data and a control member (relay or amplifier) intended to control the relative longitudinal position of the guide or vice versa of the reel. 3. Method according to claim 1 characterized in that the helix angle of the wound product is determined indirectly at each point by calculation from the information received and stored by a microprocessor and / or an arithmetic computer and from a sensor angle placed on the rectilinear portion of the product located between the guide and the reel, a sensor for the angle of rotation of the reel and a sensor for the relative longitudinal position of the reel guide system. 4. Automatic slicing method according to claim 3 characterized by the automatic detection, when the last turn of a layer is put in place, of its arrival against the cheek and the use of this information to effect the reversal of the direction of tranchanning, the arrival against the cheek being defined by the cancellation of the mean helix angle of the wound product for a predetermined angle of rotation of the loading reel. 5. Application of the method according to claims 1, 3 and / or 4 to the cutting of electric cables.

Images