Control method for a precision winding system

Abstract

Control method for a precision winding system (100) for winding fibers (22) around a liner (10), wherein the precision winding system (100) comprises: a storage unit (610) which pre-stores a reference shape of a liner (10) as well as winding conditions including a winding position and a winding angle in which a fiber (22) is wound around the liner (10) with the reference shape; a guide (110) which is movable relative to the liner (10) and is configured to feed the fiber (22) to the liner (10); a rotation device (120) which is configured to rotate the liner (10) so that the fiber (22) fed by the guide (110) is wound around the liner (10); a measuring unit (130) which is configured to measure a shape of the liner (10);and a controller (600) configured to control the guide (110) and the measuring unit (130), the method comprises, by means of the controller (600), causing the measuring unit (130) to measure the shape of the liner (10) before the fiber (22) is wound around the liner (10), and, if there is a difference between the reference shape stored in the storage unit (610) and the shape of the liner (10) measured by the measuring unit (130), correcting the winding conditions to reduce or eliminate the difference, and controlling the guide (110) according to the corrected winding conditions so that the fiber (22) is wound around the liner (10).

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe invention relates to a control method for a precision winding system.2. Description of the Prior ArtAs a method for manufacturing a high-pressure fluid tank, a precision winding method (also referred to as "FW method") is known (see, for example, JP 2014-233 852 A). According to the FW method, reinforcing fibers impregnated with a thermosetting resin in advance are wound around the outer periphery of a winding object to form a number of fiber layers on the object, and the thermosetting resin is cured. By using the FW method, it is possible to form a high-strength fiber-reinforced resin layer on a surface layer of the winding object.When a high-pressure fluid tank is manufactured using the FW method, the fibers must be properly wound around the winding object to achieve the desired strength. In JP 2014-233 852 A, a method for checking the winding position and the folding radius of the fibers at dome portions of a liner as the winding object is proposed to detect the winding position of the fibers.SUMMARY OF THE INVENTIONHowever, in the method of JP 2014-233 852 A, the shape of the winding object is ignored; therefore, winding errors may occur due to deviations in the shape of the winding object. A method for winding fiber webs around the outer circumference of a winding object, in which mispositioning of fiber tapes deposited on the winding object is compensated by a fiber placement machine which is controlled by programmable instructions, is known from US 2009 / 0 199 948 A1. In this case, after the application of a number of layers, the layer is determined in order to compensate for a possible offset by adapting the settings. Nevertheless, it is not possible with the method from US 2009 / 0 199 948 A1 to carry out an adaptation of the winding conditions before the winding of the fibers is started, in order thereby not only to compensate winding errors by subsequent layers being wound differently, but rather to avoid the generation of winding errors.In order to solve the above disadvantages, the present invention has an object to provide a control method for a precision winding system capable of preventing the generation of winding defects. This object is achieved with the features of claim 1, advantageous refinements are the subject matter of the dependent claims.The precision winding system includes a storage unit that stores in advance a reference shape of a liner as a winding object and winding conditions including a winding position and a winding angle at which a fiber is wound around the liner having the reference shape; a guide that is movable relative to the liner and configured to supply the fiber to the liner; a rotation device configured to rotate the liner so that the fiber supplied from the guide is wound around the liner; a measurement unit configured to measure a shape of the liner; and a controller configured to control the guide and the measurement unit. The method includes, by the controller, causing the measurement unit to measure the shape of the liner. When there is a difference between the reference shape stored in the storage unit and the shape of the liner measured by the measurement unit, the winding conditions are corrected to reduce or eliminate the difference, and the guide is controlled according to the corrected winding conditions so that the fiber is wound around the liner. The control method for the precision winding system of the above-described aspect can reduce or eliminate a winding error of the fibers caused by variations in the shape of the liner by correcting the winding conditions using the shape of the liner.The storage unit may further store a plurality of sets of winding conditions corresponding to a plurality of differences. When the difference occurs between the reference shape stored in the storage unit and the shape of the liner measured by the measurement unit, the controller may change the winding conditions to winding conditions corresponding to the difference, and control the guide according to the respective winding conditions so that the fiber is wound around the liner. With this arrangement, winding conditions corresponding to the difference are stored in advance, so that the calculation load can be reduced.The storage unit may further store, in advance, an n-ply reference shape as a shape obtained after n plies of the fiber are wound around the liner having the reference shape, and winding conditions for an (n+1) ply including a winding position at which the fiber is wound around the liner having the n-ply reference shape, where n is a positive integer. The method may further cause, by the controller, the measurement unit to measure the shape obtained by winding n layers of the fiber around the liner. When there is the difference between the n-ply reference shape stored in the storage unit and the measured shape obtained by winding n plies of the fiber around the liner, the winding conditions for the (n+1) ply may be corrected by the controller to reduce or eliminate the difference, and the guide may be controlled according to the corrected winding conditions for the (n+1) ply so that the fiber is wound around the liner. With this arrangement, the winding conditions are corrected using the shape of the liner around which the fiber is wound, so that a winding error of the fiber caused by variations in the shape of the liner can be effectively reduced or eliminated.The invention may be practiced in various ways. For example, the invention can be executed in the form of a precision winding system, as a computer program for realizing the control method, as storage media on which the computer program is stored, or the like.BRIEF DESCRIPTION OF THE DRAWINGSThe features and advantages, and technical and economic significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like reference numerals designate like elements, and wherein: FIG. 1 is a schematic sectional view of a tank used in a first embodiment; FIG. 2 is a schematic view showing the structure of a precision winding system; FIG. 3 is a flow chart showing a control routine of the precision winding system; FIG. 4 is a view helpful to explain a method for correcting winding conditions in the first embodiment; FIG. 5 is a flowchart showing a control routine of a second embodiment; and FIG. 6 is a flowchart showing a control routine of a third embodiment.DETAILED DESCRIPTION OF EMBODIMENTSA. First EmbodimentA1. Construction of the winding objectFIG. 1 is a schematic sectional view of a tank 50 used in a first embodiment. The schematic sectional view of FIG. 1 shows the tank 50 at the time when the tank 50 is cut along a sectional plane passing through its central axis CX. In this embodiment, a liner 10 is used as a winding object, and the tank 50 is a gas tank used for a fuel cell.The tank 50 includes the liner 10 having cap portions 13 and a fiber layer 21. The liner 10 includes a substantially cylindrical body portion 11 formed in a central portion thereof, and substantially hemispherical dome portions 12 continuously formed at opposite ends of the body portion 11. As a material for the liner 10, a high-strength aluminum material or stainless steel material or a resin material may be used.The cap portions 13 are formed at distal ends of the dome portions 12 and are formed of metal. The cap portions 13 serve as tubes through which gas is introduced into the liner 10. The fiber layer 21 serves to reinforce the strength of the tank 50. in this embodiment, the fibers constituting the fiber layer 21 are carbon fibers impregnated in advance with an epoxy resin as a thermosetting resin. As material for the fibers, rayon-containing carbon fibers, polyacrylonitrile-containing (PAN-containing) carbon fibers or pitch-containing carbon fibers can be used, for example.A2 Structure of Precision Winding System 100FIG. 2 is a schematic view showing the configuration of a precision winding system 100 as a first embodiment. The precision winding system 100 is a device for winding a bundle of fibers 22 (hereinafter referred to simply as "fiber") around the outer periphery of the liner 10 according to a precision winding method. The precision winding system 100 includes a guide 110, a rotation device 120, a measurement unit 130, a controller 600, and a storage unit 610.The guide 110 is movable relative to the liner 10 and serves to supply the fiber 22 that has been unwound from a spindle (not illustrated) to the liner 10. The guide 110 has a rectangular plane in contact with the fiber 22 in this embodiment, and swings about an axis (v-axis in FIG. 2 ) parallel to the short-side direction of the plane in contact with the fiber 22, so that the unrolled fiber 22 can move in a direction perpendicular to the x-axis and the y-axis. By controlling the guide 110, it is possible to control the winding position as well as the winding angle of the fiber 22 onto the liner 10.The rotation device 120 rotates the liner 10 to wind the fiber 22 unwound from the guide 110 around the liner 10. The rotation device 120 includes a rotation rod 122, a support rod 124, and a motor 126. One end of the rotary rod 122 is connected to the motor 126, and the other end is fixed to one of the cap portions 13 in the liner 10. One end of the support rod 124 is fixed to the other cap portion 13 in the liner 10. The rotation rod 122 and the support rod 124 are both fixed to the cap portion 13 by being inserted into the cap portions 13. When the motor 126 rotates, the liner 10 rotates about the central axis together with the rotation rod 122, so that the rotation device 120 can wind the fiber 22 around the liner 10 while applying tension to the fiber 22.The measurement unit 130 is a device for measuring the shape of the liner 10. the measurement unit 130 is movable in the longitudinal direction of the liner 10 and configured to measure the shape of the liner 10 before the fiber 22 is wound around the liner 10 and to measure the shape of the liner 10 in a state where the fiber 22 is wound around the liner 10. In this embodiment, a laser distance measuring instrument is used as the measuring unit 130.The controller 600 is a control unit for controlling each device of the precision winding system 100. The controller 600 controls at least the guide 110 and the measurement unit 130. The controller 600 includes a CPU, a RAM, and a ROM (not shown) used for controlling each device. The controller 600 controls each device of the precision winding system 100 so that the fiber 22 is wound onto (around) liner 10 at the desired tension at the desired location and angle.The storage unit 610 is electrically connected to the controller 600 and stores a reference shape and winding conditions in advance. The reference shape is a base or standard shape of the liner. The winding conditions are conditions in which the fiber 22 is wound around the liner. In this embodiment, the winding conditions include the winding position and the winding angle. The winding position here denotes a position at which the fiber 22 comes into contact with the liner. The winding angle denotes an angle formed by a straight line passing through a position at which the fiber 22 is unwound and the winding position and the central axis of the liner 10. The winding conditions may further include a winding speed. The winding speed denotes a length of the fiber that is wound around the liner per unit time.A3. Control Routine of Precision Winding System 100FIG. 3 is a flow chart showing a control routine of the precision winding system 100. In this embodiment, when the user turns ON a start button (not shown) of the precision winding system 100, the control routine of the precision winding system 100 is executed.When the start button is turned ON, the controller 600 causes the measurement unit 130 to measure the shape of the liner 10 (step S 110). In this embodiment, the measurement unit 130 longitudinally moves the liner 10 to measure the overall shape of the liner 10 from one cap portion 13 included in the liner 10 to the other cap portion 13.Then, the controller 600 determines the presence or absence of a difference between the reference shape of the liner 10 stored in the storage unit 610 and the actual shape of the liner 10 measured by the measurement unit 130 (step S 120). In this embodiment, the controller 600 determines that there is a difference when the difference is larger than a preset value, and determines that there is no difference when the difference is equal to or smaller than the preset value. In this embodiment, the determination is made using a distance between a position where the fiber 22 is assumed to come into contact with the liner 10 in the reference shape and a position where the fiber 22 is assumed to come into contact with the liner 10 in the actual shape. In this embodiment, the controller 600 determines that there is a difference when the above-described distance is greater than 5 mm, and determines that there is no difference when the above-described distance is equal to or less than 5 mm.When the controller 600 determines that there is a difference between the reference shape and the actual shape (step S 120: YES), the controller 600 corrects the winding conditions so as to eliminate the difference between the reference shape and the actual shape (step S 130). Then, the controller 600 controls the guide 110 according to the corrected winding conditions to wind the fiber 22 around the liner 10 (step S 140).When the controller 600 determines that there is no difference between the reference shape and the actual shape (step S 120: NO (see FIG. 3 )), the controller 600 controls the guide 110 according to the winding conditions stored in the storage unit 610 in advance to wind the fiber 22 around the liner 10 (step S 140). Thus, the control routine of the precision winding system 100 ends.FIG. 4 is a view helpful to explain a method for correcting the winding conditions in this embodiment. In FIG. 4, the reference shape of the liner 10 is shown by a broken line, and the actual shape of the liner 10 is shown by a solid line. In FIG. 4, the horizontal line is the x-axis as the direction of the central axis of the liner 10, and the vertical axis is the y-axis as the radial direction of the liner 10.FIG. 4 shows the case where a distal end of the cap portion 13 of the actual shape of the liner 10 is offset rightward in FIG. 4 as compared with the reference shape of the liner 10. In the reference shape (shown by the broken line) of the liner 10, the position at which the fiber 22 is assumed to come into contact with the liner 10 is assumed to be a position A 1 spaced apart from the distal end of the cap portion 13 by x 1 in the direction of the central axis (x-axis direction) and y 1 in the radial direction (y-axis direction). In this case, in the actual shape (shown by the solid line) of the liner 10, the position at which the fiber 22 is assumed to come into contact with the liner 10 is a position A 2 spaced apart from the distal end of the cap portion 13 by x 2 in the central axis direction (x-axis direction) and y 2 in the radial direction (y-axis direction). Thus, in this case, even if the fiber 22 is disposed at the position desired by the controller 600, the winding position A 1 in the reference shape of the liner 10 is different from the winding position A 2 in the actual shape of the liner 10. More specifically, the controller 600 corrects the winding position to a position A 3 spaced apart from the distal end of the cap portion 13 by x 1 in the direction of the central axis (x-axis direction) and y 1 in the radial direction (y-axis direction). In addition, the controller 600 corrects the winding angle from an angle θ 1 formed by a straight line passing through the position at which the fiber 22 is unwound from the guide 110, and the position A 1 and the center axis of the liner 10 to an angle θ 2 formed by a straight line passing through the position at which the fiber 22 is unwound from the guide 110, and the position A 3 and the center axis of the liner 10.According to the precision winding system 100 of this embodiment, it is possible to reduce or eliminate a winding error of the fiber 22 caused by changes or deviations in the shape of the respective liners 10. It is thus possible to restrain a lack of strength of the tank 50 due to the winding failure of the fiber 22.B. Second EmbodimentFIG. 5 is a flowchart showing a control routine of a second embodiment. A precision winding system of the second embodiment is different from that of the first embodiment in that a plurality of sets of winding conditions corresponding to the differences between the reference shape and the actual shape are additionally stored in the storage unit 610; the system of the second embodiment is identical to that of the first embodiment in other respects. Further, the control routine of the second embodiment is different from that of the first embodiment in that the routine includes a step S130A instead of the step S130, the control routine of the second embodiment being identical to that of the first embodiment in other respects.The winding conditions corresponding to a difference between the reference shape and the actual shape include, for example, winding conditions that the winding position is a position A 3 and the winding angle θ 2 when the winding position of the actual shape of the liner 10 becomes the position A 2 where the winding position of the reference shape of the liner 10 is A 1 and the winding angle θ 1, as shown in FIG. 4. In this embodiment, various information representing respective winding conditions that are uniquely obtained when the winding position and the winding angle of the reference shape of the liner 10 and the winding position of the actual shape of the liner 10 are determined are stored in the various condition storage unit 610 in the example described above.In the control routine of the second embodiment, the controller 600 selects winding conditions corresponding to a difference between the reference shape and the actual shape in step S 130A (see FIG. 5 ). Then, in step S 140, the controller 600 controls the guide 110 according to the winding conditions corresponding to the difference to wind the fiber 22 around the liner 10. In this embodiment, the controller 600 selects winding conditions according to the winding position and the winding angle of the reference shape of the liner 10 and the winding position of the actual shape of the liner 10.According to the precision winding system of the second embodiment, the winding conditions corresponding to the differences are stored in the storage unit 610 in advance; therefore, calculation for correcting the winding conditions becomes unnecessary. As a result, the computational load of the precision winding system of the second embodiment can be reduced as compared with the precision winding system of the first embodiment.C. Third EmbodimentFIG. 6 is a flowchart showing a control routine of a third embodiment. A precision winding system of the third embodiment is different from that of the first embodiment in that (i) an n-ply reference shape as a shape obtained after the fiber 22 is wound around the liner 10 having the reference shape to obtain "n" plies of the fiber 22 ("n" is a positive integer), and (ii) winding conditions for an (n+1) ply including a winding position at which the fiber 22 is wound around the liner 10 having the n-ply reference shape are additionally stored in the storage unit 610 in advance, the system of the third embodiment being identical to that of the first embodiment in other respects, the control routine includes step S140A instead of step S140, and further includes steps S150 to S190, wherein the control routines of the first and third embodiments are identical in other respects.In step S 140A of the control routine of the third embodiment, the guide 110 is controlled so that the fiber 22 constituting the first layer is wound around the liner 10. Here, the fiber 22 constituting the first layer refers to the fiber 22 wound around the liner 10 while the liner 10 makes one revolution around its central axis when the winding of the fiber 22 around the liner 10 is started. Similarly, the fiber 22 constituting the n-th layer denotes the fiber 22 wound around the liner 10 while the liner 10 makes one revolution about its central axis after the liner 10 makes n-1 revolutions about its central axis since starting winding the fiber 22 around the liner 10.After step S 140A, the controller 600 performs winding of the fiber 22 to form the second and other layers of fibers in a similar manner as in the case of the fiber 22 constituting the first layer. Specifically, with respect to the fiber 22 for the second and other layers, the fiber 22 is also wound around the liner 10 after the shape of the liner 10 is measured before winding the fiber 22 around the liner 10. In the following description, "n" ("n" is a positive integer) is used to facilitate understanding. More specifically, after step S 140A, the controller 600 causes the measurement unit 130 to measure the shape of the liner 10 on which "n" layers of the fiber 22 have been wound (step S 150).Then, the controller 600 determines that the presence or absence of a difference between the n-ply reference shape stored in the storage unit 610 and the actual shape of the liner 10 measured by the measurement unit 130 have been wound on the n-plies of the fiber 22 (step S 160). In this embodiment, the controller 600 determines that there is a difference when the difference is larger than a preset value, and determines that there is no difference when the difference is equal to or smaller than the preset value. In this embodiment, the determination is made using a difference between a position where the fiber 22 constituting the (n+1) layer is assumed to come into contact with the liner 10 in the n-layer reference shape of the liner 10 and a position where the fiber 22 constituting the (n+1) layer is assumed to come into contact with the liner 10 in the actual shape of the liner 10 on which n-layers of the fiber 22 have been wound. In this embodiment, the controller 600 determines that a difference is given when the distance is greater than 5 mm, and determines that no difference is given when the distance is equal to or less than 5 mm.When the controller 600 determines that there is a difference between the n-ply reference shape and the actual shape (step S 160: YES), the controller 600 corrects the winding condition for the (n+1) ply using the difference between the reference shape and the actual shape (step S 170). Then, the controller 600 controls the guide 110 according to the corrected winding conditions for the (n+1)-layer to wind the fiber 22 for the (n+1)-layer around the liner 10 (step S 180).On the other hand, when the controller 600 determines that there is no difference between the n-ply reference shape and the actual shape (step S 160: NO), the controller 600 controls the guide 110 and the rotating device 120 to wind the (n+1)-ply fiber 22 around the liner 10 according to the winding conditions for the (n+1)-ply stored in advance in the storage unit 610 (step S 180).After step S 180, the controller 600 determines whether winding of the fiber 22 is completed in step S 190. When the controller 600 determines that winding of the fiber is not completed (step S 190: NO), the control flow returns to step S 150. When the controller 600 determines that winding is completed (step S 190: YES), the control flow ends.According to the precision winding system of the third embodiment, the shape of the liner 10 after winding is measured each time a fiber 22 is wound, so that a winding error of the fiber 22 can be reduced or eliminated. As a result, it is possible to restrain a lack of strength of the tank 50 that may occur due to winding defects of the fiber 22. Like the precision winding system of the second embodiment, a plurality of sets of winding conditions for the (n+1)-layer corresponding to the respective differences between the n-layer reference shape and the actual shape may be stored in the storage unit 610 of the precision winding system of the third embodiment. In this way, the calculation for correcting the winding conditions for the (n+1) position becomes unnecessary, and the calculation load can be reduced.

Claims

A control method for a precision winding system (100) for winding fibers (22) around a liner (10), the precision winding system (100) comprising: a storage unit (610) that stores in advance a reference shape of a liner (10) as well as winding conditions including a winding position and a winding angle at which a fiber (22) is wound around the liner (10) having the reference shape; a guide (110) that is movable relative to the liner (10) and is configured to supply the fiber (22) to the liner (10); a rotation device (120) configured to rotate the liner (10) such that the fiber (22) supplied from the guide (110) is wound around the liner (10); a measurement unit (130) configured to measure a shape of the liner (10); and a controller (600) configured to control the guide (110) and the measurement unit (130), the method comprising, by the controller (600), causing the measurement unit (130) to measure the shape of the liner (10) before the fiber (22) is wound around the liner (10), and when a difference occurs between the reference shape stored in the storage unit (610) and the shape of the liner (10) measured by the measurement unit (130), correcting the winding conditions to reduce or eliminate the difference, and controlling the guide (110) according to the corrected winding conditions so that the fiber (22) is wound around the liner (10).The method according to claim 1, wherein the storage unit (610) further stores, in advance, a plurality of sets of winding conditions corresponding to a plurality of differences; and when the difference occurs between the reference shape stored in the storage unit and the shape of the liner (10) measured by the measurement unit (130), the controller (600) changes the winding conditions to winding conditions corresponding to the difference, and controls the guide (110) according to the corresponding winding conditions so that the fiber (22) is wound around the liner (10).The method according to claim 1 or 2, wherein the storage unit (610) further stores, in advance, an n-ply reference shape as a shape obtained after n plies of the fiber (22) are wound around the liner (10) having the reference shape, and winding conditions for an (n+1) ply including a winding position at which the fiber (22) is wound around the liner (10) having the n-ply reference shape, where n is a positive integer; the method further comprises, by the controller (600), causing the measurement unit (130) to measure the shape obtained by winding n plies of the fiber (22) around the liner (10); and when there occurs the difference between the n-ply reference shape stored in the storage unit (610) and the measured shape obtained by winding n plies of the fiber (22) around the liner (10), correcting the winding conditions for the (n+1) ply to reduce or eliminate the difference, and controlling the guide (110) according to the corrected winding conditions for the (n+1) ply so that the fiber (22) is wound around the liner (10).

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