Control device, control method, linear motor, and drive device

Abstract

To provide a control device or the like to reduce a thrust ripple of a multi-phase linear motor.SOLUTION: A control device is for a linear motor 1 that includes an armature having a plurality of magnetic pole teeth and a plurality of coils, and a field magnet unit with a plurality of magnets, and energizes a multi-phase AC current through the plurality of coils, and includes: a waveform generating unit 41 that generates a current waveform for each phase constituting the plurality of phases; a harmonic superposition unit 42 that generates harmonics and superposes them on the current waveform of each phase; and a driver 43 that applies the current based on the current waveform of each phase on which the harmonics are superposed, to the respective corresponding coil, in which the current waveform of one phase on which the harmonics are superposed is dissimilar to the current waveform of another phase on which the harmonics are superposed.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a control device for supplying a multi-phase alternating current to a linear motor. [Background technology]

[0002] It is known that linear motors have thrust ripples, which are fluctuations in thrust caused by the relative positions of the stator and the rotor.

[0003] Thrust ripple occurs due to variations in coil shape, coil alignment errors, variations in magnetic flux density generated by the magnets, and magnet alignment errors. If the thrust ripple is large, vibrations generated during movement of the mover increase, making positioning control difficult. As a result, positioning accuracy decreases, leading to a decrease in motor performance.

[0004] Non-Patent Document 1 proposes a method for reducing torque ripple in a motor by superimposing higher-order currents of ±1 order, the torque ripple order to be reduced, on the fundamental current. The torque ripple described in Non-Patent Document 1 can be considered to be the same as thrust ripple in a linear motor, and therefore the torque ripple reduction method is thought to be applicable to reducing thrust ripple as well. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Haruki Yashiro and 1 other author, "Torque Ripple Reduction of Electric Motors by High-Order Current Flow Rates," Transactions of the Japan Society of Mechanical Engineers (C), February 2006, Japan Society of Mechanical Engineers, Vol. 72, No. 714, pp. 435-440 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the inventors of the present invention conducted verification and found that applying known methods to reduce thrust ripple in a linear motor did not sufficiently reduce thrust ripple. The inventors conducted extensive research to reduce thrust ripple. As a result, they discovered that the key to reducing thrust ripple is to ensure that the waveforms of the higher-order currents applied to multiple phases are not similar to each other. The present invention was completed based on this knowledge. Its purpose is to provide a control device and the like that reduces thrust ripple in a multiple-phase linear motor. [Means for solving the problem]

[0007] A control device according to one aspect of the present application is a control device for a linear motor that includes an armature having a plurality of magnetic pole teeth and a plurality of coils, and a field magnet portion having a plurality of magnets, and that passes a plurality of phases of AC current through the plurality of coils, and includes a waveform generating unit that generates a current waveform for each of the phases that make up the plurality of phases, a harmonic superposition unit that generates harmonics and superimposes them on the current waveforms of the respective phases, and a driver that applies a current based on the current waveforms of the respective phases on which the harmonics are superimposed to each of the corresponding coils, and the current waveform of one phase on which the harmonics are superimposed is non-similar to the current waveforms of the other phases on which the harmonics are superimposed.

[0008] In one aspect of the present application, the current waveform of one phase is made non-similar to the current waveform of another phase on which harmonics are superimposed, thereby making it possible to reduce thrust ripple in a multi-phase linear motor.

[0009] In a control device according to one aspect of the present application, the harmonic superposition unit determines the phase of the harmonic of one of the phases constituting the multiple phases based on the phase of the harmonic of the other phase.

[0010] In one aspect of the present application, the phase of one phase is used as a reference to determine the phase of the other phase, thereby making it possible to make the waveforms of the higher-order currents non-similar to each other.

[0011] In the linear motor controlled by a control device according to one embodiment of the present application, the field magnet portion has 7n magnets, and the 6n (n is a natural number) magnetic pole teeth of the armature face the 7n magnets, forming a 7n-pole, 6n-slot configuration.

[0012] In one aspect of the present application, by configuring the linear motor with 7n poles and 6n slots, a high thrust can be obtained with a lightweight mover, making it possible to achieve high-speed response.

[0013] A control method according to one aspect of the present application is a control method for a linear motor including an armature having a plurality of magnetic pole teeth and a coil, and a field magnet portion having a plurality of magnets, and for passing a multi-phase AC current through the coil, the control method including the steps of: (1) generating a basic waveform for each of the multiple phases; (2) determining a thrust ripple of the linear motor using the basic waveform; (3) Fourier-transforming the waveform of the thrust ripple to determine the period and peak value of the thrust ripple; and (4) determining the order and peak value of the thrust ripple for each period. The method includes a step (4) of storing settings for generating ±1st order harmonics at peak values ​​determined based on the peak value, a step (5) of generating harmonics in accordance with the stored settings, a step (6) of superimposing the harmonics on the fundamental waveform, and a step (7) of applying a current based on the current waveform on which the harmonics are superimposed to the coil, wherein in the step of superimposing the harmonics on the fundamental waveform, the phase of the harmonics of one of the phases constituting the multiple phases is used as a reference to determine the phase of the harmonics of the other phase.

[0014] In the control method according to one aspect of the present application, after the steps (1) to (4) are performed, the steps (1) and the steps (5) to (7) are repeatedly performed.

[0015] In one aspect of the present application, by determining the phase of harmonics of one of the phases constituting the multiple phases based on the phase of harmonics of the other phases, the current waveform of one phase becomes non-similar to the current waveform of the other phase on which harmonics are superimposed, making it possible to reduce the thrust ripple of a multiple-phase linear motor.

[0016] A linear motor according to one aspect of the present application comprises an armature having a plurality of magnetic pole teeth and a plurality of coils, a field magnet section having a plurality of magnets, a waveform generating section that generates a current waveform for each of the plurality of phases, a harmonic superposition section that generates harmonics and superimposes them on the current waveform, and a driver that applies a current based on the current waveform of each phase on which the harmonics are superimposed to the coils, wherein the harmonic superposition section generates a current waveform for each of the phases so that the current waveform of one phase on which the harmonics are superimposed is non-similar to the current waveform of another phase on which the harmonics are superimposed, and the driver comprises a control device that applies a current based on the current waveform of each phase generated by the harmonic superposition section to each of the corresponding coils.

[0017] In one aspect of the present application, the current waveform of one phase is made non-similar to the current waveform of another phase on which harmonics are superimposed, thereby making it possible to reduce thrust ripple in a multi-phase linear motor.

[0018] A driving device according to one aspect of the present application includes two sets of the linear motors and a connecting portion that connects the two field magnet portions.

[0019] In one aspect of the present application, by providing two sets of armature units and field magnet units, it is possible to obtain a higher thrust force than in the case of using one set. [Effects of the Invention]

[0020] According to one aspect of the present application, it is possible to reduce thrust ripples in a multi-phase linear motor. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view showing a configuration example of a linear motor. [Figure 2] FIG. 2 is a perspective view showing an example of the configuration of a mover. [Figure 3] FIG. 2 is an exploded perspective view showing an example of the configuration of a mover. [Figure 4] FIG. 2 is an exploded perspective view showing an example of the configuration of a stator. [Figure 5] FIG. 2 is a functional block diagram showing a configuration example of a control device. [Figure 6] FIG. 10 is an explanatory diagram showing a procedure for determining the order of a harmonic; [Figure 7] 10 is a flowchart illustrating an example of a procedure for a harmonic definition process. [Figure 8] 10 is a flowchart illustrating an example of a procedure for an operation control process. [Figure 9] FIG. 1 is a schematic side view showing an example of the configuration of a linear motor. [Figure 10] 10 is a graph showing an example of an output current waveform. [Figure 11] 10 is a graph showing a current waveform of a U phase. [Figure 12] FIG. 10 is a perspective view showing another example of the configuration of the mover. [Figure 13] FIG. 10 is an exploded perspective view showing a part of another example of the configuration of the mover. [Figure 14] FIG. 10 is a schematic side view showing another example of the configuration of the linear motor. [Figure 15] FIG. 2 is a perspective view showing a configuration example of a drive device. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment will be described with reference to the drawings.

[0023] (Embodiment 1) FIG. 1 is a perspective view showing an example of the configuration of a linear motor. Linear motor 1 of this embodiment includes a rectangular plate-shaped mover 2 (field magnet portion), a rectangular plate-shaped stator 3 (armature), and a control device 4 (not shown in FIG. 1). In linear motor 1, mover 2 is disposed opposite stator 3 with a predetermined gap therebetween, and is movable relative to stator 3. Note that mover 2 is supported by a predetermined linear guide (not shown in FIG. 1), and is movable while maintaining a gap from stator 3 against the attractive force acting on stator 3.

[0024] Fig. 2 is a perspective view showing an example of the configuration of the mover. Fig. 3 is an exploded perspective view showing an example of the configuration of the mover. The mover 2 includes a plurality of rectangular plate-shaped permanent magnets 21, a rectangular plate-shaped back yoke 22, and a rectangular plate-shaped frame plate 23.

[0025] As shown in FIG. 3, rectangular plate-shaped permanent magnets 21 are arranged side by side on a back yoke 22 in the moving direction. Each permanent magnet 21 is magnetized in the thickness direction (the vertical direction in FIG. 3), and the magnetization directions of adjacent permanent magnets 21 are opposite to each other. That is, permanent magnets 21 magnetized in the direction from the mover 2 toward the stator 3 (the bottom-to-top direction in FIG. 3) and permanent magnets 21 magnetized in the direction from the stator 3 toward the mover 2 (the top-to-bottom direction in FIG. 3) are arranged alternately. Note that in FIGS. 2 and 3, the multiple permanent magnets 21 are arranged side by side at a predetermined skew angle with respect to the direction perpendicular to the moving direction, but a skew angle is not necessary. A skew angle may be set as needed. The permanent magnets 21 are made of, for example, neodymium magnets, ferrite magnets, or samarium-cobalt magnets, and the back yoke 22 is made of a soft magnetic metal such as silicon steel. The permanent magnet 21 may be divided in a direction perpendicular to the direction of movement (from the upper left to the lower right in FIG. 3). The frame plate 23 is made of aluminum or the like.

[0026] A back yoke 22 for fixing a plurality of permanent magnets 21 is fixed to one surface of a frame plate 23. Since the structure here is 7 poles and 6 slots, the number of permanent magnets 21 fixed to the back yoke 22 is seven.

[0027] 4 is an exploded perspective view showing an example of the configuration of the stator. As shown in FIGS. 1 and 4, the stator 3 includes a plurality of coils 32, 32,..., a plurality of magnetic pole teeth 33, 33,..., lead wires 34, 34,..., and a water cooling unit 36.

[0028] The magnetic pole teeth 33 are formed by laminating silicon steel plates or by using a powder magnetic core. The coil 32 is formed by winding copper wire around a resin bobbin in advance, and is a hollow, approximately rounded rectangle extending along the length of the magnetic pole tooth 33, with a portion of the copper wire being pulled out to form the lead wire 34.

[0029] The magnetic wedge 35 is shaped like a rectangular plate. The magnetic wedge 35 is made by molding, for example, a resin material containing magnetic powder so that the magnetic wedge 35 has high magnetic permeability and electrical resistance. The length of the magnetic wedge 35 in plan view is approximately the same as the length of the magnetic pole tooth 33, and the magnetic wedge 35 is provided so as to straddle two adjacent coils 32.

[0030] The water-cooling unit 36 ​​has a plurality of inlets and outlets for flowing water as a coolant inside. To achieve excellent cooling performance, the water-cooling unit 36 ​​is made of a metal with good thermal conductivity, such as silver, copper, gold, or aluminum.

[0031] The stator 3 is assembled as follows: A coil 32 is inserted into each of the multiple magnetic pole teeth 33, and the coils 32 are fixed side by side in a direction perpendicular to the longitudinal direction (movement direction). Adjacent coils 32 are in contact with each other in the juxtaposition direction of the magnetic pole teeth 33 and coils 32 combination. A magnetic wedge 35 is fixed onto the coil 32 between adjacent magnetic pole teeth 33. By disposing the magnetic wedge 35, the magnetic flux density at the tip of the magnetic pole tooth 33 is appropriately short-circuited, which reduces thrust ripple although the thrust is slightly reduced. Next, the fixed multiple magnetic pole teeth 33 are placed on a water-cooling unit 36 ​​and fixed. The lead wires 34 are routed and connected to the control device 4. Each of the above fixing methods can be a known fixing method using an adhesive or the like.

[0032] 5 is a functional block diagram showing an example configuration of the control device. The control device 4 includes a waveform generating unit 41, a harmonic superimposing unit 42, and a driver 43 (applying unit). In the following explanation, an example will be given in which the multi-phase AC current is a three-phase AC current. The waveform generating unit 41 receives a three-phase AC input and generates fundamental waveforms for U, V, and W phases. The harmonic superimposing unit 42 generates harmonics, for example, 3rd to 13th harmonics, and superimposes them on the fundamental waveform. The harmonic superimposing unit 42 is composed of a harmonic superimposing unit 42U, a harmonic superimposing unit 42V, and a harmonic superimposing unit 42W, which handle the waveforms of the U, V, and W phases, respectively.

[0033] The method for determining the order and amplitude of harmonics will now be described. Figure 6 is an explanatory diagram showing the procedure for determining the order of harmonics. First, a fundamental waveform (first fundamental waveform) that does not contain harmonics is generated. The thrust waveform obtained when the linear motor 1 is operated with the fundamental waveform is obtained. To obtain the thrust waveform, the actual linear motor 1 may be operated, or the thrust waveform may be obtained using analysis software. For example, JMAG (registered trademark) is used as the analysis software. The thrust waveform is subjected to a Fourier transform to determine the period and peak value of the thrust ripple. The order and peak value of the thrust ripple are obtained for each period, and the ±1st order harmonic currents of the thrust ripple order are defined (referred to as "corrected harmonic currents" in Figure 6, hereinafter simply referred to as "harmonics"). The amplitude of the harmonic is obtained from the peak value of the thrust ripple obtained by the Fourier transform. In the example of Figure 6, the third order harmonic is first defined from the second order thrust ripple. The thrust waveform is obtained when the linear motor 1 is operated by superimposing a fundamental waveform and a third harmonic. The thrust ripple rate (ripple rate) is calculated from the obtained thrust waveform (in this case). When the ripple rate becomes smaller than the target value (threshold value), the process ends. If the ripple rate is larger than the target value, a fundamental waveform (second fundamental waveform) containing harmonics is generated by superimposing the fundamental waveform (first fundamental waveform) and the third harmonic, and the harmonics are defined from the thrust waveform using the procedure described above. In the example of Figure 6, the third harmonic is followed by the thirteenth harmonic, and then the sixth harmonic is defined. If the ripple rate is larger than the target even when the second fundamental waveform and the thirteenth harmonic are superimposed, the second fundamental waveform is generated. A fundamental waveform (third fundamental waveform) including harmonics is generated by superimposing the fundamental waveform and the 13th harmonic, and the harmonics are defined from the thrust waveform using the procedure described above. In this way, the process of generating a fundamental waveform including harmonics, obtaining the thrust waveform, and defining the harmonics is repeated until the ripple rate becomes smaller than the target value (threshold value). In the example of Figure 6, the process ends when the 6th harmonic is defined after the 13th. The definitions of all harmonics are stored in the control device 4, and when operating the linear motor 1, control is performed using a waveform in which all harmonics are superimposed on the fundamental waveform.

[0034] The waveforms of each phase when operating the linear motor 1 are generated as follows. The basic waveforms obtained from three-phase AC are similar in shape with phases differing by 120 degrees (2 / 3π), but the phases of the harmonics superimposed on each phase are determined based on one phase, for example, the U phase. As a result, the waveforms of each phase with superimposed harmonics are non-similar.

[0035] The waveform output by the harmonic superimposing unit 42 is output as a current command to the driver 43. The driver 43 controls the three-phase AC current to be applied to the linear motor 1 based on the input current command.

[0036] Next, information processing will be described. FIG. 7 is a flowchart showing an example of the procedure for harmonic definition processing. Analysis software is used here. Processing is performed by a computer running the analysis software. Before performing harmonic definition processing, it is assumed that necessary preparations, such as setting the specifications of the linear motor 1, have been made. The computer generates a basic waveform (step S1) (process (1)). The computer calculates the thrust waveform when the linear motor 1 is operated with the basic waveform (step S2). The computer obtains the thrust ripple from the thrust waveform (step (2)), further calculates the ripple rate, and determines whether the calculated ripple rate is smaller than a threshold value (step S3). If the computer determines that the ripple rate is smaller than the threshold value (YES in step S3), it terminates the processing. If the computer determines that the ripple rate is equal to or greater than the threshold value (NO in step S3), it obtains the order and peak value of the waveform with large thrust pulsation to be suppressed from the thrust waveform (step S4) (process (3)). The computer stores the determined order and peak value (step S5) (process (4)). The computer generates harmonics according to the order and peak value determined in step S4, and generates a superimposed waveform by superimposing it on the fundamental waveform (step S6). The computer returns the process to step S2. The harmonic definition process obtains a definition of the harmonics that will reduce the ripple rate below the threshold value. The harmonic definition is stored in the control device 4.

[0037] FIG. 8 is a flowchart showing an example of the procedure for the operation control process. The operation control process is a process performed when operating the linear motor 1. The control device 4 reads out the definition of the harmonics obtained by the harmonic definition process, settings such as which phase the harmonic phase should be aligned to, etc. (Step S21). The control device 4 generates a fundamental waveform and a harmonic waveform (Step S22) (Steps (1) and (5)). The control device 4 generates a superimposed waveform for each phase by superimposing the harmonic waveform on the fundamental waveform (Step S23) (Step (6)). Based on the superimposed waveform, a current is applied to the coil of each phase (Step S24) (Step (7)). The control device 4 determines whether to stop the linear motor 1 (Step S25). If the control device 4 determines not to stop the linear motor 1 (NO in Step S25), the process returns to Step S22. If the control device 4 determines to stop the linear motor 1 (YES in Step S25), the process ends.

[0038] Fig. 9 is a schematic side view showing an example of the configuration of a linear motor. In Fig. 9, only the main part of the stator 3 is shown, and the magnetic wedges 35 are not shown.

[0039] Figure 9 shows a scene when the linear motor 1 is moving, with current flowing through the coil 32. Three-phase AC is applied to the stator 3. U, V, and W in Figure 9 represent the U phase, V phase, and W phase of the three-phase AC power supply, respectively, and there are six sets, each consisting of three pairs of two forward and two reverse slots, in order to perform three-phase parallel current flow.

[0040] In FIG. 9, when a current is passed through the coil 32, the magnetic field generated in the magnetic pole teeth 33 causes the permanent magnets 21 of the mover 2 to sequentially magnetically attract and repel each other, generating a thrust force in the mover 2, causing the mover 2 to move linearly relative to the stator 3. As is clear from FIG. 9, the linear motor 1 has a 7-pole, 6-slot configuration. Using this 7-pole, 6-slot configuration as a basic unit, multiple such configurations may be connected together to form a 14-pole, 12-slot configuration or other 7n-pole, 6n-slot configuration (n is a natural number). Furthermore, the configuration of the linear motor 1 is not limited to the 7n-pole, 6n-slot configuration. For example, a 4n-pole, 6n-slot configuration may be used, as in the second embodiment described below.

[0041] FIG. 10 is a graph showing an example of an output current waveform. FIG. 10A is a graph showing an example of a current waveform in this embodiment. FIG. 10B is a graph showing an example of a current waveform in the prior art. In FIG. 10A, the phase of the harmonic current is aligned with the U phase, so the U-phase waveform and the V-phase waveform are not similar in shape. The V-phase waveform and the W-phase waveform are not similar in shape. The W-phase waveform and the U-phase waveform are not similar in shape. In other words, the current waveform of one phase is not similar in shape to the current waveforms of the other two phases. The phase of the harmonic current may be aligned with the V-phase or W-phase phase instead of the U-phase.

[0042] In the prior art, the phase of the U-phase harmonic current is matched to the phase of the U-phase fundamental waveform. Similarly, the phase of the V-phase harmonic current is matched to the phase of the V-phase fundamental waveform, and the phase of the W-phase harmonic current is matched to the phase of the W-phase fundamental waveform. Therefore, as shown in Figure 10B, the current waveforms of the three phases are similar to each other.

[0043] Fig. 11 is a graph showing the current waveform of the U phase when the procedure from step S21 to step S24 in Fig. 8 is performed. The graph shows the fundamental waveform of the U phase, the harmonic current, and the current waveform after the harmonic current is superimposed.

[0044] In this embodiment, the current waveforms of the three phases are generated so that the current waveform of one phase is not similar to the current waveforms of the other two phases, thereby making it possible to reduce thrust ripple.

[0045] (Embodiment 2) Although the linear motor 1 in the first embodiment has a seven-pole, six-slot configuration, the present invention is not limited to this. In this embodiment, a linear motor 1 having a four-pole, six-slot configuration is shown.

[0046] Fig. 12 is a perspective view showing another example of the configuration of the mover. Fig. 13 is an exploded perspective view showing a part of another example of the configuration of the mover. In Figs. 12 and 13, the same reference numerals are used for components that are the same as or correspond to the components shown in Figs. 2 and 3. As is clear from comparing Figs. 2 and 3 with Figs. 12 and 13, the mover 2 in this embodiment differs from embodiment 1 in that it has four magnets 21.

[0047] 13, in this embodiment, four permanent magnets 21 each having a rectangular plate shape are arranged in a row in the moving direction on a back yoke 22. In this embodiment, the outer dimensions of the mover 2 are the same as in embodiment 1, but the number of permanent magnets 21 arranged in a row is reduced from seven to four, so the width of the permanent magnets 21 is wider, i.e., the width in the moving direction is wider. The magnetization direction of the permanent magnets 21 is the same as in embodiment 1, so a description thereof will be omitted.

[0048] The external dimensions of the frame plate 23 are the same as those of the first embodiment. The stator 3 used is the same as that of the first embodiment. In this embodiment as well, the mover 2 is disposed opposite the stator 3 so as to have a predetermined gap from the stator 3. Lead wires 34 are routed and connected to the control device 4.

[0049] Fig. 14 is a schematic side view showing another example of the configuration of a linear motor. In Fig. 14, the magnetic wedge 35 is not shown. Like Fig. 9, Fig. 14 shows a scene when the linear motor 1 is moving, and a current is flowing through the coil 32.

[0050] The operation of the linear motor 1 is the same as in the first embodiment, and therefore a description thereof will be omitted. In this embodiment, four permanent magnets 21 are arranged in parallel with the mover 2, and therefore, as is clear from Fig. 14, a four-pole, six-slot configuration is formed. This four-pole, six-slot configuration is used as a basic unit, and multiple such units may be connected together to form an eight-pole, twelve-slot configuration, or a 4n-pole, six-slot configuration (n is a natural number).

[0051] The thrust ripple reduction method described in the first embodiment is also effective in this embodiment. That is, by generating current waveforms for each of the three phases so that the current waveform of one phase is not similar to the current waveforms of the other two phases, and applying currents based on these current waveforms to the coil 32 of the linear motor 1, it becomes possible to reduce thrust ripple.

[0052] (Embodiment 3) This embodiment relates to a configuration in which a plurality of the above-described linear motors 1 are combined. This configuration is assumed when the thrust force of a single linear motor 1 is insufficient or when a linear stage is configured using the linear motor 1.

[0053] Fig. 15 is a perspective view showing an example of the configuration of a drive device. The drive device 10 is configured by combining two of the above-mentioned linear motors 1. As shown in Fig. 15, the drive device 10 has two linear motors 1 of the same specifications installed in parallel, and two movers 2, 2 are connected by a connecting portion 5. For example, by fixing a stage to the connecting portion 5, it is possible to configure a linear stage.

[0054] The driving device 10 uses two linear motors 1, and therefore two control devices 4. The two linear motors 1, 1 must operate in sync in order for the driving device 10 to function properly. Therefore, the two control devices 4, 4 communicate with each other. Alternatively, a higher-level device (not shown) may be provided to further control the two control devices 4, allowing them to operate in sync.

[0055] Alternatively, there may be only one control device 4. In this case, the drive current is supplied to two linear motors 1 from one control device 4, so the control device must have a corresponding capacity.

[0056] The driving device 10 of this embodiment has the following advantages in addition to the advantages of the first and second embodiments: Since two linear motors 1, 1 are provided, it is possible to obtain a large thrust force.

[0057] The thrust ripple described in this specification occurs commonly in multi-phase AC motors. Therefore, the thrust ripple reduction method described above, i.e., the method of making the current waveform of one phase on which harmonics are superimposed non-similar to the current waveform of another phase on which harmonics are superimposed, is applicable not only to three-phase linear motors but also to multi-phase linear motors in general, such as two-phase linear motors. Furthermore, this reduction method is considered to be effective for multi-phase AC motors other than linear motors.

[0058] In the linear motor 1 of the present specification, the functions of the mover 2 and the stator 3 may be interchanged. That is, the mover 2 may serve as the stator, and the stator 3 may serve as the mover.

[0059] The technical features (constituent elements) described in each embodiment can be combined with each other, and by combining them, new technical features can be formed. The embodiments disclosed herein are to be considered as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above meaning, and is intended to include all modifications within the meaning and scope of the claims. In addition, the claims are written in a format in which a claim cites two or more other claims (multiple claim format), but this is not limited to this. Multiple claims that cite at least one other claim (multi-multi claim format) may also be written. [Explanation of symbols]

[0060] 1: Linear motor 2: Mover 21: Permanent magnet 22: Back yoke 23: Frame plate 3: Stator 32: Coil 33: Magnetic pole tooth 34: Leader line 35:Magnetic wedge 36: Water cooling unit 4: Control device 41: Waveform generation section 42: Harmonic superposition section 42U: Harmonic superposition section 42V: Harmonic superposition section 42W: Harmonic superposition section 43: Driver 5:Connection part 10: Drive unit

Claims

1. A control device for a linear motor including an armature having a plurality of magnetic pole teeth and a plurality of coils, and a field magnet portion having a plurality of magnets, and configured to pass a plurality of phases of AC current through the plurality of coils, a waveform generating unit that generates a current waveform for each of the multiple phases; a harmonic superimposing unit that generates harmonics and superimposes the harmonics on the current waveforms of the respective phases; a driver that applies a current based on the current waveform of each phase onto which the harmonic is superimposed to each of the corresponding coils; A control device, wherein the current waveform of one phase on which harmonics are superimposed is dissimilar to the current waveform of another phase on which harmonics are superimposed.

2. The control device according to claim 1 , wherein the harmonic superimposing unit determines the phase of the harmonic of one of the phases constituting the plurality of phases based on the phase of the harmonic of the other phase.

3. 3. The control device according to claim 1, wherein in the linear motor, the field magnet portion has 7n magnets, and 6n (n is a natural number) magnetic pole teeth of the armature face the 7n magnets, forming a 7n-pole, 6n-slot configuration.

4. A control method for a linear motor including an armature having a plurality of magnetic pole teeth and a coil, and a field magnet portion having a plurality of magnets, wherein a plurality of phases of AC current is passed through the coil, A step (1) of generating a basic waveform for each of the phases constituting the plurality of phases; A step (2) of determining a thrust ripple of the linear motor using the basic waveform; (3) performing a Fourier transform on the waveform of the thrust ripple to obtain a period and a peak value of the thrust ripple; a step (4) of determining the order and peak value of the thrust ripple for each period, and storing settings for generating ±1st order harmonics of the order at peak values ​​determined based on the peak values; (5) generating harmonics according to the stored settings; (6) superimposing the harmonic on the fundamental waveform; a step (7) of applying a current based on the current waveform having the harmonics superimposed thereon to the coil; and a control method in which, in the step of superimposing the harmonics on the fundamental waveform, the phase of the harmonics of one of the phases constituting the plurality of phases is used as a reference to determine the phase of the harmonics of the other phases.

5. 5. The control method according to claim 4, wherein after the steps (1) to (4) are performed, the steps (1) and the steps (5) to (7) are repeatedly performed.

6. an armature having a plurality of magnetic pole teeth and a plurality of coils; a field magnet portion having a plurality of magnets; a waveform generating unit that generates a current waveform for each of the multiple phases; a harmonic superimposing unit that generates harmonics and superimposes the harmonics on the current waveform; a driver that applies to the coil a current based on the current waveform of each phase on which the harmonic is superimposed, the harmonic superposition unit generates a current waveform for each phase such that a current waveform of one phase on which a harmonic is superposed is dissimilar to a current waveform of another phase on which the harmonic is superposed; The driver is a linear motor including a control device that applies currents based on the current waveforms of each phase generated by the harmonic superimposing unit to the corresponding coils.

7. A driving device comprising two sets of linear motors according to claim 6 and a connecting portion that connects the two field magnet portions.

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