Linear motor

Abstract

The present invention provides a linear motor that provides sufficient thrust even with a single motor, enables high acceleration / deceleration and long stroke operations, and allows for ultra-precise positioning control. [Solution] The system has an armature unit in which multiple magnetic circuits composed of multiple armatures are arranged in the direction of movement, and a permanent magnet unit composed of multiple permanent magnets. By arranging the armatures on both sides of the permanent magnet at the same distance, the magnitude of the magnetic attractive force acting between one end of the permanent magnet and the armature is equal to the magnitude of the magnetic attractive force acting between the other end and the armature, and the direction in which these forces act is opposite. As a result, the overall magnetic attractive force generated between the permanent magnet and the armature becomes almost zero, reducing the disturbance force and cogging force on the thrust. Furthermore, by connecting some of the armature windings to different servo amplifiers, high acceleration / deceleration and ultra-precise positioning operations can be performed with a single linear motor depending on the combination of the number of windings, the current capacity of the servo amplifier, and the current control.

Description

[Technical Field]

[0001] The present invention relates to a linear motor, and more particularly to a linear motor comprising an armature consisting of an armature core around which armature windings are wound, and permanent magnets, wherein when current is passed through the armature windings, the movable element moves relative to the stator due to electromagnetic action. [Background technology]

[0002] Conventional linear motors include coreless linear motors (see, for example, Patent Document 1 below) and suction force cancellation type tunnel actuators (see, for example, Patent Document 2 below). A coreless linear motor, such as the one disclosed in Patent Document 1, comprises a permanent magnet array in which permanent magnets with different magnetic properties are arranged alternately, and an armature formed by shaping a plurality of winding groups that are arranged opposite each other with a predetermined gap between them into a flat plate, and the motor is driven relatively by using either the permanent magnet array or the armature as the stator and the other as the movable element.

[0003] The tunnel-type actuator disclosed in Patent Document 2 is a linear motor in which a movable element moves within a space enclosed by the armature of a stator. Conventional core-type linear motors have a structure in which an iron core made of electromagnetic steel sheet around which armature windings are wound faces a permanent magnet, and a greater attractive force than thrust acts on the movable element support mechanism, which is a problem. In order to reduce this magnetic attractive force, the linear motor shown in Patent Document 2 has a structure in which a permanent magnet is sandwiched between the upper and lower magnetic pole teeth of an iron core configured so that the upper and lower magnetic poles are staggered. With this structure, the magnetic attractive force between the upper magnetic pole teeth and the movable element and the magnetic attractive force between the lower magnetic pole teeth and the movable element are of the same magnitude and in opposite directions, so they cancel each other out and the overall magnetic attractive force can be reduced. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-197718 [Patent Document 2] Japanese Patent Publication No. 2002-125360 [Overview of the project] [Problems that the invention aims to solve]

[0005] Cogging force is generated by the attractive force between the core (iron core) and the permanent magnet. When the permanent magnet moves, the attractive force changes periodically due to its positional relationship with the core, causing a rough, jarring pulsation in the motor's rotation, which restricts the smooth operation of the movable element. The coreless linear motor described in Patent Document 1 has a coreless structure, so cogging force and magnetic attractive force do not occur, and there is no risk of accuracy degradation caused by these. However, coreless linear motors have less torque (thrust) than linear motors with cores, so as the weight of the movable element increases and the stroke length increases, it becomes necessary to increase the number of turns in the armature winding and flow a large current to compensate for the insufficient torque. As a result, the current value must be increased to achieve high torque, which reduces the control resolution, making it difficult to stop the movable element at the target position with high precision, and furthermore, high heat generation is a factor in accuracy degradation.

[0006] Furthermore, in the case of the tunnel-type linear motor described in Patent Document 2, the magnetic circuit becomes long, making it prone to magnetic saturation, and the support mechanism for the movable element can only be installed at the entrance and exit of the tunnel, which presents challenges in its suitability for applications requiring long strokes.

[0007] Therefore, the present invention aims to provide a linear motor that has sufficient thrust even with a single linear motor, enables high acceleration / deceleration and long stroke operations, and also allows for ultra-precise positioning control. [Effects of the Invention]

[0008] The linear motor of the present invention is composed of a plurality of permanent magnets and a plurality of armatures flanking these permanent magnets. By arranging the armatures on both sides of the permanent magnets to be at the same distance from the permanent magnets, the magnitude of the magnetic attractive force acting between one end of the permanent magnet and the armature is equal to the magnitude of the magnetic attractive force acting between the other end and the armature, and the direction in which these forces act is opposite. As a result, the overall magnetic attractive force generated between the permanent magnets and the armature becomes almost zero, and the disturbance force and cogging force on the thrust can be reduced.

[0009] Furthermore, by connecting some of the armature windings to different servo amplifiers, depending on the combination of the number of windings, the current capacity of the servo amplifiers, and the current control, a single linear motor can perform both high-speed acceleration / deceleration and ultra-precise positioning operations. [Means for solving the problem]

[0010] To solve the above problems, the linear motor of the present invention relates to an armature unit in which a plurality of magnetic circuits composed of armatures are arranged in the direction of movement, and a permanent magnet unit composed of a plurality of permanent magnets, wherein when one of the units is used as a stator, the other unit moves relatively as a movable element, and the magnetic circuit comprises a first armature having a first magnetic pole at the upper end of the first core by bending the first core and a second magnetic pole with a different polarity from the first magnetic pole at the lower end of the first core, and a second armature having a second core by bending the second core, The armature comprises: a second armature having a third magnetic pole at the upper end of the second core and a fourth magnetic pole at the lower end of the second core having a different polarity from the third magnetic pole; a third armature having a fifth magnetic pole opposite to the first magnetic pole and a sixth magnetic pole opposite to the third magnetic pole; a fourth armature having a seventh magnetic pole opposite to the second magnetic pole and an eighth magnetic pole opposite to the fourth magnetic pole; and at least one coil wound around at least one core of the first to fourth armatures, wherein the first to eighth magnetic poles form a closed-loop magnetic flux perpendicular to the direction of movement. One of the permanent magnet units is sandwiched between two magnetic poles of the first armature and magnetic poles of the third and fourth armatures facing the two magnetic poles of the first armature, and the other one of the permanent magnet units is sandwiched between two magnetic poles of the second armature and magnetic poles of the third and fourth armatures facing the two magnetic poles of the second armature. This is the gist of the invention.

[0011] Moreover, in the linear motor of the present invention, the first to fourth armatures are connected to a plurality of servo amplifiers different for each application including high acceleration / deceleration and precise positioning, and operation control including switching of the servo amplifiers is performed based on the movement of the unit serving as the mover. This is the gist of the invention.

[0012] Moreover, in the linear motor of the present invention, the number of turns of the coil wound around each core of the first to fourth armatures is determined in accordance with the current control for each application. Further, when it is determined that a yawing error, which is the inclination of the horizontal displacement angle with respect to the reference position, has occurred based on the position measurement regarding the first armature and the second armature, the servo amplifiers connected to the first armature and the second armature adjust the current values applied to the first armature and the second armature so that yawing correction is performed. This is the gist of the invention.

[0013] Moreover, in the linear motor of the present invention, the plurality of servo amplifiers are used for single-step input for suppressing vibration during startup and stop by the Posicast method, the step input time interval is set to match the natural vibration frequency of the machine having the linear motor as the drive source for each servo amplifier, and further, commands for acceleration and deceleration for the servo amplifiers are divided into a plurality of step inputs based on the time interval. This is the gist of the invention.

Brief Description of Drawings

[0014] [Figure 1] This is a diagram for explaining the magnetic circuit of a linear motor which is an embodiment of the present invention. [Figure 2]This is an external view of the armature unit of a linear motor, which is one embodiment of the present invention. [Figure 3] This is an external view of a permanent magnet unit, which is one embodiment of the present invention. [Figure 4] This is a schematic cross-sectional view of a linear motor stage with a permanent magnet unit as the movable element. [Figure 5] This diagram shows the relationship between the pole pitch of a permanent magnet and the armature pitch. [Figure 6] This is a schematic cross-sectional view of a linear motor stage with an armature unit as the movable element. [Figure 7] This diagram shows the magnetic flux flow in a typical core-type linear motor. [Figure 8] This diagram shows an example of connecting an armature unit to a servo amplifier. [Figure 9] This diagram shows an example of a connection when using two servo amplifiers. [Figure 10] This figure shows a theoretical graph of vibration suppression based on Posicast control, along with experimental results. [Figure 11] This diagram illustrates a method for shortening the settling time using multi-stage step input. [Figure 12] This diagram illustrates a method for reducing the settling time by increasing the maximum speed and performing step input. [Figure 13] This diagram shows an example connection when using three servo amplifiers. [Figure 14] This diagram illustrates a method for correcting the yawing direction. [Figure 15] This figure shows another embodiment of the armature unit. [Figure 16] This diagram shows the structure of a linear motor using a ball spline. [Best Mode for Carrying Out the Invention]

[0015] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. However, the linear motor of the present invention can be embodied in various forms and is not limited to the embodiments described herein. These embodiments are provided with the intention that those skilled in the art will be able to fully understand the scope of the invention by making full disclosures in the specification.

[0016] Figure 1(a) is a conceptual perspective view showing the configuration of the magnetic circuit 100 of a linear motor, which is one embodiment of the present invention, and Figure 1(b) is a front view. As shown in Figures 1(a) and (b), the magnetic circuit 100 consists of multiple armature core bases (hereinafter referred to as "cores") 1 to 4, multiple windings (coils) 1a-1b, 2a-2b, 3a, 4b, and multiple permanent magnets 5a-5b, 6a-6b. Windings are wound around the core of each armature. In this embodiment, the core 1 of the first armature 10 is U-shaped, with the upper winding 1a wound around the upper protrusion and the lower winding 1b wound around the lower protrusion. The core 2 of the second armature 20, which is also U-shaped, has a similar configuration, with the upper winding 2a wound around the upper protrusion and the lower winding 2b wound around the lower protrusion. The cores are manufactured from laminated steel sheets.

[0017] Hereinafter, the first armature 10 will consist of core 1 and windings 1a and 1b, the second armature 20 will consist of core 2 and windings 2a and 2b, the third armature 30 will consist of core 3 and winding 3a, and the fourth armature 40 will consist of core 4 and winding 4b. In this embodiment, one or two windings are wound around each of the cores 1 to 4, but this is not necessarily the only option. For example, core 1 may have only one winding. While this may result in a reduced magnetic flux, from the standpoint of establishing a functional magnetic circuit, the magnetic circuit 100 only needs to have at least one winding on at least one core.

[0018] A third armature 30 is positioned between the upper protrusion of the first armature 10 and the upper protrusion of the second armature 20. A fourth armature 40 is positioned between the lower protrusion of the first armature 10 and the lower protrusion of the second armature 20. The third armature 30 and the fourth armature 40 are I-shaped (straight) cores 3 and 4, with windings 3a and 4b wound around them, respectively. As will be described in detail later, one of the features of the present invention is that a third armature 30 is additionally positioned above and a fourth armature 40 below the two U-shaped armatures 10 and 20.

[0019] By winding the windings 1a and 1b around the core 1 of the first armature 10, magnetic poles with different polarities are formed on the upper and lower protrusions. In the example shown in Figure 1(b), the upper protrusion of the first armature 10 where winding 1a is located has a south pole, and the lower protrusion where winding 1b is located has a north pole. The second to fourth armatures are also given two different magnetic poles, and the magnetic circuits shown in Figures 1(a) and (b) are arranged so that the magnetic poles at the core ends of opposing armatures are directly opposite. When a current with the same phase as when the windings 1a and 1b of the first armature 10 are excited is passed through each winding of the second to fourth armatures, a magnetic flux will flow in a closed loop within the magnetic circuit 100.

[0020] Figures 2(a) and (b) show the external view and side view of the armature unit 200, which is constructed by arranging three of the magnetic circuits 100 described above. In this embodiment, three-phase (U, V, W) AC is used, and by assigning the U phase, V phase, and W phase to the three magnetic circuits, the armature unit 200 is composed of a U-phase armature, a V-phase armature, and a W-phase armature. The U-phase armature is wound with U-phase windings 1a(u), 2a(u), 3a(u), 1b(u), 2b(u), and 4b(u); the V-phase armature is wound with V-phase windings 1a(v), 2a(v), 3a(v), 1b(v), 2b(v), and 4b(v); and the W-phase armature is wound with W-phase windings 1a(w), 2a(w), 3a(w), 1b(w), 2b(w), and 4b(w). When current is passed through the U-phase winding, a first magnetic pole (e.g., a south pole) is formed at the tip of the upper protrusion where the winding 1a(u) of the first armature 10 is located, and a second magnetic pole (e.g., a north pole) with a different polarity from the first magnetic pole is formed at the tip of the lower protrusion where the winding 1b(u) is located. The polarities of the first and second magnetic poles reverse periodically.

[0021] Next, I will explain permanent magnets. As shown in Figure 1, a permanent magnet 5a is interposed between the end of the upper projection of the first armature 10 and the end of the third armature 30, and a permanent magnet 6a is interposed between the end of the upper projection of the second armature 20 and the other end of the third armature 30. Similarly, a permanent magnet 5b is interposed between the end of the lower projection of the first armature 10 and the end of the fourth armature 40, and a permanent magnet 6b is interposed between the end of the lower projection of the second armature 20 and the other end of the fourth armature 40.

[0022] In actual linear motors, a permanent magnet unit is used, which consists of multiple permanent magnets arranged in a row. Figure 3 shows an example of a permanent magnet unit 5. As shown in Figure 3(a), the permanent magnet unit 5 is composed of two magnet rows 5a(n) and 5b(n), each containing multiple permanent magnets. The magnet rows 5a(n) and 5b(n) are aligned at a predetermined interval, and each permanent magnet included in the magnet rows 5a(n) and 5b(n) is arranged at a constant pitch in the stroke direction.

[0023] Here, the permanent magnets in the two magnet rows 5a(n) and 5b(n) are arranged so that the polarity of the ends of opposing permanent magnets is exactly opposite. For example, as shown in Figure 3(b), if the right side of permanent magnet 5a1 in magnet row 5a(n) is the north pole and the left side is the south pole, then the permanent magnet 5b1 in magnet row 5b(n) is arranged so that the right side is the south pole and the left side is the north pole. Also, within the same magnet row, the opposing polarities of adjacent permanent magnets are arranged so that they are staggered. For example, if the polarity of each permanent magnet in magnet row 5a(n) is arranged as S, N, S, N... in the stroke direction, then the polarity of each permanent magnet in magnet row 5b(n) is N, S, N, S... Note that the magnet arrays 5a(n) and 5b(n) do not necessarily need to be aligned in the stroke direction; they may be skewed, as shown in Figure 3(d), with each permanent magnet offset at a certain angle.

[0024] In this embodiment, each permanent magnet in the permanent magnet unit 5 is formed in the shape of a rectangular plate and is magnetized on a base material 7. The base material 7 is a non-magnetic material such as aluminum. By making the base material 7 on which the permanent magnets are fixed non-magnetic, leakage flux in the magnetic circuit 100 formed by the armatures 10 to 40 that constitute the armature unit 200 sandwiching the permanent magnet unit 5 can be prevented.

[0025] The base material 7 has an opening (not shown) for fitting permanent magnets. If the permanent magnets are simply fitted into the opening in the base material 7, the bonding area between the permanent magnets 5a, 5b and the base material 7 is only the area of ​​the opening frame, and there is a risk that the permanent magnets 5a, 5b will come out of the base material 7. Therefore, in order to protect the permanent magnets and securely fix them to the base material 7, a plate material or sheet material 8 made of carbon fiber reinforced plastic (CFRP) or the like may be attached to the base material 7 from above the permanent magnets, as shown in Figure 3(c).

[0026] The linear motor of the present invention has the armature unit 200 and permanent magnet unit 5 described above as its basic configuration, but in order to demonstrate the advantages of motion control such as high acceleration / deceleration operation and ultra-precise positioning, the explanation will be given using a linear motor stage 300 on which a table is placed on the linear motor. Figure 4(a) is a schematic cross-sectional view of the linear motor stage 300 when the permanent magnet units 5 and 6 are used as the movable element and the armature unit is used as the stator.

[0027] The stator comprises a plurality of armature units 200 arranged in the stroke direction. In the U-phase, V-phase, and W-phase magnetic circuits constituting the armature units 200, the first armature 10 is attached to a non-magnetic armature unit fixing jig 12 fixed to the base 11. Similarly, the second armature 20 is attached to a non-magnetic armature unit fixing jig 14 fixed to the base 11. The intermediate third armature 30 and fourth armature 40 are attached to a non-magnetic armature unit fixing jig 13 fixed to the base 11.

[0028] Table 16 is fixedly mounted above permanent magnet units 5 and 6, and linear guide mechanisms 15 for supporting the permanent magnet units 5 and 6 are mounted on base 11. The armature unit fixing jigs 12, 13, and 14 constrain the movable permanent magnet units 5 and 6 in all directions except the stroke direction, and table 16 moves in conjunction with the movement of the permanent magnet units 5 and 6. The linear guide mechanism 15 comprises a rail and a block that moves along the rail. The linear guide mechanism 15 is a known type, and often has many rolling elements interposed between the rail and the block that can roll, but a detailed explanation is omitted here. It should be noted that instead of a linear ball guide, an air hydrostatic guide device or a ball spline can also be used as the linear guide mechanism 15.

[0029] As shown in Figures 1 and 4, the linear motor of the present invention has a permanent magnet unit 5 fixedly mounted in the gap between the third armature 30 and the fourth armature 40, which face the (upper and lower) protrusions of the first armature 10. The permanent magnet unit 6 is fixedly mounted in the gap between the third armature 30 and the fourth armature 40, which face the (upper and lower) protrusions of the second armature 20. The polarity and position of the magnets relative to the stroke direction of the upper and lower permanent magnet rows 5a(n) and 5b(n) must be the same. The same applies to 6a(n) and 6b(n) in the permanent magnet unit 6. Note that the permanent magnet units 5 and 6 may be composed of only one permanent magnet row, such as only the permanent magnet row 5a(n) facing the third armature 30 or only the permanent magnet row 5b(n) facing the fourth armature 40.

[0030] FIG. 4(b) is a side view of the linear motor stage 300. However, the armature fixing jig shown in FIG. 4(a) is omitted. As can be seen from the fact that there are six armatures shown in FIG. 4(b), in this embodiment, two armature units 200 are arranged on the linear motor stage 300. However, it is needless to say that it is not limited to two. The linear motor is a three-phase linear motor, and each armature unit is composed of the above-described U-phase armature, V-phase armature, and W-phase armature.

[0031] FIG. 5 shows the relationship between the pole pitch of the permanent magnet and the pitch of the armature. Let the pitch of the armature be P1 and the pole pitch of the permanent magnet be P. When the pitch of the armature is smaller than the pitch of the permanent magnet (P1 < P), the pitch P1 of adjacent armature units is 2P / 3, 4P / 3, etc.

[0032] In the case of the linear motor stage 300 shown in FIG. 4, the armature unit 200 is used as the stator, but the linear motor stage 400 shown in FIG. 6 is an example of a structure in which the permanent magnet units 5 and 6 are used as the stator. That is, the armature unit 200 becomes the mover. The permanent magnet unit 5 is fixed and attached in the gap between the third armature 30 and the fourth armature 40 facing the (upper and lower) protruding portions of the first armature 10. The permanent magnet unit 6 is fixed and attached in the gap between the third armature 30 and the fourth armature 40 facing the (upper and lower) protruding portions of the second armature 20. It is necessary to make the polarities and the positions of the magnets with respect to the stroke directions of the upper and lower permanent magnet rows 5a(n) and 5b(n) the same. The same applies to 6a(n) and 6b(n) in the permanent magnet unit 6. Furthermore, the permanent magnet units 5 and 6 may also consist of only one permanent magnet array, such as only the permanent magnet array 5a(n) facing the third armature 30 or only the permanent magnet array 5b(n) facing the fourth armature 40.

[0033] In the case of the linear motor stage 400, the first armature 10 and the second armature 20 in the armature unit are fixedly connected to the table 16 via connecting jigs 16 and 18, respectively, and linear guide mechanisms 15 are attached to these connecting jigs 16 and 18, respectively. The third armature 30, located in the center of the armature unit, is fixedly connected to the table 16 via a connecting jig 17. In this embodiment, in order to maintain the balance of the table 16, both the first armature 10 and the second armature 20 are attached to the linear guide mechanisms 15 at both ends of the armature unit via connecting jigs 16 and 18. However, in other embodiments, the linear guide mechanism 15 may be located on only one side, either the first armature 10 side or the second armature 20 side (single-sided guide).

[0034] As described above, in the case of the linear motor stage 300, the permanent magnet units 5 and 6 are attached to the linear guide mechanism 15, and in the case of the linear motor stage 400, the first armature 10 and the second armature 20 are attached to the linear guide mechanism 15. Conventional core-type linear motor stages have a large magnetic attractive force between the movable element and the stator, requiring the selection of a support mechanism with a large load capacity. Alternatively, in attractive force-canceling type tunnel actuator stages, the support mechanism for the movable element could only be installed at the entrance and exit of the tunnel. However, with the linear motor stage of this embodiment, the magnetic attractive force is canceled, and furthermore, since the linear guide mechanism 15 extends along the entire length of the stroke, the permanent magnet unit or armature, which is the movable element, is supported by the linear guide mechanism throughout the movement stroke. Therefore, even with a long stroke, it is possible to achieve stable movement without shaking, with the movable element being firmly guided.

[0035] In the linear motor of this embodiment, the magnetic circuit is constructed by interposing a permanent magnet between opposing armatures, and by arranging the permanent magnet so that the distance between the permanent magnet and the armatures on both sides is the same. As a result, the magnitude of the magnetic attractive force acting between one end of the permanent magnet and the armature is equal to the magnitude of the magnetic attractive force acting between the other end and the armature, and the direction in which these forces act is opposite, so the two magnetic attractive forces cancel each other out. As a result, the overall magnetic attractive force between the permanent magnet and the armature becomes almost zero, and the disturbance force and cogging force on the thrust can be reduced. This principle is applied not only to the permanent magnet unit 5 but also to the permanent magnet unit 6, and even if the magnetic circuit becomes electromagnetically larger due to the increase in windings and permanent magnets, the side effects caused by magnetic attractive force are small, which is a remarkable effect.

[0036] Furthermore, as shown in Figure 7, a typical core-type linear motor has a structure in which permanent magnets are attached to an iron magnet yoke and magnetic flux is passed through it. As a result, leakage flux to other phase armature occurs in areas where the magnetic flux is dense, which becomes a source of noise. In contrast, the linear motor of this embodiment has an air gap or non-magnetic material interposed between each phase, making it difficult for leakage flux to occur to other phases, thus reducing noise due to magnetic leakage.

[0037] Figure 8 shows an example of connecting one servo amplifier 21 to the linear motor of the present invention. A simplified connection diagram is shown in the upper right frame. In this connection example, all of the U-phase windings 1a(u), 2a(u), 3a(u), 1b(u), 2b(u), and 4b(u) shown in Figure 2 are connected to the U-phase terminals of the servo amplifier 21, all of the V-phase windings 1a(v), 2a(v), 3a(v), 1b(v), 2b(v), and 4b(v) are connected to the V-phase terminals of the servo amplifier 21, and all of the W-phase windings 1a(w), 2a(w), 3a(w), 1b(w), 2b(w), and 4b(w) are connected to the W-phase terminals of the servo amplifier 21.

[0038] Next, Figure 9 shows an example of connecting two servo amplifiers 21 and 22 to the linear motor of the present invention. Note that although it is a three-phase linear motor and therefore the armatures of the U-phase, V-phase, and W-phase should ideally be drawn as in Figure 8, only the armature of the U-phase is shown in Figure 9. As shown in the diagram, the U-phase windings 1a(u), 1b(u), 2a(u), and 2b(u) are connected to the U-phase terminal of servo amplifier 21. On the other hand, the U-phase windings 3a(u) and 4b(u) are connected to the U-phase terminal of servo amplifier 22. The V-phase windings 1a(v), 1b(v), 2a(v), and 2b(v) are connected to the V-phase terminal of servo amplifier 21. On the other hand, the V-phase windings 3a(v) and 4b(v) are connected to the V-phase terminal of servo amplifier 22. The same applies to the W-phase terminal. In other words, servo amplifier 21 is for the first armature 10 and the second armature 20 in the armature unit, and servo amplifier 22 is for the third armature 30 and the fourth armature 40.

[0039] As shown in Figure 9, by connecting some of the armature windings to different servo amplifiers, the linear motor of the present invention enables operation with two different characteristics even though it is a single linear motor, depending on the combination of the number of windings, the current capacity of the servo amplifier, and the current control. This is a remarkable technical effect of the linear motor of the present invention.

[0040] For example, by increasing the number of turns of the first armature 10 and the second armature 20, and selecting a servo amplifier 21 with a large current capacity, a linear motor with high thrust and large acceleration / deceleration capabilities can be formed. On the other hand, by decreasing the number of turns of the third armature 30 and the fourth armature 40, and selecting a low-noise linear amplifier 22, a linear motor capable of ultra-precise positioning can be formed. Therefore, by operating the acceleration, constant-speed, and deceleration sections with servo amplifier 21, and then switching the control by turning off servo amplifier 21 and turning on servo amplifier 22 just before stopping, it becomes possible to achieve both high acceleration / deceleration and ultra-precise positioning with a single linear motor. Incidentally, the number of turns of the third armature 30 and the fourth armature 40 may be increased, and the servo amplifier 22 may be used for high acceleration / deceleration operation. The number of turns of the first armature 10 and the second armature 20 may be decreased, and the servo amplifier 21 may be used for ultra-precise positioning. Incidentally, acceleration / deceleration may be performed by both of the servo amplifiers 21 and 22, and during the constant-speed driving section or at the time of stop, the current of the servo amplifier for high acceleration / deceleration operation may be set to zero, and only the servo amplifier for ultra-precise positioning may be operated.

[0041] Next, another embodiment in which two servo amplifiers are connected to the armature unit will be described. This is an application of the Posicast control method to vibration suppression during acceleration / deceleration and at the time of stop in the high acceleration / deceleration driving stage. The Posicast control is known as an effective method for vibration suppression, and the conventional application examples are mainly techniques used for crane anti-sway. There is no example in the scope of investigation by the applicant in which the Posicast control method is applied to vibration suppression of a high acceleration / deceleration driving stage as in the present invention.

[0042] First, the theoretical value of the Posicast control is shown in Fig. 10(a), and the experimental results using the experimental apparatus are shown in Fig. 10(b). (1) in Fig. 10(a) is a graph showing the step response when a single-step input x r is applied to the mechanism of the second-order vibration system. Regarding the peak time t p and the peak value x p , it is assumed that the following equations hold. t p =Const. γ = x r / x p =Const. In the Posicast control, γ = x r / x p is set, and the following two target inputs x r1 and x r2 are created. ·x r1 = γx r , ·x r2 = x r - x r1

[0043] At time t = 0, xr1 The waveform when this is added is the solid line in graph (2) in Figure 10(a), t=t p in x r2 The waveform when further input is added is the dashed line in (2). That is, for example, when a single step input x is given to the servo amplifier 21 r1 Give t p The servo amplifier 22 receives a step input x with a time delay. r2 This gives . As shown in the figure, t=t p The peak value x is delayed by half a cycle. p2 This occurs. The response oscillation obtained by the actual mechanism is a composite waveform of the solid line and the dashed line, so as shown in (3), the oscillation components cancel each other out and a vibration-free state is reached, t=t p From here on, the target value x r It will be held there.

[0044] Figure 10(b) shows the results of an experiment applying Posicast control to an actual experimental machine based on the configuration of the present invention, and it was confirmed that the results were almost in line with the theoretical values ​​shown in Figure 10(a). However, with a single servo amplifier, input x r1 and input x r2 If you try to input both, the timing of applying a single-step input will be a multiple of the servo cycle in the control, so input x r1 and input x r2 There are cases where both do not perfectly match the command cycle of the control system and the integer multiples of the natural frequency of the mechanical vibration. In such cases, two servo amplifiers are used, x r1 and x r2 By independently controlling the inputs and applying each single-step input at a timing that matches the natural frequency of each input, vibrations can be effectively suppressed.

[0045] Since the two vibration-suppressing servo amplifiers mentioned above are needed when the vehicle is stopped, the servo amplifier used for stroke motion to generate driving force will be used in conjunction with at least one of the two vibration-suppressing servo amplifiers, and it will be possible to switch from stroke motion to vibration suppression when the vehicle is stopped.

[0046] Incidentally, when rapid acceleration and deceleration are performed, residual vibration may remain even if vibration suppression is performed by Posicast control with only a single step input. Therefore, a method for effectively suppressing residual vibration is shown in Figure 11. The solid line in Figure 11 is the velocity waveform when the deceleration time is 5 ms, without considering vibration. The dashed line in Figure 11 is the velocity waveform when the deceleration time is 22 ms, which is calculated from the natural frequency of the mechanism and is expected to have a vibration suppression effect. While there is indeed a vibration suppression effect, residual vibration remains when the mechanism stops. The dashed line in Figure 11 is the velocity waveform when the mechanism is operated in a pattern of decelerating for 22 ms, stopping for 22 ms, and then decelerating for another 22 ms. The double dashed line in Figure 11 is the velocity waveform when the 22 ms deceleration and stopping operation is repeated 5 times. It became clear that the more repetitions there are, the smaller the residual vibration becomes, but the longer the settling time becomes. Based on these facts, if you want to minimize residual vibration and achieve ultra-precise positioning, even if it means a longer settling time, you can simply repeat the deceleration and stopping operation multiple times in Posicast control, using a deceleration time that is expected to effectively suppress residual vibration.

[0047] Furthermore, Figure 12 shows a method that not only reduces residual vibration but also shortens the settling time. By increasing the maximum speed when operating at a constant velocity, the time to reach the target position can be shortened, and deceleration and stopping can be repeated in multiple steps with deceleration times that have the effect of suppressing residual vibration. Since the effect of shortening the operating time due to the increase in speed in the constant velocity section is large, it is possible to shorten the total travel time, including the settling time, while performing deceleration and stopping with little residual vibration, with almost no impact from vibrations generated during acceleration.

[0048] The fact that a single linear motor can achieve both high-speed drive and ultra-precise positioning through vibration suppression based on Posicast control, as described above, is due to the use of multiple servo amplifiers. This can be easily achieved by connecting some of the armature (with a large number of windings) of the linear motor to one servo amplifier for high-speed drive, and other armature (with a small number of windings) to another servo amplifier for ultra-precise positioning, and then switching between the two servo amplifiers.

[0049] Next, Figure 13 shows an example of connecting three servo amplifiers 21, 22, and 23 to the linear motor of the present invention. Similar to Figure 9, Figure 13 shows only the U-phase armature, but please note that in reality, V-phase and W-phase armatures also exist. As shown in the diagram, the U-phase windings 1a(u) and 1b(u) are connected to the U-phase terminal of servo amplifier 21. The U-phase windings 3a(u) and 4b(u) are connected to the U-phase terminal of servo amplifier 22. The U-phase windings 2a(u) and 2b(u) are connected to the U-phase terminal of servo amplifier 23. The same applies to the V-phase and W-phase terminals. In other words, servo amplifier 21 is for the first armature 10 in the armature unit, servo amplifier 22 is for the third armature 30 and the fourth armature 40, and servo amplifier 23 is for the second armature 20.

[0050] The connection example in Figure 13 shows a case where the armature unit 200 acts as the movable element, as shown in the configuration in Figure 4. The movable element, which is formed by connecting the winding 3a of the third armature 30 of each phase, the winding 4b of the fourth armature 40, and the servo amplifier 22, is mainly used for stroke operation. In this case, a linear scale 25 (see Figure 14) is used to detect the position in the stroke direction. Meanwhile, the windings 1a and 1b of the first armature 10, the servo amplifier 21, and the high-precision linear scale 26 for position detection, and the windings 2a and 2b of the second armature 20, the servo amplifier 23, and the high-precision linear scale 27 for position detection are installed near the respective linear guide mechanisms 15.

[0051] Due to the effects of weight balance on the table 16, differences in mechanical friction of the linear guide mechanism, and thermal deformation, if a slight misalignment occurs between the first armature 10 and the second armature 20 near the stopping position, the table 16 will tilt in the yawing direction, causing distortion, and even if it stops at the precise position, an error may occur in the target position on the table 16. Since three servo amplifiers 21, 22, and 23 are used, servo amplifier 22 is used for stroke operation, while the remaining two servo amplifiers are used to calculate the error in the yawing direction.

[0052] In other words, the yawing error is calculated from the positional misalignment of the high-precision linear scale 26 on the first armature 10 side and the high-precision linear scale 27 on the second armature 20 side, and the outputs of servo amplifiers 21 and 23 are adjusted to eliminate this error and correct the attitude error in the yawing direction when stopped. As a result, it becomes possible to achieve ultra-precise positioning, stopping the table 16 at a distortion-free stopping position. This also demonstrates that a single linear motor can be connected to multiple different servo amplifiers to enable operation with multiple characteristics.

[0053] In this example, the third armature 30 and the fourth armature 40 are allocated for stroke motion to generate driving force, and the first armature 10 and the second armature 20 are allocated for calculating errors in the yawing direction. However, this is not necessarily the only way to use the armatures (and servo amplifiers) for any particular purpose, and the combination of armatures (and servo amplifiers) can be determined as appropriate.

[0054] Figure 15 shows an example of a magnetic circuit suitable for improving the rigidity of a movable element when the permanent magnet unit 7 is used as the movable element. Permanent magnets 5a and 6a are bonded to both ends of the core of the third armature 30, and permanent magnets 5b and 6b are also bonded to both ends of the core of the fourth armature 40, with the winding 3a in the third armature 30 and the winding 4b in the fourth armature 40 removed. The permanent magnets 5a and 5b are fitted into the opening of the base material 7 as a permanent magnet unit 5 and are integrated, but by becoming a structure that combines with the third armature 30 and the fourth armature 40, there is an advantage in that the mechanical rigidity is further improved.

[0055] Finally, Figure 16 shows an example of the linear motor structure of the present invention in which the linear guide mechanism 15 is a ball spline 28. Permanent magnets 5a and 5b are fixed to spline nuts, and the first armature 10 and the second armature 20 are fixed so as to maintain a constant air gap with the permanent magnets 5a and 5b. Compared to the structure of a linear guide mechanism 15 used in a typical XY plane that uses two rails, when using a ball spline 28, the parallelism adjustment work of the two rails is unnecessary, and it is possible to reduce uneven frictional force caused by misalignment of the rails. Therefore, it is advantageous when the purpose is to transport small and lightweight objects, or when it is desired to drive in the Z-axis direction (vertical direction in Figure 16). Furthermore, Figure 16(b) shows the linear motor structure of Figure 16(a) in a two-axis configuration. A third armature 30 is installed between the first movable elements, the permanent magnets 5a and 5b, and the second movable elements, 6a and 6b. The third armature 30 acts as an armature that provides thrust to the first movable elements, which are permanent magnets 5a and 5b, and the second movable elements, which are 6a and 6b. A similar configuration can be extended to a multi-axis configuration with three or more axes. In a multi-axis configuration, synchronous operation of the entire system can be achieved without the need for synchronous control between each axis. [Explanation of Symbols]

[0056] 1-4 Iron core base (core) 1a, 1b, 2a, 2b, 3a, 4b Winding (coil) 5a,5b,6a,6b Permanent magnet 5,6 Permanent magnet unit 7 Base material 10 First armature 11 Bass 12, 13, 14 Armature unit fixing jig 15. Linear guide mechanism 16 tables 20 Second armature 21, 22, 23 Servo amplifier 25 Linear Scale 26,27 High-precision linear scale 28 Ball Splines 30 Third armature 40. Fourth armature 100 Magnetic Circuits 200 armature units 300,400 Linear Motor Stage

Claims

1. The present invention relates to an armature unit comprising multiple magnetic circuits composed of multiple armatures arranged in the direction of movement, and a permanent magnet unit composed of multiple permanent magnets, wherein when one of the units is used as a stator, the other unit moves relatively as a movable element, and The aforementioned magnetic circuit is By bending the first core, a first armature is formed having a first magnetic pole at the upper end of the first core and a second magnetic pole with a different polarity from the first magnetic pole at the lower end of the first core. By bending the second core, a second armature is formed having a third magnetic pole at the upper end of the second core and a fourth magnetic pole at the lower end of the second core having a different polarity from the third magnetic pole. A third armature having a fifth magnetic pole opposite to the first magnetic pole and a sixth magnetic pole opposite to the third magnetic pole, A fourth armature having a seventh magnetic pole opposite to the second magnetic pole and an eighth magnetic pole opposite to the fourth magnetic pole, At least one coil wound around at least one core of the first to fourth armature, It has the first to eighth magnetic poles forming a closed-loop magnetic flux perpendicular to the direction of movement, A linear motor in which one of the permanent magnet units is sandwiched between the two magnetic poles of the first armature and the magnetic poles of the third and fourth armatures that are opposite to the two magnetic poles of the first armature, and the other permanent magnet unit is sandwiched between the two magnetic poles of the second armature and the magnetic poles of the third and fourth armatures that are opposite to the two magnetic poles of the second armature.

2. The linear motor according to claim 1, wherein the first to fourth armatures are connected to a plurality of servo amplifiers, each different for different applications including high acceleration / deceleration and precise positioning, and operation control, including switching of the servo amplifiers, is performed based on the movement of the movable unit.

3. The linear motor according to claim 1, wherein the number of turns of the coils wound around each core of the first to fourth armature is determined in accordance with the current control for the application described above.

4. The linear motor according to claim 2, wherein the servo amplifier connected to the first armature and the second armature adjusts the current value applied to the first armature and the second armature so that yawing correction is performed if it is determined that a yawing error, which is the inclination of the horizontal displacement angle with respect to a reference position, has occurred based on position measurement of the first armature and the second armature.

5. The linear motor according to claim 2, wherein the plurality of servo amplifiers are used as single-step inputs for vibration suppression during stopping using the Posicast method, and the time interval of the step input is set for each servo amplifier to match the natural frequency of the linear motor.

6. The linear motor according to claim 5, wherein the acceleration and deceleration commands to the servo amplifier are divided into a plurality of step inputs based on the time interval.

7. The linear motor according to any one of claims 1 to 6, wherein either the armature unit, which is a movable element, or the permanent magnet unit is attached to a linear guide mechanism on the base of the linear motor, and the linear guide mechanism supports the movement of the movable element over a stroke length.

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