JP7590054B1 - Linear motor - Google Patents

Abstract

[Problem] To provide a linear motor that has sufficient thrust even with a single linear motor, is capable of high acceleration/deceleration and long stroke operation, and allows ultra-precise positioning control. [Solution] The linear motor has an armature unit in which multiple magnetic circuits each consisting of multiple armatures are arranged in the direction of movement, and a permanent magnet unit consisting of multiple permanent magnets. By arranging the armatures on both sides of the permanent magnet at the same interval, the magnetic attraction force acting between one end of the permanent magnet and the armature and the magnetic attraction force acting between the other end of the permanent magnet and the armature are equal in magnitude and act in opposite directions, so that the total magnetic attraction force generated between the permanent magnet and the armature is nearly zero, reducing disturbance forces and cogging forces acting on the thrust. Also, by connecting some of the armature windings to different servo amplifiers, high acceleration/deceleration and ultra-precise positioning can be achieved with a single linear motor depending on the combination of the number of windings and the current capacity of the servo amplifier and the current control. [Selected Figure] Figure 1

Description

The present invention relates to a linear motor, and in particular to a linear motor that has an armature consisting of an armature core around which an armature winding is wound, and a permanent magnet, and that has a structure in which the mover moves relative to the stator due to electromagnetic action when a current is passed through the armature winding.

Conventional linear motors include coreless linear motors (see, for example, Japanese Patent Application Laid-Open No. 2003-233663) and attraction force cancellation type tunnel actuators (see, for example, Japanese Patent Application Laid-Open No. 2003-233663).
A coreless linear motor such as that 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 into a flat plate from a number of winding groups arranged opposite each other with a predetermined gap between them, with either the permanent magnet array or the armature acting as a stator and the other as a mover, and these running relative to one another.

The tunnel actuator disclosed in Patent Document 2 is a linear motor in which a mover moves within a space enclosed by the armature of a stator. Conventional core-equipped linear motors have a structure in which an electromagnetic steel core around which an armature winding is wound faces a permanent magnet, and there is a problem in that a burden is placed on the support mechanism of the mover because an attractive force larger than the thrust acts on the core. 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 at the upper magnetic pole teeth and mover and the magnetic attractive force at the lower magnetic pole teeth and mover are the same in magnitude but in opposite directions, so they cancel each other out, and the overall magnetic attractive force can be reduced.

JP 2001-197718 A JP 2002-125360 A

Cogging force is generated by the action of the attractive force between the core (iron core) and the permanent magnet. When the permanent magnet moves, the attractive force changes periodically due to the positional relationship with the core, causing a rough sticking phenomenon (pulsation) in the rotation of the motor, restricting the smooth operation of the mover. The coreless linear motor described in Patent Document 1 has a coreless structure, so cogging force and magnetic attractive force are not generated, and there is no risk of accuracy deterioration due to these. However, since the torque (thrust force) of a coreless linear motor is smaller than that of a linear motor with a core, the larger the weight of the mover or the longer the stroke, the more it is necessary to increase the number of turns of the armature winding and pass a large current to compensate for the insufficient torque. As a result, the current value must be increased to achieve high torque, and the decrease in control resolution makes it difficult to stop the mover at the target position with high precision, and the high heat generation is also a factor in accuracy deterioration.

In addition, the tunnel-type linear motor described in Patent Document 2 has the problem that the magnetic circuit is long, making it prone to magnetic saturation, and the support mechanism for the mover can only be installed at the entrance and exit of the tunnel, making it unsuitable for applications with long strokes.

The present invention aims to provide a linear motor that has sufficient thrust even with a single linear motor, is capable of high acceleration/deceleration and long stroke operation, and is capable of ultra-precise positioning control.

The linear motor of the present invention is composed of multiple permanent magnets and multiple armatures that sandwich these permanent magnets. By arranging the armatures so that the distance between the permanent magnets and the armatures on both sides is the same, the magnetic attraction force acting between one end of the permanent magnet and the armature is equal to the magnetic attraction force acting between the other end of the permanent magnet and the armature, and the directions of these forces are opposite. As a result, the total magnetic attraction force generated between the permanent magnets and the armature becomes nearly zero, and the disturbance force and cogging force on the thrust can be reduced.

In addition, by connecting some of the armature windings to different servo amplifiers, a single linear motor can perform both high acceleration/deceleration operations and ultra-precise positioning operations, depending on the combination of the number of windings and the current capacity of the servo amplifier and the current control.

In order to solve the above problems, the linear motor of the present invention relates to an armature unit in which a plurality of magnetic circuits each composed of a plurality of armatures are arranged in a moving direction, and a permanent magnet unit composed of a plurality of permanent magnets, in which one unit acts as a stator and the other unit acts as a mover and moves relatively therebetween, and the magnetic circuit is a first armature having a first magnetic pole at an upper end of the first core and a second magnetic pole having a polarity different from that of the first magnetic pole at a lower end of the first core by bending a first core, and a second armature having a third magnetic pole at an upper end of a second core and a fourth magnetic pole having a polarity different from that of the third magnetic pole at a lower end of the second core, a third armature having a fifth magnetic pole facing the first magnetic pole and a sixth magnetic pole facing the third magnetic pole, a fourth armature having a seventh magnetic pole facing the second magnetic pole and an eighth magnetic pole facing the fourth magnetic pole, and at least one coil wound around at least one core of the first armature to the fourth armature, wherein the first magnetic pole to the eighth magnetic pole form a closed loop magnetic flux perpendicular to the moving direction,
One of the permanent magnet units is sandwiched between two magnetic poles of the first armature and magnetic poles of the third armature and the fourth armature that face the two magnetic poles of the first armature, and the other of the permanent magnet units is sandwiched between two magnetic poles of the second armature and magnetic poles of the third armature and the fourth armature that face the two magnetic poles of the second armature.

The linear motor of the present invention is characterized in that the first to fourth armatures are connected to multiple servo amplifiers that differ depending on the application, including high acceleration/deceleration and precision positioning, and operation control, including switching of the servo amplifiers, is performed based on the movement of the unit that serves as the mover.

The linear motor of the present invention is characterized in that the number of turns of the coil wound around each core of the first to fourth armatures is determined according to the current control for each application. Furthermore, the servo amplifier connected to the first and second armatures adjusts the current value applied to the first and second armatures so as to perform yawing correction when 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 measurements of the first and second armatures.

The linear motor of the present invention is characterized in that the multiple servo amplifiers are used for single step input to suppress vibration during start-up and stoppage using the Posicast method, the step input time interval is set for each servo amplifier to match the natural frequency of the machine driven by the linear motor, and acceleration and deceleration commands to the servo amplifiers are divided into multiple step inputs based on the time interval.

1 is a diagram for explaining a magnetic circuit of a linear motor according to an embodiment of the present invention; 1 is an external view of an armature unit of a linear motor according to an embodiment of the present invention; 1 is an external view of a permanent magnet unit according to an embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of a linear motor stage in which a permanent magnet unit is used as a mover. FIG. 2 is a diagram showing the relationship between the pole pitch of a permanent magnet and the pitch of an armature. FIG. 1 is a schematic cross-sectional view of a linear motor stage in which an armature unit serves as a mover. FIG. 1 is a diagram showing the flow of magnetic flux in a typical linear motor with a core. FIG. 2 is a diagram showing an example of a connection between an armature unit and a servo amplifier. FIG. 13 is a diagram showing a connection example when there are two servo amplifiers. 1A and 1B are diagrams showing theoretical graphs of vibration suppression based on Posicast control and experimental results. FIG. 13 is a diagram showing a method for shortening settling time using multi-step input. FIG. 13 is a diagram showing a method for shortening the settling time by increasing the maximum speed and performing step input. FIG. 13 is a diagram showing a connection example when there are three servo amplifiers. FIG. 13 is a diagram showing a method of correcting the yawing direction. FIG. 13 is a diagram showing another embodiment of the armature unit. FIG. 13 is a diagram showing the structure of a linear motor when a ball spline is used.

The preferred embodiment 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 embodiment described in this specification. This embodiment is provided with the intention that those skilled in the art will be able to fully understand the scope of the invention by fully disclosing the specification.

FIG. 1A is a perspective view conceptually showing the configuration of a magnetic circuit 100 of a linear motor according to an embodiment of the present invention, and FIG. 1B is a front view.
As shown in Figures 1(a) and (b), a magnetic circuit 100 is composed of a plurality of armatures, iron core bases (hereinafter referred to as "cores") 1-4, a plurality of windings (coils) 1a-1b, 2a-2b, 3a, 4b, and a plurality of permanent magnets 5a-5b, 6a-6b. A winding is wound around each armature core. In this embodiment, the core 1 of the first armature 10 is U-shaped, with the upper winding 1a wound around the upper protruding portion and the lower winding 1b wound around the lower protruding portion. The core 2 of the second armature 20, which is another U-shaped, has a similar configuration, with the upper winding 2a wound around the upper protruding portion and the lower winding 2b wound around the lower protruding portion. The cores are manufactured from laminated steel plates.

In the following, the first armature 10 is composed of the core 1 and the windings 1a, 1b, the second armature 20 is composed of the core 2 and the windings 2a, 2b, the third armature 30 is composed of the core 3 and the winding 3a, and the fourth armature 40 is composed of the core 4 and the winding 4b.
In this embodiment, one or two windings are wound around each of the cores 1 to 4, but this is not necessarily limited to this. For example, there may be only one winding around the core 1. Although there is a possibility that the amount of magnetic flux may be reduced, from the viewpoint of establishing a magnetic circuit, it is sufficient for the magnetic circuit 100 to have at least one winding around at least one core.

A third armature 30 is disposed between the upper protrusion of the first armature 10 and the upper protrusion of the second armature 20. A fourth armature 40 is disposed 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, 4, on which windings 3a, 4b are wound, respectively. Details will be described later, but one of the features of the present invention is that the third armature 30 is additionally disposed at the top and the fourth armature 40 is additionally disposed at the bottom between the two U-shaped armatures 10, 20.

By winding the windings 1a and 1b around the core 1 of the first armature 10, magnetic poles of different polarities are formed on the upper protrusion and the lower protrusion. In the example of Fig. 1(b), the upper protrusion of the first armature 10 where the winding 1a is present has a magnetic south pole, and the lower protrusion where the winding 1b is present has a magnetic north pole. The second to fourth armatures are also given two different magnetic poles, and the magnetic circuits shown in Fig. 1(a) and (b) are arranged so that the magnetic poles of the core ends of the opposing armatures are completely opposite.
When a current of the same phase as that which is supplied to the windings 1 a and 1 b of the first armature 10 when it is excited is supplied to each of the windings of the second to fourth armatures, a magnetic flux flows in a closed loop within the magnetic circuit 100 .

2A and 2B are an external view and a side view of an armature unit 200 configured by arranging three of the above-mentioned magnetic circuits 100. In this embodiment, a three-phase (U, V, W) AC is used, and the U-phase, V-phase, and W-phase are assigned to the three magnetic circuits, so that the armature unit 200 is configured by 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 a current is passed through the U-phase winding, a first magnetic pole (e.g., an S pole) is formed at the tip of the upper protruding portion of the first armature 10 where the winding 1a(u) is located, and a second magnetic pole (e.g., an N pole) having a polarity different from that of the first magnetic pole is formed at the tip of the lower protruding portion where the winding 1b(u) is located. The polarities of the first and second magnetic poles are periodically reversed.

Next, the permanent magnet will be described.
1 , a permanent magnet 5a is interposed between an end of an upper protrusion of the first armature 10 and an end of the third armature 30, and a permanent magnet 6a is interposed between an end of an upper protrusion of the second armature 20 and the other end of the third armature 30. Similarly, a permanent magnet 5b is interposed between an end of a lower protrusion of the first armature 10 and an end of the fourth armature 40, and a permanent magnet 6b is interposed between an end of a lower protrusion of the second armature 20 and the other end of the fourth armature 40.

In an actual linear motor, a permanent magnet unit in which multiple permanent magnets are arranged in a row is used. Figure 3 shows an example of a permanent magnet unit 5. As shown in Figure 3(a), the permanent magnet unit 5 is configured with two magnet rows 5a(n) and 5b(n) in which multiple permanent magnets are arranged. 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 aligned at a constant pitch in the stroke direction.

Here, the two magnet rows 5a(n) and 5b(n) are arranged so that the polarities of the ends of the opposing permanent magnets are opposite. For example, as shown in FIG. 3B, if the right side of the permanent magnet 5a1 in the magnet row 5a(n) is an N pole and the left side is an S pole, the right side of the permanent magnet 5b1 in the magnet row 5b(n) is an S pole and the left side is an N pole. Also, in the same magnet row, the opposing polarities of adjacent permanent magnets are arranged alternately. For example, if the polarities of the permanent magnets in the magnet row 5a(n) are arranged as S, N, S, N... in the stroke direction, the polarities of the permanent magnets in the magnet row 5b(n) are N, S, N, S....
It should be noted that the permanent magnets of magnet arrays 5a(n), 5b(n) do not necessarily need to be aligned in the stroke direction, and may be skewed in a direction offset at a certain angle as shown in FIG. 3(d).

Each permanent magnet in the permanent magnet unit 5 of this embodiment is formed in a rectangular plate shape and magnetized on a substrate 7. The substrate 7 is a non-magnetic material such as aluminum. By making the substrate 7 to which the permanent magnets are fixed non-magnetic, leakage flux from the magnetic circuit 100 formed by the armatures 10 to 40 that make up the armature unit 200 that sandwiches the permanent magnet unit 5 can be prevented.

The substrate 7 has an opening (not shown) for fitting the permanent magnet. If the permanent magnet is simply fitted into the opening of the substrate 7, the adhesion area between the permanent magnets 5a and 5b and the substrate 7 is only the area of the frame of the opening, and there is a risk that the permanent magnets 5a and 5b will come off the substrate 7. Therefore, to protect the permanent magnets and secure them to the substrate 7, a plate or sheet material 8 such as a member made of carbon-fiber-reinforced plastic (CFRP) may be attached to the substrate 7 from above the permanent magnet, as shown in FIG. 3(c).

The linear motor of the present invention is basically composed of the above-mentioned armature unit 200 and permanent magnet unit 5, but in order to demonstrate the advantages of operational control such as high acceleration/deceleration operation and ultra-precise positioning, a linear motor stage 300 in which a table is placed on the linear motor will be used for explanation.
FIG. 4A is a schematic cross-sectional view of a linear motor stage 300 in which the permanent magnet units 5 and 6 serve as movers and the armature unit serves as a stator.

The stator has multiple armature units 200 arranged in the stroke direction. In each of the U-phase, V-phase, and W-phase magnetic circuits that make up the armature unit 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 third armature 30 and fourth armature 40 in the middle are attached to a non-magnetic armature unit fixing jig 13 fixed to the base 11.

The table 16 is fixedly attached above the permanent magnet units 5 and 6, and linear guide mechanisms 15 for supporting the permanent magnet units 5 and 6 are attached to the base 11. The permanent magnet units 5 and 6, which are the movers, are restrained in all directions except the stroke direction by the armature unit fixing jigs 12, 13, and 14, and the 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 well-known one, and many rolling bodies are often interposed between the rail and the block to enable rolling motion, but a detailed description will be omitted here. Note that instead of a linear ball guide, an air hydrostatic guide device, a ball spline, or the like can also be used as the linear guide mechanism 15.

1 and 4, in the linear motor of the present invention, the permanent magnet unit 5 is fixed and attached in the gap between the third armature 30 and the fourth armature 40 that face the (upper and lower) protrusions 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 that face the (upper and lower) protrusions of the second armature 20. The polarity of the upper and lower permanent magnet rows 5a(n), 5b(n) and the position of the magnets relative to the stroke direction must be the same. The same applies to 6a(n) and 6b(n) in the permanent magnet unit 6.
In addition, the permanent magnet units 5, 6 may be configured with 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.

Fig. 4B is a side view of the linear motor stage 300. However, the armature fixing jig shown in Fig. 4A is omitted.
As can be seen from the six armatures shown in Fig. 4(b), in this embodiment, two armature units 200 are arranged on the linear motor stage 300. However, it goes without saying that the number is not limited to two. The linear motor is a three-phase linear motor, and each armature unit is composed of the above-mentioned U-phase armature, V-phase armature, and W-phase armature.

Figure 5 shows the relationship between the pole pitch of the permanent magnet and the pitch of the armature. If the armature pitch is P1 and the pole pitch of the permanent magnet is P, when the armature pitch is smaller than the pitch of the permanent magnet (P1 < P), the pitch P1 of adjacent armature units is 2P/3, 4P/3, etc.

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, 6 are used as the stator. In other words, the armature unit 200 serves as the mover.
The permanent magnet unit 5 is fixedly attached in the gap between the (upper and lower) protrusions of the first armature 10 and the opposing third armature 30 and fourth armature 40. The permanent magnet unit 6 is fixedly attached in the gap between the (upper and lower) protrusions of the second armature 20 and the opposing third armature 30 and fourth armature 40. The polarity and the position of the magnets in the stroke direction of the upper and lower permanent magnet rows 5a(n), 5b(n) must be the same. The same applies to 6a(n) and 6b(n) in the permanent magnet unit 6.
In addition, the permanent magnet units 5, 6 may be configured with 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.

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 the connecting jigs 16 and 18, respectively, and the linear guide mechanism 15 is attached to each of the connecting jigs 16 and 18. The third armature 30 located in the center of the armature unit is fixedly connected to the table 16 via the 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 the connecting jigs 16 and 18, but in other embodiments, the linear guide mechanism 15 may be arranged only on either the first armature 10 side or the second armature 20 side (one-sided guide).

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. In the conventional core-equipped linear motor stage, the magnetic attraction force between the mover and the stator is large, and it was necessary to select a support mechanism with a large load capacity. Alternatively, in the attraction force cancellation type tunnel actuator stage, the support mechanism for the mover could only be installed at the entrance and exit of the tunnel, but according to the linear motor stage of this embodiment, the magnetic attraction force is canceled, and further, the linear guide mechanism 15 extends over the entire length of the stroke, so that the permanent magnet unit or armature, which is the mover, is supported by the linear guide mechanism during the movement stroke. Therefore, even if the stroke becomes long, the mover is firmly guided and stable movement without shaking can be realized.

According to the linear motor of this embodiment, the magnetic circuit is formed by a structure in which a permanent magnet is interposed between opposing armatures, and the distance between the armatures on both sides of the permanent magnet is the same. Therefore, the magnetic attraction force acting between one end of the permanent magnet and the armature and the magnetic attraction force acting between the other end of the permanent magnet and the armature are equal in magnitude and act in opposite directions, so that the two magnetic attraction forces cancel each other out. As a result, the total magnetic attraction force generated 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 has the remarkable effect of reducing the side effects caused by the magnetic attraction force even if the magnetic circuit becomes electromagnetically larger due to an increase in windings and permanent magnets.

Furthermore, as shown in FIG. 7, a typical cored linear motor is constructed such that a permanent magnet is attached to an iron magnet yoke through which magnetic flux passes, which causes leakage magnetic flux to other phase armatures in areas where the magnetic flux is dense, resulting in noise. In contrast, the linear motor of this embodiment has gaps or non-magnetic material between each phase, which makes it difficult for leakage magnetic flux to occur to other phases, thereby reducing noise caused by magnetic leakage.

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 box. 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 terminal 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 terminal 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 terminal of the servo amplifier 21. The windings of each phase can be connected in series as shown in Figure 8(a) or in parallel as shown in Figure 8(b).

Next, Fig. 9 shows an example in which two servo amplifiers 21, 22 are connected to the linear motor of the present invention. Note that since this is a three-phase linear motor, each armatures of the U-phase, V-phase, and W-phase should be drawn as in Fig. 8, but it should be noted that Fig. 9 shows only the armature of the U-phase.
As shown in the figure, U-phase windings 1a(u), 1b(u), 2a(u), and 2b(u) are connected to the U-phase terminal of servo amplifier 21. Meanwhile, U-phase windings 3a(u) and 4b(u) are connected to the U-phase terminal of servo amplifier 22. V-phase windings 1a(v), 1b(v), 2a(v), and 2b(v) are connected to the V-phase terminal of servo amplifier 21. Meanwhile, 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.
That is, the servo amplifier 21 is for the first armature 10 and the second armature 20 in the armature unit, and the servo amplifier 22 is for the third armature 30 and the fourth armature 40.

As shown in Figure 9, by connecting some of the armature windings to different servo amplifiers, a single linear motor can be made to operate with two different characteristics depending on the combination of the number of turns in the windings and the current capacity of the servo amplifier, as well as the current control. This is a notable technical effect of the linear motor of the present invention.

For example, if the number of turns of the first armature 10 and the second armature 20 is increased and an amplifier with a large current capacity is selected as the servo amplifier 21, a linear motor with large thrust and high acceleration/deceleration is formed. On the other hand, if the number of turns of the third armature 30 and the fourth armature 40 is decreased and a linear amplifier with low noise is selected as the servo amplifier 22, a linear motor capable of ultra-precise positioning is formed. Thus, by operating the servo amplifier 21 in the acceleration section, constant velocity section, and deceleration section, and switching the control by turning the servo amplifier 21 OFF and turning the servo amplifier 22 ON just before stopping, it becomes possible to achieve high acceleration/deceleration operation and ultra-precise positioning operation with a single linear motor.
Alternatively, the number of turns of the third armature 30 and the fourth armature 40 may be increased to use the servo amplifier 22 for high acceleration/deceleration operation, and the number of turns of the first armature 10 and the second armature 20 may be decreased to use the servo amplifier 21 for ultra-precise positioning. Alternatively, acceleration/deceleration may be performed by both the servo amplifiers 21 and 22, and during a constant speed drive section or stop, the current of the servo amplifier for high acceleration/deceleration operation may be set to zero so that only the servo amplifier for ultra-precise positioning is operated.

Also, another embodiment is shown in which two servo amplifiers are connected to the armature unit. In this embodiment, the Posicast control method is applied to vibration suppression during acceleration/deceleration and stopping in a high acceleration/deceleration drive stage. Posicast control is known as an effective method for vibration suppression, and its conventional application is mainly a technology used to prevent cranes from swinging. Within the scope of the applicant's research, there are no examples of applying the Posicast control method to vibration suppression in a high acceleration/deceleration drive stage such as that of the present invention.

First, the theoretical value of Posicast control is shown in Fig. 10(a), and the experimental results using an experimental device are shown in Fig. 10(b). (1) in Fig. 10(a) is a graph showing the step response when a single step input _xr is applied to the mechanism of the secondary vibration system. It is assumed that the following equation holds for the peak time _tp and peak value _xp of the vibration.
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 generated.
・x _r1 =γx _r ,
・x _r2 =x _r -x _r1

The waveform when _xr1 is added at time t=0 is shown by the solid line in the graph (2) in Fig. 10(a), and the waveform when _xr2 is further added at t= _tp is shown by the dashed line in (2). That is, for example, a single step input _xr1 is given to the servo amplifier 21, and a step input _xr2 is given to the servo amplifier 22 with a delay of _tp . As shown in the figure, a peak value _xp2 is generated half a period later than t= _tp . The response vibration obtained by the actual mechanism is a composite waveform of the solid line and the dashed line, so that the vibration components are offset as shown in (3) to create a vibration-free state, and the target value _xr is maintained after t= _tp .

The results of an experiment in which Posicast control was applied to an actual experimental machine based on the configuration of the present invention are shown in Fig. 10(b), and it was confirmed that the results were almost the same as the theoretical values shown in Fig. 10(a). However, when inputting both inputs _xr1 and _xr2 with one servo amplifier, the timing of adding the single step input is a multiple of the servo cycle in the control, so that both inputs _xr1 and _xr2 may not exactly match the command cycle of the control system and an integer multiple of the natural frequency of the mechanical vibration. In such a case, by using two servo amplifiers to independently input control _xr1 and _xr2 and adding each single step input at a timing that matches the natural frequency of each input, the vibration can be effectively suppressed.

In addition, since the two vibration suppression servo amplifiers mentioned above are required when the machine is stopped, at least one of the two vibration suppression servo amplifiers is used in combination with the servo amplifier for stroke operation to generate driving force, and when the machine is stopped, it can be switched from the servo amplifier for stroke operation to the servo amplifier for vibration suppression.

However, when a sudden acceleration/deceleration drive is performed, residual vibration may remain even if vibration suppression by Posicast control is performed with only one step input. Therefore, a method for effectively suppressing residual vibration is shown in FIG. 11. The solid line in FIG. 11 is a speed waveform when the deceleration time is set to 5 ms without considering vibration. The dashed line in FIG. 11 is a speed waveform when the deceleration time is set to 22 ms, which is calculated from the natural frequency of the mechanism and is expected to have a vibration suppression effect. Although there is certainly a vibration suppression effect, residual vibration remains when stopping. The dashed line in FIG. 11 is a speed waveform when the device is operated in a pattern of deceleration at 22 ms, stopping at 22 ms, and then deceleration at 22 ms. The two-dot chain line in FIG. 11 is a speed waveform when the deceleration and stopping operation of 22 ms is repeated five times. It was revealed that the more times it is repeated, the smaller the residual vibration is, but the longer the settling time is.
Based on these facts, if you want to minimize residual vibration for ultra-precise positioning, even if it means a long settling time, you can simply repeat the deceleration and stopping operation multiple times for a deceleration time that is expected to have the effect of suppressing residual vibration in Posicast control.

Figure 12 shows a method for not only reducing residual vibration but also shortening the settling time. The time to reach the target position can be shortened by increasing the maximum speed when moving at a constant speed, and deceleration and stopping can be repeated multiple times with a deceleration time that has the effect of suppressing residual vibration. Since the effect of shortening the operation time associated with increasing speed in the constant speed section is large, it is possible to shorten the total movement time, including the settling time, while decelerating and stopping with little residual vibration without being affected by vibrations generated during acceleration.

The reason that a single linear motor can achieve both high-speed drive and vibration suppression and ultra-precise positioning based on the Posicast control described above is that it uses multiple servo amplifiers. This can be easily achieved by connecting some of the armatures (with a large number of windings) that make up the linear motor to one servo amplifier for high-speed drive, and other armatures (with a small number of windings) to another servo amplifier for ultra-precise positioning, and then controlling the switching between the two servo amplifiers.

Next, an example in which three servo amplifiers 21, 22, and 23 are connected to the linear motor of the present invention is shown in Fig. 13. As in Fig. 9, it should be noted that although only a U-phase armature is shown in Fig. 13, in reality, V-phase and W-phase armatures are also present.
As shown in the figure, U-phase windings 1a(u) and 1b(u) are connected to the U-phase terminal of servo amplifier 21. U-phase windings 3a(u) and 4b(u) are connected to the U-phase terminal of servo amplifier 22. 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.
That is, the servo amplifier 21 is for the first armature 10 in the armature unit, the servo amplifier 22 is for the third armature 30 and the fourth armature 40, and the servo amplifier 23 is for the second armature 20.

13 is a connection example in which the armature unit 200 serves as a mover as in the configuration shown in Fig. 4, but the mover formed by connecting the winding 3a in the third armature 30 of each phase, the winding 4b in the fourth armature 40, and the servo amplifier 22 is used mainly for stroke operation. At this time, a linear scale 25 (see Fig. 14) is used for detecting the position in the stroke direction.
On the other hand, the windings 1a, 1b, servo amplifier 21, and high-precision linear scale 26 for position detection in the first armature 10, and the windings 2a, 2b, servo amplifier 23, and high-precision linear scale 27 for position detection in the second armature 20 are installed near their respective linear guide mechanisms 15.

If a slight misalignment occurs between the first armature 10 and the second armature 20 near the stopping position due to the weight balance on the table 16, differences in mechanical friction of the linear guide mechanism, thermal deformation, etc., the table 16 may tilt in the yawing direction and distortion may occur, and even if it is stopped at the correct position, an error may occur in the target position on the table 16. Three servo amplifiers 21, 22, and 23 are used, so while servo amplifier 22 is used for stroke operation, the remaining two servo amplifiers calculate the error in the yawing direction.

In other words, the error in the yawing direction is calculated from the positional deviation 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 output of the servo amplifiers 21 and 23 is adjusted to eliminate the error, correcting the attitude error in the yawing direction when stopped, thereby enabling ultra-precise positioning of the table 16, stopping it at a stop position without distortion. This also shows that one linear motor can be connected to multiple different servo amplifiers, making it possible to operate with multiple characteristics.

Note that the third armature 30 and the fourth armature 40 are assigned to the stroke operation for generating the driving force, and the first armature 10 and the second armature 20 are assigned to calculate the error in the yawing direction, but this is not necessarily limited to this, and the armatures (and servo amplifiers) can be appropriately combined to determine which purpose they are used for.

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

Finally, FIG. 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. The permanent magnets 5a and 5b are fixed to the spline nut, and the first armature 10 and the second armature 20 are fixed so as to maintain a certain gap between the permanent magnets 5a and 5b. Compared to the structure of the linear guide mechanism 15 using two rails in the general XY plane, the use of the ball spline 28 does not require the adjustment of the parallelism of the two rails, and it is possible to reduce uneven friction caused by deviation in the parallelism of the rails. Therefore, it is advantageous when the purpose is to transport small and lightweight objects or when driving in the Z-axis direction (up and down in FIG. 16). Furthermore, FIG. 16(b) shows the case where the linear motor structure of FIG. 16(a) is configured as a two-axis structure. A third armature 30 is installed between the permanent magnets 5a and 5b, which are the first movers, and the second movers 6a and 6b. The third armature 30 acts as an armature that applies thrust to the permanent magnets 5a and 5b, which are the first movers, and to the second movers 6a and 6b. A similar configuration can be expanded to a multi-axis configuration with three or more axes. In the case of a multi-axis configuration, it is possible to operate the entire system synchronously without synchronous control between each axis.

1-4 Core base
1a, 1b, 2a, 2b, 3a, 4b Windings (coils)
DESCRIPTION OF SYMBOLS 5a, 5b, 6a, 6b Permanent magnet 5, 6 Permanent magnet unit 7 Substrate 10 First armature 11 Base 12, 13, 14 Armature unit fixing jig 15 Linear guide mechanism 16 Table 20 Second armature 21, 22, 23 Servo amplifier 25 Linear scale 26, 27 High-precision linear scale 28 Ball spline 30 Third armature 40 Fourth armature 100 Magnetic circuit 200 Armature unit 300, 400 Linear motor stage

Claims (7)

A linear motor comprising an armature unit in which a magnetic circuit composed of a plurality of armatures is arranged in a moving direction, and a permanent magnet unit composed of a plurality of permanent magnets, in which one of the units acts as a stator and the other unit acts as a mover and moves relative to the stator,
The magnetic circuit includes:
a first armature having a first magnetic pole at an upper end of the first core and a second magnetic pole having a polarity different from that of the first magnetic pole at a lower end of the first core by bending the first core;
a second armature having a third magnetic pole at an upper end of the second core and a fourth magnetic pole having a polarity different from that of the third magnetic pole at a lower end of the second core by bending the second core;
a third armature having a fifth pole facing the first pole and a sixth pole facing the third pole;
a fourth armature having a seventh magnetic pole facing the second magnetic pole and an eighth magnetic pole facing the fourth magnetic pole;
at least one coil wound around at least one core of the first armature to the fourth armature;
a magnetic flux of a closed loop perpendicular to the moving direction is formed by the first magnetic pole to the eighth magnetic pole;
a linear motor, one of the permanent magnet units being sandwiched between two magnetic poles of the first armature and magnetic poles of the third armature and the fourth armature that face the two magnetic poles of the first armature, and another of the permanent magnet units being sandwiched between two magnetic poles of the second armature and magnetic poles of the third armature and the fourth armature that face the two magnetic poles of the second armature. The linear motor according to claim 1, in which the first armatures to the fourth armatures are connected to a plurality of servo amplifiers that are different for different applications, including high acceleration/deceleration and precision positioning, and the operation control, including switching of the servo amplifiers, is performed based on the movement of the unit that serves as the mover. 3. The linear motor according to claim 2, wherein the number of turns of the coils of the first to fourth armatures connected to a servo amplifier for high acceleration/deceleration is greater than the number of turns of the coils of the first to fourth armatures connected to a servo amplifier for precision positioning . The linear motor according to claim 2, wherein a 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 as to perform yawing correction when 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 measurements of the first armature and the second armature. The linear motor according to claim 2, wherein the plurality of servo amplifiers are used for single step input 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. The linear motor according to claim 5, wherein the acceleration and deceleration commands to the servo amplifier are divided into multiple step inputs based on the time interval. The linear motor according to any one of claims 1 to 6, wherein either the armature unit or the permanent magnet unit, which is a mover, is attached to a linear guide mechanism on a base of the linear motor, and the linear guide mechanism supports the movement of the mover over a stroke length.

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