JP5628140B2 - Linear motor control device and control method - Google Patents

Description

  The present invention relates to a linear motor control device and a control method.

A linear synchronous motor (hereinafter referred to as a linear motor) includes a plurality of coils provided on either the mover or the stator, and a drive magnet provided on the other of the mover or the stator. Unless energization is performed according to the relative positional relationship (magnetic pole position), torque (thrust) according to a predetermined thrust constant cannot be generated. If the sensor that detects the magnetic pole position between the mover and the stator provided in the linear motor is not provided, the initial magnetic pole position is unknown when starting the synchronous motor drive. There is a need to.
Therefore, the initial magnetic pole position is estimated by drawing the mover to the predetermined magnetic pole position by energizing (direct current excitation) corresponding to the predetermined magnetic pole position.

However, when the initial magnetic pole position is estimated using DC excitation, the mover may not be drawn into the initial magnetic pole position due to the position of the mover or friction generated when the mover moves. In this case, a difference occurs between the estimated initial magnetic pole position and the actual magnetic pole position of the mover, and an error occurs in the estimated initial magnetic pole position. When the linear motor is controlled based on the magnetic pole position including an error, there is a problem that a required torque cannot be generated. In addition, every time the linear motor is started, if the error included in the magnetic pole position changes, there is a problem that the torque generated by the linear motor varies.
On the other hand, a technique for improving the accuracy of estimating the initial magnetic pole position using direct current excitation and the amount of movement of the mover at that time has been studied (Patent Document 1).

JP 2007-049831 A

  However, the technique described in Patent Document 1 has the following problem because it is necessary to use a sensor that detects the amount of movement of the mover. Since it is necessary to secure a place for attaching a sensor for detecting the amount of movement to the linear motor, the degree of freedom in designing the linear motor is reduced. In addition, it is necessary to mount an analog circuit or a cable attached to the sensor. Moreover, since an analog circuit, a cable, etc. are required, the manufacturing cost of a linear motor increases.

  The present invention has been made to solve the above problems, and its object is to provide a linear motor that can reduce variations in errors included in the estimated magnetic pole position without providing a sensor for detecting the position and movement amount of the mover. A control device and a control method are provided.

In order to solve the above problem, the present invention provides a linear motor in which either the mover or the stator has a plurality of coils, and either the mover or the stator has a drive magnet. A linear motor control device that controls driving, wherein a voltage corresponding to a predetermined magnetic pole position is applied to the plurality of coils to estimate an initial magnetic pole position, and based on the estimated initial magnetic pole position, the mover Is moved to a predetermined contact position within a movable range, and when it is determined that the mover has reached the contact position, the magnetic pole position when the mover is located at the contact position , current characterized in that to reduce variations in thrust of each time starting the linear motor by a control unit for the magnetic pole position when the movable element in the contact position of each time starting the linear motor is located A linear motor control device for.

In order to solve the above problem, the present invention provides a linear structure in which either the mover or the stator has a plurality of coils, and either the mover or the stator has a drive magnet. A method for controlling a motor, wherein a voltage corresponding to a predetermined magnetic pole position is applied to the plurality of coils to estimate an initial magnetic pole position, and the movable element is moved within a movable range based on the estimated initial magnetic pole position. When the mover is determined to have reached the contact position , the linear motor is activated when the mover is positioned at the contact position. the current control method characterized by reducing the variation in the thrust of each time starting the linear motor by having a control step of the magnetic pole position when the movable element to the contact position is the position of each of That.

  According to the present invention, for example, after direct current excitation is performed, the mover of the linear motor is moved to a predetermined reference position within the movable range of the mover. Since the positional relationship between the coil and the driving magnet is uniquely determined at the reference position, by performing correction to change the magnetic pole position when the mover is moved to the reference position to the magnetic pole position corresponding to the reference position, It is possible to reduce an error that occurs every time the magnetic pole position is estimated, and to suppress variations in error. By reducing the error when estimating the magnetic pole position and suppressing variations in error, the accuracy of estimation can be improved, and the torque generated by the linear motor can be stabilized.

It is a schematic block diagram which shows the structure of the linear motor apparatus 1 in this embodiment. It is a perspective view (partial sectional view) of linear motor 10 in this embodiment. It is a perspective view which shows the coil unit hold | maintained at the coil holder 105 in this embodiment. It is a figure which shows the positional relationship of the magnet 103 and the coil 104 of the linear motor 10 in this embodiment. It is a flowchart which shows the process which correct | amends the magnetic pole position in this embodiment. It is a figure which shows the structural example of the processing apparatus to which the linear motor apparatus 1 is applied.

Hereinafter, a linear motor control device and a control method according to embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic block diagram illustrating a configuration of a linear motor device 1 according to the present embodiment. As shown in the figure, the linear motor device 1 includes a rod-type linear motor 10 and a linear motor control device 20 that controls the linear motor 10.

FIG. 2 is a perspective view (partially sectional view) of the linear motor 10 in the present embodiment. In the linear motor 10, the rod 101 moves in the axial direction with respect to the coil housing case 102.
A plurality of coils 104 held by a coil holder 105 are stacked (arranged) in the coil housing case 102. End cases 109 are attached to both end faces of the coil housing case 102. A bush 108 that is a bearing for guiding the linear motion of the rod 101 is attached to the end case 109.

  The rod 101 is made of a nonmagnetic material such as stainless steel and has a hollow space like a pipe. In the hollow space of the rod 101, a plurality of columnar magnets 103 (segment magnets) are stacked with the same poles facing each other. That is, each of the magnets 103 is stacked such that one of the adjacent magnets 103 is opposed to the N pole and the other of the adjacent magnets 103 is opposed to the S pole. A pole shoe 107 (magnetic pole block) made of a magnetic material such as iron is interposed between the magnets 103. The rod 101 penetrates through the laminated coils 104 and is supported by the coil housing case 102 so as to be movable in the axial direction. End stoppers 110 are attached to both ends of the rod 101 so that the rod 101 does not move beyond the movable range.

FIG. 3 is a perspective view showing the coil unit held by the coil holder 105 in the present embodiment. As shown in the figure, the coil 104 is a copper wire spirally wound and is held by a coil holder 105. That is, the plurality of coils 104 are formed by winding a copper wire along the outer periphery of the rod 101 around the direction in which the magnets 103 of the rod 101 are arranged, and each coil 104 is arranged with the magnets 103 arranged. Are arranged in the same direction as
Since adjacent coils 104 need to be insulated, a ring-shaped resin spacer 105 a is interposed between the coils 104. A printed circuit board 106 is provided on the coil holder 105. A winding end 104 a of the coil 104 is connected to the printed circuit board 106.

  In the present embodiment, the coil housing case 102 is formed integrally with the coil 104 by insert molding in which the coil 104 and the coil holder 105 are set in a mold and molten resin or special ceramics is injected into the mold. As shown in FIG. 2, a plurality of fins 102 a are formed in the coil housing case 102 in order to improve the heat dissipation of the coil 104. The coil 104 held by the coil holder 105 is housed in an aluminum coil housing case 102, the gap between the coil 104 and the coil housing case 102 is filled with an adhesive, and the coil 104 and the coil holder 105 are coiled. You may fix to the storage case 102. FIG.

  FIG. 4 is a diagram showing a positional relationship between the magnet 103 and the coil 104 of the linear motor 10 in the present embodiment. A plurality of cylindrical magnets 103 (segment magnets) are arranged in the hollow space in the rod 101 so that the same poles face each other. Three coils 104 constitute a set of three-phase coils composed of U, V, and W phases. A coil unit is configured by combining a plurality of sets of three-phase coils. When a three-phase current having a phase difference of 120 ° is passed through a plurality of coils 104 divided into U, V, and W phases, a moving magnetic field that moves in the axial direction of the coil 104 is generated. The rod 101 obtains a thrust by the action of the magnetic field generated by each magnet 103 as a driving magnet and the moving magnetic field, and moves linearly relative to the coil 104 in synchronization with the speed of the moving magnetic field. I do.

Returning to FIG. 1, the configuration of the linear motor control device 20 will be described.
The linear motor control device 20 includes a control unit 201, a power converter 202, a current transformer 203, and a correction value storage unit 204. When a control start signal is input from a host device, the control unit 201 performs estimation of the initial magnetic pole position of the linear motor 10 and origin return processing. Further, the control unit 201 determines each of the U, V, and W phases based on the position command signal input from the host device and the current value that flows through the coils 104 of the U, V, and W phases of the linear motor 10. The voltage applied to the coil is calculated. Further, the control unit 201 outputs a voltage command signal indicating the calculated voltage to the power converter 202.
The power converter 202 applies a voltage corresponding to the voltage command signal input from the control unit 201 to each of the U, V, and W phase coils 104 of the linear motor 10. The current transformer 203 is attached to a power line connecting the power converter 202 and the linear motor 10, measures a current value flowing through the power line, and outputs a measurement result to the control unit 201.
The correction value storage unit 204 stores a correction value for correcting the magnetic pole position when the origin return process is performed. Specifically, the magnetic pole position when the rod 101 of the linear motor 10 is at a predetermined reference position is stored in the correction value storage unit 204 as a correction value. The magnetic pole position stored in the correction value storage unit 204 is, for example, the magnetic pole position when one of the two end stoppers 110 is in contact with the end case 109 and the other one of the end stoppers 110. The magnetic pole position when contacting the end case 109. In this case, the reference positions are positions where the end stopper 110 and the end case 109 are in contact, that is, both ends of the movable range.

FIG. 5 is a flowchart showing processing for correcting the magnetic pole position in the present embodiment.
When a control start signal is input, for example, after power supply is started, the control unit 201 applies voltages (DC excitation) having a phase difference corresponding to a predetermined magnetic pole position to U, V, W It applies to the coil 104 of each phase, and pulls the rod 101 in a predetermined magnetic pole position (step S11).
The control unit 201 considers that the rod 101 is positioned at a predetermined magnetic pole position, and performs control for moving the rod 101 toward one predetermined end of both ends of the movable range as an origin return process ( Step S12). That is, the control unit 201 performs control to move the rod 101 until the end stopper 110 attached to one end of the rod 101 comes into contact with the end case 109.

The control unit 201 determines whether or not any of the current values of the currents flowing through the U, V, and W phases of the linear motor 10 is greater than or equal to a predetermined current threshold value (step S13). Is less than the current threshold (step S13: NO), the determination is repeated until any of the currents flowing in the U, V, and W phases becomes equal to or greater than the current threshold.
On the other hand, when any of the currents flowing in the U, V, and W phases is equal to or greater than the current threshold (step S13: YES), the control unit 201 determines that the rod 101 has reached one end of the movable range, The magnetic pole position (correction value) corresponding to the end is read from the correction value storage unit 204, the current magnetic pole position of the rod 101 is corrected to the read magnetic pole position (step S14), and the magnetic pole position is corrected. finish.
Note that the current threshold value in step S13 is determined based on a measurement result using an actual machine or a simulation result.

The linear motor control device 20 of the present embodiment pulls the rod 101 into a predetermined magnetic pole position by DC excitation from a state in which the magnetic pole position of the rod 101 is unknown immediately after power supply is started, The driving of the linear motor 10 is started by regarding the magnetic pole position as a predetermined magnetic pole position. Further, the linear motor control device 20 moves the rod 101 to one end of the movable range in order to detect the absolute position of the rod 101. At this time, the linear motor control device 20 corrects the error generated with respect to the initial magnetic pole position estimated at the time of DC excitation by correcting the current magnetic pole position to the magnetic pole position corresponding to one end of the movable range. The magnetic pole position variation is corrected.
When the initial magnetic pole position is estimated by drawing the rod 101 by direct current excitation, an error may occur in the initial magnetic pole position due to friction applied to the rod 101 or the like. On the other hand, since the magnetic pole position when the rod 101 is moved to one end of the movable range is uniquely determined by the positional relationship between the magnet 103 provided in the rod 101 and the coil 104, the estimated magnetic pole The position error can be reduced.
Further, the linear motor control device 20 determines whether or not the rod 101 has reached the end of the movable range by utilizing the fact that the current value flowing through the coil 104 increases as the torque required to move the rod 101 increases. doing. Thus, it is possible to detect whether or not the rod 101 has reached the end of the movable range without providing a sensor or the like for detecting the position of the rod 101 (movable element), and the accuracy of estimating the magnetic pole position of the rod 101. Can be improved.
Further, when the control unit 201 included in the linear motor control device 20 is mounted by a microcontroller or the like, the configuration shown in FIG. 5 is added without adding hardware to the device configuration that estimates the magnetic pole position using DC excitation. Since the control method can be implemented, the estimation accuracy of the magnetic pole position can be improved without increasing the manufacturing cost. Further, in the linear motor 10 that performs sensorless control, the return to origin is always performed, so that the magnetic pole position can be corrected without imposing a time burden on the user.

In general, the thrust (torque) generated by the linear motor 10 is calculated by the product of “thrust constant” and “current value” flowing through the linear motor 10. This thrust constant is a value when an accurate relative position (magnetic pole position) between the coil 104 and the magnet 103 can be estimated, and the apparent thrust constant decreases as the phase shifts. This relationship is a cosine (cosine function), and a thrust according to the thrust constant is obtained when the phases coincide with each other. When the phase is shifted by 60 degrees, the apparent thrust constant is halved. When the magnetic pole position is estimated by direct current excitation, thrust according to the thrust constant may not be obtained depending on the error generated in the magnetic pole position.
In contrast, the linear motor control device 20 of the present embodiment can reduce the variation in thrust when driving the linear motor 10 by reducing the error of the magnetic pole position. Further, each time the linear motor device 1 is started, the linear motor control device 20 corrects the magnetic pole position, so that the error included in the estimated magnetic pole position can be reduced and the variation in error can be suppressed. Stable thrust control can be performed.

FIG. 6 is a diagram illustrating a configuration example of a machining apparatus to which the linear motor device 1 is applied.
As shown in the figure, the machining apparatus includes a linear motor device 1, an X-axis actuator 2, a cutter 3 attached to one end of a rod 101, and a main parallel to the movable direction of the X-axis actuator. And a work table 4 having a surface. The linear motor 10 is attached to the X-axis actuator 2 so that the rod 101 moves in the vertical direction. By driving the X-axis actuator 2, the linear motor 10 moves in parallel to the main surface of the work table 4. It is like that. A cutter 3 is attached to one lower end of both ends of the rod 101, and the cutter 3 moves up and down in the vertical direction according to the drive of the linear motor 10.
The processing apparatus is an apparatus that processes the material 6 disposed on the main surface of the work table 4 by driving the linear motor 10 and the X-axis actuator 2 to move the cutter 3.

When the material 6 is composed of the first layer and the second layer (base layer), when the processing is performed to cut only the first layer using a processing apparatus, the first layer is not damaged. In order to cut, highly accurate pressing control (thrust control) is required. That is, it is required that there is little variation in thrust when driving the linear motor 10.
On the other hand, the linear motor control device 20 performs highly accurate pressing control by reducing the error generated in the estimated magnetic pole position, thereby reducing the variation in the thrust generated when the linear motor 10 is driven. Therefore, it is suitable for such a processing apparatus.
Further, in such a processing apparatus, since the rod 101 of the linear motor 10 is installed so as to be movable in the vertical direction, it is subject to disturbance due to gravity when performing direct current excitation, and therefore an error is likely to occur in the estimated magnetic pole position. However, by using the magnetic pole position correction process (control method) shown in FIG. 5, the error of the estimated magnetic pole position can be reduced, and highly accurate pressing control can be performed.

In the present embodiment, the case where the magnetic pole position correction process is performed after the start of power supply has been described. However, the correction process may be appropriately performed according to a request from a higher-level device.
In the present embodiment, the case where the linear motor control device 20 controls the rod type linear motor 10 has been described. However, the mover has U, V, and W phase coils, and the stator is arranged in the movable direction. A flat type linear motor having a driving magnet may be controlled.

  The linear motor control device 20 described above may have a computer system inside. In that case, the process of correcting the magnetic pole position described above is stored in a computer-readable recording medium in the form of a program, and the above process is performed by the computer reading and executing this program. Become. Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

  DESCRIPTION OF SYMBOLS 1 ... Linear motor apparatus, 10 ... Linear motor, 20 ... Linear motor control apparatus, 201 ... Control part, 203 ... Current transformer

Claims (3)

A linear motor control device that controls driving of a linear motor in which either the mover or the stator has a plurality of coils, and either the mover or the stator has a drive magnet,
A voltage corresponding to a predetermined magnetic pole position is applied to the plurality of coils to estimate an initial magnetic pole position, and based on the estimated initial magnetic pole position, the mover is moved to a predetermined contact position within a movable range. When the mover is controlled to determine that the mover has reached the contact position, the magnetic pole position when the mover is positioned at the contact position is set to the contact position every time a linear motor is started. A linear motor control device characterized by reducing a variation in thrust each time the linear motor is started by including a control unit that sets the current magnetic pole position when the mover is positioned . A current transformer for measuring a current value flowing through the plurality of coils;
The controller is
While performing control to move the mover to the contact position, the mover has reached the contact position when the current value measured by the current transformer is equal to or greater than a predetermined current threshold. The linear motor control device according to claim 1, wherein One of the mover or the stator has a plurality of coils, and the other of the mover or the stator has a drive magnet,
A voltage corresponding to a predetermined magnetic pole position is applied to the plurality of coils to estimate an initial magnetic pole position, and based on the estimated initial magnetic pole position, the mover is moved to a predetermined contact position within a movable range. When the mover is controlled to determine that the mover has reached the contact position, the magnetic pole position when the mover is positioned at the contact position is set to the contact position every time a linear motor is started. A control method characterized by reducing a variation in thrust each time the linear motor is started by having a control step of setting the current magnetic pole position when the mover is positioned .

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