Transfer device and control method

Abstract

A transmission device and a control method are disclosed. The transmission device includes a motor having a mover and coils, and a control device that controls the motor and includes a measurement unit and a control unit. The coils drive the mover by applying a current to each of the coils. The measurement unit measures the impedance of each coil. The control unit controls the current flowing through each of the coils based on a third current command value in which a first current command value indicating a current corresponding to a thrust command value indicating the thrust applied to the mover and a second current command value indicating a current for measuring the impedance are superimposed. When measuring the impedance, the control unit determines the second current command value such that the mover does not receive thrust due to the component corresponding to the second current command value in the current flowing through each coil.

Description

Technical Field

[0001] The present disclosure relates to a transfer device and a control method. Background Art

[0002] Japanese Patent Application Laid-Open No. 2011-137688 discloses a method for measuring the impedance of a three-phase electrical device in a hot line state without affecting its operating state. The impedance measuring device disclosed in Japanese Patent Application Laid-Open No. 2011-137688 has a circuit configuration in which the neutral point of the three-phase electrical device and the neutral point of the three-phase induction element are connected through a zero-phase power supply, and measures the impedance based on the current flowing through the zero-phase power supply and the voltage applied to the three-phase electrical device.

[0003] To perform the impedance measurement disclosed in Japanese Patent Application Laid-Open No. 2011-137688, a special circuit configuration in which the neutral point of the three-phase electrical device and the neutral point of the three-phase induction element are connected through a zero-phase power supply is required. Summary of the Invention

[0004] The present disclosure relates to providing a transfer device and a control method capable of measuring the impedance of a motor with less restriction on the circuit configuration.

[0005] According to an aspect of the present disclosure, a transfer device includes: a motor including a rotor and a plurality of coils configured to drive the rotor by applying a current to each of the plurality of coils; and a control device configured to control the motor, wherein the control device includes a measurement unit configured to measure the impedance of each of the plurality of coils, and includes a control unit configured to control the current flowing through each of the plurality of coils based on a third current command value, in which a first current command value indicating a current corresponding to a thrust command value indicating a thrust applied to the rotor and a second current command value indicating a current for measuring the impedance are superimposed, and wherein, when measuring the impedance, the control unit is configured to determine the second current command value such that the rotor does not receive a thrust due to a component corresponding to the second current command value in the current flowing through each of the plurality of coils.

[0006] Other features of the present disclosure will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Brief Description of the Drawings

[0007] Figure 1 is a top view schematically showing a configuration of a transfer device according to a first embodiment of the present disclosure.

[0008] Figure 2 is a cross-sectional view schematically showing a configuration of a transfer device according to a first embodiment of the present disclosure.

[0009] Figure 3 is a circuit diagram showing the connection between a coil, a current detector, and a voltage detector according to a first embodiment of the present disclosure.

[0010] Figure 4 is a block diagram schematically showing the configuration of a transfer device according to a first embodiment of the present disclosure.

[0011] Figure 5 is a flowchart schematically showing the operation of a transfer device according to a first embodiment of the present disclosure.

[0012] Figure 6 is a vector diagram schematically showing the current calculation in a transfer device according to a first embodiment of the present disclosure.

[0013] Figure 7 is a block diagram schematically showing the configuration of a transfer device according to a second embodiment of the present disclosure.

[0014] Figure 8 is a flowchart schematically showing the operation of a transfer device according to a second embodiment of the present disclosure.

[0015] Figure 9 is a vector diagram schematically showing the current calculation in a transfer device according to a second embodiment of the present disclosure.

[0016] Figure 10 is a cross-sectional view schematically showing the configuration of a transfer device according to a third embodiment of the present disclosure.

[0017] Figure 11 is a circuit diagram showing the connection between a coil, a current detector, and a voltage detector according to a third embodiment of the present disclosure. Detailed Description of the Preferred Embodiments

[0018] Preferred embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. Throughout the drawings, the same or corresponding elements are denoted by common reference numerals, and their description may be omitted or simplified. Multiple identical or corresponding components may be distinguished by appending a letter as an identifier at the end of the same reference numeral. In cases where separate description of the same components is not required, the identifier may be omitted, and only the reference numeral with a number may be used.

[0019] [First Embodiment]

[0020] First, the schematic configuration of the transfer device according to this embodiment will be described with reference to Figures 1 to 3 The transfer device according to this embodiment is a moving magnet (MM) type transfer device using a linear motor, in which a magnet is mounted in a mover and a coil is mounted in a stator.

[0021] Figure 1 is a top view schematically showing a configuration of a transfer device according to the present embodiment. Figure 2 is a cross-sectional view schematically showing a configuration of a transfer device according to the present embodiment. Figure 1 is a top view of the transfer device as viewed from the Z direction. Figure 2 is a cross-sectional view of the XZ cross-section of the transfer device as viewed from the Y direction. Figure 3 is a circuit diagram showing connections between a coil, a current detector, and a voltage detector.

[0022] As Figures 1 to 3 shown, the transfer device according to the present embodiment includes a control device 10, a coil 21, a position detector 22, a current detector 23, a voltage detector 24, a linear guide 31, a mover 32, scales 33, and a magnet 34. The transfer device is a device for transferring an article. The transfer device forms part of a processing system for processing a workpiece transferred by the mover 32.

[0023] The mover 32 serves as a carrier of the transfer device. The mover 32 is configured such that an article such as a workpiece can be placed or held on its upper surface. The number of movers 32 is not limited to two as shown in Figure 1 and Figure 2 but may be one or may be three or more. The workpiece transferred by the mover 32 is processed by a processing device (not shown) to manufacture an article.

[0024] A description will be given of the XYZ coordinate system as the Figure 1 and Figure 2 orthogonal coordinate system shown. The horizontal direction in which the mover 32 moves is defined as the X axis. The vertical direction in the direction orthogonal to the X axis is defined as the Z axis, and the direction orthogonal to the X axis and the Z axis is defined as the Y axis. Note that the moving direction of the mover 32 is not necessarily horizontal, but in this case, when the moving direction is the X axis, the Y axis and the Z axis can be appropriately determined to be orthogonal to the X axis.

[0025] A plurality of magnets 34 are mounted on the lower surface (the surface on the negative side of the Z axis) of the mover 32 so as to be aligned in the X-axis direction. The plurality of magnets 34 are mounted such that the polarities of the outer magnetic poles facing downward (the negative direction of the Z axis) are alternately different, that is, the N pole and the S pole are alternately arranged downward. The number of the plurality of magnets is not particularly limited and can be appropriately changed. The magnet 34 can generally be a permanent magnet, but may also be an electromagnet. In the following description, each of the magnets 34 is assumed to be a permanent magnet.

[0026] In this embodiment, each of the plurality of coils 21 is a single-phase coil and serves as an armature for driving the mover 32. The plurality of coils 21 are arranged along the moving direction of the mover 32 - that is, in the X-axis direction. The plurality of coils 21 and the plurality of magnets 34 are mounted to face each other in the Z-axis direction. By applying current to each of the plurality of coils 21, a force is generated between the plurality of coils 21 and the plurality of magnets 34. Thus, a thrust acts on the mover 32, and the mover 32 moves in the X-axis direction along the linear guide 31. In this way, the plurality of coils 21 and the linear guide 31 constitute the transfer path of the mover 32.

[0027] A plurality of position detectors 22 for detecting the position of the mover 32 are mounted above the plurality of coils 21 and the linear guide 31 (in the positive direction of the Z-axis). For example, the position detector 22 is a linear encoder. The position detector 22 measures the relative distance between the position detector 22 and the mover 32 by reading the pattern of the scale 33 attached to the mover 32. Since the position of the position detector 22 is known, the position of the mover 32 can be detected based on the position of the position detector 22 and the measured relative distance between the position detector 22 and the mover 32. The positions where the position detector 22 and the scale 33 are mounted are not limited to the positions shown, and it is sufficient if the position of the mover 32 can be detected.

[0028] As Figure 3 shown, a current detector 23 is provided in the wiring connecting each of the plurality of coils 21 and detects the current flowing through each of the plurality of coils 21. A voltage detector 24 is provided in the wiring connecting each of the plurality of coils 21 and detects the voltage applied across the two ends of each of the plurality of coils 21. The voltage detector 24 can actually measure the voltage applied across the two ends of the coil 21, or can acquire the command voltage calculated within the control device 10.

[0029] The control device 10 has a function of controlling the current flowing through the plurality of coils 21, a function of controlling the position detector 22, the current detector 23, and the voltage detector 24, and a function of arithmetic operations required for these controls. Therefore, the control device 10 executes control for moving the plurality of movers 32 to a desired position. The control device 10 can be a single controller or a system including a plurality of controllers such as a coil controller for controlling the plurality of coils 21, a sensor controller for controlling various detectors, and a transfer controller for controlling the entire transfer device.

[0030] Based on the position of the mover 32 acquired by the position detector 22, the control device 10 controls the current flowing through each of the plurality of coils 21 so that a desired thrust acts on the mover 32. As Figure 2 and Figure 3As shown in the figure, the control device 10 can independently control the current flowing through the plurality of coils 21, so that even when the number of movers 32 is plural, the plurality of movers 32 can be independently controlled.

[0031] The thrusts respectively acting on corresponding ones of the plurality of movers 32 are collectively referred to as a thrust vector F, and the current values respectively flowing in corresponding ones of the plurality of coils 21 facing the plurality of movers 32 are collectively referred to as a current vector I. The thrust vector F is a vector having the number of elements (dimensions) of the plurality of movers 32, and the current vector I is a vector having the number of elements of the plurality of coils 21. At this time, the relationship between the thrust vector F and the current vector I is expressed by the following formula (1) using a thrust constant matrix Kt.

[0032] F = Kt * I...(1)

[0033] Here, the number of rows of the thrust constant matrix Kt is equal to the number of elements of the thrust vector F, and the number of columns of the thrust constant matrix Kt is equal to the number of elements of the current vector I. Each element of the thrust constant matrix Kt represents the thrust acting on the mover 32 corresponding to the row number of the element when a unit current flows through the coil 21 corresponding to the column number of the element. The thrust constant matrix Kt changes according to the position of each of the plurality of movers 32.

[0034] Next, a method for measuring the resistance of the coil 21 in the transfer device according to the present embodiment will be described with reference to Figures 4 to 6 The control device 10 according to the present embodiment has a function of measuring the resistance of each of the plurality of coils 21. Before describing the specific measurement method, the purpose of measuring the resistance and the like will be briefly described.

[0035] Generally, the coil windings included in motors mounted on transfer devices and the like are provided with an insulating coating such as enamel. In order to reduce the deterioration of the insulating coating, it is necessary to control the motor so that the operating temperature of the motor does not exceed the heat-resistant temperature of the insulating coating. It is known that the resistance of a metal material such as copper used for the winding basically changes depending on the temperature, and the temperature of the coil can be estimated by measuring the resistance of the coil. In addition, since abnormalities such as short circuits and disconnections of the windings also cause changes in the resistance, the occurrence of these abnormalities can be estimated by measuring the resistance of the coil.

[0036] The resistance measured by the control device 10 according to the present embodiment can be used in at least one of the above applications, but is not limited to these applications. In this specification, the "resistance" of the measured coil 21 may include a reactance component caused by the inductance of the coil 21 and the pure resistance measured by a DC voltage and a DC current. In addition, not only the pure resistance of the coil 21 can be measured, but also the reactance component can be measured. Therefore, in the following description, except in cases where the pure resistance is indicated, the more common term "impedance" is used instead of "resistance".

[0037] Figure 4 is a block diagram schematically showing the configuration of the transfer device according to the present embodiment. As Figure 4 shown, the control device 10 includes a position command value generator 11, a thrust command value generator 12, a first current command value generator 13, a second current command value generator 14, a current controller 15, and an impedance meter 16. Note that some or all of the position command value generator 11, the thrust command value generator 12, the first current command value generator 13, the second current command value generator 14, and the current controller 15 may be referred to as a control unit. The impedance meter 16 may also be referred to as a measurement unit.

[0038] Figure 5 is a flowchart schematically showing the operation of the transfer device according to the present embodiment. Referring to Figure 5 the flowchart of, the impedance measurement operations performed by each of the Figure 4 blocks shown in will be outlined.

[0039] In step S11, the position command value generator 11 generates a position command value for moving the mover 32 to a desired position based on an operation from a user or a preset operation.

[0040] In step S12, the position detector 22 detects the current position of the mover 32. The position information of the mover 32 thus obtained can be supplied to the thrust command value generator 12, the first current command value generator 13, the second current command value generator 14, and the impedance meter 16. The order of steps S11 and S12 may be reversed, or steps S11 and S12 may be performed in parallel.

[0041] In step S13, the thrust command value generator 12 calculates and generates a thrust command value indicating the thrust acting on the mover 32 based on the position command value generated by the position command value generator 11 and the position of the mover 32 measured by the position detector 22. The thrust is determined such that the mover 32 moves from the current position toward the position indicated by the position command value. For example, a PID controller may be used to calculate the thrust.

[0042] In step S14, the first current command value generator 13 determines a first current command value indicating the current to be supplied to each coil 21 based on the thrust command value generated by the thrust command value generator 12 and the position of the mover 32 measured by the position detector 22. The first current command value is determined such that the mover 32 receives a thrust corresponding to the thrust command value. For example, the relational expression between the thrust vector F and the current vector I shown in the following formula (2) can be used to calculate the first current command value.

[0043] I = Kt<+> * F…(2)

[0044] Where Kt<+> is the pseudo-inverse matrix of the thrust constant matrix Kt.

[0045] In step S15, the second current command value generator 14 determines a second current command value for supplying an impedance measurement current to the coil 21 in a combination such that the mover 32 does not receive a thrust. Such a current combination is achieved by calculating a current vector ik that belongs to the null space of the thrust constant matrix Kt and is a non-zero vector and making the current vector ik the second current command value. Since the current vector ik belongs to the null space of the thrust constant matrix Kt, the mover 32 does not receive any thrust due to the component corresponding to the second current command value. Therefore, even if the current vector ik is superimposed on the drive current vector I for generating the thrust vector F corresponding to the first current command value, the sum of the thrusts applied to the mover 32 by the plurality of coils 21 is not affected.

[0046] The condition for the existence of the current vector ik as a non-zero vector in the null space of the thrust constant matrix Kt is the existence of multiple solutions of the current vector I for generating a predetermined thrust vector F. As in the Figure 1 and Figure 2 transfer device, when a plurality of magnets 34 are attached to the mover 32 and the currents of the plurality of coils 21 can be independently controlled, this condition is easily satisfied.

[0047] As an example of a method for calculating the current vector ik, there is a method using, for example, the following formula (3) with an arbitrary non-zero vector η having the same number of elements as I, the thrust constant matrix Kt, its pseudo-inverse matrix Kt<+>, and the identity matrix E.

[0048] ik = (E - Kt<+> * Kt) * η…(3)

[0049] By performing operations such as normalization and constant multiplication on the calculation result of the current vector ik as needed, the magnitude of the current vector ik can be appropriately adjusted to suit the following impedance measurement. Due to the arbitrariness of η in formula (3), the current vector after these operations also belongs to the null space of the thrust constant matrix Kt.

[0050] In step S16, the current controller 15 controls the current flowing through the coil 21 based on a third current command value obtained by superimposing the first current command value and the second current command value. This process can control the current, for example, such that a current value given by the sum of equations (2) and (3) flows through the coil 21. The current controller 15 determines the voltage to be applied to each coil 21 through a PI controller, for example, and performs control such that the current in each coil 21 indicated by the third current command value coincides with the current detected by the current detector 23.

[0051] Reference Figure 6 , an example of current calculation based on equations (2) and (3) will be described using a simplified model. Figure 6 is a vector diagram schematically showing current calculation in the transfer device according to the present embodiment.

[0052] Figure 6 shows an example of current vectors in the case where the number of movers 32 is 1 and the number of coils 21 is 2 on a two-dimensional plane. At this time, the thrust vector F is a vector with an element number of 1, the current vector I is a vector with an element number of 2, and the thrust constant matrix Kt is a matrix with one row and two columns. The elements of the thrust constant matrix Kt are Kt1 and Kt2. Note that, for the purpose of illustration, the number of the above elements is a simplified example, and in practice it can be larger than the above. If the existence of the current vector ik as a non-zero vector in the null space of the thrust constant matrix Kt - that is, the existence of multiple solutions of the current vector I that generates a predetermined thrust vector F - is satisfied, the number of elements can be other combinations.

[0053] Figure 6 shows a first coordinate system 50 indicated by O-I-ik and a second coordinate system 51 indicated by O-I1-I2. The first coordinate system 50 is a coordinate system related to the thrust vector acting on the mover 32. The I-axis in the horizontal direction corresponds to the current for applying thrust to the mover 32. The ik-axis in the vertical direction corresponds to the current for impedance measurement. That is, the current vector I calculated by equation (2) corresponds to Figure 6 the vector 52 in, and the current vector ik calculated by equation (3) corresponds to Figure 6 the vector 53 in.

[0054] The second coordinate system 51 is a coordinate system corresponding to the current flowing through each coil 21. The I1-axis corresponds to the current flowing through the first coil 21 among the two coils 21. The I2-axis corresponds to the current flowing through the second coil 21 among the two coils 21. The slope of O-I1 with respect to the first coordinate system 50 is expressed as -Kt2 / Kt1 using the elements of the thrust constant matrix Kt.

[0055] The current controller 15 determines the current flowing through each coil 21 based on the sum of the vector 52 based on the first current command value and the vector 53 based on the second current command value, and performs control. The currents flowing through the coils 21 respectively correspond to the vector 54a on the I1 axis and the vector 54b on the I2 axis. As can be understood from Figure 6 what can be understood, the component obtained by projecting the sum of the vectors 52 and 53 onto the I1 axis is the vector 54a, and the component obtained by projecting the sum onto the I2 axis is the vector 54b.

[0056] In step S17, the current detector 23 measures the current i flowing through each of the plurality of coils 21, and the voltage detector 24 measures the voltage v across each of the plurality of coils 21. The impedance meter 16 acquires the speed w of the mover 32. The method of acquiring the speed w can be based on, for example, the time change of the position of the mover 32. Specifically, the impedance meter 16 acquires the position of the mover 32 measured by the position detector 22 multiple times, and calculates the speed w of the mover 32 at the position facing each of the plurality of coils 21 based on the time change of the position.

[0057] In step S17, the impedance meter 16 calculates the impedance of each of the plurality of coils 21 based on the current i, voltage v, speed w, and back electromotive force constant Kv of each of the plurality of coils 21. For example, when measuring the resistance R with a direct current, the impedance can be calculated by the following formula (4). Formula (4) is not an arithmetic operation of matrices or vectors, but an arithmetic operation for each element performed on each of the plurality of coils 21.

[0058] R = (v - Kv * w) / i…(4)

[0059] When the above voltage v and current i have an alternating current component, the resistance R as the calculation result of formula (4) can include not only the resistance component of the coil 21 but also the inductance component. Generally, the time constant of the temperature change in the coil 21 is longer than the electrical time constant. The influence of the inductance component is small in the low-frequency region and large in the high-frequency region. Therefore, the calculation result of formula (4) can be processed by a filter such as a low-pass filter, thereby reducing the influence of the inductance component.

[0060] Note that formula (4) can be modified so that the resistance R can be calculated separately from the inductance component by adding a term of the induced voltage due to the inductance component to formula (4). Formula (4) can be modified to be able to calculate the impedance including the resistance component and the reactance component for the voltage v and current i having an alternating current component.

[0061] If it is known that the back electromotive force generates only an alternating current component, the filter can remove the influence of the back electromotive force and the influence of the inductive component. Therefore, the term Kv*w of the speed electromotive force can be removed from Equation (4). In this case, the calculation is simplified.

[0062] As described above, in the current control in the present embodiment, the second current command value indicating the current for impedance measurement is superimposed on the first current command value indicating the drive current to control the current flowing through the coil 21. That is, without providing an additional current supply circuit by processing in the control device 10, the current for impedance measurement can be superimposed on the current flowing through the coil 21. Therefore, the control device 10 and the transfer device capable of measuring the impedance of the motor with less restriction on the circuit configuration are provided.

[0063] In addition, by superimposing the first current command value and the second current command value and increasing the amount of current in each of the coils 21, the impedance measurement accuracy can be improved. Since the current for impedance measurement flows through each of the coils 21, impedance measurement can be achieved even when the drive current is zero. At this time, the current for impedance measurement is calculated to belong to the null space of the thrust constant matrix Kt, so that the mover 32 does not receive thrust. Therefore, the influence of the current for impedance measurement flowing through each of the coils 21 on the thrust of the mover 32 is reduced. Therefore, for example, even when impedance measurement is performed during the operation of the transfer device, the influence of the impedance measurement current on the operation of the transfer device is reduced.

[0064] In addition, in the method according to the present embodiment, since the current for impedance measurement can be separately supplied to each of the plurality of coils 21, the impedance of each of the plurality of coils 21 can be separately obtained.

[0065] The current waveform of the current vector ik based on the second current command value may have a direct current interval in at least a part of the period when the two current command values are superimposed. As described above, the measurement accuracy of the impedance calculated by Equation (4) etc. may deteriorate due to the influence of the alternating current component. By setting a direct current interval in the waveform of the current vector ik, the influence of the alternating current component is reduced, and the measurement accuracy of the impedance can be improved. Examples of waveforms having a direct current interval include a direct current waveform, a step waveform, etc.

[0066] The process of superimposing the second current command value on the first current command value may be always executed during the operation of the coil 21, but the above effects can be obtained if it is executed at least during the measurement of the impedance. For example, the process of superimposing the second current command value on the first current command value may be executed only during the period when impedance measurement is performed during the operation of the coil 21.

[0067] The process of superimposing the second current command value on the first current command value can be performed only when a predetermined condition is satisfied. The predetermined condition can be determined based on the first current command value. Specifically, the above-described superimposing process can be performed when the drive current is equal to or less than a threshold value, or when the drive current continues to be in a state where the drive current is equal to or less than the threshold value for a threshold time or longer. When the drive current is large enough, since impedance measurement can be performed by the drive current, the effect of reducing power consumption and heat generation caused by the impedance measurement current can be obtained by not considering the second current command value as described above.

[0068] When there are multiple candidates for the current for impedance measurement calculated by the process such as Equation (3), the multiple candidates can be switched according to time periods so that current flows through the coil 21. For example, in the first time period, a second current command value can be generated so that a first set of the current for impedance measurement flows through the coil 21, and in the second time period, a second current command value can be generated so that a second set of the coil 21 different from the first set of the current for impedance measurement flows through the coil 21. By changing the set of the coil 21 through which the impedance measurement current flows according to the time period, compared with the case where the current for impedance measurement flows through all the coils 21 simultaneously, the influence on the thrust received by the mover 32 can be further reduced.

[0069] [Second Embodiment]

[0070] Reference will be made to Figures 7 to 9 describe the transfer device according to the second embodiment. The difference from the transfer device according to the first embodiment lies in the processing procedure of current control. The structure of the transfer device according to the present embodiment is the same as that of the first embodiment, so its description is omitted. Components identical to those of the transfer device according to the first embodiment are denoted by the same reference numerals, and their description can be omitted or simplified.

[0071] In the first embodiment, the current vector ik for impedance measurement belonging to the null space of the thrust constant matrix Kt is explicitly obtained and superimposed on the current vector I for driving. On the other hand, in the present embodiment, after determining the coil 21 to which the current for impedance measurement is to be superimposed and the current to be superimposed, the remaining drive current is calculated so as to generate a desired thrust according to the thrust command value.

[0072] Figure 7 is a block diagram illustrating a schematic configuration of the transfer device according to the present embodiment. Figure 7 The blocks shown in the block diagram of Figure 4 are similar to the blocks of

[0073] Figure 8 is a flowchart schematically illustrating the operation of the transfer device according to the present embodiment. Refer to Figure 8 the flowchart of Figure 7 to outline the impedance measurement operations performed by each block shown in Figure 8 Since the steps S11, S12, S13, S16, and S17 in

[0074] are substantially the same as the steps in the first embodiment, their descriptions are omitted or simplified.

[0075] In step S21, the second current command value generator 14 determines the coil 21 to which a current for impedance measurement is to be superimposed, and the second current command value including the current I1 for impedance measurement current flowing through these coils 21.

[0076] In step S22, the first current command value generator 13 decomposes the thrust constant matrix Kt into two matrices, the thrust constant matrix Kta and the thrust constant matrix Ktb, based on the determined current I1 for impedance measurement. The thrust constant matrix Kta is a matrix composed of columns related to the coil 21 to which a current for impedance measurement is to be superimposed. The thrust constant matrix Ktb is a matrix including at least columns for all the remaining coils 21. To obtain the solution of the current vector that generates the desired thrust vector F according to the position command value, the thrust constant matrix Kt2 is selected such that the column rank of the thrust constant matrix Kt2 is equal to or higher than the row rank of the desired thrust vector F. At this time, the thrust constant matrix Kt2 may include columns related to the coil 21 to which a current for impedance measurement is to be superimposed.

[0076] In step S23, the first current command value generator 13 generates a first current command value using the thrust command value, the position of the mover 32, the pseudo-inverse matrix Ktb<+> of the thrust constant matrices Kta and Ktb, and the current vector I1 corresponding to the second current command value. The current vector I2 for driving based on the first current command value can be calculated by the following equation (5).

[0077] I2 = Ktb<+> * (F - Kta * I1)…(5)

[0078] In step S16, the current controller 15 controls the current flowing through the coil 21 based on the third current command value obtained by superimposing the first current command value and the second current command value. This process can control the current, for example, such that a current value given by the sum of the current vector I1 for resistance measurement and the current vector I2 for driving flows through the coil 21.

[0079] Here, an example of current calculation based on equation (5) will be described using a simplified model with reference to Figure 9 the vector diagram of current calculation in the transfer device according to the present embodiment. In Figure 9 is a vector diagram schematically illustrating the current calculation in the transfer device according to the present embodiment. InFigure 9 In this case, the preconditions such as the number of the mover 32 and the coils 21, the number of vector elements, and the number of matrix elements are the same as those in Figure 6 and thus the description thereof will be omitted.

[0080] Figure 9 The first coordinate system 55 indicated by O-I-ik and the second coordinate system 51 indicated by O-I1-I2 are shown. The first coordinate system 55 is a coordinate system related to the thrust vector acting on the mover 32. The I axis in the horizontal direction corresponds to the current for applying thrust to the mover 32. The ik axis in the vertical direction corresponds to the current for impedance measurement.

[0081] The second coordinate system 51 is a coordinate system corresponding to the current flowing through each coil 21. The I1 axis corresponds to the current flowing through the first coil 21 of the two coils 21. The I2 axis corresponds to the current flowing through the second coil 21 of the two coils 21. The slope of O-I1 with respect to the first coordinate system 55 is expressed as -Kt2 / Kt1 using the elements of the thrust constant matrix Kt.

[0082] The second current command value generator 14 determines the current vector 56 for impedance measurement flowing through the coil 21 of the impedance measurement object. Next, as shown in Equation (5), the first current command value generator 13 uses the difference between the current vector 57 ( Figure 9 vector OA in this case) and the current vector 58 ( Figure 9 vector OB in this case) to calculate the current vector 59 flowing through the remaining coil 21. Here, the current vector 57 is a vector composed only of the components related to the thrust acting on the mover 32 in the current vector 56. The current vector 58 is a vector indicating the current required to apply a desired thrust to the mover 32.

[0083] As described above, as in the first embodiment, also in the current control in this embodiment, the second current command value indicating the current for impedance measurement is superimposed on the first current command value indicating the drive current to control the current flowing through the coil 21. Therefore, as in the first embodiment, the control device 10 and the transfer device capable of measuring the impedance of the motor with little restriction on the circuit configuration are provided.

[0084] In this embodiment, since the current for impedance measurement flows through each of the coils 21, impedance measurement can be achieved even when the drive current is zero. At this time, the total current flowing through each of the coils 21 is determined such that after two currents based on the first current command value and the second current command value are superimposed, a desired thrust corresponding to the thrust command value is generated. That is, since the first current command value is determined such that the coils 21 do not receive an additional thrust due to the current for impedance measurement, in this embodiment, the influence of the current for impedance measurement flowing through each coil 21 on the thrust of the mover 32 is also reduced.

[0085] In addition, as in the first embodiment, in this embodiment, since the current for impedance measurement can be separately supplied to each of the plurality of coils 21, the impedance of each of the plurality of coils 21 can also be separately obtained.

[0086] The current waveform of the current vector I1 based on the second current command value may have a DC current section in at least a part of the period when the two current command values are superimposed. For the same reason as described in the first embodiment, the influence of the AC current component can be reduced, and the measurement accuracy of the impedance can be improved.

[0087] In the first period, the second current command value may be generated such that the current for impedance measurement flows through the first group of the coils 21, and in the second period, the second current command value may be generated such that the current for impedance measurement flows through the second group of the coils 21 different from the first group. By changing the group of the coils 21 through which the impedance measurement current flows according to the period, compared with the case where the current for impedance measurement flows through all the coils 21 at the same time, the influence on the thrust received by the mover 32 can be further reduced.

[0088] [Third Embodiment]

[0089] Reference will be made to Figures 10 to 11 Describe the transfer device according to the third embodiment. The difference from the transfer device according to the first embodiment is that a three-phase coil is provided as the armature for driving. Components that are the same as those of the transfer device according to the first embodiment or the second embodiment are denoted by the same reference numerals, and their descriptions may be omitted or simplified.

[0090] Figure 10 is a cross-sectional view of the XZ cross-section of the transfer device viewed from the Y direction. Figure 11 is a circuit diagram illustrating the connection of the coils, current detectors, and voltage detectors. The top view of the transfer device viewed from the Z direction is the same as Figure 1 the top view in, so it is omitted.

[0091] As Figure 10As shown in the figure, the transfer device according to the present embodiment includes a plurality of three-phase coils. Each of the three-phase coils has coils 21U, 21V, and 21W. The current flowing through each of the coils 21U, 21V, and 21W is individually controlled by the control device 10.

[0092] As Figure 10 shown in the figure, the dimensions of the coils 21U, 21V, and 21W and the mover 32 are designed such that two or more coils are always opposed to one mover 32. Therefore, even when a plurality of movers 32 are provided, the control device 10 can separately control the thrust acting on each of the movers 32.

[0093] As Figure 11 shown in the figure, the transfer device according to the present embodiment includes voltage detectors 24U, 24V, and 24W and current detectors 23U, 23V, and 23W corresponding to the coils 21U, 21V, and 21W. The current detectors 23U, 23V, and 23W respectively detect the phase currents of the coils 21U, 21V, and 21W. The voltage detectors 24U, 24V, and 24W respectively detect the phase voltages of the coils 21U, 21V, and 21W.

[0094] Based on the phase currents detected by the current detectors 23U, 23V, and 23W, the control device 10 applies a voltage to each phase of the three-phase coil such that the current flowing through the coils 21U, 21V, and 21W becomes a desired value. The voltage detectors 24U, 24V, and 24W can actually measure the phase voltage or obtain the commanded voltage calculated within the control device 10. As Figure 11 shown in the figure, the three-phase coil according to the present embodiment does not have a connection terminal to the neutral point.

[0095] When the control device 10 performs current control of a three-phase coil without a connection terminal to the neutral point, the degree of freedom of the controllable current is 2. Therefore, the control device 10 according to the present embodiment controls the transfer device by using the conversion between three-phase current and two-phase current (for example, by αβ-axis conversion or dq-axis conversion). In addition, the control device 10 according to the present embodiment uses the conversion between three-phase current and two-phase current to control the currents of the coils 21U, 21V, and 21W in the same manner as in the first embodiment or the second embodiment to measure the impedance.

[0096] Specifically, the current vector I in Equation (1) is set to the vector obtained by arranging the two-phase currents of the respective coils. Then, by using Equation (3) or Equation (5), the current command values of the two-phase currents for applying a desired thrust to the mover 32 and flowing the current for resistance measurement through each coil can be calculated.

[0097] The control device 10 can calculate the current command value corresponding to each coil by inversely converting the current command value of the two-phase current into the current command value of the three-phase current, and measure the resistance of each coil using Equation (4) as in the first and second embodiments.

[0098] As described above, according to the present embodiment, even when using a device configuration with a three-phase coil, the control device 10 and the transfer device that can achieve the same effects as those of the first or second embodiment are provided.

[0099] [Other Embodiments]

[0100] It should be noted that the above embodiments are merely examples of the embodiments of the present disclosure, and the technical scope of the present disclosure should not be construed in a restrictive manner. That is, the present disclosure can be practiced in various ways without departing from the technical idea or its basic features. For example, in another embodiment, any embodiment that adds one or some of the configurations of any one (or more) of the embodiments or replaces one or some of the configurations of another embodiment with one or some of the configurations of any one (or more) of the embodiments will also be understood to be an embodiment to which the present disclosure can be applied.

[0101] In the above embodiments, a linear motor in which a magnet is installed in the mover and a coil is installed in the stator is illustrated, but the configuration of the motor is not limited thereto. The motor can be a linear motor in which a coil is installed in the mover and a magnet is installed in the stator. The motor can be a rotary motor rather than a linear motor.

[0102] In addition, in the above embodiments, the use of the motor is illustrated by the transfer device, but the use of the motor is not limited thereto. By appropriately changing the configuration, the control device 10 according to the above embodiments can be applied to devices other than the transfer device.

[0103] According to the present disclosure, a transfer device, a control device, and a control method capable of measuring the impedance of a motor with less restrictions on the circuit configuration can be provided.

[0104] One or more embodiments of the present invention can also be implemented by a computer of a system or apparatus that reads and executes computer-executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be more fully referred to as a "non-transitory computer-readable storage medium") to perform the functions of one or more of the above-described embodiments and / or includes one or more circuits (e.g., an application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiments, and by a method executed by a computer of the system or apparatus that, for example, reads and executes computer-executable instructions to perform the functions of one or more of the above-described embodiments and / or controls one or more circuits to perform the functions of one or more of the above-described embodiments. The computer may include one or more processors (e.g., a central processing unit (CPU), a microprocessing unit (MPU)), and may include a network of separate computers or separate processors to read and execute the computer-executable instructions. The computer-executable instructions may be provided to the computer, for example, from a network or a storage medium. The storage medium may include, for example, one or more of a hard disk, a random access memory (RAM), a read only memory (ROM), a storage device of a distributed computing system, an optical disc (such as a compact disc (CD), a digital versatile disc (DVD), or a Blu-ray disc (BD) TM ), a flash device, a memory card, etc.

[0105] Other embodiments

[0106] Embodiments of the present invention can also be implemented by the following method, that is, by providing software (a program) that performs the functions of the above-described embodiments to a system or apparatus via a network or various storage media, and the method by which a computer or a central processing unit (CPU), a microprocessing unit (MPU) of the system or apparatus reads and executes the program.

[0107] Although the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the present disclosure is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation to encompass all such modifications as well as equivalent structures and functions.

Claims

1. A transfer device, comprising: A motor, including a rotor and a plurality of coils, the plurality of coils being configured to drive the rotor by applying current to each of the plurality of coils; And A control device configured to control the motor, wherein the control device includes a measurement unit configured to measure the impedance of each of the plurality of coils, and includes a control unit configured to control the current flowing through each of the plurality of coils based on a third current command value, in the third current command value, a first current command value and a second current command value indicating the current for measuring the impedance are superimposed, the first current command value indicating a current corresponding to a thrust command value indicating the thrust applied to the rotor, Wherein, when measuring the impedance, the control unit is configured to determine the second current command value such that the rotor does not receive thrust due to the component of the current flowing through each of the plurality of coils corresponding to the second current command value, and Wherein, when generating the current command value, the control unit generates the second current command value in a first period such that the current for measuring the impedance flows in a first group of the plurality of coils, and generates the second current command value in a second period different from the first period such that the current for measuring the impedance flows in a second group of the plurality of coils different from the first group of the plurality of coils.

2. The conveying device according to claim 1, wherein The measurement unit is configured to measure the impedance based on the voltage applied to both ends of each of the plurality of coils and the current flowing through each of the plurality of coils.

3. The conveying device according to claim 2, wherein, The measurement unit is further configured to measure the impedance based on the speed of the rotor.

4. The conveying device according to claim 2, wherein, The measurement unit includes a filter configured to reduce the inductive component of the impedance.

5. The conveying device according to claim 1, wherein The current waveform of the component corresponding to the second current command value includes a DC current section in at least a part of the period when the first current command value and the second current command value are superimposed.

6. The conveying device according to claim 1, wherein, The control unit determines whether the first current command value and the second current command value are to be superimposed based on the first current command value.

7. The transfer device according to claim 1, wherein The motor is a linear motor.

8. A transfer device, comprising: A motor, including a rotor and a plurality of coils, the plurality of coils being configured to drive the rotor by applying current to each of the plurality of coils; And A control device configured to control the motor, wherein the control device includes a measurement unit configured to measure the impedance of each of the plurality of coils, and includes a control unit configured to control the current flowing through each of the plurality of coils based on a third current command value, in the third current command value, a first current command value and a second current command value indicating the current for measuring the impedance are superimposed, the first current command value indicating a current corresponding to a thrust command value indicating the thrust applied to the rotor, wherein, when measuring the impedance, the control unit is configured to determine a second current command value such that due to a component corresponding to the second current command value in the current flowing through each of the plurality of coils, the mover does not receive a thrust, and wherein, the second current command value includes a non-zero vector belonging to the null space of a thrust constant matrix that shows a relationship between the thrust received by the mover and a vector having as elements the currents flowing through each of the plurality of coils respectively.

9. A conveying device, comprising: a motor including a mover and a plurality of coils configured to drive the mover by applying currents to each of the plurality of coils; and a control device configured to control the motor, wherein the control device includes a measurement unit configured to measure the impedance of each of the plurality of coils, and a control unit configured to control the currents flowing through each of the plurality of coils based on a third current command value in which a first current command value and a second current command value indicating a current for measuring the impedance are superimposed, the first current command value indicating a current corresponding to a thrust command value indicating a thrust applied to the mover, wherein, when measuring the impedance, the control unit is configured to determine a second current command value such that due to a component corresponding to the second current command value in the current flowing through each of the plurality of coils, the mover does not receive a thrust, wherein, the plurality of coils include three-phase coils, and wherein, the control unit is configured to determine the current of each phase of the three-phase coils by converting the third current command value from two-phase to three-phase.

10. A conveying device, comprising: a motor including a mover and a plurality of coils configured to drive the mover by applying currents to each of the plurality of coils; and a control device configured to control the motor, wherein the control device includes a measurement unit configured to measure the impedance of each of the plurality of coils, and a control unit configured to control the currents flowing through each of the plurality of coils based on a third current command value in which a first current command value and a second current command value indicating a current for measuring the impedance are superimposed, wherein, the control unit is configured to determine the first current command value based on the second current command value and a thrust command value indicating a thrust applied to the mover, and wherein, when generating the current command value, the control unit generates the second current command value in a first period such that the current for measuring the impedance flows in a first group of the plurality of coils, and generates the second current command value in a second period different from the first period such that the current for measuring the impedance flows in a second group of the plurality of coils different from the first group of the plurality of coils.

11. A method for a conveying device, the conveying device having a motor including a mover and a plurality of coils, the method comprising: Drive the mover using the plurality of coils of the motor by applying current to each of the plurality of coils; and Control the motor, wherein the control includes measuring the impedance of each of the plurality of coils and controlling the current flowing through each of the plurality of coils based on a third current command value in which a first current command value and a second current command value indicating the current for measuring the impedance are superimposed, the first current command value indicating a current corresponding to a thrust command value indicating the thrust applied to the mover, wherein the control includes, when measuring the impedance, determining the second current command value such that the mover does not receive thrust due to a component of the current flowing through each of the plurality of coils corresponding to the second current command value, wherein, during a first period, the second current command value is generated such that the current for measuring the impedance flows in a first group of the plurality of coils, and wherein, during a second period different from the first period, the second current command value is generated such that the current for measuring the impedance flows in a second group of the plurality of coils different from the first group of the plurality of coils.

12. The method according to claim 11, wherein, Measuring includes measuring the impedance based on the voltage applied across each of the plurality of coils and the current flowing through each of the plurality of coils.

13. The method according to claim 12, wherein, Measuring further includes measuring the impedance based on the speed of the mover.

14. The method according to claim 11, wherein, Controlling the current includes determining whether the first current command value and the second current command value are to be superimposed based on the first current command value.

15. A method for a conveying device, the conveying device having a motor including a mover and a plurality of coils, the method including: Drive the mover using the plurality of coils of the motor by applying current to each of the plurality of coils; and Control the motor, wherein the control includes measuring the impedance of each of the plurality of coils and controlling the current flowing through each of the plurality of coils based on a third current command value in which a first current command value and a second current command value indicating the current for measuring the impedance are superimposed, the first current command value indicating a current corresponding to a thrust command value indicating the thrust applied to the mover, wherein the control includes, when measuring the impedance, determining the second current command value such that the mover does not receive thrust due to a component of the current flowing through each of the plurality of coils corresponding to the second current command value, and wherein the second current command value includes a non-zero vector belonging to the null space of a thrust constant matrix that shows the relationship between the thrust received by the mover and a vector having the currents flowing through each of the plurality of coils as elements.

16. A method for a conveying device, the conveying device having a motor including a mover and a plurality of coils, the method including: Drive the mover using the plurality of coils of the motor by applying current to each of the plurality of coils; and Control the motor, wherein the control includes measuring the impedance of each of the plurality of coils, and controlling the current flowing through each of the plurality of coils based on a third current command value in which a first current command value and a second current command value indicating a current for measuring the impedance are superimposed, the first current command value indicating a current corresponding to a thrust command value indicating a thrust applied to the mover. Wherein the control includes, when measuring the impedance, determining the second current command value such that the mover does not receive thrust due to a component of the current flowing through each of the plurality of coils corresponding to the second current command value. Wherein the plurality of coils include three-phase coils, and wherein the current of each phase of the three-phase coils is determined by converting the third current command value from two-phase to three-phase.

17. A processing system, comprising: The transfer device according to any one of claims 1 to 10; and a processing device configured to process a workpiece transferred by the mover.

18. A method of manufacturing an article using a processing system having the transfer device according to claim 10 and a processing device configured to process a workpiece transferred by the mover, the method comprising: Transferring a workpiece by the mover; and Processing the workpiece transferred by the mover by the processing device.

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