Linear motor drive system and linear motor control method

Abstract

In a linear motor (1) in which a plurality of stators (10A, 10B, 10C) are arranged in a distributed manner, the position of the movable element (20) is controlled, preventing unnecessary changes in the speed of the movable element (20) and simultaneously ensuring frictionless operation. A drive device (40) calculates a deviation between a position command from a control unit (41) and a position detected by a position sensor (30) of a corresponding stator (10A, 10B, 10C). Position control is performed by calculating the speed command to be used for speed control of the movable element (20) based on the deviation and a position gain factor. The deviation is calculated at the time when the movable element (20) enters a control range (CAA, CAB, CAC).in which at least a part of the magnetic section (22) of the coil (11) of the stator (10A, 10B, 10C) lies within a region whose position is detected by the position sensor (30) of the corresponding stator (10A, 10B, 10C), and the position of the movable element (20) is calculated from the deviation from the position command and the position command, and the position detected by the position sensor (30) is corrected, wherein the calculated position is the position of the movable element (20) at a time when the movable element (20) enters the control range (CAA, CAB, CAC).

Description

TECHNICAL AREA

[0001] The present invention relates to a linear motor used to drive a base frame or the like of a conveyor system, and in particular to a drive system for a linear motor in which stators are arranged in a distributed manner, and furthermore to a control method for the linear motor. BACKGROUND TECHNOLOGY

[0002] Generally, a linear motor used for conveying parts or products has a structure in which a movable element travels on a stator. However, a structure with a long conveying path has the disadvantage of increasing plant costs, which is detrimental. To eliminate this disadvantage, a method for arranging a plurality of stators in a distributed or separate manner has been proposed. For such a distributed stator arrangement (interrupted arrangement), for example, JP 2004 080 881 A discloses a linear motor velocity change / decrease method that, even when using a bottom-side distributed arrangement system operated in an open loop manner, does not cause a non-uniform velocity by observing a relationship between the position of a side-side subframe and an acceleration.

[0003] Furthermore, a method for controlling a synchronous linear motor with a field magnet arranged on a vehicle and a drive winding arranged on the ground is known from DE 42 292 78 C2. REVELATION OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] Furthermore, in the case of stators arranged separately in a distributed manner, it is necessary to control the position of the movable element taking into account the mutual relationship between a plurality of stators and a plurality of movable elements, unlike in a structure where a (single) movable element is controlled on a (single) stator.

[0005] However, in the technology disclosed by JP 2004 080 881 A, the movable element is accelerated or decelerated in a region where it is opposite the stator, and conversely, in a region where it is not opposite the stator, the movable element is moved or driven forward by an inertial force. This means that in such conventional technology, the movable element is not always controlled, and its position is not fed back for control. Furthermore, in the region where it is opposite the stator, the movable element is accelerated and then decelerated, resulting in changes in speed.

[0006] The present invention was developed taking into account the above circumstances, and one objective of it is to provide a drive system for a linear motor and a method for controlling a linear motor in which stators are distributed or separated to prevent unnecessary changes in speed of the movable element in order to control the position of the movable element smoothly. MEANS TO SOLVE THE PROBLEMS

[0007] To achieve the above objective, the invention presented in claim 1 is a drive system for a linear motor comprising: a linear motor comprising a movable element and a plurality of stators, wherein the movable element is provided with a magnetic section and a scale section, wherein the magnetic section comprises a plurality of magnets arranged side by side, wherein the plurality of stators each comprises a coil and a position sensor to detect from the scale section a position of the movable element in a direction of movement along which the magnets are arranged side by side, wherein the movable element moves in the direction of movement, and a plurality of drive devices, each of which controls an electric current flowing through the coil of the corresponding stator, wherein the multiple stators are arranged in the direction of movement of the movable element, wherein a distance between the coils of the adjacent stators is less than a length of the magnetic section in the direction of movement of the movable element, and a distance between the position sensors of the adjacent stators is less than a length of the scale section, and wherein each of the drive devices comprises: a position control unit for performing position control by calculating a deviation between a position command value from a control unit and a position detected by the position sensor of the corresponding stator, and subsequently calculating a speed command to be used for speed control of the movable element based on the deviation and a position gain factor, and a back-calculation unit for back-calculating the deviation with the speed of movement of the movable element as a speed command, and then for back-calculating the position of the movable element from the deviation and the position command when the movable element enters a control area in which at least one of the magnets of the magnetic section of the coil of the stator is in a region opposite it,a position is detected by the position sensor of the corresponding stator, wherein the position control device performs the position control by correcting the position detected by the position sensor, wherein the position calculated by the back-calculation unit is a position of the movable element at a time when the movable element enters the control area.

[0008] The invention claimed in claim 5 is a method for controlling a linear motor comprising: a movable element provided with a magnetic section and a scale section, wherein the magnetic section comprises a plurality of magnets arranged side by side, and a plurality of stators, each comprising a coil and a position sensor, for detecting a position of the movable element in a direction of movement along which the magnets are arranged side by side, wherein the movable element moves in the direction of movement. where: the multiple stators are arranged in the direction of movement of the movable element, a distance between the coils of the adjacent stators is less than a length of the magnetic section in the direction of movement of the movable element, a distance between the position sensors of the adjacent stators is less than a length of the scale section, A deviation is calculated by multiplying a position gain factor with the speed of movement of the movable element at a time when the movable element enters a control area in which at least one of the magnets of the magnetic section of the stator coil is opposite an area whose position is detected by the stator's position sensor. The position of the movable element is recalculated by subtracting the deviation from the position command from a control device, and The feedback control of the position of the movable element is carried out by correcting the position detected by the position sensor, wherein the recalculated position is the position of the movable element at a time when the movable element enters the control area. IMPACT OF THE INVENTION

[0009] If the movable element moves in such a way that it spans a plurality of stators, it becomes possible according to the present invention to prevent the speed of the movable element from varying unnecessarily and to carry out position control of the movable element, whereby the movable element is driven frictionlessly. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings show: Fig. 1 a block diagram showing an example of a schematic structure of a drive system of a distributed-arrangement linear motor according to one embodiment, Fig. 2 a perspective view of an example in a structure diagram of a stator and a movable element of the distributed arrangement linear motor from Fig. 1, Fig. 3. A top view showing an example of a distributed arrangement of the stators of the Fig. 1 represents, Fig. 4. A side view as a structural diagram showing the relationship between the stator and the movable element. Fig. 1 represents, Fig. 5 a block diagram from which an example of a motor drive device structure is derived Fig. 1 is evident, Fig. 6 A view showing a magnetic sensor having a double set of a full bridge structure, comprising a Fig. 1 visible position detector represents (in Fig. Figure 5 is (A) a top view showing the shape of a thin ferromagnetic metal of the magnetic sensor, and (B) a view showing an equivalent circuit). Fig. 7 a graph showing a sine wave signal and a cosine wave signal, which are generated by the magnetic sensor Fig. 6 are generated, Fig. 8 a sample diagram showing an example in which the movable element moves in such a way that the stators are overstretched, and Fig. 9 a flowchart showing a flowchart example for controlling the motor drive device Fig. 5 is evident. WAYS TO EXECUTIVE THE INVENTION

[0011] A best way of carrying out the present invention is explained below with reference to the attached drawings.

[0012] First, with reference to the drawings, a schematic structure and function of a drive system of a distributed-arrangement linear motor according to the present embodiment is explained, in which a plurality of stators are arranged in a distributed manner.

[0013] Fig. 1 to Fig. Figure 4 shows schematic views illustrating a drive system of a distributed arrangement linear motor according to the present embodiment. Fig. 5 is a block diagram showing an example of the structure of the motor drive device of the Fig. Figure 1 is shown. Furthermore, it is noted that in the following disclosure, the term "distributed-arrangement linear motor" represents a linear motor in which a plurality of stators are arranged in a distributed manner.

[0014] As from Fig. As can be seen in Figure 1, the drive system of the distributed arrangement linear motor comprises: a distributed arrangement linear motor 1 for conveying parts or workpieces, a plurality of motor drives (motor drive devices) 40 (40A, 40B, 40C) for controlling the distributed arrangement linear motor 1, and a higher-level control device 50 for controlling the multiple motor drives 40 (40A, 40B, 40C).

[0015] The distributed-arrangement linear motor 1 has a plurality of stators 10 (10A, 10B, 10C). The distributed-arrangement linear motor also has a movable element 20, which is movable relative to the stators 10 by magnetic force between them. Furthermore, the distributed-arrangement linear motor 1 also has a plurality of position detectors (position detection devices) 30, which are mounted on the respective stators 10A, 10B, 10C. The respective position detectors 30 detect the positions of the movable element 20 relative to the stators. In addition, the distributed-arrangement linear motor 1 has position information switches (switching devices) 35, which are provided for the respective stators 10A, 10B, 10C.The respective position information switches 35 act to switch signals from the multiple position detectors 30 of the arranged stators, and in the distributed-arrangement linear motor 1, the stators 10A, 10B, 10C are arranged separately at predetermined intervals in the conveying direction of the moving element. Furthermore, it is noted that the distributed-arrangement linear motor 1 is an example of a flat-type linear motor.

[0016] The higher-level control unit 50 and the respective motor drives 40A, 40B, 40C are connected to each other by means of control lines 51. The motor drives 40A, 40B, 40C and the position information switches 35, which correspond to the motor drives 40, are connected to each other by means of an encoder cable 52. The position information switches 35 and the position detectors 30, which are intended for the corresponding stator 10A, 10B or 10C, are also connected to each other by means of the encoder cable 52. The motor drives 40A, 40B and 40C and the stators 10A, 10B, 10C are connected to each other by means of power cables 53.

[0017] Furthermore, the movable element 20 is guided along a predetermined track by a guide device (not shown), and a distance is maintained between the movable element 20 and each stator 10.

[0018] As from Fig. 2 and Fig. As can be seen in Figure 4, each of the stators 10 is supplied with a three-phase current and has a coil 11 that acts magnetically on the movable element 20, and a protruding pole 12 around which the coil 11 is wound. The coil 11 has three types of coils: a U-phase coil 11a, a V-phase coil 11b, and a W-phase coil 11c. The protruding pole 12 has three types of protruding poles 12, namely a pole 12a for the U-phase, a pole 12b for the V-phase, and a pole 12c for the W-phase, each corresponding to the coils 11a, 11b, and 11c, respectively. The coils 11a, 11b and 11c and the protruding poles 12a, 12b, 12c form a periodic structure in which the coils and poles are arranged periodically in one direction of the relative motion between the stators 10 and the movable element 20 in the sequence U-phase, V-phase and W-phase.This means that the coils 11 and the poles 12 form the periodic structure of the U-phase, the V-phase and the W-phase in the longitudinal direction of the stators 10 (the direction of the relative motion) as an example of a direction of motion.

[0019] Furthermore, the core section of the electromagnet of the stator 10, which has the protruding pole 12, is formed from a magnetic material that exhibits a lower magnetic hysteresis loss, such as silicon steel, and, as shown from Fig. As can be seen in Figure 2, the core section forms the protruding pole 12, which extends in the width direction of the stator 10 to protrude on one side opposite the movable element 20, with such protruding poles 12 being arranged next to each other in a comb-like manner in the longitudinal direction of the stator 10.

[0020] Furthermore, the movable element 20 is, as shown Fig. 2 shown, equipped with a table 21 on which parts or workpieces rest, and a magnet 22 for driving (drive magnet 22) is mounted on the underside of the table 21, the movable element 20 thus serving as a support for the parts or workpieces.

[0021] The driving magnets 22 each have: an N-pole magnet 22a, which has an N pole on a side opposite the stators 10, and an S-pole magnet 22b, which has an S pole, and a periodic structure in which the N-pole magnets 22a as N poles and the S-pole magnets 22b as S poles are arranged alternately periodically in the direction of the relative motion between the stators 10 and the movable element 20. This means that the movable element 20 has the periodic N-pole / S-pole structure in the direction of the relative motion between the stators 10 and the movable element 20. Furthermore, the driving magnet 22 is an example of a magnetic section or scale section.

[0022] The movable magnetic field is generated according to the direction and / or strength of the three-phase alternating current passing through each of the coils 11a, 11b, and 11c of the stator 10, and the protruding poles 12a, 12b, 12c, and the N-pole magnet 22a and the S-pole magnet 22b interact magnetically to effect the relative movement between the stator 10 and the movable element 20 in the longitudinal direction of the stator 10. This means that the stator 10 and the movable element 20 interact magnetically, and the movable element 20 performs the relative movement in the longitudinal direction of the stator 10.

[0023] The position detector 30 (30L, 30R) shows, as from Fig. Figure 4 shows: a magnetic sensor 31 for detecting magnetism and a position detection circuit 32 for converting a signal from the magnetic sensor 31 into a signal to specify a position and detecting this position. Here, the position detector 30 is an example of a position sensor.

[0024] The position detectors 30 are, as shown Fig. 1 and Fig. As can be seen in Figure 3, the detectors are arranged outside the projecting poles 12, which are located at the two longitudinal ends of the stators 10, and are arranged in the lateral direction of the stators 10 at central sections. The magnetic sensor 31 is arranged to face the side of the stator 10 opposite the movable element 20. Furthermore, it may be desirable for the positions of the detectors 30 to be spaced apart in the longitudinal direction of the stators 10, provided they are not affected by the coils 11. As shown in Figure 3, the detectors 30 are arranged outside the projecting poles 12, which are located at the two longitudinal ends of the stators 10, and are arranged in the lateral direction of the stators 10 at central sections. The magnetic sensor 31 is arranged to face the side of the stator 10 opposite the movable element 20. Fig. As can be seen in Figure 4, the position detector 30R of the stator 10A is located outside the coil 11c at the right end and the position detector 30L of the stator 10B is located outside the coil 11a at the left end.

[0025] The magnetic sensor 31 detects the magnetic field generated by the drive magnet 22, which extends in the direction of the relative motion between the stator 10 and the movable element 20. The magnetic sensor 31 detects a change in the magnetic field due to the relative motion between the stator 10 and the movable element 20. In particular, the magnetic sensor 31 is a sensor that detects the direction of the magnetic field (flux vector). In this case, the drive magnet 22 acts as an example of a scale segment for detecting the position of the movable element 20.

[0026] As from Fig. 1 and Fig. As can be seen in Figure 5, the position information switch 35 then generates an output to the motor drive 40 by selecting one of the input signals from a plurality of position detectors 30. For example, the position information switch 35 outputs an input signal that was the last input. Furthermore, if the input signal is a single signal, the position information switch 35 outputs that signal as is, and if no signal is input, no output signal is generated.

[0027] The magnetic sensor 31, which forms the position detector 30, is explained below with reference to the attached drawings.

[0028] Fig. Figure 6 shows a double set of a magnetic sensor of a full bridge structure, which serves as the position detector of the Fig. 1 forms.

[0029] The magnetic sensor 31 of the position detector 30 comprises: a magnetic resistance element formed from a silicon or glass substrate, and a thin ferromagnetic metal film formed on the substrate, consisting of an alloy whose main component is a ferromagnetic metal, for example, nickel, iron, or the like. The magnetic sensor is referred to as an AMR sensor (AMR, Anisotropic Magnetoresistance) because its resistance value varies in a specific field direction.

[0030] As from Fig. As can be seen in Figure 6, the magnetic sensor of the position detector 30 is formed on a substrate such that elements of double sets of a full-bridge structure are inclined at 45 degrees to each other to account for the direction of movement. Output powers VoutA and VoutB obtained from the double sets of full-bridge circuits form a cosine wave and a sine wave, respectively, which have a phase difference of 90 degrees to each other, as shown in Figure 6. Fig. Figure 7 shows that since magnets 22a and 22b are arranged alternately in the direction of the relative motion, the output of the position detector 30 forms cosine and sine waves. As mentioned earlier, the position detector 30 outputs the change in direction of the magnetic field, which is periodically generated by the relative motion based on the periodic structure of the drive magnet 22, in order to drive the movable element 20 as a sine wave signal and a cosine wave signal with a phase difference of 90 degrees.

[0031] The output signal from the magnetic sensor is fed into the position detection circuit 32, in which the output signal is converted into phase angle data, which have a higher resolution by adding a digital-like interpolation processing to the sine wave signal and the cosine wave signal, which have a phase difference of 90 degrees.

[0032] The position detector 32 then generates an A-phase encoder pulse signal (corresponding to the sine wave signal) and a B-phase encoder pulse signal (corresponding to the cosine wave signal) from these phase angle data, and generates a Z-phase pulse signal once per periodic cycle. The position signals of the A-phase encoder pulse signal, the B-phase encoder pulse signal, and the Z-phase pulse signal are input into the position information switch 35. As shown from Fig. As can be seen in Figure 5, the motor drive 40 controls the power converter 42 in response to the position signals from the A-phase encoder pulse signal, the B-phase encoder pulse signal and the Z-phase pulse signal.

[0033] The following describes the arrangement relationships between the stators 10A, 10B and 10C and between the stators 10A, 10B and 10C and the movable element 20 with reference to Fig. 3 and Fig. 4 explained in detail.

[0034] The stators 10A, 10B and 10C are arranged at a specific distance from each other (stator spacing), in the order shown from the left side of the figure along the longitudinal direction of the stators 10. A distance Dc between the coils of the adjacent stators 10A and 10B (distance between the adjacent stator coils) is given as an example of the stator spacing.

[0035] The adjacent stator coil spacing Dc is, for example, a distance between the right end of coil 11c of the stator at the right end and the left end of coil 11a of stator 11B at the left end.

[0036] As a further example of the stator coil spacing, a distance Ds1 between the position detectors 30 of the adjacent stators 10A and 10B (adjacent stator sensor distance) is also mentioned. This distance Ds1 between the position detectors 30 is, for example, the distance between the magnetic sensor 31 of position detector 30R of stator 10A and the magnetic sensor 31 of position detector 30L of stator 10B. This means that the adjacent stator sensor distance Ds1 is the distance between the magnetic sensor 31 of the position detector 30 closer to stator 10B and the magnetic sensor 31 of the position detector 30 closer to stator 10A and the position detector 30 of stator 10B.

[0037] Furthermore, the distance Dc between the adjacent stator coils is smaller than the length Lmv of the drive magnet 22. The length Lmv of the drive magnet 22 is, for example, as shown in Fig. 4 shows a length between the left end of the S-pole magnet 22b and the left end of the movable element 20 in Fig. 4 and the right end of the N-pole magnet 22a on its right end face. In the case where the distance Dc between the adjacent stator coils is less than the length Lmv of the drive magnet 22, at least one section of the drive magnet 22 of the movable element 20 is in a state in which it is always opposite at least one of the coils 11 of the stators 10A and 10B. This means that the movable element 20 is in a state in which it is able to receive thrust from at least one of the stators 10A and 10B. This state applies in a ratio between the stators 10B and 10C.

[0038] Furthermore, the adjacent stator sensor distance Ds1 is smaller than the length Lmv of the drive magnet 22. Additionally, the distance Ds2 between the position detector 30L (not shown) of stator 10A and the position detector 30R of the magnetic sensor 31 is also determined such that it is smaller than the length Lmv of the drive magnet 22. This configuration applies equally to stators 10B and 10C. In the state where the distances Ds1 and Ds2 satisfy the above conditions, the drive magnet 22 assumes a state for the movable element 20 in which it is always able to detect the magnetism of one of the position detectors 30 via the magnetic sensor 31.

[0039] Furthermore, the coil 11 of the stator 10 (10A, 10B, 10C) is arranged between the position detectors 30L and 30R. Accordingly, in a state where at least part of the drive magnet 22 of the movable element 20 faces the coil 11 of the stator 10, at least one of the position detectors 30L and 30R is in a state of generating the position signal, that is, in a state suitable for detecting the position of the movable element 20. A state in which thrust is imparted by the stator 10 to the movable element 20 is a state suitable for detecting the position of the movable element 20, i.e., a state suitable for controlling the position of the movable element 20. As an example of the controllable range, a region in which the position of the movable element 20 is controlled is referred to as the control range CA (CAA, CAB, CAC) of the stator 10 (10A, 10B, 10C). As can be seen from Fig. As can be seen in Figure 3, the control range CAA is a range extending from the left end of coil 11a of the left end of stator 10A to the right end of coil 11c of the right end of the same in the relative direction of movement of the movable element 20 (i.e., a range corresponding to the length of coil 11 of stator 10A in the longitudinal direction). Similarly, stators 10B and 10C also have control ranges CAB and CAC, respectively.

[0040] As from Fig. As can be seen in Figure 4, the position detector 30L is arranged in a position at a distance from the coil 11 of the stator 10B corresponding to the distance D1. On the other hand, the position detector 30R is arranged in a position at a distance from the coil 11 of the stator 10A corresponding to the distance Dr. The section between these distances is capable of detecting the position of the movable element 20, but is not controllable because the coil 11 is not opposite the drive magnet 22 of the movable element 20.

[0041] The higher-level control unit 50 has a CPU, RAM, and ROM and issues a position command, specifying a target position of the movable element 20, or a speed command, specifying a target speed of the movable element 20, to the respective motor drives 40A, 40B, and 40C. Furthermore, it is noted that the higher-level control unit 50 is an example of a control device.

[0042] Here the motor drive shows 40, as from Fig. Figure 5 shows: a control device 41 for controlling a current that is to flow to the stator 10 of the linear motor, a power converter 42 for converting power from an energy source 45 in response to information from a sensor or the like, and a current sensor 43 for detecting power that is to flow through the power converter 42 to the stator 10. Furthermore, the motor drive 40 is shown here as an example of a drive device.

[0043] The main reason for providing the motor drives 40 for the respective stators 10 lies in the independent control of the movable elements 20 in a case where multiple movable elements 20 are present. This means that if each of the multiple movable elements 20 is placed on each of the different stators 10, each motor drive can independently control the current supplied to each stator 10, so that the direction of movement, the speed of movement, and so on can be controlled independently by each of the movable elements 20.

[0044] The control unit 41 comprises a CPU, RAM, ROM, Flash ROM, and the like, and is connected to the current sensor 43, the higher-level control unit 50 via a control line 51, and the position information switch 35 via an encoder cable 52. Furthermore, the control unit 41 is described here as an example of a position control device, a feedback device, and a motion velocity calculator.

[0045] In addition, the control unit 41 controls the power converter 42, for example a PWM converter (PWM: Pulse Width Modulation), and finally controls the current to be supplied to the coil 11 of the stator 10.

[0046] In particular, the control unit 41 performs feedback control (position control) of the position of the movable element 20 as an example of position control means. In such position control, the control unit 41 calculates the current position of the movable element 20 from the pulse count of the position signal input via the encoder cable 52. The control unit 41 then calculates a position deviation by determining the difference between the position command value and the current position. Furthermore, the control unit 41 multiplies a position gain factor, which is predetermined as a proportional gain, to calculate the velocity command value. Finally, the control unit 41 differentiates the current position with respect to time and calculates the current velocity of the movable element 20.The control unit 41 then calculates a torque command value, for example using a PID controller, based on the speed command value and the current speed. The control unit 41 also controls the power converter 42 to supply current to the coil 11 according to the torque command value.

[0047] The following refers to the Fig. 8 describes a control mode in a case where the movable element 20 moves in a state in which it spans the space between stator 10A and stator 10B. It is further noted that the Fig. The 8 evident states represent the case in which the distance Ds2 between the sensors of the same stator is approximately equal to the length Lmv of the movable element 20.

[0048] In one of Fig. In the state shown in Figure 8(A), the movable element 20 is arranged in the control area CAA of the stator 10A, and the drive magnet 22 for the movable element 20 is mounted on the two position detectors 30L and 30R of the stator 10. In this arrangement, the two position detectors 30L and 30R transmit signals. Here, it is assumed that the position information switch 35 outputs the signal from position detector 30R. At this point, the higher-level control unit 50 outputs the position command value to the motor drive 40A and the motor drive 40B to move the movable element 20 from the stator 10A to the stator 10B. On the other hand, the position detectors 30L and 30R of the stator 10B do not generate a signal at this point. Furthermore, Figure 8(A) shows that the position detectors 30L and 30R of the stator 10B do not generate a signal at this point. Fig. Eight arrows indicate the presence or absence of outputs from position detectors 30L, 30R and position information switch 35. Furthermore, the types of arrows indicate which of the signals from position detectors 30L and 30R is output by position information switch 35.

[0049] The control unit 41 of the motor drive 40A performs position control in response to the position command value from the higher-level control unit 50 and the position signal from the position detector 30R of the stator 10A. At this point, the motor drive 40A supplies current to the stator 10A because a deviation occurs between the position command value and the actual position of the movable element 20. Thus, the movable element 20 moves as shown. Fig. 8(B) can be seen in the figures to the right, since the thrust force is applied from the stator 10 to the movable element 20.

[0050] As from Fig. As can be seen in Figure 8(C), the movable element 20 runs on the stator 10B and enters the control area CAB of the stator 10B. Even when the movable element 20 enters the control area CAB, it is not completely separated from the control area CAA of the stator 10A. This means that part of the magnets 22 for driving (drive magnet 22) the movable element 20 is opposite the coil 11 of the stator 10A. Thus, it can be determined that the position control by the control device 41 of the motor drive 40A has been continued.

[0051] Furthermore, at the instant the movable element 20 reaches the stator 10B, the position detector 30L of the stator 10B generates a signal that is sensitive to the drive magnet 22, which is located on the lower surface of the movable element 20. The position information switch then changes from the state in which no position signal is output to the state in which a position information signal is ready to be output. At this point, the control unit 41 of the motor drive 40B detects the change in the signal from the position information switch 35.

[0052] In an example where the position detector 30L of the stator 10B begins to generate a signal, the position of the position detector 30L is defined here as an origin (start) point. Then, the control unit 41 of the motor drive 40B initializes the position command value and the current position of the movable element 20 from this origin point into the relative positions. Subsequently, based on this position control start, the position control by the control unit 41 of the motor drive 40B and the power supply to the stator 10B by the motor drive 40B begin.

[0053] However, if the control unit 41 of the motor drive 40B performs the position control as in this state, the following phenomenon occurs.

[0054] Even when the movable element 20 moves forward into the control area CAB of the stator 10B, the control unit 41 of the motor drive 40A continues with position control, and the movable element 20 moves due to the thrust force from the stator 10A. Even when the movable element 20 is moving, as is the case when viewed from the perspective of the control unit 41 of the motor drive 40B, the position command value and the actual position of the movable element 20 remain constant. This means that no positional deviation is generated, and consequently, no current is supplied to the stator 10B by the motor drive 40B, and no thrust force is applied to the movable element 20 by the stator 10B.

[0055] However, since the thrust force is applied by the stator 10A to the movable element 20, the movable element 20 continues to move continuously, as shown in the diagram. Fig. 8D is evident until the drive magnet 22 of the movable element separates from the position opposite the coil 11 of the stator 10A. The drive magnet 22 of the movable element 20 is separated from the position opposite the coil 11 of the stator 10A, and as soon as the thrust force of the movable element 20 disappears, the movable element 20 is decelerated. By decelerating the movable element 20, the positional deviation is initially generated from the perspective of the control unit 41 of the motor drive 40B. Corresponding to such a phenomenon, the motor drive 40B supplies current to the stator 10B, and thrust force is applied by the stator 10B to the movable element 20, and it is then accelerated again and continues to move, as shown. Fig. 8(E) is evident. This means that the change in speed is caused at a time when the movable element 20 is moving in an overvoltage state between the adjacent stators.

[0056] Then, when the movable element 20 spans the adjacent stators, in the present embodiment the current position of the movable element 20 is corrected to perform position control while the movable element 20 is moved smoothly.

[0057] In particular, as can be seen from Fig. As shown in Figure 8(C), the control unit 41 of the motor drive 40B, as an example of the means for calculating the speed of movement, differentiates the position command value from the higher-level control unit 50 in a temporal manner when the movable element 20 enters the control area CAB of the stator 10B, in order to calculate the speed of movement (traveling) of the movable element in response to the position command value. After the output of the position signal from the position detector 30L of the stator 10B has begun, the movable element 20 enters the control area CAB when the movable element 20 moves through the distance corresponding to the distance D1 between the position detector 30L and the coil 11 of the stator 10B.Accordingly, the control unit 41 calculates the movement distance of the movable element 20 in the drawing in the right direction based on the pulse of the position signal after the position detector 30L starts outputting the position signal. Then, when the movable element 20 moves to the right by the distance D1 according to the drawing, the control unit 41 distinguishes that the movable element 20 enters the control area CAB. Furthermore, the distance D1 and the distance Dr of the corresponding stator are preset in a flash ROM of the control unit 41.

[0058] In the next step, the control unit 41, as an example of the back-calculation method, performs a back-calculation of the position deviation from the calculated motion velocity, which is identified as the velocity command value. This means that the control unit 41 calculates the position deviation by dividing the calculated motion velocity by the position gain factor. Subsequently, as another example of the back-calculation method, the control unit 41 calculates the current position of the movable element 20 from the back-calculated position deviation. This means that the control unit 41 calculates the current position of the movable element 20 by obtaining the difference between the position command value from the higher-level control unit 50 and the back-calculated position deviation.

[0059] The control unit 41 then begins position control using the recalculated current position of the movable element 20. This means that the control unit 41 calculates the position deviation from the recalculated current position of the movable element 20 and the input position command value, and then calculates the velocity command value by multiplying the position gain factor by the position deviation. The control unit 41 then performs position control, adding a movement distance to the current position of the movable element 20, corresponding to the pulse count of the position signal input from the position detector 30. According to the steps described above, the control unit 41 corrects the current position of the movable element 20.

[0060] According to the above-mentioned position correction, a state is brought about in which the position deviation, which corresponds to the speed of movement, is calculated when the movable element 20 enters the control area CAB of the stator 10B, and thus current is supplied to the stator 10B from the motor drive 40B and the movable element 20 receives the thrust force from the stator 10B.

[0061] This means that the movable element 20 receives the thrust force from both stator 10A and stator 10B from the in Fig. 8(C) position shown in the Fig. 8(D) visible position is obtained. After the from Fig. In the state shown in Figure 8(D), the movable element 20 receives the thrust force only from the stator 10B. Subsequently, since the position deviation is recalculated based on the speed of movement, the movable element 20 can be adjusted by differentiating the position command value over time. Fig. 8(C) position is obtained, from the control area CAA of stator 10A smoothly moved into the control area CAB of stator 10B without changing the actual speed of movement.

[0062] Although an error may be caused between the current position of the movable element 20 obtained by the correction and the actual current position of the movable element 20, which corresponds to the back-calculated position deviation, causing such an error is not a problem if this error is within a range that is permissible when using the distributed arrangement linear motor 1.

[0063] The operation of the control unit 41 of the motor drive 40 is described below with reference to the flowchart of the Fig. Section 9 explains what a flowchart is, which is a flowchart example for the control unit of the motor drive from Fig. 5 represents.

[0064] The Fig. The sequence shown in section 9 begins in a drive "on" state. First, the control unit 41 assesses whether a position command value is entered from the higher-level control unit 50 or not (step S1). At this point, if no position command value is entered (step S1: NO), the assessment of step S1 is repeated.

[0065] In a case where the position command value is entered (step S1: YES), the control unit 41 scans the entered position command value and assesses whether the movable element 20 is within the control area CA of the stator 10 or not (step S2). At this point, the process returns to step S1 if the movable element 20 is not within the control area CA (step S2: NO).

[0066] In a case where the movable element 20 is within the control range CA of the stator 10 (step S2: YES), the control unit 41 assesses whether the movable element 20 was within the control range CA at the previous sampling time or not (step S3: YES). In a case where the movable element 20 was not within the control range CA at the previous sampling time and is within the control range CA at the current sampling time, it is indicated that the movable element 20 is entering the control range for the first time during this sampling operation. Then, in a case where the movable element 20 was not within the control range CA at the previous sampling time (step S3: NO), the input position command value is time-differentiated to calculate the velocity command value (step S4).Since the position command value was entered before the movable element 20 entered the control area CA, the position command value can be differentiated over time.

[0067] The control unit 41 then calculates the position deviation by dividing the calculated velocity command value by the position gain factor (step S5). The control unit 41 then calculates the current position by subtracting the calculated position deviation from the input position command value (step S6).

[0068] The control unit 41 then performs an initial position control, whereby the current position thus calculated is the current position of the movable element 20 (step S7). This means that the control unit 41 calculates the position deviation between the input position command value and the current position calculated in step S6, and then calculates the velocity command value by multiplying this position deviation by the position gain factor. Subsequently, the control unit 41 performs the velocity control and the torque control based on the calculated velocity command value, and so on. After these calculations, the control unit 41 returns to performing step S1.

[0069] As mentioned above, when evaluating the subsequent step S3 (Step S3: Yes), at the start of the position control, it is assessed whether the movable element 20 was within the control range at the previous sampling time. If so, the control unit 41 performs a standard position control (Step S7). Here, the control unit 41 calculates the movement distance of the movable element 20 from the previous sampling time using the input position signal and the current position of the movable element 20, which is to be used for the current position control, by adding the calculated movement distance to the current position of the movable element at the previous sampling time.

[0070] As explained above, the drive system of the distributed arrangement linear motor according to the present embodiment comprises: the linear motor, which has the movable element 20 and the stators 10A, 10B, 10C, wherein the movable element 20 is provided with the magnet 22 for driving, wherein the stators 10A, 10B, 10C each have the coil 11 and the position detector 30 for detecting the position during the relative movement of the movable element 20 from the drive magnet 22, wherein the movable element 20 moves in the direction of the relative movement to the stators 10, and the motor drives 40A, 40B, 40C, which each control the electric current to be supplied to the coil 11 of the corresponding stators 10A, 10B, 10C.

[0071] The stators 10A, 10B, 10C are arranged in the direction of the relative motion of the movable element 20, wherein the distance between the coils of the adjacent stators is less than (not greater than) the length of the drive magnet 22 in the direction of the relative motion and the distance Ds1 between the sensors of the adjacent stators is less than the length of the drive magnet 22 in the direction of the relative motion.

[0072] The control unit 41 of each of the motor drives 40A, 40B, 40C calculates the position deviation between the position command value from the higher-level control unit 50 and the current position of the movable element 20, which is detected by the position detector 30 of the corresponding stator, and performs the position control to calculate the speed command value on the basis of the calculated position deviation and the position gain factor.When the movable element 20 enters the control range within the area whose position is detected by the position detector 30 of the corresponding stator, in which at least one of the magnets of the drive magnets 22 is opposite the coil of the corresponding stator, the control device 41 continues to operate to perform the recalculation of the position deviation using the speed of the movable element as the speed command value, recalculates the position of the movable element 20 from the position deviation and the position command value, and by taking the recalculated position as the current position of the movable element 20 at the time of entering the control range, the current position detected by the detector 30 is corrected in order to control the position of the movable element.

[0073] Accordingly, causing an undesirable change in the speed of movement of the movable element 20 can be prevented and the movable element can thus be controlled with respect to its position, whereby the movable element 20 is driven frictionlessly when the movable element 20 is in the state in which it spans adjacent stators.

[0074] Furthermore, the control unit 41 calculates the movement speed of the movable element 20 by differentiating the position command value and calculates the position deviation using this movement speed as the velocity command value. Accordingly, position control can begin from the moment the movable element 20 enters the control range.

[0075] Since the magnetic sensor 31 of the position sensor 30 detects the current position of the movable element 20 by detecting the magnetism of the drive magnet 22, it is also not necessary to provide the movable element 20 with the linear scale, thus simplifying the structure of the linear motor.

[0076] Although the control unit 41 calculates the movement speed of the movable element 20 by differentiating the position command value, in the embodiment described above it is also possible to calculate the movement speed of the movable element 20 by differentiating the current position of the movable element as detected by the position detector 30, and then to calculate the position deviation using this movement speed as the velocity command value. According to this modification, position control can begin by reflecting the actual movement speed of the movable element 20.

[0077] Although the magnetic sensor 31 detects the position of the movable element 20 by detecting the magnetism of the drive magnet 22, in the embodiment described above it is also possible to position the linear scale for the movable element and to position a position sensor that can read the linear scale for the stator 10 optically or magnetically. Furthermore, with such a modification it is not necessary to position the position sensor outside the coil 11, and the position sensor can be arranged at both end sections or inside the coil 11 in the direction of the relative movement of the movable element 20.In each of the above cases, the distance Dc between the coils of the adjacent stators is smaller than the length of the drive magnet 22 in the direction of the relative motion of the movable element, and the distance Ds1 between the sensors of the adjacent stators is smaller than the length of the drive magnet 22 in the direction of the relative motion.

[0078] In an arrangement where the position sensors are located at both end sections or within the coil 11 in the direction of the relative movement of the movable element 20, an area extending from the left end-side position sensor to the right end-side position sensor is considered the control area CA. Since the output start timing of the position signal from the position sensor and the entry timing of the movable element into the control area CA coincide, it is therefore not necessary for the control device 41 to compensate for the distance corresponding to distance D1 or Dr.

[0079] At a time when the control device 41 calculates the movement speed of the movable element 20 by differentiating the position command value as the velocity command value, this modification also requires the control device 41 to start the position control with a slightly delayed time adjustment from the time the movable element enters the control area CA, since it is necessary to perform several sampling operations on the position signal from the position sensor.

[0080] In a case where the control device 41 calculates the movement speed of the movable element 20 as the velocity command value by differentiating the position command value, the control device 41 can begin position control in the time alignment when the movable element 20 enters the control area CA, since the position command value is entered before the movable element 20 enters the control area CA.

[0081] Furthermore, it may be possible to extend the coil section 11 of the stator 10 such that the distance between the left end position sensor and the right end position sensor exceeds the length of the linear scale (the length Lmv of the drive magnet 22 when the position of the movable element 20 is detected by the position sensor by detecting the magnetism of the drive magnet 22). In such a case, it may also be possible to position a position sensor between the left end position sensor and the right end position sensor, so that the distance between the adjacent position sensors becomes smaller than the length of the linear scale. REFERENCE MARK

[0082] 1 --- Distributed-arrangement linear motor; 10 (10A, 10B, 10C) --- Stator; 11 --- Coil; 20 --- Moving element; 22 --- Drive magnet; 22a --- N-pole magnet; 22b --- S-pole magnet; 30, 30L, 30R --- Position detector; 40 (40A, 40B, 40C) --- Motor drive; 41 --- Control unit; 50 --- Higher-level control unit, CAA, CAB, CAC --- Control areas.

Claims

[1] A drive system for a linear motor (1), comprising: a linear motor (1) comprising: a movable element (20) and a plurality of stators (10a, 10B, 10C), wherein the movable element (20) is provided with a magnet portion and a scale portion, wherein the magnet portion has a plurality of magnets (22a, 22b) arranged side by side, wherein the plurality of stators (10A, 10B, 10C) each has a coil (11) and a position sensor (30) for detecting from the scale portion a position of the movable element (20) in a movement direction along which the magnets (22a, 22b) are arranged side by side, wherein the movable element (20) moves in the movement direction, and a plurality of drive devices, each of which controls an electric current flowing through the coil (11) of the corresponding stator (10A, 10B, 10C), wherein the plurality of stators (10A, 10B, 10C) are arranged in the direction of movement of the movable element (20), a distance (Dc) between the coils (11) of the adjacent stators (10A, 10B, 10C) is smaller than a length (Lmv) of the magnet section in the direction of movement of the movable element (20), and a distance (Ds1) between the position sensors (30) of the adjacent stators (10A, 10B, 10C) is smaller than a length (Lmv) of the scale section, and wherein each of the drive devices comprises: a position control unit for performing position control by calculating a deviation between a position command value from a control unit (41) and a position detected by the position sensor (30) of the corresponding stator (10A, 10B, 10C), and then calculating a speed command to be used for speed control of the movable element (20) on the basis of the deviation and a position gain factor, and a back-calculation unit for back-calculating the deviation using the moving speed of the movable element (20) as a speed command, and then back-calculating the position of the movable element (20) from the deviation and the position command when the movable element (20) is within a range of which a position is detected by the position sensor (30) of the corresponding stator (10A, 10B,10C) is detected, enters a control area (CAA, CAB, CAC) in which at least one of the magnets (22a, 22b) of the magnet section is opposed to the coil (11) of the stator (10A, 10B, 10C), wherein the position control device performs the position control by correcting the position calculated by the position sensor (30), wherein the position calculated by the back-calculation unit is a position of the movable element (20) at a time when the movable element (20) enters the control area (CAA, CAB, CAC). [2] The drive system of a linear motor (1) according to claim 1, wherein each of the drive devices further comprises a moving speed calculating unit for calculating a moving speed by differentiating the position command value, and the back-calculating unit performs back-calculation of the deviation from the moving speed calculated by the moving speed calculating unit. [3] The drive system of a linear motor (1) according to claim 1, further comprising a moving speed calculation unit for calculating a moving speed by differentiating the position detected by the position sensor (30), wherein the back calculation unit performs back calculation of the deviation from the moving speed calculated by the moving speed calculation unit. [4] The drive system of a linear motor (1) according to any one of claims 1 to 3, wherein the position sensor (30) detects the position of the movable member (20) by detecting the magnetism of the magnet portion as the scale portion. [5] A method for controlling a linear motor (1) comprising: a movable member (20) provided with a magnet portion and a scale portion, the magnet portion having a plurality of magnets (22a, 22b) arranged side by side, and a plurality of stators (10A, 10B, 10C) each having a coil (11) and a position sensor (30) for detecting a position of the movable member (20) in a moving direction along which the magnets (22a, 22b) are arranged side by side, the movable member (20) moving in the moving direction, wherein: the plurality of stators (10A, 10B, 10C) are arranged in the direction of movement of the movable element (20), a distance (Dc) between the coils (11) of the adjacent stators (10A, 10B, 10C) is smaller than a length (Lmv) of the magnet section in the direction of movement of the movable element (20), a distance (Ds1) between the position sensors (30) of the adjacent stators (10A, 10B, 10C) is smaller than a length (Lmv) of the scale section, a deviation is recalculated by dividing the movement speed of the movable element (20) by a position gain factor at a time when the movable element (20) enters a control area (CAA, CAB, CAC) in which at least one of the magnets (22a, 22b) of the magnet section is opposite the coil (11) of the stator (10A, 10B, 10C) in an area whose position is detected by the position sensor (30) of the stator (10A, 10B, 10C), the position of the movable element (20) is recalculated by subtracting the deviation from the position command from a control device (41), and a feedback control of the position of the movable element (20) is performed by correcting the position detected by the position sensor (30), wherein the back-calculated position is the position of the movable element (20) at a time at which the movable element (20) enters the control area (CAA, CAB, CAC).

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