Control device and transport system

Abstract

A control device (1) can be applied to a transport system (10) that comprises a mobile body (4) that moves along a transport path (8), a plurality of coil units (3) that are provided along the transport path (8), a scale head (5) that is provided to the mobile body (4), scale units (6) that are provided at a predetermined interval along the transport path (8) and detect the position of the scale head (5), and a drive device (2) that supplies drive current to the coil units (3). The control device (1) comprises a mobile body position calculator (15) that calculates a mobile body position that is position information for the mobile body (4) on the basis of detection data from the scale units (6), a mobile body speed calculator (121) that calculates a mobile body speed from the difference between a most recently calculated value and a previously calculated value for the mobile body position, and a mobile body speed corrector (122) that corrects the mobile body speed in accordance with the mobile body position.

Description

Control device and transport system

[0001] The present disclosure relates to a control device and a transport system that are configured to be applicable to a transport system that transports objects.

[0002] In production lines where factory automation is implemented, such as production lines for assembling industrial products or for packaging food, conveyance systems for transporting workpieces are commonly used. In recent years, conveyance systems have been widely used in which the conveyance path for transporting the workpieces is divided into multiple zones, and carts carrying the workpieces are driven by control devices located in each zone. This type of conveyance system is one of the conveyance systems that excels in terms of production efficiency.

[0003] One type of conveyance system utilizes a so-called moving magnet type linear motor, in which a magnet and a scale head are arranged on a carriage, which is the mover, and a coil unit and a scale unit are arranged on a stator of the conveyance path. Moving magnet type linear motors are more suitable for long-distance conveyance than moving coil type linear motors, which use a coil as the mover. On the other hand, when a moving magnet type linear motor requires conveyance over a long distance compared to the size of the mover, multiple coils are required according to the conveyance distance. Furthermore, in a conveyance system using a moving magnet type linear motor, there is a demand for the ability to individually control multiple carriages, and for the ability to control the movement of the carriages with high precision even when multiple carriages are adjacent to each other.

[0004] In addition, the conveying system may have multiple stators arranged on the conveying path, and a circular structure combining a straight conveying path and a curved conveying path, causing multiple movers to make one revolution. In this usage, the movers make one revolution while switching between conveying paths of different shapes.

[0005] Japanese Patent Application Laid-Open No. 2006-111494 (Patent Document 1) discloses a linear conveyance system including a stator having multiple coils, multiple movers that move along the stator to convey a workpiece, a scale attached to the movers, and multiple sensors that detect the scales. The multiple movers have magnets, and the multiple sensors are arranged at predetermined intervals along the stator. The linear conveyance system described in Patent Document 1 also includes a parameter recording unit and a position calculation unit. The parameter recording unit records, as separate parameters for each sensor, first cumulative values ​​obtained by accumulating error correction values ​​from an origin to correct for errors between a preset interval and a measured value. The position calculation unit calculates the position of the mover based on detection data from a sensor that detects a scale unit and the first cumulative value set for the sensor that detected the scale unit. Patent Document 1 states that the mechanical coordinate position of the mover can be calculated using only the sensor detection data and parameters set for the sensor, thereby enabling rapid calculation of the mechanical coordinate position of the mover.

[0006] Patent No. 7316554

[0007] In a conveyance system using a moving magnet type linear motor, the mover moves while switching between multiple coil units that serve as stators, and gaps of different lengths exist between the coil units. If gaps of different lengths exist between the coil units, then inevitably there will also be gaps of different lengths between the scale units that detect the position of the scale head. For this reason, a conveyance system using a moving magnet type linear motor poses the problem of an error occurring between the calculated mover speed and the actual mover speed due to variations in the gap length.

[0008] To address this problem, the technology of Patent Document 1 considers correcting for gaps of different lengths between coil units, treating the gaps of different lengths between the coil units as errors, under the assumption that gaps of different lengths exist between the coil units. Therefore, by using the technology of Patent Document 1, it is possible to improve the calculation accuracy of the mover position even when the mover switches coil units, and to reduce the error between the mover speed calculated from the difference value of the mover position and the actual mover speed.

[0009] However, with the technology of Patent Document 1, in order to reduce the error between the mover velocity calculated from the difference value of the mover position and the actual mover velocity, it is necessary to accurately measure the length of the gap, which differs for each coil unit, and the length of the gap between the coil units also differs depending on the individual system. For this reason, the technology of Patent Document 1 has the problem of increasing the number of steps required for adjustment work to build a system. Furthermore, with the technology of Patent Document 1, there is a problem in that, of the error between the mover velocity calculated from the difference value of the mover position and the actual mover velocity, the error that occurs due to deviation of the mover trajectory from the scale unit cannot be corrected.

[0010] The present disclosure has been made in consideration of the above, and aims to provide a control device that can reduce the amount of work required for adjustment work in system construction and can correct errors that occur when the trajectory of a mover deviates from the scale unit.

[0011] In order to solve the above-mentioned problems and achieve the object, a control device according to the present disclosure is configured to be applicable to a transport system including at least one mover, multiple coil units, a scale head provided on the mover, a scale unit that detects the position of the scale head, and a drive device that supplies a drive current to the coil unit. The multiple coil units are arranged along a transport path, the scale units are arranged at predetermined intervals along the transport path, and the at least one mover moves along the transport path. The control device includes a mover position calculation unit, a mover velocity calculation unit, and a mover velocity correction unit. The mover position calculation unit calculates the mover position, which is position information of the mover, based on detection data from the scale unit that detects the position of the scale head. The mover velocity calculation unit calculates the mover velocity from the difference between a current calculated value and a previous calculated value for the mover position. The mover velocity correction unit corrects the mover velocity according to the mover position.

[0012] The control device according to the present disclosure has the advantage of being able to reduce the number of steps required for adjustment work in system construction and correcting errors that occur when the trajectory of the mover deviates from the scale unit.

[0013] FIG. 1 is a diagram showing an example of the configuration of a conveyance system equipped with a control device according to embodiment 1; FIG. 2 is a diagram showing an example of the configuration of a control device and a drive device according to embodiment 1; FIG. 3 is a diagram used to explain a method of calculating a mover position in embodiment 1; FIG. 4 is a diagram showing an example of the configuration of a position and speed control unit according to embodiment 1; FIG. 5 is a diagram used to explain the operation of a trajectory error correction unit according to embodiment 1; FIG. 6 is a diagram used to explain the effect of providing an internal mover speed switching unit in a mover speed correction unit according to embodiment 1;

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A control device and a transport system according to an embodiment of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0015] First Embodiment A conveyance system according to a first embodiment is a system used to convey an object. The conveyance system conveys the object by moving a mover on which the object is placed. An example of the mover is a cart.

[0016] FIG. 1 is a diagram showing an example of the configuration of a transport system 10 including a control device 1 according to the first embodiment. As shown in FIG. 1, the transport system 10 according to the first embodiment includes a control device 1, drive devices 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H (hereinafter referred to as "2A to 2H" as appropriate, and the same applies to other reference symbols), coil units 3A to 3H, movers 4A to 4C, and scale heads 5A to 5C. Hereinafter, when the drive devices 2A to 2H are referred to individually without distinction, they will be collectively referred to as a "drive device 2." The same applies to the coil units 3A to 3H, movers 4A to 4C, and scale heads 5A to 5C.

[0017] The conveying system 10 according to the first embodiment is a moving magnet type linear motor. A plurality of driving devices 2 are connected to one another. In the conveying system 10, the plurality of driving devices 2 are connected to one another to form a conveying path 8 along which the mover 4 moves. A plurality of coil units 3 are arranged along the conveying path 8, and the mover 4 moves along the conveying path 8. A guide rail (not shown in FIG. 1) is provided on the side of the conveying path 8. The mover 4 includes a permanent magnet and a guide roller (not shown in FIG. 1), and moves on the guide rail by the rotation of the guide roller. The mover 4 moves on the side of the conveying path 8 and stops at the side of the conveying path 8. The guide rail may also be provided on the top surface of the conveying path 8.

[0018] The driving device 2 supplies a driving current to the coil unit 3. When the driving current is supplied to the coil unit 3, a thrust is applied to the mover 4, causing the mover 4 to move. The driving devices 2A, 2B, 2E, and 2F are configured as linear driving devices 2 in which the conveying path 8 is a straight path, and the driving devices 2C, 2D, 2G, and 2H are configured as curved driving devices 2 in which the conveying path 8 is a curved path.

[0019] 1 shows the conveying path 8 as a closed, circular path, but the shape of the path is arbitrary and is not limited to this example. The conveying path 8 of the conveying system 10 may be an open path. That is, the conveying path 8 of the conveying system 10 may be a path having a start point and an end point. Furthermore, the conveying path 8 may not have a straight path, but may only have a curved path.

[0020] The direction of travel of each mover 4 is either clockwise in Fig. 1 or counterclockwise in Fig. 1. Of the travel directions, the clockwise direction in Fig. 1 is referred to as the forward direction. Of the travel directions, the counterclockwise direction in Fig. 1 is referred to as the reverse direction. Arrow 17A represents the forward direction, and arrow 17B represents the reverse direction.

[0021] 1, the conveying system 10 includes eight driving devices 2 and three movers 4. The number of driving devices 2 included in the conveying system 10 is arbitrary. That is, the number of driving devices 2 that configure the conveying path 8 is arbitrary, and the number of movers 4 that move on the conveying path 8 is also arbitrary. Furthermore, the number of movers 4 that move on the conveying path 8 may be one.

[0022] The control device 1 is connected to each of the drive devices 2 via a data communication line 7. The control device 1 controls each of the multiple drive devices 2. The data communication line 7 is composed of a communication line connecting the control device 1 to one of the multiple drive devices 2, and a communication line connecting adjacent drive devices 2. That is, the conveyance system 10 is configured such that the control device 1 is connected to each of the drive devices 2 via a daisy chain connection. Note that the connection between the control device 1 and each of the drive devices 2 is not limited to a daisy chain connection. The connection between the control device 1 and each of the drive devices 2 may also be a star connection in which each drive device 2 is connected to the control device 1 via a communication hub. Alternatively, the conveyance system 10 may be configured such that the control device 1 is provided with multiple data communication lines 7, and the control device 1 and each of the drive devices 2 are directly connected by the data communication lines 7. Furthermore, the data communication line 7 may not be a physical communication line, but may be a communication path capable of wireless communication.

[0023] Next, the configurations and functions of the control device 1 and the drive device 2 will be described with reference to Fig. 2. Fig. 2 is a diagram showing an example of the configuration of the control device 1 and the drive device 2 according to the first embodiment.

[0024] Fig. 2 shows a drive device 2A, a coil unit 3A which is a stator, a mover 4A, a scale head 5A provided on the mover 4A, and a scale unit 6A which detects the position of the scale head 5A. Fig. 2 also shows a drive device 2B, a coil unit 3B, a mover 4B, a scale head 5B provided on the mover 4B, and a scale unit 6B which detects the position of the scale head 5B. Fig. 2 also shows a control device 1. The scale units 6A and 6B are arranged at a predetermined interval along the transport path 8. Hereinafter, when the scale units 6A and 6B are referred to individually without distinction, they will be collectively referred to as "scale unit 6."

[0025] The drive device 2A includes a drive unit 20A, a data communication unit 21A, a detector communication unit 24A, and a current detector 23A. The drive unit 20A includes a plurality of current control units 22A, and the coil unit 3A includes a plurality of coils 9A connected one-to-one to the current control units 22A of the drive unit 20A. Although the conveying path 8 is not shown in FIG. 2, the plurality of coils 9A are arranged along the conveying path 8. As shown in FIG. 2, the plurality of coils 9A are single-phase coils. Like the drive device 2A, the drive device 2B also includes a drive unit 20B, a data communication unit 21B, and a detector communication unit 24B.

[0026] The mover 4A includes a permanent magnet 40. The permanent magnet 40 included in the mover 4A is a permanent magnet that contributes to driving the mover 4A.

[0027] As described with reference to Fig. 1, drive units 2A, 2B, 2E, and 2F are all linear drive units 2. In the linear drive units 2, the shape of the transport path 8 is linear, and the shape of the scale unit 6 arranged along the transport path 8 is also linear. On the other hand, drive units 2C, 2D, 2G, and 2H are curved drive units 2. In the curved drive units 2, the shape of the transport path 8 is curved, and the shape of the scale unit 6 arranged along the transport path 8 is also curved.

[0028] In FIG. 2 , the five coils 9A in the coil unit 3A are labeled 9A1-9A5, the five current control units 22A in the drive unit 20A are labeled 22A1-22A5, and the current detectors 23A are labeled 23A1-23A5. Here, the five coils 9A labeled 9A1-9A5 are coils located within a range affected by the magnetic field emitted from the permanent magnet 40 of the mover 4A and contribute to driving the mover 4A. The five current control units 22A labeled 22A1-22A5 are current control units connected to the coils 9A labeled 9A1-9A5. The five current detectors 23A labeled 23A1-23A5 are current detectors that detect the currents flowing through the coils 9A1-9A5. Hereinafter, when the coils 9A1-9A5 are referred to individually without distinction, they will be collectively referred to as "coils 9A." Furthermore, when current control units 22A1 to 22A5 are referred to individually without distinction, they are collectively referred to as "current control unit 22A." Furthermore, when current detectors 23A1 to 23A5 are referred to individually without distinction, they are collectively referred to as "current detector 23A."

[0029] When the positional relationship between the mover 4A and the coil unit 3A is as shown in FIG. 2 , coils 9A far from the mover 4A do not significantly contribute to driving the mover 4A. In the first embodiment, coils 9A1 to 9A5 are described as coils that contribute to driving the mover 4A. Driving currents are supplied to the coils 9A1 to 9A5 by current control units 22A1 to 22A5, which are connected one-to-one to the coils 9A1 to 9A5, respectively. The number of coils 9A that contribute to driving one mover 4 is determined by the number of coils 9A arranged in a range affected by factors such as the size and magnetic field strength of the permanent magnet 40 of the mover 4. The number of coils 9A that drive one mover 4A described here is an example and is not limited to this example. In other words, the number of coils 9A that contribute to driving one mover 4A may be other than five.

[0030] The scale head 5 moves on the scale unit 6 together with the mover 4. The scale unit 6 detects the mover position, which is position information of the mover 4, and transmits it to the detector communication unit 24 of the drive device 2. Specifically, the scale unit 6A detects an intra-unit position yA that represents the mover position within the coil unit 3A from the position of the scale head 5A provided on the mover 4A, and transmits the detected intra-unit position yA to the detector communication unit 24A. The scale unit 6B operates in a similar manner. The scale head 5 can be composed of, for example, a permanent magnet for position detection, and the scale unit 6 can be configured to include a sensor element that detects the magnetic field of the permanent magnet for position detection.

[0031] The control device 1 includes a mover position target value generating unit 11 , a position and speed control unit 12 , a current command generating unit 13 , a data communication unit 14 , and a mover position calculating unit 15 .

[0032] The data communication unit 14 and data communication unit 21A are connected by communication line 7A, and the data communication unit 21A and data communication unit 21B are connected by communication line 7B. This connection is the daisy chain connection described above, and the communication data TxRx exchanged between the data communication unit 14 and data communication unit 21A includes not only information about the drive unit 2A but also information about the drive units 2B to 2H. The data communication unit 21A of the drive unit 2A transmits the communication data TxRx received from the data communication unit 14 to the data communication unit 21B of the drive unit 2B. Similarly, the data communication unit 21B transmits the received communication data TxRx to the drive unit 2C (not shown in FIG. 2 ) described below.

[0033] The data communication unit 14 receives information about the intra-unit position y via the data communication unit 21A of the drive device 2A. The intra-unit position y received by the data communication unit 14 includes not only the intra-unit position yA of the mover 4A but also the intra-unit positions of the movers 4B and 4C.

[0034] The mover position target value generator 11 generates a mover position target value xref that indicates the position to which the mover 4 is to be moved, and outputs the value to the position and speed controller 12. In this document, any method may be used to generate the mover position target value xref. In FIG. 2, the mover position target value xref is configured to be generated inside the control device 1, but this configuration is not limiting. The mover position target value xref may also be configured to be input to the control device 1 from outside. The mover position target value xref includes mover position target values ​​for all movers 4 present in the conveyance system 10.

[0035] The position and speed control unit 12 acquires the mover position target value xref of the mover 4 from the mover position target value generation unit 11, and acquires the mover position x from the mover position calculation unit 15. The position and speed control unit 12 generates a thrust command τref so that the mover position x follows the mover position target value xref, and outputs the thrust command τref to the current command generation unit 13. In this paper, any method may be used to generate the thrust command τref so that the mover position x follows the mover position target value xref. The thrust command τref is generated for each mover 4. Like the mover position target value xref, the thrust command τref includes thrust commands for all movers 4 present in the transportation system 10.

[0036] The current command generation unit 13 acquires a thrust command τref from the position and speed control unit 12 and acquires a mover position x from the mover position calculation unit 15. The current command generation unit 13 generates, as a current command Iref, a current target value that is a target value of a drive current to be passed through the multiple coil units 3 so that the thrust generated in the mover 4 follows the thrust command τref. The current command Iref generated by the current command generation unit 13 includes current commands for the multiple coils 9A in all coil units 3 present in the transportation system 10. Note that the current command Iref is not necessarily the same for all coils 9A, and the current command Iref may be different for each coil 9A. The current command Iref generated by the current command generation unit 13 is output to the data communication unit 14. The data communication unit 14 acquires the current command Iref generated by the current command generation unit 13 and transmits it to the data communication unit 21A.

[0037] The mover position calculation unit 15 calculates the mover position x based on detection data of the scale unit 6 that detected the scale head 5 of the mover 4. Specifically, the mover position calculation unit 15 calculates the mover position x based on the intra-unit position y acquired from the data communication unit 14 and the distance to the scale origin, which is the reference position within the coil unit 3 of the scale unit 6, and outputs the calculated mover position x to the position and speed control unit 12 and the current command generation unit 13. The method of calculating the mover position x in the mover position calculation unit 15 will be described later.

[0038] Data communication unit 21A of drive unit 2A receives communication data TxRx transmitted from data communication unit 14. The communication data TxRx transmitted from data communication unit 14 includes not only the current command Iref for drive unit 2A, but also the current commands Iref for drive units 2B to 2H. Data communication unit 21A extracts current commands IrefA1 to IrefA5, which are current commands for drive unit 2A, from the communication data TxRx, and outputs the extracted current commands IrefA1 to IrefA5 to current control units 22A1 to 22A5.

[0039] Current detectors 23A1-23A5 detect currents IA1-IA5 flowing through coils 9A1-9A5. Current control units 22A1-22A5 acquire current commands IrefA1-IrefA5 from data communication unit 21A, acquire intra-unit position yA from detector communication unit 24A, and acquire detected values ​​of currents IA1-IA5 from current detectors 23A1-23A5. Current control units 22A1-22A5 control currents IA1-IA5, which are drive currents applied to coils 9A1-9A5, so that the detected values ​​of currents IA1-IA5 follow current commands IrefA1-IrefA5. Note that any method for controlling currents IA1-IA5 may be used.

[0040] 3 is a diagram illustrating a method for calculating the mover position in embodiment 1. Fig. 3 shows coil units 3A and 3B, scale units 6A and 6B arranged at a predetermined interval along the transport path 8, and a mover 4A moving on the scale units 6A and 6B along the transport path 8.

[0041] 2 acquires the intra-unit position y, including the intra-unit position yA of the mover 4A, from the data communication unit 14. The mover position calculation unit 15 calculates the mover position xA using the distance to the scale origin of the scale unit 6B and the intra-unit position yA, using the following equation (1):

[0042] Mover position xA = distance to scale origin of scale unit 6B + radius correction value × unit position yA (1)

[0043] In Figure 3, mover position xA is the distance to mover 4A relative to the system origin, and intra-unit position yA is the distance to mover 4A relative to the scale origin of scale unit 6B. Here, the system origin is the origin as seen from the entire conveyance system 10, and the scale origin is the origin as seen from each individual scale unit 6 or each individual coil unit 3. In Figure 3, the left end position of coil unit 3A is shown as the system origin, and the left end position of coil unit 3B is shown as the scale origin of scale unit 6B, but these examples are not limiting. The system origin may be an arbitrarily selected reference position of coil unit 3 or scale unit 6. Furthermore, the scale origin may be the center position or right end position of scale unit 6 or each individual coil unit 3.

[0044] In addition, in the above formula (1), the radius correction value is "1" when the mover 4A is on a straight path, as shown in Fig. 3. In addition, when the mover 4A is on a curved path, the radius correction value is calculated by the following formula (2).

[0045] Radius correction value=radius of mover position xA / radius of intra-unit position yA (2)

[0046] In the above equation (2), the "radius of the mover position xA" means the distance from the center of curvature of the curved path to the mover 4A, and the "radius of the intra-unit position yA" means the distance from the center of curvature of the curved path to the scale head 5A. The radii of the mover position xA and the intra-unit position yA are values ​​determined from the shape of the scale unit 6 or the guide rail at the position where the mover 4A is located. For example, the distance (radius of curvature) from the center of curvature of the curved path to the surface of the mover 4A can be used as the radius of the mover position xA. For example, the radius of curvature of the guide rail can be used as the radius of the intra-unit position yA.

[0047] 3, if the scale origin of scale unit 6B is set to the left end of coil unit 3B, the distance to the scale origin of scale unit 6B relative to the system origin can be taken as the width of coil unit 3A. Therefore, if information related to the width of coil unit 3A is set in advance in mover position calculation unit 15, it becomes possible to calculate the mover position xA relative to the system origin. Note that if there is a curved path between the system origin and scale unit 6B, or if scale unit 6B has a curved path, the length along the inner periphery of the scale unit on these curved paths - more precisely, the length of the arc at the radius of the mover surface - is treated as the distance.

[0048] Furthermore, even if the scale origin of the scale unit 6B does not exist at the left or right end of the coil unit 3B, if the distance from the left or right end of the coil unit 3B to the scale origin of the scale unit 6B is known, this information can be set in advance in the mover position calculation unit 15, making it possible to calculate the mover position xA based on the system origin.

[0049] Note that Figure 3 explains the method for calculating the mover position xA when the mover 4A is on the scale unit 6B, but even if the mover 4A is on any scale unit 6 other than the scale unit 6B, it is possible to calculate the mover position xA in a similar manner.

[0050] Next, the configuration and operation of the position and speed control unit 12 will be described. Fig. 4 is a diagram showing an example of the configuration of the position and speed control unit 12 according to the first embodiment. As shown in Fig. 4, the position and speed control unit 12 can be configured to include a mover speed calculation unit 121, a mover speed correction unit 122, and a thrust command calculation unit 123. Note that the thrust command calculation unit 123 may be provided in the current command generation unit 13. In this configuration, the mover position target value xref is input to the current command generation unit 13.

[0051] The mover speed calculation unit 121 acquires the mover position x from the mover position calculation unit 15. The mover speed calculation unit 121 calculates a pre-correction internal mover speed v'' using the following equation (3) based on the difference between the mover position x input this time and the mover position x input last time. The pre-correction internal mover speed v'' is a speed calculated inside the position and speed control unit 12, and is the speed before the correction process described below is performed.

[0052] Pre-correction internal mover velocity v'' = (mover position x - previous mover position x) / one update period of mover position x (3)

[0053] In the above equation (3), one update period of the mover position x is one update period when performing the update process of the mover position x, i.e., one period of the mover position calculation. Since the mover velocity calculation unit 121 calculates the pre-correction internal mover velocity v'' each time the mover position x is updated, one period of the mover velocity calculation, which is one update period of the pre-correction internal mover velocity v'', can be considered to be the same as one update period of the mover position x. Note that in this paper, with regard to the calculated value of the mover position x calculated by the mover position calculation unit 15 and input to the position and velocity control unit 12, the calculated value of the mover position x input currently may be referred to as the "current calculated value", and the calculated value of the mover position x input previously may be referred to as the "previous calculated value".

[0054] The mover speed correcting unit 122 obtains the pre-correction internal mover speed v" from the mover speed calculating unit 121, and obtains the mover position x from the mover position calculating unit 15. The mover speed correcting unit 122 corrects the pre-correction internal mover speed v" in accordance with the mover position x, and outputs the corrected result as the internal mover speed v to the thrust command calculating unit 123. As shown in FIG. 4 , the mover speed correcting unit 122 can be configured to include a trajectory error correcting unit 1221, a scale unit changeover determining unit 1222, an internal mover speed saving unit 1223, and an internal mover speed switching unit 1224.

[0055] The trajectory error correction unit 1221 acquires the pre-correction internal mover velocity v'' from the mover velocity calculation unit 121, and acquires the mover position x from the mover position calculation unit 15. The trajectory error correction unit 1221 corrects the pre-correction internal mover velocity v'' in accordance with the mover position x, and outputs the corrected result as a current internal mover velocity v' to the internal mover velocity storage unit 1223 and the internal mover velocity switching unit 1224.

[0056] The operation of the trajectory error correction unit 1221 will be further described with reference to Fig. 5 and Fig. 6. Fig. 5 and Fig. 6 are first and second diagrams illustrating the operation of the trajectory error correction unit 1221 according to the first embodiment.

[0057] 5 shows how the mover 4A switches from a linear scale unit 6B to a curved scale unit 6C, which has a different shape. Note that the difference in length between the linear and curved shapes is not included in the "different shapes" mentioned here.

[0058] When the mover 4A passes between scale units 6 having different shapes, there is a region where the trajectory of the scale head 5A provided on the mover 4A deviates from the scale unit 6B or the scale unit 6C. The scale unit 6B detects the linear position of the mover 4A as the intra-unit position xA. Therefore, if the trajectory of the scale head 5A deviates from the scale unit 6B, the error between the pre-correction internal mover velocity v'' calculated using the mover position x including the intra-unit position xA detected by the scale unit 6B and the actual velocity of the mover 4A becomes large. Furthermore, the scale unit 6C detects the position of the mover 4A in the arc direction as the unit position xA. Therefore, if the trajectory of the scale head 5A deviates from the scale unit 6C, the error between the pre-correction internal mover velocity v'' calculated using the mover position x including the intra-unit position xA detected by the scale unit 6C and the actual velocity of the mover 4A becomes large.

[0059] 6, like FIG. 5, shows the mover 4A transferring from a linear scale unit 6B to a curved scale unit 6C. As shown in FIG. 6, a linear guide rail 18B is arranged along the linear scale unit 6B, and a curved guide rail 18C is arranged along the curved scale unit 6C. The guide roller 19F on the front side of the mover 4A in the traveling direction is located on the scale unit 6C, and the guide roller 19R on the rear side of the mover 4A in the traveling direction is located on the scale unit 6B. The mover 4A transfers between scale units 6 of different shapes by moving from the linear guide rail 18B to the curved guide rail 18C due to the rotation of the guide rollers 19F, 19R.

[0060] FIG. 6 is also a diagram showing the concept of a calculation model used to calculate a correction value for correcting the pre-correction internal mover velocity v''. In FIG. 6, the x and y coordinates of the guide roller 19R present on the scale unit 6B are expressed as (x Ｒ , y Ｒ ), and the x and y coordinates of the guide roller 19F on the scale unit 6C are (xＦ , y Ｆ ), and the x and y coordinates of the position of the mover 4A are (x Ｃ , y Ｃ ), and the x and y coordinates of the detection position of the scale head 5A are (x Ｓ , y Ｓ ) The radius of curvature of the guide rail 18C is R, the distance between the guide rollers 19R and 19F is L, the distance from the position of the mover 4A to the detection position of the scale head 5A is D, the lead angle of the guide roller 19F is θ, and the tilt angle of the mover 4A is φ. The origin of these coordinates, i.e., the coordinate origin of the calculation model, is a point moved toward the scale unit 6B by the distance L between the guide rollers 19R and 19F from the point where the scale unit 6B switches to the scale unit 6C. The lead angle θ of the guide roller 19F is the angle formed by the line connecting the center of curvature and the gap between the scale units 6B and 6C and the line connecting the center of curvature and the guide roller 19F. The position of the mover 4A is assumed to be at the center between the guide rollers 19F and 19R, and the line connecting the detection position of the scale head 5A and the position of the mover 4A and the line connecting the guide rollers 19F and 19R are assumed to be perpendicular to each other.

[0061] First, the x and y coordinates of the guide roller 19F (x Ｆ , y Ｆ ) can be expressed by the following equations (4) and (5).

[0062] x Ｆ =Rsinθ+L…(4) y Ｆ =R−Rcosθ…(5)

[0063] The lead angle θ of the guide roller 19F can be calculated using the following equations (6) to (8).

[0064] a = sin －１ {(L ２ -R ２ -(L-x Ｒ ) ２ -(R-y Ｒ ) ２ ) / √((2(L−x Ｒ ) x R) ２ +(2(R-y Ｒ ) x R) ２)}...(6) b=sin －１ {(-2×2(R-y Ｒ )×R) / √((2(L−x Ｒ ) x R) ２ +(2(R-y Ｒ ) x R) ２ )}...(7) θ=a-b...(8)

[0065] In addition, the x and y coordinates of the position of the mover 4A (x Ｃ , y Ｃ ) can be calculated using the following equations (9) and (10).

[0066] x Ｃ = (x Ｆ +x Ｒ ) / 2… (9) y Ｃ = (y Ｆ +y Ｒ ) / 2… (10)

[0067] In addition, the x and y coordinates of the detection position of the scale head 5A (x Ｓ , y Ｓ ) can be calculated using the following equations (11) and (12).

[0068] x Ｓ = x Ｃ + D × (y Ｆ -y Ｒ ) / L… (11) y Ｓ = y Ｃ +D×(x Ｆ -x Ｒ ) / L… (12)

[0069] The trajectory error correction unit 1221 calculates the x and y coordinates (x Ｃ , y Ｃ ) and the x and y coordinates of the detection position of the scale head 5A (x Ｓ , y Ｓ) is calculated. Furthermore, the trajectory error correction unit 1221 calculates the velocity of the mover 4A and the velocity of the scale head 5A from these coordinates, and calculates a correction value so that the velocity of the scale head 5A coincides with the velocity of the mover 4A. The trajectory error correction unit 1221 corrects the pre-correction internal mover velocity v'' using the calculated correction value, thereby obtaining a current internal mover velocity v', and outputs the obtained current internal mover velocity v' to the internal mover velocity storage unit 1223 and the internal mover velocity switching unit 1224.

[0070] The internal mover velocity storage unit 1223 stores the current internal mover velocity v' output from the trajectory error correction unit 1221 as data. The internal mover velocity storage unit 1223 also stores z －１ v′ is output to the internal mover speed switching unit 1224 .

[0071] The scale unit change determination unit 1222 detects that the mover 4 has changed scale units 6 from the value of the mover position x, and outputs a scale unit change signal τs, which is a signal indicating the detection result, to the internal mover velocity switching unit 1224.

[0072] The internal mover speed switching unit 1224 acquires the current internal mover speed v′ from the trajectory error correction unit 1221 and the previous internal mover speed z from the internal mover speed storage unit 1223. －１ v' and acquires a scale unit change signal τs from the scale unit change determination unit 1222. The internal mover velocity switching unit 1224 determines whether or not the mover 4 has changed scale units 6 based on the scale unit change signal τs. When the mover 4 has changed scale units 6, the internal mover velocity switching unit 1224 changes the previous internal mover velocity z －１ When the mover 4 has not been transferred to another scale unit 6, the internal mover velocity switching unit 1224 outputs the current internal mover velocity v' as the internal mover velocity v.

[0073] The thrust command calculation unit 123 acquires the mover position target value xref from the mover position target value generation unit 11, acquires the mover position x from the mover position calculation unit 15, and acquires the internal mover velocity v from the internal mover velocity switching unit 1224. The thrust command calculation unit 123 calculates a thrust command τref so that the mover position x follows the mover position target value xref, and outputs the calculated thrust command τref to the current command generation unit 13.

[0074] As described above, when the mover 4A changes over to another scale unit 6, the mover speed correction unit 122 outputs the mover speed calculated one update cycle before to the thrust command calculation unit 123.

[0075] FIG. 7 is a diagram illustrating the effect of providing the internal mover speed switching unit 1224 in the mover speed correction unit 122 according to the first embodiment.

[0076] In an ideal transport system 10, the coil units 3 are configured without gaps, as shown in FIG. 3 . However, in an actual transport system 10, gaps exist between the coil units 3, as shown in FIG. 7 . Because these gaps vary not only between the coil units but also between individual systems, it is difficult to set them before shipping the system. Therefore, at the time of shipping the system, it is assumed that there are no gaps between the coil units 3. For this reason, the distance to the scale origin of the scale unit 6B is set to the same as the width of the coil unit 3A. As a result, as shown in FIG. 7 , an error occurs between the position indicating the distance to the scale origin of the scale unit 6B relative to the system origin and the position indicating the scale origin of the scale unit 6B, by the amount indicating the gaps between the coil units 3.

[0077] As described above, the pre-correction internal mover velocity v'' calculated by the mover velocity calculation unit 121 is calculated by the following equation (3).

[0078] Pre-correction internal mover velocity v'' = (mover position x - previous mover position x) / one update period of mover position x (3) (reprinted)

[0079] On the other hand, when the mover 4A is transferred from the scale unit 6A to the scale unit 6B, a velocity error as shown in the following equation (13) occurs in the pre-correction internal mover velocity v″ calculated by the above equation (3).

[0080] Pre-correction internal mover speed v'' = (mover position x - previous mover position x) / one update period of mover position x ≈ actual mover speed - (gap between coil units 3 / one update period of mover position x) ... (13)

[0081] As shown in the above equation (13), the pre-correction internal mover speed v″ has a speed error corresponding to the error of the gap between the coil units 3 relative to the actual mover speed.

[0082] As described above, when the thrust command calculation unit 123 calculates the thrust command τref, it uses the internal mover velocity v based on the pre-correction internal mover velocity v". The phenomenon in which a velocity error occurs with respect to the actual mover velocity, corresponding to the error in the gap between the coil units 3, occurs only when the mover 4A is transferred between scale units 6. This phenomenon also occurs when transferring between scale units 6 having the same shape, as long as there is a gap between the coil units 3. If the velocity error that can be contained in the pre-correction internal mover velocity v" is large, the error in the thrust command τref calculated using the internal mover velocity v based on the pre-correction internal mover velocity v" will also be large. If the mover 4 is driven using a thrust command τref with a large error, there is a risk that shock or vibration will occur in the mover 4.

[0083] On the other hand, in the control device 1 according to the first embodiment, an internal mover speed switching unit 1224 is provided at the output stage of the mover speed correction unit 122. As described above, the internal mover speed switching unit 1224 changes the previous internal mover speed z －１v' is output as the internal mover velocity v. This makes it possible to prevent an error between the internal mover velocity v output from the mover velocity corrector 122 to the thrust command calculator 123 and the actual mover velocity from increasing, and also makes it possible to prevent a sudden change in the thrust command τref calculated by the thrust command calculator 123. As a result, it becomes possible to control the mover 4 so that no shock or vibration occurs in the mover 4.

[0084] As described above, the control device according to the first embodiment is configured to be applicable to a transport system including at least one mover, multiple coil units, a scale head provided on the mover, a scale unit that detects the position of the scale head, and a drive device that supplies a drive current to the coil unit. The multiple coil units are arranged along a transport path, the scale units are arranged at predetermined intervals along the transport path, and the at least one mover moves along the transport path. The control device includes a mover position calculation unit, a mover velocity calculation unit, and a mover velocity correction unit. The mover position calculation unit calculates the mover position, which is position information of the mover, based on detection data from the scale unit that detects the position of the scale head. The mover velocity calculation unit calculates the mover velocity from the difference between a current calculated value and a previous calculated value for the mover position. The mover velocity correction unit corrects the mover velocity in accordance with the mover position. According to the control device of embodiment 1, there is no need to measure the gaps between the coil units or the scale units as in Patent Document 1, so it is possible to reduce the number of steps required for adjustment work in building a system and to correct errors that occur when the trajectory of the mover deviates from the scale unit. Furthermore, the control device of embodiment 1 is provided with a mover speed correction unit that corrects the mover speed in accordance with the mover position, so it is possible to reduce the speed error between the mover speed and the actual mover speed and to control the mover with high precision.

[0085] The control device according to the first embodiment may include a thrust command calculation unit that calculates a thrust command so that the mover position follows the mover position target value. Furthermore, the mover speed correction unit provided in the control device according to the first embodiment may include an internal mover speed switching unit that outputs the mover speed calculated one update cycle prior to the thrust command calculation unit when the mover switches scale units. Even when there is a gap between different coil units or scale units, the internal mover speed switching unit operates to suppress a speed error that may occur when the mover switches scale units, making it possible to control the mover so that shock or vibration does not occur in the mover.

[0086] Furthermore, the mover velocity correction unit provided in the control device according to embodiment 1 may include a trajectory error correction unit that corrects the mover velocity in accordance with the shapes of the scale unit in which the mover is located and the adjacent scale unit when the mover is transferred between scale units of different shapes. The trajectory error correction unit may be configured to correct the mover velocity in accordance with the geometric trajectory of the mover calculated from the shapes of the scale unit in which the mover is located and the adjacent scale unit when the mover is transferred between scale units of different shapes. Because the trajectory error correction unit corrects the mover velocity in accordance with the geometric trajectory of the mover, the velocity error between the mover velocity and the actual mover velocity can be further reduced compared to a configuration that does not have a trajectory error correction unit, enabling the mover to be controlled with higher precision.

[0087] The transport system according to the first embodiment includes at least one mover, multiple coil units, a scale head attached to the mover, a scale unit that detects the position of the scale head, and a drive device that supplies a drive current to the coil unit. The multiple coil units are arranged along the transport path, and the scale units are arranged at predetermined intervals along the transport path, and at least one mover moves along the transport path. The control device that controls the transport system includes a mover position calculation unit, a mover velocity calculation unit, and a mover velocity correction unit. The mover position calculation unit calculates the mover position, which is position information of the mover, based on detection data from the scale unit that detects the position of the scale head. The mover velocity calculation unit calculates the mover velocity from the difference between a current calculated value and a previous calculated value for the mover position. The mover velocity correction unit corrects the mover velocity according to the mover position. The transport system according to the first embodiment does not require measuring gaps between coil units or scale units, as in Patent Document 1, thereby reducing the number of steps required for system construction adjustment work and making it possible to correct errors caused by deviations of the mover's trajectory from the scale unit. Furthermore, the control device provided in the conveying system according to embodiment 1 includes a mover speed correction unit that corrects the mover speed according to the mover position, so that the speed error between the mover speed and the actual mover speed can be reduced, enabling the mover to be controlled with high precision.

[0088] At the end of the first embodiment, a hardware configuration for realizing the functions of the control device 1 and the drive device 2 described above will be described with reference to Figs. 8 and 9. Fig. 8 is a block diagram showing an example of a hardware configuration for realizing the functions of the control device 1 and the drive device 2 according to the first embodiment. Fig. 9 is a block diagram showing another example of a hardware configuration for realizing the functions of the control device 1 and the drive device 2 according to the first embodiment.

[0089] When realizing some or all of the functions of the control device 1 and drive device 2 according to embodiment 1, the configuration can include a processor 300 that performs calculations, a memory unit 302 that stores programs read by the processor 300, and a communication circuit 304 that transmits and receives signals, as shown in FIG. 8.

[0090] The processor 300 is an example of a computing unit. The processor 300 may be a computing unit called a microprocessor, a microcomputer, a central processing unit (CPU), or a digital signal processor (DSP). Examples of the storage unit 302 include non-volatile or volatile semiconductor memory such as a random access memory (RAM), a read-only memory (ROM), a flash memory, an erasable programmable read-only memory (EPROM), or an electrically programmable read-only memory (EEPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, and a digital versatile disk (DVD).

[0091] The storage unit 302 stores a program that executes the functions of the control device 1 and the drive device 2 according to the first embodiment. The processor 300 exchanges necessary information via the communication circuit 304, executes the program stored in the storage unit 302, and refers to the table stored in the storage unit 302, thereby performing the above-described processing. The calculation results by the processor 300 can be stored in the storage unit 302. Information regarding the width of the coil unit 3A described above can also be stored in the storage unit 302.

[0092] Furthermore, when realizing part of the functions of the control device 1 and the drive device 2 according to the first embodiment, a processing circuit 303 shown in FIG. 9 can be used. The processing circuit 303 may be a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. Information input to and output from the processing circuit 303 can be exchanged via a communication circuit 304. Furthermore, the processing results by the processing circuit 303 can be stored in the storage unit 302.

[0093] It is also possible that some of the processing in the control device 1 and the drive device 2 is performed by the processing circuit 303 , and the processing that is not performed by the processing circuit 303 is performed by the processor 300 and the memory unit 302 .

[0094] Second Embodiment In a second embodiment, a control device and a transport system that can solve the problem in the first embodiment and also solve another problem will be described.

[0095] Fig. 10 is a diagram showing an example of the configuration of a control device 1 and a drive device 2 according to embodiment 2. Compared to the control device 1 shown in Fig. 2, in Fig. 10, position and speed control unit 12 is replaced with position and speed control unit 12'. The roles of mover position target value generation unit 11, current command generation unit 13, data communication unit 14, and mover position calculation unit 15 are the same as those in the above-described embodiment 1.

[0096] Fig. 11 is a diagram showing an example of the configuration of a position and velocity control unit 12' according to embodiment 2. Compared to the position and velocity control unit 12 shown in Fig. 4, in Fig. 11, the mover velocity correction unit 122 is replaced with a mover velocity correction unit 122', and the trajectory error correction unit 1221 is replaced with a trajectory error correction unit 1221'. In the position and velocity control unit 12', the roles of the mover velocity calculation unit 121 and thrust command calculation unit 123 are the same as in the above-described embodiment 1. Furthermore, in the mover velocity correction unit 122', the roles of the scale unit transfer determination unit 1222, internal mover velocity storage unit 1223, and internal mover velocity switching unit 1224 are the same as in the above-described embodiment 1.

[0097] In the case of the control device 1 according to the first embodiment, as shown in the above formulas (6) and (7), it is necessary to perform calculations with high computational loads, such as the arcsine function and square root, in real time. For this reason, the control device 1 according to the first embodiment needs to use high-performance, expensive processors 300 shown in Fig. 8 and processing circuit 303 shown in Fig. 9. In response to this issue, in the second embodiment, a control device 1 will be described that can reduce the computational load and use a less expensive processor 300 or processing circuit 303.

[0098] Fig. 12 is a diagram illustrating the operation of a trajectory error correction unit 1221' according to embodiment 2. Similar to Fig. 6, Fig. 12 shows how the mover 4A switches from the linear scale unit 6B to the curved scale unit 6C. The symbols and terms in the figure are the same as those in Fig. 6.

[0099] The various values ​​used in the above-described formulas (4) to (12) are set values ​​that are determined according to the configuration of the conveyance system 10, and can be known in advance. Therefore, the trajectory error correction unit 1221′ does not perform the calculations of formulas (4) to (12), but rather the correction values ​​obtained by performing the calculations of formulas (4) to (12) in advance are stored in the trajectory error correction unit 1221′.

[0100] FIG. 13 is a diagram illustrating the correction process performed by the trajectory error correction unit 1221′ according to the second embodiment. The horizontal axis of FIG. 13 represents the mover position, and the vertical axis represents the velocity correction value. In FIG. 12, the mover position x at which velocity correction is required extends from the position where the guide roller 19F of the mover 4A passes through the gap between the scale units 6B and 6C to the position where the guide roller 19R of the mover 4A passes through the gap between the scale units 6B and 6C. Therefore, as shown in FIG. 13, the correction value for correcting the pre-correction internal mover velocity v″ is within a range of ±L / 2 before and after the position of the gap between the scale units 6B and 6C as the origin. Note that FIG. 13 illustrates the position of the mover 4A as being at the midpoint between the guide rollers 19F and 19R. When the position of the movable element 4A is not at the midpoint of the guide rollers 19F and 19R, the length between the start position of the correction and the end position of the correction remains the same at L, but it goes without saying that the length to the start position of the correction and the length to the end position of the correction, based on the position of the gap between the scale units 6B and 6C, are different.

[0101] FIG. 14 is a diagram showing an example of a correction value table held in the trajectory error correction unit 1221′ according to the second embodiment. FIG. 15 is a diagram showing an example of a coefficient value table held in the trajectory error correction unit 1221′ according to the second embodiment. The correction value table shown in FIG. 14 is a table showing the correspondence between the mover position x and the correction value corresponding to the mover position x. This correction value is a correction value calculated in advance based on equations (4) to (12). The trajectory error correction unit 1221′ corrects the pre-correction internal mover velocity v″ by referring to the correction value table without calculating a correction value. If the correction value table does not contain a correction value corresponding to the input mover position x, an approximate value calculated by calculation processing using interpolation processing may be used as the correction value, or a correction value corresponding to a mover position close to the input mover position x may be used.

[0102] 15 is a table showing the correspondence between the degree and the coefficient value when calculating the correction value by performing n-th degree polynomial approximation. The trajectory error correction unit 1221′ refers to the coefficient value table, applies the coefficient value to the n-th degree polynomial, calculates the correction value corresponding to the input mover position x, and corrects the pre-correction internal mover velocity v″ using the calculated correction value.

[0103] As described above, the mover speed correction unit included in the control device according to the second embodiment stores in advance a correction value for correcting the internal mover speed, an approximate value that approximates the correction value, or a coefficient value for calculating the approximate value. The mover speed correction unit corrects the internal mover speed using the correction value, the approximate value, or the coefficient value. The control device and transportation system according to the second embodiment can find the correction value for correcting the pre-correction internal mover speed without performing calculation processing with a high load, so it is possible to build a control device and transportation system at lower cost while enjoying the effects of the first embodiment.

[0104] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and parts of the configurations may be omitted or modified without departing from the spirit of the invention.

[0105] 1 Control device, 2, 2A to 2H Drive device, 3, 3A to 3H Coil unit, 4, 4A to 4C Mover, 5, 5A to 5C Scale head, 6, 6A to 6C Scale unit, 7 Data communication line, 7A, 7B Communication line, 8 Conveyance path, 9A, 9A1 to 9A5 Coil, 10 Conveyance system, 11 Mover position target value generation unit, 12, 12' Position speed control unit, 13 Current command generation unit, 14, 21A, 21B Data communication unit, 15 Mover position calculation unit, 17A, 17B Arrow, 18B, 18C Guide rail, 19F, 19R Guide roller, 20A, 20B Drive unit, 22A, 22A1 to 22A5 Current control unit, 23A, 23A1 to 23A5 Current detector, 24, 24A, 24B Detector communication unit, 40 Permanent magnet, 121 mover speed calculation unit, 122, 122' mover speed correction unit, 123 thrust command calculation unit, 300 processor, 302 memory unit, 303 processing circuit, 304 communication circuit, 1221, 1221' trajectory error correction unit, 1222 scale unit transfer determination unit, 1223 internal mover speed storage unit, 1224 internal mover speed switching unit.

Claims

1. A control device configured to be applicable to a conveyance system including at least one mover that moves along a conveyance path, a plurality of coil units arranged along the conveyance path, a scale head provided on the mover, scale units arranged at predetermined intervals along the conveyance path and that detect the position of the scale head, and a drive device that supplies a drive current to the coil unit, wherein the control device comprises: a mover position calculation unit that calculates the mover position, which is position information of the mover, based on detection data from the scale unit that detects the position of the scale head; a mover speed calculation unit that calculates the mover speed from the difference between a current calculated value and a previous calculated value for the mover position; and a mover speed correction unit that corrects the mover speed in accordance with the mover position.

2. The control device according to claim 1, characterized in that the control device comprises a thrust command calculation unit that calculates a thrust command so that the mover position follows the mover position target value, and the mover speed correction unit outputs the mover speed calculated one update cycle before to the thrust command calculation unit when the mover changes scale units, and the one update cycle is one cycle of mover speed calculation.

3. A control device as described in claim 1 or 2, characterized in that the mover speed correction unit corrects the mover speed according to the shapes of the scale unit in which the mover is located and the adjacent scale unit when the mover is transferred to a scale unit with a different shape.

4. The control device described in claim 3, characterized in that when the mover is transferred to a scale unit having a different shape, the mover speed correction unit corrects the mover speed in accordance with the geometric trajectory of the mover calculated from the shapes of the scale unit in which the mover is located and the adjacent scale unit.

5. The control device described in claim 4, characterized in that the mover speed correction unit pre-stores a correction value for correcting the mover speed, an approximate value that approximates the correction value, or a coefficient value for calculating the approximate value, and the mover speed correction unit corrects the mover speed using the correction value, the approximate value, or the coefficient value.

6. A conveyance system comprising: at least one mover that moves along a conveyance path; a plurality of coil units arranged along the conveyance path; a scale head provided on the mover; scale units arranged at predetermined intervals along the conveyance path and that detect the position of the scale head; a drive unit that supplies a drive current to the coil unit; a mover position calculation unit that calculates the mover position, which is position information of the mover, based on detection data from the scale unit that has detected the position of the scale head; a mover speed calculation unit that calculates the mover speed from the difference between a current calculated value and a previous calculated value for the mover position; and a mover speed correction unit that corrects the mover speed in accordance with the mover position.

Images