Method for operating linear motor

Abstract

The invention relates to a method for operating a linear motor. In order to compensate for the cogging effect in the linear motor (1) in a simple but efficient manner, the cogging force (FCx, FCy) at least in one movement direction (x, y) of the shuttle (Tn) along the stator (2) is determined as a function of the relative position of the at least one shuttle (Tn) in the at least one movement direction (x, y) with respect to the stator (2), the drive coil (ASi) in the region of the shuttle (Tn) is not energized and at the same time the drive coil (ASi) in the region of the shuttle (Tn) is not energized, the determined cogging force (FCx, FCy) is stored in the control unit (10), and in that the cogging force (FCx, FCy) in at least one movement direction (x, y) determined by the unenergized drive coil (ASi) is used by the control unit (10) in order to generate the cogging force (FCx, FCy) during operation of the linear motor (1). The cogging force (FCx, FCy) is compensated as a function of the relative position between the shuttle (Tn) and the stator (2) that compensates for the cogging force (FCx, FCy) during operation of the linear motor (1).

Description

Technical Field

[0001] The present invention relates to a method for operating a linear motor having at least one shuttle and a stator, wherein a plurality of drive coils are arranged on the stator and a plurality of drive magnets are arranged on the shuttle, or a plurality of drive magnets are arranged on the stator and a plurality of drive coils are arranged on the shuttle, and during operation of the linear motor, the drive coils in the shuttle area are energized under the control of a control unit to generate an electromagnetic field, which interacts with the drive magnetic field generated by the drive magnets so as to generate a propulsion force that moves the shuttle along the stator. The present invention also relates to a corresponding linear motor having at least one shuttle and a stator, wherein a plurality of drive coils are arranged on the stator and a plurality of drive magnets are arranged on at least one shuttle, or a plurality of drive magnets are arranged on the stator and a plurality of drive coils are arranged on at least one shuttle, and a control unit of the linear motor is provided, which is arranged to energize the drive coils in the region of the at least one shuttle during operation of the linear motor to generate an electromagnetic field, which interacts with the drive magnetic field generated by the drive magnets so as to generate a propulsion force for moving the at least one shuttle along the stator. Background Art

[0002] Linear motors are well-established transport systems in which the moving part of the motor, often called a shuttle, is propelled along a track by means of electromagnetic forces. In a linear motor, a drive magnet (usually a permanent magnet) interacts with the electromagnetic field generated by an energized drive coil. This interaction generates a propulsion force that moves the shuttle along the track. Different types of linear motors are known. In so-called short-stator linear motors, the drive coils are arranged on the shuttle and the drive magnets are arranged along the track. In so-called long-stator linear motors, the drive coils are arranged along the track and the drive magnets are arranged on the shuttle. In this type of linear motor, the shuttle can be moved along the track, that is, the track defines the direction of movement. In a planar motor, another type of linear motor, the drive magnets or drive coils are arranged in the moving plane. Planar motors allow the shuttle to move in two directions in the moving plane.

[0003] Using linear motors, multiple shuttles can be moved simultaneously and independently of each other (except with respect to collision avoidance) by controlling the energization of the drive coils that interact with the corresponding drive magnets. This means that all drive coils do not need to be energized in a certain manner at all times, but only the drive coils that interact with the drive magnets need to be energized. The drive coils are energized by applying a drive coil voltage to the drive coils, generating an electrical drive coil current. Changing the drive coil voltage changes the drive coil current and the generated drive electromagnetic field. This allows for control of the movement of the shuttles.

[0004] Examples of long stator linear motors can be found in WO 2013 / 143783 A1, US 6,876,107 B2, US 2013 / 0074724 A1 or WO 2004 / 103792 A1. For example, US 9,202,719 B2 discloses the basic structure and operation of a planar motor.

[0005] It is well known that in linear motors of this type, so-called cogging can occur. The cause of this type of cogging is position-dependent differences in magnetic reluctance (magnetic resistance). This results in position-dependent force differences (cogging) that attempt to move the shuttle to a position where the active magnetic field reaches a state of minimum energy. During operation of the linear motor, cogging represents a disturbance acting on the shuttle that affects its movement, particularly at low shuttle speeds.

[0006] To compensate for cogging, it is known to twist the teeth around which the drive magnets or drive coils are wound. This results in a reduction in cogging due to the averaging of the aforementioned effects. The disadvantage of this approach is that, due to the averaging effect, not only the cogging force is reduced, but also the propulsion force, which is undesirable. Furthermore, skewed drive magnets or drive coils are more difficult to produce, which results in higher costs for the linear motor.

[0007] There are also some known methods that aim to compensate for the slot effect. US6,922,025B2 describes that the slot effect error is measured during the operation of the linear motor and then used to compensate for the slot effect by the motor control. In US11,718,482B2, the current reference and feedback signal of the control of the linear motor are used to determine the slot force to which the shuttle is subjected at a certain position along the track. Each time the shuttle travels along the same length of the track, the slot force is stored and used to compensate for the slot effect. In both cases, it is necessary to measure certain signals during the operation of the linear motor and use the measured signals to compensate for the slot effect. This increases the computing power required to control the linear motor and also increases the complexity of the control. Summary of the Invention

[0008] It is an object of the present invention to compensate for cogging during operation of a linear motor in a simple but effective manner.

[0009] This object is achieved by determining the cogging force in at least one direction of movement of the shuttle along the stator as a function of the relative position of the shuttle with respect to the stator in at least one direction of movement, while the drive coils in the shuttle region are not energized. This object is achieved by storing the determined cogging force in a control unit. This object is achieved by the control unit using the stored cogging force in at least one direction of movement to compensate for the cogging force during operation of the linear motor as a function of the relative position between the shuttle and the stator during operation of the linear motor. According to the present invention, the cogging force can be simply determined without energizing the drive coils. Thus, the cogging effect is determined without the magnetic influence of the active drive coils, which simplifies the method for determining the cogging force. Despite this simplified method, the cogging effect can be fully compensated during operation of the linear motor. This significantly improves the movement of the shuttle compared to a case without cogging compensation.

[0010] Furthermore, the cogging compensation can be improved if the cogging forces in a direction transverse to the direction of movement along the stator are also determined without energizing the drive coils in the shuttle region. This allows additional compensation of the cogging effects in the transverse direction.

[0011] If the cogging force in at least one direction of movement and / or the cogging force in the transverse direction is additionally determined as a function of the distance of at least one shuttle from another adjacent shuttle on the stator, cogging compensation can be significantly improved. The magnetic fields of adjacent shuttles on the stator can significantly influence each other, and such influences can be easily taken into account in this way.

[0012] Cogging is also significant when the stator includes segment gaps in at least one direction of movement, across which the shuttle moves during operation of the linear motor. Such segment gaps can also be accounted for by determining the cogging force as a function of the segment gap length. This also allows segment gaps of varying gap lengths to be accounted for during operation of the linear motor.

[0013] In a particularly simple embodiment of the cogging compensation, the cogging compensation unit calculates a compensation signal which is the inverse of the cogging force and superimposes this compensation signal on the force setpoint of the movement controller of the shuttle.

[0014] This object is also achieved by the linear motor mentioned in the introduction, which is configured to operate according to the method according to one of claims 1 to 14 . BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Reference below Figures 1 to 10 Describing the present invention in more detail, Figures 1 to 10 By way of example, exemplary and non-limiting advantageous embodiments of the present invention are shown. In the drawings:

[0016] Figure 1 is an exemplary embodiment of a long stator linear motor,

[0017] Figure 2 is an exemplary embodiment of a planar motor,

[0018] Figure 3a and Figure 3b are different views of possible embodiments of a planar motor,

[0019] Figure 4 and Figure 5 are embodiments of different segments of a stator of a linear motor,

[0020] Figure 6 and Figure 7 shows the determined cogging forces of different sections of the stator of a linear motor,

[0021] Figure 8 is an exemplary embodiment of a motion controller for a shuttle with cogging compensation,

[0022] Figure 9 is another embodiment of a motion controller for a shuttle with cogging compensation; and

[0023] Figure 10 The effect of the cogging compensation of the present invention is shown. DETAILED DESCRIPTION

[0024] As will be described below, the present invention relates to a linear motor 1. The linear motor 1 comprises a plurality of i drive coils ASi which are at least temporarily driven by a drive coil voltage V ASi The linear motor 1 is energized to generate a driving electromagnetic field that interacts with the driving magnet 4 of the linear motor 1 to drive at least one shuttle Tn of the linear motor 1. Generally speaking, the driving coil is represented by ASi, where "i" is an index so that the driving coil can be distinguished when necessary, and when no specific driving coil is specified, the reference numeral ASi is used. The linear motor 1 can be used to transport an object O on the shuttle Tn. This type of linear motor 1 is Figure 1 In the example shown in the form of a long stator linear motor. Figure 2 In the embodiment shown in Figure 2, the linear motor 1 is designed as a planar motor. In both cases, the drive coils ASi are arranged on the stator 2 of the linear motor 1, and the drive magnets 4 are arranged on the shuttle Tn. However, the opposite is also possible, i.e. the drive coils ASi are arranged on the shuttle Tn, and the drive magnets 4 are arranged on the stator 2. In this case, the drive magnets 4 will be arranged along the stator 2.

[0025] In order to better understand the present invention, refer to Figure 1 、 Figure 2and Figure 3a 、 Figure 3b The basic well-known principle and structure of the linear motor 1 as a long-stator linear motor and a planar motor are explained.

[0026] refer to Figure 3a and Figure 3b , the well-known principle and design of a planar motor (PLM) as an example of a linear motor 1 is explained by means of exemplary embodiments. Figure 3a The planar motor is shown in a partially cutaway plan view, and Figure 3b The planar motor is shown in a side view, partly cut away. The planar motor has at least one stator segment Sm. "m" is used as an index in order to be able to distinguish between different stator segments, wherein, in general, the reference symbol Sm is used when no specific stator segment is specified. The stator segment(s) Sm form a stator 2 of a PLM having a movement plane 3. At least one shuttle Tn is movable in the movement plane 3 at least two-dimensionally in two main movement directions corresponding to, for example, an X-axis and a Y-axis of a coordinate system. "n" is used as an index in order to be able to distinguish between different shuttles, wherein, in general, the reference mark Tn is used when no specific shuttle is addressed. The movement plane 3 can be oriented in any way in space, but usually forms a flat surface. For simplicity, in Figure 3a Of course, a plurality of stator segments Sm (which may have different shapes) are usually arranged adjacent to each other in order to form a stator 2 and a larger moving plane 3 (such as Figure 2 As shown in Figure 2 , the PLM can have a modular workspace within which shuttles Tn can move, defined by the arrangement of stator segments Sm. Movement planes 3 of varying shapes and sizes can be realized by arranging the stator segments Sm in a desired manner. Within the movement plane 3 of the stator 2, several shuttles Tn can naturally also move simultaneously and independently of one another. For example, shuttles Tn of varying sizes or shapes can even be used to transport different objects O on the shuttles Tn. It should be noted that the available workspace does not necessarily correspond to the entire movement plane 3 formed by the stator segments Sm. For example, some or all shuttles Tn may be prevented from entering specific areas of the movement plane 3.

[0027] A first coil group SG1 having a number of drive coils AS1 and a second coil group SG2 having a number of drive coils AS2 are arranged on each stator segment Sm, the first coil group SG1 defining a first main movement direction H1, and the second coil group SG2 defining a second main movement direction H2. The drive coils ASi of the first coil group SG1 are arranged adjacent to each other in a specific direction, in this case, in the X direction of a Cartesian coordinate system. The drive coils ASi of the second coil group SG2 are arranged adjacent to each other in a specific direction, in this case, in the Y direction of a Cartesian coordinate system. Figure 3a As shown, the drive coils AS1 , AS2 of the first coil set SG1 and the second coil set SG2 are preferably arranged relative to each other such that the two main movement directions are orthogonal to each other.

[0028] At least one drive magnet 4 is arranged on at least one shuttle Tn, which electromagnetically interacts with the drive coil ASi of at least one of the two coil groups SG1, SG2 in the area of ​​the shuttle Tn for moving the shuttle Tn. Typically, several drive magnets 4 are also arranged on the shuttle Tn with different polarities. For this purpose, the PLM shuttle Tn generally has a body 9, on the underside of which the drive magnet 4 is arranged (facing the movement plane 3), as shown in FIG. Figure 3b As shown. Figure 3a In FIG, the body 9 is shown largely cut away so that the means for driving the magnet 4 can be seen. Figure 3b As shown, the drive magnets 4 are arranged in several magnet groups MGa, MGb. The drive magnets 4 are usually arranged with alternating polarity, such as Figure 3a The drive magnets 4 can also be oriented differently in the different magnet groups MGa, MGb.

[0029] In the example shown, two first magnet groups MGa and two second magnet groups MGb are arranged on the shuttle Tn. A single first magnet group MGa and a single second magnet group MGb per shuttle Tn are generally sufficient to move the shuttle Tn in two directions in the movement plane 3. Of course, more than two first magnet groups MGa and more than two second magnet groups MGb can also be arranged per shuttle Tn. Many different arrangements of magnet groups MGa and MGb are known, such as one-dimensional arrangements, two-dimensional arrangements, Halbach arrangements, etc.

[0030] Use Figure 3a and Figure 3bIn the PLM shown, a substantially unlimited movement of the stator segment Tn in two main movement directions is possible, for example in the movement plane 3 of the stator segment 2. In this case, the shuttle Tn can be moved, for example, only along the X axis or only along the Y axis. The shuttle Tn can naturally be moved simultaneously in two main movement directions, for example, along any possible two-dimensional movement path P with X and Y coordinates lying in the movement plane 3, such as Figure 3a Of course, different movement paths P are possible for different shuttles Tn. However, the other four degrees of freedom (translational movement in the vertical direction Z and rotations about the three axes X, Y, and Z) can also be used, at least to a limited extent.

[0031] The drive coils ASi can also be arranged one above the other (here, in the Z direction). Figure 3b In the embodiment, the drive coil AS1 of the first coil group SG1 is arranged closer to the moving plane 3 than the drive coil AS2 of the second coil group SG2 in a direction perpendicular to the moving plane 3 (here, in the Z direction). Many different drive coil arrangements are known, such as a single-layer arrangement, a herringbone arrangement, a double-layer arrangement, etc.

[0032] During operation of the planar motor, in a possible embodiment, a moving magnetic field is generated in a first main movement direction by corresponding activation of the first drive coil AS1 interacting with the shuttle Tn. The moving magnetic field in the first main movement direction electromagnetically interacts primarily with the drive magnets 4 of the first magnet group(s) MGa to move the respective shuttle Tn in the first main movement direction H1. Similarly, a substantially moving magnetic field is generated in a second main movement direction by activating the second drive coil AS2 interacting with the shuttle Tn. This substantially moving magnetic field electromagnetically interacts primarily with the drive magnets 4 of the second magnet group(s) MGb to move the shuttle Tn in the second main movement direction. Depending on the activation of the drive coils AS1 and AS2 in the region of the shuttle Tn, the moving magnetic fields are superimposed, resulting in the shuttle Tn being able to move in a desired manner along a pre-specified two-dimensional movement path P in the movement plane 3. As described above, movement with more degrees of freedom can also be achieved.

[0033] The drive coil ASi is usually activated by energizing it in such a way that a force also acts on the shuttle Tn in the Z-axis direction, by means of which the shuttle Tn is kept suspended above the movement plane 3 for generating the air gap L( Figure 3b ) (This is also possible when the shuttle Tn is at rest).

[0034] As another example of the linear motor 1, Figure 1As shown, a long stator linear motor (LLM) differs from a planar motor primarily in that the drive coils ASi are arranged adjacent to one another along the stator 2, so that the plane of movement is reduced to a movement trajectory defined by the geometry of the stator 2. The LLM also includes at least one stator segment Sm forming the stator 2.

[0035] For the sake of clarity, well-known guide structures for guiding the shuttle Tn along the stator 2 of the LLM and / or retaining the shuttle Tn on the stator 2 are not shown in FIG. Figure 1 Such guide structures can be designed as desired and required, for example using rollers.

[0036] Thus, a long stator linear motor consists of a stator 2 and a plurality of shuttles Tn (n>1) that can be moved along the stator 2. "n" is used as an index to be able to distinguish between the different shuttles, wherein, in general, the reference mark Tn is used when no specific shuttle is specified. For movement, drive coils ASi (i>1) are arranged on the stator 2, one behind the other in the direction of movement along the stator 2. For the sake of clarity, Figure 1 Only a few drive coils ASi are shown in FIG. However, as is known, the drive coils ASi are arranged along the entire moving area of ​​a long stator linear motor. At least one drive magnet 4, usually a plurality of drive magnets in the form of a permanent magnet arrangement, is arranged on the shuttle Tn. For the sake of clarity, Figure 1 This is only hinted at in FIG. The drive magnet 4 faces the drive coil ASi on the stator 2 and is separated from the drive coil ASi by an air gap.

[0037] The stator 2 may be composed of a single stator segment Sm (m>1), and each stator segment Sm has a plurality of drive coils ASi, such as Figure 1 As shown. The stator 2 can also be composed of a single stator segment SAj (j≥1) (such as Figure 2 ), which can be interconnected via switch W and form stator 2. "j" is used as an index to distinguish between different stator segments, wherein, generally speaking, the reference symbol SAj is used when no specific stator segment is specified. Stator segment SAj can, in turn, be composed of multiple stator segments Sm. At switch W, shuttle Tn can switch from one stator segment SAj to another stator segment SAj+1 and continue its movement on stator segment SAj+1.

[0038] The coil can be driven by applying a voltage V ASi The drive coil ASi is energized and thereby generates a drive electromagnetic field that interacts with the drive magnet 4 of the shuttle Tn to generate a force acting on the transport unit Tn. This force then serves as a propulsion force for moving the shuttle Tn along the stator 2 in the desired direction.

[0039] In LLM, it is also possible to arrange the drive coils ASi on both sides of the stator 2 as seen in the direction of movement, and the drive magnets 4 of the shuttle Tn can move between them (e.g. Figure 1 (As shown in the transport unit Tn in FIG. ). If the drive magnets 4 are also provided on both sides of the shuttle Tn, as viewed in the direction of movement, then by energizing the drive coils ASi on both sides, forces (also different forces) acting on the shuttle Tn can also be generated simultaneously on both sides. Using this type of arrangement, the electromagnetic switch W can also be implemented, in particular, on a linear long-stator linear motor.

[0040] As already mentioned at the outset, the linear motor 1 can also be designed such that the drive coils ASi are arranged on the shuttle Tn and the drive magnets 4 are arranged on the stator 2 of the linear motor 1 .

[0041] A control unit 10 is provided, which controls the energization of the drive coils ASi of the linear motor 1 to generate the drive electromagnetic field for moving the shuttle Tn. Essentially, this means that the required drive coils ASi are energized under the control of the control unit 10 so that any shuttle Tn executes a desired movement path P in the plane of motion 3 (PLM) or along the stator 2 (LLM) with a desired movement profile (e.g., speed, acceleration). In the case of the PLM, the movement path P is not limited to movement in the main movement direction but can also specify movement in the other four degrees of freedom. In the case of the LLM, the movement path P can also include different stator segments SAj connected by switches W. The movement path P can be defined, for example, to implement a transport task using the linear motor 1 as a transport device in a machine in which the linear motor 1 is integrated. The drive coils ASi of the linear motor 1 are controlled by the control unit 10 so that the shuttle Tn moves along the desired movement path P and with a desired movement profile. To this end, the control unit 10 controls not only the movement path P, but also the dynamics of the movement, in particular the speed, acceleration, jerk at any point in time.

[0042] Actual values ​​AV of the movement of the shuttle Tn, such as the actual position (also the actual orientation of the shuttle Tn) or the actual speed, are usually also used in the control unit 10 to execute or control the movement of the shuttle Tn. For this purpose, suitable sensors, such as position sensors PS, can also be arranged on or along the stator 2, the detected measured variables of the sensors being transmitted to the control unit 10 as actual values ​​AV of the movement of the shuttle Tn, or the actual values ​​AV of the movement being determined in the control unit 10 from the detected measured variables.

[0043] In order to be able to determine the position of the shuttle Tn on the stator 2, a position sensor PS can be arranged on the stator 2, such as Figure 1 or Figure 2 For the sake of clarity, only some position sensors PS are shown. The position sensors PS provide the detected position signals, for example as actual values ​​AV, to the control unit 10. However, known sensorless position detection can also be implemented in the LLM and PLM to detect the position of the shuttle Tn.

[0044] The position sensor PS can detect the magnetic field of the shuttle Tn, for example, the magnetic field emitted by the drive magnet 4 or the magnetic field emitted by a magnet at a specific position on the shuttle Tn. This type of position sensor PS can be designed as a magnetostrictive sensor, a magnetoresistive sensor, or a Hall sensor, for example, although other types of sensors capable of detecting magnetic fields are of course available. However, sensors that detect different physical variables are also possible, such as optical or inductive sensors.

[0045] Power Electronics 15( Figure 1 ) can be provided in the linear motor 1 to generate a drive coil voltage V for the drive coil ASi. ASi The control unit 10 can control the power electronics 15 in order to energize the drive coil ASi in the desired manner, in particular with the required electrical drive coil current.

[0046] The control unit 10 can also be designed as a distributed controller (eg Figure 1 ), for example, having a plurality of coil control units 5, for example, one coil control unit 5 for each stator segment Sm, and a superordinate system control unit 6, which is connected to the plurality of coil control units 5, for example, via a communication network 7. For example, the system control unit 6 can implement the movement of the shuttle Tn and pre-assign a target point for the shuttle Tn so that the shuttle Tn can be moved according to the movement path P and according to the desired movement profile (movement dynamics) in order to perform the desired transport task. Collision monitoring and avoidance for the shuttle Tn can also be implemented in the system control unit 6. The coil control unit 5 can be configured to convert the specifications of the system control unit 6 into the drive coil voltage V ASi However, the division into coil control unit 5 and system control unit 6 is merely exemplary. Generally speaking, a control unit 10 is provided that controls the drive coils ASi in order to generate the desired movement of the shuttle Tn. However, how this control unit 10 is designed, for example in the form of a cascade controller composed of multiple interconnected controllers or as a single controller, is immaterial to the present invention.

[0047] The control unit can generally be implemented as microprocessor-based hardware, such as a computer, a microcontroller, a digital signal processor (DSP), a programmable logic controller (PLC), etc., on which corresponding control programs for implementing corresponding functions are run. Embodiments as integrated circuits, such as application-specific integrated circuits (ASICs) or field-programmable gate arrays (FPGAs), are also conceivable.

[0048] Figure 4 The figure shows a section of a stator 2 of an LLM as an example of a linear motor 1. Two stator segments Sm, Sm-1 are shown. Each stator segment Sm has a plurality of teeth 11, 12. Figure 4 In the example of , there is a main tooth 11, and the drive coil ASi is arranged on the main tooth 11. Figure 4 In the embodiment of the present invention, the teeth 11 and 12 are arranged on the stator 2, but when the drive coil ASi is on the shuttle Tn, they can also be arranged on the shuttle Tn. A secondary tooth 12 without a drive coil ASi is provided between the two main teeth 11, but the secondary tooth 11 is only optional. For the sake of clarity, Figure 4 Only some of the drive coils ASi are shown in FIG. The distance between two main teeth 11 in the moving direction x is the tooth pitch τ n , the tooth pitch is usually constant. Tooth pitch τ n is defined by the design of the linear motor 1 and is known. Also shown is a shuttle Tn having a magnet spacing τ p The device of driving magnet 4. Magnet spacing τ p The stator gap SG is defined by the design of the linear motor 1 and is known. Between two adjacent stator segments Sm, Sm-1 there may be a stator gap SG. The stator gap SG influences the magnetic field in the gap region. The stator gap SG may optionally be at least partially filled with a stator gap filler SGF (e.g. Figure 4 As shown in Figure 2, the stator gap filler SGF is usually made of a magnetically conductive material to prevent the magnetic field in the stator gap SG from dropping rapidly. In the case of a planar motor, the stator gap filler SGF is usually made of a magnetically conductive material to prevent the magnetic field in the stator gap SG from dropping rapidly. Figure 4 The same applies essentially to both directions. Figure 5 A curved section of the LLM stator 2 is shown.

[0049] According to the present invention, before the normal operation of the linear motor 1 begins, the drive coil Asi is not energized and therefore no drive magnetic field is generated. Figure 4 and Figure 5The drive magnet 4 in the embodiment of FIG is a permanent magnet, but it can also be in the form of an electromagnet (which will be energized). The drive magnet 4 generates a drive magnetic field. This drive magnetic field interacts with the magnetically conductive parts of the stator 2, such as the iron stator teeth 11, 12 and the iron yoke connecting the stator teeth 11, 12. This magnetic interaction causes a cogging force F acting on the shuttle Tn, which depends on the position of the shuttle Tn relative to the stator 2. C(x,y,z) (This symbol represents the cogging force F Cx 、F Cy 、F Cz any one or any combination of ), since the shuttle Tn tends to take a position that minimizes the energy of the acting magnetic field, which is affected by the position of the shuttle Tn relative to the stator 2. For example, the cogging force F C(x,y,z) Acts in the direction of movement x and also in the transverse direction z. In the case of a planar motor, also in the second direction of movement y. Cogging force F in the direction of movement x Cx Try to move the shuttle Tn to the minimum energy position. The cogging force F in the lateral direction Cz The force that affects the attraction between the shuttle Tn and the stator 2, or in the case of a planar motor, the force by which the shuttle Tn is kept suspended above the stator. This is referred to as the cogging force F C(x,y,z) is not constant, but varies as a function of the relative position of the shuttle Tn with respect to the stator 2. This varying cogging force F Cx 、F Cy 、F Cz The measurement or determination can be performed using a model of the linear motor 1 or using simulations. A well-known finite element model (FEM) or a well-known reluctance model of the linear motor 1 can be used as a model. A reluctance model is described, for example, in WO 2022 / 049026 A1.

[0050] Cogging force F Cx 、F Cy 、F Cz The cogging effect can be detected by providing an acceleration sensor on the shuttle Tn and moving the shuttle Tn manually or using a handling device (such as a robot or a second slave shuttle Tn) at a sufficient distance from the first shuttle to avoid energizing the coils along the stator 2 in a given direction x, y, and z in the area of ​​the shuttle used for measurement. The cogging effect can be detected by changing the acceleration, for example, by measuring it with an acceleration sensor. When the mass of the shuttle Tn is known, the detected acceleration can be converted into a cogging force F according to the relative position of the shuttle Tn with respect to the stator 2. Cx 、F Cy 、F CzWhen using a handling device, a force sensor can be set on the handling device to measure the force between the driven shuttle and the driving handling device. The force thus measured is also the cogging force F Cx 、F Cy 、F Cz The measured value.

[0051] In the case of LLM, the structure of the LLM can be used to measure the cogging force F Cx 、F Cy 、F Cz In the LLM section, there are drive coils ASi on both sides of the shuttle Tn (as seen in the direction of movement x), and the shuttle Tn has drive magnets 4 on both sides of the shuttle Tn (as seen in the direction of movement x). By energizing the drive coils ASi on this side, one side can be used to propel the shuttle Tn along the stator 2, and the other, non-energized side can be used to measure the cogging force F. Cx 、F Cy 、F Cz In this case, the LLM itself is the handling equipment of the mobile shuttle Tn.

[0052] Measurement of the cogging force F acting on the shuttle Tn Cx 、F Cy 、F Cz Another possibility is to bring the shuttle Tn to a specific speed by appropriately energizing the drive coils ASi in the area of ​​the shuttle Tn. When this speed is reached, the drive coils ASi are switched off and the shuttle Tn is allowed to stop due to the friction forces acting. The acceleration of the shuttle Tn is obtained, which in this case should correspond to the friction forces and the cogging forces. Using a known friction model for linear motors, which simulates the friction between the guide structure on the stator and the shuttle Tn, possibly depending on the speed of the shuttle Tn, the cogging force F can be obtained. Cx 、F Cy 、F Cz In this case, the acceleration can also be calculated from the measured position and / or velocity, or by using an acceleration sensor mounted on the shuttle Tn.

[0053] Due to the unenergized drive coils ASi, the model of the linear motor 1 only needs to simulate the magnetic interaction of the plurality of drive magnets 4 with magnetically conductive parts of the linear motor 1 , ie parts of the stator 2 or parts of the shuttle Tn.

[0054] For example, FEM simulates a linear motor 1 in a known manner by subdividing its individual components into smaller, simpler components called finite elements. Magnetic field variables, such as the magnetic flux density or magnetic field strength, can be numerically calculated for each finite element, which is coupled via boundary conditions. As a result, the magnetic field variables can be determined along a given geometric dimension, which in turn allows the calculation of the acting magnetic forces, such as the cogging force F. C FEM is well known and does not require a more detailed explanation.

[0055] Since the geometry and materials of the linear motor 1 with the stator 2 and the shuttle Tn are known, the FEM model can be adapted to the specific embodiment of the linear motor 1. This also allows the calculation of the cogging forces F for different embodiments of the linear motor 1 or different shuttles Tn of the linear motor 1. C .

[0056] Because according to the present invention it is not necessary to energize the drive coil ASi to determine the cogging force F C , so the cogging force F is calculated with the help of the model of the linear motor 1 C This can be done offline and can utilize models that require more computing power than would be required to calculate the model online during operation of the linear motor 1 , such as FEM.

[0057] In a linear motor 1 having a plurality of stator segments Sm, the segment gaps SG between adjacent segments Sm in the direction of movement of the shuttle Tn are not necessarily equal. Due to tolerances in the dimensions of the segments Sm forming the stator 2 and the arrangement of the segments SM, the length GL of the segment gaps SG in the direction of movement of the shuttle Tn may vary. In a determined cogging force F Cx 、F Cy 、F Cz Such changes in the segment gap SG can also be taken into account. Cx 、F Cy 、F Cz Such geometrical effects can be easily taken into account when the model is constructed, and the cogging force F is determined Cx 、F Cy 、F Cz It can also be determined and stored depending on a certain segment gap SG in the direction of movement x, y, z of the shuttle Tn. The actual length GL of the segment gap SG of the stator arrangement can then be determined, for example measured at the linear motor 1, and the cogging force F can then also be compensated depending on the actual segment gap SG in the direction of movement of the shuttle Tn. Cx 、F Cy 、F Cz .

[0058] The actual length GL of the segment gap SG can also be determined during operation of the linear motor 1 using, for example, an available position sensor PS. Figure 4 By taking into account the values ​​of the position sensors PS next to the segment gap SG on each side (as seen in the movement direction x) of the shuttle Tn (shown), it is possible to calculate the actual segment gap SG using the known dimensions and design of the shuttle Tn, in particular the arrangement and position of the position magnets on the shuttle Tn. To this end, the shuttle Tn is positioned at the gap so that the position sensors PS located on both sides of the segment gap SG provide position sensor values.

[0059] Another possibility is to determine the actual length GL of the segment gap SG using two position sensors PS on either side of the segment gap SG (as viewed in the direction of movement x). In this case, the position sensors PS do not necessarily have to be located in close proximity to the segment gap SG. At least one shuttle Tn is positioned on one side of the segment gap SG (as viewed in the direction of movement x) and measures its position a first time. At least one shuttle Tn is positioned on the other side of the segment gap SG (as viewed in the direction of movement x) and measures its position a second time. The difference between the first and second positions is a measure of the actual segment gap length GL of the segment gap SG. This difference corresponds to the distance between the two position sensors PS, which is known from the known geometry of the stator 2. The difference between the first and second positions can be compared with the expected difference given the known geometry of the stator 2. Deviations between the differences are due to the varying length GL of the segment gap SG, which allows the actual length GL of the segment gap SG to be determined. This can also be accomplished using different position sensors PS and using the average of several determined actual lengths GL of the segment gap SG.

[0060] There is another possibility to determine the actual length GL of the segment gap SG. In this method, the first drive coil ASi on the first side of the segment gap SG (as seen in the direction of movement x) is used as a transmitting coil, and the second drive coil ASi+1 on the other side of the segment gap SG (as seen in the direction of movement x) is used as a receiving coil. The transmitting coil is driven by a specific coil voltage V ASiThe electromagnetic field is driven so as to induce a voltage in the receiving coil. The induced voltage can be measured, and certain characteristics of the induced voltage, such as amplitude, phase, frequency content, integral, slope, etc., can be related to the length of the segment gap SG. When the receiving coil is switched to open loop, the induced coil voltage can be measured at the receiving coil using a voltage sensor. Alternatively, the current in the receiving coil is controlled to zero, and the voltage corresponding to the induced voltage applied by the current controller is monitored. The average value of many such determinations, also possibly using switched transmitting and receiving coils, can increase the signal-to-noise ratio (SNR), which improves the determination of the segment gap SG. It is also possible to determine the segment gap SG by using a specific coil voltage V ASi The SNR can be improved by driving several transmitting coils. The SNR can also be improved by placing a shuttle Tn or a magnetically conductive component above the segment gap SG during the determination, or by placing a magnetic component in the segment gap SG, because this reduces the air gap of the electromagnetic field and increases the sensitivity of the transmitted signal with respect to the actual length GL of the segment gap SG. The magnetic component is preferably placed at least partially in the gap between the iron yokes of adjacent segments Sm, or in the region of the axial end of the tooth 11 opposite the iron yoke.

[0061] Determining the actual segment gap SG during operation of the linear motor 1 also allows compensation for variations in the segment gap SG due to thermal expansion of the segment Sm. To this end, the temperature of the segment Sm adjacent to the segment gap SG can be determined, for example by measuring it with a temperature sensor, and the thermal expansion of the segment Sm can be determined, for example using a thermal model of the segment that measures the length of the segment Sm in the direction of movement as a function of temperature.

[0062] For a planar motor, the segment gap SG can of course be determined in the same manner as described above in both movement directions x, y.

[0063] In addition, the coupling effect between the two shuttles may affect the determined cogging force F Cx 、F Cy 、F Cz When two adjacent shuttles Tn, Tn+1 are positioned close to each other on the stator 2, which is usually the case during operation of the linear motor 1, the drive magnetic fields of the adjacent shuttles Tn, Tn+1 influence each other, which also affects the cogging force F. Cx 、F Cy 、F Cz Consider the effect of this type of coupling on the cogging force F Cx 、F Cy 、F Cz The influence of is particularly advantageous. Use the model to determine the cogging force F Cx 、F Cy 、F CzThis can of course be easily done up front by including a second shuttle Tn+1 in the model. The cogging force F on shuttle Tn can then be simulated as a function of the distance between adjacent shuttles Tn, Tn+1. Cx 、F Cy 、F Cz The influence of the cogging force F Cx 、F Cy 、F Cz It can be determined not only as a function of the relative position of the shuttle Tn relative to the stator 2, but also as a function of the distance to the second adjacent shuttle Tn+1. During operation of the linear motor 1, the positions of all shuttles Tn are known, which allows to compensate the cogging force F not only as a function of the relative position of the shuttle Tn relative to the stator 2, but also as a function of the distance to the second adjacent shuttle Tn+1. Cx 、F Cy 、F Cz .

[0064] Figure 6 is shown as a function of the position of the shuttle Tn relative to the stator 2 in the direction of movement x, Figure 4 and Figure 5 Determined (measured, calculated according to a model, simulated) cogging forces F of the linear motor 1 in the displacement direction x and in the transverse direction Z transverse to the displacement direction x Cx 、F Cz In this case, the acting magnetic field is not affected by the stator segment gap SG, which means that the shuttle Tn is sufficiently far away from the stator segment gap SG. For example, the force F in the transverse direction Z Cz is the attractive force holding the shuttle Tn on the stator 2. During operation of the linear motor 1, in which the drive coil ASi in the area of ​​the shuttle Tn is energized, the cogging force F in the direction of movement x Cx is a force acting as a disturbance to the propulsion force with which the shuttle Tn is moved along the stator 2 during operation. Figure 6 In the figure, the solid line shows the cogging force F of the straight stator section. Cx 、F Cz (like Figure 4 ), and the dashed line shows the cogging force F of the bent stator segment Cx 、F Cz (like Figure 5 In a curved section, the movement direction x is the tangent of the curved section.

[0065] from Figure 6 It can also be seen that for a given design of the linear motor 1, such as the arrangement of the drive magnet 4, the air gap L, the magnetic conductive components, the materials, etc., the cogging force F Cx 、F CzThe magnetic resistance of the magnetic device of the linear motor 1 is the cogging force F. Cx 、F Cz The reason for this is that the change cycle or the main tooth pitch τ n , for example 15 mm when there are only main teeth 11, or half the main tooth pitch Tn when there are auxiliary teeth 12 between two adjacent main teeth. This makes the cogging force F Cx 、F Cz Only needs to be determined (measured, calculated from a model, simulated) for very short lengths, usually only for the tooth pitch τ n The length or half of the length is determined because the cogging force F when the shuttle Tn moves along the stator 2 Cx 、F Cz Will simply repeat.

[0066] Figure 7 The cogging forces F determined (measured, calculated according to the model, simulated) for the transition of the shuttle Tn across the segment gap SG are shown. Cx 、F Cz , also for straight stator segments (solid line) and curved segments (dashed line), except that the cogging forces F in the stator 2 or stator segment Sm Cx 、F Cz In addition, the cogging force F can optionally be determined Cx 、F Cz In this case, the cogging force F Cx 、F Cz The main pitch Tn or half of the main pitch Tn (in the case of auxiliary teeth 12) can be seen in the curve of , but in this case, the cogging force F Cx 、F Cz Need to be determined for the complete transition, i.e. until the shuttle Tn has completely crossed the segment gap SG. However, the cogging force F in the segment gap SG region can be determined using symmetry. Cx 、F Cz In this case, only the cogging force F is determined for half the transition across the segment gap SG Cx 、F Cz For example, the cogging force F can be determined Cx 、F Cz , until the center of the shuttle Tn in the direction of movement x and the center of the segment gap SG in the direction of movement x are aligned. For the remaining transitions, symmetry can be used. Cogging force F in the transition area in the direction of movement Cx is point symmetrical, and the cogging force F in the transverse direction Cz is symmetrical about the axis. However, in this case, the cogging force F Cx 、F CzIt only needs to be dimensioned for a rather short length (compared to the entire length of the stator 2 or even the stator segment Sm), essentially a little longer than the length or half the length of the arrangement of the drive magnets 4 or drive coils ASi on the shuttle Tn.

[0067] In the case of a planar motor as the linear motor 1, similarly, the cogging force F in the additional movement direction y can also be obtained. Cy , the cogging force F Cy is a function of the position of the shuttle Tn in that direction y.

[0068] When the linear motor 1 is not running, for a given linear motor 1 design, the cogging force F Cx 、F Cy 、F Cz is predetermined and stored in the control unit 10 of the linear motor 1. Cx 、F Cy 、F Cz The values ​​can be stored in a lookup table with a given resolution (e.g. 0.1 mm). For example, the resolution can match the resolution of the position sensor PS. It is also possible to interpolate between the values ​​in the lookup table. It is also possible to determine the cogging force F. Cx 、F Cy 、F Cz Fit a mathematical function, such as a polynomial of a given order or sine and cosine functions (Fourier method), to the curve and use this mathematical function to determine the cogging force F at a certain position x. Cx 、F Cy 、F Cz This will reduce the memory required in the control unit 10 .

[0069] As mentioned above, the cogging force F of the shuttle Tn Cx 、F Cy 、F Cz In addition, other influences such as the length of the segment gap SG in the moving direction, other adjacent shuttles, etc. can also be considered. Cx 、F Cy 、F Cz Such additional effects will also be stored.

[0070] In addition to determining the cogging forces F in straight and curved sections Cx 、F Cy 、F Cz In addition, it is also possible to determine the cogging forces F only in straight or curved sections. Cx 、F Cy 、F Cz , and the determined cogging force F Cx 、F Cy 、FCz Conversion to other types of segments with given and known relationships. Such relationships can be used to determine the cogging force F from different types of stator segments. Cx 、F Cy 、F Cz It has been found that the cogging force F of the straight section Cx 、F Cy 、F Cz Multiply by a certain factor, for example by 4, the cogging force F in the curve section is Cx 、F Cy 、F Cz A good approximation of . The multiplication factor may depend on the curvature of the curved segment. Thus, knowing this relationship, for a single type of segment (e.g., straight or curved), the stored cogging force F Cx 、F Cy 、F Cz That's enough.

[0071] For the present invention, at least one cogging force F in the direction of movement x is determined. Cx For a planar motor, preferably, the cogging forces F in the two movement directions x and y are determined Cx 、F Cy In addition, the cogging force F in the transverse direction z can also be determined Cz .

[0072] For different stator segments, for example for straight stator segments and / or curved stator segments, as well as for different curved segments (eg with different curvatures), the determined cogging forces F Cx 、F Cz 、F Cy can be stored in the control unit 10. The determined cogging forces F can also be stored for different shuttles Tn or different geometries of the stator 1 or different air gaps l. Cx 、F Cz 、F Cy .

[0073] The control unit 10 then uses the cogging force F thus determined with the unenergized drive coil ASi Cx 、F Cz 、F Cy To compensate for the cogging effect during the operation of the linear motor 1. This will refer to Figure 8 Provide explanation.

[0074] In this context, “for compensation” means that the cogging force F Cx 、F Cz 、F Cy The effect on the movement of the shuttle Tn is at least reduced.Cx 、F Cz 、F Cy is determined by the unpowered drive coil ASi, so the drive electromagnetic field acts on the cogging force F Cx 、F Cz 、F Cy Therefore, the method of the present invention will not usually completely eliminate the cogging force F Cx 、F Cz 、F Cy However, the method of the present invention allows the cogging force F Cx 、F Cz 、F Cy The modeling does not require operating parameters of the linear motor 1, such as actual coil current or coil voltage values, or, for example, the current position error of the controller. All that is required is the position of the shuttle Tn relative to the stator 2, which can be guaranteed at all times during the operation of the linear motor 1. This makes the compensation of the cogging effect according to the present invention much easier and requires less computing power during the operation of the linear motor 1.

[0075] Figure 8 As an example, a control unit 10 is shown having a motion controller 20 for controlling the movement of a shuttle Tn of a linear motor 1. The motion controller 20 is implemented in the control unit 10, for example, as control software running on the computer hardware of the control unit 10. For example, the motion controller 20 can implement position control, velocity control, or force control of the shuttle Tn. The control unit 10 receives a setpoint SP for controlling the movement of the shuttle Tn. The setpoint SP can be a setpoint position, a setpoint velocity, a setpoint force of the shuttle Tn, or any other suitable setpoint. The control unit 10 also receives an actual value AV for the movement of the shuttle Tn, such as an actual position from a position sensor PS or an actual velocity of the shuttle Tn. Typically in closed-loop control, a control error CE is determined as the difference between the setpoint SP and the actual value AV. Like a well-known PID controller or any other suitable type of controller, the motion controller 20 calculates a manipulated variable MP in order to reduce the control error CE. The manipulated variable MP is used to energize the active drive coils ASi in the region of the shuttle Tn for driving the shuttle Tn and is, for example, typically the drive coil voltage V of each active drive coil ASi. ASi or drive coil current.

[0076] The control unit 10 preferably comprises a cogging compensation unit 21 which determines a compensation signal CS which is superimposed on the output value of the motion controller 20, in this case on the manipulated variable MP or alternatively on the set point SP (at Figure 8"Superposition" basically means that the value of the compensation signal CS is "added" to the output value of the motion controller 20 in some way, which can be done by any basic arithmetic operation, such as summation or multiplication.

[0077] The compensation signal CS is generated in the cogging compensation unit 21 from the determined and stored cogging force F C(x,y,z) Formed. Figure 8 In the embodiment, a data storage unit 22 similar to a computer memory is provided in the control unit 10. As described above, the cogging force F is determined. C(x,y,z) In order to be able to read out the cogging force F depending on the relative position of the shuttle Tn with respect to the stator 2 Cx 、F Cy 、F Cz , the cogging compensation unit 21 can be provided with the actual position of the shuttle Tn by means of, for example, a position sensor PS, such as Figure 8 As shown in the embodiment.

[0078] Cogging forces F stored in adjacent segments with or without stator segment gap SG C(x,y,z) are advantageously corrected together in order to avoid sudden changes in the compensation signal CS. Such sudden changes in the compensation signal CS can cause sudden changes in the setpoint value of the controller, which in turn causes an undesirable (over) reaction of the controller.

[0079] The cogging compensation unit 21 may be implemented as software running on microprocessor-based hardware of the control unit 10 , but may also be implemented as standalone hardware, such as microprocessor-based hardware or an integrated circuit.

[0080] Typically, such a motion controller 20 is implemented for each motion direction x, y, z. For LLM, this can be achieved, for example, using the well-known dq coordinate system, where the q component is responsible for the motion along the stator 2 in the motion direction x, and the d component is responsible for the transverse direction z. The controller 20 then determines the electric q current and the electric d current, which are transformed into the coil current of the active drive coil ASi using the well-known Park transformation. To this end, the slot compensation unit 21 can calculate the current according to the slot force F Cx 、F Cz The compensation signal CS is determined as an electrical compensation current using the known motor constant (force equals motor constant multiplied by current). The compensation current, which is the compensation signal CS, is then superimposed on the manipulated variable MP, which in this case is also the current for driving the coil ASi.

[0081] As is known, the mobile controller 20 can also be implemented as a cascade controller comprising several consecutive controllers. Figure 9. In this example, the movement controller 20 comprises a position controller PC, which is followed by a speed controller SC, which is followed by a current controller IC. The position controller PC receives a position setpoint and calculates a setpoint speed SPS as an output value of the position controller. The speed controller SC receives the setpoint speed SPS as an input value and calculates a force setpoint SPF for the subsequent current controller IC as an output value. The current controller IC determines the coil voltage V of the active drive coil ASi. ASi or coil current as the manipulated variable MP of the motion controller 20. In such a cascade controller, the compensation signal CS can essentially be superimposed on an input value or output value of one of the cascade controllers. The location where the compensation signal CS is superimposed naturally determines which physical quantity, such as position, velocity, force or current (voltage), the compensation signal CS is characterized by. Since the physical quantities used to control the movement of the shuttle Tn are related to each other in a known manner, the determined and stored cogging force F C(x,y,z) It can be easily converted into any desired physical quantity. For example, the force can be converted into a current using known motor constants. A changing force causes a change in the shuttle's speed. For example, a changing speed can be converted into a changing position.

[0082] exist Figure 9 In the example of FIG. 1 , the compensation unit 21 determines the cogging force F Cx 、F Cz 、F Cy The inverse of is used as the compensation signal CS, and the compensation signal CS is superimposed on the force set point SPF (output of the speed controller SC). The subsequent current controller then receives the changing force set point at its input and thus energizes the drive coil ASi so that the cogging effect is compensated. However, the compensation signal CS (in the correct physical quantity) can also be superimposed on each input value or output value in the controller cascade, such as Figure 9 Indicated by the dotted line.

[0083] Typically, the control is time-discrete. This means that the motion controller 20 determines the manipulated variable MP within a given time step, typically in the millisecond to microsecond range. The compensation signal CS is then also determined and superimposed on the desired signal in a time-discrete manner.

[0084] The cogging compensation unit 21 must ensure that the compensation signal CS corresponds to the actual relative position between the shuttle Tn and the stator 2 in order to compensate for the correct position-dependent cogging forces F Cx 、F Cz 、F Cy For this purpose, the compensation signal CS can also receive the actual position from the position sensor PS, such as Figure 8 or Figure 9In a simpler approach, the cogging compensation unit 21 can simply obtain a set point position that differs from the actual position only by the control error (in Figure 9 The cogging compensation unit 21 may also obtain the actual position from the motion controller 20 or other components of the control unit 10.

[0085] As mentioned above, the cogging force F Cx 、F Cy 、F Cz Additional dependencies may be stored, such as the length of the stator gap SG or the distance to the adjacent shuttle. In this case, the compensation unit 21 may also receive additional data, which allows the compensation unit 21 to determine such additional dependencies. The compensation unit 21 may, for example, receive the position of the adjacent shuttle Tn+1 or the segment gap length, or data that allows the compensation unit 21 to determine these quantities.

[0086] Figure 10 The effects of the present invention are shown in the exemplary embodiment. Figure 10 In the embodiment, it is assumed that the track of the linear motor 1 is formed by three stator segments Sm with a stator segment gap SG between two adjacent segments. Figure 10 The first segment (from left to right in the figure) is a curved segment that begins with a certain curvature and transitions to a straight segment at the end of the segment. The following segment is the opposite of the first segment, that is, a straight segment that transitions to a curved segment at the end of the segment. The third segment is a 45-degree curve. For this example, the cogging force F in the direction of movement x is determined as described above. Cx ( Figure 10 ). The cogging force F determined Cx The inverse of is used as compensation signal CS and is superimposed on the set point value SPF of the speed controller SC (e.g. Figure 9 shown). Figure 10 At the top, the control error CE is depicted with cogging compensation (solid line) and without cogging compensation (dashed line). It can be seen that in the example shown, the cogging effect is particularly present in the curved segments and the stator segment gap SG, while it is less pronounced in the straight segments. Cogging force F Cx The compensation results in a reduction of the control error CE in all sections.

[0087] The inventors have found that the cogging force F C(x,y,z)Compensation for cogging can require higher coil currents during operation of the linear motor 1. This is particularly true in the curve section. Higher drive coil currents result in higher losses, higher segment temperatures, and possibly a limitation in propulsion force (because cogging compensation requires higher currents). Therefore, it may be advantageous to limit the cogging compensation speed or to shut off compensation above a given speed of the shuttle Tn. Speed-dependent reduction of cogging compensation can be easily accomplished linearly or in any other suitable manner by reducing the compensation signal CS as speed increases.

[0088] Of course, the speed-dependent compensation can also be performed in different ways. For example, the speed-dependent cogging force F can be stored. C(x,y,z) .

[0089] A further advantage of the invention is that the flexibility of the point at which the compensation signal CS is applied allows compensation of cogging even when the position controller PC and the speed controller SP are switched off, e.g. Figure 9 As shown, the current controller IC will still receive input in the form of the compensation signal CS. This allows, for example, manual teaching of the movement of the shuttle Tn. When the shuttle Tn is moved manually along the stator 2 (in which case the position controller PC and the speed controller SP will be switched off), the person moving the shuttle Tn will feel cogging forces, which makes it more difficult to teach, for example, a certain position of the shuttle Tn on the stator 2. When the compensation signal CS is generated during such a manual teaching operation, the drive coil Asi will be energized, but only to compensate for the cogging forces F. C(x,y,z) This does not prevent manual teaching, but makes the movement of the shuttle Tn smoother, thus facilitating this function.

[0090] It is obvious from the above that the cogging force F is determined using the unpowered drive coil Asi. C(x,y,z) The shuttle Tn does not necessarily compensate for the cogging force F during operation of the linear motor 1 C(x,y,z) In one embodiment of the present invention, the cogging force F C(x,y,z) is determined for a certain shuttle Tn, and the cogging force F determined C(x,y,z) Only used to compensate the cogging force F of the same shuttle Tn during operation of the linear motor 1 C(x,y,z) In another embodiment, the cogging force F is determined for a particular shuttle Tn. C(x,y,z) , and during the operation of the linear motor 1, the cogging force F is determined C(x,y,z) Used to compensate for the cogging force F of the other shuttle Tn C(x,y,z) , and possibly also for the same shuttle Tn. In yet another embodiment of the invention, the cogging force F C(x,y,z) Determined by a number of shuttles Tn, and the cogging force F determined C(x,y,z)The average value of is used during the operation of the linear motor 1 to compensate for the cogging force F of the shuttle Tn C(x,y,z) .

Claims

1. A method for operating a linear motor (1) having at least one shuttle (Tn) and a stator (2), wherein a plurality of drive coils (ASi) are arranged on the stator (2) and a plurality of drive magnets (4) are arranged on the at least one shuttle (Tn), or a plurality of drive magnets (4) are arranged on the stator (2) and a plurality of drive coils (ASi) are arranged on the at least one shuttle (Tn), and during operation of the linear motor (1), under the control of a control unit (10), the drive coils (ASi) in the region of the at least one shuttle (Tn) are energized to generate an electromagnetic field, which interacts with the drive magnetic field generated by the plurality of drive magnets (4) to generate a propulsion force for moving the shuttle (Tn) along the stator (2), characterized in that The cogging force (F) of the shuttle (Tn) in at least one direction of movement (x, y) of the stator (2) Cx 、F Cy ) is determined as a function of the relative position of the at least one shuttle (Tn) with respect to the stator (2) in the at least one movement direction (x, y), while the drive coil (ASi) in the region of the shuttle (Tn) is not energized, the determined cogging force (F Cx 、F Cy ) is stored in the control unit (10) and the cogging force (F) in the at least one movement direction (x, y) determined by the unenergized drive coil (ASi) is used by the control unit (10) Cx 、F Cy ), to compensate the cogging force (F during the operation of the linear motor (1) according to Cx 、F Cy ) of the shuttle (Tn) and the stator (2) to compensate for the cogging force (F Cx 、F Cy ).

2. The method according to claim 1, characterized in that Cogging force (F Cz ) is additionally determined in a direction (z) transverse to the direction of movement (x, y) along the stator (2), while the drive coils (ASi) in the region of the at least one shuttle (Tn) are not energized, and using the cogging force (F) in the transverse direction (z) determined by the non-energized drive coils (ASi) Cz ) compensates the cogging force (F) in the transverse direction (z) of the shuttle (Tn) Cz ), which compensates the cogging force (F) for the shuttle during operation of the linear motor (1) Cz ).

3. The method according to claim 1 or 2, characterized in that The cogging force (F Cx 、F Cy ) and / or the cogging force (F Cz ) is determined by the unenergized drive coil (ASi) as a function of the distance of the at least one shuttle (Tn) to the further adjacent shuttle (Tn+1) on the stator (2), and the cogging force (F) determined is used by the control unit (10) Cx 、F Cy 、F Cz ), to further compensate the cogging force (F during the operation of the linear motor (1) according to Cx 、F Cy 、F Cz The distance between the shuttle (Tn) of the stator (2) and the other adjacent shuttle (Tn+1) on the stator (2) compensates the cogging force (F Cx 、F Cy 、F Cz ).

4. The method according to any one of claims 1 to 3, characterized in that The drive coil (ASi) is arranged on the main teeth (11), and two adjacent main teeth (11) are separated by a tooth pitch (τ) in the at least one movement direction (x, y). n ), and at least for the tooth pitch (τ n ) determines the cogging force (F Cx 、F Cy 、F Cz ), or the drive coil (ASi) is arranged on the main teeth (11), wherein the auxiliary teeth (12) are located between two adjacent main teeth (11), and the two adjacent main teeth (11) are separated by a tooth pitch (τ) in the at least one movement direction (x, y) n ), and at least for the tooth pitch (τ n ) half the length determines the cogging force (F Cx 、F Cy 、F Cz ).

5. The method according to any one of claims 1 to 4, characterized in that The stator (2) comprises a segment gap (SG) in the at least one direction of movement (x, y) of the at least one shuttle (Tn) along the stator (2), and the cogging force (F Cx 、F Cy 、F Cz ) is additionally determined and stored in the control unit (10) for the transition of the at least one shuttle (Tn) across the segment gap (SG) and when compensating the cogging forces (F Cx 、F Cy 、F Cz ) is moved across the segment gap (SG) during operation of the linear motor (1), the control unit (10) uses the cogging force (F Cx 、F Cy 、F Cz ) to compensate for the cogging force (F Cx 、F Cy 、F Cz ), the determined cogging forces are used for transition of said at least one shuttle (Tn) across said segment gap (SG).

6. The method according to claim 5, characterized in that The cogging force (F Cx 、F Cy 、F Cz ) is determined at least for half of the transition of said at least one shuttle (Tn) across said segment gap (SG) and for the other half of said transition by using symmetry.

7. The method according to claim 5 or 6, characterized in that The cogging forces (F) are determined for different lengths (GL) of the segment gap (SG) in the at least one movement direction (x, y). Cx 、F Cy 、F Cz ), the cogging force (F Cx 、F Cy 、F Cz ) is stored in the control unit (10) as a function of the length (GL) of the segment gap (SG) and is used when compensating the cogging force (F Cx 、F Cy 、F Cz When the shuttle (Tn) of the vehicle (Tn) crosses the segment gap (SG), the control unit (10) uses the stored cogging force (F Cx 、F Cy 、F Cz ) to compensate the cogging force (F) during the operation of the linear motor (1) according to the actual segment gap length (GL) of the segment gap (SG) during the operation of the linear motor (1) Cx 、F Cy 、F Cz ).

8. The method according to claim 7, characterized in that During or at the start of the operation of the linear motor (1), the at least one shuttle (Tn) is positioned above the segment gap (SG) so that position sensors (PS) on both sides of the sensor gap (SG) detect the position of the at least one shuttle (Tn), and the actual segment gap length (GL) is determined by the position determined by the two position sensors (PS) and the known geometry of the at least one shuttle (Tn).

9. The method according to claim 7, characterized in that During or at the start of operation of the linear motor (1), the at least one shuttle (Tn) is positioned on a first side of the segment gap (SG), and the first position of the at least one shuttle (Tn) is determined by a first position sensor (PS), and the at least one shuttle (Tn) is positioned on a second side of the segment gap (SG), and the second position of the at least one shuttle (Tn) is determined by a second position sensor (PS), the difference between the first position and the second position being a measure of the actual length (GL) of the segment gap (SG).

10. The method according to claim 7, characterized in that During or at the start of the operation of the linear motor (1), a first drive coil (ASi) located on a first side of the segment gap (SG) is used as a transmitting coil, and a second drive coil (ASi+1) located on the opposite side of the segment gap (SG) is used as a receiving coil, the transmitting coil being driven by a given coil voltage that generates an electromagnetic field, the electromagnetic field inducing a voltage in the receiving coil, and the induced voltage being measured and related to the segment gap length (GL) of the segment gap (SG) in a known relationship.

11. The method according to any one of claims 1 to 10, characterized in that The cogging compensation unit (21) uses the stored cogging force (F Cx 、F Cy 、F Cz ) to determine a compensation signal (CS) which is used in the control unit (10) during operation of the linear motor (1) to influence a manipulated variable (MP) for energizing an active drive coil (ASi) in order to compensate for the cogging force (F Cx 、F Cy 、F Cz ).

12. The method according to claim 11, characterized in that The mobile controller (20) compensates the cogging force (F Cx 、F Cy 、F Cz ) calculates the manipulated variable (MP) based on a given set value (SP) of the movement of the shuttle (Tn), and the cogging compensation unit (21) superimposes the compensation signal (CS) on the manipulated variable (MP) or the set value (SP).

13. The method according to claim 12, characterized in that The cogging compensation unit (21) calculates the compensation signal (CS) as the cogging force (F Cx 、F Cy 、F Cz ), and the cogging compensation unit (21) superimposes the compensation signal (CS) on the force setting value (SPF) of the movement controller (20).

14. The method according to any one of claims 1 to 13, characterized in that During the operation of the linear motor (1), the cogging force (F Cx 、F Cy 、F Cz ) depends on compensating the cogging force (F Cx 、F Cy 、F Cz ) of the shuttle, and the compensation decreases as the speed increases.

15. A linear motor having at least one shuttle (Tn) and a stator (2), a plurality of drive coils (ASi) being arranged on the stator (2) and a plurality of drive magnets (4) being arranged on the at least one shuttle (Tn), or a plurality of drive magnets (4) being arranged on the stator (2) and a plurality of drive coils (ASi) being arranged on the at least one shuttle (Tn), and a control unit (10) of the linear motor (1) being arranged to energize the drive coils (ASi) in the region of the at least one shuttle (Tn) during operation of the linear motor (1) to generate an electromagnetic field which interacts with the drive magnetic field generated by the drive magnets (4) to generate a propulsion force for moving the at least one shuttle (Tn) along the stator, characterized in that A storage unit (22) is provided in the control unit (10), and stores the cogging force (F) of the at least one shuttle (Tn) along the moving direction (x, y) of the stator (2). Cx 、F Cy ), the cogging force (F Cx 、F Cy ) is determined as a function of the relative position of the at least one shuttle (Tn) in the at least one movement direction (x, y) relative to the stator (2), while the drive coils (ASi) in the region of the at least one shuttle (Tn) are not energized, and the control unit (10) is arranged to use the stored cogging force (F) in the at least one movement direction (x, y) determined by the non-energized drive coils (ASi). Cx 、F Cy ), to compensate the cogging force (F during the operation of the linear motor (1) according to Cx 、F Cy ) of the shuttle (Tn) and the stator (2) to compensate for the cogging force (F Cx 、F Cy ).

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