Permanent magnet actuator

Abstract

In order to provide a device allowing improved sensing and generation of torque and force, a permanent magnet actuator (1) is proposed, comprising a stator (2) comprising at least one stator permanent magnet (21) interacting with at least one driven permanent magnet (31) of a driven member (3) of the actuator (1), such that a predetermined torque (Tr) or a predetermined force acting on the driven member (3) is generated depending on the relative position (phi) between the driven member (3) and the stator (2); the permanent magnet actuator comprises a position sensor (5) which generates a position measurement signal (s [phi]) describing the relative position ([phi]) of the driven member (3) with respect to the stator (2).

Description

Field of the Invention

[0001] The present invention relates to a permanent magnet actuator including a stator and a follower member, the follower member including at least one follower permanent magnet, and the stator at least partially surrounding the follower member. The present invention also relates to a tension control system including a dancer having a permanent magnet actuator according to the present invention, the permanent magnet actuator serving as a dancer actuator. Further, the present invention also relates to a continuous production system in which a permanent magnet actuator according to the present invention is used as a dancer actuator. Background Art

[0002] In various industrial fields, problems related to the generation and sensing of torque and / or force are often encountered. During the production of paper, textiles, plastic films, wires, printed products, tapes, metal strips, wires, etc., the acting torque and / or acting force usually need to be precisely generated according to a predetermined torque and / or force curve in order to precisely adjust the unwinding and / or winding of strips, wires, films, etc. according to the product to be produced. The resulting unwinding and winding tensions are usually crucial for the quality of the final product. During the winding and / or unwinding process, the product is usually required to withstand a specific winding tension (or winding force). In many cases, the specific tension remains constant, so that it is not changed from the start to the end of the production process of a certain production batch.

[0003] If the unwinding or winding tension is too large, it may cause tensile deformation of the processed material. However, if the tension is too small, the stress between the layers of the wound material may be deformed, resulting in uneven winding. For this reason, precise control of the winding tension is required, ultimately leading to the need to precisely control the winding torque and / or winding force that generates the winding tension. This problem, commonly referred to as the "winding control problem," plays an important role in most different machine systems (e.g., in strip winding systems, wire cutting systems, etc.).

[0004] Independent of the exact type of machine or system or the goods produced, a tension control system generally consists of a tension sensor for measuring the tension force and / or tension torque of interest and a tension actuator for generating the tension force or tension torque. Examples of tension actuators are non-driven rollers actuated by gravity to apply the required force, hydraulic cylinders or pneumatic cylinders, and electric motors such as servo motors, linear motors, induction machines, synchronous machines, etc. Examples of tension sensors are mainly force sensors or torque sensors such as torque measurement flanges.

[0005] When actually setting up a tension control system, several obstacles are often encountered. On the one hand, the cost of tension sensors and tension actuators can be expensive, especially when high precision and high accuracy are required. Even though the indirect measurement principle has been more frequently adopted in this regard recently, which does not measure the tension force or tension torque, but rather another physical quantity that allows the calculation ("observation") of the torque or force of interest. In addition, in such cases, expensive sensors are also required, mainly position sensors or distance sensors, in order to achieve the desired measurement accuracy level. On the other hand, mainly due to constructional reasons, tension sensors and tension actuators usually cannot be arranged close to each other spatially. However, if the sensor and the actuator are arranged far from each other, there is usually a time delay between the time point when the actuator is used to change the tension force or tension torque in a given system and the time point when the corresponding tension sensor responds to this impact and senses this impact. This phenomenon, commonly known as the "dead time problem" or "hysteresis", is a well-known problem in control engineering design and can lead to various problems usually related to the loss of stability of the tension control system. In addition, apart from the dead time problem, arranging the sensor and the actuator far from each other usually also causes other problems, such as the dynamic behavior caused by the elasticity and damping of the material used to connect the sensor and the actuator. Moreover, disposing the actuator to generate the desired torque or force is also challenging.

[0006] Some of these problems have been considered in the prior art. For example, CN 113865764 teaches a device that allows for improved measurement of the torque transmitted between a first object and a second object. The device proposed in CN 113865764 includes a first rotor coupled to the first object and a second rotor coupled to the second object, and the first rotor and the second rotor include permanent magnets. By arranging permanent magnets in the two rotors, CN 113865764 allows for effective measurement of the torque of interest, that is, by measuring the relative position between the two rotors that is directly related to the exchanged torque. However, in the case where torque is to be generated, CN 113865764 still requires a separate torque actuator because the measuring device itself does not allow the generation of any torque or force.

[0007] In contrast, EP 3 038 233 B1 discloses an improved actuator in the form of a permanent magnet synchronous motor, especially in terms of performance and safety optimization. In terms of performance, the actuator proposed in EP 3 038 233 B1 provides high power density, high output torque, low torque ripple, and low cogging torque, which is mainly attributed to the special arrangement of specific rotor segments. However, EP3 038 233 B1 has not yet solved the problem of sensing the generated torque in an appropriate manner. Summary of the Invention

[0008] In view of this background, the object of the present invention is to provide a device that allows for improved sensing and generation of torque and force, particularly in the fields of winding machines and multi-wire cutting systems. Further, the device should be produced in a cost-effective manner.

[0009] For the permanent magnet actuator mentioned at the beginning, this object is achieved in that the stator comprises at least one stator permanent magnet that interacts with at least one follower permanent magnet such that, depending on the relative position between the follower member and the stator, a predetermined torque or a predetermined force acting on the follower member is generated; and a position sensor is provided that generates a position measurement signal describing the relative position of the follower member with respect to the stator, the position measurement signal encoding the predetermined torque acting on the follower member.

[0010] By passively providing a predetermined torque curve that depends only on the relative position between the follower member and the stator and by providing information about said relative position by means of a sensor, the present invention not only allows for the generation but also for the sensing and measurement of the torque acting on the follower member. Thereby, the present invention combines the functions of both a sensor and an actuator in only one device, which ultimately achieves a series of advantages such as cost reduction and complexity reduction.

[0011] Preferably, the follower member comprises a core in which at least one rotor permanent magnet is arranged; and / or the stator comprises a stator core in which at least one stator permanent magnet is arranged. By using a core, the magnetic flux occurring in the actuator can be shaped and adjusted specifically according to the requirements of a particular use case, thereby further increasing the design flexibility and allowing the magnetic characteristics of the actuator to be optimized according to the given boundary conditions in a particular application.

[0012] Preferably, the permanent magnet actuator according to the invention is a rotary permanent magnet actuator, and the follower member can be arranged rotatably radially inside the stator to act as the rotor of the permanent magnet actuator, wherein the relative position of the follower member with respect to the stator corresponds to the rotational angle of the follower member. An important strength of the present invention is that it can be used both for rotational use cases and for linear movements.

[0013] In both the rotational and the linear cases, no electrical coil is provided in the actuator according to the invention for conducting a current to generate a driving torque or a driving force, which constitutes another important difference from typical electric motors such as induction machines or synchronous machines, in which current-carrying coils are required to generate torque or force. Thus, the electronics usually required for supplying and / or controlling the current can be omitted, thereby allowing the present invention to be employed in scenarios where traditional actuators known from the prior art could not be used hitherto, for example, due to constraints related to the power supply.

[0014] Preferably, a plurality of driven magnets are provided on the driven member, the driven magnets are equidistantly distributed along the circumference of the driven member and are separated by a predetermined gap, a plurality of stator magnets are provided on the stator, the stator magnets are equidistantly distributed along the circumference of the stator and are separated by a predetermined gap. By using more than one magnetic component on the stator and the driven member, the design freedom and the reliability of the actuator can also be improved.

[0015] In a series of applications, the permanent magnet actuator according to the present invention can be used to control the traction force acting on a material during a continuous production process, the material being conveyed from a controlled roller to another roller or from another roller to the controlled roller at a linear speed while being subjected to the traction force generated by the permanent magnet actuator. Among them, the traction force can be applied to the material by means of a pusher arm attached to the shaft of the permanent magnet actuator.

[0016] Another important use case of the present invention is a tension control system for a continuous production system, including at least two rollers and a pusher system for applying a traction force to the material conveyed between the rollers, the pusher system being composed of a permanent magnet actuator according to the present invention and a pusher arm attached to the shaft of the permanent magnet actuator. Most importantly, the continuous production system can be a multi-wire cutting machine or a wire mesh processing machine. Description of the Drawings

[0017] The following refers to Figures 1 to 4 a more detailed description of the present invention, Figures 1 to 4 and schematically and non-limitingly advantageous embodiments of the present invention are shown by way of example. The specific examples described herein are only used to explain the content of the present invention and are not intended to limit this embodiment. The following drawings are shown.

[0018] Figure 1 is a first cross-section of an embodiment of the present invention,

[0019] Figure 2 is a second cross-section of an embodiment of the present invention,

[0020] Figures 3a to 3c is a possible torque-position curve,

[0021] Figure 4 is a winding machine using the permanent magnet actuator according to the present invention as a pusher actuator and a pusher position sensing device. Detailed Description of the Invention

[0022] Figure 1 A cross-section of a permanent magnet actuator 1 according to the present invention is shown. Figure 1 The presented permanent magnet actuator 1 includes a stator 2 and a driven member 3. The driven member 3 includes at least one driven permanent magnet 31, and the stator 2 at least partially radially surrounds the driven member 3. Figure 1The cross-section shown extends perpendicular to the axis of rotation xφ of the driven member 3. In Figure 1 the case of Figure 1 , the permanent magnet actuator 1 is implemented in the form of a rotary actuator such that the driven member 3 rotates within the stator 2. Thus, the driven member 3 acts as a rotor, as in a known electric machine (e.g., a synchronous machine or an induction machine). It should be noted that the present invention is in no way limited to the rotary concept. Instead, a linear concept can also be employed, in which the driven member 3 moves linearly relative to the stator 2, which will be discussed later.

[0023] According to the invention, the stator 2 includes at least one stator permanent magnet 21, which interacts with at least one driven permanent magnet 31 of the driven member 3 such that, depending on the relative position between the driven member 3 and the stator 2, a predetermined torque Tr acting on the driven member 3 is generated. Further, a position sensor 5 is provided, which provides a position measurement signal sφ that describes the relative position φ of the driven member 3 relative to the stator 2. Since the torque curve Tr depends on the relative position φ between the driven member 3 and the stator 2, the position measurement signal sφ directly encodes the predetermined torque Tr acting on the driven member 3.

[0024] By passively providing a predetermined torque curve Tr that depends only on the relative position φ between the driven member 3 and the stator 2 (i.e., without any external energy supply) and by providing information about the relative position φ by means of the sensor 5, the present invention not only allows the generation but also the sensing and measurement of the torque Tr acting on the driven member 3 (or, in the linear case, the generation, sensing, and measurement of a force). Thus, the present invention combines the functions of an actuator and a sensor. Compared with the solutions known from the prior art, the present invention offers a number of advantages. Compared with conventional mechanical actuator devices, such as mechanical springs or hydraulic cylinders, the response time of the actuator according to the present invention is significantly shorter since the actuator 1 can be implemented using lightweight components, thereby avoiding large inertia. Compared with electrical solutions such as electric servo motor systems, no additional servo drive is required, i.e., no sophisticated electronics are needed to control the current and voltage that occur in the servo drive. Thereby, the present invention not only combines the functions of a sensor and an actuator in one device but also reduces costs and complexity, thus making the overall design simple and highly reliable.

[0025] Within the scope of the present invention, for example, the magnetic components can be arranged in a manner comparable to the magnet arrangements commonly used in permanent synchronous motors. Specifically, the magnetic components can be arranged along the circumference of the stator 2 or along the circumference of the driven member 3 in the case of alternating magnetic poles (i.e., N, S, N, S, etc.). In the axial direction, the magnetic poles generally remain the same. The magnetic components can be mounted on the stator of the stator 2 / driven member 3 by gluing with a special glue. Of course, other options for arranging the magnetic components can also be used. Selecting the arrangement / mounting option suitable for a given application is routine work for a person skilled in the art (such as electric motor design).

[0026] It is important to mention that the permanent magnet actuator 1 according to the present invention is a passive device, where the generated force or torque Tr is only caused by the stator magnets 21 arranged in the stator 2 and the driven permanent magnets 31 arranged in the driven member 3. The generated force or torque Tr only depends on the position of the driven member 3 and does not depend on any current flowing through, for example, the stator windings as in a conventional electric motor. Since there is no need to control and / or adjust any current or voltage, etc. (which may be a cumbersome and difficult task in many cases), the accuracy of the generated torque or force is very high. However, most importantly, no drive current is required, so no energy source is required, so no power supply is required, and so no control unit for the actuator 1 is required, which makes it particularly easy to implement and install the permanent magnet actuator 1 according to the present invention.

[0027] As mentioned above, the stator 2 includes at least one stator permanent magnet 21, and at least one driven permanent magnet 31 is provided as part of the driven member 3. As will be discussed later, the arrangement of these magnetic elements allows for a free and flexible design of the permanent magnet actuator 1 according to the present invention. Specifically, these magnetic elements can be arranged in a specific individual manner so as to produce a specific individual torque-position curve, which can be precisely adjusted according to the requirements and demands of a given usage scenario.

[0028] However, in a particularly advantageous manner, not only one driven permanent magnet 31 is provided beside the driven member 3, nor only one stator magnet 21 is provided as part of the stator 2, but a plurality of driven magnets 31 and stator magnets 21 can be used. In this case, it is advantageous to distribute the stator magnets 21 and the driven magnets 31 equidistantly along the circumference of the stator 2 or along the circumference of the driven member 3, etc.

[0029] In Figure 1 the specific case, two stator magnets 21 are provided as part of the stator 2, and two driven magnets 31 are provided as part of the driven member 3. As Figure 1As shown, two stator magnets 21 separate a gap Δ2, and two follower magnets 31 separate a gap Δ3. As is well known in electrical engineering design, such gaps can be used to form and guide the magnetic flux distribution inside devices such as the permanent magnet actuator 1. The magnetic flux distribution constitutes another design parameter that allows shaping of the torque Tr or force acting on the follower member 3. Moreover, through the gaps Δ2, Δ3 as shown in Figure 1 it is also possible to define the position of the follower member 3 with the minimum magnetic reluctance. In the present case, the position of the minimum magnetic reluctance corresponds to the position of the follower member 3 in which the stator axis x2 and the rotor axis x3 are aligned. Through this position of the minimum magnetic reluctance, a magnetic drag force can also be generated on the follower member 3. When shaping the force or torque Tr acting on the follower member 3, the magnetic drag force can also be taken into account. Another design variable affecting the generated torque or force is the air gap between the stator 2 and the follower member 3.

[0030] As previously mentioned, within the scope of the present invention, the follower magnets 31 and the stator magnets 21 are implemented in the form of permanent magnets. In addition, in this regard, the present invention has flexibility, so there are several design options available. Specifically, for both the follower magnets 31 and the stator magnets 21, depending on the details of the given situation, permanent magnets based on steel, neodymium, samarium cobalt, alnico alloys, ferrite, or other suitable materials can be used.

[0031] In another particularly advantageous embodiment of the present invention, the follower member 3 may include an iron core 32 in which at least one rotor permanent magnet 31 may be arranged, and the stator 2 may further include a stator iron core 22 in which at least one stator permanent magnet 21 may be arranged. Although an iron core is a suitable option in many applications, it should be noted that the present invention itself does not require the stator 2 or the follower member 3 to include iron. It is also beneficial to use other base materials (such as carbon or suitable plastics or other materials) for the follower member 3 or the stator 2.

[0032] To incorporate the permanent magnet actuator 1 into complex industrial systems, for example, into production systems, or to use it for interaction with other machinery, in addition to the stator 2, the follower member 3, the magnets 21, 31, etc. discussed so far, certain components are also required. As the main components in this regard, mention should be made of the shaft 4, the bearings 6, the end caps 8, the element capable of evaluating the position measurement signal sφ, and the housing 9. These components will be further explained below with the help of Figure 2 For this purpose, Figure 2 Another cross-section of the permanent magnet actuator 1 discussed so far is shown. In Figure 2 this case, the presented cross-section extends along the rotation axis xφ.

[0033] Most importantly, in Figure 2In [the figure], the shaft 4 extending from the driven member 3 can be seen. The shaft 4 is required to be able to mechanically couple the permanent magnet actuator 1 to other drive components, for example, to a production machine that will bear a mechanical load or is to be braked. Using the shaft 4, the actuator 1 currently under discussion can be coupled to all kinds of mechanical components, such as the shaft of a clutch, or a flange, or other machines or actuators.

[0034] Another option for coupling the permanent magnet actuator 1 to another drive component is the wobble arm 41 attached to the shaft 4, as Figure 2 shown by the dashed line in [the figure]. In the context of the present invention, such a wobble arm 41 is of course only optional and plays an important role in various settings, most prominently in winding machines or wire cutting machines, where such a wobble arm 41 allows the transmission of force by pushing the web being unwound or wound. Refer to Figure 4 for a detailed explanation of an example of such a winding machine.

[0035] In order to hold the shaft 4, in the setting according to Figure 2 , a bearing 6 is provided. As is well known, the bearing 6 transmits the axial load and radial load acting on the shaft 4 to the structure supporting it, in this case, to the stator 2. In addition, in this regard, the present invention has significant design flexibility, such that plain bearings, rolling bearings, jewel bearings or even magnetic bearings can be used as the bearing 6. In order to protect the permanent magnet actuator 1 from external influences, an end cover 8 covering the bearing 6 and a housing 9 protecting the entire actuator are also provided.

[0036] Furthermore, in Figure 2 , the above-mentioned position sensor 5 and the way it is incorporated into the setting of the permanent magnet actuator 1 can be seen in detail. Sensor concepts for measuring rotational movement (such as incremental encoders or sine / cosine encoders) are well known in the prior art, see for example EP 0 512 327 B1.

[0037] Compared with the well-known settings of conventional motors such as synchronous machines or induction machines, an important difference of the actuator 1 currently under discussion is that its stator 2 includes at least one magnetic component, and in a particularly advantageous manner, it can be composed of an iron core and a magnetic steel as the stator magnet 21. Thus, the torque of the rotor is provided by the stator and rotor magnets, such that the torque-position curve can be optimized by appropriately selecting and designing the magnets (especially regarding their thickness, pole arc coefficient, pole width, their shape, etc.). After assembly, the output torque / force is only a function of the rotor position and does not depend on any electrical parameters, such as the voltage or current flowing through the stator or rotor coils.

[0038] As mentioned before, it is also conceivable that the permanent magnet actuator 1 according to the invention can be realized in the form of a linear actuator. In this case, the driven member 3 does not rotate inside the stator, but moves linearly.

[0039] As discussed above, a range of design parameters may be adjusted and modified in order to shape the torque Tr or force generated by the actuator 1 according to the present invention. Figures 3a to 3c A possible torque-position curve that can be achieved in this way is shown, again by way of example, taking into account a rotary version of the actuator according to the invention. Figures 3a to 3c In , the torque Tr depends periodically on the rotation angle φ of the driven member 3, wherein the period length is 360 degrees or 2πrad. Figure 3a The torque-position curve is a sinusoidal curve and can be obtained by Figure 1 and Figure 2 The corresponding actuator is used to realize it.

[0040] However, it is also possible to provide different kinds of curves by adopting different structural arrangements. Figure 3b As in the case of Figure 3c As shown, a constant torque T set An extended segment of Figure 3c A torque-position curve such as the one shown is advantageous in which a constant load torque T set Provided by the permanent magnet actuator 1. Since the torque within the 180 degree range rises sharply, the driven member 3 is pushed to generate the torque T set location.

[0041] Within the scope of the invention, it is necessary to change the position of the driven member 3 in order to modify the torque Tr or force generated. This constitutes another contrast with typical servo motor systems, in which, for example, the force or torque can be changed depending on the feed current. Obviously, the ability to generate different torques Tr or forces in one position brings the following disadvantages: when only the position of the rotor, for example, is known, it is impossible to tell what torque is acting.

[0042] As mentioned at the outset, important examples in which the present invention can be used are Figure 4 The web processing machine 11 is presented. Figure 4 In the web processing machine 11 shown, the winder 12 is arranged as a controlled roller, which is designed to wind the material 13 onto a winder core 20 or to unwind the material from the winder core 20, depending on whether the winder is at the beginning or at the end of the web processing machine 1. The wound material 13 is pre-tensioned on the winder core 20 and therefore has a substantial elongation.

[0043] Further, a traction roller 16 with a pressure roller 60 is provided to convey the material 13 without slippage between the traction roller 16 and the pressure roller 60. The pressure roller 60 is not actively driven but is pressed against the traction roller 16. Since it is coupled via the material 13, a change in the rotational speed of the winder 12 also affects the traction roller 16. The traction roller 16 itself is driven at a traction roller speed v6 and there is no superimposed traction force controller. The linear speed v of the material 13 is set by the traction roller speed v6. Therefore, the linear speed v is controlled by the circumferential speed of the traction roller 16 and a linear speed v greater than 1000 m / min is possible.

[0044] The winder 12 has a winder speed v9'. The circumferential speed of the winder 12 generally remains constant, such that the set winder speed v9 varies according to the diameter of the winder 12. Since the winder 12 and the traction roller 16 are each connected to the material 13 in a non-slip manner in the contact area, the linear speed v may approximately equal the circumferential speeds of the traction roller 16 and the winder 12. However, depending on the occurring traction force F, the circumferential speed of the winder 12 may deviate from the (minimum) linear speed v. If the material 13 is unwound from the winder 12, it is advantageous to take into account a change in the winder diameter when determining the relationship between the circumferential speed of the winder 12 and the linear speed v. For this purpose, the winder diameter can be measured or estimated.

[0045] Further, Figure 1 an optional deflection roller 14 is provided, which is used to guide the material 13 but is not driven itself. The mass moment of inertia of the deflection roller 14 is very low and may generally be neglected. However, during acceleration and braking processes, it may be necessary to take into account the mass moment of inertia of the deflection roller 14 in order to generate a smooth linear speed curve and to minimize negative inertia effects.

[0046] From the perspective of the present invention, Figure 4 the most important aspect of the shown web processing machine 11 is that the permanent magnet actuator 1 according to the present invention is used as a dancer controller with a dancer arm 41 to control and / or adjust the tension force F acting on the material 13. As is known from the prior art, a dancer control system basically includes a preloaded idler arm, which has two main tasks, namely, applying and controlling the web tension to avoid web damage, which may be caused by a series of mechanical problems such as eccentric and non-circular web rolls or dynamic web speed trajectories. This is also the case for the permanent magnet actuator 1 according to the present invention and the dancer arm 41 attached to the shaft 4 of the permanent magnet actuator 1. The dancer arm 41 pushes the material 13 downwards, thereby not only generating the tension force F affecting the material 13, but also mechanically coupling the actuator 1 according to the present invention to Figure 4 the presented web processing system.

[0047] In a similar manner, the permanent magnet actuator 1 according to the invention can also be used in a multi-wire cutting machine or another continuous production process.

[0048] Typically, a dancer is used in a closed-loop tension control system. This is also Figure 4 the case in the situation shown, where, in addition to several other signals (such as the speeds of the winder 12 and the draw roll 16), the above-mentioned position signal sφ is also fed to the control unit C. The control unit C calculates control signals u12 and u16 based on these signals for controlling the speeds of the winder 12 and the draw roll 16. Possible implementations of such a control unit are provided in particular by microprocessor-based hardware, microcontrollers, and integrated circuits (ASIC, FPGA).

[0049] An important difference from the concepts known from the prior art is that the permanent magnet actuator 1 itself does not receive any control signals, since the force F depends only on the relative position between the follower member 3 and the stator 2 of the actuator 1, as discussed extensively previously. In summary, the invention not only provides a novel actuator and sensor concept, but also allows for a reduction in complexity in production systems such as Figure 4 the web processing machine 11 shown.

Claims

1. A permanent magnet actuator (1) comprising a stator (2) and a driven member (3), said driven member (3) including at least one driven permanent magnet (31) and said stator (2) at least partially surrounding said driven member (3), characterized in that, said stator (2) includes at least one stator permanent magnet (21), said at least one stator permanent magnet (21) interacting with said at least one driven permanent magnet (31) such that a predetermined torque (Tr) or a predetermined force acting on said driven member (3) is generated in accordance with a relative position (φ) between said driven member (3) and said stator (2); and in that a position sensor (5) is provided, said position sensor (5) generating a position measurement signal (sφ) describing said relative position (φ) of said driven member (3) with respect to said stator (2), said position measurement signal (sφ) encoding said predetermined torque (Tr) acting on said driven member (3).

2. The permanent magnet actuator (1) according to claim 1, characterized in that, said driven member (3) includes an iron core (32), said at least one rotor permanent magnet (31) being arranged in said iron core (32).

3. The permanent magnet actuator (1) according to any one of the preceding claims, characterized in that, said stator (2) includes a stator iron core (22), said at least one stator permanent magnet (21) being arranged in said stator iron core (22).

4. The permanent magnet actuator (1) according to any one of the preceding claims, characterized in that, said permanent magnet actuator (1) further includes a shaft (4) extending from said driven member (3), allowing said permanent magnet actuator (1) to be mechanically coupled to another drive component.

5. The permanent magnet actuator (1) according to any one of the preceding claims, characterized in that, said permanent magnet actuator (1) is a rotary permanent magnet actuator (1), said driven member (3) serving as a rotor of said permanent magnet actuator (1) and being rotatably arranged radially inside said stator (2), said relative position (φ) of said driven member (3) with respect to said stator (2) corresponding to a rotation angle of said driven member (3).

6. The permanent magnet actuator (1) according to claim 5, characterized in that, said stator (2) and said driven member (3) are arranged concentrically about a rotation axis (xφ) of said driven member (3).

7. The permanent magnet actuator (1) according to any one of the preceding claims, characterized in that, no electric coil for conducting current to generate a driving torque or a driving force is provided on said stator (2) or said driven member (3).

8. The permanent magnet actuator (1) according to any one of the preceding claims, characterized in that, A plurality of driven magnets (31) are provided on the driven member (3), the driven magnets (31) are equidistantly distributed along the circumference of the driven member (3) and are separated by a predetermined gap (Δ3); and, a plurality of stator magnets (21) are provided on the stator (2), the stator magnets (21) are equidistantly distributed along the circumference of the stator (2) and are separated by a predetermined gap (Δ2).

9. Use of a permanent magnet actuator (1) according to any one of the preceding claims, the permanent magnet actuator (1) being used for controlling the traction force (F) acting on a material (13) during a continuous production process, the material (13) being conveyed at a linear velocity (v) from a controlled roller (12) to another roller (16) or from another roller (16) to the controlled roller (12), while being subjected to the traction force (F) generated by the permanent magnet actuator (1).

10. Use of the permanent magnet actuator (1) according to claim 9, characterized in that the traction force (F) is applied to the material (13) by means of a pogo arm (41) attached to the shaft (4) of the permanent magnet actuator (1).

11. A tension control system for a continuous production system, comprising at least two rollers (12, 16) and a pogo system for applying a traction force (F) to a material (13) conveyed between the rollers (12, 16), the pogo system being constituted by a permanent magnet actuator (1) according to any one of claims 1 to 9 and a pogo arm (41) attached to the shaft (4) of the permanent magnet actuator (1).

12. The tension control system according to claim 11, characterized in that the continuous production system is a multi-wire cutting machine or a wire mesh processing machine.

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