EP2150370A1 - Positioning device - Google Patents

Abstract

The invention relates to a positioning device, in particular a clamping chuck for a machine tool, comprising a base body (12), a driven body (14) arranged in front of the base body (12) with respect to the longitudinal axis (L) for connection to a workpiece (56), a connecting element (16) connected to the base body (12) and extending along the longitudinal axis (L), and at least two eccentric actuators (18) which are fixed to the base body (12) and act transversely in relation to the longitudinal axis (L). Said eccentric actuators (18) are configured to displace the driven body (14) perpendicular to the longitudinal axis (L) with respect to the base body (12) by elastic deformation of the connecting element (6). According to the invention, the positioning device (10) comprises at least two tilt actuators (36), particularly tilt piezo actuators, for tilting the driven body (14) relative to the base body (12).

Description

 positioning

The invention relates to a positioning device, in particular a chuck for a machine tool, having a base body, arranged with respect to a longitudinal axis in front of the main body output body for connection to a workpiece, connected to the base body and extending along the longitudinal axis connecting element and at least two attached to the base body , Exzenter- actuators acting transversely to the longitudinal axis, in particular eccentric piezo actuators, which are designed for displacement of the output body perpendicular to the longitudinal axis relative to the base body by elastic deformation of the connecting element. According to a second aspect, the invention relates to a method for aligning a workpiece.

From DE 854 759 B a device for clamping workpieces for machine tools is known, in which an adjustable in two mutually perpendicular planes three-jaw chuck is used to allow an axially parallel adjustment the tensioned tool. A disadvantage of the known device that the axis-parallel alignment is only possible manually and requires a lot of time.

From DE 103 60 917 A1 discloses a tool holder for a rotatable about a rotation axis tool is known. The tool holder has a clamping shaft, on whose circumference electrostrictive material is arranged, which can be excited externally during rotation of the tool holder, so that Torkelschwingungen be avoided. A disadvantage of the tool holder is that larger geometrical deviations can not be corrected with this tool holder.

BESTATIGUNGSKOPIE From DE 41 27 770 A1 a mandrel for cutting tools is known in which adjusting elements are provided to align a tensioned with the mandrel tool. A disadvantage of this mandrel is that the alignment of the tool piece with him is very labor-intensive and can only be done manually.

From DE 38 24 462 C2 a tool adjustment device is known, which serves to set up an axis of a stationary tool on a spindle axis of a moving workpiece. A disadvantage of this device is that it is only complicated and manually adjustable.

Furthermore, generic positioning devices are known. These are used, for example, in the preparation of forged raw gear wheels for subsequent grinding. After forging and subsequent hardening, it can happen that a central bore of the raw gear is arranged eccentrically to the ring gear. If the raw gear wheel were clamped over the eccentric central bore during the subsequent grinding process, a quantity of material varying in dependence on the position on the ring gear would have to be ground off in order to obtain the desired final contour, which is disadvantageous. In order to avoid unnecessary oversizes, therefore, the central bore is formed in a hard turning process prior to grinding in such a way that the smallest possible amount of material has to be ground off.

For this purpose, the main body of the positioning device is attached to a work spindle of a hard turning machine. Subsequently, the gear is tensioned with a tensioning device arranged on the driven body and geometrically measured. Then, the clamping device is displaced parallel to the base body so that a rotation axis of the work spindle of the hard turning machine passes through the center of the central bore to be introduced. To- Following the central hole is turned out, so that the raw gear in the subsequent grinding process only has to be minimally finished.

A disadvantage of the known positioning device is that it is only suitable for narrow gears. It has been shown that the chuck for lower components, such as pinion shafts or wide gears, is unsuitable.

The object of the invention is to propose a positioning device which overcomes the disadvantages of the prior art.

The invention solves the problem by a generic positioning device which has at least two tilting actuators, in particular tilting piezoelectric actuators, which are designed and arranged to incline the drive body relative to the base body. The invention also solves the problem by a machine tool, in particular a grinding or lathe, which has a workpiece turning device for rotating a workpiece about an axis of rotation and a positioning device according to the invention, wherein the longitudinal axis of the positioning device coincides with the axis of rotation. According to a second aspect, the invention solves the problem by a method for aligning a workpiece which comprises the step of clamping the workpiece on a machine tool according to the invention.

An advantage of the invention is that wobble errors of a workpiece, such as a raw gear or a raw pinion shaft, are compensated. As a result, even longer components can be aligned exactly to a rotational axis of a machine tool. As a result, less material removal is needed so that oversizes can be reduced, grinding wheel wear is reduced, and faster and less expensive manufacturing can be achieved.

Due to the fact that eccentric and wobble errors can be corrected with the positioning device according to the invention, manufacturing errors can be corrected in the preceding process. be corrected. Committee is thus diminished. It has surprisingly been found that such a positioning device can be designed such that processing forces occurring during machining of a tensioned workpiece can be safely absorbed so that substantially the same manufacturing tolerances can be maintained with the positioning device according to the invention as with a conventional positioning chuck without actuators.

It is also advantageous that two components to be joined can be aligned particularly precisely with one another. Thus, it is possible to fix an optical component such as a lens or a lens assembly in an oversized tube. In order to align an optical axis of the optical component to a longitudinal axis of the tube, it must be clamped on a lathe only with a positioning device according to the invention. Subsequently, any deviation of the optical axis from the longitudinal axis of the tube is compensated by means of the positioning device and the tube is subsequently finished in an external turning process. In this way, the optical axis of the optical component is aligned in a simple manner to the longitudinal axis of the thus finished tube.

In the context of the present description, the term of the longitudinal axis relates in particular to an axis about which the positioning device is designed to be rotatable, for example by providing a corresponding receptacle for connection to a workpiece spindle of a machine tool. It is placed on the rest position of the actuators, so that actuation of the eccentric actuators or tilt actuators does not change the longitudinal axis.

As eccentric actuators or tilt actuators come next piezoactuators, for example, magnetostrictive actuators or electric motors, which are coupled with a threaded spindle, into consideration. In a preferred embodiment, the connecting element comprises a core, in which the at least two tilting piezoelectric actuators extend parallel to the longitudinal axis. In this way, the correction of the eccentric error is separated from the correction of the tumble error. By controlling the eccentric actuators, the eccentric error can be corrected without this influencing the wobble deviation of the workpiece from the longitudinal axis. Conversely, the tilt actuators can be actuated without changing the eccentricity of the workpiece relative to the longitudinal axis.

Preferably, the connecting element comprises a clamping element which is connected at a base to the driven body and arranged between the tilting piezoelectric actuators, wherein the clamping element and the tilting piezoelectric actuators are arranged such that a length of one of the tilting piezoelectric actuators and a shortening of all other tilting Piezoelectric actuators for tilting the output body relative to the main body leads. The clamping element can be, for example, a clamping screw which extends through a bore in the core and engages the base body and in this way applies in particular the required for the actuators bias.

It is advantageous that the tilting piezoelectric actuators are connected to the output body and / or the main body via conical cup-spherical disk joints. It is thus obtained a particularly simple arrangement.

Four tilt piezoelectric actuators are preferably provided, each of which acts on the driven body in a force introduction point, the force introduction points forming a rhombus, in particular a square. A symmetrical arrangement like this facilitates the control of the tilting piezo actuators. At the same time, the influence of a thermal expansion of the components of the positioning device on the position of the drive body relative to the base body is minimized, so that a corresponding compensation is dispensable. Therefore, the foot point is particularly preferably arranged in the geometric center of the rhombus or of the square. If more than four tilt piezoactuators are present, they are preferably arranged in pairs opposite one another and engage in respective force introduction points which have the same distances from the root point, that is, lie in one plane with respect to a direction of action of the tilting piezoactuators. It is also beneficial if the force application points are on the vertices of a regular polygon.

The base body preferably has a base ring and a base body membrane fastened to the base ring, which has a reduced bending stiffness relative to the base ring and on which the connecting element is arranged. The

Eccentric piezoelectric actuators favorably attack the base ring in this case.

The bending stiffness of the main body membrane is preferably substantially smaller than the bending stiffness of the connecting element, as a result of which a positioning device which is particularly easy to control is obtained.

The output body preferably has an eccentric ring and comprises a driven-body diaphragm fastened to the eccentric ring, which has a bending stiffness which is reduced relative to the eccentric ring and to which the connecting element is arranged. In this way, the base ring and the eccentric ring can be mounted displaceably parallel to each other, so that actuation of the eccentric actuators leads to a parallel displacement between the base ring and the eccentric ring and so the eccentric error is independent of the wobble error compensated. Such a positioning device is particularly easy to control.

According to a further embodiment, it is possible that the connecting element is connected to the eccentric body which is mounted on the base body and by means of the eccentric piezoelectric actuators displaceable parallel to the base body, wherein the output body is pivotally mounted on the eccentric terkörper. In this case, the output body preferably has a foot section and a head section for connection to the workpiece, wherein the at least two tilted piezo actuators are arranged on the eccentric body, extend transversely to the longitudinal axis and are arranged relative to the foot part such that a length of one of the tilting piezo actuators and shortening the other tilt piezo actuators leads to tilting of the output body relative to the eccentric body. It is possible in this way that the eccentric piezoelectric actuators run parallel to the tilting piezoelectric actuators, resulting in a particularly compact design for the positioning device. It is also advantageous that all piezoelectric actuators can be arranged so that they always have a completely stretched arrangement and no bending forces act on them. This increases their service life.

In a preferred embodiment, the tilting piezoelectric actuators are arranged in a counter-player arrangement and extend substantially perpendicular to the longitudinal axis. Under an antagonist arrangement is to be understood in particular that two actuators each have exactly opposite acting effective directions, which also extend in a common plane. If both actuators of the opposing pair are actuated at the same time, then there is only a pressure, but no shear stress on the loaded component. An advantage of this is the particularly simple controllability of the actuators.

It is particularly favorable when the driven body is supported adjacent to its head portion of the driven body diaphragm. In this case, the driven body can be pivoted by means of the tilting actuators about a pivot point which is close to a workpiece facing end face of the driven body. For example, a clamping device for clamping the workpiece can be arranged on the end face, such as, for example, a jaw chuck or a diaphragm chuck. If the tensioning device can be actuated by compressed air, the positioning device preferably has a compressed air channel surrounding the longitudinal axis, which extends from the base body to the Clamping runs. As a result, compressed air can be passed from a machine tool to the clamping device.

In order to minimize forces within the positioning device, according to a preferred embodiment, an electrical control is provided, which is designed to control in each case two piezoactuators arranged in opposing arrangement such that one of the piezoactuators lengthens by a predetermined amount and the other piezoactuator rotates shortened the same amount. Thus, the forces exerted by the piezo actuators forces are reduced to the minimum.

A tool according to the invention preferably has a measuring device for detecting a position of a workpiece clamped to the positioning device. This position can be specified, for example relative to a coordinate system of the machine tool. With the help of this measuring device, the position of the workpiece is detected and it can be the optimal position, for example, a central bore of the workpiece determined. The necessary change in position of the workpiece is then compensated via the eccentric actuators and the tilting actuators. In addition to its position in the x, y and z directions, the position of the workpiece is also understood to mean its orientation with respect to two or three spatial direction angles.

A method according to the invention preferably comprises the steps of detecting a position of the positioning device relative to the machine tool, detecting a machining force on the workpiece and driving the eccentric and / or tilting piezoelectric actuators such that they reduce or compensate a deflection of the workpiece due to the machining force , The processing power can be read out of a table, for example. Alternatively, the machining force can be detected by a force sensor, which is arranged on a tool holder of the machine tool. It is also possible to reduce the processing power, for example, from a grinding disk is applied to the workpiece to determine from the power of a motor that drives the grinding wheel.

In the following, embodiments of the invention will be explained in more detail with reference to the accompanying drawings. It shows

FIG. 1 shows a perspective view of a positioning device according to the invention according to a first embodiment,

FIG. 2 shows a longitudinal section through the positioning device according to FIG. 1,

FIG. 3 shows a cross section perpendicular to the longitudinal direction through the positioning device according to FIG. 1,

FIG. 4 shows a perspective view of the positioning device according to FIG. 1,

5 is a schematic representation of the operation of the positioning device according to the preceding figures,

FIG. 6 shows an alternative embodiment of a positioning device according to the invention in a section along the longitudinal axis,

FIG. 7 shows a perspective partial view of the positioning device according to FIG. 6,

8 shows a perspective view of a detail of the positioning device according to FIGS. 6 and 7, FIG.

FIG. 9 shows a second view of the detail according to FIG. 9,

10 shows a longitudinal section through the detail according to the figures 8 and 9 and Figure 11 is a detail view of the output body of a positioning device according to the invention.

1 shows a partial exploded view of a positioning device 10, which has a main body 12, a driven body 14 arranged in front of the main body 12 relative to a longitudinal axis L, a connecting element 16 connected to the main body 12 and extending along the longitudinal axis L and four attached to the main body 12 includes eccentric piezoactuators 18.1, 18.2, 18.3 and 18.4 extending transversely to the longitudinal axis L, which are arranged in a counterplay arrangement. This means that they face each other in pairs, their directions of action extend in a plane and attack on opposite sides of the connecting element 16.

The main body 12 includes, as the longitudinal section H shows through the longitudinal axis L of Figure 2, a base ring 20 whose longitudinal axis coincides with the longitudinal axis L of the positioning device, and attached to the base ring 20 body diaphragm 22, which is also formed substantially circular and whose center lies on the longitudinal axis L. The main body membrane 22 has compared to the base ring 20 to a significantly reduced flexural rigidity, which is smaller, for example by a factor of J00. The connecting element 16 is attached to the main body membrane 22, for example screwed or welded.

The eccentric piezoelectric actuators 18.1 to 18.4 are fastened to the base ring 20 and, as shown by way of example in FIG. 2 for the eccentric piezo actuators 18.2 and 18.4, act on the connecting element 16. If, for example, the eccentric piezoactuator 18.2 and the eccentric piezoactuator 18.4 shortens, the connecting element 16 deforms as indicated in FIG. 2 and the output body 14 shifts parallel to the base ring 20. For this purpose, it is via schematically drawn elasto-kinematic grating guides 26 attached to the base ring 20. Figure 3 shows a cross section through the positioning device 10, which is pulled by the eccentric piezoelectric actuators 18.1 to 18.4. The eccentric piezoelectric actuators are arranged in respective receiving sleeves 28.1 to 28.4 and act on a core 30 of the connecting element 16. All eccentric piezoelectric actuators are accommodated in the same way in the respective receiving envelope. For example, the eccentric piezoelectric actuator 18.1 is mounted on the core 30 via a first conical-ball-and-pulley joint 32a on the receiving sleeve 28.1 and on an identically constructed conical-spherical-disc joint 32b. In the core 30, four longitudinal bores 34.1,..., 34.4 are introduced, in each of which a tilting piezoelectric actuator 36.1, 36.2. 36.3 or 36.4 with little play.

Between each receiving sleeves, a fixing plate is mounted, for example, is between the receiving sleeves 28.1 and 28.2 the Fixierplat- te 38.1, which is connected via a screw not shown with a clamping ring 40 which surrounds the core 30 without play. About the fixing plates 38.1 to 38.4, the respective screws and the clamping ring 40, the receiving sleeves 28.1 to 28.4 biased to the core 30 and the drive body can be pre-adjusted. After adjustment, the receiving sleeves 28.1 to 28.4. via screws with the base ring connected conclusively. The tilting piezoelectric actuators 36.1., ..., 36.4 are provided in a square arrangement, in the middle of which a longitudinal bore 34.5 runs through the core 30, in which a pretensioning screw 42, not visible in FIG. 2, extends.

FIG. 4 shows the pretensioning screw 40, which acts on the output body 14 in a base F and thus connects it to the core 40. As FIG. 2 shows, an output body diaphragm 44 is arranged concentrically with respect to an eccentric ring 46, which are both part of the output body 14. The driven-body diaphragm 44 establishes a connection between the output body 14 and the eccentric ring 46 and is arranged between the output body 14 and the core 40. The tilting piezoactuators 36.1, 26.2, 36.3, 36.4 engage in respective forces lead points K1, K2, K3 and K4, which form a square whose center of gravity coincides with the base point F.

FIG. 5 shows the principal effect of the tilt piezoelectric sensors on the driven-body diaphragm 44. If, for example, the tilting piezoelectric actuator 36.2 and the tilting piezoactuator 36.4 shorten by the amount δ1, the driven-body diaphragm 44 inclines relative to Base 12. Since the two tilt piezoelectric actuators 36.2, 36.4 are controlled so that they extend or shorten each by equal amounts, the length of the biasing screw 42 remains constant.

FIG. 6 shows an alternative embodiment of a positioning device 10 according to the invention with the main body 12, the driven body 14, the connecting element 16 and the receiving sleeves 28.3 and 28.4., In which the corresponding eccentric piezoelectric actuators are not arranged in a manner that can be sawn.

FIG. 6 also shows an eccentric body 48, which is mounted so as to be displaceable in a parallel manner via elasto-kinematic grid guides 26 on the base body 12. The output body 14 has a head portion 50, which has an end face for mounting a tensioning device 52, and a foot portion 54, to which four Neige ge piezoelectric actuators attack, of which in Figure 6, the two tilt piezoelectric actuators 36.1 and 36.3 are shown. The output body 14 is supported adjacent to its header 50 by the output body diaphragm 44. A length of the tilting piezoelectric actuator 36.1 and a shortening of the tilting piezoelectric actuator 36.3 lead to a tilting of the output drive body 14 about a pivot point D.

FIG. 6 also shows an adapter flange 58, which is designed to be connected to a workpiece spindle 60 of a machine tool, such as a lathe. The adapter flange 58 comprises a portion of an interface 62, with the aid of electrical energy for the eccentric and tilt piezoelectric actuators 18 and 36 is transmitted. control signals for the eccentric and tilt piezo actuators 18 and 36 are transmitted via a radio link, which is constructed according to the Bluetooth standard.

Figure 7 shows a perspective view of the positioning device according to Figure 6, in which the output body 14 has been omitted for clarity.

FIG. 8 shows a perspective view from below of the driven body 14 with its foot section 54, on which the tilting piezoactuators 36. 1 to 36. 4 act, which are received in corresponding receiving sleeves. The receiving sleeves are attached to the eccentric 46. The head portion of the output body which is not visible in FIG. 8 is fastened to the output body membrane 44, so that actuation of the tilting piezo actuators 36 leads to a pivoting of the output body 14.

Figure 9 time the attachment of the output body 14 to the output body diaphragm 44 in a perspective view

FIG. 10 shows a cross section through the eccentric body 48, which reveals the two tilting piezoactuators 36. 1 and 36. 3 which act in antagonistic arrangement against the foot section 54 of the driven element 14. If, for example, the tilting piezoelectric actuator 36.1 lengthens and the tilting piezoelectric actuator 36.3 shortens, the head section 50 of the driven element 14 is pressed against the driven-body diaphragm 44 and pivots about the pivot point D by a pivot angle φ relative to the longitudinal axis L. deforms the output body diaphragm 44, but does not move relative to the eccentric 46.

FIG. 11 shows a workpiece 56, which is tensioned on the output body 14 with the aid of the tensioning device 52. The positioning device according to the invention can for example be used to precisely align an optical component such as a lens or a lens arrangement in a tube. For this purpose, first a raw tube is made with oversize, that is, it has a diameter which is greater than the target diameter of the finished tube. Subsequently, the optical component is arranged in an interior of the raw tube, aligned with a longitudinal axis of the raw tube and fixed there.

However, this alignment inevitably involves an error. To correct this error, the raw tube is clamped with a positioning device as described above, which is attached to a work spindle of a lathe. In this case, the raw tube is clamped so that its longitudinal axis is aligned as well as possible with a rotation axis of the work spindle. Subsequently, a deviation of the optical axis of the optical component relative to the axis of rotation of the work spindle is determined with a suitable measuring device, and the positioning device is actuated so that the two coincide as exactly as possible. Subsequently, the raw tube is finished by external longitudinal turning. It is thus obtained a tube whose longitudinal axis coincides with high accuracy with the optical axis of the optical component. The method can, like all methods according to the invention, also be carried out with two positioning devices according to the invention, which engage at opposite ends of the workpiece.

Claims

claims 1. Positioning device, in particular chuck for a machine tool, with (a) a base body (12), (b) a driven body (14) arranged in front of the main body (12) with respect to a longitudinal axis (L) for connection to a workpiece (56), (C) one connected to the base body (12) and along the longitudinal axis (L) extending connecting element (16) and (D) at least two on the base body (12) attached, transversely to the longitudinal axis (L) acting eccentric actuators (18) which are adapted to displace the output body (14) perpendicular to the longitudinal axis (L) relative to the base body (12) by elastic Deformation of the connecting element (16), characterized in that (E) the positioning device (10) has at least two tilting actuators (36), in particular tilting piezoelectric actuators, for tilting the output body (14) relative to the base body (12). 2. Positioning device according to one of the preceding claims, characterized in that the connecting element (16) comprises a core (30) in which the at least two tilting piezo actuators (36) extend parallel to the longitudinal axis (L). 3. Positioning device according to claim 2, characterized in that the connecting element (16) comprises a clamping element (42) which is connected in a base point (F) with the driven body (14) and disposed between the tilting piezoelectric actuators (36) the tensioning element (42) and the tilting piezoelectric actuators (36) are arranged such that a length of one of the tilting piezoactuators (36) and a shortening of all other tilting piezoactuators (36) for tilting the output body (14) to the base body (12 ) leads. 4. Positioning device according to one of claims 2 or 3, characterized by four tilt piezoelectric actuators (36), each in a force application point (K) on the driven body (14) engage, wherein the force introduction points (K) a rhombus, in particular a square, form. 5. Positioning device according to claim 4, characterized in that the foot point (F) is arranged in the geometric center of the rhombus. 6. Positioning device according to one of the preceding claims, characterized in that the base body (12) comprises a base ring (20) and a base ring (20) fixed body diaphragm (22) having a relative to the base ring (20) reduced bending stiffness and on which the connecting element (16) is arranged. 7. Positioning device according to one of the preceding claims, characterized in that the output body (14) comprises an eccentric ring (46) and an eccentric ring (46) fixed output body diaphragm (44) having a relative to the eccentric ring (46) has reduced bending stiffness and on which the connecting element (16) is arranged. 8. Positioning device according to one of claims 6 or 7, characterized in that the eccentric piezoelectric actuators (18) are arranged to act between the main body diaphragm (22) and the output body diaphragm (44) on the connecting element (16) , 9. Positioning device according to one of claims 7 or 8, characterized in that the eccentric ring (46) is mounted parallel displaceable on the base body (12). 10. Positioning device according to claim 1, characterized in that the connecting element (16) with an eccentric body (48) is mounted on the base body (12) and by means of the eccentric piezoelectric actuators (18) parallel relative to the base body (12) is displaceable in that the output body (14) is pivotally mounted on the eccentric body (48). 11. Positioning device according to claim 10, characterized in that the output body (14) comprises a foot portion (54) and a head portion (50) for connection to a workpiece (56), wherein the at least two tilt piezo actuators (36) on the eccentric body ( 48), extend transversely to the longitudinal axis (L) and are arranged to the foot portion (54) such that a length of one of the tilt piezoactuators (36) and a shortening of the other tilt piezoactuators (36) to tilt the output body ( 14) relative to the eccentric body (48) leads. 12. Positioning device according to claim 11, characterized in that the eccentric body (48) has four arranged in Gegenspielerpanordnung tilt piezo actuators (36) which are arranged substantially perpendicular to the longitudinal axis (L). 13. Positioning device according to one of claims 10 to 12, characterized in that the output body (14) adjacent to its head portion (50) is supported by the output body diaphragm (44). 14. Positioning device according to one of the preceding claims, characterized in that the base body (12) is designed to be connected to a work spindle of a machine tool, in particular a grinding or lathe. 15. Positioning device according to one of the preceding claims, characterized by four eccentric piezoelectric actuators (18) which are arranged in Gegenspieleranordnung. 16. Positioning device according to one of the preceding claims, characterized in that on the output body (14) a clamping device (52), in particular a jaw or diaphragm chuck, for clamping the workpiece (56) is attached. 17. Positioning device according to one of claims 10 to 16, characterized by an electrical control, which is designed to control in each case two arranged in Gegenspielerpanordnung piezo actuators (18, 36) so that one of the piezoelectric actuators (18, 36) by a predetermined amount lengthens and shortens the other piezoelectric actuator by the same amount. 18. Machine tool, in particular grinding or lathe, with (A) a workpiece turning device for rotating a workpiece (56) about an axis of rotation and (B) a positioning device according to any one of the preceding claims, wherein (C) the longitudinal axis (L) of the positioning device (10) coincides with the axis of rotation. 19. Machine tool according to claim 18, characterized by a measuring device for detecting a position of a tensioned with the positioning workpiece (56). 20. Machine tool according to one of claims 18 or 19, characterized by an electrical control for driving the positioning device (10) which is adapted for performing a method according to any one of claims 21 to 22nd 21. A method for aligning a workpiece, comprising the step of clamping the workpiece (56) on a machine tool according to one of claims 19 or 20. 22. The method according to claim 21, characterized by the steps: (a) detecting a contour of the workpiece (56) with a measuring device, (b) determining an eccentricity and a wobble deviation of the workpiece and (c) driving the positioning device (10) so that the eccentricity and the wobble deviation are reduced. 23. The method of claim 21 or 22, wherein the workpiece is an optical component having an optical axis, characterized by the steps: (a) detecting the optical axis of the component, (b) determining a deviation of the optical axis from the axis of rotation of the machine tool and (c) driving the positioning device so that the deviation is reduced. 24. The method according to any one of claims 22 or 23, characterized by the step of machining the workpiece (56), in particular by grinding, turning, milling and / or hard turning. 25. The method according to any one of claims 22 to 24, characterized by the step: Detecting a position of the positioning device relative to the machine tool, Detecting a machining force on the workpiece and driving the eccentric and / or tilting piezoelectric actuators so that reduce or compensate for a deflection of the workpiece due to the machining force.