NL2033724B1

NL2033724B1 - Positioner device.

Info

Publication number: NL2033724B1
Application number: NL2033724A
Authority: NL
Inventors: Johannes Van Der Zalm Diederik
Original assignee: Onnes Tech B V
Priority date: 2022-12-14
Filing date: 2022-12-14
Publication date: 2024-06-20
Also published as: EP4635068A1; WO2024128914A1

Abstract

A positioner device (200) comprises a slider (202) that is slidably coupled to a main base (201). The positioner device (200) further comprises a set of piezoelectric actuator devices (318, 319) each having a top side that faces the slider (202). The top side can be made to move towards and away from the slider (202) and along a longitudinal axis of the slider (202). The set of piezoelectric actuator devices (318, 319) is conﬁgured to operate in a stepper mode. The piezoelectric actuator devices (318, 319) are mounted on an actuator base (317) that is comprised within the main base (201). A resilient coupling (320) of the actuator base (317) with the main base (201) keeps the piezoelectric actuator devices (318, 319) abutted against the slider (202) in a state of rest. 3.

Description

Positioner device.

FIELD OF THE INVENTION

An aspect of the invention relates to a positioner device. The positioner device may be, used for example, in a cryogenic measurement setup where the positioner device has to operate at extremely low temperatures. Other aspects of the invention relate to a multi-axis manipulator, use of a positioner device for positioning an object with respect to another object, and a method of operating a positioner device.

BACKGROUND ART

A positioner device that can achieve nanoscale precision may be based on one or more piezoelectric actuators arranged to move a slider. An electrical actuation signal can cause a piezoelectric actuator to change in size or shape, or both, in at least one dimension with great precision. A motion due to this change in shape or size, or both, can be transferred to the slider. The slider can thus be made to move over macroscopic distances with nanometer resolution and even sub-nanometer resolution. This allows precise positioning of an object that is in contact with the slider.

There are several different operating principles that can be used in such a positioner device. One operating principle is a stick-slip mode of operation. The motion of a piezoelectric actuator is transferred to the slider by alternately static friction and dynamic friction, which represent stick and slip, respectively. This principle is akin to, on the one hand, slowly pulling a tablecloth on which objects are present and, on the other hand, quickly pulling the tablecloth. When pulled slowly, the objects move with the tablecloth.

This corresponds to stick. When pulled quickly, the objects hardly move with the tablecloth. This corresponds to slip.

Another operating principle is a stepper mode of operation, which requires atleast two piezoelectric actuators. One piezoelectric actuator that is in firm contact with the slider transfers its motion from a start position to an end position. Concomitantly, another piezoelectric actuator that is detached from the slider returns from an end position to a start position. Subsequently, the one and the other piezoelectric actuator change roles.

This principle is akin to leg movements of an insect in motion.

Patent publication WO2004066405A 1 discloses is a linear piezo drive unit that comprises a group of stacked piezo actuators driving an armature that is placed in a guide. The actuators are provided with several stacks that are located on a common support element. A first stack part within a stack is embodied as a longitudinal actuator starting from the support element. A second stack part within the stack is embodied as a shearing actuator. The individual stacks are in clamping contact and/or shearing contact with the armature and reciprocally perform clamping and advancing movements in a stepped operation. A connecting element is disposed between the first stack part, which 1s embodied as a longitudinal actuator, and a second stack part, which is embodied as a shearing actuator. The connecting element interconnects at least one respective part of the stacks and is configured in a non-rigid manner in the actuating direction of the longitudinal actuators while being configured in a rigid manner in the direction of movement of the armature.

It has been proven difficult to achieve reliable operation of a positioner device in extreme conditions, such as, for example, in vacuum at extremely low temperatures, in particular below 4 Kelvin (-269.15 °C). Such extremely low temperatures may be required for analysis and manipulation of samples at nanoscale. At present, positioner devices designed to operate at extremely low temperatures apply the stick-slip principle. However, the dynamic friction generates heat, which may prevent achieving the extremely low temperatures required for analysis and manipulation. Moreover, the dynamic friction causes wear, which may compromise reliable operation. Also, positioner devices operating in the stick-slip mode generally fail to achieve nano-precision at extremely low temperatures.

One factor that complicates satisfactory operation of a positioner device at extremely low temperatures is that a piezoelectric actuator has a motion range that reduces with temperature. For example, below 77K , the motion range significantly reduces to 10 to 20% of that achieved at room temperature. A positioner device operating in the stepper mode may particularly suffer from this effect. A significantly reduced motion range may make one or more piezoelectric actuators fail to detach from the slider, which is required for satisfactory operation, in particular at extremely low temperatures.

SUMMARY OF THE INVENTION

There 1s a need for a solution that allows a positioner device to reliably operate in extreme conditions, in particular at extremely low temperatures.

An aspect of the invention as defined in claim 1 provides for a positioner device comprising: - a main base; - a slider slidably coupled to the main base; - a set of piezoelectric actuator devices each having a top side that faces the slider, whereby the top side can be made to move towards and away from the slider and along a longitudinal axis of the slider, the set of piezoelectric actuator devices being configured to operate in a stepper mode, - an actuator base comprised within the main base, the piezoelectric actuator devices being mounted on the actuator base; and - a resilient coupling of the actuator base with the main base, the resilient coupling being configured to keep the piezoelectric actuator devices abutted against the slider in a state of rest.

A further aspect of the invention as defined in claim 15 provides for multi- axis manipulator comprising a positioner device as defined hereinbefore

Yet a further aspect of the invention as defined in claim 16 provides for use of a positioner device as defined hereinbefore.

In each of these aspects, since the resilient coupling keeps the piezoelectric actuator devices abutted against the slider in a state of rest, the slider may be stably maintained at rest without this requiring power consumption. The resilient coupling helps ensure that a piezoelectric actuator making a return movement is detached from the slider .

This is the case even if the piezoelectric actuator has a significantly reduced motion range due to extremely low temperatures. The set of piezoelectric actuator devices may thus drive the slider by purely clamping, moving, and releasing the slider. This avoids generation of heat and prevents wear. The positioner device may have a low power consumption when driving the slider. For example, only a few microwatt may be sufficient to drive the slider. This also contributes to achieving extremely low temperatures in an environment where the positioner device is used. All this allows reliable operation at extremely low temperatures, which may be close to 0 Kelvin (-273.15 °C).

Embodiments of the positioning device as defined hereinbefore can be relatively small and compact. There is no need for two drive units at two opposite sides of a slider as described in the patent publication cited hereinbefore. This enables easier access to the slider and to the interior of the positioning device. In addition, this allows easier construction of a multi-axis manipulator by coupling several positioning devices with each other. The positioner device may provide a high holding and moving force, strong enough to move a load of several Newtons, such as, for example, an objective lens or probe. Also, the positioner device may achieve stable positioning at an atomic level.

In an embodiment as defined in claim 2, the positioner device comprises a leaf spring structure providing, at least partially, the resilient coupling of the actuator base with the main base.

In an embodiment as defined in claim 3, the leaf spring structure extends into the actuator base and 1s coupled with the set of piezoelectric actuator devices.

In an embodiment as defined in claim 4, each piezoelectric actuator device of the set of piezoelectric actuator devices comprises: - a lifting actuator between the actuator base and the leaf spring structure, the lifting actuator being configured to make the top side of the piezoelectric actuator device move towards and away from the slider; and - a drive actuator axially aligned with the lifting actuator and protruding from the leaf spring structure toward the slider, the drive actuator being configured to make the top side of the piezoelectric actuator device move along the longitudinal axis of the slider.

In an embodiment as defined in claim 5, the leaf spring structure comprises a torsion-resilient coupling arrangement between an inner frame of the leaf spring structure that is secured to the actuator base and an outer frame of the leaf spring structure that is secured to the main base.

In an embodiment as defined in claim 6, the torsion-resilient coupling arrangement provides maximum stiffness along the longitudinal axis of the slider.

In an embodiment as defined in claim 7, the leaf spring structure comprises a set of coupling plates within the inner frame, each of which is uniquely coupled to a piezoelectric actuator device of the set of piezoelectric actuator devices.

In an embodiment as defined in claim 8, the coupling plates are coupled to the inner frame by bridge elements extending along the longitudinal axis of the slider.

In an embodiment as defined in claim 9, the coupling plates are perforated.

In an embodiment as defined in claim 10, the leaf spring structure is in the form of a monolithic leaf spring with cutouts.

In an embodiment as defined in claim 11, the leaf spring structure has a yield strength greater than 500 MPa.

In an embodiment as defined in claim 12, the set of piezoelectric actuator devices comprises four piezoelectric actuator devices in a rectangular configuration having an axis of symmetry corresponding with the longitudinal axis of the slider.

In an embodiment as defined in claim 13, the top side of each piezoelectric 5 actuator device comprises a pair of protruding contact elements arranged so that when two of the four piezoelectric actuator devices that are on a diagonal of the rectangular configuration abut against the slider, the protruding contact elements of these two piezoelectric actuator devices form corners of a diagonally oriented quadrilateral surface area on the slider.

In an embodiment as defined in claim 14, the main base has an upper portion comprising a first inwardly protruding longitudinal edge and, parallel thereto, a second inwardly protruding longitudinal edge; - the slider has a first longitudinal side edge has a longitudinal groove with a lower wall and, parallel thereto, a second longitudinal side edge having a longitudinal groove with a lower wall; - the first inwardly protruding longitudinal edge of the upper portion of the main base is received in the longitudinal groove in the first longitudinal side edge of the slider so as to form a linear roller bearing comprising roller balls between, on the one hand, a V- shaped groove in the first inwardly protruding longitudinal edge of the upper portion of the main base and, on the other hand, a V-shape groove in the lower wall of the longitudinal groove in the first longitudinal side edge of the slider; and - the second inwardly protruding longitudinal edge of the upper portion of the main base is received in the longitudinal groove in the second longitudinal side edge of the slider so as to form another linear roller bearing comprising roller balls between, on the one hand, a flat surface of the second inwardly protruding longitudinal edge that faces the lower wall of the longitudinal groove in the second longitudinal side edge of the slider and, on the other hand, a V-shape groove in the lower wall of the longitudinal groove in the second longitudinal side edge of the slider.

Yet a further aspect of the invention as defined in claim 17 provides for a method of operating an embodiment of the positioner device as defined in any of claims 12 and 13, wherein, in the stepper mode, the positioner device is made to repetitively carry out drive cycles in which two of the four piezoelectric actuator devices that are on a diagonal of the rectangular configuration form a first pair of piezoelectric actuator devices that are jointly actuated, and the other two of the four piezoelectric actuator devices, which are also on a diagonal of the rectangular configuration, form a second pair of piezoelectric actuator devices that are jointly actuated, a drive cycle comprising: - a first drive step in which the first pair of piezoelectric actuator devices is made to abut against the slider, whereas the second pair of piezoelectric actuator devices is retracted from the slider, the piezoelectric actuators of the first pair being subsequently actuated so that the top side of each piezoelectric actuator device moves in a direction along the longitudinal axis of the slider; and - a second drive step in which the second pair of piezoelectric actuator devices is made to abut against the slider, whereas the first pair of piezoelectric actuator devices is retracted from the slider, the piezoelectric actuator of the second pair being subsequently actuated so that the top side of each piezoelectric actuator devices moves in the same direction along the longitudinal axis of the slider.

For the purpose of illustration, some embodiments of the invention are described in detail with reference to accompanying drawings. In this description, additional features will be presented, some of which are defined in the dependent claims, and advantages will be apparent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram of a cryogenic measurement set-up.

FIG. 2 is a schematic top view of a positioner device that can be used in the cryogenic measurement set-up.

FIG. 3 is a schematic cross-sectional view of the positioner device along a cut line A-A indicated in FIG. 2 .

FIG. 4 is a schematic top view of a drive unit in the positioner device.

FIG. 5 is a schematic perspective view of a contact pad, which is provided on a top side of a piezoelectric actuator device in the drive unit.

FIG. 6 is a schematic top view of a leaf spring structure in the positioner device.

FIG. 7 is a simplified schematic semi-transparent top view of the positioner device with the drive unit in a first state of a drive cycle

FIG. 8 is a simplified schematic semi-transparent top view of the positioner device with the drive unit in a second state of the drive cycle.

FIG. 9 is a simplified schematic semi-transparent top view of the positioner device with the drive unit in a third state of the drive cycle,

FIG. 10 is a simplified schematic semi-transparent top view of the positioner device with the drive unit in a fourth state of the drive cycle.

FIG. 11 is a simplified schematic semi-transparent top view of the positioner device with the drive unit in a fifth state of the drive cycle.

FIG. 12 is a simplified schematic semi-transparent top view of the positioner device with the drive unit in a sixth state of the drive cycle.

DESCRIPTION OF SOME EMBODIMENTS

FIG. 1 schematically illustrates a cryogenic measurement setup 100. FIG. 1 provides a conceptual diagram of the cryogenic measurement setup 100. The cryogenic measurement setup 100 may be used for various applications. For example, the cryogenic measurement setup 100 may be used for sensing nanoscale forces, such as, for example, measuring magnetic fields of individual atoms at a near to 0 K temperature. This may be relevant for quantum computing. As another example, the cryogenic measurement setup 100 may be used for nano magnetic resonance imaging, which allows scans with atomic resolution. This may be relevant for healthcare, such as, for example, an early diagnosis of meta-stasis in cancer, or research of neurodegenerative diseases. As yet another example, the cryogenic measurement setup 100 may be used for cryogenic microscopy.

The cryogenic measurement setup 100 comprises a cryogenic vacuum generation device 101 and a cryogenic vacuum chamber 102. The cryogenic vacuum generation device 101 may create a vacuum in the cryogenic vacuum chamber 102 and bring a temperature within the cryogenic vacuum chamber 102 down to near to 0 K. For example, the temperature may go down to below 1 K and even down to a few tens of milliK, or even lower. Achieving such an extremely low temperature may be important for the applications mentioned hereinbefore, as well as for other applications.

Several objects have been placed in the cryogenic vacuum chamber 102 for carrying out measurements at such an extremely low temperature. These objects may include a sample 103 to be measured, a sensor device 104, and a multi-axis manipulator 105. In this embodiment, the multi-axis manipulator 105 is used to position the sensor device 104 with respect to the sample 103 with nanoscale precision. This nanoscale positioning is indicated in FIG. 1 by means of double-sided arrow in broken lines between the sensor device 104 and the sample 103. The multi-axis manipulator 105 may be electrically driven by a positioning controller 106, which is outside the cryogenic vacuum chamber 102. The sensor device 104 is coupled to a measurement device 107, which may also be outside the cryogenic vacuum chamber 102.

The multi-axis manipulator 105 may comprises several positioner devices 108, 109, 110 that may be juxtaposed with each other. In this embodiment, the multi-axis manipulator 105 comprises three positioner devices 108, 109, 110 for movement in the three dimensions. A first positioner device 108 may provide movement along an X-axis. A second positioner device 109 may provide movement along a Y-axis, which is orthogonal to the X-axis. A third positioner device 110 may provide movement along a Z-axis, which is orthogonal to the X-axis as well as to the Z-axis.

FIGS. 2 and 3 schematically illustrate a positioner device 200 that can be used in the cryogenic measurement setup 100. FIG. 2 provides a schematic top view of the positioner device 200. FIG. 3 provides a schematic cross-sectional view of the positioner device 200 along a cut line A-A indicated in FIG. 2. The positioner device 200 illustrated in FIGS. 2 and 3 may be any of the three positioner devices 108, 109, 110 in the multi-axis manipulator 105 represented in FIG. 1. That is, each of the three positioner devices 108, 109, 110 in the multi-axis manipulator 105 may correspond with the positioner device 200 illustrated in FIGS. 2 and 3, which is described hereinafter.

The positioner device 200 comprises a main base 201 and a slider 202, which is slidably coupled to the main base 201 as illustrated in FIG. 3. In this embodiment, the main base 201 has an upper portion 301 and a lower portion 302. The upper portion 301 has two inwardly protruding longitudinal edges 303, 304, which are parallel to each other. These two inwardly protruding longitudinal edges 303, 304 will individually be referred to as first main base top edge 303 and second main base top edge 304.

The slider 202 has two longitudinal side edges 305, 306, which are parallel to a longitudinal axis 203 of the slider 202. The two longitudinal side edges 305, 306 of the slider 202 will individually be referred to as first slider side edge 305 and second slider side edge 306. The first slider side edge 305 has a longitudinal groove 307 with a lower wall 308. Similarly, the second slider side edge 306 equally has a longitudinal groove 309 with a lower wall 310. The first main base top edge 303 is received in the longitudinal groove 307 in the first slider side edge 305. The second main base top edge 304 is received in the longitudinal groove 309 in the second slider side edge 306.

The positioner device 200 comprises two linear roller bearings, which are formed as follows in this embodiment. The first main base top edge 303 comprises a V- shaped groove 311. The lower wall 308 of the longitudinal groove 307 in the first slider side edge 305 equally comprises a V-shaped groove 312. Roller balls 313 are comprised between the aforementioned V-shaped grooves 311, 312 thus forming a first linear roller bearing. The second main base top edge 304 has a flat surface that faces the lower wall 310 of the longitudinal groove 309 in the second slider side edge 306. This lower wall 310 comprises a V-shaped groove 314. Roller balls 315 are comprised between the aforementioned flat surface and the aforementioned V-shaped groove 314 thus forming a second linear roller bearing.

The positioner device 200 comprises a drive unit 316 that can make the slider 202 move along its longitudinal axis 203 in two directions, which are opposite to each other. The drive unit 316, which is cross-sectionally represented in FIG. 3, comprises an actuator base 317 that is comprised within the main base 201. Two piezoelectric actuator devices 318, 319 are mounted on the actuator base 317. These two piezoelectric actuator devices 318, 319 form part of a set of four piezoelectric actuator devices, which are all mounted on the actuator base 317 as indicated in FIG. 3.

The drive unit 316 further comprises a leaf spring structure 320 that provides a resilient coupling of the actuator base 317 with the main base 201. In this embodiment, the leaf spring structure 320 extends into the actuator base 317 and is coupled to the two piezoelectric actuator devices 318, 319 as well as to the other two piezoelectric actuator devices, which are not represented in FIG. 3. A peripheral portion of the leaf spring structure 320 may be clamped between the upper portion 301 and the lower portion 302 of the main base 201 as illustrated in FIG. 3. The upper portion 301 and the lower portion 302 may be fixed to each other by means of, for example, screws.

FIG. 4 schematically illustrates the drive unit 316 in the positioner device 200. FIG. 4 provides a schematic top view of the drive unit 316. All the four piezoelectric actuator devices 318, 319, 401, 402 of the drive unit 316 are visible in FIG. 4. The four piezoelectric actuator devices 318, 319, 401, 402 are in a rectangular configuration having an axis of symmetry corresponding with the longitudinal axis 203 of the slider 202. The four piezoelectric actuator devices 318, 319, 401, 402 will individually be referred to as first piezoelectric actuator device 318, second piezoelectric actuator device 319, third piezoelectric actuator device 401, and fourth piezoelectric actuator device 402.

As illustrated in FIG. 4, the leaf spring structure 320 extends into the actuator base 317 and is coupled with the four piezoelectric actuator devices 318, 319, 401, 402. In this embodiment, the leaf spring structure 320 intersects with the four piezoelectric actuator devices 318, 319, 401, 402. FIG. 3 illustrates this for the first piezoelectric actuator device 318 and the second piezoelectric actuator device 319.

The first piezoelectric actuator device 318 has a top side that faces the slider 202 as illustrated in FIG. 3. In this embodiment, the top side is provided with a contact pad 322, which is also represented in FIG. 4. The same applies to the other piezoelectric actuator devices 319, 401, 402. Accordingly, the second piezoelectric actuator device 319 equally has a top side provided with a contact pad 323, which faces the slider 202, which is represented in FIGS. 3 and 4. The third piezoelectric actuator device 401 has a top side provided with a contact pad 403, which is represented in FIG. 4 only. The fourth piezoelectric actuator device 402 equally has a top side provided with a contact pad 404, which is represented in FIG. 4 only.

As illustrated in FIG. 3, the first piezoelectric actuator device 318 comprises a lifting actuator 324 between the actuator base 317 and the leaf spring structure 320. The first piezoelectric actuator device 318 further comprises a drive actuator 325 that protrudes from the leaf spring structure 320 towards the slider 202. The drive actuator 325 is axially aligned with the lifting actuator 324. The lifting actuator 324 can make the first piezoelectric actuator device 318 higher or lower with respect to the actuator base 317.

Accordingly, the contact pad 322 on the first piezoelectric actuator device 318 can move towards the slider 202 to come into contact therewith and can be retracted away from the slider 202. The drive actuator can make the contact pad 322 move along the longitudinal axis 203 of the slider 202.

The second piezoelectric actuator device 319 equally comprises a lifting actuator 326 and a drive actuator 327, which are similarly disposed as illustrated in FIG. 3.

The lifting actuator 326 and the drive actuator 327 operate similarly to the lifting actuator 324 and the drive actuator 325, respectively, described hereinbefore. The third piezoelectric actuator device 401 and the fourth piezoelectric actuator device 402 equally each comprise a lifting actuator and a drive actuator, which also operate similarly to the lifting actuator 324 and the drive actuator 325, respectively, described hereinbefore. The four piezoelectric actuator devices 318, 319, 401, 402 are thus configured to operate in a stepper mode, as described in greater detail hereinafter.

In a state of rest, the resilient coupling of the actuator base 317 with the main base 201 keeps the four piezoelectric actuator devices 318, 319, 401, 402 abutted against the slider 202. The state of rest means that the piezoelectric actuator devices are not actuated; no drive signal is applied to the piezoelectric actuator devices. Accordingly, in the state of rest, the drive unit 316 need not consume any power, which prevents heat from being produced. Moreover, the slider 202 is mechanically stable due to the fact that the slider 202 is supported by the four piezoelectric actuator devices 318, 319, 401, 402.

In the stepper mode, at least two respective lifting actuators are actuated so that two of the four piezoelectric actuator devices 318, 319, 401, 402 are momentarily longest, whereas the two other piezoelectric actuator devices are momentarily shortest.

Four respective drive actuators may be actuated so that two movements may occur. One the one hand, the respective top sides of the two momentarily longest piezoelectric actuator devices may move in a forward direction along the longitudinal axis 203 of the slider 202.

On the other hand, the respective top sides the two momentarily shortest piezoelectric actuator devices may move in a backward direction, opposite to the forward direction.

The resilient coupling provided by the leaf spring structure 320 ensures that the momentarily shortest piezoelectric actuator devices are retracted from the slider 202 while the momentarily longest piezoelectric actuator devices abut against the slider 202.

Accordingly, it is prevented that the momentarily shortest piezoelectric actuator devices are in contact with the slider 202. If any of the momentarily shortest piezoelectric actuator devices were to contact the slider 202, this would result in friction, which would undesirably generate heat and may even cause malfunctioning. The resilient coupling of the actuator base 317 with the main base 201 thus contributes to reliable operation in the stepper mode.

The contact pads 322, 323, 403, 404 may further contribute to reliable operation, in particular in the stepper mode. The contact pads 322, 323, 403, 404 allow firm and stable contact between, one the one hand, the pair of momentarily longest piezoelectric actuator devices and, on the other hand, the slider 202. In the stepper mode, the momentarily longest piezoelectric actuator devices are actuated causing their respective top sides to move in the forward direction along the longitudinal axis 203 of the slider 202.

The firm and stable contact prevents slip between these piezoelectric actuator devices and the slider 202.

The four piezoelectric actuator devices 318, 319, 401, 402 may be nominally identical, each having been designed and constructed identically. The four piezoelectric actuator devices 318, 319, 401, 402 are thus nominally identical in shape and in dimension. This implies that their contact pads are identically positioned with respect to the slider 202. Moreover, the four piezoelectric actuator devices 318, 319, 401, 402 normally have an identical effective thermal expansion coefficient . Accordingly,

nominally, the four piezoelectric actuator devices 318, 319, 401, 402 vary in dimension with temperature to an identical degree. The contact pads thus keep an identical position with respect to the slider 202 despite temperature variations.

However, due to tolerances, there may be slight differences between the four piezoelectric actuator devices 318, 319, 401, 402: differences in shape, in dimension, and also in effective thermal expansion coefficient. Consequently, there may be a slight misalignment of the four piezoelectric actuator devices 318, 319, 401, 402 with respect to the slider 202. For example, there may be slight differences in height between the four piezoelectric actuator devices 318, 319, 401, 402. Also, a contact pad may be slightly tilted with respect to the slider 202. Differences in thermal expansion coefficient may exacerbate differences in shape and in dimension and thus exacerbate a slight misalignment when a temperature changes. The latter phenomenon is particularly important when the positioner device 200 is cooled down from, for example, room temperature to an extremely low temperature, which may be near to zero (0) Kelvin in the cryogenic measurement setup 100 illustrated in FIG. 1.

The leaf spring structure 320 represented in FIGS. 3 and 4 absorbs, as it were, slight differences between the four piezoelectric actuator devices 318, 319, 401, 402.

For example, the leaf spring structure 320 may compensate for differences in height between the four piezoelectric actuator devices 318, 319, 401, 402. The leaf spring structure 320 may also compensate for a contact pad being slightly tilted with respect to the slider 202. Accordingly, the leaf spring structure 320 helps ensure that the four piezoelectric actuator devices 318, 319, 401, 402 are correctly abutted against the slider 202 in the state of rest, in particular at extremely low temperatures.

In addition, the leaf spring structure 320 provides mechanical stability when the positioner device 200 operates in the stepper mode. Namely, a piezoelectric actuator may be subject to mechanical stresses due to handling or operation. Particularly, in the stepper mode, actuation of a piezoelectric actuator device may produce lateral forces that may potentially cause an undesired deformation of the piezoelectric actuator device.

Lateral forces may produce cracks, which may reduce motion range, and may even break the piezoelectric actuator device. All this may affect proper functioning and may even result in malfunctioning. This problem particularly presents itself when the piezoelectric actuator device is relatively elongated. Relatively elongated piezoelectric actuator devices are required to achieve a sufficiently large motion range, in particular at extremely low temperatures.

The leaf spring structure 320 provides a laterally stiff coupling between the four piezoelectric actuator devices 318, 319, 401, 402, as well as a laterally stiff coupling of these devices with the actuator base 317. Accordingly, the leaf spring structure 320 absorbs, as it were, the lateral forces produced in the stepper mode, which helps preventing undesired deformation. The leaf spring structure 320 thus also contributes to reliable operation of the positioner device 200 in the stepper mode, in particular at extremely low temperatures.

FIG. 5 illustrates an exemplary embodiment of the contact pad 322 on the top side of the first piezoelectric actuator device 318 in the drive unit 316. FIG. 5 provides a schematic perspective view of this exemplary embodiment, which will be referred to hereinafter as the contact pad 322 for the sake of convenience. The contact pad 322 comprises a pair of protruding contact elements 501, 502, which may contact the slider 202. These two protruding contact elements 501, 502 are located at two corners of the contact pad 322, which diagonally face each other. The contact pads 323, 403, 404 of the other three piezoelectric actuator devices 319, 401, 402 may be similar to the contact pad 322 illustrated in FIG. 5, which belongs to the first piezoelectric actuator device 318.

The contact pads 322, 323, 403, 404 of the four piezoelectric actuator devices 318, 319, 401, 402 may be disposed as illustrated in FIG. 4. The pairs of protruding contact elements of these contact pads are indicated in FIG. 4. The contact pads are disposed so that the pair of protruding contact elements of each contact pad lie on a diagonal line that has an acute angle with the longitudinal axis 203 of the slider 202 seen from a center point in the positioner device 200. This manner in which the contact pads 322, 323, 403, 404 are disposed, as illustrated in FIG. 4, further contribute to achieving the firm and stable contact and thus to avoiding slip.

FIG. 6 schematically illustrates an embodiment of the leaf spring structure 320 that provides the resilient coupling of the actuator base 317 with the main base 201.

FIG. 6 provides a schematic top view of the leaf spring structure 320. In this embodiment, the leaf spring structure 320 is a monolithic leaf spring with cut outs. These cut outs may have been obtained by, for example, laser cutting. The leaf spring structure 320 will be referred to hereinafter as leaf spring 320 for the sake of convenience.

The leaf spring 320 may have a yield strength greater than 500 MPa. The leaf spring 320 may therefore comprise a material that has a relatively high elasticity and a relatively high stretch limit. The leaf spring 320 may comprise, for example, titanium,

phosphor-bronze, or copper-beryllium. Titanium Grade 5 has proven to be a suitable choice.

As illustrated in FIG. 6, the leaf spring 320 comprises an outer frame 601 and an inner frame 602. The outer frame 601 corresponds with the peripheral portion of the leaf spring 320 mentioned hereinbefore with reference to FIG. 3. Accordingly, the outer frame 601 may be clamped between the upper portion 301 and the lower portion 302 of the main base 201. The inner frame 602 holds the actuator base 317. In this embodiment, the inner frame 602 comprises four round apertures as illustrated in FIG. 6. These apertures allow securing the actuator base 317 to the inner frame 602 by means of screws. FIG. 4 illustrates these screws, which are indicated by reference signs 405, 406, 407, 408.

The inner frame 602 is coupled to the outer frame 601 by means of a torsion-resilient coupling arrangement 603. The torsion-resilient coupling arrangement 603 provides maximum stiffness along the longitudinal axis 203 of the slider 202. This contributes to advantages provided by the leaf spring 320 that have been discussed hereinbefore with reference to FIGS. 3 and 4. These advantages allow reliable operation in the stepper mode.

In this embodiment, the torsion-resilient coupling arrangement 603 comprises four pairs of strips. The strips of each of these four pairs are arranged in a V- shape having a narrowest end and a widest end. The narrowest end is coupled with the inner frame 602 of the leaf spring 320. The widest end is coupled with the outer frame 601 of the leaf spring 320 as illustrated in FIG. 4.

The inner frame 602 holds a set of coupling plates 604-607. In this embodiment, the leaf spring 320 comprises four coupling plates 604, 605, 606, 607. Each coupling plate is uniquely coupled to one of the four piezoelectric actuator devices 318, 319, 401, 402 as illustrated in FIG. 4. Thus, in more detail, the first piezoelectric actuator device 318 is coupled to a first coupling plate 604 in the of the leaf spring 320. The second piezoelectric actuator device 319 is coupled to a second coupling plate 605. The third piezoelectric actuator device 401 is coupled to a third coupling plate 606. The fourth piezoelectric actuator device 402 1s coupled to a fourth coupling plate 607 of the leaf spring 320.

As illustrated in FIG. 6, each of the four coupling plates 604, 605, 606, 607 is perforated. This contributes to achieving a sufficiently tight coupling between, on the one hand, the four piezoelectric actuator devices 318, 319, 401, 402 and, on the other hand, the leaf spring 320 by means of gluing.

As illustrated in FIG. 6, the first coupling plate 604 is coupled to the inner frame 602 of the leaf spring 320 by bridge elements 608, 609 extending along the longitudinal axis 203 of the slider 202. The same applies to the second coupling plate 605, the third coupling plate 606 and the fourth coupling plate coupling plate 607, These are also coupled to the inner frame 602 of the leaf spring 320 by bridge elements extending along the longitudinal axis 203 of the slider 202. For the sake of simplicity, no reference numerals have been assigned to these latter bridge elements in FIG 6.

FIGS. 7-12 schematically illustrate various states of a drive cycle that the drive unit 316 carries out, which moves the slider 202 of the positioner device 200. FIGS. 7-12 each provide a simplified schematic semi-transparent top view of the positioner device 200. The four piezoelectric actuator devices 318, 319, 401, 402 with their respective contact pads 322, 323, 403, 404 are indicated in these figures. In this example, the contact pads 322, 323, 403, 404 each correspond with the exemplary embodiment illustrated in

FIG. 5. The respective pairs of protruding contact elements of the respective contact pads are indicated as well. The aforementioned elements have, in fact, been added to the schematic top view of FIG. 2 in which the slider 202 and the main base 201 are represented.

In FIGS. 7-12, displacements of the contact pads 322, 323, 403, 404 along the longitudinal axis 203 of the slider 202 are greatly exaggerated for the sake of clarity.

As described hereinbefore, each of the four piezoelectric actuator devices 318, 319, 401, 402 can be actuated so that the contact pad provided on its top side can move along the longitudinal axis 203. More specifically, the contact pad can move along the longitudinal axis 203 in a range between two extreme positions. One of these two extreme positions will be referred to as start position, whereas the other extreme position will be referred to as end position for the sake of convenience.

FIG. 7 schematically illustrates a first state of the drive cycle. In the first state, the first and third piezoelectric actuator devices 318, 401 abut against the slider 202.

The contact pads 322, 403 of the two aforementioned piezoelectric actuator devices 318, 401 thus make firm contact with the slider 202. The aforementioned contact pads 322, 403 are in their start positions. Conversely, the second and fourth piezoelectric actuator devices 319, 402 are detached from the slider 202. The contact pads 323, 404 of the two aforementioned piezoelectric actuator devices 319, 402 thus do not make contact with the slider 202. The aforementioned contact pads 323, 404 are in their end positions.

The first state illustrated in FIG. 1 marks a start of a first drive step of the drive cycle. Starting from the first state, the first and third piezoelectric actuator devices 318, 401 are actuated so that their contact pads 322, 403 gradually move in a direction from their start positions to their end positions. Since these contact pads 322, 403 make firm contact with the slider 202, the slider 202 is made to slide along its longitudinal axis 203 in the same direction. Concomitantly, the second and fourth piezoelectric actuator devices 319, 402 are actuated so that their contact pads 323, 404 gradually move in an opposite direction from the end position to the start position, without making any contact with the slider 202.

The resilient coupling of the actuator base 317 with the main base 201, which was described hereinbefore, ensures that the contact pads 323, 404 of the second and fourth piezoelectric actuator devices 319, 402 do not contact the slider 202 in the first drive step. This prevents friction, which would undesirably generate heat and may even cause malfunctioning. Moreover, the leaf spring 320 of the drive unit 316 absorbs slight misalignments, which may be linear or angular, or both. Misalignments may be due to tolerances in manufacturing and assembly. What is more, operation at extremely low temperatures, such as in the cryogenic measurement setup 100 illustrated in FIG. 1, may exacerbate such misalignments. The leaf spring 320 thus contributes to reliable operation, in particular at extremely low temperatures.

The first and third piezoelectric actuator devices 318, 401 that abut against the slider are on a diagonal of the rectangular configuration of the four piezoelectric actuator devices 318, 319, 401, 402. The protruding contact elements on the contact pads 322, 403 of the first and third piezoelectric actuator devices 318, 401 are arranged so that these protruding contact elements form corners of a diagonally oriented quadrilateral surface area on the slider 202 as indicated in FIG. 7. This arrangement contributes to mechanical stability of the slider 202 while the first and third piezoelectric actuator devices 318, 401 are being actuated and thus contributes to reliable movement of the slider 202.

FIG. 8 schematically illustrates a second state of the drive cycle. The second state marks an end of the first drive step in the drive cycle. The contact pads 322, 403 of the first piezoelectric actuator device 318 and of the third piezoelectric actuator device 401 have reached their end positions. The contact pads 322, 403 of the aforementioned piezoelectric actuator devices 318, 403 are still firmly in contact with the slider 202. In

FIG. 8, two upward arrows in broken lines indicate a drive movement that the first and third piezoelectric actuator devices 318, 401 have made with respect to their start positions represented in FIG. 7. The aforementioned piezoelectric actuator devices 318, 401 have imposed this drive movement on the slider 202. The slider 202 represented in FIG. 8 has moved with respect to the slider 202 represented in FIG. 7.

Conversely, the contact pads 323, 404 of the second and fourth piezoelectric actuator devices 319, 402 have reached their start positions in the second state illustrated in

FIG. 8. These contact pads 323, 404 are still detached from the slider 202. In FIG. 8, two downward arrows in broken lines indicate a return movement that the second and fourth piezoelectric actuator devices 319, 402 have made with respect to their end positions represented in FIG. 7.

FIG. 9 schematically illustrates a third state of the drive cycle. The third state marks a transition from the first drive step to a subsequent, second drive step in the drive cycle. In the third state, all the four piezoelectric actuator devices 318, 319, 401, 402 abut against the slider 202. That is, all the contact pads 322, 323, 403, 404 of the four piezoelectric actuator devices 318, 319, 401, 402 make firm contact with the slider 202.

Starting from the second state illustrated in FIG. 8, the third state illustrated in FIG. 9 may be reached by actuating the second and fourth piezoelectric actuator devices 319, 402 so that these increase in height. As a result, their contact pads 323, 404 move towards the slider 202 and finally make firm contact with the slider 202. Alternatively, the first and third piezoelectric actuator devices 318, 401 may be actuated so that these decrease in height. As long as the aforementioned piezoelectric actuator devices 318, 401 abut against the slider 202, their decrease in height makes the slider 202 move towards the contact pads 323, 404 of the second and fourth piezoelectric actuator devices 319, 402.

FIG. 10 schematically illustrates a fourth state of the drive cycle, which marks a start of the second drive step of the drive cycle. In the fourth state, the second and fourth piezoelectric actuator devices 319, 402 still abut against the slider 202 as in the third state illustrated in FIG. 9. The contact pads 323, 404 of the two aforementioned piezoelectric actuator devices 319, 402 thus still make firm contact with the slider 202 and are still in their start positions. However, the first and third piezoelectric actuator devices 318, 401 are detached from the slider 202. The contact pads 322, 403 of the two aforementioned piezoelectric actuator devices 318, 401 thus do not make contact anymore with the slider 202, but are still in their end positions.

Starting from the third state illustrated in FIG. 9, the fourth state illustrated in FIG. 10 may be reached by actuating the first and third piezoelectric actuator devices 318, 401 so that these decrease in height. As a result, their contact pads 322, 403 move away the slider 202, detach from the slider 202, making no contact anymore with the slider 202. Alternatively, the second and fourth piezoelectric actuator devices 319, 402 may be actuated so that these increase in height. As long as the aforementioned piezoelectric actuator devices 319, 402 abut against the slider 202, their increase in height makes the slider 202 move away from the contact pads 322, 403, of the first and third piezoelectric actuator devices 318, 401.

The second drive step starts from the fourth state illustrated in FIG. 10. In this step, the second and fourth piezoelectric actuator devices 319, 402 are actuated so that their contact pads 323, 404 gradually move from in a direction from their start positions to their end positions. Since these contact pads 323, 404 make firm contact with the slider 202, the slider 202 is made to slide further along its longitudinal axis 203 in the same direction. Concomitantly, the first and third piezoelectric actuator devices 318, 401 are actuated so that their contact pads 322, 403 gradually move in an opposite direction from the end position to the start position.

In the second drive step too, the resilient coupling of the actuator base 317 with the main base 201 ensures that the contact pads 322, 403 of the first and third piezoelectric actuator devices 318, 401 do not contact the slider 202 in the first drive step.

As mentioned hereinbefore, this prevents friction, which would undesirably generate heat and may even cause malfunctioning. The leaf spring 320 further contributes to reliable operation by absorbing slight misalignments, as discussed hereinbefore.

Here too, the second and fourth piezoelectric actuator devices 319, 402 that abut against the slider are on a diagonal of the rectangular configuration of the four the third piezoelectric actuator devices 318, 319, 401, 402. The protruding contact elements on the contact pads 323, 404 of the second piezoelectric actuator device 319 and the fourth piezoelectric actuator device 402 are arranged so that these protruding contact elements form corners of a diagonally oriented quadrilateral surface area on the slider 202 as indicated in FIG. 10. This arrangement contributes to mechanical stability of the slider 202 while the second and fourth piezoelectric actuator devices 319, 402 are being actuated and thus contributes to reliable movement of the slider 202.

FIG. 11 schematically illustrates a fifth state of the drive cycle. The fifth state marks an end of the second drive step in the drive cycle. The contact pads 323, 404 of the second and fourth piezoelectric actuator devices 319, 402 have reached their end positions. The contact pads 323, 404 of the aforementioned piezoelectric actuator devices are still firmly in contact with the slider 202. In FIG. 11, two upward arrows in broken lines indicate a drive movement that the second and fourth piezoelectric actuator devices 319, 402 have made with respect to their start positions represented in FIG. 10. The aforementioned piezoelectric actuator devices have imposed this drive movement on the slider 202. The slider 202 represented in FIG. 11 has moved with respect to the slider 202 represented in FIG. 10 and thus moved further with respect to the slider 202 represented in

FIG. 7.

Conversely, the contact pads 322, 403 of the first and third piezoelectric actuator devices 318, 401 have reached their start positions again. These contact pads 322, 403 are still detached from the slider 202. In FIG. 10, two downward arrows in broken lines indicate a return movement that the first and third piezoelectric actuator devices 318, 401 have made with respect to their end positions represented in FIG. 10.

FIG. 12 schematically illustrates a sixth state of the drive cycle. The sixth state marks a transition from the present drive cycle to a new drive cycle. In the sixth state, all the four piezoelectric actuator devices 318, 319, 401, 402 abut against the slider 202.

That is, all the contact pads 322, 323, 403, 404 of the four piezoelectric actuator devices 318, 319, 401, 402 make firm contact with the slider 202. In this respect, the sixth state illustrated in FIG. 12 is similar to the third state illustrated in FIG. 9 apart from the contact pads 322, 323, 403, 404 having different positions. The positions represented in FIG. 12 are opposite to those represented in FIG. 9.

Starting from the fifth state illustrated in FIG. 11, the sixth state illustrated in FIG. 12 may be reached by actuating the first and third piezoelectric actuator devices 318, 401 so that these increase in height. As a result, their contact pads 322, 403 move towards the slider 202 and finally make firm contact with the slider 202. Alternatively, the second and fourth piezoelectric actuator devices 319, 402 may be actuated so that these decrease in height. As long as the aforementioned piezoelectric actuator devices abut against the slider 202, their decrease in height makes the slider 202 move towards the contact pads 322, 403 of the first and third piezoelectric actuator devices 318, 401.

The new drive cycle will equally go through the six states illustrated in

FIGS. 7-12. The first state illustrated in FIG. 7 may be reached starting from the sixth state illustrated in FIG. 12 in the following manner. The second and fourth piezoelectric actuator devices 319, 402 may be actuated so that these decrease in height. As a result, their contact pads 323, 403 move away the slider 202, detach from the slider 202, making no contact anymore with the slider 202. Alternatively, the first and third piezoelectric actuator devices 318, 401 may be actuated so that these increase in height. As long as the aforementioned piezoelectric actuator devices 318, 401 abut against the slider 202, their increase in height makes the slider 202 move away from the contact pads 323, 404 of the second piezoelectric actuator device 319 and the fourth piezoelectric actuator device 402.

The first drive step or the second drive step of the drive cycle illustrated in

FIGS. 7-12 may be followed by a fine positioning step. In that case, the drive unit 316 is brought 1n a state corresponding with the fourth state illustrated in FIG. 10 or corresponding with the first state illustrated in FIG. 7, respectively. Starting from, for example, the first state, the first and third piezoelectric actuator devices 318, 401 may be actuated so that their contact pads 322, 403 move over a desired distance, which lies before their end positions. This will make the slider 202 move over the desired distance.

Similarly, starting from the fourth state, the second and fourth piezoelectric actuator devices 319, 402 may be actuated so that there contact pads 323, 404 move over a desired distance, which lies before their end positions. Again, this will make the slider 202 move over the desired distance.

In the above described steps, the first and third piezoelectric actuator devices 318, 401, which are on a diagonal of the rectangular configuration, thus form a first pair of piezoelectric actuator devices that are jointly actuated. The second and fourth piezoelectric actuator devices 319, 402, which are also on a diagonal of the rectangular configuration, form a second pair of piezoelectric actuator devices that are jointly actuated.

A driver may electrically actuate the four piezoelectric actuator devices 318, 319, 401, 402 in the drive unit 316. The driver may be comprised in, for example, the positioning controller 106 illustrated in FIG. 1. The driver may comprise a processor that executes a software program causing the driver to actuate the four piezoelectric actuator devices 318, 319, 401, 402 in a manner as described hereinbefore. This will thus cause the drive unit 316 to carry out one or more drive cycles as illustrated in FIGS. 7-12. The driver may further comprise electrical circuits that, for example, generate appropriate drive signals from output signals of the processor.

NOTES

The embodiments described hereinbefore with reference to the drawings are presented by way of illustration. The invention may be implemented in numerous different ways. In order to illustrate this, some alternatives are briefly indicated.

The invention may be applied in numerous types of products or methods related to positioning, in particular nano positioning. The embodiments presented hereinbefore refer to an application in a cryogenic context. However, the invention may be applied to advantage in other contexts.

There are numerous different ways of implementing a positioner device in accordance with the invention. In the presented embodiments, four piezoelectric actuator devices are used to move a slider. In other embodiments, only two piezoelectric actuator devices may be used or, on the contrary, more than four piezoelectric actuator devices.

Moreover, the piezoelectric actuator devices may be arranged differently with respect to the presented embodiments.

There are numerous different ways of implementing the resilient coupling of the actuator base with the main base in a positioner device in accordance with the invention. In the presented embodiments, a leaf spring having particular features provides this resilient coupling. In other embodiments, a different leaf spring may provide the resilient coupling or another type of resilient element or resilient structure.

There are numerous different ways of slidably coupling the slider to the main base in a positioner device in accordance with the invention. In the presented embodiments, a specific roller bearing structure is used. In other embodiments, a different roller bearing structure may be used, or another structure that allows a slidable coupling.

For example, another structure may comprise flexible hinge-like elements, such as leaf springs or struts. These elements may be monolithic.

As another example, in an alternative embodiment, which need not necessarily comprise a linear bearing for guiding a slider, the slider may be enclosed between two parallel faces of a support structure allowing in-plane motion of the slider between and parallel to these two faces. In such an embodiment, a single slider plate may cooperate with several shear piezo actuator stacks comprising X and Y-oriented shear actuators, X and Y being two orthogonal in-plane directions. These actuator stacks may then drive the slider plate, simultaneously or sequentially, in both in-plane directions. An advantage of such a structure is compactness because a single positioner may provide precisely controlled movement in two directions. This solution can be more compact compared with one that comprises two positioners, one for controlled movement in one direction and another positioner for controlled movement in another direction. Any parasitic motion due to the lack of a linear bearing may be corrected by means of positioning sensors in both X and Y-directions. These positioning sensors may be included in one or more control loops ensuring a sufficiently straight in-plane movement. The control loops may also be capable of a combined linear motion in both X and Y-directions,

such as diagonal linear motion, and may even provide an in-plane rotational motion around a Z-axis orthogonal to the X and Y-directions.

There are numerous different ways of implementing a piezoelectric actuator device in a positioner device in accordance with the invention. In the presented embodiments, a piezoelectric actuator device is provided with a contact pad of which an exemplary embodiment is illustrated in FIG. 5. In other embodiments, a piezoelectric actuator device may be provided with a contact pad that has a differently shaped upper surface. There are numerous different surface shapes and structures that allow making firm, stable with a slider, in particular while the piezoelectric actuator device is actuated to make the slider move. In case the piezoelectric actuator device itself has a top side with a suitable surface shape and structure, a contact pad may not be required.

The remarks made hereinbefore demonstrate that the embodiments described with reference to the drawings illustrate the invention, rather than limit the invention. The invention can be implemented in numerous alternative ways that are within the scope of the appended claims. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope. Any reference sign in a claim should not be construed as limiting the claim. The verb “comprise” in a claim does not exclude the presence of other elements or other steps than those listed in the claim. The same applies to similar verbs such as “include” and “contain”. The mention of an element in singular in a claim pertaining to a product, does not exclude that the product may comprise a plurality of such elements. Likewise, the mention of a step in singular in a claim pertaining to a method does not exclude that the method may comprise a plurality of such steps. The mere fact that respective dependent claims define respective additional features, does not exclude combinations of additional features other than those reflected in the claims.

Claims

CONCLUSIONS:

1. A positioning device (200) comprising: - a main base (201); - a slide (202) slidably coupled to the main base; - a set of piezoelectric actuator devices (318, 319, 401, 402) each having a top facing the slide, the top being movable toward and away from the slide and along a longitudinal axis (203) of the slide, the set of piezoelectric actuator devices being configured to operate in a stepper mode; - an actuator base (317) located within the main base, the piezoelectric actuator devices being mounted to the actuator base; and - a resilient coupling of the actuator base to the main base, the resilient coupling being configured to retain the piezoelectric actuator devices in a resting position against the slide. IS

The positioning device of claim 1, comprising a leaf spring structure (320) providing, at least in part, the resilient coupling of the actuator base (317) to the main base (201).

The positioning device of claim 2, wherein the leaf spring structure (320) extends into the actuator base (317) and is coupled to the pair of piezoelectric actuator devices (318, 319, 401, 402).

The positioning device of claim 3, wherein each piezoelectric actuator device of the set of piezoelectric actuator devices (318, 319, 401, 402) comprises: - a lift actuator (324, 326) between the actuator base (317) and the leaf spring structure (320), the lift actuator configured to move the top of the piezoelectric actuator device toward and away from the slide (202); and

- a drive actuator (325, 327) axially aligned with the lift actuator and extending from the leaf spring structure toward the slider, the drive actuator configured to cause the top of the piezoelectric actuator device to move along the longitudinal axis (203) of the slider.

A positioning device according to any one of claims 3 and 4, wherein the leaf spring structure (320) comprises a torsionally resilient coupling arrangement (603) between an inner frame (602) of the leaf spring structure, which is attached to the actuator base (317), and an outer frame (601) of the leaf spring structure, which is attached to the main base (201).

6. A positioning device as claimed in claim 5, wherein the torsionally resilient coupling arrangement (603) provides maximum stiffness along the longitudinal axis (203) of the slide (202).

The positioning device of any of claims 5 and 6, wherein the leaf spring structure (320) comprises a set of coupling plates (604, 605, 606, 607) within the inner frame (602), each uniquely coupled to a piezoelectric actuator device of the set of piezoelectric actuator devices (318, 319, 401, 402).

8. A positioning device according to claim 7, wherein the coupling plates (604, 605, 606, 607) are coupled to the inner frame (602) by bridge elements (608, 609) extending along the longitudinal axis (203) of the slide (202).

9. Positioning device according to one of claims 7 and 8, wherein the coupling plates (604, 605, 606, 607) are perforated.

10. Positioning device according to any of claims 2 to 9, wherein the leaf spring structure (320) has the form of a monolithic leaf spring with cutouts.

A positioning device according to any one of claims 2 to 10, wherein the leaf spring structure (320) has a yield strength of more than 500 MPa.

A positioning device according to any one of claims 1 to 11, wherein the set of piezoelectric actuator devices (318, 319, 401, 402) comprises four piezoelectric actuator devices in a rectangular configuration with an axis of symmetry corresponding to the longitudinal axis (203) of the slide (202).

The positioning apparatus of claim 12, wherein the top of each piezoelectric actuator device includes a pair of projecting contact elements (501, 502) disposed such that when two of the four piezoelectric actuator devices located on a diagonal of the rectangular configuration contact the slide (202), the projecting contact elements of said two piezoelectric actuator devices form corners of a diagonally oriented quadrangular surface on the slide.

Positioning device according to any one of claims 1 to 13, wherein: - the main base (201) has an upper portion (301) comprising a first inwardly projecting longitudinal edge (303) and parallel thereto a second inwardly projecting longitudinal edge (304); - the slide (202) has a first longitudinal side edge (305) with a longitudinal groove (307) with a bottom wall (308) and parallel thereto a second longitudinal side edge (306) with a longitudinal groove (309) with a bottom wall (310); - the first inwardly projecting longitudinal edge of the upper portion of the main base is received in the longitudinal groove in the first longitudinal side edge of the slider so as to form a linear roller ball bearing (313) between, on the one hand, a V-shaped groove (311) in the first inwardly projecting longitudinal edge of the upper portion of the main base and, on the other hand, a V-shaped groove (312) in the bottom wall of the longitudinal groove in the first longitudinal side edge of the slider, and - the second inwardly projecting longitudinal edge of the upper portion of the main base is received in the longitudinal groove in the second longitudinal side edge of the slider so as to form another linear roller ball bearing (315) between, on the one hand, a flat surface of the second inwardly projecting longitudinal edge facing the bottom wall of the longitudinal groove in the second longitudinal side edge of the slider and, on the other hand, a V-shaped groove (314) in the bottom wall of the longitudinal groove in the second longitudinal side edge of the slider.

15. A multi-axis manipulator (105) comprising a positioning device (200) according to any one of claims 1 to 14 coupled to a further positioning device.

16. Use of a positioning device (200) according to any of claims 1 to 14 for positioning an object (104) relative to another object (103).

A method of operating a positioning device (200) according to any of claims 12 and 13, wherein, in the step mode, the positioning device is caused to repeatedly perform actuation cycles in which two of the four piezoelectric actuator devices located on a diagonal of the rectangular configuration form a first pair of piezoelectric actuators (318, 401) that are actuated together, and the other two of the four piezoelectric actuators, also located on a diagonal of the rectangular configuration, form a second pair of piezoelectric actuator devices (319, 402) that are actuated together, an actuation cycle comprising: - a first actuation step in which the first pair of piezoelectric actuator devices are positioned against the slide (202) while the second pair of piezoelectric actuator devices are retracted from the slide, subsequently actuating the piezoelectric actuator devices of the first pair so that the top of each piezoelectric actuator device of the first pair moves in a direction along the longitudinal axis (203) of the slide; and - a second actuating step of positioning the second pair of piezoelectric actuator devices against the slide while retracting the first pair of piezoelectric actuator devices from the slide, subsequently actuating the piezoelectric actuator device of the second pair so that the top of each piezoelectric actuator device of the second pair moves in the same direction along the longitudinal axis of the slide.