CN116710650A - Continuous driving SMA motor - Google Patents

Abstract

A continuous drive motor driven by a Shape Memory Alloy (SMA) actuator wire. The SMA actuator wires rotate or control the position of the drive spindle, which in turn causes the rotor or other component of the motor to rotate. Fine control of the rotational speed of the rotor/motor and continuous driving of the rotor/motor are achieved.

Description

Continuous driving SMA motor

The present technology relates generally to shape memory alloy (shape memory alloy, SMA) actuator assemblies, and in particular to continuous drive motors driven by SMA actuator wires.

In a first aspect of the present technology, there is provided an actuator assembly comprising: a first component; a second member rotatable relative to the first member; a third component coupled to the second component at a location remote from the central axis of rotation of the second component; and at least two Shape Memory Alloy (SMA) actuator wires, each SMA actuator wire coupled to the first component at a first end and arranged to apply a force to the third component upon contraction, thereby driving rotation of the second component. In some cases, the third component may be a drive spindle (drive spindle), or may be one of a pair of magnets (where the other magnet may be disposed on the first component).

In another aspect of the present technology, there is provided an actuator assembly comprising: a first component; a second part rotatable relative to the first part; a third component coupled to the second component at a location remote from the central axis of rotation of the second component; and at least two Shape Memory Alloy (SMA) actuator wires, each SMA actuator wire coupled to the first and third parts and arranged to apply a force to the third part upon contraction to drive rotation of the second part.

In another aspect of the present technology, there is provided an actuator assembly comprising: a first component; a second member rotatable relative to the first member; a first magnet magnetically coupled to the second component at a location remote from a central rotational axis of the second component; a second magnet attached to the second component at a location remote from the central axis of rotation of the second component; and at least two Shape Memory Alloy (SMA) actuator wires, each SMA actuator wire coupled to the first component at a first end and to the first magnet at a second end and arranged to apply a force to the first magnet upon contraction, thereby driving rotation of the second component.

In another aspect of the present technology, there is provided an actuator assembly comprising: a first component; a second member rotatable relative to the first member; a third component coupled to the second component at a location remote from the central axis of rotation of the second component, the third component being movable relative to the first component and coupled to the third component; and at least two Shape Memory Alloy (SMA) actuator wires, each SMA actuator wire coupled to the first component at a first end and each SMA actuator wire coupled to the third component and arranged to apply a force to the drive spindle upon contraction to drive rotation of the second component. Each SMA actuator wire may be connected to the third component at the second end or may be connected to the third component at a point along the length of the SMA wire.

In another aspect of the present technology, there is provided an actuator assembly comprising: a support structure; a rotating portion rotatable relative to the support structure about a rotation axis, the rotating portion comprising an eccentric portion; a movable member movable relative to the support structure along at least one axis of movement orthogonal to the axis of rotation; and at least two SMA wires arranged to move the movable part relative to the support structure along the at least one movement axis to drive movement of the eccentric portion relative to the support structure and continuous rotation of the rotating portion relative to the support structure.

In a related aspect of the present technology, there is provided an apparatus comprising an actuator assembly as described herein. The device may be any of the following: smart phones, cameras, foldable smart phones, foldable image capture devices, foldable smart phone cameras, image capture devices, servomotors, consumer electronics devices, mobile computing devices, notebook computers, tablet computing devices, security systems, gaming systems, augmented reality devices, virtual reality systems, virtual reality devices, micropumps, medical devices, microfluidic devices, wearable devices, unmanned aerial vehicles (air, water, underwater, etc.), airplanes, spacecraft, submarines, vehicles, and automated vehicles. It will be appreciated that this is a non-exhaustive list of example apparatuses.

Preferred features are set out in the appended dependent claims.

Embodiments of the present technology will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic view of an actuator assembly for a direct drive motor drive spindle;

FIG. 2 shows a schematic view of another actuator assembly for a drive spindle of a direct drive motor;

FIG. 3 shows a schematic view of another actuator assembly for a drive spindle of a direct drive motor;

FIG. 4 shows a schematic diagram of an actuator assembly using a magnetic force to indirectly drive a motor;

FIG. 5 shows a schematic view of an actuator assembly for indirectly driving a drive spindle of a motor;

FIGS. 6A-6C illustrate components of another actuator assembly for indirectly driving a drive spindle of a motor;

FIG. 7 shows a schematic view of another actuator assembly for indirectly driving a drive spindle of a motor;

FIGS. 8A and 8B illustrate a further embodiment of an actuator assembly including a V-shaped SMA wire;

FIGS. 9A and 9B illustrate another embodiment of an actuator assembly; and

fig. 10A and 10B illustrate a further embodiment of an actuator assembly that includes a lever arm for amplifying SMA wire travel.

In general terms, the present technology provides a continuous drive motor driven by a Shape Memory Alloy (SMA) actuator wire. The present technique uses SMA actuator wires to rotate or control the position of the drive spindle, which in turn may cause the rotor or other component of the motor to rotate. The present technique can advantageously achieve fine control of the rotational speed of the rotor/motor and/or the position of the rotor/motor, and can achieve continuous driving of the motor. The present technology may be used to actuate motors used to drive a pop-up camera in a smartphone, a panning camera in an unmanned aerial vehicle, a micropump (e.g., for a medical device), a camera shutter or iris shutter, a haptic device/mechanism, and a medical device. It should be appreciated that this is a non-exhaustive and non-limiting list of example applications/uses of the actuator assemblies described herein.

The SMA actuator wires may be used to directly move or rotationally drive the spindle and thereby cause the rotor to rotate. This may be considered as a "direct SMA drive". Alternatively, SMA actuator wires may be used to drive movement of another component, wherein movement of the other component results in rotation of the drive spindle or rotor. This may be considered as an "indirect SMA drive". These two types of driving are described in more detail below with reference to the drawings.

Fig. 1 shows a schematic view of a first actuator assembly 100 for a drive spindle of a direct drive motor. The actuator assembly 100 includes a first member (not shown) and a second member 108 rotatable relative to the first member. The second member 108 has a central rotational axis 110, and the second member 108 rotates about the central rotational axis 110. The second component may be a rotor or a rotor disc (rotor disc) of the electric machine. The actuator assembly 100 includes a drive spindle 104. The drive spindle 104 is coupled to the second component 108 at a location remote from the central rotational axis 110 of the second component 108. The actuator assembly 100 includes at least two Shape Memory Alloy (SMA) actuator wires 106. In the example shown in fig. 1, the actuator assembly includes three SMA actuator wires 106, but fig. 2 shows an example including two SMA actuator wires. At least two SMA actuator wires 106 are each coupled at a first end to the first component via a crimp (crimp) or connection component 102. The SMA actuator wires 106 are arranged to apply a force to the drive spindle 104 when contracted, thereby driving rotation of the second part 108.

The drive spindle 104 may be rotatable relative to the second component 108 such that the SMA wire outlet angle (exit angle) does not vary with rotation of the second component 108. Thus, the drive spindle 104 may be a pin or rod that moves as a sliding bearing within a bore in the second component 108. The drive spindle 104 must be able to convert the force exerted on the drive spindle by the SMA actuator wires 106 into a torque that is applied to the second component 108.

In the actuator assembly 100, two SMA actuator wires 106 are directly coupled to the drive spindle 104. Specifically, a second end of each SMA actuator wire 106 is coupled to the drive spindle 104. The second end of each SMA actuator wire 106 may be coupled to the drive spindle 104 by a crimp or connection component (not shown).

When the SMA actuator wires 106 are electrically driven, the resultant force on the drive spindle 104 acts as a torque that causes the drive spindle 104 to rotate. The torque may be controlled to rotate the drive spindle in any direction (i.e., clockwise or counterclockwise). Each SMA actuator wire 106 may be independently driven to control the position of drive spindle 104 and thereby the position of second component/rotor 108. If the SMA actuator wires 106 are driven such that there is no resultant force or such that the resultant force does not create a moment, the drive spindle 104 will be stationary.

The actuator assembly 100 may include bearings (not shown) to constrain the motion of the second component to rotation only. The bearing may be disposed between the second component 108 and the first component.

In the example actuator assembly 100 of fig. 1, a first end of each SMA actuator wire 106 is spaced apart from the other two SMA actuator wires. Preferably, the first end of each SMA actuator wire 106 may be equally spaced from the other two SMA actuator wires. However, equidistant spacing is not necessary for operation of the actuator assembly 100, as other techniques may be used to compensate for non-equidistant spacing (e.g., by applying different drive voltages to each SMA actuator wire).

Fig. 2 shows a schematic view of another actuator assembly 100 for a drive spindle of a direct drive motor. The actuator assembly 100 of fig. 2 is similar to the actuator assembly 100 described with respect to fig. 1, and thus, only the differences are described for the sake of brevity.

As described above, the actuator assembly 100 includes only two SMA actuator wires, rather than the three actuator wires shown in fig. 1. The actuator assembly 100 includes a resilient member or spring 112 in place of the third SMA actuator wire of fig. 1. Thus, the actuator assembly 100 includes two SMA actuator wires 106 and a spring 112. The first end of the spring 112 is coupled to a first component (not shown) via a crimp or connection component 102. A second end of the spring 112 may be coupled to the second member 108 or the drive shaft 104. The spring 112 applies a return force to the drive shaft 104 or the second member 108, which causes the drive shaft or the second member 108 to move to a particular position. Thus, the spring 112 performs the same function as the third SMA actuator wire 106 of the assembly 100. The resilient member (resilient component)/spring 112 can take any suitable form, such as a coil spring.

The first ends of the two SMA actuator wires 106 and the first ends of the springs 112 are spaced apart from each other. Preferably, the first ends of the two SMA actuator wires 106 and the first ends of the springs 112 may be equally spaced apart from each other. However, equidistant spacing is not necessary for operation of the actuator assembly 100, as other techniques may be used to compensate for non-equidistant spacing.

Fig. 3 shows a schematic view of another actuator assembly 100 for a drive spindle of a direct drive motor. The actuator assembly 100 is similar to the actuator assembly 100 described with respect to fig. 1, and thus, only the differences are described for the sake of brevity.

The actuator assembly 100 includes at least two Shape Memory Alloy (SMA) actuator wires 106. In the example shown in fig. 3, the actuator assembly 100 includes three SMA actuator wires 106a, 106b, and 106c directly coupled to the drive spindle 104. The three SMA actuator wires 106a-106c are each coupled at a first end to the first component via a crimp or connection 102. The three SMA actuator wires 106a-106c are each coupled to the first component at a second end via a crimp or connection component 102. Three SMA actuator wires 106a-106c are each coupled to the drive spindle 104 at a point along its length. The drive spindle 104 may include one or more holes along its length, and SMA actuator wires 106a-106c pass through the one or more holes to couple to the drive spindle 104. Thus, each SMA actuator wire 106a-106c may be slidably coupled to the drive spindle 104 at a point along its length.

The first ends of the SMA actuator wires 106a to 106c may be equally spaced apart from each other and the second ends of the SMA actuator wires 106a to 106c may be equally spaced apart from each other.

An advantage of the actuator assembly 100 over the assembly 100 may be increased travel. This is because each SMA actuator wire 106a-106c in the assembly 100 is longer than the SMA actuator wire 106 in the assembly 100, and the longer SMA actuator wire results in a greater stroke. Furthermore, the lines 106a-106c are angled, which provides a mechanical advantage that results in increased travel. The increased travel may be achieved without increasing the total footprint or size of the actuator assembly 100 relative to the total footprint or size of the assembly 100.

Another advantage of the actuator assembly 100 relative to the assembly 100 is smoother torque or torque variation (i.e., less torque variation at different stages of rotation of the second member 108). This is because in the assembly 100, each SMA actuator wire 106 is only able to apply a force in one direction when the drive spindle 104 is on a circular track along which it moves. However, in the assembly 100, each SMA actuator wire 106a-106c is capable of applying a force in two (opposite) directions (depending on which half of the circular track the rotor is in). In other words, each SMA actuator wire 106a-106c may be considered to be two wires capable of applying forces to the drive spindle 104 in opposite directions. In the assembly 100, the second part 108 is rotated 120 ° by each SMA actuator wire 106, but in the assembly 100, the second part 108 is rotated 60 ° by each SMA actuator wire 106a-106c (so that it appears that there are six actuator wires controlling the movement of the drive spindle 104 and the second part 108).

The SMA actuator wires 106a-106c pass through the second part and may form a small angle with the drive spindle 104. The SMA actuator wires 106a to 106c may be sequentially powered. For example, when the actuator assembly 100 (and in particular the second component 108) is in the position shown in fig. 3, the SMA actuator wire 106a may be energized at most (or may be the only energized wire) while the SMA actuator wire 106b is stretched. To rotate the second component, the SMA actuator wire 106c may then be energized, followed by the SMA actuator wire 106 b.

Fig. 4 shows a schematic diagram of an actuator assembly 100 using a magnetic force to indirectly drive a motor. Here, the actuator assembly 100 includes a first magnet 116. The SMA actuator wire 106 is coupled to the first component at one end and to the first magnet 116 at the other end. The first magnet 116 may be mounted on a plate or disk, or may simply be held in place by SMA actuator wires. The actuator assembly includes a second magnet 118, the second magnet 118 being disposed on the second member 108 at a location remote from the central axis of rotation of the second member 108. As described above, the SMA actuator wires 106 are driven to rotate/move the first magnet 116. Movement of the first magnet 116 relative to the second magnet 118 drives rotation of the second member 108 (because the second magnet 118 is attracted toward the first magnet 116 or repelled by the first magnet 116).

In each of the embodiments shown in fig. 1-4, at least two SMA actuator wires 106 have electrical connections that allow each SMA actuator wire 106 to receive an independent drive signal.

In some cases, drive shaft 104 may be connected to electrical ground (electrical ground). Thus, the end of each SMA actuator wire 106 connected to the drive spindle 104 is grounded and the end of each SMA actuator wire 106 connected to the first component via the crimp 102 may be driven individually. This may provide maximum control over the motion of drive spindle 104, but requires a common connection with drive spindle 104 or second component 108 (which is a moving part). The common connection with the second component 108 may be achieved by providing at least one brush (not shown) on the second component 108. Alternatively, the end of each SMA actuator wire 106 connected to the first component via the crimp 102 may be connected to electrical ground, and the drive spindle 104/second component 108 may be driven (again via one or more brush contacts). A simple DC drive can be used and the motor controlled by the area on the second part 108 connected to the different SMA actuator wires 106.

In some cases, the assembly includes three SMA actuator wires connected together using a star connection or a three-phase connection system. The voltage applied to each crimp 102 may be controlled to control the length of each SMA actuator wire 106. The resistance measurement between the three pairs of crimps may enable the determination of the resistance (and thus the length) of each individual wire.

In the case of an SMA actuator replaced by a spring 112, the spring may be electrically connected to electrical ground. This may advantageously eliminate the need to provide a common power on the moving second component 108.

It should be appreciated that the continuous rotational movement of the second member 108 may be combined with a mechanism typically used to convert rotational movement into linear movement, such as a rack and pinion or worm gear.

Fig. 5-7 illustrate further examples of indirect SMA drive actuator assemblies. In each of these examples, the actuator assembly includes a first component (also referred to herein as a support structure); a second member (also referred to as a rotating portion) rotatable with respect to the first member; a third component (which may be a drive spindle or cam, also referred to herein as an eccentric portion) coupled to the second component at a location remote from the central rotational axis of the second component; and at least two Shape Memory Alloy (SMA) actuator wires, each SMA actuator wire coupled to the first component at a first end and arranged to apply a force to the third component upon contraction, thereby driving rotation of the second component. The actuator assembly further includes a fourth component (also referred to herein as a movable component) that is movable relative to the first component, wherein the at least two SMA actuator wires are each coupled to the fourth component, and wherein the third component is coupled to the fourth component and the second component. Each SMA actuator wire may be coupled to the fourth component at the second end, or each SMA wire may be coupled to the fourth component at a point along the length of the SMA wire.

Fig. 5 shows a schematic view of an actuator assembly 100 for an indirect drive motor driven spindle. According to the actuator assembly described in international patent publications WO2013/175197 and WO2014/083318, the actuator assembly 100 is capable of actuating the movement of the movable member 122 (an example of the fourth member 122) in two dimensions perpendicular to the main axis. Movement of the movable member 122 drives rotation of the rotary portion 108 (an example of the second member 108).

These actuator assemblies comprise four SMA actuator wires connected between the movable part 122 and the support structure 101 (example of the first part). Each wire 106 is connected at one end thereof (via crimp/connector 120) to the movable member 122 and at the other end thereof (via crimp 102) to the support structure 101. A bearing arrangement (bearing arrangement) (not shown) supports the movable member 122 on the support structure and allows the movable member 122 to move relative to the support structure 101.

In addition to the features described above, the actuator assembly 100 also includes a support structure that includes or corresponds to the first component. The movable part 122 is supported on the support structure in a manner that allows the fourth part 122 to move relative to the support structure in two orthogonal directions perpendicular to an imaginary main axis (notional primary axis) extending through the third part 122. The second part 108 (rotating part 108) is rotatably arranged about 1 rotation axis R with respect to the support structure. At least two SMA actuator wires 106 are arranged to move the movable part 122 upon contraction, thereby driving rotation of the second part 108.

Thus, the actuator assembly 100 includes a total of four SMA wires 30. Each SMA wire 106 is connected between the support structure and the movable part.

Each SMA wire 106 is held in tension so as to apply a force between the movable part 122 and the support structure in a direction perpendicular to the axis of rotation R about which the second part is rotatable. In operation, the SMA wire 106 moves the movable part 122 relative to the support structure in two orthogonal directions (i.e., in the x-y plane) perpendicular to the rotation axis R, as described further below.

The SMA wires 106 may each extend perpendicular to the rotation axis R. In some embodiments, the SMA wires 106 extend in a common plane, which is advantageous in minimizing the size of the SMA actuator assembly 1 along the rotation axis R. This arrangement also minimizes forces acting on the movable member 122 (and any bearing arrangement supporting the movable member 122) in a direction parallel to the axis of rotation R.

Alternatively, the SMA wire 102 may be arranged to tilt at a non-zero angle, preferably small, with respect to an orthogonal direction perpendicular to the rotation axis R. In this case, the SMA wire 106 in operation generates a component of force along the rotation axis R that may tend to deflect or move the movable part 122 in a direction parallel to the rotation axis R. Such a component of force may be resisted by the bearing arrangement to provide movement in an orthogonal direction perpendicular to the rotation axis R. Conversely, the degree of tilting of the SMA wire 106 that provides an acceptably small deflection or movement in the direction along the rotation axis R may depend on the stiffness of the bearing arrangement along the rotation axis R. Thus, in case the bearing arrangement has a high stiffness along the rotation axis R, for example when the bearing arrangement comprises a plain bearing (plain bearing) or a ball bearing, a relatively high tilt is allowed.

In the case that the bearing arrangement comprises a sliding bearing or a ball bearing, it may even be desirable that the SMA wire 106 is inclined with a significant component in a direction parallel to the rotation axis R, such that the tension in the SMA wire 106 pushes the movable part 20 onto the sliding bearing or the ball bearing.

Regardless of whether the SMA wire 106 is perpendicular to the rotation axis R or tilted at a small angle relative to a plane perpendicular to the rotation axis R, the actuator assembly 1 can be made very compact, particularly in a direction along the rotation axis R. The SMA wire 106 itself is very thin (typically on the order of 25 μm in diameter) to ensure rapid heating and cooling. The arrangement of the SMA wire 106 hardly increases the footprint of the actuator assembly 1 and can be made very thin in the direction along the rotation axis R, since the SMA wire 106 is laid substantially in a plane perpendicular to the rotation axis R in which the SMA wire 106 remains operational. The height along the rotation axis R then depends on the thickness of the other components (such as the connecting elements described below) and on the height required to allow manufacturing.

As shown in fig. 5, the SMA wire 106 may have the following arrangement about the rotation axis R.

Each SMA wire 106 is arranged along one side of the movable part 122. Thus, the SMA wires 106 are arranged in rings at different angular positions about the rotation axis R. Thus, the four SMA wires 106 include a first pair of SMA wires disposed on opposite sides of the rotation axis R and a second pair of SMA wires disposed on opposite sides of the rotation axis R. The first pair of SMA wires is selectively actuatable to move the movable member 122 relative to the support structure in a first direction in the plane, and the second pair of SMA wires is selectively actuatable to move the movable member 122 relative to the support structure in a second direction transverse to the first direction in the plane. Movement in directions other than parallel to the SMA actuator wires 106 may be driven by a combination of actuation of the pairs of SMA actuator wires 106 to provide a linear combination of movement in the transverse direction. Another way to observe this motion is that simultaneous contraction of any pair of SMA wires 106 adjacent to each other in the ring will drive movement of the movable part 122 in a direction (diagonal in fig. 1) bisecting the two SMA wires 106.

As a result, the SMA actuator wires 106 are selectively drivable to move the movable part 122 to any position relative to the support structure in two orthogonal directions perpendicular to the rotation axis R over a range of movement. The size of the range of movement depends on the geometry of the SMA wires 106 and the range of contraction within their normal operating parameters.

The arrangement of the SMA wires 106 along the respective sides of the movable part 122 helps to provide a compact arrangement, since each SMA wire 106 fits largely or entirely within the profile of the movable part 122 as seen from that side, unlike, for example, an arrangement in which the wires extend radially along the axis of rotation R (which arrangement would increase the footprint of the SMA actuator assembly). However, because it is not radial, each SMA wire 106 applies torque to the movable part 122 individually in two planes of orthogonal directions about the axis of rotation R. Such torque may potentially increase the requirements of any bearing arrangement that needs to resist any net torque while allowing movement in that plane.

However, since no wires are collinear, the wires may be arranged to apply a counteracting torque when operated together. The continuous SMA wire 106 about the rotation axis R is connected to apply a force to the movable part 122 about the rotation axis R in alternating directions (in alternate senses). That is, one SMA wire 106 is connected at its left end to the support structure and at its right end to the movable part 122, when viewed outwardly from the rotation axis R, but the next SMA wire 106 is connected at its left end to the movable part 122 and at its right end to the support structure, and so on. As a result, the continuous SMA wire 106 about the rotation axis R also applies torque in alternating directions about the rotation axis R. That is, one SMA wire 106 applies a force to the movable part 122 in a counter-clockwise direction, but the next SMA wire 106 applies a force to the movable part 122 in a clockwise direction, and so on.

This means that the first pair of SMA wires 106 produces a net torque to the movable part 122 in a first direction (e.g. anticlockwise) about the axis of rotation R in the plane, and the second pair of SMA wires 106 produces a net torque to the movable part 122 in an opposite direction (e.g. clockwise) about the axis of rotation R in the plane. As a result, the torque tends to cancel for any degree of heating in each SMA wire 106.

Furthermore, with this arrangement, movement to any position within the range of movement can in principle be achieved without any net torque being applied to the movable part 122 in a plane of two orthogonal directions about the axis of rotation R. To understand this, the first pair of SMA wires 106 may be considered separately from the second pair of SMA wires 106. To move to any given position in two dimensions, the movement taken from the first pair of SMA wires 106 may be obtained by the stress range (and thus by the torque range in the first direction) in the first pair of SMA wires 106. Similarly, movement taken from the second pair of SMA wires 106 may be obtained by a stress range (and thus by a torque range in the second direction) in the second pair of SMA wires 106. This means that the torque can be balanced by a suitable choice of stress in each SMA wire 106 (based on simple geometric calculations related to the desired position and arrangement of SMA wires 106).

Conversely, if all SMA wires 106 are connected to apply a force to the movable part 122 in the same direction about the axis of rotation R, they will always produce a net torque about the axis of rotation R, regardless of how they are driven.

When moving the movable part 122 in other directions, which is a linear combination of movements in directions X and Y, a certain degree of balance is a natural effect of the arrangement, and in fact by appropriate selection of the forces generated in each SMA wire 106, the SMA wires 106 can be made to produce no net torque about the rotation axis R. In addition, the SMA wire 106 may be controlled to counteract any torque on the movable member 122 due to contact of the movable member 122 with the rotating portion 40. In this way, during operation of the SMA actuator assembly 1, the torque acting on the movable part 122 (due to the force from the SMA wire 106 and due to the force in contact with the rotating part 40) may be zero.

This reduction in torque about the rotation axis R reduces the tendency of the movable member 122 to rotate about the rotation axis R. The reduction or balancing of the torque about the rotation axis R reduces the constraints on the bearing arrangement. Indeed, in some embodiments, the constraint may be reduced to the point that no bearing arrangement is required, and the movable member 122 is instead supported by the SMA wire 106 itself.

It is particularly noted that these benefits can be achieved in an actuator arrangement 10 where only a single set of four SMA wires 106 is employed, which provides a very simple and compact arrangement.

In this SMA actuator assembly 1, the SMA wires 106 extend in a common plane, which is advantageous in minimizing the size of the actuator assembly 1 along the rotation axis R. Alternatively, the SMA wires 106 may be offset from each other along the rotation axis R, and the benefits described above are still obtained if they meet more general requirements (i.e. the projection of the four SMA wires 106 onto an imaginary plane perpendicular to the rotation axis R has the arrangement shown in fig. 5 when viewed in this direction).

In the example of fig. 5, the drive spindle 126 may be part of the movable member 122 and may extend through a hole 124 in the second member 108 at a location remote from the central axis of rotation of the second member 108 (where the location remote from the central axis corresponds to the third member or eccentric portion). Alternatively, the drive spindle 126 may be part of the second member 108 (the rotating member 108) so as to correspond to a third member or eccentric portion, and may extend through a hole 124 in the movable member 122 at a position remote from the central axis of rotation of the second member 108.

With respect to the example shown in fig. 1, 2, and 4, the assembly 100 of fig. 5 may advantageously provide a larger stroke actuator within the same footprint.

Fig. 6A-6C illustrate components of an actuator assembly 100 for indirectly driving a drive spindle of a motor. The assembly 100 includes a movable member 122, which movable member 122 is driven by two SMA actuator wires 106 in only one dimension (e.g., side-to-side or side-to-side). The movable member 122 includes a slot 132 and a portion of the drive spindle 128 extends through the slot 132. The width of the slot 132 is slightly greater than the diameter of the drive spindle 128 so that the drive spindle can move/run smoothly within the slot 132.

The assembly 100 may include a drive cylinder 130 coupled to the drive spindle 128 such that a central rotational axis 130a of the drive cylinder 130 is located away from a central axis 128a of the drive spindle 128. When the SMA actuator wire 106 is actuated to move the movable member 122 in one direction, the edges of the slot 132 exert a force on the drive spindle 128 that causes the drive cylinder 130 to rotate.

The assembly 100 may include a cam 136 coupled to the drive spindle 128. When the cam 136 is perpendicular to the length of the slot 132, the drive torque on the drive spindle 128 and drive cylinder 130 may drop to zero. This means that the motor drive can rely on the moment of inertia to keep rotating. The assembly 100 may include a resilient member 134, the resilient member 134 being arranged to exert a return force on a cam 136 prior to rotation of the drive spindle 128 to the zero torque position. The resilient member 134 may prevent the cam 136 from stopping and seizing when in the zero torque position. The resilient member 134 may be a leaf spring that urges the cam 136 away from the zero torque position.

Fig. 7 shows a schematic view of another actuator assembly 100 for indirectly driving a drive spindle of a motor. Here, in addition to the features described above, the actuator assembly 100 includes a first magnet 142 disposed on the drive spindle 138 and a second magnet 140 disposed on the movable member 122 at a location remote from the central axis of rotation of the movable member 122. Movement of the movable member 122 is accomplished using two, three, or four SMA actuator wires and results in movement of the second magnet 140 relative to the first magnet, which in turn drives rotation of the drive spindle 138.

Fig. 8-10 illustrate schematic views of other actuator assemblies 100 according to an aspect of the present invention. The actuator assembly 100 includes a support structure 101, a rotating portion 108, and a movable member 122. The rotating portion 108 is rotatable relative to the support structure 101 about a rotation axis R. The rotating portion 108 includes an eccentric portion 128, which may be, for example, a cam or a drive spindle.

The movable part 122 is movable relative to the support structure along an axis of movement orthogonal to the axis of rotation R. Movement of the movable member 122 in directions other than along the axis of movement may be constrained, for example, by a suitable bearing arrangement. Although not shown in fig. 8-10, in some embodiments the movable member 122 is movable in a plane orthogonal to the axis of rotation R.

Thus, the actuator assembly 100 substantially corresponds to the actuator assembly 100 already described with reference to fig. 6B. In fig. 6B, SMA wire 106 is connected between movable part 122 and support structure 101. Thus, one end of the SMA wire 106 is connected to the support structure 101 and the other end of the SMA wire 106 is connected to the movable portion 122. This arrangement of SMA wires 106 is different in fig. 8-10, as described below.

In the embodiment of fig. 8A and 8B, the SMA wire 106 is a V-shaped SMA wire 106. In particular, SMA wires 106 are connected to the support structure 101 at both ends. The SMA wire 106 is bent around the movable part 122 forming two lengths (length hs) angled with respect to each other. The angle between the SMA wires 106 of these lengths may typically be greater than 0 degrees. Preferably, the angle between the lengths of SMA wire 106 is greater than 90 degrees, further preferably greater than 120 degrees.

Although not depicted, the SMA wire 106 may likewise be connected at both ends to the movable part 122 and bent around the support structure 101.

The actuator assembly 100 includes opposing SMA wires 106. Thus, the SMA wire 106 moves the movable portion 122 in opposite directions along the movement axis. Referring to fig. 8A, for example, selective contraction of the SMA wire 106 may move the movable member 122 up and down.

In some embodiments, the rotating portion 108 includes a second eccentric portion 128b (e.g., a second cam). The second eccentric portion may differ from eccentric portion 128 in that the second eccentric portion is angularly offset from the eccentric portion angular direction about the rotational axis R. For example, as shown in fig. 8A, the second eccentric portion 128b may be angularly offset from the eccentric portion by about 90 degrees, such as in the range of 45 degrees to 135 degrees.

Although not shown in the figures, the actuator assembly 100 may also include a second movable member that is movable relative to the support structure. The second movable portion may be movable relative to the support structure 101 (e.g., along an axis of movement or in a plane of movement) in the same manner as the movable portion 122.

In alternative embodiments, the second eccentric portion 128b may be identical to the eccentric portion 128, i.e., the eccentric portions may be formed of the same components or at least have the same eccentricity. The second movable member may move relative to the support structure in a different manner than the movement of the movable member 122 (e.g., in a direction orthogonal to the axis of movement and orthogonal to the axis of rotation R).

In general, the movable member 128 and the second movable member may be stacked or offset relative to each other along the axis of rotation R.

The SMA wires are alternately (or continuously) configured to move the movable portion and the second movable portion. This may improve the continuous rotation of the rotating part, in particular in embodiments in which the movable part is movable along only a single axis.

In fig. 8A, a bearing arrangement comprising a sliding bearing 151 constrains the movable member 122 to move along the axis of movement. The movable part 122 may slide relative to the support structure 101 and may be referred to as a slider. In fig. 8B, the bearing arrangement includes a flexible bearing (flex bearing) 152. The flexible bearing 152 includes four flexible members arranged to allow movement along a movement axis. In either case, the movable part is constrained from rotating about the axis of rotation R relative to the support structure 101 by a bearing arrangement. In general, any bearing arrangement (e.g., also rolling bearings) may be used instead.

Fig. 9A and 9B depict schematic plan and side views of another actuator assembly 100. The actuator assembly 100 of fig. 9A and 9B substantially corresponds to the actuator assembly of fig. 8. However, as shown, the movable member 122 is formed as two separate elements, the movement of which is driven separately by the respective SMA wires 106. Further, the movable part 122 is integrally formed with one of the connection parts for connecting one end of the SMA wire 106 to the support structure 101. The movable member 122 may be made of a sheet material (such as sheet metal). This configuration can be particularly compact. The movable member 122 may be urged toward the rotating portion by a resilient element integral with the sheet metal member to maintain sliding contact with the rotating portion.

Fig. 9B shows a stack of two movable portions that can be alternately moved by SMA wires to drive the continuous rotation of the rotating portion.

In fig. 8 and 9, the stroke of the SMA wire 106 (i.e., the amount of contraction of the SMA wire 106) is amplified to a greater movement of the movable component. Thus, a relatively small stroke of the SMA wire 106 may enable a relatively large movement of the movable part 122. In fig. 8 and 9, this stroke amplification is achieved by the V-shape of the SMA wire. Thus, in general, the actuator assembly 100 of fig. 8 and 9 includes an amplification mechanism for amplifying the stroke of the SMA wire 106 into a greater movement of the movable member 122.

Fig. 10A and 10B schematically depict plan and side views of another SMA actuator assembly 100. The SMA actuator assembly 100 also includes an amplification mechanism for amplifying the stroke of the SMA wire 106 into a greater movement of the movable portion 122. In the embodiment of fig. 10, the amplifying mechanism comprises a movable member 122. Specifically, the movable member 122 includes a lever arm. The lever arm is arranged to pivot about a pivot point 160. The SMA wire 106 is connected to the lever arm at a location closer to the pivot point 160 than the contact of the lever arm with the eccentric portion of the rotating portion 108. In this way, the stroke of the SMA wire 106 is amplified to a greater movement for driving rotation of the rotating part.

In general, instead of the lever arm of fig. 10, i.e. instead of providing a lever arm that pivots about a pivot point, the flexible arm may be fixedly connected at one end to the support structure 101 and at the other end to the movable member 122. The SMA wire 106 may drive the flexible arm to bend around the connection point with the support structure 101 in order to move the movable part 122.

Each actuator assembly described herein may further comprise: a control circuit electrically connected to the SMA actuator wires and arranged to: measuring the resistance of each SMA actuator wire; and provides a drive signal to each SMA actuator wire.

Each actuator assembly described herein may further comprise: a bearing for restricting the movement of the second member (rotating portion) to rotation.

Those skilled in the art will recognize that while the foregoing has described what is considered to be the best mode and other modes of carrying out the present technology where appropriate, the present technology should not be limited to the particular configurations and methods disclosed in this description of the preferred embodiments. Those skilled in the art will recognize that the present technology has a wide range of applications and that the embodiments may take on a wide range of modifications without departing from any inventive concept as defined in the appended claims.

Claims (34)

1. An actuator assembly, comprising:

a first component;

a second part rotatable relative to the first part;

a third component coupled to the second component at a location remote from the central axis of rotation of the second component; and

at least two shape memory alloy SMA actuator wires, each SMA actuator wire coupled to the first part at a first end and arranged to apply a force to the third part upon contraction, thereby driving rotation of the second part.

2. The actuator assembly of claim 1, wherein the third component is a drive spindle rotatable relative to the second component.

3. An actuator assembly according to claim 1 or 2, wherein the third component is a drive spindle and the at least two SMA actuator wires are each directly coupled to the drive spindle.

4. An actuator assembly according to claim 3, wherein the second end of each SMA actuator wire is coupled to the drive spindle.

5. An actuator assembly according to claim 4, wherein the assembly comprises three SMA actuator wires, the first end of each SMA actuator wire being spaced apart from the other two SMA actuator wires.

6. An actuator assembly according to claim 4, wherein the assembly comprises two SMA actuator wires and further comprising a spring having a first end coupled to the first component and a second end coupled to one of the drive spindle or the second component, wherein the first ends of the two SMA actuator wires and the first end of the spring are spaced apart from each other.

7. An actuator assembly according to claim 3, wherein the second end of each SMA actuator wire is coupled to the first component, and wherein each SMA actuator wire is coupled to the drive spindle at a point along its length.

8. An actuator assembly according to claim 7, wherein the first ends of each SMA actuator wire are equally spaced from each other, and wherein the second ends of each SMA actuator wire are equally spaced from each other.

9. An actuator assembly according to claim 7 or 8, wherein each SMA actuator wire is slidably coupled to the drive spindle at a point along its length.

10. An actuator assembly according to any one of claims 3 to 9, wherein the at least two SMA actuator wires have electrical connections allowing each SMA actuator wire to receive an independent drive signal.

11. The actuator assembly of claim 10, wherein the drive spindle is connected to electrical ground.

12. The actuator assembly of claim 11, further comprising:

at least one brush attached to the second component and electrically connected to the electrical ground.

13. The actuator assembly of claim 10, wherein the at least two SMA actuator wires are connected to electrical ground at the first component.

14. An actuator assembly according to any one of claims 3 to 6, wherein the assembly comprises three SMA actuator wires connected together using a star connection or a three phase connection system.

15. The actuator assembly of claim 6, wherein the spring is electrically connected to electrical ground.

16. The actuator assembly of claim 1, wherein the third component is a first magnet and the at least two SMA actuator wires are each directly coupled to the first magnet, and wherein the actuator assembly further comprises:

a second magnet disposed on the second component at a location remote from a central axis of rotation of the second component, wherein the third component is magnetically coupled to the second component;

Wherein movement of the first magnet drives rotation of the second member.

17. The actuator assembly of claim 1 or 2, further comprising a fourth component movable relative to the first component, wherein the at least two SMA actuator wires are each coupled to the fourth component, and wherein the third component is coupled to the fourth component and the second component.

18. An actuator assembly according to claim 17, wherein the at least two SMA actuator wires are each coupled to the fourth component at a second end.

19. The actuator assembly of claim 17 or 18, further comprising:

a support structure comprising the first component;

wherein the fourth component is supported on the support structure in a manner that allows movement of the fourth component relative to the support structure in two orthogonal directions perpendicular to an imaginary main axis extending through the fourth component; and is also provided with

Wherein the at least two SMA actuator wires are arranged to move the fourth part upon contraction and thereby drive rotation of the second part.

20. The actuator assembly of claim 19, wherein the third component is part of the fourth component and extends through an aperture in the second component, the aperture being located at a position remote from a central axis of rotation of the second component.

21. The actuator assembly of claim 17 or 18, wherein the third component extends through a slot in the fourth component, and the actuator assembly further comprises:

a drive cylinder coupled to the third component such that a central rotational axis of the drive cylinder is located at a position away from a central axis of the third component;

a cam coupled to the third component; and

a resilient member arranged to exert a return force on the cam before the third member rotates to a zero torque position.

22. The actuator assembly of claim 17, 18 or 19, further comprising:

a first magnet disposed on the third component; and

a second magnet disposed on the fourth member at a position distant from a central rotation axis of the fourth member,

wherein movement of the fourth member moves the second magnet relative to the first magnet and drives rotation of the third member.

23. The actuator assembly of any one of the preceding claims, further comprising:

a control circuit electrically connected to the SMA actuator wires and arranged to:

Measuring the resistance of each SMA actuator wire; and

a drive signal is provided to each SMA actuator wire.

24. The actuator assembly of any one of the preceding claims, further comprising:

a bearing that constrains movement of the second component to rotation.

25. An actuator assembly, comprising:

a support structure;

a rotating portion rotatable relative to the support structure about a rotation axis, the rotating portion comprising an eccentric portion;

a movable member movable relative to the support structure along at least one axis of movement orthogonal to the axis of rotation; and

at least two SMA wires arranged to move the movable part relative to the support structure along the at least one axis of movement to drive movement of the eccentric portion relative to the support structure and continuous rotation of the rotating portion relative to the support structure.

26. The actuator assembly of claim 25, wherein the movable member is movable relative to the support structure only along the axis of movement.

27. An actuator assembly according to claim 25, wherein the movable member is movable relative to the support structure in a plane orthogonal to the axis of rotation, wherein the at least two SMA wires are arranged to move the movable member in the plane.

28. An actuator assembly according to claim 27, wherein the at least two SMA wires comprise a total of four SMA wires in an arrangement in which the forces applied by the SMA wires are not collinear, and wherein the SMA wires are selectively drivable to move the movable part relative to the support structure to any position within a plane orthogonal to the axis of rotation without rotating the movable part.

29. An actuator assembly according to claim 28, wherein two of the SMA wires are arranged to apply torque to the movable part in the plane in a first direction about the axis of rotation and the other two SMA wires are arranged to apply torque to the movable part in the plane in a second, opposite direction about the axis of rotation.

30. An actuator assembly according to claim 28 or 29, wherein the four SMA actuator wires are arranged in a ring at different angular positions about the axis of rotation, successive SMA wires about the axis of rotation being connected to apply a force to the movable element in alternating directions about the axis of rotation.

31. An actuator assembly according to any one of claims 25 to 27, wherein the at least two SMA wires are coupled at both ends to one of the support structure and the movable part and are bent around the other of the support structure and the movable part, thereby forming two lengths angled relative to each other.

32. An actuator assembly according to any one of claims 25 to 27, comprising an amplifying mechanism configured to amplify the stroke of the SMA wire into movement of the movable part for driving rotation of the rotating part.

33. An actuator assembly according to claim 31, wherein the movable member comprises a lever arm or flexible arm for amplifying the stroke of the SMA wire.

34. The actuator assembly of any one of claims 25 to 27 and 31 to 33, wherein the rotating portion comprises a second eccentric portion, and

the actuator assembly further comprising a second movable part movable relative to the support structure along at least one axis of movement orthogonal to the axis of rotation, and at least two SMA wires arranged to move the second movable part relative to the support structure along the axis of movement, thereby driving movement of the second eccentric part relative to the support structure and continuous rotation of the rotating part relative to the support structure,

wherein the SMA wires are alternately configured to move the movable portion and the second movable portion.