Joystick assembly and button

Abstract

A joystick 10 assembly comprises a support structure, a stick 11, a bearing arrangement 12, 14 mounted to the support structure and configured to support movement of the stick relative to the support

Description

Field The present application relates to a joystick assembly and a button. Background A joystick may be used as a controller. A button may be used as a controller. There is growing interest in application of haptics in joysticks and buttons, for example in the context of gaming controllers. A joystick and a button may be used as inputs to a game for example. It is desirable to provide a controller such as a joystick or a button that has more variable functionality. Summary According to an aspect of the present invention, there is provided a joystick assembly comprising: a support structure; a stick; a bearing arrangement mounted to the support structure and configured to support movement of the stick relative to the support structure in at least one degree of freedom; a sensor arrangement configured to sense a position and / or an orientation of the stick relative to the support structure; and at least one shape memory alloy, SMA, actuator, each SMA actuator comprising a movable element and at least one SMA element arranged, on contraction, to drive movement of the movable element relative to the support structure or the bearing arrangement so as to adjust at least one characteristic of the joystick assembly. By providing the joystick assembly with at least one SMA actuator, the at least one SMA actuator can be used to vary the functionality of the joystick assembly. For example, an SMA actuator may be used to toggle between different behaviours of the joystick assembly. 2Optionally, for one of the at least one SMA actuator, the characteristic of the joystick assembly comprises sensitivity indicative of a magnitude of an input force required by a user to move the stick relative to the support structure. Accordingly, the sensitivity of the joystick assembly can be controllably varied in a reliable way. Optionally, the joystick assembly comprises: a return arrangement configurable to apply a return force to the stick so as to urge the stick to return to a reference position and / or orientation relative to the support structure. The return arrangement allows a user to more intuitively provide an input control in a stable way. Optionally, for one of the at least one SMA actuator, the movable element of one of the at least one SMA actuator comprises the return arrangement and the at least one SMA element is arranged, on contraction, to drive movement of the return arrangement relative to the support structure, so as to adjust the return force. By moving the return arrangement, the return force may be adjusted. By adjusting the return force, the sensitivity of the joystick assembly may be controllably varied. By adjusting the return force, the joystick assembly may be more easily controlled when operating in modes corresponding to different neutral positions of the stick. Optionally, the at least one SMA element is arranged, on contraction, to drive movement of the return arrangement relative to the support structure, so as to control whether the return arrangement is configured to apply the return force. By toggling the return force on / off, the sensitivity can be readily adjusted. The return force can be turned off when the neutral position is temporarily moved away from a central position. Optionally, the return arrangement comprises at least one return spring configured to urge the stick to return to a reference position and / or orientation in a respective at least one degree of freedom. By providing one or more return springs, the stick may be returned to a neutral position (e.g. the centre) when released in an energy efficient manner. Optionally, the return arrangement comprises at least two return springs configured to apply respective return forces, wherein the at least one SMA element is arranged, on contraction, to drive movement of the return arrangement relative to the support structure, so as to control which of the at least two return springs is configured to apply its respective return force to the stick. By controlling engagement of a plurality of return springs, the sensitivity of the joystick assembly may be adjusted without unduly increasing a power requirement of the joystick assembly. The return springs do not require power in order to apply the return force. Optionally, the at least one SMA element is arranged, on contraction, to deform the at least one or two return springs, thereby adjusting the return force applied by the at least one or two return springs to the stick. By deforming the return spring, the return force may be adjusted between at least two non-zero values without unduly increasing the number of components of the joystick assembly. For example, it may not be necessary to increase the number of return springs. Optionally, the joystick assembly comprises: a first friction surface secured to the bearing arrangement or the stick; wherein for one of the at least one SMA actuator, the movable element comprises a second friction surface configured to engage with the first friction surface so as to oppose movement of the stick relative to the support structure, wherein the at least one SMA element is arranged, on contraction, to drive movement of the second friction surface into engagement with the first friction surface, so as to apply a variable braking force that opposes movement of the stick relative to the support structure. By providing a variable braking force, the sensitivity of the joystick assembly may be adjusted in a reliable manner, for example by applying a direct force on the stick gimbal axes. A variable braking mechanism may be used to allow the joystick assembly to provide force feedback. Optionally, the bearing arrangement is configured to engage with the stick at one of a plurality of pivot points at respective distances from a tip of the stick, wherein the at least one SMA element is arranged, on contraction, to selectably control at which of the plurality of pivot points the bearing arrangement engages with the stick. By controlling the pivot point, the effective length of the stick may be adjusted. This may allow the sensitivity of the joystick assembly to be controllably adjusted. Optionally, the joystick assembly comprises a plurality of bearing engagement members connected to the bearing arrangement at respective locations corresponding to the plurality of pivot points, wherein the bearing engagement members are configured to pivotably secure the stick to the bearing arrangement. The bearing engagement members may allow the pivot point to be controlled without unduly reducing the reliability of the joystick assembly. Optionally, for a plurality of the at least one SMA actuator, the movable elements comprise respective bearing engagement members, and the SMA actuators are configured to drive movement of the respective bearing engagement members relative to the bearing arrangement so as to control engagement of the respective bearing engagement members with the stick. By providing separate SMA actuators for different bearing engagement members, the engagement between the bearing arrangement and the stick may be adjusted in a reliable way without unduly increasing the volume of the joystick assembly. Optionally, the joystick assembly comprises a bearing engagement member connected to the bearing arrangement and configured to pivotably secure the stick to the bearing arrangement at the pivot point. By providing a bearing engagement member, the stick may be reliably secured to the bearing arrangement, so as to provide a robust joystick assembly. Optionally, for one of the at least one SMA actuator, the movable element comprises the stick, and the at least one SMA element is arranged, on contraction, to drive movement of the stick axially relative to the bearing arrangement so as to adjust an axial location of the stick at which the bearing engagement member pivotably secures the stick to the bearing arrangement. By moving the stick, the effective length of the stick may be adjusted while minimising the number of moving parts of the joystick assembly. Optionally, for one of the at least one SMA actuator, the characteristic of the joystick assembly comprises a range of possible movement of the stick relative to the support structure. By adjusting the range of possible movements, the functionality of the joystick assembly may be more varied. The joystick assembly may provide a more realistic experience for a user of the joystick assembly. Optionally, the joystick assembly comprises at least one end stop configured to limit a range of possible movement of the stick relative to the support structure. By providing an end stop, the joystick assembly may be prevented from being moved in such a way that might damage the joystick assembly. Optionally, for one of the at least one SMA actuator, the movable element comprises the end stop, and the at least one SMA element is arranged, on contraction, to drive movement of the end stop relative to the support structure so as to adjust a limit to the range of possible movement of the stick relative to the support structure. By moving the end stop, the range of possible movements may be adjusted without unduly increasing the number of components of the joystick assembly. Optionally, the joystick assembly comprises a plurality of blades pivotably connected to the support structure and configurable to limit a range of possible movement of the stick relative to the support structure, wherein for one of the at least one SMA actuator, the movable element comprises at least one of the blades, and the at least one SMA element is arranged, on contraction, to drive movement of the at least one of the plurality of blades so as to adjust a limit to the range of possible movement of the stick relative to the support structure. By providing blades, an iris mechanism may be used to efficiently adjust the range of possible movements of the stick. The blades may allow the stroke window to be adjusted, potentially asymmetrically, in a reliable manner. Optionally, for one of the at least one SMA actuator, the characteristic of the joystick assembly comprises force feedback. By providing force feedback, the user of the joystick assembly may be given a more realistic experience. The force feedback may provide intuitive desired sensations. Optionally, for one of the at least one SMA actuator, the movable element comprises the stick, and the at least one SMA element is connected between the stick and the support structure and is configured, on contraction, to apply a feedback force on the stick dependent on the sensed position and / or orientation of the stick relative to the support structure. By reading the position of the stick, adaptive feedback may be provided. OptionaIly, the feedback force is for opposing an input force on the stick by a user. The user may experience varying levels of resistance, for example depending on the situation in which the user is providing a control via the joystick assembly. Optionally, for one of the at least one SMA actuator, the characteristic of the joystick assembly comprises a reference position and / or orientation of the stick relative to the support structure. By adjusting the reference position and / or orientation of the stick, the joystick assembly may be operated in different modes corresponding to different reference positions and / or orientations. For example, depending on the type of situation or apparatus being controlled using the joystick assembly, as appropriate reference position may be selected. This may improve how realistic the feel of the joystick assembly is for the given situation or apparatus. Optionally, the joystick assembly comprises a detent member comprising a plurality of detents configured to engage with the stick, wherein for one of the at least one SMA actuator, the movable element comprises the detent member, and the at least one SMA element is configured, on contraction, to drive movement of the detent member relative to the support structure or the bearing arrangement such that the detent member is movable between a first position at which the detent member is distanced from the stick and a second position at which the stick is engageable with the detents depending on a position and / or orientation of the stick. By providing detents, the user of the joystick assembly may experience controlling between a plurality of slots (i.e. preset positions). This may provide a more intuitive experience to the user, for example when the user is controlling a selection from a plurality of discrete options. Optionally, the joystick assembly comprises a haptic device, wherein the at least one SMA element is configured, on contraction, to drive the haptic device. By providing a haptic device controlled by an SMA actuator, the haptic device may be particularly reliable. Optionally, the haptic device comprises a surface angled relative to a plane perpendicular to a primary axis of the joystick assembly and a roller, wherein for one of the at least one SMA actuator, the movable element comprises the surface, and the at least one SMA element is configured, on contraction, to drive movement of the surface relative to the support structure such that the roller moves along the primary axis. The haptic device may provide tactile feedback to the user of the joystick assembly. Optionally, the haptic device comprises an array of haptic elements, wherein the at least one SMA actuator comprises a plurality of SMA elements configured, on contraction, to actuate an addressed haptic element more than the other haptic elements. The array may provide a plurality of different sensations to the user of the joystick assembly. For example, textural feedback may be provided. Optionally, the haptic device is configured to tilt a tip surface at a tip of the stick relative to an axial direction of the stick. Tilt and shift may be used to provide further possible sensations to the user of the joystick assembly. Optionally, the haptic device is configured to rotate the stick about an axial direction of the stick. Rotation may be used to provide further possible sensations to the user of the joystick assembly. Optionally, the haptic device is located between the stick and a base of the support structure. The haptic device may be located so as to provide feedback to the user via the stick. The haptic device may be reliably toggled on / off by use of the stick. Optionally, the haptic device is located at or near a tip of the stick. The haptic device may provide direct sensations to the thumb, for example, of the user. Optionally, the sensor arrangement comprises at least one position transducer configured to sense the position and / or orientation of the stick in a respective at least one degree of freedom. The position and / or orientation of the stick may be accurately determined. Optionally, the at least one position transducer comprises a respective at least one potentiometer. A potentiometer provides a reliably technique for accurately determining the position and / or orientation of the stick. Optionally, the sensor arrangement comprises at least one optical sensor configured to sense the position and / or orientation of the stick. The joystick assembly may be of the type in which an analog stick uses optical sensors to provide positional feedback of the stick and optionally springs to suspend the stick with six degrees of freedom. Optionally, the joystick assembly comprises a push button switch. Such a push button switch is a particularly reliable way of providing some tactile feedback to the user. According to another aspect of the present invention, there is provided a button comprising: a push button switch configured to be pressed when a force is applied to a push surface of the button; and a haptic device comprising: at least one haptic element; and a shape memory alloy, SMA, actuator comprising at least one SMA element arranged, on contraction, to actuate the at least one haptic element. By combining a push button switch with a haptic actuator, the reliability of the push button switch as a trigger, for example, of the haptic actuator may be exploited. The haptic device may be improved in reliability. The haptic event may be more reliably actuated through the tactile switch button. This integration enables haptic feedback from the tactile switch without the SMA haptic actuator triggering, thus giving to option for reducing power consumption and life cycles whilst maintaining basic haptic feedback. Optionally, the push button switch is located between the push surface and the haptic device. By positioning a tactile switch mechanism on top of a haptic actuator, a tactile switch mechanism may be integrated into the haptic actuator design. Optionally, the haptic device is located between the push surface and the push button switch. By positioning a haptic actuator on top of a tactile switch mechanism, a tactile switch mechanism may be integrated into the haptic actuator design. Optionally, the button comprises a plurality of push button switches, wherein the haptic device is located between the push surface and the push button switches. The two tactile mechanisms may provide more varied sensations to the user. Optionally, the push button switches have different stiffnesses. By using two tactile mechanisms of different stiffness, a dual force haptic button can be created. The relative forces of the two tactile mechanisms may be balanced with the force generated by the haptic actuator to reduce any possibility of the haptic force triggering the stiffer tactile mechanism. Optionally, the push button switch comprises an elastically deformable conductor and conductive tracks, wherein the elastically deformable conductor is configured to elastically deform so as to electrically connect the conductive tracks when the push button switch is pressed. The elastically deformable conductor used as both the electrical connection switch and haptic sensation. Optionally, the elastically deformable conductor is configured to apply a return force to the at least one haptic element that opposes the actuation by the at least one SMA element. One of the advantages of having a tactile switch integrated with a haptic actuator is that the elastically deformable conductor used as both the electrical connection switch and haptic sensation can be loaded so as to act as a return spring for the SMA, thus minimising sensation loss for both passive and active haptic events. Brief description of the drawings Certain embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic perspective view of a joystick; Figure 2 is a schematic view of part of the joystick assembly of Figure 1; Figure 3 is a schematic view of part of the joystick assembly of Figure 1; Figure 4 is a schematic view of part of the joystick assembly of Figure 1 according to an alternative arrangement; Figure 5 is a schematic view of a return arrangement of the joystick assembly of Figure 1; Figure 6 is a side view of the joystick assembly of Figure 1; Figure 7 is a schematic view of a stick of the joystick assembly of Figure 1; Figure 8 is a schematic view of a stick of the joystick assembly of Figure 1; Figure 9 is a schematic view of the stick of Figure 8 in a different position; Figure 10 is a schematic view of stroke ranges of the joystick assembly of Figure 1; Figure 11 is a schematic view of part of the joystick assembly of Figure 1; Figure 12 is a schematic view of a detent member of a joystick assembly; Figure 13 is a schematic view of a haptic device of the joystick assembly of Figure 1; Figure 14 is a schematic view of a stick and a push button switch; Figure 15 is a schematic view of a stick with a haptic device; Figure 16 is a schematic view of a button; Figure 17 is a schematic view of an alternative button; and Figure 18 is a schematic view of an alternative button. Detailed description Joystick assembly Figure 1 is a schematic view of a joystick assembly 10. As shown in Figure 1, optionally the joystick assembly comprises a support structure. The support structure may comprise a housing 16. The housing 16 is arranged to remain substantially stationary during use of the joystick assembly 10. The housing 16 may form one or more external surfaces of the joystick assembly 10. The housing 16 may be configured to house one or more components of the joystick assembly 10. As shown in Figure 1, the joystick assembly comprises a stick 11. The stick 11 may be elongate. The stick 11 may have an axial direction. In the orientation shown in Figure 1, the axial direction of the stick 11 is approximately vertical. Figure 1 shows the stick 11 in a neutral position. The neutral position of the stick 11 may correspond to the position of the stick 11 when a user is not applying force to the stick 11. The neutral position may correspond to a reference position and / or orientation of the stick 11. In use of the joystick assembly 10, a user may move the stick 11 so as to control an apparatus or software such as a computer game. As shown in Figure 10, optionally the joystick assembly 10 comprises a bearing arrangement 12,14. The bearing arrangement is mounted to the support structure. The bearing arrangement 12,14 is configured to support movement of the stick 11 relative to the support structure in at least one degree of freedom. For example, in the arrangement shown in Figure 1, the bearing arrangement comprises a first gimbal member 12. The bearing arrangement 12,14 may comprise a second gimbal member 14. Each gimbal member may correspond to a respective degree of freedom of movement of the stick 11 relative to the support structure. Figure 2 schematically depicts part of the joystick assembly 10 shown in Figure 1. Figure 2 shows the first gimbal member 12. As shown in Figure 2, optionally the stick 11 is pivotably mounted to the first gimbal member 12 at a pivot point 18. The stick 11 may be configured to rotate about the pivot point 18 relative to the first gimbal member 12. As shown in Figure 1 and Figure 2, optionally the first gimbal member 12 comprises mounting elements 13. The mounting elements 13 may be provided at ends of the first gimbal member 12. The mounting elements 13 may be configured to allow the first gimbal member 12 to be mounted relative to the support structure. For example, as shown in Figure 1, optionally the housing 16 comprises apertures 17. The apertures 17 may be configured to receive the mounting elements 13 of the first gimbal member 12. As shown in Figure 1, optionally the second gimbal member 14 may comprise corresponding mounting elements 15. The mounting elements 15 may be configured to engage with complementary features of the support structure. For example, as shown in Figure 1, the housing 16 may comprise further apertures 17 configured to accommodate the mounting elements 15 of the second gimbal member 14. During use of the joystick assembly 10, the gimbal members 12,14 are configured to rotate about an axis extending between the mounting elements of that gimbal element. The stick 11 may be moved in two degrees of freedom relative to the support structure, for example relative to the housing 16. Although the joystick assembly 10 shows movement in two degrees of freedom relative to the support structure, the joystick assembly may allow one degree of freedom or three degrees of freedom or more than three degrees of freedom (e.g. six degrees of freedom) for relative movement between the stick 11 and the support structure. For example, optionally the stick 11 may be rotated about its own axis relative to the support structure. The joystick assembly 10 may have a primary axis. The primary axis may be defined relative to the support structure. For example, in the joystick assembly shown in Figure 10, the primary axis of the joystick assembly 10 may be in the vertical direction. In the position shown in Figure 1, the axis of the stick 11 may be aligned with the primary axis of the joystick assembly 10. SMA actuator Optionally, the joystick assembly 10 comprises at least one shape memory alloy (SMA) actuator. Each SMA actuator comprises at least one SMA element. The invention is described in the context of the SMA element being an SMA wire 40. However, it will be understood that it is not essential for the SMA element to be an SMA wire and other types of SMA element are possible. The SMA wire 40 is arranged, on contraction, to drive movement of a moveable element of the joystick assembly 10 relative to the support structure or relative to the bearing arrangement 12,14, so as to adjust a characteristic of the joystick assembly 10. By providing the SMA actuator, haptics may be incorporated into the joystick assembly 10. The SMA actuator allows the functionality of the joystick assembly 10 to be varied. An SMA element may, on contraction, provide a relatively compact high force. An embodiment of the invention is expected to achieve an increase in the force of haptics incorporated into a joystick assembly. Zero hold actuators have a benefit of using no power when holding a position. This is a particularly large advantage for devices that have limited power (e.g. a limited peak power) and / or energy (e.g. a limited average power). Optionally, one or more of the SMA actuators of the joystick assembly 10 may comprise a bearing that has sufficient friction when loaded that the moveable element remains in position when the SMA wire is not driving movement of the moveable element. This allows the power and energy requirements of the SMA actuator to be reduced while allowing the position of the moveable element to be controlled and maintained. By providing zero hold power capabilities, the joystick assembly 10 can have power consumption advantages over other technologies. Variable sensitivity Optionally, the at least one characteristic of the joystick assembly 10 comprises sensitivity. The SMA actuator may be configured to controllably adjust the sensitivity of the joystick assembly 10. The sensitivity may be indicative of a magnitude of an input force required by a user to move the stick 11 relative to the support structure. The sensitivity may impact the feel of the stick 11 by the user. For example, the sensitivity may be varied so as to allow switching between fine control and coarse control. Depending on how fine or coarse control is desired to be, the sensitivity of the joystick assembly 10 may be adjusted. For example, within the context of a computer game it may be desirable to adjust the sensitivity when a player is fine tuning aim in a shooting game. Variable return force As shown in Figure 2, optionally the joystick assembly 10 comprises a return arrangement. The return arrangement shown in Figure 2 comprises a return spring 20. The joystick assembly 10 may comprise on or more return springs 20. The return arrangement is configured to apply a return force to the stick 11. The return force urges the stick 11 to return to its reference position and / or orientation relative to the support structure. For example, the return spring 20 may be arranged so as to urge the stick 11 back to its position shown in Figure 1. Optionally, the reference position of the stick 11 corresponds to the stick 11 being positioned such that its axial direction is in line with the primary axis of the joystick assembly 10. As shown in Figure 2, optionally the return arrangement is located generally below the stick 11. The joystick assembly 10 may comprise a base element 19. The base element 19 may be part of the support structure. As shown in Figure 2, optionally the return arrangement is arranged between the base element 19 and the stick 11. The return arrangement may overlap with the stick 11. For example, as shown in Figure 2, part of the return spring may surround a lower end of the stick 11. Optionally, the moveable element (i.e. the moveable element that is driven by the SMA element) comprises the return arrangement, or at least part of the return arrangement. For example, the moveable element may comprise a return spring 20. In an arrangement, the at least one SMA element is arranged, on contraction, to drive movement of the return arrangement relative to the support structure, so as to adjust the return force. By adjusting the return force, the sensitivity of the joystick assembly may be varied. When the return force is greater, then a user may be required to input more force in order to move the stick 11 relative to the support structure. When the return force is lower, the user may be required to use a lower input force in order to move the stick 11 relative to the support structure. The SMA actuator is configured to adjust the return force of the return arrangement. As shown in Figure 2, the return arrangement may comprise at least one return spring. Although only one return spring 20 is shown in Figure 2, the joystick assembly 10 may comprise a plurality of return springs. The return spring 20 is configured to urge the stick 11 to return to its reference position and / or orientation. When the return arrangement comprises a plurality of return springs 20, optionally each return spring 20 is configured to urge the stick 11 to return to a reference position and / or orientation in a respective degree of freedom. For example, separate return springs 20 may be provided for orthogonal directions of movement of the stick 11 relative to the support structure. Optionally, the effective force required to move the stick 11 may be varied through direct force on the stick gimbal axes. For example, the return arrangement may be adjusted and / or a variable braking force actuator may be implemented so as to change the amount of resistance. Optionally, each return spring 20 of the return arrangement is engageable with and disengageable from the stick 11. When the return spring 20 is engaged with the stick 11, then the return spring 20 may apply the return force to the stick 11. When the return spring 20 is disengaged from the stick 11, then the return spring applies no return force to the stick 11. Optionally, an SMA actuator of the joystick assembly 10 is configured to control engagement of the return spring 20 to the stick 11. The SMA actuator may be configured to toggle the joystick assembly 10 between different modes. In one mode, a return spring 20 applies the return force to the stick 11. In another mode, substantially no return force may be applied to the stick 11. Optionally, the SMA actuator is configured to actuate the return spring 20 so as to control its engagement with the stick 11. Figure 3 is a schematic view of SMA wires 40 within a joystick assembly 10 as shown in Figure 1. As shown in Figure 3, optionally the joystick assembly 10 comprises at least one SMA wire 40 connected between the return spring 20 and a base 21 of the support structure. The base element 19 may be secured to the base 21. It is not essential for the SMA wires 40 to be connected to the base 21. The SMA wires 40 may be connected alternatively to another part of the support structure or to part of the bearing arrangement, for example. In the arrangement shown in Figure 3, when the SMA wires 40 contract, then the return spring 20 is actuated. Movement of the return spring 20 is driven by the SMA actuator. When the SMA wires 40 contract, then the return spring 20 may disengage from the stick 11. Accordingly, the application of the return spring 20 may be toggled on and off. Although two SMA wires 40 are shown in Figure 3, the number of SMA wires may be one, or more than two. When one SMA wire is used, a resilient element may be provided so as to provide a force that opposes the force due to contraction of the SMA wire 40. Figure 4 is schematic view of part of the joystick assembly 10 of Figure 1. As shown in Figure 4, optionally the at least one SMA wire 40 is arranged, on contraction, to deform the return spring 20. By deforming the return spring 20, the return force that can be applied by the return spring 20 on the stick 11 may be adjusted. For example, when the SMA wire 40 is contracted, the return spring 20 may be deformed. When the return spring 20 is deformed, then the stiffness of the return spring 20 may be reduced. When the stiffness of the return spring 20 is reduced, the return force that can be applied by the return spring 20 on the stick 11 may be reduced. The SMA actuator may be configured to adjust the stiffness of the return spring 20. When a plurality of return springs is provided, then there may be a corresponding plurality of SMA actuators configured to adjust the stiffnesses of the return springs. As shown in Figure 4, optionally the SMA wire 40 extends between the return spring 20 and the support structure. For example, the SMA wire 40 may be connected between the return spring 20 and the housing 16. Alternatively, the SMA wire 40 may extend between the return spring 20 and the base 21 or base element 19 or part of the bearing arrangement 12, 14 of the joystick assembly 10. Optionally, the joystick assembly 10 comprises an SMA actuator configured to toggle between two different return springs 20 by toggling between two different return springs 20, it is possible to switch between different modes having different sensitivities. Optionally, the joystick assembly 10 comprises a stick engagement member (not shown). The stick engagement member is configured to be secured to the stick 11. Optionally, the stick engagement member may be formed integrally with the stick 11. The stick engagement member is configured to engage with a complementary engagement member of a return spring 20. For example, as shown in Figure 5, optionally a return spring 20 comprises a first engagement member 22. The first engagement member 22 is configured to engage with the stick engagement member. When the first engagement member 22 is engaged with the stick engagement member, then the return spring 20 is engaged with the stick 11 such that that the return spring 20 applies a return force to the stick 11. Optionally, an SMA actuator is configured to engage and disengage the first engagement member 22 and the stick engagement member. The SMA actuator may be configured to lock and unlock the return spring 20 with the stick 11. As shown in Figure 5, optionally a return spring 20 comprises a second engagement member 23. The return spring 20 may comprise a plurality of engagement members 22, 23. Depending on which engagement member is engaged, the return spring 20 may apply a different return force on the stick 11. Accordingly, the sensitivity of the joystick assembly 10 may be adjusted by using the SMA actuators to control engagement between the return spring 20 and the stick 11. Alternatively, the joystick assembly 10 may comprise a plurality of return springs 20. Each return spring 20 may have a corresponding engagement member. The joystick assembly 10 may comprise a plurality of SMA actuators. Each SMA actuator may be configured to control engagement between the engagement member of a respective return spring 20 and the stick 11 (e.g. the stick engagement member secured to the stick 11). As shown in Figure 5, optionally the engagement members 22, 23 are provided at different heights. Optionally, the engagement members 22, 23 may be comprised in the same engaging part. The engaging part may have two settings at two different heights. A feature on the stick 11 such as the stick engagement member matches the feature on the return spring 20, i.e. the engagement members 22, 23. Optionally, the joystick assembly 10 comprises an SMA actuator configured to move the return springs 20. For example, a plurality of return springs 20 may be moved together. By moving the return springs 20, it is possible for the SMA actuator to control which return spring 20 is engaged with the stick 11. Optionally, the bearing arrangement is configured to support rotation of the stick 11 about the axis of the stick 11. The joystick assembly 10 may comprise an SMA actuator configured to drive rotation of the stick 11 about its own axis. The stick 11 may be rotated so as to lock or unlock the stick 11 and a return spring 20. As mentioned above, optionally the one or more return springs 20 are moved so as to control engagement with the stick 11. By moving the return spring 20, the position of the stick 11 along the primary axis of the joystick assembly 10 may remain constant. This helps to keep the length of the stick 11 that protrudes from the housing 16 constant while allowing the sensitivity of the joystick assembly 10 to be adjusted. In an alternative arrangement, the return spring 20 may remain in place. Optionally, the stick 11 is telescopic. The length of the stick 11 in its axial direction may be adjusted. By adjusting the 15 length of the stick 11, the engagement of the stick 11 with the one or more return springs 20 may be controlled. For example, a different return spring 20 may engage with the stick 11 depending on the length of the stick 11. The joystick assembly 10 may comprise an SMA actuator configured to control the length of the stick 11, for example so as to control engagement with a return spring 20. Variable braking force actuator Optionally, the joystick assembly 10 comprises an SMA actuator that functions as a variable braking force actuator. The SMA actuator is configured to control a braking force. The braking force is a force opposing the force input by a user for moving the stick 11. By varying the braking force, it is possible to vary the sensitivity of the joystick assembly 10. The sensitivity may be adjusted through direct force on the stick gimbal axes. Figure 6 is a schematic view of the part of the joystick assembly 10 shown in Figure 1. Figure 6 is a view of one side of the joystick assembly 10. Figure 6 shows the mounting element 15 protruding through one side of the housing 16. Optionally, the joystick assembly 10 comprises a first friction surface. The first friction surface may be secured to the bearing arrangement or to the stick 11. For example, as shown in Figure 6, optionally the joystick assembly 10 comprises a disc 24. The disc 24 may be formed as a plate. The disc 24 may be substantially circular. As shown in Figure 6, the disc 24 may be connected to the bearing arrangement. In particular, in an arrangement the disc 24 is connected to the mounting element 15. For example, the disc 24 may be centred on the mounting element 15. The mounting element 15 may extend through an aperture of the disc 24. When the second gimbal member 14 rotates, the disc 24 rotates together with the second gimbal member 14. The disc 24 may comprise the first friction surface. Optionally, only one or both major surfaces of the disc 24 may function as the first friction surface. As shown in Figure 6, optionally the joystick assembly 10 comprises an SMA actuator 30 configured to control a braking force. For the SMA actuator 30, the moveable element (i.e. the moveable element driven by the SMA actuator 30) comprises a second friction surface. The second friction surface is different from the first friction surface. The second friction surface is configured to engage with the first friction surface. When the second friction surface engages with the first friction surface, a frictional force opposes movement of the stick 11 relative to the support structure. For example, as shown in Figure 6, optionally, the joystick assembly 10 comprises calipers 25. The calipers 25 may comprise the second friction surface. The calipers 25 may be comprised as part of the SMA actuator 30. When the SMA wire is contracted, the calipers 25 may clamp around the disc 24 such that the first friction surface and the second friction surface engage with each other. Depending on the extent of contraction of the SMA wire, the friction force may be controlled. The friction functions as a braking force opposing movement of the second gimbal member 14. The SMA actuator 30 is configured to provide the variable braking force. Figure 6 shows one SMA actuator 30 and Figure 2 applies variable braking force to one side of the second gimbal member 14. Optionally, a further SMA actuator is provided for applying a variable braking force for movement of the first gimbal member 12. Optionally, a plurality of SMA actuators are provided for generating variable braking force in respective different degrees of freedom. In Figure 6, variable braking force is provided on one end of the second gimbal member 14. Optionally, a second SMA actuator providing a variable braking force may be located at the opposite end of the second gimbal member 14. A plurality of variable braking force actuators may be provided for a given degree of freedom of movement of the stick 11 relative to the support structure. Figure 6 shows an arrangement in which the variable braking force actuator functions as a disc brake. However, it is not essential for a disc brake to be used. The variable braking force actuator may be implemented in different ways. Changing the effective length of the stick to pivot Optionally, the sensitivity of the joystick assembly 10 is adjusted by changing the effective length of the stick 11. In particular, the distance from the tip of the stick 11 to the pivot, where the stick 11 pivots with the bearing arrangement may be changed. Optionally, the joystick assembly 10 comprises an SMA actuator configured to lock and unlock a secondary pivot a distance along the stick 11. Figure 7 is a schematic view of the stick 11 of the joystick assembly 10. Optionally, the bearing arrangement 12,14 is configured to engage with the stick 11 at one of a plurality of pivot points at respective distances from a tip of the stick 11. The SMA actuator is configured to control which pivot point is used. Optionally, the at least one SMA element is arranged, on contraction, to selectively control at which of the plurality of pivot points the bearing arrangement 12, 14 engages with the stick 11. For example, as shown in Figure 7, optionally the joystick assembly 10 comprises a plurality of bearing engagement members 26, 27. The joystick assembly 10 may comprise a first bearing engagement member 26 and a second bearing engagement member 27. The first bearing engagement member 26 and the second bearing engagement member 27 may be provided at different locations. The locations may correspond to different pivot points. The different locations may be at different positions along the axial direction of the stick 11. The bearing engagement members 26, 27 are configured to pivotably secure the stick 11 to the bearing arrangement 12, 14. For example, the bearing engagement members 26, 27 may be provided as collars. The collar is configured to grip the stick 11 so as to secure the stick 11 to the bearing arrangement 12, 14. Depending on which of the collars is engaged with the stick 11, the pivot point may be controlled. For example, when the first bearing engagement member 26 engages with the stick 11, then the effective length of the stick 11 is longer. When the second bearing engagement member 27 engages with the stick 11, then the effective length of the stick 11 is shorter. Figure 7 shows two bearing engagement members 26, 27. In an alternative arrangement, three, four or more than four bearing engagement members may be provided. Each bearing engagement member may correspond to a different pivot point. By adjusting the location of the pivot point, the sensitivity of the joystick assembly 10 may be adjusted. By adjusting the effective length of the stick 11, the force applied to the lever arm may be adjusted. Optionally, the joystick assembly 10 comprises a plurality of SMA actuators corresponding to respective bearing engagement members. For example, a first SMA actuator may be configured to control engagement of the first bearing engagement member 26 with the stick 11. A second SMA actuator may be configured to control engagement of the second bearing engagement member 27 with the stick 11. Optionally, for the SMA actuators, the respective moveable elements may comprise the respective bearing engagement members 26, 27. The SMA actuators maybe configured to drive movement of the respective bearing engagement members 26, 27 relative to the bearing arrangement 12, 14 so as to control engagement of the respective bearing engagement members 26, T1 with the stick 11. For example, SMA wires may extend between the bearing engagement member and the bearing arrangement. On contraction of the SMA wire, the bearing engagement member may disengage from the stick 11. For example, in Figure 7 the first bearing engagement member 26 is engaged with the stick 11. The second bearing engagement member 27 is shown in dashed lines because it is not engaged with the stick 11. The bearing engagement members 26, 27 may be connected to the bearing arrangement 12, 14. Optionally, the joystick assembly 10 comprises a controller configured to control the SMA actuators. Optionally, the controller is configured to selectively control which bearing engagement member is engaged with the stick 11 so as to adjust the pivot points. Optionally, the controller is configured to ensure that only one of the bearing engagement members is engaged with the stick 11 at any one time. It is not essential for the joystick assembly 10 to be provided with a plurality of bearing engagement members in order for the effective length of the stick 11 to be adjusted. As shown in Figure 8, optionally the joystick assembly 10 comprises one bearing engagement member 26. The bearing engagement member 26 may be connected to the bearing arrangement. For example, the bearing engagement member 26 may be connected to the first gimbal member 12. The bearing engagement member 27 may be configured to pivotably secure the stick 11 to the bearing arrangement at the pivot point. Optionally, the joystick assembly 10 comprises an SMA actuator configured to control sliding of the stick 11 to adjust the effective length of the stick 11. The SMA actuator may be configured to control movement of the stick 11 along the primary axis of the joystick assembly 10 and / or along the axial direction of the stick 11. The SMA actuator may be configured to control movement of the stick 11 relative to the bearing engagement member 26. Optionally, for the SMA actuator, the moveable element comprises the stick 11. The at least one SMA wire may be arranged, on contraction, to drive movement of the stick 11 axially relative to the bearing arrangement so as to adjust the axial location of the stick 11 at which the bearing arrangement member 26 pivotably secures the stick 11 to the bearing arrangement. For example, Figure 9 shows the stick 11 in a different axial position compared to in Figure 8. The SMA actuator may be configured to move the stick 11 from its position shown in Figure 8 to its position shown in Figure 9 so as to shorten the effective length of the stick 11. The effective length of the stick 11 may correspond to the distance between the pivot point, i.e. where the bearing engagement member 26 engages with the stick 11 and a tip of the stick 11. In Figure 8 and Figure 9, the tip of the stick 11 corresponds to the top of the stick 11. The tip of the stick may be the location of the stick 11 that is controlled directly by the user. For example, the user may place their finger or thumb on the tip of the stick 11 so as to control the movement of the stick 11 relative to the support structure. Variable range of movement Optionally, the joystick assembly 10 comprises an SMA actuator configured to adjust a range of possible movement of the stick 11 relative to the support structure. The range of possible movement of the stick 11 relative to the support structure may be referred to as the stroke window or the stroke range. Optionally, each degree of freedom of movement of the stick 11, relative to the support structure may have a corresponding range of possible movement. Optionally, the joystick assembly 10 comprises at least one end stop. An end stop may be provided to limit the movement of the stick 11. The end stop may provide an end point to a range of possible movement of the stick 11 relative to the support structure. Optionally, for each degree of freedom two end stops are provided for either end of the range of possible movement Optionally, a plurality of end stops may be formed integrally with each other. The joystick assembly 10 may comprise an SMA actuator comprising a moveable element that comprises the end stop. Optionally, the joystick assembly 10 comprises a plurality of SMA actuators comprising respective moveable elements. The moveable elements may comprise respective end stops. Alternatively, one SMA actuator may be configured to control movement of a plurality of end stops. The at least one SMA wire may be arranged, on contraction, to drive movement of the end stop (or a plurality of end stops) relative to the support structure so as to adjust a limit to the range of possible movement of the stick 11 relative to the support structure. Figure 10 schematically depicts possible changes to the range of possible movement of the stick 11. Figure 10 may correspond to a plan view of the joystick assembly 10 shown in Figure 1. Figure 10 shows a full stroke range 75. As shown in Figure 10, optionally the full stroke range is substantially circular. The full stroke range 75 may be centred on the reference position 71 of the stick 11. The reference position 71 may correspond to the position of the stick 11 when the user does not input any force on the stick 11. The reference position 71 may correspond to the position towards which the return arrangement urges the stick 11. The full stroke range 75 may be formed by an X direction stroke range 76 and a Y direction stroke range 74. The X direction stroke range 76 may correspond to possible movement of the stick 11 within the first gimbal member 12. The Y direction stroke range 74 may correspond to possible movement of the stick 11 within the second gimbal member 14. As shown in Figure 10, optionally the joystick assembly 10 may have a restricted stroke range 72. The restricted stroke range 72 may be smaller than the full stroke range 75. Optionally, the joystick assembly 10 is configured to operate in a plurality of modes. The different modes may correspond to different stroke ranges, i.e. different ranges of possible movement of the stick 11 relative to the support structure. The restricted stroke range 72 may be formed by there being a restricted stroke range in the X direction and / or a restricted stroke range in the Y direction. In the example shown in Figure 10, the restricted stroke range 72 has a restricted X direction / range 73. The restricted stroke range 72 shown in Figure 10 has the same Y direction stroke range 74 as the full stroke range 75. In an alternative arrangement, the stroke range in both the X and Y directions may be restricted so as to form the restricted stroke range. Optionally, the stroke range in each degree of freedom may be independently controlled. Optionally, one or more SMA actuators are configured to control movement of end stops so as to restrict the stroke range in the different degrees of freedom. The joystick assembly 10 may comprise an iris mechanism so as to restrict the stroke range of the stick 11. For example, the joystick assembly 10 may comprise a plurality of blades pivotably connected to the support structure. The blades may be configurable to limit the range of possible movement of the stick 11 relative to the support structure. For an SMA actuator of the joystick assembly 10, the moveable element of the SMA actuator may comprise at least one of the blades, and optionally all of the blades. The at least one SMA wire is arranged on contraction, to drive movement of the blades to as to adjust the limit to range of possible movement of the stick relative to the support structure. For example, a plurality of blades may be connected to the same rotatable element. The rotatable element may be configured to rotate relative to the support structure. When the rotatable element rotates, the blades may pivot so as to adjust the range of possible movement of the stick 11. For example, the blades may pivot so as to be located in the space 77 shown in Figure 10. By being located in the space 77, the stroke range may be restricted from the full stroke range 75 to the restricted stroke range 72. An SMA actuator may be configured to control rotation of the rotatable part relative to the support structure so as to control movement of the blades. As shown in Figure 10, optionally the restricted stroke range 72 range is symmetrical. However, it is not essential for the stroke range to be symmetrical. Optionally, the SMA actuator is configured to restrict stroke range asymmetrically. For example, a plurality of SMA actuators may be configured to limit opposite ends of the range of movement within a given degree of freedom. By changing the range of possible movement of the stick, the feel of the analogue stick 11 can be altered. For example, in the context of controlling a character in a computer game, the range of possible movement of the stick 11 may be adjusted dependent on a situation of the character. For example, if the character is running down a narrow closing passage, then the stroke range may be restricted to the restricted stroke range 72 as shown in Figure 10, for example. This may help to make the movement feel more cramped in one axis as opposed to another. As another example, the range of possible movement may be restricted asymmetrically. For example, the extent of possible movement in one direction from the reference position 71 may be different from in the opposite direction from the reference position 71. By restricting the stroke asymmetrically, it may be possible for the feel of the analogue stick 11 to be adjusted dependent on the situation of a character in a game. For example, when the character is in a dark room, then the stroke may be restricted asymmetrically such that the user has the impression of having to "feel" around to move. Force feedback Optionally, the joystick assembly 10 comprises at least one SMA actuator configured to adjust force feedback of the joystick assembly 10. Force feedback may be used in, for example, a gaming controller for a racing or driving simulator. For example, the feedback force may be for opposing an input force on the stick 11 by a user. Optionally, the force feedback is adjusted by an SMA actuator that functions as a variable breaking force actuator. As described above, optionally an SMA actuator may be part of a disc brake system for opposing an input force by the user. Additionally, or alternatively, the joystick assembly 10 may comprise one or more SMA actuators configured to drive against the user input. Figure 11 is a schematic view of part of a joystick assembly 10 as shown in Figure 1. As shown in Figure 11, optionally the joystick assembly 10 comprises an SMA actuator comprising at least one SMA wire 40 and a moveable element comprising the stick 11. The SMA wires 40 may be connected between the stick 11 and the support structure. For example, as shown in Figure 11, the SMA wires 40 may be coupled between the stick 11 and a surface of the housing 16. The SMA wires 40 may be configured, on contraction, to apply a feedback force on the stick 11. The feedback force may be dependent on the sensed position and / or orientation of the stick 11 relative to the support structure. As shown in Figure 11, optionally the SMA wires 40 are connected to the bottom of the stick 11. The pivot point 18 of the stick 11 may be located between the tip of the stick 11 and the SMA actuator for adjusting force feedback. The SMA wires 40 may be attached to the stick 11 at a position between the pivot point 18 and a base of the support structure. Alternatively, the SMA actuator may be attached to a location of the stick 11 above the pivot point 18. As shown in Figure 11, the SMA actuator may comprise a plurality of SMA wires 40. Alternatively, the SMA actuator may comprise only one SMA wire 40. A resilient element such as a spring may be provided to apply a force that opposes the force applied on contraction of the SMA wire 40. In an alternative arrangement, the SMA actuator may comprise three or more than three SMA wires 40. Optionally, the joystick assembly 10 comprises a plurality of SMA actuators configured to adjust force feedback for respective degrees of freedom. For example, a first SMA actuator may be configured to adjust force feedback in the X direction. A second SMA actuator may be provided to adjust force feedback in the Y direction. The SMA actuator for adjusting forced feedback may be configured to apply force directly to the stick 11 relative to the support structure. Alternatively, the SMA actuator for adjusting force feedback may be configured to apply frictional force between the stick 11 and a static component. The SMA actuator may be configured to adjust the sensitivity of the joystick assembly 10. Variable neutral position Optionally, the joystick assembly 10 comprises an SMA actuator configured to adjust a reference position and / or orientation of the stick 11 relative to the support structure. Optionally, the joystick assembly 10 has a plurality of reference positions and / or orientations. The reference positions and / or orientations may be pre-determined. Alternatively, one or more reference positions and / or orientations may be determined during use by control of an SMA actuator of the joystick assembly 10. The reference position may be referred to as the centre position. An SMA actuator may be configured to toggle between different reference positions. For example, a first reference position may correspond to the primary axis of the joystick assembly 10, for example the reference position 71 shown in Figure 10. A second reference position may correspond to a different position from the first reference position. For example, in the context of controlling a computer game, a first reference position may be used when controlling a land vehicle, for example to control the accelerator or brake for the land vehicle. A second reference position may be used for when the joystick assembly 10 is in a mode for controlling an aircraft, for example, functioning as a throttle control for an aircraft. When functioning as a throttle control for an aircraft, it may be desirable for the reference position to be offset from the centre, for example, to one end of the Y axis. Optionally, the joystick assembly 10 comprises an SMA actuator configured to toggle between engagement and disengagement of a return spring 20. By disengaging and engaging a return spring 20, the reference position may be adjusted. For example, the return spring 20 may be disengaged for when the reference position is desired to be off-centre. The return spring 20 may be reengaged for when the reference position is desired to be central. Such an SMA actuator for toggling engagement of a return spring may be as described above. Alternatively, joystick assembly 10 may comprise a plurality of SMA actuators configured to toggle engagement of one of a plurality of return springs. The different return springs may correspond to respective different reference positions. The SMA actuators for toggling engagement of one of a plurality of return springs 20 may be as described above. Discrete mode Optionally, the joystick assembly 10 comprises an SMA actuator configured to toggle between a continuous mode and a discrete mode of the joystick assembly 10. The continuous mode may refer to the stick 11 being moveable to any position within its range of possible movements. The discrete mode refers to the stick 11 being moveable between discrete locations. For example, optionally the joystick assembly 10 comprises a detent member 28. Figure 12 schematically shows a detent member 28. As shown in Figure 12, the detent member 28 may comprise a plurality of detents 29. The detents 29 may be concave portions or depressions for example. Alternatively, the detents 29 may comprise hooks or other types of engagement members. The detents are configured to engage with the stick 11 of the joystick assembly 10. The joystick assembly 10 may comprise an SMA actuator comprising a moveable element that comprises the detent member 28. The SMA actuator comprises at least one SMA wire configured to, on contraction, drive movement of the detent member 28. For example, the detent member 28 may be driven relative to the support structure or the bearing arrangement. The detent member 28 may be moveable between a first position and a second position. In the first position, the detent member 28 may be distanced from the stick 11. As a result of being distanced from the stick 11, the stick 11 does not engage with the detents 29. The detent member 28 may be moveable to a second position. When the detent member 28 is in the second position, then the stick 11 may be engageable with the detents 29. The second position is close enough to the stick 11 that the stick 11 can engage with the detents 29. When the stick 11 is engageable with the detents 29 (i.e. when the detent member 28 is in the second position), then the joystick assembly 10 may be operated in the discrete mode. Meanwhile, the first position of the detent member 28 may correspond to the continuous mode of the joystick assembly 10. During the discrete mode, the stick 11 may be configured to engage with one of the detents 29 of the detent member 28 depending on the input by the user on the stick 11. For example, the discrete mode may be used when a character is selecting a weapon from several slots. The SMA actuator is configured to be used to simulate detents corresponding to a particular slot. This makes it more intuitive to select a particular slot. Which detent 29 engages with the stick depends on the position and / or orientation of the stick 11. Tactile feedback Optionally, the joystick assembly 10 comprises a haptic device. A haptic device may be configured to provide tactile feedback to a user. For example, the haptic device may be configured to provide a force that is felt by the user. Optionally, the joystick assembly 10 comprises at least one SMA actuator comprising at least one SMA wire configured on, on contraction, to drive the haptic device. Various different types of haptic device may be used. The haptic device may be located in various different positions within the joystick assembly 10. As one example, the haptic device may be located and or near the tip of the stick 11. For example, the stick 11 may comprise a tip that is wider (i.e. extends further from the axis of the stick 11) at the tip of the stick 11 compared to along the shaft of the stick 11. The tip of the stick 11 may accommodate the haptic device. Optionally, the haptic device comprises an array of haptic elements. For example, a 3X3 array of haptic elements may be provided in the haptic device. Optionally, the joystick assembly 10 comprises at least one SMA actuator that comprises a plurality of SMA wires configured, on contraction, to actuate an addressed haptic element more than the other haptic elements. For example, a plurality of SMA wires may correspond to respective rows of the array of haptic elements. Another plurality of SMA wires may correspond to respective columns of the array of haptic elements. By activating an SMA wire corresponding to a particular row and another SMA wire corresponding to a particular column, then the haptic element that corresponds to that combination of column and row may be actuated more than the other haptic elements. When a haptic element is actuated, the haptic element may move, for example, in a direction parallel to the axis of the stick 11. The actuation of the haptic element may be felt by the user. Figure 13 schematically depicts a haptic device. As shown in Figure 13, the haptic device comprises a plurality of haptic elements 32. One row of haptic elements is shown in Figure 13. The row may extend to include any number of haptic elements. Similarly, any number of rows may be provided within the array. As shown in Figure 13, optionally an SMA wire 31 corresponds to that given row. There may be a plurality of SMA wires for the different rows. Similarly, another plurality of SMA wires correspond to the different columns. The SMA wire 31 may extend between the haptic elements 32 and support members 33 provided on a base 34. When the SMA wire 31 is activated, then the haptic elements 32 in that row may be raised slightly. Similarly, when the SMA wire corresponding to a particular column is activated, then the haptic elements in that column may be raised slightly. One of the haptic elements is doubly raised. Other haptic elements in the activated row / column may be actuated to a certain extent, but less than the addressed haptic element. Figure 13 shows only one example of a possible haptic device. However, other possible arrangements of haptic device may be used. For example, optionally the haptic device comprises a surface that is angled relative to a plane perpendicular to the primary axis of the joystick assembly 10. The haptic device may further comprise a roller, for example a ball bearing. The joystick assembly 10 may comprise an SMA actuator comprising a moveable element that comprises the surface. For example, the angled surface may be provided as a wedge element that constitutes the moveable element of the SMA actuator. The SMA actuator may comprise at least one SMA wire configured, on contraction to drive movement of the surface relative to the support structure such that the roller moves along the primary axis. For example, contraction of an SMA wire may result in the wedge moving sideways, which causes the roller to roll up the angled surface and thereby be moved along the primary axis of the joystick assembly 10. Optionally, the haptic device is not limited to actuating movements in the axial direction. For example, the haptic device may be configured to tilt a tip surface at the tip of the stick 11 relative to an axial direction of the stick 11. The user may feel the tipping of the tip surface. The tip surface may be the surface that the user touches with their finger or thumb. Additionally or alternatively, the haptic device may be configured to rotate the stick 11 about the axial direction of the stick 11. Although the haptic device may be located at the tip of the stick 11, this is not an essential feature. Figure 15 schematically shows an arrangement in which a haptic device 36 is located below the stick 11. The haptic device 36 may be located between the stick 11 and the base of the support structure. Optionally, the haptic device 36 is switched on (i.e. activated) when the user pushes down the stick 11. Push button switch Figure 14 schematically depicts an arrangement in which a joystick assembly 10 comprises a push button switch 35. As shown in Figure 14, optionally the push button switch 35 is located below the stick 11. The push button switch 35 may be located between the stick 11 and a base of the support structure. The push button switch 35 may be configured to be pressed when the user pushes down on the stick 11. The push button switch may be configured to provide some tactile feedback to the user. Figure 16 schematically depicts a button. The button may be comprised as part of the joystick assembly 10. Alternatively, the button may be provided separately from the joystick assembly 10. As shown in Figure 16, optionally the button comprises a push button switch 35. The button may further comprise a haptic actuator. For example, the haptic actuator may comprise an upper plate and a lower plate 54. The haptic actuator may comprise one or more rollers 53 (e.g. ball bearings) disposed between the upper plate 51 and the lower plate 54. Optionally, the button comprises at least one SMA actuator comprising at least one SMA wire. The SMA wire is configured, on contraction, to drive movement of the lower plate 54. For example, the lower plate 54 may be driven to the left in the orientation shown in Figure 16. When the lower plate 54 is moved to the left, then the rollers 53 may roll up the angled surfaces 55 of the lower plate 54. As the rollers 53 roll up the angled surfaces 55, the rollers 53 may cause the upper plate 51 to the raised. The raising of the upper plate 51 may provide a haptic feedback force. Optionally, the haptic actuator 50 is triggered when the push button switch 35 is pressed. The push button switch 35 may provide a reliable way of activating the haptic actuator 50. It is not essential for the button to be provided as part of the joystick assembly 10. For example, the button may be provided as part of a different device such as a mobile phone. A mobile phone may comprise the button. Optionally, the upper plate 51 is restricted such that it can move only in the vertical direction in the orientation shown in Figure 16. As shown in Figure 16, optionally the push button switch 35 is provided on top of the haptic actuator 50. The push button switch 35 may be integrated with the haptic actuator 50. Figure 17 schematically depicts an alternative button in which the haptic actuator 50 is located on top of the push button switch. As shown in Figure 17, optionally the push button switch comprises a circuit substrate 61, a conductive track 62, an elastically deformable conductor such as a metal dome 63 and an overlay 64. The haptic actuator 50 may be provided as part of the overlay 64 or connected to the overlay 64. When force is applied downwards on the push button switch, then the metal dome 63 elastically deforms so as to form an electrical connection between the conductive tracks 62. Figure 18 schematically depicts a further alternative button. As shown in Figure 18, optionally the button comprises a plurality of push button switches 35. The push button switches 35 may be located below the haptic actuator 50. Optionally the push button switches 35 have different stiffnesses. By providing different stiffnesses, a dual force haptic button can be provided. Optionally, the elastically deformable conductor such as the metal dome 63 is configured to apply a return force to the at least one haptic element of the haptic device that opposes the actuation of the haptic element. The metal dome 63 may be loaded so as to act as a return spring for the SMA actuator of the haptic actuator 50. This may help to reduce sensation loss for passive and active haptic events. Sensing arrangement Optionally, the sensor arrangement of the joystick assembly 10 comprises at least one position transducer. The position transducer is configured to sense the position and / or orientation of the stick 11 in a degree of freedom. A plurality of position transducers may be provided for a corresponding plurality of degrees of freedom. For example, a position transducer may be located on the side of the housing 16. For example, the position transducer may be configured to engage with the mounting elements 13,15 so as to determine the position and / or orientation of the stick 11 relative to the support structure. Optionally, the position transducer may comprise a potentiometer. The joystick assembly 10 may comprise a plurality of potentiometers for the different degrees of freedom. Additionally, or alternatively, the sensor arrangement may comprise at least one optical sensor. The optical sensor may be configured to sense the position and / or orientation of the stick 11, for example, relative to the support structure. For example, the joystick assembly 10 may comprise a plurality of optical sensors configured to detect light from a corresponding plurality of light sources. For example, the light sources may be LEDs. The joystick assembly 10 may comprise a plurality of light slits through which light from the LEDs may pass to the optical sensors. Depending on the position and / or orientation of the stick 11, different amounts or light from different light sources may be detected by the optical sensors. Paragraph relating to SMA wire The above-described SMA actuator assemblies comprise an SMA wire. The term 'shape memory alloy (SMA) wire' may refer to any element comprising SMA. The SMA wire may have any shape that is suitable for the purposes described herein. The SMA wire may be elongate and may have a round cross section or any other shape cross section. The cross section may vary along the length of the SMA wire. It is also possible that the length of the SMA wire (however defined) may be similar to one or more of its other dimensions. The SMA wire may be pliant or, in other words, flexible. In some examples, when connected in a straight line between two elements, the SMA wire can apply only a tensile force which urges the two elements together. In other examples, the SMA wire may be bent around an element and can apply a force to the element as the SMA wire tends to straighten under tension. The SMA wire may be beam-like or rigid and may be able to apply different (e.g. non-tensile) forces to elements. The SMA wire may or may not include material(s) and / or component(s) that are not SMA. For example, the SMA wire may comprise a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term 'SMA wire' may refer to any configuration of SMA wire acting as a single actuating element which, for example, can be individually controlled to produce a force on an element. For example, the SMA wire may comprise two or more portions of SMA wire that are arranged mechanically 5 in parallel and / or in series. In some arrangements, the SMA wire may be part of a larger piece of SMA wire. Such a larger piece of SMA wire might comprise two or more parts that are individually controllable, thereby forming two or more SMA wires. Paragraph introducing other variations 10 It will be appreciated that there may be many other variations of the above-described examples. For example, although Figure 1 and the described embodiments focus on a two-dimensional joystick assembly 10, the joystick assembly 10 is not limited to two-dimensions. In an alternative arrangement, the joystick assembly 10 may be three-dimensional. As another example, It is not essential for the 15 joystick assembly 10 to comprise a return arrangement.

Claims

1. A joystick assembly comprising:a support structure;a stick;a bearing arrangement mounted to the support structure and configured to support movement of the stick relative to the support structure in at least one degree of freedom;a sensor arrangement configured to sense a position and / or an orientation of the stick relative to the support structure; andat least one shape memory alloy, SMA, actuator, each SMA actuator comprising a movable element and at least one SMA element arranged, on contraction, to drive movement of the movable element relative to the support structure or the bearing arrangement so as to adjust at least one characteristic of the joystick assembly.

2. A joystick assembly according to claim 1, wherein for one of the at least one SMA actuator, the characteristic of the joystick assembly comprises:sensitivity indicative of a magnitude of an input force required by a user to move the stick relative to the support structure;a range of possible movement of the stick relative to the support structure;force feedback; and / ora reference position and / or orientation of the stick relative to the support structure.

3. A joystick assembly according to claim 1 or 2 comprising:a return arrangement configurable to apply a return force to the stick so as to urge the stick to return to a reference position and / or orientation relative to the support structure.

4. A joystick assembly according to claim 3, wherein for one of the at least one SMA actuator, the movable element of one of the at least one SMA actuator comprises the return arrangement and the at least one SMA element is arranged, on contraction, to drive movement of the return arrangement relative to the support structure, so as to adjust the return force.

5. A joystick assembly according to claim 3 or 4, wherein the at least one SMA element is arranged, on contraction, to drive movement of the return arrangement relative to the support structure, so as to control whether the return arrangement is configured to apply the return force.

6. A joystick assembly according to any of claims 3-5, wherein the return arrangement comprises at least one return spring configured to urge the stick to return to a reference position and / or orientation in a respective at least one degree of freedom.

7. A joystick assembly according to any of claims 3-6, wherein the return arrangement comprises at least two return springs configured to apply respective return forces, wherein the at least one SMA element is arranged, on contraction, to drive movement of the return arrangement relative to the support structure, so as to control which of the at least two return springs is configured to apply its respective return force to the stick.

8. A joystick assembly according to claim 6 or 7, wherein the at least one SMA element is arranged, on contraction, to deform the at least one or two return springs, thereby adjusting the return force applied by the at least one or two return springs to the stick.

9. A joystick assembly according to any preceding claim comprising:a first friction surface secured to the bearing arrangement or the stick;wherein for one of the at least one SMA actuator, the movable element comprises a second friction surface configured to engage with the first friction surface so as to oppose movement of the stick relative to the support structure, wherein the at least one SMA element is arranged, on contraction, to drive movement of the second friction surface into engagement with the first friction surface, so as to apply a variable braking force that opposes movement of the stick relative to the support structure.

10. A joystick assembly according to any preceding claim, wherein the bearing arrangement is configured to engage with the stick at one of a plurality of pivot points at respective distances from a tip of the stick, wherein the at least one SMA element is arranged, on contraction, to selectably control at which of the plurality of pivot points the bearing arrangement engages with the stick.

11. A joystick assembly according to claim 10 comprising a plurality of bearing engagement members connected to the bearing arrangement at respective locations corresponding to the plurality of pivot points, wherein the bearing engagement members are configured to pivotably secure the stick to the bearing arrangement,optionally wherein for a plurality of the at least one SMA actuator, the movable elements comprise respective bearing engagement members, and the SMA actuators are configured to drive movement of the respective bearing engagement members relative to the bearing arrangement so as tocontrol engagement of the respective bearing engagement members with the stick.

12. A joystick assembly according to claim 9 comprising a bearing engagement member connected to the bearing arrangement and configured to pivotably secure the stick to the bearing arrangement at the pivot point, wherein for one of the at least one SMA actuator, the movable element comprises the stick, and the at least one SMA element is arranged, on contraction, to drive movement of the stick axially relative to the bearing arrangement so as to adjust an axial location of the stick at which the bearing engagement member pivotably secures the stick to the bearing arrangement.

13. A joystick assembly according to any preceding claim comprising at least one end stop configured to limit a range of possible movement of the stick relative to the support structure, wherein for one of the at least one SMA actuator, the movable element comprises the end stop, and the at least one SMA element is arranged, on contraction, to drive movement of the end stop relative to the support structure so as to adjust a limit to the range of possible movement of the stick relative to the support structure.

14. A joystick assembly according to any preceding claim comprising a plurality of blades pivotably connected to the support structure and configurable to limit a range of possible movement of the stick relative to the support structure, wherein for one of the at least one SMA actuator, the movable element comprises at least one of the blades, and the at least one SMA element is arranged, on contraction, to drive movement of the at least one of the plurality of blades so as to adjust a limit to the range of possible movement of the stick relative to the support structure.

15. A joystick assembly according to any preceding claim, wherein for one of the at least one SMA actuator, the movable element comprises the stick, and the at least one SMA element is connected between the stick and the support structure and is configured, on contraction, to apply a feedback force on the stick dependent on the sensed position and / or orientation of the stick relative to the support structure.

16. A joystick assembly according to any preceding claim comprising a detent member comprising a plurality of detents configured to engage with the stick, wherein for one of the at least one SMA actuator, the movable element comprises the detent member, and the at least one SMA element is configured, on contraction, to drive movement of the detent member relative to the support structure or the bearing arrangement such that the detent member is movable between a first position at which the detent member is distanced from the stick and a second position at which the stick is engageablewith the detents depending on a position and / or orientation of the stick.

17. A joystick assembly according to any preceding claim comprising a haptic device, wherein the at least one SMA element is configured, on contraction, to drive the haptic device.

18. A button comprising:a push button switch configured to be pressed when a force is applied to a push surface of the button; anda haptic device comprising:at least one haptic element; anda shape memory alloy, SMA, actuator comprising at least one SMA element arranged, on contraction, to actuate the at least one haptic element.

19. A button according to claim 18, comprising a plurality of push button switches, wherein the haptic device is located between the push surface and the push button switches, wherein the push button switches have different stiffnesses.

20. A button according to claim 18 or 19, wherein the push button switch comprises an elastically deformable conductor and conductive tracks, wherein the elastically deformable conductor is configured to elastically deform so as to electrically connect the conductive tracks when the push button switch is pressed, wherein the elastically deformable conductor is configured to apply a return force to the at least one haptic element that opposes the actuation by the at least one SMA element.33

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