CN109661641B - Haptic feedback control components - Google Patents

Abstract

The control assembly provides tactile feedback to a user of a device such as a smart phone. The button includes a shape memory alloy actuator that moves the button laterally relative to a finger press. The actuator can be programmed and controlled to provide a variety of tactile waveforms. The control assembly can be used in combination with a capacitive sensor that provides tactile feedback that would otherwise not be present in the capacitive control. The control assembly used in combination with a mechanical control provides a range of tactile waveforms that are not possible with a mechanical control. The control assembly can be used in smart phones, wearable devices, keyboards, and other portable electronic devices.

Description

Haptic feedback control assembly

The present invention relates to a user operated control assembly for electrical and electronic products. In particular, the present invention relates to a user operated control assembly that provides tactile feedback to a user when operated.

User-operated controls (controls) on electronic products come in a variety of forms, such as buttons, switches, keys (e.g., keys on a keyboard), or highlighted areas on a touch screen. These controls are used to provide inputs to or interact with electronic circuitry, typically as switches to turn the circuitry on or off or otherwise affect such circuitry. In this context, the term "smart control" is considered to refer to any such user-operated control component that provides haptic effects in addition to input or switching functions.

Consumer electronic devices employ different control designs to give the user feedback that they have successfully established electrical contact inside the button. In the case of computer keyboards and smart phone controls, the most popular designs are "dome" switches and "leaf springs (LEAF SPRING)". The exact force profile itself during operation can be adjusted in the design to meet the preferences of the target user, but it is noted that the preferences of different users may vary greatly.

There are a number of button designs and variants to choose from to meet the user's different preferences. However, a given button design can only provide a single response. Thus, this means that a given button selection will satisfy a certain number of users, but will be unsatisfactory for a significant portion of customers who prefer different experiences.

Computer keyboard buttons are typically pressed only once to select a particular character. However, in the case of a smartphone button, the button may be pressed or held down quickly for a sustained period of time to access a different function. For example, in the case of a "power" button, the button may be pressed quickly to power down the display, or held for a longer period of time to power down the entire handset. Since the smartphone buttons are of a derivative design similar to computer keyboard buttons, the tactile feedback of continuous pressing is the same as that of quick operation, although it is desirable to perform completely different operations. This is counterintuitive (counterintuitive) and is therefore prone to user annoyance and misinterpretation.

Many common mechanical buttons on the front of smartphones (e.g., dome switches and leaf spring switches) have been replaced with capacitive buttons. In this technique, the button does not need to protrude from the device and the force required to establish electrical contact is zero. This allows for a smooth mechanical design of the smart phone case (casework) and prevents fatigue of the user if the button is pressed multiple times in a short time. However, unlike mechanical designs, these products are entirely mechanically passive and thus do not provide any mechanical tactile feedback themselves.

It is desirable to solve the above problems, or at least to provide an alternative to the currently used devices.

According to the present invention, there is provided a control assembly comprising: a button suspended in the case; and an actuator arranged to communicate tactile feedback by moving the button relative to the watch case.

Thus, the current limitations of mechanical and capacitive buttons are addressed by including actuators in the control assembly for moving the buttons, thereby forming "smart" controls. Movement of the button by the actuator conveys haptic (tactile (tactile)) feedback to the user, which is the effect perceived by the user by touch. Such haptic feedback may, for example, enhance the mechanical response profile of a standard mechanical button, or add haptic effects to a capacitive button.

With miniaturization of electronic devices, such actuators are required to have very small dimensions. For example, a typical smart phone button has a spatial envelope, with associated fixtures, electronics, and connections, both external to the phone as a typical button and internal to the phone, with typical envelope dimensions of about 15 x 4 x 1mm. Furthermore, the actuator needs to be able to transmit rapid movements. In a time of 2ms to 10ms, the movement requirement is expected to be typically between 50 μm and 300 μm. Furthermore, the actuator needs to be able to transmit sufficient force to be easily sensed by the user. The force required will depend on the size and use case scenario of the intelligent control, but is expected to be between 200mN and a few newtons. While standard electromagnetic actuators (EM motors or VCMs) are available and used in many applications, including in smart phones, they do not achieve a minimum size or sufficient force.

Advantageously, the actuator is a Shape Memory Alloy (SMA) actuator, preferably an SMA actuator comprising at least one SMA wire.

Embodiments of the invention will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional side view of a button assembly;

FIGS. 2-4 are side views of alternative arrangements of SMA actuators in a button assembly;

FIG. 5 is a cross-sectional view of a modified form of a button assembly;

FIGS. 6 and 7 are side views of modified forms of the button assembly;

FIG. 8 is a perspective view of a modified form of a button assembly; and

Fig. 9-12 are side views of modified forms of the button assembly.

A button assembly 1 as an example of a control assembly is shown in fig. 1 and arranged as follows. Various modifications to the button assembly 1 are also described herein and may be applied to the button assembly 1 in any combination.

The button assembly 1 comprises a button 2 suspended in a case 3 of an electronic device, such as a mobile phone, the button 2 comprising a contact surface 4, the contact surface 4 being presented to a user through the case 3 to be pressed by a finger of the user in a pressing direction P. The button assembly 1 comprises a housing 5, the housing 5 being rigidly attached to the case 3 by a mount 6 or alternatively by any other suitable means. The push button 2 is suspended in the housing 5 on the mobile fixture 7, the mobile fixture 7 protruding rearwards and being supported on the housing 5, thus acting as a suspension system. The mobile fixing means 7 act as sliding bearings (although other bearings may alternatively be used) and thus allow the push button 2 to move laterally with respect to the watch case 3, i.e. in a lateral direction L transversal to the pressing direction P. In this example, the transverse direction L is perpendicular to the pressing direction P, i.e. parallel to the contact surface 4, but this is not necessary and in general the transverse direction L may be angularly offset with respect to the pressing direction.

Although in this example the mobile fixing means 7 acting as a sliding bearing form a suspension, it can be replaced more generally by any suspension system allowing the push button 2 to move in a desired manner with respect to the case 3, for example at least one sliding bearing; at least one ball bearing; or at least one flexure (flexure).

Below the button 2, the button assembly 1 comprises SMA wires 8, the SMA wires 8 forming SMA actuators. Good performance can be obtained with SMA wires 8 having a diameter of less than 100 μm. The SMA wire 8 is connected between the push button 2 and the housing 5 by being connected at one end (right hand end in fig. 1) to the moving fixture 7 and at the other end (left hand end in fig. 1) to a stationary fixture 9 formed on the housing 5. Thus, contraction of SMA wire 8 drives the relative movement of button 2 with respect to case 3.

The spring 12 is also connected between the button 2 and the housing 5 by being connected at one end (right hand end in fig. 1) to the movement fixture 7 opposite to the one to which the SMA wire 8 is connected and at the other end (left hand end in fig. 1) to the housing 5. The spring 12 is in a compressed state and thus acts as a resilient biasing element against the SMA wire 8, the spring 12 extending the SMA wire 8 and providing movement of the button 2 in a direction opposite to the SMA wire 8. The spring 12 may be replaced by any other resilient biasing element that provides a similar effect, such as a tension spring, a resilient member, or a flexure.

The button assembly 1 includes a driver Integrated Circuit (IC) 10 electrically connected to the SMA wire 8. The driver IC 10 provides an electrical signal to the SMA wire 8 which causes the SMA wire 8 to heat and contract, thereby causing the button 2 to move in the lateral direction L (to the left in fig. 1) in a first sense. When the power of the heated electrical signal is reduced or terminated, the SMA wire 8 cools and is stretched by the spring 12, moving the button 2 in the opposite sense (to the right in fig. 1). In this way, the SMA wire 8 moves the button 2 laterally back and forth under control of the driver IC 10.

The electrical signal is selected such that movement of the button 2 conveys haptic feedback that is perceptible to a user touching the button 2. Surprisingly, the lateral movement of the button 2 gives the user a tactile sensation which can be perceived as a change in resistance against the pressing of the button 2 even though the downward movement of the button is minimal.

For aesthetic reasons, it may be desirable for the contact surface 4 of the button 2 to be flush with the case 3, or to protrude from the case.

Since the button 3 needs to be moved laterally, a gap is required between the button 2 and the case 3. This is small and sealed fairly well, but can be considered unsightly and allow ingress of dust and/or water, and is therefore undesirable. As an optional feature, the button assembly 1 may include a sealing membrane 15 between the button 2 and the case 3. The sealing membrane 15 may fill or cover the gap between the button 2 and the case 3. The sealing membrane 15 may be formed of any suitable flexible material, for example an elastomer such as silicone. The sealing membrane 15 may be a labyrinth (labyrinth) membrane to provide a complete seal while allowing complete movement. Desirably, the sealing membrane 15 provides a smooth surface to the user while allowing lateral movement of the button 2 for tactile feedback.

For example, the button 2 may be designed to enhance tactile feedback as follows.

The size and height of the button 2 may be selected to provide the best tactile effect. For example, the button 2 may protrude from the watch case, for example up to 1mm.

The contact surface 4 may have various shapes. For example, the contact surface 4 may be circular and 7mm or more in diameter, or it may be any other shape, such as oval, square, rectangular or rod-like, but desirably extends 5mm or more in at least one direction.

The contact surface 4 may be textured, for example: a roughened surface; profiling (contoured) surfaces; texture that varies within its range; one or more sharp edges on or at the surface edge; a folded (concerta) structure; one or more ridges (ridges) across part or all of the button.

Alternatively, for example in some modified forms of the underlying button assembly 1, a single SMA wire 8 may be replaced by a plurality of SMA wires 8. In this case, the plurality of SMA wires 8 may be oriented such that some SMA wires 8 are arranged to pull the button 2 in a substantially different direction than other SMA wires 8, i.e. the SMA wires 8 are opposite. In this arrangement, the button 2 can be moved in different directions by heating different SMA wires 8 or combinations of SMA wires 8. In this case, the spring 12 may not be required, as the SMA wire 8 may be used to move the button 2 to any desired position.

Preferably, the electrical connection between the SMA wire 8 and the driver IC 10 is on a stationary part of the push button assembly 1, i.e. on a stationary fixture 9. This means that no moving electrical leads are required, simplifying product design and optimizing operational reliability. This is most easily achieved by modifying the push button assembly 1 to replace a single SMA wire 8 by an arrangement of a plurality of even numbered segments (lengths) of SMA wire that span the gap between the push button 2 and the case 3 and are electrically connected in series. The SMA wires of such segments may be different SMA wires or different portions of the same SMA wire.

Some examples of modifying the button assembly 1 in this way are shown in fig. 2 to 4, which illustrate the replacement of SMA wires 8 connected between the mobile fixture 7 and the stationary fixture 9 (other components of the button assembly 1 are omitted for clarity).

In the example of fig. 2, two SMA wires 8 are connected between the moving fixture 7 and the stationary fixture 9, each SMA wire providing a length of SMA wire. In this case, the two SMA wires 8 are electrically connected together at the mobile fixture 7 such that the segments of SMA wires are electrically connected in series.

In the example of fig. 3, a single SMA wire is connected at both ends to a stationary fixture 9 and hooked to a retaining member (feature) 11 on the moving fixture 7. Thus, the portions of the SMA wire on either side of the retaining member 11 are segments of SMA wire that are electrically connected in series.

There may be more pairs of segments of SMA wire (e.g. four segments of SMA wire in total) connected in series or in parallel. In the example of fig. 4, four SMA wires 8 are connected between the moving fixture 7 and the stationary fixture 9, but are electrically connected in series.

The configuration of the one or more SMA wires 8, including their number, length and diameter, is selected not only to provide the desired range of movement, but also to match the device resistance to the specifications of the driver IC 10. For example, the configuration of the one or more SMA wires 8 may be adapted to match the power output of the driver IC 10. The driver IC 10 typically contains a control chip and power stages that feed into one or more SMA wires 8. The control chip may use pulse width modulation to control the power in the feed line. The pulses are output in the form of square waves and amplified by a power stage to heat the wire. As the resistance of the SMA wire 8 changes as it is heated, the power stage is configured to maintain a constant voltage for the duration of the pulse. The resistance of the SMA wire 8 changes as it is heated and may rise or fall as the wire heats up, depending on the location of its resistance temperature curve, so that when the SMA wire 8 is actuated, the power required from the power stage will change.

The configuration of the one or more SMA wires 8 is selected to achieve the force required for haptic feedback to be detected by the user while remaining within the power envelope available from the power level. For example, thicker SMA wires 8 generate more force than thinner SMA wires 8, but thicker SMA wires 8 have lower resistance and may need to be lengthened, for example by using two SMA wires 8 arranged mechanically in parallel and electrically in series. However, thicker SMA wires 8 have a greater mass and the response time will increase as there are more wires to be heated. The wire length, number of SMA wires 8, whether they are arranged in series or parallel, can be used to match the power envelope of the driver IC 10, judiciously chosen according to the design requirements.

For example, calculations indicate that four SMA wires 8 of 25 μm diameter (where two pairs of SMA wires 8 are connected in parallel and the pairs are connected in series) provide an appropriate balance of force, power and operating window time requirements, and deliver an appropriate value of resistance compatible with a typical driver IC 10. Similarly, two wires connected in series with a diameter of 35 μm provide an appropriate balance of force, power and operating window time requirements and deliver an appropriate value of resistance compatible with a typical driver IC 10.

The button assembly 1 further comprises a capacitive sensor 20 behind the button 2. The capacitive sensor 20 senses the pressing of the button 2 in a conventional manner. In this example, capacitive sensor 20 is fixed to casing 5 and is therefore located on a surface that is stationary with respect to case 3. As discussed above, this allows for a stationary electrical connection, which provides the same benefits as SMA wire 8. The capacitive sensor IC 21 is connected to the capacitive sensor 20 to detect the capacitance of the capacitive sensor 20 and thereby obtain an output signal indicative of the pressing of the button 2.

The capacitive sensor IC 21 is connected to the driver IC 10. When a press of the button 2 is detected, the capacitive sensor IC 21 communicates with the driver IC 10. In response, the driver IC 10 applies an electrical signal to the SMA wire 8 to move the button 2, thereby delivering a haptic effect to the user who is touching the button 2 at the time.

More generally, the capacitive sensor 20 may be replaced by any other sensor that senses the pressing of the button 2. Even more generally, the capacitive sensor 20 may be replaced by a sensor that senses some other operation (e.g. lateral movement or force) of the button 2 than pressing. For example, the capacitive sensor 20 may be replaced by a switch of the type commonly used in mechanical buttons or by a force sensitive sensor (e.g., a piezoelectric sensor, a resistive strain gauge sensor, or other type of sensor).

One benefit of using capacitive sensor 20, however, is that button 2 is not required to travel a significant distance (e.g., 0.5 mm) in the direction of case 3 for activation. This means that the button 2 does not need to protrude from the case and allows the button to be flush with the surface of the main product and thus create an attractive design for the case of a mobile phone.

Another benefit of using a capacitive sensor 20 is that it requires little or no force. This ensures that the case 3 does not deform or shift when the button assembly 1 is operated. This is particularly suitable in the case of wearable devices such as augmented reality or virtual reality glasses and headphones.

The driver IC 10 can obtain a measurement result that varies with the ambient temperature. For example, the measurement results may be obtained from a temperature sensor such as a thermistor or thermocouple. Alternatively, the measurement may be derived from an electrical characteristic of the electrical signal provided to the SMA wire 8, for example, by measuring the power or energy required to change the resistance of the SMA wire 8 by an amount, or the power of the energy required for the resistance to begin to decrease with increasing wire temperature. Thus, information about the ambient temperature of the environment surrounding the button assembly 1 may be measured directly or inferred from the behaviour of the SMA wire 8. The driver IC 10 may vary the electrical signal provided to the SMA wire 8 in accordance with the measurement results. In this way, the electrical signal can be adjusted according to the ambient temperature.

The goal of the design is to heat the SMA wire 8 using the minimum possible power to reach a transformation temperature from martensite to austenite phase change. The power required to reach the transformation temperature depends on the difference between the temperature of the SMA wire 8 and the transformation temperature. If the SMA wire 8 was recently actuated, it may be at a higher temperature than ambient temperature, and thus a model is used that calculates the required power (and hence the drive pulse duration) based on the ambient temperature and the difference between the power used in the last actuation and the power lost since that actuation. The power loss term will depend on the structure of the SMA wire 8. When the SMA wire 8 is heated by power input, this temperature is dissipated by radiation transmission through the air passing through, but is also dissipated by heating of mechanical components attached to the SMA wire 8, such as curlers (crimps). The cooling rate of the SMA wire 8 and the temperature of the SMA wire 8 thus depend on the configuration of the SMA wire 8 and the design of the device to which it is attached.

One of the benefits of the button assembly 1 is that the haptic effect can be changed by selecting an appropriate form of electrical signal. Thus, haptic effects can have a variety of haptic waveforms. This allows the button assembly 1 to be tuned to the user's preferences and/or to change the movement profile and amplitude, which replicates various designs of wave forms that a dome switch, leaf spring or conventional mechanical design cannot deliver. The preferred haptic waveform may be pre-designed or may be variable, in which case it is selectable or adjustable by the user. For example, a plurality of haptic waveforms may be stored in the button assembly 1, in which case the driver IC 10 may be arranged to provide an electrical signal that conveys haptic feedback in accordance with one of the stored haptic waveforms that may be selected by a user. In this way, haptic effects may be selected by a user, for example, on an electronic device, such that each electronic device may provide a unique user experience tailored to the user's preferences.

Accurate control of the haptic waveform may be achieved by the driver IC 10 providing an electrical signal using resistive feedback control to control the delivered haptic waveform. In this case, the driver IC 10 takes a measurement of the resistance of the SMA wire 8 and uses this measurement as a feedback signal to drive the resistance to a target value that follows the desired haptic waveform. In this case, the resistive feedback control may further maintain the SMA material within safe mechanical and temperature operating limits.

Alternatively, the haptic effect may comprise a repeated haptic waveform after a single press of button 2. In this way, there may be multiple movements for a single press. This allows improved feedback to the user through haptic effects. For example, when a volume button is pressed to increase or decrease volume, the haptic effect may be a tactile pulse to identify that the user has pressed the button, and then another potentially different waveform when the maximum or minimum volume is reached. This would be particularly useful when the user holds the electronic device on their ear or in their pocket and cannot see the screen for other feedback of the event. Additionally, when the power button is pressed, a single haptic waveform may be generated to identify that the user has pressed the button, and then if the button is continuously pressed and a handset shutdown event is imminent, another, possibly different waveform may be generated.

Alternatively, when the button assembly is arranged to operate as a toggle switch, feedback may be used to inform the user of the toggle state of the control. For example, a short press achieves switching on or off, and generates tactile feedback representing the feel of a button click. However, upon prolonged pressing, the button will lock, giving a tactile feedback of the setting to indicate that locking has been achieved. Further short presses of the button will not have an effect and no feedback will be given; a second prolonged press is required to unlock the button, which again gives a locking or unlocking waveform to indicate to the user that the button is unlocked.

The haptic effect may also present different or additional waveforms to inform the user of the status of the handset or particular application. For example, a different pulse or pulses may be applied to the power button to inform the user device that the power is low or that there is a waiting message. In addition, when the button assembly 1 is used to control a camera, then the haptic effect may generate a waveform to inform the user that the image has achieved focus so that the user may focus on objects other than on-screen icons and notifications.

It is contemplated that other use cases may be generated that are limited only by the number and type of applications.

The button assembly 1 may be applied to any type of electronic device, such as any consumer electronic product having buttons and controls, in particular mobile or handheld devices (e.g. smart phones, tablet computers and wearable devices). In addition, the button assembly 1 may be applied to a remote controller, a stylus, an earphone and a headset (headphone), especially in a wireless product.

The button assembly 1 can also be used to produce very thin computer keyboards, which would be well suited for combination devices of ultra thin laptops and tablet computers with detachable keyboards.

Various modified forms of the button assembly 1 will now be described. A modified form is shown in fig. 5 to 12, in which only the modified components of the push button assembly 1 are shown for clarity, the other components being as described above.

The button assembly 1 may comprise two (or more) buttons 2, all actuated by the same actuator. In this case, the two buttons 2 may be formed of a common member. A modified version of this type of button assembly 1 is shown in fig. 5, which shows two buttons 2 formed by a common member 13. As a result, there are two contact surfaces 4 and two capacitive sensors 20 to detect their pressing. The SMA wires 8 are connected to a common member and thus deliver a haptic effect in response to the pressing of any of the buttons 2. Because in a typical usage scenario only one button 2 is operated at a time, the user does not notice that both buttons 2 are actuated together.

In a modified form of the button assembly shown in fig. 5, the spring 12 is connected between the button 2 and the housing 5 by being connected at one end to the same movement fixture 7 as the SMA wire 8 is connected to, which allows the spring 12 to be longer than in fig. 1.

In the example of the button assembly 1 shown in fig. 1, the button 2 moves in a lateral direction L perpendicular to the pressing direction P. This allows the SMA wire to be oriented in this lateral direction to allow the button to be designed with an elongated form factor (e.g. 1 mm). It will be appreciated that a lateral movement such as this is perceived by the user as similar or identical to a more standard vertical movement and will deliver a suitable user experience. However, other designs are possible in which the SMA wire is oriented so as to provide movement in other directions, such as a lateral direction that deviates from perpendicular to the pressing direction P or in the pressing direction P itself (i.e. perpendicular to the contact surface 4).

In fig. 6 to 8a modified form of the push button assembly 1 is shown, which provides movement in the pressing direction.

In a modified form of the button assembly 1 shown in fig. 6, the SMA wire 8 is arranged in a V-shape, the SMA wire 8 being oriented to provide movement of the button 2 in the pressing direction P. Specifically, the button 2 is provided with a protrusion 31 on its rear side. The SMA wire 8 is attached at both ends thereof to the case 3 (optionally via a component attached to the case 3) and is arranged in tension in a V-shape through the projection 31. The V-shape of the SMA wire 8 is thus located in a plane perpendicular to the contact surface 4 of the push button 2.

Upon actuation, the SMA wire 8 heats up and contracts, lifting the button 2 upwards in the pressing direction P. A return spring and suspension (not shown) may be provided. The movement may provide a haptic effect for the user pressing the button 2. Furthermore, the SMA wire 8 of this arrangement may be used to detect a user's finger, as the force applied by the user will press the button downwards and elongate the wire, resulting in a change in resistance of the SMA wire 8, so that detection of the change in resistance may be used to detect a user's button press.

In the modified version of the push button assembly 1 shown in fig. 7, there are two inclined SMA wires 8 inclined with respect to the contact surface 4 of the push button 2. Each SMA wire 8 extends across the width of the button 2 and is connected between the button 2 and the watch case 3. This allows the SMA wire 8 to be longer, providing a larger stroke, as compared to fig. 6. The two SMA wires 8 may operate in opposite directions, i.e. one SMA wire 8 is heated and the other SMA wire 8 is cooled, such that each SMA wire 8 is used to extend the other SMA wire 8. This also improves the frequency response. As above, a suspension system may also be provided.

In a modified form of the push button assembly 1 shown in fig. 8, the SMA wires 8 are arranged in a V-shape, the SMA wires 8 lying in a plane inclined with respect to the contact surface 4 of the push button 2. Specifically, the button 2 is provided with a protrusion 51 at the back surface at the outer edge of the button 2. In this example, the button 2 has a square shape, and the protrusions 51 are at corners 52 of the square shape. The SMA wire 8 extends across the projection 51 and is fixed to the case 3 such that the plane containing the SMA wire 8 is inclined relative to the contact surface 4.

When actuated, the wire 8 contracts and moves the button 2 in a direction having vertical and horizontal directional components. This may provide improved haptic effects to the user. In addition, the SMA wire 8 is longer in length than other forms of the button assembly described above, which may give a larger tap. A return spring and suspension (not shown) may be provided.

In the modified form of the button assembly 1 shown in fig. 9, the button assembly 1 includes a hinge 61 connecting one side of the button 2 to the case 3. In this example, the hinge 61 is a simple pivot (pivot), but in general the hinge 61 may be of any type. The SMA wire 8 is attached at one end to the watchcase 3 and at the other end to the button 2. Contraction of SMA wire 8 causes button 2 to rotate about hinge 61 and move in direction R. This may give improved haptic effects. The leverage effect of the hinge 61 amplifies the contraction of the SMA wire 8, giving an increased rattle. A return spring and suspension (not shown) may be provided.

In a modified form of the push button assembly 1 shown in fig. 10, the push button 2 is moved in a transverse direction inclined relative to the contact surface 4. The back surface 71 of the button 2 is inclined with respect to the contact surface 4 of the button 2. The watch case 3 comprises a recess 72, the recess 72 having a bearing surface 73 inclined like the back surface 71 of the push button 2. As a suspension system for the push button 2, the push button assembly 1 comprises two ball bearings 74 between the back surface 71 and the support surface 73 of the push button 2. More generally, the ball bearing 74 may be replaced by any number of any type of bearings, such as a plain bearing or ball bearing. The SMA wire 8 is attached at one end to the watchcase 3 and at the other end to the button 2. This allows the push button 2 to move in direction I in an oblique direction parallel to the back surface 71 of the push button 2 when the SMA wire 8 contracts.

In a modified form of the button assembly 1 shown in fig. 11 and 12, the SMA wire 8 is combined with a spring 81 to provide modified tactile feedback. In known buttons with mechanical springs, when the user presses the button, the spring is compressed and then springs back when released, giving the user a click or bump (bump) feel. In a modified form of the button assembly 1 shown in fig. 11, the SMA wire 8 modifies the force profile of such a button. The user then feels the mechanical impact and some other tactile sensation generated by the SMA wire 8, which gives a richer experience.

Specifically, the button 2 is located in a recess 82 in the case 3. The back of the button 2 has a small recess 83 for locating the spring 81, the spring 81 being a coil spring, so that the spring 81 stretches from the recess 83 in the button 2 to the base of the recess 82 in the case 3. The button 2 is suspended by a spring 81 and an alternative suspension system (not shown) such that when the user presses the button 2, the button 2 travels down into a recess 82 in the case 3 and compresses the spring 81. When the user releases the pressure on button 2, spring 81 expands back and provides a haptic effect on the user's finger. In such a button assembly 1, the haptic effect may typically be enhanced by having the button 2 travel over a mechanical component, such as a bump or ridge (not shown), to provide a clicking sensation to the user.

In a modified form of the button assembly 1 shown in fig. 11, the SMA wire has the same configuration as in fig. 1. In a modified form of the push button assembly 1 shown in fig. 12, there are two SMA wires 8, the configuration of which is the same as in fig. 7. The SMA wire or wires 8 may be used both as a detector to detect that the button 2 has been pressed by a change in length, tension or resistance, and as an actuator to provide the user with a tactile waveform and a modified tactile sensation. One or more SMA wires 8 may simulate the feel of a mechanical impact.

Claims (34)

1. A control assembly, comprising:

a button suspended in the case; and

A shape memory alloy actuator arranged to transmit tactile feedback by moving the button relative to the case when contracted, wherein the shape memory alloy actuator comprises a plurality of segments of shape memory alloy wire spanning a gap between the button and the case,

Wherein the control assembly further comprises a driver integrated circuit arranged to provide an electrical signal to the actuator to move the button, wherein the driver integrated circuit is arranged to vary the electrical signal in dependence on measurements that vary with ambient temperature.

2. The control assembly of claim 1, wherein the shape memory alloy wire has a diameter of less than 100 microns.

3. The control assembly of claim 1 or 2, wherein the shape memory alloy wires are arranged in a V-shape.

4. A control assembly as claimed in claim 3, wherein the V-shaped shape memory alloy wire lies in a plane inclined relative to the contact surface of the button.

5. The control assembly of claim 4, wherein the shape memory alloy wire comprises two shape memory alloy wires that are inclined relative to a contact surface of the button.

6. The control assembly of claim 1, wherein the plurality of numbers are even numbers.

7. The control assembly of claim 1 or 6, further comprising a driver integrated circuit arranged to provide an electrical signal to the actuator to move the button, wherein the number, length and diameter of the shape memory alloy wires match a device resistance to a specification of the driver integrated circuit.

8. The control assembly of claim 1, wherein a plurality of haptic waveforms are stored in the control assembly, and the driver integrated circuit is arranged to provide an electrical signal that conveys haptic feedback in accordance with one of the stored haptic waveforms, one of the stored haptic waveforms being selectable by a user.

9. The control assembly of claim 7, wherein the driver integrated circuit is arranged to provide the electrical signal using resistive feedback control to control the delivered haptic waveform.

10. The control assembly of claim 9, wherein the resistive feedback control further maintains the shape memory alloy material within safe mechanical and temperature operating limits.

11. The control assembly of any of claims 1-2, 4-6, and 8-10, wherein the actuator is arranged to deliver haptic feedback with a variable haptic waveform.

12. The control assembly of claim 11, wherein the haptic waveform is selectable or adjustable by a user.

13. The control assembly of any of claims 1-2, 4-6, 8-10, and 12, wherein the actuator is arranged to deliver haptic feedback with repeated haptic waveforms after a single operation of the button.

14. The control assembly of any of claims 1-2, 4-6, 8-10 and 12, wherein the actuator is arranged to move the button relative to the watch case parallel to a contact surface of the button.

15. The control assembly of any of claims 1-2, 4-6, 8-10, and 12, further comprising a sensor for sensing operation of the button.

16. The control assembly of claim 15, wherein the sensor is a capacitive sensor.

17. The control assembly of claim 15, wherein the sensor is located on a surface that is stationary relative to the watchcase.

18. The control assembly of any of claims 1-2, 4-6, 8-10, 12, and 16-17, comprising a plurality of buttons each actuated by the same actuator.

19. The control assembly of claim 18, wherein the plurality of buttons are formed from a common member.

20. The control assembly of any of claims 1-2, 4-6, 8-10, 12, 16-17, and 19, further comprising a suspension system that suspends the button in the case.

21. The control assembly of claim 20, wherein the suspension system comprises: at least one sliding bearing; at least one ball bearing; or at least one flexure.

22. The control assembly of claim 20, wherein the back of the button is inclined relative to the front of the button, the watch case includes a similarly inclined recess, and the suspension system includes at least one bearing between the back of the button and the recess.

23. The control assembly of claim 22, wherein the bearing comprises at least one sliding bearing or ball bearing.

24. The control assembly of any of claims 1-2, 4-6, 8-10, 12, 16-17, 19, and 21-23, further comprising a sealing membrane between the button and the case.

25. The control assembly of claim 24, wherein the sealing membrane is an elastomer.

26. The control assembly of any of claims 1-2, 4-6, 8-10, 12, 16-17, 19, 21-23, and 25, wherein the button has a contact surface that extends 5mm or more in at least one direction.

27. The control assembly of any of claims 1-2, 4-6, 8-10, 12, 16-17, 19, 21-23, and 25, wherein the stationary button protrudes from the case.

28. The control assembly of any of claims 1-2, 4-6, 8-10, 12, 16-17, 19, 21-23, and 25, wherein the button has a textured contact surface.

29. The control assembly of claim 28, wherein the textured contact surface comprises: a roughened surface; a contoured surface; a varying texture on the surface; one or more sharp edges; one or more ridges; a folding structure.

30. The control assembly of any one of claims 1-2, 4-6, 8-10, 12, 16-17, 19, 21-23, 25, and 29, further comprising a hinge connecting one side of the button to the case.

31. The control assembly of any of claims 1-2, 4-6, 8-10, 12, 16-17, 19, 21-23, 25, and 29, further comprising a mechanical spring.

32. The control assembly of any of claims 1-2, 4-6, 8-10, 12, 16-17, 19, 21-23, 25 and 29, arranged to operate as a toggle switch.

33. A portable electronic device equipped with a control assembly according to any one of claims 1-32.

34. A computer keyboard wherein at least one key is a control assembly according to any one of claims 1-32.