EP3582851A2

EP3582851A2 - Methods for pulse-driven enhanced vibration modes in shape memory alloy massager

Info

Publication number: EP3582851A2
Application number: EP18754476.2A
Authority: EP
Inventors: Mark A. Gummin
Original assignee: Miga Motor Co
Current assignee: Miga Motor Co
Priority date: 2017-02-19
Filing date: 2018-02-19
Publication date: 2019-12-25
Also published as: EP3582851A4; WO2018152476A2; WO2018152476A3

Abstract

Pulse schemes employ voltage pulses to drive SMA wires to heat and contract and also cause the SMA wires to emit a percussive response and vibrate vigorously as they are heated from a cool state through the transition temperature range. Multiple pulses are delivered to each SMA wire, the first one or few pulses heating the SMA material into the transformation temperature range. Each subsequent pulse delivered to the transitioning SMA material causes a throbbing percussive vibrational report. The spacing of the pulses by intervening cooling pauses extends the time that the material remains in the transformation temperature range and prolongs the time in which the audible and percussive outputs are generated. These vibration effects are useful for any number of applications such as massage, haptic feedback or other 'warning' systems employing SMA wires built into a seat or chair. Pulses to plural SMA wires may be alternated rapidly to enable a small power supply to operate multiple wires virtually simultaneously.

Description

Methods for Pulse-Driven Enhanced Vibration Modes in Shape Memory Alloy Massager

Description Technical Field

This invention relates to an apparatus that employs shape memory elements that are ohmically heated, such as a massage or haptic feedback device that employs shape memory wire as the moving elements.

Background Art

A typical construction employing shape memory elements is a massage apparatus known in the prior art. As described in PCT/US 16/22852 filed March 17, 2016 and published as WO2016153917 on September 29, 2016, the massage apparatus includes a frame that is substantially rigid or slightly flexible and resilient, the frame defining a central opening. A plurality of SMA wire segments are extended to span the central opening, and the wire segments are connected to a power circuit that provides ohmic heating for the wires. The power circuit may include a current source and a programmable controller or the like that operates a MOSFET or similar power gating device. The controller may be programmed to pulse width modulate the current from the source to control the ohmic heating of the wires. As is known, the wires may be heated past their shape transition temperature, causing them to contract in length and to relax and extend when cooled.

In the prior art, a user of the massage device may rest a portion of the body (back, for example) against a mesh or cloth spanning the central opening. The SMA wires thus are caused to follow the curvature of the body portion and extend therealong. The wires may be actuated singly and

sequentially, the contraction of each wire providing a compression of the body portion upon which it impinges. The compression is felt as a squeeze of the impinging flesh, and experienced as a massage stroke. At the same time, the heat required to activate the wire is conducted partially into the impinging flesh, providing warmth as well as a massage stroke. This process is substantially silent, unlike prior art powered massage devices.

The SMA wires may be operated sequentially to provide a massage "wave" that proceeds along the impinging flesh of the body portion, in a peristaltic manner. The massage wave may be directed so that it encourages blood flow in the body portion toward the heart, or for some purposes it may be reversed. The massage wave may also be directed laterally; that is, not necessarily respective of the blood flow direction.

The SMA massage device may be embodied as a portable device that is lightweight, so that it may be used in conjunction with an existing chair or bed. In addition, it may be used in a wheelchair to serve disabled individuals, and powered by a battery pack that is rechargeable. Likewise, the device may be employed in conjunction with automobile and truck seats to treat drivers, and may be powered by the onboard vehicle power system.

Alternatively, the SMA massage device may be built into a chair as a portion of the chair back and/or seat construction, and may be powered by rechargeable battery pack or plug-in source.

Likewise, the device may be incorporated in a bed construction or a wearable massage device.

Generally, the power supply for the SMA wires is selected to be as lightweight and small as possible; e.g., to optimize the portability of the massage device. Accordingly, the power supply generally has a maximum power output sufficient to continuously operate only one SMA wire segment at a time.

Disclosure Of Invention

The present invention generally comprises an improvement and enhancement to the prior art massage apparatus that employs shape memory alloy (SMA) wire to create a massage effect. The improvement goes beyond merely heating the SMA wires to contraction, to provide a strong vibratory response from the SMA wires for use as massage devices, including massaging chairs or seatbacks, and wearable compression devices, in addition to the contraction and squeezing provided by the prior art devices. A combination of Pulse Width Modulation (PWM) and other complex pulse sequencing can be applied to the SMA wires to provide a very satisfying and aggressive massage. Sharing or alternating these pulse sequences in various ways across multi-zone SMA wire circuits results in a myriad of different massage effects - by combining the well-known contraction of the SMA wires with various over-riding vibratory pulses.

The vibration effects are due to rapid heating pulses, timed in such a way that the SMA wires are permitted to cool and relax momentarily before the next contraction (heat) pulse is applied. For typical SMA wire diameters useful in the above-mentioned devices, the SMA wires are in the range of 0.006" to 0.015" in diameter. As can be imagined, the smaller wire diameters cool more quickly, and so the amplitude of the vibration is seen to increase for smaller wire diameters (which generally provide less actual force output than do larger diameter wires). Shape Memory Alloys (SMAs) are well known to provide useful force and stroke when heated beyond their phase transition temperature. For the most popular Nickel-Titanium (NiTi) SMAs, the transition temperatures can be selectively determined by varying the Nickel-to-Titanium ratio of the alloy. The "transition temperature" is more clearly defined as a transition temperature range that includes the rated temperature but is relatively broad, so that the degree of contraction is seen to progress gradually and organically if the alloy is heated slowly.

SMA wires can be heated beyond their transition temperatures by nearly any suitable means, in particular ohmic heating (wherein electrical current is used to heat the resistive SMA wire). It is also well known that Pulse Width Modulation (PWM) can be used to heat the SMA wires at various frequencies. PWM helps to provide additional control over the heating rates, and many modern applications of SMA wire include microprocessors with built-in PWM drivers to do so. PWM is particularly useful if higher voltages must be used, so that the overall power level can be reduced: and PWM is especially useful if the intended actuation speed is low (slow). In that case, a low duty cycle, higher voltage PWM signal can be applied, without the fear of overheating the SMA wire.

PWM is a digital control system, in that the actual current pulses heating the SMA wire are controlled by 'logic' level changes. Transistors or MOSFET switches are typically used to switch power-supply current, based on those logic level changes. The PWM outputs are 'ON' or 'OFF', resembling a 'picket fence' with a stated frequency and duty cycle. The duty cycle is defined as:

Duty Cycle (%) = 100 * (Pulse Width)/Period

Where the Pulse Width is the time that the signal is at logic level 'FIIGH', and the Period (T) is the duration of a single ON-OFF cycle. The frequency (j=\IT) of each ON-OFF cycle is also a controlled or defined parameter, and can span a wide range from millions of cycles per second (Hertz) to single- digit Hertz. Figure 1 illustrates the relevant nomenclature for PWM control. Generally, each SMA wire circuit is addressed and powered by the PWM signal and heated beyond the threshold temperature for contraction, then allowed to cool while the next SMA wire circuit is addressed and heated.

A salient aspect of this invention is the introduction of pulse schemes for driving the SMA wires. In one aspect, the pulse schemes involve delivering pulse trains or pulse sequences to more than one SMA wire zone, with the ON time of one wire zone occurring during the OFF time of another wire zone. In this manner a power supply sufficient for only one SMA wire segment is used to drive more than one wire segment, virtually simultaneously.

Furthermore, the pulses sequences and pulse trains are selected to drive the SMA wires to emit a percussive response and vibrate vigorously as they are heated from a cool state through the transition temperature range. Multiple pulses are delivered to each SMA wire, but not according to a PWM regimen of fixed clock timing and variable square wave pulses. Rather, the first one or few pulses heat the SMA material into the transformation temperature range. Each subsequent pulse delivered to the SMA material causes a percussive report, or thump, which is not an audible tone, but rather a percussive beat. The spacing of the pulses by intervening cooling pauses extends the time that the material remains in the transformation temperature range and prolongs the time in which the percussive outputs are generated. Thus complex pulse timing algorithms applied to an SMA wire may provide a multitude of software-determined vibrating modes and multi-zone compressions. These control algorithms can be used to produce similar vibration effects for any number of applications such as massage, haptic feedback or other 'warning' systems employing SMA wires built into a seat or chair.

Brief Description Of The Drawings

Fig. 1 is a graph depicting voltage versus time for a PWM power supply, as known in the prior art. Fig. 2A is a plan view of a representative chair back supporting an SMA multi-wire-zone apparatus, and Fig 2B is a similar view showing just the SMA wire segments for clarity.

Fig. 3 is a plan view of a representative chair back supporting another SMA multi-wire-zone apparatus. Fig. 4 and 5 are graphs depicting voltage versus time, showing pulsed voltage methods for a PWM power supply to drive the SMA apparatus of the invention.

Figs. 6-15 are graphs depicting voltage versus time, showing further pulsed voltage methods for a PWM power supply to drive the SMA apparatus of the invention.

Best Modes For Carrying Out The Invention

With regard to Figs. 2 A and 2B, typically a frame 41 is provided to define a circumscribed central opening that is spanned by a fabric component 42 (in Fig. 2A only) that may be a mesh material or an upholstery material. The frame may comprise a back or seat portion of a piece of furniture, or may comprise a free-standing component that can be used in conjunction with any type of chair or seat. A salient feature is a plurality of overlapping horizontal 'V segments 51 extending from both sides of the frame 41 and overlapping in a medial portion of the fabric component 42. A first plurality of segments 51 are each comprised of SMA legs 52a and 52b which extend from electrically active anchors 54a and 54b secured at one side of the frame 41, respectively, and converge at the opposite side at anchor 57 in a V configuration. A second plurality of segments 51 are each comprised of SMA legs 53a and 53b which extend from electrically active anchors 56a and 56b secured at the other side of the frame 41, respectively, and converge at the opposite side at anchor 58 in a V ( or 'U')

configuration.

When a voltage is applied between anchors 54a-54b, the SMA wire legs contract as described above with regard to previous embodiments; likewise, a voltage applied between anchors 56a and 56b will activate legs 53a and 53b. Due to the overlapping V arrangement, when a pair of overlapping V segments are energized simultaneously, large forces can be exerted on the frame, and consequently provide large normal forces to the mesh or fabric (to press into the back muscles of the user). Forces can be approximately doubled using this arrangement of SMA wires, providing a more forceful massage effect. The overlapping pairs of V segments 51 may be activated in a sequential manner, as described above, to provide a wave-like contraction moving through the massage device.

A further elaboration of the SMA wire layout, shown in Figure 3, also includes a closed frame 61 that defines a circumscribed central opening that is spanned by a fabric or mesh component 62. A plurality of single SMA wire segments 65 extend across the frame, each secured at opposed ends to respective electrically active anchors 63 and 64. In this wiring scheme, each SMA wire is of shorter length, spanning simply from left to right of the frame. Voltage can be applied entirely to any of the left side anchors 63, for example, which are separately addressable by a power supply, while the right side anchors 64 are all electrically grounded. Both ends of the SMA wire need to be mechanically fastened to the frame, so the contraction of the SMA wire leads to compression into the body during

energization (increasing the radius of curvature, essentially).

In the layouts of Figs. 2A-2B, and Fig. 3, each SMA wire segment is also termed a zone, due to the fact that each wire segment delivers a massage effect to a respective zone of the body, depending on the positioning of the user and the structure on which the massager is supported or installed. In the disclosed multi-zone SMA wire massage/compression devices, empirical results show that overall compressions of roughly 2 seconds provides a very satisfying 'massage' or 'squeeze' as the SMA wires slowly contract and displace tissue around the area in contact with the SMA wire(s). A typical compression or massage zone can contain 32" of SMA wire, spanning the 16" wide back in U-shape (SMA wires separated by about 1.5") for larger area of coverage. If the actual large-scale contraction is done more quickly than about 2 seconds, the effect is quite jarring, while slower contractions may become less noticeable (and also inject large amounts of waste heat into the body). An optimal massage device may have 6 or more U-shaped zones that can be energized individually in a series or sequence. (Figure 3 shows 8 zones, but the number of zones is not germane to the methodology of the invention.) That is, Zone 1 (upper back area) is energized first, and contracts roughly 0.75", causing the SMA wires to be pressed into the soft tissue of the back. Subsequent zones can then be energized in series (that is, Zone 2, then Zone 3, and so on toward the lumbar region), or they can be energized in any desired order (starting in the lumbar region and moving upward, for example).

For a typical input voltage of about 20 volts, a PWM duty cycle of -75% may be required to provide a 2-second compression to a 32"-long SMA wire, for example. But since a duty cycle of >50% is required for such long lengths of SMA wire, it is not known to be feasible to run multiple SMA wire zones directly in parallel due to the maximum power capabilities of typical power sources, which is less than 100 watts.

A salient aspect of this invention is the introduction of pulse schemes for the PWM that cause the SMA wires to emit a percussive response with each pulse and vibrate vigorously as they are heated from a cool state through the transition temperature zone.

The simplest way to prevent overheating of the SMA wires is to heat the SMA wires slowly enough that an energy balance is struck between input and lost heat energy: disallowing the SMA wire to be heated beyond a safe temperature. For any given length and diameter of SMA wire, a safe operating voltage can be found by 'sneaking up' on the voltage, to safely find the 'safe' operating voltage. A generally accepted rule of thumb is that the 'safe' operating voltage V _safe = I*R, (where R is the wire resistance, and I is the current drawn by the wire) is the driving voltage that produces a transformation from fully Martensitic to fully Austenitic in roughly one (1) second (or longer). If the 'safe' voltage is not exceeded, the SMA wire cannot be overheated.

But for the application of SMA body massagers or haptic-feedback devices and the like, much more desirable 'effects' can be produced by exceeding the 'safe' voltage, so more complex algorithms must be employed to a) provide pleasing massage effects including vibration or pulsing, and b) to prevent the SMA wires from being overheated. A new technique for producing strong vibration of SMA wires is provided herein.

In addition, each rapid pulse such as those described above could actually be a PWM 'chirp' (Fig. 4) done at high frequency so that the vibration is not 'felt' or perceived, because the SMA wire cannot cool between pulses exceeding, say 5khz. But the PWM 'chirps' could also be in the range of 100 to 1,000 hertz, for example, which is in the audible range. In that event, a pleasing audio signal can also be added to the vibrating compression or massage. This effectively produces a haptic feedback signal: indicating to the user that the device is 'ON' and is 'working' . It has been found that the audio signal is rather pleasing, and may even add to the therapeutic effect of the device. Since SMA wire activation is completely silent otherwise, the haptic or audio effects can be turned ON or can be left OFF as desired (by adjusting the chirp pulse frequencies).

The vibration frequency and PWM duty cycles controlling the overall compression can be managed to provide numerous different modes or effects. For example, high frequency pulses in the range of lkhz (1ms pulses) produces a barely noticeable vibration if using largest SMA wire diameters, but is more pronounced with smaller SMA wire diameters. Additionally, instead of using pure square wave current pulses, the leading and trailing pulse edges could be controlled by modulating the voltage. This could be used to reduce the audio effect altogether, if desired.

Lower frequency (or longer period pulses in the 10-20 hertz range) produce a much more 'choppy', percussive effect. In addition, energizing the various zones in different orders also produces wildly different effects.

When the cooling time for a given SMA wire diameter is on the same order as the OFF TIME in a warming burst, a significant vibration of the SMA wire is observed. The PWM Duty Cycles, the Burst Frequencies, and the Burst Duty Cycles can also be controlled to significantly enhance the vibration effect.

If desired, one could provide a heating pulse that produces little or no contraction. If the SMA wire is heated only to the initial transformation temperature (known as the Austenite Start temperature), then one can use the SMA wire as a seat heater.

With reference to Fig. 5 there is depicted a fundamental powering scheme of switching pulses or chirped pulses from one zone to the next, etc., to vibrate them while gradually raising their temperature and reaching the transition temperature to achieve the massage contraction. Variations of this power scheme comprise differing operating modes, as follows, Simultaneous Two-Zone Compression with Vibration: Alternate 'chirps' of PWM pulses at 50% duty cycle between two adjacent zones, so that the pulses to one zone are OFF while the pulses to the other zone are ON, and vice versa. Given the thermal buildup in the SMA material and short cooling pauses between pulses, both zones are contracted virtually simultaneously. This technique effectively doubles the compression force exerted by the two adjacent zones acting together, producing a stronger massage movement. After full contraction is achieved, the system moves on to subsequent two-zone pairs, and the pulse pattern may be reiterated, until all of the zones are activated. The period of the chirp determines the vibration frequency, while the carrier wave PWM controls the overall heating (compression rate).

Simultaneous Three-Zone Compression with Vibration: Same as above, except the first 3 zones are energized with 33% duty cycles (Zone 1, then 2, then 3) in rapid succession. This produces an even stronger overall compression (since 3 zones are pressed into service for the overall compression).

Shiver Mode: If all six zones are pulsed in rapid succession with 20ms pulses, repeating until overall full compression is reached, the effect is one of the entire seat back vibrating rapidly as it presses into the back, shoulders and lumbar area at the same time.

Quiver Mode: Similar to Shiver Mode, except that each zone is pulsed for only 4ms, and then there is a 4ms 'wait' before energizing the next zone. After cycling through all six zones, there is a 9-second cooling HOLD before repeating the cycle. The additional 'wait' allows slightly more cooling time for each SMA wire zone: producing a more pronounced vibration than would otherwise be obtained by rapid cycling without the wait.

In all of the modes described above, a modest power supply that has sufficient output to drive one SMA wire zone is used synergistically to activate two or more SMA wire zones in virtual simultaneous fashion. The small power supply comports with the portable embodiments of the invention described herein.

When a safe maximum operating voltage is determined, the power to heat the SMA wire can be applied with a Direct Current (DC) pulse. That is, one with a Duty Cycle of 100%. For even slower compressions, the voltage can be reduced further, but at some point, full contraction or full Austenite Transformation will not be achieved. Such slow contractions of longer than the 'safe' 1 -second rule do produce a pleasing 'massage' or compression effect, especially if multiple zones are operated in succession.

But SMA wires require several seconds to cool from the Austenite back to the Martensite phases. If embedded within materials or fabrics, etc, and for the larger SMA wire diameters, the cooling time can be significantly longer (in the 10-15 second range). Long pauses are not conducive to an enjoyable massage, so by employing multiple SMA wire zones, the additional zones can be energized while the first is cooling, thus providing for a continuous massage effect, while allowing sufficient time for an already energized SMA wire to cool sufficiently. We will assume that 6 different SMA wire zones are to be used, which generally allows for only short additional cooling time built into the massage effect.

If more aggressive or assertive massage or compressions are desired, higher voltages must be used. Using higher voltages exposes one to the risk of overheating the SMA wire, so careful control schemes must be employed to assure full transformation without overheating. The most obvious way to decrease the input power to an SMA wire is to use Pulse Width Modulation (PWM) to drive the applied voltages. If higher voltages are used, the PWM Duty Cycle must be decreased from the safe voltage DC (100% duty cycle) case.

In a particular embodiment of this invention the pulse control scheme is designed to employ voltages beyond the "safe" voltage defined above, while preventing overheating of the SMA wires. It uses brief high voltage pulses to heat the SMA material into the lower range of the Austenite/ Martensite transition temperature range, and the material starts to cool as soon as each pulse ends. Each following brief pulse heats the material to a slightly higher temperature within the transition range, so that full contraction of the SMA material is determined by the opposing influences of the ohmic heating rate versus the cooling effect between pulses. Moreover, it has been found that each pulse delivered to the partially contracted SMA material generates a percussive vibrational report or thump. Proper grouping and spacing of the high voltage pulses results in creating various acoustic and vibration massage effects that are pleasing and soothing.

If the voltage is high enough so that the required Duty Cycle is below 50% for a given actuation (full transformation) time, two wire zones can be driven in an alternating sequence, thus providing an additional massage operating mode. Using such alternating pulses, we can provide numerous vibrating or pulsing and other complex modes using, for example, only a modest 70W power supply. Similarly, if the voltage is high enough so that the Duty Cycles are less than 33%, then three different SMA wire zones can be operated simultaneously (again, by sequentially pulsing them). That is, by applying power to zone A, then zone B, then zone C, then repeating until full contraction is achieved.)

In the simplest form of multi-zone control, the frequency of the PWM does not need to be controlled. Standard PWM outputs from micro-controllers such as the popular ATmega328 may provide a fixed frequency of 490 hertz or 980 hertz. These frequencies fall in the audible range, and the SMA wires can be heard to 'sing' at those driving frequencies. Different micro-controllers or more complex software coding allows for total control of the frequency as well as the duty cycle, so the audible sounds can be controlled as desired. We have found that some of the gentle audible tones help to indicate (provide feedback) that the massage functions are operating properly.

If the PWM driving frequency is low enough (in the 10 hertz range), AND if the duty cycle is low enough that there are long pauses between the ON and OFF or HIGH and LOW power cycles driving a given zone (that is, if the voltages are high enough to allow low duty-cycle operation), the SMA wire is able to heat into the transition temperature range, then cool slightly during the pause or OFF part of the cycle, and a very noticeable percussive pulse or thump or throb can be generated by the forceful resumption of contraction during the subsequent pulse. This effect can be exploited to produce a very interesting pulsating massage effect. Again, the frequency of those vibrations can also be controlled by the PWM frequency for individual pulse trains, in addition to the frequency and duration of the pause or OFF periods. These terminologies are described below, along with pulse- timing charts to illustrate potential effects. Together, these effects can be used to create a wide array of software controllable massage functions with various vibration frequencies for multi-zone massager operation.

In summary: the use of high applied voltages (in the 24 volt range for 30" of SMA wire) that are switched on and off rapidly enough to heat the SMA wire into the transition temperature range and use the inherent cooling rate of the SMA wire to extend the transition temperature period while the pulses create percussive vibrational reports that are perceived as throbbing outputs from the wire. Thus complex pulse timing algorithms applied to an SMA wire provide for a multitude of software driven vibrating modes and multi-zone compressions. These control algorithms can be used to produce similar vibration effects for any number of other applications beyond massage, including haptic feedback or other 'alerting' systems employing SMA wires built into a seat or chair.

Further embodiments of the invention, shown in Fig. 6-15, illustrate various voltage pulse techniques that apply the observed SMA wire responses to voltage pulses described above to drive an SMA wire to contract in such a way as to produce complex vibration or pulsating effects for use as haptic feedback or massaging functions. In these figures the axis at the left shows increasing power, and the axis at the right shows decreasing SMA wire length.

With regard to Fig. 6, the contraction speed for an SMA wire changes with voltage and wire length. Higher voltages and/or shorter wire lengths result in faster contraction speed. SMA wires contract when heated with electrical current: transforming from the fully Martensite to the fully Austenite (contracted) phase. SMA wire can be quickly overheated at faster contraction speeds, so proper timing of pulses is critical. In this example, the voltage is selected such that the SMA wire is heated to the fully contracted Austenitic state ("short (warm)") in 0.5 seconds. (The SMA wire length scale on these graphs on increases downwardly.) If applied as a DC pulse as shown in Fig. 6, the massage seat compression from the Martensite state ("long (cool)") to Austenite is quick and forceful. Note that the cooling cycle extends for a few seconds after the pulse ends.

If that 0.5-second pulse is instead applied in two, or more, shorter pulses adding up to a total 0.5-second ON time (Fig. 7), complete SMA wire contraction is still achieved, but with a slightly different massage sensation. If the first pulse heats the wire into the transition temperature range, the subsequent pulse after the cooling pause will initiate a percussive vibrational report, likely from forceful resumption of wire contraction, as indicated graphically by the burst symbol (*) displayed in Figs. 7-10. If the OFF time (Pause) between pulses is long enough for the SMA wire to cool slightly, a distinct throbbing or vibration effect is created. Such beat vibrations are found to provide a pleasing adjunct effect for a massaging apparatus.

As soon as power is removed from the SMA wire, some energy is lost as the wire cools by conduction, convection, or radiation. If pulses are spread out over longer than roughly one second, additional heat energy is required to compensate for the cooling pauses and cause the SMA wire to reach full Austenite contraction. Again, care must be taken not to overheat the SMA wire. The higher number of pulses shown in Fig. 8 would likely cause full contraction of the SMA wire, with more percussive vibration outputs, and strong massage compressions due to the relatively long pauses.

With regard to Fig. 9, the 0.5-second total pulse energy depicted in Figs. 6-8 is spread further in time by expanding the temporal spacing of the pulses. An added pulse is provided to compensate for thermal energy lost during the multiple cooling pauses of the pulse sequence. Cooling of the SMA wire between pulses is significant enough to create very noticeable 'thumps' each time the SMA wire is reenergized. A 2-second pulse train here is illustrated in Fig. 9, because we have found that a ~2-second cadence for a massaging back device is pleasing to the user. Note that the time required for full contraction of the SMA wire increases in the examples of Figs. 6-9, due to the increasing number of pulses and cooling pauses and the length of the cooling pauses. (The same pulse voltage is used in all cases.)

A further aspect of the invention is the use of pulse trains to power the SMA wire segments (zones). Pulse Trains, as shown in Fig. 10 are virtual PWM pulses with 50% Duty Cycle and a frequency of 32 Hertz (Hz). The 5 pulse trains illustrated have the same total ON-time as pulses in Fig. 9, so we achieve full contraction of the SMA wire (100% Austenite transformation) by the end of the 5th pulse-train. But the feeling or 'texture' of the SMA wire contraction is distinct from those shown in Fig. 9 due to the shorter pauses between Pulse Trains. The shorter pauses do not permit the same degree of SMA wire cooling, so the vibrations will not be quite so pronounced. (The burst symbols are omitted in Figs. 10-15 due to lack of space, but each pulse does generate a similar percussive vibrational report, or thump, as described previously.)

It should be noted that, even at 32 Hz, there is enough cooling time between individual pulses in the pulse train, to produce a slight but noticeable 32 Hz vibration, in addition to a stronger throbbing sensation at the 2 Hz beat output caused by the cooling pauses between pulse trains. Note that both audible and sub-audible percussive reports may be produced by the pulse train.

With regard to Fig. 11, a pulse train power arrangement is illustrated in which the pulses have the same total ON time as shown in Fig. 10, but with higher frequency PWM pulse trains, and therefore necessarily shorter pauses between those pulse trains. Again, the power delivered is sufficient to fully contract the SMA wires in the same time as those shown in Fig. 10. Also shown with 50% Duty Cycle, the higher frequency vibrations within those pulse-trains will not produce vibration effects, since the cooling time within the pulse trains is so short that contraction proceeds virtually continuously. But the cooling pauses between the pulse trains cause acoustic reports at a roughly 4 Hz frequency, and these are perceived by the user as beats or thumps which are experienced as a pronounced throbbing effect. Since the pulse train pauses are selectively adjustable and variably programmable, one can 'tune' the heating contraction time for nearly any desired vibration effect.

For example, with reference to Fig. 12, if the pulse power arrangement is generated with even shorter cooling time between individual pulse trains, the 'beat' frequency caused by the cooling pauses between pulse trains can be further increased, while suppressing the vibration of the wire during the individual pulse trains.

As illustrated in Fig. 13, modifying the duty cycles within the individual pulse trains can produce yet another massage mode. All of these pulse modifications provide a very complex, sophisticated control scheme for a) delivering the proper energy pulse to fully contract the SMA wires without overheating them, while b) providing highly configurable vibration and massage modes from slow, smooth compressions to rapid, strong vibrations and beats.

Furthermore, operation at higher voltages and the use of programmable pulse modulation also provides a means to rapidly switch between SMA wire zones. Rapid switching is used to drive multiple zones virtually simultaneously, using a power supply that is modest in output power. One zone is pulsed while another is between pulses or experiencing a cooling pause, so that the vibration and beat effects described above can be provided concurrently. Thus the system compresses two or more zones in the same timeframe by quickly switching power among zones. Alternating between zones is critical so that no two SMA wire zones are 'ON' at the same time, which would double the power output requirements for the power supply.

One of the benefits of energizing multiple zones simultaneously is that the overall compression force is higher (approximately double) due to two wire-segments contracting simultaneously and pressing in on the body. The use of pulse trains, switching among alternating zones, and selective cooling pause lengths provides the total energy dose required to fully contract the SMA wires without overheating, while minimizing power supply requirements, so that a power supply having an output sufficient to continuously drive only one SMA wire zone may be used to drive a plurality of zones.

With regard to Fig. 14, zone 1 and zone 2 are addressed with pulse trains that alternate between the zones on a 0.5 Hz tempo: zone 1 is off (cooling pause) while zone 2 is on, and vice versa. Each pulse train comprises 8 pulses in 0.5 sec. followed by a cooling pause of 0.5 sec. If the switching frequency is low as shown in Fig. 14, one can feel each zone 'thudding' individually when each pulse train is delivered to its respective zone, because of the relatively long 'pause' between a each zone being energized. If the switching frequency between zones is high, one simply feels both zones compressing (and/or vibrating) in unison. Of course, after zones 1 and 2 are fully activated the power supply is switched to zones 3 and 4, etc, to operate all the other zones in the same manner while zones 1 and 2 cool down to full expansion.

Another technique for driving two SMA wire zones is illustrated in Fig. 15. In this arrangement the pulses going to the two zones are interleaved in time, so that the power supply is delivering 8 pulses to each zone within 0.5 sec, and each pulse to one zone is followed by a pulse to the other zone.

Following the pulse trains switching quickly between the two zones, there is a relatively long cooling pause of 0.5 sec. This creates the impression that both zones are contracting simultaneously. This is quite different from what is shown in Fig. 14, where a distinct thumping could be felt between the two zone operations. The pulse frequencies in Fig. 15 are high enough that the switching cannot be distinguished. For high enough voltages (up to 24 volts for 30" of SMA wire), multiple zones can be heated in rapid sequence, producing an overall contraction and compression of the entire surface covered by the SMA wires. The parameters for the pulse frequency, cooling pause timing, multi-zone pulse switching, are described and shown by way of example only, and may be varied widely without departing from the spirit of the invention.

In addition, the SMA wire zones may be driven by delivering a plurality of subsufficient voltage pulses to heat the SMA wire segments to a temperature below said transition temperature range and maintain a sub-threshold temperature. The apparatus may thus be adapted to serve as a heater for a user of the apparatus, whether it is embodied in a portable unit or a fixed chair or passenger seat or the like.

The terms PWM and Duty Cycles are generally used to describe prior art methods for microprocessor control of digital signals, typically based on a clocked pulse generator producing pulses of variable width to reduce the average voltage seen by a device or to drive stepper motors, for example. But one does not need to actually use these rigidly clocked PWM or 'duty cycles' techniques to drive an SMA wire massaging system. Rather, the embodiments described above comprise a Smart Switching Pulse technique, which enables using a voltage greater than the safe voltage described above. The digital outputs are individually controlled to perform exactly as desired, with all timing, frequency, and digital outputs controlled according to a user-defined scheme.

The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teaching without deviating from the spirit and the scope of the invention. The embodiments described are selected to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as suited to the particular purpose contemplated. Industrial Applicability

This invention may be applied to any apparatus employing shape memory materials.

Sequence Listing

Not applicable

Claims

1. A method for operating a massage apparatus employing at least one SMA wire segment, including the steps of:

delivering at least one voltage pulse to said at least one SMA wire segment to heat said wire segment into its transition temperature range;

delivering further voltage pulses to said at least one wire segment, each subsequent pulse heating said wire segment higher into said transition temperature range;

each of said further voltage pulses generating a percussive vibrational report from said wire segment that enhances the massage effect of said apparatus.

2. The method of claim 1, further including at least one cooling pause interspersed with said further voltage pulses to enable cooling of said wire segment lower into said transition temperature range.

3. The method of claim 2, wherein said further voltage pulses heat said wire segment progressively to a fully contracted austenitic state over a full contraction period of time. 4. The method of claim 3, further including a plurality of said cooling pauses, each interposed between two successive further voltage pulses to enable further cooling of said wire segment to prolong said full contraction period.

5. The method of claim 1, further including the step of delivering a plurality of subsufficient voltage pulses to heat said at least one SMA wire segment to a temperature below said transition temperature range to serve as a heater for a user of said apparatus.

6. A method for operating a massage apparatus employing at least two SMA wire segments, including the steps of:

providing a power supply having an output sufficient to continuously drive only one of said

SMA wire segments; delivering at least one first voltage pulse from said power supply to the first of said SMA wire segments to heat said first wire segment into its transition temperature range;

delivering at least one second voltage pulse from said power supply to the second of said SMA wire segments to heat said second wire segment into its transition temperature range;

delivering further first and second voltage pulses from said power supply to said first and second wire segments, each subsequent pulse heating the respective wire segments higher into said transition temperature range;

wherein said further first and second voltage pulses are interspersed so that further first voltage pulses are ON while further second voltage pulses are OFF, and vice-versa, whereby said power supply drives said at least two wire segments to a fully contracted austenitic state.

7. The method of claim 6, wherein each of said further first and second voltage pulses generate percussive vibrational reports from said first and second wire segments until said SMA wire segments are heated to the fully contracted austenitic state, said percussive vibrational reports enhancing the massage effect of said apparatus.

8. The method of claim 6, further including a plurality of cooling pauses interspersed with said further first and second voltage pulses to enable cooling of said wire segments lower into said transition temperature range.

9. The method of claim 8, wherein said cooling pauses are timed to occur during said OFF states of said further first and second voltage pulses.

10. The method of claim 6, wherein said first voltage pulses and said second voltage pulses are comprised of pulse trains of closely spaced chirped pulses.

11. The method of claim 10, wherein said closely spaced chirped pulses generate

corresponding audio outputs from said first and second SMA wire segments in addition to said percussive vibrational reports.

12. A method for operating a massage apparatus employing at least two SMA wire segments, including the steps of:

delivering at least one first voltage pulse train from a power supply to the first of said SMA wire segments to heat said first wire segment into its transition temperature range;

delivering at least one second voltage pulse train from the power supply to the second of said SMA wire segments to heat said second wire segment into its transition temperature range;

delivering further first and second voltage pulse trains to said first and second wire segments, each subsequent pulse train heating the respective wire segments higher into said transition temperature range; until said at least two wire segments are heated to a fully contracted austenitic state. 13. The method of claim 12, wherein said power supply has an output sufficient to continuously drive only one of said SMA wire segments; and wherein said further first and second voltage pulse trains are temporally spaced so that further first voltage pulse trains are ON while further second voltage pulse trains are OFF, and vice-versa; whereby said power supply may drive said at least two SMA wire segments to said fully contracted austenitic state without becoming overloaded.

14. The method of claim 12, wherein each of said further first and second voltage pulse trains generate percussive vibrational reports from said respective wire segments until said at least two SMA wire segments are heated to the fully contracted austenitic state, said percussive vibrational reports comprising a repeated throbbing effect that enhances the massage effect of said apparatus.

15. The method of claim 14, wherein said first voltage pulse trains and said second voltage pulse trains are comprised of closely spaced chirped pulses, said closely spaced chirped pulses generating corresponding audio outputs from said first and second SMA wire segments in addition to said percussive vibrational reports.

21

Claims

3. The method of claim 2, wherein said further voltage pulses heat said wire segment progressively to a fully contracted austenitic state over a full contraction period of time.

4. The method of claim 3, further including a plurality of said cooling pauses, each interposed between two successive further voltage pulses to enable further cooling of said wire segment to prolong said full contraction period.

SMA wire segments; 22 delivering at least one first voltage pulse from said power supply to the first of said SMA wire segments to heat said first wire segment into its transition temperature range;

11. The method of claim 10, wherein said closely spaced chirped pulses generate

12. A method for operating a massage apparatus employing at least two SMA wire segments, 23 including the steps of:

delivering further first and second voltage pulse trains to said first and second wire segments, each subsequent pulse train heating the respective wire segments higher into said transition temperature range; until said at least two wire segments are heated to a fully contracted austenitic state.

13. The method of claim 12, wherein said power supply has an output sufficient to continuously drive only one of said SMA wire segments; and wherein said further first and second voltage pulse trains are temporally spaced so that further first voltage pulse trains are ON while further second voltage pulse trains are OFF, and vice-versa; whereby said power supply may drive said at least two SMA wire segments to said fully contracted austenitic state without becoming overloaded.