Abstract:
An electronic device and method of operating comprises a housing; a base coupled to the housing; and an electro-mechanical transducer coupled to the base, the electro-mechanical transducer configured to operate in a resonant mode and output a haptic effect upon receiving a drive signal at a predetermined drive frequency. In an embodiment, the electro-mechanical transducer further comprises a plurality of electro-mechanical transducers, each electro-mechanical transducer configured to operate in its respective resonant mode and output a respective haptic effect upon receiving a drive signal having a predetermined drive frequency. Alternatively or additionally, the electro-mechanical transducer further comprises a plurality of spaced apart electro-mechanical devices coupled thereto in a serial fashion between a first end proximal to the base and a second end distal to the base.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This application is continuation of U.S. patent application Ser. No. 10/792,279, filed Mar. 4, 2004, entitled, “Haptic Devices Having Multiple Operational Modes Including At Least One Resonant Mode” which is a continuation-in-part and claims priority to U.S. patent application Ser. No. 10/301,809, entitled “Haptic Feedback Using Rotary Harmonic Moving Mass” and filed Nov. 22, 2002; and U.S. Patent Application No. 60/375,930, entitled “Haptic Feedback Using Rotary Harmonic Moving Mass” and filed Apr. 25, 2002. 
     
    
     TECHNICAL FIELD 
       [0002]    The subject matter relates to a haptic feedback device having multiple operational modes including multiple resonant modes. 
       BACKGROUND 
       [0003]    Generally, electro-mechanical transducers exhibit a level of power consumption that may be higher than desired. Furthermore, such electro-mechanical transducers may not be able to produce haptic feedback of a desired magnitude or bandwidth due to space constraints. 
         [0004]    What is needed is an electro-mechanical transducer that is configured to produce vibrotactile feedback having a relatively high magnitude and/or an adjustable bandwidth. Additionally, it would be desirable to have an electro-mechanical transducer that can generate haptic feedback having relatively low energy consumption. 
       OVERVIEW 
       [0005]    An electronic device and method of operating comprises a housing; a base coupled to the housing; and an electro-mechanical transducer coupled to the base, the electro-mechanical transducer configured to operate in a resonant mode and output a haptic effect upon receiving a drive signal at a predetermined drive frequency. In an embodiment, the electro-mechanical transducer further comprises a plurality of electro-mechanical transducers, each electro-mechanical transducer configured to operate in its respective resonant mode and output a respective haptic effect upon receiving a drive signal having a predetermined drive frequency. Alternatively or additionally, the electro-mechanical transducer further comprises a plurality of spaced apart electro-mechanical devices coupled thereto in a serial fashion between a first end proximal to the base and a second end distal to the base. In an embodiment, at least one mass is located a different predetermined distance from the base than a mass of another electro-mechanical device in the plurality. In an embodiment, at least one mass has a weight different than a mass of another electro-mechanical device in the plurality. In an embodiment, the drive frequency of the drive signal applied to two or more of the electro-mechanical transducers in the plurality has a substantially same value. In an embodiment, the drive frequency of the drive signal applied to at least one electro-mechanical transducer in the plurality is at a higher order of the resonant frequency of another electro-mechanical transducer in the plurality. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0006]      FIG. 1  is a system block diagram of an electro-mechanical transducer, according to an embodiment. 
           [0007]      FIG. 2  shows a perspective view of an electro-mechanical device according to an embodiment. 
           [0008]      FIG. 3  shows a perspective view of an electro-mechanical transducer according to an embodiment. 
           [0009]      FIG. 4  shows a perspective view of an electro-mechanical transducer according to another embodiment. 
           [0010]      FIG. 5  shows a perspective view of an electro-mechanical transducer in a parallel arrangement, according to an embodiment. 
           [0011]      FIG. 6  illustrates a plot of a gain profile for a single resonant mode output from single electro-mechanical transducer according to one embodiment. 
           [0012]      FIG. 7  illustrates a plot of a gain profile for multiple resonant modes output by an electro-mechanical transducer according to an embodiment. 
           [0013]      FIG. 8  shows a perspective view of an electro-mechanical transducer in a series arrangement according to another embodiment. 
           [0014]      FIG. 9  shows a side view of an electro-mechanical transducer shown in  FIG. 8  in a rest position. 
           [0015]      FIG. 10  illustrates the electro-mechanical transducer according to the embodiment depicted in  FIG. 8  operating in a first resonant mode. 
           [0016]      FIG. 11  illustrates the electro-mechanical transducer according to the embodiment depicted in  FIG. 8  operating in a second resonant mode. 
           [0017]      FIG. 12  illustrates the electro-mechanical transducer according to the embodiment depicted in  FIG. 8  operating in a third resonant mode. 
           [0018]      FIG. 13  is a flow chart illustrating a method for producing an operational mode of an electro-mechanical transducer according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION  
       [0019]    An apparatus comprises a signal source, a driver and an electro-mechanical transducer having a cantilever. The signal source is configured to output a haptic feedback signal. The driver is configured to receive the haptic feedback signal and output a drive signal. The electro-mechanical transducer has a cantilever and is configured to receive the drive signal. The electro-mechanical transducer is configured to have a set of operational modes. Each operational mode from the set of operational modes has at least one resonant mode from a set of resonant modes. 
         [0020]    In one embodiment, electro-mechanical devices are used in an electro-mechanical transducer that is configured to output haptic feedback in an operational mode having one or more resonant modes. The electro-mechanical transducer is also configured to have multiple operational modes. Such a device can produce diverse and robust haptic feedback that can exhibit relatively low power consumption in a space-efficient manner. Although many embodiments described herein relate to using cantilevers as resonant structures, analogous devices are also possible. For example, such resonant structures can use acoustic cavities, membranes, mass-springs, wheel-torsional springs, and/or other structures capable of exhibiting mechanical resonance. Some embodiment, for example, can have a combination of different types of structure capable of exhibiting mechanical resonance. 
         [0021]    As used herein, the term “operational mode” means a method or manner of functioning in a particular condition at a given time. For example, if a first electro-mechanical device is operating in a first resonant mode and a second electro-mechanical device is operating in a second resonant mode, the electro-mechanical transducer is operating collectively in, for example, a first operational mode. Alternatively, for example, if the first electro-mechanical device is operating in a third resonant mode, and the second electro-mechanical device is operating in a fourth resonant mode, the electro-mechanical transducer is operating collectively in a second operational mode. In another example, if the first electro-mechanical device is operating in a first resonant mode, and the second electro-mechanical device is not operating, the electro-mechanical transducer is operating collectively in a third operational mode. In other words, a given operation mode can be based on one electro-mechanical device operating in a resonant mode and another electro-mechanical device not being activated. 
         [0022]    The term “resonant mode” means any mode of an electro-mechanical device operating in a frequency band centered around a resonant frequency. When an electro-mechanical device operates at or near a resonant frequency, several consequences occur. For example, when a transducer operates at or near a resonant frequency, the inertial term and the elastic terms substantially cancel. The power consumed by the actuator is then dedicated to balance dissipation (e.g. damping). If the dissipation is low, for example, in a cantilevered piezo-electric beam (i.e. a resonator with a high Q factor), the displacement is relatively large and limited by dissipative forces. In addition, if the mass that resonates is comparable to the mass of the structure to which the transducer is attached (e.g. case of a telephone), then the structure vibrates with a relatively large magnitude. Power lost during activation is in the dissipation. The remaining power is transmitted to the anatomy of the person with which the device is in contact. 
         [0023]    The term “electro-mechanical device” as used herein, means an individual active component configured to provide haptic feedback. The term “active component” refers to a single component that provides a mechanical response to the application of an electrical signal. For example, for the embodiment illustrated in  FIG. 5  and discussed below, a single length of, for example, piezoelectric material (for example, piezoelectric bar  410 ) and the associated mass (for example, mass  412 ) is referred to herein as the electro-mechanical device. In the example illustrated in  FIG. 8  and discussed below, the electro-mechanical transducer includes only one electro-mechanical device. 
         [0024]    The term “electro-mechanical transducer” means an apparatus having one or more electro-mechanical devices coupled to a mechanical ground. For example, in the illustrated in  FIG. 5 , the electro-mechanical transducer includes all three lengths of piezoelectric material, each having a mass coupled thereto. In the embodiment illustrated in  FIG. 8 , the electro-mechanical transducer includes piezoelectric bar  610  and the masses  620 ,  630 , and  640 . 
         [0025]    An embodiment of an electro-mechanical transducer is illustrated in  FIG. 1 . An electro-mechanical transducer according to this embodiment includes a drive circuit  110  having an amplifier and includes an electro-mechanical transducer  120 . The electro-mechanical transducer  120  includes one or more electro-mechanical (E-M) devices  121 . 
         [0026]    Drive  110  receives a haptic feedback signal and outputs a drive signal to electro-mechanical transducer  120 . The haptic feedback signal may be based on a command from a microprocessor within, for example, a computer or a portable communications device (not shown). The electro-mechanical transducer  120  is configured to selectively operate in one of multiple possible operational modes at a given time. The operational mode of the electro-mechanical transducer  120  at a given time will depend, for example, on the characteristics of the drive signal received from driver  10 . For a given operational mode, an electro-mechanical transducer can operate in multiple resonant modes as will be described in greater detail below. The one or more electro-mechanical devices  121  of electro-mechanical transducer  120  collectively output haptic feedback based on the drive signal, as illustrated in  FIG. 7 . 
         [0027]      FIG. 2  illustrates a piezoelectric bar in accordance with one embodiment. As described below in more detail, such a piezoelectric bar can be used as an electro-mechanical device within an electro-mechanical transducer. 
         [0028]    The piezoelectric bar  200  is a bimorph piezoelectric device that is a two-layer bending motor having a length (L)  220  substantially larger than a width (W)  210 . In one embodiment, the piezoelectric bar  200  has a width (W)  210  of approximately 0.6 mm, a length (L)  220  of approximately 25 mm and a height (H)  230  of approximately 5 mm. Alternatively, the piezoelectric bar can have any suitable dimensions depending on the desired use. 
         [0029]    When a voltage  240  from, for example, a drive source (not shown), is applied across the piezoelectric bar  200 , the piezoelectric bar  200  will flex. An appropriate level of voltage  240  to be applied to the piezoelectric bar  200  can be selected, based at least in part, on the material and the thickness of the material used to construct the piezoelectric bar  200 . 
         [0030]    The piezoelectric bar  200  can be driven near a resonant frequency. When the piezoelectric bar  200  is driven near a resonant frequency, impedance transformation may be obtained. Impedance transformation results in large mechanical displacements as described above. 
         [0031]    An electro-mechanical device  300  that can be used in combination with other electro-mechanical devices to construct an electro-mechanical transducer is illustrated as  FIG. 3 . Multiple electro-mechanical devices  300  can be configured to operate in a selected operational mode from a set of possible operational modes, each operational mode having one or more resonant modes, as will be described in further detail with respect to  FIG. 5 . 
         [0032]    The electro-mechanical device  300  illustrated in  FIG. 3  includes a piezoelectric bar  310  having mass  320  coupled to an end portion  325  of the piezoelectric bar  310 . A second end portion  335  of the piezoelectric bar  310  is coupled to a base member  330 . Base member  330  acts as a mechanical ground and is configured to remain stationary relative to the movement of the piezoelectric bar  310 . 
         [0033]    The electro-mechanical device illustrated in  FIG. 3  can operate as follows. A voltage  340  from a voltage source (not shown) can be applied to piezoelectric bar  310 . The piezoelectric bar can be, for example, a bimorph piezoelectric device as described above in connection with  FIG. 2 . Voltage  340  causes piezoelectric bar  310  to flex in a first direction D 1 . Voltage  340  can be modulated at a frequency, f d , which is referred to herein as the drive frequency of the electro-mechanical device  300 . As described above, the frequency f d  can be selected such that the electro-mechanical device  300  operates near a resonant frequency the electro-mechanical device  300 . Frequency f d  is a function of the type of electro-mechanical device used in the electro-mechanical transducer, the dimensions of the electro-mechanical device (e.g., the length, width, height or thickness), and the position and weight of the masses in the electro-mechanical device. 
         [0034]    When the drive frequency f d  of the voltage  340  is such that the electro-mechanical device  300  operates near its resonant frequency, the electro-mechanical device  300  can produce a large vibration sensation relative to the voltage  340  applied to the electro-mechanical device  300 . 
         [0035]    Both the weight of mass  320  and the length of the piezoelectric bar  310  affect the amplitude of the displacement. Furthermore, the weight of mass  320  and the length of the piezoelectric bar  310  affect the resonant frequencies of the electro-mechanical device  300 . Therefore, the particular resonant frequencies may be tailored by selecting the appropriate length of the piezoelectric bar and/or weight of the mass  320  for a desired resonant frequency. When voltage  340  is applied to the piezoelectric bar  310 , the electro-mechanical device  300  will move in a plane oriented as vertical for the depiction in  FIG. 3 . 
         [0036]    The embodiment illustrated in  FIG. 4  is similar to that illustrated in  FIG. 3 .  FIG. 4  shows an electro-mechanical device  350  including a piezoelectric bar  360  having mass  370  coupled to an end portion  375  of piezoelectric bar  360 . The piezoelectric bar  360  has its second end portion  385  coupled to a base member  380 , which acts as a ground and is configured to remain stationary with respect to movement of the piezoelectric bar  360 . 
         [0037]    The operation of the electro-mechanical device  350  is similar to the embodiment described with reference to  FIG. 3  except that when voltage  390  is applied to piezoelectric bar  360 , the electro-mechanical device  350  will vibrate in direction D 2  (i.e., relative to the perspective shown in  FIG. 4 ) due to the orientation of the bimorph piezoelectric bar  360  relative to base member  380 . 
         [0038]      FIG. 5  illustrates an electro-mechanical transducer  400 , according to another embodiment. The electro-mechanical transducer  400  includes three electro-mechanical devices  410 ,  420 , and  430 . In the illustrated embodiment, each of the electro-mechanical devices  410 ,  420  and  430  includes a piezoelectric bar  411 ,  421 , and  431 , respectively. A mass  412 ,  422 , and  432  can be coupled to an end portion  413 ,  423 , or  433 , of each piezoelectric bar  411 ,  421  and  431 , respectively. The second end portion  414 ,  424 , and  434 , of each piezoelectric bar  411 ,  421 , and  431 , respectively, is coupled to a base member  440 . Base member  440  can be configured to remain stationary with respect to movement of the piezoelectric bars  411 ,  421  and  431 . More specifically, base member  440  is stationary relative to any movement of piezoelectric bars  411 ,  421  and  431 , but can move in the context of the overall product or device (e.g., mobile phone, game controller, etc.) with which the electro-mechanical device  400  is disposed. In fact, base member  440  can relay the vibrations produced by the movement of piezoelectric bars  411 ,  421  and  431  to the product or device. Base member  440  may be a single contiguous mechanical ground, as illustrated in  FIG. 5 . Alternatively, each piezoelectric bar  411 ,  421 , and  431  may be coupled to a different mechanical ground. 
         [0039]    Piezoelectric bars  411 ,  421 , and  431  have lengths L 1 , L 2 , and L 3 , respectively. In one embodiment, these lengths may be the same. Alternatively, lengths L 1 , L 2 , and L 3  can be different. Additionally, the weights of masses  412 ,  422 , and  432 , can be equal to one another. Alternatively, weights of the masses  412 ,  422 , and  432  can be different from one another. The particular configuration of the masses  412 ,  422  and  432  and the lengths of the piezoelectric bars  411 ,  421 , and  431  can be based on the desired frequency response from the electro-mechanical transducer  400 . 
         [0040]    The operation of the electro-mechanical transducer in  FIG. 5  will be described with reference to  FIGS. 4 and 5 . Voltage  450  can be applied to the electro-mechanical devices through contacts  451 . The voltage may by modulated at approximately the resonant frequency of the electro-mechanical devices  410 ,  420 , and/or  430 . The voltage may be applied by a single voltage source via contacts  451 , or alternatively, each electro-mechanical device  410 ,  420 ,  430 , may have an independent voltage source (not shown) that is modulated approximately at the resonant frequency of the respective electro-mechanical device, or a resonant mode of the respective electro-mechanical device. Alternatively, voltage  450  may be modulated at a higher order resonant frequency of the electro-mechanical devices  410 ,  420 , and/or  430 . 
         [0041]    In an alternative arrangement, the electro-mechanical transducer  400  can include electro-mechanical devices  410 ,  420 , and  430  that have different lengths L 1 , L 2 , L 3 . In this arrangement, each of the electro-mechanical devices  410 ,  420 , and  430  has a different resonant frequency f 1 , f 2  and f 3 , respectively. These different resonant frequencies can be driven at different drive frequencies f 1 , f 2  and f 3 . An example of the frequency response for an electro-mechanical transducer  400  is illustrated in  FIG. 7 . As depicted in the plot in  FIG. 7 , an electro-mechanical transducer with three electro-mechanical devices each operating at a different resonant frequency (or resonants thereof) has a frequency response with a greater bandwidth than the frequency response for an electro-mechanical transducer having a single electro-mechanical device, which is illustrated in  FIG. 7 . Note that the gain values shown on the y-axes in  FIGS. 6 and 7  relate to the magnitude of the device position divided by the magnitude of the input voltage to the device. 
         [0042]    In another arrangement, masses  412 ,  422 , and  432  and lengths L 1 , L 2 , and L 3  of electro-mechanical devices  411 ,  421 , and  431  can be configured such that a single drive frequency, f d , may be used to drive, for example, the resonant mode in electro-mechanical device  411 , the first resonant mode in electro-mechanical device  422 , and the second resonant mode in electro-mechanical device  432 . 
         [0043]    In yet another arrangement, the bandwidth of the electro-mechanical transducer  400  may be adjusted by selectively operating one or more of the electro-mechanical devices  410 ,  420 ,  430  in different resonant modes. Each one of these combinations of resonant frequencies collectively superpose into a different operational mode of the electro-mechanical transducer  400 . 
         [0044]    In a first operational mode, for example, the electro-mechanical transducer  400  can be operated such that electro-mechanical devices  410  and  430  may be operating at frequencies f, and f 3 , respectively, with f 1  and f 3  being resonant modes of the electro-mechanical devices  410  and  430 , respectively. A voltage need not be applied to electro-mechanical device  420  in this operational mode. In this operational mode, the output of the electro-mechanical transducer  400  would include peaks  510  and  530  illustrated in  FIG. 7 . 
         [0045]    In a second operational mode, for example, the electro-mechanical transducer  400  can be operated such that electro-mechanical devices  410  and  420  are operating at frequencies f 1  and f 2 , respectively, where f 1  and f 2  are resonant modes of the electro-mechanical devices  410  and  420 . In this operational mode, the electro-mechanical transducer  400  can produce an output having only two peaks, as illustrated, for example, in  FIG. 7  as  510  and  520 . This operational mode can have two frequencies that are different from the two frequencies of the first operational mode described above. Therefore, by changing the operational mode of the electro-mechanical transducer  400 , the resultant frequencies of the tactile feedback can be changed. 
         [0046]    In a third operational mode, for example, the electro-mechanical transducer  400  can be operated such that electro-mechanical devices  420  and  430  may be operating at frequencies f 2  and f 3 , respectively, where f 2  and f 3  are resonant modes of each of the electro-mechanical devices  420  and  430 . In this operational mode, the electro-mechanical transducer  400  can produce an output having only two peaks, as illustrated, for example, in  FIG. 7  as  520  and  530 . This operational mode can have two frequencies that are different from the two frequencies for first operational mode described above. Additionally, the third operational mode can have two frequencies that are different from the two frequencies of the second operational mode. Therefore, by changing the operational mode of the electro-mechanical transducer  400 , the resultant frequencies of the haptic feedback can be changed. 
         [0047]    In other operational modes, the electro-mechanical transducer  400  can be operated such that one of electro-mechanical devices  410 ,  420  and  430  is operating at frequencies f 1 , f 2  and f 3 , respectively, where f 1 , f 2  and f 3  are resonant modes of each of the electro-mechanical devices  410 ,  420  and  430 . In these operational modes, the electro-mechanical transducer  400  can produce an output having only one peak at a time. In other words, operational modes are possible where only a single electro-mechanical device is actuated at a given time. 
         [0048]    The voltage can be modulated at a number of different drive frequencies, f d . For example, the drive frequency f d  can approximate a resonant mode of the electro-mechanical devices. Alternatively, f d  can include any other frequency that is an integral multiple of the electro-mechanical device&#39;s resonant frequency. 
         [0049]    While certain operational modes have been described with reference to  FIG. 5 , it will be apparent from this discussion that many other operational modes are possible. For example, by providing additional electro-mechanical devices, the number of possible operational modes increases. Additionally, while only three piezoelectric bars were illustrated in  FIG. 5 , any number of piezoelectric bars may be employed. 
         [0050]    Additionally, while the embodiments were described above with reference to electro-mechanical devices that included piezoelectric bars, any electro-active material or device can be used. For example, the electro-mechanical devices can include electro-active polymers (EAP), voice coil transducers or other electromagnetic device, an inertial resonant device, or a resonant eccentric rotating mass (HERM) device. An example of an inertial resonant device is described in U.S. Pat. No. 6,088,019. An example of a HERM device is described in U.S. Pat. No. 7,161,580. 
         [0051]      FIG. 8  illustrates an alternative embodiment of an electro-mechanical transducer  600  having multiple masses  620 ,  630 , and  640  disposed on the same piezoelectric bar  610 . 
         [0052]    In this embodiment, electro-mechanical transducer  600  comprises one electro-mechanical device, the structure of which corresponds to the structure of electro-mechanical transducer  600 . The piezoelectric bar  610  is secured to a base member  650 , which acts as a mechanical ground and remains substantially fixed with respect to the movement of the electro-mechanical device  600 . Masses  620 ,  630 , and  640  can have equal weights or can have different weights. Alternatively, the weights of the two masses can be equal to one another, while the weight of the third mass can be different. Additionally, the masses  620 ,  630 , and  640  can be equally spaced along the length of the piezoelectric bar  610  or can be spaced at any desired location along the length of the piezoelectric bar  610 . The weight of and spacing between masses  620 ,  630 , and  640  allow the electro-mechanical device to be designed to have a predetermined number of resonant frequencies. 
         [0053]    Next, the operation of the embodiment illustrated in  FIG. 8  will be described with reference to  FIGS. 6-10 .  FIGS. 7-10  illustrate an example of the different operational modes that can be obtained with an electro-mechanical transducer  600  bearing three masses. The bends in the piezoelectric bar  610  are exaggerated in this figure to illustrate the bending of the piezoelectric bar  610  more clearly. 
         [0054]    Frequency modulated voltage can be applied to the piezoelectric bar  610 . As illustrated in  FIG. 9 , the electro-mechanical device is initially in a resting position.  FIG. 10  illustrates a first resonant mode of the electro-mechanical device.  FIG. 11  illustrates a second resonant mode of the electro-mechanical device.  FIG. 12  illustrates a third resonant mode of the electro-mechanical device. The modes illustrated in  FIGS. 7-10  will produce a resultant output having frequencies that are similar to the frequencies illustrated in  FIG. 7  due to the superposition of the three resonant modes produced by the electro-mechanical device. 
         [0055]      FIG. 13  illustrates a method for producing an operational mode of an electro-mechanical transducer, according to an embodiment. At step  1110 , a haptic feedback signal is generated. At step  1120 , the haptic feedback signal is supplied to a driver. At step  1130 , the drive signal is then applied to a first electro-mechanical device. At step  1140 , a drive signal is also applied to the second electro-mechanical device. At step  1150 , the electro-mechanical devices output haptic feedback that includes haptic feedback at a first resonant mode (step  1151 ) and haptic feedback at a second resonant mode (step  1152 ). The output of haptic feedback at a first resonant mode by a first electro-mechanical device and/or at a second resonant mode by a second electro-mechanical device correspond to an operational mode of the electro-mechanical transducer having the first electro-mechanical device and/or the second electro-mechanical device, respectively. 
         [0056]    Additional electro-mechanical devices can be added and can have the drive signal selectively applied thereto to collectively yield a variety of different operational modes of the electro-mechanical transducer. Alternatively, the electro-mechanical transducer may include multiple masses, as illustrated in  FIG. 8 . By altering the frequency of the drive signal such that it substantially corresponds to the resonant frequencies of the electro-mechanical device, the electro-mechanical transducer can output haptic feedback having multiple frequencies for a given operational mode. 
         [0057]    In another embodiment, a number of electro-mechanical devices in a serial configuration, as illustrated in  FIG. 8 , can be arranged in parallel as illustrated in  FIG. 5 . 
         [0058]    The devices described above are capable of being used in small, portable devices where energy consumption needs to be low. For example, electro-mechanical transducers can be used in cellular phones, electronic pagers, laptop touch pads, a cordless mouse or other computer peripherals whether cordless or otherwise, a personal digital assistant (PDA), along with a variety of other portable and non-portable devices. 
         [0059]    While the particular embodiments were described above with respect to piezoelectric bars, they are not limited to the use of piezoelectric bars and piezoelectric devices having various structures can be used depending on the desired application of the electro-mechanical transducer. For example, the piezoelectric device can have a planar shape where the width is approximately the same as the length. 
         [0060]    While particular embodiments have been described with reference to piezoelectric ceramics, numerous other electro-mechanical devices may be used. For example, the electro-mechanical devices may include electro-active polymers (EAP), voice coil transducers or other electromagnetic device, or resonant eccentric rotating mass (HERM) devices. 
         [0061]    While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of should not be limited by any of the above-described embodiments, but should be defined only in accordance with the following claims and their equivalence. 
         [0062]    The previous description of the embodiments is provided to enable any person skilled in the art to make or use the embodiments. While various electro-mechanical transducers have been described including at least one electro-mechanical device including a piezoelectric substance, various other electro-mechanical devices may be utilized that can be configured to operate in multiple operational modes, each one of the multiple operational modes including a number of resonant modes. Other modifications to the overall structure of the electro-mechanical devices and arrangement of the selector-mechanical transducers can be made without departing from the spirit and scope of the embodiments.