Patent ID: 12244253

DETAILED DESCRIPTION

The description below sets forth example embodiments according to this disclosure. Further example embodiments and implementations will be apparent to those having ordinary skill in the art. Further, those having ordinary skill in the art will recognize that various equivalent techniques may be applied in lieu of, or in conjunction with, the embodiment discussed below, and all such equivalents should be deemed as being encompassed by the present disclosure.

Various electronic devices or smart devices may have transducers, speakers, and acoustic output transducers, for example any transducer for converting a suitable electrical driving signal into an acoustic output such as a sonic pressure wave or mechanical vibration. For example, many electronic devices may include one or more speakers or loudspeakers for sound generation, for example, for playback of audio content, voice communications and/or for providing audible notifications.

Such speakers or loudspeakers may comprise an electromagnetic actuator, for example a voice coil motor, which is mechanically coupled to a flexible diaphragm, for example a conventional loudspeaker cone, or which is mechanically coupled to a surface of a device, for example the glass screen of a mobile device. Some electronic devices may also include acoustic output transducers capable of generating ultrasonic waves, for example for use in proximity detection type applications and/or machine-to-machine communication.

Many electronic devices may additionally or alternatively include more specialized acoustic output transducers, for example, haptic transducers, tailored for generating vibrations for haptic control feedback or notifications to a user. Additionally or alternatively, an electronic device may have a connector, e.g., a socket, for making a removable mating connection with a corresponding connector of an accessory apparatus, and may be arranged to provide a driving signal to the connector so as to drive a transducer, of one or more of the types mentioned above, of the accessory apparatus when connected. Such an electronic device will thus comprise driving circuitry for driving the transducer of the host device or connected accessory with a suitable driving signal. For acoustic or haptic transducers, the driving signal may generally be an analog time-varying voltage signal, for example, a time-varying waveform.

FIG.3illustrates selected components of an example host device300A incorporating force sensing using an electromagnetic load301of host device300A, in accordance with embodiments of the present disclosure. Host device300A may include, without limitation, a mobile device, home application, a vehicle, and/or any other system, device, or apparatus that includes a human-machine interface. Electromagnetic load301may include any suitable load with a complex impedance, including without limitation a haptic transducer, a loudspeaker, a microspeaker, a piezoelectric transducer, or other suitable transducer.

In operation, a signal generator324of a processing subsystem305of host device300A may generate a signal x(t) (which, in some embodiments, may be a waveform signal, such as a haptic waveform signal or audio signal). Signal x(t) may be generated based on a desired playback waveform received by signal generator324. Signal x(t) may in turn be amplified by amplifier306to generate the driving signal V(t) for driving electromagnetic load301. Responsive to driving signal V(t), a sensed terminal voltage VT(t) of electromagnetic load301may be converted to a digital representation by a first analog-to-digital converter (ADC)303. Similarly, sensed current I(t) may be converted to a digital representation by a second ADC304. Current I(t) may be sensed across a shunt resistor302having resistance Rscoupled to a terminal of electromagnetic load301. The terminal voltage VT(t) may be sensed by a terminal voltage sensing block307, for example a volt meter.

As shown inFIG.3, processing subsystem305may include a back-EMF estimate block308that may estimate back-EMF voltage VB(t). In general, back EMF voltage VB(t) may not be directly measured from outside of the haptic transducer. However, the terminal voltage VT(t) measured at the terminals of the haptic transducer may be related to VB(t) by:

VT⁡(t)=VB⁡(r)+Re·I⁡(t)+L⁢e⁢dI⁡(t)dt(2)
where the parameters are defined as described with reference toFIG.2. Consequently, back-EMF voltage VB(t) may be estimated according to equation (2) which may be rearranged as:

VB⁡(t)=VT⁡(t)-Re·I⁡(t)-L⁢e⁢dI⁡(t)dt(3)
Because back-EMF voltage VB(t) may be proportional to velocity of the moving mass of electromagnetic load301, back-EMF voltage VB(t) may in turn provide an estimate of such velocity.

In some embodiments, back-EMF estimate block308may be implemented as a digital filter with a proportional and parallel difference path. The estimates of DC resistance Re and inductance Le may not need to be accurate (e.g., within an approximate 10% error may be acceptable), and thus, fixed values from an offline calibration or from a data sheet specification may be sufficient. As an example, in some embodiments, back-EMF estimate block308may determine estimated back-EMF voltage VB(t) in accordance with the teachings of U.S. patent application Ser. No. 16/559,238, filed Sep. 3, 2019 (the “'238 application”), which is incorporated by reference herein in its entirety.

Based on such estimated back-EMF voltage VB(t), a braking subsystem310of processing subsystem305may generate a braking signal xBRK(t), in order to minimize a post-playback settling time of electromagnetic load301, as described in greater detail below. Signal generator324may receive braking signal xBRK(t) and sum it with a playback waveform to generate signal x(t) communicated to amplifier306.

In general, braking subsystem310may, at the conclusion of a playback waveform, generate braking signal xBRK(t) as a piecewise square signal with an amplitude in each piece of the square given by:

AB⁢R⁢K=-KB⁢R⁢K⁢dVB⁡(t)dt⁢⁢when⁢⁢VB⁡(t)=0(4)
where KBRKis an arbitrary positive gain constant which may be determined for each model or type of electromagnetic load301.

Thus, braking subsystem310may reverse polarity of the braking signal at the zero crossings of the velocity of the moving mass of electromagnetic load301, which may be given by zero crossings of estimated back-EMF voltage VB(t). Further, braking subsystem310may, for each piece of braking signal xBRK(t), adaptively determine an amplitude of such piece based on the derivative with respect to time at the previous zero crossing of estimated back-EMF voltage VB(t). Accordingly, braking subsystem310may cause amplitude of braking signal xBRK(t) to be reduced as the moving mass of electromagnetic load301is decelerated, to prevent reacceleration in the opposite direction. The derivative with respect to time at the previous zero crossing of estimated back-EMF voltage VB(t) may provide an indication of the instantaneous oscillation amplitude of estimated back-EMF voltage VB(t), and thus may provide a magnitude scalar to adapt amplitude ABRKof braking signal xBRK(t).

FIG.4illustrates a graph depicting an estimated back-EMF voltage VB(t) and braking signal xBRK(t) generated based on estimated back-EMF voltage VB(t), in accordance with embodiments of the present disclosure. As is shown inFIG.4, at a time t=0, corresponding to the end of a playback signal (and thus, the beginning of a braking phase) for electromagnetic load301, braking subsystem310may begin generating braking signal xBRK(t) with a magnitude proportional to and opposite in polarity from the derivative with respect to time of estimated back-EMF voltage VB(t) at the previous zero crossing of estimated back-EMF voltage VB(t) in accordance with equation (4) above. At subsequent zero crossings of estimated back-EMF voltage VB(t), braking subsystem310may adaptively modify amplitude ABRKof braking signal xBRK(t) in accordance with equation (4) above, with such zero crossing serving to synchronize modification of amplitude ABRK. Braking subsystem310may generate braking signal xBRK(t) and adapt its magnitude until such time as estimated back-EMF voltage VB(t), its derivative with respect to time at a zero crossing of estimated back-EMF voltage VB(t), or some other parameter indicates that electromagnetic load301has settled to an acceptable amount.

In some embodiments, braking subsystem310may simplify calculation and generation of braking signal xBRK(t) compared to that discussed above. For instance, if coil inductance Le of electromagnetic load301is very small compared to its DC resistance Re, equation (3) above may be approximated by:
VB(t)=VT(t)−Re·I(t)  (5)
Use of such approximation for estimated back-EMF voltage VB(t) by braking subsystem310may simplify calculation or may reduce processing resource requirements by eliminating the need to calculate

dI⁡(t)dt.

Furthermore, if DC resistance Re is not available, the polarity and derivative of estimated back-EMF voltage VB(t) may still be determined if VT(t)=0, which further simplifies equation (4) above to:
VB(t)≈−Re·I(t)∝−I(t)  (6)
Under this approximation, estimated back-EMF voltage VB(t) is in phase with current I(t). When the moving mass of electromagnetic load301is at a no-rest state and driving signal V(t) is set to zero, the mass of electromagnetic load301may oscillate at its resonance frequency f0with an exponentially decaying amplitude. In this state, electromagnetic load301may also be considered at resonance, meaning that the residual motion of the mass in the LRA may elicit current I(t) which is in phase with the velocity of the oscillation of the mass. Thus, in such scenario, braking subsystem310may effectively minimize settling time by measuring current I(t) alone, determining a direction and magnitude of the velocity of the moving mass of electromagnetic load301based on measured current I(t), and generating braking signal xBRK(t) to oppose such motion indicated by measured current I(t).

Although the foregoing contemplates that measurement of estimated back-EMF voltage VB(t) and the application of braking signal xBRK(t) may occur at the same time, in some embodiments the measurement of estimated back-EMF voltage VB(t) and the application of braking signal xBRK(t) may occur at different times. In such other embodiments, piecewise periods of sensing and braking may lead to a desired minimization of settling time.

Furthermore, in some embodiments, braking subsystem310may appropriately limit braking signal xBRK(t) so as to not exceed allowable operational ranges for parameters associated with electromagnetic load301(e.g., to ensure a maximum voltage and maximum current applied to electromagnetic load301does not exceed maximum ratings of electromagnetic load301).

In addition, while the foregoing contemplates braking subsystem310generating a piecewise square braking signal xBRK(t), in some embodiments, braking subsystem310may generate pieces of braking signal xBRK(t) to have any suitable waveform shape provided such shape and amplitude thereof serve to reduce a velocity of the moving mass of electromagnetic load301.

In these and other embodiments, braking subsystem310may also be configured to compensate for undesired effects that may lead to measurement inaccuracy. For example, in some embodiments, braking subsystem310may determine a measurement offset for estimated back-EMF voltage VB(t) by measuring estimated back-EMF voltage VB(t) when driving signal V(t) is set to zero, and add a compensation factor to its measurements of estimated back-EMF voltage VB(t) to counter such offset. As another example, in these and other embodiments, braking subsystem310may compensate for noise in measurement of estimated back-EMF voltage VB(t) by applying filtering (e.g., low-pass filtering) to measurements of estimated back-EMF voltage VB(t).

In addition or alternatively to providing a braking signal xBRK(t) for minimizing settling time after driving of a playback waveform, in some embodiments, braking subsystem310may also be configured to, in the absence of a playback waveform provided to signal generator324, use estimated back-EMF voltage VB(t) (which as described above, may be proportional to velocity of an electromagnetic load) to determine if undesired movement of electromagnetic load301is occurring, and apply braking signal xBRK(t) to reduce or eliminate such undesired motion. An example method500for reducing or eliminating such undesired motion is described below with respect toFIG.5. An advantage of such approach is that processing subsystem305may be capable of detecting undesired movement of electromagnetic load301without using separate inertial measurement units (e.g., accelerometers) to detect such undesired movements.

FIG.5illustrates a flow chart of an example method500for restricting undesired movements of a haptic transducer, in accordance with embodiments of the present disclosure. According to some embodiments, method500may begin at step502. As noted above, teachings of the present disclosure may be implemented in a variety of configurations of host device300A. As such, the preferred initialization point for method500and the order of the steps comprising method500may depend on the implementation chosen.

At step502, braking subsystem310may receive estimated back-EMF voltage VB(t) from back-EMF estimate block308. At step504, braking subsystem310may determine whether the estimated back-EMF voltage VB(t) resulted from a playback waveform being input to signal generator324. If the estimated back-EMF voltage VB(t) resulted from a playback waveform being input to signal generator324, method500may proceed to step506. Otherwise, if the estimated back-EMF voltage VB(t) resulted despite an absence of a playback waveform being input to signal generator324, method500may proceed to step508.

At step506, responsive to the estimated back-EMF voltage VB(t) resulting from a playback waveform being input to signal generator324, braking subsystem310may generate braking signal xBRK(t) to minimize settling time of electromagnetic load301after completion of playback of the playback waveform to electromagnetic load301. After completion of step506, method500may proceed again to step502.

At step508, responsive to the estimated back-EMF voltage VB(t) resulting despite an absence of a playback waveform being input to signal generator324, braking subsystem310may determine a time rate of change of estimated back-EMF voltage VB(t), which may be proportional to an acceleration of a moving mass of electromagnetic load301. To illustrate, estimated velocity u(t) of electromagnetic load301may be determined from the relationship:
VB(t)=Bl·u(t)
where Bl is the magnetic force factor of the coil of electromagnetic load301. Because acceleration a(t) of a moving mass may be given by the mathematical derivative of its velocity with respect to time (e.g., a(t)=du(t)/dt), the mathematical derivative of estimated back-EMF voltage VB(t) with respect to time may be proportional to acceleration a(t) of a moving mass of electromagnetic load301. In some embodiments, braking subsystem310may implement a differentiator (e.g., a first-order high-pass circuit) to determine the mathematical derivative VB′(t) of estimated back-EMF voltage VB(t) with respect to time.

At step510, braking subsystem310may compare mathematical derivative VB′(t) to a pre-determined acceleration threshold amax. In some embodiments, mathematical derivative VB′(t) may be scaled by magnetic force factor Bl prior to being compared to pre-determined acceleration threshold amax. If mathematical derivative VB′(t) exceeds acceleration threshold amax, method500may proceed to step512. Otherwise, method500may proceed again to step502.

At512, responsive to mathematical derivative VB′(t) exceeding acceleration threshold amax, braking subsystem310may generate braking signal xBRK(t) to reduce or eliminate the undesired movement of electromagnetic load301. In some embodiments, braking subsystem310may generate braking signal xBRK(t) as a piecewise square signal as described above and depicted inFIG.4and in the '238 application.

AlthoughFIG.5discloses a particular number of steps to be taken with respect to method500, method500may be executed with greater or fewer steps than those depicted inFIG.5. In addition, althoughFIG.3discloses a certain order of steps to be taken with respect to method500, the steps comprising method500may be completed in any suitable order.

Method500may be implemented in whole or part using host device300A and/or any other system operable to implement method500. In certain embodiments, method500may be implemented partially or fully in software and/or firmware embodied in computer-readable media.

FIG.6illustrates selected components of another example host device300B incorporating force sensing using an electromagnetic load301of host device300B, in accordance with embodiments of the present disclosure. Host device300B may include, without limitation, a mobile device, home appliance, a vehicle, and/or any other system, device, or apparatus that includes a human-machine interface. In some embodiments, host device300B ofFIG.6may be similar in many respects to host device300A ofFIG.3. Accordingly, only certain differences between host device300B ofFIG.6and host device300A ofFIG.3may be described below.

As shown inFIG.6, rather than generating transducer waveform signal x(t) as was the case in host device300A, signal generator324in host device300B may generate a raw transducer waveform signal x′(t) which may be filtered by negative impedance filter326to generate transducer waveform signal x(t) for driving amplifier306. Negative impedance filter326may, when applied to raw transducer waveform signal x′(t), reduce an effective quality factor q of electromagnetic load301, which may in turn decrease ringing occurring after raw transducer driving signal x′(t) has ended or to reduce or eliminate movements of a moving mass of electromagnetic load301caused by motion induced upon host device300B.

In operation, rather than generating braking signal xBRK(t) as shown inFIG.3, braking system310in host device300B may generate a negative DC resistance signal Re_neg to partially or fully offset DC resistance Re of electromagnetic load301described above, thus effectively decreasing DC resistance Re and decreasing quality factor q of electromagnetic load301. Examples of implementing negative impedance filter326or using a negative impedance to decrease quality factor q of an electromagnetic load are described in U.S. patent application Ser. No. 16/369,556, filed Mar. 29, 2019, and titled “Driver Circuitry” as well as U.S. patent application Ser. No. 16/816,790, filed Mar. 12, 2020, and titled “Methods and Systems for Improving Transducer Dynamics,” both of which are incorporated by reference herein in their entireties.

As used herein, when two or more elements are referred to as “coupled” to one another, such term indicates that such two or more elements are in electronic communication or mechanical communication, as applicable, whether connected indirectly or directly, with or without intervening elements.

This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, or component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. Accordingly, modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, the components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components and the methods described may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. As used in this document, “each” refers to each member of a set or each member of a subset of a set.

Although exemplary embodiments are illustrated in the figures and described below, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and described above.

Unless otherwise specifically noted, articles depicted in the drawings are not necessarily drawn to scale.

All examples and conditional language recited herein are intended for pedagogical objects to aid the reader in understanding the disclosure and the concepts contributed by the inventor to furthering the art, and are construed as being without limitation to such specifically recited examples and conditions. Although embodiments of the present disclosure have been described in detail, it should be understood that various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the disclosure.

Although specific advantages have been enumerated above, various embodiments may include some, none, or all of the enumerated advantages. Additionally, other technical advantages may become readily apparent to one of ordinary skill in the art after review of the foregoing figures and description.

To aid the Patent Office and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims or claim elements to invoke 35 U.S.C. § 112(f) unless the words “means for” or “step for” are explicitly used in the particular claim.