MINIMIZING TRANSIENT ARTIFACT OF POSITION ESTIMATE IN INDUCTIVELY-SENSED ELECTROMAGNETIC ACTUATOR SYSTEM WITH SHARED INDUCTIVE SENSOR

Abstract

A system may include an electromagnetic actuator, a first coil configured to drive mechanical displacement of the electromagnetic actuator, a second coil configured to drive mechanical displacement of the electromagnetic actuator, and an inductance sensing subsystem having an inductance sensing path coupled to the first coil and the second coil. The inductance sensing subsystem may be configured to select one of the first coil and the second coil for driving mechanical displacement of the electromagnetic actuator, select the other of the first coil and the second coil as a sensing coil for sensing displacement of the electromagnetic actuator, determine a displacement of the electromagnetic actuator based on a measurement of estimated inductance of the sensing coil, and when switching selection of the sensing coil from the first coil to the second coil determine the displacement of the first coil based on a measured inductance of the first coil at approximately the time of switching selection, estimate state variables of the inductance sensing path to be used with the second coil based on the displacement, and apply the state variables to the inductance sensing path after switching selection of the sensing coil from the first coil to the second coil.

Claims

1. A system comprising: an electromagnetic actuator; a first coil configured to drive mechanical displacement of the electromagnetic actuator; a second coil configured to drive mechanical displacement of the electromagnetic actuator; and an impedance sensing subsystem having an impedance sensing path coupled to the first coil and the second coil and configured to: select one of the first coil and the second coil for driving mechanical displacement of the electromagnetic actuator; select the other of the first coil and the second coil as a sensing coil for sensing displacement of the electromagnetic actuator; determine a displacement of the electromagnetic actuator based on a measurement of estimated impedance of the sensing coil; and when switching selection of the sensing coil from the first coil to the second coil: determine the displacement of the first coil based on a measured impedance of the first coil at approximately the time of switching selection; estimate state variables of the impedance sensing path to be used with the second coil based on the displacement; and apply the state variables to the impedance sensing path after switching selection of the sensing coil from the first coil to the second coil.

2. The system of claim 1, the impedance sensing subsystem further configured to, during a period when the electromagnetic actuator is at rest: measure impedance of each of the first coil and the second coil at a position of rest; detect a difference in impedance between the first coil and the second coil at the position of rest; and calibrate determination of the displacement of the electromagnetic actuator based on the difference.

3. The system of claim 1, the impedance sensing subsystem further configured to duty cycle between: selection of the first coil and the second coil as an actuating coil for driving mechanical displacement of the electromagnetic actuator; and selection of the first coil and the second coil as the sensing coil for sensing displacement of the electromagnetic actuator.

4. The system of claim 1, the impedance sensing subsystem further configured to calibrate the first coil and the second coil by: driving a direct current to one of the first coil and the second coil in order to displace the electromagnetic actuator to a displacement from a position of rest; sensing a first impedance of the first coil and a second impedance of the second coil; determining an impedance versus displacement function for each of the first coil and the second coil; and mapping the displacement function of the first coil to the displacement function of the second coil.

5. A method comprising: selecting one of a first coil and a second coil for driving mechanical displacement of an electromagnetic actuator, wherein the first coil is configured to drive mechanical displacement of the electromagnetic actuator and the second coil is configured to drive mechanical displacement of the electromagnetic actuator; selecting the other of the first coil and the second coil as a sensing coil for sensing displacement of the electromagnetic actuator; determining a displacement of the electromagnetic actuator based on a measurement of estimated impedance of the sensing coil; and when switching selection of the sensing coil from the first coil to the second coil: determining the displacement of the first coil based on a measured impedance of the first coil at approximately the time of switching selection; estimating state variables of the impedance sensing path to be used with the second coil based on the displacement; and applying the state variables to the impedance sensing path after switching selection of the sensing coil from the first coil to the second coil.

6. The method of claim 5, further comprising, during a period when the electromagnetic actuator is at rest: measuring impedance of each of the first coil and the second coil at a position of rest; detecting a difference in impedance between the first coil and the second coil at the position of rest; and calibrating determination of the displacement of the electromagnetic actuator based on the difference.

7. The method of claim 5, further comprising duty cycling between: selection of the first coil and the second coil as an actuating coil for driving mechanical displacement of the electromagnetic actuator; and selection of the first coil and the second coil as the sensing coil for sensing displacement of the electromagnetic actuator.

8. The method of claim 5, further comprising calibrating the first coil and the second coil by: driving a direct current to one of the first coil and the second coil in order to displace the electromagnetic actuator to a displacement from a position of rest; sensing a first impedance of the first coil and a second impedance of the second coil; determining an impedance versus displacement function for each of the first coil and the second coil; and mapping the displacement function of the first coil to the displacement function of the second coil.

9. A processing subsystem comprising: a first output configured to drive a first coil configured to drive mechanical displacement of an electromagnetic actuator; a second output configured to drive a second coil configured to drive mechanical displacement of the electromagnetic actuator; and an impedance sensing subsystem coupled to the first coil and the second coil and configured to: select one of the first coil and the second coil for driving mechanical displacement of the electromagnetic actuator; select the other of the first coil and the second coil as a sensing coil for sensing displacement of the electromagnetic actuator; determine a displacement of the electromagnetic actuator based on a measurement of estimated impedance of the sensing coil; and when switching selection of the sensing coil from the first coil to the second coil: determine the displacement of the first coil based on a measured impedance of the first coil at approximately the time of switching selection; estimate state variables of the impedance sensing path to be used with the second coil based on the displacement; and apply the state variables to the impedance sensing path after switching selection of the sensing coil from the first coil to the second coil.

10. The processing subsystem of claim 19 the impedance sensing subsystem further configured to, during a period when the electromagnetic actuator is at rest: measure impedance of each of the first coil and the second coil at a position of rest; detect a difference in impedance between the first coil and the second coil at the position of rest; and calibrate determination of the displacement of the electromagnetic actuator based on the difference.

11. The processing subsystem of claim 9, the impedance sensing subsystem further configured to duty cycle between: selection of the first coil and the second coil as an actuating coil for driving mechanical displacement of the electromagnetic actuator; and selection of the first coil and the second coil as the sensing coil for sensing displacement of the electromagnetic actuator.

12. The processing subsystem of claim 9, the impedance sensing subsystem further configured to calibrate the first coil and the second coil by: driving a direct current to one of the first coil and the second coil in order to displace the electromagnetic actuator to a displacement from a position of rest; sensing a first impedance of the first coil and a second impedance of the second coil; determining an impedance versus displacement function for each of the first coil and the second coil; and mapping the displacement function of the first coil to the displacement function of the second coil.

13. The processing system of claim 9, wherein the estimated impedance is an estimated inductance.

14. The system of claim 1, wherein the estimated impedance is an estimated inductance.

15. The method of claim 5, wherein the estimated impedance is an estimated inductance.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:

[0019] FIG. 1 illustrates an example of a vibro-haptic system in a device, as is known in the art;

[0020] FIG. 2 illustrates an example of a Linear Resonant Actuator (LRA) modelled as a linear system, as is known in the art;

[0021] FIG. 3 illustrates selected components of an example host device, in accordance with embodiments of the present disclosure; and

[0022] FIG. 4 illustrates selected components of an example inductance measurement subsystem, in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] To accurately sense displacement of an electromagnetic load, methods and systems of the present disclosure may determine an inductance of the electromagnetic load, and then convert the inductance to a position signal, as described in greater detail below. Further, to measure inductance of an electromagnetic load, methods and systems of the present disclosure may utilize either a phase measurement approach and/or a high-frequency pilot-tone driven approach, as also described in greater detail below.

[0028] To illustrate, an electromagnetic load may be driven by a driving signal V(t) to generate a sensed terminal voltage V.sub.T(t) across a coil of the electromagnetic load. Sensed terminal voltage V.sub.T(t) may be given by:

V.sub.T(t)=Z.sub.COILI(t)+V.sub.B(t)

wherein I(t) is a sensed current through the electromagnetic load, Z.sub.COIL, is an impedance of the electromagnetic load, and V.sub.B(t) is the back-electromotive force (back-EMF) associated with the electromagnetic load.

[0029] As used herein, to “drive” an electromagnetic load means to generate and communicate a driving signal to the electromagnetic load to cause displacement of a movable mass of the electromagnetic load. Further, to “drive” an electromagnetic load may also mean driving of a pilot signal or other test signal to the electromagnetic load from which electrical parameters of the electromagnetic load may be measured.

[0030] Because back-EMF voltage V.sub.B(t) may be proportional to velocity of the moving mass of the electromagnetic load, back-EMF voltage V.sub.B(t) may in turn provide an estimate of such velocity. Thus, velocity of the moving mass may be recovered from sensed terminal voltage V.sub.T(t) and sensed current I(t) provided that either: (a) sensed current I(t) is equal to zero, in which case V.sub.B=V.sub.T; or (b) coil impedance Z.sub.COIL is known or is accurately estimated.

[0031] Position of the moving mass may be related to a coil inductance L.sub.COIL, of the electromagnetic load. At high frequencies significantly above the bandwidth of the electromagnetic load, back-EMF voltage V.sub.B(t) may become negligible and inductance may dominate the coil impedance Z.sub.COIL Sensed terminal voltage V.sub.T@HF(t) at high frequencies may be estimated by:

V.sub.T@HF(t)=Z.sub.COILI.sub.@HF(t)

An inductance component of coil impedance Z.sub.COIL, may be indicative of a position or a displacement of the moving mass of the electromagnetic load. To illustrate, such inductance may be a nominal value when the moving mass is at rest. When the mass moves, the magnetic field strength may be modulated by the position of the mass which leads to a small alternating-current (AC) modulation signal of the inductance that is a function of the mass position.

[0032] Hence, at high frequencies, the position of the moving mass of the electromagnetic load may be recovered from sensed terminal voltage V.sub.T(t) and sensed current I(t) by: (a) estimating the coil impedance at high frequency as Z.sub.COIL@HF≅R.sub.@HF+L.sub.@HF.Math.s, where R.sub.@HF is the resistive part of the coil impedance at high frequency, L.sub.@HF is the coil inductance at high frequency, and s is the Laplace transform; and (b) converting the measured inductance to a position signal. Velocity and/or position may be used to control vibration of the moving mass of the electromagnetic load.

[0033] FIG. 3 illustrates selected components of an example host device 300 having an electromagnetic actuator 304. Host device 300 may include, without limitation, a mobile device, home application, vehicle, and/or any other system, device, or apparatus that includes a human-machine interface. Electromagnetic actuator 304 may include any suitable load with a complex impedance, including without limitation a haptic transducer, a loudspeaker, a microspeaker, a voice-coil actuator, a solenoid, or other suitable transducer.

[0034] In operation, a signal generator 324 of a processing subsystem 305 of host device 300 may generate a raw transducer driving signal x′ (t) (which, in some embodiments, may be a waveform signal, such as a haptic waveform signal or audio signal). Raw transducer driving signal x′ (t) may be generated based on a desired playback waveform received by signal generator 324.

[0035] Raw transducer driving signal x′ (t) may be received by waveform preprocessor 326 which may modify raw transducer driving signal x′(t) based on parameters received from inductance measurement subsystem 308 and/or based on any other factor in order to generate processed transducer driving signals x.sub.1(t) and x.sub.2(t). For example, such modification may include control of processed transducer driving signals x.sub.1(t) and x.sub.2(t) in order to prevent overexcursion of electromagnetic actuator 304 that could lead to damage.

[0036] Processed transducer driving signal x.sub.1(t) may in turn be amplified by amplifier 306a to generate a driving signal V.sub.1(t) for driving electromagnetic load 301a. Similarly, processed transducer driving signal x.sub.2(t) may in turn be amplified by amplifier 306b to generate a driving signal V.sub.2(t) for driving electromagnetic load 301b. Accordingly, host device 300 may operate such that electromagnetic actuator 304 is alternatingly driven by driving signal V.sub.1(t) and driving signal V.sub.2(t). Accordingly, host device 300 may operate in a series of alternating phases: a first phase in which driving signal V.sub.1(t) driven to electromagnetic load 301a drives electromagnetic actuator 304 and electromagnetic load 301b is used to measure a displacement of electromagnetic actuator 304, and a second phase in which driving signal V.sub.2(t) driven to electromagnetic load 301b drives electromagnetic actuator 304 and electromagnetic load 301a is used to measure a displacement of electromagnetic actuator 304.

[0037] A sensed terminal voltage V.sub.T1(t) of electromagnetic load 301a may be sensed by inductance measurement subsystem 308 (e.g., using a volt-meter). Similarly, sensed current I.sub.1(t) through electromagnetic load 301a may be sensed by inductance measurement subsystem 308. For example, current I.sub.1(t) may be sensed by a sense voltage V.sub.S1(t) across a shunt resistor 302a having resistance R.sub.s coupled to a terminal of electromagnetic load 301a.

[0038] Likewise, a sensed terminal voltage V.sub.T2(t) of electromagnetic load 301b may be sensed by inductance measurement subsystem 308 (e.g., using a volt-meter). Similarly, sensed current I.sub.2(t) through electromagnetic load 301b may be sensed by inductance measurement subsystem 308. For example, current I.sub.2(t) may be sensed by a sense voltage V.sub.S2(t) across a shunt resistor 302b having resistance R.sub.s coupled to a terminal of electromagnetic load 301b.

[0039] As shown in FIG. 3, and as described in greater detail below, processing subsystem 305 may include an inductance measurement subsystem 308 that may estimate respective coil inductances L.sub.COIL of electromagnetic loads 301a and 301b. From such estimated coil inductance L.sub.COIL, inductance measurement subsystem 308 may determine a displacement associated with electromagnetic load 304. Based on such determined displacement, inductance measurement subsystem 308 may communicate one or more parameters to waveform preprocessor 326 (including, without limitation, the value of such displacement), which may cause waveform preprocessor 326 to modify raw transducer driving signal x′(t). In some embodiments, such displacement may also be indicative of a human interaction (e.g., applied force) to electromagnetic actuator 304.

[0040] In operation, to estimate impedance Z.sub.COIL, inductance measurement subsystem 308 may measure impedance in any suitable manner, including without limitation using the approaches set forth in U.S. patent application Ser. No. 17/497,110 filed Oct. 8, 2021, which is incorporated in its entirety by reference herein.

[0041] As a particular example, in order to estimate coil impedance Z.sub.COIL waveform preprocessor 326 may generate a processed transducer driving signal x.sub.1(t) or x.sub.2(t) (depending on which electromagnetic coil 301 is the actuating coil used to drive movement of electromagnetic load 304 and which electromagnetic coil 301 is used for sensing) comprising a high-frequency stimulus for driving the sensing coil. Such high-frequency stimulus may be a tone or a carrier signal (e.g., pulse-width modulation carrier for an amplifier 306). In response, inductance measurement system 308 may measure inductance of the sensing coil.

[0042] FIG. 4 illustrates selected components of an example inductance measurement subsystem 308, in accordance with embodiments of the present disclosure. As shown in FIG. 4, sensed terminal voltage V.sub.T1(t) of electromagnetic load 301a may be converted to a digital representation by an analog-to-digital converter (ADC) 403a. Similarly, sensed voltage V.sub.S1(t), indicative of current I.sub.1(t), may be converted to a digital representation by an ADC 404a. Likewise, sensed terminal voltage V.sub.T2(t) of electromagnetic load 301b may converted to a digital representation by an ADC 403b and sensed voltage V.sub.S2(t), indicative of current I.sub.2(t), may be converted to a digital representation by an ADC 404b.

[0043] As further shown in FIG. 4, the digital representations of sensed terminal voltage V.sub.T1(t) and sensed terminal voltage V.sub.T2(t) may be received by a multiplexer 406, which may select one of such digital representations based on a control signal SENSE_SELECT. Control signal SENSE_SELECT may indicate whether host device 300 is in a first phase (e.g., electromagnetic load 301a is used to drive electromagnetic actuator 304 and electromagnetic load 301b is used for measurement) or a second phase (e.g., electromagnetic load 301b is used to drive electromagnetic actuator 304 and electromagnetic load 301a is used for measurement). Accordingly, multiplexer 406 may select the digital representation of the sensed terminal voltage of the electromagnetic load actively being used to perform sensing. In some embodiments, multiplexer 406 may periodically duty cycle selection between electromagnetic load 301a and electromagnetic load 301b.

[0044] Similarly, the digital representations of sensed voltage V.sub.S1(t) and sensed voltage V.sub.S2(t) may be received by a multiplexer 408, which may select one of such digital representations based on a control signal SENSE_SELECT. Accordingly, multiplexer 408 will select the digital representation of the current through the electromagnetic load actively being used to perform sensing.

[0045] Although FIG. 4 contemplates duty-cycles selection between processing sensed voltage V.sub.S1(t) and sensed voltage V.sub.S2(t) and between processing sensed terminal voltage V.sub.T1(t) and sensed terminal voltage V.sub.T2(t), in some embodiments, inductance measurement subsystem 308 may perform parallel estimates of inductance based on sensed voltage V.sub.S1(t), sensed voltage V.sub.S2(t), sensed terminal voltage V.sub.T1(t), and sensed terminal voltage V.sub.T2(t).

[0046] Based on the selected measured current and voltage signals, an inductance estimator 410 may estimate inductance L of the electromagnetic load actively being used to perform sensing. For example, inductance estimator 410 may calculate inductance based on magnitudes of the selected measured current and voltage signals and/or a phase difference between the selected measured current and voltage signals. As mentioned above, inductance estimator 410 may estimate impedance in any suitable manner, including without limitation using the approaches set forth in U.S. patent application Ser. No. 17/497,110. Based on the estimated inductance L, a displacement estimator 412 may estimate a displacement D of electromagnetic actuator 304.

[0047] In operation, inductance measurement subsystem 308 may experience transient effects when switching between the electromagnetic loads actively being used to perform sensing, as indicated by a change of control signal SENSE_SELECT. Such transient effects may occur due to path delays present in inductance estimator 410, including one or more filters (e.g., low-pass filters) used within inductance estimator 410 to smooth and/or otherwise condition estimation of inductance L. To illustrate, at the beginning of a phase, immediately after control signal SENSE_SELECT changes, the valid displacement information may be delayed from the start of the phase until the one or more filters of inductance estimator 410 have fully settled. This may create a dead-zone in which no displacement information is valid around the phase boundaries. For example, when the electromagnetic load actively being used to perform sensing switches from electromagnetic load 301a to electromagnetic load 301b, the sensed inductance value may abruptly change which may cause filtering artifacts, in turn leading to distorted position estimation. Such delay may lead to latency between an event that triggers an actuation and the start of the actuation period. In some applications, such as where electromagnetic transducer 304 is a haptic actuator, it may be critical that latency be minimized to ensure the actuator response is perceived as a mechanical button response to a human interaction.

[0048] To reduce or eliminate such challenges, reverse inductance estimator 414 may be configured to receive the estimated displacement D from displacement estimator 412 and based thereon, calculate expected state variables (e.g., filter coefficients) associated with the sensing-inactive electromagnetic load (e.g., the electromagnetic load other than the electromagnetic load actively being used to perform sensing). Thus, displacement information estimated from the electromagnetic load actively being used to perform sensing prior to switching between phases may be used to estimate expected values of state variables of the inductance estimator 410 if the inactive load were hypothetically actively sensing. Accordingly, in response to switching of control signal SENSE_SELECT, inductance estimator 410 may update its state variables based on estimations from reverse inductance estimator 414, to reflect the then-current displacement estimate. Further, to reduce lag between a haptic or other triggering event and start of actuation, state variables of inductance estimator 410 may be updated to reflect the correct displacement estimate.

[0049] When actuation of electromagnetic actuator 304 is first triggered (e.g., from rest), the expected state variables may be preset based on an estimate of inductance of the electromagnetic load actively being used to perform sensing following such triggering assuming a displacement D at which electromagnetic actuator 304 is in its resting position.

[0050] Such update of state variables may serve to reduce or eliminate transient effects caused by differences between impedances of electromagnetic coil 301a and electromagnetic coil 301b. Accordingly, such differences in impedances may need to be calibrated with one another, to ensure the estimation performed by reverse inductance estimator 414 remains accurate and precise. In some embodiments, a calibration procedure may involve driving a high frequency sensing tone on both coils and estimating the high frequency inductance value on both coils simultaneously while also driving a direct current on one of the coils to displace the moving mass of electromagnetic coil 301 into a fixed displacement. An inductance versus displacement function of each electromagnetic coil 301 may then be inferred such that an impedance L.sub.1(x) of electromagnetic coil 301a may be mapped to an impedance L.sub.2(x) of electromagnetic coil 301b for a given displacement x of the moving mass away from its rest position.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] Unless otherwise specifically noted, articles depicted in the drawings are not necessarily drawn to scale.

[0055] 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.

[0056] 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.

[0057] 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.