JP2016530740

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DESCRIPTION JP2016530740
A plurality of control points (10) are defined such that each has a known spatial relationship
relative to the array of transducers. An amplitude is assigned to each control point (12). The
generation of a modeled sound field having an assigned amplitude with a specific phase at the
control point at each of the control points results in the amplitude and (14) resulting from the
modeled sound field at the other control points A matrix (16) is generated that contains elements
indicating the effect on phase. The eigenvectors (18) of the matrix are determined as each
indicates a set of phase and relative amplitude of the modeled sound field at the control point.
Select one of the sets (20) and one or more of the transducers so that the phase and amplitude of
the resulting sound field at the control point matches the phase and relative amplitude of the
selected set (22, 24) The transducer array is operated to output an acoustic wave each having an
initial amplitude and phase. [Selected figure] Figure 2
Method and apparatus for generating a sound field
[0001]
It is known to use the continuous distribution of acoustic energy referred to herein as the "sound
field" in applications involving haptic feedback.
[0002]
It is known to control the sound field by defining one or more control points in a space in which
the sound field may exist.
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Each control point is assigned an amplitude value equal to the desired amplitude of the sound
field at the control point. The transducers are then controlled to create a sound field that exhibits
the desired amplitude at each of the control points.
[0003]
However, known systems for generating sound fields using control points are limited when using
a large number of control points.
[0004]
In accordance with a first aspect of the present invention, there is provided a method of
generating a sound field using an array of transducers having known relative position and
orientation.
The method comprises:-defining a plurality of control points each having a known spatial
relationship relative to the array of transducers;-assigning an amplitude to each control pointcontrolling at each of the control points Contains elements that show the effect of the modeled
sound field with assigned amplitude with a specific phase at the point on the resulting amplitude
and phase of the modeled sound field at other control points Calculating a matrix; determining
the eigenvectors of the matrix, each of its eigenvectors representing a set of phase and relative
amplitudes of the modeled sound field at the control point; selecting one of the set Initial phase
and amplitude of one or more of the transducers so that the phase and amplitude of the resulting
sound field at the control point match the phase and relative amplitude of the selected set. It
includes operate the transducer array so as to output an acoustic wave having phases are each a.
[0005]
Therefore, the first aspect of the present invention involves formulating an eigenvalue problem in
which the effective phase at the control point can be detected by solving. We use the eigenvalue
problem in embodiments of the present invention to obtain a faster and more predictable
solution time compared to known methods, which in turn replaces a larger number of control
points. We have found that it means that we can support and real-time updating of control points
is possible. Faster and more predictable solution times also mean that a larger volume of sound
field can be controlled compared to known methods.
03-05-2019
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[0006]
Control points are markers at specific locations. The distance between adjacent control points
should be sufficient to allow sound waves in the sound field according to the phase shift from
one control point to the next control point. In some embodiments, the separation distance may be
equal to the wavelength of the sound waves in the sound field.
[0007]
In embodiments of the present invention, the transducer array comprises one or more
transducers in any suitable configuration, such as one or more two-dimensional arrays arranged
in parallel.
[0008]
A modeled sound field with assigned amplitude and specific phase at the control point can be
modeled as being generated by a virtual transducer located directly below the control point.
In some embodiments, the virtual transducers may be located in the plane of the actual
transducer array. However, one skilled in the art can model the sound field as being generated by
other arrangements of virtual transducers, ie it can be positioned directly below the control point
or have different spatial relationships to the control point It will be appreciated that one or more
virtual transducers, which may have a, can produce a modeled sound field. The use of virtual
transducers allows pre-computing lookup tables. Preferably, the virtual transducers match
multiple transducers of the transducer array.
[0009]
The method can include the step of calculating the eigenvalues of the matrix. The eigenvalues
represent some of them relatively high relative to one another, and some of them relatively low
scaling factors. The method can include selecting, as the selected set, a set of phase and relative
amplitude with relatively high corresponding eigenvalues. Preferably, the method may include
selecting, as the selected set, the set of phase and relative amplitude with the largest
03-05-2019
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corresponding eigenvalue.
[0010]
The eigenvalues define how much the corresponding eigenvectors scale when transformed by the
matrix. In other words, the eigenvalues are the relative amplitudes of the sound field at the
control point, given the indirect contribution to the amplitude at each control point caused by
generating the assigned amplitudes at the other control points. Shows how much scale up is
done. Thus, detection of large eigenvalues implies a corresponding set of relative amplitude and
phase using a large amount of constructive interference. The selection of a set of relative
amplitude and phase with relatively high corresponding eigenvalues taking into account the
relative values of all the eigenvalues of the matrix is therefore relative because the power output
by the transducer is used more efficiently Have advantages over the selection of very low
eigenvalues.
[0011]
The method uses a look-up function to determine how spatially the amplitude and phase of the
acoustic wave change spatially due to attenuation and propagation, generating the assigned
amplitude at one of the control points Calculating the effect on the amplitude and phase at each
of the control points of The look-up function can take into account either or both of two causes
for the amplitude and phase change to occur. First, the attenuation of the amplitude of the
acoustic wave output by the transducer, which increases with the distance from the transducer,
and secondly, the change in phase that occurs when the acoustic wave propagates in space.
[0012]
When using such a look-up function, spatial variations in the acoustic wave phase due to
attenuation and propagation need only be calculated once for a particular transducer array,
thereby modeling the sound field. The time required to calculate the initial amplitude and phase
of the transducer producing the phase and amplitude of the resulting sound field is reduced.
[0013]
The method can include a regularization step to capture an error in the initial amplitude and
phase output by the transducer.
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[0014]
The advantage of including the regularization step is that the output efficiency of the array can
be improved by increasing their average amplitude to make more of the transducers have higher
amplitude.
For example, to avoid the situation where one transducer operates at 100% and all others at
0.1%, instead of raising the average amplitude of the transducers to eg 80%, how many in the
regularization step Capture some errors.
[0015]
The regularization method may be a weighted Tikhonov regularization.
The advantage of using weighted Tikhonov regularization is that it has an easily defined matrix
growth.
[0016]
The power output by the transducer array can be scaled so that the transducer that outputs the
maximum value of the initial amplitude operates at substantially full power. The scaling of the
power output in this way has the advantage, as a result, to make the power output of the
transducer array as high as possible in a predetermined set of initial amplitudes, while
maintaining the level of the initial amplitudes relative to one another.
[0017]
The transducer may be an ultrasound transducer.
[0018]
The use of an ultrasonic transducer can operate the transducer array so that the user perceives
the acoustic radiation force generated by the sound field, or, for example, in the manufacturing
03-05-2019
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industry for drying the adhesive in the product on the production line Produces advantages in
the field of tactile feedback such as
[0019]
The acoustic wave can be tuned to a frequency between 0 Hz and half the carrier frequency.
In some embodiments, the carrier frequency is 40 kHz.
In some embodiments, the acoustic wave can be adjusted to a frequency of 0.1 Hz to 500 Hz, and
sometimes 200 Hz to 300 Hz.
[0020]
The adjustment of acoustic waves to frequencies of 0.1 Hz to 500 Hz has the advantage of
increasing the suitability of the method used in haptic feedback applications as the tactile
receptors on the skin are most sensitive to changes in skin deformation at these frequencies
Produce
[0021]
The locations of the control points can be chosen to define a portion of a virtual threedimensional shape that occupies volume in the sound field.
For example, the control point may be located adjacent to the end of the shape or the end of the
shape or may be located within the volume of the shape. The control points can define the whole
of the shape, more preferably a part of the shape. For example, the control points may define the
shape perceived by the user as part of a haptic feedback system that may need to define only a
portion of the shape that the user is touching. Alternatively, this shape may be in the form of a
product having a point of interest that can focus the acoustic radiation force in manufacturing
applications such as adhesive drying.
[0022]
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The control points may be divided into a first group of control points in which the sound field has
a relatively high amplitude and a second group of control points in which the sound field has a
relatively low amplitude compared to the high amplitude. Can. The ends of the virtual shape can
be defined by the first group of control points. The control points in the second group can be
adjacent to the control points of the first group such that a gradient in the amplitude of the
sound field is generated at the end of the virtual shape. In some embodiments, the control points
of the first group may be spaced from the adjacent control points from the second group by at
least half the wavelength of the sound waves in the sound field.
[0023]
Providing a group of control points where the sound field has a relatively high amplitude and a
group of control points where the sound field has a relatively low amplitude so as to provide a
gradient in the amplitude of the sound field at the end of the virtual shape It offers the advantage
in haptic feedback applications that it renders the edges of virtual shapes that are more easily
detected by the user to create more detectable differences in the amplitude of the sound field.
Also, in the case of haptic feedback, the relatively low amplitude control points can ensure that
the part of the user's hand not touching the shape does not perceive residual ultrasound
surrounding the shape. If low amplitude control points are not present, there may be some
constructive regions that the hand can perceive, as the ultrasound at those points is not
controlled.
[0024]
At least some of the control points can be located at points where the object intersects the virtual
shape. At least some of the control points can be positioned adjacent to the intersection point.
[0025]
Positioning a control point at a point in the area where an object, such as the user's hand,
intersects the virtual shape, only needs to control the sound field at the point on the virtual shape
touched by the object, at these control points It offers the advantage of being able to generate
higher amplitudes. The points at which objects intersect virtual shapes can be observed in real
03-05-2019
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time by object tracking, and control points can be located at different points in the sound field
depending on the object position.
[0026]
In some embodiments, the low amplitude control point may be supported by the high amplitude
control point to define a pocket that can hold the object at the low amplitude control point.
[0027]
The number of control points may be at least 10, preferably at least 50.
The upper limit of the number of control points can be managed according to how large a matrix
linear algebra algorithm can be processed.
[0028]
With a larger number of control points, the generated sound field can have more points whose
amplitude can be controlled. This feature can, for example, define more complex threedimensional or two-dimensional virtual shapes, or, if only a portion of the virtual shapes is
defined, representing more detail about that portion of the shape it can.
[0029]
The method can include a method of generating haptic feedback, a method of levitating a small
object, a method of manufacturing, or a method for nondestructive inspection.
[0030]
According to a second aspect of the present invention there is provided an apparatus for
generating a sound field comprising an array of transducers having known relative position and
orientation, and a data processor.
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The data processor comprises: a specific phase at a control point at each of a plurality of control
points, each having a known spatial relationship relative to the array of transducers, each having
an amplitude assigned to them Calculate a matrix containing elements that indicate the influence
of the generation of the modeled sound field with assigned amplitude on the amplitude and
phase resulting from the modeled sound field at other control points, Select one of the sets, each
with an initial amplitude and phase on one or more of the transducers, such that the phase and
amplitude of the resulting sound field at the control point match the phase and relative
amplitude of the selected control set A set of phase and relative amplitudes of the modeled sound
field at the control point so that the transducer array can be operated to output an acoustic wave
with It represents each is configured to determine the eigenvectors of the matrix.
[0031]
Therefore, the device according to the second aspect is configured to formulate an eigenvalue
problem which can be detected to detect the effective phase at the control point. We find that
using the eigenvalue problem in embodiments of the present invention results in faster and more
predictable solution times compared to known devices, which in turn replaces a larger number of
control points. I found that I could support it, and I could do real-time updating of many control
points. The required data processor may be less efficient than if, for example, the data processor
is configured to perform an iterative method to detect valid phases at control points. Faster and
more predictable solution times also mean that a larger volume of sound field can be controlled
compared to known methods.
[0032]
The device can be designed to determine the eigenvalues of the matrix. The eigenvalues are such
that some of them represent relatively high and some represent relatively low scaling factors,
and as a selected set, the set of phases and relative amplitudes with relatively high corresponding
eigenvalues It is selected.
[0033]
The eigenvalues define how much the corresponding eigenvectors scale when transformed by the
matrix. In other words, the eigenvalues are the relative amplitudes of the sound field at the
control point, given the indirect contribution to the amplitude at each control point caused by
03-05-2019
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generating the assigned amplitudes at the other control points. Shows how much scale up is
done. Thus, detection of large eigenvalues implies a corresponding set of relative amplitude and
phase using a large amount of constructive interference. A device designed to pick a set of
relative amplitudes and phases with relatively high corresponding eigenvalues, taking into
account the relative values of all the eigenvalues of the matrix, therefore makes the power output
by the transducer more efficient And have advantages over devices that can pick relatively low
eigenvalues.
[0034]
The data processor can be designed to perform a regularization step that incorporates errors in
the initial amplitude and phase output by the transducer.
[0035]
An advantage of performing the regularization step is that the output efficiency of the array can
be improved by increasing their average amplitude to make more of the transducers have higher
amplitude.
For example, to avoid the situation where one transducer operates at 100% and all others at
0.1%, instead of raising the average amplitude of the transducers to eg 80%, how many in the
regularization step Capture some errors.
[0036]
The regularization step may be a weighted Tikhonov regularization. The advantage of using
weighted Tikhonov regularization is that it has an easily defined matrix growth.
[0037]
The device can be designed to adjust the acoustic wave to a frequency between 0 Hz and half the
carrier frequency. In some embodiments, the carrier frequency is 40 kHz. In some embodiments,
the acoustic wave can be adjusted to a frequency of 0.1 Hz to 500 Hz, and sometimes 200 Hz to
300 Hz.
03-05-2019
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[0038]
The adjustment of acoustic waves to frequencies of 0.1 Hz to 500 Hz has the advantage of
increasing the adaptability of devices used in tactile feedback applications, as the tactile
receptors on the skin are most sensitive to changes in skin deformation at these frequencies.
Produce
[0039]
The device comprises object tracking and can be configured to define control points based on
where the object intersects with the modeled shape.
[0040]
The use of object tracking, such as hand tracking, offers the advantage that the position of the
control point can be updated in real time, for example, depending on the position of the user's
hand which may be moving.
[0041]
According to a third aspect of the present invention there is provided a data processor
configured to perform the method of the first aspect of the present invention.
[0042]
The data processor according to the third aspect provides faster and more predictable solution
time, which means that it can support a larger number of control points in turn, and real time
control points by the data processor Update is possible.
Furthermore, the data processor required to perform the method of the first aspect of the present
invention may be of lower performance than if the data processor were configured to perform
the iterative method.
Faster and more predictable solution times also mean that a larger volume of sound field can be
controlled compared to known methods.
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[0043]
Embodiments of the invention will now be described, by way of example only, with reference to
the accompanying drawings in which:
[0044]
3 is a flow chart schematically illustrating a method according to an embodiment of the present
invention.
1 is a schematic diagram showing an apparatus according to an embodiment of the present
invention.
Fig. 5 is a flow chart schematically illustrating a method according to a further embodiment of
the present invention.
Fig. 5 is a schematic view showing an apparatus according to a further embodiment of the
present invention.
[0045]
FIG. 1 shows a flow chart schematically illustrating a method of generating a sound field
according to a first embodiment of the present invention.
[0046]
The method begins at step 10 where a plurality of control points are defined.
A control point is a point located in the space through which the sound field can propagate, at
which the amplitude or phase of the sound field can be controlled. Control points are markers at
specific locations. The distance between adjacent control points should be sufficient to allow
sound waves in the sound field according to the phase shift from one control point to the next
control point. In some embodiments, the separation distance may be equal to the wavelength of
03-05-2019
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the sound waves in the sound field. For example, for a 40 kHz carrier the separation is 8.5 mm.
In some embodiments, the separation distance may be equal to half the wavelength of the sound
waves in the sound field. In some embodiments, the separation may be greater than the
wavelength of the sound waves in the sound field. One skilled in the art will recognize that other
suitable separation distances can be used.
[0047]
An array of transducers is arranged to generate a sound field. In embodiments of the present
invention, the transducer array comprises one or more transducers in any suitable configuration,
such as one or more two-dimensional arrays arranged in parallel.
[0048]
The position of the control point relative to the array of transducers is determined. The use of
control points to control the sound field is described in L.S. R. Gavrilov, 2008, Acoustical Physics
Volume 54, Issue 2, pp 269-278, Print ISSN 1063-7710 A study entitled "The possibility of
generating focal regions of complex configurations in applications to problems of stimulation of
human receptors structures by focused ultrasound" It is known from the paper.
[0049]
In the first embodiment, a sound field is generated in the air. However, in some embodiments, the
sound field can be generated on another medium, such as water, which sound waves can pass
through.
[0050]
In step 12, the control points are assigned an amplitude. The assigned amplitude represents the
target amplitude of the sound field at the control point, which forms the basis for modeling the
sound field. Control points are assigned by the user. However, in other embodiments, control
points can be assigned by automatic processing.
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[0051]
In step 14, the sound field at each control point is modeled. According to the first embodiment,
modeling of the sound field at the control point comprises modeling the sound field generated by
a virtual transducer located directly below the control point in the plane of the actual transducer
array The initial amplitude and phase of the virtual transducer are modeled such that the sound
field has an assigned amplitude at the control point. However, in some embodiments, alternative
methods of modeling the sound field can be used, for example, virtual transducers of different
arrangements. That is, the modeled sound field can be generated using one or more virtual
transducers that can be located directly below the control point or have different spatial
relationships to the control point. In a first embodiment, step 14 comprises modeling the sound
field separately at each control point.
[0052]
In step 16, the generation of the sound field modeled in step 14 is modeled at the other control
points, with the amplitude assigned in step 12 with a specific phase at the control point in each
of the control points A matrix is calculated that contains elements that indicate the resulting
effect of the sound field on amplitude and phase. In a first embodiment, the matrix calculated in
step 16 is an NxN matrix, where N is equal to the number of control points. However, other
suitable forms of matrix are apparent.
[0053]
In step 18, the eigenvectors of the matrix are determined. In a first embodiment, step 18
comprises determining the right eigenvectors of the matrix, each of which represents a set of
phase and relative amplitudes of the modeled sound field at the control points.
[0054]
At step 20, by selecting one of the eigenvectors determined at step 18, a set of relative phase and
amplitude is selected.
[0055]
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At step 22, initial phases and amplitudes output by the individual transducers of the array of
transducers are calculated.
Initial phases and amplitudes are calculated such that the individual transducers produce a
resulting sound field having a phase and amplitude that matches the selected set of phases and
relative amplitudes. In the embodiment of the present invention, the term "matching" means that
the phase and amplitude of the resulting sound field at the control point is selected, taking into
account any errors that may be captured as part of the regularization step. It can be used to
mean substantially equal to phase and relative amplitude. Hence, an algorithm according to an
embodiment of the present invention can calculate phase delays and amplitudes at transducers in
the array that produce a sound field that best matches the assigned amplitude of the control
point.
[0056]
At step 24, the plurality of transducers of the transducer array are operated such that the
transducer array outputs acoustic waves having the initial amplitude and phase calculated at step
22.
[0057]
In some embodiments, the transducer is operable to continue outputting one or more acoustic
waves.
In some embodiments, control points can be redefined and the method can be repeated at
different sets of control points.
[0058]
In some embodiments, the method can include calculating the eigenvalues of the matrix. The
eigenvalues represent some of them relatively high relative to one another, and some of them
relatively low scaling factors. In some embodiments, the method can include selecting, as the
selected set, a set of phases and relative amplitudes with relatively high corresponding
03-05-2019
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eigenvalues. In some embodiments, the method can include selecting, as the selected set, the set
of phase and relative amplitude with the largest corresponding eigenvalue.
[0059]
The eigenvalues define how much the corresponding eigenvectors scale when transformed by the
matrix. In other words, the eigenvalues are the relative amplitudes of the sound field at the
control point, given the indirect contribution to the amplitude at each control point caused by
generating the assigned amplitudes at the other control points. Shows how much scale up is
done. Thus, detection of large eigenvalues implies a corresponding set of relative amplitude and
phase using a large amount of constructive interference.
[0060]
The selection of a set of relative amplitude and phase with relatively high corresponding
eigenvalues, taking into account the relative values of all the eigenvalues of the matrix, is
relatively efficient as the power output by the transducer is used more efficiently It has the
advantage over low eigenvalue selection.
[0061]
In some embodiments, the method is assigned at one of the control points using a look-up
function that determines how spatially the acoustic wave's amplitude and phase change spatially
due to attenuation and propagation. Generating the amplitude can include calculating the effect
on the amplitude and phase at each of the other control points.
[0062]
In some embodiments using a look-up function, spatial variations in acoustic wave phase due to
attenuation and propagation need only be calculated once for a particular transducer array,
thereby modeling the sound field. The time required, and the time required to calculate the initial
amplitude and phase of the transducer that produces the phase and amplitude of the resulting
sound field, is reduced.
[0063]
In some embodiments, the method can include a regularization step that captures an error in the
initial amplitude and phase output by the transducer.
03-05-2019
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[0064]
The advantage of including the regularization step is that the output efficiency of the array can
be improved by increasing their average amplitude to make more of the transducers have higher
amplitude.
For example, to avoid the situation where one transducer operates at 100% and all others at
0.1%, instead of raising the average amplitude of the transducers to eg 80%, how many in the
regularization step Capture some errors.
[0065]
In some embodiments, the regularization method may be a weighted Tikhonov regularization.
The advantage of using weighted Tikhonov regularization is that it has an easily defined matrix
growth.
[0066]
In some embodiments, the power output by the transducer array can be scaled so that the
transducer that outputs the maximum value of the initial amplitude operates at substantially full
power.
The scaling of the power output in this way has the advantage, as a result, to make the power
output of the transducer array as high as possible in a predetermined set of initial amplitudes,
while maintaining the level of the initial amplitudes relative to one another.
[0067]
In some embodiments, the transducer may be an ultrasound transducer.
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[0068]
The use of an ultrasonic transducer can operate the transducer array so that the user perceives
the acoustic radiation force generated by the sound field, or, for example, in the manufacturing
industry for drying the adhesive in the product on the production line Produces advantages in
the field of tactile feedback such as
[0069]
In some embodiments, the acoustic wave can be tuned to a frequency between 0 Hz and half the
carrier frequency.
In some embodiments, the carrier frequency is 40 kHz.
In some embodiments, the acoustic wave can be adjusted to a frequency of 0.1 Hz to 500 Hz, and
sometimes 200 Hz to 300 Hz.
[0070]
The adjustment of acoustic waves to frequencies of 0.1 Hz to 500 Hz has the advantage of
increasing the suitability of the method used in haptic feedback applications as the tactile
receptors on the skin are most sensitive to changes in skin deformation at these frequencies
Produce
[0071]
In some embodiments, the locations of control points can be chosen to define a portion of a
virtual three-dimensional shape that occupies a volume in the sound field.
In some embodiments, the control points may be located adjacent to the end of the shape or the
end of the shape.
In some embodiments, the control points may be located within the volume of the shape. In some
embodiments, control points can define the entire shape. In some embodiments, control points
03-05-2019
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can define a portion of the shape. In some embodiments, the control points can define the shape
perceived by the user as part of a haptic feedback system that may need to define only a portion
of the shape that the user is touching. In some embodiments, this shape may be in the form of a
product having a point of interest that may focus the acoustic radiation force in manufacturing
applications such as adhesive drying.
[0072]
In some embodiments, the control points are a first group of control points where the sound field
has a relatively high amplitude, and a second group where the sound field has a relatively low
amplitude compared to the high amplitudes. And control points. The amplitude of the control
point may be between maximum and minimum values. For example, some control points may be
half the amplitude. Some applications may have a wide distribution of amplitudes over the full
range of control points, for example to vary the intensity of haptic feedback over a region.
[0073]
In some embodiments, the ends of the virtual shape may be defined by a first group of control
points. The control points in the second group can each be placed adjacent to the control points
of the first group such that a gradient in the amplitude of the sound field is generated at the end
of the virtual shape.
[0074]
Providing a group of control points where the sound field has a relatively high amplitude and a
group of control points where the sound field has a relatively low amplitude so as to provide a
gradient in the amplitude of the sound field at the end of the virtual shape It offers the advantage
in haptic feedback applications that it renders the edges of virtual shapes that are more easily
detected by the user to create more detectable differences in the amplitude of the sound field.
[0075]
At least some of the control points can be located at points where the object intersects the virtual
shape.
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At least some of the control points can be positioned adjacent to the intersection point.
[0076]
Positioning a control point within the area of the point where an object, such as the user's hand,
intersects the virtual shape, only needs to control the sound field at the point on the virtual shape
that the object is touching. It offers the advantage of being able to generate higher amplitudes.
The points at which objects intersect virtual shapes can be observed in real time by object
tracking, and control points can be located at different points in the sound field depending on the
object position.
[0077]
In some embodiments, the number of control points may be at least 10, preferably at least 50.
[0078]
With a larger number of control points, the generated sound field can have more points whose
amplitude can be controlled.
This feature can, for example, define a larger or more complex three-dimensional or twodimensional virtual shape, or, if only a portion of the virtual shape is defined, more detail about
that portion of the shape Can be represented.
[0079]
FIG. 2 shows an apparatus 26 according to an embodiment of the invention for generating a
sound field.
[0080]
Device 26 comprises an array 68 of transducers having known relative positions and
orientations.
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Array 68 may be a two-dimensional planar array, a regular array, or any other suitable set of
transducers with any suitable arrangement, 16 × 16. Any suitable number of transducers, such
as an array, can be provided. The array preferably comprises at least four transducers. Any
suitable type of acoustic transducer may be used, such as a muRata MA40S4S ultrasonic
transducer. The muRata MA40S4S transducer provides the advantage of producing a relatively
large amount of sound pressure (20 Pascals at a distance of 30 cm) and having relatively wideangle directivity (60 degrees).
[0081]
In the embodiment shown in FIG. 2, the acoustic wave output by the transducer has a frequency
of 40 kHz. The advantage of using acoustic waves of this frequency is that the acoustic waves of
this frequency maintain 90% of their energy even at a distance of 400 mm from the emission
plane of the air. A further advantage is that piezoelectric transducers emitting acoustic waves
having a frequency of 40 kHz are commercially available due to their use in parking sensors.
However, acoustic waves of any suitable frequency may be used. In the embodiment shown in
FIG. 2, all of the acoustic waves used to generate the sound field have the same frequency.
However, in some embodiments, acoustic waves of two or more different frequencies may be
used to generate the sound field.
[0082]
Transducers 68 are driven by driver boards 62, each of which includes a processor 64 and an
amplifier 66. Any suitable type of processor may be used, such as an XMOS Ll-128 processor
operating at 400 MHz. Data processor 64 has a synchronous clock and generates signals to be
sent to each transducer. This signal causes the transducer to output an acoustic wave having the
initial amplitude and phase necessary to generate the acoustic field. In the embodiment shown in
FIG. 2, the data processor outputs a square wave to each transducer. The amplifier 66 amplifies
the signal output by the data processor to a level suitable for driving the transducer. In the
embodiment shown in FIG. 2, the square wave signal is amplified by amplifier 66 from 5V peak
to peak to 15V.
[0083]
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In the embodiment shown in FIG. 2, the device further comprises a PC 74 which comprises a data
processor. The data processor has a specific phase at a control point at each of a plurality of
control points each having a known spatial relationship relative to the array of transducers and
each having an amplitude assigned to them. Configured to calculate a matrix containing elements
that indicate the impact of modeled acoustic field generation with assigned amplitudes on the
resulting amplitude and phase of modeled acoustic fields at other control points Be done. The
data processor is also configured to determine the eigenvectors of the matrix whose respective
eigenvectors represent the set of phase and relative amplitudes of the modeled sound field at the
control point. In some embodiments, the data processor can comprise one or more discrete data
processors. Any suitable type of data processor, such as a microcontroller or ASIC may be used in
embodiments of the present invention.
[0084]
In some embodiments, control points can be user defined. In some embodiments, control points
can be automatically determined in response to data collected by another piece of equipment,
such as hand tracking. In some embodiments, the control point amplitudes can be assigned by
the user. In some embodiments, the amplitudes of control points can be assigned by automatic
processing.
[0085]
In some embodiments, the data processor configured to calculate the matrix may be part of PC
74. In some embodiments, the data processor configured to calculate the matrix selects one of
the set of phase and relative amplitude, and the phase and amplitude of the resulting sound field
at the control point is selected There may be stand alone units that can be further configured to
operate the transducer array to cause one or more of the transducers to output an acoustic wave
each having an initial amplitude and phase to match the phase and relative amplitude of the set.
[0086]
In the embodiment shown in FIG. 2, data processed by the PC 74 is sent to the driver board 62
via the Ethernet controller 76. The Ethernet controller comprises an Ethernet interface and a
processor. The Ethernet controller 76 classifies the received data and transfers it to the
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processor 64 of the driver board 62. However, other protocols may be used, such as, for
example, Thunderbolt, USB, Firewire.
[0087]
In some embodiments, the data processor can be designed to determine the eigenvalues of the
matrix. The eigenvalues are such that some of them represent relatively high and some represent
relatively low scaling factors, and as a selected set, the set of phases and relative amplitudes with
relatively high corresponding eigenvalues It is selected. In some embodiments, the device can be
designed to select the eigenvector with the largest corresponding eigenvalue.
[0088]
The eigenvalues define how much the corresponding eigenvectors scale when transformed by the
matrix. In other words, the eigenvalues are the relative amplitudes of the sound field at the
control point, given the indirect contribution to the amplitude at each control point caused by
generating the assigned amplitudes at the other control points. Shows how much scale up is
done. Thus, detection of large eigenvalues implies a corresponding set of relative amplitude and
phase using a large amount of constructive interference. A device designed to pick a set of
relative amplitudes and phases with relatively high corresponding eigenvalues, taking into
account the relative values of all the eigenvalues of the matrix, therefore makes the power output
by the transducer more efficient And have advantages over devices that can pick relatively low
eigenvalues.
[0089]
Any suitable method of calculating the eigenvectors and eigenvalues of a matrix can be used. For
example, the CGEEV routine of the MAGMA GPU linear algebra library can be used. Any suitable
method of calculating the initial amplitude and phase to generate the sound field can be used. For
example, the CGELS LAPACK routine of the MAGMA GPU linear algebra library can be used.
[0090]
In some embodiments, the device can be designed to perform a regularization step that captures
an error in the initial amplitude and phase output by the transducer.
03-05-2019
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[0091]
An advantage of performing the regularization step is that the output efficiency of the array can
be improved by increasing their average amplitude to make more of the transducers have higher
amplitude.
For example, to avoid the situation where one transducer operates at 100% and all others at
0.1%, instead of raising the average amplitude of the transducers to eg 80%, how many in the
regularization step Capture some errors. In the embodiment shown in FIG. 2, the regularization
step is performed by the PC 74.
[0092]
In some embodiments, the regularization step may be a weighted Tikhonov regularization. The
advantage of using weighted Tikhonov regularization is that it has an easily defined matrix
growth.
[0093]
In some embodiments, the device can be designed to adjust the acoustic wave to a frequency
between 0 Hz and half the carrier frequency. In some embodiments, the carrier frequency is 40
kHz. In some embodiments, the acoustic wave can be adjusted to a frequency of 0.1 Hz to 500
Hz, and sometimes 200 Hz to 300 Hz.
[0094]
The adjustment of acoustic waves to frequencies of 0.1 Hz to 500 Hz has the advantage of
increasing the adaptability of devices used in tactile feedback applications, as the tactile
receptors on the skin are most sensitive to changes in skin deformation at these frequencies.
Produce
[0095]
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The device comprises object tracking and can be configured to define control points based on
where the object intersects with the modeled shape.
[0096]
FIG. 3 shows a flow chart that schematically illustrates a method for haptic feedback applications
in accordance with an embodiment of the present invention.
[0097]
In step 30, a look-up function is calculated which determines how spatially the amplitude and
phase of the acoustic wave change due to attenuation and propagation.
The look-up function of the embodiment of the present invention shown in FIG. 3 takes into
account two causes for amplitude and phase changes to occur.
First, the attenuation of the amplitude of the acoustic wave output by the transducer, which
increases with the distance from the transducer, and secondly, the change in phase that occurs
when the acoustic wave propagates in space.
[0098]
In step 32, a three-dimensional virtual shape is defined within the volume occupied by the sound
field.
The three-dimensional shape may be determined by the user or may be determined by an
automatic process.
[0099]
At step 34, the position of the hand within the volume occupied by the sound field is tracked.
Hand tracking can be performed by known hand tracking, such as the Leap Motion (RTM)
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Controller produced by Leap Motion Inc, with a 100 cm range and a 140 degree viewing angle.
In the embodiment shown in FIG. 3, tracking data is recorded at 60 fps. However, in some
embodiments, tracking data can be recorded at other speeds. Step 34 additionally includes
determining the position of any point at which the hand intersects the virtual shape.
[0100]
At step 36, control points are defined. In the embodiment shown in FIG. 3, the locations of
control points are chosen to define at least a portion of the three-dimensional virtual shape. For
example, the control points may be located at the end of the virtual three-dimensional shape, or
may be located on or adjacent to it. Control points are defined at portions of the virtual threedimensional shape where the hands meet.
[0101]
In some embodiments, step 32 may be excluded and control points may be defined according to
the dimensions of the user's hand. In embodiments that exclude step 32, for example, in
applications such as conveying Braille to the user's hand, control points may be located on the
fingertip or palm of the user's hand.
[0102]
In the embodiment shown in FIG. 3, the control points are divided into two groups. The first
group of control points is located at the end of the virtual three-dimensional shape, and the
second group of control points, for example, creates a bounding box around the hand and then
includes the control points in the immediate vicinity By expanding it slightly, it is positioned
adjacent to the first group of control points outside the volume occupied by the threedimensional shape. In the embodiment shown in FIG. 3, the three-dimensional shape is defined
by control points located at the end of the shape. However, in some embodiments, the threedimensional shape may additionally or alternatively be defined by having control points located
within the volume of the shape.
[0103]
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At step 38, an amplitude is assigned to the control point. The first group of control points is
assigned a relatively high amplitude and the second group of control points is assigned a
relatively low amplitude to create a gradient at the end of the three dimensional virtual shape.
[0104]
At step 40, the sound field at each control point is modeled. Modeling of the sound field at the
control point includes modeling the sound field generated by a virtual transducer located directly
below the control point in the plane of the actual transducer array, the modeled sound field at
the control point The initial amplitude and phase of the virtual transducer are modeled to have
an assigned amplitude. This calculation is performed using the look-up function calculated in
step 30. Step 40 thus involves modeling the sound field separately at each control point.
[0105]
In step 42, the generation of the sound field modeled in step 40 is modeled in the other control
points, with the amplitude assigned in step 38 having a specific phase at the control point in each
of the control points A matrix is calculated that contains elements that indicate the resulting
effect of the sound field on amplitude and phase. In the embodiment shown in FIG. 3, the matrix
calculated in step 42 is an NxN matrix, where N is equal to the number of control points.
However, other suitable forms of matrix are apparent.
[0106]
At step 44, the eigenvectors of the matrix are determined. In the embodiment shown in FIG. 3,
step 44 comprises determining the right eigenvectors of the matrix whose respective
eigenvectors represent the set of phase and relative amplitudes of the modeled sound field at the
control points.
[0107]
The embodiment shown in FIG. 3 additionally includes a step 46 which comprises determining
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the eigenvalues of the matrix. In some embodiments, the determination of eigenvectors and
eigenvalues of a matrix can include a single step in the method.
[0108]
At step 48, a set of relative phase and amplitude is selected. In the embodiment shown in FIG. 3,
a set of relative phase and amplitude is selected by selecting eigenvectors with relatively high
corresponding eigenvalues, taking into account the relative values of all the eigenvalues of the
matrix. Preferably, the eigenvector with the largest corresponding eigenvalue is selected.
[0109]
In step 50, the initial phase and amplitude output by each transducer of the array of transducers
is calculated such that the phase and amplitude of the resulting sound field at the control point
matches the phase and relative amplitude of the selected set . In the embodiment shown in FIG.
3, the calculation of step 50 is performed using the look-up table previously calculated in step
30. In the embodiment shown in FIG. 3, the array of transducers comprises 64 transducers
positioned in a single plane. However, in alternative embodiments, different numbers and
arrangements of transducers can be used to form the transducer array.
[0110]
In step 52, a regularization step is performed to ensure that the acoustic waves output by the
transducer do not exceed the power limitations of the transducer. The regularization step is
output by the transducer such that the transducer does not exceed the array power limit and the
total power available to the array is used more efficiently than if the method did not perform the
regularization step Weighted Tikhonov regularization to introduce errors into the initial
amplitude and phase.
[0111]
In step 52, the gain for normalizing the power output of the array is also captured, and by
capturing this gain, the transducer is operated at substantially full power at the maximum
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calculated initial amplitude, and relative in amplitude Increases the power output by the other
transducers in the array so as not to change the value. The value of the relative amplitude can be
changed slightly during step 52 due to the errors introduced during the regularization step.
Thus, the initial amplitude and phase used in step 54 are adjusted values of the initial amplitude
and phase in step 50, and any adjustments to the initial amplitude and phase values given in step
52 are taken into account. It is a thing.
[0112]
At step 54, the plurality of transducers of the transducer array are operated such that the
transducer array outputs one or more acoustic waves having the adjusted initial amplitude and
phase calculated at step 52. In the embodiment shown in FIG. 3, the transducer array is an
ultrasonic transducer array, which outputs an acoustic wave tuned to a frequency of 200 Hz to
300 Hz.
[0113]
FIG. 4 illustrates an apparatus 60 arranged to perform the method described with reference to
FIG. Parts of this device that are equivalent to parts of the device shown in FIG. 2 are numbered
with like reference numerals.
[0114]
The device 60 comprises an array 68 of transducers, a driver board 62 with a data processor 64
and an amplifier 66, a PC 75 and an Ethernet controller 76.
[0115]
The apparatus further comprises a hand tracker 70.
The hand tracking 70 may be, for example, a Leap Motion (RTM) Controller. The hand tracking
70 is set to detect the position of the user's hand 72 in the sound field.
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[0116]
In the embodiment shown in FIG. 4, the PC 74 receives data measured by hand tracking,
processes the hand tracking data, and sets the processing data to be sent to the driver board 62
via the Ethernet controller 76. Be done.
[0117]
A three-dimensional virtual shape 78 is defined in the space where the sound field can be
generated.
The hand tracker 70 is set to detect when the hand 72 is touching the virtual shape 78. Next, in
accordance with the method of the embodiment shown in FIG. 3, the transducer array 68
operates to generate a sound field having a relatively high amplitude at the intersection 80, 82
between the hand 72 and the virtual shape 78.
[0118]
In the embodiment shown in FIG. 4, the transducer array 68 is an ultrasound transducer array,
and the individual transducers are configured to output ultrasound waves tuned to a frequency
of 200 Hz to 300 Hz.
[0119]
The use of object tracking, such as hand tracking, offers the advantage that the position of the
control point can be updated in real time, for example, depending on the position of the user's
hand which may be moving.
[0120]
Embodiments of the present invention provide faster and more predictable control point
resolution times compared to known methods, meaning that they can in turn support a larger
number of control points and control It enables real-time updates of points.
Faster and more predictable solution times also mean that a larger volume of sound field can be
controlled compared to known methods.
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[0121]
As will be clear from the example described with reference to FIG. 3, embodiments of the present
invention can be used to provide haptic feedback.
The use of the term "tactile feedback" in embodiments of the present invention means providing
tactile sensation as feedback. Haptic feedback has many uses. One example of a possible
application of haptic feedback is to provide feedback in a system that can be controlled by a
gesture, such as a computer, mobile device or interface for operating the control in a car. Another
application of haptic feedback is virtual reality simulation, such as medical simulation that can be
used to train games or surgery. Another application of haptic feedback is three-dimensional CAD,
which allows the user to work on aerial three-dimensional modeling that exploits haptic
feedback. Haptic feedback can also be used to cue blind people, such as the generation of Braille
that is conveyed to the user's hand. Another application of haptic feedback is to provide feedback
to indicate that a touchless button has been pressed. Touchless buttons may have applications,
such as in public interfaces such as ATMs, for security and hygiene reasons. A further potential
application of haptic feedback is research that can use haptic feedback to indicate microscopic
objects and microscopic planes so that the user can perceive objects studied on a microscopic
scale.
[0122]
Embodiments of the invention can be used to levitate objects. For example, it may be
advantageous to be able to experiment with the drug sample without touching it to avoid
contamination. If the transducer operates continuously without change, the resulting acoustic
wave has a generally constant shape. Therefore, small objects can be held in the pocket defined
by the low amplitude control points that are horizontally surrounded and vertically located above
the high amplitude control points. A plurality of such pockets can be defined. Control points can
be dynamically reassigned to move small objects independently in three-dimensional space.
Another application that uses the sound field for levitation is data visualization, in which many
small objects can be levitated in three-dimensional space to show a large data set so that the data
can be viewed from all angles There is. An advantage of the present invention over known
systems for levitation of small objects is that it does not require a reflector surface. In some
embodiments, the thickness of the object may be less than one wavelength of sound waves in the
sound field, and the width of the object may be greater than one wavelength.
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[0123]
Embodiments of the present invention can be used in the manufacturing industry. For example,
an algorithm can be used to create a target air flow that can be a target in a specific area of a
production line to dry the surface quickly, and to speed up manufacturing time.
[0124]
Embodiments of the present invention can be applied to nondestructive testing.
[0125]
While the present invention has been described above with reference to one or more preferred
embodiments, various changes or modifications can be made without departing from the scope of
the invention as defined in the appended claims. Is recognized.
The word "comprising" may mean "comprising" or "consisting of", and thus does not exclude the
presence of elements or steps other than those listed in any claim or claim generally. The mere
fact that certain measures are recited in mutually different dependent claims does not indicate
that a combination of these measures can not be used to advantage.
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