Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS AND METHOD FOR DETECTING UNBALANCED
LOADS IN A WASHING MACHINE
BACKGROUND OF THE INVENTION
The subject matter disclosed herein relates to appliances such as washing
machines, and more particularly to detecting unbalanced loads and the like.
Washing machines typically employ a "spin" cycle to extract water from
clothing. The washer basket rotates at a relatively high speed during such
"spin" cycle. If the wet clothes are not distributed in a uniform manner, that
is,
if the load of wet clothes is out of balance, undesirable vibration will
occur.
BRIEF DESCRIPTION OF THE INVENTION
As described herein, the exemplary embodiments of the present invention
overcome one or more disadvantages known in the art.
One aspect of the present invention relates to a method comprising the steps
of: accelerating a clothes basket rotating about an axis, the clothes basket
containing a load of clothing; as the clothes basket passes a first
predetermined rotational speed, limiting one of power and torque applied to
the clothes basket to a level less than a maximum available level of one of
power and torque; determining whether the clothes basket reaches a second
predetermined rotational speed within a predetermined time; and, responsive
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to the clothes basket not reaching the second predetermined rotational speed
within the predetermined time, determining that an out-of-balance condition
exists as to the load of clothing. The second predetermined rotational speed
is greater than the first predetermined rotational speed. No resonance of the
machine lies between the first and second predetermined rotational speeds.
Another aspect relates to a method comprising the steps of: accelerating a
clothes basket rotating about an axis to a first predetermined rotational
speed,
the clothes basket containing a load of clothing; determining whether the
clothes basket reaches a second predetermined rotational speed within a
predetermined time from reaching the first predetermined rotational speed;
and, responsive to the clothes basket not reaching the second predetermined
rotational speed within the predetermined time from reaching the first
predetermined rotational speed, determining that an out-of-balance condition
exists as to the load of clothing. The second predetermined rotational speed
is greater than the first predetermined rotational speed. A resonance of the
machine lies between the first and second predetermined rotational speeds.
Yet another aspect relates to an apparatus comprising: a clothes basket
rotatable about an axis; a motor coupled to the clothes basket; a sensor
configured to determine a rotational speed indicative of a rotational speed of
the clothes basket; and a processor coupled to the motor and the sensor. The
processor is operative to carry out one or more of the aforementioned
methods.
These and other aspects and advantages of the present invention will become
apparent from the following detailed description considered in conjunction
with
the accompanying drawings. It is to be understood, however, that the
drawings are designed solely for purposes of illustration and not as a
definition of the limits of the invention, for which reference should be made
to
the appended claims. Moreover, the drawings are not necessarily drawn to
scale and, unless otherwise indicated, they are merely intended to
conceptually illustrate the structures and procedures described herein.
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BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a block diagram of an exemplary system, in accordance with a non-
limiting exemplary embodiment of the invention;
FIG. 2 is a flow chart of an exemplary method, in accordance with a non-
limiting exemplary embodiment of the invention;
FIG. 3 is an exemplary graph of speed versus time, in accordance with a non-
limiting exemplary embodiment of the invention;
FIG. 4 depicts non-limiting exemplary test data;
FIG. 5 is a pictorial view of an exemplary top-loading washing machine;
FIG. 6 is a cross-sectional side elevation of an exemplary top-loading washing
machine similar to that depicted in FIG. 5;
FIG. 7 is a semi-schematic rear elevation of an exemplary front-loading
washing machine; and
FIG. 8 is a semi-schematic cross-sectional side elevation taken along line
VIII-
VIII of FIG. 7.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE
INVENTION
One or more embodiments of the invention provide a method and/or
apparatus to detect and prevent unbalanced washer loads from spinning
beyond a desirable spin speed. In at least some instances, this is achieved
by limiting the available motor torque (or power) during the spin ramp-up
between a predetermined range of angular velocities; by way of example and
not limitation 150-210 RPM (basket speed). If the
load is sufficiently
balanced, the loaded basket will accelerate through this region successfully
within a given amount of time. If the loaded basket is unbalanced, there will
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be insufficient torque (or power) to accelerate the unbalanced load beyond the
predetermined angular velocity range and the loaded basket will "stall" (not
accelerate past the range). If the load is determined to have stalled or is
taking an excessive amount of time to pass through the angular velocity
range, the load is considered unbalanced and corrective action is taken. The
corrective action may be, by way of example and not limitation, reduction of
spin speed, clothes redistribution, or any other action deemed appropriate.
Thus, in one or more embodiments, torque or power is limited for a particular
speed range and the amount of time it takes to accelerate through the speed
range is measured. If the basket takes too long to accelerate through the
predetermined speed range, then the load is considered to be unbalanced.
This technique may be implemented for multiple speed ranges and may also
be repeated multiple times.
It should be noted that the skilled artisan will be familiar with the well-
known
formula relating power and torque, namely power = torque times angular
velocity. Thus, a specification of a given torque limit in a certain RPM range
is
in essence also a specification of a certain power, and vice versa.
Reference should now be had to block diagram 100 of FIG. 1. AC line voltage
is supplied to inverter hardware 102. The AC is converted to DC in block 104
using a rectifier or the like. Relatively high voltage DC is provided to a DC
power bus and then to inverter 106 to provide 3-phase AC to 3-phase motor
108. Relatively low voltage DC is provided to microprocessor 116 which can
include a suitable timer (not separately numbered). Motor 108 is coupled to
basket 112 for receiving clothes to be washed, with a suitable drive 110.
While in theory there could be a direct coupling, in practice, a suitable
reduction arrangement is preferably employed, such as a pulley and belt
arrangement, gearing, or the like, wherein basket 112 turns at a lower RPM
than motor 108. In a specific non-limiting example, the reduction is about
13.2
such that the RPM of basket 112 must be multiplied by 13.2 to obtain the
motor shaft speed. Unless otherwise noted, the RPM values given herein are
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for the basket 112. A suitable sensor 114 is employed to provide feedback
regarding the basket RPM value (or motor RPM value, since the relationship
between the two is known based on the reduction of drive 110) to
microprocessor 116. Microprocessor 116 is programmed, for example, with
suitable software or firmware, to implement one or more techniques as
described herein. In other embodiments, an ASIC or other arrangement could
be employed.
The skilled artisan will be familiar with conventional washer systems and
given
the teachings herein will be enabled to make and use one or more
embodiments of the invention; for example, by programming a microprocessor
116 with suitable software or firmware.
In a non-limiting embodiment, microprocessor 116 senses the RPM value
from speed sensor 114 and limits the amount of torque (or power) in a
predetermined RPM range, say, between 150 ¨ 210 RPM, to prevent
significantly out-of-balance (00B) loads from making it through the
predetermined RPM range. Accordingly, the task of controlling the power
and/or torque is carried out via the microprocessor 116 (through the power
stage inverter 106). The skilled artisan will appreciate that in order to
accelerate through the predetermined range, an 00B load requires more
torque (or power) than is allowed by the torque (or power) limit, and thus by
limiting the motor torque to a level sufficient to accelerate a balanced load
through the predetermined angular velocity range, but less than that required
to accelerate an 00B load through the RPM range within a predetermined
amount of time, the motor 108 will not satisfactorily accelerate through the
predetermined RPM range.
Additionally, the microprocessor 116 (controlled by suitable software or
firmware) analyzes the amount of time that the motor 108 takes to pass
through the RPM range (e.g., using a suitable timer, not separately
numbered). If the load takes longer than the allowed time threshold, it is
considered to be 00B.
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In a preferred approach, the predetermined RPM range is between the first
and second resonant frequencies of the machine (the first resonant frequency
might be, for example, Res1 = -80 RPM, and the second resonant frequency
might be, for example, Res2 = -278 RPM). Accordingly, it should be known if
the load is 00B before reaching the second resonant frequency.
As used herein, a clothes washer refers to a system with a rotating clothes
container. The axis of rotation of the clothes container may be vertical
(e.g.,
top load), substantially horizontal (e.g., front load), or may even have an
intermediate value. Typically, the system will include washing and spinning
cycles, but one or more embodiments are applicable to systems with only a
spin cycle; e.g., an extraction machine. As noted, the rotational speed
(angular velocity) of the basket (clothes container) 112 and/or the motor 108
is
a significant parameter. It may be specified in RPM, radians per second, and
so on. In a power (or torque) limiting region, the applied motor power (or
torque) is limited to less than the maximum available power (or torque) at a
given speed. A speed range refers to rotational velocity of either the motor
output shaft or the clothes container for detecting an out of balance load.
Again, an out of balance (00B) load is an unbalanced load that results in an
undesirable machine response such as vibration or noise. As will be
explained in greater detail below with respect to FIG. 3, in some instances,
an
00B load is detected before rotational velocity reaches a system resonant
frequency (e.g., before the second resonance). In other instances, an 00B
load is detected at a system resonant frequency (e.g., at or near the second
resonance). In still other instances, combinations of the preceding two
aspects may be employed during the same wash cycle.
FIG. 5 shows an exemplary top-loading washing machine 10 including a
control panel or portion 44 and a loading door 11. Machine 10 is a non-
limiting example of a machine with which one or more aspects of the invention
may be implemented.
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FIG. 6 shows a cross-sectional side elevation of an exemplary top-loading
washing machine 10 similar to that depicted in FIG. 5. Clothes are loaded
through door 11 into clothes-receiving opening 25. The machine has an
external cabinet 20. A structure 22 is suspended with springs (not separately
numbered) and includes basket 112 and agitator 26 revolving about axis 28.
The basket 112 is driven by motor 108 via drive arrangement 110; in this
case, the latter includes a pulley mounted to motor drive shaft 36 connected
by belt 29 to a pulley mechanically linked to basket driveshaft 30 and spin
tube 32, which are concentric shafts. Driveshaft 30 is directly coupled to the
pulley and belt 29, and drives the agitator. Spin tube 32 is directly coupled
to
the basket 112. A clutch locks elements 30 and 32 together during spin.
Speed sensor 114 is provided on motor driveshaft 36. Motor 108 is controlled
by a control unit 103 which may include components such as 104, 106, and
116. As would be appreciated by one skilled in the art, FIG. 6 serves merely
as an example, and, as such, additional and/or separate embodiments can be
implemented in connection with the invention (such as, for example, the use
of an impeller, a direct drive motor, etc.). Additionally, one or more
embodiments of the invention can be implemented with additional types of
motors such as, a permanent magnet, a direct drive motor, or any motor
driven by an inverter.
FIG. 7 is a semi-schematic rear elevation of an exemplary front-loading
washing machine 10' and FIG. 8 is a semi-schematic cross-sectional side
elevation taken along line VIII-VIII of FIG. 7. Machine 10' is another non-
limiting example of a machine with which one or more aspects of the invention
may be implemented. Clothes are loaded through door 11'. The machine has
an external cabinet 20 and a control panel or portion 44. A structure 22 is
suspended with springs and dampers (not separately numbered) and may
include a basket and agitator revolving about axis 28. The basket is driven by
motor 108 via a drive arrangement; in this case, the latter includes a pulley
mounted to motor drive shaft 36 connected to a pulley mounted to basket
driveshaft 30 by belt 29. A speed sensor can be provided. Motor 108 is
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controlled by a control unit 103 which may include components such as 104,
106, and 116.
Refer now to flow chart 200 of FIG. 2. In block 202, motor 108 is
accelerating.
In decision block 204, determine if one of the predetermined speed ranges
has been entered. If not, exit in block 206. If so, as per the yes branch,
proceed to decision block 208 and determine whether the speed is less than
the range end (i.e., predetermined speed range has not yet been successfully
traversed); if not, as per the "no" branch, then the predetermined speed range
has been successfully traversed and the timer is stopped in block 210 and the
torque or power limit is removed in block 212, followed by exit as per block
206. On the
other hand, if so, as per the "yes" branch, then the
predetermined speed range has not yet been successfully traversed, so apply
the torque or power limit in block 214 and monitor the elapsed time in block
216 with the timer of microprocessor 116. If the time limit is exceeded, as
per
the yes branch of block 218, the load is unbalanced as in block 220 and
appropriate corrective action can be taken. If the time limit is not exceeded
during this pass through the routine, then exit as per block 206, and the
system can, in one or more embodiments of the invention, periodically re-
enter this routine at 202 and proceed through 204, 208, 214, 216 and 218,
until either the time limit is exceeded at 218, indicating an unbalanced load,
or
the speed exceeds the range end at 208 before the time limit is exceeded,
indicating that the predetermined speed range was successfully traversed.
With reference now to FIG. 3, basket RPM is plotted against time. The
particular machine of the illustrative embodiment exhibits a first resonance
near 80 RPM and a second resonance near 278 RPM. Solid line 302 shows
the desired basket RPM (that is, an example RPM curve that successfully
proceeds without failing either filter 1 or filter 2) as a function of time.
By way
of illustration, curve 302 includes plateaus to depict, by way of example,
speed control for water extraction (from the clothing) moments of a cycle.
Line/curve 304 represents a successful spin that proceeds without failing
either filter 1 or filter 2. Lines/curves 306 and 308 represent example RPM
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curves that proceed such that they do not successfully pass filter 1 and
filter 2,
respectively. In a first predetermined RPM range, from 150 to 210 RPM, a
first filter is employed, wherein a power (or torque) limit is imposed and
wherein the basket is expected to pass through the first predetermined RPM
range in no more than 25 seconds (between points T1 and T2). Here, the first
range is between the first and second resonant frequencies. Curves 304 and
308 pass this first test. Curve 306 stalls and fails. In a second
predetermined
RPM range, from 220 to 310 RPM, a second filter is applied. In this example,
no torque or power limit is applied, but the basket is expected to pass
through
the second predetermined range in no more than 10 seconds (between points
T3 and T4). Here, the second range brackets the second resonant frequency.
Curve 304 passes this second test. Curve 308 stalls and fails. The goal for
filter 1, which applies a power or torque limit, is to stop an unbalanced load
before it approaches a resonant (because once such a load reaches a
resonant, the imbalance become amplified and the machine can produce
significant vibration. With filter 2, if an unbalanced load were to reach a
resonant and stall there, the lack of a power/torque limit would enable the
machine to power the load through the resonant.
Thus, in one aspect, one or more embodiments of the invention provide a
clothes washer that incorporates a technique that identifies a highly out of
balance mass at a speed outside any resonant frequency, as shown with
respect to the first filter. This technique applies a predetermined power (or
torque) while accelerating through a predetermined speed range and
observes if the instantaneous speed reaches a predetermined level within a
predetermined time limit. In some
cases, the applied power is a
predetermined level; in other cases, the applied torque is a predetermined
level; in still other cases, the applied power and/or torque are non linear
(for
example, the curve of the applied power/torque can appear more like a curve
or a slope line (that is, it does not have to be flat)). The technique
described
with respect to Filter 1 can be repeated for multiple speed ranges and/or can
be repeated at the same speed range (power may be varied during these
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repetitions). In some cases, the technique may be repeated multiple times at
the same speed range with a varying time limit. By way of example, one or
more embodiments of the invention can include using, as a starting point, very
conservative power limits, and then if failures occurred, those power limits
would be weakened (that is, allow more power/torque) incrementally until it is
determined how much power/torque is required to send the a load through a
resonance band (which also may indicate what the out of balance mass is).
Accordingly, the goal and criterion used for defining a power/torque limit
includes preventing a severe vibration issue caused by an imbalance.
Furthermore, in another aspect, one or more embodiments of the invention
provide a clothes washer that incorporates a technique that identifies a high
out of balance mass at or near a resonant frequency. As described, for
example, with regard to Filter 2, this technique applies a predetermined power
or torque (which in general may or may not be limited) while accelerating
through a predetermined speed range that encompasses a resonant
frequency and observes if the instantaneous speed reaches a predetermined
level within a predetermined time limit. In some cases, the applied power is a
predetermined level; in other cases, the applied torque is a predetermined
level; in still other cases, the applied power and/or torque are non linear.
In
one or more embodiments of the invention, the criteria and/or design
considerations can include determining which loads will desirably be stopped
(that is, which loads should be allowed to spin up and which loads should not
be allowed to spin up). The technique described with respect to Filter 2 can
be repeated for multiple speed ranges and/or can be repeated at the same
speed range (power may be varied during these repetitions). In some cases,
the technique may be repeated multiple times at the same speed range with a
varying time limit.
Filter 2 advantageously provides an additional margin of safety in the event
an
unbalanced load makes it through Filter 1. The goal in one or more
embodiments is to attain, for loads that are not 00B, a spin speed beyond the
second resonance and beyond the second filter range.
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Again, in one aspect, torque (or power) is limited in a predetermined angular
velocity or RPM range, such as between 150 - 210 basket RPM, such that
balanced loads will pass through, but unbalanced loads will fail to pass
through. When ramping up in the spin cycle, the machine must pass through
the predetermined speed range. If the clothes load is unbalanced, the torque
or power applied by motor 108 will be insufficient to accelerate through this
predetermined speed region within the allowed amount of time and the motor
control 103 will stop accelerating the motor 108. The microprocessor 116 (for
example, under the influence of suitable firmware or software) will also
monitor the time (using, e.g., the timer not separately numbered) it takes for
the load to get through the predetermined speed range. If the allowed time is
exceeded, the load is considered unbalanced and corrective action will be
taken. This aspect advantageously catches the case where an unbalanced
load may eventually make it through the predetermined speed range if given
enough time.
One advantage that may be realized in the practice of some embodiments of
the described systems and techniques is prevention of undesirable noise or
vibration, and excessive wear to the machine caused by spinning unbalanced
loads. Another advantage that may be realized in the practice of some
embodiments of the described systems and techniques is ease of
implementation in vertical axis washing machines that currently do not prevent
spinning unbalanced loads (can also be used with machines having other
orientations of the axis). Still another advantage that may be realized in the
practice of some embodiments of the described systems and techniques is
that there is no need to employ a position detector to detect the position of
an
eccentric (out of balance) load. Yet another advantage that may be realized
in the practice of some embodiments of the described systems and
techniques is that there is no need to look at DC bus current ripple. A still
further advantage that may be realized in the practice of some embodiments
of the described systems and techniques is that there is no need to detect the
unbalance using mechanical devices such as accelerometers, magnets, and
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the like. An even further advantage that may be realized in the practice of
some embodiments of the described systems and techniques is that there is
no need to detect the unbalance using various motor feedback signals such
as current, speed, torque, etc. to look for ripple or other variations that
correlate to unbalanced loads.
Thus, one or more embodiments limit torque (or power) to "filter" out
unbalanced loads during ramp-up, taking advantage of the fact that as the
load becomes more unbalanced, it requires more torque (or power) to
accelerate (for example, since power that would otherwise accelerate the
basket instead is absorbed in the mechanical vibrations of the springs and
other components of system).
One or more embodiments can be implemented in the software or firmware
that controls microprocessor 116 and drives the motor 108 for the washing
machine.
FIG. 4 presents non-limiting exemplary results wherein it was sought to
accelerate the machine to 350 RPM. The first column is the mass of the
distributed load, the second column is the height of the distributed load, as
measured from the bottom of the basket, the third column is the height of the
00B load as measured from the bottom of the basket, and the fourth column
is the mass of the 00B load. In the non-limiting exemplary experiment, the
time measurement portion of the above-described technique was not
implemented in software, so the experimental machine was manually stopped
whenever the load leveled off in the torque limiting region (due to high 00B).
The exemplary technique successfully stopped all severe 00B loads from
spinning up beyond 210 RPM. See the last column ("GO" means successfully
passed through test region; "NO GO" means stopped due to 00B). The GO/
NO GO determinations facilitate in defining parameter boundaries. That is,
certain load weights (balanced and 00B) at certain heights are determined to
be acceptable (that is, those loads can be spun to the resonant or higher
speeds, based on the vibrations). Also, the height of a load can affect the
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status of a load as balanced or 00B, as, for example, the higher a load is in
the machine the more an out-of-balance is magnified.
In a non-limiting example, with respect to the specific power limit that is
used
for the first 00B (out-of-balance) filter from 150-210 RPM, the average power
that could be delivered over this speed range, in the particular experimental
set-up, was 313 W. When implementing the 00B detection filter, the power
was limited to an average value of 50 W. Thus, with a maximum deliverable
power of around 313 W, the power was deliberately limited in the
predetermined range to approximately 16% of the maximum deliverable
power, (50/313)*100 = 16 %.
In one or more embodiments, when employing power or torque limiting, the
power or torque should be limited to a values slightly above that which would
normally be required by a properly balanced load to pass through the
predetermined range. The skilled artisan will appreciate that undesirable
vibrations due to an 00B condition are typically particularly severe at or
near
a resonant frequency, and so the filter range is selected to detect out of
balance conditions before reaching resonant frequency.
Given the discussion thus far, it will be appreciated that, in general terms,
an
exemplary method, according to one aspect of the invention, includes the step
of accelerating a clothes basket 112 of a machine such as 10 or 10'. The
clothes basket rotates about an axis 28. The clothes basket contains a load
of clothing. An additional step includes, as the clothes basket passes a first
predetermined rotational speed (e.g., at Ti), limiting power or torque applied
to the clothes basket, as at 214 (for example, limiting power or torque to a
level less than a maximum available level of one of power and torque). A
further step includes determining whether the clothes basket reaches a
second predetermined rotational speed within a predetermined time (e.g., by
T2) from passing the first rotational speed, as per step 218. A still further
step
includes, responsive to the clothes basket not reaching the second
predetermined rotational speed within the predetermined time (e.g., "YES"
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branch of block 220), determining that an out-of-balance condition exists as
to
the load of clothing. The second predetermined rotational speed is greater
than the first predetermined rotational speed, and no resonance of the
machine lies between the first and second predetermined rotational speeds.
Furthermore, in the event that the clothes basket does reach the second
predetermined rotational speed within the predetermined time, it can be
determined that the out-of-balance condition does not exist as to the load of
clothing, and the limiting of power or torque applied to the clothes basket
can
cease, as per the "NO" branch of block 218. "Ceasing" in this context may
include removing the power or torque limit or changing the power or torque
limit to a different value.
In one or more instances, if no stall occurs (i.e., the clothes basket reaches
the second predetermined rotational speed within the predetermined time) in
the just-mentioned filter, additional steps include again accelerating the
clothes basket, to a third predetermined rotational speed; determining whether
the clothes basket reaches a fourth predetermined rotational speed within a
predetermined time from reaching the third predetermined rotational speed;
and responsive to the clothes basket not reaching the fourth predetermined
rotational speed within the predetermined time from reaching the third
predetermined rotational speed, determining that the out-of-balance condition
exists as to the load of clothing. The fourth predetermined rotational speed
is
greater than the third predetermined rotational speed, and a resonance of the
machine does lie between the third and fourth predetermined rotational
speeds. See, e.g., curve 308.
In some cases, additional filtering could be carried out in another range that
does not include a resonance. For example, responsive to the clothes basket
reaching the second predetermined rotational speed within the predetermined
time, in such cases, additional steps could include again accelerating the
clothes basket, to a third predetermined rotational speed; and as the clothes
basket passes the third predetermined rotational speed, limiting one of power
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and torque applied to the clothes basket. Furthermore, steps 216 and 218
could again be carried out to determine whether the clothes basket reaches a
fourth predetermined rotational speed within a predetermined time from
reaching the third predetermined rotational speed. If such is not the case, as
per block 220, it is determined that the out-of-balance condition exists as to
the load of clothing. The fourth predetermined rotational speed is greater
than
the third predetermined rotational speed, the third predetermined rotational
speed is greater than the second predetermined rotational speed, and as
noted, no resonance of the machine lies between the third and fourth
predetermined rotational speeds.
In some cases, if a stall occurs, the same range can be repeated again.
Thus, in some cases, responsive to the clothes basket not reaching the
second predetermined rotational speed within the predetermined time, again
accelerate the clothes basket, to the first predetermined rotational speed;
and
as the clothes basket again passes the first predetermined rotational speed,
again limit power or torque applied to the clothes basket. Again, determine
whether the clothes basket reaches the second predetermined rotational
speed within another predetermined time from reaching the first
predetermined rotational speed. Note that the applied power or torque might
be the same or different than the first time. Furthermore, the time limit
might
be the same or different than the first time. If the clothes basket does not
reach the second predetermined rotational speed within the (same or
different) predetermined time from reaching the first predetermined rotational
speed, determine that the out-of-balance condition exists as to the load of
clothing.
This type of repetition at the same RPM range could also be done deliberately
for calibration purposes. For example, start with a very short time limit that
almost any load might fail, and gradually lengthen the allowed time (or vice-
versa). Similarly, start with a low torque or power that almost any load might
fail, and gradually increase the torque or power (or vice-versa). By way of
example, if the time is gradually lengthened or power level gradually
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increased, one or more embodiments of the invention can determine/ascertain
what the out-of-balance is.
Furthermore, given the discussion thus far, it will be appreciated that, in
general terms, another exemplary method, according to another aspect of the
invention, includes the step of accelerating a clothes basket 112 of a machine
such as 10, 10'. The clothes basket rotates about an axis 28. The basket is
accelerated to a first predetermined rotational speed (e.g., at T3). The
clothes
basket contains a load of clothing. It is determined whether the clothes
basket
reaches a second predetermined rotational speed within a predetermined time
(e.g., by T4) from reaching the first predetermined rotational speed. If such
is
not the case, it is determined that an out-of-balance condition exists as to
the
load of clothing. The second predetermined rotational speed is greater than
the first predetermined rotational speed, and a resonance of the machine
does lie between the first and second predetermined rotational speeds.
In some instances, power or torque is not limited near the resonance, but in
other instances, this can be done, linearly or non-linearly.
The technique applied near a resonance can also be repeated in the same
RPM range if desired, for calibration or, for example, responsive to the
clothes
basket not reaching the second predetermined rotational speed within the
predetermined time. Accordingly, one or more embodiments of the invention
can perform repeated implementations in order to take an average of the
resulting data. Thus, it is possible to again accelerate the clothes basket,
to
the first predetermined rotational speed; determine whether the clothes basket
reaches the second predetermined rotational speed within another
predetermined time from reaching the first predetermined rotational speed;
and, responsive to the clothes basket not reaching the second predetermined
rotational speed within the another predetermined time from reaching the first
predetermined rotational speed, determining that the out-of-balance condition
exists as to the load of clothing. Again, this other predetermined time could
be the same or different than the first predetermined time used for this RPM
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range, and torque or power limiting might or might not be applied, and if
applied, could be the same or different than any previous repetition. In one
or
more embodiments of the invention, example implementations can be carried
out to determine an appropriate time range for performing successful spins of
certain loads (using both successful and failed spins as guiding parameters).
Furthermore, given the discussion thus far, it will be appreciated that, in
general terms, an exemplary apparatus, according to still another aspect of
the invention, includes a clothes basket 112 rotatable about an axis 28; a
motor 108 coupled to the clothes basket; a sensor 114 configured to
determine a rotational speed indicative of a rotational speed of the clothes
basket; and a processor (e.g., microprocessor 116 or alternative) coupled to
the motor and the sensor. The processor is operative to control the motor to
implement one or more techniques as described herein. The axis 28 can
have any orientation; in some cases, such as FIGS. 5 and 6, it may be
vertical; in other cases, such as FIGS. 7 and 8, it may be horizontal.
Software includes but is not limited to firmware, resident software,
microcode,
etc. As is known in the art, part or all of one or more aspects of the methods
and apparatus discussed herein may be distributed as an article of
manufacture that itself comprises a tangible computer readable recordable
storage medium having computer readable code means embodied thereon.
The computer readable program code means is operable, in conjunction with
a computer system or microprocessor, to carry out all or some of the steps to
perform the methods or create the apparatuses discussed herein. A
computer-usable medium may, in general, be a recordable medium (e.g.,
floppy disks, hard drives, compact disks, EEPROMs, or memory cards) or
may be a transmission medium (e.g., a network comprising fiber-optics, the
world-wide web, cables, or a wireless channel using time-division multiple
access, code-division multiple access, or other radio-frequency channel). Any
medium known or developed that can store information suitable for use with a
computer system may be used. The computer-readable code means is any
mechanism for allowing a computer (e.g., processor 116) to read instructions
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and data, such as magnetic variations on a magnetic media or height
variations on the surface of a compact disk. The medium can be distributed
on multiple physical devices (or over multiple networks). As used herein, a
tangible computer-readable recordable storage medium is intended to
encompass a recordable medium, examples of which are set forth above, but
is not intended to encompass a transmission medium or disembodied signal.
Processor 116 may include and/or be coupled to a suitable memory.
Thus, while there have shown and described and pointed out fundamental
novel features of the invention as applied to exemplary embodiments thereof,
it will be understood that various omissions and substitutions and changes in
the form and details of the devices illustrated, and in their operation, may
be
made by those skilled in the art without departing from the scope of the
invention described. Moreover, it is expressly intended that all combinations
of those elements and/or method steps which perform substantially the same
function in substantially the same way to achieve the same results are within
the scope of the invention. Furthermore, it should be recognized that
structures and/or elements and/or method steps shown and/or described in
connection with any disclosed form or embodiment of the invention may be
incorporated in any other disclosed or described or suggested form or
embodiment as a general matter of design choice. It is the intention,
therefore, to be limited only as indicated by the scope of the claims appended
hereto.
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