Patent Publication Number: US-2015059416-A1

Title: Systems and Methods for Detecting an Imbalanced Load in a Washing Machine Appliance Having a Balancing Apparatus

Description:
FIELD OF THE INVENTION 
     The present disclosure relates generally to washing machine appliances. In particular, the present disclosure relates to systems and methods for detecting an imbalanced load in a washing machine appliance having a balancing apparatus. 
     BACKGROUND OF THE INVENTION 
     Washing machine appliances generally include a tub with a drum rotatably mounted therein. The drum defines a wash chamber for receiving articles for washing. During operation of washing machine appliances, wash fluid is directed into the tub and onto articles within the wash chamber of the drum. The motor can rotate the drum at various speeds to agitate articles within the wash chamber in wash fluid, to wring wash fluid from articles within the wash chamber, etc. 
     In particular, after the articles of clothing have been washed, the washing machine can drain the wash fluid and then spin the drum at a high speed in order to relieve the articles of clothing of remaining moisture and fluid. This process is generally known as a spin cycle or a spin out process. 
     In certain circumstances, prior to a spin cycle, the load in the washing machine can become imbalanced. In particular, the articles of clothing can become disproportionately distributed to a single location and form an out of balance mass. For example, the articles of clothing can adhere together at a single location. 
     Such out of balance mass can cause a number of problems if it remains uncorrected and present during the spin cycle. In particular, the imbalanced mass can alter the center of mass for the drum and load as a whole so that the center of mass is no longer aligned with a shaft center of the washing machine. Rotating the drum at high speeds in such condition can cause undesirable vibration, noise, or other damage to system components, including damage caused by the drum becoming so far misaligned that is strikes the washing machine tub. 
     One known solution to an out of balance mass is the inclusion of a balancing apparatus within the washing machine. In general, a balancing apparatus can include a balancing material, such as a fluid or balance balls, that is allowed to freely rotate and move about the axis of rotation of the drum or motor. The balancing apparatus attempts to naturally counter the imbalance caused by the out of balance mass. However, a balancing apparatus is still insufficient to resolve the problems caused by a major imbalance or out of balance mass. 
     Therefore, systems and methods for detecting an imbalanced load in a washing machine appliance having a balancing apparatus are desired. In particular, knowledge of the presence of an imbalance can help determine whether a rebalancing process should be performed prior to a spin out process. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Additional aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention. 
     One aspect of the present disclosure is directed to a washing machine appliance. The washing machine appliance includes a cabinet, a tub positioned within the cabinet, and a drum rotatably mounted within the tub. The drum defines a wash chamber for receipt of articles for washing. The washing machine appliance includes a balancing apparatus configured to offset an imbalance created by the articles in the drum. The washing machine appliance includes a motor in mechanical communication with the drum. The motor is configured for selectively rotating the drum within the tub. The washing machine appliance includes a controller configured to perform operations. The operations include receiving a signal indicative of a speed of the motor. The operations include determining a deviation of the speed of the motor from a target motor speed and comparing the deviation to one or more threshold values. The operations include determining whether to perform a rebalancing process or a spin out process based on the comparison of the deviation to the one or more threshold values. 
     Another aspect of the present disclosure is directed to a method for detecting an imbalance of a load in a basket of a washing machine. The washing machine includes a motor configured to rotate the basket. The washing machine includes a balancing apparatus configured to counteract the imbalance of the load. The method includes operating the motor to rotate the basket and determining one or more characteristics of a deviation of a speed of the motor from a target motor speed. The method includes determining a total size of the load. The method includes detecting the imbalance of the load based on the one or more characteristics of the deviation and the total size of the load. 
     Another aspect of the present disclosure is directed to a method for determining whether to rebalance or spin out a load in a washing machine. The load includes an out of balance mass. The washing machine includes a motor and one or more balancing rings. The method includes operating the motor such that the one or more balancing rings and the out of balance mass come in and out of phase with each other. The method includes monitoring one or more characteristics of a deviation signal over a sampling period. The deviation signal describes an absolute difference between a speed of the motor and a motor set speed. The method includes obtaining one or more threshold values based on a total mass of the load. The method includes determining whether to rebalance or spin out the load based on a comparison of the one or more characteristics to the one or more threshold values. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  depicts a front, elevation view of a washing machine appliance according to an exemplary embodiment of the present disclosure; 
         FIG. 2  depicts a side, section view of the exemplary washing machine appliance of  FIG. 1 ; 
         FIGS. 3A and 3B  depict a method for operating a washing machine appliance according to an exemplary embodiment of the present disclosure; 
         FIG. 4  depicts a diagram of a washing machine appliance according to an exemplary embodiment of the present disclosure; 
         FIG. 5  depicts a graphical diagram of a motor speed signal over time according to an exemplary embodiment of the present disclosure; 
         FIG. 6  depicts a graphical diagram of speed deviation versus out of balance mass according to an exemplary embodiment of the present disclosure; and 
         FIG. 7  depicts a graphical diagram of threshold values versus total load mass according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
       FIG. 1  provides a front, elevation view of an exemplary horizontal axis washing machine appliance  100 .  FIG. 2  provides a side, section view of washing machine appliance  100 . As may be seen in  FIG. 1 , washing machine appliance  100  includes a cabinet  102  that extends between a top portion  103  and a bottom portion  105 , e.g., along a vertical direction. Cabinet  102  also includes a front panel  104 . A door  112  is mounted to front panel  104  and is rotatable about a hinge (not shown) between an open position facilitating access to a wash drum or basket  120  ( FIG. 2 ) located within cabinet  102 , and a closed position (shown in  FIG. 1 ) hindering access to basket  120 . A user may pull on a handle  113  in order to adjust door  112  between the open position and the closed position. 
     A control panel  108  including a plurality of input selectors  110  is coupled to front panel  104 . Control panel  108  and input selectors  110  collectively form a user interface input for operator selection of machine cycles and features. For example, in one embodiment, a display  111  indicates selected features, a countdown timer, and/or other items of interest to machine users. 
     Referring now to  FIG. 2 , a tub  114  defines a wash compartment  119  configured for receipt of a washing fluid. Thus, tub  114  is configured for containing washing fluid, e.g., during operation of washing machine appliance  100 . Washing fluid disposed within tub  114  may include at least one of water, fabric softener, bleach, and detergent. Tub  114  includes a back wall  116  and a sidewall  118  and also extends between a top  115  and a bottom  117 , e.g., along the vertical direction. 
     Basket  120  is rotatably mounted within tub  114  in a spaced apart relationship from tub sidewall  118  and the tub back wall  116 . Basket  120  defines a wash chamber  121  and an opening  122 . Opening  122  of basket  120  permits access to wash chamber  121  of basket  120 , e.g., in order to load articles into basket  120  and remove articles from basket  120 . Basket  120  also defines a plurality of perforations  124  to facilitate fluid communication between an interior of basket  120  and tub  114 . A sump  107  is defined by tub  114  and is configured for receipt of washing fluid during operation of appliance  100 . For example, during operation of appliance  100 , washing fluid may be urged by gravity from basket  120  to sump  107  through plurality of perforations  124 . 
     A spout  130  is configured for directing a flow of fluid into tub  114 . Spout  130  may be in fluid communication with a water supply (not shown) in order to direct fluid (e.g., clean water) into tub  114 . A pump assembly  150  (shown schematically in  FIG. 2 ) is located beneath tub  114  for draining tub  114  of fluid. Pump assembly  150  is in fluid communication with sump  107  of tub  114  via a conduit  170 . Thus, conduit  170  directs fluid from tub  114  to pump assembly  150 . Pump assembly  150  is also in fluid communication with a drain  140  via piping  174 . Pump assembly  150  can urge fluid disposed in sump  107  to drain  140  during operation of appliance  100  in order to remove fluid from tub  114 . Fluid received by drain  140  from pump assembly  150  is directed out of appliance  100 , e.g., to a sewer or septic system. 
     In addition, pump assembly  150  is configured for recirculating washing fluid within tub  114 . Thus, pump assembly  150  is configured for urging fluid from sump  107 , e.g., to spout  130 . For example, pump assembly  150  may urge washing fluid in sump  107  to spout  130  via hose  176  during operation of appliance  100  in order to assist in cleaning articles disposed in basket  120 . It should be understood that conduit  170 , piping  174 , and hose  176  may be constructed of any suitable mechanism for directing fluid, e.g., a pipe, duct, conduit, hose, or tube, and are not limited to any particular type of mechanism. 
     A motor  128  is in mechanical communication with basket  120  in order to selectively rotate basket  120 , e.g., during an agitation or a rinse cycle of washing machine appliance  100  as described below. Ribs  126  extend from basket  120  into wash compartment  119 . Ribs  126  assist agitation of articles disposed within wash compartment  119  during operation of washing machine appliance  100 . For example, ribs  126  may lift articles disposed in basket  120  during rotation of basket  120 . 
     A drawer  109  is slidably mounted within front panel  104 . Drawer  109  receives a fluid additive (e.g., detergent, fabric softener, bleach, or any other suitable liquid) and directs the fluid additive to wash compartment  119  during operation of washing machine appliance  100 . Additionally, a reservoir  160  is disposed within cabinet  102 . Reservoir  160  is also configured for receipt of fluid additive for use during operation of washing machine appliance  100  (shown in  FIG. 1 ). Reservoir  160  is sized such that a volume of fluid additive sufficient for a plurality or multitude of wash cycles of washing machine appliance  100  may fill reservoir  160 . Thus, for example, a user can fill reservoir  160  with fluid additive and operate washing machine appliance  100  for a plurality of wash cycles without refilling reservoir  160  with fluid additive. A reservoir pump  162  is configured for selective delivery of the fluid additive from reservoir  160  to tub  114 . 
     Also shown in  FIG. 2  is a balancing apparatus  190 . For example, balancing apparatus  190  can include a balancing ring. The balancing ring can have an annular cavity in which a balancing material is free to rotate and move about. For example, the balancing material can be a fluid such as water or can be balancing balls. The balancing ring can include one or more interior baffles. 
     Although a single balancing ring or apparatus  190  is shown in  FIG. 2 , any number of such rings or apparatuses can be included in washing machine appliance  100  and can be placed according to any known or desirable configuration. For example, two balancing rings can be respectively placed at the front and back of basket  120 . 
     Operation of washing machine appliance  100  is controlled by a processing device or controller  180  that is operatively coupled to control panel  108  for user manipulation to select washing machine cycles and features. In response to user manipulation of control panel  108 , controller  180  operates the various components of washing machine appliance  100  to execute selected machine cycles and features. 
     Controller  180  may include a memory and microprocessor, such as a general or special purpose microprocessor operable to execute programming instructions or micro-control code associated with a cleaning cycle. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. The memory may be a separate component from the processor or may be included onboard within the processor. Alternatively, controller  180  may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software. Control panel  58  and other components of washing machine appliance  50  may be in communication with controller  180  via one or more signal lines or shared communication busses. 
     Controller  180  is in operative communication with motor  128 . Thus, controller  180  can selectively activate and operate motor  128 , e.g., depending upon a wash cycle selected by a user of washing machine appliance  100 . Controller  180  is also configured for monitoring a power delivered to motor  128 . As will be understood by those skilled in the art, power delivered to motor  128  can be measured or determined by controller  180  utilizing various methods. As an example, controller  180  or motor  128  may include a power measurement circuit. In alternative exemplary embodiments, controller  180  may monitor the power delivered to motor  128  utilizing any other suitable mechanism or method. 
     Likewise, controller  180  or other processing components of washing machine appliance  100  can determine a current speed of motor  128  according to any known techniques. For example, a speed signal describing the current speed of the motor can be created and provided to controller  180  according to back electromotive force techniques or based on the output of one or more sensors or other components. 
     In an illustrative example of operation of washing machine appliance  100 , laundry items are loaded into basket  120 , and washing operation is initiated through operator manipulation of input selectors  110 . Tub  114  is filled with water and detergent to form a wash fluid. One or more valves (not shown) can be actuated by controller  180  to provide for filling tub  114  to the appropriate level for the amount of articles being washed. Once tub  114  is properly filled with wash fluid, the contents of basket  120  are agitated with ribs  126  for cleansing of laundry items in basket  120 . 
     After the agitation phase of the wash cycle is completed, tub  114  is drained. Laundry articles can then be rinsed by again adding wash fluid to tub  114 , depending on the particulars of the cleaning cycle selected by a user, ribs  126  may again provide agitation within wash compartment  119 . One or more spin cycles may also be used. In particular, a spin cycle may be applied after the wash cycle and/or after the rinse cycle in order to wring wash fluid from the articles being washed. During a spin cycle, basket  120  is rotated at relatively high speeds. 
     While described in the context of a specific embodiment of horizontal axis washing machine appliance  100 , using the teachings disclosed herein it will be understood that horizontal axis washing machine appliance  100  is provided by way of example only. Other washing machine appliances having different configurations, different appearances, and/or different features may also be utilized with the present subject matter as well, e.g., vertical axis washing machine appliances. 
       FIGS. 3A and 3B  depict an exemplary method ( 300 ) for operating a washing machine appliance according to an exemplary embodiment of the present disclosure. Method ( 300 ) can be implemented using any suitable appliance or other device, including, for example, washing machine appliance  100  of  FIG. 1 . 
     In addition,  FIGS. 3A and 3B  depict steps performed in a particular order for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that the various steps method ( 300 ) can be omitted, adapted, and/or rearranged in various ways. 
     Referring now to  FIG. 3A , at ( 302 ) a total load size can be determined. For example, one or more load size determination algorithms or processes can be performed by washing machine appliance  100  to determine a total size of the load in pounds or other units of mass. For example, the total load size can be determined based upon an amount of power, current, or other electrical characteristics required to operate the motor to bring the load to a particular rotational speed. As another example, one or more sensors can be used to determine the weight of the contents of the drum. As yet another example, user inputs can be analyzed or water displacement can be measured to assist in determining the total load size. Generally, any known technique can be performed at ( 302 ). 
     At ( 304 ) one or more threshold values can be obtained based on the total load size determined at ( 302 ). As an example, a first, second, and third threshold value can be obtained based on the total load size. The threshold value(s) can be obtained from a lookup table stored in system memory or can be obtained by entering the total load size into one or more transfer functions. 
     At ( 306 ) the motor can be operated such that a target motor speed is achieved and a balancing apparatus is allowed to come in and out of phase with an out of balance mass or other existing load imbalance. As an example, a controller can operate the motor such that it spins at 100 RPM. After achieving such speed, control of the motor can be switched from a constant speed control to a constant power or constant torque control. When in constant power mode, the basket speed can fluctuate and the balancing apparatus can come in and out of phases with the out of balance mass. 
     To illustrate these principles reference will now be made to  FIGS. 4 and 5 .  FIG. 4  depicts a diagram of a washing machine appliance according to an exemplary embodiment of the present disclosure. In particular, diagrams  400  and  450  depict a drum  402  rotatably mounted about a shaft  404 . In the wash chamber of drum  402  is an out of balance mass  406 . Surrounding drum  402  is a balancing ring  408 . A balancing material, such as balance balls  410  rotate about shaft  404  through an interior cavity of balancing ring  408 . 
     In diagram  400 , the balancing ring  408  is completely out of phase with the out of balance mass  406  (i.e. 180 degrees out of phase). In particular, the center of mass of balance balls  410  is on the rotationally opposite side of shaft  404  from the out of balance mass  406 . 
     To the contrary, in diagram  450 , the balancing ring  408  is in phase with the out of balance mass  406 . In particular, the center of mass of balance balls  410  is aligned with out of balance mass  406  with respect to shaft  404 . 
       FIG. 5  depicts a graphical diagram  500  of a motor speed signal  502  over time according to an exemplary embodiment of the present disclosure. In particular, graphical diagram  500  shows a deviation of motor speed signal  502  from a target speed or set speed  504  over time while a balancing apparatus comes in and out of phase with an out of balance mass. For example, the deviation of motor speed signal  502  from set speed  504  at any given time can equal an absolute value of the difference between motor speed signal  502  and set speed  504  at such time. 
     According to an aspect of the present disclosure, when the balancing apparatus is directly in phase with the out of balance mass, the deviation of motor speed signal  502  from the set speed  504  will be at its greatest, as the balancing apparatus contributes to the imbalance caused by the out of balance mass. To the contrary, when the balancing apparatus is 180 degrees out of phase with the out of balance mass, the deviation of motor speed signal  502  from set speed  504  will be at its smallest, as the balancing apparatus successfully offsets the out of balance mass. 
     As can generally be seen from graphical depiction  500 , the deviation of motor speed signal  502  from set speed  504  exhibits a local maximum at time  506 . Therefore, as discussed above, time  506  can correspond to an instance in which the balancing apparatus is in phase with the out of balance mass, such as, for example, depicted in diagram  450 . 
     To the contrary, as can generally be seen from graphical depiction  500 , the deviation of motor speed signal  502  from set speed  504  exhibits a local minimum at time  508 . Therefore, time  508  can correspond to an instance in which the balancing apparatus is 180 degrees out of phase with the out of balance mass, such as, for example, depicted in diagram  400 . 
     Thus, one of skill in the art will appreciate, in light of the disclosures contained herein, that operating the motor such that the balancing apparatus comes in and out of phase with the out of balance mass can result in a motor speed signal that exhibits a periodic increase and decrease in deviation from a target speed, as generally shown in  FIG. 5 . 
     Returning again to  FIG. 3A , once the balancing apparatus begins to come in and out of phase with the load imbalance at ( 306 ), a deviation of the motor speed from a target motor speed can be monitored at ( 308 ). As an example, the deviation of the motor speed from the target speed can equal an absolute value of the difference between the motor speed and the target speed. In some embodiments, monitoring the deviation of the motor speed from the target speed at ( 306 ) can include determining a maximum deviation and a minimum deviation exhibited over a sampling period. The sampling period can be any suitable length, such as, for example, 60 or 75 seconds. 
     In further embodiments of the present disclosure, monitoring the deviation of the motor speed from the target speed at ( 306 ) can include continuously calculating a moving average of the deviation. As an example, a rolling window of 3 seconds can be used to calculate a plurality of moving average values over the sampling period. The maximum deviation can be the maximum moving average value calculated during the sampling period and the minimum deviation can be the minimum moving average value calculated during the sampling period. 
     As yet another example, monitoring the deviation of the motor speed from the target speed at ( 306 ) can include calculating a deviation score based on the deviation of the motor speed from the target speed and other parameters. The maximum deviation can be the maximum deviation score and the minimum deviation can be the minimum deviation score. Other characteristics of the motor speed signal can be analyzed as well, including, for example, a median deviation, a mean deviation, a median moving average deviation, a mean moving average deviation, frequency, or any other suitable motor speed signal or deviation signal characteristics. 
     According to another aspect of the present disclosure, the deviation of the motor speed signal from the target speed can be generally proportional to a ratio of the out of balance mass to the total load size. Thus, as the degree of imbalance of the load in the wash chamber increases, the deviation of the motor speed signal from the target speed signal will also increase. To illustrate such principle, reference will now be made to  FIGS. 6 and 7 . 
       FIG. 6  depicts a graphical diagram  600  of speed deviation versus out of balance mass according to an exemplary embodiment of the present disclosure. In particular, graphical diagram  600  shows eight sets of data corresponding to eight different mass values for an out of balance mass. 
     Each set of data includes three data groupings respectively corresponding to maximum observed deviations, middle deviations, and minimum observed deviations for a plurality of measurement cycles. In particular, the washing machine can have been operated according to aspects of method ( 300 ) for each of such plurality of measurement cycles. In some implementations, including the exemplary data shown in  FIG. 6 , the middle deviation for each measurement cycle can equal an average of the maximum deviation and the minimum deviation for such measurement cycle. 
     As an example, data grouping  602  shows a first plurality of maximum deviations respectively associated with a first plurality of measurement cycles conducted with an out of balance mass of 2 pounds present in the wash basket; data grouping  604  shows a first plurality of middle deviations respectively associated with such first plurality of measurement cycles; and data grouping  606  shows a first plurality of minimum deviations respectively associated with the first plurality of measurement cycles. 
     Likewise, data grouping  612  shows a second plurality of maximum deviations respectively associated with a second plurality of measurement cycles conducted with an out of balance mass of 2.5 pounds present in the wash basket; data grouping  614  shows a second plurality of middle deviations respectively associated with such second plurality of measurement cycles; and data grouping  616  shows a second plurality of minimum deviations respectively associated with the second plurality of measurement cycles. 
     Thus, it can be seen from graphical depiction  600  that the deviation values generally increase as the out of balance mass increases. In particular, beginning at about 1.5 or 2 pounds of out of balance mass and upwards, it can be seen that there is generally a linear relationship between an increase in out of balance mass and each of the three data groupings of deviation values for each data set. 
     It should be appreciated, however, that the data provided in  FIGS. 6 and 7  are representative of an exemplary embodiment of a washing machine. The present disclosure is in no way limited to the particular values or relationships shown by such data. As different washing machine appliances have varying components, designs, attributes, operational parameters, or other design variables or objectives, application of the teachings and disclosures of the present disclosure to different washing appliances can result in varying operational data. 
       FIG. 7  depicts a graphical diagram  700  of threshold values versus total load mass according to an exemplary embodiment of the present disclosure. In particular, plots  702 ,  704 , and  706  respectively graph a first threshold value, a second threshold value, and a third threshold value versus total load mass. More particularly, plot  702  graphs a first threshold value that can be compared to a maximum deviation, plot  704  graphs a second threshold value that can be compared to a minimum deviation, and plot  706  graphs a third threshold value that can be compared to a middle deviation, according to aspects of the present disclosure. 
     Also shown on graphical diagram  700  is ten sets of data forming five associated pairs. As an example, a first data set can include data groupings  712 ,  714 , and  716 , while a second data set can include data groupings  722 ,  724 , and  726 . The first data set and the second data set are an associated pair. 
     Each pair of data sets shown in  FIG. 7  represents maximum, middle, and minimum deviations for a plurality of measurement cycles conducted with a 2 pound out of balance mass and a plurality of measurement cycles conducted with a 2.5 pound out of balance mass. 
     As an example, the first data set that includes data groupings  712 ,  714 , and  716  represents a plurality of measurement cycles conducted with a distributed load size of about 24 pounds and an out of balance mass of about 2 pounds. Thus, the first data set represents measurement cycles conducted with a total load size of about 26 pounds. Data groupings  712 ,  714 , and  716  respectively represent maximum, middle, and minimum deviations associated with such plurality of measurement cycles. 
     Likewise, the second data set that includes data groupings  722 ,  724 , and  726  represents a plurality of measurement cycles conducted with a distributed load size of about 24 pounds and an out of balance mass of about 2.5 pounds. Thus, the second data set represents measurement cycles conducted with a total load size of about 26.5 pounds. Data groupings  722 ,  724 , and  726  respectively represent maximum, middle, and minimum deviations associated with such plurality of measurement cycles. 
     Thus, the five associated pairs of data sets depicted in  FIG. 7  provide an indication of expected deviations for an exemplary washing machine having a 2 or 2.5 pounds out of balance mass across a variety of total load sizes. 
     One of skill in the art, in light of the disclosures provided herein, will appreciate that the data provided by such associated pairs of data sets has been used to design, select, or otherwise obtain the plots  702 ,  704 , and  706  for the threshold values. In particular, such threshold values have been designed so as to assist in classifying later observed deviation data as generally indicative of an imbalanced load as either greater than or less than 2.5 or 2 pounds. 
     It will be appreciated, however, that the selection of threshold values based on deviation data representing 2 pounds and 2.5 pounds out of balance mass is exemplary in nature and driven by the particular design goals and constraints of a particular exemplary washing machine appliance. 
     Instead, according to aspects of the present disclosure, threshold values can be designed, selected, or obtained to assist in classifying later observed deviation data as indicative of an imbalanced load either greater or less than any acceptable limit of out of balance mass. Such acceptable limit can be generally based on machine capabilities, design choices with respect to noise, vibration, tub strike avoidance, or any other attributes, operational parameters, or other design variables or objectives. The selection of threshold values can also take into account spin cycle speed, spin cycle duration, balancing apparatus capabilities, component reliabilities, wet load dynamics, total load size measurement accuracy or expected error, out of balance mass measurement accuracy (e.g. standard deviation), or system component variation. 
     Thus, the first, second, and third threshold values respectively represented by plots  702 ,  704 , and  706  can be derived from data observed during measurement cycles. In particular, the first, second, and third threshold values can be stored in memory as a lookup table or can otherwise be described by one or more transfer functions that provide an approximation of plots  702 ,  704 , and  706 . Such threshold values can be the values obtained at ( 304 ) of  FIG. 3A . 
     Returning now to  FIG. 3A , once monitoring of the deviation of the motor speed from the target motor speed has begun at ( 308 ), then at ( 310 ) it can be determined whether a maximum deviation is greater than a first threshold value. For example, the maximum deviation presently observed during the sampling period can be compared to a first threshold value that was obtained at ( 304 ). 
     If it is determined at ( 310 ) that the maximum deviation is greater than the first threshold value, then method ( 300 ) can proceed to ( 312 ) and rebalance the load. In particular, if the maximum deviation is greater than the first threshold value, then it can be assumed that the load contains an unacceptably large imbalance such the rebalancing should be performed prior to any spin cycle so as to prevent unacceptable noise, vibration, or damage. Rebalancing the load at ( 312 ) can include any operational process or technique that provides for a rebalancing of the load. For example, the basket can rotate slowly to allow the out of balance mass to tumble down and be disrupted by the center shaft. Generally, any known technique to rebalance the load can be performed at ( 312 ). 
     However, if it is determined at ( 310 ) that the maximum deviation is less than or equal to the first threshold value, then method ( 300 ) can proceed to ( 314 ). At ( 314 ) it can be determined whether a minimum deviation is less than a second threshold value. For example, the minimum deviation presently observed during the sampling period can be compared to a second threshold value that was obtained at ( 304 ). 
     If it is determined at ( 314 ) that the minimum deviation is less than the second threshold value, then method ( 300 ) can proceed to ( 316 ) and spin out the load. In particular, if the minimum deviation is less than the second threshold value, then it can be assumed that the load does not contain an unacceptably large imbalance and, therefore, the spin cycle can be performed without unacceptable noise, vibration, or damage. Spinning out the load at ( 316 ) can include any known process or technique for reducing the fluid content of the articles of clothing in the basket, including spinning the basket at a high speed. 
     However, if it is determined at ( 314 ) that the minimum deviation is greater than or equal to the second threshold value, then method ( 300 ) can proceed to ( 318 ). At ( 318 ) it is determined whether the sampling period is over. For example, a timer can count down or up to a predetermined sampling period value. 
     If it is determined at ( 318 ) that the sampling period is not completed, then method ( 300 ) can return to ( 308 ) and continue monitoring the deviation of the motor speed from the target motor speed. In such fashion, if the maximum deviation is greater than the first threshold value or the minimum deviation is less than the second threshold value at any point during the sampling period, then the appropriate actions can be taken. However, if neither of such conditions are met, method ( 300 ) will continue monitoring for the remainder of the sampling period. 
     However, if it is determined at ( 318 ) that the sampling period has been completed, then method ( 300 ) can proceed to ( 320 ) of  FIG. 3B . 
     Referring now to  FIG. 3B , at ( 320 ) a middle deviation value can be determined. In some implementations, the middle deviation value can be an average of the maximum deviation and the minimum deviation value observed during the sampling period. However, other techniques can be used to obtain the middle deviation value at ( 320 ), including identifying a median value for all observed deviation values, a mean value for all observed deviation values, or any other suitable technique, including weighted averages or transfer functions. 
     At ( 322 ) it can be determined whether the middle deviation value is greater than a third threshold value. For example, the middle deviation value determined at ( 320 ) can be compared to a third threshold value that was obtained at ( 304 ) of  FIG. 3A . 
     If it is determined at ( 322 ) that the middle deviation value is greater than the third threshold value, then method ( 300 ) can proceed to ( 324 ) and rebalance the load. However, if it is determined at ( 322 ) that the middle deviation value is less than or equal to the third threshold value, then method ( 300 ) can proceed to ( 326 ) and spin out the load. 
     In such fashion, a washing machine appliance implementing method ( 300 ) can analyze a deviation of a motor speed from a target speed while a balancing apparatus comes in and out of phase with an out of balance load to detect and resolve an unacceptably large load imbalance prior to performing a high speed spin out cycle. 
     Furthermore, while method ( 300 ) includes determining the total load size at ( 302 ) prior to monitoring deviation for a sampling period at ( 308 ), it will be appreciated that, in alternative implementations, the total load size could be determined subsequent to monitoring of the deviation such that the results of monitoring can then be interpreted. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.