Patent Publication Number: US-11021825-B2

Title: Washing machine appliance with location detection of imbalanced loads

Description:
FIELD OF THE INVENTION 
     The present disclosure relates generally to washing machine appliances and more particularly to washing machine appliances configured to detect a location of an imbalanced load. 
     BACKGROUND OF THE INVENTION 
     Washing machine appliances generally include a drum or basket rotatably mounted within a tub of a cabinet. The basket defines a wash chamber for receiving articles for washing. During operation, wash fluid is directed into the tub and onto articles within the wash chamber. A motor can rotate the basket 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 basket 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 or load. For example, the articles of clothing can bunch together at a single location in the rear of the tub. An out-of-balance mass can cause a number of problems if it remains uncorrected during the spin cycle. Specifically, the imbalanced mass can alter the center of mass of the basket 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 basket at high speeds in such a condition can cause undesirable vibration, noise, or damage to system components. 
     Conventionally, washing machine appliances have been configured to detect such imbalanced masses, as well as some of the characteristics of the imbalanced mass, such as e.g., the mass or size of the imbalanced mass and the location of the imbalanced mass. Detecting the location of an imbalanced mass has conventionally been determined by utilizing various inputs, such as motor speed and/or basket speed. However, use of such inputs to determine the location of an imbalanced load has provided less than ideal estimates of the location of such imbalanced masses and use of such inputs require that the motor be operated in order to detect the location of an imbalanced load, which consumes energy. 
     Therefore, a washing machine appliance and methods for determining a location of an imbalanced load that address one or more of the challenges noted above would be useful. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present disclosure provides a washing machine appliance configured to detect a location of an imbalanced load. The washing machine appliance utilizes the displacement or a component of the displacement of a tub of the washing machine appliance to determine the location of an out-of-balance load. More particularly, the washing machine compares the displacement or a component of the displacement of the tub at a first point with the displacement of the tub at a second point that is positioned forward of the first point. By comparing the displacement or component of the displacement of the tub at these two points, the location of the imbalanced load may be determined. Methods for determining such imbalanced loads are also provided. 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 method for determining a location of an imbalanced load in a washing machine appliance. The washing machine appliance extending between a front and a rear and comprising a tub and a basket rotatably mounted within the tub, the tub defining a first point and a second point positioned forward of the first point, the first point positioned at a first origin and the second point positioned at a second origin when the washing machine appliance is in a resting state. The method includes ascertaining a first displacement of the first point relative to the first origin for a first time period. The method also includes ascertaining a second displacement of the second point relative to the second origin for the first time period. Further, the method includes determining the location of the imbalanced load for the first time period based at least in part on the first displacement and the second displacement. 
     In some implementations, the method includes generating a control action in response to the location of the imbalanced load. 
     Another aspect of the present disclosure is directed a horizontal axis washing machine appliance. The horizontal axis washing machine appliance includes a cabinet and a tub positioned within the cabinet and extending between a front and a rear, the tub defining a first point and a second point positioned forward of the first point, the first point positioned at a first origin and the second point positioned at a second origin when the horizontal axis washing machine appliance is in a resting state. Further, the horizontal axis washing machine appliance includes a basket rotatably mounted within the tub, the basket defining a wash chamber for receipt of articles for washing. The horizontal axis washing machine appliance also includes a displacement measurement unit attached to the tub and a controller in operative communication with the displacement measurement unit. The controller is configured to: receive an input generated by the displacement measurement unit that is indicative of a displacement of the tub relative to its position in the resting state for a first time period; ascertain a first displacement of the first point relative to the first origin for the first time period based at least in part on the input; ascertain a second displacement of the second point relative to the second origin for the first time period based at least in part on the input; determine the location of the imbalanced load for the first time period based at least in part on the first displacement and the second displacement; and generate a control action in response to the location of the imbalanced load. 
     Yet another aspect of the present disclosure is directed to a method for determining a location of an imbalanced load in a washing machine appliance, the washing machine appliance extending between a front and a rear and comprising a tub and a basket rotatably mounted within the tub, the tub defining a first point and a second point positioned forward of the first point, the first point positioned at a first origin and the second point positioned at a second origin when the washing machine appliance is in a resting state. The method includes ascertaining a first distance between the first point and the first origin along a first direction for a first time period. The method also includes ascertaining a second distance between the second point and the second origin along the first direction for the first time period. In addition, the method includes determining the location of the imbalanced load for the first time period based at least in part on the first distance and the second distance. Moreover, the method includes generating a control action in response to the location of the imbalanced load. 
     In some implementations, the first direction is a lateral direction defined by washing machine appliance. 
     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 ; 
         FIG. 3  provides a flow chart of an exemplary method for determining a location of an imbalanced load in a washing machine appliance according to an exemplary embodiment of the present disclosure; 
         FIG. 4  provides a schematic, top plan view of an exemplary subwasher in a resting state according to an exemplary embodiment of the present disclosure; 
         FIG. 5  provides a schematic, top plan view of the subwasher of  FIG. 4  depicting a tub thereof displaced from its resting state position by an imbalanced load according to an exemplary embodiment of the present disclosure; 
         FIG. 6  provides an exemplary chart graphically depicting the displacement of a first point defined by a tub of a subwasher of a washing machine appliance relative to a first origin as a function of time according to an exemplary embodiment of the present disclosure; 
         FIG. 7  provides a schematic, top plan view of an exemplary subwasher in a resting state according to an exemplary embodiment of the present disclosure; 
         FIG. 8  provides a schematic, top plan view of the subwasher of  FIG. 7  depicting a tub thereof displaced from its resting state position by an imbalanced load according to an exemplary embodiment of the present disclosure; 
         FIG. 9  provides a displacement envelope of a tub depicting a rear imbalanced load according to an exemplary embodiment of the present disclosure; 
         FIG. 10  provides a displacement envelope of a tub depicting a front imbalanced load according to an exemplary embodiment of the present disclosure; 
         FIG. 11  provides a chart depicting the displacement ratio of three imbalanced loads plotted as a function of basket speed according to an exemplary embodiment of the present disclosure; 
         FIG. 12  provides a schematic, top plan view of an exemplary subwasher in a resting state according to an exemplary embodiment of the present disclosure; 
         FIG. 13  provides a schematic, top plan view of the subwasher of  FIG. 12  depicting a tub thereof displaced from its resting state position by an imbalanced load according to an exemplary embodiment of the present disclosure; 
         FIG. 14  provides a flow chart of another exemplary method for determining a location of an imbalanced load in a washing machine appliance according to an exemplary embodiment of the present disclosure; and 
         FIG. 15  provides a schematic, top plan view of a subwasher depicting a tub thereof displaced from its resting state position by an imbalanced load 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 shown 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 V. Cabinet  102  also extends between a first side  123  and a second side  125 , e.g., along a lateral direction L, and between a front  127  and a rear  129  ( FIG. 2 ), e.g., along a transverse direction T. The vertical, lateral, and transverse directions V, L, T defined by washing machine appliance  100  are mutually perpendicular and together define an orthogonal direction system. 
     Cabinet  102  includes a front panel  104 . A door  112  ( FIG. 1 ) 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  ( FIG. 1 ) 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  ( FIG. 1 ) indicates selected features, a countdown timer, and/or other items of interest to machine users. 
     As shown in  FIG. 2 , a tub  114  defines a wash fluid 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 V. Further, tub  114  extends between a front  132  and a rear  134 , e.g., along the transverse direction T. 
     Basket  120  is rotatably mounted within tub  114  in a spaced apart relationship from tub sidewall  118  and tub back wall  116 . One or more bearing assemblies may be placed between basket  120  and tub  114  and may allow for rotational movement of basket  120  relative to tub  114 . 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. In particular, a shaft  136  mechanically couples motor  128  with basket  120  and drivingly rotates basket  120  about a shaft or central axis A, e.g., during a spin cycle. Ribs  126  extend from basket  120  into wash chamber  121 . Ribs  126  assist agitation of articles disposed within wash chamber  121  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 fluid 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 . 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 . Balancing apparatus  190  can include a balancing ring, for example. 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 . 
     As further depicted in  FIG. 2 , a displacement measurement unit  195  is shown attached to tub  114 . In particular, for this embodiment, displacement measurement unit  195  is attached to backwall  116  of tub  114 . In alternative embodiments, displacement measurement unit  195  may be attached to tub  114  in any other suitable location, such as e.g., to sidewall  118 . Displacement measurement unit  195  is operatively configured to sense or measure the motion of tub  114  at a point during operation. For this embodiment, displacement measurement unit  195  includes an accelerometer and a gyroscope. Accordingly, displacement measurement unit  195  is configured to sense or measure the translational movement of tub  114  at a point (via the accelerometer) and the rotational movement of tub  114  at the point (via the gyroscope). In accordance with exemplary aspects of the present disclosure, displacement measurement unit  195  may generate a signal indicative of a displacement of the tub relative to its position in its resting state (i.e., a state in which there are no articles within basket  120  and basket  120  is not in motion). Such input signals may be routed to a controller, as will be explained further below, such that the location of an imbalanced mass or load may ultimately be determined. 
     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  108  and other components of washing machine appliance  100  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  may also be 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. Further, controller  180  may further be configured for determining 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 including, for example, an optical sensor or magnetic-based sensors such as hall effect sensors. 
     In addition, controller  180  is also in operative communication with displacement measurement unit  195 . Accordingly, controller  180  may receive signal inputs from displacement measurement unit  195  indicative of the displacement of tub  114  during operation. Such inputs may be used, as noted above, to determine the location of an imbalanced load. 
     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, and ribs  126  may again provide agitation within wash chamber  121 . 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 , 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, including, for example, vertical axis washing machine appliances. Thus, the teachings of the present disclosure are not limited to use with washing machine appliance  100 . 
       FIG. 3  depicts an exemplary method ( 300 ) for determining a location of an imbalanced load in a washing machine appliance according to an exemplary embodiment of the present disclosure. Method ( 300 ) can be implemented using any suitable appliance, including for example, horizontal axis washing machine appliance  100  of  FIGS. 1 and 2 . Accordingly, to provide context to method ( 300 ), reference numerals utilized to describe the features of washing machine appliance  100  in  FIGS. 1 and 2  will be used below. 
     In some exemplary implementations of method ( 300 ), washing machine appliance  100  extends between front  127  and rear  129  and includes tub  114  and basket  120  rotatably mounted within tub  114 . Basket  120  is configured for receipt of articles for washing. Further, as will be explained further below, tub  114  defines a first point and a second point. The second point is positioned forward of the first point. For example, tub  114  may define the first point at a rear portion of tub  114  and tub  114  may define the second point at a front portion of tub  114 . When washing machine appliance  100  is in a resting state (i.e., a state in which basket  120  is at rest without any articles within wash chamber  121  of basket  120 ), the first point is positioned at a first origin and the second point is positioned at a second origin. When washing machine appliance  100  is in an active state (i.e., there is a load within basket  120  and/or basket  120  is in motion), the displacement of the first point relative to the first origin and the displacement of the second point relative to the second origin are used to determine the relative motion of the tub at the first and second points, which in accordance with exemplary aspects of the present disclosure, may be used to determine the location of an imbalanced load within washing machine appliance  100 . 
     At ( 302 ), method ( 300 ) includes ascertaining a first displacement of the first point relative to the first origin for a first time period. As will be appreciated, tub  114  may be displaced. For instance, when articles are placed within basket  120 , tub  114  may be displaced from its position in the resting state due to the mass of the articles. In addition, when articles are placed within basket  120  and basket  120  is rotated about the central axis A, tub  114  may be displaced due to the mass of the articles within basket  120  and the rotation of basket  120 . In ascertaining the displacement of the first point relative to the first origin, the displacement of tub  114  relative to its position in the resting state is determined at the first point. The first time period may be any suitable period of time. For instance, the first time period may be a time step of controller  180 . 
     At ( 304 ), method ( 300 ) includes ascertaining a second displacement of the second point relative to the second origin for the first time period. In ascertaining the displacement of the second point relative to the second origin, the displacement of tub  114  relative to its position in the resting state is determined at the second point. An exemplary manner in which the first displacement and the second displacement may be ascertained is provided below. 
       FIG. 4  provides a schematic, top plan view of an exemplary subwasher  200  of washing machine appliance  100  of  FIGS. 1 and 2  depicting subwasher  200  in its resting state according to an exemplary embodiment of the present disclosure. Subwasher  200  includes tub  114  and basket  120  rotatably mounted therein. As shown, tub  114  defines a first point P 1  and a second point P 2 . Second point P 2  is positioned forward of first point P 1 . More particularly, for this embodiment, first point P 1  is defined at rear  134  of tub  114  and second point P 2  is defined at a center of gravity CG of subwasher  200 . Further, for this embodiment, first point P 1  and second point P 2  are positioned along the central axis A defined by shaft  136  ( FIG. 2 ). In addition, as shown in  FIG. 4 , when subwasher  200  is in a resting state, first point P 1  is positioned at a first origin OR 1  and second point P 2  is positioned at a second origin OR 2 . By positioning at least one of the points at or near the center of gravity of subwasher  200 , calculation of the location of the imbalanced load may be more accurate for a wider variety of loads. 
       FIG. 5  provides a schematic, top plan view of subwasher  200  of  FIG. 4  depicting tub  114  displaced from its resting state position by an imbalanced load  202  according to an exemplary embodiment of the present disclosure. As shown in  FIG. 5 , first point P 1  is displaced from first origin OR 1  and second point P 2  is displaced from second origin OR 2  by imbalanced load  202  located within basket  120 . For this embodiment, as depicted, a first displacement D 1  or distance between first point P 1  and first origin OR 1  caused by imbalanced load  202  is greater than a second displacement D 2  or distance between second point P 2  and second origin OR 2 . Stated differently, rear  134  of tub  114  is displaced from its resting state position a greater distance than the portion of tub  114  at or proximate the center of gravity CG of subwasher  200 . In this context, “proximate” the center of gravity means within six (6) inches of the center of gravity. At ( 302 ) and ( 304 ) ( FIG. 3 ), the first and second displacements D 1 , D 2  are ascertained. 
     For this exemplary embodiment, displacement measurement unit  195  is attached to tub  114  at first point P 1  and is configured to sense or measure the first displacement D 1 , or the distance between first point P 1  and first origin OR 1 . To ascertain first displacement D 1 , displacement measurement unit  195  provides input signals (e.g., a voltage or an acceleration reading generated by displacement measurement unit  195 ) to controller  180  indicative of the first displacement D 1 . In this way, first point P 1  is a sensed or measured point. That is, first displacement D 1  is sensed or measured by displacement measurement unit  195 . 
     As further shown in  FIGS. 4 and 5 , for this exemplary embodiment, tub  114  of subwasher  200  does not include a displacement measurement unit at second point P 2 . Thus, to ascertain the second displacement D 2 , controller  180  estimates or predicts the displacement between second point P 2  and second origin OR 2 , or second displacement D 2 . In this way, second point P 2  is a virtual point. That is, assuming tub  114  is a rigid body and knowing the dimensional configuration of tub  114 , the position of any point, including the second point P 2 , may be predicted based on the measured position of the first point P 1 . As the second displacement D 2  is determined by using a virtual point at second point P 2 , washing machine appliance  100  need not include multiple displacement measurement units. 
     In alternative exemplary embodiments, the second point P 2  may be a measured point and the first point P 1  may be a virtual point. In yet other alternative exemplary embodiments, the first point P 1  and the second point P 2  may both be sensed or measured points. In such embodiments, washing machine appliance  100  may include two displacement measurement unit  195  positioned at the first and second points. In yet other embodiments, the first point P 1  and the second point P 2  may both be virtual points. In such embodiments, displacement measurement unit  195  may be attached to tub  114  at a given location, and the first displacement D 1  of first point P 1  relative to first origin OR 1  and the second displacement D 2  of second point P 2  relative to second origin OR 2  may be predicted. 
     Further, for this embodiment, the first displacement D 1  is ascertained by taking or calculating the absolute value of the amplitudes of the displacement between first point P 1  and first origin OR 1  or the amplitude of a signal indicative of the first displacement for the first time period. In this way, the second displacement D 2  of second point relative to second origin OR 2  need not be calculated or predicted for every displacement value measured by displacement measurement unit  195 . Rather, when controller  180  recognizes that the first displacement D 1  has reached a maximum displacement for that particular oscillation (i.e., the displacement has reached its amplitude), the second displacement D 2  can be calculated based at least in part on the absolute value of the amplitude of the first displacement for the first time period at that particular point in time. In this manner, the computational resources of controller  180  may be conserved. 
       FIG. 6  provides an exemplary chart graphically depicting the displacement of first point P 1  relative to first origin OR 1  as a function of time. As shown, as tub  114  oscillates back and forth during operation of washing machine appliance  100  due to imbalanced load  202  ( FIG. 5 ), the signal generated by displacement measurement unit  195  indicative of the displacement of first point P 1  relative to first origin OR 1  oscillates back and forth in a sinusoidal wave. When controller  180  receives the input of raw displacement data from displacement measurement unit  195 , controller  180  is configured to recognize the amplitudes A 1  of the displacement or signal indicative of the displacement. Such amplitudes A 1  may be stored for further use. For example, the amplitudes A 1  of the displacement between the first point P 1  and first origin OR 1  may be used to calculate the amplitudes of the displacement between the second point P 2  and second origin O 2 , as noted above. For instance, controller  180  may include a look up table that corresponds the amplitudes A 1  of the displacement between first point P 1  and first origin OR 1  with amplitudes of the displacement between second point P 2  and second origin O 2 . Once the amplitudes of the first and second displacements D 1 , D 2  are ascertained, the amplitudes are compared such that the location of the imbalanced load may be determined. 
     In alternative exemplary embodiments, points P 1  and P 2  may be defined by tub  114  at different locations than as shown in  FIGS. 4 and 5 . For instance, as shown in  FIGS. 7 and 8 , first point P 1  is defined at rear  134  of tub  114  and second point P 2  is defined at front  132  of tub  114 . Further, first point P 1  and second point P 2  are positioned along the central axis A defined by shaft  136  ( FIG. 2 ), however, in alternative embodiments, one or both of first point P 1  and second point P 2  need not be positioned along the central axis A. In addition, as shown in  FIG. 7 , when subwasher  200  is in a resting state, first point P 1  is positioned at a first origin OR 1  and second point P 2  is positioned at a second origin OR 2 . As shown in  FIG. 8 , tub  114  is displaced from its resting state position by imbalanced load  202 . First point P 1  is displaced from first origin OR 1  and second point P 2  is displaced from second origin OR 2  by imbalanced load  202  located within basket  120 . As depicted, first displacement D 1  or distance between first point P 1  and first origin OR 1  caused by imbalanced load  202  is greater than second displacement D 2  or distance between second point P 2  and second origin OR 2 . Stated differently, rear  134  of tub  114  is displaced from its resting state position a greater distance than front  132  of tub  114 . 
     At ( 306 ), with reference again to  FIG. 3 , method ( 300 ) includes determining the location of the imbalanced load based at least in part on the first displacement and the second displacement. The location of the imbalanced load may be determined utilizing the first displacement D 1  determined at ( 302 ) and the second displacement D 2  determined at ( 304 ) in a number of exemplary manners. Exemplary manners are provided below. 
     As one example, the location of the imbalanced load may be determined based at least in part on the first displacement and the second displacement by comparing the first displacement with the second displacement for the predetermined time period. More particularly, the amplitude of the first displacement D 1  may be compared against the amplitude of the second displacement D 2 . If the amplitude of the first displacement D 1  is greater than the amplitude of the second displacement D 2 , then the imbalanced load is located at a location of tub  114  that is towards the first point P 1 . In contrast, if the amplitude of the first displacement D 1  is less than the amplitude of the second displacement D 2 , then the imbalanced load is located at a location of tub  114  that is towards the second point P 2 . If the amplitude of the first displacement D 1  is equal to or about equal to the amplitude of the second displacement D 2 , then the imbalanced load is located approximately between the first and second points. 
     For instance, for implementations in which first point P 1  is defined at rear  134  of tub  114  and second point P 2  is defined at front  132  of tub  114 , both points P 1 , P 2  being aligned along the central axis A when subwasher  200  is positioned in the resting state, then if the amplitude of the first displacement D 1  is greater than the amplitude of the second displacement D 2 , then the imbalanced load is located at a location towards rear  134  of tub  114  (i.e., towards first point P 1 ).  FIG. 7  depicts a displacement envelope  210  of tub  114  showing such a scenario. As shown in  FIG. 7 , the amplitude of the displacement of first point P 1  relative to the first origin OR 1 , denoted as Amp  1 , is greater than the amplitude of the displacement of second point P 2  relative to the second origin OR 2 , denoted as Amp  2 . Thus, the imbalanced load is determined to be located toward rear  134  of tub  114 . 
     If, however, the amplitude of the first displacement D 1  is less than the amplitude of the second displacement D 2 , then the imbalanced load is located at a location towards front  132  of tub  114  (i.e., towards second point P 2 ).  FIG. 8  depicts a displacement envelope  220  of tub  114  showing such a scenario. As shown in  FIG. 8 , the amplitude of the displacement of first point P 1  relative to the first origin OR 1 , denoted as Amp  1 , is less than the displacement of second point P 2  relative to the second origin OR 2 , denoted as Amp  2 , and thus, the imbalanced load is determined to be located toward front  132  of tub  114 . Further, although not depicted, if the amplitude of the first displacement D 1  is equal to or about equal to the amplitude of the second displacement D 2 , then the imbalanced load is located at a location approximately between front  132  and rear  134  of tub  114 . 
     As another example, determining the location of the imbalanced load based at least in part on the first displacement and the second displacement includes determining a displacement ratio. For this embodiment, the displacement ratio is a ratio of the first displacement to the second displacement (D 1 :D 2 ). However, in alternative exemplary embodiments, the displacement ratio is a ratio of the second displacement to the first displacement (D 2 :D 1 ). For instance, for implementations in which first point P 1  is defined at rear  134  of tub  114  and second point P 2  is defined at front  132  of tub  114 , both points P 1 , P 2  being aligned along the central axis A when subwasher  200  is positioned in the resting state, then if the displacement ratio is greater than one (1), then the imbalanced load is located at a location towards rear  134  of tub  114  (i.e., towards first point P 1 ). On the other hand, if the displacement ratio is less than one (1), then the imbalanced load is located at a location towards front  132  of tub  114  (i.e., towards second point P 2 ). If the displacement ratio is equal to or about equal to one (1), then the imbalanced load is located at a location approximately between front  132  and rear  134  of tub  114 . 
     In some implementations, method ( 300 ) includes comparing the displacement ratio to one or more displacement thresholds. Such displacement thresholds may provide additional resolution as to the location of the imbalanced load. As one example, controller  180  may be configured to classify the location of the imbalanced load as one of a front, front-middle, middle, rear middle, or rear location. Accordingly, the one or more displacement thresholds may include a first threshold delineating the front and front-middle locations, a second threshold delineating the front-middle and middle locations, a third threshold delineating the middle and rear-middle locations, and a fourth threshold delineating the rear-middle and rear locations within tub  114 . Once the displacement ratio is known, the displacement ratio may systematically be compared to the displacement thresholds until the location of the imbalanced load is determined. It will be appreciated that controller  180  may also be configured to classify imbalanced locations with greater or fewer classifications than the example above. 
     The predetermined thresholds may change as a function of basket speed (i.e., the rpm of basket  120 ). Accordingly, in some implementations, method ( 300 ) includes plotting the displacement ratio as a function of basket speed and then comparing the displacement ratio to one or more displacement thresholds. By way of example,  FIG. 11  graphically depicts the displacement ratio of three imbalanced loads plotted as a function of basket speed (rpm). The three imbalanced loads were run in separate wash cycles and the load size and load location were held constant. In particular,  FIG. 11  graphically depicts the displacement ratio of a first imbalanced load L 1  as a function of basket speed, a second imbalanced load L 2  as a function of basket speed, and a third imbalanced load L 3  as a function of basket speed. Further, for this embodiment, controller  180  is configured to classify the location of the imbalanced load as one of a front F, middle M, or rear R location. Accordingly, as shown, a first displacement threshold T 1  delineates the front F and middle M locations and a second displacement threshold T 2  delineates the middle M and rear R locations. 
     With reference still to  FIG. 11 , as shown, the displacement ratio of the first imbalanced load L 1  is plotted as a function of basket speed. After being plotted, the displacement ratio of the first imbalanced load L 1  is compared to one or more of the displacement thresholds. In particular, the displacement ratio of the first imbalanced load L 1  is compared to the first displacement threshold T 1 . As the displacement ratio of the first imbalanced load L 1  is less than the first threshold T 1 , the first imbalanced load L 1  is determined to be located within the front F location (i.e., towards front  132  of tub  114 ). 
     Similarly, the displacement ratio of the second imbalanced load L 2  is plotted as a function of basket speed. After being plotted, the displacement ratio of the second imbalanced load L 2  is compared to one or more of the displacement thresholds. In particular, the displacement ratio of the second imbalanced load L 2  is compared to the first displacement threshold T 1 , and it is determined that the displacement ratio of the second imbalanced load L 2  is greater than the first threshold T 1 . The displacement ratio of the second imbalanced load L 2  is then compared to the second displacement threshold T 2 , and it is determined that the displacement ratio of the second imbalanced load L 2  is less than the second threshold T 2 . Thus, the second imbalanced load L 2  is determined to be located within the middle location M or class (i.e., approximately at the middle of tub  114 ). 
     The displacement ratio of the third imbalanced load L 3  is likewise plotted as a function of basket speed. After being plotted, the displacement ratio of the third imbalanced load L 3  is compared to one or more of the displacement thresholds. In particular, the displacement ratio of the third imbalanced load L 3  is compared to the first displacement threshold T 1 , and it is determined that the displacement ratio of the third imbalanced load L 3  is greater than the first threshold T 1 . The displacement ratio of the third imbalanced load L 3  is then compared to the second displacement threshold T 2 , and it is determined that the displacement ratio of the third imbalanced load L 3  is greater than the second threshold T 2 . Thus, the third imbalanced load L 3  is determined to be located within the rear location R or class (i.e., towards rear  134  of tub  114 ). 
     Notably, the displacement ratios of the imbalanced loads L 1 , L 2 , L 3  change as basket speed increases while maintaining all other variables constant. Accordingly, the displacement thresholds can be set such that they account for the change in the displacement ratio as basket speed changes. This may provide further resolution as to the location of the imbalanced load within washing machine appliance  100  at various basket speeds. As will be appreciated, the displacement ratio may be plotted as a function of any characteristic that is indicative of basket speed. For example, the displacement ratio may alternatively be plotted against the power output of motor  128 , basket acceleration, shaft speed of shaft  136 , etc. Further, in some implementations, the displacement thresholds may remain static. In this way, computational resources are conserved and motor speed, basket speed, shaft speed, motor power output, etc. need not be taken into account to determine the location of an imbalanced load within washing machine appliance  100 . Further, as the location of an imbalanced load may be determined without using motor speed, basket speed, shaft speed, motor power output, etc., it may be determined if a load of articles placed within basket  120  creates an out-of-balance load without rotating basket  120 , which may conserve energy, among other potential benefits. 
     Further, in some implementations, based on the determined location of the imbalanced load, method ( 300 ) includes generating a control action in response to the location of the imbalanced load. As one example, if the imbalanced load is towards front  132  of tub  114 , a current spin cycle being performed may be stopped, basket  120  may then be pulsed or otherwise rotated in a way to even out the load, and then wash basket  120  may be spun up once more to complete the spin cycle. Other control actions are also possible. 
     In some exemplary implementations, the location of an imbalanced load for the first time period may be determined at ( 306 ) based at least in part on the first displacement, the second displacement, and a third displacement. In such implementations, method ( 300 ) includes ascertaining a third displacement of a third point relative to a third origin for the first time period. For instance, as shown in  FIG. 12 , subwasher  200  is depicted in its resting state according to an exemplary embodiment of the present disclosure. Subwasher  200  includes tub  114  and basket  120  rotatably mounted therein. As shown, tub  114  defines first point P 1 , second point P 2 , and a third point P 3 . Second point P 2  is positioned forward of first point P 1  and third point P 3  is positioned forward of P 2 . In particular, for this embodiment, first point P 1  is defined at rear  134  of tub  114 , second point P 2  is defined at a center of gravity CG of subwasher  200 , and third point P 3  is defined at front  132  of tub  114 . Further, for this embodiment, first point P 1 , second point P 2 , and third point P 3  are positioned along the central axis A defined by shaft  136  ( FIG. 2 ). In addition, as shown in  FIG. 12 , when subwasher  200  is in a resting state, first point P 1  is positioned at first origin OR 1 , second point P 2  is positioned at second origin OR 2 , and third point P 3  is positioned at a third origin OR 3 . 
       FIG. 13  provides a schematic, top plan view of subwasher  200  of  FIG. 12  depicting tub  114  displaced from its resting state position by an imbalanced load  202  according to an exemplary embodiment of the present disclosure. As shown in  FIG. 13 , first point P 1  is displaced from first origin OR 1 , second point P 2  is displaced from second origin OR 2 , and third point P 3  is displaced from third origin OR 3  by imbalanced load  202  located within basket  120 . For this embodiment, as depicted, first displacement D 1  or distance between first point P 1  and first origin OR 1  caused by imbalanced load  202  is greater than second displacement D 2  or distance between second point P 2  and second origin OR 2 , and further, second displacement D 2  is greater than a third displacement D 3  or distance between third point P 3  and third origin OR 3 . 
     Advantageously, by positioning points P 1 , P 2 , and P 3  as noted above, various out-of-balance loading conditions may be distinguished. For instance, suppose in one case that a pure coupling of front  132  and rear  134  exists (i.e., the out-of-balance load at front  132  is equal to the out-of-balance load at rear  134  but with a rotation of one hundred eighty degrees (180°) of rotation), and suppose in another case that there is a middle out-of-balance load. By strictly utilizing the P 1 -P 3  combination to detect the location of the imbalanced load, these two loads will look the same, that is the front motion will appear to equal the rear motion of tub  114 . By using the P 1 -P 2  combination, the loads will look differently. That is, by using P 2 , the difference between the middle out-of-balanced load and the pure coupling out-of-balanced load may be determined. 
       FIG. 14  depicts an exemplary method ( 400 ) for determining a location of an imbalanced load in a washing machine appliance according to an exemplary embodiment of the present disclosure. Method ( 400 ) can be implemented using any suitable appliance, including for example, horizontal axis washing machine appliance  100  of  FIGS. 1 and 2 . Accordingly, to provide context to method ( 400 ), reference numerals utilized to describe the features of washing machine appliance  100  in  FIGS. 1 and 2  will be used below. 
     In some exemplary implementations of method ( 400 ), washing machine appliance  100  extends between front  127  and rear  129  and includes tub  114  and basket  120  rotatably mounted within tub  114 . Basket  120  is configured for receipt of articles for washing. Further, as will be explained further below, tub  114  defines a first point P 1  and a second point P 2 . The second point P 2  is positioned forward of the first point P 1 . For example, tub  114  may define the first point at a rear portion of tub  114  and tub  114  may define the second point at a front portion of tub  114 . When washing machine appliance  100  is in a resting state (i.e., a state in which basket  120  is at rest without any articles within wash chamber  121  of basket  120 ), the first point is positioned at a first origin and the second point is positioned at a second origin. When washing machine appliance  100  is in an active state (i.e., there is a load within basket  120  and/or basket  120  is in motion), a first distance between the first point and the first origin along a first direction and a second distance between the second point and the second origin along the first direction are used to determine the relative motion of the tub at the first and second points, which in accordance with exemplary aspects of the present disclosure, may be used to determine the location of an imbalanced load within washing machine appliance  100 . 
     At ( 402 ), method ( 400 ) includes ascertaining a first distance between the first point and the first origin along a first direction for a first time period. For instance, controller  180  may receive a signal generated by displacement measurement unit  195  indicative of the distance between the first point and the first origin along the first direction. For instance, a signal representative of the acceleration of the first point relative to the first origin along the first direction may be generated by displacement measurement unit  195 . Upon receiving the signal, controller  180  may utilize the acceleration signal and a time step or other interval as the time parameter, and from these inputs, the distance between the first point and the first origin may be determined. Preferably, the first distance is determined as the maximum distance between the first point and the first origin during the first time period. The first direction may be any suitable direction. For example, the first direction may be a direction along the lateral direction L, along the transverse direction T, or along the vertical direction V. 
     At ( 404 ), method ( 400 ) includes ascertaining a second distance between the second point and the second origin along the first direction for the first time period. For instance, upon controller  180  ascertaining the first distance, the second distance may be predicted as will be explained further below. An exemplary manner in which the first distance and the second distance may be ascertained is provided below. 
       FIG. 15  provides a schematic, top plan view of subwasher  200  depicting tub  114  thereof displaced from its resting state position by an imbalanced load  202  according to an exemplary embodiment of the present disclosure. In this implementation, the first direction is a direction along the lateral direction L. As shown, the imbalanced load  202  located within basket  120  has caused the first point P 1  to be spaced from first origin OR 1  along the lateral direction L a first distance D 1  and second point P 2  to be spaced from second origin OR 2  along the lateral direction L a second distance D 2 . For this embodiment, as depicted, the first distance D 1  or distance between first point P 1  and first origin OR 1  along the first direction (e.g., the lateral direction L) is greater than the second distance D 2  or distance between second point P 2  and second origin OR 2  along the first direction. 
     For the depicted embodiment of  FIG. 15 , displacement measurement unit  195  is attached to tub  114  at first point P 1  and is configured to sense or measure the first distance D 1 , or the distance between first point P 1  and first origin OR 1  along the first direction. To ascertain first distance D 1 , displacement measurement unit  195  provides input signals (e.g., a voltage or an acceleration reading generated by displacement measurement unit  195 ) to controller  180  indicative of the first distance D 1 . In this way, first point P 1  is a sensed or measured point. That is, first distance D 1  is sensed or measured by displacement measurement unit  195 . 
     As further shown in  FIG. 15 , for this exemplary embodiment, tub  114  of subwasher  200  does not include a displacement measurement unit at second point P 2 . Thus, to ascertain the second distance D 2 , controller  180  estimates or predicts the distance between second point P 2  and second origin OR 2 . In this way, second point P 2  is a virtual point. That is, assuming tub  114  is a rigid body and knowing the dimensional configuration of tub  114 , the position of any point, including the second point P 2 , may be predicted based on the measured position of the first point P 1 . As the second distance D 2  is determined by using a virtual point at second point P 2 , washing machine appliance  100  need not include multiple displacement measurement units. 
     In alternative exemplary embodiments, the second point P 2  may be a measured point and the first point P 1  may be a virtual point. In yet other alternative exemplary embodiments, the first point P 1  and the second point P 2  may both be sensed or measured points. In such embodiments, washing machine appliance  100  may include two displacement measurement unit  195  positioned at the first and second points. In yet other embodiments, the first point P 1  and the second point P 2  may both be virtual points. In such embodiments, displacement measurement unit  195  may be attached to tub  114  at a given location, and the first distance D 1  and the second distance may be predicted. 
     Further, for this embodiment, the first distance D 1  is ascertained by taking or calculating the absolute value of the amplitude of the distance between first point P 1  and first origin OR 1  along the first direction for the first time period. In this way, the second distance D 2  need not be calculated or predicted for every distance value measured by displacement measurement unit  195 . Rather, when controller  180  recognizes that the first point P 1  has reached a maximum distance from first origin OR 1  along the first direction for that particular oscillation (i.e., the distance has reached its amplitude), the second distance D 2  can be calculated based at least in part on the absolute value of the amplitude of the first distance for the first time period at that particular point in time. In this manner, the computational resources of controller  180  may be conserved. 
     At ( 406 ), with reference again to  FIG. 14 , method ( 400 ) includes determining the location of the imbalanced load for the first time period based at least in part on the first distance and the second distance. As one example, determining the location of the imbalanced load for the first time period based at least in part on the first distance and the second distance includes determining a distance ratio. The distance ratio may either be a ratio of the second distance to the first distance (D 2 :D 1 ) or a ratio of the first distance to the second distance (D 1 :D 2 ). Thereafter, the distance ratio may be compared to one or more distance thresholds, e.g., in a like or similar manner as described above with respect to comparing the displacement ration to the displacement thresholds. Furthermore, the location of the imbalanced load may be determined in other suitable manners, such as e.g., any of the manners described above with respect to how the imbalanced load may be determined based at least in part on the first and second displacements. 
     At ( 408 ), method ( 400 ) includes generating a control action in response to the location of the imbalanced load. As one example, if the imbalanced load is towards front  132  of tub  114 , a current spin cycle being performed may be stopped, basket  120  may then be pulsed or otherwise rotated in a way to even out the load, and then wash basket  120  may be spun up once more to complete the spin cycle. Other control actions are also possible. 
     In using method ( 400 ), components of the displacement vector (e.g., the distance between the points and their respective origins along the lateral direction, the distance between the points and their respective origins along the transverse direction, and/or the distance between the points and their respective origins along the vertical direction) may be used to determine the location of imbalanced loads within washing machine appliance  100 . As a single component of the displacement vector (e.g., distance between the points and their respective origins along the lateral direction) may be used to determine the location of an imbalanced load, the number of computations needed to be performed by a processing device of controller  180  may be reduced, for example. That is, instead of potentially calculating the displacement of the points relative to their respective origins, which may include translational and rotational motion along all three (3) directions, in using method ( 400 ), motion need only be calculated for a single component of the displacement vector. 
     Further, in implementing method ( 400 ), more than two points may be used to determine the location of the imbalanced load for the first time period. For instance, in such implementations, method ( 400 ) includes ascertaining a third distance between a third point and a third origin along the first direction for the first time period. For instance, second point P 2  may be positioned forward of first point P 1  and third point P 3  may be positioned forward of P 2 . For example, first point P 1  may be defined at rear  134  of tub  114 , second point P 2  may be defined at a center of gravity CG of subwasher  200 , and third point P 3  may be defined at front  132  of tub  114 . First point P 1 , second point P 2 , and third point P 3  may be positioned along the central axis A defined by shaft  136  ( FIG. 2 ). When subwasher  200  is in a resting state, first point P 1  is positioned at first origin OR 1 , second point P 2  is positioned at second origin OR 2 , and third point P 3  is positioned at third origin OR 3 . Further, in such implementations, the method also includes determining the location of the imbalanced load for the first time period based at least in part on the first distance, the second distance, and the third distance. 
     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.