Patent Publication Number: US-11639571-B2

Title: System and method for determining dry load weight within a washing machine appliance

Description:
FIELD OF THE INVENTION 
     The present subject matter relates generally to washing machine appliances, or more specifically, to systems and methods for determining dry load weight within a washing machine appliance. 
     BACKGROUND OF THE INVENTION 
     Washing machine appliances generally include a tub for containing water or wash fluid, e.g., water and detergent, bleach, and/or other wash additives. A basket is rotatably mounted within the tub and defines a wash chamber for receipt of articles for washing. During normal operation of such washing machine appliances, the wash fluid is directed into the tub and onto articles within the wash chamber of the basket. The basket or an agitation element can rotate at various speeds to agitate articles within the wash chamber, to wring wash fluid from articles within the wash chamber, etc. During a spin or drain cycle, a drain pump assembly may operate to discharge water from within sump. 
     Notably, it is frequently desirable to determine the dry load size or weight of a load of clothes within the washing machine appliance, e.g., in order to optimize water usage, agitation profile selection, and other wash parameters. In addition, the spin speed of the basket may frequently need to be limited based on dry load weight, e.g., due to the allowed system stresses and operating dynamics. However, conventional dry load weight detection methods are complex, time-consuming, and require costly sensors. In addition, such systems and methods suffer from inaccurate measurements, resulting in compromised wash performance and consumer dissatisfaction. 
     Accordingly, a washing machine appliance with features for improved dry load weight detection would be desirable. More specifically, a system and method for monitoring dry load weight without complex sensors or algorithms would be particularly beneficial. 
     BRIEF DESCRIPTION OF THE INVENTION 
     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. 
     In accordance with one exemplary embodiment of the present disclosure, a washing machine appliance is provided including a wash tub positioned within a cabinet and defining a wash chamber, a wash basket rotatably mounted within the wash tub and being configured for receiving of a load of articles for washing, and a motor operably coupled to the wash basket for selectively rotating the wash basket. A controller is operably coupled to the motor and is configured for accelerating the wash basket to a predetermined speed during an acceleration period, obtaining an acceleration power of the motor during the acceleration period, maintaining rotation of the wash basket at the predetermined speed during a steady state period, obtaining a steady state power of the motor during the steady state period, and determining a dry load weight based on a power drop between the acceleration power and the steady state power. 
     In accordance with another exemplary embodiment of the present disclosure, a method of operating a washing machine appliance is provided. The washing machine appliance includes a wash basket rotatably mounted within a wash tub and a motor operably coupled to the wash basket for selectively rotating the wash basket. The method includes accelerating the wash basket to a predetermined speed during an acceleration period, obtaining an acceleration power of the motor during the acceleration period, maintaining rotation of the wash basket at the predetermined speed during a steady state period, obtaining a steady state power of the motor during the steady state period, and determining a dry load weight based on a power drop between the acceleration power and the steady state power. 
     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. 
         FIG.  1    provides a perspective view of an exemplary washing machine appliance according to an exemplary embodiment of the present subject matter. 
         FIG.  2    provides a side cross-sectional view of the exemplary washing machine appliance of  FIG.  1   . 
         FIG.  3    illustrates a method for determining a dry load weight in a washing machine appliance in accordance with one embodiment of the present disclosure. 
         FIG.  4    provides an exemplary plot of a wash basket speed and a motor power over a typically load weight detection cycle according to an exemplary embodiment of the present subject matter. 
     
    
    
     Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention. 
     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. 
     Referring now to the figures,  FIG.  1    is a perspective view of an exemplary horizontal axis washing machine appliance  100  and  FIG.  2    is a side cross-sectional view of washing machine appliance  100 . As illustrated, washing machine appliance  100  generally defines a vertical direction V, a lateral direction L, and a transverse direction T, each of which is mutually perpendicular, such that an orthogonal coordinate system is generally defined. Washing machine appliance  100  includes a cabinet  102  that extends between a top  104  and a bottom  106  along the vertical direction V, between a left side  108  and a right side  110  along the lateral direction, and between a front  112  and a rear  114  along the transverse direction T. 
     Referring to  FIG.  2   , a wash basket  120  is rotatably mounted within cabinet  102  such that it is rotatable about an axis of rotation A. A motor  122 , e.g., such as a pancake motor, is in mechanical communication with wash basket  120  to selectively rotate wash basket  120  (e.g., during an agitation or a rinse cycle of washing machine appliance  100 ). Wash basket  120  is received within a wash tub  124  and defines a wash chamber  126  that is configured for receipt of articles for washing. The wash tub  124  holds wash and rinse fluids for agitation in wash basket  120  within wash tub  124 . As used herein, “wash fluid” may refer to water, detergent, fabric softener, bleach, or any other suitable wash additive or combination thereof. Indeed, for simplicity of discussion, these terms may all be used interchangeably herein without limiting the present subject matter to any particular “wash fluid.” 
     Wash basket  120  may define one or more agitator features that extend into wash chamber  126  to assist in agitation and cleaning articles disposed within wash chamber  126  during operation of washing machine appliance  100 . For example, as illustrated in  FIG.  2   , a plurality of ribs  128  extends from basket  120  into wash chamber  126 . In this manner, for example, ribs  128  may lift articles disposed in wash basket  120  during rotation of wash basket  120 . 
     Referring generally to  FIGS.  1  and  2   , cabinet  102  also includes a front panel  130  which defines an opening  132  that permits user access to wash basket  120  of wash tub  124 . More specifically, washing machine appliance  100  includes a door  134  that is positioned over opening  132  and is rotatably mounted to front panel  130 . In this manner, door  134  permits selective access to opening  132  by being movable between an open position (not shown) facilitating access to a wash tub  124  and a closed position ( FIG.  1   ) prohibiting access to wash tub  124 . 
     A window  136  in door  134  permits viewing of wash basket  120  when door  134  is in the closed position, e.g., during operation of washing machine appliance  100 . Door  134  also includes a handle (not shown) that, e.g., a user may pull when opening and closing door  134 . Further, although door  134  is illustrated as mounted to front panel  130 , it should be appreciated that door  134  may be mounted to another side of cabinet  102  or any other suitable support according to alternative embodiments. 
     Referring again to  FIG.  2   , wash basket  120  also defines a plurality of perforations  140  in order to facilitate fluid communication between an interior of basket  120  and wash tub  124 . A sump  142  is defined by wash tub  124  at a bottom of wash tub  124  along the vertical direction V. Thus, sump  142  is configured for receipt of and generally collects wash fluid during operation of washing machine appliance  100 . For example, during operation of washing machine appliance  100 , wash fluid may be urged by gravity from basket  120  to sump  142  through plurality of perforations  140 . 
     A drain pump assembly  144  is located beneath wash tub  124  and is in fluid communication with sump  142  for periodically discharging soiled wash fluid from washing machine appliance  100 . Drain pump assembly  144  may generally include a drain pump  146  which is in fluid communication with sump  142  and with an external drain  148  through a drain hose  150 . During a drain cycle, drain pump  146  urges a flow of wash fluid from sump  142 , through drain hose  150 , and to external drain  148 . More specifically, drain pump  146  includes a motor (not shown) which is energized during a drain cycle such that drain pump  146  draws wash fluid from sump  142  and urges it through drain hose  150  to external drain  148 . 
     A spout  152  is configured for directing a flow of fluid into wash tub  124 . For example, spout  152  may be in fluid communication with a water supply  154  ( FIG.  2   ) in order to direct fluid (e.g., clean water or wash fluid) into wash tub  124 . Spout  152  may also be in fluid communication with the sump  142 . For example, pump assembly  144  may direct wash fluid disposed in sump  142  to spout  152  in order to circulate wash fluid in wash tub  124 . 
     As illustrated in  FIG.  2   , a detergent drawer  156  is slidably mounted within front panel  130 . Detergent drawer  156  receives a wash additive (e.g., detergent, fabric softener, bleach, or any other suitable liquid or powder) and directs the fluid additive to wash tub  124  during operation of washing machine appliance  100 . According to the illustrated embodiment, detergent drawer  156  may also be fluidly coupled to spout  152  to facilitate the complete and accurate dispensing of wash additive. 
     In addition, a water supply valve or control valve  158  may provide a flow of water from a water supply source (such as a municipal water supply  154 ) into detergent dispenser  156  and into wash tub  124 . In this manner, control valve  158  may generally be operable to supply water into detergent dispenser  156  to generate a wash fluid, e.g., for use in a wash cycle, or a flow of fresh water, e.g., for a rinse cycle. It should be appreciated that control valve  158  may be positioned at any other suitable location within cabinet  102 . In addition, although control valve  158  is described herein as regulating the flow of “wash fluid,” it should be appreciated that this term includes, water, detergent, other additives, or some mixture thereof. 
     A control panel  160  including a plurality of input selectors  162  is coupled to front panel  130 . Control panel  160  and input selectors  162  collectively form a user interface input for operator selection of machine cycles and features. For example, in one embodiment, a display  164  indicates selected features, a countdown timer, and/or other items of interest to machine users. 
     Operation of washing machine appliance  100  is controlled by a controller or processing device  166  ( FIG.  1   ) that is operatively coupled to control panel  160  for user manipulation to select washing machine cycles and features. In response to user manipulation of control panel  160 , controller  166  operates the various components of washing machine appliance  100  to execute selected machine cycles and features. 
     Controller  166  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  166  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  160  and other components of washing machine appliance  100  may be in communication with controller  166  via one or more signal lines or shared communication busses. 
     During operation of washing machine appliance  100 , laundry items are loaded into wash basket  120  through opening  132 , and washing operation is initiated through operator manipulation of input selectors  162 . Wash tub  124  is filled with water, detergent, and/or other fluid additives, e.g., via spout  152  and or detergent drawer  156 . One or more valves (e.g., control valve  158 ) can be controlled by washing machine appliance  100  to provide for filling wash basket  120  to the appropriate level for the amount of articles being washed and/or rinsed. By way of example for a wash mode, once wash basket  120  is properly filled with fluid, the contents of wash basket  120  can be agitated (e.g., with ribs  128 ) for washing of laundry items in wash basket  120 . 
     After the agitation phase of the wash cycle is completed, wash tub  124  can be drained. Laundry articles can then be rinsed by again adding fluid to wash tub  124 , depending on the particulars of the cleaning cycle selected by a user. Ribs  128  may again provide agitation within wash basket  120 . 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 final spin cycle, basket  120  is rotated at relatively high speeds and drain pump assembly  144  may discharge wash fluid from sump  142 . After articles disposed in wash basket  120  are cleaned, washed, and/or rinsed, the user can remove the articles from wash basket  120 , e.g., by opening door  134  and reaching into wash basket  120  through opening  132 . 
     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. 
     Now that the construction of washing machine appliance  100  and the configuration of controller  166  according to exemplary embodiments have been presented, an exemplary method  200  of operating a washing machine appliance will be described. Although the discussion below refers to the exemplary method  200  of operating washing machine appliance  100 , one skilled in the art will appreciate that the exemplary method  200  is applicable to the operation of a variety of other washing machine appliances, such as vertical axis washing machine appliances. In exemplary embodiments, the various method steps as disclosed herein may be performed by controller  166  or a separate, dedicated controller. 
     Referring generally to  FIGS.  3  and  4   , a method of determining a dry load size or weight during a load weight detection cycle and a plot of such a load weight detection cycle, respectively, are provided. For example, referring briefly to  FIG.  4   , a plot of the basket speed (e.g., in revolutions per minute, identified by reference numeral  300 ) and the motor power (e.g., in Watts, identified by reference numeral  302 ) over time during a load weight detection cycle is provided according to an exemplary embodiment of the present subject matter. As shown, method  200  may be a part of a dry load weight or load score detection cycle performed before a wash cycle for each new load of clothes. The load weight detection cycle generally includes a sequence of spin operations and corresponding measurements of the wash basket speed and motor power, as described in detail below. 
     Referring again to  FIG.  3   , method  200  includes, at step  210 , accelerating a wash basket of a washing machine appliance to a predetermined speed during an acceleration period (e.g., as identified by reference numeral  304  in  FIG.  4   ). Specifically, according to the illustrated embodiment, motor  122  is regulated to accelerate wash basket  120  at a predetermined acceleration rate during the acceleration period, though other suitable acceleration profiles may be used according to alternative embodiments. In this regard, continuing the example from above, controller  166  may operate motor  122  to spin or rotate wash basket  120  after a new load of clothes has been added, and the load weight may be approximated based at least in part on the motor power required during the acceleration period. 
     Specifically, aspects of the present subject matter relate to approximating a load score or a dry load weight of the new load of clothes based at least in part on the motor power required to rotate wash basket  120  during the acceleration period  304  and a subsequent steady state period  306  (described below). Although exemplary systems and methods for making such measurements and implementing such spin profiles are described herein, it should be appreciated that variations and modifications may be made to washing machine appliance, its operation, and associated sensors and methods for detecting various operating parameters while remaining within the scope of the present subject matter. 
     For example, step  220  may include obtaining an acceleration power of a motor of the washing machine appliance during the acceleration period. In this manner, controller  166  may monitor the power required by motor  122  to drive wash basket  120  during all or part of the acceleration period  304 . Although the present subject matter describes monitoring only motor power, it should be appreciated that according to alternative embodiments, any other suitable acceleration parameters that might be useful for determining a load score or size may be monitored. For example, other acceleration parameters that might be measured include basket speeds, motor voltage, currents, etc. 
     As explained in more detail below, aspects of the present subject matter are directed to determining a power drop between the amount of power required to accelerate the wash basket to a particular basket speed and the amount of power required to maintain the basket speed. According to exemplary embodiments, it may be desirable to determine the peak acceleration during the acceleration period  304 . In this regard, according to an exemplary embodiment, obtaining the acceleration power may include obtaining a maximum power exerted by the motor during the acceleration period  304 . In this regard, for example, controller  166  may monitor the motor power curve  302  and may use any suitable method for determining the maximum power (e.g., as identified by reference numeral  308  in  FIG.  4   ). 
     According to alternative embodiments, obtaining the acceleration power may include measuring the power exerted by motor  122  during an acceleration measurement period that precedes the end of the acceleration period  304 . Specifically, as shown for example in  FIG.  4   , the acceleration measurement period is identified by reference numeral  310 . Controller  166  may continuously or periodically take power samples during this acceleration measurement period  310 , and these samples may be averaged to determine the acceleration power. These measurements may be taken at a fixed rate or at a variable rate throughout the entire acceleration period  304  or during a subset of the acceleration period  304 , e.g., such as the acceleration measurement period  310 . It should be appreciated that the acceleration measurement period  310  may have any suitable duration and may include any suitable number of measurements or power samples. For example, according to exemplary embodiments, the acceleration measurement period  310  may be between about 0.1 and 10 seconds, between about 0.5 and 7 seconds, between about 1 and 5 seconds, or about 3 seconds in duration. 
     It should be appreciated that any suitable measurement method, sampling rate, or measured variables may be used as a proxy for motor power. For example, according to an exemplary embodiment, motor current and/or voltage is measured and used as a proxy for motor power. In addition, motor voltage may be approximated using system or appliance voltage. Furthermore, basket speeds may be determined by measuring a motor frequency, a back electromotive force (EMF) on the motor, or a motor shaft speed (e.g., using a tachometer). It should be appreciated that other systems and methods for monitoring motor power and/or basket speeds may be used while remaining within the scope of the present subject matter. 
     Step  230  includes maintaining rotation of the wash basket at the predetermined speed during a steady state period (e.g., as identified by reference numeral  306  in  FIG.  4   ). According to the illustrated embodiment shown in  FIG.  4   , the steady state period  306  occurs after the acceleration period  304 . In general, during the steady state period  306 , the motor  122  maintains the rotation of the wash basket at a predetermined speed. In this regard, for example, the acceleration period  304  may continue until the wash basket is spinning at a predetermined speed, e.g., such as 150 revolutions per minute (RPM), after which the steady state period  306  commences to maintain that speed. 
     Step  240  includes obtaining a steady state power of the motor during the steady state period  306 . In this regard, the steady state motor power may be an average power (e.g., as identified by reference numeral  312  in  FIG.  4   ). It should be appreciated that motor power during the steady state period  306  may be measured in a manner similar to that described above with respect to the acceleration period  304 . According to exemplary embodiments, the average power  312  may be measured over the entire steady state period  306  or a subset of the steady state period  306 . For example, obtaining the steady state power may include measuring power exerted by motor  122  during a steady state measurement period  314  that begins after the wash basket  122  has stabilized at the predetermined speed. In this regard, controller  166  may monitor the motor power over steady state measurement period  314  and may take a statistical average at step  240 . Alternatively, controller  166  may take a single measurement that may be used as the statistical average. Other methods of sampling and statistically determining the motor power over the steady state period  306  or the steady state measurement period  314  may be used while remaining within the scope of the present subject matter. 
     Method  200  further includes, at step  250 , determining a dry load weight based on a power drop between the acceleration power and the steady state power. For example, according to one exemplary embodiment, the power drop may be equivalent to the acceleration power  308  determined at step  220  minus the steady state power  312  determined at step  240 . This power drop may be passed into a transfer function, such as a weighted transfer function with empirically determined constants or scaling values to determine an accurate dry load size or weight, e.g., in kilograms. More specifically, according to an exemplary embodiment, determining the dry load weight may include using the following equation:
 
 M=c   m ( P   acc   −P   ss )− C  
         where: M=dry load weight or mass;
           P acc =the acceleration power during the acceleration period;   P ss =the steady state power during the steady state period;   c m =a coefficient correlating load mass and motor power; and   C=a constant.   
               

     It should be appreciated that the equation provided above may vary while remaining within the scope of the present subject matter. For example, the number of samples taken, the frequency of samples taken, the variables measured, and other scaling factors may vary according to alternative embodiments. Such variations shall remain within the scope of the present subject matter. Furthermore, it should be appreciated that method  200  for determining the dry load weight is only one exemplary method used for the purpose of explaining aspects of the present subject matter. For example, the weighting values c m  through C may vary depending on the specific appliance, the appliance model, or any other suitable factors. These scaling factors may be determined empirically, based on models, or using any other suitable calculations. Such variations shall remain within the scope of the present subject matter. 
     Notably, as explained above, the load weight or load score may affect the washing performance of washing machine appliance  100 . Therefore, method  200  may further include, at step  260 , adjusting at least one operating parameter of the washing machine appliance based at least in part on the dry load weight. As used herein, an “operating parameter” of washing machine appliance  100  is any cycle setting, operating time, component setting, spin speed, part configuration, or other operating characteristic that may affect the performance of washing machine appliance  100 . Thus, references to operating parameter adjustments or “adjusting at least one operating parameter” are intended to refer to control actions intended to improve system performance based on the dry load weight or other system parameters. For example, adjusting an operating parameter may include adjusting an additive dispense amount, adjusting an agitation profile, adjusting a water level, limiting a spin speed of wash basket  120 , etc. Other operating parameter adjustments are possible and within the scope of the present subject matter. 
       FIG.  3    depicts 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 steps of any of the methods discussed herein can be adapted, rearranged, expanded, omitted, or modified in various ways without deviating from the scope of the present disclosure. Moreover, although aspects of method  200  are explained using washing machine appliance  100  as an example, it should be appreciated that these methods may be applied to the operation of any suitable washing machine appliance. 
     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.