Patent Publication Number: US-9840805-B2

Title: Methods for determining load mass in washing machine appliances

Description:
FIELD OF THE INVENTION 
     The present disclosure relates generally to washing machine appliances, and more particularly to methods for determining load masses in washing machine appliances. 
     BACKGROUND OF THE INVENTION 
     Washing machine appliances generally include a tub for containing 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 operation of such washing machine appliances, 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 in the wash fluid, to wring wash fluid from articles within the wash chamber, etc. 
     One issue with washing machine appliance performance has been the varying masses of articles being washed in the appliance. Operation of the appliance at, for example, a specified speed for a specified time period may not provide optimal performance for every mass. Accordingly, it is generally useful to determine the load mass, in order to tailor appliance performance to these variables. 
     Attempts have been made to determine load mass in washing machine appliances, and to monitor water levels during operation. However, known methods and apparatus typically involve complex software and sensors, thus increasing the cost of the appliance or preventing commercial use from being viable, or are relatively inaccurate. Additionally, many such methods require calibration before use. 
     Accordingly, improved methods for determining load masses in washing machine appliances are desired in the art. In particular, methods which have reduced complexity and are generally viable, cost-effective and accurate would be advantageous. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In accordance with one embodiment of the present disclosure, a method for determining a load mass in a washing machine appliance, is provided. The method includes accelerating rotation of a basket about a central axis within a tub of the washing machine appliance from a first speed to a second speed greater than the first speed and for a predetermined time measured for acceleration of the basket from the first speed; measuring, during the accelerating step, a check speed of the basket at the predetermined time; and measuring, during the accelerating step, an acceleration time for the tub to accelerate from the first speed to the second speed. The method further includes discontinuing acceleration of the basket after the second speed and the predetermined time have been reached; and measuring a coast time for coasting of the basket from the check speed to the first speed. The method further includes determining a load mass in the basket based on the check speed, the acceleration time, and the coast time. 
     In accordance with another embodiment of the present disclosure, a washing machine appliance is provided. The washing machine appliance includes a cabinet, a tub disposed within the cabinet, a basket disposed within the tub and rotatable relative to the tub about a central axis, and a motor connected to the basket and operable to rotate the basket. The washing machine appliance further includes a controller in communication with the motor. The controller is configured for accelerating rotation of the basket about the central axis from a first speed to a second speed greater than the first speed and for a predetermined time measured for acceleration of the basket from the first speed; measuring, during the accelerating step, a check speed of the basket at the predetermined time; and measuring, during the accelerating step, an acceleration time for the tub to accelerate from the first speed to the second speed. The controller is further configured for discontinuing acceleration of the basket after the second speed and the predetermined time have been reached; and measuring a coast time for coasting of the basket from the check speed to the first speed. The controller is further configured for determining a load mass in the basket based on the check speed, the acceleration time, and the coast time. 
     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 a washing machine appliance in accordance with one embodiment of the present disclosure; 
         FIG. 2  provides a front, section view of a washing machine appliance in accordance with one embodiment of the present disclosure; 
         FIG. 3  provides a flow chart of various steps of an exemplary method for determining a load mass in a washing machine appliance in accordance with one embodiment of the present disclosure; and 
         FIG. 4  provides a flow chart of various steps of an exemplary method for determining a load mass in a washing machine appliance in accordance with one 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  is a perspective view of a washing machine appliance  50  according to an exemplary embodiment of the present subject matter. As may be seen in  FIG. 1 , washing machine appliance  50  includes a cabinet  52  and a cover  54 . A backsplash  56  extends from cover  54 , and a control panel  58  including a plurality of input selectors  60  is coupled to backsplash  56 . Control panel  58  and input selectors  60  collectively form a user interface input for operator selection of machine cycles and features, and in one embodiment, a display  61  indicates selected features, a countdown timer, and/or other items of interest to machine users. A lid  62  is mounted to cover  54  and is rotatable between an open position (not shown) facilitating access to a wash tub  64  ( FIG. 2 ) located within cabinet  52  and a closed position (shown in  FIG. 1 ) forming an enclosure over tub  64 . 
     Lid  62  in exemplary embodiment includes a transparent panel  63 , which may be formed of for example glass, plastic, or any other suitable material. The transparency of the panel  63  allows users to see through the panel  63 , and into the tub  64  when the lid  62  is in the closed position. In some embodiments, the panel  63  may itself generally form the lid  62 . In other embodiments, the lid  62  may include the panel  63  and a frame  65  surrounding and encasing the panel  63 . Alternatively, panel  63  need not be transparent. 
       FIG. 2  provides a front, cross-section views of washing machine appliance  50 . As may be seen in  FIG. 2 , tub  64  includes a bottom wall  66  and a sidewall  68 . A wash drum or wash basket  70  is rotatably mounted within tub  64 . In particular, basket  70  is rotatable about a vertical axis V. Thus, washing machine appliance is generally referred to as a vertical axis washing machine appliance. Basket  70  defines a wash chamber  73  for receipt of articles for washing and extends, e.g., vertically, between a bottom portion  80  and a top portion  82 . Basket  70  includes a plurality of openings or perforations  71  therein to facilitate fluid communication between an interior of basket  70  and tub  64 . 
     A nozzle  72  is configured for flowing a liquid into tub  64 . In particular, nozzle  72  may be positioned at or adjacent top portion  82  of basket  70 . Nozzle  72  may be in fluid communication with one or more liquid sources  75 ,  76  in order to direct liquid (e.g. water) into tub  64  and/or onto articles within chamber  73  of basket  70 . Nozzle  72  may further include apertures  79  through which liquid may be sprayed into the tub  64 . Apertures  79  may, for example, be tubes extending from the nozzles  72  as illustrated, or simply holes defined in the nozzles  72  or any other suitable openings through which liquid may be sprayed. Nozzle  72  may additionally include other openings, holes, etc. (not shown) through which liquid may be flowed, i.e. sprayed or poured, into the tub  64 . 
     A main valve  74  regulates the flow of fluid through nozzle  72 . For example, valve  74  can selectively adjust to a closed position in order to terminate or obstruct the flow of liquid through nozzle  72 . The main valve  74  may be in fluid communication with one or more external liquid sources, such as a cold water source  75  and a hot water source  76 . The cold water source  75  may, for example, be a commercial water supply, while the hot water source  76  may be, for example, a water heater. Such external water sources  75 ,  76  may supply water to the appliance  50  through the main valve  74 . A cold water conduit  77  and a hot water conduit  78  may supply cold and hot water, respectively, from the sources  75 ,  76  through valve  74 . Valve  74  may further be operable to regulate the flow of hot and cold liquid, and thus the temperature of the resulting liquid flowed into tub  64 , such as through the nozzle  72 . 
     An additive dispenser  84  may additionally be provided for directing a wash additive, such as detergent, bleach, liquid fabric softener, etc., into the tub  64 . For example, dispenser  84  may be in fluid communication with nozzle  72  such that liquid flowing through nozzle  72  flows through dispenser  84 , mixing with wash additive at a desired time during operation to form a wash fluid before being flowed into tub  64 . In some embodiments, nozzle  72  is a separate downstream component from dispenser  84 . In other embodiments, nozzle  72  and dispenser  84  may be integral, with a portion of dispenser  84  serving as the nozzle  72 . A pump assembly  90  (shown schematically in  FIG. 2 ) is located beneath tub  64  and basket  70  for gravity assisted flow to drain tub  64 . 
     An agitation element  92 , shown as an impeller in  FIG. 2 , may be disposed in basket  70  to impart an oscillatory motion to articles and liquid in chamber  73  of basket  70 . In various exemplary embodiments, agitation element  92  includes a single action element (i.e., oscillatory only), double action (oscillatory movement at one end, single direction rotation at the other end) or triple action (oscillatory movement plus single direction rotation at one end, singe direction rotation at the other end). As illustrated in  FIG. 2 , agitation element  92  is oriented to rotate about vertical axis V. Alternatively, basket  70  may provide such agitating movement, and agitation element  92  is not required. Basket  70  and agitation element  92  are driven by a motor  94 , such as a pancake motor, which may be operably connected to the basket  70  and/or agitation element  92 . For example, as motor output shaft  98  is rotated, basket  70  and agitation element  92  are operated for rotatable movement within tub  64 , e.g., about vertical axis V. Washing machine appliance  50  may also include a brake assembly (not shown) selectively applied or released for respectively maintaining basket  70  in a stationary position within tub  64  or for allowing basket  70  to spin within tub  64 . 
     Various sensors may additionally be included in the washing machine appliance  50 . For example, a suitable speed sensor  112  can be connected to the motor  94 , such as to the output shaft  98  thereof, to measure rotational speed and indicate operation of the motor  94 . Other suitable sensors, such as temperature sensors, pressure sensors, etc., may additionally be provided in the washing machine appliance  50 . 
     Operation of washing machine appliance  50  is controlled by a processing device or controller  100 , that is operatively coupled to the input selectors  60  located on washing machine backsplash  56  (shown in  FIGS. 1 and 2 ) for user manipulation to select washing machine cycles and features. Controller  100  may further be operatively coupled to various other components of appliance  50 , such as main valve  74 , motor  94 , speed sensor  112 , and other suitable sensors, etc. In response to user manipulation of the input selectors  60 , controller  100  may operate the various components of washing machine appliance  50  to execute selected machine cycles and features. 
     Controller  100  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  100  may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software. Control panel  58  and other components of washing machine appliance  50  may be in communication with controller  100  via one or more signal lines or shared communication busses. 
     In an illustrative embodiment, a load of laundry articles are loaded into chamber  73  of basket  70 , and washing operation is initiated through operator manipulation of control input selectors  60 . Tub  64  is filled with water and mixed with detergent to form a liquid or wash fluid. Main valve  74  can be opened to initiate a flow of water into tub  64  via nozzle  72 , and tub  64  can be filled to the appropriate level for the amount of articles being washed. Once tub  64  is properly filled with wash fluid, the contents of the basket  70  are agitated with agitation element  92  or by movement of the basket  70  for cleaning of articles in basket  70 . More specifically, agitation element  92  or basket  70  is moved back and forth in an oscillatory motion. 
     After the agitation phase of the wash cycle is completed, tub  64  is drained. Laundry articles can then be rinsed by again adding fluid to tub  64 , depending on the particulars of the cleaning cycle selected by a user, agitation element  92  or basket  70  may again provide agitation within basket  70 . 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  70  is rotated at relatively high speeds. 
     While described in the context of specific embodiments of washing machine appliance  50 , using the teachings disclosed herein it will be understood that washing machine appliance  50  is provided by way of example only. Other washing machine appliances having different configurations (such as horizontal-axis washing machine appliances), different appearances, and/or different features may also be utilized with the present subject matter as well. 
     Referring now to  FIGS. 3 and 4 , various methods may be provided for use with washing machine appliances  50  in accordance with the present disclosure. In general, the various steps of methods as disclosed herein may in exemplary embodiments be performed by the controller  100 , which may receive inputs and transmit outputs from various other components of the appliance  50 . 
     For example, as illustrated in  FIGS. 3 and 4  and indicated by reference number  200 , methods for determining a load mass in a washing machine appliance  50  are provided. Such methods  200  generally accurately and efficiently determined the mass of a load of articles loaded into a basket  70  for washing. Such mass calculation can advantageously be utilized to tailor various operating conditions of the appliance  50 , such as agitation time, agitation profile, spin speed, spin time, etc. for optimal wash and energy performance, and can further be utilized to predict a load type for the load and tailor the operating conditions for such load. Additionally, such methods  200  may provide improved accuracy by being relatively more robust to factors such as friction, motor temperature, line voltage variations, etc. 
     Method  200  may, for example, include the step  202  of performing a load sense spin. The step  202  of performing the load sense spin may include a variety of sub-steps, as discussed herein. A load mass  204  may be determined for and as an output of the step  202 . The load mass  204  may be a calculated estimate, based on various inputs and steps as discussed herein, for the mass of a load contained within basket  70 . 
     Method  200  may further include the step  206  of repeating the step  202 . Step  206  may be performed once, twice, three times or more, as desired. In exemplary embodiments, step  206  may be performed twice, such that the step  202  is performed a total of three times. 
     Method  200  may further include the step  208  of averaging the load mass  204  from each performance of the load sense spin step  202  to determine an average load mass  204 ′. 
     Alternatively, rather than determining a plurality of load masses  204 ′ and then averaging the load masses  204  to determine average load mass  204 ′, various of the variables utilized in the sub-steps of step  202  as discussed herein may be individually collected, without a load mass  204  initially determined. Upon repeating of step  202 , the result for each variable from each performance of step  202  may be averaged with other results for that variable. These average variables may then be utilized in accordance with the present disclosure to determine the load mass  204 . 
     Method  200 , and step  202  thereof, may, for example, include the step  210  of accelerating rotation of the basket  70  about the central axis V within the tub  64  from a first speed  212  to a second speed  214  which is greater than the first speed  212  and for a predetermined time  216 . Notably, acceleration of the basket  70  may continue in accordance with step  210  for the longer of the predetermined time  216  and a time from the first speed  212  to the second speed  214 . Controller  100  may operate motor  94  to accelerate rotation of the basket  70 . Notably, in exemplary embodiments such acceleration is at 100% power, with no braking or other modulating of the motor  94 , etc. Alternatively, less than 100% power may be utilized. 
     Step  210  is generally performed after articles forming a load are loaded into the basket  70 , and before any substantial amount of water is flowed into the tub  64  to begin washing of the load. Notably, minimal amounts of water may be initially flowed into the tub  64  before such step  210  for various purposes, such as for use in entrapment protection programs. Accordingly, the load mass determined utilizing method  200  is generally a dry load mass. 
     Method  200 , and step  202  thereof, may further include, for example, the step  220  of measuring a check speed  222  of the basket  70  at predetermined time  216 . Such step  220  may be performed during the accelerating step  210 . The predetermined time  216  may be measured for acceleration of the basket  70  from the first speed  212 . Accordingly, a timer (which may be a feature of controller  100  or a separate component in communication with controller  100 ) may begin keeping time when the basket  70  reaches or exceeds the first speed  212 . When the predetermined time  216  is reached, the check speed  222 , which is the speed of the basket  70  at such time  216 , may be measured. 
     In some embodiments, one or more sensors  112  may be utilized to detect check speed  222 , as well as first and second speeds  212 ,  214  and other speeds discussed herein. Alternatively, other suitable components or the motor  94 , motor shaft  98 , controller  100 , and/or components thereof may be utilized to detect such speeds. 
     In some embodiments, the first speed  212  is zero revolutions per minute, and the basket  70  is thus rotationally stationary. Alternatively, however, the first speed may be greater than 0 revolutions per minute (“RPMs”). For example, in some embodiments, the first speed  212  may be between approximately 10 and approximately 30 RPMs. Before the accelerating step  210 , the basket  70  may for example be accelerated to the first speed  212 . The basket  70  may then continue accelerating through the first speed  212 , with step  210  beginning when the first speed  212  is reached as discussed above. 
     As discussed, the second speed  214  may be greater than the first speed  212 . In some embodiments, for example, the second speed  214  is between approximately 120 and approximately 180 RPMs. Additionally, the predetermined time  216  may, for example, be between approximately 1 and approximately 5 seconds. 
     It should be understood that the first speed  212 , second speed  214  and predetermined time  216  are not limited to the above disclosed embodiments, and rather that any suitable speeds, times or ranges thereof are within the scope and spirit of the present disclosure. 
     Method  200 , and step  202  thereof, may further include, for example, the step  230  of measuring an acceleration time  232  for the tub  70  to accelerate from the first speed  212  to the second speed  214 . For example, a timer (which may be independent from the above-discussed timer) may start when the tub  70  meets or exceeds the first speed  212  and may stop when the tub  70  meets or exceeds the second speed  214 . The resulting time may be the acceleration time  232 . 
     Notably, while in some embodiments acceleration time  232  may be greater than predetermined time  216 , in alternative embodiments acceleration time  226  may be equal to or less than predetermined time  216 . 
     Method  200 , and step  202  thereof, may further include, for example, the step  240  of continuing accelerating rotation of the basket  70  to an overshoot speed  242  after the second speed  214  and predetermined time  216  are reached. Overshoot speed  242  may be greater than second speed  214  and may further be greater than check speed  222  and, for example, in some embodiments may be in the range between approximately 140 and approximately 200 RPMs. 
     Method  200 , and step  202  thereof, may further include, for example, the step  250  of discontinuing acceleration of the basket after the second speed  214  and the predetermined time  216  have been reached. For example, operation of the motor  94 , such as by controller  100 , may be discontinued. In some embodiments, after such discontinuation in accordance with the present disclosure, no braking may occur. Alternatively, however, braking may occur. Rather the basket  70  may be allowed to freely rotate, i.e. coast, after such discontinuation. Step  250  may occur in some embodiments after step  240 . Alternatively, however, step  240  may not be utilized, and step  250  may occur immediately upon the second speed  214  and predetermined time  216  both being reached. 
     Method  200 , and step  202  thereof, may further include, for example, the step  260  of measuring a coast time  262 , such as a first coast time  262 , for coasting of the basket  70  from the second speed  214  to the first speed  212 . For example, as the basket  70  is coasting and thus decelerating, a timer (which may be independent of other timers discussed herein) may start when the second speed  214  is reached (i.e. met or passed during deceleration) and stopped when the first speed  212  is reached (i.e. met or passed during deceleration). 
     Method  200 , and step  202  thereof, may further include, for example, the step  270  of measuring a coast time  272 , such as a second coast time  272 , for coasting of the basket  70  from the check speed  222  to the first speed  212 . For example, as the basket  70  is coasting and thus decelerating, a timer (which may be independent of other timers discussed herein) may start when the check speed  222  is reached (i.e. met or passed during deceleration) and stopped when the first speed  212  is reached (i.e. met or passed during deceleration). 
     Further, in some embodiments, various electrical measurements may be made, such as of the motor  94 , during the accelerating step  210  and/or after the discontinuing step  250 . These electrical measurements, which may for example, be current and/or voltage measurements, may, for example, be measured by the controller  100  in communication with the motor  94 , such as through the use of suitable sensors included in or in communication with the motor  94 . 
     For example, method  200 , and step  202 , may further include the step  280  of measuring a current  282  to the appliance  50 , such as to the motor  94  thereof. Such step  280  may, for example, occur during the accelerating step  210 . For example, during the accelerating step  210 , the current  282  may be sampled at a suitable rate, and the collected samples averaged as current  282 . 
     Method  200 , and step  202 , may further include the step  290  of measuring a voltage  292  to the appliance  50 , such as to the motor  94  thereof (i.e. of the electrical line providing power to the appliance  50 , such as to the motor  94  thereof). Such step  290  may, for example, occur during the accelerating step  210 . For example, during the accelerating step  210 , the voltage  292  may be sampled at a suitable rate, and the collected samples averaged as voltage  292 . Notably, in exemplary embodiments, the root mean square voltage may be utilized, and may be sampled and averaged. Alternatively, the peak voltage or another suitable voltage value may be utilized. 
     Method  200 , and step  202 , may further include the step  294  of measuring a voltage  296  to the appliance  50  (i.e. of the electrical line providing power to the appliance  50 ). Such step  294  may, for example, occur after the discontinuing step  250 , i.e. during coasting of the basket  70 . For example, during this period, the voltage  296  may be sampled at a suitable rate, and the collected samples averaged as voltage  296 . Notably, in exemplary embodiments, the root mean square voltage may be utilized, and may be sampled and averaged. Alternatively, the peak voltage or another suitable voltage value may be utilized. 
     Further, in some embodiments a voltage sag value  299  may be determined. For example, method  200 , and step  202 , may further include the step  298  of subtracting the voltage  296  from the voltage  292  to determine the voltage sag  299 . 
     Method  200 , and step  202 , may further include the step  300  of determining a load mass  204  in the basket  70 . The determining step  300  may be based on, for example, one or more of the check speed  222 , the acceleration time  232 , the first coast time  262 , the second coast time  272 , the current  282 , the voltage  292 , the voltage  296  and/or the voltage sag  299 . For example, in some embodiments, step  300  may include the step of utilizing a transfer function to determine the load mass  204 . The one or more of the check speed  222 , the acceleration time  232 , the first coast time  262 , the second coast time  272 , the current  282 , the voltage  292 , the voltage  296  and/or the voltage sag  299  may be inputs to the transfer function. One embodiment of a suitable transfer function for use in accordance with the present disclosure is as follows:
 
 W=A+Bω   c   +Ct   r2   +Et   c2   +GV   2   +It+Jω   c   2   +Kt   r2   2   +Mt   c2   2   +OV   2   2   +Qt   2  
 
wherein:
 
     W is the load mass; 
     ω c  is the check speed; 
     t r2  is the acceleration time; 
     t c2  is the second coast time; 
     V 2  is the voltage measured after the discontinuing step  250 ; 
     i is the current; and 
     A, B, C, E, G, I, J, K, M, O and Q are constants. 
     Another embodiment of a suitable transfer function for use in accordance with the present disclosure is as follows:
 
 W=A+Bω   c   +Ct   r2   +Dt   c1   +Et   c2   +FV   1   +GV   2   +HV   sag   +It+Jω   c   2   +Kt   r2   2   +Lt   c1   2   +Mt   c2   2   +NV   1   2   +OV   2   2   +PV   sag   2   +Qt   2  
 
wherein:
 
     W is the load mass; 
     ω c  is the check speed; 
     t r2  is the acceleration time; 
     t c1  is the first coast time; 
     t c2  is the second coast time; 
     V 1  is the voltage measured during the accelerating step  210 ; 
     V 2  is the voltage measured after the discontinuing step  250 ; 
     V sag  is the voltage sag; 
     i is the current; and 
     A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P and Q are constants. 
     Notably, constants A through Q utilized in the above disclosed embodiments of the transfer function may in exemplary embodiments be empirically determined, such as through reasonable experimentation, and these constants and the transfer function itself may, for example, be programmed into controller  100 . 
     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.