METHOD FOR PREVENTING SPIN OUT-OF-BALANCE CONDITIONS IN A WASHING MACHINE APPLIANCE

Abstract

A washing machine appliance includes a tub positioned within a cabinet, a basket rotatably mounted within the tub and defining a wash chamber for receipt of articles for washing, an agitation element positioned in the wash basket, a motor in mechanical communication with the wash basket and agitation element and being configured for selectively rotating the wash basket and agitation element, a measurement device mounted to the tub for detecting the displacement amount of the tub, and a controller operatively coupled to the motor and measurement device. The controller is configured to control an operation of the motor to rotate the agitation element for a first agitation stroke distance, determine the displacement amount of the tub relative to first and second tub displacement thresholds based on the displacement amount detected by the measurement device, and perform an out-of-balance agitation cycle based on the displacement amount relative to the displacement thresholds.

Claims

1. A washing machine appliance, comprising: a tub positioned within a cabinet; a basket rotatably mounted within the tub, the basket defining a wash chamber for receipt of articles for washing; an agitation element positioned in the wash basket; a motor in mechanical communication with the wash basket and the agitation element, the motor being configured for selectively rotating the wash basket and the agitation element within the tub; a measurement device mounted to the tub for detecting a displacement amount of the tub; and a controller operatively coupled to the motor and the measurement device, the controller configured to: control an operation of the motor to rotate the agitation element for a first agitation stroke distance; determine the displacement amount of the tub, based on the displacement amount of the tub detected by the measurement device, relative to a first tub displacement threshold and a second tub displacement threshold; and perform an out-of-balance agitation cycle based on the determined displacement amount relative to the first and second tub displacement thresholds.

2. The washing machine appliance of claim 1, wherein the controller is configured to: perform a first out-of-balance agitation cycle when the determined displacement amount exceeds the first tub displacement threshold.

3. The washing machine appliance of claim 2, further comprising: a water control valve for regulating a flow of water from a water supply source into the tub, wherein, performing the first out-of-balance agitation cycle, comprises: controlling an operation of the water control valve to dispense a volume of water into the tub.

4. The washing machine appliance of claim 3, wherein, after the volume of water is dispensed into the tub, the controller is configured to: control the operation of the motor to rotate the agitation element for the first agitation stroke distance; determine the displacement amount of the tub based on the displacement amount of the tub detected by the measurement device; and perform a second out-of-balance agitation cycle when the determined displacement amount falls between the first tub displacement threshold and the second tub displacement threshold.

5. The washing machine appliance of claim 1, wherein the controller is configured to: perform a second out-of-balance agitation cycle when the determined displacement amount falls between the first tub displacement threshold and the second tub displacement threshold.

6. The washing machine appliance of claim 5, wherein, performing the second out-of-balance agitation cycle comprises: controlling the operation of the motor to rotate the agitation element for a second agitation stroke distance greater than or equal to the first agitation stroke distance.

7. The washing machine appliance of claim 5, wherein, the controller is configured to: repeat performing the second out-of-balance agitation cycle until the second out-of-balance agitation cycle has been performed for a predetermined number of times or the determined displacement amount falls below the second tub displacement threshold.

8. The washing machine appliance of claim 7, wherein the controller is configured to: increase the second tub displacement threshold when the second out-of-balance agitation cycle has been performed for the predetermined number of times.

9. The washing machine appliance of claim 8, wherein the controller is further configured to: control the operation of the motor to rotate the agitation element for the first agitation stroke distance; determine the displacement amount of the tub based on the displacement amount of the tub detected by the measurement device; and perform the second out-of-balance agitation cycle when the determined displacement amount falls between the first tub displacement threshold and the increased second tub displacement threshold.

10. The washing machine appliance of claim 1, wherein the controller is configured to: initiate a spin cycle when the determined displacement amount falls below the second tub displacement threshold.

11. The washing machine appliance of claim 1, wherein the first tub displacement threshold is greater than the second tub displacement threshold.

12. The washing machine appliance of claim 1, wherein the measurement device comprises an accelerometer or a gyroscope.

13. The washing machine appliance of claim 1, wherein the controller is configured to: calculate a trendline based on the determined displacement amount of the tub.

14. The washing machine appliance of claim 13, wherein the trend line is calculated utilizing a linear regression technique.

15. A method for operating a washing machine appliance, the washing machine appliance including a tub positioned within a cabinet, a basket rotatably mounted within the tub, the basket defining a wash chamber for receipt of articles for washing, an agitation element positioned in the wash basket, a motor in mechanical communication with the wash basket and the agitation element, the motor being configured for selectively rotating the wash basket and the agitation element within the tub, and a water control valve for regulating a flow of water from a water supply source into the tub, the method comprising: controlling an operation of the motor to rotate the agitation element for a first agitation stroke distance; determining a displacement amount of the tub relative to a first tub displacement threshold and a second tub displacement threshold; and performing an out-of-balance agitation cycle based on the determined displacement amount relative to the first and second tub displacement thresholds.

16. The method of claim 15, further comprising: performing a first out-of-balance agitation cycle when the determined displacement amount exceeds the first tub displacement threshold.

17. The method of claim 16, wherein performing the first out-of-balance agitation cycle comprises: controlling an operation of the water control valve to dispense a volume of water into the tub.

18. The method of claim 15, further comprising: performing a second out-of-balance agitation cycle when the determined displacement amount falls between the first tub displacement threshold and the second tub displacement threshold.

19. The method of claim 18, wherein performing the second out-of-balance agitation cycle comprises: controlling the operation of the motor to rotate the agitation element for a second agitation stroke distance greater than or equal to the first agitation stroke distance.

20. The method of claim 18, further comprising: repeating performing the second out-of-balance agitation cycle until the second out-of-balance agitation cycle has been performed for a predetermined number of times or the determined displacement amount falls below the second tub displacement threshold.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] 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:

[0011] FIG. 1 provides a perspective view of a washing machine appliance according to an exemplary embodiment of the present subject matter with a door of the washing machine appliance shown in a closed position.

[0012] FIG. 2 provides a perspective view of the washing machine appliance of FIG. 1 with the door of the exemplary washing machine appliance shown in an open position.

[0013] FIG. 3 provides a side, cross-sectional view of the washing machine appliance of FIG. 1 according to an exemplary embodiment of the present subject matter.

[0014] FIG. 4 provides a schematic, front view of the washing machine appliance of FIG. 1 according to an exemplary embodiments of the present subject matter.

[0015] FIG. 5 depicts certain components of a controller according to example embodiments of the present subject matter.

[0016] FIG. 6 provides a flow diagram of an exemplary method for operating a washing machine appliance according to example embodiments of the present subject matter.

[0017] FIG. 7 provides a graph specifying tub movement as a function of time according to example embodiments of the present subject matter.

[0018] FIG. 8 provides a graph specifying tub movement as a function of time according to example embodiments of the present subject matter.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. The word exemplary is used herein to mean serving as an example, instance, or illustration. In addition, references to an embodiment or one embodiment does not necessarily refer to the same embodiment, although it may. Any implementation described herein as exemplary or an embodiment is not necessarily to be construed as preferred or advantageous over other implementations. Moreover, 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 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.

[0020] As used herein, the terms first, second, and third may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms includes and including are intended to be inclusive in a manner similar to the term comprising. Similarly, the term or is generally intended to be inclusive (i.e., A or B is intended to mean A or B or both). The term at least one of in the context of, e.g., at least one of A, B, and C refers to only A, only B, only C, or any combination of A, B, and C. In addition, here and throughout the specification and claims, range limitations may be combined and/or interchanged. Such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. The singular forms a, an, and the include plural references unless the context clearly dictates otherwise.

[0021] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as generally, about, approximately, and substantially, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components and/or systems. For example, the approximating language may refer to being within a 10 percent margin, i.e., including values within ten percent greater or less than the stated value. In this regard, for example, when used in the context of an angle or direction, such terms include within ten degrees greater or less than the stated angle or direction, e.g., generally vertical includes forming an angle of up to ten degrees in any direction, e.g., clockwise or counterclockwise, with the vertical direction V.

[0022] FIGS. 1 through 4 illustrate an exemplary embodiment of a vertical axis washing machine appliance 100. Specifically, FIGS. 1 and 2 illustrate perspective views of washing machine appliance 100 in a closed and an open position, respectively. FIGS. 3 and 4 provide side and front cross-sectional views of washing machine appliance 100, respectively. 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.

[0023] While described in the context of a specific embodiment of vertical axis washing machine appliance 100, it should be appreciated that vertical axis washing machine appliance 100 is provided by way of example only. It will be understood that aspects of the present subject matter may be used in any other suitable washing machine appliance, such as a horizontal axis washing machine appliance. Indeed, modifications and variations may be made to washing machine appliance 100, including different configurations, different appearances, and/or different features while remaining within the scope of the present subject matter.

[0024] Washing machine appliance 100 has a cabinet 102 that extends between a top portion 104 and a bottom portion 106 along the vertical direction V. As best shown in FIG. 3, a tub 108 is positioned within cabinet 102 and is generally configured for retaining wash fluids during an operating cycle. Washing machine appliance 100 further includes a primary dispenser 110 (FIG. 2) for dispensing wash fluid into tub 108. The term wash fluid refers to a fluid, such as a liquid and/or vapor (e.g., steam), used for washing and/or rinsing articles during an operating cycle and may include any combination of water, detergent, fabric softener, bleach, and other wash additives or treatments.

[0025] In addition, washing machine appliance 100 includes a wash basket 112 that is positioned within tub 108 and generally defines a wash chamber 114 including an opening 116 for receipt of articles for washing. More specifically, wash basket 112 is rotatably mounted within tub 108 such that it is rotatable about an axis of rotation A. According to the illustrated embodiment, the axis of rotation A is substantially parallel to the vertical direction V. In this regard, washing machine appliance 100 is generally referred to as a vertical axis or top load washing machine appliance 100. However, as noted above, it should be appreciated that aspects of the present subject matter may be used within the context of a horizontal axis or front load washing machine appliance as well.

[0026] As illustrated, cabinet 102 of washing machine appliance 100 has a top panel 118. Top panel 118 defines an opening (FIG. 2) that coincides with opening 116 of wash basket 112 to permit a user access to wash basket 112. Washing machine appliance 100 further includes a door 120 which is rotatably mounted to top panel 118 to permit selective access to opening 116. In particular, door 120 selectively rotates between the closed position (as shown in FIGS. 1 and 3) and the open position (as shown in FIG. 2). In the closed position, door 120 inhibits access to wash basket 112. Conversely, in the open position, a user can access wash basket 112. A window 122 in door 120 permits viewing of wash basket 112 when door 120 is in the closed position, e.g., during operation of washing machine appliance 100. Door 120 also includes a handle 124 that, e.g., a user may pull and/or lift when opening and closing door 120. Further, although door 120 is illustrated as mounted to top panel 118, door 120 may alternatively be mounted to cabinet 102 or any other suitable support.

[0027] As best shown in FIGS. 2 and 3, wash basket 112 further defines a plurality of perforations 126 to facilitate fluid communication between an interior of wash basket 112 and tub 108. In this regard, wash basket 112 is spaced apart from tub 108 to define a space for wash fluid to escape wash chamber 114. During a spin cycle, wash fluid within articles of clothing and within wash chamber 114 is urged through perforations 126 wherein it may collect in a sump 128 defined by tub 108. Washing machine appliance 100 further includes a pump assembly 130 (FIG. 3) that is located beneath tub 108 and wash basket 112 for gravity assisted flow when draining tub 108, e.g., after a wash or rinse cycle.

[0028] An impeller or agitation element 132 (FIG. 3), such as a vane agitator, impeller, auger, oscillatory basket mechanism, or some combination thereof is disposed in wash basket 112 to impart an oscillatory motion to articles and liquid in wash basket 112. More specifically, agitation element 132 extends into wash basket and assists agitation of articles disposed within wash basket 112 during operation of washing machine appliance 100, e.g., to facilitate improved cleaning. In different embodiments, agitation element 132 includes a single action element (i.e., oscillatory only), a double action element (oscillatory movement at one end, single direction rotation at the other end) or a triple action element (oscillatory movement plus single direction rotation at one end, single direction rotation at the other end). As illustrated in FIG. 3, agitation element 132 and wash basket 112 are oriented to rotate about the axis of rotation A (which is substantially parallel to vertical direction V).

[0029] As best illustrated in FIGS. 3 and 4, washing machine appliance 100 includes a drive assembly 138 in mechanical communication with wash basket 112 to selectively rotate wash basket 112 (e.g., during an agitation or a rinse cycle of washing machine appliance 100). In addition, drive assembly 138 may also be in mechanical communication with agitation element 132. In this manner, drive assembly 138 may be configured for selectively rotating or oscillating wash basket 112 and/or agitation element 132 during various operating cycles of washing machine appliance 100.

[0030] More specifically, drive assembly 138 may generally include one or more of a drive motor 140 and a transmission assembly 142, e.g., such as a clutch assembly, for engaging and disengaging wash basket 112 and/or agitation element 132. According to the illustrated embodiment, drive motor 140 is a brushless DC electric motor, e.g., a pancake motor. However, according to alternative embodiments, drive motor 140 may be any other suitable type of motor. For example, drive motor 140 may be an AC motor, an induction motor, a permanent magnet synchronous motor, or any other suitable type of motor. In addition, drive assembly 138 may include any other suitable number, types, and configurations of support bearings or drive mechanisms.

[0031] Turning to FIG. 4, washing machine appliance 100 may include a vibration damping system or suspension system 144 which generally operates to damp or reduce dynamic motion and absorb vibrations of a subwasher 146. As used herein, the term subwasher is used generally to refer to those components of a washing machine appliance suspended within the appliance cabinet by a suspension system or assembly. For example, according to the illustrated embodiment, subwasher 146 is suspended within cabinet 102 by suspension system 144 and includes tub 108, wash basket 112, agitation element 132, drive assembly 138, and other components.

[0032] Suspension system 144 can include one or more suspension springs 148 for supporting subwasher 146 and absorbing the forces resulting from the movement of wash basket 112 within the tub 108. Specifically, according to an exemplary embodiment, suspension system 144 includes four suspension springs 148 which are spaced apart about the tub 108. For example, each suspension spring 148 may be connected at one end proximate a corner of cabinet 102 and at an opposite end to tub 108. According to alternative embodiments, washing machine appliance 100 may further include other vibration dampening elements, such as balance rings positioned around the upper and/or lower circumferential surfaces of the wash basket 112. Balance rings may be used to counterbalance an out-of-balance condition for washing machine appliance 100 as wash basket 112 rotates within tub 108.

[0033] Referring to FIGS. 1 through 4, a control panel 150 with at least one input selector 152 (FIG. 1) extends from top panel 118. Control panel 150 and input selector 152 collectively form a user interface input for operator selection of machine cycles and features. A display 154 of control panel 150 indicates selected features, operation mode, a countdown timer, and/or other items of interest to appliance users regarding operation.

[0034] Operation of washing machine appliance 100 is controlled by a controller or processing device 156 that is communicatively coupled with control panel 150 for user manipulation to select washing machine cycles and features. In response to user manipulation of control panel 150, controller 156 operates the various components of washing machine appliance 100 to execute selected machine cycles and features. As described in more detail below with respect to FIG. 5, controller 156 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 methods described herein. Alternatively, controller 156 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 150 and other components of washing machine appliance 100 may be in communication with controller 156 via one or more signal lines or shared communication buses.

[0035] FIG. 5 provides a schematic view of various components of controller 156 according to example embodiments of the present disclosure. Controller 156 can include one or more computing device(s) 156A which may be used to implement methods as described herein. Computing device(s) 156A can include one or more processor(s) 156B and one or more memory device(s) 156C. The one or more processor(s) 156B can include any suitable processing device, such as a microprocessor, microcontroller, integrated circuit, an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field-programmable gate array (FPGA), logic device, one or more central processing units (CPUs), graphics processing units (GPUs) (e.g., dedicated to efficiently rendering images), processing units performing other specialized calculations, etc. The memory device(s) 156C can include one or more non-transitory computer-readable storage medium(s), such as RAM, ROM, EEPROM, EPROM, flash memory devices, magnetic disks, etc., and/or combinations thereof.

[0036] The memory device(s) 156C can include one or more computer-readable media and can store information accessible by the one or more processor(s) 156B, including instructions 156D that can be executed by the one or more processor(s) 156B. For instance, the memory device(s) 156C can store instructions 156D for running one or more software applications, displaying a user interface, receiving user input, processing user input, etc. In some implementations, the instructions 156D can be executed by the one or more processor(s) 156B to cause the one or more processor(s) 156B to perform operations, e.g., such as one or more portions of methods described herein. The instructions 156D can be software written in any suitable programming language or can be implemented in hardware. Additionally, and/or alternatively, the instructions 156D can be executed in logically and/or virtually separate threads on processor(s) 156B.

[0037] The one or more memory device(s) 156C can also store data 156E that can be retrieved, manipulated, created, or stored by the one or more processor(s) 156B. The data 156E can include, for instance, data to facilitate performance of methods described herein. The data 156E can be stored in one or more database(s). The one or more database(s) can be connected to controller 156 by a high bandwidth LAN or WAN, or can also be connected to controller through network(s) (not shown). The one or more database(s) can be split up so that they are located in multiple locales. In some implementations, the data 156E can be received from another device.

[0038] The computing device(s) 156A can also include a communication module or interface 156F used to communicate with one or more other component(s) of controller 156 or washing machine appliance 100 over the network(s). The communication interface 156F can include any suitable components for interfacing with one or more network(s), including for example, transmitters, receivers, ports, controllers, antennas, or other suitable components.

[0039] With reference to FIGS. 1 through 5, during operation of washing machine appliance 100, laundry items are loaded into wash basket 112 through opening 116, and washing operation is initiated through operator manipulation of input selectors 152. Wash basket 112 is filled with water and detergent and/or other fluid additives via primary dispenser 110. One or more valves may be controlled by washing machine appliance 100 to provide for filling tub 108 and wash basket 112 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 112 is filled with fluid to the appropriate level, the contents of wash basket 112 may be agitated (e.g., with agitation element 132 as discussed previously) for washing of laundry items in wash basket 112.

[0040] More specifically, referring to FIGS. 3 and 4, a water fill process will be described according to an exemplary embodiment. As illustrated, washing machine appliance 100 includes a water supply conduit 160 (FIG. 3) that provides fluid communication between a water supply source 162 (FIG. 3; such as a municipal water supply) and a discharge nozzle 164 for directing a flow of water into tub 108, and more specifically, into wash chamber 114. In addition, washing machine appliance 100 includes a water fill valve or water control valve 166 which is fluidly coupled with water supply conduit 160 and communicatively coupled to controller 156. In this manner, controller 156 may regulate the operation of water control valve 166 to regulate the amount of water within tub 108. In addition, washing machine appliance 100 may include one or more pressure sensors 170 (FIG. 4) for detecting the amount of water and or clothes within tub 108. For example, pressure sensor 170 may be operably coupled to a side of tub 108 for detecting the weight of tub 108.

[0041] After tub 108 is filled and the agitation phase of the wash cycle is completed, wash basket 112 can be drained, e.g., by drain pump assembly 130. Laundry articles can then be rinsed by again adding fluid to wash basket 112 depending on the specifics of the cleaning cycle selected by a user. The impeller or agitation element 132 may again provide agitation within wash basket 112. One or more spin cycles may also be used as part of the cleaning process. 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, wash basket 112 is rotated at relatively high speeds to help wring fluid from the laundry articles through perforations 126. After articles disposed in wash basket 112 are cleaned and/or washed, the user can remove the articles from wash basket 112, e.g., by reaching into wash basket 112 through opening 116.

[0042] Referring still to FIGS. 3 and 4, one or more measurement devices 172 may be provided in the washing machine appliance 100 for detecting movement of tub 108, in particular during rotation of wash basket 112 prior to the spin cycle. Specifically, for example, movement of tub 108 may be detected as one or more displacements amounts of the tub, e.g., certain displacement amplitudes detected at the center of gravity of tub 108. Measurement devices 172 may measure a variety of suitable variables that can be correlated to movement of tub 108. The movement detected by such devices 172 can be utilized, for example, by the controller 156, to e.g., determine the displacement amounts (e.g., amplitudes) of tub 108 at the center of gravity or other locations, and to adjust operation of washing machine appliance 100 to facilitate agitation in a particular manner and/or for particular time periods to adjust the load balance state, e.g., to attempt to balance articles within wash basket 112 prior to a spin cycle.

[0043] In some embodiments, measurement device 172 may include an accelerometer which detects translational motion, such as acceleration along one or more directions. Additionally, or alternatively, measurement device 172 may include a gyroscope, which detects rotational motion, such as rotational velocity about an axis. Moreover, according to exemplary embodiments, measurement device 172 may include more than one gyroscope and/or more than one accelerometer.

[0044] Control panel 150 and other components of washing machine appliance 100, such as drive assembly 138 and measurement device 172, may be communicatively coupled with controller 156 via one or more signal lines or shared communication buses. According to exemplary embodiments, measurement devices 172 may include a dedicated microprocessor that performs the calculations specific to the detection of motion with the calculation results being used by controller 156. However, in some embodiments, the measurement devices 172 may detect the motion with one or more microprocessors of controller 156 performing calculations specific to the detection of motion with the calculation results being used by controller 156.

[0045] According to the illustrated embodiment, measurement device 172 is mounted to tub 108 to detect movement of tub 108 relative to the cabinet 102, e.g., by detecting uniform periodic motion, non-uniform periodic motion, or excursions of the tub 108 during appliance 100 operation. For instance, movement may be detected as discrete identifiable components (e.g., in a predetermined direction). More specifically, according to the illustrated embodiment, measurement device 172 is mounted to a bottom wall of tub 108, though other suitable positions on subwasher 146 are possible. Controller 156 may use measurement device 172 to determine the movement of any other position on tub 108, such as the center of gravity of tub 108. However, it should be appreciated that according to alternative embodiments, any suitable number, type, and position of measurement devices may be used.

[0046] The measurement device 172 may be mounted to tub 108 (e.g., via a suitable mechanical fastener, adhesive, etc.) and may be oriented such that the various sub-components (e.g., the gyroscope and accelerometer) are oriented to detect movement along or about particular directions as discussed herein. Notably, the gyroscope and accelerometer in exemplary embodiments are advantageously mounted to tub 108 at a single location (e.g., the location of the printed circuit board or other component of the measurement device 172 on which the gyroscope and accelerometer are grouped). Such positioning at a single location advantageously reduces the costs and complexity (e.g., due to additional wiring, etc.) of out-of-balance detection, while still providing relatively accurate out-of-balance detection as discussed herein. Alternatively, however, the gyroscope and accelerometer need not be mounted at a single location. For example, a gyroscope located at one location on tub 108 can detect the rotation of a gyroscope located at a different location on tub 108, because rotation about a given axis is the same everywhere on a solid object such as tub 108.

[0047] FIG. 6 provides a flow diagram of an exemplary method (200) for operating a washing machine appliance according to example embodiments of the present subject matter. For instance, the exemplary method (200) may be utilized to operate the washing machine appliance 100 and components thereof of FIGS. 1 through 5. Accordingly, the method (200) will be described below in the context of operating washing machine appliance 100. However, it will be appreciated that the exemplary method (200) is applicable to operation of a variety of other washing machine appliances, such as horizontal axis washing machine appliances. Further, it should be appreciated that variations and modifications to method (200) are possible and within the scope of the present subject matter. Moreover, it should be appreciated that specific quantities or values (e.g., time periods, displacements, threshold levels, etc.) used or described herein and/or illustrated in the figures are for purposes of example and illustration only. Specific quantities may vary or be different from those used or described herein and/or illustrated in the figures.

[0048] At (202), the method (200) includes initiating an out-of-balance detection operation after a wash cycle has been commenced. For instance, to initiate the out-of-balance detection operation, the measurement device 172 may begin detection of the displacement amount of the tub 108 and the controller 156 may begin determining the displacement amount of the tub 108 as detected by the measurement device 172. The out-of-balance detection operation may be initiated after the wash cycle has commenced. A volume of water and/or detergent (i.e., wash fluid) may be dispensed into tub 108 of washing machine appliance 100 during commencement of the wash cycle at a first water level FWL (FIG. 8). For example, controller 156 may regulate water control valve 166 to dispense a predetermined amount of water from water supply source 162 into tub 108 through discharge nozzle 164.

[0049] At (204), the method (200) includes agitating articles within the tub for a first time period. For instance, during the agitation phase of the wash cycle, agitation element 132 may be driven about the axis of rotation A by drive motor 140 of drive assembly 138 to agitate the articles within tub 108. As such, controller 156 may control the operation of the drive motor 140 to rotate the agitation element 132. Additionally, at (204), the agitation element 132 may be rotated for a first agitation stroke distance, which, as will be described below, may be less than a second agitation stroke distance of which the agitation element 132 may also be rotated. Furthermore, the first time period may be any suitable length of time. The first time period may be dictated by the size of the load, the cycle selected by the user, etc. The first time period extends from a start time to an end time. In some embodiments, the end time of the first time period may correspond to a predetermined or preset end time. Additionally, controller 156 may track the first time period. According to an exemplary implementation of method (200), articles within tub 108 are agitated during the first time period at (204) prior to a spin cycle of washing machine appliance 100. In this manner, an out-of-balance prevention process may be performed prior to spinning wash basket 112 at high speeds during the spin cycle, thereby reducing the likelihood of excessive tub displacement, vibrations, noise, and impact during the spin cycle.

[0050] At (206), the method (200) includes determining the displacement amount of the tub during the first time period. For instance, in some embodiments, determining the displacement amount of tub 108 during the first time period includes determining the displacement amount (e.g., amplitude) of tub 108 during the first time period based on the displacement amount of tub 108 detected by measurement device 172. In some embodiments, measurement device 172 may be used to detect the displacement amount at the center of gravity of tub 108. Additionally, or alternatively, in some embodiments of method (200), the displacement amount of tub 108 may be determined by other parameters. For instance, instantaneous, local maximum, or local averages of tub displacement amounts may be used as well.

[0051] The displacement amounts of tub 108 (e.g., displacement amplitudes) over the first time period, as well second time period, third time period, and fourth time period described below, may be stored (e.g., in a memory device 156C of controller 156) as a plurality of data points. The data points are representative of displacement of tub 108 during each of the time periods. The data points may be plotted as a function of time. For instance, as shown in FIGS. 7 and 8, a plurality of data points are plotted as tub displacement TD, which corresponds to displacement amounts or amplitudes of tub 108 over the time periods. Specifically shown in FIG. 7, the start time of the first time period is labeled as t.sub.S1 at time t=0 seconds and the end time of the first time period is labeled as t.sub.E1 at t=400 seconds. Likewise, specifically shown in FIG. 8, the start time of the first time period is labeled as t.sub.S1 at time t=0 seconds and the end time of the first time period is labeled as t.sub.E1 att=116 seconds. The first time period is labeled as TP1. As will be explained below in reference to FIG. 7, a trend line or function, labeled as TL, may be calculated based on the movement of the tub during the first time period, or more specifically, the plurality of data points measured over the time period. However, it should be appreciated that the trend line provided in FIG. 7 calculated based on the movement of the tub during the first time period may be calculated during any suitable time period, such as the second time period, the third time period, and/or the fourth time period described below in the same or similar manner. Furthermore, as mentioned previously, it should be appreciated that specific quantities or values (e.g., time periods, displacements, threshold levels, etc.) used or described herein and/or illustrated in the figures are for purposes of example and illustration only. Specific quantities may vary or be different from those used or described herein and/or illustrated in the figures.

[0052] At (208), with reference again to FIG. 6, the method (200) includes calculating a trend line based at least in part on the determined displacement amount of the tub during the first time period. In some implementations, the trend line specifies the displacement amplitude of the tub versus time. The trend line may be calculated as a linear trend line, an exponential function, a polynomial function, a moving average, etc. As one example, the trend line may be calculated as a linear trend line via a linear regression technique, e.g., using the exemplary linear regression equation below:

[00001]$\begin{array}{cc}Y=\mathrm{mX}+b& \left(\mathrm{Eq}.1\right)\end{array}$

where Y the dependent value is tub displacement amount (e.g., a displacement amplitude), X the independent value is time, m is the slope of the linear function, and b is the Y-intercept. The slope m and the Y-intercept b may be calculated for n number of data points by the following equations, respectively:

[00002]$\begin{array}{cc}m=\frac{n.Math.\left(\mathrm{XY}\right)-.Math.\left(X\right).Math.\left(Y\right)}{n.Math.\left(X^2\right)-.Math.{\left(X\right)}^2}& \left(\mathrm{EQ}.2\right)\end{array}$$\begin{array}{cc}b=\frac{.Math.\left(Y\right).Math.\left(X^2\right)-.Math.\left(X\right).Math.\left(\mathrm{XY}\right)}{n.Math.\left(X^2\right)-.Math.{\left(X\right)}^2}& \left(\mathrm{EQ}.3\right)\end{array}$

[0053] As shown in FIG. 7, continuing with the example above, the trend line TL was calculated based at least in part on the plurality of data points. Particularly, the trend line TL was calculated utilizing the linear regression equation noted above (i.e., Eq. 1). Thus, based on the data points measured for the time period TP1, the trend line TL was calculated having the following equation:

[00003]$\begin{array}{cc}Y=-0.0002X+0.2984& \left(\mathrm{Eq}.4\right)\end{array}$

The load distribution evenness of the articles within wash chamber 114 of basket 112 may evaluated over time using the trend line TL. A decreasing trend line TL indicates a decrease in tub displacement over time and that the load (i.e., the articles within wash basket 112) is becoming more evenly distributed within basket 112. In contrast, an increasing trend line TL indicates an increase in tub displacement over time and that the load is becoming less evenly distributed over time. A neither decreasing nor increasing trend line TL indicates that the tub displacement is neither decreasing nor increasing over time and that the load is neither becoming less or more evenly distributed over time. For the illustrated example of FIG. 7, the trend line TL is decreasing over time, and consequently, the trend line TL indicates a decrease in tub displacement over time and that the load (i.e., the articles within wash basket 112) is becoming more evenly distributed within basket 112. However, if the trend line TL had a positive slope m, the trend line TL would indicate an increase in tub displacement over time and that the load is becoming less evenly distributed over time.

[0054] With reference again to FIG. 6, in some embodiments, the method (200) includes determining when a displacement of the tub during the first time period exceeds a first tub displacement threshold, falls between and inclusive of the first tub displacement threshold and a second tub displacement threshold, or falls below the second tub displacement threshold. For instance, controller 156 may compare the displacement (e.g., the displacement amplitude) of tub 108 during the first time period to the first tub displacement threshold and the second tub displacement threshold, e.g., as illustrated in FIG. 6, method (200) may include (210) determining whether the displacement falls below the second tub displacement threshold and, if not, (211) determining whether the displacement exceeds the first tub displacement threshold. That is, method (200) includes determining the displacement of the tub during the first time period falls below the second tub displacement threshold when the outcome of (210) is positive, falls between and inclusive of the first tub displacement threshold and the second tub displacement threshold when the outcome of (210) is negative and the outcome of (211) is negative, or exceeds a first tub displacement threshold when the outcome of (210) is negative and the outcome of (211) is positive. The first tub displacement threshold may be a maximum tub displacement threshold which is greater than the second or minimum tub displacement threshold. For example, with reference to FIGS. 7 and 8, the first tub displacement threshold FTDT may be set at a displacement amplitude of 0.6 inches and the second tub displacement threshold STDT may be set at a displacement amplitude of 0.23 inches. However, as mentioned previously, it should be appreciated that specific quantities or values (e.g., time periods, displacements, threshold levels, etc.) used or described herein and/or illustrated in the figures are for purposes of example and illustration only. Specific quantities may vary or be different from those used or described herein and/or illustrated in the figures.

[0055] The first or maximum tub displacement threshold may correspond to a tub displacement threshold above which the tub may be experiencing a severe out-of-balance tub scenario. A severe out-of-balance tub scenario typically cannot be resolved only with agitation. As will be described below, when the displacement exceeds the first tub displacement threshold FTDT, an additional volume of water and/or detergent (i.e., wash fluid) may be dispensed into tub 108 of washing machine appliance 100 along with additional agitation of articles within tub 108 to distribute the load more evenly (i.e., the articles within wash basket 112) within basket 112. In this way, action may be taken to even the load within basket 112 prior to entering a spin cycle, and consequently, out-of-balance conditions may be prevented, among other benefits. Thus, when the displacement (e.g., the displacement amplitude) of the tub at any point during the first time period TP1, even before the end time t.sub.E1 of the first time period TP1, exceeds the first tub displacement threshold FTDT, the method (200) immediately proceeds to (212) as shown in FIG. 6. In the example of FIG. 8, the displacement of the tub during the first time period TP1 is above/exceeds the first tub displacement threshold FTDT as the displacement of the tub was detected having a displacement amplitude of about 1.01 inches and the first tub displacement threshold FTDT was set at a displacement amplitude of 0.6 inches. However, as mentioned previously, it should be appreciated that specific quantities or values (e.g., time periods, displacements, threshold levels, etc.) used or described herein and/or illustrated in the figures are for purposes of example and illustration only. Specific quantities may vary or be different from those used or described herein and/or illustrated in the figures.

[0056] Alternatively, when the displacement of the tub at the end time t.sub.E1 of the first time period TP1 equals or exceeds the second tub displacement threshold STDT (i.e., the displacement of the tub at the end time of the time period equals or exceeds the second tub displacement threshold) and equals or falls below the first tub displacement threshold FTDT, then the method (200) proceeds to (222). The second tub displacement threshold STDT may correspond to a tub displacement threshold at or above which the tub may be experiencing an out-of-balance tub scenario. When the displacement of the tub is equal to or higher than the second tub displacement threshold STDT and equal to or lower than the first tub displacement threshold FTDT, the tub may be experiencing a minor out-of-balance tub scenario. A minor out-of-balance tub scenario typically may be resolved with only agitation. As will be described below, when the displacement equals or exceeds the second tub displacement threshold STDT and equals or falls below the first tub displacement threshold FTDT, redistribution of articles with within tub 108 may be performed to distribute the load more evenly (i.e., the articles within wash basket 112) within basket 112. In this way, action may be taken to even the load within basket 112 prior to entering a spin cycle, and consequently, out-of-balance conditions may be prevented, among other benefits.

[0057] Alternatively, when the displacement of the tub at the end time tri of the first time period TP1 falls below the second tub displacement threshold STDT (i.e., the displacement of the tub at the end time of the time period falls below the second tub displacement threshold), then the method (200) proceeds from (210) to (240). When the displacement of the tub falls below the second tub displacement threshold STDT, the tub is not experiencing an out-of-balance tub scenario. As will be described below, when the displacement falls below the second tub displacement threshold STDT, a spin cycle may be initiated.

[0058] At (212), once the displacement is above/exceeds the first tub displacement threshold as determined at (211), the method (200) includes stopping out-of-balance detection. For instance, to stop the out-of-balance detection operation, the measurement device 172 may stop detection of the displacement amount of the tub 108 of the washing machine appliance 100.

[0059] Method (200) may include a first out-of-balance agitation cycle, e.g., which may include fill (214) and agitation (218). For example, as illustrated at (214), the first out-of-balance agitation cycle may include an additional volume of water and/or detergent (i.e., wash fluid) dispensed into tub 108 of washing machine appliance 100. For example, controller 156 may regulate water control valve 166 to dispense an additional predetermined amount of water from water supply source 162 into tub 108 through discharge nozzle 164 such that the water or wash fluid within the tub 108 is at a second water level SWL (FIG. 8) greater than the first water level FWL.

[0060] At (216), once the additional volume of water and/or detergent has been dispensed into the tub at (214), the method (200) includes starting a second out-of-balance detection. For instance, to start the second out-of-balance detection operation, the measurement device 172 may start detection of the displacement amount of the tub 108 of the washing machine appliance 100.

[0061] At (218), once the second out-of-balance detection has been started at (216), the method (200) includes continuing the first out-of-balance agitation cycle, which includes agitating articles within the tub during a second time period. The second time period TP2 may be same as or different from the first time period TP1. For instance, controller 156 may control the operation of the drive motor 140 to rotate the agitation element 132 for the first agitation stroke distance.

[0062] At (220), once the first out-of-balance agitation cycle has been performed at (218), the method (200) includes determining when a displacement of the tub during the second time period of the second out-of-balance detection operation falls below the second tub displacement threshold. For instance, controller 156 may compare the displacement (e.g., the displacement amplitude) of tub 108 during the second time period TP2 to the second tub displacement threshold. Thus, when the displacement (e.g., the displacement amplitude) of tub 108 at any point during the second time period TP2, even before the end time t.sub.E2 of the second time period TP2, falls below the second tub displacement threshold STDT, the method (200) immediately proceeds to (240) as shown in FIG. 6. Alternatively, when the displacement (e.g., the displacement amplitude) of tub 108 during the second time period TP2 does not fall below the second tub displacement threshold STDT at any point during the second time period TP2, the method (200) proceeds to (222) as shown in FIG. 6.

[0063] At (222), when it is determined that the displacement of the tub during the second out-of-balance detection operation does not fall below the second tub displacement threshold at (220) or the displacement of the tub during the first out-of-balance detection operation falls between the first tub displacement threshold and the second tub displacement threshold, e.g., as determined by (210) and/or (211), the method (200) includes performing a second out-of-balance agitation cycle which includes agitating articles for the second agitation stroke distance within the tub during a third time period. The third time period TP3 may be the same as or different from the first time period TP1 and/or the second time period TP2. As such, controller 156 may control the operation of the drive motor 140 to rotate the agitation element 132 for the second agitation stroke distance, which is greater than the first agitation stroke distance.

[0064] At (224), once the second out-of-balance agitation cycle has been performed at (222), the method (200) includes increasing a cycle count of the second out-of-balance agitation cycle. For instance, the controller 156 may count or otherwise keep track of the number of times the second out-of-balance agitation cycle has been performed. As will be described below, the number of times the second out-of-balance agitation cycle has been performed determines when the method (200) returns to (204) or continues to (228).

[0065] At (226), once the cycle count of the second out-of-balance agitation cycle has been increased, the method (200) includes determining when the cycle count exceeds a first predetermined cycle count. For example, the first predetermined cycle count may be two counts. In this respect, once the second out-of-balance agitation cycle has been performed more than twice, the method (200) will continue to (228). Otherwise, the method (200) returns to (204).

[0066] At (228), when determined that the count of the second out-of-balance agitation cycle exceeds the first predetermined cycle count, the method (200) includes increasing the second tub displacement threshold. For instance, the controller 156 may increase the second tub displacement threshold STDT by some predetermined amount. As such, in other steps of method (200), when the displacement of tub 108 of washing machine appliance 100 is compared to the increased second tub displacement threshold ISTDT, the displacement may fall below the increased second tub displacement threshold ISTDT and, as will be described below, the spin cycle may be performed. Increasing the second tub displacement threshold STDT allows an increased chance of an earlier spin cycle performance without the method (200) repeating steps. Furthermore, earlier spin cycle performance may reduce the likelihood of further agitation cycles worsening the distribution of the articles within the basket 112.

[0067] At (230), once the second tub displacement threshold has been increased, the method (200) includes agitating articles within the tub during a fourth time period. The fourth time period TP4 may be the same as or different from the first time period TP1, the second time period TP2, and/or the third time period TP3. For instance, controller 156 may control the operation of the drive motor 140 to rotate the agitation element 132 for the first agitation stroke distance.

[0068] At (232), once the articles have been agitated at (230), the method (200) includes determining the displacement amount of the tub during the fourth time period. For instance, in some embodiments, determining the displacement amount of tub 108 during the fourth time period includes determining the displacement amount (e.g., amplitude) of tub 108 during the fourth time period TP4 based on the displacement amount of tub 108 detected by measurement device 172.

[0069] At (234), once the displacement amount of the tub during the fourth time period has been determined at (232), the method (200) includes calculating a trend line based at least in part on the determined displacement amount of the tub during the fourth time period TP4 similar to how the trend line was calculated at (208).

[0070] At (236), once the trendline has been calculated at (234), the method (200) includes determining when a displacement of the tub during the fourth time period exceeds the increased second tub displacement threshold of (228). For instance, controller 156 may compare the displacement (e.g., the displacement amplitude) of tub 108 during the fourth time period TP4 to the increased second tub displacement threshold. When the displacement of tub 108 does not exceed the increased second tub displacement threshold ISTDT at any point during the fourth time period TP4, the method (200) proceeds to (240). When the displacement of tub 108 exceeds the increased second tub displacement threshold ISTDT, the method (200) proceeds to (238).

[0071] At (238), when determined at (236) that the displacement of the tub during the fourth time period does not fall below the increased second tub displacement threshold of (228), the method (200) includes determining when the cycle count of the second out-of-balance cycle exceeds a second predetermined cycle count. The second predetermined cycle count may be greater than the first predetermined cycle count. For example, the second predetermined cycle count may be three counts. In this respect, once the second out-of-balance agitation cycle has been performed more than three times, the method (200) will return to (204). Otherwise, the method (200) proceeds to (240).

[0072] At (240), the method (200) includes stopping out-of-balance detection similar to (212). For instance, to stop the out-of-balance detection operation, the measurement device 172 may stop detection of the displacement amount of the tub 108 of the washing machine appliance 100.

[0073] At (242), the method (200) includes terminating agitation of the articles within the wash chamber and/or initiating a spin cycle of the washing machine appliance. For example, when the displacement of the tub falls below the second tub displacement threshold at (210) or (220), when the displacement of the tub falls below the increased second tub displacement threshold at (236), or when the cycle count of the second out-of-balance cycle exceeds the second predetermined cycle count at (238), the controller 156 may initiate the spin cycle of the washing machine appliance 100. In such scenarios, the load is evenly distributed within basket 112 and a spin cycle may thus be initiated. In general, terminating agitation of articles within basket 112 includes disengaging agitation element 132 from drive assembly 138 (e.g., via a clutch mechanism) such that agitation element 132 ceases being driven about the axis of rotation A. Basket 112 may remain engaged with drive assembly 138 so that basket 112 may be spun about the axis of rotation A during the spin cycle. Initiating the spin cycle may include activating a drain pump assembly (e.g., drain pump assembly 130) to drain the liquid from tub 108. The spin cycle may then include operating the motor to spin the wash basket at a relatively high speed.

[0074] As mentioned previously, it should be appreciated that specific quantities or values (e.g., time periods, displacements, threshold levels, etc.) used or described herein and/or illustrated in the figures are for purposes of example and illustration only. Specific quantities may vary or be different from those used or described herein and/or illustrated in the figures.

[0075] Advantages and benefits may be realized with implementation of method (200). Notably, method (200) provides a control scheme for washing machine appliance 100 to mitigate or prevent out-of-balance loads from entering a high-speed spin cycle. Particularly, during the wash cycle, the displacement of the tub 108 is monitored during the agitation phase, e.g., by a measurement device 172, such as an accelerometer and gyroscope. The trend of the tub displacement with respect to time is utilized to determine whether further agitation and/or water/wash fluid are necessary to distribute the load more evenly prior to the spin cycle. Additional agitation time can be scheduled by controller 156 so that washing machine appliance 100 may attempt more evenly distribute the load prior to the spin cycle. With loads more evenly distributed prior to the spin cycle, issues associated with operating the washing machine appliance 100 at high speeds with an out-of-balance load during a spin cycle may be avoided. Specifically, undesirable vibrations and noise emanating from washing machine appliance 100 may be reduced and the probability of tub contact may also be reduced. Other advantages and benefits not specifically listed may also be achieved or realized.

[0076] 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.