Patent Publication Number: US-2022218176-A1

Title: Control method of dishwasher

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0003117, filed in Korea on Jan. 11, 2021, the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a method of controlling a dishwasher, and more particularly, to a method of controlling a dishwasher capable of suppressing damage to a washing target during operation of the dishwasher. 
     BACKGROUND ART 
     Contents described in this section merely provide background information on the present disclosure and do not constitute the related art. 
     In general, dishwashers are devices that spray washing water to accommodated dishes at a high pressure, wash the dishes, and then dry the dishes. In detail, the dishwashers are operated so that the washing water is sprayed at a high pressure into a tub in which the dishes are accommodated, and the sprayed washing water comes into contact with the dishes to wash foreign substances such as food waste stuck to the surfaces of the dishes. 
     The dishwasher generally includes the tub forming a washing chamber and a sump mounted on a bottom of the tub to store the washing water. 
     Further, the washing water is moved to a spray arm by pumping action of a washing pump mounted inside the sump, and the washing water having been moved to the spray arm is sprayed at a high pressure through a spray port formed in the spray arm. 
     Further, the washing water sprayed at a high pressure collides with the surface of the washing target, and thus dirt stuck to the washing target falls to the bottom of the tub. 
     Due to a difference of materials, some of the washing targets accommodated in the dishwasher collide with the washing water sprayed during a washing process and thus may be moved from original locations thereof or may be damaged. 
     Whether this serious problem occurs may be determined on the basis of, for example, sound waves generated inside the dishwasher during the washing process of the dishes. 
     Korean Patent Application Publication No. 10-1996-0016128, which is a related art, discloses a dish amount detection device and method for a dishwasher, which determines the amount of the dishes by detecting the volume of a sound generated when the washing water sprayed during the washing process collides with an inner surface of the tub. 
     However, the related art does not disclose any method of controlling a dishwasher, in which the dishes are suppressed from being moved from original locations thereof or being damaged as the dishes collide with the washing water, on the basis of a sound detected in a washing chamber. 
     SUMMARY 
     The present disclosure is directed to providing a method of controlling a dishwasher that may effectively suppress a dish made of a specific material from being moved or damaged due to the water pressure of washing water sprayed from the dishwasher. 
     The present disclosure is also directed to providing a method of controlling a dishwasher that may reduce the water pressure of the washing water sprayed from the spray nozzle when the spray nozzle approaches the dish made of the specific material. 
     The present disclosure is also directed to providing a method of controlling a dishwasher that may control a number of rotations of the washing motor to reduce the water pressure of the washing water sprayed from the spray nozzle. 
     The purposes of the present disclosure may be not limited to the purposes described above, and other purposes and advantages of the present disclosure that are not described may be understood by the following description and may be more clearly understood by embodiments of the present disclosure. Further, it may be easily identified that the purposes and advantages of the present disclosure may be implemented by units and combinations thereof described in the appended claims. 
     A dishwasher according to an embodiment may include a controller, a washing motor, a microphone, and a location sensor. 
     The controller may be provided in the dishwasher and control the operation of the dishwasher. To control the dishwasher, the controller may be connected to the washing motor, the microphone, the location sensor, and other components of the dishwasher so as to communicate therebetween in a wired or wireless manner. 
     The washing motor may be connected to the controller, and a rotational speed of the washing motor may be changed according to a command of the controller. The washing motor may be connected to the washing pump through a rotary shaft. The controller may control the rotational speed of the washing motor to control a rotational speed of the washing pump. 
     The controller may control the rotational speed of the washing pump to control a flow rate and a spray speed of the washing water sprayed from the spray nozzle and a water pressure of the washing water colliding with the dish. 
     The microphone may be provided in a tub and collect a sound wave generated when the disk held on the rack collides with the washing water. The microphone may be disposed at an appropriate location in which noise inside the tub may be collected without interfering with the operation of the spray nozzle inside the tub. The microphone may be connected to the controller and transmit a collected sound signal to the controller. 
     The location sensor may be mounted on the spray nozzle and detect a rotation angle of the spray nozzle. The location sensor may be connected to the controller and transmit location information on the spray nozzle to the controller. 
     The location sensor may be provided in each of a lower spray nozzle and an upper spray nozzle that rotate. In the dishwasher according to the embodiment, since a top spray nozzle is not rotated, the location sensor may be provided in each of the lower spray nozzle and the upper spray nozzle except for the top spray nozzle. 
     A method of controlling a dishwasher according to the embodiment may include the following operations. 
     The washing motor may be operated to spray the washing water to the dish held on the rack while the spray nozzle is rotated. The washing motor may be operated to spray the washing water to the dish held on the rack while the spray nozzle is rotated. 
     The controller may receive a sound signal from the microphone and analyze characteristics of the sound wave input to the microphone. The controller may analyze at least one of the amplitude or frequency of the sound wave input to the microphone. A set material of the washing target may be at least one of, for example, plastic or glass. 
     The controller may determine whether the washing target made of the set material is present on the basis of the analyzed characteristics of the sound wave. For example, the controller may determine that the washing target made of the set material is present when an impact sound generated in the washing target made of plastic or glass is detected through the analyzed sound wave. 
     The controller may determine whether the dish made of the set material is present on the basis of a currently collected sound wave by comparing stored data that is a comparison target with the currently collected sound wave. 
     The stored data that is the comparison target may be, for example, first data provided by collecting and storing the sound wave generated in the tub when the dishwasher is operated in a state in which the dish made of plastic or glass is not held on the rack. 
     When the first data is compared with the currently collected sound wave, for example, when at least one of the amplitude or frequency of the sound wave input to the microphone deviates from a set range in comparison to the characteristics of the sound wave when the washing target made of a pre-stored set material is not present, the controller may determine that the washing target made of the set material is present in the washing chamber. 
     In another embodiment, the stored data that is the comparison target may be second data provided by collecting and storing the sound wave generated in the tub when the dishwasher is operated in a state in which the dish made of plastic or glass is held on the rack. 
     When the second data is compared with the currently collected sound wave, for example, when at least one of the amplitude or frequency of the sound wave input to the microphone is within a set range in comparison to the characteristics of the sound wave when the washing target made of the pre-stored set material is present, the controller may determine that the washing target made of the set material is present in the washing chamber. 
     When the washing target made of the set material is present, the controller may determine a location in which the washing target made of the set material is present on the basis of the analyzed characteristics of the sound wave. 
     In the dishwasher according to the embodiment, a plurality of racks may be provided in the washing chamber in a vertical direction, a plurality of spray nozzles may be provided, and the spray nozzles may be arranged to correspond to the plurality of racks in the vertical direction. 
     The controller may determine whether the washing target made of the set material is present in any one rack among the plurality of racks by identifying whether the impact sound is generated when any one of the plurality of racks is operated. 
     When the dish made of the set material is present, the controller may reduce the amount of impact applied to the washing target made of the set material by the washing water sprayed from the spray nozzles. 
     In this case, at least one of a spraying amount and the spray speed of the washing water sprayed from the spray nozzle or a rotational speed of the spray nozzle is reduced, and thus the amount of impact applied to the washing target made of the set material may be reduced. 
     The controller may control the rotational speed of the washing motor to reduce at least one of the spray amount and the spray speed of the washing water sprayed from the spray nozzle or the rotational speed of the spray nozzle. 
     According to a method of controlling a dishwasher, in a dish washing process, a washing target made of a specific material may be effectively suppressed from being moved or damaged due to the washing water. 
     Further, according to the method of controlling a dishwasher, when the impact sound is generated by the dish held on the rack and made of plastic or glass, the controller may reduce the rotational speed of the washing motor to reduce the amount of impact applied to the dish by the washing water and thus may effectively suppress the dish made of plastic or glass from being moved from an original location thereof or being damaged due to the water pressure of the washing water. 
     Further, according to the method of controlling a dishwasher according to the present disclosure, the controller may reduce the rotational speed of the washing motor when the spray nozzle passes through the dish made of plastic or glass, and thus a washing time can be reduced and washing efficiency can be increased, as compared to a case in which the overall rotational speed of the washing motor is reduced uniformly. 
     In addition to the above-described effects, the detailed effects of the present disclosure will be described together while specific details for implementing the disclosure are described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a dishwasher according to an embodiment; 
         FIG. 2  is a flowchart for describing a method of controlling a dishwasher according to the embodiment; 
         FIG. 3  is a graph showing a waveform of a sound wave according to a change in rotation angle of a spray nozzle, the sound wave being input by a microphone provided in the dishwasher; 
         FIG. 4  is a view for describing a configuration for controlling the dishwasher according to the embodiment; 
         FIG. 5  is a flowchart for describing a method of controlling a dishwasher according to another embodiment; 
         FIG. 6  is a flowchart for describing a method of controlling a dishwasher according to still another embodiment; and 
         FIG. 7  is a flowchart for describing a method of controlling a dishwasher according to yet another embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The above-described purposes, features, and advantages will be described in detail with reference to the accompanying drawings, and accordingly, those skilled in the art to which the present disclosure pertains may easily implement the technical spirit of the present disclosure. In the description of the present disclosure, when it is determined that a detailed description of widely known technologies related to the present disclosure may make the subject matter of the present disclosure unclear, the detailed description be omitted. Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components. 
     Although first, second, and the like are used to describe various components, it is apparent that these components are not limited by these terms. These terms are only used to distinguish one component from another component, and it is apparent that a first component may be a second component unless particularly otherwise stated. 
     Throughout the specification, unless particularly otherwise stated, each component may be singular or plural. 
     Singular expressions used herein include plural expressions unless clearly otherwise indicated in the context. In the present application, terms such as “configuring” or “including” should not be interpreted as necessarily including all of various components or various steps described in the specification and should be interpreted as not including some components or some steps thereof or further including additional components or additional steps. 
     Throughout the specification, when “A and/or B” is used, this means A, B or A and B unless otherwise stated, and when “C to D” is used, this means that a value is greater than or equal to C and less than or equal to D unless otherwise stated. 
       FIG. 1  is a schematic cross-sectional view of a dishwasher according to an embodiment. 
     The dishwasher according to the present embodiment includes a case  12  forming an exterior, a tub  16  provided inside the case  12  and forming a washing chamber  16   a  in which a washing target is accommodated, a door  14  that is provided on a front surface of the tub  16  and opens or closes the washing chamber  16   a , and a sump  40  which is disposed below the tub  16  and in which washing water is stored. 
     A filter  42  for filtering the washing water supplied from an external unit or the washing water introduced from the tub  16  may be provided in the sump  40  according to the present embodiment. 
     The dishwasher according to the present embodiment includes one or more spray nozzles  20 ,  22 , and  24  that are rotatably provided in the washing chamber  16   a  and spray the washing water to the washing chamber  16   a  in the tub  16 , a washing pump  60  that supplies the washing water stored in the sump  40  to the one or more spray nozzles  20 ,  22 , and  24 , a switching valve  59  for connecting the washing water supplied from the washing pump  60  to at least one of the spray nozzles  20 ,  22 , and  24 , and racks  30   a  and  30   b  which are accommodated in the washing chamber  16   a  and on which the washing target is held. 
     The racks  30   a  and  30   b  according to the present embodiment may have a structure on which the washing target is held so that the washing target is washed using the washing water sprayed by the plurality of spray nozzles  20 ,  22 , and  24 , and may include an upper rack  30   a  disposed on an upper side with respect to a location disposed inside the washing chamber  16   a  and a lower rack  30   b  disposed on a lower side with respect to the location. 
     The plurality of spray nozzles  22 ,  22 , and  24  may be vertically arranged. The plurality of spray nozzles  20 ,  22 , and  24  according to the present embodiment include a lower spray nozzle  20  that is disposed at a lowermost end and sprays the washing water from the lower side to the upper side toward the lower rack  30   b , an upper spray nozzle  22  that is disposed between the upper rack  30   a  and the lower rack  30   b  and sprays the washing water to the lower rack  30   b  and the upper rack  30   a , and a top spray nozzle  24  that is disposed at an upper end of the washing chamber  16   a  which is the upper side of the upper rack  30   a  and that sprays the washing water to a space of the washing chamber  16   a . The plurality of spray nozzles  20 ,  22 , and  24  may receive the washing water from the washing pump  60  through a plurality of spray nozzle connection pipes  20   a ,  22   a , and  24   a.    
     The switching valve  59  may selectively supply the washing water pumped by the washing pump  60  to at least one of the lower spray nozzle  20 , the upper spray nozzle  22 , and the top spray nozzle  24 . The switching valve  59  may selectively connect a washing water supply pipe  100 , in which the washing water discharged from the washing pump  60  flows, and at least one of the plurality of spray nozzle connection pipes  20   a ,  22   a , and  24   a.    
     The washing pump  60  may be connected to the sump  40  through a water collection pipe  54  having a water collection passage formed therein. A valve that opens or closes a space between the sump  40  and the washing pump  60  may be disposed in an inlet of the water collection pipe  54  or the washing pump  60 . 
     The dishwasher according to the present embodiment may include a water supply assembly that supplies the washing water into the dishwasher and a drainage assembly that drains water stored inside the dishwasher. 
     The water supply assembly according to the present embodiment may include a water supply pipe  44  forming a water supply passage to which the washing water is supplied from an external water source, a water supply valve  46  that opens or closes the water supply passage formed in the water supply pipe  44 , and a flow meter  48  that measures the flow rate of the washing water flowing to the sump  40  through the water supply passage. 
     The drainage assembly according to the present embodiment may include a drainage pipe  50  that has a drainage passage formed therein to guide the water stored in the sump  40  to the outside and a drainage pump  52  that is disposed on the drainage passage formed in the drainage pipe  50  and drains the washing water in the sump  40  to the outside. The drainage pump  52  may include a drainage motor that generates a rotational force. 
     The washing pump  60  according to the present embodiment may be coupled to the sump  40  and may be connected to the spray nozzles  20 ,  22 , and  24  and a steam nozzle  32 . 
     The washing pump  60  according to the present embodiment may supply the water stored in the sump  40  to the plurality of spray nozzles  20 ,  22 , and  24  or generate steam to supply the generated steam to the steam nozzle  32 . The steam nozzle  32  may supply the steam to the washing chamber  16   a.    
     The dishwasher may further include the water collection pipe  54  and the washing water supply pipe  100 . The water collection pipe  54  may connect the sump  40  and the washing pump  60 . The water collection pipe  54  may connect the washing pump  60  and the spray nozzles  20 ,  22 , and  24 . 
     The washing pump  60  according to the present embodiment is connected to the sump  40  through the water collection pipe  54 . The washing pump  60  according to the present embodiment may be connected to the switching valve  59  and the spray nozzles  20 ,  22 , and  24  through the washing water supply pipe  100  and may be connected to the steam nozzle  32  through a steam supply pipe  88 . 
     The washing pump  60  according to the embodiment of the present disclosure may include a housing  62  that is coupled to the sump  40  and forms an exterior of the washing pump  60 , an impeller  64  that is disposed inside the housing  62  and forms a flow of the washing water stored inside the housing  62 , a washing motor  65  that rotates the impeller  64 , and a heater  70  that is mounted on the outside of the housing  62  of the washing pump  60  and heats the washing water to generate the steam. 
     The washing pump  60  may be connected to the spray nozzles  20 ,  22 , and  24  and may supply the washing water to the spray nozzles  20 ,  22 , and  24 . The washing motor  65  may be connected to the washing pump  60  through a rotary shaft and may provide a rotational force to the washing pump  60 . 
     When the drainage pump  52  and the washing motor  65  are stopped, that is, are not operated, the washing pump  60  may store the washing water inside the housing  62 . In this case, the heater  70  heats the stored washing water to generate the steam. 
     The washing water flowing inside the dishwasher according to the present embodiment may flow through the sump  40  and the tub  16  to wash the washing target. Further, the washing water stored in the sump  40  may be supplied from an external water source through the water supply assembly and may be discharged to the outside through the drainage assembly. 
     The washing water stored in the sump  40  may flow into the tub  16  as the washing motor  65  of the washing pump  60  rotates the impeller  64 . That is, by operating the washing motor  65 , the washing water inside the sump  40  may flow into the washing pump  60 , may be pumped from the washing pump  60  to the switching valve  59 , and may flow to at least one of the plurality of spray nozzles  20 ,  22 , and  24 . 
     The washing water stored in the sump  40  flows into the housing  62  through the water collection pipe  54  connected to the washing pump  60 . Further, the washing water may flow to the switching valve  59  through the washing water supply pipe  100  connected to the washing pump  60 . 
     The sump  40  and the washing pump  60  are connected through the water collection pipe  54 , and the washing pump  60  and the switching valve  59  are connected through the washing water supply pipe  100 . The switching valve  59  may be connected to the plurality of spray nozzles  20 ,  22 , and  24  through the respective connection pipes  20   a ,  22   a , and  24   a , and the switching valve  59  supplies the washing water pumped by the washing pump  60  to at least one of the spray nozzles  20 ,  22 , and  24 . 
     The washing water sprayed into the tub  16  through the spray nozzles  20 ,  22 , and  24  may flow into the sump  40  through a hole formed in a bottom part  16   b  of the tub  16 . 
     The steam flowing inside the dishwasher according to the present embodiment is generated by the washing pump  60 . The heater  70  is operated to generate the steam using the washing water that is present inside the housing  62  of the washing pump  60 . In this case, it is preferable that the flow of the washing water inside the washing pump  60  is minimized. 
     Thus, when the steam is generated inside the housing  62  of the washing pump  60 , it is appropriate to stop the operation of the washing motor  65  and the impeller  64 . Alternatively, it is appropriate to rotate the impeller  64  at a set rotational speed or less even when the washing motor  65  is operated. 
     The steam generated in the washing pump  60  may flow to a steam supply pipe  88  connected to the washing pump  60  and may flow into the washing chamber  16   a.    
       FIG. 2  is a flowchart for describing a method of controlling a dishwasher according to the embodiment.  FIG. 3  is a graph showing a waveform of a sound wave according to a change in rotation angle of a spray nozzle, the sound wave being input by a microphone  400  provided in the dishwasher.  FIG. 4  is a view for describing a configuration for controlling the dishwasher according to the embodiment. 
     When the dishwasher is operated, the washing water sprayed from the spray nozzles may collide with the washing targets, for example, dishes, plates, glasses, spoons, and chopsticks, held on the racks. In this case, the dish with which the sprayed washing water collides may receive a serious impact according to a material. 
     For example, since the dish made of plastic is light, the dish may be moved from an original location thereof on the rack due to the water pressure of the sprayed washing water. When the dish is moved, the dish may overlap other dishes, and accordingly, the dish held on the rack may not be washed well. 
     Further, for example, a glass dish such as a wine glass may be shaken due to the water pressure of the sprayed washing water, may collide with other dishes held on the rack, and thus may be damaged. 
     The embodiment provides a method of controlling a dishwasher that may effectively suppress a dish made of a specific material such as plastic or glass from being moved or damaged due to the water pressure of the washing water sprayed from the dishwasher. 
     First, a configuration for controlling the dishwasher will be described with reference to  FIG. 4 . A system for controlling the dishwasher may include a controller  300 , a washing motor  65 , a microphone  400 , and location sensors  200 . 
     The controller  300  may be provided in the dishwasher and control the operation of the dishwasher. To control the dishwasher, the controller  300  may be connected to the washing motor  65 , the microphone  400 , the location sensor  200 , and other components of the dishwasher so as to communicate therebetween in a wired or wireless manner. 
     The washing motor  65  may be connected to the controller  300 , and a rotational speed of the washing motor  65  may be changed according to a command of the controller  300 . Further, the washing motor  65  may be connected to the washing pump  60  through a rotary shaft. Thus, the controller  300  may control the rotational speed of the washing motor  65  to control a rotational speed of the washing pump  60 . 
     The controller  300  may control the rotational speed of the washing pump  60  to control a flow rate and a spray speed of the washing water sprayed from the spray nozzles and a water pressure of the washing water colliding with the dish. 
     The microphone  400  may be provided in the washing chamber  16   a  and collect the sound wave generated when the washing water collides with the dish held on the rack. The microphone  400  may be disposed at an appropriate location in which noise inside the washing chamber  16   a  may be collected without interfering with the operation of the spray nozzles inside the washing chamber  16   a . The microphone  400  may be connected to the controller  300  to transmit a collected sound signal to the controller  300 . 
     The location sensor  200  may be mounted on the spray nozzles and detect rotation angles of the spray nozzles. The location sensor  200  may be connected to the controller  300  and transmit location information on the spray nozzles to the controller  300 . The location sensor  200  may be provided as, for example, a Hall sensor, but the present disclosure is not limited thereto. 
     The location sensors  200  may be provided in the lower spray nozzle  20  and the upper spray nozzle  22  that rotate. In the dishwasher according to the embodiment, since the top spray nozzle  24  is not rotated, the location sensors  200  may be provided in the lower spray nozzle  20  and the upper spray nozzle  22  excluding the top spray nozzle  24 . 
     Hereinafter, a method of controlling the dishwasher will be described in detail. Referring to  FIG. 2 , while the washing motor  65  is operated to rotate the spray nozzles, the washing water may be sprayed onto the dish held on the rack (S 110 ). In this case, the microphone  400  provided in the washing chamber  16   a  may collect noise, that is, the sound wave, which is generated while the washing water collides with the dish. 
     The controller  300  may receive the sound signal from the microphone  400  and analyze characteristics of the sound wave input to the microphone  400  (S 120 ). The controller  300  may analyze at least one of the amplitude or the frequency of the sound wave input to the microphone  400 . In this case, a set material of the washing target may be at least one of, for example, plastic or glass. 
     The controller  300  may determine whether the washing target made of the set material is present on the basis of the analyzed characteristics of the sound wave (S 130 ). For example, the controller  300  may determine that the washing target made of the set material is present when an impact sound generated in the washing target made of plastic or glass is detected through the analyzed sound wave. 
     A light dish made of plastic may generate the impact sound while being moved due to the water pressure of the washing water and colliding with other dishes held on the rack. Further, a dish made of glass may generate the impact sound while being shaken due to the water pressure of the sprayed washing water and colliding with other dishes held on the racks. 
     The controller  300  may determine whether the dish made of the set material such as plastic or glass is present by analyzing the amplitude and the frequency of the collected sound wave. The controller  300  may determine whether the dish made of the set material is present on the basis of a currently collected sound wave by comparing stored data that is a comparison target with the currently collected sound wave. 
     The data that is the comparison target may be stored in a storage device provided in the dishwasher. Alternatively, the dishwasher may be communicatively connected to a server, and the data that is the comparison target may be stored in the server. 
     In this case, the stored data that is the comparison target may be, for example, first data provided by collecting and storing the sound wave generated in the washing chamber  16   a  when the dishwasher is operated in a state in which the dish made of plastic or glass is not held on the rack. 
     When the first data is compared with the currently collected sound wave, for example, when at least one of the amplitude or frequency of the sound wave input to the microphone  400  deviates from a set range in comparison to the characteristics of the sound wave when the washing target made of a pre-stored set material is not present, the controller  300  may determine that the washing target made of the set material is present in the washing chamber. 
     In another embodiment, the stored data that is the comparison target may be second data provided by collecting and storing the sound wave generated in the washing chamber  16   a  when the dishwasher is operated in a state in which the dish made of plastic or glass is held on the rack. The second data may include the impact sound generated by the dish made of plastic or glass. 
     When the second data is compared with the currently collected sound wave, for example, when at least one of the amplitude or frequency of the sound wave input to the microphone  400  is within a set range in comparison to the characteristics of the sound wave when the washing target made of the pre-stored set material is present, the controller  300  may determine that the washing target made of the set material is present in the washing chamber. 
     When operation S 130  is performed using the first data or the second data and when the impact sound is not generated in the currently collected sound wave, the controller  300  may determine that the washing target made of the set material is not present regardless of whether the washing target made of the set material is actually present. 
     In this case, since the dish made of the set material is sufficiently heavy or is stably supported on the rack, the impact sound is not generated. Thus, the dish made of plastic is not moved or the dish made of glass is not damaged due to an impact. Thus, there is no need to perform operations S 140  and S 150  on the premise that the washing target made of the set material is present. 
     In another embodiment, the controller  300  may determine whether the dish made of plastic or glass is present on the basis of characteristics of the sound wave generated when the washing water collides with the dish made of plastic or glass. 
     That is, data related to the amplitude or frequency of the sound wave generated when the washing water collides with the dish made of plastic or glass is stored, and the controller  300  may determine whether the dish made of plastic or glass is currently present in the dishwasher by comparing the currently collected sound wave with the stored data. 
     According to this method, even when the impact sound is not generated, the controller  300  may determine whether the washing target made of the set material is present in the rack. 
     Further, according to this method, regardless of whether the impact sound is generated, the controller  300  may or may not perform operations S 140  and S 150  according to whether the dish made of the set material is actually present in the rack. 
     Meanwhile, in performing operation S 130 , a series of processes of collecting, processing, and storing data for comparison, comparing the stored data with the currently collected sound wave, and determining whether the dish made of the set material is present may be performed using machine learning and deep learning. 
     When it is determined that the washing target made of the set material is not present, the controller  300  may terminate the control process of the dishwasher. When it is determined that the washing target made of the set material is present, the controller  300  may perform operations S 140  and S 150 . 
     When the washing target made of the set material is present, the controller  300  may determine a location in which the washing target made of the set material is present, on the basis of the analyzed characteristics of the sound wave (S 140 ). 
       FIG. 3  illustrates a waveform of a currently input sound wave. In the graph of  FIG. 3 , a horizontal axis represents the change in rotation angle of the spray nozzle, and a vertical axis represents the amplitude. 
     In the horizontal axis, 0° is a reference angle, and 360° indicates a state in which the spray nozzle is rotated once and is located at the reference angle again. The rotation angle of the spray nozzle may be determined using the location sensor  200  disposed at each spray nozzle. 
     When the spray nozzle is rotated, the controller  300  may determine the location in which the washing target made of the set material is present on the same rack on the basis of the rotation angle and a time point at which the impact sound is generated. 
     In  FIG. 3 , it may be seen that, in particular, the amplitude is significantly changed at locations ( 1 ) and ( 2 ) as compared to locations at other angles. That is, in the locations ( 1 ) and ( 2 ), since the washing water collides with the dish made of plastic or glass, the impact sound is generated. 
     Thus, the controller  300  may determine that the dish made of a specific material is present in the rack in operation S 130  and may determine that the dish made of the specific material is present in locations corresponding to the angles at locations ( 1 ) and ( 2 ) in operation S 140 . 
     In the dishwasher according to the embodiment, the plurality of racks may be provided in the washing chamber in a vertical direction, a plurality of spray nozzles may be provided, and the spray nozzles may be arranged to correspond to the plurality of racks in the vertical direction. 
     The controller  300  may determine in which rack among the plurality of racks the washing target made of the set material is present by identifying whether the impact sound is generated when any one of the plurality of racks is operated. 
     Referring to  FIG. 1 , the rack may include the upper rack  30   a  and the lower rack  30   b , and the spray nozzles may include the upper spray nozzle  22  and the lower spray nozzle  20 . In this case, the upper spray nozzle  22  may be disposed to correspond to the upper rack  30   a  in the vertical direction, and the lower spray nozzle  20  may be disposed to correspond to the lower rack  30   b  in the vertical direction. 
     Due to this structure, when the impact sound is generated by spraying the washing water to the upper rack  30   a  through the upper spray nozzle  22 , it may be determined that the dish made of plastic or glass is present in the upper rack  30   a . Further, when the impact sound is generated by spraying the washing water to the lower rack  30   b  through the lower spray nozzle  20 , it may be determined that the dish made of plastic or glass is present in the lower rack  30   b.    
     In order to determine whether a dish made of a specific material is present in the upper rack  30   a , the lower rack  30   b , or both the upper rack  30   a  and the lower rack  30   b , the controller  300  may control the switching valve  59  so that the washing water is sprayed from only the upper spray nozzle  22  or from only the lower spray nozzle  20 . 
     In the above-described manner, the controller  300  may accurately determine in which rack among the upper rack  30   a  or the lower rack  30   b  the dish made of the set material is present and may also determine a location in which the dish is present by collecting the rotation angles of the spray nozzles. 
     When the dish made of the set material is present, the controller  300  may reduce the amount of impact applied to the washing target made of the set material by the washing water sprayed from the spray nozzles (S 150 ). 
     In this case, at least one of a spraying amount and the spray speed of the washing water sprayed from the spray nozzle or a rotational speed of the spray nozzle is reduced, and thus the amount of impact applied to the washing target made of the set material may be reduced. 
     The controller  300  may control the rotational speed of the washing motor  65  to reduce at least one of the spray amount and the spray speed of the washing water sprayed from the spray nozzle or the rotational speed of the spray nozzle. 
     When the controller  300  controls the rotational speed of the washing motor  65  to be reduced, the spray amount and the spray speed of the washing water sprayed from the spray nozzle may be reduced, and the rotational speed of the spray nozzle may be also reduced. Accordingly, the amount of the impact applied to the dish made of the set material may be reduced. 
       FIG. 5  is a flowchart for describing a method of controlling a dishwasher according to another embodiment.  FIG. 5  illustrates a method in which the controller  300  controls the rotational speed of the washing motor  65  according to another embodiment. 
     The controller  300  may determine whether the impact sound is generated from the sound wave input to the microphone  400  (S 210 ). Since operation S 210  is an embodiment of operation S 130  described above, operation S 210  may be performed in operation S 130  without a separate process. When the impact sound is not generated, the controller  300  may terminate the process without reducing the rotational speed of the washing motor  65 . 
     When the impact sound is generated, the controller  300  may reduce the rotational speed of the washing motor  65  (S 220 ). The controller  300  may reduce the rotational speed of the washing motor  65  to reduce the amount of impact applied to the dish made of the specific material and caused by the washing water, thereby suppressing movement or damage of the dish made of the specific material. A rotational speed reduction ratio of the washing motor  65  may be appropriately set. 
     In operation S 220  and operations S 221  and S 222  described below, the overall rotational speed of the washing motor  65  may be reduced without considering a location in which the impact sound is generated. 
     In this case, the determination of whether the impact sound is generated and the reduction of the rotational speed of the washing motor  65  may be alternately performed multiple times. The determination of whether the impact sound is generated and the reduction of the rotational speed of the washing motor  65  may be set to an appropriate number of times. In the embodiment, the number of repetitions is set to three, but the present disclosure is not limited thereto. 
     After performing operation S 220 , the controller  300  may secondarily determine whether the impact sound is generated from the sound wave input to the microphone  400  (S 211 ). When the impact sound is not generated in operation S 211 , the controller  300  may terminate the process without reducing the rotational speed of the washing motor  65 . 
     When the impact sound is generated, the controller  300  may secondarily reduce the rotational speed of the washing motor  65  (S 221 ). In this case, the rotational speed of the washing motor  65  after operation S 221  is performed is further reduced as compared to the rotational speed of the washing motor  65  after operation S 220  is terminated. 
     After performing operation S 221 , the controller  300  may tertiarily determine whether the impact sound is generated from the sound wave input to the microphone  400  (S 212 ). When the impact sound is not generated in operation S 212 , the controller  300  may terminate the process without reducing the rotational speed of the washing motor  65 . 
     When the impact sound is generated, the controller  300  may tertiarily reduce the rotational speed of the washing motor  65  (S 222 ). In this case, the rotational speed of the washing motor  65  after operation S 222  is terminated is further reduced as compared to the rotational speed of the washing motor  65  after operation S 221  is terminated. 
     When the impact sound is generated even after the rotational speed of the washing motor  65  is reduced, the controller  300  may notify a user of this situation (S 230 ). 
     In detail, the controller  300  may determine whether the impact sound is generated from the sound wave input to the microphone  400  again after operation S 222  is terminated and may notify the user of the fact that the impact sound is generated when the impact sound is generated. 
     In this case, in the method of notifying the user, the notification may be made by a text displayed on a display provided in the dishwasher or a voice output through a speaker provided in the dishwasher. 
     After operation S 222  is terminated, when the impact sound is still generated, the controller  300  may stop the operation of the washing motor  65  and the spray nozzle for safety and notify the user of the fact that the impact sound is generated. 
     In the embodiment, when the impact sound is generated by the dish held on the rack and made of plastic or glass, the controller  300  may reduce the rotational speed of the washing motor to reduce the amount of impact applied to the dish by the washing water, and thus may effectively suppress the dish made of plastic or glass from being moved from an original location thereof or being damaged. 
       FIG. 6  is a flowchart for describing a method of controlling a dishwasher according to still another embodiment.  FIG. 6  illustrates a method in which the controller  300  controls the rotational speed of the washing motor  65  according to still another embodiment. 
     The controller  300  may determine whether the impact sound is generated from the sound wave input to the microphone  400  (S 310 ). Since operation S 310  is an embodiment of operation S 130  described above, operation S 310  may be performed in operation S 130  without a separate process. When the impact sound is not generated, the controller  300  may terminate the process without reducing the rotational speed of the washing motor  65 . 
     When the impact sound is generated, the controller  300  may determine the location in which the washing target made of the set material is present (S 320 ). Since operation S 320  is an embodiment of operation S 140  described above, operation S 320  may be performed in operation S 140  without a separate process. That is, the controller  300  may determine a location in which the impact sound is present as the location in which the dish made of the set material, that is, plastic or glass, is present. 
     When the spray nozzle passes through the location in which the washing target made of the set material is present, the controller  300  may reduce the rotational speed of the washing motor  65  on the basis of the location, derived in operation S 320 , in which the dish made of plastic or glass is present (S 330 ). 
     The controller  300  may reduce the rotational speed of the washing motor  65  when the spray nozzle passes through the location in which the washing target made of the set material is present, and may restore the rotational speed of the washing motor  65  to an original speed when the spray nozzle deviates from the location. In this case, the original speed of the washing motor  65  may be the same as the rotational speed of the washing motor  65  when the washing target made of the set material is not present in the rack. 
     A time point when the spray nozzle passes through the location in which the washing target made of the set material is present may be provided by appropriately setting a range of the rotation angle of the spray nozzle with respect to a location in which the spray nozzle and the dish made of plastic or glass overlap each other in the vertical direction of the dishwasher. 
     The controller  300  may reduce the rotational speed of the washing motor  65  to reduce the amount of impact applied to the dish made of the specific material and caused by the washing water, thereby suppressing the movement or damage of the dish made of the specific material. A rotational speed reduction ratio of the washing motor  65  may be appropriately set. 
     In the embodiment, when the spray nozzle passes over the dish made of plastic or glass, the controller  300  may reduce the rotational speed of the washing motor  65 , thereby reducing a washing time and increasing washing efficiency as compared to a case in which the overall rotational speed of the washing motor  65  is reduced uniformly. 
     In this case, the determination of whether the impact sound is generated and the reduction of the rotational speed of the washing motor  65  may be alternately performed multiple times. In the reduction of the rotational speed of the washing motor  65 , the controller  300  may reduce the rotational speed of the washing motor  65  when the spray nozzle passes through the location in which the washing target made of the set material is present, and may restore the rotational speed of the washing motor  65  to an original speed when the spray nozzle deviates from the location. This control may be commonly performed in operation S 330  and operations S 331  and S 332  described below. 
     The determination of whether the impact sound is generated and the reduction of the rotational speed of the washing motor  65  may be set to an appropriate number of times. In the embodiment, the number of repetitions is set to three, but the present disclosure is not limited thereto. 
     After performing operation S 330 , the controller  300  may secondarily determine whether the impact sound is generated from the sound wave input to the microphone  400  (S 311 ). When the impact sound is not generated in operation S 311 , the controller  300  may terminate the process without reducing the rotational speed of the washing motor  65 . 
     When the impact sound is generated, the controller  300  may secondarily reduce the rotational speed of the washing motor  65  (S 331 ). In this case, the rotational speed of the washing motor  65  after operation S 331  is terminated is further reduced as compared to the rotational speed of the washing motor  65  after operation S 330  is terminated. 
     After performing operation S 331 , the controller  300  may tertiarily determine whether the impact sound is generated from the sound wave input to the microphone  400  (S 312 ). When the impact sound is not generated in operation S 312 , the controller  300  may terminate the process without reducing the rotational speed of the washing motor  65 . 
     When the impact sound is generated, the controller  300  may tertiarily reduce the rotational speed of the washing motor  65  (S 332 ). In this case, the rotational speed of the washing motor  65  after operation S 332  is terminated is further reduced as compared to the rotational speed of the washing motor  65  after operation S 331  is terminated. 
     When the impact sound is generated even after the rotational speed of the washing motor  65  is reduced, the controller  300  may notify the user of this situation (S 340 ). 
     In detail, the controller  300  may determine whether the impact sound is generated from the sound wave input to the microphone  400  again after operation S 332  is terminated, and may notify the user of the fact that the impact sound is generated when the impact sound is generated. 
       FIG. 7  is a flowchart for describing a method of controlling a dishwasher according to still another embodiment. According to the method of controlling a dishwasher illustrated in  FIG. 7 , when the impact sound is generated in the dish held on the rack, the rotational speed of the washing motor  65  may be reduced to prevent the generation of the impact sound, thereby suppressing the movement and damage of the dish that generates the impact sound. Hereinafter, description of parts overlapping the above description may be omitted. 
     First, while the washing motor  65  is operated to rotate the spray nozzle, the washing water may be sprayed onto the dish held on the rack (S 410 ). In this case, the microphone  400  provided in the washing chamber  16   a  may collect noise, that is, the sound wave, which is generated while the washing water collides with the dish. 
     The controller  300  may receive the sound signal from the microphone  400  and analyze characteristics of the sound wave input to the microphone  400  (S 420 ). The controller  300  may analyze at least one of the amplitude or the frequency of the sound wave input to the microphone  400 . 
     The controller  300  may determine whether the impact sound is generated from the sound wave input to the microphone  400  on the basis of the result obtained by analyzing the characteristics of the sound wave (S 430 ). When the impact sound is not present, the process may be completed. 
     When the impact sound is present, the controller  300  may determine the location in which the impact sound is present (S 440 ). 
     When the spray nozzle passes through the location in which the impact sound is present, the rotational speed of the washing motor  65  may be reduced (S 450 ). In this case, the controller  300  may reduce the rotational speed of the washing motor  65  when the spray nozzle passes through the location in which the washing target made of the set material is present, and may restore the rotational speed of the washing motor  65  to an original speed when the spray nozzle deviates from the location. The reduction of the rotational speed of the washing motor  65  and the restoration may be common in operation S 450  and operations S 451  and S 452  described below. 
     After performing operation S 450 , the controller  300  may secondarily determine whether the impact sound is generated from the sound wave input to the microphone  400  (S 431 ). When the impact sound is not generated in operation S 431 , the controller  300  may terminate the process without reducing the rotational speed of the washing motor  65 . 
     When the impact sound is generated, the controller  300  may secondarily reduce the rotational speed of the washing motor  65  (S 451 ). In this case, the rotational speed of the washing motor  65  after operation S 4511  is terminated is further reduced as compared to the rotational speed of the washing motor  65  after operation S 450  is terminated. 
     After performing operation S 451 , the controller  300  may tertiarily determine whether the impact sound is generated from the sound wave input to the microphone  400  (S 432 ). When the impact sound is not generated in operation S 432 , the controller  300  may terminate the process without reducing the rotational speed of the washing motor  65 . 
     When the impact sound is generated, the controller  300  may tertiarily reduce the rotational speed of the washing motor  65  (S 452 ). In this case, the rotational speed of the washing motor  65  after operation S 452  is terminated is further reduced as compared to the rotational speed of the washing motor  65  after operation S 451  is terminated. 
     When the impact sound is generated even after the rotational speed of the washing motor  65  is reduced, the controller  300  may notify the user of this situation (S 460 ). 
     In detail, the controller  300  may determine whether the impact sound is generated from the sound wave input to the microphone  400  again after operation S 451  is terminated and may notify the user of the fact that the impact sound is generated when the impact sound is generated. 
     As described above, the present disclosure has been described with reference to the accompanying drawings, but the present disclosure is not limited by the embodiments disclosed in the present specification and the drawings, and various modifications may be made by those skilled in the art within the scope of the technical spirit of the present disclosure. In addition, although the effects according to the configuration of the present disclosure have not been explicitly described while the embodiments of the present disclosure are described, it is apparent that the effects predictable by the corresponding configuration should also be recognized.