Patent Description:
Generally, a washing machine is an appliance for performing washing, rinsing, and spin-drying cycles to remove contaminants from clothing, bedding, and the like (hereinafter referred to as "laundry") by using water, detergent, and mechanical operations.

The washing machine is provided with a balancer to reduce imbalance which occurs when laundry in a drum is unevenly distributed. As the balancer used in the washing machine, a ball balancer or a liquid balancer is used. However, there is a problem that the ball balancer or the liquid balancer moves passively in response to rotation of a drum, such that as the ball balancer or the liquid balancer moves to an opposite side of the center of mass of laundry, and accordingly, the drum continuously rotates until the imbalance is reduced. In order to solve such a problem, a method of actively moving the balancer is suggested.

The actively movable balancer is controlled to move to the opposite side of the center of gravity of the laundry. It is necessary to grasp the position of the balancer in order to control the balancer, but it is difficult to grasp the position of the balancer by rotating together with the drum when the drum rotates.

<CIT> relates to a washing machine which is provided to supply power to actively moving a balancing unit. The washing machine includes a drum, a guide rail, and a balancing unit. The drum houses clothes, bedding, and so on, and is rotatable. The guide rail is coupled to one edge of the drum. The balancing unit moves along the guide rail, and varies the gravitational center of the drum.

It is an object of the present invention to provide a washing machine capable of positively detecting a position of a movable balancer, and a method of controlling the same. This object is achieved with the features of the claims.

The object of the present invention is not limited to the aforementioned object and other objects undescribed herein will be clearly understood by those skilled in the art from the following description.

The above and other objects can be accomplished by providing a method according to independent claim <NUM>. Preferred embodiments of the invention are the subject-matter of the dependent claims.

The specifics of other embodiments are included in the detailed description and drawings.

The method of controlling a washing machine has one or more of the following effects.

First, there is an advantage that it is possible to determine a relative position of a plurality of dispersion units by constructing a circuit of a simple element for detecting the magnetic field of the transmission coil.

Secondly, there is also an advantage of accurately detecting the magnetic field of the transmission coil by appropriately arranging the inductor components.

Thirdly, there is also an advantage that the relative position of a plurality of dispersion units can be determined by using a hall sensor that detects the rotation angle of the drum motor.

Fourthly, there is also an advantage that it is possible to calculate the angle between a plurality of dispersion units using the pulse signal of the hall sensor and the position signal generated by the inductor component.

Effects of the present invention should not be limited to the aforementioned effects and other unmentioned effects will be clearly understood by those skilled in the art from the claims.

Advantages and features of the present invention and methods for accomplishing the same will be more clearly understood from exemplary embodiments described below with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, but may be implemented in various different forms. The embodiments are provided only to complete disclosure of the present disclosure and to fully provide a person having ordinary skill in the art to which the present disclosure pertains with the category of the present disclosure, and the present invention will be defined by the scope of the appended claims. Like reference numerals generally denote like elements through the specification.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings for explaining a washing machine and a method of controlling the same.

<FIG> is a cross-sectional view of a washing machine; <FIG> is a perspective view of a tub of a washing machine; and <FIG> is a perspective view of a drum of a washing machine.

A washing machine <NUM> according to an embodiment of the present disclosure includes: a cabinet <NUM> which forms an external appearance of the washing machine <NUM>; a door <NUM> which opens and closes one side of the cabinet <NUM> so that laundry may be put into the cabinet <NUM>; a tub <NUM> which is provided in the cabinet <NUM> and supported by the cabinet <NUM> and in which wash water is contained; a drum <NUM> having a cylindrical shape, which is provided in the tub <NUM> and which rotates when the laundry is loaded; a drum motor <NUM> which provides torque to the drum <NUM> to rotate the drum <NUM>; a balancing unit <NUM> which moves along the circumference of the drum <NUM> to reduce imbalance caused by unbalanced distribution of laundry leaning to one side when the drum <NUM> rotates; a detergent box <NUM> in which detergent is held; and a control panel <NUM> which receives a user's input and displays status of a washing machine.

The cabinet <NUM> is provided with a laundry inlet hole 111a, through which laundry is loaded into the cabinet <NUM>. The door <NUM> is rotatably connected with the cabinet <NUM> to open and close the laundry inlet hole 111a. The cabinet <NUM> is provided with the control panel <NUM>. The cabinet <NUM> is provided with the detergent box <NUM> which may be withdrawn therefrom.

A spring <NUM> and a damper <NUM> are provided in the cabinet <NUM> to absorb shock of the tub <NUM>. The tub <NUM> contains wash water. The tub <NUM> is disposed outside the drum <NUM> to surround the drum <NUM>.

The tub <NUM> includes: a tub main body 122a having a cylindrical shape and both ends which are open; a front tub cover 122b having a ring shape and disposed at a front side of the tub main body 122a; a rear tub cover 122c having a disc shape and disposed at a rear side of the tub main body 122a. Hereinafter, the front side refers to the side of the door <NUM>, and the rear side refers to the side of the drum motor <NUM>. A tub hole 122d is formed at the front tub cover 122b. The tub hole 122d is formed to communicate with the laundry inlet hole 111a to allow the laundry to be put into the drum <NUM>.

The drum motor <NUM> is provided at the rear tub cover 122c to generate torque. The drum motor <NUM> is connected with a rotation axis <NUM> to rotate the drum <NUM>. The drum motor <NUM> may rotate the drum <NUM> at various speeds and directions. The drum motor <NUM> includes: a stator 113a wound with a coil; and a rotor 113b which rotates by generating electromagnetic interaction with the coil.

The stator 113a is provided with a plurality of winded coils. The rotor 113b is provided with a plurality of magnets for electromagnetic interaction with the coils. The rotor 113b rotates by the electromagnetic interaction between the coil and the magnet, and the rotational force of the rotor 113b is transmitted to the drum <NUM> to rotate the drum <NUM>.

The drum motor <NUM> is provided with a hall sensor 113c for detecting the rotation angle of the rotor 113b. The hall sensor 113c generates a pulse signal whenever the rotor 113b rotates by a set unit angle. The speed and position of the rotor 113b are estimated using the pulse signal generated by the hall sensor 113c.

The rotation axis <NUM> connects the drum motor <NUM> with the drum <NUM>. The rotation axis <NUM> transfers torque of the drum motor <NUM> to the drum <NUM> to rotate the drum <NUM>. One end of the rotation axis <NUM> is connected to the center of rotation at the rear side of the drum <NUM>, and the other end of the rotation axis <NUM> is connected with the rotor 113b of the drum motor <NUM>.

The drum <NUM> rotates with the laundry loaded therein. The drum <NUM> is disposed in the tub <NUM>. The drum <NUM> is formed in a cylindrical shape and is rotatable. The drum <NUM> has a plurality of through-holes through which wash water may pass. The drum <NUM> rotates by receiving the torque of the drum motor <NUM>.

A drum hole 124a is provided at a front side of the drum <NUM>. The drum hole 124a is formed to communicate with the laundry inlet hole 111a and the tub hole 122d so that the laundry may put into the drum <NUM>. A guide rail <NUM> is connected to a front and/or a rear circumference of the drum <NUM>. In the embodiment, the guide rail <NUM> is provided on a front circumference of the drum <NUM>.

A gasket <NUM> seals a space between the tub <NUM> and the cabinet <NUM>. The gasket <NUM> is interposed between the opening of the tub <NUM> and the laundry inlet hole 111a. The gasket <NUM> absorbs shock which is delivered to the door <NUM> when the drum <NUM> rotates, and prevents wash water in the tub <NUM> from leaking to the outside. The gasket <NUM> may be provided with a circulation nozzle <NUM> which sprays wash water into the drum <NUM>.

The detergent box <NUM> may hold a detergent, a fabric softener, bleach, and the like. The detergent box <NUM> may be retractably provided at the front surface of the cabinet <NUM>. When wash water is supplied, the detergent in the detergent box <NUM> is mixed with the wash water to be introduced into the tub <NUM>.

The cabinet <NUM> may include: a water supply valve <NUM> which adjusts introduction of the wash water supplied from an external water source; a water supply passage <NUM> through which the wash water, introduced into the water supply valve, flows to the detergent box <NUM>; and a water supply pipe <NUM> through which the wash water, mixed with the detergent in the detergent box <NUM>, is introduced into the tub <NUM>.

The cabinet <NUM> may include: a drain pipe <NUM> through which the wash water in the tub <NUM> is drained; a pump <NUM> which discharges the wash water in the tub <NUM>; a circulation passage <NUM> which circulates the wash water; a circulation nozzle <NUM> which introduces the wash water is into the drum <NUM>; and a drain passage <NUM> through which the wash water is drained to the outside. In some implementations, the pump <NUM> may include a circulation pump and a drain pump which may be connected to the circulation passage <NUM> and the drain passage <NUM> respectively.

A plurality of balancing units <NUM> move along the guide rail <NUM> of the drum <NUM>, to change the center of gravity of the drum <NUM>. In this case, the center of gravity of the drum <NUM> does not refer to the center of mass of the drum <NUM> itself, but refers to a common center of gravity of objects, including the drum <NUM>, the laundry which is loaded in the drum <NUM>, the guide rail <NUM>, the plurality of balancing units <NUM>, and other elements attached to the drum <NUM>, which rotate along with the drum <NUM> when the drum <NUM> rotates.

The plurality of balancing units <NUM> move along the front circumference of the drum <NUM>, to adjust the center of gravity of the drum <NUM> when laundry is unevenly distributed. When the drum <NUM> rotates with the unbalanced laundry leaning to one side, vibration and noise are caused by imbalance, in which a geometrical center of the rotation axis <NUM> (the center of gravity) of the drum <NUM> does not coincide with a real center of gravity of the drum <NUM>. The plurality of balancing units <NUM> may reduce the imbalance of the drum <NUM> by causing the center of gravity of the drum <NUM> to be close to the rotation axis <NUM>. In this embodiment, the plurality of balancing units <NUM> are two units of a first balancing unit 300a and a second balancing unit 300b.

The plurality of balancing units <NUM> move actively along the guide rail <NUM>. The active movement refers to movement of the plurality of balancing units <NUM> along the guide rail <NUM> by using their own power.

The guide rail <NUM> is a passage where the plurality of balancing units <NUM> move. The guide rail <NUM> is formed in a ring shape and is connected to a front end circumference of the drum <NUM>.

A transmission coil <NUM> for wireless power transmission to the plurality of balancing units <NUM> is disposed at the front tub cover 122b and/or the rear tub cover 122c. In this embodiment, the transmission coil <NUM> is disposed at the front tub cover 122b. The transmission coil <NUM> is disposed at a position facing the guide rail <NUM>. The transmission coil <NUM> wirelessly transmits power to the plurality of balancing units <NUM> as a coil generating a magnetic field.

The control panel <NUM> may include: an input unit (not shown) which receives user inputs for various operations, for example, selecting a washing course, a time required for each execution, reservation, etc.;; and a display unit (not shown) which displays an operation state of the washing machine <NUM>.

<FIG> is a partial perspective view of a washing machine; <FIG> is a partial cross-sectional view of a washing machine; and <FIG> is an exploded perspective view of a balancing unit of a washing machine.

The balancing unit <NUM> includes: a reception coil <NUM> which generates electric power from the magnetic field formed by the transmission coil <NUM>; a driving module <NUM> which generates driving power by using the electric power generated by the reception coil <NUM>; a pinion gear <NUM> which rotates by receiving the driving power from the driving module <NUM>; an upper frame <NUM> which includes the driving module <NUM> and the pinion gear <NUM>; a lower frame <NUM> which is slidably connected with the upper frame <NUM>; an elastic body <NUM> interposed between the upper frame <NUM> and the lower frame <NUM>; and an electronic component module <NUM> in which electronic components are included.

The reception coil <NUM> generates electric power from the magnetic field formed by the transmission coil <NUM>. The reception coil <NUM> is disposed on a surface that faces the tub <NUM> of the upper frame <NUM> so as to oppose the transmission coil <NUM>. The reception coil <NUM> is formed as a coil which generates electric power from a magnetic field.

The driving module <NUM> may generate driving power by using electric power, which is supplied from an external source and transmitted wirelessly through the transmission coil <NUM> and the reception coil <NUM>. The driving module <NUM> may be a motor which generates torque. The driving module <NUM> rotates the pinion gear <NUM>. In the case where the driving module <NUM> is a motor, a worm gear (not shown) is interposed between the motor and the pinion gear <NUM> such that the worm gear rotates the pinion gear <NUM>. The driving module <NUM> may be disposed at the upper frame <NUM>.

The pinion gear <NUM> rotates by receiving driving power from the driving module <NUM>. A rack gear 125a is disposed on an inner diameter surface of the guide rail <NUM>; and the pinion gear <NUM> is engaged with the rack gear 125a.

The rack gear 125a is formed along the inner diameter surface of the guide rail <NUM>. The cross-section of the guide rail <NUM> is formed in a square shape, and the inner diameter surface of the guide rail <NUM> refers to a surface which is located close to the center of rotation of the drum <NUM> among the inner side surfaces of the guide rail <NUM>.

The pinion gear <NUM> rotates while being engaged with the rack gear 125a to actively move the balancing unit <NUM>. As the pinion gear <NUM> is engaged with the rack gear 125a, the balancing unit <NUM> may be prevented from moving freely by the dead load or rotation of the drum <NUM>.

The upper frame <NUM> forms the frame of the balancing unit <NUM>. The upper frame <NUM> is disposed on the inner diameter surface of the guide rail <NUM>. The upper frame <NUM> has a side surface which is formed in an arc shape so as to move along the guide rail <NUM>.

The upper frame <NUM> includes the driving module <NUM>, the pinion gear <NUM>, the electronic component module <NUM>, an upper roller <NUM>, and the transmission coil <NUM>. The upper frame <NUM> is connected with the lower frame <NUM>, and the elastic body <NUM> is interposed between the upper frame <NUM> and the lower frame <NUM>.

The electronic component module <NUM> may include various electronic components, which are provided for driving the driving module <NUM> by using electric power generated by the reception coil <NUM>.

The electronic component module <NUM> may include an inductor component 322a which generates an electromotive force by a magnetic field formed by the transmission coil <NUM>. The inductor component 322a is a radial type inductor component and is formed into a cylindrical shape.

The upper roller <NUM> is rotatably provided at the upper frame <NUM>. The upper roller <NUM> may roll while being firmly pressed against the inner diameter surface of the guide rail <NUM>. The upper roller <NUM> is provided to prevent the upper frame <NUM> from being directly in contact with the inner diameter surface of the guide rail <NUM>. When the pinion gear <NUM> is engaged with the rack gear 125a, the upper roller <NUM> prevents an elastic force, provided by the elastic body <NUM>, from being concentrated on the pinion gear <NUM>. A plurality of upper rollers <NUM> may be provided.

The lower frame <NUM> forms a lower frame of the balancing unit <NUM>. The lower frame <NUM> is disposed on an outer diameter surface of the guide rail <NUM>. The outer diameter surface of the guide rail <NUM> refers to a surface that faces the inner diameter surface on the inner side of the guide rail <NUM>. The lower frame <NUM> is formed in an arc shape so as to move along the guide rail <NUM>. The lower frame <NUM> includes a lower roller <NUM>.

The lower roller <NUM> is rotatably provided at the lower frame <NUM>. The lower roller <NUM> may roll while being firmly pressed against the outer diameter surface of the guide rail <NUM>. The lower roller <NUM> is provided to prevent the lower frame <NUM> from being directly in contact with the outer diameter surface of the guide rail <NUM>. A plurality of lower rollers <NUM> may be provided.

<FIG> is a block diagram of a washing machine; <FIG> is a circuit diagram of a position detecting unit of a washing machine; and <FIG> is a view exemplifying generation of a position signal in the position detecting unit of the washing machine.

The washing machine includes: a power supply <NUM> which is connected with an external power source to provide power; the aforementioned transmission coil <NUM> which generates a magnetic field to transmit power to the balancing unit <NUM> wirelessly; an inverter <NUM> which converts the DC input supplied from the power supply <NUM> into an AC waveform to apply to the transmission coil <NUM>; a transmission communication unit <NUM> which receives the position signal transmitted from the balancing unit <NUM>; and a transmission controller <NUM> which controls the inverter <NUM> and determines positions of the first balancing unit 300a and the second balancing unit 300b from the position signal received by the transmission communication unit <NUM> and the rotation angle of the drum motor <NUM> detected by the hall sensor 113c.

The power supply <NUM> converts commercial electric power, which is an alternating current supplied from an external power source, into a direct current, and supplies the direct current to the inverter <NUM>. The power supply <NUM> may be provided in the cabinet <NUM> or at the control panel <NUM>. The power supplied after conversion by the power supply <NUM> may also be supplied to the drum motor <NUM>.

The inverter <NUM> includes a switching device which converts the direct current (DC) into the alternating current (AC). A driving frequency of the switching device is set by the transmission controller <NUM>. The alternating current (AC) may drive the transmission coil <NUM> to form a magnetic field around the transmission coil <NUM>.

As described above, the transmission coil <NUM> is disposed at the tub <NUM> and forms a magnetic field. The transmission coil <NUM> is connected with a transmitting capacitor (not shown) to form a resonance circuit. As the alternating current (AC) converted by the inverter <NUM> flows to the transmission coil <NUM>, a magnetic field is formed around transmission coil <NUM> according to a change in current.

The transmission communication unit <NUM> communicates with a receiving communication unit <NUM> which will be described later. The transmission communication unit <NUM> and the receiving communication unit <NUM> communicate with each other through Radio Frequency (RF) or infrared rays. The transmission communication unit <NUM> receives the position signal of the balancing unit <NUM> from the receiving communication unit <NUM>. The transmission communication unit <NUM> transmits, to the receiving communication unit <NUM>, a control signal for controlling the driving module <NUM> of the balancing unit <NUM>.

The transmission controller <NUM> controls a driving frequency of the inverter <NUM> so as to control a resonant frequency of the resonance circuit formed by the transmission coil <NUM>. The transmission controller <NUM> receives the position signal of the balancing unit <NUM> from the transmission communication unit <NUM> and receives the pulse signal from the hall sensor 113c to determine the positions of the first balancing unit 300a and the second balancing unit 300b. The positions of the first balancing unit 300a and the second balancing unit 300b are changed in response to the rotation of the drum <NUM>, and thus, such positions are positions of the first balancing unit 300a and the second balancing unit 300a relative thereto. In this embodiment, the positions of the first balancing unit 300a and the second balancing unit 300b are an angle therebetween. In this embodiment, the transmission controller <NUM> calculates the angle between the first balancing unit 300a and the second balancing unit 300b from the position signal of the balancing units <NUM> and the pulse signal of the hall sensor 113c. Detailed description thereof will be given later with reference to <FIG> and <FIG>.

The transmission controller <NUM> generates a control signal to move the balancing unit <NUM> by a degree of imbalance of the drum <NUM>. The degree of imbalance of the drum <NUM> can be measured using a vibration sensor (not shown) which senses vibration of the tub <NUM> or may be measured using change in the rotational speed of the drum <NUM>, which is measured using the hall sensor 113c. The transmission controller <NUM> may move the first balancing unit 300a and the second balancing unit 300b to have a set angle therebetween, move the first balancing unit 300a and the second balancing unit 300b in the same rotational direction, or move the first balancing unit 300a and the second balancing unit 300b in different rotational directions to change an angle therebetween.

The transmission controller <NUM> transmits, through the receiving communication unit <NUM>, a control signal for controlling the driving module <NUM> of the balancing unit <NUM>.

The balancing unit <NUM> includes: a reception coil <NUM> which generates electric power from the magnetic field formed by the transmission coil <NUM>; a rectifier <NUM> which converts the power generated in the reception coil <NUM> from the alternating current (AC) to the direct current (DC); a position sensing unit <NUM> which senses a magnetic field formed by the transmission coil <NUM> when passing through the transmission coil <NUM>, to generate a position signal; and a reception controller <NUM> which transfers the position signal generated by the position sensing unit <NUM> to the receiving communication unit <NUM> and controls the driving module <NUM> by using the control signal received by the receiving communication unit <NUM>. The rectifier <NUM>, the position sensing unit <NUM>, the receiving communication unit <NUM>, and the reception controller <NUM> are provided in the electronic component module <NUM>.

As described above, the reception coil <NUM> generates electric power from the magnetic field formed by the transmission coil <NUM>. The reception coil <NUM> is connected to a receiving capacitor (not shown) to form a resonant circuit. When the reception coil <NUM> passes the transmission coil <NUM> in response to rotation of the balancing unit <NUM> together with the drum <NUM>, the reception coil <NUM> receives a magnetic field formed by the transmission coil <NUM> and generates an AC waveform power.

The rectifier <NUM> converts the power, generated by reception coil <NUM>, from the alternating current (AC) to the direct current (DC). The rectifier <NUM> includes a smoother which make the rectified current smooth and stable current.

The driving module <NUM> generates power by the rectified power from the rectifier <NUM> to move the balancing unit <NUM>. The power rectified by the rectifier <NUM> may be temporarily stored in a capacitor (not shown) and then applied to the driving module <NUM>.

The position sensing unit <NUM> senses a magnetic field formed by the transmission coil <NUM> to generate a position signal. When the position sensing unit <NUM> passes the transmission coil <NUM> in response to rotation of the balancing unit <NUM> together with the drum <NUM>, the position sensing unit <NUM> generates a position signal.

Referring to <FIG>, the position sensing unit <NUM> includes: the inductor component 322a which generates an electromotive force from the magnetic field formed by the transmission coil <NUM>; and a zener diode element 322b which generates a position signal by adjusting the electromotive force, generated by the inductor component 322a, to a constant voltage magnitude. The position sensing unit <NUM> may further include a diode and a capacitor for rectifying the electromotive force generated by the inductor component 322a.

The inductor component 322a is arranged such that a cylindrical upper surface thereof is arranged parallel to a surface formed by the transmission coil <NUM>, while facing the surface formed by the transmission coil <NUM>. When the inductor component 322a enters above the transmission coil <NUM> in response to the rotation of the drum <NUM>, an electromotive force is generated. On the contrary, when the inductor component 322a leaves from the transmission coil <NUM>, no electromotive force is generated. The zener diode element 322b generates a position signal by adjusting the electromotive force, which is generated between entering and leaving of the inductor component 322a, to a constant voltage magnitude.

The receiving communication unit <NUM> communicates with the transmission communication unit <NUM>. The receiving communication unit <NUM> transmits the position signal of the balancing unit <NUM> to the transmission communication unit <NUM>. The receiving communication unit <NUM> receives a control signal for controlling the driving module <NUM> of the balancing unit <NUM> from the transmission communication unit <NUM>. The receiving communication unit <NUM> may transmit identification information to the position signal.

The reception controller <NUM> controls the rectifier <NUM> to regulate the voltage output from the rectifier <NUM>. The reception controller <NUM> receives the control signal from the receiving communication unit <NUM> to control the driving module <NUM>.

The reception controller <NUM> receives the position signal generated by the position sensing unit <NUM>, and transmits the position signal to the transmission communication unit <NUM> through the receiving communication unit <NUM>. The reception controller <NUM> may transmit the position signal generated by the position sensing unit <NUM> to the receiving communication unit <NUM> including identification information. That is, the reception controller <NUM> of the first balancing unit 300a transmits identification information indicating a position signal of the first balancing unit 300a to the position signal through the receiving communication unit <NUM>, and the reception controller <NUM> of the second balancing unit 300b transmits identification information indicating a position signal of the second balancing unit 300b to the position signal through the receiving communication unit <NUM>.

While the driving module <NUM> operates, the reception controller <NUM> does not transmit the position signal generated by the position sensing unit <NUM> through the receiving communication unit <NUM>. Since the position of the balancing unit <NUM> determined by the transmission controller <NUM> is a relative position, the reception controller <NUM> does not transmit the position signal when the balancing unit <NUM> is moved.

<FIG> is a flowchart of a method of controlling a washing machine according to an embodiment of the present invention; and <FIG> is a diagram how to determine a position of a balancing unit of a washing machine according to the embodiment of the present invention.

The transmission controller <NUM> receives a position signal of the first balancing unit 300a through the transmission communication unit <NUM> (S11). Upon rotation of the drum <NUM>, the position sensing unit <NUM> of the first balancing unit 300a generates a position signal at a time when passing through the transmission coil <NUM>, and transmits the position signal to the reception controller <NUM>. The reception controller <NUM> transmits the position signal, generated by the position sensing unit <NUM>, through the receiving communication unit <NUM>. The transmission communication unit <NUM> receives the position signal of the first balancing unit 300a and transmits the position signal to the transmission controller <NUM>.

The transmission controller <NUM> counts the number of pulse signals generated by the hall sensor 113c (S12). The hall sensor 113c generates a pulse signal whenever the rotor 113b rotates by the set unit angle (P). The hall sensor 113c transmits the generated pulse signal to the reception controller <NUM> and the transmission controller <NUM> counts the number of the pulse signals transmitted from immediately after receiving the position signal of the first balancing unit 300a.

The transmission controller <NUM> receives the position signal of the second balancing unit 300b through the transmission communication unit <NUM> (S13). Upon rotation of the drum <NUM>, the position sensing unit <NUM> of the second balancing unit 300b generates a position signal at a time when passing through the transmission coil <NUM>, and transmits the position signal to the reception controller <NUM>. The reception controller <NUM> transmits the position signal, generated by the position sensing unit <NUM>, through the receiving communication unit <NUM>. The transmission communication unit <NUM> receives the position signal of the second balancing unit 300b and transmits the position signal to the transmission controller <NUM>.

The transmission controller <NUM> calculates an angle C between the first balancing unit 300a and the second balancing unit 300b (S14). The transmission controller <NUM> calculates the angle (C) between the first balancing unit 300a and the second balancing unit 300b by counting the number of pulse signals (S) which are received after receipt of the position signal of the first balancing unit and before receipt of the position signal of the second balancing unit.

In the case where the unit angle P and the unit of the angle (C) are on the basis of degree, the angle (C) between the first balancing unit 300a and the second balancing unit 300b is calculated as follows.

Claim 1:
A method of controlling a washing machine comprising
a drum (<NUM>) rotated by a drum motor (<NUM>),
first and second balancing units (300a, 300b) to move along a circumference of the drum (<NUM>) with laundry loaded therein,
and a transmission coil (<NUM>) provided at a tub (<NUM>) containing wash water to generate a magnetic field and transmit power wirelessly to the first and second balancing units (300a, 300b),
the method being characterized by the steps:
sensing the magnetic field formed by the transmission coil (<NUM>), and
receiving (S11) a position signal generated by a position sensing unit (<NUM>) to sense a magnetic field formed by the transmission coil (<NUM>) when the first balancing unit (300a) passes through the transmission coil (<NUM>);
counting (S12) a pulse signal for each set unit angle (P) generated by a hall sensor (113c) detecting a rotation angle of the drum motor (<NUM>);
receiving (S13) the position signal generated by the position sensing unit (<NUM>) to sense the magnetic field formed by the transmission coil (<NUM>), when the second balancing unit (300b) pass through the transmission coil (<NUM>); and
calculating (S14) an angle (C) between the first balancing unit (300a) and the second balancing unit (300b) from counting a number of pulse signals (S) and the unit angle (P) which are received after receipt of the position signal of the first balancing unit (300a) and before receipt of the position signal of the second balancing unit (300b).