US20050028299A1

US20050028299A1 - Method for sensing amount of clothes in washing machine

Info

Publication number: US20050028299A1
Application number: US10/833,134
Authority: US
Inventors: Si Jeon; Seung Park; Gwan Park; Jae Kim; Hyun Seo; Tae Lee; Sang Hong; Byung Choi; Moon Hong
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2003-08-07
Filing date: 2004-04-28
Publication date: 2005-02-10
Also published as: CN1580362A

Abstract

A clothes amount sensing method in a washing machine which is capable of reducing clothes amount sensing errors caused by frictional forces, thereby achieving an enhancement in accuracy and reliability. The method includes an acceleration step for accelerating, to a predetermined RPM, a motor adapted to rotate the wash tub, a constant-speed step for maintaining the motor at the predetermined RPM when an RPM of the motor reaches the predetermined RPM in accordance with the acceleration step, a deceleration step for turning off the motor to decelerate the motor, following the constant-speed step, and a clothes amount determination step for determining the amount of the clothes by use of equations of motion respectively established in the acceleration, constant-speed, and deceleration steps.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a method for sensing the amount of clothes contained in a washing machine, and more particularly to a clothes amount sensing method in a washing machine which is capable of reducing clothes amount sensing errors caused by frictional forces.
2. Description of the Related Art
Generally, a washing machine is an appliance adapted to remove contaminants attached to clothes by utilizing actions of detergent and water. The recent trend of such a washing machine is to sense the amount of clothes contained in the washing machine to perform wash, rinse, spin-dry, and dry cycles in accordance with a wash water level, wash time, amount of detergent, and water flows for rinse and wash cycles determined based on the sensed clothes amount.
FIG. 1 is a sectional view illustrating an inner configuration of a general washing machine.
As shown in FIG. 1, the washing machine includes a casing 2, a water tub 10 mounted in the casing 2, and adapted to contain wash water w therein, a wash tub 20 rotatably mounted in the water tub 10, and adapted to contain clothes m to be washed, and a motor 30 adapted to support the wash tub 20 while rotating the wash tub 20.
The casing 2 is provided, at one wall thereof, with a clothes loading/unloading opening 2 a. A door 4 is also hingably mounted to the wall of the casing 2 to open and close the clothes loading/unloading opening 2 a.
The door 4 includes a door frame 5 hingably coupled to the casing 2, and a door glass 6 mounted to the door frame 5.
The wash tub 20 is provided with a clothes loading/unloading opening 21 for allowing the user to load clothes m into the wash tub 20 and to unload the loaded clothes m from the wash tub 20. The wash tub 20 is also provided with water holes 22, through which wash water w is introduced into and discharged from the wash tub 20.
The motor 30 includes a rotating shaft 32 extending through the water tub 10 while being supported by a bearing 34 mounted to the water tub 10. The rotating shaft 32 is connected to the wash tub 20 at an end thereof spaced away from the motor 30.
The washing machine also includes a water supply unit for supplying wash water w fed from the external of the washing machine into the water tub 10. The water supply unit includes a water supply valve 42 connected to an external hose 41, and adapted to control supply of clean water through the external hose 41, and a detergent box 43 provided with a detergent storing space, a water supply passage, and an outlet to discharge water supplied into the washing machine in a state of being mixed with detergent stored therein.
The washing machine further includes a drainage unit for externally draining wash water w contained in the water tub 10. The drainage unit includes a drainage hose 45 connected to the water tub 10, and a drainage pump 46 for pumping wash water w from the water tub 10 through the drainage hose 45. The drainage hose 45 may have the form of a bellows tube. In some cases, the drainage pump 46 may be dispensed with. In this case, a drainage valve may be installed in the drainage hose 45 to control drainage of wash water w through the drainage hose 45.
The washing machine also includes a control unit 49 for controlling the motor 30, water supply valve 42, and drainage pump 46 in accordance with an operation of the user or a sensed clothes amount.
The washing machine further includes a braking unit for performing an electricity generating operation when the motor is switched to an OFF state thereof.
FIG. 2 is a block diagram illustrating a circuit configuration of the braking unit.
As shown in FIG. 2, the braking unit, which is designated by reference numeral 50, includes a rectifying unit 51 for converting a commercial AC voltage supplied to the washing machine into a DC voltage, a smoothing unit 52 for smoothing the DC voltage rectified by the rectifying unit 51, a motor driving unit 53 for driving the motor 30, using the DC voltage supplied thereto via the rectifying unit 51, and a voltage sensing unit 54 for sensing a voltage applied across the washing machine, and generating a sensing signal indicative of the sensed voltage. The braking unit 50 also includes a voltage comparing unit 55 for comparing the sensed voltage with a reference voltage predetermined for the washing machine, a switching unit 56 for turning on/off a braking resistor R in accordance with the sensed result from the voltage comparing unit 55, and a sensor 57 for sensing operating conditions of the motor 30 such as rotated position and rotating speed. The braking unit 50 further includes a microcomputer 58 for controlling the motor 30 in accordance with the sensed operating conditions of the motor 30, and performing a control operation associated with discharge of over-voltage caused by a braking operation, and a signal output unit 59 for generating a control signal based on the controlled result from the microcomputer 58, and outputting the generated control signal to the motor driving unit 52.
The braking unit 50 converts, into electrical energy, inertial energy of the motor 30 and clothes during a braking operation thereof for the motor 30. The electrical energy is recovered by the motor driving unit 53 in the form of a DC voltage, and is then accumulated in the smoothing unit 52.
The microcomputer 58 switches on the switching unit 56 when the DC voltage accumulated in the smoothing unit 52 is higher than the predetermined reference voltage, thereby turning on the braking resistor R. In the ON state thereof, the braking resistor R consumes the DC voltage accumulated in the smoothing unit 52, in the form of heat, thereby protecting the smoothing unit 52, etc.
On the other hand, when the DC voltage accumulated in the smoothing unit 52 is not higher than the predetermined reference voltage, the microcomputer 58 switches off the switching unit 56, thereby turning off the braking resistor R. In this state, the DC voltage recovered by the motor driving unit 53 is accumulated in the smoothing unit 52.
Meanwhile, where the braking resistor R is turned on, irrespective of the level of the voltage sensed by the voltage sensing unit 54 when the motor 30 is turned off, electricity generated by the braking unit 50 is consumed in the form of heat, without being recovered. On the other hand, where the braking resistor R is turned off, irrespective of the level of the voltage sensed by the voltage sensing unit 54, electricity generated by the braking unit 50 is accumulated in the smoothing unit 52.
Now, operation of the conventional washing machine having the above mentioned configuration will be described.
When the washing machine is operated under the condition in which the door 4 has been closed after clothes m have been loaded in the wash tub 20, the control unit 49 senses the amount of the loaded clothes m while turning on/off the motor 30, and then sets a desired wash water level, a desired wash time, a desired amount of detergent, and desired water flows for rinse and wash cycles, based on the sensed clothes amount. In accordance with the set conditions, the control unit 49 then performs wash, rinse, and spin-dry cycles in a sequential fashion.
That is, the control unit 49 controls the water supply valve 42 for a time set in accordance with the sensed clothes amount, thereby supplying wash water w into the washing machine until the supplied wash water w reaches the set wash water level. The supplied wash water w is fed into the water tub 10, so that it is contained in the water tub 10. Thereafter, the control unit 49 drives the motor 30 to rotate the wash tub 20 at a predetermined RPM for a predetermined time. Thus, the clothes m contained in the wash tub 20 are washed in accordance with action of the wash water w. That is, stains are removed from the clothes m. After completion of this wash cycle, the wash water existing in the water tub 10 in a contaminated state is externally drained from the washing machine through the drainage unit.
Subsequently, the washing machine performs, several times, a rinse cycle for rinsing the washed clothes m to remove bubbles remaining on the clothes m. This rinse cycle is carried out under the condition in which the water supply valve 42 and motor 30 are controlled, based on the sensed clothes amount, as in the wash cycle. The contaminated water containing the removed bubbles is externally drained from the washing machine through the drainage unit.
After performing the rinse cycle several times, the washing machine performs a spin-dry cycle in which the motor 30 is controlled to rotate at high speed, thereby centrifugally removing moisture form the clothes m.
FIG. 3 is a flow chart illustrating a conventional method for sensing the amount of clothes contained in the above mentioned conventional washing machine. FIG. 4 is a graph depicting an operating condition of a motor adapted for sensing of the clothes amount in the washing machine.
In accordance with the conventional clothes amount sensing method, as shown in FIGS. 3 and 4, the motor 30 is first started up (S1), and is then accelerated until an RPM thereof reaches a predetermined reference RPM rpm′ (S2). When the RPM of the motor 30 reaches the reference RPM rpm′, the motor 30 is driven in a constant speed state for a predetermined time Ts, and is then turned off (S3 and S4).
Meanwhile, a variation in pulse width modulation (PWM) duty value occurring in a duration from the start-up state to the constant speed state of the motor 30 is measured to measure a mean PWM duty value, in accordance with the clothes amount sensing method (S5).
A rotated angle of the motor 30 caused by a surplus rotation of the motor 30 is then measured (S6).
Finally, a clothes amount is calculated by adding a product of the mean PWM duty value by a proportional constant a to a product of the rotated angle by a proportional constant b (S7).
In accordance with the above mentioned conventional clothes amount sensing method, however, the calculated clothes amount value may have an error caused by friction generated during the rotation of the wash tub 20, for example, friction of the bearing 34, friction generated between the door glass 6 and the clothes m, etc. Such friction may vary, depending on the kind of the washing machine.
Furthermore, in accordance with the conventional clothes amount sensing method, the static frictional force generated upon the start-up of the motor influences the sensing of the clothes amount because the calculated clothes amount is proportional to a mean value of PWM duty values measured in a duration from the start-up state to the constant speed state of the motor. For this reason, it is impossible to sense an accurate clothes amount.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above mentioned problems involved with the related art, and an object of the invention is to provide a clothes amount sensing method in a washing machine which is capable of reducing clothes amount sensing errors caused by frictional forces, thereby achieving an enhancement in accuracy and reliability.
In accordance with one aspect, the present invention provides a method for sensing an amount of clothes contained in a wash tub included in a washing machine, comprising: an acceleration step for accelerating, to a predetermined RPM, a motor adapted to rotate the wash tub; a constant-speed step for maintaining the motor at the predetermined RPM when an RPM of the motor reaches the predetermined RPM in accordance with the acceleration step; a deceleration step for turning off the motor to decelerate the motor, following the constant-speed step; and a clothes amount determination step for determining the amount of the clothes by use of equations of motion respectively established in the acceleration, constant-speed, and deceleration steps.
In accordance with another aspect, the present invention provides a method for sensing an amount of clothes contained in a wash tub included in a washing machine, comprising: an acceleration step for accelerating, to a predetermined RPM, a motor adapted to rotate the wash tub; a constant-speed step for maintaining the motor at the predetermined RPM when an RPM of the motor reaches the predetermined RPM in accordance with the acceleration step; a deceleration step for turning off the motor while braking the motor in an electricity generating mode to decelerate the motor, following the constant-speed step; and a clothes amount determination step for determining the amount of the clothes by use of the principle of the conservation of energy established in the step of braking the motor in the electricity generating mode.
In accordance with another aspect, the present invention provides a method for sensing an amount of clothes contained in a wash tub included in a washing machine, comprising: an acceleration step for accelerating, to a predetermined RPM, a motor adapted to rotate the wash tub; a constant-speed step for maintaining the motor at the predetermined RPM for a predetermined time when an RPM of the motor reaches the predetermined RPM in accordance with the acceleration step; a deceleration step for, following the constant-speed. step, turning off the motor to decelerate the motor, thereby stopping the motor; and a clothes amount determination step for determining the amount of the clothes by use of an equation of energy established in a duration from an acceleration start point of the motor to a constant-speed end point of the motor, and an equation of energy established in a duration from a turn-off point of the motor to a rotation stop point of the motor.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects, and other features and advantages of the present invention will become more apparent after reading the following detailed description when taken in conjunction with the drawings, in which:
FIG. 1 is a sectional view illustrating an inner configuration of a general washing machine;
FIG. 2 is a block diagram illustrating a circuit configuration of a braking unit included in the general washing machine;
FIG. 3 is a flow chart illustrating a conventional method for sensing the amount of clothes contained in the general washing machine;
FIG. 4 is a graph depicting an operating condition of a motor adapted for sensing of the clothes amount in the general washing machine in accordance with the conventional method;
FIG. 5 is a flow chart illustrating a clothes amount sensing method according to a first embodiment of the present invention;
FIG. 6 is a graph depicting an operating condition of a motor adapted for sensing of the clothes amount in accordance with the first embodiment of the present invention;
FIG. 7 is a flow chart illustrating a clothes amount sensing method according to a second embodiment of the present invention;
FIG. 8 is a graph depicting an operating condition of the motor adapted for sensing of the clothes amount in accordance with the second embodiment of the present invention;
FIG. 9 is a graph depicting a variation in clothes amount sensing error depending on a frictional torque measuring error generated in the clothes amount sensing method according to the second embodiment of the present invention;
FIG. 10 is a graph depicting a variation in clothes amount sensing error depending on an acceleration in the clothes amount sensing method according to the second embodiment of the present invention;
FIG. 11 is a graph depicting a variation in clothes amount sensing error depending on an acceleration measuring error generated in the clothes amount sensing method according to the second embodiment of the present invention;
FIG. 12 is a flow chart illustrating a clothes amount sensing method according to a third embodiment of the present invention;
FIG. 13 is a graph depicting an operating condition of a motor adapted for sensing of the clothes amount in accordance with the third embodiment of the present invention;
FIG. 14 is a flow chart illustrating a clothes amount sensing method according to a fourth embodiment of the present invention; and
FIG. 15 is a graph depicting an operating condition of a motor adapted for sensing of the clothes amount in accordance with the fourth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, preferred embodiments of a clothes amount sensing method in a washing machine according to the present invention will be described with reference to the annexed drawings.
FIG. 5 is a flow chart illustrating a clothes amount sensing method according to a first embodiment of the present invention. FIG. 6 is a graph depicting an operating condition of a motor adapted for sensing of the clothes amount in accordance with the first embodiment of the present invention.
The washing machine, to which the clothes amount sensing method according to the present invention is applied, has the same configuration as that of the general washing machine shown in FIG. 1. In the following description, accordingly, respective constituent elements of the washing machine are designated by the same reference numerals as those of FIG. 1, and no detailed description thereof will be given.
In accordance with the clothes amount sensing method according to the first embodiment of the present invention, as shown in FIGS. 5 and 6, the motor 30 is first started up, and is then accelerated (S101). When the RPM of the motor 30 reaches a first predetermined RPM rpm₀, for example, 50 rpm, the motor 30 is maintained at the first predetermined RPM rpm₀(S102).
The start-up, acceleration, and maintenance at the first predetermined RPM rpmo of the motor 30, as described above, are adapted to eliminate the influence of a static frictional force, generated upon an operation of sensing a clothes amount, on the sensing of the clothes amount. It is preferred that the first predetermined RPM rpmo, correspond to an RPM sufficiently low to cause clothes m, to be washed, to come into constant contact with an inner peripheral surface of the wash tub 10.
Following the start-up, acceleration, and maintenance at the first predetermined RPM rpm₀, the motor 30 is driven in a mode for determining the amount of the clothes m. That is, the motor 30 is maintained at the first predetermined RPM rpm₀for a first predetermined time Δt₀(S103), and is then accelerated until the RPM thereof reaches to a second predetermined RPM rpm₁, for example, 130 rpm (Stage 1) (S104).
When the RPM of the motor 30 reaches the second predetermined RPM rpm₁, the motor 30 is maintained at the second predetermined RPM rpm₁(Stage 2) (SlO5). When the motor 30 is turned off after being maintained at the second predetermined RPM rpm₁for a second predetermined time Δt₂(S106), it is decelerated in accordance with a surplus rotation thereof (Stage 3) (S107).
When the RPM of the motor 30 subsequently reaches the first predetermined RPM rpm₀, the motor 30 is again maintained at the first predetermined RPM rpm₀(S108).
In accordance with the clothes amount sensing method according to the first embodiment of the present invention, the clothes amount I_L1′ sensed in the acceleration stage Stage 1 of the motor 30 and the clothes amount I_L3′ sensed in the deceleration stage Stage 3 of the motor 30 are calculated, using the following Expressions 1 and 2, respectively (S109).
The clothes amount I_L1′ sensed in the acceleration stage Stage 1 is calculated, based on an inertial moment I_L1of the clothes m generated in the acceleration stage Stage 1. On the other hand, the clothes amount I_L3′ sensed in the deceleration stage Stage 3 is calculated, based on an inertial moment I_L3of the clothes m generated in the deceleration stage Stage 3. The inertial moment I_L1and inertial moment I_L3can be derived, using equations of motion respectively established in the acceleration, constant-speed, and deceleration stages.
That is, an equation “(I₀+I_L1)α₁=T_d1−T_f” is established in the acceleration stage Stage 1, an equation “0=T_d2−T_f” is established in the constant-speed stage Stage 2, and an equation “(I₀+I_L3)α₃=−T_f” is established in the deceleration stage Stage 3.
Here, “I₀” represents an inertial moment of a rotating body, for example, the wash tub, “I_L1” represents an inertial moment of the clothes in the acceleration stage, “I_L3” represents an inertial moment of the clothes in the deceleration stage, “α₁” represents an angular acceleration in the acceleration stage, “α₃” represents an angular acceleration in the deceleration stage, “T_d1” represents a motor torque in the acceleration stage, “T_f” represents a frictional torque, and “T_d2” represents a motor torque in the constant-speed sage.
The equations of motion in respective stages can be expressed as follows. That is, the inertial moment I_L1of the clothes in the acceleration stage 1 can be expressed by Expression 1, and the inertial moment I_L3of the clothes in the deceleration stage 3 can be expressed by Expression 2. $\begin{matrix} I_{L1} = \frac{(T_{d1} - T_{f})}{α_{1}} - I_{o} = k \frac{({PWM}_{1} - {PWM}_{2})}{α_{1}} - I_{o} = k \frac{({PWM}_{1} - {PWM}_{2}) \times Δ t_{1}}{(w_{2} - w_{1})} - I_{o} & [Expression 1] \\ I_{L1} = \frac{- T_{f}}{α_{3}} - I_{o} = k \frac{{PWM}_{2}}{α_{3}} - I_{o} = k \frac{{PWM}_{2} \times Δ t_{3}}{(w_{2} - w_{3})} - I_{o} & [Expression 2] \end{matrix}$
In the clothes amount sensing mode, the motor is typically driven in a speed range relatively lower than those of wash and spin-dry cycles. In this mode, accordingly, the motor torques T_d1and T_d2are quantitatively proportional to the PWM duty value of the motor. Thus, the motor torque in the acceleration stage T_d1corresponds to k×PWM₁(T_d1=k×PWM₁), and the frictional torque T_fcorresponds to T_d2, that is, k×PWM₂(T_f=T_d2=k×PWM₂). “k” is a proportional constant between the motor torque and the PWM duty value in each stage. The proportional constant k can be experimentally determined.
Referring to Expressions 1 and 2, it can be understood that the inertial moment I_L1of the clothes in the acceleration stage 1 and the inertial moment I_L3of the clothes in the deceleration stage 3 can be calculated by measuring respective angular velocities ω₁and ω₂at start and end points of the acceleration stage Stage 1, respective angular velocities ω′₂and ω₃at start and end points of the deceleration stage Stage 3, the PWM duty value PWM₁, in the acceleration stage Stage 1, the PWM duty value PWM₂in the constant-speed stage Stage 2, the acceleration time Δt₁, the deceleration time Δt₂, and the inertial moment I₀of the rotating body.
Based on the calculated inertial moment I_L1of the clothes in the acceleration stage 1 and the calculated inertial moment I_L3Of the clothes in the deceleration stage 3, the clothes amount I_L1′ in the acceleration stage Stage 1 and the clothes amount I_L3′ in the deceleration stage Stage 3 are calculated, respectively.
Thereafter, an absolute value of the difference between the clothes amount I_L1′ in the acceleration stage Stage 1 and the clothes amount I_L3′ in the deceleration stage Stage 3 is calculated. The calculated absolute value is then compared with a predetermined error value I_err′ (S110).
When it is determined, based on the compared result, that the absolute value of the difference between the clothes amount I_L1′ in the acceleration stage Stage 1 and the clothes amount I_L3′ in the deceleration stage Stage 3 is not more than a predetermined error value l_err′, a larger one of the clothes amount I_L1′ in the acceleration stage Stage 1 and the clothes amount I_L3′ in the deceleration stage Stage 3 is selected, and the selected clothes amount is finally determined as a target clothes amount I_L′ to be sensed (S111).
Based on the determined clothes amount I_L′, a desired wash water level, a desired wash time, a desired amount of detergent, and desired water flows for rinse and wash cycles are determined. Thereafter, the washing machine performs wash, rinse, and spin-dry cycles, based on the determined conditions.
On the other hand, when it is determined that the absolute value of the clothes amount difference is more than the predetermined error value I_err′, the acceleration stage Stage 1, constant-speed stage Stage 2, deceleration stage Stage 3, and clothes amount calculation stage are repeated until the absolute value of the clothes amount difference is not more than the predetermined error value I_err′.
When the absolute value of the clothes amount difference is still more than the predetermined error value I_err′ even after the repetition of the acceleration stage Stage 1, constant-speed stage Stage 2, deceleration stage Stage 3, and clothes amount calculation stage is carried out a predetermined number of times, for example, three times, the washing machine determines that there are clothes amount sensing errors. Based on this determination, the washing machine is turned off. In this case, it is also possible to display or externally inform of the current situation that the clothes amount sensing is impossible. Of course, it may also be possible to control the washing machine to operate in a standard course, without being controlled based on a sensed clothes amount.
FIG. 7 is a flow chart illustrating a clothes amount sensing method according to a second embodiment of the present invention. FIG. 8 is a graph depicting an operating condition of the motor adapted for sensing of the clothes amount in accordance with the second embodiment of the present invention.
In accordance with the clothes amount sensing method according to the second embodiment of the present invention, as shown in FIGS. 7 and 8, the motor 30 is first started up, and is then accelerated (S201). When the RPM of the motor 30 reaches a first predetermined RPM rpm₀, for example, 50 rpm, the motor 30 is maintained at the first predetermined RPM rpm₀(S202).
The start-up, acceleration, and maintenance at the first predetermined RPM rpm₀of the motor 30, as described above, are adapted to eliminate the influence of a static frictional force, generated upon an operation of sensing a clothes amount, on the sensing of the clothes amount. It is preferred that the first predetermined RPM rpm₀, correspond to an RPM sufficiently low to cause clothes m, to be washed, to come into constant contact with the inner peripheral surface of the wash tub 20.
Following the start-up, acceleration, and maintenance at the first predetermined RPM rpm₀, the motor 30 is driven in a mode for determining the amount of the clothes m. That is, the motor 30 is maintained at the first predetermined RPM rpm₀for a first predetermined time Δt₀(S203), and is then accelerated until the RPM thereof reaches to a second predetermined RPM rpm₁, for example, 130 rpm (Stage 1) (S204).
When the RPM of the motor 30 reaches the second predetermined RPM rpm₁, the motor 30 is maintained at the second predetermined RPM rpm₁, (Stage 2) (S205).
When the motor 30 is turned off after being maintained at the second predetermined RPM rpm₁, for a second predetermined time Δt₂(S206), it is decelerated in accordance with a surplus rotation thereof (Stage 3) (S207).
When the RPM of the motor 30 subsequently reaches the first predetermined RPM rpm₀, the motor 30 is again maintained at the first predetermined RPM rpm₀(S208).
In accordance with the clothes amount sensing method according to the second embodiment of the present invention, an estimated value of an inertial moment of the wash tub 20 and clothes m, I^(k), (hereinafter, referred to as an “estimated inertial moment value”), and an estimated frictional torque value T_f ^(k)are iteratively calculated, using equations of motion respectively established in the acceleration stage Stage 1, constant-speed stage Stage 2, and deceleration stage Stage 3 while taking an error ε into consideration.
That is, an equation $“ I = \frac{(T_{d1} - T_{f})}{α_{1}} = \frac{\frac{k \times {PWM}_{1} - T_{f}}{(w_{2} - w_{1})}}{Δ t_{1}} ”$
is established in the acceleration stage Stage 1, an equation “T_d2=T_f=k×PWM₂” is established in the constant-speed stage Stage 2, and an equation $“ T_{f} = I \times (α_{3}) = I \times (\frac{(w_{2} - w_{3})}{Δ t_{3}}) ”$
is established in the deceleration stage Stage 3.
Here, “T_d1” represents a motor torque in the acceleration stage, and “T_d2” represents a motor torque in the constant-speed sage. Since the wash tub 20 is driven in a relatively low speed range in the clothes amount sensing mode, the relation between the motor torque and the PWM duty value in each stage can be approximately expressed by a linear function “T_d1=k×PWM₁” or “T_d2=k×PWM₂”. Accordingly, “T_d1” and “T_d2” can be calculated by measuring the PWM duty value PWM₁in the acceleration stage Stage 1 and the PWM duty value PWM₂in the constant-speed stage Stage 2. “k” is a proportional constant between the motor torque and the PWM duty value in each stage. The proportional constant k can be experimentally determined.
Also, “α₁” represents an angular acceleration in the acceleration stage, and can be expressed by $“ (α_{1} = \frac{w_{2} - w_{1}}{Δ t_{1}}) ” .$
“α₃” represents an angular acceleration in the deceleration stage, and can be expressed by $“ (α_{3} = \frac{w_{2} - w_{1}}{Δ t_{1}}) ” .$
“α₁” and “α₃” can be calculated by measuring respective angular velocities ω₁and ω₂at start and end points of the acceleration stage Stage 1, respective angular velocities ω′₂and ω₃at start and end points of the deceleration stage Stage 3, the acceleration time Δt₁, and the deceleration time Δt₂.
Now, procedures for iteratively calculating the estimated inertial moment value I^(k)and the estimated frictional torque value T_f ^(k), taking an error ε into consideration, will be described in detail.
In a first procedure, an estimated value of an initial frictional torque corresponding to a frictional torque generated in the constant-speed stage Stage 2, T_f ⁰(T_f ⁰=T_d2=k ×PWM₂), is calculated. In a second procedure, an estimated value of an initial inertial moment I⁰is calculated by applying, to the equation of motion established in the acceleration stage Stage 1, a value obtained after adding the error ε to the estimated initial frictional torque value T_f ⁰calculated in the first procedure (S209).
That is, in the first procedure, the PWM duty value PWM₂in the constant-speed stage Stage 2 is first measured. Based on the calculated PWM duty value PWM₂, the estimated initial frictional torque value T_f ⁰is then calculated.
In the second procedure, the angular velocities ω₁and ω₂and acceleration time Δt₁of the motor 30 in the acceleration stage Stage 1 are first measured. Based on the measured angular velocities ω₁and ω₂and acceleration time Δt₁, an angular acceleration α₁in the acceleration stage Stage 1 is then calculated. Also, the PWM duty value PWM₁, in the acceleration stage Stage 1 is measured. Based on the calculated PWM duty value PWM₁, a motor torque T_d1in the acceleration stage Stage 1 is calculated. Finally, the estimated initial inertial moment value I⁰is calculated by applying the calculated angular acceleration α₁and motor torque T_d1, to the equation of motion established in the acceleration stage, and applying, to an item “T_f” in the equation of motion established in the acceleration stage, a value obtained after adding the error ε to the estimated initial frictional torque value T_f ⁰.
In a third procedure, the calculated frictional torque, which corresponds to the calculated estimated frictional torque value T_f ⁰, is updated by a next estimated frictional torque value T_f ¹. The next estimated frictional torque value T_f ¹is calculated by applying the estimated inertial moment value I⁰calculated in the second procedure to the equation of motion established in the deceleration stage Stage 3 (S210). In a fourth procedure, the calculated inertial moment, which corresponds to the calculated estimated inertial moment value I⁰, is updated by a next estimated inertial moment value I¹. The next estimated inertial moment value I¹is calculated by applying the estimated frictional torque value T_f ¹updated in the third procedure to the equation of motion established in the acceleration stage Stage 1 (S211).
In the third procedure, the angular velocities ω₂′ and ω₃and deceleration time Δt₂of the motor 30 in the deceleration stage Stage 3 are first measured. Based on the measured angular velocities ω₂′ and ω₃and deceleration time Δt₂, an angular acceleration α₃in the deceleration stage Stage 3 is then calculated. Thereafter, the estimated frictional torque, value T_f ¹is calculated by applying the calculated angular acceleration α₃and the estimated initial inertial moment value I⁰calculated in the second procedure to the equation of motion established in the deceleration stage. Using the calculated estimated frictional torque value T_f ¹, the calculated frictional torque is updated.
In the fourth procedure, the estimated inertial moment value I¹is calculated by applying, to the equation of motion established in the acceleration stage Stage 1, the angular acceleration aL and motor torque T_d1in the acceleration stage Stage 1 calculated in the second procedure, while applying the estimated frictional torque value T_f ¹updated in the third procedure to the item “T_f” in the equation of motion established in the acceleration stage. Using the calculated estimated inertial moment value I¹, the calculated inertial moment is updated.
In a fifth procedure, the updated frictional torque, which corresponds to the estimated frictional torque value T_f ¹, is again updated by a next estimated frictional torque value T_f ². The next estimated frictional torque value T_f ²is calculated by applying the estimated inertial moment value I¹updated in the fourth procedure to the equation of motion established in the deceleration stage Stage 3. In a sixth procedure, the updated inertial moment, which corresponds to the estimated inertial moment value I¹, is again updated by a next estimated inertial moment value I². The next estimated inertial moment value I²is calculated by applying the estimated frictional torque value T_f ²updated in the fifth procedure to the equation of motion established in the acceleration stage Stage 1.
In the fifth procedure, the estimated frictional torque value T_f ²is calculated by applying, to the equation of motion established in the deceleration stage, the angular acceleration α₃in the acceleration stage Stage 1 calculated in the third procedure and the estimated inertial moment value I²updated in the fourth procedure. Using the calculated estimated frictional torque value T_f ², the updated frictional torque is again updated.
In the sixth procedure, the estimated inertial moment value I²is calculated by applying, to the equation of motion established in the acceleration stage Stage 1, the angular acceleration α₁and motor torque T_d1in the acceleration stage Stage 1 calculated in the second procedure, while applying the estimated frictional torque value T_f ²updated in the fifth procedure to the item “T_f” in the equation of motion established in the acceleration stage. Using the calculated estimated inertial moment value I², the updated inertial moment is again updated.
Following the sixth procedure, the fifth and sixth procedures are repetitively carried out to iteratively calculate an estimated inertial moment value I^(k)and an estimated frictional moment value T_f ^(k).
That is, the estimated frictional moment value T_f ^(k)can be calculated in accordance with the above described iterative calculation, which is expressed as follows: $\begin{matrix} Iteration 0: I_{total} = \frac{T_{d1} - T_{f}}{α_{1}} - \frac{ɛ}{α_{1}} & [Expression 3] \\ Iteration 1: I_{total} = \frac{(α_{1} + α_{3}) T_{d1} - α_{3} T_{f}}{α_{1}^{2}} - \frac{ɛ}{α_{1}} \times (\frac{α_{3}}{α_{1}}) \\ Iteration 2: I_{total} = \frac{(α_{1}^{2} + α_{1} α_{3} + α_{3}^{2}) T_{d1} - α_{3}^{2} T_{f}}{α_{1}^{3}} - \frac{ɛ}{α_{1}} \times {(\frac{α_{3}}{α_{1}})}^{2} \\ Iteration 3: I_{total} = \frac{(α_{1}^{3} + α_{1}^{2} α_{3} + α_{1} α_{3}^{2} + α_{3}^{3}) T_{d1} - α_{3}^{2} T_{f}}{α_{1}^{4}} - \frac{ɛ}{α_{1}} \times {(\frac{α_{3}}{α_{1}})}^{3} \\ Iteration 4: I_{total} = \frac{(α_{1}^{4} + α_{1}^{3} α_{3} + α_{1}^{2} α_{3}^{2} + α_{1} α_{3}^{2} + α_{3}^{4}) T_{d1} - α_{3}^{4} T_{f}}{α_{1}^{5}} - \frac{ɛ}{α_{1}} \times {(\frac{α_{3}}{α_{1}})}^{4} \end{matrix}$
In accordance with the clothes amount sensing method according to the second embodiment of the present invention, the iterative calculation is completed when the difference between the iteratively calculated successive estimated inertial moment values, that is, a final estimated inertial moment value I^(k+1)calculated just before the completion of the iterative calculation and an inertial moment I^(k)updated just before the calculation of the final estimated inertial moment value I^(k+1), represented by “|I^(k)−I^(k+1)|” is not more than a predetermined value A (S212). In this case, one of the final estimated inertial moment value I^(k+1)and the inertial moment I^(k)is selected. Based on the selected inertial moment, the amount of the clothes m is determined (S213).
FIG. 9 is a graph depicting a variation in clothes amount sensing error depending on a frictional torque measuring error generated in the clothes amount sensing method according to the second embodiment of the present invention.
In accordance with the clothes amount sensing method according to the second embodiment of the present invention, it is possible to achieve a more accurate clothes amount calculation as an iterative calculation is repetitively carried out. Referring to FIG. 9, it can be seen that even where the error ε for the frictional torque T_fis set to a large value, for example, a value corresponding to 50% of the estimated initial frictional torque value T_f ⁰, convergence of an inertial moment I to a true value is achieved after the iterative calculation is repeated five times or more.
FIG. 10 is a graph depicting a variation in clothes amount sensing error depending on an acceleration in the clothes amount sensing method according to the second embodiment of the present invention.
In accordance with the clothes amount sensing method according to the second embodiment of the present invention, the convergence of the inertial moment to a true value is more rapidly achieved in the case of a higher ratio of the angular acceleration α₁in the acceleration stage Stage 1 to the angular acceleration α₃in the deceleration stage Stage 3, as shown in FIG. 10. Accordingly, it is desirable that the angular acceleration α₁in the acceleration stage Stage 1 be higher than the angular acceleration α₃in the deceleration stage Stage 3.
FIG. 11 is a graph depicting a variation in clothes amount sensing error depending on an acceleration measuring error generated in the clothes amount sensing method according to the second embodiment of the present invention.
Referring to FIG. 11, it can be seen that there is little influence on the convergence of the inertial moment to a true value in accordance with the iterative calculation in the clothes amount sensing method according to the second embodiment of the present invention by other measuring errors (for example, the acceleration measuring error in FIG. 11).
FIG. 12 is a flow chart illustrating a clothes amount sensing method according to a third embodiment of the present invention. FIG. 13 is a graph depicting an operating condition of a motor adapted for sensing of the clothes amount in accordance with the third embodiment of the present invention.
In accordance with the clothes amount sensing method according to the third embodiment of the present invention, as shown in FIGS. 12 and 13, the control unit 49 first starts up the motor 30, and then accelerates the motor 30 until the RPM of the motor 30 reaches a predetermined RPM rpm₁, for example, 130 rpm (acceleration stage Stage 1)(S301 and S302).
When the RPM of the motor 30 reaches the predetermined RPM rpm₁, the control unit 49 maintains the motor 30 at the predetermined RPM rpm₀for a predetermined time At (constant-speed stage Stage 2) (S303).
After maintaining the motor 30 at the predetermined RPM rpm₀for the predetermined time Δt, the control unit 49 turns off the motor 30, and controls the braking unit 50 to perform a braking operation involving generation of electricity. As the motor 30 is braked in accordance with the braking operation, it is decelerated (deceleration stage Stage 3) (S304 and S305).
In accordance with the clothes amount sensing method according to the third embodiment of the present invention, the inertial moment I_Lof the clothes m is calculated, taking into consideration the fact that the drive torque T_dand frictional torque T_fin the constant-speed stage Stage 2 are equal, while utilizing the principle of the conservation of energy established in the deceleration stage Stage 3.
That is, conditions established in the constant-speed stage Stage 2 can be expressed as follows:
T_f=T_d=k₁PWM* [Expression 4]
where, “k₁” represents a proportional constant in the constant-speed stage, and “PWM*” represents a PWM duty value in the constant-speed stage.
Also, conditions established in the deceleration stage Stage 3 can be expressed as follows: $\begin{matrix} \frac{1}{2} (I_{D} + I_{L}) ω_{1}^{2} = T_{f} s_{1} + \int_{s_{1}} k_{2} \cdot ω ⅆ s & [Expression 5] \end{matrix}$
where, “I_D” represents the inertial moment of the wash tub 20, “ω₁” represents an angular velocity in the constant-speed stage, “s₁” represents a total rotated angle in the deceleration stage, “∫_s ₁k₂·ωds ” represents electricity-generating braking energy in the deceleration stage, “k₂” represents a proportional constant of electricity-generating braking energy, “ω” represents an angular velocity in the deceleration stage, and “s” represents a rotated angle in the deceleration stage.
Expressions 4 and 5 can be arranged with respect to the inertial moment I_Lof the clothes m, as expressed in the following Expression: $\begin{matrix} I_{L} = \frac{1}{ω_{1}^{2}} (k_{1} \cdot {PWM}^{*} \cdot s_{1} + k_{2} \sum_{s_{1}} ω \cdot Δ s) - I_{D} & [Expression 6] \end{matrix}$
Thus, the control unit 49 can calculate the inertial moment I_Lof the clothes m, based on the angular velocity ω₁and PWM duty value PWM* in the constant-speed stage Stage 2, the rotated angle s₁in the deceleration stage Stage 3, the electricity-generating braking energy $k$ $_{2} \sum_{s_{1}} ω \cdot Δ s$
in the deceleration stage Stage 3, and the previously calculated inertial moment I_Dof the wash tub 20.
In accordance with the clothes amount sensing method according to the third embodiment of the present invention, the following Expression can be established by taking, as a value approximate to a true value of the electricity-generating braking energy, an intermediate value between maximum and minimum values of braking torques caused by the electricity-generating braking operation, and applying the taken value to Expression 6. $\begin{matrix} I_{L} = \frac{1}{ω_{1}^{2}} (k_{1} \cdot {PWM}^{*} \cdot s_{1} + k_{2} \frac{ω}{2} s_{1}) - I_{D} & [Expression 7] \end{matrix}$
Thus, the control unit 49 can simply calculate the inertial moment I_Lof the clothes m, based on the angular velocity ω₁and PWM duty value PWM* in the constant-speed stage Stage 2, the rotated angle s₁in the deceleration stage Stage 3.
That is, the control unit 49 applies, to Expression 7, the angular velocity ω₁, PWM duty value PWM*, and rotated angle s₁measured by the sensor 57, which may be a Hall sensor or motor encoder, thereby calculating the inertial moment I_Lof the clothes m (S306 and S307).
Thereafter, the control unit 49 determines the amount of the clothes m, based on the calculated inertial moment I_Lof the clothes m (S308).
That is, the inertial moment I_Lof the clothes m performing a rotating movement is equivalent to the mass of the clothes m, so that it is used as an index of clothes amount.
FIG. 14 is a flow chart illustrating a clothes amount sensing method according to a fourth embodiment of the present invention. FIG. 15 is a graph depicting an operating condition of a motor adapted for sensing of the clothes amount in accordance with the fourth embodiment of the present invention.
In accordance with the clothes amount sensing method according to the fourth embodiment of the present invention, as shown in FIGS. 14 and 15, the motor 30 is first started up, and then accelerated until the RPM thereof reaches a predetermined RPM rpm′, for example, 130 rpm (acceleration stage Stage 1) (S401).
When the RPM of the motor 30 reaches the predetermined RPM rpm′, the motor 30 is maintained at the predetermined RPM rpm′ (constant-speed stage Stage 2) (S402).
When the motor 30 is turned off after being maintained at the predetermined RPM rpm′ for a predetermined time Δt, it is decelerated in accordance with a surplus rotation thereof (Stage 3) (S403 and S404).
In accordance with the clothes amount sensing method according to the fourth embodiment of the present invention, the amount of the clothes m is determined, based on an equation of energy established in a duration from the acceleration start point of the motor 30 to the constant-speed end point of the motor 30, and an equation of energy established in a duration from the turn-off point of the motor 30 to the rotation stop point of the motor 30. In this case, it is possible to minimize clothes amount determination errors caused by a variation in friction depending on the kind of a washing machine, for which the clothes amount determination is carried out.
The input energy in the washing machine corresponds to the sum of PWM duty values in the duration from the acceleration start point to of the motor 30 to the constant-speed end point t₁of the motor 30. The kinetic energy of the wash tub 20 and clothes m corresponds to “αIω₀ ²”. In the acceleration and constant-speed stages of the motor 30, a frictional torque is generated which is proportional to an angular velocity of the wash tub 20 in a direction opposite to the rotation direction of the wash tub 20. Accordingly, the following Expression is established: $\begin{matrix} PWM sum = A \int_{0}^{s^{1}} PWM ⅆ s = α {Iw}_{0}^{2} + β T_{n} s_{1} & [Expression 8] \end{matrix}$
where, “PWMsum” represents the sum of PWM duty values in the duration from the acceleration start point t₀of the motor 30 to the constant-speed end point t₁of the motor 30, “s₁” represents the sum of rotated angles in the duration from the acceleration start point t₀of the motor 30 to the constant-speed speed end point t₁of the motor 30, and “I” represents the inertial moment of the wash tub 20 and clothes m, that is, the sum of the inertial moment I_Dof the wash tub 20, which can be experimentally calculated, and the inertial moment I_C, of the clothes m to be determined (I=I_D+I_C), “ω₀” represents a mean angular velocity in a duration in which the motor 30 performs a surplus rotation by one turn after a turn-off thereof, that is, a duration from t₁to t₁′, “T_n” represents a frictional force generated during the rotation of the wash tub 20, and “A”, “α” and “β” represent proportional constants.
Meanwhile, in a duration from the turn-off point t₁of the motor 30 to the rotation stop point t₂of the motor 30, a frictional torque is generated which is proportional to the angular velocity of the wash tub in a direction opposite to the rotation direction of the wash tub 20. Accordingly, the following Expression is established: $\begin{matrix} \frac{{Iw}_{0}^{2}}{2} = γ \int_{s_{1}}^{s_{1} + s_{2}} w ⅆ s + δ T_{n} s_{2} = γ w sum + δ T_{n} s_{2} & [Expression 9] \end{matrix}$
where, “ωsum” represents the sum of angular velocities of the motor 30 in the duration from the turn-off point t₁of the motor 30 to the rotation stop point t₂of the motor 30, “s₂” represents the sum of rotated angles in the duration from the turn-off point t₁of the motor 30 to the rotation stop point t₂of the motor 30, and “γ” and “δ” represent proportional constants. “ωsum” can be calculated by accumulating angular velocities ω measured when respective PWM signals are generated in the duration from the turn-off point t₁of the motor 30 to the rotation stop point t₂of the motor 30.
Expressions 8 and 9 can be arranged with respect to the inertial moment I of the wash tub 20 and clothes m after eliminating the frictional force T_ntherefrom, as expressed in the following Expression: $\begin{matrix} I = \frac{δ PWMsum + γβ \frac{s_{1}}{s_{2}} w sum}{(δ α + \frac{1}{2} β \frac{s_{1}}{s_{2}}) w_{0}^{2}} = \frac{PWMsum + c \frac{s_{1}}{s_{2}} wsum}{(a + b \frac{s_{1}}{s_{2}}) w_{0}^{2}} & [Expression 10] \end{matrix}$
where, “a”, “b”, and “c” are proportional constants caused by the arrangement of the proportional constants α, β, γ, and δ.
In accordance with the clothes amount sensing method according to the fourth embodiment of the present invention, the inertial moment I of the wash tub 20 and clothes m is calculated by measuring the PWM duty value sum PWMsum and rotated angle sum s₁in the duration from the acceleration start point t₀of the motor 30 to the turn-off point t₁of the motor 30, measuring the mean angular velocity ω₀in the duration in which the motor 30 performs a surplus rotation by one turn after a turn-off thereof, measuring the angular velocity sum ωsum and the rotated angle sum s₂in the duration from the turn-off off point t₁of the motor 30 to the rotation stop point t₂of the motor 30, and applying the measured values to Expression 10 (S405 and S406).
Thereafter, the inertial moment I_Cof the clothes m is calculated by deducting the previously-calculated and stored inertial moment I_Dof the wash tub 20 from the calculated inertial moment I of the wash tub 20 and clothes m (S407). Based on the calculated inertial moment I_Cof the clothes m, the clothes amount is determined (S408).
That is, the inertial moment I_Cof the clothes m performing a rotating movement is equivalent to the mass of the clothes m, so that it is used as an index of clothes amount.
As apparent from the above description, in accordance with the clothes amount sensing method according to the present invention, the amount of clothes to be washed may be sensed by calculating the clothes amount sensed in the acceleration stage and the clothes amount sensed in the deceleration stage, calculating an absolute value of the difference between the clothes amounts in the acceleration and deceleration stages, comparing the calculated absolute value with a predetermined error value, selecting a larger one of the clothes amoiunts in the acceleration and deceleration stages when the absolute value is not more than the predetermined error value, and determining the selected clothes amount as a target clothes amount to be sensed. In this case, the sensing of the clothes amount is achieved by carrying out, one time, a clothes amount sensing process using the load values sensed in the acceleration and deceleration stages. Accordingly, there are advantages capable of reducing clothes amount sensing errors caused by frictional forces while achieving an enhancement in accuracy and reliability.
When it is determined, based on the result of the comparison, that the absolute value is more than the predetermined error value, the acceleration, constant-speed, and deceleration stages are repetitively carried out until the absolute value is more than the predetermined error value. Accordingly, it is possible to accurately sense the amount of the clothes, to be washed, within an allowable error range.
The clothes amount sensed in the acceleration stage corresponds to the inertial moment of the clothes in the acceleration stage, whereas the clothes amount sensed in the deceleration stage corresponds to the inertial moment of the clothes in the deceleration stage. Accordingly, it is possible to accurately and rapidly calculate the clothes amount in the acceleration stage and the clothes amount in the deceleration stage by measuring respective angular velocities, respective PWM duty values, and respective inertial moments of the rotating body in the acceleration and deceleration stages, and acceleration and deceleration times, in accordance with the clothes amount sensing method of the present invention.
In accordance with the clothes amount sensing method of the present invention, the amount of clothes to be washed may also be sensed by iteratively calculating an estimated inertial moment value of the wash tub and clothes and an estimated frictional torque value, by use of equations of motion respectively established in the acceleration, constant-speed, and deceleration stages, while taking an error into consideration, comparing, with a predetermined value, an absolute value of the difference between two successive estimated inertial moment values calculated in accordance with the iterative calculation, completing the iterative calculation when the absolute value is not more than the predetermined value, selecting the finally-calculated estimated inertial moment value or the estimated inertial moment value just preceding the final estimated inertial moment value, and determining the selected value as a target clothes amount to be sensed. In this case, the sensing of the clothes amount is achieved by carrying out a clothes amount sensing process only one time. Accordingly, there are advantages capable of reducing clothes amount sensing errors caused by an inaccurate frictional force measurement while achieving an enhancement in accuracy and reliability.
In accordance with the clothes amount sensing method of the present invention, an initial stage may also be carried out, prior to the acceleration stage, to accelerate the motor to a predetermined RPM lower than an RPM set for the acceleration stage, after the start-up thereof, and then to maintain the motor at the predetermined RPM for a predetermined time. In this case, it is possible to eliminate clothes amount sensing errors caused by a static frictional force generated upon the start-up of the motor. Accordingly, there is an advantage of more accurately sensing the amount of the clothes to be washed.
In accordance with the clothes amount sensing method of the present invention, the inertial moment of the clothes may also be calculated, taking into consideration the fact that the drive torque and frictional torque in the constant-speed stage are equal, while utilizing the principle of the conservation of energy in the deceleration stage, in which a braking operation involving generation of electricity is carried out. In this case, accordingly, there are advantages capable of reducing clothes amount sensing errors caused by frictional forces while achieving an enhancement in accuracy and reliability.
In accordance with the clothes amount sensing method of the present invention, the amount of the clothes may also be determined, based on energy acting in a duration from the acceleration start point of the motor to the constant-speed end point of the motor, and energy acting in a duration from the turn-off point of the motor to the rotation stop point of the motor. In this case, it is possible to minimize clothes amount determination errors caused by a variation in friction depending on the kind of a washing machine, for which the clothes amount determination is carried out.
Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. A method for sensing an amount of clothes contained in a wash tub included in a washing machine, comprising:

an acceleration step for accelerating, to a predetermined RPM, a motor adapted to rotate the wash tub;

a constant-speed step for maintaining the motor at the predetermined RPM when an RPM of the motor reaches the predetermined RPM in accordance with the acceleration step;

a deceleration step for turning off the motor to decelerate the motor, following the constant-speed step; and

a clothes amount determination step for determining the amount of the clothes by use of equations of motion respectively established in the acceleration, constant-speed, and deceleration steps.

2. The method according to claim 1, further comprising:

an initial step for starting up the motor, accelerating the motor to a predetermined RPM lower than the predetermined RPM of the acceleration step, and maintaining the motor at the lower predetermined RPM,

where the acceleration step is carried out after the initial step.

3. The method according to claim 1, wherein the clothes amount determination step comprises:

a clothes amount calculating step for calculating a clothes amount sensed in the acceleration step and a clothes amount sensed in the deceleration step;

a comparison step for calculating an absolute value of a difference between the calculated clothes amounts in the acceleration and deceleration steps, and comparing the calculated absolute value with a predetermined error value; and

a selection step for, if it is determined at the comparison step that the absolute value is not more than the predetermined error value, selecting a larger one of the clothes amounts respectively sensed in the acceleration and deceleration steps.

4. The method according to claim 3, wherein the clothes amount in the acceleration step is calculated, based on an inertial moment of the clothes generated in the acceleration step.

5. The method according to claim 3, wherein the clothes amount in the deceleration step is calculated, based on an inertial moment of the clothes generated in the deceleration step.

6. The method according to claim 3, further comprising the step of:

if it is determined at the comparison step that the absolute value is more than the predetermined error value, repeating the acceleration step, constant-speed step, deceleration step, and clothes amount calculation step.

7. The method according to claim 1, wherein the clothes amount determination step comprises:

a calculation step for iteratively calculating an estimated value of an inertial moment of the wash tub and clothes, and an estimated value of a frictional torque generated during the rotation of the wash tub, by use of the equations of motion respectively established in the acceleration, constant-speed, and deceleration steps;

a comparison step for comparing, with a predetermined value, an absolute value of a difference between two successive estimated inertial moment values calculated in accordance with the iterative calculation at the calculation step; and

a selection step for, if it is determined at the comparison step that the absolute value is not more than the predetermined value, completing the iterative calculation, selecting a finally-calculated one of the estimated inertial moment values or the estimated inertial moment value just preceding the final estimated inertial moment value, and determining the selected value as a target clothes amount to be sensed.

8. The method according to claim 7, wherein the calculation step comprises the steps of:

(A) calculating an estimated value of an initial frictional torque corresponding to a frictional torque generated in the constant-speed step;

(B) applying, to the equation of motion established in the acceleration step, a value obtained after adding a predetermined error value to the estimated initial frictional torque value calculated at the step (A), thereby calculating an estimated value of an initial inertial moment of the wash tub and clothes;

(C) applying the estimated initial inertial moment value calculated at the step (B) to the equation of motion established in the deceleration step, thereby calculating an estimated frictional torque value, and updating the estimated initial frictional torque value calculated at the step (A) with the calculated estimated frictional torque value;

(D) applying the estimated frictional torque value updated at the step (C) to the equation of motion established in the acceleration step, thereby calculating an estimated inertial moment value, and updating the estimated initial inertial moment value calculated at the step (B) with the calculated estimated inertial moment value;

(E) applying the estimated inertial moment value updated at the step (D) to the equation of motion established in the deceleration step, thereby calculating a next estimated frictional torque value, and updating the updated estimated frictional torque value with the next estimated frictional torque value;

(F) applying the estimated frictional torque value updated at the step (E) to the equation of motion established in the acceleration step, thereby calculating a next estimated inertial moment value, and updating the updated estimated inertial moment value with the next estimated inertial moment value; and

(G) repeating the steps (E) and (F), following the step (F).

9. The method according to claim 8, wherein the step (A) comprises the steps of:

measuring a pulse width modulation (PWM) duty value of the motor in the constant-speed step; and

calculating the estimated initial frictional torque value, based on the measured PWM duty value.

10. The method according to claim 8, wherein the step (B) comprises the steps of:

measuring an angular velocity of the motor and an acceleration time in the acceleration step;

calculating an angular acceleration, based on the measured angular velocity and acceleration time;

measuring a pulse width modulation (PWM) duty value of the motor in the acceleration step;

calculating a motor torque in the acceleration step, based on the measured PWM duty value; and

applying the calculated angular acceleration and motor torque to the equation of motion established in the acceleration step while applying, to a frictional torque item of the equation of motion established in the acceleration step, a value obtained after adding a predetermined error value to the estimated initial frictional torque value, thereby calculating the estimated initial inertial moment value.

11. The method according to claim 8, wherein the step (C) comprises the steps of:

measuring an angular velocity of the motor and a deceleration time in the deceleration step;

calculating an angular acceleration, based on the measured angular velocity and deceleration time;

applying, to the equation of motion established in the deceleration step, the calculated angular acceleration and the estimated initial inertial moment value calculated at the step (B), thereby calculating an estimated frictional torque value; and

updating the estimated initial frictional torque value with the calculated estimated frictional torque value.

12. A method for sensing an amount of clothes contained in a wash tub included in a washing machine, comprising:

a deceleration step for turning off the motor while braking the motor in an electricity generating mode to decelerate the motor, following the constant-speed step; and

a clothes amount determination step for determining the amount of the clothes by use of the principle of the conservation of energy established in the step of braking the motor in the electricity generating mode.

13. The method according to claim 12, wherein the clothes amount determination step comprises:

a measurement step for measuring a pulse width modulation (PWM) duty value and angular velocity of the motor in the constant-speed step, and measuring a rotated angle of the motor in the deceleration step;

a calculation step for calculating an inertial moment of the clothes by use of the values measured at the measurement step, an equation of energy established in the constant-speed step, and an equation of energy established in the deceleration step; and

selecting the inertial moment of the clothes calculated at the calculation step, as an index of clothes amount.

14. The method according to claim 13, wherein at the calculation step, the inertial moment of the clothes is calculated, taking into consideration a fact that drive and frictional torques in the constant-speed step are equal, while utilizing the principle of the conservation of energy established in the deceleration step.

15. The method according to claim 14, wherein at the calculation step, the inertial moment of the clothes is calculated, using the following Expression 1:

\begin{matrix} I_{L} = \frac{1}{ω_{1}^{2}} (k_{1} \cdot {PWM}^{*} \cdot s_{1} + k_{2} \sum_{s_{1}} ω \cdot Δ s) - I_{D} & [Expression 1] \end{matrix}

where, “I_L” represents the inertial moment of the clothes, “ω₁” represents the angular velocity of the motor in the constant-speed step, “k₁” represents a proportional constant in the constant-speed step, “PWM*” represents the PWM duty value of the motor in the constant-speed step, “s₁” represents a total rotated angle in the deceleration step, “k₂” represents a proportional constant of electricity-generating braking energy, “ω” represents an angular velocity of the motor in the deceleration step, “s” represents a rotated angle of the motor in the deceleration step, and “I_D” represents an inertial moment of the wash tub.

16. The method according to claim 13, wherein at the calculation step, the inertial moment of the clothes is calculated, taking into consideration a fact that drive and frictional torques in the constant-speed step are equal, while utilizing the principle of the conservation of energy established in the deceleration step, and taking, as a value approximate to a true value of electricity-generating braking energy, an intermediate value between maximum and minimum values of braking torques caused by the electricity-generating braking operation.

17. The method according to claim 16, wherein at the calculation step, the inertial moment of the clothes is calculated, using the following Expression 2:

\begin{matrix} I_{L} = \frac{1}{ω_{1}^{2}} (k_{1} \cdot {PWM}^{*} \cdot s_{1} + k_{2} \frac{ω_{1}}{2} s_{1}) - I_{D} & [Expression 2] \end{matrix}

where, “I_L” represents the inertial moment of the clothes, “ω” represents the angular velocity of the motor in the constant-speed step, “k₁” represents a proportional constant in the constant-speed step, “PWM*” represents the PWM duty value of the motor in the constant-speed step, “s₁” represents a total rotated angle in the deceleration step, “k₂” represents a proportional constant of electricity-generating braking energy, and “I_D” represents an inertial moment of the wash tub.

18. A method for sensing an amount of clothes contained in a wash tub included in a washing machine, comprising:

a constant-speed step for maintaining the motor at the predetermined RPM for a predetermined time when an RPM of the motor reaches the predetermined RPM in accordance with the acceleration step;

a deceleration step for, following the constant-speed step, turning off the motor to decelerate the motor, Thereby stopping the motor; and

a clothes amount determination step for determining the amount of the clothes by use of an equation of energy established in a duration from an acceleration start point of the motor to a constant-speed end point of the motor, and an equation of energy established in a duration from a turn-off point of the motor to a rotation stop point of the motor.

19. The method according to claim 18, wherein the clothes amount determination step comprises:

a measurement step for measuring a sum of pulse width modulation (PWM) duty values and a sum of rotated angles in the duration from the acceleration start point of the motor to the constant-speed end point of the motor, measuring a mean angular velocity in a duration in which the motor performs a surplus rotation by one turn after the turn-off thereof, and measuring a sum of angular velocities and a sum of rotated angles in the duration from the turn-off point of the motor to the rotation stop point of the motor;

a calculation step for calculating an inertial moment of the wash tub and clothes, by use of the values measured at the measurement step and the equations of energy; and

a selection step for selecting the inertial moment of the wash tub and clothes calculated at the calculation step, as a target clothes amount to be sensed.

20. The method according to claim 19, wherein at the calculation step, the inertial moment of the clothes is calculated, using the following Expression 3:

\begin{matrix} I = \frac{PWMsum + c \frac{s_{1}}{s_{2}} wsum}{(a + b \frac{s_{1}}{s_{2}}) w_{0}^{2}} & [Expression 3] \end{matrix}

where, “I” represents the inertial moment of the wash tub and clothes, “PWMsum” represents the PWM duty value sum in the duration from the acceleration start point of the motor to the constant-speed end point of the motor, “s₁” represents the rotated angle sum in the duration from the acceleration start point of the motor to the constant-speed end point of the motor, “s₂” represents a sum of surplus rotated angles in the duration from the turn-off point of the motor to the rotation stop point of the motor, “ωsum” represents a sum of angular velocities of the motor in the duration from the turn-off point of the motor to the rotation stop point of the motor, “ω₀” represents a mean angular velocity in a duration in which the motor performs a surplus rotation by one turn after the turn-off thereof, and “a”, “b” and “c” represent experimentally determined proportional constants.