Washing machine control method

• US 20040144135A1
• Filed: 12/09/2003
• Published: 07/29/2004
• Est. Priority Date: 12/10/2002
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Oh, Soo Young, Kim, Jin Woong, Woo, Kyung Chul, Lee, Tae Hee, Seo, Hyun Seok, Kim, Joon Woo
• Granted Patent: US 7,299,515 B2
• Time in Patent Office: Days
• US Class Current: 68/12.16
• CPC Class Codes: D06F 2103/04 Quantity, e.g. weight or variation of weight
• CPC Class Codes: D06F 2105/48 Drum speed
• CPC Class Codes: D06F 34/18 Condition of the laundry, e.g. nature or weight
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers

Abstract

A washing machine control method accurately determines an amount of laundry in the washing machine, while driving a motor coupled to a drum under load, based on a computed average of pulse width modulation values at the time of stopping the drive of a motor and the motor'"'"'s rotational angle as the motor freewheels to a stop, in order to conserve water and reduce the time required for performing a washing step. The method includes steps accelerating a motor to a target rotational speed, by periodically applying to the motor a pulse width modulation (PWM) signal having a predetermined duty ratio; storing in a memory a set of PWM values corresponding to the signal applied in the accelerating step, by sensing a rotational speed of the motor; outputting a PWM signal having a duty ratio of zero, after the sensed motor speed reaches the target rotational speed, to allow the motor to freewheel to a stop; computing an average of the stored PWM values; measuring a rotational angle of the motor as the motor freewheels to a stop; calculating a laundry amount estimation value based on the average of the stored PWM values and the motor'"'"'s rotational angle; and determining a laundry amount by comparing the calculated laundry amount estimation value to a set of laundry amount reference values stored in a lookup table. The laundry amount estimation value equals w₁PWM_ave+w₂θ_motor, where PWM_ave is the computed average of the stored PWM values, θ_motor is the measured rotational angle, and w₁, and w₂ are weight constants.

Claims

1. A washing machine control method comprising steps of:

accelerating a motor to a target rotational speed, by periodically applying to the motor a pulse width modulation (PWM) signal having a predetermined duty ratio;

storing in a memory a set of PWM values corresponding to the signal applied in said accelerating step, by sensing a rotational speed of the motor;

outputting a PWM signal having a duty ratio of zero, after the sensed motor speed reaches the target rotational speed, to allow the motor to freewheel to a stop;

computing an average of the stored PWM values;

measuring a rotational angle of the motor as the motor freewheels to a stop; and

calculating a laundry amount estimation value based on the average of the stored PWM values and the motor'"'"'s rotational angle.

2. The method as claimed in claim 1, further comprising a step of determining a laundry amount by comparing the calculated laundry amount estimation value to a set of laundry amount reference values stored in a lookup table.

3. The method as claimed in claim 1, wherein the laundry amount estimation value equals w₁PWM_ave+w₂θ

_motor, where PWM_ave is the computed average of the stored PWM values, θ

_motor is the measured rotational angle, and w₁ and w₂ are weight constants.

4. The method as claimed in claim 3, wherein the weight constants w₁ and w₂ are arbitrarily set to render the laundry amount estimation as a specific value when the motor is driven without a load.

5. The method as claimed in claim 1, wherein the stored PWM values of said average computing step are the PWM values corresponding to the PWM signal applied to the motor, from a motor drive initiating point to the time of discontinuing the drive of the motor.

6. The method as claimed in claim 1, wherein the motor is driven at a constant speed corresponding to the target rotational speed for a predetermined time before said outputting step.

7. The method as claimed in claim 6, wherein the stored PWM values of said average computing step are the PWM values corresponding to the PWM signal applied to the motor, from a motor drive initiating point to the time of discontinuing the drive of the motor.

8. The method as claimed in claim 1, wherein the PWM value is applied to the motor according to a 4 ms cycle.