Method for sensing amount of clothes in washing machine

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.

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: 
 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.    
   
   
       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:  
     
       
         
           
             
               
                 
                   
                     I 
                     L 
                   
                   = 
                   
                     
                       
                         1 
                         
                           ω 
                           1 
                           2 
                         
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             
                               k 
                               1 
                             
                             · 
                             
                               PWM 
                               * 
                             
                             · 
                             
                               s 
                               1 
                             
                           
                           + 
                           
                             
                               k 
                               2 
                             
                             ⁢ 
                             
                               
                                 ∑ 
                                 
                                   s 
                                   1 
                                 
                               
                               ⁢ 
                               
                                 
                                   ω 
                                   · 
                                   Δ 
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 s 
                               
                             
                           
                         
                         ) 
                       
                     
                     - 
                     
                       I 
                       D 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Expression 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ] 
                 
               
             
           
         
       
       where, “I L ” represents the inertial moment of the clothes, “ω 1 ” represents the angular velocity of the motor in the constant-speed step, “k 1 ” represents a proportional constant in the constant-speed step, “PWM*” represents the PWM duty value of the motor in the constant-speed step, “s 1 ” represents a total rotated angle in the deceleration step, “k 2 ” 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:  
     
       
         
           
             
               
                 
                   
                     I 
                     L 
                   
                   = 
                   
                     
                       
                         1 
                         
                           ω 
                           1 
                           2 
                         
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             
                               k 
                               1 
                             
                             · 
                             
                               PWM 
                               * 
                             
                             · 
                             
                               s 
                               1 
                             
                           
                           + 
                           
                             
                               k 
                               2 
                             
                             ⁢ 
                             
                               
                                 ω 
                                 1 
                               
                               2 
                             
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               s 
                               1 
                             
                           
                         
                         ) 
                       
                     
                     - 
                     
                       I 
                       D 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Expression 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   ] 
                 
               
             
           
         
       
       where, “I L ” represents the inertial moment of the clothes, “ω” represents the angular velocity of the motor in the constant-speed step, “k 1 ” represents a proportional constant in the constant-speed step, “PWM*” represents the PWM duty value of the motor in the constant-speed step, “s 1 ” represents a total rotated angle in the deceleration step, “k 2 ” 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: 
 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.    
   
   
       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:  
     
       
         
           
             
               
                 
                   I 
                   = 
                   
                     
                       PWMsum 
                       + 
                       
                         c 
                         ⁢ 
                         
                           
                             s 
                             1 
                           
                           
                             s 
                             2 
                           
                         
                         ⁢ 
                         wsum 
                       
                     
                     
                       
                         ( 
                         
                           a 
                           + 
                           
                             b 
                             ⁢ 
                             
                               
                                 s 
                                 1 
                               
                               
                                 s 
                                 2 
                               
                             
                           
                         
                         ) 
                       
                       ⁢ 
                       
                         w 
                         0 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Expression 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     3 
                   
                   ] 
                 
               
             
           
         
       
       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, “s 1 ” 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, “s 2 ” 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, “ω 0 ” 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.