Method for operating a washing machine appliance

Abstract

A method for operating a washing machine appliance is provided. The method includes determining a power delivered to a motor of the washing machine appliance while an angular velocity of a drum of the washing machine appliance is increasing. The method also includes establishing a slope of the power delivered to the motor. The slope of the power delivered to the motor is monitored in order to establish if the slope of the power delivered to the motor exceeds a threshold value.

What is claimed is: 
     
         1 . A method for operating a washing machine appliance, the washing machine having a drum rotatably mounted within a tub, the washing machine appliance also having a motor configured for selectively rotating the drum within the tub, the method comprising:
 rotating the drum at a first angular velocity with the motor;   determining a power delivered to the motor at said step of rotating the drum at the first angular velocity;   rotating the drum at a second angular velocity with the motor;   determining the power delivered to the motor at said step of rotating the drum at the second angular velocity;   calculating a change in the power delivered to the motor over time based at least in part on the power delivered to the motor at said step of rotating the drum at the first angular velocity and the power delivered to the motor at said step of rotating the drum at the second angular velocity; and   establishing whether the change in the power delivered to the motor over time exceeds a threshold value.   
     
     
         2 . The method of  claim 1 , wherein the first angular velocity is less than the second angular velocity. 
     
     
         3 . The method of  claim 2 , wherein the first angular velocity is greater than about one hundred radians per second. 
     
     
         4 . The method of  claim 1 , wherein said step of determining the power delivered to the motor at said step of rotating the drum at the first angular velocity comprises determining an average power delivered to the motor at said step of rotating the drum at the first angular velocity, and said step of determining the power delivered to the motor at said step of rotating the drum at the second angular velocity comprises determining an average power delivered to the motor at said step of rotating the drum at the second angular velocity. 
     
     
         5 . The method of  claim 1 , further comprising monitoring the power delivered to the motor at said step of rotating the drum at the first angular velocity and the power delivered to the motor at said step of rotating the drum at the second angular velocity in order to determine whether the power delivered to the motor exceeds a threshold power. 
     
     
         6 . The method of  claim 5 , wherein the threshold power is about seven hundred watts. 
     
     
         7 . The method of  claim 5 , further comprising activating a fault mode of the washing machine appliance if the change in the power delivered to the motor over time exceeds the threshold value or if the power delivered to the motor exceeds the threshold power. 
     
     
         8 . The method of  claim 1 , further comprising repeating said steps of rotating the drum at the first angular velocity, determining the power delivered to the motor at said step of rotating the drum at the first angular velocity, rotating the drum at the second angular velocity, determining the power delivered to the motor at said step of rotating the drum at the second angular velocity, calculating the change in the power delivered to the motor over time and establishing whether the change in the power delivered to the motor over time exceeds the threshold value while the motor is accelerating the drum to a target speed. 
     
     
         9 . A method for operating a washing machine appliance, the washing machine having a drum rotatably mounted within a tub, the washing machine appliance also having a motor configured for selectively rotating the drum within the tub, the method comprising:
 spinning the drum with the motor;   increasing an angular velocity of the drum at a first acceleration rate during said step of spinning;   increasing the angular velocity of the drum at a second acceleration rate after said step of increasing the angular velocity of the drum at the first acceleration rate;   determining an average power delivered to the motor during said step of increasing the angular velocity of the drum at the second acceleration rate;   establishing a slope of the average power delivered to the motor; and   monitoring the slope of the average power delivered to the motor in order to establish if the slope of the average power delivered to the motor exceeds a threshold value.   
     
     
         10 . The method of  claim 9 , wherein the first acceleration rate is greater than the second acceleration rate. 
     
     
         11 . The method of  claim 10 , wherein the first acceleration rate is about one radian per second squared. 
     
     
         12 . The method of  claim 10 , wherein the second acceleration rate is about two-tenths of a radian per second squared. 
     
     
         13 . The method of  claim 9 , wherein the average power delivered to the motor comprises a rolling average power delivered to the motor during a window, the window being about eight seconds. 
     
     
         14 . The method of  claim 9 , wherein said step of increasing the angular velocity of the drum at the first acceleration rate comprises increasing the angular velocity of the drum at the first acceleration rate until the angular velocity of the drum exceeds a threshold velocity. 
     
     
         15 . The method of  claim 14 , wherein the threshold velocity is greater than about ninety radians per second. 
     
     
         16 . The method of  claim 9 , further comprising monitoring the average power delivered to the motor during said step of monitoring the slope of the average power delivered to the motor in order to determine whether the average power delivered to the motor exceeds a threshold power. 
     
     
         17 . The method of  claim 16 , wherein the threshold power is about seven hundred watts. 
     
     
         18 . The method of  claim 16 , further comprising activating a fault mode of the washing machine appliance if the slope of the average power delivered to the motor exceeds the threshold value at said step of monitoring the slope of the average power delivered to the motor or if the average power delivered to the motor exceeds the threshold power at said step of monitoring the average power delivered to the motor. 
     
     
         19 . A washing machine appliance, comprising:
 a cabinet;   a tub positioned within the cabinet;   a drum rotatably mounted within the tub, the drum defining a wash chamber for receipt of articles for washing;   a motor in mechanical communication with the drum, the motor configured for selectively rotating the drum within the tub; and   a controller in operative communication with the motor, the controller configured for
 rotating the drum at a first angular velocity with the motor; 
 determining a power delivered to the motor at said step of rotating the drum at the first angular velocity; 
 rotating the drum at a second angular velocity with the motor; 
 determining the power delivered to the motor at said step of rotating the drum at the second angular velocity; 
 calculating a change in the power delivered to the motor over time based at least in part on the power delivered to the motor at said step of rotating the drum at the first angular velocity and the power delivered to the motor at said step of rotating the drum at the second angular velocity; and 
 establishing whether the change in the power delivered to the motor over time exceeds a threshold value. 
   
     
     
         20 . The washing machine appliance of  claim 19 , wherein the controller is further configured for repeating said steps of rotating the drum at the first angular velocity, determining the power delivered to the motor at said step of rotating the drum at the first angular velocity, rotating the drum at the second angular velocity, determining the power delivered to the motor at said step of rotating the drum at the second angular velocity, calculating the change in the power delivered to the motor over time and establishing whether the change in the power delivered to the motor over time exceeds the threshold value while the motor is accelerating the drum to a target speed.