Cooking appliance and method for initializing controller terms for cooking operations

Abstract

A cooking appliance includes at least one heating element; a temperature sensor; and a controller operably connected with the at least one heating element and the temperature sensor, the controller configured to perform a heating operation, the heating operation including determining that a temperature rate of change at the temperature sensor has reached a threshold rate of change; determining a threshold time point at which the temperature rate of change reaches the threshold rate of change; and determining one or more parameters for a feedback controlled cooking phase according to the determined threshold time point, the one or more parameters comprising at least one initial controller term value.

What is claimed is: 
     
         1 . A cooking appliance comprising:
 at least one heating element to selectively supply heat to a cookware item;   a temperature sensor configured to selectively monitor a temperature of the cookware item; and   a controller operably connected with the at least one heating element and the temperature sensor, the controller configured to perform a heating operation, the heating operation comprising:
 determining a temperature setpoint; 
 directing the at least one heating element based on the determined temperature setpoint over a preheating phase; 
 monitoring a temperature rate of change at the temperature sensor over the preheating phase; 
 determining that the temperature rate of change has reached a threshold rate of change; 
 determining a threshold time point at which the temperature rate of change reaches the threshold rate of change; 
 determining one or more parameters for a feedback controlled cooking phase according to the determined threshold time point, the one or more parameters comprising at least one initial controller term value; and 
 directing the at least one heating element according to the one or more determined parameters for a duration of the feedback controlled cooking phase. 
   
     
     
         2 . The cooking appliance of  claim 1 , wherein monitoring the temperature rate of change at the temperature sensor at regular intervals comprises:
 determining a first temperature rate of change over a first time window, the first time window spanning between an A 1  time point and a B 1  time point;   comparing the first temperature rate of change against the threshold rate of change;   determining a second temperature rate of change over a second time window, the second time window spanning between an A 2  time point and a B 2  time point; and   comparing the second temperature rate of change against the threshold rate of change.   
     
     
         3 . The cooking appliance of  claim 2 , wherein the A 2  time point is determined between the A 1  time point and the B 1  time point, and the B 2  time point is determined after the B 1  time point. 
     
     
         4 . The cooking appliance of  claim 2 , wherein the temperature rate of change is monitored over a fixed-length rolling time window having a predetermined advancement period, the predetermined advancement period being between 0.5 second and 1.5 seconds. 
     
     
         5 . The cooking appliance of  claim 1 , wherein directing the at least one heating element based on the temperature setpoint over the preheating phase comprises:
 determining a power level for the at least one heating element based on the determined temperature setpoint; and   directing the at least one heating element at the determined power level for a duration of the preheating phase.   
     
     
         6 . The cooking appliance of  claim 1 , wherein determining the one or more parameters for a feedback controlled cooking phase comprises:
 retrieving the at least one initial controller term value from a lookup table.   
     
     
         7 . The cooking appliance of  claim 1 , wherein the at least one initial controller term value comprises:
 an initial integral term value; and   an initial derivative term value.   
     
     
         8 . The cooking appliance of  claim 7 , wherein the initial derivative term value is a filtered derivative term value using a filter smoothing factor. 
     
     
         9 . The cooking appliance of  claim 1 , wherein determining the threshold time point comprises:
 calculating a length of time from an initiation of the preheating phase to the threshold time point.   
     
     
         10 . A method of operating a cooking appliance, the cooking appliance comprising at least one heating element and a temperature sensor, the method comprising:
 determining a temperature setpoint;   directing the at least one heating element based on the determined temperature setpoint over a preheating phase;   monitoring a temperature rate of change at the temperature sensor over the preheating phase;   determining that the temperature rate of change has reached a threshold rate of change;   determining a threshold time point at which the temperature rate of change reaches the threshold rate of change;   determining one or more parameters for a feedback controlled cooking phase according to the determined threshold time point, the one or more parameters comprising at least one initial controller term value; and   directing the at least one heating element according to the one or more determined parameters for a duration of the feedback controlled cooking phase.   
     
     
         11 . The method of  claim 10 , wherein monitoring the temperature rate of change at the temperature sensor at regular intervals comprises:
 determining a first temperature rate of change over a first time window, the first time window spanning between an A 1  time point and a B 1  time point;   comparing the first temperature rate of change against the threshold rate of change;   determining a second temperature rate of change over a second time window, the second time window spanning between an A 2  time point and a B 2  time point; and   comparing the second temperature rate of change against the threshold rate of change.   
     
     
         12 . The method of  claim 11 , wherein the A 2  time point is determined between the A 1  time point and the B 1  time point, and the B 2  time point is determined after the B 1  time point. 
     
     
         13 . The method of  claim 11 , wherein the temperature rate of change is monitored over a fixed-length rolling time window having a predetermined advancement period, the predetermined advancement period being between 0.5 second and 1.5 seconds. 
     
     
         14 . The method of  claim 10 , wherein directing the at least one heating element based on the temperature setpoint over the preheating phase comprises:
 determining a power level for the at least one heating element based on the determined temperature setpoint; and   directing the at least one heating element at the determined power level for a duration of the preheating phase.   
     
     
         15 . The method of  claim 10 , wherein determining the one or more parameters for a feedback controlled cooking phase comprises:
 retrieving the at least one initial controller term value from a lookup table.   
     
     
         16 . The method of  claim 10 , wherein the at least one initial controller term value comprises:
 an initial integral term value; and   an initial derivative term value.   
     
     
         17 . The method of  claim 16 , wherein the initial derivative term value is a filtered derivative term value using a filter smoothing factor. 
     
     
         18 . The method of  claim 10 , wherein determining the threshold time point comprises:
 calculating a length of time from an initiation of the preheating phase to the threshold time point.