COOKING APPLIANCE AND METHOD OF OPERATING THE SAME INCORPORATING ADJUSTED CONTROLLER GAIN VALUES

Description

FIELD OF THE INVENTION

The present subject matter relates generally to cooking appliances, and more particularly to methods of operating cooking appliances according to detected controller outputs during a cooking operation.

BACKGROUND OF THE INVENTION

Cooking appliances generally have one or more heating elements configured for heating a cookware item. The cookware item, e.g., a pot or a pan, may be positioned on or near the one or more heating elements and food products (including, e.g., food solids, liquid, or water) may be placed inside the cookware item for cooking. A controller may selectively energize the heating element(s) to provide thermal energy to the cookware item and the food products placed therein. Alternatively, certain cooking appliances, often referred to as induction cooktops, provide energy in the form of an alternating magnetic field which causes the cookware item to generate heat. In both types of appliances, a controller selectively energizes either the heating element(s) or a magnetic coil to heat the food products until they are properly cooked.

For cooking appliances that are capable of performing feedback controlled heating operations, one or more algorithms may be used to incorporate certain feedback information (e.g., temperature change, temperature rate of change, etc.) over a heating period to intelligently control a power level of the heating element(s). A set of controller gains (e.g., derivative, integral, etc.) may be utilized when the feedback controlled portion of the heating operation begins. When certain events happen, such as when food is added to the cookware item, the controller output may be automatically adjusted based on the set of controller gains in use to compensate for the sudden change in temperature. However, existing methods of operating such cooking appliances suffer certain drawbacks. For instance, one or more of the controller gains may not be optimized to properly adjust the controller output during such events.

Accordingly, a cooking appliance and method of operating a cooking appliance which obviates one or more of the above-mentioned drawbacks would be beneficial. In particular, a cooking appliance capable of adjusting the amount of controller output in response to events would be useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In one exemplary aspect of the present disclosure, a cooking appliance is provided. The cooking appliance may include 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 feedback controlled heating operation. The feedback controlled heating operation may include retrieving a default set of controller gain values for the feedback controlled heating operation, the default set of controller gain values including a default proportional gain value, a default integral gain value, and a default derivative gain value; directing the at least one heating element according to the default set of controller gain values; detecting a food event while directing the at least one heating element according to the default set of controller gain values; determining a total amount of change in a power level of the at least one heating element in response to detecting the food event; determining an adjusted set of controller gain values in response to determining the total amount of change in the power level of the at least one heating element; and directing the at least one heating element according to the adjusted set of controller gain values.

In another exemplary aspect of the present disclosure, a method of operating a cooking appliance is provided. The cooking appliance may include at least one heating element and a temperature sensor. The method may include retrieving a default set of controller gain values for a feedback controlled heating operation, the default set of controller gain values including a default proportional gain value, a default integral gain value, and a default derivative gain value; directing the at least one heating element according to the default set of controller gain values; detecting a food event while directing the at least one heating element according to the default set of controller gain values; determining a total amount of change in a power level of the at least one heating element in response to detecting the food event; determining an adjusted set of controller gain values in response to determining the total amount of change in the power level of the at least one heating element; and directing the at least one heating element according to the adjusted set of controller gain values.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 provides a perspective view of an oven range according to exemplary embodiments of the present disclosure.

FIG. 2 provides a side cut-away view of the exemplary oven range of FIG. 1.

FIG. 3 provides a graph illustrating a cookware temperature, a sensor temperature, and controller terms over time for a cookware item according to exemplary embodiments of the present disclosure.

FIG. 4 provides a graph illustrating a cooking operation incorporating a first derivative gain value and a second derivative gain value according to exemplary embodiments of the present disclosure.

FIG. 5 provides a flow chart illustrating a method of operating a cooking appliance according to exemplary embodiments of the present disclosure.

Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

As used herein, the terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms “includes” and “including” are intended to be inclusive in a manner similar to the term “comprising.” Similarly, the term “or” is generally intended to be inclusive (i.e., “A or B” is intended to mean “A or B or both”). In addition, here and throughout the specification and claims, range limitations may be combined and/or interchanged. Such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.

Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “generally,” “about,” “approximately,” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components and/or systems. For example, the approximating language may refer to being within a 10 percent margin, i.e., including values within ten percent greater or less than the stated value. In this regard, for example, when used in the context of an angle or direction, such terms include within ten degrees greater or less than the stated angle or direction, e.g., “generally vertical” includes forming an angle of up to ten degrees in any direction, e.g., clockwise or counterclockwise, with the vertical direction V.

The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” In addition, references to “an embodiment” or “one embodiment” does not necessarily refer to the same embodiment, although it may. Any implementation described herein as “exemplary” or “an embodiment” is not necessarily to be construed as preferred or advantageous over other implementations. Moreover, each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

FIG. 1 provides a perspective view of a cooking appliance, or oven range 10, including a cooktop 12, and FIG. 2 provides a side cut-away view of the cooking appliance 10. Cooking appliance 10 is provided by way of example only and is not intended to limit the present subject matter to the arrangement shown in FIGS. 1 and 2. Thus, the present subject matter may be used with other range 10 and/or cooktop 12 configurations, e.g., double oven range appliances. As illustrated, cooking appliance 10 generally defines a vertical direction V, a lateral direction L, and a transverse direction T, each of which is mutually perpendicular, such that an orthogonal coordinate system is generally defined. Cooking appliance 10 may include a cabinet 101 that extends between a top 103 and a bottom 105 along the vertical direction V, between a left side 107 and a right side 109 along the lateral direction, and between a front 111 and a rear 113 along the transverse direction T.

A cooking surface 14 of cooktop 12 may include a plurality of heating elements 16. For the embodiment depicted, cooktop 12 includes five heating elements 16 spaced along cooking surface 14. Heating elements 16 may be electric heating elements and are positioned at, e.g., on or proximate to, the cooking surface 14. In certain exemplary embodiments, cooktop 12 is a radiant cooktop with resistive heating elements or coils mounted below cooking surface 14. However, in other embodiments, the cooktop appliance 12 includes other suitable shape, configuration, and/or number of heating elements 16, for example, cooktop 12 may be an open coil cooktop with heating elements 16 positioned on or above surface 14. Additionally or alternatively, in other embodiments, cooktop 12 may include any other suitable type of heating element 16, such as an induction heating element. Each of the heating elements 16 may be the same type of heating element 16, or cooktop 12 may include a combination of different types of heating elements 16.

As mentioned, heating element 16 may be an induction style heating element. Thus, as would be understood by those skilled in the art, appliance 10 may supply a current to heating element 16 (e.g., such as a Lenz coil). As such, current may pass through heating element 16 to generate a magnetic field. The magnetic field may be a high frequency circulating magnetic field. The magnetic field may be directed towards and through cooktop appliance 12 to a cookware item (e.g., cookware item 18, described below). In particular, when the magnetic field penetrates cookware item 18, the magnetic field induces a circulating electrical current within cookware item 18. The material properties of cookware item 18 may restrict a flow of the induced electrical current and convert the induced electrical current into heat within cookware item 18. As cookware item 18 heats up, contents of cookware item 18 contained therein heat up as well. In such a manner, the induction heating element can cook the contents of cookware item 18.

As shown in FIG. 1, a cooking utensil (or cookware item) 18, such as a pot, pan, or the like, may be placed on a heating element 16 to heat cookware item 18 and cook or heat food items placed within cookware item 18. Cooking appliance 10 may also include a door 20 that permits access to a cooking chamber 104 of oven range 10, e.g., for cooking or baking of food items therein. A control panel 22 having controls 24 may permit a user to make selections for cooking of food items. Although shown on a backsplash or back panel 26 of oven range 10, control panel 22 may be positioned in any suitable location.

Controls 24 may include buttons, knobs, and the like, as well as combinations thereof, and/or controls 24 may be implemented on a remote user interface device such as a smartphone. As an example, a user may manipulate one or more controls 24 to select a temperature and/or a heat or power output for each heating element 16 and the cooking chamber 104. The selected temperature or heat output of heating element 16 affects the heat transferred to cookware item 18 placed on heating element 16. A display 28 may be provided (e.g., on or in control panel 22). Display 28 may display information regarding cooking operations or inputs from a user regarding the cooking operation. Display 28 may be any suitable display capable of providing visual feedback, such as a liquid crystal display (LCD), a light emitting diode (LED) display, a segmented display, or the like. Additionally or alternatively, display 28 may be a touch display capable of receiving touch inputs from a user.

Cooktop appliance 12 may further include or be in operative communication with a processing device or a controller 50 that may be generally configured to facilitate appliance operation. In this regard, control panel 22, controls 24, and display 28 may be in communication with controller 50 such that controller 50 may receive control inputs from controls 24, may display information using display 28, and may otherwise regulate operation of cooking appliance 10. For example, signals generated by controller 50 may operate cooking appliance 10, including any or all system components, subsystems, or interconnected devices, in response to the position of controls 24 and other control commands. Control panel 22 and other components of appliance 10 may be in communication with controller 50 via, for example, one or more signal lines or shared communication busses. In this manner, Input/Output (“I/O”) signals may be routed between controller 50 and various operational components of appliance 10.

As used herein, the terms “processing device,” “computing device,” “controller,” or the like may generally refer to any suitable processing device, such as a general or special purpose microprocessor, a microcontroller, an integrated circuit, an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field-programmable gate array (FPGA), a logic device, one or more central processing units (CPUs), a graphics processing units (GPUs), processing units performing other specialized calculations, semiconductor devices, etc. In addition, these “controllers” are not necessarily restricted to a single element but may include any suitable number, type, and configuration of processing devices integrated in any suitable manner to facilitate appliance operation. Alternatively, controller 50 may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND/OR gates, and the like) to perform control functionality instead of relying upon software.

Controller 50 may include, or be associated with, one or more memory elements or non-transitory computer-readable storage mediums, such as RAM, ROM, EEPROM, EPROM, flash memory devices, magnetic disks, or other suitable memory devices (including combinations thereof). These memory devices may be a separate component from the processor or may be included onboard within the processor. In addition, these memory devices can store information and/or data accessible by the one or more processors, including instructions that can be executed by the one or more processors. It should be appreciated that the instructions can be software written in any suitable programming language or can be implemented in hardware. Additionally, or alternatively, the instructions can be executed logically and/or virtually using separate threads on one or more processors.

For example, controller 50 may be operable to execute programming instructions or micro-control code associated with an operating cycle of cooking appliance 10. In this regard, the instructions may be software or any set of instructions that when executed by the processing device, cause the processing device to perform operations, such as running one or more software applications, displaying a user interface, receiving user input, processing user input, etc. Moreover, it should be noted that controller 50 as disclosed herein is capable of and may be operable to perform any methods, method steps, or portions of methods as disclosed herein. For example, in some embodiments, methods disclosed herein may be embodied in programming instructions stored in the memory and executed by controller 50.

The memory devices may also store data that can be retrieved, manipulated, created, or stored by the one or more processors or portions of controller 50. The data can include, for instance, data to facilitate performance of methods described herein. The data can be stored locally (e.g., on controller 50) in one or more databases and/or may be split up so that the data is stored in multiple locations. In addition, or alternatively, the one or more database(s) can be connected to controller 50 through any suitable network(s), such as through a high bandwidth local area network (LAN) or wide area network (WAN). In this regard, for example, controller 50 may further include a communication module or interface that may be used to communicate with one or more other component(s) of appliance 10, controller 50, an external appliance controller, or any other suitable device, e.g., via any suitable communication lines or network(s) and using any suitable communication protocol. The communication interface can include any suitable components for interfacing with one or more network(s), including for example, transmitters, receivers, ports, controllers, antennas, or other suitable components.

Cooking appliance 10 may include a temperature sensor 40. Temperature sensor 40 may be configured to selectively sense a temperature of a cookware item (e.g., cookware item 18) as it is heated. For instance, temperature sensor 40 may be integrally formed with cooking appliance 10 (e.g., within cooktop 12, within cooking chamber 104, etc.). In some embodiments, temperature sensor 40 is operably connected to cooking appliance 10 (e.g., via a port or socket, via a remote connection, etc.). For one example, temperature sensor 40 is provided within cookware item 18 and operably connected to controller 50 during a cooking operation. Temperature sensor 40 may monitor a temperature of cookware item 18 or a food item provided within cookware item 18. Accordingly, temperature sensor 40 may deliver signals (e.g., voltage signals) representing the temperature of cookware item 18 to controller 50. The signals may be sent according to a predetermined frequency (e.g., at predetermined time intervals). Thus, controller 50 may analyze a temperature or temperature change of cookware item 18.

As used herein, “temperature sensor” or the equivalent is intended to refer to any suitable type of temperature measuring system or device positioned at any suitable location for measuring the desired temperature. Thus, for example, temperature sensor 40 may be any suitable type of temperature sensor, such as a thermistor, a thermocouple, a resistance temperature detector, a semiconductor-based integrated circuit temperature sensor, etc. In addition, temperature sensor 40 may be positioned at any suitable location and may output a signal, such as a voltage, to a controller that is proportional to or indicative of the temperature being measured. Although exemplary positioning of temperature sensors is described herein, it should be appreciated that appliance 10 may include any other suitable number, type, and position of temperature or other sensors according to alternative embodiments.

FIG. 3 provides a graph illustrating a cookware item temperature and setpoint (e.g., a temperature setpoint described below for method 300), a sensor temperature and setpoint, a proportional term, an integral term, a derivative term, and a proportion-integral-derivative (PID) output value for an exemplary cookware item during a cooking or heating operation. The sensor temperature setpoint may be different from the cookware setpoint. For instance, the sensor setpoint or target may be based on the cookware setpoint mentioned above (determined temperature setpoint in method 300 below). The heating operation may include a preheating phase and a cooking phase. The preheating phase may be a constant heating preheating phase. For instance, during the preheating phase, heating element 16 may be driven (e.g., powered) at a constant predetermined power level for a duration of the preheating phase.

The cooking phase may be a feedback controlled cooking phase. In detail, the cooking phase may intelligently adjust one or more parameters according to feedback with respect to cookware item 18, a food being cooked, cooking appliance 10, or the like. Additionally or alternatively, the feedback controlled heating operation may start at the beginning of the preheating phase. Temperature sensor 40 may continually send temperature signals to controller 50 which may then determine, for instance, an error value associated with the feedback controlled heating operation. The error value may be a difference between a temperature setpoint (e.g., sensor temperature setpoint) and an actual observed temperature (e.g., via temperature sensor 40). The error value may be substituted into a feedback equation to determine an adjustment to be made to a control variable. For instance, the control variable may be a power level of heating element 16.

According to at least some embodiments, controller 50 includes a closed-loop feedback control algorithm. The closed-loop feedback control algorithm may be a proportional-integral-derivative (PID) algorithm or equation (e.g., equation or set of equations). In some embodiments, the algorithm may include a proportional algorithm, a proportional-integral algorithm, a proportional-derivative algorithm, or any suitable combination of terms. The PID controller may determine a proportional term (P), an integral term (I), and a derivative term (D). The PID algorithm may be:

C ⁢ V = P + I + D

• • where CV is a controlled variable (e.g., power input to heating element 16), P is the proportional term, I is the integral term, and D is the derivative term. As can be seen, adding each of the P, I, and D terms generates a value for the power level of heating element 16. Each of the P, I, and D terms may be found as follows:

P = K p * e ⁢ I = I prev + K i * e * T s ⁢ D = K d * ( e - e prev ) / T s

• • where K_p is a proportional gain value, K_i is an integral gain value, K_d is a derivative gain value, e is an error value (e.g., a difference between a temperature setpoint and an observed temperature), Ts is a sampling time or sampling time rate (e.g., a rate at which a discrete system samples inputs), I_prev is a previous integral term (e.g., at the previous sampling event), and e_prev is a previous error value (e.g., at the previous sampling event). As noted above, however, in some instances any suitable combination of P, I, and D terms may be incorporated into the algorithm.

In some instances, the derivative (D) term may be susceptible to high levels of noise. Thus, large oscillations of the D term may be observed throughout the feedback controlled heating operation. Accordingly, the D term may be subjected to a filtering technique to reduce the noise and obtain a more steady, predictable term over the heating operation. For one example:

D filtered = α * D + ( 1 - α ) * D filtered prev

• • where D_filtered is the filtered D term, D_filteredprev is the previous filtered D term (e.g., from a measuring point immediately preceding the current measuring point [previous sampling event]), and a is a filter smoothing factor, such that 0≤α≤1. As would be understood, a smaller value of a (e.g., closer to 0) would result in greater smoothing of the D term. Additionally or alternatively, the filtered D term incorporates previous D terms to provide smoother adjustments to the D term of the PID controller algorithm. With a smoother D term, fluctuations of the PID controller outputs may be reduced. Thus, the PID algorithm may be adjusted to:

CV = P + I + D filtered

According to some instances, the feedback controlled heating operation (e.g., the PID feedback controlled cooking operation) may initiate at the beginning of the cooking cycle (e.g., at the start of the preheating phase). In additional or alternative embodiments, the feedback controlled heating operation may initiate at the completion of the preheating phase. As shown in FIG. 3, for instance, the PID-based feedback controlled heating operation may initiate at 2.5 minutes (e.g., at the conclusion of the preheating phase). At the initiation of the feedback controlled cooking operation, the/term and/or the D term may be initialized to zero or non-zero values. For instance, the initial/term incorporated at the beginning of the feedback controlled heating operation may be a positive, non-zero value. However, in some instances, the initial/term may be a negative value. Advantageously, a more accurate and effective control algorithm may be utilized during the PID-based feedback controlled cooking phase.

Now that the construction of cooking appliance 10 and a configuration of controller 50 according to exemplary embodiments have been presented, exemplary method 300 of operating a cooking appliance will be described. Although the discussion below refers to the exemplary method 300 of operating cooking appliance 10, one skilled in the art will appreciate that the exemplary method 300 is applicable to the operation of a variety of other cooking appliances. In exemplary embodiments, the various method steps as disclosed herein may be performed by controller 50 or a separate, dedicated controller. Additionally or alternatively, the various method steps may be performed in a different order, including additional steps or omitting certain steps according to specific embodiments.

Method 300 may include determining a temperature setpoint (e.g., cookware setpoint described above). In detail, a user may communicate with the cooking appliance (e.g., cooking appliance 10) a desire to initiate a cooking operation, a heating operation, or the like. For example, the heating operation may include a feedback controlled preheating and heating (or cooking) phases incorporating a PID algorithm to continually monitor the heating operation and perform adjustments as needed. Additionally or alternatively, the heating operation may include a non-feedback controlled preheating phase and a feedback controlled heating (or cooking) phase. For instance, as will be discussed, the heating operation may incorporate the preheating phase before the cooking phase. According to at least some embodiments, the preheating phase may not utilize or incorporate feedback control (e.g., PID feedback control). The user may manually enter a temperature setpoint (e.g., a temperature at which the user desires to have the item cooked). Thus, using a user interface (e.g., control panel 22), the user may enter a specific cooking temperature as the temperature setpoint (e.g., 250° F., 300° F., 350° F., etc.). In additional or alternative embodiments, the user may provide information regarding a specific food item to be cooked (e.g., eggs, meat, vegetables, etc.). For instance, the cooking appliance may include features for selecting predetermined food items from the user interface or the cooking appliance may include a remote connectivity (e.g., wireless fidelity [WiFi], Bluetooth®, etc.), through which the user may select a food item (e.g., via a remote device). Further still, the user may input a particular recipe to be cooked on or in the cooking appliance. The temperature setpoint may be stored within the cooking appliance (e.g., within a controller or a memory therein).

At step 302, method 300 may include retrieving a default set of controller gain values for a feedback controlled heating operation. The default set of controller gain values may be based on the determined temperature setpoint. The default set of controller gain values may include a default proportional gain value, a default integral gain value, and a default derivative gain value. According to some embodiments, the default set of controller gain values may be unique. In additional or alternative embodiments, the appliance may include a plurality of sets of controller gain values based on different temperature setpoints. Additionally or alternatively, the appliance may include a plurality of sets of controller gain values based on different specific cookware items. Each set of controller gain values may be stored, for instance, within a lookup table. Each set of controller gain values may be predetermined according to normal expected thermal behavior of the associated cookware item.

At step 304, method 300 may include directing the at least one heating element according to the default set of controller gain values. As mentioned above, the cooking appliance may include a feedback controlled algorithm such as a proportional-integral-derivative (PID) controller. The controller may utilize each of the default set of controller gain values to determine a controller output (e.g., a PID output). The controller output may thus dictate or otherwise determine a power level at which to drive the at least one heating element. For instance, method 300 may determine a baseline power level at which to drive or direct the at least one heating element based on the default set of controller gain values and/or cooking conditions. As would be expected, certain inputs or events (e.g., such as temperature changes, power changes, food addition, or the like) may adjust the controller output and thus adjust the power level of the at least one heating element. Accordingly, the “baseline power level” may be associated with a power level at the at least one heating element immediately preceding a detected event (explained below).

As mentioned, the default set of controller gain values may be based on expected thermal behavior of the associated cookware item. Accordingly, certain adjustments or deviations from an expected thermal behavior (e.g., as caused by different types of cookware or foods) may result in unexpected or undesirable responses from the controller output. For instance, one of the controller gain values may result in a slower than expected or desired response time. For another example, one of the controller gain values may result in a lower than expected or desired power level adjustment in response to the event. Thus, the default set of controller gain values may be implemented to perform the feedback controller heating or cooking operation and drive the at least one heating element to the determined power level based on the current cooking temperature conditions or cooking events.

At step 306, method 300 may include detecting a food event while directing the at least one heating element according to the default set of controller gain values. As mentioned, certain events (e.g., food events) may occur during the feedback controlled heating operation. For instance, a food item may be added to the cookware item (e.g., an egg, a meat, a vegetable, etc.). The food event may be detected based on a change to the controller output. As mentioned above, the controller (e.g., algorithm) may adjust the power level of the at least one heating element based on received feedback. As seen in FIG. 3, the controller (e.g., PID) output may respond to a change in temperature at the temperature sensor or cookware item. Accordingly, the food event may be detected based on a change in the controller output (e.g., a power level change of the at least one heating element). Additionally or alternatively, the food event may be detected based on a change in the derivative term value within the controller (e.g., as seen in FIG. 3).

In some instances, the food event is detected by detecting or determining that a power level of the at least one heating element has changed by a predetermined minimum amount within a predetermined length of time. For example, method 300 detects or determines that the power level at the at least one heating element has changed or adjusted from the baseline power level. In at least some instances, the power level at the at least one heating element is adjusted higher. The power level at the at least one heating element may be expected to change by a predetermined minimum amount (e.g., in levels). For instance, the predetermined minimum amount may be about 5 levels, about 7 levels, about 10 levels, or the like. Additionally or alternatively, in detecting the food event, method 300 may determine that the power level change occurs within a predetermined amount of time. For instance, the power level may change by the predetermined minimum amount (e.g., 5 levels, 7 levels, etc.) within a predetermined amount or length of time. The predetermined amount or length of time may be between about 20 seconds and about 40 seconds. The predetermined minimum amount of power level change and the predetermined amount or length of time may be defined such that food addition events are detected, but food turning events are not. As seen in FIG. 3, the amount of power level change is typically smaller for a food turning event than a food addition event. Thus, conveniently, method 300 may detect and analyze food addition events while ignoring food turning events, to prevent inconsistent results. Additionally or alternatively, method 300, at step 306, may ignore food events detected within a period of time (e.g. 5 minutes) after a previously detected food event. It should be noted that the ranges provided herein are by way of example only, and that any suitable minimum power level and/or length of time may be incorporated depending on specific applications.

At step 308, method 300 may include determining a total amount of change in the power level of the at least one heating element in response to detecting the food event. In detail, after determining that the food event has occurred, method 300 may calculate a total change in the power level from the initiation of the food event to a maximum power level (e.g., controller output) change. For instance, method 300 may determine the maximum power level after the food event as a point at which the controller output levels off or begins to drop. After determining the maximum power level value, method 300 compares the maximum power level value against a power level value immediately preceding the detection of the food event. In some instances, the maximum power level value is compared against the baseline power level or power level value. Thus, the total amount of change in the power level may be determined from the food event. In additional or alternative embodiments, method 300 may average a total amount of change in the power level of the at least one heating element after detecting multiple food events (e.g., three or more food events).

According to some embodiments, method 300 includes determining that the total amount of change in the power level of the at least one heating element is outside of a predetermined range. For instance, the appliance may store a predetermined expected power level change range for when the food event occurs. The predetermined expected power level change range may include a minimum change in power level and a maximum change in power level. According to some embodiments, the predetermined expected power level change range is between about 10 power levels and about 15 power levels. Accordingly, in determining the total amount of change in the power level of the at least one heating elements, method 300 may determine that the power change is less than the minimum change value or greater than the maximum change value. Additionally or alternatively, the predetermined expected power change range may be based on empirical data (e.g., according to the temperature setpoint, the specific cookware item, the food being cooked, etc.).

At step 310, method 300 may include determining an adjusted set of controller gain values in response to determining the total amount of change in the power level of the at least one heating element. For instance, upon determining that the total amount of change in the power level is outside of the predetermined range, method 300 may calculate, retrieve, or otherwise determine the adjusted set of controller gain values. As mentioned previously, the default set of controller gain values may be incorporated based on one or more initial settings (e.g., temperature setpoint, cookware item, food selection, etc.). Adjustments to the controller gain values may be necessary based on the amount of change in power level (or controller output) after an event (e.g., addition of food) in order to efficiently and effectively maintain the temperature at the cookware item after certain food events.

In determining the adjusted set of controller gain values, method 300 may determine an adjusted derivative gain value. The adjusted derivative gain value may be based on the total amount of change in the power level of the at least one heating element. For instance, as mentioned, the total amount of change in the power level may be compared against a desired or expected change in power level (e.g., based on the empirical data). Accordingly, the adjusted derivative gain value may be determined according to the following equation:

K d ⁢ 2 = K d ⁢ 1 * P ⁢ L ⁢ Change des P ⁢ L ⁢ Change d ⁢ et

• • wherein K_d2 is the adjusted derivative gain value, K_d1 is the default controller gain value (e.g., derivative value), PL Change_des is the desired or expected total change in power level, and PL Change_det is the determined total change in power level. In some instances, the equation may be additionally adjusted by an adjustment factor. As can be seen, the adjusted derivative gain value may be increased in the event the total determined change in power level is less than the desired or expected change in power level. For instance, referring to FIG. 4, a cooking operation incorporating the default set of controller gain values (e.g., a first derivative gain value) and adjusting to the adjusted controller gain values (e.g., a second derivative gain value) is shown. As can be seen, as a result of the first food event, the total output of the controller and subsequently the power level of the at least one heating element is modified to a first changed level (e.g., around the 16 minute time point). Thereafter, the derivative gain value is adjusted such that a second food event causes the controller output and subsequently the power level of the at least one heating element to modify or change to a second changed level (e.g., around the 27 minute time point). As can be seen, with the adjusted derivative gain value, the controller output and power level of the at least one heating element experiences a greater or higher change, resulting in a quicker recovery of the temperature at the cookware item and thus more stable temperature maintenance.

In some instances, the adjusted derivative gain value may be reduced (e.g., if the total determined change in power level is greater than the desired or expected change in power level). Additionally or alternatively, the derivative gain value may remain unchanged. For instance, if the change in power level is within the predetermined range, method 300 may conclude that the correct or efficient gain values are already incorporated. The adjusted derivative gain value (and, in some instances, other adjusted gain values) may be stored within the cooking appliance (e.g., within a lookup table). Accordingly, the adjusted gain values may be retrieved in future cooking operations with similar settings (e.g., temperature setpoint, cookware item, food to be cooked, etc.).

At step 312, method 300 may include directing the at least one heating element according to the adjusted set of controller gain values. For instance, the feedback controlled heating algorithm (e.g., the PID algorithm) may be adjusted to incorporate the adjusted controller gain values (e.g., the adjusted derivative gain value). Advantageously, the feedback controlled heating operation may be more precisely controlled according to the adjusted controller gain values such that a more even heating or cooking is applied to the item to be cooked or heated.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.