Rules of a cooking process with a core temperature probe and oven

Abstract

The invention relates to a method for controlling a cooking process for cooking food (G) located in a cooking chamber (2) of an oven (1) in which a core temperature probe (10) is positioned, a cooking time is specified, a pre-calculated control curve (Fw1, Fw2) adapted to the cooking time is provided, and actual measured values ​​(KT(t)) of the core temperature probe (10) are controlled to corresponding values ​​(w(t)) of the control curve (Fw1, Fw2). The invention also relates to an oven (1) configured to carry out the method.

Description

[0001] The invention relates to a method for controlling a cooking process for cooking food in a cooking chamber of an oven in which a core temperature sensor is positioned, wherein a cooking time is specified in the method. The invention also relates to an oven configured to carry out the method.

[0002] A well-known technique is the so-called "ΔT" control, in which the temperature difference between the measured core temperature of a food and the cooking chamber or oven temperature is regulated to a constant value. It is also known to measure the core temperature and switch off the oven when the desired target core temperature is reached.

[0003] EP 2 689 699 A1 discloses a method for adjusting a microwave power to be delivered during a cooking process for cooking at least one item of food, comprising the steps of: determining at least one first temperature, preferably the core temperature of the item of food, at a first location, determining at least one second temperature, preferably the warmest temperature and / or the surface temperature of the item of food, at a second location, wherein the first location and the second location are spatially spaced from one another, determining a first reference variable, in particular a reference variable characteristic of an average temperature of the item of food, preferably by evaluating at least the first temperature, the second temperature and / or the spatial distance between the first location and the second location,Determining at least one control parameter, in particular temperature-dependent and / or food-specific, from the first reference variable and adjusting the microwave power as a function of the at least one control parameter; and a cooking appliance for carrying out a cooking process for cooking at least one food.

[0004] EP 2 136 604 A1 describes a method for adjusting a microwave power output in a cooking chamber of a cooking appliance during a cooking process for cooking a food item as a function of at least one detected core temperature, characterized by the following steps: a) measuring the core temperature KT(t) at least at two times t1 and t2; b) determining the difference quotient of the core temperatures KT' = ΔKT / Δt from the change in the measured core temperatures ΔKT = KT (t2) - KT (t1) in the time interval Δt = t2 - t1 or the gradient of the core temperature from the first derivative of the measured core temperature KT(t) in the time interval Δt or the C value from the curve of the measured core temperature KT (t);c) comparing the determined difference quotient with a target difference quotient previously determined for the food and / or the cooking process, or the determined gradient with a target gradient previously determined for the food and / or the cooking process, or the determined C-value with a target C-value previously determined for the food and / or the cooking process; and d) adjusting the microwave power depending on the result of said comparison; and a cooking appliance for carrying out such a method.

[0005] DE 3 119 496 A1 discloses a food thermometer, particularly for microwave ovens. To achieve the smallest possible temperature gradient between the food surface and the food core when heating, particularly frozen food, in microwave ovens, and to prevent burning, overcooking, or drying out of the food surface, a skewer-like food thermometer is provided. This thermometer has several temperature sensors in different insertion positions, particularly at the level of the food surface, which are used for temperature control.

[0006] DE 10 2017 214 753 A1 discloses a household cooking appliance comprising a cooking chamber, a data connection device for establishing a data connection with a core temperature sensor, and a control device. The control device is configured to control the household cooking appliance based on temperature measurements from the core temperature sensor, calculate a cooking time for food based on the temperature measurements, and display the calculated cooking time and / or a calculated remaining cooking time. The control device is configured to calculate the cooking time assuming a proportional increase in the core temperature of the food with a first-order delay and taking a dead time into account. A system comprises a household cooking appliance and at least one core temperature sensor.A method is used to determine a cooking time and / or remaining cooking time of food, in which the cooking time and / or remaining cooking time is calculated assuming a proportional increase in a core temperature of the food with a first-order delay and taking into account a dead time.

[0007] It is the object of the present invention to at least partially overcome the disadvantages of the prior art and in particular to provide an improved possibility of providing a target-optimized control for controlling a cooking process for cooking food located in a cooking chamber of an oven.

[0008] This object is achieved according to the features of the independent claims. Preferred embodiments can be found in particular in the dependent claims.

[0009] The object is achieved by a method for controlling a cooking process for cooking food located in a cooking chamber of an oven in which a core temperature sensor is positioned, in which - a cooking time is specified, - a pre-calculated guide curve is provided which is tailored to the cooking time and - Actual measured values ​​of the core temperature sensor are regulated to the corresponding values ​​of the guide curve.

[0010] One advantage of using a control curve is a better response to the oven and food system due to the dynamic control, which, unlike "ΔT" control, does not use a constant "ΔT." Advantageously, the oven's operating settings can be dynamically controlled without using a constant ΔT between the core and cooking chamber temperatures. Furthermore, the core temperature can be consistently controlled at a defined level over a longer period of time, as is the case with so-called "slow cooking" or "sous vide" cooking, for example.

[0011] The oven is, in particular, a household oven. The oven can be a standalone oven or part of a stove. The oven can be a dedicated oven or a combination oven, meaning it can have additional functions such as a microwave and / or steam cooking function. The cooking chamber of the oven can also be referred to as the oven cavity.

[0012] The core temperature probe, also known as a "food thermometer," "roasting thermometer," or "grill thermometer," is designed to measure the internal or core temperature of the food being cooked and transmit the measured values ​​to the oven or its control unit. For this purpose, the core temperature probe is typically inserted into the food and transmits its measured data to the oven either wired or wirelessly.

[0013] To carry out the method, at least the cooking duration, remaining cooking duration, or cooking time is specified. The end of the cooking time can be specified equally. In the following, cooking duration and end of cooking time can be used interchangeably unless the context indicates otherwise. The fact that the cooking duration is specified can mean that it has been specified, e.g., set, by a user or a cooking program. Therefore, the cooking duration is not predicted by the method.

[0014] The guide curve, which can also be referred to as a “reference value profile”, corresponds to a curve or a progression of target values ​​for the core temperature for the specified cooking time. In particular, the guide curve is not constant, but corresponds to values ​​determined or calculated, for example, through simulation and / or experiments, which are adjusted so that the actual core temperature in the food has reached a certain target core temperature after the specified cooking time has elapsed. The guide curve therefore includes both the specified cooking time and a target core temperature. It is created based on the desired cooking time and the target core temperature. The fact that the guide curve is adjusted to the cooking time means, in particular, that the guide curve is dependent on the specified cooking time, i.e. different guide curves are provided for at least noticeably different cooking times.The guide curves can, for example, be stored in a data storage device of the oven or in a network storage device that can be communicatively linked to the oven.

[0015] The cooking time can be adjusted during a cooking process, i.e. extended or shortened. It is also possible to pause the cooking process and keep the core temperature at a certain level for a longer period of time. If this is the case, the process can use a new guide curve that is tailored to the changed cooking time and the remaining cooking time. The new guide curve can, for example, be recalculated using the old and new limit parameters (for example comprising the original start time, a new end time, a current temperature and / or a new end temperature). Various curve profiles can be used for this, e.g. a second-order function that starts “in the middle”, i.e. without any dead time in the profile.

[0016] Control elements can generally be components of the oven, especially those components that significantly change the cooking chamber temperature or significantly change the energy input into the food in terms of its thickness or location. Possible control elements can include, for example: - at least one heating element such as a top heat, bottom heat, grill and / or hot air heater (control variable: impressed electrical power); - a recirculation fan (control variables: direction of rotation, speed of rotation); - Supply air fan for blowing ambient air into the cooking chamber (control variable: rotation speed); - Vapour extraction (control variable: rotation speed of a vapour fan and / or angle position of a vapour flap); and / or - Door opening mechanism for automatically opening and closing the cooking chamber door by a gap (control value: position “open” or “closed”).

[0017] However, the actuators may additionally or alternatively comprise a microwave device and / or a steam generating device.

[0018] The precalculated guide curves can be stored – for example, ex works – in a database that the oven can access. The database can be stored in a data storage device of the oven and / or in an external storage device such as cloud storage, a data storage device of a mobile user device, etc. It is a further development that the precalculated guide curves stored in the data storage device can be updated and / or supplemented. The group of precalculated guide curves can, for example, include differentiated precalculated guide curves regarding the cooking time, the target core temperature, the food category, the weight of the food, etc. Alternatively, the guide curves can be individually calculated before the start of a cooking process (possibly even during a heating phase) based on settings for a cooking process currently being carried out, e.g.using a cloud computer, a network computer, or the oven itself. They are still precalculated.

[0019] In one embodiment, the control curve has been calculated based on an energy-optimized simulation of the cooking process. This has the advantage that the food is cooked in a particularly energy-efficient manner. For this purpose, the simulation environment can, for example, model the heating control implemented by the oven and the oven's energy loss. Furthermore, it can be estimated how much energy is required to heat a specific type of food. The simulation determines the energy-optimized operating parameters. When the user selects a specific type of food, the oven sets the operating parameters stored for that type of food. These operating parameters can change during the cooking process.

[0020] The simulation environment can, for example, simulate thermal conductivity within the food and / or heat transfer from a cooking chamber atmosphere to the surface of the food.

[0021] A further development is that the simulation or simulation environment uses input variables and / or boundary conditions determined from experiments, which allows for particularly good cooking results. Such input variables determined from experiments can include, for example, the thermal conductivity within the food and / or the heat transfer from the cooking chamber atmosphere to the surface of the food, and can be particularly dependent on the type of food being cooked.

[0022] Additionally or alternatively, the guide curve can also be simulated towards other optimization goals, e.g. towards a target degree of browning, towards a cooking time (e.g. towards a particularly short cooking time, towards a small time deviation from a specification), towards an improvement in the control accuracy of the core temperature, etc. The use of a simulation to calculate the guide curve has the further advantage that many unrealistic user settings or boundary conditions can be easily and precisely recognized, for example an excessive shortening of the cooking process or that prolonged high cooking temperatures are detrimental to browning and can, for example, lead to the food or cooked item burning.

[0023] Furthermore, it is advantageous to generally provide feedback to a customer based on a self-diagnosis by comparing a simulation with a running process that his user settings are not sensible or impossible to fulfill.

[0024] It is a further development that the guide curve or reference value profile represents the "ideal" core temperature curve determined through simulation and / or experiments. It is then continuous. However, the guide curve can also be a curve or profile that is continuous but does not correspond to a real or actually achievable core temperature curve.

[0025] One design feature is that the control curve is not continuous. The control curve then does not correspond to a real core temperature curve, where no jumps can occur. The use of a non-continuous control curve offers the advantage that actuators can be adjusted in a particularly versatile way and can be switched on and off if necessary. For example, the control system can switch on certain actuators such as radiators based on a sudden increase in the control curve and / or switch off certain actuators such as radiators based on a sudden decrease in the control curve, or switch on actuators that can be used to cool the cooking chamber, such as a vapor extractor, an automatic door opener, etc.

[0026] In one embodiment, the guide curve provides for the deactivation of at least one actuator in the form of an energy input device before the end of the cooking time is reached. As a result, toward the end of a cooking process, energy input into the cooking chamber or the food can be converted only or almost only through residual heat. An energy input device or an energy input device can be, for example, a heating element such as an electric resistance heater, a microwave device, and / or a steam generator. The heating element can be, for example, a top heat, bottom heat, grill, and / or hot air heater.

[0027] One embodiment provides, in addition to the cooking time, at least the target core temperature of the food being cooked is specified or variably adjusted, and a guide curve tailored to the cooking time and at least the specified target core temperature is provided. This advantageously allows the cooking process to be adjusted to an individually adjustable degree of doneness, thus achieving better cooking results, e.g., with steaks. The target core temperature can be specified by a user or automatically by a cooking program.

[0028] Alternatively, the target core temperature is fixed, particularly depending on an (intrinsic) cooking property, as described in more detail below. This is particularly easy to implement and user-friendly. It takes advantage of the fact that a satisfactory cooking result can often be achieved with a fixed target core temperature. It also covers the case where variations are generally not permitted for certain types or categories of food. For example, poultry can be specified to always be cooked "well done."

[0029] One embodiment provides that, in addition to the cooking time, at least one (intrinsic) food property is specified, and a guide curve tailored to the cooking time and the at least one food property is provided. This (intrinsic) "food property" is a property inherent in the food, independent of the cooking process. The food property comprises at least one property from the group of category, weight, and / or shape of the food.

[0030] One embodiment provides that, in addition to the cooking time, at least the category or type of food to be cooked is specified, and a guide curve tailored to the cooking time and to at least this category is provided. This advantageously enables the cooking process to be adapted to an individually adjustable category, thus achieving better cooking results. The category can be specified by a user or a cooking program. The category can, for example, be an entire food group such as meat, poultry, fish, vegetables, etc. However, the category can also include more finely divided food subgroups, such as beef, veal or pork for meat, or chicken or turkey for poultry, etc.

[0031] One embodiment specifies, in addition to the cooking time, at least the weight, and provides a guide curve tailored to the cooking time and at least the weight. This advantageously allows the cooking process to be adjusted to an individually adjustable weight, thus achieving better cooking results. The weight can be specified by a user or a cooking program.

[0032] One embodiment specifies, in addition to the cooking time, at least the shape, and provides a guide curve tailored to the cooking time and at least the shape. This advantageously allows the cooking process to be adapted to an individually adjustable shape, thus achieving better cooking results. The shape can be specified by a user or a cooking program. For example, a distinction can be made between a whole chicken, a half chicken, chicken legs, or chicken schnitzels. The shape can be a caliber size.

[0033] A further development is that at least the category or type, the weight, and / or the shape are specified by the oven being automatically determined using at least one associated sensor. The sensor can, for example, comprise a camera and / or a weight sensor. Thus, by taking at least one image of the food and subsequently identifying it, the category of the food can be determined, its weight can be determined by measuring its volume, and / or its shape can be directly recognized.

[0034] One embodiment of the invention is that, in addition to the cooking time, at least one cooking property in the form of a target browning level is specified, and a control curve tailored to the cooking time and at least to the target browning level is provided. This advantageously enables particularly versatile adaptation of the cooking process to user preferences. Using the present method, the desired browning level can be achieved without camera monitoring. The linking of core temperature control with the specification of a target browning level can also be viewed as multi-variable control in a MIMO (Multiple Input Multiple Output) system.

[0035] It is also possible for the user to download special cooking curves for a specific food or recipe to further improve the cooking result. Such cooking curves can be downloaded from external databases, for example, from the user's smartphone or from a network-capable storage device, such as a network server or cloud storage. The external database can be a free database or a proprietary database, such as one belonging to the cooking appliance manufacturer.

[0036] In one embodiment, control is performed using a PID controller. The use of a PID controller results in particularly energy-saving cooking processes, for example, compared to P, PI, or PD controllers, which can also be used in principle. The PID controller is, in particular, a component of a closed control loop, whose control system includes, in particular, the system consisting of the oven and the food being cooked. The control parameters or coefficients, e.g., Kp, K iand K d can be adapted to the cooking time, target core temperature, category of food, weight of food, shape of food, etc.

[0037] In one embodiment, control is carried out using compensation control. This can also be referred to as control using a pole specification or eigenvalue specification. This has the advantage that the selection of "ideal" PID control parameters is no longer necessary, since the compensation control also takes these "ideal" control parameters (Ki, Kp, Kd) into account. Compensation control requires the system's transfer function, which can be calculated before the cooking process begins or during the cooking process. For example, the system's transfer function can be estimated based on the system identification. The transfer function completely describes a linear system. Using the transfer function, the output signal of the controlled system can be calculated if its input signal is known. This transfer function can be calculated in advance or during a cooking process.The transfer function can also be updated during a cooking process. For example, in Fourier domain, an input signal multiplied by a transfer function equals the output signal, and analogously, an input signal equals an output signal divided by the transfer function. This allows the "ideal" input signal to be calculated with a known transfer function and a given (desired) output signal. In principle, this only applies to linear transfer functions. If the transfer function is nonlinear, the accuracy decreases with increasing nonlinear component. Compensation control is generally well known; see, for example, Prof. Dr. S. Zacher: "The ineffective controlled system. A study on compensation structures for model-based control"; Automation-Letter No. 6, January 10, 2016; Dr. Serge Zacher Verlag, Stuttgart.

[0038] A further development is the modification of the control concept by means of a suitable pre-filter upstream of the controller used, especially a PID controller, so that the controlled system is inverted, thus creating an "ideal" control system. This takes into account that compensation control is theoretically an ideal control system, but in practice can exhibit certain uncertainties due to incomplete causality. The pre-filter can be used to keep these uncertainties particularly small.

[0039] The problem is also solved by an oven configured to carry out the method described above. The oven can be designed analogously to the method, and vice versa, and has the same advantages.

[0040] The oven can have at least one energy source, fan, etc.

[0041] In a further development, the oven comprises a data processing device, in particular a control device, which is configured to initiate the method. The data processing device can be programmed accordingly for this purpose, for example. The oven can comprise a data storage device integrated into the data processing device or separate from it, in which the guide curves are stored. The oven can be a network-capable oven and configured to download guide curves from an external instance, such as a network server or a cloud storage device, via a wireless and / or wired data connection.

[0042] It is a further development that the oven is set up to make user-guided adjustments to a guide curve (e.g. increasing or decreasing the target core temperature), which allows customer wishes to be taken into account even better.

[0043] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of an embodiment, which is explained in more detail in connection with the drawings. Fig. 1 shows a sectional side view of an oven equipped to carry out the method with a core temperature sensor inserted; and Fig. 2 shows a possible closed control system for controlling a cooking process for cooking in a cooking chamber of the oven from Fig. 1 food in the oven.

[0044] Fig. 1 shows a sectional side view of a sketch of an oven 1 equipped to carry out the method. The oven 1 has a cooking chamber 2 whose front loading opening can be closed by means of a door 3. The oven 1 further has a top heat element 4 and a bottom heat element 5, whose impressed electrical heating output can be adjusted by a control device 6. The control device 6 is also connected to a front-facing operating device 7, e.g., a touchscreen, via which a user can make inputs, e.g., menu-guided, and have information displayed. The oven 1 is also equipped with a connection 8 for a data and, if applicable, power supply cable 9 of a core temperature sensor 10. Measured values ​​from the core temperature sensor 10 can be transmitted to the control device 7 via the cable 9 and the connection 8.When the core temperature sensor 10 is inserted into the food G, the core or internal temperature KT prevailing inside the food G can be measured.

[0045] The control device 6 has a PID controller 11 and a data memory 12, wherein the PID controller 11 is configured to regulate the core temperature KT according to a specific control curve Fw1, Fw2, which has been selected from a group of control curves Fw1, Fw2 stored in the data memory 12. As indicated in an enlarged manner, the control curves Fw1, Fw2 stored in the data memory 12 correspond, at least for a respective cooking time and a respective target core temperature, to model-based simulated courses of control values ​​w(t), in which at the end t endthe cooking time, the target core temperature KT is reached. The guide curves Fw1, Fw2 have been optimized with regard to specific optimization goals, e.g., low energy consumption. The guide values ​​w(t) correspond dimensionally to a core temperature KT, but do not need to correspond to an actual core temperature KT(t). For example, the guide curves can be discontinuous, as indicated here by the guide curve Fw2. The guide curve Fw1, Fw2 currently to be used can be selected or specified, for example, by directly entering a user specification on the control device 7 or indirectly via a selected cooking program. Thus, the guide curve Fw1, Fw2 can be determined at least by the specified cooking time, if necessary also in relation to the target core temperature, the category of the food G (here, for example, chicken), the weight of the food G (e.g. 750 g), the shape of the food G (e.g. a whole chicken) and / or a target browning degree of the food G (e.g.B. kross) or have been pre-calculated in this regard.

[0046] For example, a user can set a cooking time ΔT on the control device 7 gar and a target core temperature KT ziel and start the cooking process at time t start start. Here is an example t start = 0. The cooking process is then stopped at the end time t end = t start + ΔT gar The current time t, based on which the current reference value w(t) is selected, corresponds in particular to the progress time of the cooking process.

[0047] Fig.Figure 2 shows a possible closed control loop for controlling a cooking process for cooking the food G located in the cooking chamber 2. At a respective time t between the start and end of the cooking time, a reference variable w(t) of the selected reference curve Fw1, Fw2 is specified during a cooking process and compared with the core temperature KT(t) currently measured by the core temperature sensor 10. The control deviation e(t) is fed into the PID controller 11, which outputs the electrical power impressed into the top heat element 4 and / or the bottom heat element 5 as a control variable. The heaters 4, 5 generate the radiated heat output as a control variable, which acts on the control loop. Here, the control loop includes, for example, the cooking chamber 2, the door 3, the food G, etc., including possible heat losses, etc. It determines the core temperature KT in the food G.

[0048] Possible disturbances (not shown) can include, for example: measurement errors in the core temperature measurement, for example due to a core temperature sensor being incorrectly inserted into the food, random and systematic measurement errors in the evaluation electronics, etc.; heat losses in the oven, for example due to insulation, leaky doors, additional heat storage devices such as metal parts, cooking accessories, etc.; incorrectly set heating outputs, for example due to aging radiators; etc. Of course, the present invention is not limited to the embodiment shown.

[0049] In general, “a”, “an”, etc. can be understood as a singular or a plural, in particular in the sense of “at least one” or “one or more”, etc., unless this is explicitly excluded, e.g. by the expression “exactly one”, etc.

[0050] A numerical value may also include the exact number stated as well as a usual tolerance range, as long as this is not explicitly excluded. List of reference symbols 1 oven 2 cooking chamber 3 Door 4 top heat radiators 5 bottom heat radiators 6 Control device 7 Operating device 8 Connection 9 cables 10 core temperature sensors 11 PID controller 12 data storage Fw1 guide curve Fw2 guidance curve G Food KT core temperature t time t end End time w(t) time-dependent reference variable QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 2 689 699 A1

[0003] EP 2 136 604 A1

[0004] DE 3 119 496 A1

[0005] DE 10 2017 214 753 A1

[0006] Cited non-patent literature

[0000] Prof. Dr. S. Zacher: "The Ineffective Control System. A Study on Compensation Structures for Model-Based Control"; Automation-Letter No. 6, January 10, 2016; Dr. Serge Zacher Verlag, Stuttgart

[0037]

Claims

[1] Method for controlling a cooking process for cooking food (G) located in a cooking chamber (2) of an oven (1) in which a core temperature sensor (10) is positioned, in which - a cooking time is specified, - a pre-calculated guide curve (Fw1, Fw2) is provided, which is adjusted to the cooking time, and - Actual measured values ​​(KT(t)) of the core temperature sensor (10) are regulated to corresponding values ​​(w(t)) of the guide curve (Fw1, Fw2). [2] Method according to claim 1, wherein the guide curve (Fw1, Fw2) has been calculated based on an energy-optimized simulation of the cooking of the food (G). [3] Method according to one of the preceding claims, in which the guide curve (Fw2) is not continuous. [4] Method according to one of the preceding claims, in which the guide curve (Fw1, Fw2) switches off at least one actuator (4, 5) in the form of an energy source before reaching an end (tend ) of the cooking time. [5] Method according to one of the preceding claims, in which, in addition to the cooking time, at least one target core temperature of the food (G) is specified and a guide curve (Fw1, Fw2) adapted to the cooking time and at least the specified target core temperature is provided. [6] Method according to one of the preceding claims, in which, in addition to the cooking time, at least one cooking product property is specified and a guide curve (Fw1, Fw2) adapted to the cooking time and to at least one cooking product property is provided, wherein the at least one cooking product property comprises at least one property from the group - Category; - Weight; - Shape of the food to be cooked (G). [7] Method according to one of the preceding claims, in which, in addition to the cooking time, at least one property of the food to be cooked is specified in the form of a target degree of browning and a guide curve (Fw1, Fw2) adapted to the cooking time and at least to the target degree of browning is provided. [8] Method according to one of the preceding claims, in which the actuators (4, 5) of the control system comprise at least one actuator from the group: - at least one radiator; - a recirculation fan; - a vapor extractor; - a door opening mechanism for automatically opening and closing the cooking chamber door by a gap. [9] Method according to one of the preceding claims, in which the control is carried out by means of a PID control (11). [10] Method according to one of the preceding claims, in which the control is carried out by means of a compensation control. [11] Baking oven (1) which is designed to carry out the method according to one of the preceding claims.

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