Weighing device using spectrum analysis

Abstract

The present invention relates to a weighing device, for example, a weighing device for use in a kitchen. It has a support plate (1) for supporting an object to be measured and a control device (16). In addition, an excitation mechanism (12) for generating mechanical vibrations in the support plate (1) and a measuring mechanism (14) for measuring the mechanical vibrations of the support plate (1) are provided. By means of the excitation mechanism (12) and the measuring mechanism (14), one or more resonance frequencies and / or other spectral characteristics of the support plate (1) are determined, and these resonance frequencies and / or spectral characteristics are used, for example, to determine the mass of the object.

Description

Field of the Invention

[0001] The present invention relates to a weighing device, in particular a weighing device for a kitchen, and a stove or a piece of furniture, in particular kitchen furniture, having a weighing device. The present invention also relates to a method for operating such a weighing device and to a device unit for such a weighing device or for carrying out the method according to the invention. Background Art

[0002] Scales of very different known structural types are known, which measure the elastic deformation of the support of the support plate, for example, by means of strain gauges, or by means of capacitive or optical sensors.

[0003] WO02 / 26002 describes a stove having a built-in scale, in which the weight of the object to be measured is determined by detecting the static deformation of the support plate of the stove. For this purpose, suitable detectors are required at the central position below the support plate. These detectors must be able to accurately measure the deformation, which is very difficult because the absolute position must be determined without a suitable reference position. Summary of the Invention

[0004] The object of the present invention is to provide a weighing device and in particular a stove, a piece of furniture, in particular kitchen furniture, or a method of the type mentioned at the beginning, which allows simple and accurate weighing.

[0005] This object is solved by a weighing device, a stove, a piece of furniture and a method according to the invention.

[0006] Thus, a weighing device, in particular a weighing device suitable for a kitchen, has the following elements:

[0007] - A support plate: The support plate is used to support the object whose mass is to be measured.

[0008] - A control device: The control device controls the weighing process.

[0009] - At least one excitation mechanism: The excitation mechanism is arranged and constructed in such a way that it can generate mechanical vibrations in the support plate.

[0010] - At least one measuring mechanism: The measuring mechanism is arranged and constructed in such a way that it can measure the mechanical vibrations.

[0011] Furthermore, the weighing device (preferably its control device) is constructed for the following purposes:

[0012] - Determining at least one spectral characteristic of the vibration of the support plate (on which an object is placed) by means of the excitation mechanism and the measuring mechanism, and

[0013] - Determine the mass of the object using the spectral characteristics.

[0014] The present invention is based on the recognition that (as will be explained in more detail later) the spectral characteristics of the vibration of the support plate together with the object to be measured placed thereon are related to the mass of the object. Such spectral characteristics can be accurately determined in a simple manner and used for mass measurement.

[0015] In particular, the spectral characteristics at least include the resonance frequency of the support plate, for example, in such a way that the spectral characteristics are this resonance frequency or are directly or indirectly related to this resonance frequency.

[0016] To determine the mass from the spectral characteristics of the support plate, there are different possibilities depending on the actual situation, which will be described in more detail later.

[0017] In particular, the control device is configured to,

[0018] measure at least two different spectral characteristics of the vibration, and

[0019] use the at least two spectral characteristics to determine the mass of the object.

[0020] Thereby, higher accuracy can be achieved, and / or in addition to the mass, other unknown parameters can be determined or excluded, that is, for example, the diameter of the object (for example, when the object is a pot) or the position parameter of the object on the support plate.

[0021] Advantageously, the control device is configured to,

[0022] measure the resonance frequencies of at least two eigenmodes of the support plate, and

[0023] use the resonance frequencies of the at least two eigenmodes to determine the mass of the object.

[0024] For a rectangular or square support plate, the excitation mechanism and / or the measurement mechanism are advantageously arranged within a tolerance T on at least one of the diagonals of the support plate, where the tolerance T is at most 10% of the shortest side length of the support plate. In addition, the distance D1 between the excitation mechanism and the midpoint of the diagonal and / or the distance D2 between the measurement mechanism and the midpoint of the diagonal are in the range of 5% to 45% of the diagonal length L, especially in the range of 25% to 45%.

[0025] If both the excitation mechanism and the measurement mechanism are on at least one of the diagonals in the defined sense, here, the two mechanisms can be on the same diagonal or on different diagonals.

[0026] In a preferred embodiment, the excitation means and the measurement means are on different diagonals, and an operating area is provided below the support plate between the excitation means and the measurement means, because in this case, generally no heating element is provided at the positions of the said means.

[0027] This is based on the understanding that at least most of the low modes do not have vibration nodes in the said area on the diagonal, that is, if the excitation means and / or the measurement means are arranged in this area, the measurement can be well performed.

[0028] If there are a plurality of excitation means and / or measurement means, preferably at least one of them should have the said arrangement relative to the diagonal and its midpoint.

[0029] The invention also relates to a stove having a weighing device of this type, the stove having a plurality of heating elements which are arranged below the support plate such that the support plate forms the cooking surface of the stove.

[0030] Furthermore, the invention also relates to a piece of furniture, in particular kitchen furniture, having a weighing device of this type. The support plate is preferably arranged on the upper side of the kitchen furniture such that the support plate forms the working surface of the kitchen furniture.

[0031] Finally, the invention also relates to a method for operating a weighing device of this type. The method at least comprises the following steps:

[0032] - generating mechanical vibrations in the support plate by means of the excitation means,

[0033] - measuring at least one spectral characteristic of the vibrations by means of the measurement means, and

[0034] - determining the mass of an object on the support plate by using the at least one spectral characteristic of the vibrations.

[0035] Advantageously, the excitation means can also be used to communicate with the user, for example by generating tactile or acoustic signals for the user by means of the excitation means.

[0036] The invention also relates to a measuring device for a stove, furniture or method according to this specification, the measuring device being suitable for being arranged on the support plate. It at least comprises the following elements:

[0037] - at least one excitation means for generating mechanical vibrations in the support plate, and

[0038] - at least one measurement means for measuring the mechanical vibrations.

[0039] The device unit is configured to:

[0040] - Determining at least one spectral characteristic of the vibration by means of an excitation mechanism and a measurement mechanism, and

[0041] - Using the spectral characteristic to determine the mass of an object.

[0042] Furthermore, the measuring device can for example be configured as a smartphone, a tablet computer, a computer, etc.

[0043] The invention can for example be used to weigh a cooking vessel or its contents on a support plate. The invention can also be used to control a cooking process based on a weight measurement (or a change in weight) and / or to generate instructions for a user. Description of the Drawings

[0044] Further configurations, advantages and applications of the invention result from the following description with reference to the drawings. The drawings are as follows:

[0045] Figure 1 Showing a cross-section of a first embodiment of a stove along Figure 2 line I-I,

[0046] Figure 2 Showing the stove Figure 1 from above,

[0047] Figure 3 Showing a block diagram of several components of a weighing device,

[0048] Figure 4 Showing an example of the value of the lowest resonance frequency f1 according to the mass of a load,

[0049] Figure 5 Showing the lowest resonance frequency according to the mass and radius of a load,

[0050] Figure 6 Showing the second resonance frequency according to the mass and diameter of a load,

[0051] Figure 7 Showing possible values of mass and radius at a given first resonance frequency and second resonance frequency,

[0052] Figure 8 Showing a cross-section of a second embodiment of a stove along Figure 2 line I-I,

[0053] Figure 9 Showing a cross-section of kitchen furniture with a weighing device,

[0054] Figure 10 Showing a diagram for determining an optimized position for an excitation mechanism and a measurement mechanism from a modal analysis of a support plate,

[0055] Figure 11Shows an embodiment of a control device with a neural network, and

[0056] Figure 12 Shows an embodiment in which the excitation mechanism and the measuring mechanism are arranged above the support plate and integrated in the measuring device. Detailed description

[0057] Definition

[0058] The "diameter" of the object to be measured can be understood as the diameter of the contact surface of the object with the support surface, where (ideally) it is assumed that the surface of the support plate and the bottom side of the object are completely flat. As an alternative, this concept can be understood as the "true" diameter seen by the scale.

[0059] The feature that the support plate "is made of glass-ceramics" can be understood as meaning that, apart from possible nameplates, coatings and / or other surface elements, at least 90% of the support plate is made of glass-ceramics.

[0060] The "spectral characteristics" of the vibration describe at least one characteristic of the movement of the support plate when it is excited. Here, this can be, for example, the amplitude or phase at a specific frequency, the frequency of a specific spectral characteristic (such as a peak in the spectrum), the time delay between excitation and response or between the movements at different positions on the support plate, the rise characteristic or decay characteristic in the case of short-term excitation, etc.

[0061] Basic structure

[0062] Figures 1 to 3 Shows a stove having a support plate 1 made of, for example, glass-ceramics and four heating elements 2 below the support plate 1, for example.

[0063] On the bottom side of the support plate 1, a device structure 3 is provided, which houses the electrical components and other mechanical components of the stove. The device structure has a device frame 4, which is fixed to the bottom side of the support plate 1.

[0064] In the shown embodiment, the device frame 4 has the same shape as the contour of the support plate 1, but it is spaced apart from the outer edge 5 of the support plate 1 on all sides, such that the support plate 1 forms a projection 6 that extends horizontally beyond the device frame 4. However, the device frame 4 can also differ from the support plate 1 in terms of its shape.

[0065] The projection 6 can be used to mount the support plate in an opening of a board 7 of a kitchen furniture.

[0066] Advantageously, the device frame 4 is connected to the support plate at a plurality of points on each long side, in particular along the respective entire length, for example by adhesion. Thereby, the device frame 4 forms a defined vibration frame for the vibration movement within the central region of the support plate, which makes the mechanical resonance of the support plate 1 less relevant to the mounting details of the device on the outer edge 5. This is advantageous for the measurement method described below.

[0067] Furthermore, the device frame 4 preferably has a diameter that is at least 80% but at most 98% of that of the support plate 1, such that for all diagonal directions, a relatively large area remains radially inside the device frame, within which the support plate 1 can vibrate substantially freely, but at the same time there are sufficient protrusions 6 available for mounting.

[0068] Advantageously, the support plate 1 should be able to vibrate freely inside the device frame 4 in such a way that, for example, no rigid and bulky components are fixed there, with the exception of the excitation mechanism if necessary.

[0069] Measurement technology

[0070] Regardless of the specific construction of the weighing device (for example, whether the weighing device is a part of a stove or other components), the measurement technology of the present invention is based on the idea of determining at least one mechanical resonance frequency of the support plate 1. Thereby, the mass of the load 10 provided on the support plate can be determined. This will be described in more detail below.

[0071] The support plate 1 has different resonance vibration modes (hereinafter referred to as "eigenmodes" or "modes") for deflections perpendicular to the support plate 1. For example, if it is assumed that in the eigenmode with the lowest natural frequency, no movement occurs in the region of the device frame 4, then in this mode, the center of the plate moves most violently, that is, an antinode is formed in the center of the support plate 1 and nodes are formed along the device frame 4. In the mode with the second lowest frequency, in the case of a rectangular plate, two vibration antinodes with opposite deflections are spaced apart from each other on the longitudinal central axis of the support plate 1, and so on.

[0072] Here, the vibration movement (i.e., deflection) of the support plate 1 in the lowest mode occurs substantially in the vertical direction.

[0073] If the load 10 is placed on the support plate 1 at this time, the resonance frequency usually decreases, and the mode may also change in terms of shape and amplitude distribution. The change is related on the one hand to the mass of the load 10, but on the other hand also to its shape (i.e., to the shape and especially the diameter of the contact surface between the load 10 and the support plate 1) and its position.

[0074] Thus, by measuring at least one or, if necessary, a plurality of resonance frequencies, the mass of the load and possibly further parameters can be measured.

[0075] To perform the corresponding measurement, the weighing device has at least one excitation mechanism 12 and at least one measurement mechanism 14, as Figure 2 shown therein.

[0076] The support plate 1 is caused to vibrate mechanically by means of the excitation mechanism 12, in particular perpendicular to the surface of the support plate 1. The vibration can be measured by means of the measurement mechanism 14.

[0077] The excitation mechanism 12 can for example be an electromechanical hammer which exerts a short impact on the plate. Thereby vibrations are excited in a wide frequency range. Here, the strongest vibration amplitude is generated at the resonance frequency. The vibration amplitude can be measured by spectral analysis of the signal of the measurement mechanism 14, for example by means of Fourier analysis.

[0078] The measurement mechanism 14 can for example be a microphone, or can determine the time-dependent deflection of the support plate at a given point as a capacitive or optical measurement mechanism. The measurement mechanism can in particular be an acceleration sensor.

[0079] In a further embodiment, the excitation mechanism 12 can for example be configured as a mass body which can be excited to vibrate with a desired frequency, or as a loudspeaker by means of which a periodic force can be applied to the support plate 1 at a certain location.

[0080] In this case, the frequency of the excitation mechanism 12 can for example be tuned through a plurality of frequencies, and then the signal of the measurement mechanism 14 is analyzed for each frequency in order to thereby determine the frequency with the strongest vibration amplitude.

[0081] In a further embodiment, a plurality of frequency components can be generated simultaneously by means of the excitation mechanism, in the form of a superimposed signal. Here, for example, it can be the superposition of a plurality of periodic signals, or noise can also be generated, in particular white noise or pink noise. In these cases, the signal of the measurement mechanism can be analyzed by means of spectral analysis, in particular by means of Fourier transform.

[0082] In a further embodiment, the excitation means 12 and the measuring means 14 can be formed by the same component, for example an electric coil arranged near a permanent magnet, where either the coil is connected to the support plate or the permanent magnet is connected to the support plate. A force pulse is applied to the support plate 1 by a short current impulse through the coil, and then the current curve through the coil is measured to analyze the movement of the plate after the force pulse. As an alternative, for example, the excitation means 12 can be operated with a known voltage (or with a known current), and then the current (or voltage) is measured in order to derive a signal for the vibration therefrom.

[0083] Advantageously, the excitation means 12 and the measuring means 14 are at the point on the support plate 1 where the lowest frequency resonance shows violent movement, that is, they are far from the respective vibration nodes. Therefore, they are preferably arranged either exactly or at least within a specific tolerance T on at least one of the diagonals D of the support plate, that is, the spacing between the diagonal and the measuring means 14 should be less than the tolerance T. This tolerance T only accounts for a very small proportion of the shorter side length H of the support plate 1, preferably at most 10% of the side length H.

[0084] Here, the diagonal D can be understood as the connecting line between two opposite corner points of the support plate 1, or if the support plate 1 is connected to the rigid device frame 4 that generates vibration nodes, the length D is the connecting line between two opposite corner points of the device frame 4.

[0085] For the same reason, the spacing D1 of the excitation means 12 from the midpoint of the diagonal D is preferably in the range between 5% and 45% of the length L of the diagonal D, in particular in the range between 25% and 45%. Similarly, the spacing D2 of the measuring means 14 from the midpoint of the diagonal D is preferably in the range between 5% and 45% of the length L of the diagonal D, in particular in the range between 25% and 45%.

[0086] In a particularly preferred embodiment, the excitation means 12 and the measuring means 14 are on different diagonals, as shown for the measuring means 14'' in Figure 2 Here, the position is advantageously chosen such that the operating area 18 of the stove is arranged between the two means 12, 14'', because in the case of a stove, the heating element 2 is usually slightly recessed on the side of the operating area 18. Thereby, it is easier to arrange the means 12, 14'' in a low-temperature area.

[0087] Figure 3Block diagram showing several components of a weighing device used in connection with weighing. In particular, a control device 16 is provided, which is connected to an excitation mechanism 12 and a measuring mechanism 14 via a suitable interface circuit. In addition, there is provided the operation area 18, such as a touch-sensitive screen, to display the mass and / or other parameters if necessary and / or to receive instructions from the user.

[0088] Figure 4 Shows the resonance frequency f1 of the lowest frequency mode of a rectangular support plate 1 made of glass-ceramics, with a width of 910 mm, a length of 514 mm, and a thickness of 4 mm, for load objects of different masses. Here, a container with a diameter of 148 mm has been placed at the center of the support plate 1 and gradually filled with water to increase its mass.

[0089] As can be seen, the resonance frequency f1 decreases as the load increases.

[0090] Thus, the mass can be easily determined from the frequency.

[0091] However, the prerequisite for determining the mass solely from the lowest frequency resonance is that the actual diameter and position of the load object are known.

[0092] For example, if it is assumed that the diameter of the load object also changes, but it is placed at the center of the support plate 1 during each measurement, then the lowest frequency resonance f1 is related to the diameter and the mass. This is illustrated in Figure 5 where "pan radius" represents the radius of the load object, "mass" represents the mass of the load object, and "mode 1" represents the frequency f1.

[0093] In the graph space, the curves of mass versus frequency are shown for different radii. In the "mass" versus "pan radius" plane, the possible value pairs curve is shown as an example for the measured frequency f1 = 45,092 Hz.

[0094] Figure 2 The same diagram is shown, but the second lowest resonance frequency f2 is shown on the vertical axis, and the curve in the "mass" versus "pan radius" plane shows the possible value pairs as an example for the measured frequency f2 = 109,878 Hz.

[0095] If at this time Figure 5 and Figure 6 the two curves in the "mass" versus "pan radius" planes are observed together, then the diagram according to Figure 7 is obtained. This diagram shows that in the device structure of the present invention, in the case of f1 = 45,092 Hz and f2 = 109,878 Hz, the mass is approximately 1.5 kg and the radius is approximately 100 mm.

[0096] This shows that, in addition to the mass, a second parameter can be determined or compensated for from the measurement of at least two resonance frequencies f1, f2, here for example the diameter of the load.

[0097] Quite approximately, the resonance frequency of a given eigenmode depends on the parameters of the mass m, the diameter d, and the position represented by the x- and y-coordinates, for example. In other words, for the frequencies of modes 1, 2, 3, etc., the following applies:

[0098] f1 = F1(m, d, x, y) (1)

[0099] f2 = F2(m, d, x, y)

[0100] f3 = F3(m, d, x, y)

[0101] …

[0102] Here, the functions F1, F2, etc. can be determined, for example, from calibration measurements and / or theoretical calculations. For theoretical calculations, modal analysis can be performed, for example, in the context of finite element simulations.

[0103] (1) represents a system of equations consisting of N independent equations, the left sides of which can be measured separately and whose functions F1, F2…FN are known respectively. The mass m is usually unknown. If the other parameters d, x, and y are known, measuring one mode (N = 1), preferably the mode of f1, is sufficient to determine the mass.

[0104] However, it is also possible to measure more than one mode. In this case, there is an overdetermined system of equations, from which a more accurate result can be determined, for example, by means of adjustment calculations.

[0105] If the diameter d is also unknown, the frequencies of N = 2 or more modes must be measured.

[0106] For example, if, in addition to the diameter d, the position coordinates x and y are also unknown, it is advantageous to measure at least N = 4 modes.

[0107] Preferably, the resonance frequencies of at least N = 2, especially at least N = 3 eigenmodes, are determined and used to determine the mass m.

[0108] Advantageously, the measured resonance frequencies are the lowest resonance frequencies of the support plate. These resonance frequencies are preferably distinguishable from each other and, moreover, correspond to large “wavelengths”, so that the resonance frequencies are less sensitive to position and diameter, if possible.

[0109] It should be noted that, in addition to or instead of the resonance frequency, other characteristics of the vibration of the support plate 1 can also be used for weight measurement, see the later paragraph "Other spectral characteristics and / or analysis".

[0110] Calibration

[0111] In addition to the parameters of the load, the resonance frequency is also related to how the support plate is installed, for example.

[0112] For example, the frequency is related to the installation of the support plate 1 in the corresponding kitchen furniture, especially when the device frame 4 cannot completely decouple the vibration in the protrusion 6 from the vibration in the inner area of the support plate 1.

[0113] Therefore, it is preferably calibrated after the device is installed.

[0114] In a particularly simple embodiment, the control device 16 of the device can be configured, for example, to perform a calibration measurement in the case of a known load m, especially in the no-load state (m = 0).

[0115] For example, in this way, the length L of the diagonal D of the free vibration can be determined as a calibration parameter, and then the functions F1, F2, etc. of Equation 1 can be determined.

[0116] Gross weight measurement and tare weight measurement

[0117] In addition to or instead of this, the control device 16 is configured to perform measurements on an empty container ("tare weight measurement") and a full container ("gross weight measurement"). If the mass of the container is m1 and the mass of the filling (which the user wishes to measure as the net value) is m2, four values f11 and f12 (for f1) and f21 and f22 (for f2) can thus be determined for the first resonance frequency f1 and the second resonance frequency f2:

[0118] f11 = F1(m1, d, x, y) (2)

[0119] f12 = F1 (m1+m2, d, x, y)

[0120] f21 = F2(m1, d, x, y)

[0121] f22 = F2(m1+m2, d, x, y)

[0122] Here, the control device 16 preferably assumes that the position x, y and diameter d of the container do not change between the tare weight measurement and the gross weight measurement.

[0123] In this way, two measurement values can be obtained for each modality, such that additional measurement values are available, which allows the determination of additional unknown parameters or (e.g., through adjustment calculations) more precise measurement of overdetermined parameters.

[0124] Here, the control device 16 can be configured to display to the user after the tare weight measurement that the container must be filled to perform the gross weight measurement, or can be provided with an input device that allows the user to specify whether the measurement is a tare weight measurement or a gross weight measurement.

[0125] Positioning aid, reinforcement area

[0126] As described, the position coordinates x, y are generally unknown. This increases the uncertainty of the measurement and / or a larger number of modalities must be measured.

[0127] Therefore, the weighing device is advantageously equipped with a positioning aid 22 (see Figure 2 ), which marks the nominal position for the object to be measured. Here, for example, it can be concentric rings or similar markings mounted on the support plate 1.

[0128] The positioning aid 22 is advantageously arranged in the center of the support plate 1, because very precise measurements can usually be performed on centered objects. However, the positioning aid can also be arranged slightly further away from the center, for example, a positioning aid can be provided for each "cooking zone" separately.

[0129] In Figure 8 In a further embodiment shown, the positioning aid 22 forms a preferably annular protruding area 24 in the support plate, i.e., an area that protrudes upward from the average height of the upper side of the support plate 1, preferably protruding at least 1 mm.

[0130] This construction has the advantage that the effective contact diameter d can be determined independently of the diameter dimension of the actual load 10 (at least when the actual diameter is greater than d), and the effective contact diameter is used, for example, in equation (1).

[0131] In particular, the diameter d of the protruding area 24 is at least 5 cm but not more than 15 cm, especially not more than 10 cm, for the stable support of common cooking containers, so that it is smaller than most of the common cooking containers.

[0132] The protruding area 24 can also be configured, for example, as a ring or as a discontinuous plurality of sub-areas.

[0133] Instead of or in addition to the positioning aid, the support plate 1 can have a reinforcement area 25a, wherein the support plate 1 has a greater rigidity inside the reinforcement area 25a than outside, preferably at least 50% greater. This reinforcement area constitutes the rated support position of the object. Due to this reinforcement, the mode becomes more independent of the diameter of the object.

[0134] For example, the reinforcement area can be achieved by a thickening 25b of the support plate 1. Here, the thickening 25b is formed integrally with the support plate 1 or installed as an additional structural element, for example by bonding. Advantageously, the thickening 25b is arranged below the support plate 1 so that the upper side of the support plate 1 remains flat.

[0135] Preferably, the diameter of the reinforcement area is at least 10 cm, in particular at least 20 cm, and / or less than 25% of the maximum diameter of the support plate 1.

[0136] Preferably, the center of the support plate is within the reinforcement area 25a.

[0137] As an alternative or in addition, the support plate 1 can have a thinning area 25c that extends around the desired support area for the object. This can also better decouple the mode from the diameter of the object.

[0138] The thickness of the support plate at the position of the thinning area 25c is advantageously less than 75% of the thickness of the support plate 1 inside and outside the thinning area 25c in the radial direction.

[0139] The inner diameter of the thinning area is in turn advantageously at least 10 cm, in particular at least 20 cm, and / or the outer diameter of the thinning area is advantageously at most 25% of the maximum diameter of the support plate 1.

[0140] Preferably, the thinning area 25c extends around the center of the support plate 1.

[0141] A plurality of excitation and / or manipulation mechanisms

[0142] Different modes can be distinguished by their frequencies during measurement. However, this cannot always be ensured in the case of higher modes because, depending on the load, its position and / or its diameter, the modes may also be swapped in the frequency order.

[0143] Therefore, in order to be able to better distinguish the individual modes, it may be advantageous to provide a plurality of measuring mechanisms at different positions on the support plate 1. Thus, for example Figure 2 shows a second measuring mechanism 14', which is arranged at the position where a particular mode has a node, for example on the connecting line between the midpoints of two opposite sides. This can better distinguish the modes and assign them to the corresponding functions Fi in the system of equations (1).

[0144] In the case of a plurality of measuring mechanisms 14, 14', the control device 16 is preferably configured to determine the amplitude ratio and / or the phase shift between the signals of the respective measuring mechanisms at the respective resonance frequencies.

[0145] It is also conceivable that a plurality of excitation mechanisms 12 are provided, which, for example, run in the opposite direction during a first measurement and in the same direction during a further second measurement in order to specifically excite or suppress specific modes.

[0146] Arrangement of the excitation mechanism and the measuring mechanism

[0147] It has been stated above with reference to Figure 2 that the excitation mechanism 12 and / or the measuring mechanism 14 are preferably arranged in a specific area, for example on one or both diagonals of the rectangular support plate 1, since most modes do not have any nodes on the diagonals.

[0148] This consideration will now be generalized slightly.

[0149] If it is assumed that the weighing device is configured to determine the resonance frequencies of a given set of modes, then the excitation mechanism 12 and / or the measuring mechanism 14 should be arranged at locations where the vibration amplitude (deflection amplitude) of all these modes is at least 25% of the maximum vibration amplitude of the respective mode.

[0150] For example, if the control device 16 measures modes 0, 1 and 2 and mode 0 (in the center of the support plate) has the maximum amplitude A0max, mode 1 (in the right and left halves of the support plate) has the maximum amplitude A1max, and mode 2 (in the upper and lower halves of the support plate) has the maximum amplitude A2max, then the deflection amplitude at the location of the excitation mechanism 12 and / or the measuring mechanism 14 should preferably be at least A0max × 0.25 for mode 0, at least A1max × 0.25 for mode 1 and at least A2max × 0.25 for mode 2.

[0151] In other words, the excitation mechanism 12 and / or the measuring mechanism 14 should not be too close to any of the nodal lines of the modes measured by the control device 16.

[0152] This is in Figure 10This is described in more detail there. In that case, the cross-hatched areas show the nodal lines for the respective modes, and it is explained which nodal lines apply to which modes. Thus, depending on the installation, all modes have nodal lines at the edges of the support plate 1 or on the device frame 4. In addition, modes 2 and 4 have nodal lines along the connecting line at the midpoints of the lengths of the longer sides, and modes 3 and 4 have nodal lines along the connecting line at the midpoints of the lengths of the shorter sides. Furthermore, the higher modes 5 and 6, which each form three vibration antinodes along one of the main directions, also have nodal lines at approximately one-third and two-thirds of the length or width of the plate.

[0153] Accordingly, there are regions A1, A2, …, on which all modes have a relatively strong vibration amplitude, i.e., for example, the regions A1 - A4 on the diagonal (the regions corresponding to Figure 2 the positions described), or, for example, the regions A5 - A8 slightly farther from the diagonal. The excitation mechanism 12 and / or the measuring mechanism 14 are advantageously arranged in one of these regions A1 - A8.

[0154] Advantageously, this condition described here is achieved not only for the excitation mechanism 12 but also for the measuring mechanism 14. If there are multiple excitation mechanisms and / or multiple measuring mechanisms, this condition should advantageously be achieved for at least one excitation mechanism or at least one measuring mechanism.

[0155] Other spectral characteristics and / or analysis

[0156] In the above examples, the resonance frequencies of the support plate have been mentioned separately as spectral characteristics. However, it is also possible to use other spectral characteristics of the vibration of the support plate during excitation, i.e., for example, one or more of the following characteristics:

[0157] - The vibration phase at a specific frequency. This especially refers to the relative phase between excitation and vibration at a given frequency. As an alternative or in addition, it can also be the relative phase between the vibrations at different locations on the support plate 1 at the same frequency.

[0158] - The amplitude or amplitude ratio. Here, this can be, for example, the absolute vibration amplitude at a given frequency or in the case of resonance, and / or can be the relative vibration at different frequencies and / or at different locations on the support plate 1.

[0159] - The spectral width (e.g., FWHM) of at least one resonance.

[0160] - The spectrum at low-amplitude positions, e.g., one or more minima in the Fourier spectrum of the vibration.

[0161] - The ratio between the maximum (peak) and the minimum (valley).

[0162] - At one or more fixed frequencies, one or more amplitudes in the spectrum.

[0163] - The intersection points of the Fourier spectrum and a given curve.

[0164] - The decay time of the excitation.

[0165] Generally, any characteristic of the vibration spectrum can be used for analysis.

[0166] A particularly advantageous embodiment of the control device 16 is shown in Figure 11 Here, the control device 16 has a spectrum analyzer 30, which determines a plurality of spectral components of the signal of at least one measuring mechanism 14.

[0167] The spectrum analyzer 30 can, for example, perform a Fourier analysis. In this case, the Fourier components of the signal are calculated, in particular the complex Fourier components, which also indicate the phase of each component. In particular, the spectrum analyzer can be configured as an FFT or DFT unit.

[0168] In addition hereto or alternatively thereto, the spectrum analyzer can, for example, use a discrete Laplace transform or can use other mathematical operations (such as wavelet transforms) that can generate components related to the spectrum.

[0169] The parameters that describe the spectral characteristics of the vibration of the support plate generated by the spectrum analyzer 30 are analyzed in a suitable manner. For example, one or more peaks of the spectrum can be detected to determine the resonance frequency and analyzed in the above manner.

[0170] In another advantageous embodiment, the data generated by the spectrum analyzer 30 are transmitted to a deep neural network 32, which preferably has a depth greater than 2. The network 32 has one, two or more output terminals, which correspond to the parameters to be determined by the weighing device, such as the weight g and the diameter d of the object.

[0171] The neural network 32 is preferably a "feed fordward" neural network.

[0172] The network 32 is trained by means of calibration measurements, in which the parameters of the load (such as the diameter and position of the object on the support plate) are changed. The signal of the measuring mechanism 14 is recorded for each such parameter set and the input values of the neural network 32 are calculated therefrom by means of the spectrum analyzer 30.

[0173] It is also possible to use numerical simulation instead of calibration measurement for training, and within the scope of numerical simulation, the parameters of the load are changed, but then, for example, with the help of "finite element simulation", the numerical values of the input parameters (such as Fourier components) of the network are determined therefrom.

[0174] More generally, the control device 16 of the weighing device advantageously has a neural network 32, to which the spectral characteristics measured by the measuring mechanism are transmitted, in particular the Fourier spectrum of the signal of the measuring mechanism 14, and the neural network is trained to determine therefrom the mass of the object on the support plate and, if necessary, other parameters of the object.

[0175] Components of this type can process a large number of spectral characteristics and obtain more accurate results therefrom.

[0176] With the help of a spectrum analyzer, it is also possible to measure a plurality of spectra within the scope of the measurement process. This is particularly beneficial if the excitation mechanism 12 performs a frequency scan either continuously or step by step. In this case, the spectra of the vibrations can be detected separately for each excitation frequency or excitation spectrum. Then, for example, these spectra can be combined, for example with the help of a "Peak-Hold" algorithm. Here, each of the spectra in the spectra can also be ignored or weighted differently, for example. It is also possible to directly analyze each spectrum, for example with the help of the above method.

[0177] Tactile or acoustic feedback

[0178] The excitation mechanism 12 that generates mechanical vibrations in the support plate 1 can be used not only for the weighing process but also for other applications.

[0179] In particular, the control device 16 can be configured to use the excitation mechanism 12 as an output device for communicating with the user, in particular for communicating the state of the device or responding to the user's operation.

[0180] For this purpose, the control device can in particular use at least one of the following communication methods:

[0181] - For example, if the user touches the support plate 1, the control device 16 can control the excitation mechanism 12 to generate tactile feedback for the user. This is particularly advantageous if an operating area 18 (see Figure 2 ) is provided on the support plate 1, for example in the form of one or more touch-sensitive areas. To generate tactile feedback, the excitation mechanism 12 is advantageously controlled to generate short mechanical pulses, for example between 0.05 and 1 second.

[0182] The control device 16 can control the excitation mechanism 12 for generating acoustic feedback for the user. To this end, the excitation mechanism 12 is excited to generate audible vibrations, in particular vibrations in a frequency range between 100 and 10,000 Hz.

[0183] Accordingly, the control device is advantageously designed to use the excitation device 12 as an output means for communicating with a user. In particular, the control device 16 can be designed to generate an acoustic or haptic feedback in the support plate 1 .

[0184] Therefore, within the scope of the operating method, a step is advantageously provided in which the excitation device is used for communication with the user. For this purpose, in particular, haptic and / or acoustic signals can be generated in the support plate 1 by means of the excitation device 12 .

[0185] Arrangement of excitation and measurement mechanisms

[0186] The excitation mechanism 12 and the measuring mechanism 14 can be fixed from below to the support plate 1 , thereby protecting them from damage from above.

[0187] Figure 12 An embodiment is shown in which the excitation and measuring devices 12 , 14 are arranged, for example, as at least one device unit from above on the support plate 1 .

[0188] In the embodiment shown, the excitation mechanism and the measuring mechanism 12, 14 are configured as a measuring device 40 and are shown as a single component by way of example, and they are integrated in a common device unit. However, they can also be implemented as two separate components, in which case they can be arranged in one or more device units.

[0189] The arrangement of the excitation and measuring devices 12 , 14 also enables, for example, a subsequent or temporary positioning of the measuring device according to the invention on the support plate 1 .

[0190] In particular, the measuring device 40 can be configured as a unit separate from the support plate 1, which can be placed on the support plate 1 as required, for example. In particular, the measuring device 40 can be, for example, a smartphone, which is programmed via an application to perform the method described here. In this case, for example, a loudspeaker and / or a vibration sensor of the smartphone can be used as the excitation mechanism 12, while a microphone and / or an acceleration sensor can be used as the measuring mechanism 14. It is also conceivable to provide separate excitation mechanisms and / or measuring mechanisms 12, 14 for wireless or wired connection to a smartphone or tablet.

[0191] Notes

[0192] Advantageously, the excitation does not occur at all frequencies, but only at frequencies where important and analyzable resonances are expected to be present. Thereby, for example, individual modes can be excited in a targeted manner.

[0193] In the above embodiments, a stove with four heating elements 2 is shown. However, the number of heating elements can be changed. In particular, a two-dimensional array of heating elements that can be freely configured can also be provided, in which shaped heating zones can be activated in relation to the cooking load. The corresponding devices are known to those skilled in the art.

[0194] Advantageously, the support plate 1 has a rectangular shape. However, for example, circular, oval or polygonal shapes can also be considered.

[0195] As described above, it is advantageous to integrate the weighing device into the stove. However, it can also be arranged in any piece of furniture 26, for example on its upper side as a work surface, as Figure 9 explained. Advantageously, the furniture 26 is kitchen furniture.

[0196] The support plate 1 is advantageously made of glass ceramic because this material is strong and / or also heat-resistant.

[0197] Preferably, the support plate has an extension dimension of at least 30 cm in each horizontal direction. Thereby, a greater independence from the corresponding diameters and positions of commonly used cooking vessels is obtained.

[0198] In order to perform calibration measurements and / or in order to train the neural network, a ring with a known diameter can alternatively be arranged between the support plate 1 and the corresponding reference object. Thereby, a defined support dimension can be achieved.

[0199] When analyzing the signals of the measuring mechanism 14, specific frequency ranges can be selectively masked, for example when it is shown in the context of calibration that these frequency ranges are mainly dominated by the arrangement of the support plate 1 in the surrounding furniture.

[0200] For the analysis, the convolution between the signals of the excitation mechanism 12 and the measuring mechanism 14 can also be calculated, for example by multiplication in the Fourier space. Thereby, for example, harmonic or other source signals can be masked.

[0201] Furthermore, the analysis can also be performed with a lock-in amplifier, which filters the signal of the measuring element 14 with the excitation mechanism and provides the phase and amplitude at the excitation signal frequency.

[0202] In order to calibrate the device, for example, a standard weight of known size can also be provided, which the user or installer places on one or more parts of the support plate 1, and then test measurements are performed by the device control device.

[0203] Although the preferred embodiments of the present invention are described in this application, it should be clearly pointed out that the present invention is not limited to these embodiments and can also be implemented in other ways within the scope of the present invention.

Claims

1. A weighing device for weighing an object, the weighing device having a support plate (1) for supporting the object and a control device (16), characterized in that, the weighing device has - at least one excitation mechanism (12) for generating mechanical vibrations in the support plate (1), and - at least one measuring mechanism (14) for measuring the mechanical vibrations, wherein the weighing device is configured to: determine at least one spectral characteristic of the vibrations by means of the excitation mechanism (12) and the measuring mechanism (14), and determine the mass of the object using the spectral characteristic, wherein the control device (16) is configured to: determine at least two different spectral characteristics of the vibrations, and determine the mass of the object using the at least two spectral characteristics and determine or rule out at least one further unknown parameter of the object.

2. The weighing device according to claim 1, wherein, the spectral characteristic includes at least one resonance frequency of the support plate (1).

3. The weighing device according to claim 1 or 2, wherein, the weighing device is a weighing device for the kitchen.

4. The weighing device according to claim 1 or 2, wherein, the control device (16) is configured to, determine the resonance frequencies of at least two eigenmodes of the support plate (1), and determine the mass of the object using the resonance frequencies of the at least two eigenmodes.

5. The weighing device according to claim 1 or 2, wherein, the control device (16) is configured to, determine the resonance frequencies of at least three eigenmodes, and determine the mass of the object using the resonance frequencies of the at least three eigenmodes.

6. The weighing device according to claim 4, wherein, the measured resonance frequency is the lowest resonance frequency of the support plate (1).

7. The weighing device according to claim 1 or 2, wherein, the at least one further unknown parameter is the diameter of the object on the support plate (1) and / or at least one position parameter.

8. The weighing device according to claim 1 or 2, wherein, the support plate (1) has an extension dimension of at least 30 cm in each direction and / or the support plate (1) is made of glass-ceramics.

9. The weighing device according to claim 1 or 2, wherein, the weighing device is configured to determine the spectral characteristics of a given set of modes, and the excitation mechanism (12) and / or the measuring mechanism (14) is arranged on a part of the support plate (1) where the vibration amplitude of all modes in the set of modes is at least 25% of the maximum vibration amplitude of the corresponding mode.

10. The weighing device according to claim 1 or 2, wherein, The support plate (1) is rectangular or square and the excitation mechanism (12) and / or the measuring mechanism (14) are arranged on at least one diagonal D of the support plate (1) within a tolerance T, where the tolerance T is at most 10% of the shorter side length H of the support plate (1), and the distance D1 of the excitation mechanism (12) from the midpoint of the diagonal D and / or the distance D2 of the measuring mechanism (14) from the midpoint of the diagonal D are in the range between 5% and 45% of the length L of the diagonal D.

11. The weighing device according to claim 10, wherein, the excitation mechanism (12) and the measuring mechanism are arranged on different diagonals D, and an operating area is provided below the support plate (1) between the excitation mechanism (12) and the measuring mechanism.

12. The weighing device according to claim 1 or 2, wherein, the weighing device has a plurality of measuring mechanisms at different positions.

13. The weighing device according to claim 12, wherein, the control device (16) is configured to determine the amplitude ratio and / or phase shift between the signals of the measuring mechanisms at the resonance frequency.

14. The weighing device according to claim 1 or 2, the weighing device having a device frame (4) which is fixed to the bottom side of the support plate (1) spaced apart from the outer edge (5) of the support plate (1) on all sides.

15. The weighing device according to claim 1 or 2, wherein, the control device (16) of the weighing device is configured to determine at least one calibration parameter in the case of a known load.

16. The weighing device according to claim 1 or 2, wherein, the control device (16) of the weighing device is configured to perform gross weight measurement and tare weight measurement on the same container.

17. The weighing device according to claim 1 or 2, the weighing device having a positioning aid device (22) for positioning an object on the support plate (1).

18. The weighing device according to claim 17, wherein, the positioning aid device (22) forms a protruding area (24) on the support plate (1).

19. The weighing device according to claim 1 or 2, wherein, the support plate (1) has a strengthening area (25a), wherein the support plate (1) is more rigid inside the strengthening area (25a) than outside.

20. The weighing device according to claim 1 or 2, wherein, the support plate (1) has a thinning area (25c) which extends around the desired support area for the object.

21. The weighing device according to claim 1 or 2, wherein, the control device (16) has a neural network (32), the spectral characteristics of the signals of the measuring mechanism (14) are transmitted to the neural network, and the neural network is trained in order to thereby determine at least the mass of the object on the support plate (1).

22. The weighing device according to claim 1 or 2, wherein, the control device (16) is configured to use the excitation mechanism (12) as an output device for communication with the user.

23. The weighing device according to claim 22, wherein, the control device (16) is configured to generate an acoustic or tactile feedback in the support plate (1).

24. A stove having the weighing device according to claim 1 or 2, wherein, the stove has a plurality of heating elements (2) arranged below the support plate (1) such that the support plate (1) forms the cooking surface of the stove.

25. Furniture having the weighing device according to claim 1 or 2.

26. A method for operating the weighing device according to claim 1 or 2, the method comprising at least the following steps: - generating mechanical vibrations in the support plate (1) by means of an excitation mechanism (12), - measuring at least one spectral characteristic of the vibrations by means of a measuring mechanism (14), and - determining the mass of an object on the support plate (1) using the at least one spectral characteristic of the vibrations.

27. The method according to claim 26, further comprising the following steps: - using the excitation mechanism (12) for communication with a user.

28. The method according to claim 27, wherein, for communication with the user, a tactile and / or acoustic signal is generated in the support plate (1) by means of the excitation mechanism (12).

29. A measuring device (40) for the weighing device according to claim 1 or 2, the stove according to claim 24, the furniture according to claim 25 or the method according to claim 26, the measuring device being adapted to be arranged on the support plate (1), the measuring device comprising - at least one excitation mechanism (12) for generating mechanical vibrations in the support plate (1), and - at least one measuring mechanism (14) for measuring the mechanical vibrations, wherein, the measuring device (40) is configured to determine at least one spectral characteristic of the vibrations by means of the excitation mechanism (12) and the measuring mechanism (14), and determine the mass of an object using the spectral characteristic, wherein the measuring device (40) is configured to: determine at least two different spectral characteristics of the vibrations, and determine the mass of an object using the at least two spectral characteristics.

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