Determining the amount of coffee beans needed for a coffee grinder

Abstract

A method for determining a supply (115) of coffee beans (120) for a coffee grinder (100) comprises steps of recording a series of time-spaced current consumptions of an electric drive motor of the coffee grinder (100) during a grinding process; determining a series of probabilities with which the supply (115) is exhausted, based on the determined current consumptions, by means of a feedback neural network; and determining that the supply (115) is exhausted if the series of probabilities has a predetermined property.

Description

[0001] The present invention relates to determining the supply of coffee beans for a coffee grinder. In particular, the invention relates to determining whether there are still coffee beans available for the coffee grinder.

[0002] A coffee grinder contains coffee beans in its hopper. The grinder can be part of an automatic coffee machine designed to prepare various coffee specialties automatically or semi-automatically. The grinder is powered by an electric motor. To determine whether the supply of coffee beans is exhausted, the electric current flowing through the motor is measured. An average current over a predetermined number of previous grinding cycles is compared to the current current. If the difference between the two values ​​exceeds a predetermined threshold, the grinder concludes that the supply is exhausted.

[0003] This approach is easy to implement, but it doesn't always provide an accurate reading. Furthermore, it can take a relatively long time to determine when the supply is depleted, so a user might conclude that the supply is exhausted simply from the change in the operating noise of the empty coffee grinder. This could lead them to believe that the supply reading is incorrect.

[0004] One of the problems underlying the present invention is to provide an improved technique for determining the quantity of coffee beans for a coffee grinder. This problem is achieved by the subject matter of the independent claims. Dependent claims describe preferred embodiments.

[0005] A method for determining a supply of coffee beans for a coffee grinder comprises steps of recording a series of time-spaced current consumptions of an electric drive motor of the coffee grinder during a grinding process; determining a series of probabilities with which the supply is exhausted, based on the determined current consumptions, using a feedback neural network; and determining that the supply is exhausted if the series of probabilities exhibits a predetermined property.

[0006] By employing a machine learning technique, a significantly more accurate determination of whether coffee beans are still available in the coffee machine can be achieved. This determination can also be made faster than with prior art methods, allowing a signal indicating a depleted supply to be provided with minimal delay after the supply is exhausted. The signal can be directed to a user of the coffee grinder, prompting them to replenish the coffee bean supply. Alternatively, the signal can be directed to a control device of the coffee grinder, which can then, for example, switch off the drive motor in response. The coffee grinder is preferably part of a coffee machine, particularly an automatic coffee machine.

[0007] The proposed feedback neural network can also be called a recurrent neural network (RNN). Unlike a feedforward network, an RNN includes connections from neurons in one layer to neurons in the same or a previous layer. A recurrent neural network has a memory because it uses information from previous inputs to influence current input and output. For example, past observations of the electric current through the drive motor can be better taken into account. This allows for improved determination of probabilities indicating the likelihood of the supply running out.

[0008] To determine whether the supply is exhausted based on a series of probabilities, different approaches can be used. It's important to note that multiple properties can be checked and the results combined. Typically, an OR operator is used, determining that the supply is exhausted if the series—or a value within the series—exhibits at least one of several predetermined properties. Alternatively, multiple results can be combined using AND, requiring all predetermined properties to be present for the supply to be considered exhausted.

[0009] In one embodiment, the property includes exceeding a predetermined threshold. For example, if a certain probability exceeds approximately 0.7, it can be determined that the supply is exhausted. The threshold can also be chosen higher to better prevent incorrect determinations of exhaustion. The threshold can easily be determined empirically based on observed probabilities.

[0010] In another embodiment, the feature includes the property that a gradient of the series exceeds a predetermined value. For example, this property might exist if the gradient of several probabilities exceeds approximately 0.6. Typically, more than two probabilities are used to form the gradient in order to achieve a certain level of noise immunity. Optionally, the feature can include the requirement that the specified gradient is present for at least a predetermined time. For example, the gradient over the past two seconds can be determined and compared with the threshold value.

[0011] The feedback neural network preferably incorporates an LSTM (Long Term Short Memory) network. An LSTM can solve the vanishing gradient problem of conventional RNNs. Its relative insensitivity to gap lengths in values ​​is a significant advantage over other RNNs, hidden Markov models, and other sequence learning methods. It aims to provide a short-term memory for RNNs that can theoretically persist for an unlimited number of determinations, thus representing a "long short-term memory" suitable for classifying, processing, or predicting data based on time series. Using the LSTM can greatly improve the detection of the depletion of the coffee bean supply within a series of determined stream values.

[0012] In a particularly preferred embodiment, the network comprises a layer with four LSTM cells. Each cell can be supplied with a specific electrical current as its input value. The output values ​​of each cell can be aggregated in a final layer (dense layer). This final layer can also be referred to as a fully connected layer and preferably has sigmoidal activation. The layer is preferably configured to represent input data abstractly. Through the aggregation performed by this layer, the LSTM readings can be summarized, weighted, and evaluated to determine the probability of the supply being depleted.

[0013] The feedback neural network is preferably trained on the basis of grinding processes in which the supply is exhausted during the grinding process, is exhausted from the start, or is not exhausted at all. A training method is proposed for this purpose, in which a number of grinding processes are carried out with varying quantities of coffee beans.

[0014] For example, the supply can be deliberately set so small that it is insufficient to complete a typical grinding process. If, for instance, approximately 12 g of coffee beans are ground in one cycle, the supply can be varied in different runs with approximately 3 g, 6 g, and 9 g to trigger depletion at different points during the grinding process. Larger or smaller numbers of different quantities are also possible. It is also advantageous to conduct grinding processes with both an exhausted and an unlimited supply. It is recommended to use roughly the same amount of training data for each quantity.

[0015] In a further refinement, the grinding processes are carried out with different grind sizes. Typically, approximately three different grind sizes (fine / medium / coarse) are sufficient to train the RNN across an expected range of applications. A different number of grind sizes is also possible. The grind sizes used are preferably distributed relatively evenly throughout the training data.

[0016] Optionally, training data can be collected and provided under other influencing factors to reflect, for example, different grinders, grinders with different tolerances or wear levels, different coffee beans, or different environmental conditions.

[0017] It has been shown that accurate detection of fatigue can be achieved using a randomized neural network (RNN) trained on approximately 100 datasets. Using a larger number of datasets may lead to more accurate detections. Suitable training data can be systematically provided as described. The effort required to provide the training data is manageable. The quality of the detection using the RNN can be determined based on additional training data. Ideally, roughly the same amount of data should be used for quality assessment as for training.

[0018] According to a further aspect of the present invention, a control device for a coffee grinder comprises a sensor for detecting the current consumption of an electric drive motor of the coffee grinder; and a processing unit. The processing unit is configured to detect a series of time-spaced current consumptions of the drive motor during a grinding process; to determine, based on the determined current consumptions, a series of probabilities with which the supply is exhausted by means of a feedback neural network; and to determine that the supply is exhausted if the series of probabilities exhibits a predetermined property.

[0019] The processing equipment may be configured to partially or completely execute a method described herein. For this purpose, the processing equipment may be electronic and may, for example, include a programmable microcomputer or microcontroller. The method may be in the form of a computer program product containing program code. The computer program product may also be stored on a computer-readable data carrier. Features or advantages of the method may be transferred to the equipment and vice versa.

[0020] The control device may further include an output device for providing a notification of a depleted supply. The output device may be directed at a user of the device and may, for example, include a visual, audible, and / or haptic signal. Furthermore, the output device may include an interface that leads to another control device. The notification may be provided in the form of an electrical or logical signal.

[0021] According to yet another aspect of the invention, a coffee grinder comprises a control device as described herein. The coffee grinder can be part of a coffee machine, which is preferably configured to grind and brew coffee beans semi- or fully automatically in order to provide a coffee specialty.

[0022] The invention will now be described in more detail with reference to the accompanying figures, in which: Fig.1 a coffee grinder in a coffee machine; Fig. 2. A control device for a coffee grinder and a method for determining whether a supply of coffee beans for a coffee grinder is exhausted; and Fig. 3 an exemplary presentation of recognitions of exhaustion.

[0023] Fig.Figure 1 shows a schematic representation of a coffee grinder 100. The coffee grinder 100 can be part of a coffee machine 105, which preferably operates automatically to prepare a coffee beverage. The coffee grinder 100 comprises a grinding mechanism 110, which is supplied with coffee beans 120 from a container 115. An electric drive motor 125 is provided for driving the grinding mechanism 110. The drive motor 125 is controlled by a control unit 130, the control of which can, in particular, include switching the drive motor 125 on and off. In one embodiment, the drive motor 125 is switched off after a predetermined time has elapsed since it was switched on. The duration can depend on a grind setting that can be adjusted on the grinding mechanism 110. In another embodiment, the drive motor 125 is switched off when a predetermined quantity of coffee beans 120 has been ground into coffee powder.when a predetermined amount of coffee powder has been provided.

[0024] The current draw of the drive motor 125 can be determined using a sensor 135. In this case, the sensor 135 is implemented as a series resistor (shunt) in a current line of the drive motor 125. In different embodiments, the drive motor 125 is operated with either direct or alternating current.

[0025] A control device 140 is configured to determine, based on a series of specific currents flowing through the drive motor 125, whether the supply of coffee beans 120 is exhausted or not. A result of this determination can be provided by means of an output device 145. The output device 145 can, for example, include a signal light. Alternatively, a message can be displayed on a graphic, symbolic, or textual display when the supply is exhausted.

[0026] Fig.Figure 2 shows a flowchart of a process 200 for determining whether the supply of coffee beans 120 in the coffee machine 100 is exhausted. The process steps shown can be carried out by functional blocks, which are preferably formed by the processing unit 140.

[0027] In step 205, a current can be measured or a measured value recorded. The current can be determined, for example, on an AC-powered drive motor 125 by determining an average current for each half-cycle. The current can be recorded as a voltage value at the sensor 135. Preferably, the current is digitized to facilitate further processing. Current measurements are preferably provided at regular time intervals. A provided value can correspond to an average of several measurements.

[0028] In step 210, a specific current value is applied to a layer of four parallel-connected LSTMs 215-230. The LSTMs 215-230 are trained to detect a current transition indicating that the supply of coffee beans 120 is exhausted. The outputs of the LSTMs 215-230 are aggregated in step 235. A dense layer can be used for this purpose. Based on the output signals of the LSTMs 215-230, the final layer determines a probability value that the current current value, or a series of recently determined current values, indicates that the supply of coffee beans 120 for the coffee grinder 100 is exhausted. For each received current value, the final layer preferentially provides a probability value, so that a series of probability values ​​is provided corresponding to the series of current values.

[0029] In step 240, a probability value or a sequence of a predetermined number of probability values ​​can be examined for the presence of a predetermined property. A first exemplary property concerns the exceeding of a predetermined threshold by a probability value. A second exemplary property concerns a gradient of a predetermined magnitude over a predetermined number of probability values. Several specific properties can be combined using Boolean algebra in a predetermined manner to provide a binary parameter. The parameter can take a first value indicating that the supply is exhausted, or a second value indicating that the supply is not exhausted.

[0030] The specified parameter can be provided by means of output device 145.

[0031] Fig.Figure 3 shows an exemplary diagram 300 of exhaustion detections. Time is plotted horizontally and probability vertically. Diagram 300 relates to a grinding process of a predetermined quantity of coffee beans 120, where the container 115 does not contain enough beans 120 to complete the grinding process. The supply of coffee beans 120 is therefore exhausted during the grinding process. Diagram 300 is based on 15 exemplary grinding processes under identical conditions.

[0032] In the lower section of diagram 300, some initial curves 305 are shown, corresponding to specific current values ​​during a grinding process. For the initial curves 305, the magnitude of an electric current in A is plotted in the vertical direction.

[0033] A second sequence 310 shows a determination carried out by a neutral human observer. This second sequence 310 serves as a reference in the following analysis, allowing us to determine how quickly another determination arrives at the same result. The observer can make the determination, for example, based on visual inspection or the sound produced by the grinding mechanism 110.

[0034] A third curve 315 reflects a determination according to the state of the art. In diagram 300, a difference is determined between a moving average of current values ​​and a predetermined constant current value. If the difference is greater than a further threshold value, it is concluded that the supply is exhausted.

[0035] A fourth curve 320 shows a determination using an RNN described herein with respect to an absolute threshold value. A fifth curve 325 shows a corresponding determination with respect to a predetermined gradient.

[0036] It can be seen that the determinations 320 and 325 using RNN occur significantly earlier than those using the prior art method 315. While method 315 determines exhaustion with a delay of approximately 2.5 s, the correct determination according to method 325 occurs after approximately 0.6 s, and according to method 320 even after approximately 0.55 s. Thus, the determination presented here is approximately 1.9 s faster than the known technique. The detection method 325, based on the gradient, triggers even earlier than the detection method 320 with respect to the threshold value.

[0037] The following table shows the reliability of the determination proposed herein. In an exemplary dataset of 45 grinding processes, the prior art determination 315 missed 30 out of 135 depletions, corresponding to an accuracy of only 78%. If the supply is depleted in the last quarter of the grinding process (9g initial quantity), the accuracy deteriorates further to approximately 40%. If the container 115 is already empty at the beginning of the grinding process, depletion cannot be detected at all in this way.

[0038] The RNN model presented here, however, missed only a single empty bean container, which corresponds to a detection accuracy of 99%. In the worst-case scenario, the RNN model detects an empty container 115 after approximately 1.7 seconds. Neither the RNN model nor the known model produces false detections of an exhausted supply. category Label (ideal) Determination according to the state of the art Determination using RNN and absolute threshold Determination using RNN and gradient unrecognized - 0 0 0 Average detection time [s] 3,4 4,8 3,7 3,6 Standard deviation detection time - 0,64 0,36 0,43

[0039] Of course, both criteria can also be evaluated in combination, so that exhaustion, which cannot initially be detected on the basis of the gradient, can be detected on the basis of the threshold. Reference sign 100 coffee grinder 105 Coffee machine 110 grinder 115 containers 120 coffee beans 125 drive motor 130 control unit 135 Sensor 140 Control device 145 Dispensing device 200 procedures 205 Measuring current 215 first LSTM 220 second LSTM 225 third LSTM 230 fourth LSTM 235 last shift 240 Determine property 300 illustration 305 first course: based on a current value 310 second course: by visual inspection 315 Third course: Determination according to the state of the art 320 fourth course: RNN with absolute threshold 325 fifth course: RNN with gradient

Claims

[1] Method (200) for determining a supply (115) of coffee beans (120) for a coffee grinder (100), wherein the method (200) comprises the following steps: - Recording (205) a series of time-spaced current consumptions of an electric drive motor (125) of the coffee grinder (100) during a grinding process; - Determining (215-235) a series of probabilities with which the supply (115) is exhausted, based on the determined current inputs using a feedback neural network; and - Determine (240) that the supply (115) is exhausted if the series of probabilities has a predetermined property. [2] Method (200) according to claim 1, wherein the property comprises exceeding a predetermined threshold. [3] Method (200) according to claim 1 or 2 wherein the feature comprises that a gradient of the series exceeds a predetermined value. [4] Method (200) according to claim 3, wherein the increase is over a predetermined time. [5] Method (200) according to one of the preceding claims, wherein the feedback neural network comprises an LSTM (215-230). [6] Method (200) according to claim 5, wherein the network comprises a layer with four LSTM cells (215-230). [7] Method (200) according to claim 5 or 6, wherein the network comprises a final layer whose inputs are connected to the outputs of all LSTM cells (215-230). [8] Method (200) according to any of the preceding claims, wherein the feedback neural network is trained on the basis of milling operations in which the supply (115) is exhausted during the milling process, is exhausted from the beginning or is not exhausted at all. [9] Method (200) according to claim 8, wherein the grinding processes are carried out with different degrees of grinding. [10] Control device (140) for a coffee grinder (100), the control device comprising the following: - a sensor for detecting the current consumption of an electric drive motor (125) of the coffee grinder (100); and - a processing device configured to record a series of time-spaced current consumptions of the drive motor (125) during a grinding process; to determine, on the basis of the determined current consumptions, a series of probabilities with which the supply (115) is exhausted by means of a feedback neural network; and to determine that the supply (115) is exhausted if the series of probabilities exhibits a predetermined property. [11] Control device (140) according to claim 10, further comprising an output device (145) for providing a notification of an exhausted supply (115). [12] Coffee grinder (100) comprising a control device (140) according to claim 10 of the 11th. [13] Coffee machine (105) comprising a coffee grinder (100) according to claim 12.

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