Device for detecting and evaluating particles

Abstract

The invention relates to a device for detecting and evaluating particles, in particular in a suction flow of a vacuum cleaner, comprising a light source (34), in particular an infrared LED (35), which is designed to emit a light beam along an optical path (39) and through a measuring space (38); and a light sensor (36) which is designed to receive the light beam after it has passed through the measuring space, wherein the light sensor (36) emits an analogue measuring signal. The invention is characterised by an analogue-to-digital converter (64) designed to convert the analogue measuring signal into time-discrete digital measurement values; a buffer memory (68) designed to temporarily store a predefined number of measurement values; a frequency evaluation unit (74) connected to the buffer memory and having: a frequency transformation unit (90) designed to break down the time-discrete measurement values from the buffer memory into frequency spectrum values of a predefined number (n1) of frequency ranges; and first weighting and summation unit (92) designed to multiply the number of n1 frequency spectrum values each by a first weighting value and to add the weighted n1 frequency spectrum values so as to obtain a first weighted sum value; and a transmission unit (72) designed to provide a digital output signal of the frequency evaluation unit at a digital output (73) as a digital output value for transmission.

Description

Device for detecting and evaluating particles

[0001] The present invention relates to a device for detecting and evaluating particles, particularly in the suction flow of a vacuum cleaner, comprising a light source, in particular an infrared LED, configured to emit a light beam along an optical path and through a measuring chamber; and a light sensor configured to receive the light beam after it has passed through the measuring chamber, the light sensor outputting an analog measurement signal. The invention further relates to a method for detecting and evaluating particles. Finally, the invention relates to a vacuum cleaner with such a device.

[0002] The applicant has previously used various dust sensors in vacuum cleaners to detect the amount of particles in the vacuum cleaner's suction flow and then display this information to the user. These sensors typically employed analog evaluation circuits with direct control of an LED. An optically operating dust sensor is known, for example, from DE 38 03 824 C2.

[0003] In addition to optical dust sensors, sensors using piezoelectric components for dust detection are also available on the market. DE102009005598 A1 discloses such a dust sensor and an evaluation circuit for processing the measurement signal. One disadvantage of these dust sensors is that they are located in the suction flow and thus obstruct it. Furthermore, particles sucked in can become lodged on the dust sensor, for example, and further impede the suction flow. Finally, the measurement result of these dust sensors is not independent of the suction power, with lower suction power tending to lead to poorer results. This would be disadvantageous, for example, when used in robotic vacuum cleaners, as these operate with small batteries and therefore require lower suction power.

[0004] Although existing solutions have proven effective in a few specific application areas, they lack the flexibility for broader, more comprehensive use. Furthermore, they are expensive and difficult to integrate into modern digital systems.

[0005] Against this background, the object of the invention is to further develop a device of the type mentioned above in such a way that it can be manufactured cost-effectively and adapted flexibly to different areas of application.

[0006] This problem is solved by the device defined in claim 1 for detecting and evaluating particles, in particular in a suction stream of a vacuum cleaner.

[0007] The device according to the invention comprises an analog-to-digital converter designed to convert the analog measurement signal into discrete-time digital measured values; an intermediate memory designed to temporarily store a predefined number of measured values; a frequency evaluation device connected to the intermediate memory and comprising: a frequency transformation device designed to decompose the discrete-time measured values ​​from the intermediate memory into frequency spectrum values ​​of a predefined number n1 of frequency ranges; and a first weighting and summing device designed to determine the number of n1 frequency spectrum values. to multiply each value by a first weighting value and to add the weighted n1 frequency spectrum values ​​to obtain a first weighted sum value; and a transmission device designed to provide a digital output value of the frequency evaluation device at a digital output for transmission.

[0008] The device according to the invention has the advantage that, due to its digital design, it is cost-effective and can be flexibly integrated into various vacuum cleaners. Signal evaluation is performed entirely digitally, so that the evaluation process can be easily adapted using freely programmable parameters. The result of the evaluation is provided by the transmission device in digital form, so that another control device, e.g., in a vacuum cleaner, can take over the result and use it for further control purposes.

[0009] Furthermore, by evaluating different frequency ranges, an evaluation of the particle size can be made, whereby the weighting allows for adaptation to the application area.

[0010] The problem is thus completely solved.

[0011] In a preferred further training, the frequency transformation device has a unit for carrying out the Görzel algorithm.

[0012] The advantage of this algorithm is that it requires less computing power than, for example, an FFT (Fast Fourier Transform) method.

[0013] For preferred further training, the first n1 weighting values ​​can be set.

[0014] This has the advantage of improving flexibility and adaptability.

[0015] In a preferred further training process, a first low-pass filter is provided, to which the first weighted sum value is fed.

[0016] This measure has the advantage of allowing for a certain smoothing and thus an improvement of the evaluation result.

[0017] In a preferred embodiment, the device has an amplitude evaluation unit which is connected to the intermediate storage on the input side, wherein the amplitude evaluation unit comprises: a differentiation unit which determines the maximum and minimum values ​​of the values ​​stored in the intermediate storage and generates a difference value from them, a first filter array with a number of n2 parallel low-pass filters with different time constants, to which the difference value is supplied, and a second weighting and summing unit which is designed to receive the individual values ​​from the n2 low-pass filters, to multiply the filtered values ​​by a second weighting value, and to sum the weighted values ​​to a sum difference value.

[0018] The amplitude evaluation unit leads to a further improvement in the evaluation results. By evaluating the amplitude values, changes in particle size can be detected and thus displayed dynamically. Furthermore, processing via multiple parallel low-pass filters allows for a temporal classification of these changes, i.e., within which time periods the changes occur.

[0019] In a preferred advanced training, the time constants of the low-pass filters in the first filter array can be changed in powers of two.

[0020] This measure has proven to be particularly advantageous.

[0021] For preferred further training, the number of n2 second weighting values ​​can be set.

[0022] This measure increases the flexibility of the device, i.e., its adaptability to different areas of application.

[0023] In a preferred embodiment, an integral evaluation device is provided which is connected to the intermediate storage on the input side, wherein the integral evaluation device comprises: a summing unit which generates the sum of the absolute values ​​of the difference between a value in the intermediate storage and the average value of all values ​​in the intermediate storage as an integral value, a second filter array with a number of n3 parallel low-pass filters with different time constants, to each of which the integral value is fed, and a third weighting and summing device which is designed to receive the individual values ​​from the n3 low-pass filters of the second filter array, to multiply the received values ​​each by a third weighting value and to sum the weighted values ​​to a sum integral value.

[0024] This measure has the advantage of further increasing the evaluation possibilities. The integrated evaluation unit enables the temporal recording of changes in the particle quantity. This allows it to be determined whether the cleaning level of the vacuumed area is improving or stagnating.

[0025] These measures have proven to be particularly advantageous.

[0026] In a preferred further development, the time constants of the low-pass filters in the second filter array change in increments of two. Furthermore, the number of n3 third weighting values ​​is also preferably adjustable.

[0027] In a preferred further development, a fourth weighting and summation device is provided, to which the values ​​from the frequency evaluation device, the amplitude evaluation device and the integral evaluation device are fed, and which The system is designed to multiply each input value by a fourth weighting value and sum the weighted values ​​to produce a total output value.

[0028] This measure allows for further customization of the analysis. Different analyses can be weighted differently in the output.

[0029] In a preferred embodiment, a first operational amplifier and a second operational amplifier are provided, wherein the first operational amplifier controls the light source and the second operational amplifier is connected to the light sensor at its input and outputs the analog measurement signal. Preferably, the signal from the light sensor is fed to the first operational amplifier, which, based on this signal, controls the light source with a control signal such that the signal from the light sensor has a predefined value when the path is clear.

[0030] This measure has the advantage that the operating point is set in a controlled manner, so that the measurement is independent of contamination.

[0031] In a preferred further development, a monitoring unit is provided which is designed to monitor the control signal and to signal when the control signal exceeds a predetermined, in particular predefinable, value. Preferably, a message signal is transmitted to the transmission device.

[0032] This measure has the advantage that a warning can be issued if the device can no longer correctly adjust the operating point, e.g. due to excessive contamination.

[0033] The problem underlying the invention is also solved by a method as defined in claim 19.

[0034] The advantages are the same as those of the aforementioned device.

[0035] Finally, the task is also solved by a cleaning device, in particular a vacuum cleaner, as defined in claim 22.

[0036] It is particularly advantageous to use the device according to the invention in a robotic vacuum cleaner. The digital output value provided by the device according to the invention, as a result of the evaluation, can be used by a controller for the vacuum motor and / or the drive. For example, based on the degree of cleaning of the vacuumed area, certain areas could be targeted multiple times, or other already cleaned areas could be excluded from the cleaning area.

[0037] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0038] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings. These show:

[0039] Fig. 1 shows a block diagram of a vacuum cleaner with the components relevant to the present invention; Fig. 2 shows a block diagram of a device according to the invention for detecting and evaluating particles in a suction stream of a vacuum cleaner; Fig. 3 shows a block diagram of a frequency evaluation device; Fig. 4 shows a block diagram of an amplitude evaluation device. Fig. 5 shows a block diagram of an integral evaluation device; Fig. 6 shows a block diagram of a vacuum robot with a device according to the invention.

[0040] The device for detecting and evaluating particles in a gaseous stream, described in detail below, essentially serves as a flexibly adjustable, dynamic display of the quantity and quality of the particles present in the gaseous stream. In particular, it is designed to detect and display changes in the quantity and quality of the particles over time. The device is used especially in vacuum cleaners to detect and appropriately display the quality and quantity of dust particles in the aspirated air.

[0041] Figure 1 shows a block diagram illustrating the components of a vacuum cleaner 10 relevant to the invention. The vacuum cleaner 10 can be, for example, a handheld vacuum cleaner, a canister vacuum cleaner, or a robotic vacuum cleaner. The vacuum cleaner 10 has a motor 12 that draws in air through a nozzle (not shown) via a suction tube 14 and expels it through an exhaust tube 16. The drawn-in air 18 is a mixture of particles, in particular dust particles 20, and air, a mixture typically referred to as a two-phase flow or two-phase mixture. The motor 12 is controlled, for example, by a higher-level control unit 26 to adjust the power of the motor 14. This higher-level control unit 26 can also perform other control and regulation tasks within the vacuum cleaner.

[0042] The 2-phase flow typically passes through a collection container (not shown) which filters the dust particles from the mixture and then blows the essentially particle-free air out via the exhaust pipe 16.

[0043] To detect the particles 20 in the two-phase flow 18, a device 30 is provided, comprising a measuring device 31 and a circuit 32. The measuring device 31 is assigned to a section of the intake pipe 14 and comprises, on the one hand, a light source 34 and, on the other hand, a light sensor 36, which are aligned with each other such that an optical path 39, traversed by a light beam, is created between the light source 34 and the light sensor 36. This optical path 39 lies within the intake pipe 14, so that this section of the intake pipe serves as the measuring chamber 38. Preferably, the light source and light sensor are located behind translucent but dustproof and / or Gas-tight incisions / windows in the suction pipe 14. The two-phase mixture flowing through this measuring chamber 38 changes the amount of light arriving at the light sensor 36, which can be measured and evaluated, allowing a statement to be made about the degree of cleaning of the vacuumed surface or how the degree of cleaning is currently changing. Since the light sensor is located outside the measuring chamber, the flow through the sensor is not affected.

[0044] The circuit 32 controls the light source 34, which is preferably designed as an infrared LED 35, and the light sensor 36, which is preferably designed as a photodiode 37, sends the measurement signal back to the circuit 32 for evaluation.

[0045] The result of the evaluation of the received measurement signal is then transmitted by the circuit 32, for example, to an output device 33, which has a display device 40, for example, with LEDs 42 for the visual representation of the evaluation result. At this point, it should be noted that, alternatively or in addition to the visual display device 40, an acoustic reproduction of the result is also possible.

[0046] The visually / acoustically output result is intended to provide the user of the vacuum cleaner with information about the degree of soiling or the degree of cleaning of the vacuumed area, and / or information about how the degree of cleaning changes over time.

[0047] Alternatively or additionally, the result of the evaluation is transmitted to the higher-level control unit 26 of the vacuum cleaner 10, which can, for example, control the power of the motor 12 depending on the result of the evaluation.

[0048] The device 30 is shown schematically in Figure 2 in the form of a block diagram. The measuring device 31 with the infrared LED 35 (IR LED) and the phototransistor 37, and the circuit 32, which in the present embodiment comprises an analog circuit section 50 and a digital circuit section 60, can be seen therein. The digital circuit section 60 can be provided in a controller 61.

[0049] The analog circuit section 50 of the circuit 32 comprises a first operational amplifier 52 with a low-pass filter, which adjusts the infrared LED 35 to the desired operating point. The phototransistor 37 supplies the measurement signal to a second operational amplifier 54 with a high-pass filter, as well as to the first operational amplifier 52. The second operational amplifier 54 has a high gain to provide the phototransistor's signal with high dynamic range. The measurement signal provided by the second operational amplifier 54 is fed to an analog-to-digital converter 64, which provides, for example, a digital signal or two-discrete digital values ​​at the output with a sampling rate of 50,000 samples per second.

[0050] The signal generated by the first operational amplifier 52, which is supplied to the infrared LED 35 and determines its brightness, is also transmitted to a second analog-to-digital converter 66, which generates a digital signal or time-discrete digital values ​​at a sampling rate of 5 samples per second.

[0051] The feedback of the measurement signal from phototransistor 37 to the first operational amplifier 52 serves to set the operating point of the infrared LED 35. In other words, the first operational amplifier is designed so that a predetermined light intensity / amount always reaches the phototransistor 37 (provided that no particles are present in the measuring chamber during the setting of the operating point). The low-pass filter in the first operational amplifier smooths the incoming measurement signal so that short-term fluctuations in the measurement signal have no influence on the setting of the operating point.

[0052] This regulation of the operating point prevents contamination in the area of ​​the optical path, for example at the light-transmitting cutouts in the intake pipe, from having an influence on the measurement.

[0053] The digital circuit section 60 comprises the two analog-to-digital converters 64,66 as well as other digital functional elements, which are explained below.

[0054] The second analog-to-digital converter 66, which receives the control signal for the IR LED 35, delivers the digital signal or values ​​to an operating point monitoring device 70. This device compares the digital values ​​with a predetermined, and in particular adjustable, threshold value. If this threshold value is reached or exceeded, it indicates that, for example, the areas in front of the phototransistor 37 or the IR LED 35 are dirty. The operating point monitoring device 70 sends a warning signal to a transmission device 72 when the predetermined threshold value is reached or exceeded. The transmission device 72 processes the warning signal and transmits it via a digital interface 73 to the control device 26 and / or the output device 33. The output device 33 can then, for example, visually and / or audibly inform the user of the vacuum cleaner 10 that the measuring chamber 38 should be cleaned.

[0055] The first analog-to-digital converter 64 delivers the digital measurement signals, i.e., measured values, to a buffer memory 68, which is preferably configured as a ring buffer. This buffer memory 68 stores the discrete-time digital measured values, for example, within a time window of 0.2 seconds. At a sampling rate of 50,000 samples per second, the buffer memory 68 holds 10,000 measured values. Since the buffer memory 68 is configured as a ring buffer, the oldest measured value is removed from the buffer memory 68 when a new measured value supplied by the analog-to-digital converter 64 is stored. Thus, the time window shifts by one value with each sample.

[0056] However, it should be noted that the mentioned sampling rate and buffer size are exemplary values ​​that can be chosen differently depending on the application.

[0057] Based on the measured values ​​stored in the buffer memory 68, three different evaluations are performed: a frequency evaluation, an amplitude evaluation, and an integral evaluation. For this purpose, a frequency evaluation unit 74, an amplitude evaluation unit 76, and an integral evaluation unit 78 are provided.

[0058] The results of these evaluations are transmitted as digital data A1, A2, and A3 to a weighting and summing unit 80, which weights the corresponding data and sums them to a total value. The sequence of total values ​​is then transmitted to a low-pass filter 82, which smooths the total values, for example, with a time constant of 0.1 seconds, and transmits the smoothed values ​​to the transmission unit 72. The transmission unit processes the values ​​and outputs them via interface 73 to the output unit 33 and / or the control unit 26. Of course, it would also be conceivable for the control unit 26 and / or the output unit 33 to retrieve the values ​​independently and as needed. The output unit 33 could, for example, be configured to dynamically visualize the values, using linear interpolation for improved display.

[0059] Figure 3 shows the frequency evaluation device 74 in the form of a block diagram. The frequency evaluation device 74 comprises a frequency transformation device 90, which subjects the time-discrete digital values ​​supplied to it to a frequency transformation and divides them into a number n of frequency ranges. The value n is an integer greater than 0, preferably 16. Consequently, n frequency values ​​are provided at the output of the frequency transformation device 90. Since the conversion of a sequence of time-discrete values ​​into the frequency domain is known from a technical perspective, it will not be discussed in further detail. In the present embodiment, for example, a known Fast Fourier Transform (FFT) method can be used. Alternatively, a so-called Görzel algorithm could also be used, which has the advantage of being less computationally intensive.

[0060] The frequency transformation device 90 retrieves the discrete-time values ​​to be converted from the buffer memory 68, preferably reading all values ​​from the memory and then subjecting them to a frequency transformation. That is, with a time window of 0.2 seconds, the buffer memory 68 is read by the frequency transformation device 90 every 0.2 seconds. Of course, it would also be conceivable to read the data from the buffer memory 68 in a different temporal sequence.

[0061] The number n calculated frequency values ​​for the frequency ranges 1 to n are fed to a weighting and summing device 92. The value n, i.e., the number of frequency ranges considered, is preferably in the range of 8-20, preferably 16. Considering frequency ranges allows for an evaluation of the particle size in the two-phase mixture. Thus, fine dust appears in high frequency ranges, while larger particles are detectable in lower frequency ranges.

[0062] The weighting and summing unit 92 multiplies each of the input frequency values ​​by a weighting factor, where the n weighting factors can be different, but preferably sum to 1. The weighting factors can be supplied to the weighting and summing unit 92 in the form of an application-specific weighting vector 94. It is particularly advantageous to make this weighting vector adjustable for the user. The weighting factors allow the user to adjust which particle size in the two-phase mixture is given greater weight in the visualization. By individually adjusting the weighting factors, the user can, for example, react to and display different types of contamination. It would also be conceivable, for example, to store various predefined and selectable weighting vectors, e.g., for prioritizing fine dust or coarser particles.

[0063] The n weighted frequency values ​​are then summed into a single value and fed to a low-pass filter 96. The low-pass filter 96 provides a signal or digital values ​​A2 at its output, which represent a smoothed form of the weighted and summed values ​​from the weighting and summing device. The low-pass filter 96, in effect, allows the inertia of the measurement to be defined.

[0064] Figure 4 shows the amplitude evaluation unit 76 in the form of a block diagram. It comprises a differentiation unit 100, which is designed to read the values ​​from the buffer memory 68, identify the maximum and minimum values ​​from these values, and calculate the difference between them. This difference value is then provided at the output of the differentiation unit 100. Unlike the frequency transformation unit 90, the difference value is calculated for each new time window (time window that has advanced by one unit). In other words, The difference value is recalculated whenever a new sampled value is written to buffer memory 68. The difference value provides information about the size of the particles in the two-phase mixture. Specifically, it identifies the largest particle in the two-phase mixture, i.e., the largest particle in the suction flow. For example, if a single large piece of paper passes through the measuring chamber, there will be a large spike in the measured values, meaning the difference value will be high. If the two-phase mixture contains only small dust particles, the measured value will be small, and therefore the difference value will also be smaller than if a larger particle were present.

[0065] The amplitude evaluation device 76 further comprises a number n of low-pass filters 102.1-102.n, which are arranged in parallel and each receive the difference value from the differentiation unit 100. The value n is an integer greater than 0, preferably 16. The low-pass filters 102.1-102.n have different time constants, which in the present embodiment are increased in powers of two. That is, for example, the low-pass filter 102.1 has a time constant t of 2 ms, the second low-pass filter 102.2 a time constant t of 4 ms, the third low-pass filter 102.3 a time constant t of 8 ms, and the last low-pass filter 102.n a time constant t of 2 ms. A n ms. However, it should be noted that these values ​​are purely exemplary, but have proven particularly advantageous in one embodiment.

[0066] Using this series of low-pass filters 102, the temporal evolution of changing difference values ​​can be analyzed. For example, the low-pass filter 102.1, with its short time constant, is better able to represent short-term changes in the difference value than the low-pass filter 102.n, which is better able to represent changes in the difference value over longer time intervals. As already mentioned, a large difference value indicates that a single large particle was detected by the measuring device as a singular event, while a very small difference value indicates that a smaller particle is flowing through the measuring chamber.

[0067] The low-pass filters 102.1-102.n are fed to a weighting and summing device 104, which multiplies each value by a weighting factor and calculates these weighted values. Values ​​summed to a single value, which is provided at the output as value A2.

[0068] The weighting factors are supplied to the weighting and summing unit 104 in the form of an application-specific weighting vector 106, whereby each weighting factor can be different. The sum of the weighting factors is preferably 1. As before, it is advantageous to provide the user with a user-adjustable weighting vector, or several predefined weighting vectors. Alternatively, it is of course also conceivable to set the weighting vector at the factory, e.g., after a calibration process.

[0069] Finally, Figure 5 shows the integral evaluation unit 78 as a block diagram. It comprises a summing unit 110, to which the values ​​from the buffer memory 78 are fed. This unit calculates the difference between each individual buffer value and the mean value of the values ​​in the buffer memory 78 and sums the resulting absolute values ​​to a single value. This calculation is performed with each new value that is written into the buffer memory 68.

[0070] The integral evaluation unit 78 further comprises a number n of low-pass filters 112.1-112.n, arranged in parallel to each other, to each of which the sum value of the summing unit 110 is supplied. The value n is an integer greater than 0, preferably 16. It should be noted here that the number n of low-pass filters 112 does not necessarily correspond to the number n of low-pass filters 102 in the amplitude evaluation unit 76 or the number n of frequency ranges generated by the frequency transformation unit 90. The number n can be the same or different.

[0071] The number n of low-pass filters 112.1-112.n have different time constants t, with these time constants preferentially increasing by a power of two. In other words, for example, low-pass filter 112.1 has a time constant t of 2 ms, the second low-pass filter 112.2 has a time constant t of 4 ms, and the last low-pass filter 112.n has a time constant of 2 ms. A n ms. Of course, this is about These are exemplary values ​​that have proven particularly advantageous in practice. Using these different low-pass filters, the temporal changes in the total value at the output of the summing unit 110 can be analyzed. Changes within short time periods can be identified with the first low-pass filter 112.1, while differences over longer time intervals can be detected with the last low-pass filter 112.n. If the value A3 decreases, for example, this indicates that the degree of cleaning is increasing. Or, in other words, the cleaning result is improving because fewer and fewer particles are flowing through the measuring chamber. Conversely, if the value increases, the contamination is increasing, i.e., the number of particles is rising.

[0072] The number n values ​​of the low-pass filters 112 are fed to the weighting and summing unit 114. There, each value is multiplied by a weighting factor and then fed to a summing unit, which calculates a sum value. This value is provided at the output as value A3.

[0073] The weighting factors are supplied to the weighting and summing device 114 in the form of a weighting vector 116, the weighting vector preferably being adjustable by the user. Preferably, the sum of the weighting factors, which can be different, is 1. It is also conceivable that several different weighting vectors are stored, in which case the user has the option of selecting a weighting vector. In this way, the evaluation can be set and adapted to different cleaning or soiling situations.

[0074] It should be noted here that the previously described weighting vectors 94, 106, and 116 can differ. The optimal values ​​of the weighting vectors are usually set at the factory through a calibration process.

[0075] The temporal sequence of digital values ​​A1, A2, and A3 is fed to the weighting and summing device 80, which weights these values ​​and sums them into a single value. The weighting factors used are preferably in the sum of 1 and They can vary. Preferably, the three weighting factors are adjustable by the user.

[0076] The summed value or sequence of summed values ​​is fed to the low-pass filter 82, which operates with a time constant of, for example, 0.1 seconds. The values ​​are smoothed by this low-pass filter 82 and fed to the transmission device 72. The values ​​are then fed to the output device 33 via the digital interface 73 for display, preferably optical display. The optical display can be performed using the display device 40, which has a plurality of LEDs 42, preferably of different colors. Thus, the display can visualize a high degree of contamination via red LEDs and a high degree of cleaning via green LEDs. Simultaneously, the values ​​can be fed to the control device 26 via the interface 73, so that, for example, the motor 14 can be controlled depending on the degree of contamination.

[0077] The previously described evaluation device 30 analyzes the two-phase mixture in various ways, allowing statements to be made about the quality and quantity of particles in this two-phase mixture and their changes over time. This evaluation can then be displayed to the vacuum cleaner user in various ways, with an optical display being particularly advantageous.

[0078] The evaluation itself can be performed digitally and parameterized very flexibly. This makes it possible to provide a cost-effective circuit that can be easily used in different types of vacuum cleaners for different applications.

[0079] For example, it is conceivable to set the weighting vectors via software using the digital interface 73. Device 30 could communicate with a computer via this interface. The parameters of the operating point monitoring device could then also be set via this interface 73.

[0080] Finally, Figure 6 shows an example of how the device according to the invention can be used. A robotic vacuum cleaner 120 is shown, which includes the suction motor 14 and the device 30. The results of the evaluation are transmitted via the digital interface 73 to the higher-level control unit 26, which then controls a drive motor 118. This makes it possible, for example, to have the robotic vacuum cleaner travel more frequently to those areas of the room where the level of soiling is high. Alternatively or additionally, it can be provided that those areas of the room that have already reached a desired level of cleaning are excluded from the robot's operating range. Using such control of the robotic vacuum cleaner based on the level of soiling saves energy, since only those areas with an undesirably high level of soiling are visited and vacuumed.Despite the high accuracy of the evaluation, a good level of cleaning can still be achieved.

Claims

Patent claims 1. A device for detecting and evaluating particles, in particular in a suction stream of a vacuum cleaner, comprising a light source (34), in particular an infrared LED (35), which is designed to emit a light beam along an optical path (39) and through a measuring chamber (38); and a light sensor (36) which is designed to receive the light beam after it has passed through the measuring chamber, the light sensor (36) emitting an analog measurement signal; characterized by an analog-to-digital converter (64) which is designed to convert the analog measurement signal into time-discrete digital measurement values; a buffer (68) which is designed to buffer a predefined number of measurement values;a frequency evaluation device (74) connected to the buffer and comprising: a frequency transformation device (90) designed to decompose the time-discrete measured values from the buffer into frequency spectrum values of a predefined number n1 of frequency ranges; and a first weighting and summing device (92) designed to multiply the number of n1 frequency spectrum values by a first weighting value and to add the weighted n1 frequency spectrum values to obtain a first weighted sum value; and a transmission device (72) designed to provide a digital output signal of the frequency evaluation device at a digital output (73) as a digital output value for transmission.

2. Device according to claim 1, characterized in that the frequency transformation device (90) has a Fast Fourier Transformation unit, FFT, or a unit for carrying out the Görzel algorithm.

3. Device according to claim 1 or 2, characterized in that the n1 first weighting values are adjustable.

4. Device according to claim 1, 2 or 3, characterized in that a first low-pass filter (96) is provided, to which the first weighted sum value is supplied.

5. Device according to one of the preceding claims, characterized by an amplitude evaluation device (76) which is connected on the input side to the buffer (68), the amplitude evaluation device having: a differentiation unit (100) which determines the maximum and minimum value of the values stored in the buffer and generates a difference value therefrom, a first filter array with a number of n2 low-pass filters (102.1-102.n) arranged in parallel with different time constants, to each of which the difference value is supplied, and a second weighting and summing device (104) which is designed to receive the individual values from the n2 low-pass filters (102), to multiply the filtered values in each case by a second weighting value (106) and to sum the weighted values to form a total difference value.

6. Device according to claim 5, characterized in that the time constants of the low-pass filters (102) in the first filter array change in powers of two.

7. Device according to claim 5 or 6, characterized in that the number of n2 second weighting values is adjustable.

8. Device according to one of the preceding claims, characterized by an integral evaluation device (78) which is connected on the input side to the buffer (68), the integral evaluation device comprising: a summing unit (110) which generates the sum of the absolute values of the difference between a value in the buffer and the average value of all values in the buffer as an integral value, a second filter array with a number of n3 low-pass filters (112.1-112.n) arranged in parallel with different time constants, to each of which the integral value is supplied, and a third weighting and summing device (114) which is designed to receive the individual values from the n3 low-pass filters of the second filter array, to multiply the received values in each case by a third weighting value and to sum the weighted values to form a sum integral value.

9. Device according to claim 8, characterized in that the time constants of the low-pass filters in the second filter array change in powers of two.

10. Device according to claim 8 or 9, characterized in that the number of n3 third weighting values is adjustable. 11 . Device according to one of the preceding claims, characterized by a fourth weighting and summing device (80) to which the values from the frequency evaluation device, the amplitude evaluation device and the integral evaluation device, and which is designed to multiply the supplied values by a fourth weighting value and to sum the weighted values to a total output value, 12 Device according to claim 11, characterized by a low-pass filter (82), the output of which is connected to the transmission device (72) and the input of which is connected to the fourth weighting and summing device (80).

13. Device according to one of the preceding claims, characterized in that the buffer (68) is designed as a ring buffer.

14. Device according to one of the preceding claims, characterized in that a first operational amplifier (52) and a second operational amplifier (54) are provided, wherein the first operational amplifier controls the light source (34) and the second operational amplifier is connected to the light sensor (36) on the input side and outputs the analogue measuring signal on the output side.

15. Device according to claim 14, characterized in that the signal of the light sensor is fed to the first operational amplifier (52), which, based on this signal, controls the light source with a control signal such that the signal of the light sensor has a predefined value.

16. Device according to claim 15, characterized in that a monitoring unit (70) is provided which is designed to monitor the control signal and to signal an exceeding of the control signal above a predetermined, in particular predefinable, value.

17. Device according to claim 16, characterized in that the control signal is fed to a further analog-digital converter (66) and whose digital output values are monitored by the monitoring unit (70).

18. Device according to one of the preceding claims, characterized in that n1, n2 and n3 are each integers, preferably integers greater than 1.

19. Procedure with Emitting a light beam along an optical path and through a measuring space; and Receiving the light beam with a light sensor after passing through the measuring space, whereby the light sensor emits an analog measuring signal; Converting the analog measurement signal into digital measured values; Buffering a predefined number of digital measured values in a buffer; Perform a frequency evaluation of the values in the buffer, with the steps: Decomposing the time-discrete measured values from the buffer into frequency spectrum values of a predefined number n1 of frequency ranges; and Multiplying the number of n1 frequency spectrum values by a first weighting value and adding the weighted n1 frequency spectrum values to obtain a first weighted sum value; and providing the result of the frequency evaluation as a digital output value.

20. Method according to claim 19, characterized by: Perform an amplitude evaluation of the measured values stored in the buffer, with the following steps: Determining the maximum and minimum values of the values stored in the buffer and generating a difference value therefrom, Filtering the difference values through a first filter array with a number of n2 low-pass filters arranged in parallel with different time constants, and Multiply the filtered values by a second weighting value and sum the weighted values to a sum difference value. 21 . Method according to claim 20, characterized by: Perform an integral evaluation of the measured values stored in the buffer, with the following steps: Summing the absolute values of the difference between a value in the buffer and the average value of all values in the buffer and outputting it as an integral value, Filtering the integral values through a second filter array with a number of n3 parallel low-pass filters with different time constants, each of which is supplied with the integral value, and Multiply the filtered integral values from the n3 low-pass filters by a third weighting value and sum the weighted values to a sum integral value.

22. Cleaning system, in particular vacuum cleaner (10, 120), with a device according to one of claims 1 to 18, a suction nozzle, a suction motor (12); a pipe (14) between the suction nozzle and the suction motor (12), wherein the pipe is flowed through by the sucked-in air and a section of the pipe encloses the measuring chamber (38); a first light-permeable region on the pipe section, to which the light source (34) is assigned, a second light-permeable region on the pipe section, which is opposite the first region and to which the light sensor (36) is assigned, wherein the optical path (39) extends from the first region to the second region; and a control device (26) which is connected to the transmission device and receives the digital output value and uses it for control purposes, and / or an output device (33) which is connected to the transmission device and receives the digital output value and uses it for optical and / or acoustic display.

23. Cleaning system according to claim 22, characterized in that the control device (26) is designed to adjust the power of the suction motor based on the output value.

24. Cleaning system according to claim 22 or 23, characterized in that an output device (33, 40) is provided which displays the output value optically and / or acoustically.

25. Cleaning system according to one of claims 22 to 24, characterized in that the cleaning system is a vacuum robot (120) with a controllable drive (118) for traveling over and cleaning a surface, wherein the output values are included in the control of the drive.

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