scrubber-dryer, a method for controlling it and a storage medium

Abstract

A scrubber-dryer for wet cleaning surfaces (51, 52) is disclosed. The surfaces (51, 52) can be subdivided into at least a first surface class (51) and a second surface class (52), in particular into smooth and rough surfaces, and each surface class (51, 52) has one or more associated values ​​of control variables. The scrubber-dryer comprises: a suction blower (100) for generating a negative pressure to pick up moist dirt from the surface (51, 52); a sensor unit (200) for detecting a change in the surface (51, 52); and a device control unit (300) configured to detect a change between the first surface class (51) and the second surface class (52) and, upon detection of a change to a new surface class (51, 52), to use the associated values ​​of control variables for the new surface class (51, 52) to control the suction blower (100).

Description

The present invention relates to a scrubber-dryer for wet cleaning of surfaces, to a method for controlling a suction blower of a scrubber-dryer, to a storage medium and in particular to a control of a suction device on a negative pressure adapted to the floor (adaptive negative pressure control). BACKGROUND Conventional floor cleaning machines use a floor sensor, such as a laser or camera, to distinguish between smooth and unfinished floors. Vacuum cleaners, on the other hand, detect the floor type by measuring the vacuum pressure. The distinction between hard floors and carpets is based on this vacuum pressure and a corresponding adjustment of the cleaning power. EP 3 003 113 B1 discloses a floor cleaning machine with a conventional vacuum control system that adjusts to a fixed vacuum value to optimize the cleaning result. The fixed vacuum value is a target pressure or vacuum level to which the floor cleaning machine regulates the suction fan. EP 3 338 151 B1 discloses another conventional floor cleaning machine that has optical sensors for detecting floor types. DE 10 2015 100 636 A1 discloses a conventional vacuum cleaner with power regulation that activates when a change between hard flooring and carpeting is detected. WO 2017 / 031364 A1 discloses another conventional floor cleaning machine with a sensor for detecting a blockage or wear in the suction line. US 2018 / 0249 875 A1 , EP 3 589 180 B1 and DE 44 33 181 A1 disclose further conventional vacuum cleaners with sensors for detecting the floor type.EP 0 379 680 A1 and EP 1 997 412 B1 disclose conventional methods for controlling the power of vacuum cleaners depending on the floor covering. One disadvantage of existing methods is that the cleaning effect is insufficient at transitions between rough and smooth floors. In particular, pressure regulation to a single setpoint is inadequate – especially when the floor surface changes suddenly and significantly. For example, readjusting the pressure at transitions from a very smooth floor, such as screed, to a heavily textured floor often takes too long. Furthermore, the setpoints are often not optimal for different floor types. This is especially true for scrubber-dryers, where a change in floor surface leads to significantly greater pressure fluctuations than with vacuum cleaners, which, for example, adjust their suction power for different types of carpet (smooth and coarse). Therefore, there is a need for scrubber-dryers that ensure high-quality cleaning even with suddenly changing floor conditions. BRIEF DESCRIPTION OF THE INVENTION At least some of the aforementioned problems are solved by a scrubber-dryer according to claim 1, a method according to claim 12, and a storage medium according to claim 15. The dependent claims relate to further advantageous embodiments of the subject matter of the independent claims. The present invention relates to a scrubber-dryer for wet cleaning surfaces. The surfaces can be divided into at least a first surface class and a second surface class – in particular, smooth and rough surfaces. Each surface class has one or more associated values ​​of control variables. The scrubber-dryer comprises a suction blower, a sensor unit, and a control unit. The suction blower serves to generate a vacuum in order to pick up moist dirt from the surface. The sensor unit serves to detect changes in the surface. The control unit is designed to detect a change between the first and second surface classes and, upon detection of a change to a new surface class, to use the corresponding value of a control variable for the new surface class to control the suction blower. A scrubber-dryer, also known as an automatic scrubber-dryer, can be defined as a semi-automatic or fully automatic cleaning machine for the efficient cleaning of hard floors. Hard floors can also be defined as non-absorbent floors (non-capillary floors) where applied water does not penetrate or only penetrates with difficulty. Typically, scrubber-dryers apply water, with or without cleaning agents, to the floor and perform mechanical cleaning using brushes or rollers. Finally, the dirty water is vacuumed up. Scrubber-dryers typically have two tanks: one for clean water with or without detergent, and one for dirty water. They also often feature a brush unit (e.g., with disc brushes or roller brushes for dirt removal) and a squeegee connected to the vacuum blower to extract the dirty water. Ideally, the floor should be as dry as possible afterward. Within the scope of this disclosure, a control system is understood to mean anything that provides control over another component, i.e., also regulation (i.e., with feedback). Thus, the device control system according to the exemplary embodiments can also provide regulation. In particular, the sensor unit can determine the negative pressure generated by the blower. This can be done, for example, by direct measurement, but the negative pressure can also be determined indirectly (e.g., by calculation). The aim of the control system is to ensure the most uniform possible absorption of the wastewater from the surface. According to exemplary embodiments, surface classes are divided into at least two categories: for example, "smooth" and "heavily textured." On smooth floors, the machines operate with low blower power, while on heavily textured floors, high blower power is advantageous. For each type of flooring or flooring material (e.g., stone, wood, linoleum), there can be a multitude of different surface finishes. Therefore, exemplary embodiments define two or more surface classes. The number can be selected, for example, depending on the required measurement accuracy and other relevant factors. For example, tiled floors can be categorized as follows: smooth tiles, various classes of slip-resistant tiles, highly textured safety tiles, natural stone tiles, or their imitations. The classification of surface types can be analogous to the classification according to standards (DIN EN 14411, DIN 51130, etc.). The laying method, laying quality, tile size, and joint width can also determine the classification. Small tiles, for instance, have many joints and are therefore typically more textured. Examples of surfaces that fall into the (smooth) category (smooth surface class), for which a low blower output can be selected, include screed, coated screed, well-laid smooth tiles, smooth linoleum, and PVC / rubber flooring. High blower outputs could be used for the rough surface class, which would include heavily textured safety tiles, poorly laid small tiles, rubber studded flooring, etc. The surface classes can be chosen arbitrarily, whereby the classification, as mentioned, can be based on the surface structure (e.g., highly or coarsely structured, or unstructured). Further gradations are possible according to the exemplary embodiments. In particular, all surfaces that can be wet-cleaned should be classified into a few classes, where the number can be 2, 3, 4, 5, ... For each surface class, there are characteristic vacuum values ​​and / or power consumption values ​​that are changed as controlled variables when the surface changes. These characteristic values ​​are thus functions of the surface, but these functions do not need to be continuous; they are discrete function values. The step size of the discrete values ​​can be, for example, at least 15% or 30% of the values ​​for the controlled variables (e.g., for power consumption and / or vacuum). This discrete class-based control therefore differs significantly from a continuous adjustment of the controlled variables, even for changing surfaces. According to exemplary embodiments, the associated values ​​linked to the different surface classes are stored in a data storage device (e.g., in the device control or elsewhere). Optionally, each surface class includes at least one associated threshold value for at least one of the controlled variables. The device control can then be configured to determine a change in surface class based on whether at least one of the associated threshold values ​​is exceeded. Optionally, the device control system can be further developed to detect a change in surface class only when at least one associated threshold is exceeded for a minimum period of time. Two or more thresholds can be defined for each surface class. The technical effect of the threshold(s) lies in defining a tolerable range of variations in measured variables. The control system does not need to adjust immediately. Only a significant exceedance of the threshold can thus trigger a change in surface class. Optionally, the device control is further developed to also detect at least one of the following (for example, as an error) based on the sensor data: - blockage of an intake duct, - intake of secondary air, - defect of the suction blower, - a full dirty water tank, - an empty fresh water tank. For example, if the lower vacuum threshold is exceeded, this likely indicates the intake of unmetered air (due to an unusually large vacuum loss). Conversely, if the upper vacuum threshold is exceeded, it may indicate a blockage (due to an unusually large increase in vacuum). Another fault occurs when there is no fresh water present. In this case, the scrubber-dryer runs "dry," and the vacuum may drop because the sealing film of water is missing, making it easier for unmetered air to be drawn in. Optionally, the device control is further developed to perform regulation with respect to or based on at least one of the following control variables: - a negative pressure value, - a power consumption value of the suction blower, - a pulse width modulation for the suction blower, - a speed of the suction blower, - a residual moisture on the surface, - a conductivity value of the surface. It is well known to experts that the controlled variables can be interdependent. For example, a higher power consumption of the suction fan generally leads to a higher rotational speed, which in turn changes the vacuum. The power consumption can be adjusted by pulse-width modulation (PWM) for the electric motor drive, meaning that both variables can correspond. The power consumption values ​​can be defined as percentages of a maximum power output. It is also understood that the vacuum value is not necessarily measured directly, but can also be determined based on PWM or rotational speed using a fan characteristic curve. Optionally, the device control is further developed to achieve at least one of the following: - if the value of a first controlled variable is below a first threshold, issue an error message; - if the value of the first controlled variable is between the first and a second threshold, activate the suction fan with an increased value for a second controlled variable; - if the value of the first controlled variable is between the second and a third threshold, maintain the existing control of the suction fan; - if the value of the first controlled variable is between the third and a fourth threshold, activate the suction fan with a decreased value for the second controlled variable; - if the value of the first controlled variable is above the fourth threshold, issue another error message.- If the value of the first controlled variable is above the fourth threshold or below the first threshold, switch off the suction fan. The described hysteresis or delays in switching have the advantageous effect that many class changes do not occur in a short time, for example, when the surface's classification is uncertain. Instead, a change is only performed when a clear boundary between different surface classes has been clearly crossed. The first controlled variable can be the vacuum level, and the second controlled variable can be the power consumption or the speed of the suction blower. The increased power consumption can be, for example, 100% (or between 90% and 100%), and the reduced power consumption can be 85% (or between 70% and 90%). It should be understood, however, that these values ​​are only examples and can be changed as needed or adapted to specific requirements. Example error messages include: unusual pressure increase / decrease, air being drawn in, (waste)water tank full / empty, blockage / closure in a channel. Optionally, the sensor unit is designed to detect a vacuum value for the generated vacuum. The device control can then be configured to determine a target value (or setpoint) for the power consumption of the suction blower based on the detected vacuum value and to adjust the suction blower to this target value. In contrast to conventional floor cleaning machines, which use a control based on a fixed vacuum setpoint or vacuum setpoint range, exemplary embodiments change the vacuum setpoint in discrete steps according to the floor condition. For example, the fan speed will be kept as constant as possible as long as the vacuum value remains within a tolerance range. In this case, there is no control to achieve a desired vacuum; instead, the corresponding fan output (fan speed, power consumption, or current draw) is regulated. As previously explained, the relationship to the vacuum value can be established in combination with a fan characteristic curve and the specific PWM signal. The vacuum value in the system can be calculated using the fan characteristic curve and the PWM signal and compared with the measured values. Alternatively or additionally, the device control can also be configured to maintain the measured negative pressure value at a constant level by controlling the suction fan. If a parameter of the suction fan deviates from a predetermined range (defined, for example, by corresponding threshold values), the device control can detect the change to a new surface class. For example, the suction fan parameter could be at least one of the following: fan power, current, voltage, pulse width modulation, or a dependent variable. Optionally, the sensor unit has at least one of the following sensors or access to them: - a pressure sensor, - a flow meter for intake air and / or exhaust air, - a power meter for the suction fan, - an ammeter for the suction fan, - a tachometer for the suction fan, - a floor sensor for detecting surface properties (e.g., a camera), - a moisture meter for the surface or for the suction air of the suction fan, - a spectrometer (for floor detection, moisture detection, etc.), - a conductivity meter. The device control system can then utilize the acquired sensor data. The example ground sensor could be any sensor capable of determining surface properties, such as a camera, a laser (Lidar), radar, an ultrasonic unit, etc. The sensors can be positioned in various locations – as long as relevant sensor data can be acquired there. In principle, (all) parameters that influence or are affected by the negative pressure can be recorded or determined. Alternatively or additionally, other parameters can be measured to ensure uniform drying. Residual moisture can be measured, for example, optically or via conductivity measurement (e.g., for the surface area after absorption). Optionally, the scrubber-dryer also includes: a squeegee for suctioning damp dirt from the surface and / or a suction hose for drawing suction air from the squeegee to the blower. The pressure sensor can be located on the squeegee or between the squeegee and the suction hose. Optionally, the sensor unit and / or the device control can be configured to perform averaging of sensor values ​​and / or controlled variables. Averaging serves, for example, to stabilize the measured values ​​and increase reliability. Exemplary embodiments also relate to a method for controlling a suction blower of a scrubber-dryer. The scrubber-dryer comprises (at least) one sensor unit that detects a change in the surface. The surfaces can be divided into at least two surface classes, in particular smooth and rough surfaces. Each surface class has one or more associated values ​​of controlled variables. The method comprises: - detecting a change between the at least two surface classes based on sensor data from the sensor unit; and - upon a detected change to a new surface class, controlling the suction blower with an associated value of a controlled variable. Optionally, the procedure further includes at least one of the following: - Determining a setpoint of a first controlled variable for a first surface, - Determining a setpoint of the first controlled variable for a second surface, - Determining a setpoint of a second controlled variable for the first surface, - Determining a setpoint of the second controlled variable for the second surface, - Determining a vacuum value using a characteristic curve of the suction blower. Optionally, the first controlled variable can be one of the following: a vacuum value, a residual moisture content of the surface, a conductivity value of the surface, or another parameter. Optionally, the second controlled variable can be one of the following: a power consumption of the suction fan, a rotational speed of the suction fan, or another parameter. This method, or at least parts thereof, can also be implemented or stored in the form of instructions in software or on a computer program product, wherein the stored instructions are capable of executing the steps according to the method when the method is running on a processor. Therefore, embodiments also refer to a computer program product or a machine-readable storage medium containing software code (instructions) configured to execute one of the previously described methods when the software code is executed by a processing unit (e.g., the device controller). The processing unit can be any type of computer or control unit that includes a suitable microprocessor capable of executing software code. BRIEF DESCRIPTION OF THE FIGURES The embodiments of the present invention are better understood with reference to the following detailed description and the accompanying drawings of the different embodiments, which, however, should not be interpreted as limiting the disclosure to the specific embodiments, but merely as serving for explanation and understanding. Fig. 1 shows a scrubber-dryer according to an embodiment of the present invention. Fig. 2 shows an embodiment for a vacuum-based control system. Fig. 3A and Fig. 3B show embodiments for automatic control of the blower output as a function of measured vacuum values. Fig. 4 shows an exemplary flowchart for a method for controlling a scrubber-dryer according to embodiments. DETAILED DESCRIPTION Fig. 1 shows an embodiment of a scrubber-dryer for wet cleaning surfaces, in particular hard floors (e.g., non-absorbent), which can be subdivided into different surface classes 51, 52. The scrubber-dryer is located, for example, on a first surface class 51 (e.g., a smooth surface), followed by a second surface class 52 (e.g., a structured or rough surface), which in turn is followed by the first surface class 51 or a further surface class. The scrubber-dryer shown comprises a suction blower 100 (e.g., a turbine), a sensor unit 200, and a control unit 300. The suction blower 100 generates a vacuum to pick up moist dirt from the surface 51, 52. The sensor unit 200 detects a change in the surface 51, 52. This surface change is reflected, for example, in the sensor data recorded by the sensor unit 200. The control unit 300 is designed to adjust the control of the suction blower 100 when a surface change is detected, e.g., from the first surface class 51 to the second surface class 52. For example, the suction blower 100 can be adjusted to a new control variable, where the new control variable is a new control value for the suction blower 100. According to exemplary embodiments, the control can be based on various control variables, such as the blower power, a negative pressure value, flow values ​​during air extraction, a humidity value on the surface, etc. The scrubber-dryer shown includes, as additional optional features, a first tank 410 as a dirty water tank, a second tank 420 as a clean water tank, a squeegee 430, a drive unit 440, and a cleaning unit 450. The cleaning unit 450 uses fresh water from the second tank 420 to clean surfaces 51 and 52. For this purpose, the cleaning unit 450 can, for example, have cleaning brushes or cleaning rollers with which surfaces 51 and 52 can be wet-cleaned. The non-absorbent surface remains wet until the squeegee 430 of the scrubber-dryer vacuums up the dirty water (wet dirt). The suction blower 100 draws the dirty water into the first tank 410. After cleaning, the residual moisture on the surface 51, 52 should be below a threshold value, which can then dry quickly. Within the scope of this disclosure, a hard floor is defined as, for example, a stone floor (tiles, screed, etc.), a wooden floor (planks, parquet, etc.), or a plastic-coated floor (linoleum, rubber, etc.). In contrast to non-absorbent hard floors, carpets, fitted carpets, and fabric floors are considered soft floors that can absorb water. According to the embodiments described, the scrubber-dryer is unsuitable for soft floors. The hard floor surfaces to be cleaned are classified according to their surface texture, as shown in the examples. For instance, a first surface class 51 can have a smooth surface, and a second surface class 52 a rough surface. Smooth surface class 51 could be, for example, screed, linoleum, or tiles with few grout lines and minimal texture, while rough surface class 52 could be a highly textured surface, such as tiles with wide grout lines or poorly laid tiles, or rubber studded floor coverings. Surface classes 51 and 52 can also be defined by achieving a specific negative pressure in the suction bar 430 for a predetermined blower output. The negative pressure values ​​achieved at the predetermined blower output are then specific to each surface class and differ by a predetermined minimum value. For example, a higher negative pressure value is achieved on a smooth surface than on a rough surface, where more ambient air is drawn in due to the increased roughness. By means of appropriate threshold values, all surfaces can thus be classified into a discrete set of classes. The sensor unit 200 can have at least one of the following sensors or has access to them: - a pressure sensor, - a flow meter for intake air and / or for exhaust air, - a power meter for the suction blower 100, - an ammeter for the suction blower 100, - a tachometer for the suction blower 100, - a floor sensor for detecting surface properties 51, 52, - a moisture meter for the surface 51, 52 or for the intake air of the suction blower 100, - a spectrometer (e.g. for floor detection), - a conductivity meter. The control unit of device 300 uses the sensor data to determine the roughness of surface 51, 52 and thus the surface class. A ground sensor can be understood to be anything capable of determining surface properties (camera, laser, radar, ultrasound, etc.). Sensors can also be arranged in several different positions. According to the exemplary embodiments, the sensor unit 200 can detect or determine all parameters that influence or are affected by the negative pressure value, or that enable uniform drying. Residual moisture measurement can be performed optically or via conductivity measurement of the surface (after absorption). Optionally, residual moisture can also be measured spectrometrically. For this purpose, the sensor unit 200 can also include a spectrometer that detects the moisture on the floor and / or determines the amount of residual moisture. Corresponding measurement data on residual moisture can be provided to the device control unit 300. The pressure sensor used for the control system can be positioned anywhere within the scrubber-dryer in the area of ​​the vacuum-operated flow path. In the preferred embodiment, the sensor is located at the suction nozzle, i.e., between the suction bar 430 and the suction hose 435. The power output of the 300 suction blower can be adjusted via pulse width modulation (PWM). This adjustment can be achieved using a control algorithm that uses a feedback loop to continuously adjust the output until a desired value (e.g., setpoint) is reached. Fig. 2 shows an embodiment for controlling the vacuum as a function of time, which can be measured, for example, by a pressure sensor 200, e.g., on the suction bar 430 or on the suction hose 435. By way of example, it is shown that the vacuum is first controlled to a first vacuum value p1, then to a second vacuum value p2, and subsequently back to the first vacuum value p1. For example, the scrubber-dryer is started up at an initial time t0. The vacuum is then regulated to the first vacuum value p1. At a first time t1, the surface changes, e.g., from the smooth surface 51 to the rough or more heavily textured surface 52. This causes the regulated vacuum to drop. The roughness leads to an increased intake of ambient air at the squeegee 430, resulting in the pressure drop shown at the first time t1. If the vacuum drop at the first time t1 falls below a first threshold value S1, the device control 300 detects a change in surface class. Accordingly, at a second time t2, the control of the suction blower 100 is changed to achieve the second vacuum value p2, which is associated with the rough surface 52. At the third time point t3, for example, the floor surface changes again, from a rough surface 52 back to a smooth surface 51. This causes the negative pressure to suddenly increase, as very little ambient air is drawn in on a smooth floor. Consequently, if the negative pressure exceeds a second threshold S2, the device control unit 300 detects another change in surface type. The device control unit 300 then adjusts the suction fan 100 back to the first surface type 51. As a result, the negative pressure returns to the initial p1 value. Referring to Fig. 1, the first time t1 can correspond to the change from the first surface class 51 to the second surface class 52, while the second change at the third time t3 can correspond to the change from the second surface class 52 to the first surface class 51. It is understood that the smooth surfaces 51 before the first time t1 and after the third time t3 do not necessarily have to be the same surface. Both surfaces are only of the same surface class. One smooth surface could be a smooth stone floor, while the other smooth surface could be a smooth rubber floor. According to exemplary embodiments, the device control 300 can therefore be configured such that the control of the suction blower 100 changes only when a change in surface class occurs, but not with every change in surface type. According to the exemplary embodiments, as shown, a change in surface class results in a jump in the controlled variable (e.g., the vacuum value). This is not a continuous or stepwise adjustment until a setpoint is reached. The steps are therefore not intermediate stages in the adjustment of a setpoint, which is generally independent of the specific surface. In other words, Fig. 2 illustrates two examples or scenarios. In the first example, the scrubber-dryer operates with active vacuum control on a smooth floor 51. The power of the suction fan 100 (e.g., the PWM) is therefore at a typical low level for this type of surface. When switching to a rough surface 52, the vacuum at the suction nozzle (suction bar 430) drops due to the more open surface structure 52, even with a constant PWM. The controller attempts to compensate for this drop in vacuum by increasing the PWM. Up to this point, no other type of floor has been detected, so the target vacuum for a smooth floor 51 still applies. However, if the PWM exceeds a threshold value S1 defined for rough floor 52, the controller recognizes the new surface as rough and switches to the target vacuum p2 for rough floors 52. The PWM (power) is then increased further. In another example, the scrubber-dryer operates with active vacuum control on the rough floor 52. The blower output (e.g., the PWM) is therefore at a typical high level p2 for this type of surface. When switching to the smooth floor 51, the vacuum at the suction nozzle increases due to the smooth and dense floor structure, even with a constant PWM. The controller attempts to compensate for this increase in vacuum by reducing the PWM. Up to this point, no other floor type has been detected, so the target vacuum p2 for rough floor 52 still applies. If the PWM exceeds a threshold value S2 defined for smooth floor 51, the controller recognizes the new surface as smooth floor 51 and switches to the target vacuum p1 for smooth floor 51. The PWM is then reduced. According to the exemplary embodiments, a change in the negative pressure in the extraction system detects a difference in the floor surface. If the negative pressure changes due to a change in the floor surface, the suction blower 100 is controlled accordingly and the suction power is adjusted to achieve a constant negative pressure and thus a consistent extraction result. This makes it clear that exemplary embodiments specifically utilize surface classes 51 and 52, to which corresponding values ​​of controlled variables are assigned and which are predefined and can be stored accordingly in the device controller 300. According to these exemplary embodiments, the classification of surfaces includes a classification of associated or assigned values ​​of the controlled variables. Upon a detected change in the surface class, a switch (a jump) to the new class and thus to the new values ​​for the controlled variable occurs. Unlike conventional cleaning machines, this system does not continuously adjust to setpoints. Instead, it uses discrete jumps between a limited number of surface classes. For example, all hard floors can be grouped into just two surface classes, between which the suction fan's control switches. In this sense, the 300 control unit can perform binary control. Alternatively or additionally, the 300 control unit can also perform ternary control (control in three classes) or control in a maximum of four or five classes, or any other number. However, a small number of classes offers the advantage of less frequent switching of the control settings. One advantage of the very limited control options is that a sudden change in surface texture triggers a very rapid adjustment. In contrast, conventional cleaning machines require a longer adjustment period because the control variables must be adapted gradually. This results in surfaces remaining damp during transitions, as the suction power is not adjusted quickly enough. The abrupt changes overcome this problem. Furthermore, it has been shown that different setpoints are appropriate for rough surfaces than for smooth floors. Figures 3A and 3B show automatic control of the blower output as a function of measured vacuum values. The pressure values ​​can again be measured by the exemplary sensor unit 200 on the suction hose 435 or elsewhere (see Figure 1). Fig. 3A shows the relationship between the blower output and the vacuum value, as it can be implemented according to exemplary embodiments. First, the scrubber-dryer is positioned on a rough surface 52, where a high blower output P1 is regulated to ensure sufficient vacuum in the squeegee 430. The high blower output P1 is selected such that the dirty water is reliably absorbed from the rough surface 52. For example, the high blower output P1 can be the maximum output (100%) of the suction blower 100, but a lower value can also be selected. When the vacuum level rises and exceeds a first threshold S1, no change in the control system occurs initially. Only when the vacuum level continues to fall and exceeds a second threshold S2 will the control unit 300 detect the change in surface type and accordingly reduce the fan speed from high P1 to reduced P2. This increase beyond the second threshold S2 indicates a change from a rough surface 52 to a smooth surface 51; that is, the control unit 300 detects the change in surface type through this change. In the reduced fan speed state P2, the suction fan 100 remains active as long as the negative pressure value stays above the first threshold S1, where S1 < S2. Only if the negative pressure value falls below the first threshold S1 does the device control 300 detect a change in surface class again, this time from a smooth surface 51 to a rough surface 52. Accordingly, when the change to a rough surface 52 is detected, the fan speed is adjusted back to a high fan speed P1, which can again be a selectable, predetermined value. According to the exemplary embodiments, the switch from high fan speed P1 to reduced fan speed P2, or vice versa, cannot occur immediately upon exceeding the threshold values ​​S1 and S2, but only after the threshold values ​​have been exceeded for a predetermined minimum duration (e.g., 2 s, 3 s, 4 s, 5 s, ...). When using a predetermined minimum duration, only one threshold value S is required; that is, S1 can be set equal to S2 (e.g., to an average value). The predetermined minimum duration achieves the same effect as two different threshold values ​​S1 and S2, namely, that a constant switching between the classes in a transitional area or under unclear soil conditions is avoided. According to exemplary embodiments, the control of the blower power can again be achieved via pulse width modulation or a control that, for example, changes the speed of the blower by 100. As described in Fig. 2, the control unit can compensate for 300 slow variations in the vacuum value via a setpoint control to maintain a pressure value that is as constant as possible. However, a change in surface type from smooth to rough or vice versa leads to a sudden increase or decrease in the vacuum value, so the setpoint control does not adjust quickly enough and the first threshold value S1 or the second threshold value S2 is exceeded. According to exemplary embodiments, this immediately leads to a sudden increase / decrease in blower power. Thus, the suction power of the scrubber-dryer is immediately adjusted to the changed floor surface and not gradually readjusted, as is the case with conventional floor cleaning machines. Fig. 3B shows the same control system as shown in Fig. 3A, but according to the illustrated embodiment, two further threshold values ​​are defined: a third threshold value S3 and a fourth threshold value S4. The following can apply to the threshold values, for example: S3 < S1 < S2 < S4. For example, the following values ​​can be used: S3 = 5 mbar, S1 = 21 mbar, S2 = 26 mbar, S4 = 100 mbar. It should be understood, however, that these values ​​are only examples and that the values ​​can be adapted to the specific circumstances or set as desired and can vary over a wide range (e.g., + / - 50%). If the third threshold value S3 is breached, the device control unit 300 can detect a significant pressure drop, which could indicate a fault such as the intake of unmetered air or a full dirty water tank 410. As a response to a breach of the third threshold S3, an error message can be displayed, allowing the user to take corrective action. Optionally, the scrubber-dryer can also stop, as proper cleaning can no longer be guaranteed. The fourth threshold, S4, indicates an unexpected increase in vacuum pressure, which can also point to a fault. For example, the fourth threshold, S4, could indicate a blockage or obstruction of the suction nozzle. In response to exceeding the fourth threshold, S4, an error message may be displayed, allowing the user to take corrective action. Optionally, the scrubber-dryer can also be switched off or stopped to prevent damage to the suction blower 300 due to the increased vacuum pressure. According to the examples given, only one of the mentioned threshold values ​​needs to be defined. The additionally defined threshold values ​​S3 and S4 serve to detect faults. It goes without saying that other measured control variables can also be used for fault detection (e.g., the power consumption of the suction fan 100, the residual moisture content of the surface 51, 52, the conductivity value on the surface 51, 52). The threshold values ​​S3 and S4 are just one way to detect problems in the suction system. In general, various faults can be detected by evaluating the measured values. This includes how quickly a new negative pressure is reached or what fan output is required to set the first negative pressure value p1 or the second negative pressure value p2. According to the exemplary implementations, the described behavior is used in automatic mode. The control via hysteresis shown in Fig. 3A and Fig. 3B offers the advantage that the scrubber-dryer does not switch back and forth between the two states in rapid succession, but only switches when there is a clear change in surface condition. Alternatively or additionally, the suction blower 100 can be regulated to a defined negative pressure value. If the blower power and / or the (electrical) current and / or the (electrical) voltage and / or the pulse width modulation now exceed or fall below a predefined threshold value, the device control 300 can, according to exemplary embodiments, detect or recognize the change of floor (i.e., surfaces 51, 52). According to exemplary embodiments, the scrubber-dryer then regulates to the (new) negative pressure value that is associated with or assigned to the newly detected floor (i.e., surfaces 51, 52). Fig. 4 shows an exemplary flowchart for a method for controlling a scrubber-dryer during the wet cleaning of surfaces, which in turn are divided into different classes. The process starts at step 410, which triggers the acquisition of sensor data at step 420. The sensor data can be continuously acquired by the sensor unit 200 and can, in particular, include a measurement of a vacuum value. The corresponding pressure sensor can again be located on an intake port and / or on the intake hose 435 and / or on the intake manifold 430. Alternatively or additionally, vacuum measurement can also be performed at other points, as long as the recorded vacuum values ​​allow for inferences about the underlying surface. In step 430, the sensor data are analyzed with regard to a change in surface class 51, 52. According to exemplary embodiments, this can be done by continuously comparing the measured vacuum values ​​with one or more threshold values ​​(see Fig. 2, Fig. 3A, Fig. 3B). If no new surface class was detected in step 430, a return to step 425 (acquiring sensor data) occurs. If a new surface class is detected in step 430, a corresponding trigger signal is issued in step 435, which in turn causes a change in the control of the suction fan 100 in step 440. The associated value for the controlled variable can be changed according to the new surface class. For example, the fan speed can be set to a new setpoint (e.g., high fan speed P1 or reduced fan speed P2 from Fig. 3A). The method, or parts thereof, can also be computer-implemented; that is, it can be implemented by instructions stored on a storage medium that are capable of executing the steps of the method when run on a processor. The instructions typically comprise one or more instructions that may be stored on different media in or on peripheral units. When read and executed by the control unit (e.g., Device Control 300), these instructions cause the control unit to perform functions, functionalities, and operations that result in the execution of a method according to the exemplary embodiments. It is understood that all functions described in this disclosure (e.g., of the device control 300) can be implemented as further optional process steps. Furthermore, it is understood that the order in which the process steps are listed does not necessarily imply a sequence for their execution. The steps can be executed in a different order, and it is also necessary to execute only a subset of the process steps. Advantageous aspects of exemplary implementations can be summarized as follows. According to exemplary embodiments, a vacuum sensor can be installed on the suction hose 435 of a machine (scrubber-dryer). This sensor continuously measures the vacuum in the suction hose 435. If the vacuum drops or increases, the turbine's power (suction blower 100) is adjusted accordingly. This ensures that a constant vacuum is maintained in the suction hose 435. This, in turn, results in consistently good suction performance, even when the machine is cleaning different types of flooring (rough, smooth, etc.). In particular, the vacuum can be quickly adjusted to the optimal value for the specific floor type. If the measured values ​​exceed or fall below certain thresholds (e.g., the third threshold S3 or the fourth threshold S4), this can indicate a blockage or a defect. According to the examples provided, these defects can be detected and corresponding error messages or warnings issued. According to exemplary embodiments, a soil type (surface class 51, 52) can be detected by monitoring the turbines 100. The turbine output can be adjusted to the detected soil type. According to exemplary embodiments, the suction blower 100 is controlled between a limited number of power levels, in particular two levels. According to the exemplary embodiments, there is a delay between a change in the vacuum pressure and / or the setting of the power level. According to exemplary embodiments, the substrate (e.g. surface classes 51, 52) can also be detected via pressure in the extraction system and / or the modulation (PWM) of the blower. According to exemplary embodiments, the substrate (e.g., surface classes 51, 52) can be detected by means of additional sensors. The sensor unit 200 can therefore have one or more sensors arranged at predetermined positions in or on the scrubber-dryer. According to the exemplary embodiments, an optimal negative pressure at the suction bar 430 can be predefined, for example, by measuring the residual moisture content of the floor in question. To maintain the residual moisture within a desired range, the substrate value is selected accordingly, as shown in the exemplary embodiments. In contrast to a rough floor type 52, for example, significantly less negative pressure – and thus less blower power – is required for a smooth floor 51 to achieve good suction results. According to the exemplary embodiments, the scrubber-dryer regulates the vacuum value at the squeegee to the optimal value defined for the respective floor type. This can be achieved, as described, by adjusting the blower output. The optimal vacuum value, according to the exemplary embodiments, is defined by the minimum drying result to be achieved. If the scrubber-dryer changes, for example, from a smooth floor type 51 to a rough floor type 52, this is detected and the scrubber-dryer adjusts the vacuum value to the value appropriate for the floor. Depending on the substrate, significantly higher energy savings are therefore possible than with conventional controls based on a fixed defined negative pressure value (setpoint). It has been shown that the conventional evaluation of turbine current values ​​is too inaccurate. Therefore, exemplary embodiments use turbine power control based on the vacuum, whereby the vacuum in the suction hose 435 can be measured. Alternatively or additionally, instead of regulation based on negative pressure, ground detection is carried out using additional sensors (e.g. camera, spectrometer, ...). Alternatively or additionally, no control is based on the negative pressure, but rather a measurement / detection of residual moisture in the soil (e.g. optically or via conductivity measurement, ...) and an adjustment of the control until a target residual moisture is reached. Alternatively or additionally, control is not based on negative pressure, but on fan measurements (fan speed, power consumption, or current draw) in combination with the fan characteristics and PWM. The negative pressure in the system can be calculated using the measurements, the fan characteristics, and / or the PWM. The features of the invention disclosed in the description, claims and figures may be essential for the realization of the invention, either individually or in any combination. REFERENCE MARK LIST 51, 52 Surfaces, surface class 100 Suction blower (turbine, suction device) 200 Sensor unit 300 Device control (control unit) 410 First tank (e.g., for fresh water) 420 Second tank (e.g., for dirty water) 430 Suction bar 435 Suction hose 440 Drive 450 Cleaning unit S1, S2 Threshold values ​​S3, S4 Error threshold values, Threshold values ​​p1 First vacuum p2 Second vacuum P1 High blower power P2 Reduced blower power

Claims

A scrubber-dryer for wet cleaning surfaces, wherein the surfaces (51, 52) are divisible into at least a first surface class (51) and a second surface class (52), in particular into smooth and rough surfaces, and each surface class (51, 52) has one or more associated values ​​of control variables, the scrubber-dryer comprising: a suction blower (100) for generating a negative pressure to pick up moist dirt from the surface (51, 52); a sensor unit (200) for detecting a change in the surface (51, 52); and a device control unit (300) configured to detect a change between the first surface class (51) and the second surface class (52) and, upon a detected change to a new surface class (51, 52), to use an associated value of a control variable for the new surface class (51, 52) to control the suction blower (100). scrubber-dryer according to claim 1, wherein each surface class (51, 52) has at least one associated threshold value (S1, S2) for at least one of the control variables and the device control (300) is designed to determine the change of the surface class (51, 52) based on an exceedance of the at least one associated threshold value (S1, S2). scrubber-dryer according to claim 2, wherein the device control (300) is further designed to detect the change of the surface class (51, 52) only when the at least one associated threshold value (S1, S2) is exceeded for a minimum period of time. Scrubber dryer according to one of claims 1 to 3, wherein the device control (300) is further designed to also detect at least one of the following based on the sensor data: - blockage of a suction channel, - intake of secondary air, - defect of the suction blower, - a full dirty water tank, - an empty fresh water tank. Scrubber-dryer according to one of claims 1 to 4, wherein the device control (300) is further developed to perform control with respect to or based on at least one of the following control variables: - a vacuum value, - a power input value of the suction blower (100), - a pulse width modulation for the suction blower (100), - a speed of the suction blower (100), - a residual moisture on the surface (51, 52), - a conductivity value of the surface (51, 52). Scrubber-dryer according to claim 5, wherein the device control (300) is further configured to perform at least one of the following actions: - if the value of a first controlled variable is below a first threshold (S1), output an error message; - if the value of the first controlled variable is between the first threshold (S1) and a second threshold (S2), control the suction fan (100) with an increased value for a second controlled variable; - if the value of the first controlled variable is between the second threshold (S2) and a third threshold (S3), maintain the existing control of the suction fan (100); - if the value of the first controlled variable is between the third threshold (S3) and a fourth threshold (S4), control the suction fan (100) with a decreased value for the second controlled variable; - if the value of the first controlled variable is above the fourth threshold (S4), output a further error message.- if the value of the first controlled variable is above the fourth threshold (S4) or below the first threshold (S1), switch off the suction fan (100). Scrubber-dryer according to one of claims 1 to 6, wherein the sensor unit (200) is configured to detect a vacuum value for the generated vacuum, and the device control (300) is configured to determine a target value for a power consumption of the suction blower (100) based on the detected vacuum and to adjust the suction blower (100) to the target value. Scrubber-dryer according to claim 7, wherein the device control (300) is configured to maintain the detected vacuum value at a constant value by controlling the suction blower (100) and, if a parameter of the suction blower (100) leaves a predetermined range, to detect the change to a new surface class (51, 52), wherein the parameter of the suction blower (100) is at least one of the following: a blower power, a current, a voltage, a pulse width modulation, a quantity dependent thereon. Scrubber-dryer according to one of claims 1 to 8, wherein the sensor unit (200) has or accesses at least one of the following sensors: - a pressure sensor, - a flow meter for intake air and / or for the exhaust air, - a power meter for the suction blower (100), - an ammeter for the suction blower (100), - a tachometer for the suction blower (100), - a floor sensor for detecting the condition of the surface (51, 52), - a moisture meter for the surface (51, 52) or for the intake air of the suction blower (100), - a spectrometer, - a conductivity meter. Scrubber dryer according to claim 9, further comprising: a suction bar (430) for suctioning moist dirt from the surface (51, 52); a suction hose (435) for extracting suction air from the suction bar (430) to the suction blower (100), wherein the pressure sensor is arranged on the suction bar (430) or between the suction bar (430) and the suction hose (435). scrubber-dryer according to one of claims 1 to 10, wherein the sensor unit (200) and / or the device control (300) are configured to perform averaging for sensor values ​​and / or for control variables. Method for controlling a suction blower (100) of a scrubber-dryer, wherein the scrubber-dryer also has a sensor unit (200) that detects a change in the surface (51, 52), wherein the surfaces are divisible into at least two surface classes (51, 52), in particular smooth and rough surfaces, and each surface class (51, 52) has one or more associated values ​​of controlled variables, the method comprises: detecting a change between the at least two surface classes (51, 52) based on sensor data from the sensor unit (200); and on a detected change to a new surface class (51, 52), controlling the suction blower (100) with the associated values ​​of controlled variables. The method of claim 12, further comprising at least one of the following: - determining a setpoint of a first controlled variable for a first surface (51), - determining a setpoint of the first controlled variable for a second surface (52), - determining a setpoint of a second controlled variable for the first surface (51), - determining a setpoint of the second controlled variable for the second surface (52), - determining a vacuum value using a characteristic curve of the suction blower (100). Method according to claim 13, wherein the first controlled variable is one of the following: a vacuum value, a residual moisture of the surface, a conductivity value of the surface, and wherein the second controlled variable is a power input of the suction blower (100) or a rotational speed of the suction blower (100). Machine-readable storage medium with instructions stored thereon configured to execute the method according to any one of claims 12 to 14 when the instructions are executed on a data processing unit.

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