WO2016096045A1

WO2016096045A1 - Using digital pressure switch for detecting dust container fill-up level

Info

Publication number: WO2016096045A1
Application number: PCT/EP2014/078801
Authority: WO
Inventors: Niklas WINDH
Original assignee: Aktiebolaget Electrolux
Priority date: 2014-12-19
Filing date: 2014-12-19
Publication date: 2016-06-23

Abstract

The invention relates to a vacuum cleaner and a method at the vacuum cleaner of calibrating a digital pressure switch configured to measure pressure over a dust container of the vacuum cleaner to determine whether the dust container is full. A method at a vacuum cleaner, being capable of being operated in at least a lower-power mode and a higher-power mode, is provided for calibrating a digital pressure switch configured to measure differential pressure over a dust container of the vacuum cleaner to determine whether the dust container is full. The method comprises increasing speed of a suction fan configured to transport debris into the dust container from zero up to a value of a lowest fan speed defined in the lower-power mode, with the dust container being full, and registering speed of the suction fan at a moment of the digital pressure switch triggering, the digital pressure switch having been set to trigger at a measured pressure value being reached before the fan speed has been increased to attain said value of a lowest fan speed.

Description

USING DIGITAL PRESSURE SWITCH FOR DETECTING DUST CONTAINER FILL-UP LEVEL

TECHNICAL FIELD

The invention relates to a vacuum cleaner and a method at the vacuum cleaner of calibrating a digital pressure switch configured to measure pressure over a dust container of the vacuum cleaner to determine whether the dust container is full.

BACKGROUND

In a vacuum cleaner, there is a correlation between a pressure drop measured over a dust container and how full the dust container is. Hence, by measuring the pressure, it can be determined how much dust and debris has been collected in the dust container. Typically, a visual indication is provided to the user when the container is full such that the user can empty the container.

Generally, the pressure drop over the dust container is measured by an analog or digital pressure sensor. The analog pressure sensor outputs an analog signal corresponding to the measure pressure level, and by comparing a value of the signal with a predetermined threshold value, it can be determined whether the container is full or not.

For instance, EP o 36 191 discloses a variable power suction cleaner including an analog pressure switch at the entrance to a dust filter bag, and an air flow switch which measures the differential pressure between a point upstream of a diffuser of the fan, and a point within the body of the cleaner upstream of an exhaust filter. Signals from the pressure switches are compared with limit values stored within a microprocessor memory, to determine whether, for example, the bag is full or the suction hose is blocked.

When using a digital sensor, also referred to as a digital pressure switch, the digital sensor is calibrated in production using an adjusting screw to determine at which pressure threshold value the switch should trigger. Thus, the digital sensor will output a digital signal when the pressure measured by the digital sensor exceeds the pressure threshold.

For reasons of sustainability, modern vacuum cleaners is capable of operating at different cleaning modes where a lower-power mode for instance can be selected, thereby causing the vacuum cleaner to consume less power due to a suction fan of the vacuum cleaner operating at a lower speed.

Further, it is desirable to provide a vacuum cleaner operating in a more silent manner, which is facilitated by means the lower-power mode.

However, this has as an effect that the pressure drop created over the dust container will not reach the threshold value that was required to trigger the digital pressure switch when the fan was running at full speed in a higher- power mode. For an analog switch, this is no problem as a micro controller of the vacuum cleaner knows what value the fan is running with and can adjust the threshold accordingly. In contrast, a digital pressure switch is hard coded using the adjusting screw to trigger at a specific threshold which has as a consequence that if lower-power modes shall be supported, a digital pressure switch cannot be used since it will not reach the threshold value required for triggering in the higher-power mode when it changes mode and enters the lower-power mode.

SUMMARY

An object of the present invention is to solve, or at least mitigate, this problem in the art and provide an improved method of calibrating a digital pressure switch in a vacuum cleaner.

This object is attained in a first aspect of the present invention by a method at a vacuum cleaner, being capable of being operated in at least a lower-power mode and a higher-power mode, of calibrating a digital pressure switch configured to measure differential pressure over a dust container of the vacuum cleaner to determine whether the dust container is full. The method comprises increasing speed of a suction fan configured to transport debris into the dust container from zero up to a value of a lowest fan speed defined in the lower-power mode, with the dust container being full, and registering speed of the suction fan at a moment of the digital pressure switch triggering, the digital pressure switch having been set to trigger at a measured pressure value being reached before the fan speed has been increased to attain said value of a lowest fan speed.

This object is attained in a second aspect of the present invention by a vacuum cleaner being capable of operating in at least a lower-power mode and a higher-power mode. The vacuum cleaner comprises a digital pressure switch, a dust container, a suction fan, and a controller. The digital pressure switch is configured to measure differential pressure over the dust container of the vacuum cleaner to determine whether the dust container is full. The suction fan is configured to transport debris into the dust container. The controller is configured to calibrate the digital pressure switch by increasing speed of the suction fan from zero up to a value of a lowest fan speed defined in the lower-power mode, with the dust container being full, and to register speed of the suction fan at a moment of the digital pressure switch triggering, the digital pressure switch having been set to trigger at a measured pressure value being reached before the fan speed has been increased to attain said value of a lowest fan speed.

Thus, during a calibration phase of the digital pressure switch, for instance undertaken during manufacturing of the vacuum cleaner, the speed of the suction fan is increased by the controller from zero (i.e. standstill) to a value RPMLP being a lowest fan speed defined in the lower-power mode, with the dust container being full. In case there are further power modes, RPMLP applies to a lowest-power mode.

The controller registers a speed RPMTR of the suction fan at a moment of the digital pressure switch triggering. The digital pressure switch must be set to trigger at a pressure value being reached before the fan speed has been increased to RPMLP. This pressure value is thus selected to be the digital switch trigger threshold TTR. Advantageously, a trigger threshold value TTR is arrived at which can be reached also in the lower-power mode. Further, the registered fan speed RPMTR at switch triggering can advantageously be used subsequently during normal vacuum cleaner operation to determine whether the dust container is full or not.

An advantage of using a digital pressure switch in favor of an analog switch is that digital pressure switches are less expensive then their analog

counterparts.

In an embodiment of the present invention, the registered fan speed value RPMTR registered at digital switch triggering during the calibration phase is subsequently used for advantageously determining whether the dust container is full or not. Thus, during subsequent normal operation of the vacuum cleaner by a user, a current speed of the suction fan at digital pressure switch triggering is registered by the controller. The controller compares the current suction fan speed value with the suction fan speed value RPMTR, which previously was registered for a full container at switch triggering during initial calibration. If the current value of the speed of the suction fan corresponds to the previously registered suction fan speed value RPMTR, at switch triggering, the dust container is considered full.

Accordingly, this can be signaled to a user of the vacuum cleaner by means of e.g. audio or visual indications.

Preferred embodiments will be described in the following.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

BRIEF DES CRIPTION OF THE DRAWINGS

The invention is now described, by way of example, with reference to the accompanying drawings, in which: Figure l shows a robotic vacuum cleaner in which the present application can be implemented;

Figure 2 shows a front view of the robotic vacuum cleaner of Figure 1;

Figure 3 illustrates a sectional side view of the robotic vacuum cleaner of Figure 1;

Figure 4 shows a graph illustrating a problem in the art of using a digital pressure switch for the purpose of determining whether the dust container is full;

Figure 5a shows a flowchart of a method at a vacuum cleaner of calibrating the digital pressure switch according to an embodiment of the present invention;

Figure 5b illustrates suction fan speed as a function of pressure drop over the dust container;

Figure 6 illustrates a flowchart of an embodiment of the present invention where the initially registered fan speed is used during normal operation of the vacuum cleaner to determine whether the dust container is full or not; and

Figure 7 illustrates a further embodiment of the present invention, where the pressure value required to trigger the digital pressure switch is allowed to vary within a range being defined by a lower pressure value and an upper pressure value.

DETAILED DESCRIPTION

The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description.

Figure l shows a robotic vacuum cleaner in which the present application can be implemented. However, it should be noted that the present invention may be implemented in any vacuum cleaner utilizing a dust container, such as an upright cleaner, a canister cleaner, a drum cleaner, a hand-held, etc., where the robotic cleaner of Figure 1 is an example. The robotic vacuum cleaner can be mains-operated and have a cord, be battery-operated or use any other kind of suitable energy source, for example solar energy.

The robotic vacuum cleaner is illustrated from underneath, i.e. the bottom side of the robotic vacuum cleaner is shown. The arrow indicates the forward direction of the robotic vacuum cleaner. The robotic vacuum cleaner 10 comprises a main body 11 housing components such as a propulsion system comprising driving means in the form of two electric wheel motors 15a, 15b for enabling movement of the driving wheels 12, 13 such that the vacuum cleaner can be moved over a surface to be cleaned. Each wheel motor 15a, 15b is capable of controlling the respective driving wheel 12, 13 to rotate independently of each other in order to move the robotic vacuum cleaner 10 across the surface to be cleaned. A number of different driving wheel arrangements, as well as various wheel motor arrangements, can be envisaged. It should be noted that the robotic vacuum cleaner may have any appropriate shape, such as a device having a more traditional circular-shaped main body, or a triangular-shaped main body. As an alternative, a track propulsion system may be used or even a hovercraft propulsion system. The propulsion system may further be arranged to cause the robotic vacuum cleaner 10 to perform any one or more of a yaw, pitch, translation or roll movement.

A controller 16 such as a microprocessor controls the wheel motors 15a, 15b to rotate the driving wheels 12, 13 as required in view of information received from an obstacle detecting device (not shown in Figure 1) for detecting obstacles in the form of walls, floor lamps, table legs, around which the robotic vacuum cleaner must navigate. The obstacle detecting device may be embodied in the form of a 3D sensor system registering its surroundings, implemented by means of e.g. a 3D camera, a camera in combination with lasers, a laser scanner, etc. for detecting obstacles and communicating information about any detected obstacle to the microprocessor 16. The microprocessor 16 communicates with the wheel motors 15a, 15b to control movement of the wheels 12, 13 in accordance with information provided by the obstacle detecting device such that the robotic vacuum cleaner 10 can move as desired across the surface to be cleaned. This will be described in more detail with reference to subsequent drawings.

Further, the main body 11 may optionally be arranged with a cleaning member 17 for removing debris and dust from the surface to be cleaned in the form of a rotatable brush roll arranged in an opening 18 at the bottom of the robotic cleaner 10. Thus, the rotatable brush roll 17 is arranged along a horizontal axis in the opening 18 to enhance the dust and debris collecting properties of the vacuum cleaner 10. In order to rotate the brush roll 17, a brush roll motor 19 is operatively coupled to the brush roll to control its rotation in line with instructions received from the controller 16.

Moreover, the main body 11 of the robotic cleaner 10 comprises a suction fan

20 creating an air flow for transporting debris to a dust bag or cyclone arrangement (not shown) housed in the main body via the opening 18 in the bottom side of the main body 11. The suction fan 20 is driven by a fan motor

21 communicatively connected to the controller 16 from which the fan motor 21 receives instructions for controlling the suction fan 20.

The main body 11 of the robotic vacuum cleaner 10 is further equipped with an angle-measuring device 24, such as e.g. a gyroscope 24 and/or an accelerometer or any other appropriate device for measuring orientation of the robotic vacuum cleaner 10. A three-axis gyroscope is capable of measuring rotational velocity in a roll, pitch and yaw movement of the robotic vacuum cleaner 10. A three-axis accelerometer is capable of measuring acceleration in all directions, which is mainly used to determine whether the robotic vacuum cleaner is bumped or lifted or if it is stuck (i.e. not moving even though the wheels are turning). The robotic vacuum cleaner 10 further comprises encoders (not shown in Figure l) on each drive wheel 12, 13 which generate pulses when the wheels turn. The encoders may for instance be magnetic or optical. By counting the pulses at the controller 16, the speed of each wheel 12, 13 can be determined. By combining wheel speed readings with gyroscope information, the controller 16 can perform so called dead reckoning to determine position and heading of the vacuum cleaner 10.

The main body 11 may further be arranged with a rotating side brush 14 adjacent to the opening 18, the rotation of which could be controlled by the drive motors 15a, 15b, the brush roll motor 19, or alternatively a separate side brush motor (not shown). Advantageously, the rotating side brush 14 sweeps debris and dust such from the surface to be cleaned such that the debris ends up under the main body 11 at the opening 18 and thus can be transported to a dust chamber of the robotic vacuum cleaner. Further advantageous is that the reach of the robotic vacuum cleaner 10 will be improved, and e.g. corners and areas where a floor meets a wall are much more effectively cleaned. As is illustrated in Figure 1, the rotating side brush 14 rotates in a direction such that it sweeps debris towards the opening 18 such that the suction fan 20 can transport the debris to a dust chamber. The robotic vacuum cleaner 10 may comprise two rotating side brushes arranged laterally on each side of, and adjacent to, the opening 18.

With further reference to Figure 1, the controller/processing unit 16 embodied in the form of one or more microprocessors is arranged to execute a computer program 25 downloaded to a suitable storage medium 26 associated with the microprocessor, such as a Random Access Memory (RAM), a Flash memory or a hard disk drive. The controller 16 is arranged to carry out a method according to embodiments of the present invention when the appropriate computer program 25 comprising computer-executable instructions is downloaded to the storage medium 26 and executed by the controller 16. The storage medium 26 may also be a computer program product comprising the computer program 25. Alternatively, the computer program 25 may be transferred to the storage medium 26 by means of a suitable computer program product, such as a digital versatile disc (DVD), compact disc (CD) or a memory stick. As a further alternative, the computer program 25 may be downloaded to the storage medium 26 over a network. The controller 16 may alternatively be embodied in the form of a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field- programmable gate array (FPGA), a complex programmable logic device (CPLD), etc.

Figure 2 shows a front view of the robotic vacuum cleaner 10 of Figure 1 illustrating the previously mentioned obstacle detecting device in the form of a 3D sensor system 22 comprising at least a camera 23 and a first and a second line laser 27, 28, which may be horizontally or vertically oriented line lasers. Further shown is the controller 16, the main body 11, the driving wheels 12, 13, and the rotatable brush roll 17 previously discussed with reference to Figure la. The controller 16 is operatively coupled to the camera 23 for recording images of a vicinity of the robotic vacuum cleaner 10. The first and second line lasers 27, 28 may preferably be vertical line lasers and are arranged lateral of the camera 23 and configured to illuminate a height and a width that is greater than the height and width of the robotic vacuum cleaner 10. Further, the angle of the field of view of the camera 23 is preferably smaller than the space illuminated by the first and second line lasers 27, 28. The camera 23 is controlled by the controller 16 to capture and record a plurality of images per second. Data from the images is extracted by the controller 16 and the data is typically saved in the memory 26 along with the computer program 25.

The first and second line lasers 27, 28 are typically arranged on a respective side of the camera 23 along an axis being perpendicular to an optical axis of the camera. Further, the line lasers 27, 28 are directed such that their respective laser beams intersect within the field of view of the camera 23. Typically, the intersection coincides with the optical axis of the camera 23. The first and second line laser 27, 28 are configured to scan, preferably in a vertical orientation, the vicinity of the robotic vacuum cleaner 10, normally in the direction of movement of the robotic vacuum cleaner 10. The first and second line lasers 27, 28 are configured to send out laser beams, which illuminate furniture, walls and other objects of e.g. a room to be cleaned. The camera 23 is controlled by the controller 16 to capture and record images from which the controller 16 creates a representation or layout of the surroundings that the robotic vacuum cleaner 10 is operating in, by extracting features from the images and by measuring the distance covered by the robotic vacuum cleaner 10, while the robotic vacuum cleaner 10 is moving across the surface to be cleaned. Thus, the controller 16 derives positional data of the robotic vacuum cleaner 10 with respect to the surface to be cleaned from the recorded images, generates a 3D representation of the surroundings from the derived positional data and controls the driving motors 15a, 15b to move the robotic vacuum cleaner across the surface to be cleaned in accordance with the generated 3D representation and navigation information supplied to the robotic vacuum cleaner 10 such that the surface to be cleaned can be navigated by taking into account the generated 3D representation. Since the derived positional data will serve as a foundation for the navigation of the robotic vacuum cleaner, it is important that the positioning is correct; the robotic device will otherwise navigate according to a "map" of its surroundings that is misleading.

The 3D representation generated from the images recorded by the 3D sensor system 22 thus facilitates detection of obstacles in the form of walls, floor lamps, table legs, around which the robotic vacuum cleaner must navigate as well as rugs, carpets, doorsteps, etc., that the robotic vacuum cleaner 10 must traverse. The robotic vacuum cleaner 10 is hence configured to learn about its environment or surroundings by operating/cleaning.

With reference to Figure 2, for illustrational purposes, the 3D sensor system 22 is separated from the main body 11 of the robotic vacuum cleaner 10. However, in a practical implementation, the 3D sensor system 22 is preferably integrated with the main body 11 of the robotic vacuum cleaner 10 to minimize the height of the robotic vacuum cleaner 10, thereby allowing it to pass under obstacles, such as e.g. a sofa.

Hence, the 3D sensor system 22 comprising the camera 23 and the first and second vertical line lasers 27, 28 is arranged to record images of a vicinity of the robotic cleaning from which objects/obstacles may be detected. The controller 16 is capable of positioning the robotic vacuum cleaner 10 with respect to the detected obstacles and hence a surface to be cleaned by deriving positional data from the recorded images. From the positioning, the controller 16 controls movement of the robotic vacuum cleaner 10 by means of controlling the wheels 12, 13 via the wheel drive motors 15a, 15b, across the surface to be cleaned.

The derived positional data facilitates control of the movement of the robotic vacuum cleaner 10 such that vacuum cleaner can be navigated to move very close to an object, and to move closely around the object to remove debris from the surface on which the object is located. Hence, the derived positional data is utilized to move flush against the object, being e.g. a thick rug or a wall. Typically, the controller 16 continuously generates and transfers control signals to the drive wheels 12, 13 via the drive motors 15a, 15b such that the robotic vacuum cleaner 10 is navigated close to the object.

Figure 3 illustrates a sectional side view of the robotic vacuum cleaner 10 of Figure 1, where a dust transport channel 35 leads from the opening 18 in the bottom of the vacuum cleaner 10 to a dust container 31 for collecting dust and debris. A filter 32 is arranged between the dust container 31 and the suction fan 20, which fan 20 creates an air flow for transporting debris into the dust container 31. Now, with the air flow, a pressure drop ΔΡ is created over the container 31; the fuller the container, the higher the pressure drop. The pressure drop over ΔΡ is measured by digital pressure switch 30 by measuring a respective pressure Pi, P₂ on each side of the dust container 31, where ΔΡ = Pi - P₂. When the measured pressure ΔΡ over the dust container 32 exceeds a predetermined switch trigger threshold TTR, the digital pressure switch 30 will trigger and cause an output signal to be sent to the controller 16 accordingly. If the switch trigger threshold TTR is appropriately set, the switch will trigger as soon as the dust container is full. Typically, a user of the robotic vacuum cleaner 10 will receive a visual indication via indicator 36 that the dust container 31 is full and must be emptied.

As is illustrated in the dotted oval, the digital switch comprises two

measurement terminals for measuring Pi and P₂, and an internal membrane 34 separating two compartments with pressure Pi and P₂. As soon as the difference in pressure between the terminals is sufficiently high, as stipulated by the switch trigger threshold, the membrane 34 will deform and contact a spring 33, which will generate an out signal from the digital switch 30 by having the membrane 34 short circuit two pins (not shown). The spring is arranged with an adjusting screw (not shown) for setting the switch trigger threshold TTR, typically during a manufacturing phase of the robotic vacuum cleaner 10. The spring causes a force to act on the membrane and with the screw, the force of the spring can be adjusted to be higher or lower. It should be noted that the illustrated switch 30 is an example of a digital switch which can be used, and other types of digital switches can be envisaged.

Figure 4 shows a graph illustrating a problem in the art of using a digital pressure switch 30 for the purpose of determining whether the dust container 31 is full. The graph shows a relationship between measured pressure ΔΡ and fan speed. The graph illustrates a graph corresponding to a completely full dust container 31. Thus, in this particular example, the digital pressure switch has been adjusted such that the switch trigger threshold TTR is reached when the fan speed is RPMTR. NOW, if this corresponds to a higher-power mode of the vacuum cleaner 10, the trigger threshold cannot be reached when the fan speed of the robot cleaner 10 is decreased to RPMLP in order to enter the cleaner into its lower-power mode. As can be seen in Figure 4, this corresponds to a pressure drop of APLP which is substantially lower than the pressure value of trigger threshold. Thus, the controller 16 will not receive a trigger signal from the digital pressure switch 30 that the dust container 30 is full in the lower-power mode. Figure 5a shows a flowchart of a method at a vacuum cleaner 10 of calibrating the digital pressure switch 30 according to an embodiment of the present invention. Reference will further be made to Figure 5b for illustrating fan speed as a function of pressure drop ΔΡ. The method may be undertaken during production of the robotic vacuum cleaner 10 and is typically carried out by having the controller 16 execute an appropriate test program. In a first step S101, the speed of the suction fan 20 is increased by the controller 16 from zero (i.e. standstill) to the value RPMLP being a lowest fan speed defined in the lower-power mode, with the dust container 31 being full. In step S102, the controller 16 registers the speed RPMTR of the suction fan 20 at a moment of the digital pressure switch 30 triggering. The digital pressure switch 30 must be set (by setting the adjusting screw) to trigger at a pressure value being reached before the fan speed has been increased to RPMLP. This pressure value is thus selected to be the digital switch trigger threshold TTR. Advantageously, with this embodiment of the present invention a trigger threshold value TTR is arrived at which can be reached also in the lower- power mode. Further, the registered fan speed RPMTR at switch triggering can advantageously be used subsequently to determine whether the dust container 31 is full or not.

Figure 5b illustrates fan speed as a function of pressure drop ΔΡ, and as can be deducted, the digital pressure switch trigger value TTR is reached at a fan speed of RPMTR for a full dust container 31. The dust container 31 will thus be indicated as being full, typically by means of the visual indicator 36, at a fan speed of RPMTR.

Further illustrated in Figure 5b is a scenario where the dust container is filled up to 80%, and further a scenario where the dust container is only filled up to 60% of full capacity. Hence, for the dust container being filled up to 80%, the fan speed would need to reach a value of RPMi before the digital switch 30 triggers, while for the dust container being filled up to 60%, the fan speed would need to reach a value of RPM₂ before the digital switch 30 triggers. In an embodiment of the present invention, the speed of the suction fan 20 at a moment of the digital pressure switch 30 triggering is advantageously registered for different levels of fill-up of the dust container 31 during production. As can be seen in Figure 5B, for the digital switch 30 triggering at a value of TTR the following observations can be made:

RPMTR = > 100% dust container fill-up,

RPMi => 80% dust container fill-up,

RPM₂ => 60% dust container fill-up, and

RPM₃ => 40% dust container fill-up.

Now, at least some of these observed fan speeds are registered and

subsequently used during normal operation of the vacuum cleaner 10. For instance, in case the digital pressure switch 30 triggers at a speed of RPM₂, the controller 16 of the vacuum cleaner 10 advantageously concludes that the dust container 31 is not full, but only filled up to about 60%, in contrast to what is indicated by the digital pressure switch 30. The controller 16 will thus advantageously control visual indicator 36 not to signal that the dust container 31 is full at RPM₂. A similar process is undertaken e.g. at a fan speed of RPMi corresponding to 80% while for RPM₃ the lower-power mode fan speed of RPMLP is exceeded and for a fill-up of 20%, the switch 30 will not trigger no matter the fan speed. Thus, in this particular example, fan speeds at a dust container fill-up of 40% and 20% are not necessarily registered. However, for the digital pressure switch 31 triggering at a fan speed of RPMTR, the controller 16 will conclude that the dust container 31 indeed is full, and signal accordingly to a user via the visual indicator 36.

A further advantage is that fan speed at different fill-up levels is registered, as it is thus possible to display to the user not only a completely full dust container, but different levels of fill-up range. Figure 6 illustrates a flowchart of an embodiment of the present invention where the previously registered fan speed is used during normal operation of the vacuum cleaner 10 to determine whether the dust container is full or not.

As previously has been described with reference to Figures 5a and 5b, during an initial calibration of the digital switch 30, in a first step S101, the speed of the suction fan 20 is increased by the controller 16 from zero to the value RPMLP being a lowest fan speed defined in the lower-power mode, with the dust container 31 being full. In step S102, the controller 16 registers the speed of the suction fan 20 at a moment of the digital pressure switch 30 triggering. The digital pressure switch 30 must be set to trigger at a pressure value being reached before the fan speed has been increased to RPMLP. Subsequently, during normal operation of the vacuum cleaner 10 by a user, a current speed of the suction fan 20 at digital pressure switch triggering is registered by the controller 16 in step S103. The controller 16 compares in step S104 the current suction fan speed value with the suction fan speed value RPMTR, which previously was registered for a full container at switch triggering during initial calibration. If the current value of the speed of the suction fan corresponds to the previously registered suction fan speed value RPMTR, at switch triggering, the dust container 31 is considered full.

Figure 7 illustrates a further embodiment of the present invention, where the pressure value required to trigger the digital pressure switch 30

advantageously is allowed to vary within a range being defined by a lower pressure value TTRL and an upper pressure value TTRH, wherein a respective fan speed RPMTRL, RPMTRH corresponding to the lower pressure value TTRL and the upper pressure value TTRH is registered for subsequent use during normal operation of the vacuum cleaner 10. Hence, for the digital pressure switch 31 triggering at a fan speed in the range of RPMTRL - RPMTRH, the controller 16 will conclude that the dust container 31 is full, and signal accordingly to a user via the visual indicator 36.

It can be further be envisaged that later versions of the computer program 25, which is downloaded to the storage medium 26 and executed by the controller 16 to perform the previously described test program for registering the fan speed at the switch trigger value, released to customers for vacuum cleaner update can adjust the fan speed RPMTR attained at the reached digital pressure switch trigger value TTR to take into account e.g. the fact that structure of dust and debris varies with physical location. For instance, the fan speed RPMTR attained at the reached digital pressure switch trigger value TTR may be higher in one particular part of the world as compared to another part due to the differing structure of the dust. This advantageously overcomes the problem of hard-coded digital switches in the art.

The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

Claims

1. Method at a vacuum cleaner, being capable of being operated in at least a lower-power mode and a higher-power mode, of calibrating a digital pressure switch configured to measure differential pressure over a dust container of the vacuum cleaner to determine whether the dust container is full, the method comprises:

increasing (S101) speed of a suction fan configured to transport debris into the dust container from zero up to a value of a lowest fan speed defined in the lower-power mode, with the dust container being full; and

registering (S102) speed of the suction fan at a moment of the digital pressure switch triggering, the digital pressure switch having been set to trigger at a measured pressure value being reached before the fan speed has been increased to attain said value of a lowest fan speed.

2. The method of claim 1, further comprising:

allowing the pressure value required to trigger the digital pressure switch to vary within a range being defined by a lower pressure value and an upper pressure value, wherein a respective fan speed corresponding to the lower pressure value and the upper pressure value is registered.

3. The method of claims 1 or 2, wherein the registering (S102) of the speed further comprises:

registering speed of the suction fan at a moment of the digital pressure switch triggering, for different levels of dust container fill-up.

4. The method of any one of the preceding claims, further comprising: registering (S103) during operation of the vacuum cleaner a current speed of the suction fan at digital pressure switch triggering; and

comparing (S104) the registered current suction fan speed value with the speed of the suction fan previously registered at the moment of the digital pressure switch triggering, wherein the dust container is considered full if the current value of the speed of the suction fan corresponds to the previously registered suction fan speed value. l8

5. The method according to any one of the preceding claims, further comprising:

indicating to a user of the vacuum cleaner that the dust container is full.

6. A vacuum cleaner (10) being capable of operating in at least a lower- power mode and a higher-power mode, comprising:

a digital pressure switch (30);

a dust container (31);

a suction fan (20); and

a controller (16); wherein

the digital pressure switch (30) is configured to measure differential pressure (ΔΡ) over the dust container (31) of the vacuum cleaner to determine whether the dust container is full,

the suction fan (20) is configured to transport debris into the dust container (31), and

the controller (16) is configured to calibrate the digital pressure switch (30) by increasing speed of the suction fan (20) from zero up to a value of a lowest fan speed (RPMLP) defined in the lower-power mode, with the dust container (31) being full, and to register speed (RPMTR) of the suction fan at a moment of the digital pressure switch triggering, the digital pressure switch having been set to trigger at a measured pressure value (TTR) being reached before the fan speed has been increased to attain said value of a lowest fan speed.

7. The vacuum cleaner (10) of claim 6, the controller (16) further being configured to:

allow the pressure value (TTR) required to trigger the digital pressure switch (20) to vary within a range being defined by a lower pressure value (TTRL) and an upper pressure value (TTRH), wherein a respective fan speed (RPMTRL, RPMTRH) corresponding to the lower pressure value and the upper pressure value is registered.

8. The vacuum cleaner (10) of claims 6 or 7, the controller (16) further being configured to:

register speed of the suction fan at a moment of the digital pressure switch triggering, for different levels of dust container fill-up.

9. The vacuum cleaner (10) of any one of claims 6-8, the controller (16) further being configured to:

register during operation of the vacuum cleaner (10) a current speed of the suction fan (20) at digital pressure switch triggering; and

compare the registered current suction fan speed value with the speed (RPMTR) of the suction fan (20) previously registered at the moment of the digital pressure switch triggering, wherein the dust container (31) is considered full if the current value of the speed of the suction fan

corresponds to the previously registered suction fan speed value (RPMTR).

10. The vacuum cleaner (10) of any one of claims 6-9, further comprising: an indicator (36) configured to be controllable by the controller (16), thereby indicating to a user of the vacuum cleaner (10) that the dust container (31) is full.

11. The vacuum cleaner (10) of any one of claims 6-10, the vacuum cleaner being any one of a robotic vacuum cleaner, an upright vacuum cleaner, a canister vacuum cleaner, a hand-held vacuum cleaner.

12. A computer program (25) comprising computer-executable instructions for causing a device (10) to perform the steps recited in any one of claims 1-5 when the computer-executable instructions are executed on a processing unit (16) included in the device.

13. A computer program product comprising a computer readable medium (26), the computer readable medium having the computer program (25) according to claim 12 embodied therein.