METHOD FOR DETERMINING AN INITIAL FILTER-LOADING VALUE OF AN AIR-MOVING DEVICE

FIELD OF THE INVENTION

[0001]The present invention relates to determining an initial filter-loading value of an air-moving device, and, in particular but not exclusively, to a set of machine-readable instructions, and to an air-moving device having a storage comprising instructions and a processor configured to determine an initial filter-loading value of an air-moving device by executing the instructions. Further, the present invention relates to a system comprising one or more processors and a storage comprising a set of machine-readable instructions for determining an initial filter-loading value of an air-moving device.

BACKGROUND OF THE INVENTION

[0002]There is a general desire to improve air-moving devices, such as vacuum cleaners, in a number of ways. For example, improvements may be desired in terms of efficiency, manufacturing cost, flexibility of use and reliability.

SUMMARY OF THE INVENTION

[0003]According to a first aspect of the invention, there is provided a method for determining an initial filter-loading value of an air-moving device, the method comprising: arranging the device in a calibration mode, the calibration mode setting a pre-determined inlet restriction value for the device; operating the device while in the calibration mode; during the operating, performing a measurement process to determine a first value of an operating parameter of the device, the first value of the operating parameter depending on a degree of filter loading of an installed filter; and performing a determination process to determine the initial filter-loading value based on a first pre-determined relationship between values of the operating parameter and a set of filter-loading values.

[0004]The method may allow for an initial filter-loading value of an air-moving device to be determined reliably and accurately. The method may allow for the measurement of the filter-loading value to be calibrated following an event where the level of loading of a filter of the device may have changed while the device is not in operation. For example, the method may allow for an initial filter-loading value to be determined following washing of a filter of the device. In certain examples, by arranging the device in a calibration mode which sets a pre-determined inlet restriction value on the air-moving device, the first pre-determined relationship may be used to more-reliably relate values of the operating parameter of the device to an initial filter-loading value.

[0005]The method may allow for the filter-loading value to be determined based on an observable parameter of the device which is correlated with the value of the filter loading. In certain examples, the method may also allow for the value of the filter loading to be obtained, based on the measured value of the operating parameter, without, for example, introducing to the device the capability to directly measure a pressure across the filter in order to determine the level of filter loading. In certain examples, this may allow for fewer sensors on-board the device which may contribute to minimising product size, complexity and cost.

[0006]In certain examples, the method may allow for flexible determination of the value of the filter loading by use of an operating parameter which is obtained for other purposes during the operation of the device and which may be reused to determine the value of the filter loading. Since the first pre-determined relationship takes into account, in the relationship between values of the operating parameter and values of the filter loading, the inlet restriction, the first pre-determined relationship may allow for an accurate and reliable way of translating values of the operating parameter to values of the filter loading across various different inlet restriction conditions.

[0007]In the calibration mode, the pre-determined inlet restriction value may be set by no tool being attached to the device or by a pre-determined tool being attached to the device.

[0008]The device may be arranged with the pre-determined inlet restriction value by, for example, attaching a given tool to the device or removing all tools from the device. The removal of all tools from the device or the attaching of a given tool to the device may provide a simple and easily repeatable way of providing a pre-determined inlet restriction for the device.

[0009]The method may comprise, in the calibration mode, prompting a user to arrange the device with the pre-determined inlet restriction value or to indicate that the device is arranged with the pre-determined inlet restriction value.

[0010]The prompting may comprise prompting the user to remove all tools from the device or to indicate that no tools are attached to the device.

[0011]The user may, for example, be prompted by a user interface of the air-moving device to arrange the device with the pre-determined inlet restriction value. Alternatively, a prompt may be provided by another device which may be in communication with the air-moving device, for example a smartphone operating an app.

[0012]The method may comprise, in the calibration mode, receiving an indication that the device is arranged with the pre-determined inlet restriction value.

[0013]The indication may allow the air-moving device to determine that the device is arranged with the pre-determined inlet restriction value and is therefore arranged for performing the steps to determine the initial filter-loading value.

[0014]The receiving an indication may comprise detecting that the device is arranged with the pre-determined inlet restriction value.

[0015]For example, the device may be configured to detect whether a tool is attached to the device and/or a given type of tool attached to the device. This may allow the device to detect whether the device is arranged to operate with the pre-determined inlet restriction value or, for example, to detect a given pre-determined inlet restriction value for use in the determining the initial filter-loading value.

[0016]The receiving an indication may comprise receiving the indication from the user.

[0017]Receiving the indication from the user may allow the device to determine that the device is arranged to operate with the pre-determined inlet restriction value without, for example, detecting whether a given tool is attached to the device or whether no tool is attached to the device.

[0018]The operating parameter may be: an operating pressure of a motor of the air-moving device; or a speed of the motor of the air-moving device.

[0019]Determining the value of the filter loading based on the operating pressure of the motor or the speed of the motor may allow the filter loading to be determined reliably and accurately, based on an observable physical parameter which is correlated in a pre-determined manner with the value of the filter loading. Both the operating pressure of the motor and the speed of the motor may be parameters which can be reliably measured and which may be determined for other purposes, for example for monitoring a power output of the device. Thus, the use of these parameters to determine the value of the filter loading may obviate the need for additional sensors or processing to perform this task.

[0020]The operating parameter may be the operating pressure of the motor of the air-moving device and the first value of the operating parameter may be a first value of the operating pressure of the motor, and the measurement process may comprise determining the first value of the operating pressure of the motor based on: an ambient pressure measurement; and a motor-inlet pressure measurement during operation of the motor.

[0021]Determining the first value of the operating pressure based on an ambient pressure measurement and a motor-inlet pressure measurement during operation of the motor may provide for the value of the first operating pressure to be a differential operating pressure which correlates in a reliable and accurate way with the level of filter loading under a given inlet restriction condition. It may also allow measurements taken for other purposes relating to the operation of the air-moving device, for example, the ambient pressure, to be used to obtain the first value of the operating pressure of the motor.

[0022]The ambient pressure measurement and the motor-inlet pressure measurement may be measured at different times by a single pressure sensor.

[0023]Measuring the ambient pressure measurement and the motor-inlet pressure measurement at different times by a single pressure sensor may allow the first value of the operating pressure to be obtained by use of a single pressure sensor. This may allow for the operating pressure to be measured in a cost- and space-efficient manner.

[0024]The operating parameter may be the operating pressure of the motor of the air-moving device and the first value of the operating parameter may be a first value of the operating pressure of the motor, and the measurement process may comprise determining the first value of the operating pressure of the motor based on: a first pressure measurement of a pressure upstream of the motor; and a second pressure measurement of a pressure downstream of the motor.

[0025]Using a pressure measurement upstream of the motor and a pressure measurement downstream of the motor may allow for an accurate and reliable measurement of the operating pressure to be obtained in a simple manner.

[0026]The determination process may comprise: selecting, based on the pre-determined inlet restriction value, the first pre-determined relationship.

[0027]This may allow for a suitable pre-determined relationship between operating parameter values and filter-loading values to be selected. For example, different relationships between operating parameter values and filter-loading values may be pre-determined for different pre-determined inlet restriction values.

[0028]The determination process may comprise determining a first normalised value of the operating parameter by normalising the first value of the operating parameter by use of one or more values of one or more respective normalisation parameters, and, in the determination process: the first pre-determined relationship may be between normalised values of the operating parameter and values of the filter loading; and the determining the initial filter-loading value may be on the basis of the first normalised value of the operating parameter.

[0029]Normalising values of the operating parameter by use of one or more normalisation parameters may provide an efficient way of obtaining values which map robustly and accurately to filter-loading values.

[0030]The one or more normalisation parameters may comprise one or more of: an ambient pressure; an ambient temperature; a motor input power; and a build tolerance of the air-moving device.

[0031]These parameters may be readily determinable, for example by use or sensors, or may be pre-determined, for example by a calibration procedure. Normalising the value of the operating parameter by use of these parameters may provide for first values of the operating parameter to be effectively mapped to values of the filter loading.

[0032]The method may be performed responsive to a replacing of a filter of the air-moving device.

[0033]The replacing of the filter of the air-moving device may be a replacing of the filter following a filter-wash event.

[0034]The state of the filter or filters of the device may change when the device is not in operation. For example, the filters may be removed from the device and washed to remove dirt and/or dust.

[0035]The filter-wash event may be performed responsive to the device issuing to a or the user a filter-wash alert.

[0036]A filter-wash event may be performed when a given amount of dirt or dust has accumulated on the filter/s. For example, the user may be prompted to wash the filter/s when the level of filter loading reaches a given value. The method may be performed, for example, responsive to a user replacing a filter in the device after the user has removed the filters for washing following such a prompt. For example, the device may be configured to detect when a filter is removed and/or replaced, for example, by use of a suitable sensor, such as a magnetic sensor. In one example, the device may be configured to cause the method to performed, for example, on start-up of the device, whenever a filter wash prompt has been provided. Accordingly, even if the removal and/or replacement of the filter is not detected, for example, because the device is turned off when this occurs, the device may still appropriately trigger the calibration process to be performed.

[0037]The method may provide the initial filter-loading value as a baseline value following such a filter-wash event. This may provide a reliable initial baseline value for the filter-loading value, on the basis of which changes in the level of filter-loading during operation of the device may be determined.

[0038]According to a second aspect of the invention, there is provided a set of machine-readable instructions which when executed by one or more processors cause the method according to the first aspect of the invention to be performed. The method may, for example, be a computer-implemented method implemented by one or more processors of an air-moving device or one or more processors of a system comprising an air-moving device and a control device, such as a smartphone configured to communicate with and control aspects of the operation of the air-moving device.

[0039]According to a third aspect of the invention, there is provided an air-moving device comprising: a processor; and a storage comprising a set of machine-readable instructions which when executed by the processor cause the processor to perform a method according to the first aspect of the invention.

[0040]The air-moving device may be a vacuum cleaner.

[0041]According to a fourth aspect of the invention, there is provided a system comprising one or more processors and a storage comprising a set of machine-readable instructions which when executed by at least one of the one or more processors cause the at least one of the one or more processors to perform a method according to the first aspect of the present invention.

[0042]Optional features of aspects of the present invention may be equally applied to other aspects of the present invention, where appropriate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043]The present invention will now be described, by way of example only, with reference to the following figures, in which:

[0044]FIG. 1 is a schematic diagram of an example motor assembly of an air-moving device;

[0045]FIG. 2 is an illustration of an example of an air-moving device;

[0046]FIG. 3 is a flow chart representation of a method to determine an initial filter-loading value of an air-moving device;

[0047]FIG. 4 is a graph illustrating a plot of values of an operating pressure against inlet-restriction values;

[0048]FIG. 5 is a graph illustrating further examples of plots of values of operating pressure against inlet-restriction values;

[0049]FIG. 6 is a graph illustrating an example of a plot of filter loading values against operating pressure values; and

[0050]FIG. 7 is a block diagram of a system for implementing an example method of determining the initial filter-loading value.

DETAILED DESCRIPTION OF THE INVENTION

[0051]FIG. 1 shows an example schematic representation of a motor assembly 100 of an air-moving device. The motor assembly 100 comprises set of coils 102, a shaft 104 with magnets (not shown) mounted thereon, bearings 106 and an impeller 108. The motor assembly 100 comprises motor air inlets 110, and air outlets/a diffuser 112. The motor assembly comprises a circuit board 114 on which are mounted sensors including an ambient temperature sensor 116 and a first pressure sensor 118. The motor assembly 100 comprises a housing 124 in which the other components are housed. The motor assembly 100 further comprises a pre-motor filter 126 for filtering air which is drawn into the motor in use.

[0052]FIG. 2 shows an example air-moving device 200 comprising the motor assembly 100. The example air-moving device 200 is a vacuum cleaner. The vacuum cleaner 200 comprises an inlet tube 202 with a tool 204 attached to a distal end of the inlet tube 202. The tool 204 is for engaging with a surface to be cleaned by the vacuum cleaner and comprises an air inlet (not shown) to the vacuum cleaner 200. The tool 204 may be active, comprising one or more mechanically operated components, for example, a rotating brush bar, to assist with cleaning tasks. Alternatively, the tool 204 may be passive and not comprise any such mechanically operated components. A passive tool may nevertheless comprise elements such as bristles or the like to assist with cleaning tasks. In examples, the inlet tube 202 or a portion thereof may be removable. A tool, such as a passive tool, may be attached to the device 200 when the inlet tube 202 or the portion thereof is removed. The vacuum cleaner 200 also comprises a dirt-separating chamber 206, which may, for example, be a cyclone chamber. The vacuum cleaner 200 further comprises a processor 208 and a storage 210 for storing machine-readable instructions for execution by the processor 208 to control operation of components of the vacuum cleaner 200 including the motor 100. In examples, the machine-readable instructions when executed may cause the processor 208 to carry out any of the example methods described herein or aspects such methods.

[0053]In use, the motor of the motor assembly 100 draws air through the air inlet to the air-moving device 200, through the air-moving device 200, and out of an exhaust. Air is drawn through the device 200 along an airflow path 128 which passes through the inlet tube 202, through the dirt-separating chamber 206, through the motor assembly 100 and exits the device 200 through an exhaust 212.

[0054]Returning to FIG. 1, when the motor is in use in the air-moving device 200, an electric current is passed through the coils 102, in a manner which causes a varying magnetic field. This varying magnetic field acts on the magnets 106 on the shaft 104 to cause the shaft 104 to rotate about its longitudinal axis. This in turn rotates the impeller 108. Air, driven by the impeller 108, is drawn into the air-moving device 200 and along the airflow path 128. The airflow path 128 enters the motor assembly 100, passing through the pre-motor filter 126, which removes particulate matter from the air, and into the housing 124 through the air inlets 110 (shown, in FIG. 1, as gaps in the housing 124). The airflow path 128 continues through the motor to the impeller 108 and, after passing over the impeller 108, exits the motor assembly 100 through the air outlets 112.

[0055]FIG. 3 shows a flow chart representation of an example method 300 to determine an initial filter-loading value of an air-moving device 200.

[0056]A filter-loading value may be a value of loading of a filter which filters particulate matter from the airflow as it passes through the motor. For example, the filter loading may be a level of loading of the pre-motor filter 126. Alternatively, the filter loading may be a level of loading a post-motor filter (not shown). In some examples, the filter-loading value may take into account a level of loading of a plurality of filters, for example, a pre-motor filter and a post-motor filter. The level of loading of a filter may be indicative of an amount of dirt or dust collected in the filter, and/or a measure of initial effectiveness of a filter after it has been cleaned (for example, the filter may have been cleaned but may not be ‘as new’ due to a residue of dirt or dust that can remain after cleaning). The level of loading of the filter may have an effect on the flow of air through the device 200. For example, as more dirt is collected by the filter/s, the flow of air through the device may become more restricted.

[0057]In examples, the filter-loading value may be expressed in terms of percentage. For example, a filter-loading value of 100% may represent a level of loading of the filter which is indicative that the filter should be washed or replaced. A filter loading value of 100% may, for example, correspond with a state in which the filter or filters are restricting airflow by an amount which reduces the efficiency of the operation of the device by a given degree. A filter-loading value of 100% may, for example, correspond with a state in which the filter or filters are not completely blocked but in which the degree of blockage is sufficient that washing or replacing of the filter/s may be desirable. A filter-loading value of 0% may represent that the filter has a minimum level of loading. For example, a filter-loading value of 0% may correspond with a state in which the filter or filters provide a minimum level of restriction to airflow through the device. For example, a filter-loading value of 0% may correspond with a level of filter loading provided by a new filter which has collected no dirt or a filter which has been fully cleaned and is ‘as new’. The actual degree of blockage or dirt collected by the filter or filters which is corresponded with a given filter-loading value may vary, for example, depending on what degree of blockage is considered acceptable for allowing the device to operate with sufficient efficiency. Typically, the level of filter loading may increase gradually during use of the device 200 as air passes through the device and dirt is filtered from the air and collected by the filter. When a filter is deemed in need of replacing or cleaning, it may be removed from the device. The filter may then be washed and replaced in the device. Alternatively, a new filter may replace the previous filter.

[0058]The initial filter-loading value may, for example, be a value measured following an event which may have resulted in a change in the level of the filter loading, for example, while the device 200 was not in operation. For example, the initial filter-loading value may be a value of the filter loading following replacement of one or more filters in the device 200, for example, after washing a filter or replacing a filter with a new filter. Washing the filter may be done with the intention of reducing the level of filter loading. However, the filter-loading value following a filter wash event may be unknown. For example, washing the filter may not always reduce the filter-loading value to zero, as has been mentioned. The method may allow the filter-loading value following such a washing event to be measured.

[0059]The method 300 comprises, at block 302, arranging the device in a calibration mode, the calibration mode setting a pre-determined inlet restriction value for the device. The method 300 also comprises, at block 304, operating the device while in the calibration mode.

[0060]An inlet restriction value of the air-moving device 200 defines a level of restriction acting on the air inlet through which air flows into the device 200. The level of inlet restriction may, typically, vary based on various factors such as obstructions blocking the flow of air into the device 200. The inlet restriction value may vary depending on a type of tool attached to the vacuum cleaner 200. Different tools may, for example, have different geometries and thus restrict the flow of airflow into the vacuum cleaner 200 by different amounts. For example, different tools may have different air inlet diameters. Further, certain tools may include elements which obstruct the flow of air-flow into the device 200, such as bristles for cleaning carpet, while other tools may not include such elements. Moreover, the level of inlet restriction may vary depending on a type of surface the vacuum cleaner 200 is being used to clean. For instance, a carpeted surface or similar may place a greater restriction on the flow of air into the vacuum cleaner 200 than a smooth surface such as a wood or tile surface. Typically, operating the tool in free air, that is, with the device not engaged with a surface such that there is no external obstruction to the flow of air into the device 200, will provide the lowest inlet restriction value when the device is operating with a given tool attached or with no tool attached.

[0061]An inlet restriction value of the device in operation may be defined in terms of the diameter of an orifice which would provide an equivalent level of restriction to airflow into the device 200 under test conditions. As an example, the vacuum cleaner 200 when being used to clean a carpeted surface may be operating under a high level of inlet restriction which may be equivalent to operating in known conditions with an orifice plate having an orifice of small diameter restricting airflow into the vacuum cleaner 200. Conversely, the vacuum cleaner 200 when cleaning a wood surface may be operating under a lower level of inlet restriction, equivalent to that presented by an orifice of larger diameter.

[0062]The calibration mode sets a pre-determined inlet restriction value for the device 200. For example, in the calibration mode, the device 200 may be arranged to run under a pre-determined inlet restriction state in which no tool is attached to the device 200 or in which a specific tool is attached to the device 200. The pre-determined inlet restriction state, in one example, comprises the device 200 operating in free air with no tool attached. In another example, the pre-determined inlet restriction state may comprise the device 200 operating in free air with a specific tool attached. The removal of all tools from the device or the attaching of a specific tool to the device may provide a simple and easily repeatable way of providing a pre-determined inlet restriction for the device.

[0063]The method 300 may comprise, in the calibration mode, prompting a user to arrange the device 200 with the pre-determined inlet restriction value, such that a calibration can be performed.

[0064]For example, when the pre-determined inlet restriction value is provided by removing all tools from the device, the user may be prompted to remove all tools from the device or, where no tools were attached to the device to begin with, to indicate that no tools are attached to the device. The user may be asked to indicate when no tool is attached to the device, for example, once they have removed all tools from the device 200. Alternatively, where the pre-determined inlet restriction is provided by a specific tool being attached to the device, the user may be prompted to attach the specific tool to the device and, for example, to indicate when they have done so. The prompting and/or the receiving of an indication may be performed by the device itself, for example, by a user interface of the device, or may, for example, be performed by a different device, such as a smartphone in communication with the device operating an app.

[0065]In some examples, the device 200 may be configured to detect whether a tool is attached to the device and/or what type of tool is attached to the device. In such examples, in the calibration mode the device may determine the pre-determined inlet restriction value based on the detected tool or lack thereof. For example, one or more inlet restriction values for the device may be pre-determined with each pre-determined inlet restriction value corresponding to the device when operating with a given respective tool attached. The device 200 may detect whether a tool is attached to the device and, if so, which tool is attached to the device. Using this information, the device may determine the pre-determined inlet restriction value to use in the method to determine the initial filter-loading value. In another example, whether or not the device is configured to detect which tool is attached to the device, the user may be asked to indicate which tool is attached to the device and the device may then use this information to determine the pre-determined inlet restriction value to use in the calibration process.

[0066]In another example, the device may be configured to operate with a given pre-determined inlet restriction value in the calibration mode. The device may then be configured to detect whether the correct tool is attached (which may be no tool) or for the user to indicate that the correct tool is attached to allow a calibration to be performed.

[0067]The device 200 may be configured to run the method 300 following an event where the filter-loading value may have changed when the device was not in operation. For example, the device 200 may be configured to determine when a filter has been replaced, for example, after washing of the filter or replacing an old filter with a new filter, and, in response, to trigger the calibration mode. This may allow an accurate initial filter-loading value to be determined. This initial filter-loading value may then be used as a baseline for determining changes to the filter-loading value and other operational parameters of the device 200.

[0068]As mentioned above, at block 304, the method comprises operating the device while in the calibration mode. In some examples, the user may be prompted to operate the device. For example, the user may be prompted to operate the device once the device has received an indication that the device is arranged with the pre-determined inlet restriction value. As described above, the indication may be provided, for example, via the user providing an input confirming that the correct tool (which may be no tool) is attached to the device or via the device detecting which tool is attached to the device. In some examples, the device may be configured to operate automatically once an indication has been received that the device is arranged with the pre-determined inlet restriction value. For example, in an example where the device is configured to detect which tool is attached, when the calibration mode is initiated, the device may operate automatically as part of a calibration sequence if the device detects that the correct tool is attached.

[0069]The method 300 comprises, at block 306, during the operating, performing a measurement process to determine a first value of an operating parameter of the device, the first value of the operating parameter depending on a degree of filter loading of an installed filter.

[0070]The operating parameter may be an operating pressure of the motor of the air-moving device 200. The operating pressure of the motor is an air pressure relating to the motor when the motor is in operation, that is, when the motor is running. The operating pressure may relate to an air pressure at one or more locations along the airflow path 128. The operating pressure may be a differential air pressure. The operating pressure may, for example, be a pressure difference between an upstream and a downstream location, in the motor assembly, along the airflow path 128.

[0071]In another example, the operating pressure is a difference between a first pressure measured when the motor is not running and a second pressure measured when the motor is running. The first pressure and the second pressure may be measured at the same location. A value of an operating pressure may, for example, be obtained by determining a difference between an ambient pressure measurement, taken when the motor is not running, for example, before start-up of the air-moving device 200, and a pressure measurement taken during operation of the motor. In some examples described herein, such an operating pressure is referred to as delta-P. The pressure measurement taken during operation of the motor may, for example, be taken at the air inlet 110. Alternatively, the measurement may be taken at an air outlet from the motor. In some examples, the pressure measurements used to obtain a value of an operating pressure may be taken by the same pressure sensor. This allows for a value of the operating pressure to be obtained using a single pressure sensor, which may be cost- and space-efficient.

[0072]In another example, an operating pressure used in an example method may be determined based on a difference in pressures between two locations in the motor assembly 100, for example, an upstream location and a downstream location. For example, an additional pressure sensor (not shown) may be configured to take pressure measurements at a position, along the airflow path 128, downstream of the first pressure sensor 118. The additional pressure sensor may be configured to measure pressure at an air inlet 109 to the impeller 108. A difference between a pressure measured by the first pressure sensor 118 and a pressure measured by the additional pressure sensor, or, for example, a dynamic pressure value derived from these two pressures, may then be used as the operating parameter.

[0073]In other examples, the operating parameter may be a parameter other than an operating pressure, such as a speed of the motor of the air-moving device 200. This speed may be measured, for example, by a suitable sensor (not shown in the figures). In other examples, the operating parameter may be an airflow rate through the device 200. An example of determining an airflow rate will be described below.

[0074]The value of the operating parameter depends on a degree of filter loading of an installed filter. For example, as mentioned above, the level of filter loading may affect airflow through the device which may in turn affect the value of the operating parameter, such as an operating pressure of the device or a speed of the motor of the device.

[0075]The device may be configured to operate for a pre-determined time to allow the value of the operating parameter to be reliably measured. For example, the device may be configured to operate for a period which allows the operating parameter to stabilise following start-up of the device. In one example, the device is configured to operate for 3 seconds to allow the operating parameter to be measured. In some examples, the measured value of the operating parameter may be obtained by averaging multiple measurements. For example, the device may measure the operating pressure once every second and the operating pressure value used to determine the initial filter-loading value may be an average of two or more such measurements.

[0076]The method 300 also comprises, at block 308, performing a determination process to determine the initial filter-loading value based on a first pre-determined relationship between values of the operating parameter and a set of filter-loading values.

[0077]The first pre-determined relationship may, for example, comprise a curve or a look-up table relating values of the operating parameter to the set of filter-loading values. The first pre-determined relationship allows a filter-loading value to be determined based on a measured value of the operating parameter.

[0078]The relationship between values of the operating parameter and filter-loading values may, for example, be obtained by measuring the values under pre-determined test conditions. This may involve, for example, operating the device 200 with a controlled, pre-defined value of inlet restriction, for example, using an orifice plate having an orifice of a given diameter, and measuring values of the operating parameter and filter-loading values. The value of the inlet restriction may be set by operating the device 200 with orifice plates having orifices of differing diameters restricting airflow into the device 200. Measurement may be made for different values of inlet restriction to build up a relationship between values of the operating parameter and filter-loading values for different inlet restriction values. In an example, this process may be done as part of a manufacturing or initial setup process for the device 200.

[0079]In examples, a given value for the operating parameter may correspond with different filter-loading values, depending on the inlet restriction value. Therefore, if the inlet restriction value is not known, it may be difficult to unambiguously determine a filter-loading value from a measured value of the operating parameter. However, by arranging the device with the pre-determined inlet restriction value, a value of the operating parameter may be determined based on a relationship between values of the operating parameter and filter-loading values which is applicable when the device is operating with the pre-determined inlet restriction value.

[0080]Once the initial filter-loading value is determined, the initial filter-loading value may provide a baseline value which the device may use to determine changes in the filter-loading value over time during the operation of the device.

[0081]In certain examples, one or more further parameters of the device may also be used to relate values of the operating parameter to filter-loading values at a given inlet restriction value. A filter-loading value may then be determined based on a first value of the operating parameter, the pre-determined inlet restriction value, and respective values of the one or more further parameters. The further parameters may be parameters of the air-moving device 200 which influence the value of the operating parameter which is measured for a given value of the inlet restriction. For example, in certain examples, different values for parameters such as the ambient pressure, ambient temperature, motor input power, and build tolerance of the air-moving device may result in different values of the operating parameter for the same value of inlet restriction and same filter-loading value.

[0082]Ambient pressure and ambient temperature form part of the external conditions under which the device 200 is operating. In some examples, ambient pressure may be measured prior to start-up of the motor by the first pressure sensor 118.

[0083]Ambient temperature may be measured by the temperature sensor 116. Motor input power is the power which is supplied to drive the motor.

[0084]The motor input power may be controlled by the processor 208 and supply a DC or AC power, for example from a battery (not shown) of the device 200 or from a mains supply. The motor input power may control the suction power of the air-moving device.

[0085]The build tolerance of the air-moving device 200 may account for the variability in operation between different devices. For example, various operating parameters of the device may be measured during a calibration process following assembly of the device. The build tolerance of a particular device may be expressed as a percentage of a total allowable tolerance. In one example, at an end of a production line for a device, an orifice plate having an orifice of a given diameter is connected to an inlet of the device, wherein the device is known to have clean filters, that is, the filter loading value is 0%. The ambient temperature and pressure are measured. The device is operated at a given power level and the operating parameter, for example, delta-P, is measured. With values of the input power, ambient temperature, ambient pressure, filter loading, being measured or otherwise known, the measured delta-P is indicative of the build tolerance factor. This process may be repeated at multiple power levels and at different orifice diameters.

[0086]In some examples, the normalised values of the operating pressure are obtained by normalising values of the operating parameter with respect to one or more further parameters, such as those mentioned above. For example, a five-dimensional look-up table may be defined which maps respective values of build tolerance, ambient pressure, ambient temperature, motor input power, and a value of the operating pressure to a normalised value of the operating pressure. A pre-determined relationship between the normalised values of the operating pressure and filter-loading values at the pre-determined inlet restriction value may then be used to determine the initial filter-loading value.

[0087]An example of a curve relating normalised values of the operating pressure to the values of inlet restriction is shown in FIG. 4. This example is for the motor of a vacuum cleaner.

[0088]In the example of FIG. 4, the operating parameter, shown on the y-axis, is a normalised operating pressure, namely a normalised delta-P value, defining a difference between an ambient pressure of the motor prior to start-up and a pressure at a motor inlet during operation. Delta-P is in units of kPa. Orifice diameter in mm is along the x-axis and represents values of an inlet restriction. A first curve 402 mapping values of normalised delta-P to values of inlet restriction has been obtained by a suitable calibration process involving operating the vacuum cleaner under known conditions with inlet restrictions provided by orifices of various diameter. Corresponding values of the orifice diameter and delta-P have been measured. The first curve 402 has been obtained by normalising values of delta-P with respect to values of build tolerance, ambient pressure, ambient temperature and motor input power. The first curve 402 maps a normalised value of the operating pressure to a value of the inlet restriction for a single filter-loading value.

[0089]FIG. 5 shows a set of curves 402, 504, 506, 508, 510 relating normalised values of delta-P to inlet restriction values. Each curve corresponds to a different filter-loading value. The first curve 402 of FIG. 4 is also shown in FIG. 5 and corresponds to a value of filter loading of 0%. A second curve 504 corresponds to a value of filter loading of 25%. A third curve 506 corresponds to a value of filter loading of 50%. A fourth curve 508 corresponds to a value of filter loading of 75%. A fifth curve 510 corresponds to a value of filter loading of 100%.

[0090]FIG. 6 shows plots relating, for different inlet restriction values, filter-loading values (%) on the y-axis to normalised delta-P values (kPa) on the x-axis. FIG. 6 shows a first filter loading curve 602, which corresponds to a first inlet restriction value, a second filter loading curve 604, which corresponds to a second inlet restriction value, and a third filter loading curve 606, which corresponds to a third inlet restriction value. FIG. 6 illustrates how normalised values of delta-P map to different filter-loading values given different inlet restriction values.

[0091]As described above, by setting a pre-determined inlet restriction value, an applicable curve can be selected from which to determine a filter loading value from a normalised delta-P value. For example, curve 602 may correspond to an inlet restriction value of the device 200 when the device 200 is operating in free air with no tool attached. In one example, this is the pre-determined inlet restriction value set by arranging the device 200 in the calibration mode. Curves 604 and 606 may correspond to the device operating in free air with different respective tools attached. Accordingly, in such an example, to determine the initial filter-loading value, a value of normalised delta-P is measured and a filter loading value is determined using the measured value of normalised delta-P and the curve 602.

[0092]Examples of the above-described method may allow for the filter-loading value to be determined based on a correspondence between filter loading values and an operating parameter of the motor. This may in some examples allow for the filter loading value to be determined without use of further additional sensors, such as pressure sensors upstream and downstream of the filter. Furthermore, the method may contribute to overall computational efficiency in the control of the device 200 since the parameters needed to determine filter loading may also be used for other purposes, such as to control an input power of the motor.

[0093]The value of the filter-loading may be used for various purposes. For example, the filter loading value may be determined, for example, at regular intervals during operation of the device, to be used in control method of the device, such as to control the input power of the motor. Further, the filter loading may be continuously monitored in order to provide an alert when the value reaches a threshold that indicates that cleaning or replacement of the filter is required.

[0094]FIG. 7 shows a schematic representation of a system comprising the air-moving device 200 and a control device 750 according to one example. In this example, aspects of the method of determining the initial filter-loading value are performed by the device 200 while other aspects of the method are performed by the control device 750. The air-moving device 200 may comprise any of the features described above in relation to earlier figures. The control device 750 is a device in communication with the air-moving device 200, for example, via a suitable communication protocol such as Bluetooth or NFC. The control device 750 comprises a processor 752 and a storage 754. The storage 754 comprises machine-readable instructions for causing the control device 750 to perform certain aspects of example methods described herein.

[0095]In one example, the control device 750 may be notified by the air-moving device 200 when the air-moving device 200 is arranged in the calibration mode, for example, responsive to the device 200 detecting that a filter has been replaced. Responsive to the receiving the notification that the air-moving device 200 is arranged in the calibration mode, the control device 750 may prompt the user to perform certain tasks, such as arranging the device with the pre-determined inlet restriction value, for example, removing all tools from the device 200. The control device 750 may also be configured to receive indications from the user, for example, to confirm that the user has removed all tools from the device 200. The control device 750 may also be configured to provide commands or indications to the device 200. For example, the control device 750 may indicate to the device 200 when the user has confirmed that all tools have been removed from the device. In response, the device 200 may proceed with other aspects of the method, including operating the device 200 to determine the operating parameter value and determining the initial filter-loading value based on the operating parameter value. In other examples, other aspects of the invention may be performed by the control device 750. For example, certain processing involved in determining the initial filter-loading value may be performed by the control device 750 or by another device in communication with the control device 750 (for example, a cloud computing device).

[0096]The above embodiments are to be understood as illustrative examples of the invention. Other embodiments are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.