Vacuum Cleaner, Controller, and a Method Therefor

Abstract

A method of determining an airflow parameter in a vacuum cleaner comprising a motor-fan assembly comprises receiving one or more signals relating to one or more operational parameters of the motor. The method further comprises determining a torque of a rotatable shaft of the motor based on the one or more operational parameters. The method also comprises determining an airflow parameter based on the determined torque of the rotatable shaft of the motor.

Description

FIELD

The present disclosure relates to a vacuum cleaner, controller, and a method therefor. In particular, the present disclosure relates to vacuum cleaner, controller, and a method for determining airflow in the vacuum cleaner.

BACKGROUND

Rotary power tools such as drills and hammer drills generally have clutch mechanisms to prevent damage to the tool and danger to the user if the bit becomes stuck when rotating. Both mechanical and electrical clutches are known which disconnect rotary drive from the bit when the torque encountered by the bit passes a predetermined threshold indicating that the bit is impeded or stuck. This is known as a blocking event.

EP1539434B1 describes various embodiments of mechanical and electronic clutches used in a rotary hammer drill. For example, one embodiment describes using an accelerometer to provide signals to a microprocessor which analyses acceleration of the tool housing to determine when a blocking event is occurring. The microprocessor can then provide a signal to operate an electromagnet which causes a mechanical clutch to actuate and disconnect drive from the motor to the spindle.

EP1539434B1 also describes a two-torque mechanical clutch. The two-torque mechanical clutch has two torque settings. A low torque setting is the default setting at which the clutch slips when the torque encountered by the bit exceeds a predetermined low torque threshold. However, a user can manually select a higher torque setting to increase the level of torque encountered by the bit at which the clutch slips. As a safety feature, after operation of the tool the clutch automatically defaults to the low torque setting to prevent the user initiating the tool in the high torque setting. The user must select the high torque setting during operation.

Electronic clutches are also known which measure the current being drawn by a power tool. When the current exceeds a predetermined threshold, the motor is turned off. This type of clutch suffers from the drawback that it does not take into account speed and mode settings of the tool.

Vacuum cleaners are often used in workshops to make sure waste particles are not dispersed into the air or distributed over the surfaces of the workshops. Some vacuum cleaners are rated to maintain a specific airflow velocity in order to remove potentially harmful particles for the user.

For example, an H class vacuum cleaner is rated for collection of dust hazardous to health and the airflow velocity is maintained above 20 m/s in the suction hose.

This means that the vacuum cleaner must detect the airflow velocity to ensure it is compliant with the relevant safety regulations. One known method of determining the air velocity in a vacuum cleaner is with differential pressure sensors. However, pressure sensors are expensive, sensitive to shocks, and susceptible to failure. This means that the vacuum cleaner must be repaired before being safe to use in a hazardous environment.

SUMMARY

Examples of the present disclosure aim to address the aforementioned problems.

According to an aspect of the present disclosure there is a method of determining an airflow parameter in a vacuum cleaner comprising a motor-fan assembly comprising: receiving one or more signals relating to one or more operational parameters of the motor; determining a torque of a rotatable shaft of the motor based on the one or more operational parameters; and determining an airflow parameter based on the determined torque of the rotatable shaft of the motor.

Optionally, the receiving one or more signals relating to one or more operational parameters comprises receiving one or more signals relating to one or more operational electrical parameters of the motor-fan assembly during operation of the motor-fan assembly.

Optionally, the receiving one or more signals comprises receiving a signal relating to the voltage.

Optionally, the receiving one or more signals comprises receiving a signal relating to the current.

Optionally, the method comprises determining the power based on the received signals relating to the current and the voltage.

Optionally, the determining the torque is based on the determined power.

Optionally, the method comprises determining the rotational speed of the motor.

Optionally, the determining the speed is based on a received signal from a motor rotational speed sensor and/or the motor.

Optionally, the method comprises determining one or more other operational parameters of the motor-fan assembly in dependence of the received one or more signals and/or stored parameter information of the motor-fan assembly.

Optionally, the determining one or more other operational parameters of the motor-fan assembly comprises determining an efficiency of the motor-fan assembly.

Optionally, the determining the efficiency of the motor-fan assembly comprises receiving a stored efficiency parameter for the motor-fan assembly.

Optionally, the determining the efficiency of the motor-fan assembly comprises determining the efficiency parameter for one or more actuating variables of the motor-fan assembly.

Optionally, the determining the airflow parameter is based on the determined torque and the determined efficiency of the motor-fan assembly.

Optionally, the functional relationship between the airflow and the torque is predetermined.

Optionally, the method comprises determining that the airflow parameter is below a first threshold value.

Optionally, the method comprises issuing an alert to a user in dependence of the determining that the airflow parameter is below the first threshold value.

Optionally, the method comprises initiating a filter cleaning procedure in dependence of the determining that the airflow parameter is below the first threshold value.

Optionally, the filter cleaning procedure comprises reversing the motor-fan assembly such that the direction of airflow reverses through a filter.

Optionally, the method comprises that the airflow parameter is above a second threshold value.

Optionally, the method comprises modifying the operational electrical parameters to reduce the airflow flow parameter below the second threshold value.

Optionally, the airflow parameter is air velocity.

In another aspect of the present disclosure there is provided a vacuum cleaner comprising: a motor-fan assembly; at least one sensor for measuring one or more operational parameters of the motor during operation of the motor-fan assembly; a controller configured to receiving signals from the at least one sensors, wherein the controller is configured to: determine a torque of a rotatable shaft of the motor based on the one or more operational parameters; and determine an airflow parameter based on the determined torque of the rotatable shaft of the motor.

In yet another aspect of the present disclosure there is provided a controller for a vacuum cleaner, the controller comprising: at least one communication port configured to receiving signals from the at least one sensors, wherein the controller is configured to: determine a torque of a rotatable shaft of the motor based on the one or more operational parameters; and determine an airflow parameter based on the determined torque of the rotatable shaft of the motor.

In another aspect of the present disclosure there is provided a method of controlling a power tool comprising a motor comprising: receiving one or more signals relating to one or more operational parameters of the motor; determining a torque of a rotatable shaft of the motor based on the one or more operational parameters; determining that the torque of the rotatable shaft of the motor exceeds or drops below a threshold value; and issuing a control signal to the power tool in dependence of the determined torque exceeding or dropping below the threshold value.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings in which:

FIG. 1A is a schematic of a power tool embodying the present invention.

FIG. 1B shows a schematic view of a vacuum device;

FIG. 2 shows a schematic diagram of a controller and a vacuum device;

FIG. 3 shows a graph of airflow of a vacuum device over time representing different operational scenarios of a vacuum device; and

FIG. 4 shows a flow diagram of a control process implemented in a controller of the vacuum device.

DETAILED DESCRIPTION

Referring to FIG. 1A, a power tool 2 comprises a housing 4 and an electric motor 6 disposed in the housing 4. A rotary output 8 is driven by the motor 6. In the embodiment shown, the power tool 2 is a hammer drill having a transmission 10 adapted to both rotate the rotary output 8 to rotate a bit 12 and also impart a reciprocal hammering action to bit 12 as will be familiar to persons skilled in the art. A mechanical clutch 28 is configured to disconnect drive from the motor 6 to the rotary output 8 when the torque M encountered by the rotary output 8 exceeds a predetermined threshold.

The power tool also comprises a handle portion 14 formed in housing 4 and a trigger 16 to enable a user input to drive the motor 6. A power source 18 is provided which may be either a battery or a corded connection to the mains as will be familiar to persons skilled in the art.

Electronic sensing means configured to sense operating parameters of the power tool includes a voltage sensor 20 arranged to detect the voltage across the electric motor 6, a current sensor 22 arranged to detect the current through the tool 2 and a speed sensor 24 arranged to detect the angular velocity ω of the output spindle 8. The electronic sensing means is therefore arranged to provide parameter output signals including voltage parameter output signal 20V, current parameter output signal 22i and rotary output speed parameter output signal 24ω to an electronic control apparatus 26.

The electronic control apparatus 26 is microprocessor based and is configured to determine from the operating parameter output signals 20V, 22i and 24ω the torque M of the rotary output 8. The electronic control apparatus 26 is also configured to control the angular velocity ω of the rotary output 8 in response to the calculation of the torque of the rotary output 8. The electronic control apparatus 28 is operable to change the angular velocity ω of the rotary output when a predetermined value of torque M is exceeded. For example, the motor speed may be reduced to reduce angular velocity. Alternatively, the motor 6 may be switched off or the electronic control apparatus 26 could provide a signal to actuate mechanical clutch 28.

The torque M of the rotary output 8 is calculated as set out below. In the following equations, the symbols used are as follows:

Symbol Quantity
i      current through the whole tool 2
u      voltage across the motor 6
ω      angular velocity of rotary output 8
n      motor armature speed
M      torque of rotary output 8
P      power
T      period time
μ      efficiency
N      Number of samples/line cycle

It is known that the electrical power input into the power tool 2, P_el, is a function of voltage across the motor 6 and the current through the power tool 2. The electronic control apparatus 26 samples either continuously or discretely voltage parameter output signal 20v provided by voltage sensor 20 and current parameter output signal 22i provided by current sensor 22. When these parameter outputs are monitored continuously, the average power is provided by:

$\begin{array}{cc}{P}_{\mathrm{el}}=\frac{1}{T}{\int }_0^{T}u\left(t\right)i\left(t\right)\mathrm{dt}& \left[1\right]\end{array}$

Where the current and voltage are sampled discretely at time intervals N, the average power is provided by:

$\begin{array}{cc}{P}_{\mathrm{el}}=\frac{1}{N}\sum _{m=0}^{N-1}u\left(m\right)i\left(m\right)& \left[2\right]\end{array}$

The angular velocity ω of rotary output 8 is determined by speed sensor 24 providing speed output parameter signal 24ω to the electronic control apparatus. It is known that the mechanical power output, P_mech, is equal to the product of the output torque and the angular velocity of rotary output 8:

P _mech =Mω  [3]

The mechanical power output mech is P_mech also equal to an efficiency factor μ multiplied by the electrical power to account for the power losses which incur internally within the power tool 2, for example friction in transmission 10, sound, vibration and heat. In the case of discrete sampling, this gives:

$\begin{array}{cc}M\omega =\mu \frac{1}{N}\sum _{m=0}^{N-1}u\left(m\right)i\left(m\right)& \left[4\right]\end{array}$

The above equation can be rearranged to give an equation for the value of torque M in terms of current and voltage:

$\begin{array}{cc}M\omega =\mu \frac{1}{N}\sum _{m=0}^{N-1}u\left(m\right)i\left(m\right)\to M=\frac{\mu \sum _{m=0}^{N-1}u\left(m\right)i\left(m\right)}{N\omega };\omega =2\pi n& \left[5\right]\end{array}$

The efficiency μ of the hammer drill is determined in advance using a test rig and is programmed into electronic control apparatus 26 in the form of a look up table.

The mechanical clutch 28 can be entirely independent of the electronic control apparatus 26 and therefore a two-torque clutching system is provided. For example, mechanical clutch 28 in one embodiment is a high torque clutch which is operable at all times. The electronic clutch provided by electronic control apparatus 26 is a low torque clutch operable as a safety feature. During operation of the power tool 4, a user can deactivate the low torque electronic clutch provided by electronic control apparatus 26.

It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims. For example, the electronic control system described can be used with any rotary power tool that requires a clutch, such as saws, routers etc. The electronic control system comprising electronic control apparatus 26 and electronic sensing means 20, 22, 24 could be provided as an upgrade to existing power tools.

Another aspect of the invention is described here with reference to FIGS. 1B-5.

FIG. 1B shows a side view of a vacuum device 100 according to an example. In some examples, the vacuum device 100 is a vacuum device 100 arranged to be used on a construction site or in a tool shop e.g. a workshop vacuum device 100. In some examples, the vacuum device 100 is a wet-dry vacuum cleaner. However, in other examples the vacuum device 100 is any other type of vacuum device 100 such as an upright vacuum cleaner, a stickvac, a handheld vacuum cleaner, a canister vacuum cleaner, or any other type of vacuum cleaner.

The vacuum device 100 comprises a housing 102. The housing 102 comprises a lower housing portion 104 and an upper lid portion 106. The upper lid portion 106 is securable to the lower housing portion 104 with one or more latches (not shown). The upper lid portion 106 can be separated from the lower housing portion 104 to empty the vacuum device 100. Furthermore, the upper lid portion 106 can be removed from the lower housing portion 104 to conduct maintenance and cleaning of the vacuum device 100.

The lower housing portion 104 comprises a collection chamber 108 for receiving, dirt, debris and/or liquid entrained in the dirty airflow. In some examples, the collection chamber 108 may possess any dimensions and shapes suitable for receiving debris and/or liquid.

In the example as shown in FIG. 1B, the lower housing portion 104 and the collection chamber 108 are generally cylindrical. In another example, the collection chamber 108 may possesses a generally frustoconical shape. Additionally or alternatively, the collection chamber 108 may include one or more curved side walls 110. In other examples, the vacuum device 100 can comprise any suitable shape. For example, the vacuum device 100 can be an elongate shape whereby the length of the housing 102 is greater than the height of the housing 102.

Optionally, (although not shown in FIG. 1B), an interior surface of a base 112 of the lower housing portion 104 and the collection chamber 108 may be generally concave. For example, the bottom of the lower housing portion 104 and the collection chamber 108 may possess a slightly upward curve to, e.g., prevent the collection chamber 108 from sagging when filled with a predetermined amount of debris and/or liquid.

The vacuum device 100 comprises a motor-fan assembly 114 mounted within the housing 102. The motor-fan assembly 114 comprises a motor 116 and a fan 118 is mounted on a rotatable motor shaft 200 (as shown in FIG. 2). The motor-fan assembly 114 is arranged to generate a negative pressure and create an airflow.

In the examples as shown in FIG. 1B, the fan 118 is mounted directly to the rotatable motor shaft 200 of the motor 116. However, in other examples, the rotatable motor shaft 200 can be coupled to a gearbox (not shown) configured to transmit rotation to a drive shaft (not shown) and the fan 118 is mounted on the drive shaft. In this way, the gearbox can step up or step down the rotational speed of the drive shaft with respect to the rotational speed of the rotatable motor shaft 200.

The generated airflow air is configured to move along an airflow path between a dirty air inlet 122 and a clean air exhaust outlet 124. In some examples, the clean air exhaust outlet 124 is a plurality of holes in the housing 102 e.g. the upper lid portion 106. In other examples, the clean air exhaust outlet 124 can be any hole, slot, or orifice in the housing 102 to let the clean air exhaust out of the vacuum device 100. The collection chamber 108 is positioned along the airflow path and arranged to capture debris, dirt and/or liquid droplets entrained in the dirty airflow. The captured dirt, debris, liquid droplets etc. (and other debris) collects at the bottom of the collection chamber 108.

As shown in FIG. 1B, the upper lid portion 106 houses a motor-fan assembly 114 configured to generate an airflow. The motor-fan assembly 114 in some examples is electrically connected to a power source 206 (as shown in FIG. 2). In some examples, the power source 206 is an AC power source e.g. a mains power supply. In some other examples the power source 206 is a DC power source e.g. a battery. In some examples, the power source 206 is a mains power supply. In some examples, the motor-fan assembly 114 is additionally or alternatively electrically connected to a battery (not shown).

In some examples, the vacuum device 100 comprises one or more filters 126 which is mounted to the upper lid portion 106. The filter 126 is positioned such that the filter 126 is positioned on the airflow path between the dirty air inlet 122 and the clean air exhaust outlet 124.

In some examples, the filter 126 is optionally removably mounted on a safety valve 128. The safety valve 128 is arranged to prevent liquid from overflowing form the collection chamber 108 into the upper lid portion 106 when the vacuum device 100 is operated in a “wet mode”. The safety valve 128 is known and will not be discussed any further. In order to prepare the wet-dry vacuum device 100 for wet mode operation, the filter 126 is removed from the safety valve 128. The arrangement of the vacuum device 100 as shown in FIG. 1B is with the filter 126 and the vacuum device 100 is operable in a “dry mode”.

Referring back to FIG. 1B again, the upper lid portion 106 comprises one or more electrical and electronic components of the vacuum device 100. Whilst FIG. 1B shows the one or more electrical and electronic components mounted in the upper lid portion 106, the one or more electrical and electronic components can be mounted anywhere within the housing 102.

In some examples, the vacuum device 100 comprises a control panel 132 having one or more actuators 134 (e.g., a control knob) operable to control the operational parameters of the device. For example, the control panel 132 is configured to control the power (ON/OFF) with a main ON/OFF switch (not shown) and the fan speed of the motor-fan assembly 114 with a fan control speed dial (not shown). The control panel 132 may optionally further include one or more power outlets 136 or other power connections (not shown). In this way, a power tool (not shown) can be connected by a power cord and receive electrical power from the vacuum device 100. The electrical components may be controlled via a circuit board or a controller 130 mounted in the housing 102.

In another example, the controller 130 is mounted within the housing 102 of the motor 116 e.g. inside the motor can housing (not shown). In this way, the motor 116 and the controller 130 are a unitary component.

In some other examples, the controller 130 is mounted to the interior surface of the control panel 132 on the upper lid portion 106. In some other examples, the controller 130 is mounted in any other location within the housing 102. The controller 130 may be implemented on hardware, firmware or software operating on one or more processors or computers. A single processor can operate the different functionalities or separate individual processors, or separate groups of processors can operate each functionality.

Turning to FIG. 2, the controller 130 will be discussed in further detail. FIG. 2 shows a schematic diagram of the controller 130 and the vacuum device 100.

The controller 130 is configured to control the motor-fan assembly 114 to change the torque on the rotatable motor shaft 200 and the airflow speed generated by the fan 118 as discussed hereinafter.

The controller 130 is connected to one or more sensors configured to detect one or more operating electrical parameters of the motor 116. In some examples, the controller 130 is connected to a voltage sensor 202 and a current sensor 204 for respectively detecting the voltage across the motor 116 and the current through the motor 116. In some examples, the voltage sensor 202 and the current sensor 204 are mounted within the housing of the motor 116 e.g. inside the motor can housing. In this way, the motor 116 and the voltage sensor 202 and the current sensor 204 are a unitary component.

The controller 130 is configured to receive at least one signal relating to one or more operational parameters of the motor 116 during operation of the motor-fan assembly 114 as show in step 400 of FIG. 4. FIG. 4 shows a flow diagram of a control process implemented in the controller 130.

In some examples, the controller 130 is configured to receive a plurality of signals relating to one or more operational electrical parameters of the motor 116 during operation of the motor-fan assembly 114.

The controller 130 then determines one or more operational electrical parameters of the motor-fan assembly 114 based on the received signals as shown in step 402 of FIG. 4. For example, the controller 130 determines the voltage and the current respectively from the received signals from the voltage sensor 202 and the current sensor 204.

In this way, the controller 130 receives a signal from the voltage sensor 202 and a signal from the current sensor 204 during operation of the motor-fan assembly 114. In some examples, the voltage sensor 202 and the current sensor 204 periodically send the signals to the controller 130. In other examples, the voltage sensor 202 and the current sensor 204 constantly send the signals to the controller 130. The voltage sensor 202 is configured to send information relating to the voltage across the motor 116 during operation to the controller 130. The current sensor 204 is configured to send information relating to the current through the vacuum device 100 during operation to the controller 130.

In some examples, the controller 130 is configured to determine one or more other operational parameters of the motor-fan assembly 114 as shown in step 404 in FIG. 4. The other operational parameters of the motor-fan assembly 114 can be any parameters of the motor-fan assembly 114 that can affect the functionality of the motor-fan assembly 114 during operation.

In some examples, the controller 130 is optionally connected to a speed sensor 208. In some examples the speed sensor 208 is a hall sensor configured to detect each revolution of the motor 116. In some alternative examples, the speed sensor 208 can be an optical sensor or any other suitable sensor configured to detect rotation of the motor 116, the rotatable motor shaft 200, or the fan 118 etc. The speed sensor 208 is configured to send a signal to the controller 130. The controller 130 is configured to determine the rotational speed of the motor 116 in dependence of the received signal from the speed sensor 208.

In some examples, the controller 130 is not connected to a speed sensor 208 and instead, the controller 130 receives information from a look-up table stored in memory (not shown) relating to the speed of the motor 116. For example, the controller 130 can receive estimated speed information based on the voltage and current signals during operation.

Alternatively, the controller 130 receives a signal from the motor 116 corresponding to the number of times the rotatable motor shaft 200 rotates with respect to the poles (not shown). Similarly, the controller 130 determines the rotational speed of the rotatable motor shaft 200 based on the signal received from the motor 116. In some examples, the controller 130 determines the rotation speed of the motor shaft 200 based on the voltage, current and model of the motor 116 and the vacuum device 100. In this example, the motor 116 may be an AC induction motor. In some other examples, the rotation speed and position of the motor shaft 200 may be determined by the controller 130 via other sensorless algorithms.

For example, the motor 116 may be a BLDC (brushless DC) motor, an induction motor, an ASM (asynchronous motor) or any other motor which generates a back EMF. The rotation speed and position of the motor shaft 200 may optionally be determined based on back EMF measurements or variation of the motor induction.

Alternatively, in some other examples the motor 116 may be a brushed DC motor or an AC brushed motor. The rotational speed may be estimated based on the motor model and the measurement of the voltage and current.

In some examples, the controller 130 is configured to determine an efficiency parameter or efficiency factor μ of the motor 116 as shown in step 404 of FIG. 4. The controller 130 is configured to determine the efficiency factor μ for one or more actuating variables of the motor 116 and/or motor-fan assembly 114.

The controller 130 is the controller 130 receives information from a look-up table stored in memory (not shown) relating to the efficiency of the motor 116. For example, the controller 130 determines the phase angle of the motor 116 during operation and receives information relating to the efficiency of the motor 116 based on the determined phase angle.

Alternatively, the controller 130 is configured to determine the efficiency of the motor 116 during a calibration operation based on operational parameters of the motor 116. In some examples, the phase angle of the motor 116 is determined by the controller 130. Alternatively, the information relating to the phase angle (° phase) of the motor 116 is sent from the motor 116 to the controller 130.

In some examples, the vacuum device 100 is powered by an AC voltage. Since the grid voltage U_grid follows a sin wave, the controller 130 must determine the phase angle of the voltage in order to determine the electrical power P_elec. For example, the phase angle is the angle or the moment of the sin-wave of the voltage where the triac switches (not shown) on. The controller 130 is determines the ° phase such that the controller 130 can control the power and speed of the motor 116.

The controller 130 is configured to determine the phase angle for every half of the sine wave of the grid voltage U_grid in order to determine how much power is delivered to the motor 116. In some examples, the controller 130 is configured to determine the phase angle more frequently e.g. every quarter, sixth, eighth, or tenth etc. of the sine wave of the grid voltage U_grid. Furthermore, the controller 130 determines the phase angle because this affects the power of the motor 116 and in turn the operation point of the motor 116.

The operation point of the motor 116 is specific point within the operation characteristic of the motor-fan assembly 114.

The efficiency factor μ depends on the operation point of the motor-fan assembly 114 and therefore the efficiency factor μ depends indirectly on the phase angle. In some examples, the phase angle is calculated by a motor control part (not shown) of the motor 116. In this way, the controller 130 can be configured to receive information relating to the phase angle during operation of the motor 116. In some other examples, the controller 130 is configured to measure and determine the phase angle.

In some examples, the vacuum device 100 optionally undergoes a calibration process. The one or more parameters of the vacuum device 100 are determined during the calibration process. An efficiency look-up table corresponding to the determined parameters of the vacuum device 100 during calibration are stored in a memory of the controller 130. Alternatively, the look-up table is stored in the memory of the controller 130 without performing a calibration process in a factory set up process.

The controller 130 is configured to receive sensor information relating to the motor current and the motor voltage and motor speed. Based on the received motor current, motor voltage and motor speed, the controller 130 is configured to determine the efficiency of the motor by using the efficiency look-up table. Accordingly, the controller 130 is able to determine the efficiency of the motor 116 in real time or near real time.

In contrast, in some examples the motor-fan assembly 114 is powered by a DC power source 206. In this case, the phase angle is constant and the efficiency factor is also constant.

In some examples, the controller 130 is configured to determine the operational electrical parameters of the motor-fan assembly 114 as shown in step 402 as follows.

The mechanical power P_mec is equal to the electrical power P_elec multiplied by an efficiency factor pt.

P _mec =μP _elec  [6]

The average electrical power P_elec is determined by the product of the current I(i) and voltage U(i) which are sampled discretely at time intervals i. The controller 130 is configured to control the frequency of sampling the current and/or the voltage. In some examples, the controller 130 receives signals from the voltage sensor 202 and the current sensor 204 a plurality of times during a half wave of the grid frequency.

In some examples, the nominal power is calculated by the controller 130 over the sinus half wave of the grid voltage. The grid frequency is e.g. 50 Hz and comprises two half waves and the controller 130 is configured to received signals comprising measured voltage values and current values in one halve wave several times. This means that the controller 130 can determine a good estimation of the electrical power. With an adequate number k of samples per half-wave, the controller 130 is configured to update active power calculation by summation and averaging of the instantaneous power each half-cycle of the mains frequency. In some examples, the number k of samples per half-wave is 5, 10, 15, 20, 25, 50 or any other suitable number of samples per half-wave needed to provide a good resolution for determining the power.

$\begin{array}{cc}{P}_{\mathrm{elec}}=\frac{1}{k}\sum _{i=1}^{k}U\left(i\right)·I\left(i\right)& \left[7\right]\end{array}$

The mechanical power P_mech is determined by the torque M on the rotatable motor shaft 200 multiplied by the angular velocity co of the rotatable motor shaft 200. As mentioned above, n can be determined from the speed sensor 208.

P _mech =Mω=M2πn  [8]

Accordingly, when equation [6] is combined with equation [8], for an AC power source 206:

$\begin{array}{cc}M2\pi n=\mu \left(P_{\mathrm{elec},}\mathrm{°phase}\right)P_{\mathrm{elec}}=\mu \left(P_{\mathrm{elec},}\mathrm{°phase}\right)\frac{1}{k}\sum _{i=1}^k{U}_i·I_i& \left[9a\right]\end{array}$

In contrast, if a DC power source 206 is alternatively used, then the efficiency μ may vary. The efficiency μ may be calculated in a similar way as described above except one or more parameters of the DC power source need to be considered e.g. duty cycle. For example, the following equation may be used:

$\begin{array}{cc}M2\pi n=\mu P_{\mathrm{elec}}=\mu \frac{1}{k}\sum _{i=1}^k{U}_i·I_i& \left[9b\right]\end{array}$

As mentioned above, the controller 130 is configured to determine the efficiency factor μ for one or more actuating variables of the motor 116 and/or motor-fan assembly 114. The one or more actuating variables may be the phase angle for an AC motor or a duty cycle for a DC brushless motor.

As mentioned above, the controller 130 either determines or receives a signal relating to the phase angle of the voltage across the motor 116.

$\begin{array}{cc}{U}_{\mathrm{grid}}=\frac{U_{\mathrm{ADC}}·U_{\mathrm{ref}}}{128}\frac{R_1}{R_2}=\frac{U_{\mathrm{ADC}}·U_{\mathrm{ref}}}{128}\frac{390k\Omega }{5.1k\Omega }=A·U_{\mathrm{ADC}}& \left[10\right]\end{array}$

Where U_grid is the voltage of the mains power source 206, U_ADc is the voltage across an analog to digital converter (ADC) (not shown) and U_ref is the reference voltage used by the ADC. R₁ and R₂ are the circuit resistances. Accordingly, U_grid can be simplified to U_ADC multiplied by a factor A which corresponds to the specific characteristics of the circuit of the vacuum device 100. The factor A can be calculated during factory setting or a calibration process of the vacuum device 100.

$\begin{array}{cc}I=\frac{I_{\mathrm{ADC}}\text{/}128·U_{\mathrm{ref}}-U_{\mathrm{off}}}{V_{\mathrm{Op}}·R_{\mathrm{shunt}}}=B·I_{\mathrm{ADC}}-b& \left[11\right]\end{array}$

Where I is the current through the motor 116, and I_ADC is the digital value for the current.

U_off is the offset voltage. The operational amplifier or Opamp (not shown) is configured to operate as a summing amplifier. This means the voltage over the shunt resistor is amplified with a fixed factor and fixed voltage is added to the Opamp output. Accordingly, an offset to the current is added in the circuit hardware. The controller 130 is configured to subsequently remove the current offset, V_Op is the voltage in the Opamp, R_shunt is the resistance of the shunt in the circuit. Accordingly, I can be simplified to I_ADC multiplied by a factor B minus an offset factor b which corresponds to the specific characteristics of the circuit of the vacuum device 100. The factors B, b can be calculated during a factory setting or a calibration process of the vacuum device 100.

Rearranging [7] with [10] and [11] the following can be calculated by the controller 130.

$\begin{array}{cc}{P}_{\mathrm{elec}}=\frac{1}{k}\sum _{i=1}^{k}A·U_{\mathrm{ADCi}}·\left(B·I_{\mathrm{ADCi}}-b\right)=\frac{A·B}{k}\left(\sum _{i=1}^k{U}_{\mathrm{ADCi}}·I_{\mathrm{ADCi}}-\frac{b}{B}\sum _{i=1}^k{U}_{\mathrm{ADCi}}\right)& \left[12\right]\end{array}$

In this way using [12] and [9], the torque M can be determined by the controller 130 as shown in step 406 of FIG. 4. In some examples, the controller 130 is arranged to use the following equation for the AC power source 206:

$\begin{array}{cc}M=\frac{\mu \sum _{i=1}^{k}U\left(i\right)·I\left(i\right)}{k2\pi n}=\mu ·\frac{\frac{A·B}{k}\left(\sum _{i=1}^k{U}_{\mathrm{ADCi}}·I_{\mathrm{ADCi}}-\frac{b}{B}\sum _{i=1}^k{U}_{\mathrm{ADCi}}\right)}{k2\pi n}& \left[13a\right]\end{array}$

Alternatively, the controller 130 can use the following equation for the DC power source 206:

$\begin{array}{cc}M=\frac{\mu \sum _{i=1}^{k}U\left(i\right)·I\left(i\right)}{k2\pi n}& \left[13b\right]\end{array}$

The velocity of the air v_air in the vacuum device 100, can be determined from torque M as a function of M by the controller 130 as shown in step 408 of FIG. 4.

v _air =f(M)  [14]

In some examples, the air velocity v_air is a linear function of the torque M. In some examples, the linear function varies in dependence on the operation point of the turbine and motor, and so indirect to the phase angle. The linear relationship between air velocity v_air and the torque M and be determined by the controller 130 during a factory setting or a calibration procedure.

Accordingly, in some examples, since the functional relationship between the torque and the air velocity v_air can be predetermined e.g., in a calibration process, the controller 130 can determine the air velocity v_air indirectly by determining only the torque M. In other words, the step 408 can be carried out before operation of the vacuum device 100 in a calibration process. Accordingly, the controller 130 may save processing power by only determining the torque during operation and then inferring the air velocity v_air from the predetermined functional relationship between the torque and the air velocity v_air.

Turning now to FIG. 3, further operation of the vacuum device 100 and the controller 130 will now be discussed. FIG. 3 shows a graph of airflow of a vacuum device 100 over time representing different operational scenarios of the vacuum device 100.

FIG. 3 shows three different scenarios of the vacuum device 100. The three difference operational scenarios 1, 2 and 3 are respectively labelled “1”, “2” and “3” in circles in FIG. 3.

Scenario 1 represents the vacuum device 100 with the motor-fan assembly 114 operating at maximum airflow but subsequently suffers a catastrophic failure. FIG. 3 shows a maximum air velocity 300 at which the vacuum device 100 is operating. In some examples, the maximum air velocity 300 can be the air velocity generated with the maximum operating speed of the fan 118. Alternatively, the maximum air velocity 300 can be air velocity generated at the most efficient speed of the fan 118 with respect to the other parameters of the motor-fan assembly 114 and the other parameters of the vacuum device 100.

In some examples, the vacuum device 100 is designed to operate over a minimum air velocity 302 represented by line 302. In some examples, the minimum air velocity 302 is predetermined and corresponds to the air velocity to remove hazardous particles from a work environment. In some examples, the predetermined minimum air velocity 302 is 20 m/s.

In some examples, the minimum air velocity 302 can be adjusted by the user. For example, the user can select the minimum air velocity 302 suited for a particular job. Alternatively, the minimum air velocity 302 is fixed and cannot be adjusted by the user. This means that the vacuum device 100 can be certified that the vacuum device 100 is rated to a particular standard e.g., H Class or M class.

In some examples, the controller 130 determines that an airflow parameter or the determined torque of the rotatable motor shaft 200 is below a threshold value as shown in step 410 in FIG. 4. In some examples, the controller 130 determines when the airflow parameter is above or below the minimum air velocity 302.

In some examples, the controller 130 determines that the vacuum device 100 is operating normally when the determined airflow velocity is between the minimum air velocity 302 and the maximum air velocity 300. For example, the controller 130 determines that the air velocity is at the maximum air velocity 300 at the time T1. In this case, the controller 130 takes no action based on the determined airflow velocity. Accordingly, the method returns to step 400 and controller 130 continues determining the airflow velocity.

However, in some examples the vacuum device 100 ceases to operate normally. For example, in scenario 1 the fan 118 breaks, or the dirty air inlet 122 becomes blocked. In this case, the determined airflow will suddenly decrease and reduce to zero or below the minimum air velocity 302 at time T2. Accordingly, when the controller 130 determines that the air velocity has fallen below the minimum air velocity 302 in step 410, the controller 130 can take one or more actions.

In some examples, the controller 130 can issue an alert to the user as shown in step 412FIG. 4. The controller 130 can display the alert in the form of a visual signal such as an LED (not shown) indicating operational status on the vacuum device 100. Alternatively, the controller 130 can issue a display message (not shown) on the control panel 132. Additionally, or alternatively, the controller 130 can send a signal to a loudspeaker to issue an audible warning. In this way, the user can receive information warning that the vacuum device 100 is not generating sufficient air velocity to remove hazardous particles from the workplace. Once the user receives the alert, the user can perform maintenance on the vacuum device 100 to clear the alert.

In some examples, the controller 130 is configured to determine the rate of change of the air velocity. The controller 130 can determine the type of operating issue with the vacuum device 100 depending on the how the air velocity changes over time. For example, in scenario 1, the controller 130 is able to determine that there is a blockage or a fan 118 failure because the air velocity drops rapidly below the minimum air velocity 302 and possibly to 0 m/s.

In scenario 2, the filter 126 becomes blocked over time. At time T3 the controller 130 instructs the motor-fan assembly 114 to spin up to a fan speed for generating the maximum air velocity 300. Thereafter, the vacuum device 100 operates normally. However, after a period of time, the air velocity gradually decreases. Accordingly, the controller 130 determines that the air velocity at time T4 is below the maximum air velocity 300 despite instructing the motor-fan assembly 114 to generate the maximum air velocity 300. The controller 130 then determines that the air velocity drops below the minimum air velocity 302 at time T5.

The controller 130 can then issue an alert as previously discussed in reference to step 412. Since the controller 130 has determined the air velocity has been gradually decreasing over time e.g., at T4 and T5, the controller 130 determines that the filter 126 has become clogged due to a buildup of dirt and debris during operation of the vacuum device 100.

Accordingly, the controller 130 can include information about the type of error with the vacuum device 100 in the alert in step 412. Additionally, or alternatively, the controller 130 can initiate a filter cleaning procedure based on the determination that the filter 126 has become clogged.

In some examples, the controller 130 sends a control instruction to the motor-fan assembly 114 to reverse the airflow through the filter 126 as shown in step 414 in FIG. 4. The reversed airflow can dislodge the dirt and debris on the filter 126. The air velocity will then return to the maximum air velocity 300 and the vacuum device 100 can return to normal operation. This automatic filter cleaning process is advantageous because the filter cleaning process only occurs when the filter 126 is blocked. This means that the vacuum device 100 does not need to carry out a filter cleaning process based on a timer expiring. Accordingly, the user does not experience as much disruption when using the vacuum device 100.

In scenario 3, the motor-fan assembly 114 is generating an airflow at an air velocity which is above the maximum air velocity 300. At time T6, the controller 130 sends a control signal to the motor-fan assembly 114 to spin the motor-fan assembly 114 at the maximum air velocity 300. However, at that time there is not much dirt or debris in the air and therefore there is less load on the fan 118. This means that the motor-fan assembly 114 is generating an airflow at an air velocity which is above the maximum air velocity 300. The controller 130 determines that the air velocity is above maximum air velocity 300 and sends a control instruction to reduce the speed of the motor-fan assembly 114 as shown at time T7 and step 416 as shown in FIG. 4. Similarly, the controller 130 can determine that the air velocity is below minimum air velocity 302 and sends a control instruction to increase the speed of the motor-fan assembly 114. For example, there is an increase amount of dirt or debris in the air and therefore there is more load on the fan 118.

In this way, the controller 130 can perform a dynamic control on the motor-fan assembly 114 speed to control the air velocity within a predetermined range e.g., between the maximum air velocity 300 and the minimum air velocity 302. Alternatively, the controller 130 can perform a dynamic control on the motor-fan assembly 114 speed to control the air velocity about a predetermined value e.g., the maximum air velocity 300.

In general, the various examples of the disclosure may be implemented in hardware or special purpose circuits, software, logic, or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor, or other computing device, although the disclosure is not limited thereto. While various aspects of the disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques, or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The examples of this disclosure may be implemented by computer software executable by a data processor, such as in the processor entity, or by hardware, or by a combination of software and hardware. The data processing may be provided by means of one or more data processors. Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks, and functions.

Appropriately adapted computer program code product may be used for implementing the examples, when loaded to a computer. The program code product for providing the operation may be stored on and provided by means of a carrier medium such as a carrier disc, card, or tape.

The controller in some examples may comprise a memory. The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi core processor architecture, as non-limiting examples.

Some examples of the disclosure may be implemented as a chipset, in other words a series of integrated circuits communicating among each other. The chipset may comprise microprocessors arranged to run code, application specific integrated circuits (ASICs), or programmable digital signal processors for performing the operations described above.

Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

Claims

1. A method of determining an airflow parameter in a vacuum cleaner comprising a motor-fan assembly comprising: receiving one or more signals relating to one or more operational parameters of the motor;determining a torque of a rotatable shaft of the motor based on the one or more operational parameters; anddetermining an airflow parameter based on the determined torque of the rotatable shaft of the motor.

2. The method of claim 1, wherein the receiving one or more signals relating to one or more operational parameters comprises receiving one or more signals relating to one or more operational electrical parameters of the motor-fan assembly during operation of the motor-fan assembly.

3. The method of claim 2, wherein the receiving one or more signals comprises receiving a signal relating to the voltage.

4. The method of claim 3, wherein the receiving one or more signals comprises receiving a signal relating to the current.

5. The method of claim 4, wherein the method comprises determining the power based on the received signals relating to the current and the voltage.

6. The method of claim 5, wherein the determining the torque is based on the determined power.

7. The method of claim 1, wherein the method comprises determining the rotational speed of the motor.

8. The method of claim 7, wherein the determining the speed is based on a received signal from a motor rotational speed sensor and/or the motor.

9. The method of claim 1, wherein the method comprises determining one or more other operational parameters of the motor-fan assembly in dependence of the received one or more signals and/or stored parameter information of the motor-fan assembly.

10. The method of claim 9, wherein the determining one or more other operational parameters of the motor-fan assembly comprises determining an efficiency of the motor-fan assembly.

11. The method of claim 10, wherein the determining the efficiency of the motor-fan assembly comprises receiving a stored efficiency parameter for the motor-fan assembly.

12. The method of claim 11, wherein the determining the efficiency of the motor-fan assembly comprises determining the efficiency parameter for one or more actuating variables of the motor-fan assembly.

13. The method of claim 10, wherein the determining the airflow parameter is based on the determined torque and the determined efficiency of the motor-fan assembly.

14. The method of claim 13, wherein the functional relationship between the airflow and the torque is predetermined.

15. The method of claim 1, wherein the method comprises determining that the airflow parameter is below a first threshold value.

16. The method of claim 15, wherein the method comprises issuing an alert to a user in dependence of the determining that the airflow parameter is below the first threshold value.

17. The method of claim 15, wherein the method comprises initiating a filter cleaning procedure in dependence of the determining that the airflow parameter is below the first threshold value.

18. The method of claim 17, wherein the filter cleaning procedure comprises reversing the motor-fan assembly such that the direction of airflow reverses through a filter.

19. The method of claim 15, wherein the method comprises that the airflow parameter is above a second threshold value.

20. The method of claim 19, wherein the method comprises modifying the operational electrical parameters to reduce the airflow flow parameter below the second threshold value.

21. The method of claim 1, wherein the airflow parameter is air velocity.

22. A vacuum cleaner comprising: a motor-fan assembly;at least one sensor for measuring one or more operational parameters of the motor during operation of the motor-fan assembly;a controller configured to receiving signals from the at least one sensors, wherein the controller is configured to: determine a torque of a rotatable shaft of the motor based on the one or more operational parameters; anddetermine an airflow parameter based on the determined torque of the rotatable shaft of the motor.

23. A controller for a vacuum cleaner, the controller comprising: at least one communication port configured to receiving signals from the at least one sensors, wherein the controller is configured to: determine a torque of a rotatable shaft of the motor based on the one or more operational parameters; anddetermine an airflow parameter based on the determined torque of the rotatable shaft of the motor.

24. A method of controlling a power tool comprising a motor comprising: receiving one or more signals relating to one or more operational parameters of the motor;determining a torque of a rotatable shaft of the motor based on the one or more operational parameters;determining that the torque of the rotatable shaft of the motor exceeds or drops below a threshold value; andissuing a control signal to the power tool in dependence of the determined torque exceeding or dropping below the threshold value.