EP4617003A1

EP4617003A1 - Power tool status indicator

Info

Publication number: EP4617003A1
Application number: EP24163328.8A
Authority: EP
Inventors: Xin Jiang; Hai Ming LUO; Yong Sheng Gao; Chao Wen
Original assignee: Techtronic Cordless GP
Current assignee: Techtronic Cordless GP
Priority date: 2024-03-13
Filing date: 2024-03-13
Publication date: 2025-09-17
Also published as: AU2025200725A1; CN120645172A

Abstract

There is provided a power tool device and method of operating the same. The power tool device has at least one sensor for detecting one or operating parameters of said power tool; a motor comprising a rotor and a stator for driving a working component. The motor is electrically coupled to a power supply module. A controller is coupled to the at least one sensor for controlling the operation of the motor by issuing a motor driving signal. The controller is configured to drive the motor so that the motor produces an audible sound and/or perceivable vibration upon determination the power tool is in predetermined operating state which may be an active state or an abnormal state.

Description

FIELD OF THE DISCLOSURE

The present disclosure relates to a status indicator for a power tool, especially a power tool with an electric motor.

BACKGROUND OF THE DISCLOSURE

Battery operated and corded electrical motor driven tools are operated by users in a variety of environments to perform numerous activities inside and around home/garden/workshop environments. The activities may range from pruning trees or hedges, drilling holes, blowing leaves from paths, sawing lumber and the like without limitation. It would be appreciated that the tools are operated in a variety of environmental conditions of light, ambient noise etc.
Occasionally power tools may enter an abnormal or fault state in which debris may become stuck in the tool, a tool member may become jammed on the workpiece or there may be a battery or electrical fault which may lead to excessive current, voltage or temperature or some other abnormal condition. For some power tools, upon of such abnormal states protective circuits may be configured to render the tool inoperable. In such circumstances it is important that the fact that the tool is in an abnormal state of the tool is communicated to the user.
Typical approaches to the communication of the abnormal or fault state to the user may be by using a visual indication on a screen, or emission of light or a sequence of lights from a light emitter such as a LED or bulb array. Other approaches to indicating a fault state may be by notifications communicated to a personal electronic device over a short range wireless technology or sounds emitted from a loudspeaker included in the device.
Unfortunately, such notification approaches may be inconvenient for the user or they may simply fail to attract user attention because of the ambient environmental conditions in which the powered tool is operated. For example, it may be difficult for a user to see light is being emitted from a light indication means where the tool is being used in bright daylight, or they may be confused as to what a particular sequence of emitted lights means.
Accordingly, it is an object of the present disclosure to address or at least partially ameliorate some of the above problems of the current approaches to indicating that a powered tool has entered into an abnormal state.

SUMMARY OF THE DISCLOSURE

Features and advantages of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or can be learned by practice of the herein disclosed principles. The features and advantages of the disclosure can be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.
In accordance with a first aspect of the present disclosure, there may be provided a power tool device, which may comprise: at least one sensor for detecting one or more operating parameters of said power tool; a motor comprising a rotor and a stator for driving a working component, said motor may be electrically coupled to a power supply module; a controller coupled to the at least one sensor for controlling the operation of the motor by issuing one or more motor driving signal(s); wherein the controller may be configured to drive the motor so that the motor may produce an audible sound and/or perceivable vibration upon determination the power tool is in a predetermined state.
The predetermined state of the power tool may be selected from a group comprising an abnormal operating state or an operable state.
The sensor may comprise at least one of: a temperature sensor for detecting temperature of the motor and generating a temperature signal; a current sensor for detecting a current flow through the motor and generating a current signal; a voltage sensor for detecting a voltage flow across the motor and generating a voltage signal; a user input sensor for detecting a selected working mode of the power tool device and user actuation of one or more trigger devices and generating an input signal; and wherein the controller may receive at least one of the temperature signal, current signal, voltage signal or input signals for determination of whether the tool is in said predetermined state.
The signal(s) received by the controller may be processed to determine the state of the power tool based upon whether said signal(s) may exceed a predetermined threshold, said signal(s) may exceed a predetermined threshold for a predetermined period of time or the rate of change of the underlying value of said signal(s) may exceed a predetermined acceptable rate of change.
The audible signal and/or vibration may be emitted by controlling the rotor to change directions at a predetermined frequency.
The motor may be a brushless DC motor, and the controller may be configured such that after the initial position of the rotor of said motor is detected;

A first motor driving signal may be emitted by the controller such that the direction of current flow through at least two coils of the stator and the magnetic field generated therefrom may drive the rotor to rotate in a first direction for a first predetermined period of time; and
A second motor driving signal may be emitted by the controller such that the direction of current flow through at least two coils of the stator and the magnetic field generated therefrom may drive the rotor to rotate in a second direction opposite to the first direction for a second predetermined period of time; and
The controller may repeatedly change between emitting said first and second motor driving signals to switch the direction of rotation of said rotor over a third predetermined time period.

The motor may be a brushed DC motor and the controller may be configured such that:

A first motor driving signal may be emitted by the controller such that the direction of current flow through the rotor and the magnetic field generated therefrom may drive the rotor to rotate in a first direction for a first predetermined period of time; and
A second motor driving signal may be emitted by the controller such that the direction of current flow through the rotor and the magnetic field generated therefrom may drive the rotor to rotate in a second direction opposite to the first direction for a second predetermined period of time; and
The controller may repeatedly change between emitting said first and second motor driving signals to switch the direction of rotation of said rotor over a third predetermined time period.

The first and second predetermined time periods may be selected for switching of the direction of current flow through the stator coils to maximise the magnetic driving force on the rotor.
A first motor driving signal may be emitted by the controller such that the direction of current flow through at least two coils of the stator and the magnetic field generated therefrom may drive the rotor to rotate in a first direction for a first predetermined period of time; and the rotor may be urged by cogging torque to rotate in a second direction opposite to the first direction;
The controller may repeatedly change between emitting said first driving signal and allowing the cogging torque to switch the direction of rotation of said rotor over another predetermined time period.
The audible signal and/or vibration may be emitted by controlling the stator to resonate in a predetermined frequency.
The power supply module may be configured to receive a detachable electrical power source or is configured to connect to a power supply.
In accordance with a second aspect of the present disclosure, there may be provided a method of operating a motor of a power tool to issue an audible sound and/or perceivable vibration upon determination the power tool is in a predetermined state, which may comprise:

A motor controller may control the direction of current flow through one or more selected coils of the coils of the stator such that the magnetic field generated therefrom may drive the rotor to rotate in a first direction for a first predetermined period of time;
The motor controller may control the direction of current flow through one or more selected coils of the coils of the stator such that the magnetic field generated therefrom may drive the rotor to rotate in second direction opposite to the first direction for a second predetermined period of time;
The motor controller may repeatedly switch by the direction of rotation of said rotor for a third predetermined time period by controlling said direction of current flow and the selection of coils of the stator in which said current flows so as to produce an audible sound and/or perceivable vibration.

The above method of operating the motor of a power tool to issue an audible sound and/or perceivable vibration may further comprise the step of detecting an initial position of a rotor of said motor relative to coils of a stator of said motor positioned thereabout, wherein said motor may be a brushless motor.
In accordance with a third aspect of the present disclosure, there may be provided a method of operating the motor of a power tool to issue an audible sound and/or perceivable vibration upon determination the power tool is in a predetermined operating state, which may comprise:

A motor controller may control the direction of current flow through one or more selected coils of the coils of the stator such that the magnetic field generated therefrom may drive the rotor to rotate in a first direction for a first predetermined period of time;
The rotor may be allowed to rotate in second direction opposite to the first direction for a second predetermined period of time;
The motor controller may repeatedly switch the direction of rotation of said rotor for a third predetermined time period by controlling said direction of current flow and the selection of coils of the stator in said first predetermined period of time and permitting the cogging torque to drive the rotor so as to produce an audible sound and/or perceivable vibration.

In accordance with a fourth aspect of the present disclosure, there may be provided a controller for a power tool configured to drive the rotor of the motor of said power tool to operate according to any of the above methods.
In accordance with a fifth aspect of the present disclosure there may be provided a method of operating a motor of a power tool to issue an audible sound and/or perceivable vibration upon determination the power tool is in a predetermined state, comprising: determining the natural resonant frequency of the stator of a motor; and controlling by a motor controller the current flow through one or more selected coils of the coils of the stator to generate resonance of said stator substantially at the same frequency as the natural resonant frequency of the stator.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and other advantages and features of the disclosure can be obtained, a more particular description of the principles briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended Figures. Understanding that these Figures depict only exemplary embodiments of the disclosure and are not therefore to be considered to be limiting of its scope, the principles herein are described and explained with additional specificity and detail through the use of the accompanying Figures.
Preferred embodiments of the present disclosure will be explained in further detail below by way of examples and with reference to the accompanying Figures, in which: -

FIG 1A depicts an exemplary tool according to an embodiment of the present disclosure.
FIG 1B depicts an exemplary schematic modular diagram of the exemplary tool of FIG 1A.
FIG 1C depicts an exemplary overview of the sensors of FIG 1B.
FIG 2A depicts an exemplary representation of an exemplary motor which may be used in the tool of FIG 1A in a predetermined state, in which the rotor is stationary relative to the stator coils.
FIG 2B depicts an exemplary representation of the motor of FIG 2A having energised coils A-C and the resultant initial direction of rotation of the rotor.
FIG 2C depicts an exemplary representation of the motor of FIG 2A after the current has flowed through coils A-C.
FIG 2D depicts an exemplary representation of the motor of FIG 2A having energised coils B-C and the resultant direction of rotation of the rotor.
FIG 2E depicts an exemplary representation of the motor of FIG 2A in the same state as that depicted in FIG 2A.
FIG 3A depicts an exemplary flowchart showing an exemplary manner of operation of the motor controller signals for a brushless motor as the rotor moves through the states depicted in FIGS 2A-2E for generating audible noise and/or vibration,
FIG 3B depicts an exemplary flowchart showing an alternative mode of operation of the motor controller whereby the current pulse is controlled for moving the rotor through the states depicted in FIG 2A-2E for generating audible noise and/or vibration.
FIG 3C depicts a further exemplary flowchart showing an alternative mode of operation of the motor controller whereby the stator resonance is controlled for generating audible noise and/or vibration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various embodiments of the disclosure are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without departing from the spirit and scope of the disclosure.
The disclosed technology addresses the need in the art for an approach to issuing one or more notifications to the operator of a power tool through audible or vibration means upon entry into an abnormal or fault state, said notification generated by controlling the operation of the motor to admit sound and/or vibration as described further herein.
The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the disclosure as defined in the appended claims.
Referring to Fig 1A, there is depicted an exemplary portable power tool 10. It would be appreciated that this exemplary power tool 10 may be powered directly through connection to a main power supply line or may be powered from an on-board battery source without restriction. The power tool 10 may be a tool such as a screwdriver, drill, impact driver, chainsaw, hedge trimmer, blower or the like. The power tool 10 includes a housing 12 in which components are enclosed including typical components such as a motor 14, gear assembly 16, and a driven member 18. Advantageously the motor 14 may be coupled via the gear assembly to the driven member so as to provide variable output torque and/or rotational speed.
A controller circuit 20 is coupled via a user actuation means 22 to the power module 24. It will be appreciated that the power module 24 may receive therein a power source such as a battery or a transformer configured to change alternating current (AC) of a mains supply line to direct current (DC).
Referring now to Fig 1B, there is depicted an exemplary schematic diagram of the components of the tool of Fig 1A and which controls the operation of the motor 14. As depicted, there is shown a sensor 30 which is coupled to the power supply module and or motor 14 and in communication with the controller 20. The user actuation means 22 is advantageously a switch or trigger which is also coupled to the controller 20.
Referring now to Fig 1C, there is depicted variants of the exemplary sensors 30, which provides information to the controller 20. As depicted, there is shown a temperature sensor 30a a current sensor 30b, a voltage sensor 30c, and a rotation speed sensor 30d. It would be appreciated that other sensors could also be included without limitation.
Further, as depicted, there is provided a user input sensor 30e which may issue a signal to the controller 20. Advantageously, this signal may reflect various operational parameters such as the selected working mode 32, or the actuated position of the trigger 34 without restriction.
Advantageously, the operating parameters of the power tool as indicated by said sensors may be provided to the controller and used to determine the entry of the power tool into an abnormal or fault state. It would be appreciated that such fault or abnormal state may be caused by jamming of the driven member, insufficient operating voltage or current, an electrical fault within the power tool, or numerous other causes.
Alternatively, the insertion of one or more stored current power cells or batteries or connection to mains power may also be indicated as the power tool being in an operable state using the vibration and or audible noise generation by the motor described further herein. It would be appreciated the vibration of the motor would pass through to the tool housing and alert the operator that the tool is operable or that the tool is in an abnormal or fault state depending on the configuration as described further herein.
Other potential causes of the fault state include: machine jamming, excessive use (which will force the tool to rest), over-temperature, overload, low voltage, etc. It would be appreciated by persons skilled in the art that in addition to indication of a fault status or operation status, the audible sound and/or vibration of the present disclosure can be used to provide an indication of any situation either determined by the manufacturer or potentially even allocated to specific operational conditions by the user. For example, when the battery capacity is too low, or the temperature of the battery is too high, or the battery is overloaded (the current is too high), an audible prompt and/or vibration can also be produced in accordance with the teachings of the present disclosure.
Advantageously, the controller 20 may be configured so as to receive measurement signals said sensors and determine that the received signal is above or below a predetermined threshold. Alternatively, the controller may be configured to determine that the rate of change of the received signal is excessive. Various other approaches may be employed to determine from a received signal from one or more sensors that the power tool has entered into a fault or abnormal state without departing from the scope of the present disclosure.
Advantageously, the operational mode of the power tool in which the signal measurement is received may also be determined in assessing whether the power tool has entered into the fault or abnormal state. Optionally and alternatively, the state of actuation of the user actuation means by the user may also be provided to the controller in order to determine the operating state of said power tool. It will be appreciated that the determination by the controller may be made in conjunction with measurement signals received via from one or more sensors indicating changes in operating parameters of one or more measured parameters without departing from the scope of the present disclosure.
Upon the determination that the received signal from the sensor indicates that the tool as entered into a fault or abnormal state, the controller may be configured to prevent or restrict further operation of the motor 14 for example by terminating or reducing the operation of the motor by controlling power supplied to the motor, causing pulsing of the motor, or otherwise causing an exceptional operational state of said motor.
It would be appreciated that the above components of the exemplary power tool depicted in Figs 1A - 1C and operations thereof are known in the art, and will not be described further herein.
Referring to Figs 2A-2E, there is depicted an exemplary schematic representation of the operational stages of an exemplary brushless electric motor 50 in a power tool in one exemplary way in which sound and or vibration may be generated by the motor. It would be appreciated that the motor may be brushed or brushless permanent magnet type electric motor without limitation.
As depicted, the rotor 60 has permanent magnetic poles north and south (indicated by N and S) and is rotatably supported in the centre of a stator. For ease of description, various sectors in through which the rotor rotates are depicted in the figures. It would be appreciated that notwithstanding there are six sectors depicted the selection, position, and number of sectors is arbitrary and such sectors are depicted solely for the purposes of explaining the movement of the rotor as described further herein.
As depicted, encircling the rotor is a stator which is schematically depicted as comprising three separate coils labelled A, B and C. It would be appreciated by person skilled in the art that these coils are connected with each other by electrically conductive wires. Typically, the coils are excited by voltage shifted by 120° to produce a changing magnetic field which variously attracts or repels the poles of the permanent magnets of the rotor. Successive changes in the voltage (and therefore current) flowing through the coils thereby cause rotation of the shaft connected to the rotor. Accordingly, the changing electrical current supplied to the stator coils is effectively converted into a rotating magnetic field which is used to drive the rotor.
More specifically, as depicted, upon detection of a fault state or upon the initial power being supplied to the motor by the controller 20 based on signals received from one or more of the sensors 30, the motor is in a stationary position. The position of the rotor relative to the various sectors is then determined as described herein for brushless motors, while for brushed motors there is no need to detect the initial position.
In Fig 2A, the north pole of the rotor in the initial position lies in sector one, although it would be appreciated that it is not limiting which sector the position of the rotor is determined to be in, and the rotor could just as easily be in another sector.
As depicted in Fig 2B, the switching mode is then configured such that the coil A is positive and coil C is negative such that the excited phase current flows from A to C. It would be appreciated that the combined magnetic field that is generated by such current will cause the rotor to rotate in a clockwise direction as depicted by the arrow in Fig 2B.
This magnetic field causes the rotor to move such that the north pole of the rotor 60 is moves so that it is positioned in sector two as depicted in Fig 2C.
After a predetermined amount of time in which the current flows from A through to C, voltage is changed so that coil B is positive and C is negative. This causes the excited phase current to flow in the direction of from B to C and means that the magnetic field generated will push the rotor in a counter-clockwise direction as depicted in Fig 2D.
Finally, the rotor will be urged into the position as depicted in Fig 2E whereby the north pole of the rotor 60 is positioned in sector one.
Accordingly, by changing the voltage applied to the coils, the resultant current flowing through the coils generates changing magnetic fields which are used to drive the rotor backwards and forwards between the sectors one and two in the example depicted.
The oscillation of the rotor between these two sectors at a certain resonant frequency produces the noise which is used as an indication means to notify the user that the tool has entered into a fault or abnormal state.
Ensuring that the voltage switching mode and phase current are configured so as to maximise the magnetic field generated is critical for maximising the volume of the sound produced by the resonating rotor. The beep volume generated by the motor is maximized by firmware for a given current drawn from power supply or battery for a given motor.

In an exemplary arrangement of a brushless motor the following readings were obtained for a variety of time periods used in the resonance/oscillation process. The frequency measurement range is from 0-10KHz, in a motor having the following parameters: Field Winding/Magnet: 1.0/15T Armature Winding/Magnet: N45SH. The main frequency recorded is specified below in Table 1, although it would be appreciated that other frequencies are also obtained.

Table 1:

PWM duty	Time Period	Sound Decibel(dB) level	Main Sound frequency/Hz	Subjective Observations
Duty1	Period	57	7594	The noise produced sounds muffled
	1(0.1ms)			The noise produced sounds muffled
	Period 2	62	1688	The noise produced sounds muffled
	(0.2ms)			The noise produced sounds muffled
	Period 3	61	3750	This period was selected
	(0.3ms)			High pitch noise produced.
	Period 4	59	3047	High pitch
	(0.4ms)
	Period 5	58/55	844	Different rotor position resulted in different sounds produced
	(0.5ms)
	Period 6	67/61	1441	Different rotor position resulted in different sound levels produced.
	(0.6ms)
	Period 7	61/58	1898	Different rotor position resulted in different sound levels produced
	(0.7ms)

If other motors with different characteristics were utilised, it would be appreciated that different time periods may also be needed to obtain the optimum oscillation frequency as can be seen from a different brushless motor type whereby the Field Winding/Magnet: 0.9/8.5T and the armature Winding/Magnet: N45M. In this case the period selected for a loud clear high pitch noise notification was 0.3 milliseconds.

Table 2:

PWM duty cycle	Timer Period	Sound Decibel(dB)	Main Sound frequency/Hz	Subjective Observations
Duty1	Period 1	64	2555	The noise produced sounds muffled
	(0.1ms)
	Period 2	53	5016	The noise produced sounds muffled
	(0.2ms)
	Period 3 (0.3ms)	61	3750	This period was selected
	Period 3 (0.3ms)			High pitch noise produced
	Period 4	53	3938	High pitch
	(0.4ms)

The vibration and decibels increase as the PWM duty cycle and timer period increase, but it would be appreciated that the current drawn for these also increases. As shown above in Table 2, it was also noted that by varying the timer period within a certain timer period range, as the timer period becomes larger, more low-frequency signals are added so there is an optimum timer period which can be determined for this arrangement.
Referring now to Fig 3A, there is depicted in exemplary schematic flowchart of the process depicted in Figs 2A to 2E.
As depicted at step 62, this process is commenced upon the determination of a fault or abnormal state of operation of the power tool, or upon the power tool entering a predetermined state.
The initial position of the rotor is detected in step 64 for brushless motors and the rotor resonation or oscillation process commences. (This step is not performed for brushed motors but other subsequent steps are the same).
Next, a first timer (timer CW) is started for the current sequence and rotor position in step 66. (It would be appreciated that this mode could be selected as counter clock wise (CCW) depending on the rotor position without departing from the scope of the present disclosure. This step is performed in brushed and brushless motors).
Next, the voltage output switching mode is configured so as to generate a clockwise rotation from the determined rotor position in step 68. Once the first timer expires in step 70, the first timer (in this case timer CW) is disabled in step 72.
Next, the second timer (in this case timer CCW) is started for the rotor position for the current sequence in step 74 (It would be appreciated that this mode could be selected as clockwise (CW) depending on the rotor position and previous timer without departing from the scope of the present disclosure).
The output switching mode of the voltage is then changed so as to generate a counter-clockwise rotation from the rotor position for a predetermined time period in step 76. Once the second timer has expired in step 78, this timer is disabled in step 80.
Each motor has a predetermined third time period in which the cycling of the first and second timers takes place.
If the predetermined time period for motor resonation has expired, as indicated by branch 82a, the rotor resonation/oscillation finishes and the aforementioned rapid switching of the coils described above ceases.
Alternatively, if the predetermined resonation time for that motor has not yet expired, as indicated by the branch denoted by 82b, the process returns to step 66 in which the first timer is initiated for switching of the voltage of the requisite coils to drive the rotor in clockwise rotation, and the process repeats until expiry of the predetermined resonation time for that motor.
The emission of the audible noise and or vibration emitted by the rotor resonation then ceases, as is denoted by step 84.
The volume generated by the rapid oscillation of the rotor is maximized when the rotor resonates by sitting in a known one of six sections which rotor positions are divided into. It would be appreciated that especially when the power tool device is employed outside in open and noisy environments the maximized volume facilitates the user being able to hear/feel the indication of the operable state, or in the alternative an indication of an abnormal fault state and then take appropriate corrective action.
In an alternate arrangement as depicted in Fig 3B, there is provided an alternative way in which the rotor resonation or oscillation may be achieved for a motor (brushed or brushless) using cogging torque.
In the arrangement depicted, the initial position of the rotor may optionally be detected in step 90 for a brushless motor and the resonation process is commenced. A person skilled in the art would appreciate that it is not necessary to detect this rotor position for a brushed motor, and optional for a brushless motor.
A clockwise (CW) or counter-clockwise (CCW) timer is initiated in step 92 for the current sequence, and the output switching mode selected in step 93.
When the requisite timer is initiated, current flows in the appropriate direction for pushing and/or pulling the rotor to the next position based on the interaction between the permanent magnetic poles of the rotor and the generated magnetic poles of the stator.
As is known to person skilled in the art, in this stage the variable cogging torque is generated between the permanent magnets in the rotor and the slots of the stator depending on the position of the rotor relative to the stator teeth, and opposes the driving torque especially at low speed.
Using cogging torque to drive the motor while detecting rotor initial position is only adapted for a brushless motor. Meanwhile, using cogging torque without detecting rotor initial position can be adapted for either a brushed motor or a brushless motor.
For brushless or brushed motors, if the rotor position and the current direction drives the rotor in the clockwise direction, suspension of the current allows cogging torque to drive the rotor in the counter-clockwise direction. In this way the relevant timer (CW or CCW) for a rotor in a specific position may be activated for driving the rotor in one direction only, and the opposite direction rotor movement is achieved under the influence of inherent cogging torque to drive the rotor in the reverse direction.
If the CW / CCW timer for driving the rotor between positions for the current sequence has not expired as depicted in step 94b, then the current sequence for driving the rotor continues.
Once the CW / CCW timer time expires, in step 94a, cogging torque drives the motor in a reverse direction and a predetermined timer for controlling the resonance/oscillation of the rotor is checked to determine whether this timer has also expired in step 98.
If the predetermined timer for the resonance/oscillation of the rotor between positions has not expired as depicted in step 98b, then the activation (driving rotation in one direction) and deactivation (permitting rotation in the opposite direction under the urging of cogging torque) steps are repeated.
Once the resonation time expires, in step 98a the rotor stops resonating in step 99.

In an exemplary embodiment, this approach was measured as set out below in Table 3. It should be noted that the frequencies of the sound emitted are composed of multiple frequencies, although Table 3 only shows the frequency with the most dominant component.

Table 3:

PWM duty	Timer Period	Sound Decibel(dB)	Main Sound frequency/Hz	Subjective User Observations
Duty1	Period	65	5016
	1(0.1ms)
	Period 2	63	5062
	(0.2ms)
	Period 3	61	5062
	(0.3ms)
	Period 4	65	4031	Sounds clearest, but produces more rotation
	(0.4ms)			Sounds clearest, but produces more rotation

In yet a further arrangement of the resonance/oscillation described herein, the stator itself may be permitted to resonate instead of the rotor.
As depicted in Fig 3C, in step 100 the appropriate pulse wave modulation and frequency and timer period for the stator vibration of a specific motor is selected according to predetermined experimentation such as that depicted in Tables 1 and 2 above (which were described in respect of rotation of the rotors in the brushless motors).
Studies have shown that the main cause of electromagnetic vibration and noise in permanent magnet synchronous motors (PMSMs) with integer slot multi-pole pair is the resonance of the 0-order electromagnetic force wave and the natural frequency of the motor, and therefore this may be studied further in order to determine the optimum stator resonance.
The timer is enabled for the specific current sequence in step 102 and the output switching mode is entered in step 104. If the predetermined time period for the resonance of the stator has not expired as depicted in step 106b, then this process is repeated and the stator is driven to resonate. This produces an audible sound and/or vibration.
Alternatively, if the predetermined time period for the specific current sequence has expired as depicted in step 106a, the timer is disabled in step 108.
If the resonation time has not yet expired (see step 112b) the timer is recommenced and the process returns to step 102. Alternatively, if the time period for resonance has expired (step 112a), the sequence of current output switching ceases and the rotor ceases resonance and hence the audible noise and/or vibration ceases as depicted by step 114.
The methods and devices used to generate an audible noise and/or vibration in the motor which is transmitted via the housing to the operator provides an effective and efficient way of providing a notification to the operator of the entry of the power tool into a predetermined state. The predetermined state may be the active state of the power tool (for example once a battery has been inserted) or a fault state of some sort (for example that the operating temperature of the tool exceeds a predetermined threshold) as has been further described herein. Without needing a separate buzzer or transducer, the size and reliability of the power tool is not affected.
Additional advantages of the audible and/or vibration arrangement of the present disclosure can include: less additional electronic components which in turn lead to cost saving, and less wear of electronic components. It would be appreciated that given the standards of motors used in electrical power tools, the additional load placed on the motor by operation according to the present disclosure does not shorten overall lifespan.
For clarity of explanation, in some instances the present technology may be presented as including individual functional blocks including functional blocks comprising devices, device components, steps or routines.
Although a variety of examples and other information was used to explain aspects within the scope of the appended claims, no limitation of the claims should be implied based on particular features or arrangements in such examples, as one of ordinary skill would be able to use these examples to derive a wide variety of implementations. Further, although some subject matter may have been described in language specific to examples of structural features and/or method steps, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to these described features or acts. For example, such functionality can be distributed differently or performed in components other than those identified herein. Rather, the described features and steps are disclosed as examples of components of systems and methods within the scope of the appended claims.

Claims

A power tool device (10) comprising:
at least one sensor (30, 30a-e) for detecting one or more operating parameters of said power tool device (10);

a motor (14, 50) comprising a rotor (60) and a stator for driving a working component, said motor (14, 50) being electrically coupled to a power supply module (24);

a controller (20) coupled to the at least one sensor (30, 30a-e) for controlling the operation of the motor (14, 50) by issuing one or more motor driving signal(s);

wherein the controller (20) is configured to drive the motor (14, 50) so that the motor (14, 50) produces an audible sound and/or perceivable vibration upon determination the power tool device (10) is in a predetermined state.
The power tool device (10) according to claim 1 wherein the predetermined state of the power tool device (10) is selected from a group comprising an abnormal operating state or an operable state.
The power tool device (10) according to claim 1 or claim 2 wherein the sensor (30, 30a-e) comprises at least one of:
a temperature sensor (30a) for detecting temperature of the motor (14, 50) and generating a temperature signal;

a current sensor (30b) for detecting a current flow through the motor (14, 50) and generating a current signal;

a voltage sensor (30c) for detecting a voltage flow across the motor (14, 50) and generating a voltage signal;

a user input sensor (30e) for detecting a selected working mode of the power tool device (10) and user actuation of one or more trigger devices and generating an input signal; and

wherein the controller (20) receives at least one of the temperature signal, current signal, voltage signal or input signals for determination of whether the power tool device (10) is in said predetermined state.
The power tool device (10) according to claim 3 wherein said signal(s) received by the controller (20) are processed to determine the state of the power tool device (10) based upon whether said signal(s) exceeds a predetermined threshold, said signal(s) exceeds a predetermined threshold for a predetermined period of time or the rate of change of the underlying value of said signal(s) exceeds a predetermined acceptable rate of change.
The power tool device (10) of any one of the claims 1 to 4 wherein the audible signal and/or vibration is emitted by controlling the rotor (60) to change directions at a predetermined frequency.
The power tool device (10) of any one of the claims 1 to 5 wherein the motor (14, 50) is a brushless DC motor, and the controller (20) is configured such that after the initial position of the rotor (60) of said motor (14, 50) is detected;
a first motor driving signal is emitted by the controller (20) such that the direction of current flow through at least two coils (A, B, C) of the stator and the magnetic field generated therefrom drives the rotor (60) to rotate in a first direction for a first predetermined period of time; and

a second motor driving signal is emitted by the controller (20) such that the direction of current flow through at least two coils (A, B, C) of the stator and the magnetic field generated therefrom drives the rotor (60) to rotate in a second direction opposite to the first direction for a second predetermined period of time; and

wherein said controller (20) repeatedly changes between emitting said first and second motor driving signals to switch the direction of rotation of said rotor (60) over a third predetermined time period.
The power tool device (10) of any one of the claims 1 to 5 wherein the motor (14, 50) is a brushed DC motor and the controller (20) is configured such that
a first motor driving signal is emitted by the controller (20) such that the direction of current flow through the rotor (60) and the magnetic field generated therefrom drives the rotor (60) to rotate in a first direction for a first predetermined period of time; and

a second motor driving signal is emitted by the controller (20) such that the direction of current flow through the rotor (60) and the magnetic field generated therefrom drives the rotor (60) to rotate in a second direction opposite to the first direction for a second predetermined period of time; and

wherein said controller (20) repeatedly changes between emitting said first and second motor driving signals to switch the direction of rotation of said rotor (60) over a third predetermined time period.
The power tool device (10) according to any one of the claims 5 to 7 wherein the first and second predetermined time periods are selected for switching of the direction of current flow through the stator coils (A, B, C) to maximise the magnetic driving force on the rotor (60).
The power tool device (10) of any one of the claims 1 to 5 wherein
a first motor driving signal is emitted by the controller (20) such that the direction of current flow through at least two coils (A, B, C) of the stator and the magnetic field generated therefrom drives the rotor (60) to rotate in a first direction for a first predetermined period of time; and

the rotor (60) is urged by cogging torque to rotate in a second direction opposite to the first direction;

wherein said controller (20) repeatedly changes between emitting said first driving signal and allowing the cogging torque to switch the direction of rotation of said rotor (60) over another predetermined time period.
The power tool device (10) according to claim 1 wherein the audible signal and/or vibration is emitted by controlling the stator to resonate in a predetermined frequency.
The power tool device (10) according to any one of the claims 1 to 10 wherein the power supply module (24) is configured to receive a detachable electrical power source or is configured to connect to a power supply.
A method of operating a motor of a power tool device (10) to issue an audible sound and/or perceivable vibration upon determination the power tool device (10) is in a predetermined state, comprising:
controlling by a motor controller (20) the direction of current flow through one or more selected coils (A, B, C) of the stator such that the magnetic field generated therefrom drives the rotor (60) to rotate in a first direction for a first predetermined period of time;

controlling by the motor controller (20) the direction of current flow through one or more selected coils (A, B, C) of the stator such that the magnetic field generated therefrom drives the rotor (60) to rotate in second direction opposite to the first direction for a second predetermined period of time;

repeatedly switching by the motor controller (20) the direction of rotation of said rotor (60) for a third predetermined time period by controlling said direction of current flow and the selection of coils (A, B, C) of the stator in which said current flows so as to produce an audible sound and/or perceivable vibration.
A method of operating the motor (14, 50) of a power tool device (10) to issue an audible sound and/or perceivable vibration according to claim 12 further comprising the step of:
Detecting an initial position of a rotor (60) of said motor (14, 50) relative to coils (A, B, C) of a stator of said motor (14, 50) positioned thereabout, wherein said motor (14, 50) is a brushless motor.
A method of operating the motor (14, 50) of a power tool device (10) to issue an audible sound and/or perceivable vibration upon determination the power tool device (10) is in a predetermined operating state, comprising:
controlling by a motor controller (20) the direction of current flow through one or more selected coils (A, B, C) of the stator such that the magnetic field generated therefrom drives the rotor (60) to rotate in a first direction for a first predetermined period of time;

allowing the rotor (60) to rotate in second direction opposite to the first direction;

repeatedly switching by a motor controller (20) the direction of rotation of said rotor (60) for another predetermined time period by controlling said direction of current flow and the selection of coils (A, B, C) of the stator in said first predetermined period of time and permitting the cogging torque to drive the rotor (60) for a second predetermined period of time so as to produce an audible sound and/or perceivable vibration.
A controller (20) for a power tool device (10) configured to drive the rotor (60) of the motor of said power tool device (10) to operate according to the method of any one of claims 12 to 14.