EP4646314A1

EP4646314A1 - Fall detection in power tools

Info

Publication number: EP4646314A1
Application number: EP23914087.4A
Authority: EP
Inventors: Zicong CHEN; Chao Wen
Original assignee: Techtronic Cordless GP
Current assignee: Techtronic Cordless GP
Priority date: 2023-01-06
Filing date: 2023-01-06
Publication date: 2025-11-12
Also published as: AU2023420960A1; CN120418043A; WO2024145930A1

Abstract

A fall detection module for a power tool, comprises an accelerometer arranged to detect acceleration of the power tool; a power controller configured to control an operational state of the power tool; and a processor configured to determine a free-fall state of the power tool followed by an impact state of the power tool using detected acceleration of the power tool, and instruct the power controller to cease operation of the power tool in response to determining the impact state following the free-fall state.

Description

FALL DETECTION IN POWER TOOLS

FIELD OF THE DISCLOSURE
The present disclosure relates to the detection of a falling power tool and, in particular, to a mechanism for detecting the fall of the power tool and ceasing operation as a result.
BACKGROUND OF THE DISCLOSURE
Many handheld power tools are operated using a simple push button trigger, that is, the tool is powered as long as the trigger button is depressed. The user must hold the trigger down for the tool to continue running. Certain tools, e.g. many angle grinders and other tools, have a “lock-on” function whereby the trigger is locked in the active position and the tool continues running regardless of whether the user is applying pressure to the trigger. This can reduce strain for the user, and allow the user to change hands, work at different angles and even put the tool down.
However, the lock-on function can be hazardous if the user drops the tool while the lock-on function is engaged, as the tool will continue running as it falls and potentially bounces in an out-of-control manner.
It is an object of the present disclosure to address or at least partially ameliorate some of the above limitations of the current approaches.
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 is provided a fall detection module for a power tool, including an accelerometer arranged to detect acceleration of the power tool; a power controller configured to control an operational state of the power tool; and a processor configured to determine a free-fall state of the power tool followed by an impact state of the power tool using detected acceleration of the power tool, and instruct the power controller to cease operation of the power tool in response to determining the impact state following the free-fall state.
Determining the free-fall state may include determining that the detected acceleration of the power tool is substantially zero for a minimum period of time.
Determining the impact state may include determining that the detected acceleration of the power tool rises above a predefined threshold acceleration.
Determining the impact state may include determining a return to the free fall state within a predetermined time from the detected acceleration of the power tool rising above the predefined threshold acceleration
The processor may be configured to instruct the power controller to actively decelerate a motor of the power tool in response to determining the impact state following the free-fall state.
The processor may be configured to instruct the power controller to apply a preselected braking profile to actively decelerate the motor of the power tool.
The fall detection module may include an active braking mechanism.
The processor may be configured to activate the active braking mechanism in response to determining the impact state following the free-fall state.
In accordance with a second aspect of the present disclosure, there is provided power tool comprising the fall detection module of the first aspect.
In accordance with a third aspect of the present disclosure, there is provided a computer-implemented method of controlling an operational state of a power tool, comprising detecting an acceleration of the power tool; determining a free-fall state of the power tool followed by an impact state of the power tool using the detected acceleration of the power tool; and ceasing operation of the power tool in response to determining the impact state following the free-fall state.
Determining the free-fall state may include determining that the detected acceleration of the power tool is substantially zero for a minimum period of time.
Determining the impact state may include determining that the detected acceleration of the power tool rises above a predefined threshold acceleration.
Determining the impact state further may include determining a return to the free fall state within a predetermined time from the detected acceleration of the power tool rising above the predefined threshold acceleration.
The method may include actively decelerating a motor of the power tool in response to determining the impact state following the free-fall state.
The method may include applying a preselected braking profile to actively decelerate the motor of the power tool.
The method may include activating an active braking mechanism in response to determining the impact state following the free-fall state.
In accordance with a first aspect of the present disclosure, there is provided a computer-readable medium configured to store instructions which, when executed by a processor, cause the processor to perform the method of the third aspect.

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: -
Figure 1 shows a schematic diagram of a power tool having a fall detection module, according to an embodiment.
Figure 2 shows an exemplary acceleration chart for a power tool.
Figure 3 shows an exemplary acceleration chart for a power tool.
Figure 4 shows accelerometer test data for an implementation of the fall detection module.
Figure 5 shows a method of controlling an operational state of a power tool, according to an embodiment.
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 scope of the disclosure.
Referring to the drawings, there is shown in Figure 1 a power tool 1 comprising a fall detection module 10, according to an embodiment. The fall detection module 10 comprises an accelerometer 100, a processor 200 and a power controller 300.
The accelerometer 100 is arranged to detect acceleration of the power tool 1. In some examples, the accelerometer 100 may be a 3-axis accelerometer 100, configured to sense acceleration along 3 axes which are mutually perpendicular.
The processor 200 is configured to determine a free-fall state of the power tool 1 using detected acceleration of the power tool 1. An object at rest may experience the force of gravity in a downwards direction, which is equivalent to an upwards acceleration at approximately 9.81 ms-2 (or “1g” ) . As such, when the power tool 1 is at rest, the accelerometer 100 may detect an acceleration which is substantially equal to 1g. During normal operation of the power tool 1, e.g. while being moved around by a user, the acceleration of tool may remain close to 1g.
However, if the power tool 1 is allowed to fall, the acceleration may tend quickly to zero. As such, when the power tool 1 is falling, the accelerometer 100 may detect an acceleration which is substantially equal to zero. In some examples, when the detected acceleration is substantially zero, the power tool 1 may be determined to be in the free fall state.
In some examples, the processor 200 may be configured to determine the free-fall state using a magnitude of the detected acceleration. For example, the magnitude may be an average or modulus value of the acceleration in the three axes.
The processor 200 is further configured to determine an impact state of the power tool 1 following the free-fall state using detected acceleration of the power tool 1. If the falling power tool 1 strikes the ground, the accelerometer 100 may detect an acceleration which increases sharply from zero, as the tool stops and/or bounces off the ground. In some examples, when the detected acceleration increases rapidly from zero, the power tool 1 may be determined to be in the impact state.
The processor 200 is further configured to instruct the power controller 300 to cease operation of the power tool 1 in response to determining the impact state following the free-fall state.
The power controller 300 is configured to control an operational state of the power tool 1. The power controller 300 may be configured to cease operation of the power tool 1 in response to an instruction from the processor 200. In some examples, the power tool 1 may comprise a motor 20 and the power controller 300 may controls an operational state of the motor 20. For example, the power controller 300 may be configured to stop the motor 20 running. In some examples, the power controller 300 may be configured to override a trigger or lock-on mechanism of the power tool 1 to cease operation of the power tool 1. Alternatively, or in addition, the power controller 300 may be configured to interrupt a power supply to the power tool 1 or to the motor 20 specifically.
In this way, the safety of operation of the power tool 1 can be significantly improved. By ceasing operation of the power tool 1 in response to a fall, the fall detection module 10 can reduce the potential for damage or harm caused by a running power tool 1 falling or bouncing in an uncontrolled manner.
Furthermore, by triggering using the impact state following the free fall state, the fall detection module 10 can prevent accidentally ceasing operation of the power tool 1 by mistake during normal operation, which may occur if triggering using only the free-fall state. For example, a user may cause the power tool 1 to briefly enter a free fall state when squatting down or picking up the tool, and so triggering using the impact state can prevent unintentional stoppage of the power tool 1.
Figure 2 shows an exemplary acceleration chart for a power tool 1. The chart shows a normal state of the power tool 1, a free fall state and a touchdown impact state (or “impact state” ) .
As described above, in the normal state, the total acceleration of the power tool 1 may tend to 1g as the tool is used normally or placed at rest. In addition, when the power tool 1 is in the free fall state, the total acceleration of the power tool 1 may tend to zero.
In some examples, determining the free-fall state may include determining that the detected acceleration of the power tool 1 is substantially zero for a minimum period of time.
As the relationship between a free fall height and time can be calculated as H = 1/2gT ², in some examples a safety height H _S may be set and a corresponding free fall time T _S may be calculated. The free fall time T _S may be set as the minimum period of time, such that if the actual free fall time T _A > T _S then the actual free fall height H _A > H _S. Alternatively, in some examples the free-fall state may be identified as soon as the detected acceleration is substantially zero.
The term “substantially zero” , as used herein, means at or near the value of zero, as the acceleration may not reach an exact value of zero due to air resistance or other physical effects. The required tolerance on a zero reading of the accelerometer 100 may be established through testing and or calibration, and may be a value which is e.g. below 0.1 ms ^-2 or 0.5 ms ^-2.
In some embodiments, determining the impact state may include determining that the detected acceleration of the power tool 1 rises above a predefined threshold acceleration. In some examples, when the power tool 1 makes contact with ground and changes from the free fall state to the impact state, the total acceleration of the tool may oscillate from zero. As shown, the acceleration may oscillate between a touchdown rebound and a further free fall state in turn, finally stabilizing and tending to 1g.
In some examples, the predefined threshold acceleration may be established by testing and or calibration. For example, the predefined threshold acceleration may be 0.5g or 1g.
In some examples, the predefined threshold acceleration is based on a magnitude of acceleration only. Alternatively, in some examples the predefined threshold of acceleration may be based on direction using the 3-axis sensor. For example, if the direction of acceleration is substantially changed, potentially indicating a dangerous bounce in another direction, then the predefined threshold of acceleration may lowered.
Figure 3 shows an exemplary acceleration chart for a power tool 1, showing only the impact state.
In some embodiments, determining the impact state may further include determining a return to the free fall state within a predetermined time from the detected acceleration of the power tool 1 rising above the predefined threshold acceleration.
At the point (1) , it is detected that the acceleration increases from a very low value to a value greater than the predefined threshold acceleration, which may indicate the tool bouncing off the ground. Subsequently, at point (2) , it is detected that the value of the acceleration after bouncing off the ground has dropped back towards zero, which may indicate a further free fall state after the tool bounces off the ground. In some examples, when (1) is triggered, (2) must be triggered within the predetermined time to trigger the impact state, otherwise it may considered as normal use.
Figure 4 shows accelerometer 100 test data for an implementation of the fall detection module 10.The first chart shows acceleration of the power tool 1 after a drop from 10 cm. The second chart shows acceleration of the power tool 1 after a drop from 20cm. The free fall state and impact state are highlighted on each chart. It is noted that the free fall state is longer when the power tool 1 is dropped from a higher point, and the acceleration in the touch down impact state is more sharply oscillating. However, it is noted that the feature of the impact state following the free fall state can be detected in both instances, in order to correctly cease operation of the power tool 1.
In some embodiments, the processor 200 may be configured to instruct the power controller 300 to actively decelerate the motor 20 of the power tool 1 in response to determining the impact state following the free-fall state. For example, where the motor 20 is a brushless motor 20, the power controller 300 may be configured to transmit signals which are out of sync with the rotation of the motor 20 and cause the magnetic elements of the motor 20 to act in opposition to the motion of the motor 20, decelerating the motor 20. In some examples, the signals transmitted to the motor 20 may be selected from a plurality of signals which correspond to different braking profiles e.g. to cause faster or slower braking of the power tool 1.
In some embodiments, the processor 200 is configure to instruct the power controller 300 to apply a preselected braking profile to actively decelerate the motor 20 of the power tool 1. For example, where the power tool 1 is configured to employ a certain braking profile in normal use (e.g. when the power tool 1 trigger is released) , the power controller 300 may be configured to select a faster profile in response to determining the impact state following the free-fall state. In this way, the power tool 1 may be braked more quickly in an emergency situation. In some examples, a particular braking profile may be also selected based on the 3-axis sensor e.g. a faster braking profile may be selected if a dangerous sideways bounce is detected.
In some implementations, the power tool 1 may include an active braking mechanism. In some embodiments, the processor 200 may be configured to activate the active braking mechanism in response to determining the impact state following the free-fall state. In some examples, the active braking mechanism may include a friction component e.g. including one or more brake pads arranged to make contact with a moving component of the power tool 1 such as the disc of an angle grinder. In some examples, the active braking mechanism may include a blocking component e.g. an element which physically obstructs the moving component of the power tool 1.In some examples, the active braking mechanism may be designed for single-use e.g. due to damaged caused to the power tool 1 or the active braking mechanism itself, or may be used multiple times.
In some examples, the accelerometer 100 may be placed as far away from the motor 20 as possible. In this way, it is possible to reduce the impact of the vibration of the power tool 1 itself on the accelerometer 100. In some examples, the accelerometer 100 may be placed at a base of the power tool 1 e.g. where the power tool 1 is connected with a battery pack.
In some implementations, the fall detection module 10 may be provided as part of the power tool 1. Alternatively, in some implementations the fall detection module 10 may be provided separately.
A separate module may be connected with a control logic board of the tool e.g. through an available bus connection. Alternatively the module may be configured to interface with the battery pack or battery connection, in order to interrupt the power supply in the event of a detected fall.
In some examples, the accelerometer 100 may operate in a range of, for example, ±2g, ±4g, ±8g or ±16g. In some examples, the range may be user selectable, so as to configure the fall detection module 10. In some examples, a resolution of the accelerometer 100 may be 14 bits, or may be any suitable value e.g. selected in a range of 8 –32 bits. In some examples, a data output rate of the accelerometer 100 may be in a range from 1Hz to 1000Hz.
Figure 5 is a flowchart showing a method of controlling an operational state of a power tool. The method starts at step S01.
At step S02, an acceleration of the power tool is detected.
At step S03, a free-fall state of the power tool is determined using the detected acceleration of the power tool.
At step S04, an impact state of the power tool is determined using the detected acceleration of the power tool.
At step S05, operation of the power tool is ceased in response to determining the impact state following the free-fall state.
The method finishes at step S06.
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.
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 in a method embodied in software, or combinations of hardware and software.
Methods according to the above-described examples can be implemented using computer-executable instructions that are stored or otherwise available from computer readable media. Such instructions can comprise, for example, instructions and data which cause or otherwise configure a general purpose computer, special purpose computer, or special purpose processing device to perform a certain function or group of functions. Portions of computer resources used can be accessible over a network. The computer executable instructions may be, for example, binaries, intermediate format instructions such as assembly language, firmware, or source code. Examples of computer-readable media that may be used to store instructions, information used, and/or information created during methods according to described examples include magnetic or optical disks, flash memory, Universal Serial Bus (USB) devices provided with non-volatile memory, networked storage devices, and so on.
Devices implementing methods according to these disclosures can comprise hardware, firmware and/or software, and can take any of a variety of form factors. Typical examples of such form factors include laptops, smart phones, small form factor personal computers, personal digital assistants, and so on. Functionality described herein also can be embodied in peripherals or add-in cards. Such functionality can also be implemented on a circuit board among different chips or different processes executing in a single device, by way of further example.
The instructions, media for conveying such instructions, computing resources for executing them, and other structures for supporting such computing resources are means for providing the functions described in these disclosures.
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 and 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 fall detection module for a power tool, comprising:

an accelerometer arranged to detect acceleration of the power tool;

a power controller configured to control an operational state of the power tool; and

a processor configured to:

determine a free-fall state of the power tool followed by an impact state of the power tool using detected acceleration of the power tool, and

instruct the power controller to cease operation of the power tool in response to determining the impact state following the free-fall state.
The fall detection module of claim 1, wherein determining the free-fall state comprises determining that the detected acceleration of the power tool is substantially zero for a minimum period of time.
The fall detection module of claim 1 or claim 2, wherein determining the impact state comprises determining that the detected acceleration of the power tool rises above a predefined threshold acceleration.
The fall detection module of claim 3, wherein determining the impact state further comprises determining a return to the free fall state within a predetermined time from the detected acceleration of the power tool rising above the predefined threshold acceleration
The fall detection module of any preceding claim, wherein the processor is further configured to instruct the power controller to actively decelerate a motor of the power tool in response to determining the impact state following the free-fall state.
The fall detection module of claim 5, wherein the processor is configured to instruct the power controller to apply a preselected braking profile to actively decelerate the motor of the power tool.
The fall detection module of any preceding claim, further comprising an active braking mechanism, wherein the processor is further configured to activate the active braking mechanism in response to determining the impact state following the free-fall state.
A power tool comprising the fall detection module of any preceding claim.
A computer-implemented method of controlling an operational state of a power tool, comprising:

detecting an acceleration of the power tool;

determining a free-fall state of the power tool followed by an impact state of the power tool using the detected acceleration of the power tool; and

ceasing operation of the power tool in response to determining the impact state following the free-fall state.
The computer-implemented method of claim 9, wherein determining the free-fall state comprises determining that the detected acceleration of the power tool is substantially zero for a minimum period of time.
The computer-implemented method of claim 9 or claim 10, wherein determining the impact state comprises determining that the detected acceleration of the power tool rises above a predefined threshold acceleration.
The computer-implemented method of claim 11, wherein determining the impact state further comprises determining a return to the free fall state within a predetermined time from the detected acceleration of the power tool rising above the predefined threshold acceleration.
The computer-implemented method of any one of claims 9 to 12, further comprising actively decelerating a motor of the power tool in response to determining the impact state following the free-fall state.
The computer-implemented method of claim 13, comprising applying a preselected braking profile to actively decelerate the motor of the power tool.
The computer-implemented method of any one of claims 9 to 14, further comprising activating an active braking mechanism in response to determining the impact state following the free-fall state.
A computer-readable medium configured to store instructions which, when executed by a processor, cause the processor to perform the method of any one of claims 9 to 15.