Portable power cutting tool with contactless security system and control process of safety system

Abstract

The invention concerns a portable power cutting tool like a chainsaw (100) comprising : a housing (101) intended to be handheld by an operator (O), a cutting tool, a motor enclosed in the housing (101) for operating said cutting tool, and a security system provided to protect said operator (O); wherein said security system comprises: a tracking system comprising at least one electromagnetic signal source (emitter) (22) located on the operator (O) or the portable power cutting tool (100) and at least one electromagnetic signal sensor (receiver) (21) located on the portable power cutting tool (100) or on the operator (O), the sensor(s) (21) being configured to detect the electromagnetic signal emitted by the source(s) (22); a control unit configured : - to calculate the position and orientation data of the source(s) (22) in three-dimensional space, on the basis of the data detected by the sensor(s) (21), to determine the relative position and orientation of the source (22) and the sensor (21), - to process the relative position and orientation data of sources (22) and sensors (21) to determine the relative position and orientation of the cutting tool operator (o) and the portable power cutting tool (100) - to compare the actual position and orientation of the portable power cutting tool operator (O) and the portable power cutting tool (100) to known safety critical positions and orientations of the portable power cutting tool operator (o) and the portable power cutting tool and; - to trigger a protection signal if safety critical position and orientation of the portable power cutting tool operator (O) and the portable power cutting tool (100) is identified.

Description

[0001] PORTABLE POWER CUTTING TOOL WITH CONTACTLESS SECURITY SYSTEM AND CONTROL PROCESS OF SAFETY SYSTEM

[0002] The present invention relates to portable power cutting tool like a chainsaw equipped with contactless security system.

[0003] The field of the invention is the field of the portable power cutting tool chainsaws or hedge trimmer, equipped with security system preventing a user of the tool from injury.

[0004] Background

[0005] A chainsaw is a portable power cutting with a cutting bar connected to a motor, and a driving endless chain bearing cutting teeth. The chainsaw is a very effective and efficient device for cutting timber. Today chainsaws are widely used as cutting tools for a variety of purposes, situations, and environments and they are used by professional and non-professional people.

[0006] But, the use of these tools can be very dangerous, and some fatal accidents often occur.

[0007] The document US-A-2010 / 0064532 describes a power tool operator protection system intended for protecting a chainsaw operator from cutting him / herself. The system keeps track of the separation distances between sensors placed on the chainsaw cutting bar and the operator's body, and stops the power tool if the separation distances fall within a threshold.

[0008] The sensors are equipped with radio signal measurement modules (emitters / receivers) for detecting distance and movement measurements; an electro-mechanical interface with the power and / or drive mechanism of the cutting device; and a signal processor receiving input from the modules, processing and validating said signals, determining distance and movement measurements, comparing the measurements to preset thresholds, and providing output to the cutting device by way of the electro-mechanical interface. The proposed device seems to be complex to implement as it involves a plurality of sensors on the operator and on the cutting tool to cover all the possible critical situations.

[0009] Proposed device only provides 3D relative distance measurement using 3D signal triangulation in relation to a human user. Each receiver or transmitter will only provide ID of information. To get 3D relative distance measurements, one would need at least one receiver and three transmitters, or, three receivers and one transmitter.

[0010] In the document WO-A-2021002794 describes a power tool operator protection system that comprises a plurality of wearable position sensors configured to be worn by an operator of a handheld power tool A; a power tool position sensor configured to detect the position of a handheld power tool; and processing equipment configured to generate a model of the operator based on the mutual positions of the respective wearable sensors relative to each other, the mutual positions defining the operator's posture; associate each of a plurality of limbs of the operator with a respective protection volume; and based on the position and / or motion of the power tool in relation to the protection volume indicating an imminent danger that the working implement enters a protection volume, generate a protection signal.

[0011] The position system comprises an RTK, real-time kinematic, base station B, wherein each of said wearable position sensors worn by the operator C comprises an RTK enabled GNSS (A) receiver (see figure 1). Such a protection system would be difficult, if not impossible, to make work satisfactorily due to high-frequency vagus absorption of GPS signals (1.5GHz) inside a forest.

[0012] A purpose of the present invention is to overcome at least one of these drawbacks.

[0013] Another purpose of the invention is to propose a portable power cutting tool safer to use.

[0014] Yet another purpose of the present invention is to propose a portable power cutting tool that completely avoids injury of the operator using it. of the invention

[0015] In order to achieve at least one of these aims, the present invention provides A portable power cutting tool like a chainsaw comprising : a housing intended to be handheld by an operator, a cutting tool, a motor enclosed in the housing for operating said cutting tool, and a security system provided to protect said operator; wherein said security system comprises: a tracking system comprising at least one electromagnetic signal source (emitter) located on the operator or the portable power cutting tool and at least one electromagnetic signal sensor (receiver) located on the portable power cutting tool or on the operator, the sensor(s) being configured to detect the electromagnetic signal emitted by the source(s); a control unit configured :

[0016] - to calculate the position and orientation data of the source(s) in three- dimensional space, on the basis of the data detected by the sensor(s), to determine the relative position and orientation of the source and the sensor,

[0017] - to process the relative position and orientation data of sources and sensors to determine the relative position and orientation of the cutting tool operator and the portable power cutting tool,

[0018] - to compare the actual position and orientation of the portable power cutting tool operator and the portable power cutting tool to known safety critical positions and orientations of the portable power cutting tool operator and the portable power cutting tool and;

[0019] - to trigger a protection signal if safety critical position and orientation of the portable power cutting tool operator and the portable power cutting tool is identified.

[0020] Thus, the present invention provides portable power cutting tool like a chainsaw equipped with a contactless security system based on the use of electromagnetic fields as signals emitted by the emitters. Low frequency (LF) electromagnetic field emitters are not sensitive to humidity, compared to ultrahigh frequency (UHF) systems like GPS. Thus, the security system of the cutting tool of the present invention is not sensitive to environmental conditions compared to existing security system equipping the chainsaw. As a consequence, the cutting tool of the present invention provides better security of use compared to existing ones, even in a harsh environment.

[0021] Plus, the security system of the cutting tool, like a chainsaw, of the present invention is configured to detect the electromagnetic fields generated by the sources placed on the body of the operator or on the cutting tool and, based on the measure of the strength and orientation of the electromagnetic field at multiple points using sensors, the system can calculate the precise position (within mm) and orientation of the tracked objects in three-dimensional space. This method does not require a physical contact between the operator (user) and the tool. Thus, the tool of the present invention completely avoids injury of the operator because its security system can be programmed to stop, the electrical actuation of the cutting tool before the tool is too close to the tool operator.

[0022] Furthermore, the tracking system of the security system tracks the relative position and orientation, i.e the pose of the sensors and the sources in real time and provides electromagnetic tracking pose data. These data are obtained from the electromagnetic fields emitted by the sources on the operator or on the tool and directly capture by the sensors on the cutting tool or on the operator. So, the contactless security system provides higher security compared to existing contactless safety systems, which use receivers placed respectively on the operator and the chainsaw.

[0023] In fact, in a previous contactless safety system, each receiver calculates its global earth position based on GPS signals received from a series of satellites in the sky. Since GPS inherited global accuracy is limited to meters, a RTK reference base station is needed to improve the accuracy from meters to cm.

[0024] Such a previous security system may be difficult to implement in an environment with a poor network coverage, in forestry, mountain area.

[0025] Thus, the present invention, as it uses electromagnetic sources (emitters) and sensors (receivers) that contactless and directly "communicate", provides a portable power cutting tool like a chainsaw capable of stopping the movement of the chain, as a function of the direct measurement of the variation in the electromagnetic fields generated by the emitters. The safety system of the present invention avoids any risks of interruption of the tracking operation.

[0026] Advantageously, the protection signal may alert the operator of the critical proximity between the operator and the cutting tool so the operator could adjust the respective positions or activate a safety function of the tool to stop the operating of this tool.

[0027] The alert may be an audible alert transmitted via a buzzer or a speaker a visual alert which may be transmitted via a display unit or light source or a haptic alert by vibrations. The control unit may be configured to take different control actions associated with different safety distance, in example first an audible alert signal to warn the operator that the safety distance is critical and secondly a stop of the tool.

[0028] An electromagnetic source or emitter refers to any object, device, or system that generates electromagnetic signals, more precisely only B-field. Driving current into coils of wire generates electromagnetic signals.

[0029] In a preferred embodiment of the cutting tool like a chainsaw of the present invention, one or more sources, preferably two sources, are mounted on the portable power cutting tool, preferably inside the housing of the portable power cutting tool and preferably, at least five sensors are placed on the operator, preferably the operator's body.

[0030] Advantageously, the sensors can be integral with wearable apparatus like clothes worn by the operator of the chainsaw, preferably work clothes intended to be worn by the operator of the portable cutting tool like chainsaw.

[0031] In first variant, the sensors are wired sensors, linked to a sensor hub worn by the operator of the chainsaw, the sensor hub being configured to detect the electromagnetic signal emitted by the sources. The sensor hub is associated with a classifier MCU, a battery and a low frequency data link.

[0032] In a second variant, each sensor worn by the operator, preferably with a low frequency (13 MHz) data link is configured to detect the electromagnetic signal emitted from each source and a classifier provided in the portable housing on the portable cutting tool.

[0033] The sensors are then located on the operator and the sensors can efficiently send a signal to the control unit on wireless transmission such as Bluetooth or on wired transmission. The reactivity of the safety system of the portable power cutting tool is improved.

[0034] In one another embodiment of the tool like a chainsaw of the present invention, one, preferably, two sensors (receivers) are mounted on the portable cutting tool (chainsaw), preferably in the housing of the portable cutting tool (chainsaw) and preferably, at least five emitters are placed on the operator, preferably on the operator's body. Advantageously, the sensor or emitters can be integral with wearable apparatus like clothes worn by the operator, preferably work clothes intended to be worn by the operator of the portable cutting tool, like the chainsaw.

[0035] The system topology, having the electromagnetic fields sources and sensors placement on the human body (operator) I in the chainsaw respectively, is mainly chosen based on the need for as fast chainsaw motor cutoff as possible, in a dangerous situation.

[0036] Having the sensor located on or in the chainsaw, especially also when the sensor is also the device (microcontroller) that calculates system pose data and output system data, enables the safety system to cut off the chainsaw motor as fast as possible by wired connection directly from the safety system sensors microcontroller to the chainsaw motor controller.

[0037] Furthermore, locating two sensors or sources on the cutting tool, provide definition of a safety volume around the blade of the tool.

[0038] Furthermore, the localization of the sources or sensors on the operator body is used to define safety zone for body parts. Each source or / sensor can be placed on the operator to emit electromagnetic field that can define body zone to keep away from the cutting tool. Consequently, it is preferred to use five sources / emitters, in different work wear pieces of the operator to define five safety zones for the operator's body.

[0039] Advantageously, the sources or sensors are located on the operator's body such as one source or sensor at each wrist, an source or sensor at the waist and one source or sensor at each knee of the portable power cutting tool operator.

[0040] Then, one source or sensor is located in each glove, corresponding to the centre of the back of the hand of the operator, so it can be used to define a safety volume for each arm. One source or sensor can be placed in the waist belt of the operator to define a safety torso volume and one source or sensor can be placed in each pant leg, near the knee to define a safety volume for each leg. Other sources ou sensors can be used and be placed in supplemental positions like in each safety shoe, in a safety helmet. These emitters or receivers may be integrated in the workwear such as jacket, trousers, glooves, boots or helmet. Preferably, the operator wears gloves with one emitter or sensor, corresponding to the wrist articulation, a jacket or a belt with one emitter or sensor at the waist and a trouser with one emitter or sensor located on each knee articulation. Advantageously, an emitter comprises several emitting modules, each emitting a different signal in a different direction. Preferably, one emitter comprises three emitting modules arranged so that the emitter can emit signals in three different directions, each perpendicular to each another, corresponding to the three orthogonal directions in space.

[0041] Advantageously, at least one, in particular each, emitting module can comprise an emitting coil.

[0042] Each coil of the emitter or source will be tuned to run at a unique frequency. This is preferred to prevent the different sources on the body's operator to interfere with each other, but it also permits for the sensors in the tool to decode each source position on the operator's body. In a preferential embodiment, the sources are emitters that can emit signals in three different directions, each perpendicular to each another, corresponding to three orthogonal directions in space.

[0043] Thus, the present invention provides a chainsaw equipped with tracking systems comprising emitting module that is widely available and can be miniaturised to a small form factor and still remain fully functional.

[0044] The small footprint of the emitting module makes it easy to position and integrate to a new or to a pre-existing chainsaw security system.

[0045] The tracking system also includes at least one electromagnetic signal sensor or receiver. The main function of this sensor is to be sensitive (capture) the electromagnetic signals (fields) emitted by the sources and provide data that can be processed to determine the precise position and orientation of the tracked objects, herein the user, in three-dimensional space.

[0046] A receiver can comprise only one receiving module.

[0047] Advantageously, a receiver can comprise several receiving modules, each receiving a signal incident in a different direction. Thus, the present invention provides a receiver capable of detecting the position of an emitter in different directions. As a consequence, the security system can more reliably track the position of the emitter, therefore increasing the safety of the security system.

[0048] In a preferred embodiment, the receiving modules of the receiver may be arranged so that the receiver can receive signals incident in directions that are perpendicular to each other.

[0049] In a preferential embodiment, the receiving modules of the receiver may be arranged so that the receiver can receive incident signals in three different directions, each being perpendicular to the other directions, corresponding to the three directions in space.

[0050] In a more preferential embodiment, the receiver comprise three receiving modules arranged so that the receiver can receive incident signals in three different directions, each being perpendicular to the other directions, corresponding to the three directions in space.

[0051] Advantageously, at least one receiving module can comprise a receiving coil.

[0052] Thus, the present invention provides a cutting tool like a chainsaw equipped with a receiving module that is widely available and can be miniaturised to a small form factor and still remain fully functional.

[0053] The sensors or receivers typically consist of coils or antennae that are sensitive to the electromagnetic fields generated by the tracking system's sources. They can be placed on objects, devices, or even integrated into specialized equipment to capture the electromagnetic signals emitted by the sources.

[0054] In a first embodiment, at least one receiving module can comprise a receiving coil that can detect and measure the strength and orientation of electromagnetic fields. In another embodiment, the sensor can be a magnetic field detector, designed specifically to detect and analyze the strength, direction, and characteristics of the magnetic fields emitted by the electromagnetic sources.

[0055] In a variant embodiment, the receiver can be an array of antennas or specialized antenna configurations that can capture the emitted electromagnetic signals from multiple angles, aiding in more accurate triangulation and positioning.

[0056] Thus, the present invention provides a sensor capable of detecting the position of a source in different directions. As a consequence, the security system can more reliably track the position of the source, therefore increasing the safety of the security system.

[0057] Each receiver (sensor) and transmitter (source) in the presented EMF tracking system have three dimensions (3D) by design, which as a tracking system provides six directions of freedom (6ODF) out the box for each sensor / source combination. Therefore, besides 3D position, the present system also provides 3D orientation, usually named yaw, pitch and roll. All together this are important features, since knowledge of the orientation of the chainsaw in respect to the human body / limbs is of crucial importance in such a protection system.

[0058] The electromagnetic sensors are placed on the chainsaw and the sources placed on the operator's body would track the emitter positions and movements in three-dimensional space, providing data that can be processed to determine the precise position and orientation of the tracked objects.

[0059] The sensors are then located on the portable cutting tool to send a signal to the control unit, especially for, but not limited to, an embodiment with the control unit also integral with, or embedded in, the housing of the cutting tool. The sensors can efficiently send a signal to the control unit on wireless transmission such as Bluetooth or on wired transmission. The reactivity of the safety system of the portable power cutting tool is improved.

[0060] Advantageously, the sensors can be integral with, or embedded in a removable piece of a casing of said portable cutting tool housing. Thus, the present invention provides sensors (receivers) that can be easily attached to and removed from the chainsaw. As a consequence, the ease of maintenance of the security system is improved.

[0061] Preferentially, the removable sensors can be connected to a circuit board of the cutting tool via a connector present on the circuit board. As a consequence, the removable receivers can easily be implemented onto existing chainsaw.

[0062] Advantageously, the sensors can be powered with the power supply of the chainsaw. As a consequence, both the chainsaw and the sensors are relying on the same power source. This makes the chainsaw more secure by reducing the risks of operating chainsaw when the receiver isn't powered.

[0063] Plus, there is no need for and additional power supply individual or dedicated for the sensors, reducing the cost and the footprint of the safety system.

[0064] Alternatively, the sensors can be powered with a dedicated embedded battery, in particular a rechargeable battery.

[0065] The portable power cutting tool like a chainsaw according to the invention may comprise an accelerometer. Thereby a cutting tool rebound can be identified. As the rebounds happen at very high speed, and the accelerometer has a higher band width than the electromagnetic tracking system, the identification of the rebound is improved by using the accelerometer. Accelerometer data are embedded into the process equipment of the safety system, to stop the chainsaw motor when a rebound is detected.

[0066] According to the most preferred embodiment of the invention, the control unit comprises :

[0067] - a first sub-module configured to receive data from the sensors and to calculate the position and orientation data of the sources in three- dimensional space, based on the signal(s) detected by the sensor (s); a second sub-module configured to process the position and orientation data of the source(s) in three-dimensional space by inverse kinematics for a human body, to calculate the joint angles and configurations of the operator's limbs and the cutting tool;

[0068] - a third sub-module configured to fuse and process the data received from : o the electromagnetic sensors, o the inverse kinematics calculations and o data concerning the system configuration and constrains, to generate a comprehensive representation of operator-tool system's movements, i.e the position and orientation of the cutting tool operator and the cutting tool; the data of the system configuration and constrains consisting in the type of the cutting tool, for a chainsaw the blade length, the dimension), the localization of the sources and receivers, the time necessary to stop the motor (latency), the definition of safety zone for body parts and for cutting tool (volume, form), etc.

[0069] - a fourth sub-module configured to extract relevant combined tracking and kinematic data. These relevant features may include joint angles, positons, velocities, acceleration patterns, and spatial relationships between the cutting tool and the operator's body.

[0070] - a fifth sub-moduleconfigured, by use of a machine learning or rule-based classifiers, to assess the safety of the cutting tool operation based on the extracted features according to the following positions and orientations of the cutting tool operator and the cutting tool : o proper handling, by identification that the operator is correctly handling the tool, maintaining safe postures and movements; o unsafe movement, by detection of abrupt or unsafe movements, such as sudden jerks, improper cutting angles, or risky gestures that could lead to accidents; o operator positioning, by assessment of the operator's proximity to potential hazards or unsafe areas; - and to trigger appropriate response if a critical safety position and orientation of the portable power cutting tool operator and the portable power cutting tool.

[0071] The first sub-module can be part of the receiver in a form of micro-controller unit.

[0072] The appropriate responses based on the classification results could be : o Real-time Feedback by providing immediate feedback to the operator through visual, auditory, or haptic alerts to invite him to correct unsafe actions o Automatic Intervention: by stopping or limiting the tool's operation if extremely unsafe conditions are detected; o Emergency Communication: by transmitting alerts or distress signals to nearby devices or emergency services if an accident occurs.

[0073] Advantageously, the classifier could continually learn from new data to improve its ability to recognize and classify safety-related patterns or behaviors.

[0074] Advantageously, the model of the operator's body parts could be generated by the tracked data processed by inverse kinematics calculations.

[0075] According to a variant of embodiment of the invention, the control unit can be configured to:

[0076] - calculate the position of each source in a tridimensional coordinate system of each sensor, based on the signal(s) detected by the sensor,

[0077] - compare said position to a predetermined volume in said tridimensional coordinate system of each sensor; and

[0078] - act on the operating of the portable power cutting tool, when said position is comprised in said predetermined volume.

[0079] In this embodiment, the relative position and orientation data of the emitters and each receiver, are processed to determine the relative position and orientation of the cutting tool operator and the cutting tool, by calculating the position of each emitter in a tridimensional coordinate system of each receiver, based on the signal(s) detected by the receiver.

[0080] Then, the known safety critical positions are determined when the relative position and orientations of the emitters are close or in a predetermined volume in the tri-dimensional coordinate system of the each receiver.

[0081] Thus, the present invention provides a cutting tool like a chainsaw capable of acting on the operating of the cutting tool when at least one of the emitter and, more specifically a safety zone defined by this emitter, is detected close or in a predetermined volume set in the tri-dimensional coordinate system of the receivers. That means that a defined threshold value can form a safety zone around the chainsaw for example and preferably around the moving chain. Thus, the present invention provides a chainsaw capable of acting on the operating of the moving chain when at least one emitter is at a distance from one receiver lower than a pre-set value.

[0082] As a consequence, it is possible to set as constrains data, for example a tubular volume that comprises the entire chainsaw, around the sensors, with a radius equal to the threshold value.

[0083] It is then impossible for an emitter and then the operator's body part wearing it, to come in that tubular volume without the calculated distance passing below the threshold and sending a warning signal.

[0084] Alternatively, it is possible to create a plan shield defined thanks to the use of a six degrees of freedom receiver and the knowledge of the orientation of the chainsaw that allows to deduce dangerous postures.

[0085] As a consequence, it is possible to set, for example a plan shield interposed between the operator and the tool or a volume that comprise the entire cutting tool, around one of said emitter or receiver, with a radius equal to the threshold value. It is then impossible for the receiver, respectively emitter, to come in contact with the cutting tool without the calculated distance passing below the threshold and sending a warning alarm.

[0086] Preferentially, the volume is positioned as close as possible to the portable power cutting tool. As a consequence, it is possible to define the volume to comprise the chainsaw and surround it more closely. It is also possible to define the volume so that it does not comprise the receiver(s). Consequently, the security system is more efficient and the chainsaw more useable as the control unit will generate less false positives, especially when the emitters approach the receivers from the proximal end of the chainsaw, the distal end corresponding to the extremity of the guide bar with the moving chain.

[0087] Advantageously, the control unit can also be configured to:

[0088] - calculate a speed, said approaching speed, at which at least one of the sources approaches each sensor, and

[0089] - act on the operating of the chainsaw as a function of said approaching speed.

[0090] Thus, the present invention provides a chainsaw capable of acting on the operating of the moving chain also based on the approaching speed of the emitter(s).

[0091] As a consequence, the operating of the cutting tool like chainsaw can be stopped if the emitter approaches the receiver too rapidly. This drastically reduces the chance of a leg for example touching the chainsaw while it is being operated. Therefore, the safety of the chainsaw is improved.

[0092] For example, the control unit is also configured to determine the approaching speed by:

[0093] - calculating a first distance of each emitter with respect to the receivers and a first position of each emitter in a tri-dimensional coordinate system of the receivers, based on the signal(s) received by the receivers,

[0094] - memorising said first distance and position and the time at which it was calculated,

[0095] - calculating a second distance of each emitter with respect to the receivers and a second position of each emitter in a tri-dimensional coordinate system of the receivers, based on the signal(s) received by the receivers,

[0096] - memorising said second distance and position and the time at which it was calculated, calculating the approaching speed of the emitter from:

[0097] • the variation of the distance between the emitter and the receiver, calculated either from the first and second calculated distances or the first and second calculated positions of the emitter in the tridimensional coordinate system of the receiver, and

[0098] • the variation of time between first and second calculated distances or positions.

[0099] In an embodiment, the distances and positions as well as the approaching speed is calculated at regular and short intervals, for example at an interval comprised between 1 second and 4 milliseconds.

[0100] In an embodiment, the control unit of a security system can act on the operating of the chainsaw when the approaching speed reaches a pre-set value.

[0101] Advantageously, the threshold distance value, and the size of the predetermined volume can vary as a function of the approaching speed.

[0102] Thus, the present invention provides a chainsaw capable of acting on the operating of the moving chain based on the distance and position of the emitters with respect to the receiver as well as the approaching speed of the emitters.

[0103] As a consequence, it is possible to increase the threshold value and / or the predetermined volume if the emitter approaches the receiver too rapidly. It is also possible to set a smaller predetermined distance and / or volume that allows the emitter to come closer to the chainsaw when moved at a slow and controlled pace. This can be done without compromising the safety of use of the chainsaw as the distance and / or volume used to decide whether or not to act on the operating of the moving chain is adapted with regard to the approaching speed. Therefore, the security system is more efficient and the chainsaw more useable.

[0104] In a preferred embodiment, predetermined threshold value and / or a predetermined volume is only adapted if the approaching speed is positive, in other words if the emitter is getting closer to the receiver.

[0105] The predetermined threshold value and / or a predetermined volume can for example be adapted proportionally to the approaching speed.

[0106] Alternatively, or in addition, the threshold value and / or a predetermined volume can be adapted only if the approaching speed reaches a pre-set value. Advantageously, the control unit of the security system can be integrated in a controller of the cutting tool like chainsaw.

[0107] Thus, the present invention provides a chainsaw with a better integration of the control unit. The control unit being integrated in the controller, this reduce the cables and connections required which in turn reduces the points of failure and therefore makes the chainsaw more reliable.

[0108] Advantageously, the control unit can act on the electrical motor, or on a controller of the cutting tool like a chainsaw, in order to trigger a command directed to said motor or said controller for modifying the operating of the chainsaw.

[0109] The command may request stopping the chainsaw. The stopping of the chainsaw may be obtained by:

[0110] - stopping the motor;

[0111] - activating a breaking means, for example mechanical or electrical means; and / or

[0112] - the engine break of the motor.

[0113] As a consequence, the safety of the chainsaw is improved. Indeed, the safety system is able to stop the moving chain of the chainsaw before the operator comes in contact with the set of teeth.

[0114] Thus, the location of the emitters within the clothes can be chosen, or at least be known.

[0115] Additionally, integrating the emitter to a wearable apparatus improves the ease of use of the security system and the portable electric pruning shears.

[0116] Advantageously, the emitter can be powered with an embedded battery, in particular a rechargeable embedded battery.

[0117] Consequently, the emitter is also less cumbersome and can be easily placed at the different appropriate positions on the user.

[0118] The present invention also concern a control process of safety system for a portable power cutting tool comprising : a housing intended to be handheld by an operator, a cutting tool a motor enclosed in the housing for operating said cutting tool, and the safety system provided to protect said operator comprising a tracking system comprising at least one electromagnetic field source (emitter) located on the operator and at least one electromagnetic field sensor (receiver) located on the cutting tool wherein said control process comprises:

[0119] - to calculate the position and orientation data of the emitter(s) in three- dimensional space, on the basis of the data detected by the receiver (s), to determine the relative position and orientation of the emitter and the receiver,

[0120] - to process the relative position and orientation data of emitters and receivers to determine the relative position and orientation of the cutting tool operator and the cutting tool

[0121] - to compare the actual relative position and orientation of the cutting tool operator and the cutting tool to known safety critical positions and orientations of the cutting tool operator and the cutting tool and; to trigger a protection signal if safety critical position and orientation of the cutting tool operator and the cutting tool is identified.

[0122] Description of the figures and embodiments

[0123] Other advantages and characteristics will become apparent from the detailed description of embodiments that are in no way limitative, and the attached figures, where:

[0124] - Figure 1 is a schematic representation of an example of prior art chainsaw with a safety system ;

[0125] - Figure 2 is a schematic representation of a chainsaw with a safety system according to a variant of a first embodiment of the invention;

[0126] Figure 3 is a schematic representation of a chainsaw with a safety system according to another variant of the first embodiment of the invention;

[0127] - Figure 4 is a representation of a non-limitative example of chainsaw and its user according to a second embodiment of the invention;

[0128] -Figure 5 is a schematic representation of the example of chainsaw and its user according to figure 4; Figure 6 a schematic representation of the operator's body with safety zones;

[0129] - Figure 7 is a block diagram illustrating the control unit;

[0130] - Figure 8 is a detailed block diagram illustrating the control unit part.

[0131] It is understood that the embodiments that will be described below are in no way limitative. In particular, it is possible to imagine variants of the invention comprising only a selection of the characteristics described hereinafter, in isolation from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention with respect to the state of the prior art. Such a selection comprises at least one, preferably functional, characteristic without structural details, or with only a part of the structural details if this part alone is sufficient to confer a technical advantage or to differentiate the invention with respect to the prior art.

[0132] In the figures, elements common to several figures retain the same reference.

[0133] Figure 2 is a schematic representation of a non-limitative example of a chainsaw equipped with a safety system according to a first embodiment of the the invention.

[0134] The chainsaw 100, represented in Figure 2 and Figure 3, comprises a body 101 intended to be held by an operator O, a set of teeth 102 attached to a rotating chain driven along a guide bar 103. An electric motor operates the said rotating chain. The chainsaw 100 also comprises a safety system provided to protect said operator O.

[0135] The safety system comprises several electromagnetic signal sensors or receivers 21 that can be placed on the operator body O and one preferably two electromagnetic signal emitters or sources 22, positioned on the body 101 of the chainsaw 100.

[0136] The electromagnetic field sources 22 are used for position tracking as the employment of electromagnetic fields precisely track the movement and position of persons in three-dimensional space. Actually, by measuring the strength and orientation of the electromagnetic field (EMF) emitted by the sources 22 at multiple points using sensors 21, the tracking system can calculate the precise position and orientation of the tracked objects, in this case the chainsaw 100 in three-dimensional space. Electromagnetic fields (EMF) are generated by driving current into coils of wire in the source 22, for example.

[0137] Then, each source 22 is tuned preferably to run at a unique frequency. In consequence, the different sources 22 on the chainsaw 100 do not interfere with each other, and the sensors 21 on the operator O decode each source 22 position on the chainsaw 100.

[0138] As already mentioned, the sensors 21 are detecting and interpreting the electromagnetic fields EMF emitted by the sources 22 for accurate positioning and tracking in three-dimensional space. The sensors 21 typically consist of coils or antennae that are sensitive to the electromagnetic fields generated by the sources 22.

[0139] The sensors 21 placed on the operator O detect the electromagnetic signals emitted by the sources 22 and provide data (strength I orientation) concerning each source 22 on the chainsaw 100 relative to each sensor 21 on the operator O, these data can be processed to determine the precise position and orientation of the chainsaw 100 relative to the operator O.

[0140] The sensors 21 are located in different work wear pieces. One sensor 21 can be placed in each glove, corresponding to the centre of the back of the hand of the operator O. One sensor 21 can be placed in the waist belt of the user U and one sensor 21 can be placed in each pant leg, near the knee. Sensors 21 can also be placed in supplemental positions like in each safety shoe, in a safety helmet.

[0141] As a function of the signal(s) received by the sensor (receiver) 21, a control unit (CPU) can act on the operating of the chainsaw 100, by acting on the controller in order to trigger a command stopping the operating of the chainsaw 100. Alternatively, or in addition, the control unit could act on the operating of the chainsaw 110, by acting directly on the electric motor.

[0142] In a first variant, see figure (2) each electromagnetic frequence sensor 21 worn by the operator with a low frequency (13 MHz) data link is configured to detect the electromagnetic signal emitted from the EMF source 22 and classifier provided on the chainsaw 100.

[0143] In first variant, (see figure 2) the sensors 21 are wired sensors and relied with a sensor hub 23 worn by the operator O and being configured to detect the electromagnetic signal emitted by the sources 22. The sensor hub 23 is associated with a classifier MCU, a battery and a low frequency data link.

[0144] Figure 4 is a schematic representation of a non-limitative example of a chainsaw equipped with a safety system according to a second embodiment of the invention.

[0145] The chainsaw 100, represented in Figures 4, 5 and 6, comprises a body 101 intended to be held by an operator O, a set of teeth 102 attached to a rotating chain driven along a guide bar 103. An electric motor operates the said rotating chain.

[0146] The safety system comprises several electromagnetic signal sources 22 that can be placed on the operator body O and one, preferably two, electromagnetic signal sensors 21, positioned on the body 101 of the chainsaw 100.

[0147] The electromagnetic sources 22 are used for position tracking as the employment of electromagnetic fields precisely track the movement and position of persons in three-dimensional space. Actually, by measuring the strength and orientation of the electromagnetic field EMF emitted by the sources 22 at points using sensors 21, the tracking system can calculate the precise position and orientation of the tracked objects, in this case the operator body O in three- dimensional space.

[0148] Electromagnetic fields (EMF) are generated by driving current into coils of wire in the source 22, for example.

[0149] Then, each source 22 is tuned preferably to run at a unique frequency. In consequence, the different sources 22 on the operator O do not interfere with each other, and the sensors 21 in the chainsaw 100 decode each source 22 position on the operator O.

[0150] As already mentioned, the sensors 21 are detecting and interpreting the electromagnetic fields EMF emitted by the sources 22 for accurate positioning and tracking in three-dimensional space. The sensors 21 typically consist of coils or antennae that are sensitive to the electromagnetic fields generated by the sources 22.

[0151] The sensors 21 placed on the chainsaw 100 detect the electromagnetic signals emitted by the sources 22 and provide data (strength I orientation) concerning each source 22 on the chainsaw 100 relative to each sensor 21 on the operator O, these data can be processed to determine the precise position and orientation of the operator O relative to the chainsaw 100.

[0152] The sources 22 are located in different work wear pieces. One source 22 can be placed in each glove, corresponding to the centre of the back of the hand of the operator O. One source 22 can be placed in the waist belt of the user U and one source 22 can be placed in each pant leg, near the knee. Sources 22 can also be placed in supplemental positions like in each safety shoe, in a safety helmet.

[0153] As a function of the signal(s) received by the sensor 21, the control unit (CPU) can act on the operating of the chainsaw 100, by acting on the controller in order to trigger a command stopping the operating of the chainsaw 100. Alternatively, or in addition, the control unit could act on the operating of the chainsaw 110, by acting directly on the electric motor.

[0154] Figure 6 is a schematic representation of a non-limitative example of a chainsaw according to the invention.

[0155] The safety system of the chainsaw 100 is configured to generate safety zone around the limbs of the operator O and around the moving chain of the chainsaw 100.

[0156] To do so, the control unit CPU of the chainsaw 100 has constrains concerning the definition of a safety zone via a safety zone algorithm.

[0157] The threshold distance set with respect of the receivers 21 forms a tubular volume VC surrounding the guide bar 103 and the moving chain, schematically illustrated in figure 4. If one or more emitters 22 were to enter said volume VC it would trigger the control unit CPU that would then act on the operating of the chainsaw 100.

[0158] The threshold distance is preferably configured so that the tubular volume VC only includes the moving chain of the chainsaw 100.

[0159] The threshold distance around the emitters 22 is set to define the safety zones around the different limbs of the operator O, VL (volume leg), VT (volume torso), VA (volume arm).

[0160] In the figure 7, is illustrated an example of system architecture block diagram.

[0161] The sources 22 emit electromagnetic signals that are captured by the receivers 21. The main function of these sensors or receivers 21 is to capture the electromagnetic signals (fields) emitted by the sources 22 by measuring their strength and orientation to provide data that can be processed in A to determine the precise position and orientation of the tracked objects in three-dimensional space. The position and orientation data of the emitters 22 in three-dimensional space of each receiver data 21 are processed by inverse kinematics for a human body, in B, to calculate the joint angles and configurations of the operator's limbs and the cutting tool. In C are stored the data concening the system configuration and constrains like the type of chainsaw (blade length / dimensions), the placement of sources and sensors, the motor stop time (latency), the definition of safety zone body parts, etc.

[0162] In D, the data from the A, B, and C parts are fused and processed to create a comprehensive representation of the operator-chainsaw system's movements. Relevant features are extracted from the combined tracking and kinematic data and this might include joint angles, positions, velocities, acceleration patterns, and spatial relationships between the chainsaw and the operator's body. The assesment of the safety of the chainsaw operation is based on the extracted features by utilizing a rule-based classifiers. Based on the classification results, the safety system could trigger appropriate responses to the motor controller E.

[0163] In the figure 8, the part D is described in more details. The part DI represent the sensor fusion and data processing of the data coming from the A, B and C parts. The feature extraction are then treated in the classifier D2 and the part D3 could trigger appropriate responses based on the classification results.

[0164] The classifier D2 could continually learn from new data to improve its ability to recognize and classify safety- related patterns or behaviors

[0165] Other embodiments will appear obvious to the man skilled in the art, for example embodiments where the predetermined volume has a more complex shape if necessary.

[0166] Of course, the invention is not limited to the examples detailed above.

Claims

CLAIMS1. A portable power cutting tool like a chainsaw (100) comprising : a housing (101) intended to be handheld by an operator (O), a cutting tool, a motor enclosed in the housing (101) for operating said cutting tool, and a security system provided to protect said operator (O); wherein said security system comprises: a tracking system comprising at least one electromagnetic signal source (emitter) (22) located on the operator (O) or the portable power cutting tool (100) and at least one electromagnetic signal sensor (receiver) (21) located on the portable power cutting tool (100) or on the operator (O), the electromagnetic signal sensor(s) (21) being configured to detect the electromagnetic signal emitted by the electromagnetic signal source(s) (22); a control unit configured :- to calculate the position and orientation data of the electromagnetic signal source(s) (22) in three-dimensional space, on the basis of the data detected by the electromagnetic signal sensor(s) (21), to determine the relative position and orientation of the electromagnetic signal source (22) and the electromagnetic signal sensor (21),- to process the relative position and orientation data of electromagnetic signal sources (22) and electromagnetic signal sensors (21) to determine the relative position and orientation of the cutting tool operator (o) and the portable power cutting tool (100)- to compare the actual position and orientation of the portable power cutting tool operator (O) and the portable power cutting tool (100) to known safety critical positions and orientations of the portable power cutting tool operator (o) and the portable power cutting tool and;- to trigger a protection signal if safety critical position and orientation of the portable power cutting tool operator (O) and the portable power cutting tool (100) is identified.

2. A portable power cutting tool (100) according to the claim 1, wherein one or more electromagnetic signal sources (22), preferably two electromagnetic signal sources (22), are mounted on the portable power cuttingtool, preferably inside the housing of the portable power cutting tool and preferably, at least five electromagnetic signal sensors (21) are placed on the operator (O), preferably the operator's body.

3. A portable power cutting tool (100) according to the claim 3, wherein the electromagnetic signal sensors (21) are wired sensors, linked to a sensor hub (23) worn by the operator (O), the sensor hub (23) being configured to detect the electromagnetic signal emitted by the electromagnetic signal sources (22).

4. A portable power cutting tool (100) according to the claim 2 or 3, wherein each electromagnetic signal sensor (21) worn by the operator (O) is configured to detect the electromagnetic signal emitted from a electromagnetic signal source (22) and classifier provided on the portable power cutting tool (100).

5. A portable power cutting tool (100) according to the claim 1, wherein one, preferably two, electromagnetic signal sensor(s) (21) are mounted located on the portable power cutting tool (100), preferably in the housing (101) of the portable power cutting tool (100) and preferably, at least five sources (22) are placed on the operator (O) preferably on the operator's body.

6. A portable power cutting tool (100) according to the claim 2 or claim 5, wherein the electromagnetic signal sensors (21) or electromagnetic signal sources (22) are integral with wearable apparatus like clothes worn by the operator (O), preferably work clothes intended to be worn by the operator (O) of the portable power cutting tool (100).

7. A portable power cutting tool (100) according to the claim 6, wherein the electromagnetic signal sources (22) or electromagnetic signal sensors (21) are located on the operator's body such as one electromagnetic signal source (22) or electromagnetic signal sensor (21) at each wrist, one electromagnetic signal source (22) or electromagnetic signal sensor (21) at the waist and one electromagnetic signal source (22) or electromagnetic signal sensor (21) at each knee of the portable power cutting tool operator (100).

8. A portable power cutting tool (100) according to anyone of the claims 1 to 7, wherein the control unit comprises :- a first sub-unit configured to receive data from the electromagnetic signal sensors (21) and to calculate the position and orientation data of the electromagnetic signal sources (22) in three-dimensional space, based on the signal(s) received by the electromagnetic signal sensor(s) (21);- a second sub-unit configured to process the position and orientation data of the electromagnetic signal sensors (s) (21) in three-dimensional space by inverse kinematics for a human body, to calculate the joint angles and configurations of the operator's limbs and the cutting tool;- a third sub-unit configured to fuse and process the data received from the electromagnetic signal sensors (21), the inverse kinematics calculations and data concerning the system configuration and constrains, to generate a comprehensive representation of operator-tool system's movements;- a fourth sub-unit configured to extract relevant combined tracking and kinematic data;- a fifth sub-unit configured, by use of a machine learning or rule-based classifiers, to assess the safety of the cutting tool operation based on the extracted features according to the following positions and orientations of the cutting tool operator and the cutting tool : o proper handling, by identification that the operator is correctly handling the tool, maintaining safe postures and movements; o unsafe movement, by detection of abrupt or unsafe movements, such as sudden jerks, improper cutting angles, or risky gestures that could lead to accidents; o operator positioning, by assessment of the operator's proximity to potential hazards or unsafe areas;- and to trigger appropriate response if a critical safety position and orientation of the portable power cutting tool operator and the portable power cutting tool.

9. A portable power cutting tool according to the claim 8, wherein the appropriate responses based on the classification results are : o Real-time Feedback by providing immediate feedback to the operator through visual, auditory, or haptic alerts to invite him to correct unsafe actionso Automatic Intervention : by stopping or limiting the tool's operation if extremely unsafe conditions are detected; o Emergency Communication : by transmitting alerts or distress signals to nearby devices or emergency services if an accident occurs.

10. A portable power cutting tool according to anyone of the claims 1 to 7, wherein the control unit is configured to:- calculate the position of each electromagnetic signal source (22) in a tridimensional coordinate system of each electromagnetic signal sensor (21), based on the signal(s) received by the electromagnetic signal sensor (21),- compare said position to a predetermined volume in said tri-dimensional coordinate system of each electromagnetic signal sensor (21); and- act on the operating of the portable power cutting tool (100), when said position is comprised in said predetermined volume.

11. A portable ower cutting tool according to anyone of the claims 1 to 7, wherein the control unit is configured to:- calculate a speed, said approaching speed, at which at least one of the sources (22) approaches each electromagnetic signal sensor (21), and- act on the operating of the portable power cutting tool (100) as a function of said approaching speed.

12. A portable power cutting tool according to the claim 11, wherein the control unit is also configured to determine the approaching speed by: calculating a first distance of each electromagnetic signal source (22) with respect to the electromagnetic signal sensors (21) and a first position of each source (22) in a tri-dimensional coordinate system of the electromagnetic signal sensors (21), based on the signal(s) received by the electromagnetic signal sensors (21), memorising said first distance and position and the time at which it was calculated, calculating a second distance of each emitter with respect to the sensors (21) and a second position of each electromagnetic signal electromagnetic signal source (22) in a tri-dimensional coordinate system of the sensors (21), based on the signal(s) received by the sensors (21),memorising said second distance and position and the time at which it was calculated, calculating the approaching speed of the electromagnetic signal source (22) from:• the variation of the distance between the source electromagnetic signal (22) and the electromagnetic signal sensor (21), calculated either from the first and second calculated distances or the first and second calculated positions of the emitter in the tri-dimensional coordinate system of the sensor (11), and• the variation of time between first and second calculated distances or positions.

13. A portable power cutting tool (100) according to anyone of the claims 1 to 12, wherein the electromagnetic signal sources (22) or sensors (21) are integrated in the workwear such as jacket, trousers, glooves, boots or helmet.

14. A control process of safety system for a portable power cutting tool (100) according to anyone of the claims 1 to 13, comprising : a housing (101) intended to be handheld by an operator (o), a cutting tool a motor enclosed in the housing for operating said cutting tool, and the safety system provided to protect said operator comprising a tracking system comprising at least one electromagnetic signal source (22) located on the operator (O) or on the portable power cutting tool (100) and at least one electromagnetic signal sensor (21) located on the portable power cutting tool (100) or o the operator (O) wherein said control process comprises:- to calculate the position and orientation data of the electromagnetic signal source(s) (22) in three-dimensional space, on the basis of the data detected by the electromagnetic signal sensor(s) (21), to determine the relative position and orientation of the electromagnetic signal source (22) and the sensor (21),- to process the relative position and orientation data of electromagnetic signal sources (22) and electromagnetic signal sensors (21) to determine the relative position and orientation of the portable power cutting tool operator (O) and the portable power cutting tool (100)- to compare the actual relative position and orientation of the portable power cutting tool operator (O) and the portable power cutting tool (100) to known safety critical positions and orientations of the portable power cutting tool operator (O) and the portable power cutting tool (100) and; to trigger a protection signal if safety critical position and orientation of the portable power cutting tool operator (O) and the portable power cutting tool (100) is identified.

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