DEVICE AND METHOD FOR DETECTING A SAFETY DISTANCE.

Technical field

This invention relates to a device and a method for detecting a distance.

Background art

In the sector of technologies for detecting distances there are prior art devices which use radio frequencies to determine a distance between objects passing in an operating space. According to these solutions, used in an industrial context for assessing a distance between movable objects, the device for detecting the distance exchanges signals with the other objects and determines a distance with these objects on the basis of the flight time of the signal.

The increasing concern regarding contagion due to infectious diseases focuses attention on an increasingly accurate detection of the distance between individuals, even in the order of centimetres, as well as easy portability of the device.

The prior art solutions on the market with reference to the objects are not, however, suitable for implementation on the operators since they have an excessive size, a significant weight and a limited precision. In fact, in the case of objects, the solutions comprise avoiding, for example, the collision between the objects. For this reason, the detection of the distance is performed when the two objects are already positioned at a reduced distance. The market need, on the other hand, requires a measurement precision in the presence of bodies which are already at a relatively considerable distance from each other. The prior art solutions do not propose, on this point, a high performance solution. Aim of the invention

The aim of the invention is to provide a device and a method which overcome the above-mentioned drawbacks of the prior art.

Said aim is fully achieved by the device and the method according to the invention as characterised in the appended claims.

According to one aspect of the invention, the invention provides a device for detecting a distance. The device can be worn by a first operator for detecting a distance with a second operator positioned in the same operating space. Preferably, the device is removably wearable by the first operator.

The device comprises a communication interface, for example an antenna. The communication interface is configured for transmitting a distance signal to a receiver integral with the second operator. The communication interface is configured to receive in response the distance signal from an emitter integral with the second operator. According to a preferred embodiment, the distance signal comprises an ultra-wideband signal (UWB).

The device comprises a control unit. The control unit is configured to determine a flight time, as a function of the distance signal. The control unit is configured for calculating in real time, as a function of the flight time, an operating distance between the first operator and the second operator. The control unit is configured for calculating in real time an operating distance between the first operator and the second operator.

The device comprises a power supply unit. The power supply unit is configured to power the processor and/or the communication interface. According to an embodiment, the device comprises a warning device. The warning device is connected to the control unit. The control unit has access to a limit distance value.

According to an embodiment, the control unit is configured for comparing in real time the operating distance with the limit distance value.

The control unit is configured for generating, on the basis of said comparison, an alert signal. The control unit is configured for sending to the warning device said alert signal, for alerting the first operator.

These features allow the device to warn the operator when he/she is close to another operator. This warning reduces the probability that the operators will remain close together for lengthy periods, thereby increasing the risk of contagion.

According to an aspect of the invention, the device further comprises a communication interface, configured for sending a discrimination signal using Bluetooth technology.

According to an embodiment, more generally speaking, the distance signal or the discrimination signal may be any type of signal included in the radio wave spectrum.

According to this embodiment, the control unit is configured to receive the discrimination signal with Bluetooth technology from an emitter associated with the second operator. The control unit is configured to detect the power of the discrimination signal. The control unit is configured to determine, on the basis of the power of the discrimination signal, a distance of the first operator from the second operator (or, more precisely, of the first device from the emitter associated with the second operator). The device uses in combination the distance signal using UWB technology and the discrimination signal using Bluetooth technology.

The use of the Bluetooth signal has a reduced energy consumption and therefore allows the autonomy of the device to be increased, at the expense of measurement precision. On the other hand, the use of UWB signals allows a high level of precision with a greater energy consumption which therefore reduces the autonomy of the device.

Lastly, the use of both solutions, suitably combined by the control unit according to the conditions, allows a high precision to be obtained in combination with an excellent energy autonomy.

It should be noted that, instead of the Bluetooth signal solution, RFID technology might also be used. It should be noted that, according to an embodiment, the sending and receiving of the signal depends on the decision of how and when to send the distance signal by means of UWB technology.

In an embodiment, the device comprises a local memory.

The control unit is configured to save in the local memory the value of the operating distance, calculated with more precise methods (more specifically, with the UWB distance signal), in association with the power of the Bluetooth discrimination signal received at the same instant as the distance signal. This allows the power of the discrimination signal to be correlated with a corresponding operating distance. This saving is performed at various distances and makes it possible to construct a log including, for each distance, a corresponding value of the power of the discrimination signal. This log can be updated. In particular, the control unit is configured to eliminate a predetermined power-distance pairing, after a predetermined time interval from the acquisition.

The control unit is configured to determine recursively the power of the discrimination signal. In particular, the control unit is configured to instruct the communication interface to send the distance signal on the basis of a variation in the power of the discrimination signal, preferably in response to an increase in the power of the discrimination signal over time. In addition or alternatively, the control unit is configured to instruct the communication interface to send the distance signal after a predetermined time interval after the last sending of the distance signal.

It should be noted that, according to one embodiment, the control unit is configured to determine the power of a plurality of discrimination signals, each associated with a corresponding emitter device. The control unit, for each discrimination signal of said plurality, is configured for assessing the trend of the power of the discrimination signal over time and is configured to instruct the communication interface to send a respective distance signal to the device which has emitted the corresponding discrimination signal, based on the trend of the power over time of said discrimination signal.

In effect, the discrimination signal emitted by each device is emitted in broadcast mode, that is to say, directed to all the surrounding devices. The distance signal is, on the other hand, sent to a specific device, enabled for receiving the UWB distance signal.

The control unit is configured to filter the discrimination signals received, eliminating those signals which do not correspond to discrimination signals of devices associated with the operators.

According to an embodiment, the control unit comprises means for filtering the signal, configured for filtering the discrimination signal. In particular, according to one embodiment, the control unit comprises a low-pass filter applied to the discrimination signal, to allow a reduction in the peaks due to possible measurement noise.

According to an embodiment, the device comprises an accelerometer. The accelerometer is configured to detect an acceleration signal representing an acceleration of the device. The accelerometer is connected to the control unit to send it the acceleration signal.

The presence of an accelerometer makes it possible to obtain information regarding the movement of the first operator who is constrained to the device.

In particular, according to one embodiment, the control unit is configured for generating stationary signal. The stationary signal is generated in response to a value of the acceleration of the device, calculated as a function of the acceleration signal, less than a predetermined acceleration value, preferably if this condition is continued over time for a predetermined period of time.

The control unit is configured to send the stationary signal to the warning device, to alert the first operator.

The presence of the accelerometer and the above-mentioned control logic makes it possible to check and inform the first operator of any abandonment of the device, which is recognised due to the stationary nature of the device. Moreover, the control unit might also be configured to send the stationary signal to an external supervision unit which could therefore have news on the abandonment of the device or on any incident which lead to the first operator being stationary.

According to an embodiment, the control unit instructs the communication interface to send the distance signal on the basis of the acceleration data and on the basis of the trend of the power of the discrimination signal over time.

In particular, the control unit is configured to determine, on the basis of the acceleration data, a direction of movement of the first operator. If the direction of movement of the first operator is not concordant with a variation in the power of the discrimination signal, the control unit delays the instruction to send the UWB distance signal.

This feature makes it possible to take into consideration the movement of the body, which, when moving, could change and reduce the power of the discrimination signal.

According to an embodiment, the device comprises a recharging interface. The recharging interface is connected to, or possibly integrated with, the power supply unit. The recharging interface is configured to receive a wireless recharging current. This feature makes it possible to not have electrical sockets on the device and therefore not to have water infiltration points on the device. This feature is very important in the context described because it allows the device to be sanitised safely, if necessary also immersing it in a sanitising liquid. According to an embodiment, the casing is resistant to jets of water but not designed to be immersed.

More specifically, the device comprises a casing, including an inner space. The control unit, the communication interface and the power supply unit are located in the space inside the casing. Preferably, the casing is fluid- tight, to allow the device to be sanitised and cleaned.

The warning device comprises one or more of the following characteristics: - a light indicator; - an audio warning device;

- a vibration actuator, to allow a vibration of the device;

- a video display for visual signalling of a message.

According to an embodiment, the control unit may comprise a counter. The counter is actuated (initialised, set up) by the control unit. Preferably, the counter is actuated (initialised, set up) by the control unit in response to reaching, by the operating distance, the limit distance value. According to an embodiment, the counter is interrupted by the control unit, preferably in response to the decrease in the operating distance below the limit distance value. This allows the control unit to calculate a contact interval, in which the first operator has remained in a position close to the second operator, in order to assess a probability (a risk) of contagion.

According to an embodiment, the control unit is configured for setting a control parameter on a first value (which will be referred to below as CONT), representing a potential contagion which has occurred between the first and the second operator. In other words, when certain conditions occur, the control unit sets the control parameter, which is, for example, variable between two values (hereinafter referred to as CONT and NON- CONT), on the CONT value, which identifies a potential contagion which has occurred between the operators. According to an embodiment, the warning device varies its status as a function of the control parameter value.

The control parameter is set by default on the NON-CONT value.

According to an embodiment, the control unit is configured for setting the control parameter on the CONT value, in response to the exceeding, by the contact time interval, of a predetermined time interval.

In addition or alternatively, the control unit is configured to count the number of times, in the arc of use of the device by the first operator, that the operating distance has dropped below the limit distance value (which will be referred to below, for simplicity, with the term number of contacts). According to this embodiment, the control unit is configured for setting the control parameter on the CONT value if the operating distance has dropped below the limit distance value a number of times greater than a limit value.

According to an embodiment, the control unit is configured to count, each time the operating distance has dropped below the limit distance value, a corresponding interval of contact. On the basis of the number of contacts and their respective contact intervals, the control unit is configured for calculating an identification value of the risk of contagion, with the common statistical techniques known to an expert in the trade.

According to this embodiment, the control unit is configured for setting the control parameter on the CONT value if said risk identification value is greater than a predetermined risk value.

Lastly, according to an embodiment, the control unit is configured for setting the control parameter on the CONT value if the operating distance has dropped below a critical distance value, less than the limit distance value. This might allow the setting of a first safety distance (limit distance value), below which not to drop during work but which does not necessarily identify a potential contagion, and a second distance (critical distance value) below which the risk of contagion is very high.

According to an embodiment, the control unit is configured for receiving configuration data representing one or more of the following parameters:

- limit distance value;

- critical distance value;

- predetermined time interval for assessing the risk of contagion;

- predetermined time interval for assessing the stationary nature of the device and sending the stationary signal;

- limit value of the number of contacts;

- predetermined risk value;

- predetermined acceleration value.

According to an embodiment, the device comprises a remote access interface, for connection to a remote server. The control unit is configured to exchange operating data with said remote server, preferably in real time.

In an embodiment, the device comprises a local memory. According to an embodiment, the control unit is configured to save the operating data in the local memory. Preferably, in the presence of a remote server, the control unit is configured to perform a backup of the operating data on the remote server, so as to be able to subsequently clean the local memory of the device.

According to an embodiment, the operating data comprises one or more of the following parameters:

- number of contacts;

- relative contact intervals;

- instant of switching on the device;

- switching off instant;

- value of the control parameter.

According to an embodiment, the discrimination signal comprises a data set. The device is therefore configured to receive, using the distance signal, the data set representing information of the emitter associated with the second operator.

In particular, according to an embodiment, the data set comprises one or more of the following parameters:

- first unique identifier, associated with the device which emits the discrimination signal during an operating configuration of the device, in which the distance is checked;

- second unique identifier, associated with the device which emits the discrimination signal during a lost device configuration, wherein the device is being found by means of a mobile device;

- Unique code of the communication interface (UWB);

- MAC address of the further communication interface (Bluetooth);

- request for UWB activation, representing a request, by the emitter, to activate the communication interface, to receive ultra-wideband signals.

According to an embodiment, the data set comprises a unique identification code of the emitter associated with the second operator (that is, an identification code of a further device associated with the second operator).

According to an embodiment, the data set comprises the value of the control parameter (CONT or NON-CONT) of the further device. Alternatively, the control unit is configured to read, in the remote server, the control parameter associated with the specific unique identification code received. In other words, the device comprises a remote interface, for a connection to the remote server, for example a Wi-Fi connection. According to an embodiment, the control unit is configured for updating the value of the limit distance and/or the critical distance, as a function of the control parameter read or received.

This aspect makes it possible to update in a dynamic manner the safety conditions as a function of the daily log of the movements of the operators, allowing, where there is a device which has a probability of high contagion, an increase in the safety distances accordingly, to prevent a diffusion of the contagion.

According to an embodiment, the device comprises a gyroscope, for setting a reference for the acceleration data. With the presence of a gyroscope and an accelerometer it is possible to map the movements of the operators, also providing a possible direction of movement. This also allows the warning to be made in advance. Moreover, the presence of the gyroscope allows a violation of the minimum distance to be foreseen and to warn the operator before it occurs, thereby limiting the use of the UWB distance signal, which has a very high energy consumption, in order to increase autonomy.

According to an aspect of the invention, the invention provides a safety system for detecting reciprocal distances between operators operating in an operating space. The system includes a plurality of devices according to one or more of the characteristics described in the invention.

Each device is associated with a corresponding operator, for assessing a relative distance from the other devices of said plurality.

The system comprises a charging station, configured to charge the power supply unit of each of said devices. According to an embodiment, the recharging station is a wireless recharging station, configured for working according to the principle of transmitting electricity by induction.

According to an embodiment, the system comprises a supervision unit, configured for supervising the devices in use. According to an embodiment, the system comprises a remote server.

According to an embodiment, the supervision unit is configured to vary the configuration data of the device by sending Bluetooth signals to the device itself.

According to an embodiment, the supervision unit is connected to the remote server to exchange and read data on the remote server. According to an embodiment, the supervision unit is configured to modify the data associated with a specific device which are stored on the remote server. The control unit is designed for reading said data on the remote server for varying in a dynamic manner the operating conditions of the device. In particular, the supervision unit can modify one or more of the configuration data.

The supervision unit also has access to the control parameter of each device. This allows a supervisor user, who has access to the supervision unit, to intervene on the operators whose associated device has a control parameter set on the first value, that is to say, the CONT value.

According to an embodiment, the supervision unit is configured to display in real time the presence of operators in a predetermined zone of the operating space and to alert the supervisor user if there are a number of operators in the predetermined zone which is greater than a limit number of operators. According to an aspect of the invention, the invention provides a method for detecting a distance between a first operator and second operator positioned in an operating space.

The method comprises a step of associating a first device with the first operator.

Preferably, the method comprises a step of sending a distance signal, preferably in ultra-wideband, UWB, from the first device to a receiver integral with the second operator, using a communication interface. The method comprises a step of receiving, via the communication interface, the distance signal emitted by an emitter attached to the second operator. Preferably, the method comprises a step of determining a flight time of the distance signal. The method comprises a step of calculating a working distance between the first operator and the second operator, based on flight time, by a control unit.

The method comprises a step of powering the control unit and/or the communication interface.

According to an embodiment, the method comprises a step of comparing in real time between the operating distance and a limit distance value to which the control unit has access.

The method comprises a step of generating an alert signal, on the basis of an outcome of the comparison step (between the operating distance and the limit distance value). The method comprises a step of sending the alert signal to a warning device of the first device, to alert the first operator. The method comprises a step of signalling to the first operator that a distance is reached which is less than the limit distance value.

According to an embodiment, the method comprises a step of receiving a discrimination signal using Bluetooth technology. According to an embodiment, the method comprises a step for receiving a plurality of discrimination signals using Bluetooth technology, each associated with a respective emitter device.

According to this embodiment, the control unit receives the discrimination signal using Bluetooth technology from an emitter associated with the second operator. The control unit detects the power of the discrimination signal. The control unit determines, on the basis of the power of the discrimination signal, a distance of the first operator from the second operator (or, more precisely, of the first device from the emitter associated with the second operator).

According to an embodiment, the method comprises a step of sending/receiving the distance signal with UWB technology and a receiving/sending signal of the discrimination signal with Bluetooth technology, as a function of external conditions which determine which technology is most performing.

The method comprises a step of assessing the use of the UWB technology, wherein the control unit instructs the communication interface to send the distance signal, on the basis of the value of the power of the discrimination signal.

The control unit saves in a local memory the value of the operating distance, calculated with the UWB distance signal, associating it with the power of the Bluetooth discrimination signal received at the same instant as the distance signal. This allows the power of the discrimination signal to be correlated with a corresponding operating distance. The control unit saves, for each operating distance calculated with the UWB distance signal, a corresponding power value of the discrimination signal. The method comprises a step of generating a log, including, for each operating distance, a corresponding power value of the discrimination signal. The method comprises a step of updating the log, wherein a predetermined power-distance pairing is eliminated after a predetermined time interval from the acquisition.

The control unit determines recursively the power of the discrimination signal. In particular, the control unit instructs the communication interface to send the distance signal when it detects an increase in the power of the discrimination signal over time, representing a potential approach between the two devices. In addition or alternatively, the control unit instructs the communication interface to send the distance signal after a predetermined time interval after the last sending of the distance signal.

The control unit, for each discrimination signal of said plurality, assesses the trend of the power of the discrimination signal over time and instructs the communication interface to send a respective distance signal to the device which has emitted the corresponding discrimination signal, based on the trend of the power over time of said discrimination signal.

In effect, the discrimination signal emitted by each device is emitted in broadcast mode, that is to say, directed to all the surrounding devices. The distance signal is, on the other hand, sent to a specific device, enabled (or previously alerted by a data set included in the discrimination signal) upon receiving the UWB distance signal.

The method comprises a filtering step, wherein the control unit filters the discrimination signals received, eliminating those signals which do not correspond to discrimination signals of devices associated with the operators.

According to an embodiment, during the filtration step, the filtering signal is filtered by means of signal filtering tools. In particular, according to an embodiment, a low-pass filter is applied to the discrimination signal (to the plurality of discrimination signals), to allow a reduction in the peaks due to any measuring noise.

According to an embodiment, the method comprises a stationary control step. During the stationary control step, an accelerometer detects an acceleration signal, representing an acceleration of the device. The accelerometer sends the acceleration signal to the control unit.

During the stationary control step, the control unit generates a stationary signal, in response to a value of the acceleration of the device, calculated as a function of the acceleration signal, less than a predetermined acceleration value, preferably if this condition is continued over time for a predetermined period of time. The control unit sends the stationary signal to the warning device, for alerting the first operator.

According to an embodiment, the control unit sends the stationary signal to an external supervision unit which could therefore have news on the abandonment of the device or on any incident which lead to the first operator being stationary.

According to an embodiment, the control unit instructs the communication interface to send the distance signal on the basis of the acceleration data and on the basis of the trend of the power of the discrimination signal over time.

In particular, the control unit determines, on the basis of the acceleration data, a direction of movement of the first operator. When the direction of movement of the first operator is not concordant with a variation in the power of the discrimination signal, the control unit delays the instruction to send the UWB distance signal, to assess whether the variation in power of the discrimination signal is due to different factors with respect to a true approach between the operators.

According to an embodiment, the method comprises a recharging step, wherein a recharging station, using a recharging interface, recharges a power supply unit of the device.

The recharging interface receives a wireless recharging current.

According to an embodiment, the signalling step comprises one or more of the following steps:

- luminous warning;

- audio warning;

- vibration of the device;

- visual illustration of a message on a display unit of the device. According to an embodiment, the method comprises a risk assessment step.

During the risk assessment step, the control unit activates a counter when the operating distance is less than the limit distance value the control unit interrupts thecounter when the operating distance is greater than the limit distance value. The control unit therefore calculates a contact interval. According to an embodiment, during the risk assessment step, the control unit sets a control parameter on a first value (which will be referred to below as CONT), representing a potential contagion which has occurred between the first and the second operator.

According to an embodiment, the control unit sets the control parameter on the value CONT, when the contact interval (time interval) exceeds a predetermined time interval.

In addition or alternatively, the control unit counts the number of times, in the arc of use of the device by the first operator, that the operating distance has dropped below the limit distance value (which will be referred to below, for simplicity, with the term number of contacts). According to this embodiment, the control unit sets the control parameter on the CONT value when the operating distance drops below the limit distance value by a number of times greater than a limit value.

According to an embodiment, each time the operating distance falls below the limit distance value, the control unit counts a corresponding contact interval. On the basis of the number of contacts and their respective contact intervals, the control unit calculates a value identifying the risk of contagion, with the common statistical techniques known to experts in the field.

According to this embodiment, the control unit sets the control parameter on the CONT value when said risk identification value is greater than a predetermined risk value.

Lastly, according to an embodiment, the control unit sets the control parameter on the CONT value when the operating distance drops below a critical distance value, less than the limit distance value.

According to an embodiment, the method comprises a step of configuring the device, wherein the control unit receives configuration data representing one or more of the following parameters: - limit distance value;

- critical distance value;

- predetermined time interval for assessing the risk of contagion;

- predetermined time interval for assessing the stationary nature of the device and sending the stationary signal;

- limit value of the number of contacts;

- predetermined risk value;

- predetermined acceleration value.

According to an embodiment, the method comprises a step of connection to a remote server. The method comprises a step of exchanging operating data with said remote server, preferably in real time.

According to an embodiment, the method comprises a step for saving operating data on a local memory of the device and/or on the remote server.

In particular, according to an embodiment, the method comprises a backup step, wherein the operating data are stored firstly on the local memory, subsequently re-written in the remote server and deleted from the local memory to allow a new data storage. In this way it is possible to maintain a log of the events in the remote server.

According to an embodiment, the method comprises a step of updating settings.

During the step for updating the settings, the control unit receives the distance signal which comprises a data set, representing information of the emitter associated with the second operator.

According to an embodiment, wherein the data set comprises a unique identification code of the emitter associated with the second operator (that is, an identification code of a further device associated with the second operator), the control unit reads in the remote server the value of the control parameter associated with the unique identification code (that is, associated with the second device). According to other embodiments, the control unit receives the control parameter value by means of the distance signal, included in the data set. The control unit updates the limit distance and/or critical distance value as a function of the control parameter read or received.

Brief description of the drawings

These and other features will become more apparent from the following detailed description of a preferred embodiment, illustrated by way of non limiting example in the accompanying drawings, in which:

- Figures 1A and 1 B illustrate, respectively a first embodiment and a second embodiment of a device according to the invention;

- Figure 2 schematically illustrates the internal components of the device of Figure 1 A or 1 B;

- Figure 3 schematically illustrates an operation of the device of Figure 1 A;

- Figure 4 is a block diagram indicating the steps of a method for detecting a distance;

- Figure 5 is a block diagram of a risk assessment step of the method of Figure 4;

- Figure 6 is a block diagram of a stationary control step of the method of Figure 4.

Detailed description of preferred embodiments of the invention

With reference to the accompanying drawings, the numeral 1 denotes a device for detecting a distance of a first operator OP1 from a second operator OP2 positioned in an operating space.

The device 1 is a device which can be worn and transported by a user. The device 1 is removable from the first operator OP1.

The device 1 preferably comprises a support 2 which allows it to be worn or held by a first operator OP1. For example, but without limiting the scope of the invention, the support 2 is a strap 21 which may be worn on the wrist of the first operator OP1. According to other examples, the support 2 is a cord 22. The device 1 comprises a coupling 10, to which the strap 21 and/or the cord 22 are connected.

According to an embodiment, the device 1 comprises a case 11 , which is configured to contain the components of the device 1. The case 11 may be made of polymeric material or metallic material. According to an embodiment, the case 11 comprises a first shell and a second shell, which can be coupled to define an inner space VI of the case, which, preferably, is hydraulically isolated to prevent infiltration of liquid which can adversely affect the components positioned in the inner space VI.

According to an embodiment, the case 11 comprises a signalling opening. According to an embodiment, the device 1 comprises a communication interface, for example an antenna 14, configured for exchanging radio waves with a further device 1' associated with the second operator OP2. In particular, according to a preferred embodiment, the antenna 14 is configured for transmitting an ultra-wideband UWB distance signal 121 to the further device 1 ’ and to receive in response from (from an emitter of) the further device 1 ’ the distance signal 121. According to an embodiment, the antenna 14 is configured for receiving the distance signal 121 by Bluetooth technology.

According to an embodiment, the antenna 14 is configured for working in an ultra-wideband UWB whilst a further antenna 14' is configured for working with Bluetooth technology. This makes it possible to use the antenna 14 and/or the antenna 14' in combination or alternatively, alternating one and the other technology according to requirements.

In an embodiment, the device 1 comprises a control unit 12. The control unit 12 is configured to control the antenna 14 when sending the distance signal 121. The control unit is configured to send control signals 124 to the antenna 14 for instructing it to send and receive the distance signal using the ultra-wideband UWB technology.

According to an embodiment, the device comprises a further antenna 14', for sending and receiving a discrimination signal using Bluetooth technology.

According to an embodiment, the control unit 12 is configured to determine the flight time of the distance signal 121 and to derive the operating distance between the first operator OP1 and the second operator OP2. According to an embodiment, the control unit 12 is configured to determine a power of the discrimination signal 121', received using Bluetooth technology and for deriving, starting from said power of the signal, the operating distance between the first operator OP1 and the second operator OP2. According to an embodiment, the control unit 12 is configured to derive, on the basis of the power of the discrimination signal 121', an indication on the operating distance between the first operator OP1 and the second operator OP2 which is, however, calculated with precision using the distance signal 121 and the UWB technology.

In an embodiment, the device 1 comprises a local memory. The local memory comprises some parameters for setting up the device 1 , for example a limit distance value D1. The control unit 12 is configured for reading the limit distance value D1 in the local memory.

The device 1 comprises a warning device 15, configured to alert the first operator OP1 of a predetermined event which has occurred. For example, but without limiting the scope of the invention, the warning device 15 is a LED 151 and/or a vibration actuator 152, configured to vibrate the device 1.

According to an embodiment, the control unit 12 is configured for comparing the operating distance with the limit distance value D1. The control unit 12 is configured to send an alert signal 122.

The control unit 12 is configured to send the alert signal 122 to the warning device 15, to alert the first operator OP1 of the fact that the first operator OP1 and the second operator OP2 are too close to each other. According to an embodiment, the control unit 12 is configured to count a contact interval, defined as the time interval in which the operating distance remains below the limit distance value D1. The control unit 12 is configured for setting a control parameter on a first value, representing the fact that the first operator OP1 (and the corresponding second operator OP2) have been subject to a high risk of contact. The local memory has saved a predetermined first time interval T1. The control unit 12 is configured for setting a control parameter on the first value, in response to the fact that the contact interval is greater than the first predetermined time interval T1.

The device 1 comprises an accelerometer 16 configured to determine an acceleration of the device 1. The accelerometer 16 detects an acceleration signal 125 representing the acceleration of the device 1.

The accelerometer 16 is configured to send the acceleration signal 125 to the control unit 12. The local memory has saved a predetermined acceleration value and a second predetermined time interval T2. The control unit 12 is configured to compare the acceleration of the device 1 , calculated using the acceleration signal 125, with the predetermined acceleration value. The control unit 12 is configured to count a stationary time, defined as the time interval during which the acceleration of the device 1 remains below the predetermined acceleration. The control unit 12 is configured to compare the stationary time with the second predetermined time interval T2. The control unit 12 is configured to send a stationary signal to the warning device for stationary time values greater than the second predetermined time interval T2.

The device 1 comprises a recharging interface 17 configured to allow electricity to be transferred to the power supply unit 13. In particular, the recharging interface 17 is configured to receive wireless electricity, in the absence, therefore, of physical connectors. The device 1 may be recharged by transferring induction energy.

The operation of (the method developed by) the device 1 will be operatively explained below.

Upon accessing the operating space of the first operator OP1 and of the second operator OP2, a supervision unit assigns to each a respective first device 1 and second device 1 \ Each of said first 1 and second 1 ’ devices has a unique identification code.

During the work of the two operators, each antenna 14 of the first device 1 and of the second device 1’ sends and receives F1 distance signals 121 by means of radio waves, preferably ultra-wideband, UWB, and/or using Bluetooth technology. In that way, each control unit 12 of the first device 1 and of the second device 1’ determines a corresponding operating distance F2.

The control unit compares the operating distance with the limit distance value F3.

Until the operating distance falls below the limit distance value D1 , the antenna 14 continues to send the distance signal 121 to update the operating distance in real time.

When the operating distance falls below the limit distance value D1, each control unit 12 generates F4 the alert signal 122 switching on the respective LED 151 , for example with a red flashing light, and activates the respective vibration actuator 152 for alerting the first and the second operator OP1 , OP2.

Moreover, when the operating distance falls below the limit distance value D1 , the control unit 12 starts a counter F5 to count the time passed. Moreover, when the operating distance returns to be greater than the limit distance value D1 , the control unit 12 interrupts a counter F7 to determine a contact interval.

The method comprises a step of comparing C1 between the contact interval and the first predetermined time interval T1 If the contact interval exceeds the first predetermined time interval T1 , the control unit 12 sends the alert signal 122 to the warning device 15 to instruct it to modify its status. In particular, according to a preferred embodiment, the LED adopts a specific colour, for example red, with fixed light. Moreover, if the time passed exceeds the first predetermined time interval T1 , the control unit 12 sets F6 the control parameter to the first value.

If the contact interval is less than the first predetermined time interval T1 , the control unit 12 keeps the control parameter on the second value (default value) and continues to check the operating distance.

During the work of the first and second operator OP1, OP2, it is possible that one of the two operators forgets the device 1 in a place. In this regard, there is a stationary control step.

The stationary step comprises a step of determining the acceleration F8 of the device 1 , by means of an accelerometer 16.

The method comprises a step C2 of comparing the acceleration of the device 1 with the limit acceleration value.

If the acceleration is greater than the limit acceleration value, the control unit 12 starts a counter F5 to count the time passed. Moreover, the moment the acceleration returns to be greater than the limit acceleration value, the control unit 12 interrupts the counter F7 to determine a stationary interval.

The stationary control step comprises a step C3 of comparing the stationary time with the second predetermined time interval T2.

If the stationary time is greater than the second predetermined time interval T2, the method comprises a step F9 for generating a stationary signal, to set the warning device 15, that is to say, the LED 151 , on a corresponding status (luminous and intermittent light). If the stationary time is greater than the second predetermined time interval T2, the control unit continues to control the stationary time, whilst continuing to perform the comparison step C2 between the acceleration of the device 1 and the limit acceleration value.

According to a preferred embodiment, this invention provides a method comprising one or more of the following steps:

- initialising the device 1 ;

- checking that the device 1 is worn, based on the acceleration data 125 received from the accelerometer 16; - reading a UWB use parameter, representing the need or not to activate the communication interface 14, for sending and receiving UWB distance signals 121 ;

- activating, or not, the communication interface 14, on the basis of the UWB use parameter;

- receiving a discrimination signal 121' using Bluetooth technology, emitted by the second device and having a specific power (intensity);

- determining the power of the discrimination signal 121 ';

- reading a data set included in the discrimination signal 121 ', comprising information on a request to switch on the communication interface 14, to receive UWB distance signals;

- if there is a request for switching on, setting the UWB use parameter to a positive value;

- sending the distance signal 121 using the communication interface 14; - determining the operating distance;

- saving the operating distance in association with the power of the discrimination signal 121' on the local memory;

- updating the determination of the power of the discrimination signal;

- if the value of the power of the updated discrimination signal is increased, sending a further distance signal 121 , for re-determining the precise operating distance, which is associated with the power of the updated discrimination signal;

- if the value of the power of the updated discrimination signal remains constant or reduced, continuous monitoring of the power of the discrimination signal 121';

- starting a counter starting from the sending of the last distance signal 121 ;

- sending a new UWB distance signal after a predetermined time interval after sending the last distance signal 121.