Technical field

The present invention concerns a method and system for alerting a person near a vehicle when said vehicle performs a movement. In particular, the invention aims at alerting a worker and/or a bystander near a construction vehicle when said construction vehicle performs a movement. The construction vehicle may be a transport truck, an excavator, a crane, a truck crane, etc.

Background of the invention

In the field of construction, it is known to equip the vehicles with a speaker for emitting a sound alarm when the vehicle is moving. The amplitude of the sound alarm is set to a predetermined level that cannot be changed. However, construction sites are relatively noisy areas and the sound alarm may be covered by ambient noise around the vehicle. For example, the alarm may be covered by the noise of a jackhammer and/or by the noise of a highway. Accordingly, a worker or a bystander, i.e. any person near the vehicle, may not hear the sound alarm when the vehicle is moving and may be surprised by the movement of the vehicle, which can be very dangerous.

To the contrary, in restricted sound level areas (e.g. Hospital, indoor areas) or during night work, the amplitude of the speaker is too high. The speaker then disturbs the persons around the vehicle and the working environment.

The aim of the present invention is to propose an improved method that remedies the abovementioned drawbacks.

Summary of the invention

To this end, the invention concerns a method for alerting a person near a vehicle when said vehicle performs a movement, the method comprising steps consisting in:

a) recording, an audio signal corresponding to ambient noise nearby the vehicle, b) adjusting a sound alarm at an amplitude and/or frequency that is function of at least one parameter of the audio signal, and

c) when the vehicle performs the movement, emitting said adjusted sound alarm.

Thanks to the invention, the amplitude of the speaker can be adapted to the working environment. In particular, the amplitude of the speaker can be adjusted to a level that is only a few dB above ambient noise, i.e. at a level that is just enough to be heard by any person near the vehicle. Therefore, when the ambient noise level is low, the speaker will not be disturbing and when the ambient noise level is high, the amplitude of the speaker will be high enough to cover ambient noise.

Further advantageous features of the method are specified below:

The method comprises an additional step consisting in filtering the audio signal to remove the sound alarm.

Said additional step is implemented before step b).

The sound alarm is continuous, with at least one known frequency, and the additional step consists in digitally removing each component of the audio signal at the known frequency.

During step a), said audio signal is recorded during a predetermined sliding time frame.

Said predetermined sliding time frame corresponds to the last seconds before implementation of step b) and preferably corresponds to a sliding time frame that is inferior to 30 seconds.

The sound alarm is discontinuous and wherein, at step a), the audio signal is recorded during at least one mute period of the sound alarm.

According to step b), said parameter of the audio signal is the amplitude of the audio signal.

The amplitude of the audio signal corresponds to an average of the amplitudes of the different frequencies of the audio signal and wherein step b) further comprises a sub-step of averaging, over a predetermined time frame, amplitudes of the different frequencies of the audio signal recorded at step a). The amplitude of the audio signal corresponds to an average of the amplitudes of the different frequencies of the filtered audio signal and wherein step b) further comprises a sub-step of averaging, over a predetermined time frame, amplitudes of the different frequencies of the filtered audio signal.

During step b), the adjustment of the sound alarm consists in adjusting the amplitude of the sound alarm to have it above the amplitude of the audio signal, preferably at least 5 dB above the amplitude of the audio signal.

During step b), the adjustment of the sound alarm also consists in adjusting the frequency spectrum of the sound alarm to have frequency spectrum of the sound alarm that is different from the frequency spectrum of the audio signal. The person is a worker or a bystander and the vehicle is a construction vehicle. According to step b) said adjustment is performed continuously or at time interval. The invention also concerns a system for alerting a person near a vehicle when said vehicle performs a movement, the system comprising the vehicle, which is equipped with at least one speaker for emitting a sound alarm when the vehicle performs the movement, at least one microphone, for recording an audio signal corresponding to ambient noise nearby the vehicle, wherein the vehicle is also equipped with an electronic control unit for controlling the amplitude and/or the frequency of the sound alarm emitted by the speaker and wherein the system includes transmitting means for transmitting the audio signal to the electronic control unit, the electronic control unit being programmed to adjust the amplitude and/or the frequency of the sound alarm emitted by the speaker depending on at least one parameter of the audio signal.

Further advantageous features of the system are specified below:

The microphone is carried on the vehicle.

The vehicle carries at least two microphones for recording ambient noise on two opposite sides of the vehicle.

The microphone is remote from the vehicle.

The transmitting means are wireless.

Brief description of the drawings

The invention will be better understood from reading the following description, given solely by way of two non-limiting examples and with reference to the appended drawings, which are schematic depictions, in which:

- Figure 1 shows a first embodiment of a system for alerting a person near a vehicle according to the invention; and

- Figure 2 shows a second embodiment of the system.

Detailed description of example embodiments of the invention

Figure 1 shows a system for alerting a person (not represented) near a vehicle 2 when said vehicle 2 performs a movement. The person is a worker or a bystander and the vehicle is a construction vehicle.

The system includes the vehicle 2 itself, which is preferably a construction vehicle, in particular an excavator. However, in a non-represented alternative embodiment, the vehicle may be any other construction vehicle, such as a transport truck, a crane, a truck crane, etc. The vehicle 2 includes a boom 21 and caterpillars for moving on the ground surface. However, in a non-represented alternative embodiment, the caterpillars may be replaced by wheels. The vehicle 2 is equipped with a speaker 24 for emitting a sound alarm when the vehicle 2 performs a movement. The movement is not necessarily a displacement over the ground surface. In the meaning of the invention, a rotation or an extension of the excavator boom 21 is a movement performed by the vehicle. Indeed, the movements of the excavator boom 21 , and in particular the rotation, is one of the most dangerous movements performed by a construction vehicle.

Accordingly, in the example, speaker 24 emits a sound alarm when the excavator boom 21 is moved. Alternatively, or additionally, speaker 24 emits a sound alarm when the vehicle is moving over the ground surface (back and/or forward).

The system includes one microphone 22, for recording an audio signal corresponding to ambient noise nearby the vehicle 2. The audio signal is an analog signal. For the purpose of understanding, a generator 1 of ambient noise is represented on figure 1.

In the configuration of figure 1 , the microphone 22 is carried on the vehicle 2. Preferably, the microphone 22 is positioned remotely from to the noise sources of the vehicle (engine for instance). In this way, the microphone does not directly pick up the noise from these sources. The noise sources of the vehicle are part of the ambient noise, but the signals perceived by the microphone would be too loud, and not representative of the noise perceived by the persons (workers, bystanders) near the vehicle.

Also, the microphone 22 should preferably not be oriented towards the speaker 24. Preferably, the speaker 24 and the microphone 22 are oriented in opposite directions. This means that the detection cone of the microphone 22 and the emission cone of the speaker 24 are oriented in opposite directions.

The vehicle 2 further includes an electronic control unit (ECU) 20 for controlling (i.e. adjusting) the amplitude and/or the frequency of the speaker 24. Transmitting means 26 allow transmitting the audio signal recorded by the microphone 22 to the electronic control unit 20. In the example of figure 1 , transmitting means 26 include a wire (cable) adapted for the transmission of an analog signal. However, the connection between ECU 20 and microphone 22 may be wireless.

Transmitting means 28 allow transmitting a command signal (generated by the ECU 20) to the speaker 24. In the example, transmitting means 28 include a wire (cable). However, the connection between ECU 20 and speaker 24 may be wireless.

The electronic control unit 20 is programmed to adjust the amplitude and/or frequency of a sound alarm generated by the speaker 24 in function of at least one parameter of the audio signal corresponding to ambient noise. The method consists then in using the microphone 22 to record, at a step a), an audio signal corresponding to ambient noise nearby the vehicle 2.

Typically, when the sound alarm is continuous, said audio signal is recorded during a predetermined sliding time frame At. At a given time t, the predetermined sliding time frame At is a time period between t and t-At. For example, the predetermined sliding time frame At may be of the order of 30 seconds. One speaks of a“sliding” time frame because the lower and upper limits of the time frame evolve with time.

However, when the sound alarm is discontinuous (beep), the audio signal is recorded during mute periods of the sound alarm. Preferably, the audio signal is recorded during at least one time slot within a mute period.

Advantageously, the audio signal recorded by microphone 22 is filtered to remove the sound alarm generated by the speaker itself. In the example, the sound alarm is continuous with a known frequency. Therefore, the sound alarm can be digitally removed from the audio signal. To this end, the audio signal is subjected to a fast Fourier transform (FFT) in order to convert the audio signal from a representation in time domain to a representation in the frequency domain, which is called the frequency spectrum. Then, the spectrum is digitally modified to remove the signal component having the frequency of the sound alarm and the audio signal is subjected to an inverse Fourier transform in order to get back to a representation in time domain.

Preferably, the amplitudes of the different frequencies of the audio signal recorded by the microphone 22 are averaged over the predetermined sliding time frame At.

Optionally, the audio signal may be low pass filtered to remove short disturbances, like the passing by of a car or a car horn.

Afterwards, the audio signal is transmitted via means 26 to the electronic control unit

20.

The electronic control unit 20 then adjusts, at a step b), the amplitude and/or frequency of the sound alarm in function of at least one parameter of the audio signal. Typically, said at least one parameter is the amplitude of the audio signal.

Accordingly, the predetermined sliding time frame mentioned supra corresponds to the last seconds before implementation of step b) and preferably corresponds to a sliding time frame that is inferior to 30 seconds.

Advantageously, the amplitude of the audio signal is the average of the amplitudes of the different frequencies of the audio signal over the predetermined sliding time frame At. In practice, this means that the audio signal is continuously recorded but that only the last 30 seconds (At) before sound alarm emission or before the movement of the vehicle are considered to adjust the amplitude of the sound alarm. For example, the recordings before the time t-At may be automatically erased.

In the example, the adjustment of the amplitude of the sound alarm consists in setting the amplitude of the sound alarm above the amplitude of the audio signal, preferably at least 5 dB above the amplitude of the audio signal. Optionally, the adjustment of the sound alarm also consists in modifying the frequency spectrum of the sound alarm to differ from the frequency spectrum of the audio signal.

Typically, the adjustment step is performed in a regular basis (discrete). In such case, the adjustment is performed at a predetermined time interval that may be of the same duration than the predetermined sliding time frame, i.e. of 30s or of a different duration. For example, the predetermined time interval is between 5s and 60 s, preferably of 10s.

The adjustment step may also be performed in a continuous basis, meaning that the amplitude of the sound alarm is adjusted dynamically (in real time), depending on the clock speed of the ECU 20 and on the reactivity of the other electronic components.

Then, when the vehicle 2 performs a movement, the speaker 24 emits, at a step c), the adjusted sound alarm, i.e. a sound alarm that has been adjusted by the ECU 20.

Thanks to this method, the sound volume of the speaker is adjusted depending on the ambient noise level, and more particularly on the evolution of the ambient noise level in time. For example, in the early morning, when the ambient level is low, the amplitude of the speaker 24 will be relatively low. However, at peak times, during which the working environment is noisy, the amplitude of the speaker 24 will be relatively high to cover ambient noise.

In conclusion, the sound volume of the speaker 24 is adjusted depending on the localization of the vehicle, i.e. the working environment, and on the time of the day, i.e. the evolution of ambient noise in time.

Figure 2 shows a second embodiment wherein the microphone 22 is remote from the vehicle 2. In this case, the transmitting means 26 between microphone 22 and ECU 20 are wireless (Wi-Fi, Bluetooth, radio, etc.). In particular, the microphone 22 may include a radio transmitter and the ECU 20 may include a radio receiver (antenna).

Figure 2 shows only one microphone, but in a non-represented alternative embodiment, a plurality of microphones can be used, in particular spread on the construction site.

In another non-represented alternative embodiment, the vehicle carries two or more microphones for recording ambient noise on two or more opposite sides of the vehicle. The features described above in connection with the figures and the features of the non-represented alternative embodiments may be combined to generate new embodiments of the invention.