Underwater wireless optical communication method and system

Abstract

The invention discloses an underwater wireless optical communication method and system, and the method comprises the steps: controlling a second transmitting module in a second communication terminal to generate a second initial optical signal through employing a link guide beacon sequence, and adjusting the position and direction of a first communication terminal according to the initial optical signal, so as to enable the first communication terminal to enter a communication coverage range of each other; establishing a half-duplex communication link for the two terminals according to a handshake protocol; transmitting data from a first communication data interface to a second communication terminal through the first communication terminal by using a first optical signal, and outputting the data to external equipment from a second communication data interface of the second communication terminal; transmitting the data from the second communication data interface to the first communication terminal through the second communication terminal by using a second optical signal, and outputting the data from the first communication data interface to the external equipment; the first communication terminal monitors and adjusts the relative poses of the two terminals according to the second optical signal, so that the two terminals are located in the communication coverage range of each other, the communication complexity is reduced, and the measurement precision is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of underwater photoelectric technology, and particularly relates to an underwater wireless optical communication method and system. BACKGROUND

[0002] Underwater wireless optical communication technology uses visible light transmission in water to realize information transmission, and can be used to solve the non-contact communication problem of underwater robots in engineering operation. In such application scenarios, a wireless optical communication device is installed on a movable underwater robot platform such as a manned submersible, an autonomous underwater vehicle, or a remotely operated vehicle. When the underwater robot swims to the vicinity of another cooperative communication target, the position and attitude of the underwater robot are adjusted so that the wireless optical communication devices in the two platforms can receive the light signals emitted by each other, and then bidirectional information interaction is carried out. In this process, the underwater robot not only needs to realize bidirectional data transmission with the cooperative communication target through the optical link, but also needs to measure the relative pose of each other as the basis for adjusting the position and direction. For such short-range underwater pose measurement, the traditional acoustic detection method has certain limitations in application due to its low precision and detection blind area. In contrast, the optical measurement method has the advantage of high positioning accuracy and is suitable for underwater short-range applications, but needs to solve the compatibility problem with the wireless optical communication system.

[0003] In related technologies, Chinese invention patent 202310905660.3 (application number) discloses a cooperative target pose measurement method for underwater wireless optical communication. In this method, a light array is installed in the underwater cooperative target as a guide beacon, and a camera is installed in the underwater robot to take pictures of the guide beacon; the influence of the communication light source is suppressed by using the colorimetric method, the effective guide beacon spot is identified from the image taken by the camera, and the pose of the underwater cooperative target is measured by using the spot pattern characteristics of the guide beacon. Chinese invention patent 202410930272.5 (application number) discloses an underwater non-contact optical communication method and system, and a storage medium, which uses the position characteristics of communication light and guide beacon light to identify the effective guide beacon spot from the image taken by the camera, and then realizes the pose measurement of the underwater cooperative target. In these two visual measurement-based methods, the pose measurement device and the wireless optical communication device of the underwater cooperative target are independent of each other at the hardware level, which greatly increases the complexity of the communication process. In addition, the spot taken by the underwater camera may have too high or too low brightness, resulting in too large pose measurement error.

[0004] Therefore, how to provide an underwater wireless optical communication method with low complexity and high measurement accuracy has become an important problem. SUMMARY

[0005] In order to solve the above problems existing in the prior art, the application provides an underwater wireless optical communication method and system.

[0006] The technical problem to be solved by the application is solved by the following technical scheme: In a first aspect, the application provides an underwater wireless optical communication method, which comprises: controlling a second transmitting module in a second communication terminal to generate a second initial optical signal by using a preset link guidance beacon sequence, and adjusting the position and direction of the first communication terminal according to the second initial optical signal, so that the first communication terminal and the second communication terminal enter the communication coverage range of each other; the link guidance beacon is a group of pulse width modulation signals with periodically changed duty cycles; the second transmitting module comprises four semiconductor light sources; establishing a half-duplex communication link for the first communication terminal and the second communication terminal according to a preset handshake protocol; transmitting data from a first communication data interface to the second communication terminal by the first optical signal through the first communication terminal, and outputting the data from a second communication data interface of the second communication terminal to an external device; transmitting data from the second communication data interface to the first communication terminal by the second optical signal through the second transmitting module in the second communication terminal, and outputting the data from a first communication data interface of the first communication terminal to an external device; monitoring and adjusting the relative pose of the first communication terminal and the second communication terminal according to the second optical signal by the first communication terminal, so that the first communication terminal and the second communication terminal continuously locate in the communication coverage range of each other.

[0007] Optionally, adjusting the position and direction of the first communication terminal according to the second initial optical signal, so that the first communication terminal and the second communication terminal enter the communication coverage range of each other, comprises: photographing the second initial optical signal to form a light spot image of the second initial optical signal; calculating the relative pose information of the first communication terminal and the second communication terminal according to the light spot image; adjusting the position and direction of the first communication terminal according to the relative pose information, until the first communication terminal and the second communication terminal enter the communication coverage range of each other.

[0008] Optionally, calculating the relative pose information of the first communication terminal and the second communication terminal according to the light spot image comprises: detecting light spot information from the light spot image; judging the number of light spots and the coverage area of light spots according to the light spot information to obtain effective light spot information; The effective light spot information is calculated to obtain relative position information of the first communication terminal and the second communication terminal.

[0009] Optionally, the relative posture information of the first communication terminal and the second communication terminal includes: The distance, yaw angle, pitch angle and roll angle of the second communication terminal relative to the first communication terminal.

[0010] Optionally, calculating the effective light spot information to obtain relative position information of the first communication terminal and the second communication terminal includes: The effective light spot information is calculated according to the PnP algorithm to obtain relative position information of the first communication terminal and the second communication terminal.

[0011] Optionally, establishing a half-duplex communication link for the first communication terminal and the second communication terminal according to a preset handshake protocol includes: The first communication terminal sends a first optical signal to the second communication terminal based on a preset link inquiry sequence; After detecting the first optical signal, the second communication terminal sends a second optical signal to the first communication terminal based on a preset response sequence; After receiving the second optical signal, the first communication terminal returns to executing the step of sending the first optical signal to the second communication terminal based on a preset link inquiry sequence, until the first communication terminal and the second communication terminal respectively receive the second optical signal and the first optical signal a preset number of times, and then the first communication terminal and the second communication terminal establish a half-duplex communication link.

[0012] In a second aspect, the present invention provides an underwater wireless optical communication system, the underwater wireless optical communication system comprising a first communication terminal and a second communication terminal; The second communication terminal is configured to generate a second initial optical signal using a preset link pilot beacon sequence through a second transmitting module; the link pilot beacon is a set of pulse width modulated signals with a periodically varying duty cycle; the second transmitting module includes four semiconductor light sources; the first communication terminal being configured to adjust its own position and orientation according to the second initial optical signal so that the first communication terminal and the second communication terminal enter each other's communication coverage; The first communication terminal and the second communication terminal are used to establish a half-duplex communication link according to a preset handshake protocol; The first communication terminal is configured to transmit data from the first communication data interface to the second communication terminal using a first optical signal; The second communication terminal is configured to identify data from the first communication data interface from the first optical signal and output the data from the second communication data interface of the second communication terminal to an external device; The second communication terminal is configured to transmit data from the second communication data interface to the first communication terminal by the second emission module using a second optical signal. The first communication terminal is configured to identify data from the second communication data interface from the second optical signal and output the data from the first communication data interface of the first communication terminal to an external device. The first communication terminal is configured to monitor and adjust the relative pose of the first communication terminal and the second communication terminal according to the second optical signal, so that the first communication terminal and the second communication terminal are continuously located within the communication coverage of each other.

[0013] The second emission module in the second communication terminal of the underwater wireless optical communication method provided by the present application includes four semiconductor light sources. The second emission module can emit a second optical signal and generate a second initial optical signal using a preset link guide beacon sequence as a guide beacon for optical pose measurement, thereby reducing the number of light sources in the entire system and reducing the complexity of underwater wireless optical communication. Since the link guide beacon is a group of pulse width modulation signals with periodically changing duty cycles, the light intensity of the guide beacon for optical pose measurement emitted by the second communication terminal is periodically changed, which can effectively avoid the case that the pose measurement error is too large due to the too large or too small light spot brightness captured by the underwater camera, and helps to improve the accuracy of pose measurement.

[0014] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a flowchart of an underwater wireless optical communication method provided by an embodiment of the present application; Figure 2 is a structural schematic diagram of an underwater wireless optical communication system provided by an embodiment of the present application; Figure 3 is a simulation experiment schematic diagram of an underwater wireless optical communication method and system provided by an embodiment of the present application. DETAILED DESCRIPTION

[0016] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0017] In order to solve the problems of high complexity and low measurement accuracy of the existing underwater wireless optical communication method, an underwater wireless optical communication method is provided by an embodiment of the present application, as shown inFigure 1 , Figure 1 is a flowchart of a method for underwater wireless optical communication according to an embodiment of the present application, and specifically includes the following steps: In step S101, a second initial optical signal is generated by a second transmitting module in the second communication terminal using a preset link guidance beacon sequence, and the position and direction of the first communication terminal are adjusted according to the second initial optical signal, so that the first communication terminal and the second communication terminal enter the communication coverage of each other; the link guidance beacon is a group of pulse width modulation signals with periodically changing duty cycles; the second transmitting module includes four semiconductor light sources.

[0018] First, through the working parameter setting, the first communication terminal is the host of the half-duplex communication system, and the second communication terminal is the slave of the half-duplex communication system, both of which have the ability to perform bidirectional data transmission at a preset modulation rate and half-duplex link switching period.

[0019] In the embodiment of the present application, the link guidance beacon is a group of pulse width modulation signals with periodically changing duty cycles, which can control the second communication terminal to generate a second optical signal with periodically changing brightness.

[0020] In the embodiment of the present application, the second transmitting module includes four semiconductor light sources, specifically, the second transmitting module is composed of four visible light band semiconductor light sources and their driving circuit units arranged separately on the same plane. The driving circuit can convert the voltage signal from the second processing module into a current signal, and drive the light source to generate an intensity-modulated optical signal through the current signal.

[0021] In the embodiment of the present application, the position and direction of the first communication terminal are adjusted according to the second initial optical signal, so that the first communication terminal and the second communication terminal enter the communication coverage of each other, including: The second initial optical signal is photographed to form a light spot image of the second initial optical signal; The relative pose information of the first communication terminal and the second communication terminal is calculated according to the light spot image; According to the relative pose information, the position and direction of the first communication terminal are adjusted until the first communication terminal and the second communication terminal enter the communication coverage of each other.

[0022] In one implementation, the relative pose information of the first communication terminal and the second communication terminal is calculated according to the light spot image, including: The light spot information is detected from the light spot image; The number of light spots and the coverage area of the light spots are judged according to the light spot information to obtain effective light spot information; The effective light spot information is calculated to obtain the relative pose information of the first communication terminal and the second communication terminal.

[0023] Specifically, the effective spot information can be calculated according to the PnP (Perspective-n-Point) algorithm, which is a pose estimation algorithm.

[0024] In the embodiment of the present invention, light spot information can be detected from the light spot image using an image processing method. The light spot information includes the number of light spots, and the positions and coordinates of all light spots.

[0025] The number of spots and the area covered by the spots are determined based on the spot information to obtain effective spot information, including: The number of light spots is judged. When the number of light spots is not equal to 4, the light spot information is judged to be invalid and the analysis of the light spot information is terminated. Otherwise, the analysis of the light spot information continues. Calculate the coverage area of ​​all the spots in the spot image according to the spot coordinates and radius of the spot image. If there is an intersection, the spot information is determined to be invalid and the analysis of the spot information is terminated. Otherwise, the analysis of the spot information is continued. The radii of all light spots are analyzed. When the light spot radius is less than the preset minimum radius parameter or greater than the preset maximum radius parameter, the light spot information is determined to be invalid and the analysis of the light spot information is terminated. Otherwise, the light spot information is used as valid light spot information, and the valid light spot information is calculated according to the PnP algorithm to obtain the posture information of the second communication device, wherein the posture information takes the underwater camera in the first communication terminal as the reference position of the first communication terminal, and any point in the plane where the four light sources in the second communication device are located as the reference position of the second communication device, and obtains the distance, yaw angle, pitch angle and roll angle of the reference position relative to the first communication terminal, thereby determining the relative posture information of the first communication terminal and the second communication terminal.

[0026] Step S102: establishing a half-duplex communication link for the first communication terminal and the second communication terminal according to a preset handshake protocol.

[0027] In the embodiment of the present invention, a half-duplex communication link is established for the first communication terminal and the second communication terminal according to a preset handshake protocol, so that the first communication terminal and the second communication terminal send the first optical signal and the second optical signal in a preset half-duplex link switching period.

[0028] In an embodiment of the present invention, establishing a half-duplex communication link for a first communication terminal and a second communication terminal according to a preset handshake protocol includes: The first communication terminal sends a first optical signal to the second communication terminal based on a preset link inquiry sequence; After detecting the first optical signal, the second communication terminal sends a second optical signal to the first communication terminal based on a preset response sequence; After the first communication terminal receives the second optical signal, the first communication terminal returns to the step of transmitting the first optical signal to the second communication terminal based on the preset link inquiry sequence until the first communication terminal and the second communication terminal respectively receive a preset number of second optical signals and first optical signals, and then the first communication terminal and the second communication terminal establish a half-duplex communication link.

[0029] Specifically, the first communication terminal transmits the first optical signal to the second communication terminal in a preset link inquiry sequence, and the first optical signal is used to transmit the link inquiry sequence. After the second communication terminal detects the first optical signal, the second communication terminal stops transmitting the preset link guide beacon sequence, generates a second optical signal in a preset response sequence, and transmits the response sequence through the second optical signal. After the first communication terminal receives the response sequence, the first communication terminal continues to transmit the link inquiry sequence to the second communication terminal through the first optical signal, and the second communication terminal continues to transmit the response sequence to the first communication terminal through the second optical signal after receiving the link inquiry sequence, and so on until the first communication terminal and the second communication terminal respectively receive a preset number of response sequences and link inquiry sequences, indicating that the half-duplex link has been established, at which time the two communication terminals respectively transmit the first optical signal and the second optical signal to the water in a preset modulation rate and half-duplex link switching period.

[0030] In step S103, the first communication terminal transmits data from the first communication data interface to the second communication terminal using the first optical signal and outputs the data from the second communication data interface of the second communication terminal to an external device; the second communication terminal transmits data from the second communication data interface to the first communication terminal using the second optical signal and outputs the data from the first communication data interface of the first communication terminal to an external device.

[0031] In the embodiment of the application, the first communication terminal buffers the data input from the first communication data interface to obtain first buffered data; and the second communication terminal buffers the data input from the second communication data interface to obtain second buffered data.

[0032] The first communication terminal divides the first buffered data into a plurality of data segments of a preset length in a preset time sequence to obtain first communication data segments; and the second communication terminal divides the second buffered data into a plurality of data segments of a preset length in a preset time sequence to obtain second communication data segments.

[0033] The second communication terminal adds a link monitoring sequence to the second communication data segment to obtain a second data segment; wherein the link monitoring sequence is a group of pulse width modulation signals with periodically changed duty cycles, which can control the second communication terminal to generate a second optical signal with periodically changed brightness.

[0034] Based on the half-duplex communication mode, the first communication terminal generates a first optical signal according to a first communication data segment, and transmits the first communication data segment to the second communication terminal in the form of the first optical signal through the water body; the second communication terminal generates a second optical signal according to a second data segment, and transmits the second data segment to the first communication terminal in the form of the second optical signal through the water body.

[0035] In step S104, the first communication terminal monitors and adjusts the relative pose of the first communication terminal and the second communication terminal according to the second optical signal, so that the first communication terminal and the second communication terminal are continuously located within the communication coverage of each other.

[0036] In the embodiment of the application, the first communication terminal converts the second optical signal entering the first communication device into a second voltage signal, and converts the second optical signal entering the first communication terminal into a light spot image; the second communication terminal converts the first optical signal entering the second communication device into a first voltage signal; The relative pose information of the first communication terminal and the second communication terminal is calculated according to the light spot image, and the underwater robot is controlled to adjust its position and orientation so that the first communication terminal and the second communication terminal are located within the communication range of each other. The implementation process of the process is as described above, and will not be described here.

[0037] The first communication terminal recovers the second data segment from the second voltage signal and obtains the second communication data segment by eliminating the link monitoring sequence, and the second communication terminal recovers the first communication data segment from the first voltage signal; The first communication terminal frames the second communication data segment into second cache data according to a preset order, and transmits the second cache data through the first communication data interface; and the second communication terminal frames the first communication data segment into first cache data according to a preset order, and transmits the first cache data through the second communication data interface.

[0038] In the embodiment of the application, according to the relative pose information, if the first communication terminal and the second communication terminal are not within the communication range of each other, the first communication terminal adjusts its position and orientation so that the first communication terminal and the second communication terminal are located within the communication range of each other, otherwise the first communication terminal remains stationary.

[0039] In the embodiment of the application, the second transmitting module in the second communication terminal includes four semiconductor light sources, the second transmitting module can not only emit the second optical signal, but also generate a second initial optical signal by using a preset link guiding beacon sequence as a guiding beacon for optical pose measurement, which reduces the number of light sources of the entire system and reduces the complexity of underwater wireless optical communication. And since the link guidance beacon is a group of pulse width modulation signals with periodically changed duty cycles, the light intensity of the guidance beacon for optical pose measurement emitted by the second communication terminal is periodically changed, which can effectively avoid the situation that the pose measurement error is too large due to the too large or too small light spot brightness captured by the underwater camera, and helps to improve the accuracy of pose measurement.

[0040] Based on the same inventive concept, the embodiment of the present application also provides an underwater wireless optical communication system, referring to Figure 2 , Figure 2 is a structural schematic diagram of an underwater wireless optical communication system provided by the embodiment of the present application, which comprises a first communication terminal and a second communication terminal.

[0041] The second communication terminal is configured to generate a second initial optical signal by using a preset link guidance beacon sequence through the second transmitting module; the link guidance beacon is a group of pulse width modulation signals with periodically changed duty cycles; and the second transmitting module comprises four semiconductor light sources. The first communication terminal is configured to adjust the position and direction of itself according to the second initial optical signal, so that the first communication terminal and the second communication terminal enter the communication coverage range of each other. The first communication terminal and the second communication terminal are configured to establish a half-duplex communication link according to a preset handshake protocol. The first communication terminal is configured to transmit data from a first communication data interface to the second communication terminal by using a first optical signal. The second communication terminal is configured to identify the data from the first communication data interface from the first optical signal, and output the data from a second communication data interface of the second communication terminal to an external device. The second communication terminal is configured to transmit data from the second communication data interface to the first communication terminal by using a second optical signal through the second transmitting module. The first communication terminal is configured to identify the data from the second communication data interface from the second optical signal, and output the data from a first communication data interface of the first communication terminal to an external device. The first communication terminal is configured to monitor and adjust the relative pose of the first communication terminal and the second communication terminal according to the second optical signal, so that the first communication terminal and the second communication terminal are continuously located in the communication coverage range of each other.

[0042] In the embodiment of the present application, the first communication terminal comprises an underwater robot, a first transmitting module, a first receiving module, a first processing module, an underwater camera and a pose measurement module; and the second communication terminal is a cooperative communication target, comprising a second transmitting module, a second receiving module and a second processing module.

[0043] An underwater robot for moving in water, used to carry a first transmitting module, a first receiving module, a first control module and a pose measurement module; The first transmitting module is used for controlling a light source to generate a first light signal with intensity modulation by using a first modulated voltage signal input by the first processing module; The first receiving module is used for receiving a second light signal in water and converting it into a second voltage signal; The first processing module is used for converting communication data to be transmitted in the first communication terminal into the first modulated voltage signal, for controlling the first transmitting module to generate the first light signal, and for identifying data from the second communication terminal from the second voltage signal; An underwater camera is used for taking a light spot image of the light from the second communication device; The pose measurement module is used for calculating the relative pose of the first communication terminal and the second communication terminal according to the light spot image taken by the underwater camera.

[0044] The second transmitting module is used for controlling a light source to generate a second light signal with intensity modulation by using a second modulated voltage signal input by the first processing module; The second receiving module is used for receiving the first light signal in water and converting it into a first voltage signal; The second processing module is used for converting communication data to be transmitted in the second communication terminal into the second modulated voltage signal, for controlling the second transmitting module to generate the second light signal, and for identifying data from the first communication terminal from the first voltage signal; The second transmitting module is composed of four semiconductor light sources in the visible light band and their driving circuit units which are separately arranged in the same plane.

[0045] In the embodiment of the application, the working parameters of the first processing module and the second processing module are set so that the first communication terminal is the master of the half-duplex communication system and the second communication terminal is the slave of the half-duplex communication system, and both have the ability of bidirectional data transmission at a preset modulation rate and a half-duplex link switching period, wherein when the transmitting module of any communication terminal is working, the processing module considers the signal detected by the docking receiving module as invalid signal and does not process it.

[0046] Optionally, the first communication terminal is used for adjusting the position and direction of the first communication terminal according to the second initial light signal generated by the second transmitting module of the second communication terminal by using a preset link guide beacon sequence, so that the first communication terminal and the second communication terminal enter the communication coverage range of each other, and the adjustment is realized by the following way: The underwater camera is used for taking the second initial light signal and forming a light spot image of the second initial light signal; A pose measurement module is configured to calculate relative pose information of the first communication terminal and the second communication terminal according to the spot image. An underwater robot is configured to adjust the position and orientation of the first communication terminal according to the relative pose information until the first communication terminal and the second communication terminal enter the communication coverage range of each other.

[0047] In the embodiment, the second communication terminal is configured to generate a second initial optical signal by using a preset link guidance beacon sequence, including: a second processing module in the second communication terminal controls a second emitting module to generate a second optical signal by using the preset link guidance beacon sequence; the link guidance beacon is a group of pulse width modulation signals with periodically changed duty cycles, and is capable of controlling the second emitting module to generate a second optical signal with periodically changed brightness.

[0048] In an implementation, the pose measurement module calculates the relative pose information of the first communication terminal and the second communication terminal according to the spot image by the following steps: The spot information is detected from the spot image by using an image processing method, including the number of spots, the positions and coordinates of all the spots; The number of spots is judged, and when the number of spots is not equal to 4, it is determined that the spot information is invalid, the analysis of the spot information is terminated, otherwise the analysis of the spot information is continued; The coverage areas of all the spots in the spot image are calculated according to the spot coordinates and radii of the spot image, and when there is an intersection, it is determined that the spot information is invalid, the analysis of the spot information is terminated, otherwise the analysis of the spot information is continued; The radii of all the spots are analyzed, and when the spot radius is less than a preset minimum radius parameter or greater than a preset maximum radius parameter, it is determined that the spot information is invalid, the analysis of the spot information is terminated, otherwise valid spot information is obtained, and the pose information of the second communication device is obtained according to a PnP algorithm, wherein the pose information is the distance, the yaw angle, the pitch angle and the roll angle of the second reference position relative to the first communication terminal, with the underwater camera as the reference position of the first communication terminal and any point in the plane where the four light sources in the second emitting module are located as the reference position of the second communication device.

[0049] In an implementation, the first communication terminal and the second communication terminal are configured to establish a half-duplex communication link according to a preset handshake protocol, including: A first processing module in the first communication terminal controls a first emitting module to send a first optical signal to the second communication terminal by using a preset link inquiry sequence, and sends the link inquiry sequence; After the second receiving module in the second communication terminal detects the first optical signal, the second processing module controls the second transmitting module to stop sending the preset link guide beacon sequence and instead controls the second transmitting module to generate a second optical signal using a preset response sequence, and sends the response sequence; After the first communication terminal receives the response sequence, it continues to send a link inquiry sequence to the second communication terminal, and after the second communication terminal receives the link inquiry sequence, it continues to send a response sequence to the first communication terminal, and this continues until the first communication terminal and the second communication terminal each receive a preset number of response sequences and link inquiry sequences, indicating that a half-duplex link has been established. At this time, the two communication terminals transmit first optical signals and second optical signals to the water at a preset modulation rate and half-duplex link switching period, respectively.

[0050] In an implementation, a first communication terminal is configured to transmit data from a first communication data interface to a second communication terminal using a first optical signal; a second communication terminal is configured to output the first optical signal from a second communication data interface of the second communication terminal to an external device; the second communication terminal is configured to transmit data from the second communication data interface to the first communication terminal using a second optical signal; and the first communication terminal is configured to output the second optical signal from the first communication data interface of the first communication terminal to the external device, in the following specific implementation process: The first processing module buffers data input from the first communication data interface to obtain first buffered data; and the second processing module buffers data input from the second communication data interface to obtain second buffered data. The first processing module divides the first buffered data into a plurality of data segments of a preset length in a preset time sequence to obtain first communication data segments; and the second processing module divides the second buffered data into a plurality of data segments of a preset length in a preset time sequence to obtain second communication data segments. The second processing module adds a link monitoring sequence to the second communication data segments to obtain second data segments. Based on a half-duplex communication mode, the first processing module modulates the first transmitting module to generate the first optical signal based on the first communication data segments, and transmits the first communication data segments to the second communication terminal in the form of the first optical signal through the water body; and the second processing module modulates the second transmitting module to generate the second optical signal based on the second data segments, and transmits the second data segments to the first communication terminal in the form of the second optical signal through the water body.

[0051] In an implementation, a first communication terminal is configured to monitor and adjust a relative pose of the first communication terminal and a second communication terminal based on a second optical signal, so that the first communication terminal and the second communication terminal are located within a communication coverage range of each other, and the first communication terminal comprises: The first receiving module converts the second optical signal entering the first communication device into a second voltage signal and delivers the second voltage signal to the first processing module; the underwater camera converts the second optical signal entering the first communication device into a light spot image and delivers the light spot image to the pose measurement module; the second receiving module converts the first optical signal entering the second communication device into a first voltage signal and delivers the first voltage signal to the second processing module; The pose measurement module calculates the relative pose information of the first communication terminal and the second communication terminal according to the light spot image, and controls the underwater robot to adjust its position and orientation so that the first communication terminal and the second communication terminal are located within the communication range of each other. The first processing module recovers the second data segment from the second voltage signal and obtains the second communication data segment by eliminating the link monitoring sequence, and the second processing module recovers the first communication data segment from the first voltage signal. The first processing module frames the second communication data segment into second cache data according to a preset order and transmits the second cache data through the first communication data interface; and the second processing module frames the first communication data segment into first cache data according to the preset order and transmits the first cache data through the second communication data interface.

[0052] In an implementation manner, the pose measurement module calculates the relative pose information of the first communication terminal and the second communication terminal according to the light spot image, and controls the underwater robot to adjust its position and orientation so that the first communication terminal and the second communication terminal are located within the communication range of each other, by the following steps: The light spot information is detected from the light spot image by using an image processing method, including the number of light spots, the positions and coordinates of all light spots. A criterion is performed on the number of light spots, when the number of light spots is not equal to 4, it is determined that the light spot information is invalid, the analysis of the light spot information is terminated, otherwise the analysis of the light spot information is continued. The coverage areas of all light spots in the light spot image are calculated according to the light spot coordinates and radii of the light spot image, when there is an intersection, it is determined that the light spot information is invalid, the analysis of the light spot information is terminated, otherwise the analysis of the light spot information is continued. The radii of all light spots are analyzed, when the radius of a light spot is less than a preset minimum radius parameter or greater than a preset maximum radius parameter, it is determined that the light spot information is invalid, the analysis of the light spot information is terminated, otherwise the pose information of the second communication device is obtained according to a PnP algorithm, wherein the pose information is the distance, the yaw angle, the pitch angle and the roll angle of the second reference position relative to the first communication terminal, with the underwater camera as the reference position of the first communication terminal and any point in the plane where the four light sources in the second transmitting module are located as the reference position of the second communication device.

[0053] According to the distance, the yaw angle, the pitch angle and the roll angle, if the first communication terminal and the second communication terminal are not in the communication range of each other, the underwater robot adjusts the position and the orientation of itself, so that the first communication terminal and the second communication terminal are located in the communication range of each other, otherwise the underwater robot keeps still.

[0054] In the embodiment of the present application, the second transmitting module of the second communication terminal can transmit the second optical signal, or generate the second initial optical signal by using the preset link guiding beacon sequence as the guiding beacon for optical pose measurement, thereby reducing the number of light sources of the whole system and lowering the complexity of underwater wireless optical communication. Since the link guiding beacon is a group of pulse width modulation signals with periodically changed duty cycles, the light intensity of the guiding beacon for optical pose measurement emitted by the second transmitting module of the second communication terminal is periodically changed, which can effectively avoid the situation that the pose measurement error is too large due to the too large or too small light spot brightness captured by the underwater camera, and is helpful to improve the accuracy of pose measurement.

[0055] In addition, since the optical device for pose measurement is a camera, it has a larger field of view and spatial resolution, and therefore can increase the field of view range and accuracy of pose measurement.

[0056] The simulation experiment of the underwater wireless optical communication method and system provided by the embodiment of the present application is as follows: Referring to Figure 3 , Figure 3is a simulation experiment schematic diagram of an underwater wireless optical communication method and system provided by an embodiment of the present application. The experiment system is composed of a first processing module, a first transmitting module, a first receiving module, an underwater camera, a second processing module, a second transmitting module, a second receiving module, and a computer 1#, a switch 1#, a network camera 1#, a computer 3#, a computer 2#, a switch 2# and a network camera 2# located above the water surface. The first processing module, the first transmitting module, the first receiving module and the underwater camera are installed on a support that can rotate horizontally, and different poses can be simulated by rotating the support above the water surface. The first processing module and the second processing module are made based on a Zynq7020 chip of Xilinx Company; the first receiving module and the second receiving module are made based on a photomultiplier tube, and the receiving field of view is about 50°; the first transmitting module and the second transmitting module are made based on a 478nm light-emitting diode, and the emission angle is about 70°, wherein the second transmitting module contains four light sources located in the same plane, and the centers of the four light sources form a rectangle with a length of 32cm and a width of 26cm; the underwater camera is made based on an industrial camera. The computer 1# and the network camera 1# are connected with the first processing module through the switch 1#, the computer 2# and the network camera 2# are connected with the second processing module through the switch 2#, and are respectively used to simulate the data to be transmitted in the bidirectional communication link. The computer 3# is connected with the underwater camera, and is used to simulate a pose measurement module. The relative pose between the center of the optical window of the underwater camera and the centers of the four light sources in the second transmitting module is calculated through the light spot image input by the underwater camera.

[0057] During the experiment, the communication system is set to a half-duplex communication mode, and the modulation rate of the optical link is 12.5Mbps. The optical signals in two directions of the communication system are switched at a period of 100ms, wherein the protection time slot during link switching is 2ms; the time for transmitting the first optical signal in each period is 30ms, the time for transmitting the second optical signal under the control of the second communication data segment is 30ms, and the time for transmitting the second optical signal under the control of the periodic pulse width modulation signal is 38ms. The periodic pulse width modulation signal is used to simulate a link monitoring sequence and a link guide beacon sequence, and 5 link switching periods are taken as a group, and the duty cycles in each group are 100%, 50%, 10%, 5% and 1% respectively.

[0058] After the half-duplex communication link is established, the computer 1 accesses the network camera 2 and displays the captured image, and the computer 2 accesses the network camera 1 and displays the captured image, to simulate the bidirectional communication service. During the test, the center of the optical window of the underwater camera and the centers of the four light sources in the second emission module are adjusted to be at the same height, the optical window of the underwater camera and the plane where the four light sources in the second emission module are located are parallel, and the distances are 4 m, 3.5 m and 3 m respectively. At this time, the pointing direction of the underwater camera is changed in the horizontal plane by using the rotating support, so that the pointing direction is changed in the range of-8° and 8°. The light spot image under different conditions is captured by using the underwater camera, the light spot coordinate parameters in the light spot image captured by the underwater optical camera are identified in the computer 3 based on the Hough transform method, and the effective light spot information is screened out; and then the relative pose of the center of the optical window of the underwater camera and the center of the four light sources in the second emission module is obtained based on the PnP algorithm.

[0059] During the test, the computer 1 can normally display the image captured by the network camera 2, and the computer 2 can normally display the image captured by the network camera 1. In all tests, the pitch angle and the roll angle test results are around 0°, the azimuth angle and the distance test results are shown in Table 1, and the application requirements can be basically met. These results verify the feasibility and effectiveness of the present application.

[0060] Table 1 Azimuth angle and distance test results

[0061] Therefore, the embodiment of the present application provides a low-complexity and high-precision underwater wireless optical communication method and system.

[0062] It should be noted that the terms "first", "second", and the like are used to distinguish similar objects, and do not necessarily have to be used to describe a particular order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are only examples of devices and methods consistent with some aspects of the present application.

[0063] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the specification.

[0064] Although the present application is described herein in conjunction with various embodiments, those skilled in the art, with the benefit of the drawings and the disclosure, can understand and implement other variations of the disclosed embodiments in the implementation of the claimed application. In the description of the present application, the word "comprising" does not exclude other components or steps, "a" or "one" does not exclude a plurality, and "plurality" means two or more, unless otherwise expressly specified. In addition, some measures are described in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0065] The above is a further detailed description of the present application in conjunction with specific preferred embodiments, and cannot be considered as limiting the specific implementation of the present application to these descriptions. For those skilled in the art, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be considered as falling within the scope of protection of the present application.

Claims

1. An underwater wireless optical communication method, characterized in that: The underwater wireless optical communication method comprises: controlling a second transmitting module in a second communication terminal to generate a second initial optical signal using a preset link pilot beacon sequence, and adjusting the position and orientation of the first communication terminal based on the second initial optical signal so that the first communication terminal and the second communication terminal enter each other's communication coverage; the link pilot beacon is a set of pulse width modulated signals with a periodically varying duty cycle; the second transmitting module includes four semiconductor light sources; Establishing a half-duplex communication link for the first communication terminal and the second communication terminal according to a preset handshake protocol; transmitting data from the first communication data interface to the second communication terminal using a first optical signal through the first communication terminal, and outputting the data from the second communication data interface of the second communication terminal to an external device; transmitting data from the second communication data interface to the first communication terminal using a second optical signal through the second transmitting module in the second communication terminal, and outputting the data from the first communication data interface of the first communication terminal to an external device; The first communication terminal monitors and adjusts the relative positions of the first communication terminal and the second communication terminal according to the second optical signal, so that the first communication terminal and the second communication terminal are continuously located within each other's communication coverage.

2. The underwater wireless optical communication method according to claim 1, wherein: Adjusting the position and orientation of the first communication terminal according to the second initial optical signal so that the first communication terminal and the second communication terminal enter each other's communication coverage range includes: photographing the second initial light signal to form a spot image of the second initial light signal; Calculating relative position information of the first communication terminal and the second communication terminal according to the light spot image; According to the relative position information, the position and orientation of the first communication terminal are adjusted until the first communication terminal and the second communication terminal enter the communication coverage range of each other.

3. The underwater wireless optical communication method according to claim 2, characterized in that: Calculating relative position information of the first communication terminal and the second communication terminal according to the light spot image includes: detecting light spot information from the light spot image; Determine the number of light spots and the area covered by the light spots according to the light spot information to obtain effective light spot information; The effective light spot information is calculated to obtain relative position information of the first communication terminal and the second communication terminal.

4. The underwater wireless optical communication method according to claim 3, characterized in that: The relative position information of the first communication terminal and the second communication terminal includes: The distance, yaw angle, pitch angle and roll angle of the second communication terminal relative to the first communication terminal.

5. The underwater wireless optical communication method according to claim 3, wherein: Calculating the effective light spot information to obtain relative position information of the first communication terminal and the second communication terminal includes: The effective light spot information is calculated according to the PnP algorithm to obtain relative position information of the first communication terminal and the second communication terminal.

6. The underwater wireless optical communication method according to claim 1, wherein: Establishing a half-duplex communication link for the first communication terminal and the second communication terminal according to a preset handshake protocol, including: The first communication terminal sends a first optical signal to the second communication terminal based on a preset link inquiry sequence; After detecting the first optical signal, the second communication terminal sends a second optical signal to the first communication terminal based on a preset response sequence; After receiving the second optical signal, the first communication terminal returns to executing the step of sending the first optical signal to the second communication terminal based on a preset link inquiry sequence, until the first communication terminal and the second communication terminal respectively receive the second optical signal and the first optical signal a preset number of times, and then the first communication terminal and the second communication terminal establish a half-duplex communication link.

7. An underwater wireless optical communication system, characterized in that: The underwater wireless optical communication system includes a first communication terminal and a second communication terminal; The second communication terminal is configured to generate a second initial optical signal using a preset link pilot beacon sequence through a second transmitting module; the link pilot beacon is a set of pulse width modulated signals with a periodically varying duty cycle; the second transmitting module includes four semiconductor light sources; the first communication terminal being configured to adjust its own position and orientation according to the second initial optical signal so that the first communication terminal and the second communication terminal enter each other's communication coverage; The first communication terminal and the second communication terminal are used to establish a half-duplex communication link according to a preset handshake protocol; The first communication terminal is configured to transmit data from the first communication data interface to the second communication terminal using a first optical signal; the second communication terminal being configured to identify data from the first communication data interface from the first optical signal, and output the data from the second communication data interface of the second communication terminal to an external device; the second communication terminal being configured to transmit data from the second communication data interface to the first communication terminal using a second optical signal via the second transmitting module; The first communication terminal is configured to identify data from the second communication data interface from the second optical signal, and output the data from the first communication data interface of the first communication terminal to an external device; The first communication terminal is configured to monitor and adjust the relative position of the first communication terminal and the second communication terminal according to the second optical signal, so that the first communication terminal and the second communication terminal are continuously located within each other's communication coverage.

8. The underwater wireless optical communication system according to claim 7, characterized in that: The first communication terminal also includes an underwater camera, a posture measurement module and an underwater robot; The underwater camera is configured to capture the second initial light signal to form a spot image of the second initial light signal; The posture measurement module is used to calculate the relative posture information of the first communication terminal and the second communication terminal according to the spot image; The underwater robot is configured to adjust the position and orientation of the first communication terminal according to the relative posture information until the first communication terminal and the second communication terminal enter each other's communication coverage.

9. The underwater wireless optical communication system according to claim 8, characterized in that: The underwater robot adjusting the position and orientation of the first communication terminal according to the relative posture information includes: detecting light spot information from the light spot image; Determine the number of light spots and the area covered by the light spots according to the light spot information to obtain effective light spot information; The effective light spot information is calculated to obtain relative position information of the first communication terminal and the second communication terminal.

10. The underwater wireless optical communication system according to claim 9, characterized in that: The relative position information of the first communication terminal and the second communication terminal includes: The distance, yaw angle, pitch angle and roll angle of the second communication terminal relative to the first communication terminal.

Images