Underwater positioning device and underwater robot

Abstract

The utility model belongs to the technical field of underwater positioning, and provides an underwater positioning device and an underwater robot. The underwater positioning device comprises a visual sensor, a mechanical scanning sonar, an inertial sensor, a water depth pressure sensor and a calculation unit. The calculation unit is connected with the visual sensor, the mechanical scanning sonar, the inertial sensor and the water depth pressure sensor through middleware; and the calculation unit is used for receiving sensor data acquired by the visual sensor, the mechanical scanning sonar, the inertial sensor and the water depth pressure sensor, and positioning the underwater robot according to the sensor data. By adopting the underwater positioning device, the intelligent degree of positioning of the underwater robot can be improved, and the dependence on operators is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of underwater positioning, and particularly relates to an underwater positioning device and an underwater robot. BACKGROUND

[0002] The underwater robot refers to a robot capable of performing work in an underwater environment, such as a ship body cleaning robot, a swimming pool cleaning robot, and an underwater pipeline detection robot. When the underwater robot works in the underwater environment, underwater positioning technology needs to be used to enable the underwater robot to construct a map of the underwater environment in real time and determine the position of the underwater robot, thereby providing a spatial reference for path planning and obstacle avoidance.

[0003] At present, the positioning of the underwater robot mainly relies on artificial naked-eye observation and traditional visual technology, that is, an image is obtained through direct observation or using a camera, and an operator observes image information on a monitor to evaluate the position and working state of the underwater robot. Although this way is simple to operate, the degree of intelligence is low, and the dependence on the operator is high. SUMMARY

[0004] Therefore, the embodiments of the application provide an underwater positioning device and an underwater robot to solve the technical problem that the degree of intelligence of underwater robot positioning in the prior art is low, and the dependence on the operator is high.

[0005] In a first aspect, the embodiments of the application provide an underwater positioning device, which comprises a visual sensor, a mechanical scanning sonar, an inertial sensor, a water depth pressure sensor, and a computing unit; the computing unit is connected with the visual sensor, the mechanical scanning sonar, the inertial sensor, and the water depth pressure sensor through middleware; the computing unit is configured to receive sensor data collected by the visual sensor, the mechanical scanning sonar, the inertial sensor, and the water depth pressure sensor, and to realize positioning of an underwater robot according to the sensor data.

[0006] In an implementation manner of the embodiments of the application, the underwater positioning device further comprises a sensor kit, and the visual sensor, the mechanical scanning sonar, and the inertial sensor are fixed to a main body of the sensor kit.

[0007] In an implementation manner of the embodiments of the application, the sensor kit is provided with a water-tight cable, and the visual sensor and the inertial sensor are connected with the computing unit through the water-tight cable.

[0008] In an implementation manner of the embodiments of the application, the sensor kit is provided with a detachable and angle-adjustable sonar support, and the mechanical scanning sonar is fixed to the main body of the sensor kit through the sonar support.

[0009] In an implementation manner of the embodiments of the application, the sensor kit is provided with a flange seat, and the sensor kit is fixed to a main body of the underwater robot through the flange seat.

[0010] In an implementation form of the embodiment of the application, the sensor kit is provided with an angle-adjustable camera support, and the visual sensor is fixed inside the main body of the sensor kit through the camera support.

[0011] In an implementation form of the embodiment of the application, a transparent window is arranged in front of the main body of the sensor kit.

[0012] In an implementation form of the embodiment of the application, the water depth pressure sensor is installed on the main body of the sensor kit or the main body of the underwater robot.

[0013] In an implementation form of the embodiment of the application, the visual sensor is a binocular camera.

[0014] In a second aspect, the embodiment of the application provides an underwater robot provided with the underwater positioning device provided in the first aspect of the embodiment of the application.

[0015] The underwater positioning device provided in the embodiment of the application has the following beneficial effects:

[0016] The underwater positioning device is provided with a plurality of different sensors, including a visual sensor, a mechanical scanning sonar, an inertial sensor and a water depth pressure sensor, which are connected with the computing unit through the middleware. The visual sensor can collect image information of the underwater environment; the mechanical scanning sonar can provide stable distance measurement and depth information in the turbid and insufficient light underwater environment by using the sound wave propagation characteristics; the inertial sensor can detect the angular velocity and acceleration of the underwater robot to assist in completing the attitude estimation and motion compensation; and the water depth pressure sensor can provide accurate water depth information by measuring the water pressure change to provide key constraints for the positioning in the depth direction. The data collected by each sensor is transmitted to the computing unit, and the positioning of the underwater robot is realized by the computing unit according to the sensor data. Compared with the traditional manual positioning method, the underwater positioning device can fuse the data of multiple sensors to realize high-precision underwater automatic positioning, which does not need manual observation by the operator, can effectively improve the intelligent degree and reduce the dependence on the operator. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0018] Figure 1 FIG. 1 is a structural schematic diagram of an underwater positioning device provided in an embodiment of the application; and

[0019] Figure 2 A structural schematic diagram of a sensor kit provided for an embodiment of the present application is shown in FIG. 1.

[0020] Figure 3 A frame schematic diagram of an underwater robot positioning system provided for an embodiment of the present application is shown in FIG. 2. DETAILED DESCRIPTION

[0021] It should be noted that the terms used in the embodiments of the present application are only used to explain the specific embodiments of the present application, and are not intended to limit the present application. In the description of the embodiments of the present application, unless otherwise specified, "a plurality of" means two or more than two, "at least one", "one or more" means one, two or more than two. The terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the "first", "second" features can explicitly or implicitly include one or more features.

[0022] In this specification, the phrase "one embodiment" or "some embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Therefore, the phrases "in one embodiment", "in some embodiments", "in other some embodiments", "in yet some embodiments" appearing in different places in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized. The terms "include", "contain", "have" and their variants mean "including but not limited to", unless otherwise specifically emphasized.

[0023] Accurate positioning of underwater robots in underwater environments is crucial for the successful completion of underwater robots. In underwater environments, due to factors such as water flow disturbance, light refraction, laser and GPS signal failure, it is difficult for underwater robots to achieve autonomous perception and accurate positioning. For the positioning of underwater robots, the prior art mainly installs a camera on the main body of the underwater robot, and the operator determines the position of the underwater robot by observing the image information transmitted back by the camera. However, this operation method is less intelligent and heavily dependent on the manual operation of the operator.

[0024] To solve the above problems existing in the prior art, the embodiments of the present application provide an underwater positioning device, which is provided with a plurality of different sensors and can fuse the data of multiple sensors to achieve high-precision underwater automatic positioning, improve the intelligent degree of underwater robot positioning, and reduce the dependence on operators.

[0025] Please refer to Figure 1Fig. 1 shows a structure of an underwater positioning device provided by an embodiment of the present application. Figure 1 The underwater positioning device shown includes a visual sensor, a mechanical scanning sonar, an inertial sensor, a water depth pressure sensor, and a computing unit. The computing unit is connected with the visual sensor, the mechanical scanning sonar, the inertial sensor, and the water depth pressure sensor through middleware; the computing unit is configured to receive sensor data collected by the visual sensor, the mechanical scanning sonar, the inertial sensor, and the water depth pressure sensor, and to realize positioning of the underwater robot according to the sensor data. The visual sensor, the mechanical scanning sonar, the inertial sensor, and the water depth pressure sensor each has its own advantages and collectively provides comprehensive environmental perception and positioning capability for the underwater robot in the underwater environment. The visual sensor can adopt various types of cameras, such as monocular cameras, RGBD cameras, binocular cameras, etc., and is configured to collect image information of the underwater environment; the mechanical scanning sonar utilizes the propagation characteristics of sound waves to provide stable distance measurement and depth information in turbid and insufficient light underwater environments, making up for the limitations of the visual sensor, and the orientation of the sonar should be ensured to scan the surface of the area in the forward direction of the underwater robot and prevent the sound waves from being blocked by the body; the inertial sensor is configured to detect the angular velocity and acceleration of the underwater robot in real time, has environmental independence, and can assist in completing attitude estimation and motion compensation to enhance the robustness of the system; the water depth pressure sensor can provide accurate water depth information by measuring water pressure changes, and provide key constraints for depth direction positioning to further improve the overall robustness and positioning accuracy of the system; the water depth pressure sensor itself has water tightness, but needs to be kept relatively stationary with the main body of the underwater robot during the working process. The cooperative use of the four sensors can significantly improve the accuracy, stability, and adaptability of the underwater robot positioning. The computing unit, as the core processing unit of the system, is connected with each sensor through middleware, is responsible for receiving sensor data for fusion and cooperative work, and executes positioning algorithms to realize positioning of the underwater robot. Compared with traditional manual positioning methods, the underwater positioning device can fuse multi-sensor data to realize high-precision underwater automatic positioning, which does not require manual observation by operators, can effectively improve the intelligent degree, and reduce the dependence on operators.

[0026] In an implementation form of the embodiment of the application, the visual sensor is a binocular camera. Compared with a monocular camera and an RGBD camera, the binocular camera can provide depth information with absolute scale through parallax calculation, avoid the problem that the monocular camera can only obtain depth with relative scale and the problem that the RGBD camera relies on infrared light which is invalid underwater, and is more suitable for the needs of complex underwater environment. In actual operation, the binocular camera can be directed towards the front of the underwater robot or slightly tilted downward, so as to better observe the surface of the ship body and other areas. In addition, the binocular camera needs to be equipped with a customized watertight cabin, the front of which can be made of transparent acrylic plate or other materials, so as to avoid blocking the line of sight of the binocular camera.

[0027] In an implementation form of the embodiment of the application, the underwater positioning device further comprises a sensor suite, all sensors or part of the sensors can be integrated and fixed on the sensor suite or integrated and fixed on the main body of the underwater robot. For example, the visual sensor, the mechanical scanning sonar and the inertial sensor can be fixed on the main body of the sensor suite, and the water depth pressure sensor can be fixed on the main body of the underwater robot, or the visual sensor, the mechanical scanning sonar, the inertial sensor and the water depth pressure sensor can be fixed on the main body of the sensor suite.

[0028] In an implementation form of the embodiment of the application, the sensor suite is provided with a watertight cable, and the visual sensor and the inertial sensor are connected with the computing unit through the watertight cable. The watertight cable can provide stable and reliable data transmission in the underwater environment, and is used for realizing the communication between the visual sensor, the inertial sensor and the computing unit, so as to ensure the reliability and stability of underwater data transmission. The watertight cable can be fixed at the rear part of the main body of the sensor suite, so as to avoid blocking the line of sight of the visual sensor.

[0029] In an implementation form of the embodiment of the application, the sensor suite is provided with a detachable and angle-adjustable sonar support, and the mechanical scanning sonar is fixed on the main body of the sensor suite through the sonar support. The sonar support is designed to be detachable and angle-adjustable, so as to flexibly control the measurement direction of the sonar. In actual operation, the sonar support and the mechanical scanning sonar can be fixed above the main body of the sensor suite, so as not to interfere with the visual sensor.

[0030] In an implementation form of the embodiment of the application, the sensor suite is provided with an angle-adjustable camera support, and the visual sensor is fixed inside the main body of the sensor suite through the camera support. The main body of the sensor suite can serve as a waterproof cabin of the visual sensor, and the visual sensor is fixed inside the waterproof cabin through the camera support, so as to provide watertight protection for the visual sensor. In addition, the camera support is designed to be angle-adjustable, so as to flexibly adjust the viewing angle of the visual sensor according to needs.

[0031] In an implementation form of the embodiment of the application, a transparent window is arranged in front of the main body of the sensor kit, which can be made of transparent glass or acrylic plate. With the transparent window, the visual sensor inside the main body of the sensor kit can clearly observe the environment in front, while reducing the influence of the underwater environment on the visual sensor.

[0032] In an implementation form of the embodiment of the application, the water depth pressure sensor is installed on the main body of the sensor kit or the main body of the underwater robot. Since the water depth pressure sensor itself has water tightness and does not need the protection of the waterproof cabin, the water depth pressure sensor can be installed on the main body of the sensor kit or directly installed on the main body of the underwater robot, for example, on the main cabin wall of the underwater robot.

[0033] In an implementation form of the embodiment of the application, the sensor kit is provided with a flange seat, and the sensor kit is fixed to the main body of the underwater robot through the flange seat. The flange seat is used to connect the sensor kit and the underwater robot, which can ensure the stable connection between the sensors and the main body of the robot.

[0034] In an implementation form of the embodiment of the application, the computing unit can also be integrated with the sensor kit, and the sensor kit integrated with the computing unit constitutes an underwater positioning device. The sensor kit is not necessarily installed on the underwater robot, and the diver can also hold the sensor kit to scan and reconstruct the underwater environment or object.

[0035] As an example, Figure 2 A structural schematic diagram of a sensor kit is provided in the embodiment of the application. In Figure 2 In the above embodiment, 1 represents the main body of the sensor kit, which is a waterproof cabin of the binocular camera and is also a core support of the binocular camera, the mechanical scanning sonar and the inertial sensor, for fixing the sensors; 2 represents a water-tight cable for realizing data communication between the binocular camera, the inertial sensor and the computing unit, ensuring the reliability and stability of underwater data transmission; 3 represents a sonar support for fixing the mechanical scanning sonar on the main body of the sensor kit; 4 represents the mechanical scanning sonar for detecting the distance and direction information of the underwater environment; 5 represents a flange seat for fixing the sensor kit to the main body of the underwater robot; 6 represents the binocular camera, which can be integrated with a six-axis inertial sensor inside, for capturing visual information; 7 represents a camera support for fixing the binocular camera inside the waterproof cabin; 8 represents a transparent window, which can be made of glass or acrylic plate, to ensure that the binocular camera can clearly observe the environment in front in the waterproof cabin, while reducing the influence of the underwater environment on the camera.

[0036] Each sensor is calibrated before use, for example, the internal parameters of the binocular camera such as focal length, principal point coordinates and lens distortion coefficients are calibrated, the random error of the inertial sensor is calibrated, and the joint calibration of the binocular camera and the inertial sensor, the binocular camera and the mechanical scanning sonar is performed. Through calibration, the relative position between each sensor and the coordinate system conversion relationship can be determined, and accurate sensor calibration result is an important prerequisite for accurate implementation of positioning algorithm.

[0037] After receiving the data collected by each sensor, the computing unit can run the positioning algorithm to determine the real-time position of the underwater robot, thereby realizing the positioning of the underwater robot. The positioning algorithm can adopt a SLAM (Simultaneous Localization and Mapping) method based on multi-sensor fusion, which combines the particularity of underwater environment, fuses visual information, sonar information, inertial information and depth information, and on the basis of mature visual information combined with inertial information, uses mechanical scanning sonar to replace laser to realize ranging function, and provides direct constraint in depth direction through depth gauge, which can realize efficient and accurate positioning in underwater environment.

[0038] Specifically, the SLAM positioning algorithm can be divided into four parts: data preprocessing, data initialization, nonlinear optimization, and loop detection and repositioning, which are briefly introduced as follows:

[0039] (1) Data preprocessing: feature detection and tracking are performed on the image data collected by the camera; pre-integration is performed on the data collected by the inertial sensor; the intensity data collected by the mechanical scanning sonar is filtered and converted into distance data to the obstacle.

[0040] (2) Data initialization: first, the initial scale factor of the camera is refined by using the depth sensor, and then the scale factor is further optimized by aligning the camera measurement with the pre-integrated data of the inertial sensor; then, the initial velocity, gravity vector and bias parameters are estimated by the pre-integrated data of the inertial sensor to ensure that the system can accurately predict the motion state of the underwater robot.

[0041] (3) Nonlinear optimization: a tight coupling nonlinear optimization method based on sliding window is adopted to realize high-precision robot state estimation by fusing the data of visual, inertial, sonar and depth sensors; the core of the optimization process is to construct a unified cost function to minimize error terms such as re-projection error, inertial error, sonar error and depth error to optimize the state estimation of the underwater robot; in addition, the information matrix and Jacobian matrix of each error term can be calculated and included in the Ceres Solver nonlinear optimization framework during the optimization process, and the state of the underwater robot is estimated through iterative optimization, which can effectively fuse multi-sensor data and improve the positioning accuracy and robustness of the system in underwater complex environment.

[0042] (4) Loop detection and relocalization: the loop detection method based on the bag-of-words model (DBoW2) is adopted, the loop is detected and the cumulative error is corrected through feature point matching and geometric consistency verification; through the pose graph optimization and relocalization mechanism, the accumulated pose drift in long time operation can be eliminated, and the global consistency and positioning accuracy of the system are improved.

[0043] By using the underwater positioning device and the positioning algorithm, the underwater robot can be positioned in the environment with low underwater visibility, water flow disturbance, laser sensor failure and lack of absolute positioning of GPS, and has high precision.

[0044] As an example, Figure 3 A framework schematic diagram of an underwater robot positioning system provided by the embodiment of the present application is provided. Figure 3 The framework shown includes an application layer, an algorithm layer, a data layer, a driver layer and a hardware layer, wherein the application layer includes a sensor control center application and a real-time positioning visualization application, which can provide an intuitive interface for users to facilitate monitoring and controlling the operation of each sensor; the algorithm layer integrates underwater positioning algorithms, which are the core modules of underwater robot positioning and self-navigation, and can realize accurate positioning and map construction; the data layer is responsible for the collection, publication and synchronization of sensor data, and can use the message_filters function package of the robot operating system (ROS) to realize the time synchronization of different sensor data and reduce the error introduced by the difference in sensor output frequency; the driver layer includes camera driver, IMU (inertial sensor) driver, sonar driver and depth gauge driver, which are used to ensure accurate collection and transmission of sensor data; the driver layer also has middleware, which can realize efficient communication between hardware and software platforms through USB3.0 and I / O expansion; the hardware layer integrates four sensors, including high-definition binocular camera, six-axis IMU, mechanical ring scanning sonar and high-precision depth gauge, and a computing unit, which are used for real-time data collection and processing to realize accurate positioning and navigation of the underwater robot.

[0045] As can be seen from the above, the embodiment of the present application constructs a multi-sensor fusion software and hardware platform, provides a relatively comprehensive perception capability for underwater environment, designs and realizes a positioning algorithm for underwater environment, and can effectively cope with the complex underwater environment to realize relatively accurate real-time positioning of the underwater robot.

[0046] The embodiment of the present application also provides an underwater robot, which is provided with the underwater positioning device provided by the embodiment of the present application, and the underwater robot can realize accurate positioning in underwater environment by using the underwater positioning device.

[0047] In the above embodiments, the description of each embodiment is focused on, and the parts not described or recorded in a certain embodiment can be referred to the relevant description of other embodiments.

[0048] Those skilled in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized in electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0049] The above-described embodiments are only used to illustrate the technical solutions of the present application, but not limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. An underwater positioning device, characterized in that, The underwater positioning device comprises a visual sensor, a mechanical scanning sonar, an inertial sensor, a water depth pressure sensor and a computing unit; the computing unit is connected with the visual sensor, the mechanical scanning sonar, the inertial sensor and the water depth pressure sensor through middleware; the computing unit is used for receiving sensor data collected by the visual sensor, the mechanical scanning sonar, the inertial sensor and the water depth pressure sensor, and realizing positioning of the underwater robot according to the sensor data.

2. The underwater positioning device of claim 1, wherein, The underwater positioning device further comprises a sensor kit, and the visual sensor, the mechanical scanning sonar and the inertial sensor are fixed on a main body of the sensor kit.

3. The underwater positioning device of claim 2, wherein, The sensor kit is provided with a water-tight cable, and the visual sensor and the inertial sensor are connected with the computing unit through the water-tight cable.

4. The underwater positioning device of claim 2, wherein, The sensor kit is provided with a detachable and angle-adjustable sonar support, and the mechanical scanning sonar is fixed on the main body of the sensor kit through the sonar support.

5. The underwater positioning device of claim 2, wherein, The sensor kit is provided with a flange seat, and the sensor kit is fixed on the main body of the underwater robot through the flange seat.

6. The underwater positioning device of claim 2, wherein, The sensor kit is provided with an angle-adjustable camera support, and the visual sensor is fixed inside the main body of the sensor kit through the camera support.

7. The underwater positioning device of claim 6, wherein, The main body of the sensor kit is provided with a transparent window in front.

8. The underwater positioning device of claim 2, wherein, The water depth pressure sensor is installed on the main body of the sensor kit or the main body of the underwater robot.

9. An underwater positioning device according to any one of claims 1 to 8, characterised in that, The visual sensor is a binocular camera.

10. An underwater robot, characterized in that, The underwater robot is provided with the underwater positioning device as claimed in any one of claims 1 to 9.

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