Air-water collaborative navigation-based shallow sea precise load delivery system and method

Abstract

This invention discloses a shallow-sea precision payload delivery system and method based on air-water cooperative navigation, comprising an aerial platform configured to hover at a payload delivery point in a target area based on a planned flight path; an underwater unit for carrying the payload and correcting its trajectory in the water until it reaches a preset delivery position and releases the payload; and a cooperative control and communication unit for controlling the aerial platform to hover at the initial position and controlling the underwater unit to release the payload upon reaching the delivery position. This shallow-sea precision payload delivery system and method based on air-water cooperative navigation constructs a cooperative navigation system with a rotary-wing UAV as the reference point and an underwater UAV as the execution unit. The aerial platform is transmitted to the underwater unit through physical connection and information interaction. The underwater unit uses the initial position of the aerial platform's hovering point as an absolute reference and relies on an inertial navigation system for underwater navigation.

Description

Technical Field

[0001] This invention belongs to the fields of marine engineering, unmanned systems and precision delivery technology, and in particular a shallow-sea precision payload delivery system and method based on air-water cooperative navigation. Background Technology

[0002] Currently, the following methods are mainly used for payload delivery in shallow sea areas:

[0003] Traditional ship-based point deployment is greatly affected by waves and currents, with positioning accuracy typically at the 5-10 meter level. It also has low operational efficiency and high costs.

[0004] Direct drone delivery: The drone hovers above the target point and releases the payload directly. However, after the payload enters the water, it is affected by water flow and waves, and the landing point deviation can reach 2-8 meters, which cannot meet the requirements of high-precision delivery.

[0005] Gravity settling device: It reduces the impact of water flow through streamlined design, but it cannot actively correct its trajectory, and its accuracy is limited by the deployment height and hydrological conditions.

[0006] Therefore, when deploying payloads in shallow sea areas using existing technologies, surface waves cause the payload's trajectory to deviate after entering the water, especially in shallow water areas of 2-6 meters, where the impact of waves on the payload is significant; there is no GPS signal underwater, and traditional navigation methods cannot provide real-time position feedback for underwater payloads; there is a lack of active trajectory correction capability after the payload enters the water, making it difficult to control the deployment accuracy within 1 meter; and it is also unable to adapt to dynamic changes in different hydrological conditions (current velocity, water depth, wave height, etc.). Summary of the Invention

[0007] Purpose of the invention: To provide a shallow-sea precision payload delivery system and method based on air-water cooperative navigation, which combines an air-to-air rotary-wing unmanned aerial vehicle (UAV) platform with an underwater unmanned aerial vehicle (UUV) for high-precision payload delivery in shallow sea areas (water depth 2-6 meters), applicable to applications such as marine scientific research equipment deployment, underwater sensor deployment, and seabed sampling.

[0008] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0009] Firstly, a shallow-sea precision payload delivery system based on air-water cooperative navigation is provided, comprising:

[0010] The aerial platform is configured to hover directly above the payload delivery point in the target area based on a planned flight path to determine its initial position;

[0011] The underwater unit, connected to the aerial platform, is used to carry the load and correct its trajectory in the water until it reaches the preset deployment position and releases the load. The deployment position and the initial position are at opposite ends of the same ideal vertical line.

[0012] The collaborative control and communication unit is communicatively connected to both the airborne platform and the underwater unit, and is used to control the airborne platform to hover at the initial position and to control the underwater unit to release the payload when it reaches the deployment position.

[0013] In some possible embodiments, the aerial platform includes a rotary-wing drone, an RTK-GNSS positioning module mounted on the rotary-wing drone, and a hovering positioning module;

[0014] The RTK-GNSS positioning module is configured to provide real-time location information to the rotary-wing UAV to support the rotary-wing UAV in flying to the initial position according to the flight path;

[0015] The hovering positioning module includes an IMU, a barometer, an altitude sensor, and a position fusion module, which is used to enable the rotary-wing UAV to hover at a position ±0.1m directly above the deployment point.

[0016] In a further embodiment, the IMU is configured to predict the instantaneous displacement and attitude of the airborne platform using high-frequency acceleration and angular velocity integration.

[0017] The barometer is used to provide an altitude reference for the target area;

[0018] The altitude sensor is used to measure the relative distance between the aerial platform and the sea surface;

[0019] The position fusion module is configured to fuse the instantaneous displacement and attitude, the altitude reference, and the relative distance through an extended Kalman filter, and to remove instantaneous wave jitter from the ranging data through a low-pass filter based on the wave frequency, and output a fused three-dimensional position command.

[0020] In a further embodiment, the underwater unit includes an underwater drone, a dead reckoning module mounted on the underwater drone, a six-degree-of-freedom vector propulsion module, a payload hook mechanism, an inertial navigation accuracy module, and a filtering and fusion module.

[0021] In a further embodiment, the dead reckoning module is configured to use high-bandwidth acceleration and angular velocity integration to perform underwater dead reckoning to obtain INS integral velocity, and the dead reckoning module includes a high-precision fiber optic gyroscope.

[0022] The six-degree-of-freedom vector propulsion module is configured to decompose the thrust into six independent control components in three-dimensional space based on the propulsion tilt angle and rotational speed, thereby decoupling the six-degree-of-freedom motion. The six-degree-of-freedom vector propulsion module includes at least four tiltable vector thrusters.

[0023] The load hook mechanism includes a connecting hook, which is disposed on the underwater drone. The connecting hook is used to bear and release the load, and the winch is used to lower the underwater drone at a preset rate.

[0024] The inertial navigation accuracy module is configured to observe the underwater drone from the outside and acquire DVL velocity and depth information. The inertial navigation accuracy module includes a pressure sensor and a Doppler velocimeter.

[0025] The filtering and fusion module is configured to fuse the DVL velocity, the depth information and the INS integral velocity through Kalman filtering, and correct the cumulative error caused by the drift of the high-precision fiber optic gyroscope in real time.

[0026] In a further embodiment, the cooperative control and communication unit includes:

[0027] The air-to-water cross-medium communication module is configured to enable communication between the air platform and the underwater unit via wired communication using armored cables;

[0028] The closed-loop trajectory control module is configured to calculate the real-time values ​​of the horizontal deviation and vertical depth of the underwater UAV relative to the ideal plumb line within a preset time period, and drive the underwater unit to return to the ideal plumb line when the real-time values ​​exceed a preset threshold.

[0029] In a further embodiment, the real-time value is obtained based on the DVL velocity, the depth information, and the INS integral velocity.

[0030] The six-degree-of-freedom vector propulsion module adjusts the horizontal distance between the underwater drone and the ideal plumb line based on the deviation vector between the real-time value and the preset threshold.

[0031] In a further embodiment, the preset time period is 0.1 seconds and the preset threshold is 0.1 meters.

[0032] In a further embodiment, when the deviation vector exceeds 0.1 meters, the six-degree-of-freedom vector propulsion module distributes thrust according to the direction and magnitude of the deviation vector, generating a horizontal correction force to drive the underwater drone back to the ideal plumb line.

[0033] Secondly, a method for precise payload delivery in shallow waters based on air-water cooperative navigation is provided, the method comprising:

[0034] The initial position is determined when the aerial platform carrying the underwater unit hovers directly above the target area delivery point based on the planned flight path;

[0035] After entering the water, the underwater unit corrects its trajectory based on the initial position and reaches the preset deployment position, then releases the load at the deployment position.

[0036] The beneficial effects of this invention are as follows: It constructs a collaborative navigation system with a rotary-wing UAV as the reference point and an underwater UAV as the execution unit. The high-precision RTK-GNSS positioning capability of the aerial platform is transmitted to the underwater unit through physical connection and information interaction. The underwater unit uses the initial position of the hovering point of the aerial platform as the absolute reference and relies on the inertial navigation system for underwater navigation.

[0037] By providing an initial and accurate initial position reference through an aerial platform, the influence of waves and ocean currents on the payload trajectory can be overcome, and the initial position uncertainty of the underwater inertial navigation system can be eliminated. This enables the underwater unit to achieve sub-meter-level relative positioning capability in the absence of external positioning signals, thus breaking through the limitation of insufficient accuracy in traditional underwater payload deployment. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the system structure of the present invention.

[0039] Figure 2 This is a system workflow diagram of the present invention.

[0040] The attached diagram is labeled as follows: aerial platform 1, suspended unit 2, underwater unit 3, load 4. Detailed Implementation

[0041] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0042] The present invention will be further described in detail below with reference to the accompanying drawings.

[0043] Example 1: Refer to Figure 1 and Figure 2 This embodiment discloses a shallow-sea precision payload delivery system based on air-water cooperative navigation, which includes an air platform 1, an underwater unit 3, and a cooperative control and communication unit.

[0044] Aerial platform 1 is configured to hover directly above the payload delivery point in the target area based on a planned flight path to determine its initial position.

[0045] Specifically, the aerial platform 1 includes a rotary-wing drone, an RTK-GNSS positioning module and a hovering positioning module mounted on the rotary-wing drone. Optionally, the rotary-wing drone can be four-winged or six-winged.

[0046] The RTK-GNSS positioning module is configured to provide real-time location information to the rotary-wing UAV to support the rotary-wing UAV in flying to the initial position according to the flight path.

[0047] The hovering and positioning module includes an IMU, a barometer, an altitude sensor, and a position fusion module, which enables the rotorcraft UAV to hover at a position ±0.1m directly above the deployment point by dynamically adjusting the rotor thrust at a closed-loop rate of 50 Hz or higher.

[0048] Furthermore, the IMU is configured to predict the instantaneous displacement and attitude of the aerial platform 1 using high-frequency acceleration and angular velocity integration.

[0049] The barometer is used to provide an altitude reference for the target area to suppress long-term drift;

[0050] The altitude sensor is used to measure the relative distance between the aerial platform 1 and the sea surface as the primary altitude control source; optionally, the altitude sensor is a laser sensor or an ultrasonic sensor.

[0051] The position fusion module is configured to fuse the instantaneous displacement and attitude, the altitude reference, and the relative distance using an extended Kalman filter, and to remove instantaneous wave jitter from the ranging data using a low-pass filter based on the wave frequency, outputting a fused three-dimensional position command to obtain the initial hovering position of the rotary-wing UAV. Under typical sea conditions, the wave frequency is 0.07-0.2Hz; removing jitter from the distance data using a filter yields a more accurate hovering altitude.

[0052] The underwater unit 3 is connected to the aerial platform 1 via the suspension unit 2. It is used to carry the load 4 and corrects its running trajectory in the water until it reaches the preset deployment position, at which point the load 4 is released. The deployment position and the initial position are at opposite ends of the same ideal vertical line.

[0053] Optionally, the suspension unit 2 includes a winch for lowering the underwater unit 3 at a preset rate. Optionally, the preset rate is 0.3 m / s, the maximum lifting force of the winch is ≥30 kg, and the line laying accuracy is controlled within ±0.01 m.

[0054] Specifically, the underwater unit 3 includes an underwater drone, a dead reckoning module mounted on the underwater drone, a six-degree-of-freedom vector propulsion module, a payload hook mechanism, an inertial navigation accuracy module, and a filtering and fusion module.

[0055] The underwater drone weighs 8-12kg and is compact in size (≤0.03m³).

[0056] The dead reckoning module is configured to use high-bandwidth acceleration and angular velocity integrals to perform underwater dead reckoning to obtain the INS integral velocity. The dead reckoning module includes a high-precision fiber optic gyroscope, and the zero-bias stability of the high-precision fiber optic gyroscope is better than 0.01° / h.

[0057] The six-degree-of-freedom vector propulsion module is configured to decompose the thrust into six independent control components in three-dimensional space based on the propulsion tilt angle and rotational speed, thereby decoupling the six-degree-of-freedom motion. The six-degree-of-freedom vector propulsion module includes at least four tiltable vector thrusters.

[0058] The load hook mechanism includes a connecting hook, which is mounted on the underwater drone. The connecting hook is used to carry and release the load 4, and can carry a 20kg load. It has an underwater electric release function.

[0059] The inertial navigation accuracy module is configured to observe the underwater drone from the outside and acquire DVL velocity and depth information. The inertial navigation accuracy module includes a pressure sensor and a Doppler velocimeter.

[0060] The filtering and fusion module is configured to fuse the DVL velocity, the depth information, and the INS integral velocity using Kalman filtering, thereby correcting the accumulated error caused by the drift of the high-precision fiber optic gyroscope in real time. Using the RTK-GNSS hovering point of the airborne platform as the underwater absolute position reference, the deployment position corresponding to the initial underwater position is calibrated at the moment of water entry. Combined with periodic airborne coordinate correction via cable communication, multi-source information is tightly integrated for navigation, achieving a dead reckoning error of less than 0.1% of the travel distance.

[0061] The collaborative control and communication unit is communicatively connected to the aerial platform 1 and the underwater unit 3, respectively, and is used to control the aerial platform 1 to hover at the initial position and to control the underwater unit 3 to release the payload 4 when it reaches the deployment position.

[0062] Specifically, the collaborative control and communication unit includes:

[0063] The air-to-water cross-medium communication module is configured to enable communication between the air platform 1 and the underwater unit 3 via wired communication using armored cables;

[0064] The closed-loop trajectory control module is configured to calculate the real-time values ​​of the horizontal deviation and vertical depth of the underwater UAV relative to the ideal plumb line within a preset time period, and drive the underwater unit 3 to return to the ideal plumb line when the real-time values ​​exceed a preset threshold.

[0065] The preset time period is 0.1 seconds, and the preset threshold is 0.1 meters.

[0066] The real-time values ​​are obtained based on the DVL velocity, the depth information, and the INS integral velocity.

[0067] The six-degree-of-freedom vector propulsion module adjusts the horizontal distance between the underwater drone and the ideal plumb line based on the deviation vector between the real-time value and the preset threshold.

[0068] When the deviation vector exceeds 0.1 meters, the six-degree-of-freedom vector propulsion module distributes thrust according to the direction and magnitude of the deviation vector, generating a horizontal correction force to counteract ocean currents and wave disturbances, driving the underwater drone back to the ideal vertical line. Simultaneously, the winch lowers the cable at a uniform speed of 0.3 meters per second. The vertical channel is monitored in a closed loop by pressure sensors, and the horizontal and vertical channels are decoupled to form a millisecond-level closed loop of "detection-calculation-correction-re-detection," ensuring that the underwater unit 3 moves precisely along the ideal vertical line to the preset depth throughout the descent. Once the pressure sensor confirms that the underwater unit 3 has reached the preset depth, the connecting hook is energized, and the load 4 is released within 0.5 seconds. After the load 4 is released, the underwater unit 3 immediately rises to the surface, the winch retrieves the cable and the underwater unit 3, and the aerial platform 1 returns to base.

[0069] Example 2: Based on Example 1, this example discloses a method for precise payload delivery in shallow seas based on air-water cooperative navigation. The method includes:

[0070] When the aerial platform 1 carrying the underwater unit 3 hovers directly above the target area delivery point based on the planned flight path, the initial position is determined;

[0071] After entering the water, the underwater unit 3 corrects its trajectory based on the initial position and reaches the preset deployment position, then releases the load 4 at the deployment position.

[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0073] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and all such equivalent transformations fall within the protection scope of the present invention.

Claims

1. A shallow-sea precision payload delivery system based on air-water cooperative navigation, characterized in that: include: The aerial platform is configured to hover directly above the payload delivery point in the target area based on a planned flight path to determine its initial position; The underwater unit, connected to the aerial platform, is used to carry the load and correct its trajectory in the water until it reaches the preset deployment position and releases the load. The deployment position and the initial position are at opposite ends of the same ideal vertical line. The collaborative control and communication unit is communicatively connected to both the airborne platform and the underwater unit, and is used to control the airborne platform to hover at the initial position and to control the underwater unit to release the payload when it reaches the deployment position.

2. The shallow-sea precision payload delivery system based on air-water cooperative navigation according to claim 1, characterized in that: The aerial platform includes a rotary-wing drone, an RTK-GNSS positioning module and a hovering positioning module mounted on the rotary-wing drone; The RTK-GNSS positioning module is configured to provide real-time location information to the rotary-wing UAV to support the rotary-wing UAV in flying to the initial position according to the flight path; The hovering positioning module includes an IMU, a barometer, an altitude sensor, and a position fusion module, which is used to enable the rotary-wing UAV to hover at a position ±0.1m directly above the deployment point.

3. The shallow-sea precision payload delivery system based on air-water cooperative navigation according to claim 2, characterized in that: The IMU is configured to predict the instantaneous displacement and attitude of the airborne platform using high-frequency acceleration and angular velocity integration. The barometer is used to provide an altitude reference for the target area; The altitude sensor is used to measure the relative distance between the aerial platform and the sea surface; The position fusion module is configured to fuse the instantaneous displacement and attitude, the altitude reference, and the relative distance through an extended Kalman filter, and to remove instantaneous wave jitter from the ranging data through a low-pass filter based on the wave frequency, and output a fused three-dimensional position command.

4. The shallow-sea precision payload delivery system based on air-water cooperative navigation according to claim 1, characterized in that: The underwater unit includes an underwater drone, a dead reckoning module mounted on the underwater drone, a six-degree-of-freedom vector propulsion module, a payload hook mechanism, an inertial navigation accuracy module, and a filtering and fusion module.

5. The shallow-sea precision payload delivery system based on air-water cooperative navigation according to claim 4, characterized in that: The dead reckoning module is configured to use high-bandwidth acceleration and angular velocity integrals to perform underwater dead reckoning to obtain INS integral velocity. The dead reckoning module includes a high-precision fiber optic gyroscope. The six-degree-of-freedom vector propulsion module is configured to decompose the thrust into six independent control components in three-dimensional space based on the propulsion tilt angle and rotational speed, thereby decoupling the six-degree-of-freedom motion. The six-degree-of-freedom vector propulsion module includes at least four tiltable vector thrusters. The load hook mechanism includes a connecting hook, which is disposed on the underwater drone. The connecting hook is used to bear and release the load, and the winch is used to lower the underwater drone at a preset rate. The inertial navigation accuracy module is configured to observe the underwater drone from the outside and acquire DVL velocity and depth information. The inertial navigation accuracy module includes a pressure sensor and a Doppler velocimeter. The filtering and fusion module is configured to fuse the DVL velocity, the depth information and the INS integral velocity through Kalman filtering, and correct the cumulative error caused by the drift of the high-precision fiber optic gyroscope in real time.

6. The shallow-sea precision payload delivery system based on air-water cooperative navigation according to claim 5, characterized in that: The collaborative control and communication unit includes: The air-to-water cross-medium communication module is configured to enable communication between the air platform and the underwater unit via wired communication using armored cables; The closed-loop trajectory control module is configured to calculate the real-time values ​​of the horizontal deviation and vertical depth of the underwater UAV relative to the ideal plumb line within a preset time period, and drive the underwater unit to return to the ideal plumb line when the real-time values ​​exceed a preset threshold.

7. The shallow-sea precision payload delivery system based on air-water cooperative navigation according to claim 6, characterized in that: The real-time values ​​are calculated based on the DVL velocity, the depth information, and the INS integral velocity. The six-degree-of-freedom vector propulsion module adjusts the horizontal distance between the underwater drone and the ideal plumb line based on the deviation vector between the real-time value and the preset threshold.

8. The shallow-sea precision payload delivery system based on air-water cooperative navigation according to claim 5, characterized in that: The preset time period is 0.1 seconds, and the preset threshold is 0.1 meters.

9. The shallow-sea precision payload delivery system based on air-water cooperative navigation according to claim 8, characterized in that: When the deviation vector exceeds 0.1 meters, the six-degree-of-freedom vector propulsion module distributes thrust according to the direction and magnitude of the deviation vector, generating a corrective force on the horizontal plane, driving the underwater drone back to the ideal vertical line.

10. A method for precise shallow-sea payload delivery based on air-water cooperative navigation, implemented based on the air-water cooperative navigation-based precise shallow-sea payload delivery system according to any one of claims 1-9, characterized in that: The method includes: The initial position is determined when the aerial platform carrying the underwater unit hovers directly above the target area delivery point based on the planned flight path; After entering the water, the underwater unit corrects its trajectory based on the initial position and reaches the preset deployment position, then releases the load at the deployment position.

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