A method and system for collaborative observation of an air-water cross-domain heterogeneous platform supported by mobile acoustic reference

Abstract

The application discloses a mobile acoustic reference support air-water cross-domain heterogeneous platform cooperative observation method and system, and belongs to the technical field of marine environment cooperative observation. A water-air amphibious vehicle carries an underwater acoustic beacon and is launched from a shore base, searches along a predetermined path and determines a target area, and after landing on the water surface, establishes a fixed or mobile acoustic reference in a fixed-point keeping, discrete transfer or continuous navigation mode. An autonomous underwater vehicle fuses acoustic measurement information obtained by a passive inverse super short baseline receiving array and inertial measurement information, estimates a motion state relative to the underwater acoustic beacon, and carries out underwater observation in a close, surrounding, following or area covering mode. The scheme can reduce the number of independent platforms and deployment coordination links, and realizes rapid migration of an acoustic reference, continuous relative navigation and multi-target cooperative observation in a near-shore shallow water environment.

Description

Technical Field

[0001] This invention relates to the field of marine environmental collaborative observation and underwater robot navigation technology, and in particular to a collaborative observation method and system for air-water cross-domain heterogeneous platforms supported by a mobile acoustic reference. Background Technology

[0002] Marine observation is a crucial technological foundation for acquiring marine environmental information, utilizing marine resources, and protecting the ecosystem. Nearshore shallow water areas are influenced by tides, waves, topography, habitat, and human activities. Water depth, hydrodynamic conditions, shoreline exposure, navigable platform areas, and the accessibility of observation targets vary over time, exhibiting strong spatiotemporal heterogeneity. For shallow water ecosystems such as coral reefs, observation systems not only need to rapidly search for and identify priority observation targets but also guide underwater platforms to approach these targets for detailed observations or in-situ sampling. Therefore, this places high demands on the rapid deployment, cross-domain transfer, positioning guidance, and data retrieval capabilities of observation platforms.

[0003] Current shallow-water observation methods mainly include fixed observation equipment, survey vessels, unmanned surface vessels (USVs), autonomous underwater vehicles (AUVs), and unmanned aerial vehicles (UAVs). Fixed observation equipment is limited by its deployment location and coverage area, making it difficult to conduct mobile observations based on changes in target location; intertidal field observations are also constrained by low tide exposure time and wave conditions. Traditional survey vessels and large surface platforms have deep drafts and limited maneuverability, making it difficult to enter areas with limited navigable ranges, such as shoals and reefs. While USVs and AUVs can conduct mobile observations, the search range, target identification capabilities, and mission sustainability of a single platform are still limited by payload, energy, and communication conditions. UAVs can quickly search a large area and preliminarily identify observation targets, but they are difficult to independently complete close-range underwater observations and in-situ sampling.

[0004] To leverage the strengths of different platform types, existing technologies employ unmanned aerial vehicles (UAVs), unmanned surface vessels (USVs), and autonomous underwater vehicles (AUVs) to construct heterogeneous collaborative observation systems. Typical forms include air-to-surface, surface-to-underwater, and air-to-surface-to-underwater collaborative systems. These systems can organize search, location, guidance, and observation tasks according to the environmental adaptability of each platform. However, in near-shore shallow water environments, multiple independent platforms need to be deployed, networked, coordinated, and recovered separately, and their mission plans must be adjusted based on changes in water depth, shoreline exposure, and target accessibility. With limited underwater communication bandwidth and operating range, status sharing and mission coordination among multiple platforms are challenging, resulting in complex system composition, numerous deployment and coordination steps, and hindering rapid response and flexible operation.

[0005] In underwater platform positioning and navigation, inertial navigation systems (INS) are characterized by strong autonomy and independence from external signals. However, without external observation correction, their positioning errors accumulate over time, typically requiring correction through surfacing or other external information, thus affecting continuous underwater observation. Long-baseline acoustic positioning systems offer high positioning accuracy, but require pre-deployment and calibration of multiple underwater transponders, making deployment and retrieval complex and unsuitable for rapid deployment or temporary observation missions. Short-baseline and ultra-short-baseline acoustic positioning systems are relatively easy to deploy, but typically rely on accessible and relatively stable surface platforms. In near-shore shallow water environments with limited navigable areas, significant depth variations, and susceptibility to wind and wave disturbances, the coverage and usage conditions of fixed surface acoustic references are limited.

[0006] Furthermore, multipath propagation in shallow water environments, environmental noise, and the movement of the acoustic reference platform can lead to low acoustic measurement update frequencies, measurement anomalies, or intermittent data gaps. When the acoustic reference position changes or acoustic measurements become temporarily unavailable, positioning and guidance methods relying solely on acoustic measurements are insufficient to continuously obtain the relative motion state between the surface platform and the underwater vehicle, thus affecting the stable tracking of the underwater vehicle and the continuous implementation of collaborative observation missions.

[0007] Amphibious vehicles can switch between air and surface flight modes, enabling them to quickly reach target areas using air flight capabilities and perform surface operations using surface navigation or stationary maintenance capabilities. Compared to deploying drones and unmanned surface vessels separately, this type of platform helps reduce the number of independent platforms and simplifies the deployment process. However, existing technologies mainly focus on the configuration design, dynamic modeling, mode-switching control, and prototype verification of the cross-media platform itself. Their payload and continuous sensing capabilities remain limited, and their positioning, guidance, and mission coordination capabilities with underwater observation platforms are still imperfect.

[0008] Therefore, existing technologies struggle to simultaneously address target perception in nearshore shallow water environments, rapid cross-domain deployment, flexible acoustic reference transfer, continuous relative state acquisition under intermittent acoustic measurement conditions, and stable collaborative guidance across multiple observation tasks. How to effectively connect rapid aerial search and transfer, surface positioning support, and underwater close-range observation while reducing the number of independent platforms and deployment coordination links is a pressing technical challenge in the field of cross-domain collaborative observation in nearshore shallow water. Summary of the Invention

[0009] To address the problems of existing nearshore shallow water observation systems, such as the large number of independent platforms, complex deployment and recovery processes, limited coverage of fixed acoustic references, and difficulty in maintaining continuous relative positioning and stable cooperative guidance between surface platforms and underwater vehicles under low-frequency, anomalous, or intermittent acoustic measurement conditions, this invention provides a method and system for cooperative observation of heterogeneous air-water platforms supported by mobile acoustic references.

[0010] The purpose of this invention is to utilize the capabilities of an amphibious vehicle, which combines rapid aerial search and relocation, surface navigation, and surface stationary maintenance, to establish a surface acoustic reference that can be rapidly deployed, migrated, and maintained by carrying an underwater acoustic beacon; an autonomous underwater vehicle carries a passive inverse ultra-short baseline receiving array and fuses acoustic measurement and inertial measurement information to obtain a continuous state estimate relative to the acoustic reference; based on this, local observation, multi-target discrete observation, or corridor target continuous observation are performed according to the spatial distribution of the target and the observation task.

[0011] To achieve the above objectives, this invention provides a collaborative observation method for air-water cross-domain heterogeneous platforms supported by a mobile acoustic reference, comprising the following steps, such as... Figure 1 As shown.

[0012] S1, an amphibious vehicle carrying an underwater acoustic beacon takes off from a shore-based work platform and flies to the airspace above the sea area to be observed.

[0013] S2, the amphibious vehicle searches for the sea area to be observed along a predetermined aerial path, determines at least one observation target area, and determines the acoustic reference operation mode, the observation maneuver mode of the autonomous underwater vehicle, and the observation sequence based on the location, range, spatial distribution of the observation target area or the predetermined observation path.

[0014] S3, after completing the aerial search mission, the amphibious vehicle carrying an underwater acoustic beacon lands on the water surface, switches from aerial flight mode to surface operation mode, and enters the initial observation target area.

[0015] S4. The amphibious vehicle, according to the observation sequence and acoustic reference operation mode, transfers to the acoustic reference operation position corresponding to the current observation target area through surface navigation or air flight, and enters the surface operation state.

[0016] S5, the amphibious vehicle can maintain a fixed position on the water surface, perform discrete transfers on the water surface, perform discrete transfers in the air, or navigate continuously on the water surface according to the acoustic reference operation mode; when it is in the water surface operation state and the underwater acoustic beacon is immersed in the water, the underwater acoustic beacon transmits acoustic positioning signals to the underwater area to establish a fixed acoustic reference, a discrete moving acoustic reference, or a continuous moving acoustic reference in the current observation target area.

[0017] S6, the autonomous underwater vehicle integrates acoustic measurement information acquired by the passive inverse ultra-short baseline receiving array with motion information acquired by the inertial measurement unit to estimate its motion state relative to the underwater acoustic beacon, and performs navigation and guidance based on the estimation results and observation maneuvering mode to carry out underwater observation in approach, circling, following or area coverage modes.

[0018] When there are multiple observation target areas, after completing the underwater observation of the current observation target area, return to step S4 to allow the amphibious vehicle to move to the next observation target area and re-establish the acoustic reference. Under the guidance of the re-established acoustic reference, the autonomous underwater vehicle continues to carry out underwater observation until the observation tasks of all observation target areas are completed.

[0019] Furthermore, the amphibious vehicle possesses at least an air flight mode, a surface navigation mode, and a surface stationary mode. In air flight mode, the amphibious vehicle carries an underwater acoustic beacon to cross surface obstacles or rapidly transfer between distant target areas; in surface navigation mode, the amphibious vehicle carries an underwater acoustic beacon to move along the water surface; in surface stationary mode, the amphibious vehicle utilizes a surface propulsion unit to compensate for positional deviations caused by wind, waves, and currents.

[0020] Furthermore, the surface stationary mode adopts dynamic positioning, setting the predetermined surface position as a virtual anchor point. The position and heading of the amphibious vehicle relative to the virtual anchor point are estimated based on satellite navigation information and inertial navigation information. The surface propulsion unit is controlled based on the position error and heading error to keep the amphibious vehicle and its carried underwater acoustic beacon within the predetermined area.

[0021] Furthermore, based on the spatial distribution of the observation target area and the navigability between target areas, an operating mode is selected from the fixed acoustic reference observation mode, the water surface discrete point guided observation mode, the air discrete point guided observation mode, and the water surface continuous guided observation mode.

[0022] Furthermore, the underwater acoustic beacon is suspended below the amphibious vehicle by a tether and is submerged in water when the amphibious vehicle is in a surface operation state. Before the mission begins, the underwater acoustic beacon and the passive inverse USMR receiver array calibrate their local clocks using a one-pulse-per-second signal provided by the satellite navigation system, and maintain the time reference using a local oscillator during mission execution.

[0023] Furthermore, the passive inverse ultra-short baseline receiving array estimates the one-way propagation time of the acoustic positioning signal through matched filtering, and calculates the slant range between the underwater acoustic beacon and the receiving array based on the one-way propagation time; through array beamforming processing, the arrival direction of the acoustic positioning signal is determined based on the phase difference of the signals received by multiple hydrophones, and the horizontal wave direction of arrival is extracted from the arrival direction.

[0024] Furthermore, the acoustic positioning signal is equipped with a communication payload for transmitting mission commands, operating modes, or status information between the amphibious vehicle and the autonomous underwater vehicle.

[0025] Furthermore, the validity of the acoustic measurement information is determined, and the valid acoustic measurement information is fused with the motion information obtained by the inertial measurement unit to obtain the relative state estimate of the autonomous underwater vehicle relative to the underwater acoustic beacon. When the acoustic measurement is abnormal or temporarily missing, the state prediction is maintained by using the inertial measurement information, or the autonomous underwater vehicle is controlled to enter a preset safe operating state.

[0026] Furthermore, based on the relative state estimation and observation mission requirements, the appropriate geometric guidance mode is selected to generate navigation and control commands for the autonomous underwater vehicle, enabling the autonomous underwater vehicle to perform at least one observation maneuver among target approach, circling observation, area coverage, or continuous following.

[0027] Furthermore, in the fixed acoustic reference observation mode, the amphibious vehicle maintains a fixed position on the water surface near the target area, so that the underwater acoustic beacon forms a relatively fixed surface acoustic reference; the autonomous underwater vehicle performs local observation tasks based on this surface acoustic reference.

[0028] Furthermore, in the surface discrete point guided observation mode, the amphibious vehicle navigates sequentially between multiple predetermined acoustic reference operation positions and maintains a fixed position on the surface at each acoustic reference operation position; the autonomous underwater vehicle performs target approach and local observation sequentially according to each acoustic reference operation position.

[0029] Furthermore, in the air-based discrete point guided observation mode, the amphibious vehicle traverses impassable areas on the water surface or moves between distant acoustic reference operation positions by flying through the air, and re-establishes the acoustic reference after each landing on the water.

[0030] Furthermore, during the aerial transfer of the amphibious vehicle and the temporary interruption of the acoustic link, the autonomous underwater vehicle maintains a fixed depth waiting, moves along a preset waiting trajectory, or enters a safe operating state; after the amphibious vehicle reaches the next acoustic reference operation position and re-enters the water, the acoustic link is re-established, and the autonomous underwater vehicle resumes tracking the moving acoustic reference.

[0031] Furthermore, in the continuous surface guidance observation mode, the amphibious vehicle continuously navigates along a predetermined surface path, and the underwater acoustic beacon continuously provides acoustic positioning signals to the autonomous underwater vehicle. The autonomous underwater vehicle adjusts its motion based on continuous relative state estimation to maintain a predetermined relative relationship with the amphibious vehicle, and performs continuous observations along coral reef edges, shorelines, underwater pipelines, breakwaters, underwater channels, or other corridor-like targets.

[0032] This invention also provides a collaborative observation system for heterogeneous air-water platforms supported by a mobile acoustic reference, used to implement the aforementioned collaborative observation method. The collaborative observation system includes an amphibious vehicle, an underwater acoustic beacon, an autonomous underwater vehicle, and a passive inverse ultra-short baseline receiving array.

[0033] An amphibious vehicle comprises an air propulsion unit, a surface propulsion unit, a buoyancy unit, an airborne navigation unit, and a navigation control unit. The air propulsion unit enables flight, vertical takeoff and landing, and aerial transfer; the surface propulsion unit enables surface navigation, yaw control, and surface stationary maneuvering; the airborne navigation unit acquires the amphibious vehicle's position, speed, attitude, and heading; and the navigation control unit coordinates the air propulsion unit and the surface propulsion unit according to the current operating mode.

[0034] The underwater acoustic beacon and the passive inverse USMR receiver array constitute a passive inverse USMR underwater acoustic positioning system. The underwater acoustic beacon is mounted on the amphibious vehicle and is submerged in water when the amphibious vehicle is on the surface to transmit acoustic positioning signals, thereby forming a surface acoustic reference that moves with the amphibious vehicle.

[0035] An autonomous underwater vehicle includes an underwater propulsion unit, a depth sensor, an inertial measurement unit, a relative state estimation module, a guidance module, and a low-level motion controller.

[0036] A passive inverse ultra-short baseline receiver array is mounted on the autonomous underwater vehicle and includes multiple hydrophones for receiving acoustic positioning signals emitted by underwater acoustic beacons and obtaining the horizontal wave direction of arrival and slant range based on the multi-channel received signals; an inertial measurement unit is used to acquire motion information of the autonomous underwater vehicle at a frequency higher than the acoustic measurement update frequency.

[0037] The relative state estimation module is used to identify anomalous acoustic measurements, use inertial measurement information to predict the state between adjacent valid acoustic measurements, and correct the predicted state when a valid acoustic measurement is obtained, so as to output a continuous relative state estimate of the autonomous underwater vehicle relative to the underwater acoustic beacon.

[0038] The guidance module is used to generate desired heading, desired depth, or speed commands based on relative state estimation, desired observation depth, and geometric parameters corresponding to the observation maneuvering mode; the underlying motion controller is used to convert the commands into control commands for the underwater propulsion unit.

[0039] The task management module is used to select a fixed acoustic reference observation mode, a surface discrete point guided observation mode, an air discrete point guided observation mode, or a surface continuous guided observation mode based on the spatial distribution of the observation target area, and to coordinate the working mode of the amphibious vehicle with the observation maneuvering mode of the autonomous underwater vehicle.

[0040] Compared with the prior art, the present invention has at least the following beneficial effects.

[0041] First, this invention utilizes an amphibious vehicle to simultaneously undertake rapid aerial search and transfer as well as surface acoustic support tasks, eliminating the need to deploy separate aerial and surface acoustic reference platforms. This reduces the number of platforms, as well as platform deployment, communication networking, and task coordination, thereby improving the rapid response capability of nearshore shallow water observation missions.

[0042] Secondly, this invention mounts an underwater acoustic beacon on an amphibious vehicle, enabling the acoustic reference to migrate between different observation areas via surface navigation or air flight, and to maintain a relatively stable acoustic reference by being fixed at a point on the surface, thereby expanding the effective observation range of the autonomous underwater vehicle and reducing the dependence on pre-deployed and calibrated fixed acoustic base stations.

[0043] Third, this invention combines passive inverse ultra-short baseline acoustic measurement with inertial measurement, using inertial measurement information to maintain state prediction between adjacent acoustic measurements and performing state correction when effective acoustic measurements are obtained, which can improve the continuity and stability of relative state estimation under low-frequency, abnormal or intermittent acoustic measurement conditions.

[0044] Fourth, the present invention adopts a parametric geometric guidance method, which can generate underwater observation trajectories such as homing, fixed radius circling, involute expansion and outward spiral by changing the geometric parameters corresponding to the observation maneuver mode, so as to facilitate the adjustment of the autonomous underwater vehicle's movement mode according to the target type and observation range.

[0045] Fifth, the present invention sets up a fixed acoustic reference observation mode, a water surface discrete point guided observation mode, an air discrete point guided observation mode, and a water surface continuous guided observation mode, which can respectively adapt to the local fine observation of a single target, the sequential observation of multiple targets, the observation of multiple targets across obstacles, and the continuous tracking observation of corridor-shaped targets.

[0046] Sixth, this invention integrates rapid aerial search and transfer, underwater acoustic reference establishment and migration, underwater relative positioning, collaborative guidance and fine observation into an integrated operation process, which can be used for coral reef ecological surveys, underwater structure inspections, aquaculture monitoring, wharf and breakwater inspections, underwater pipeline inspections and emergency underwater searches. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the overall process of collaborative observation of the air-water cross-domain heterogeneous platform supported by the mobile acoustic reference of the present invention.

[0048] Figure 2 This is a schematic diagram of the structure of the amphibious vehicle carrying an underwater acoustic beacon according to the present invention.

[0049] Figure 3This is a schematic diagram of the structure of the autonomous underwater vehicle and its passive inverse ultra-short baseline receiving array of the present invention.

[0050] Figure 4 This is a schematic diagram of the relative state estimation and guidance framework for the fusion of acoustic and inertial information of this invention.

[0051] Figure 5 This is a flowchart of the collaborative observation method of the present invention.

[0052] Figure 6 This is a schematic diagram of the fixed acoustic reference observation mode, the moving acoustic reference observation mode, and the local observation actions of the autonomous underwater vehicle according to the present invention.

[0053] Explanation of reference numerals in the attached figures: 110, amphibious vehicle; 120, underwater acoustic beacon; 210, autonomous underwater vehicle; 220, passive inverse ultra-short baseline receiver array. Detailed Implementation

[0054] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention; where there is no conflict, the technical features of the various embodiments can be combined with each other.

[0055] like Figures 1 to 3 As shown, the collaborative observation system of this embodiment includes an amphibious vehicle 110, an underwater acoustic beacon 120, an autonomous underwater vehicle 210, and a passive inverse USMR receiver array 220. The amphibious vehicle 110 and the underwater acoustic beacon 120 constitute a mobile acoustic reference capable of cross-domain migration, while the autonomous underwater vehicle 210 and the passive inverse USMR receiver array 220 constitute an underwater observation platform.

[0056] The amphibious vehicle 110 has an air propulsion unit on its upper part and a buoyancy unit and a surface propulsion unit on its lower part. The air propulsion unit provides the thrust required for vertical takeoff and landing, air cruise, and obstacle crossing; the buoyancy unit keeps the vehicle in a predetermined floating state on the water; and the surface propulsion unit generates longitudinal thrust and yaw moment on the water.

[0057] The amphibious vehicle 110 is also equipped with an airborne navigation unit, a navigation control unit, a mission computing unit, and a communication unit. The airborne navigation unit can integrate satellite navigation, inertial measurement, and altitude or surface status information; the navigation control unit selects the appropriate propulsion unit based on whether the vehicle is in the air, on the surface, or maintaining a fixed position on the surface; and the mission computing unit stores the air search path, acoustic reference operating position, and target observation sequence.

[0058] In the air flight state, the surface propulsion unit is in a stopped or low power state, and the air propulsion unit controls the amphibious vehicle 110 to fly along a predetermined route; in the water surface operation state, the air propulsion unit stops or enters a standby state, and the surface propulsion unit controls the water surface navigation or stationary maintenance according to the heading and position commands.

[0059] When maintaining a fixed position on the water surface, the acoustic reference operating position is used as a virtual anchor point. The navigation control unit calculates the position error and heading error based on the real-time position and heading of the amphibious vehicle 110 and the virtual anchor point, and distributes thrust to the surface propulsion unit to compensate for drift caused by wind, waves and water currents.

[0060] The underwater acoustic beacon 120 is attached to the amphibious vehicle 110 via a tether. During flight, the beacon 120 is carried by the vehicle; after the amphibious vehicle 110 lands on the water, the beacon 120 is positioned at a predetermined depth below the water surface to reduce the impact of surface bubbles and platform structures on acoustic signal propagation. The tether length can be adjusted according to draft, wave conditions, and acoustic propagation conditions.

[0061] The underwater acoustic beacon 120 transmits acoustic positioning signals underwater according to a predetermined timing sequence. Before the mission begins, the underwater acoustic beacon 120 and the passive inverse USMR receiver array 220 calibrate their local clocks using a pulse-per-second signal provided by the satellite navigation system, and then maintain their time references using their local clocks, thereby supporting one-way propagation time ranging.

[0062] The passive inverse ultra-short baseline receiving array 220 includes multiple hydrophones arranged in a predetermined geometric relationship. After each hydrophone receives the same acoustic positioning signal, it determines the signal arrival time through matched filtering, calculates the one-way propagation time based on the difference between the transmission time and the arrival time, and obtains the slant distance between the underwater acoustic beacon 120 and the receiving array 220 by combining a preset or real-time sound velocity.

[0063] The receiving array 220 also obtains the direction of arrival of the acoustic positioning signal based on the phase difference between the signals received by each hydrophone and the array geometry, and extracts the horizontal direction of arrival from it. The acoustic positioning signal can also carry mission number, operating mode, target number or status command, enabling a low-bandwidth underwater acoustic information channel to be formed between the amphibious vehicle 110 and the autonomous underwater vehicle 210.

[0064] The autonomous underwater vehicle 210 includes an underwater propulsion unit, a depth sensor, an inertial measurement unit, a state estimation and guidance calculation unit, a low-level motion controller, and an observation payload.

[0065] like Figure 4As shown, the passive inverse ultra-short baseline receiving array 220 outputs the horizontal direction of arrival and slant range at a first update frequency (1Hz), while the inertial measurement unit outputs yaw rate or other motion information at a second update frequency (20Hz) higher than the first update frequency. The relative state estimation module fuses the information from the two different update frequencies.

[0066] The validity of passive inverse ultra-short baseline acoustic measurement data is assessed and preprocessed. Specifically, when assessing the validity of the horizontal direction of arrival, the periodic angle difference between the current horizontal direction of arrival and the previous valid horizontal direction of arrival is calculated, and measurements exceeding a preset range or with signal quality below a preset requirement are marked as abnormal. When assessing the validity of the slant range, abnormal measurements are eliminated based on range, signal quality, rate of change of adjacent measurements, or a combination thereof.

[0067] Between adjacent effective acoustic measurements, the relative state estimation module uses inertial measurement information and the relative state at the previous moment to predict the horizontal wave direction of arrival, slant range, or their changing trends. When a new effective acoustic measurement arrives, it uses that measurement to correct the prediction results. Thus, even if the acoustic measurement update frequency is lower than the control frequency, it can continuously provide relative state estimates to the guidance module.

[0068] When acoustic measurements are continuously lost within a preset time period, the relative state estimation module marks the navigation state as invalid. The underlying motion controller controls the autonomous underwater vehicle 210 to hover, hold at a fixed depth, move along a preset small-range trajectory, or enter a safe surfacing state according to the mission settings; after obtaining valid acoustic measurements again, it resumes relative state correction and cooperative guidance.

[0069] The guidance module generates desired heading, desired depth, or speed commands based on relative state estimation and the selected observation maneuver mode, which are then converted into control inputs for the underwater propulsion unit by the underlying motion controller. Observation maneuver modes include homing, constant radius circling, involute spreading, and outward spiral.

[0070] The homing mode is used to bring the autonomous underwater vehicle 210 from its current position closer to the acoustic beacon 120 or the observation target area indicated by the acoustic beacon 120. It is applicable to the mission start phase, the transfer phase between observation points, and the continuous following phase.

[0071] The fixed-radius circling mode is used to enable the autonomous underwater vehicle 210 to circulate within a predetermined range of the underwater acoustic beacon 120 or the observation target in order to obtain target images, sonar data or environmental measurement data from different directions.

[0072] The involute expansion mode is used to gradually expand the autonomous underwater vehicle 210 outward from the vicinity of the acoustic reference, while the outward spiral mode is used to form an expansion trajectory by continuously changing the desired orbital radius. Both can be used for local area search and coverage observation.

[0073] The aforementioned geometric guidance modes share a common relative state input. By setting at least one of the direction parameters, desired radius, extension angle, radius growth rate, and desired depth, different trajectories can be generated. Therefore, different target shapes can be adapted without changing the underlying motion controller.

[0074] like Figure 1 and Figure 5 As shown, a complete collaborative observation mission can be executed according to steps S1 to S6. Before the mission begins, the mission management module loads the area to be observed, the aerial search path, the initial position of the autonomous underwater vehicle 210, and safety constraints.

[0075] In step S1, the amphibious vehicle 110, carrying the underwater acoustic beacon 120, takes off vertically from the shore-based operating platform and arrives at the airspace above the sea area to be observed along the transfer route. The shore-based operating platform can be a fixed shore station or a temporary shore-based take-off and landing platform.

[0076] In step S2, the amphibious vehicle 110 uses onboard optical, infrared, laser, or other remote sensing payloads to search for targets on the sea surface, intertidal zone, and shallow water, and determines one or more observation target areas based on the search results. The mission management module combines the target location, range, spatial distribution, water surface navigability, and predetermined observation path to determine the acoustic reference operating mode, observation maneuver mode, and target observation sequence.

[0077] In step S3, the amphibious vehicle 110 lands on the water near the initial observation target area, completing the switch from air flight state to water surface operation state, and immerses the underwater acoustic beacon 120 in the water and waits for the acoustic link to be established.

[0078] In steps S4 and S5, the amphibious vehicle 110 transfers to the acoustic reference operation position by water surface navigation or air flight and enters the water surface operation state. Depending on the mission type, it enters the water surface fixed-point maintenance, discrete transfer or continuous water surface navigation state. In the water surface operation state, the underwater acoustic beacon 120 immersed in the water emits an acoustic positioning signal, thereby forming a fixed acoustic reference or a moving acoustic reference.

[0079] In step S6, the autonomous underwater vehicle 210 receives acoustic positioning signals, fuses acoustic and inertial measurement information to obtain a relative state estimate, and performs target approach, circling, following, or area coverage according to the selected observation maneuver mode. After completing the current target, the mission management module decides whether to transfer to the next observation target area by surface navigation or aerial flight based on the remaining targets and surface navigability conditions.

[0080] Figure 6The left side illustrates the implementation of the fixed acoustic reference observation mode. The amphibious vehicle 110 lands near a single observation target and enters a virtual anchor point dynamic positioning, maintaining the underwater acoustic beacon 120 within a predetermined area; the autonomous underwater vehicle 210 first approaches the target using a homing mode.

[0081] Upon approaching the target, the autonomous underwater vehicle 210 selects a fixed-radius circling, involute expansion, or outward spiral mode based on the target size and the line-of-sight of the observation payload. For isolated coral reefs, single underwater structures, or predetermined sampling points, circling motion can be used to obtain multi-directional data; for target areas of a certain size, an expanded trajectory can be used to obtain coverage data.

[0082] In this mode, the amphibious vehicle 110 maintains a relatively stable position and can serve as a surface marker in the target area, while the underwater acoustic beacon 120 provides relative navigation reference. During the mission, the amphibious vehicle 110 can transmit its own status and aerial search results back to the shore-based operation platform via a wireless link.

[0083] After completing local observations, the autonomous underwater vehicle 210 can return to the pre-set rendezvous area near the acoustic beacon 120, maintain a fixed depth and wait, or proceed to the next observation maneuver according to subsequent tasks.

[0084] The fixed acoustic reference observation mode is suitable for areas where targets are concentrated and the water surface can be maintained at a fixed point, including isolated reef patches, underwater equipment, parts of aquaculture cages, underwater components, and nearshore sampling points.

[0085] Figure 6 The upper center section illustrates the implementation of the discrete-point guided observation mode on the water surface. The task management module sets acoustic reference operation positions near multiple adjacent target areas and determines the access order according to target priority or path cost.

[0086] The amphibious vehicle 110 first maintains a fixed position at the first acoustic reference working position, while the autonomous underwater vehicle 210 approaches and completes local observations using the homing mode; subsequently, the amphibious vehicle 110 exits the fixed-point maintenance state and sails along the water surface to the second acoustic reference working position.

[0087] During the surface relocation, the underwater acoustic beacon 120 remains submerged and continuously emits acoustic positioning signals, while the autonomous underwater vehicle 210 adjusts its course and follows the moving acoustic reference. Upon reaching the next acoustic reference operating position, the amphibious vehicle 110 maintains its position again, and the autonomous underwater vehicle 210 completes local observation of the next target.

[0088] The above process is repeated for three or more observation target areas to form a sequential mission chain of surface transfer of the amphibious vehicle 110, dynamic positioning of the virtual anchor point, and target approach of the autonomous underwater vehicle 210.

[0089] The distance between targets, the order of access, and the holding time can be adjusted online based on observation priority, remaining energy, effective acoustic range, and surface flow field.

[0090] The discrete-point guided observation mode is suitable for discrete targets that are adjacent to each other and accessible by surface paths, such as multiple reefs, underwater structures, aquaculture facilities, or pre-set environmental sampling points.

[0091] Figure 6 The upper right side shows the implementation of the aerial discrete point guided observation mode. When there are shoals, reefs, buoy arrays or other surface obstacles between adjacent target areas, or when the target distance is large, the amphibious vehicle 110 takes off from its current surface position and carries the underwater acoustic beacon 120 to fly over impassable areas.

[0092] During the aerial transfer, the underwater acoustic beacon 120 leaves the water, and the acoustic link is temporarily interrupted. The autonomous underwater vehicle 210 maintains a constant depth waiting position, moves along a preset waiting trajectory, or enters other safe operating states according to the mission settings to avoid continuing long-distance navigation without effective relative navigation information.

[0093] After reaching the next observation target area, the amphibious vehicle 110 lands on the water and re-establishes an acoustic reference. After the receiver array 220 detects a valid acoustic positioning signal, the relative state estimation module resumes correction, and the guidance module controls the autonomous underwater vehicle 210 to approach the new acoustic reference operating position.

[0094] By repeating this process of aerial transfer, landing on the water, re-establishing acoustic reference, and approaching the underwater target, sequential observations can be conducted across multiple target areas where surface access is restricted or where targets are far apart but have underwater paths accessible to autonomous underwater vehicles (AUVs). The next acoustic reference position should ensure that the underwater beacon and the waiting AUV can re-establish a valid acoustic link.

[0095] The airborne discrete point guided observation mode is suitable for reef-separated waters, areas where the above-mentioned underwater passage and acoustic link restoration conditions are met, areas where the surface path is periodically interrupted by tides, and temporary observation tasks that require rapid crossing of large distances.

[0096] Figure 6 The following illustrates the implementation of the continuous surface guidance observation mode. The task management module plans the surface guidance path based on the reef edge, coastline, underwater pipelines, breakwater, pier edge, or the extension direction of underwater channels.

[0097] The amphibious vehicle 110 continuously navigates along the surface guidance path, while the underwater acoustic beacon 120 remains submerged and continuously emits acoustic positioning signals. The autonomous underwater vehicle 210 employs geometric guidance in the form of homing or following, adjusting its own course and speed based on relative state estimation.

[0098] During the stable following phase, the desired relative distance between the autonomous underwater vehicle 210 and the underwater acoustic beacon 120 can be set to a value that is adapted to the observation payload's operating distance and water depth, so that the two platforms move in the same overall direction.

[0099] When the surface guidance path turns, the guidance module continuously adjusts the desired course according to the change in the horizontal wave direction; when the distance between platforms deviates from the predetermined range, the relative distance is restored by course correction or speed command.

[0100] The continuous surface-guided observation mode can use the surface path as a guiding reference for underwater observation corridors, and is suitable for continuous inspection of corridor-shaped ecological targets and nearshore engineering structures.

[0101] The configuration of the amphibious vehicle, the type of underwater acoustic beacon, the number of hydrophones in the receiving array, the state estimation method, and the observation payload in the above embodiments can all be adjusted according to mission requirements. As long as the surface acoustic reference is moved using a platform with both air and surface mobility capabilities, and relative navigation and cooperative observation of the autonomous underwater vehicle are performed based on the acoustic reference, equivalent technical means can be used.

[0102] This invention is not limited to nearshore ecological surveys; it can also be used for underwater engineering structure inspection, aquaculture monitoring, port facility inspection, emergency search and rescue, and multi-site environmental sampling. All equivalent substitutions or modifications made based on the concept of this invention should fall within the scope of protection of this invention.

Claims

1. A collaborative observation method for air-water cross-domain heterogeneous platforms supported by a mobile acoustic reference, characterized in that, include: An amphibious vehicle carrying an underwater acoustic beacon takes off from a shore-based work platform and flies to the airspace above the sea area to be observed. The amphibious vehicle searches the sea area along a predetermined aerial path, identifies at least one observation target area, and determines the acoustic reference operating mode, the observation maneuver mode of the autonomous underwater vehicle, and the observation sequence based on the location, range, spatial distribution, or predetermined observation path of the observation target area. After completing the aerial search, the amphibious vehicle carrying the underwater acoustic beacon lands on the water surface and enters the initial observation target area. The amphibious vehicle then proceeds according to the predetermined observation path... The observation sequence and acoustic reference operation mode are determined by transferring the amphibious vehicle to the acoustic reference operation position corresponding to the current observation target area via surface navigation or air flight, and then entering the surface operation state. The amphibious vehicle performs surface fixed-point maintenance, surface discrete transfer, air discrete transfer, or continuous surface navigation according to the acoustic reference operation mode. When the amphibious vehicle is in the surface operation state and the underwater acoustic beacon is submerged in water, the underwater acoustic beacon transmits acoustic positioning signals underwater to establish a fixed acoustic reference, a discrete moving acoustic reference, or a continuously moving acoustic reference. The autonomous underwater vehicle integrates acoustic measurement information and inertial measurement information to estimate its motion state relative to the underwater acoustic beacon, and performs navigation and guidance based on the motion state and the observation maneuver mode to conduct underwater observation of the observation target area in the manner of approaching, circling, following, or area coverage.

2. The collaborative observation method according to claim 1, characterized in that, The amphibious vehicle has at least an air flight mode, a surface navigation mode, and a surface stationary mode. It can cross surface obstacles or move between distant observation target areas by air flight, and move between observation target areas with passable surface paths by surface navigation.

3. The collaborative observation method according to claim 1, characterized in that, The water surface positioning is achieved using dynamic positioning, where a predetermined water surface position is set as a virtual anchor point. The position and heading of the amphibious vehicle relative to the virtual anchor point are estimated based on satellite navigation information and inertial navigation information, and the water surface propulsion unit is controlled based on the position error and heading error.

4. The collaborative observation method according to claim 1, characterized in that, In the fixed acoustic reference operation mode, the amphibious vehicle maintains a fixed position on the water surface near the observation target area; in the discrete moving acoustic reference operation mode, the amphibious vehicle moves sequentially between multiple acoustic reference operation positions and maintains a fixed position on the water surface at each position. In the continuous moving acoustic reference operation mode, the amphibious vehicle continuously navigates along a predetermined water surface path.

5. The collaborative observation method according to claim 4, characterized in that, When the surface path between adjacent acoustic reference work positions is passable and the distance between the work positions does not exceed a preset value, the amphibious vehicle moves by surface navigation; when the surface path is impassable or the distance between adjacent acoustic reference work positions exceeds a preset value, the amphibious vehicle moves by air flight.

6. The collaborative observation method according to claim 5, characterized in that, During the aerial transfer of the amphibious vehicle and the interruption of the acoustic link, the autonomous underwater vehicle is controlled to maintain a fixed depth waiting, move along a preset waiting trajectory, or enter a safe operation state, and resume collaborative observation after the amphibious vehicle re-establishes the acoustic link at the next acoustic reference operation position.

7. The collaborative observation method according to claim 1, characterized in that, The autonomous underwater vehicle acquires the horizontal wave direction and slant range relative to the underwater acoustic beacon through its onboard passive inverse ultra-short baseline receiving array, and acquires its own motion information through its inertial measurement unit. It then predicts and corrects the horizontal wave direction, slant range, and its own motion information to form a continuous relative motion state estimate.

8. The collaborative observation method according to claim 7, characterized in that, Before the mission begins, the underwater acoustic beacon and the passive inverse USMR receiver array calibrate their local clocks using a pulse-per-second signal provided by the satellite navigation system. The passive inverse USMR receiver array obtains the slant range based on the one-way propagation time of the acoustic positioning signal and the direction of arrival based on the phase difference of the signals received by multiple hydrophones.

9. The collaborative observation method according to claim 1 or 7, characterized in that, The observation maneuvering modes include at least one of the following: homing mode, fixed radius circling mode, involute expansion mode, and outward spiral mode.

10. A collaborative observation system for a cross-domain heterogeneous air-water platform supported by a mobile acoustic reference, characterized in that, The system includes an amphibious vehicle, an underwater acoustic beacon, an autonomous underwater vehicle (AUV), a passive inverse USMR receiver array, an inertial measurement unit, a relative state estimation module, a guidance module, and a mission management module. The amphibious vehicle carries the underwater acoustic beacon for aerial search, aerial transfer, surface navigation, and surface stationary maintenance to establish a fixed or moving acoustic reference. The passive inverse USMR receiver array is mounted on the AUV and is used to receive acoustic positioning signals emitted by the underwater acoustic beacon and obtain acoustic measurement information. The relative state estimation module is used to fuse the acoustic measurement information and the motion information acquired by the inertial measurement unit to estimate the motion state of the autonomous underwater vehicle relative to the underwater acoustic beacon; the guidance module is used to generate navigation and guidance commands for the autonomous underwater vehicle based on the motion state and the observation maneuver mode; the mission management module is used to coordinate the cooperative operation of the amphibious vehicle and the autonomous underwater vehicle based on the spatial distribution of the observation target area.

11. The cooperative observation system according to claim 10, characterized in that, The amphibious vehicle includes an air propulsion unit, a surface propulsion unit, a buoyancy unit, an airborne navigation unit, and a navigation control unit. The navigation control unit is used to coordinate the air propulsion unit and the surface propulsion unit according to the current operating mode.

12. The collaborative observation system according to claim 10, characterized in that, The underwater acoustic beacon is suspended below the amphibious vehicle by a tether and is submerged in water when the amphibious vehicle is in a surface operation state; the passive inverse ultra-short baseline receiver array includes multiple hydrophones.

13. The cooperative observation system according to claim 10, characterized in that, The autonomous underwater vehicle also includes an underwater propulsion unit, a depth sensor, a bottom-level motion controller, and an observation payload. The bottom-level motion controller is used to control the underwater propulsion unit according to the navigation and guidance commands.

14. The collaborative observation system according to claim 10, characterized in that, The relative state estimation module is used to determine the validity of acoustic measurement information, maintain the state prediction using inertial measurement information between adjacent valid acoustic measurements, and correct the state prediction when a valid acoustic measurement is obtained. If no valid acoustic measurement is obtained for a continuous preset duration, the relative motion state will be marked as invalid and the preset safe operation state will be triggered.

15. The collaborative observation system according to claim 10, characterized in that, The task management module is used to select a fixed acoustic reference observation mode, a surface discrete point guided observation mode, an air discrete point guided observation mode, or a surface continuous guided observation mode, and to coordinate the working mode of the amphibious vehicle and the observation maneuvering mode of the autonomous underwater vehicle.

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