Underwater vehicle trim control method, system, and underwater vehicle based on elevators and moving ballast

Abstract

The application discloses a kind of based on horizontal rudder and mobile weight's underwater vehicle fixed height navigation control method, system and underwater vehicle.The method is perceived front terrain trend by obtaining vertical distance from bottom and oblique distance from bottom, and the slope angle of seabed terrain is calculated in combination with geometric configuration parameters;Further, the target pitch angle is calculated based on the slope angle and height tracking error;Finally, according to the size of attitude deviation and the slope angle, the corresponding cooperative control mode is selected, and the horizontal rudder and the mobile weight are driven to cooperate to maintain the set navigation height.The application solves the problems of high energy consumption under single rudder control, limited control boundary under complex terrain or low speed working condition and lack of redundancy mechanism through dynamic combination control of multiple mechanisms, significantly reduces the navigation resistance, and improves the fixed height stability, safety and endurance of underwater vehicle in complex seabed environment.

Description

Technical Field

[0001] This invention belongs to the field of underwater vehicle control technology, and particularly relates to an underwater vehicle altitude-holding navigation control method, system and underwater vehicle based on horizontal rudder and moving weight. Background Technology

[0002] Underwater vehicles are widely used in fields such as marine resource exploration, seabed topography mapping, and environmental monitoring. When performing tasks such as near-seabed observation, altitude-holding navigation is crucial for ensuring operational effectiveness and safety. Stable altitude-holding capability not only ensures the acquisition of clear, continuous, and consistent observation data but also effectively reduces the risk of collisions caused by topographical undulations, improving navigation stability and energy efficiency.

[0003] Existing research on altitude hold control largely focuses on terrain perception and path planning, typically employing a combination of thrusters and horizontal rudders to adjust altitude and attitude at the execution level. While this approach is simple in structure and highly responsive, it faces several challenges in complex terrain or prolonged bottom-fishing missions: First, the system is highly dependent on rudder surface adjustments, requiring frequent maneuvers during terrain changes and continuous yaw to maintain altitude at constant slopes, generating additional drag and limiting endurance. Second, single-rudder surface control has inherent capability limitations, potentially lacking sufficient torque for large pitch adjustments, and at low speeds, rudder surface control effectiveness decays with the square of speed, significantly reducing control capability. Finally, the system lacks effective alternative execution mechanisms; if rudder surfaces fail or their movements are restricted, instability risks arise. Furthermore, existing strategies are simplistic, making it difficult to achieve an optimal balance between energy consumption, accuracy, and responsiveness. For example, although patent CN201910618905.8 enhances the terrain prediction capability at the perception level, it still relies on a single horizontal rudder at the execution level, failing to solve the problems of high energy consumption and lack of redundancy mechanism. Once control fails, it will directly endanger navigation safety.

[0004] Therefore, developing a method for altitude-keeping navigation control of underwater vehicles based on horizontal rudders and moving weights, and realizing the coordinated and dynamic combination control of multiple mechanisms, is of great significance for improving the stability, safety and endurance of underwater vehicles in complex seabed environments. Summary of the Invention

[0005] To address the navigation safety risks arising from the high energy consumption, limited control boundaries in complex terrain or low-speed conditions, and lack of actuator redundancy mechanisms in existing technologies for altitude hold control of underwater vehicles relying solely on a single horizontal rudder, this invention provides an underwater vehicle altitude hold navigation control method, system, and underwater vehicle based on a horizontal rudder and a moving weight.

[0006] This invention is implemented as follows: a method for altitude-holding navigation control of an underwater vehicle based on a horizontal rudder and a moving weight, characterized by comprising the following steps: a) Obtain the vertical distance to the bottom of the underwater vehicle at its current position. and oblique distance from the bottom To perceive the changing trends of the terrain ahead; b) Based on the vertical bottom distance , oblique distance from bottom And the geometric configuration parameters of the altitude detection mechanism, to calculate the seabed topographic slope angle. ; c) Based on the seabed topographic slope angle And altitude tracking error, calculate target pitch angle ; d) Based on the target pitch angle Attitude deviation from the current pitch angle and the seabed topographic slope angle The size of the scale determines the corresponding cooperative control mode, and accordingly drives the horizontal rudder and the moving weight to cooperate in order to maintain the set target sailing altitude of the underwater vehicle.

[0007] In the above technical solution, preferably, in step b), the seabed topographic slope angle is calculated. The specific method is as follows: Calculate the horizontal projected distance between the two ranging points based on the installation angle of the altitude detection mechanism and the current pitch angle of the aircraft. and vertical height difference ; According to the formula Calculate the slope of the seabed topography ; Based on the seabed topographic slope Obtain the seabed topographic slope angle .

[0008] In the above technical solution, preferably, in step c), the target pitch angle is calculated. The formula is:

[0009] in, For high tracking error, This indicates that the height tracking error is calculated using proportional-integral-differential operations.

[0010] In the above technical solution, preferably, the cooperative control mode in step d) includes a fast cooperative control mode, the triggering condition of which is: when the attitude deviation exceeds a preset deviation threshold, and the seabed topographic slope angle... When the slope exceeds the preset threshold; In the rapid coordinated control mode, the horizontal rudder and the moving weight simultaneously adjust according to the target pitch angle. Perform the action to provide a rapid pitching torque.

[0011] In the above technical solution, preferably, in the rapid collaborative control mode, the total control torque is distributed to the rudder adjustment system and the center of gravity adjustment system by a preset allocation weight according to the physical response characteristics of the horizontal rudder and the moving weight.

[0012] In the above technical solution, preferably, the cooperative control mode in step d) includes a smooth substitution transition mode, the triggering condition of which is: when the attitude deviation is less than a preset deviation threshold; In the smooth replacement transition mode, the static attitude torque provided by the moving weight is gradually increased, while the deflection angle of the horizontal rudder is decreased, so that the moving weight can replace the horizontal rudder in bearing the steady-state torque demand caused by seabed topographic changes.

[0013] In the above technical solution, preferably, the collaborative control mode in step d) includes an emergency safety control mode, the triggering condition of which is: when the target pitch angle is detected. When the kinematic limits of the underwater vehicle are exceeded, or when the distance to an obstacle is detected to be less than a safety threshold; In the emergency safety control mode, the horizontal rudder, the moving weight, and the buoyancy adjustment system work together to perform obstacle avoidance or safety protection actions.

[0014] Compared with the prior art, the underwater vehicle altitude-holding navigation control method based on horizontal rudder and moving weight proposed in this invention has the following advantages: First, this method significantly reduces system energy consumption and improves endurance. Through multi-mechanism coordinated control, the center of gravity adjustment system can share the altitude control task with the control surface adjustment system, reducing the deflection angle and time of the horizontal rudder. It can even achieve a new equilibrium state of control surface return to center during stable navigation, thereby reducing the additional drag generated by control surface deflection, reducing the extra power consumption of the thruster to overcome drag, significantly reducing overall energy consumption, and extending endurance.

[0015] Secondly, this method improves the reliability and safety of the system. Addressing the single-point-of-failure risk of existing technologies, this invention provides a multi-redundant control mechanism. When the control surface adjustment fails, the center of gravity adjustment system can still continue to perform altitude adjustment tasks, avoiding control failure caused by the failure of a single actuator. Even if the performance of one mechanism degrades, other mechanisms can compensate, ensuring the continuity and safety of the mission. This invention employs a combination of vertical and oblique altimeter detection, simultaneously considering both current seabed safety and the ability to predict the terrain ahead. Therefore, compared to a single bottom altimeter, it is more suitable for constant-altitude navigation in complex seabed environments such as trench edges, steep slopes, and uneven seabeds, thereby improving terrain adaptability and operational stability under complex terrain conditions.

[0016] Furthermore, this method expands control capabilities and improves control precision. This invention, through multi-mechanism coordinated control, breaks through the upper limit of the horizontal rudder's control torque, achieving a greater range of pitch adjustment; the variable buoyancy system and center of gravity adjustment system can still work effectively at low speeds, compensating for the reduced control effect of the rudder surfaces at low speeds; simultaneously, the multiple mechanisms can achieve a combination of coarse and fine adjustments, improving control precision.

[0017] Finally, this control method is simple and easy to implement, making it highly applicable. The combined control technology of the control surface adjustment, variable buoyancy adjustment system, and center of gravity adjustment system does not require complex hardware modifications or sophisticated software algorithms, making it relatively easy to implement. Furthermore, its control logic is concise and clear, making it easy to integrate and apply on existing underwater vehicle platforms. This not only reduces development and maintenance costs but also accelerates the promotion and application of new technologies.

[0018] In summary, the multi-mechanism cooperative control method proposed in this invention achieves significant reduction in energy consumption, substantial improvement in system reliability, and comprehensive expansion of control capabilities through the coordinated operation of the control surfaces, variable buoyancy system, and center of gravity adjustment system. It has significant advantages such as high control precision, good response performance, and strong adaptability, providing an efficient, reliable, and practical technical solution for underwater vehicles to accurately determine altitude and navigate in complex seabed environments. It has important engineering application value and broad application prospects.

[0019] This invention proposes an altitude-holding navigation control system for underwater vehicles. This system is used to execute the aforementioned altitude-holding navigation control method for underwater vehicles based on horizontal rudders and moving weights. Its features include: The sensing module is used to obtain the vertical distance to the bottom and the oblique distance from the bottom of the underwater vehicle at its current position; The processing module is used to estimate the seabed topographic slope angle based on the vertical distance to the bottom, the oblique distance from the bottom, and the geometric configuration parameters of the sensing module, and to calculate the target pitch angle in combination with the altitude tracking error; The control module is used to output control commands based on the attitude deviation between the target pitch angle and the current pitch angle and the seabed topographic slope angle; The actuators, including a rudder adjustment system and a center of gravity adjustment system, are used to drive the horizontal rudder to deflect and the moving weight to shift, respectively, in response to the control commands.

[0020] In the above technical solution, preferably, the actuator further includes a buoyancy adjustment system; when the control module detects an emergency condition, it coordinates and schedules the rudder adjustment system, the center of gravity adjustment system, and the buoyancy adjustment system.

[0021] The present invention proposes an underwater vehicle, characterized in that it includes the above-mentioned underwater vehicle altitude-holding navigation control system. Attached Figure Description

[0022] Figure 1 This is a general structural diagram of the underwater vehicle used in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the installation of a dual altimeter detection assembly according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the underwater vehicle altimeter detection in Embodiment 2 of the present invention; Figure 4 This is a block diagram illustrating the principle of the multi-mechanism collaborative underwater vehicle altitude control method in Embodiment 2 of the present invention. Figure 5 This is a schematic diagram of the seabed topographic features in Embodiment 2 of the present invention; Figure 6 This is a flowchart illustrating the altitude-holding navigation process of the underwater vehicle in Embodiment 2 of the present invention. Figure 7 This is a simulation trajectory diagram of constant altitude navigation under continuously undulating terrain in Example 2 of the present invention; Figure 8 This is a timing diagram of the horizontal rudder angle under continuously undulating terrain in Example 2 of the present invention; Figure 9 This is a simulation trajectory diagram of a fixed-altitude navigation under a continuous slope terrain in Example 2 of the present invention; Figure 10 This is a timing diagram of the horizontal rudder angle under a continuous slope terrain in Example 2 of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] To address the problems of rapid energy consumption, insufficient altitude control capability, inadequate actuator redundancy, and weak terrain adaptability of traditional underwater vehicles (UVs) during altitude-holding navigation in complex seabed environments, this invention provides an underwater vehicle altitude-holding navigation control method based on horizontal rudders and a moving weight. This method combines a rudder adjustment system, a variable buoyancy system, and a center of gravity adjustment system, and, based on real-time terrain perception and attitude estimation results, achieves continuous adjustment of the underwater vehicle's pitch angle and multi-mechanism allocation control, thereby effectively improving the vehicle's safety, stability, and energy efficiency in complex seabed terrain. To further illustrate the overall structure and control logic of this invention, a detailed description is provided below with reference to the accompanying drawings: Example 1 like Figure 1 The diagram illustrates the underwater vehicle used in this invention. It is an underwater vehicle equipped with a propeller propulsion system, a rudder adjustment system, a variable buoyancy adjustment system, and a center of gravity adjustment system. The vehicle includes a fuselage 1, an altimeter 2 (obliquely downward detection), an altimeter 3 (vertically downward detection), a variable buoyancy adjustment unit 4, a control and status sensing unit 5, a center of gravity adjustment unit 6, an energy unit 7, a communication and positioning unit 8, a depth sensor 9, a propulsion unit 10, a vertical rudder 11, and a horizontal rudder 12. From bow to stern, these units are sequentially: a terrain detection unit (i.e., a dual altimeter combination), a variable buoyancy adjustment unit, a control unit, a center of gravity adjustment unit, a communication and positioning unit, a propulsion unit, a horizontal rudder, and a vertical rudder. The variable buoyancy adjustment system includes an oil pump motor, an oil pump, a valve block, a check valve, an internal oil tank, an external bladder solenoid valve, and a linear displacement sensor. The system calculates the buoyancy change generated by the buoyancy adjustment system based on data from the linear displacement sensor and estimates the attitude change of the vehicle. The center of gravity adjustment unit achieves attitude adjustment by moving a weight along the vehicle's axis. This unit includes a linear displacement sensor to acquire the direction and distance of the weight's movement, further estimating the magnitude of attitude change caused by the weight's movement. The control integration unit includes deck software, a main controller, attitude sensors, an inertial navigation unit, a pitch motor driver, a wireless module, a satellite communication module, a buoyancy unit motor driver, and a propulsion unit driver. The navigation and positioning unit includes: GPS positioning, Iridium communication and positioning, BeiDou communication and positioning, and a wireless data transmission module.

[0025] like Figure 2As shown, the seabed topography detection configuration applied in this invention is a topography detection scheme composed of dual altimeters. This dual altimeter layout allows the vehicle to acquire both current ground clearance information and advance awareness of terrain changes ahead, making it particularly suitable for constant-altitude navigation in complex and uneven seabed environments such as trenches, steep slopes, and locally undulating seabeds. Since a single altimeter may experience ranging deviations due to sonar beamwidth in complex terrain, local edges, or large pitch angle conditions, this invention employs a combination of vertical and oblique altimeter detection. By simultaneously utilizing current ground clearance information and forward terrain trend information, it avoids directly using the ranging results of a single altimeter as the control basis, thereby mitigating the adverse effects of single altimeter ranging deviations on terrain assessment. Altimeters are installed at the bow of the underwater vehicle to achieve real-time detection of the seabed topography. This includes a forward fairing 1, an oblique altimeter mounting plate 2, a bottom-aligning altimeter clamping ring 3, an altimeter fixing plate 4, a vertically downward-mounted altimeter 5, and an obliquely mounted altimeter 6. The forward fairing, with its streamlined design, reduces the vehicle's drag in the water, improving speed and energy efficiency; it also protects the altimeter installed inside. The altimeter 5 is used to obtain the vertical distance to the seabed directly below the vehicle in real time, while the angled altimeter 6 is used to detect the seabed morphology in the area ahead of the vehicle in advance. The angled altimeter mounting plate 2 is used to fix the altimeter that detects at an angle downwards and forwards. Preferably, the structural angle of the angled altimeter mounting plate 2 can be changed, thereby changing the angle between the two altimeters to adapt to the different mission requirements for detecting the seabed terrain ahead, improving the flexibility and adaptability of terrain perception. Figure 7 shows a schematic diagram of the rotatable adjustment range of the altimeter 6; the dotted line indicates the extreme position of the altimeter after angle adjustment, and its installation angle range is preferably 30° to 90°. The altimeter 6, which probes obliquely downwards, and the altimeter 5, which probes vertically downwards, are respectively fixedly mounted on the oblique altimeter mounting plate 2 and the bottom-aligning altimeter clamping ring 3 with screws. The mounting plate 2 and the clamping ring 3 are connected to the altimeter fixing plate 4, thereby achieving a reliable connection between the two altimeters and the fixed structure. The fixing plate 4 is connected to the bow structure of the vehicle with screws, completing the integrated installation of the altimeter and the vehicle body, ensuring that the altimeter has good structural stability and detection accuracy under complex sea conditions.

[0026] Example 2 This embodiment provides a method for altitude-holding navigation control of an underwater vehicle based on a horizontal rudder and a moving weight, including the following steps: Obtain the vertical distance to the bottom of the underwater vehicle at its current position. and oblique distance from the bottom To perceive the changing trends of the terrain ahead.

[0027] Based on vertical bottom distance , oblique distance from bottom And the geometric configuration parameters of the altitude detection mechanism, to calculate the seabed topographic slope angle. Calculate the seabed topographic slope angle. The specific method is as follows: Calculate the horizontal projected distance between two ranging points based on the installation angle of the altitude detection mechanism and the current pitch angle of the aircraft. and vertical height difference According to the formula Calculate the slope of the seabed topography According to the seabed topography and slope Obtain the seabed topographic slope angle .

[0028] Based on the slope angle of the seabed topography And altitude tracking error, calculate target pitch angle Calculate the target pitch angle. The formula is: , in, As a terrain feedback gain coefficient For high tracking error, This indicates that the height tracking error is calculated using proportional-integral-differential operations.

[0029] Based on the target pitch angle Attitude deviation from the current pitch angle and seabed topographic slope angle The size of the scale determines the corresponding cooperative control mode, which in turn drives the horizontal rudder and the moving weight to work together to keep the underwater vehicle at the set target altitude.

[0030] Among them, the cooperative control mode includes a rapid cooperative control mode, which is triggered when the attitude deviation exceeds a preset deviation threshold and the seabed topographic slope angle... When the slope threshold is exceeded; in rapid coordinated control mode, the horizontal rudder and the moving weight simultaneously adjust according to the target pitch angle. Perform actions to provide rapid pitch torque. In rapid coordinated control mode, based on the physical response characteristics of the horizontal rudder and the moving weight, the total control torque is distributed to the rudder adjustment system and the center of gravity adjustment system through preset distribution weights.

[0031] The cooperative control mode includes a smooth substitution transition mode, which is triggered when the attitude deviation is less than a preset deviation threshold. In the smooth substitution transition mode, the static attitude torque provided by the moving weight is gradually increased, while the deflection angle of the horizontal rudder is reduced, so that the moving weight can replace the horizontal rudder to bear the steady-state torque demand caused by seabed topographic changes.

[0032] The collaborative control mode also includes an emergency safety control mode, which is triggered when a target pitch angle is detected. When the underwater vehicle exceeds its kinematic limits, or when an obstacle is detected to be less than a safe threshold, in emergency safety control mode, the horizontal rudder, moving weight, and buoyancy adjustment system work together to perform obstacle avoidance or safety protection actions.

[0033] In this embodiment, specifically, as shown in... Figure 3 As shown, the method includes the following steps: 1. Altimeter information acquisition.

[0034] 1.1 Working principle of altimeter: An altimeter is an active underwater acoustic detection device that uses the principle of sound wave propagation to measure distance. Its working principle is based on the known speed of sound in water; by measuring the round-trip time of the sound wave from transmission to reception, the distance to the target object or seabed is calculated.

[0035] 1.2 Data Acquisition: Combination Figure 3 This invention describes the data acquisition information and the vehicle's status information during navigation using the method described in this invention. The vertically downward-mounted altimeter can obtain the vertical distance of the underwater vehicle to the bottom in each measurement. It is used to reflect the current ground clearance of the vehicle; the altimeter, which probes diagonally downwards, can obtain the diagonal ground clearance distance of the vehicle's front and lower surface with each measurement. These two altimeters are primarily used to reflect the changing trends of the local terrain ahead. Combining them helps the vehicle simultaneously ensure current safety above the seabed and the ability to predict the terrain ahead, even when operating on trench edges, steep slopes, and uneven seabeds. The installation angle between the two altimeters is... The pitch angle of the underwater vehicle is determined by the attitude sensor. Looking up is considered correct; 1.3 Data Processing: First, the original ranging values ​​are preprocessed to remove outliers and noise interference. In this embodiment, median filtering is selected for oblique ranging. and vertical distance measurement Perform filtering operations synchronously and set the filter window size. For any measurement point in the ranging sequence Extract its total amount before and after The set of nearest neighbors is used to calculate the median as the output: For data points at the beginning and end boundaries of the sequence, methods such as mirror extension and endpoint repetition can be used to fill in the window.

[0036] 2. Topographic feature extraction.

[0037] After completing the filtering and preprocessing of the raw ranging data, the terrain feature extraction stage begins, such as... Figure 5As shown, the aim is to estimate the equivalent slope of the underwater terrain and its corresponding terrain angle in real time based on the measurement results of dual altimeters and the current attitude information, so as to provide key input for the generation of target pitch attitude and the determination of control strategy.

[0038] 2.1 Calculation of horizontal projection and height difference: like Figure 4 As shown, the horizontal projected distance between the two ranging points Vertical height difference They are expressed as follows:

[0039]

[0040] 2.2 Calculation of terrain slope and terrain angle: Based on the horizontal projected distance of the above ranging points Vertical height difference The seabed slope of the current terrain can be calculated. (Local equivalent slope), this slope is used to describe the relative degree of terrain undulation between two measurement points, and is an important basis for judging the trend of uphill, downhill, or gentle terrain. The calculation formula is: Furthermore, the corresponding seabed topographic slope angle can be calculated. The calculation formula is: By estimating the slope of the local terrain, it is possible to avoid directly inputting single data into the control system, which to some extent alleviates the adverse effects of the ranging deviation caused by the sonar beam width of a single altimeter on altitude control.

[0041] 3. Target pitch angle generation 3.1 Control Objective Description: This control system aims to achieve two core objectives: altitude-holding navigation and terrain-following attitude. First, it must ensure that the vehicle can continuously maintain the desired altitude above the seabed during operation; the actual altitude of the vehicle above the seabed is denoted as... It is directly measured by a vertically downward-mounted altimeter, and the formula is: Set the desired flight altitude as Then the height error Represented as The control target is Simultaneously, to enhance the vehicle's terrain adaptability and ensure that its pitch angle dynamically matches the underwater terrain slope, the pitch angle should be made as consistent as possible with the seabed slope angle, i.e. .

[0042] 3.2 Target pitch angle generation: To achieve the unified goal of altitude hold control and terrain-following control, this system employs a target pitch angle generation strategy that integrates terrain slope feedforward and altitude error feedback. By fusing terrain change trends and the vehicle's real-time altitude error, the target pitch angle in the control command is generated comprehensively, as detailed below:

[0043] in, The target pitch angle is denoted by , and the input command for the attitude controller is denoted by . This is the seabed topographic slope angle, calculated from ranging data and attitude information, reflecting the current topographic trend; This is the feedforward gain coefficient, used to adjust the degree of influence of terrain changes on the target's attitude. , and The proportional, integral, and derivative coefficients form a PID controller with high error.

[0044] 4. Identification of special cases.

[0045] 4.1 Target pitch angle exceeds limit: If the target pitch angle is within the control range allowed by the system design, i.e. Then, proceed to step five, the collaborative control strategy determination stage, and perform routine attitude control.

[0046] like Figure 5 As shown in the seventh feature of the steep terrain, if the calculated target pitch angle is... If the slope is too large, the slope over-limit emergency control strategy will be triggered.

[0047] When in extreme uphill conditions At this time, the thrusters are turned off, the variable buoyancy system is adjusted to put the vehicle in the maximum safe buoyancy state, and the movable weight is moved towards the stern of the vehicle to raise the bow of the vehicle, forming a passive buoyancy climbing trend.

[0048] When in extreme downhill conditions When the altitude is fixed, the vehicle will switch from altitude-fixed navigation mode to depth-fixed navigation mode to ensure the safety of the vehicle. When the terrain angle enters a controllable range, it will switch back to altitude-fixed navigation mode.

[0049] 4.2 Detection data failure: like Figure 5 As shown in feature ⑧ (blind zone), if the oblique altimeter fails or there is no valid echo data in the current frame, the control system automatically enters the single altimeter working mode, temporarily disabling the attitude guidance control based on terrain slope and retaining only the altitude control item. At this time, the expression for generating the target pitch angle is:

[0050] Through the aforementioned degradation processing, when terrain detection information diagonally downwards is temporarily unavailable, the system can still rely on the vertical altimeter to maintain closed-loop control of the current altitude error, thereby ensuring the continuity and safety of altitude-keeping navigation control in complex seabed environments.

[0051] 4.3 Pitch angle exceeds limit: like Figure 5 As shown in the ninth characteristic of the attitude over-limit, if the current pitch angle Beyond safe range The system does not immediately enter emergency control mode, but first attempts to adjust the vehicle's pitch angle by moving the weight. If the weight moves 10mm axially toward the bow of the vehicle; The weight is then moved 10mm axially towards the stern of the vehicle, where 10mm represents 25% of the weight's one-way travel. This proportion balances the effectiveness of a single adjustment with the safety of the adjustment process. If the proportion is too small, the adjustment amount will be insufficient to change the attitude; if the proportion is too large, the excessive weight movement may cause new attitude impacts. Experiments have verified that adjustments within the range of 20% to 30% can achieve effective attitude recovery within three attempts, with 25% being the preferred value. This process is repeated three times, and after each adjustment, the pitch angle is reassessed to ensure it has returned to a safe range. If the attitude is not effectively recovered after three consecutive adjustments, the system determines that the current attitude is unrecoverable and immediately triggers an emergency control strategy. The variable buoyancy system is adjusted to bring the vehicle to its maximum safe buoyancy state, while the movable weight is moved towards the stern to raise the bow and ensure the vehicle's safety.

[0052] 5. Determining the control strategy.

[0053] like Figure 5 As shown in features one, two, three, four, five, and six, when navigating within a controllable pitch angle range, a coordinated control system using a moving weight and horizontal rudder is employed. This is achieved when generating the target pitch angle. Then, based on the target's pitch angle By rationally coordinating different actuators on the aircraft to work together to adjust its attitude, a constant altitude navigation can be achieved.

[0054] 5.1 Attitude Error Calculation: Based on the current actual pitch angle of the aircraft The attitude error is constructed between the pitch angle and the target. The expression is .

[0055] 5.2 Control adjustment output: A PID controller is used to control attitude error. Adjustments are made, and a master control command is output. , representing the required attitude adjustment range of the current system, is expressed as:

[0056] 5.3 Rapid Cooperative Control Mode: When the error is large (i.e.) , here (For pitch angle tolerance threshold), a fixed weighting method is used to... Simultaneously assigned to both the rudder surface and the weight block, the expression is:

[0057] The pitch angle allowable error threshold This is obtained through calibration. The calibration method is as follows: Apply pitch angle disturbances of different amplitudes in the experimental environment, activate only the center of gravity adjustment system for attitude recovery, and record the time required to recover to the target pitch angle. The maximum pitch angle error that can be recovered within 3 seconds is used as the threshold. Preferably, the recovery time is 3 seconds, but it can also be set to 2 to 5 seconds depending on the mission requirements. In the underwater vehicle calibration experiment applied in this embodiment, preferably, the pitch angle allowable error threshold is... It is 5°.

[0058] The 3-second recovery time calibration threshold is not an arbitrarily set empirical parameter, but a key technical parameter related to the pitch dynamics characteristics of the aircraft. When the aircraft relies solely on the moving weight for attitude recovery, its recovery process is jointly affected by the pitch moment of inertia, static stability margin, and the recovery torque and movement response speed provided by the center of gravity adjustment system. For aircraft with a large moment of inertia, a small static stability margin, or a slow movement response, the maximum initial pitch error that can be independently recovered by relying solely on the moving weight will decrease under the same recovery time requirement; conversely, the threshold can be increased accordingly. In this embodiment, the maximum moving speed of the moving battery pack is 1.5 mm / s, so a displacement of approximately 4.5 mm can be achieved within the preferred preset recovery time of 3 seconds, corresponding to a pitch angle adjustment capability of approximately 5°. Therefore, the 3s setting directly corresponds to the actual attitude adjustment capability of the mobile battery pack within a limited time. When the initial pitch error is small, the mobile battery pack can independently complete attitude recovery within this time. When the initial error exceeds a certain boundary, relying solely on the mobile battery pack for recovery will be too slow due to inertia and response speed limitations. In this case, the horizontal rudder needs to participate in rapid correction first to compensate for the response requirements under large error conditions. Subsequently, the mobile heavy block gradually takes over to complete steady-state maintenance. Therefore, the threshold... Essentially, it is the boundary parameter of the mobile battery pack's ability to independently recover attitude, used to distinguish between the fast cooperative control mode and the smooth alternative control mode, thereby achieving effective coordination between the fast response characteristics of the horizontal rudder and the stable adjustment characteristics of the mobile battery pack.

[0059] The For horizontal rudder angle and ; The distance the moving block travels relative to its initial position and Set the rudder angle that produces the lifting effect to positive and the opposite to negative; set the direction of movement that causes the moving weight to produce a pitching moment to positive and the opposite to negative. and These are the fixed control weight coefficients for the control surfaces and the moving weight, respectively. When the speed is greater than 2 knots, the rudder effect is high, and the speed should be increased appropriately. The value of the preferred one is... , To take advantage of the rapid response of the control surfaces; when the speed is less than 2 knots, the control effectiveness decreases, and the control surface should be increased. The value of the preferred one is... , It relies more on the active torque generated by the center of gravity adjustment. The optimal weight coefficient can be obtained by optimizing the control allocation algorithm after identifying the hydrodynamic model of the vehicle. To consider practical control applications, control commands are rounded down to the smallest executable unit for the horizontal rudder and the moving weight. As mentioned above, the horizontal rudder and the moving weight each play to their strengths: the rudder angle response is fast, and the weight generates a stable and continuous high torque. Together, they enable the aircraft to quickly approach the target pitch angle.

[0060] 5.4 Smooth Substitution Transition Mode: When the error enters the allowable range (i.e.) At this point, the aircraft has essentially reached the target pitch attitude, but the horizontal rudder still maintains a large deflection. To reduce drag generated by the rudder angle, a smooth substitution control phase between the rudder surface and the weight is initiated. Here, the aircraft no longer relies on the horizontal rudder and the moving weight to maintain attitude; instead, the weight gradually replaces the control effect of the rudder surface to achieve attitude stability and energy optimization. Each adjustment returns the rudder surface to center. Simultaneously, the heavy block moves. ,in The equivalent conversion coefficients for the attitude adjustment capability of the weight and horizontal rudder are calculated through torque balance, with the center of buoyancy as the origin of the body coordinate system. The calculation method is as follows:

[0061] in The mass of the moving heavy block; The density of water; The speed of the aircraft; The horizontal rudder area; The lift coefficient, This is the distance from the horizontal rudder to the center of buoyancy under neutral conditions. In engineering practice, an experimental calibration method can be used: in a water tank, while maintaining stable navigation at rated speed, apply a unit rudder angle independently. and a unit weight displacement And measure the steady-state pitch angle change caused by each independent operation. and Then this coefficient can be calibrated as This experimental calibration method can eliminate errors caused by inaccuracies in the theoretical model, improving the smoothness and accuracy of the alternative control. The updated control expression is:

[0062] Ultimately, the rudder angle returns to near zero, the weight moves to the appropriate position and holds, and the vehicle maintains the target pitch angle with minimal energy consumption and drag. If interference disrupts the stable navigation state... The system can then restart the fast collaboration mode.

[0063] 5.5 Simulation Results: The simulation results of an AUV traveling at a speed of 1.0 m / s in continuously undulating terrain are as follows: Figure 7 As shown, both the cooperative control strategy and the simple horizontal rudder control strategy have good altitude holding performance under continuously undulating terrain conditions, but from... Figure 8 The results show that the horizontal rudder angle is significantly reduced under the cooperative control method. Because the seabed slope angle is used as a feedforward term to generate the target pitch angle in advance, the vehicle can perform partial attitude pre-adjustment via the battery pack before the terrain change arrives. This reduces the frequent correction requirements of the horizontal rudder to sudden terrain changes under pure feedback control, thus reducing the frequency of horizontal rudder action. Compared to single-rudder control, the root mean square reduction of the horizontal rudder deflection angle under the cooperative control strategy is approximately 70.7%, and the peak rudder angle is reduced by approximately 57.8%. The horizontal rudder angle is released or even returns to its neutral position under the action of the battery pack, reducing the drag caused by continuous rudder angle deflection and lowering navigation energy consumption.

[0064] The simulation results of an AUV traveling at a speed of 0.5 m / s on a continuous slope are as follows: Figure 9As shown, at a terrain slope of 10°, both the coordinated control strategy and the single-rudder control strategy of the AUV can maintain a stable altitude. However, at a terrain slope of 20°, the single-rudder control of the AUV cannot meet the pitch requirements, and the rudder angle is always limited, resulting in high energy consumption. But the AUV can achieve constant altitude navigation by using coordinated control of the battery pack and the horizontal rudder. The horizontal rudder angle is only rapidly adjusted when the terrain changes, and then released or even eliminated under the action of the battery pack. This can reduce navigation drag and energy consumption, and also verify that the introduction of the battery pack can improve the capability boundary of the AUV's altitude navigation at low speeds.

[0065] The above results demonstrate that the cooperative control strategy described in this invention not only reduces the horizontal rudder deflection amplitude but also decreases the frequency of horizontal rudder maneuvers required during terrain following. Since the mobile battery pack performs static attitude adjustment during steady-state operation, while the horizontal rudder is primarily used for dynamic correction during terrain changes, energy consumption can be reduced and vehicle stealth improved while maintaining high performance.

[0066] Example 3 This embodiment provides an altitude-holding navigation control system for an underwater vehicle, which includes a sensing module, a processing module, a control module, and an actuator.

[0067] The sensing module is used to obtain the vertical distance to the bottom of the underwater vehicle at its current position. and oblique distance from the bottom The processing module is used to determine the vertical distance to the bottom. , oblique distance from bottom And the geometric configuration parameters of the sensing module to estimate the seabed topography slope angle. And calculate the target pitch angle by combining the altitude tracking error. The control module is used to determine the target pitch angle. Attitude deviation from the current pitch angle and seabed topographic slope angle Output control commands.

[0068] The actuators include a control surface adjustment system, a center of gravity adjustment system, and a buoyancy adjustment system. The control surface adjustment system drives the horizontal rudder deflection, and the center of gravity adjustment system drives the displacement of the moving weight, each responding to control commands output by the control module. When an emergency situation is detected, the control module coordinates the control surface adjustment system, the center of gravity adjustment system, and the buoyancy adjustment system to achieve attitude or altitude control of the underwater vehicle through the coupling of multiple mechanisms.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for altitude-holding navigation control of an underwater vehicle based on a horizontal rudder and a moving weight, characterized in that, Includes the following steps: a) Obtain the vertical distance to the bottom of the underwater vehicle at its current position. and oblique distance from the bottom To perceive the changing trends of the terrain ahead; b) Based on the vertical bottom distance , oblique distance from bottom And the geometric configuration parameters of the altitude detection mechanism, to calculate the seabed topographic slope angle. ; c) Based on the seabed topographic slope angle And altitude tracking error, calculate target pitch angle ; d) Based on the target pitch angle Attitude deviation from the current pitch angle and the seabed topographic slope angle The size of the scale determines the corresponding cooperative control mode, and accordingly drives the horizontal rudder and the moving weight to cooperate in order to maintain the set target sailing altitude of the underwater vehicle.

2. The underwater vehicle altitude-holding navigation control method based on horizontal rudder and moving weight according to claim 1, characterized in that, In step b), the seabed topographic slope angle is calculated. The specific method is as follows: Calculate the horizontal projected distance between the two ranging points based on the installation angle of the altitude detection mechanism and the current pitch angle of the aircraft. and vertical height difference ; According to the formula Calculate the slope of the seabed topography ; Based on the seabed topographic slope Obtain the seabed topographic slope angle .

3. The underwater vehicle altitude-holding navigation control method based on horizontal rudder and moving weight according to claim 1, characterized in that, In step c), the target pitch angle is calculated. The formula is: in, For high tracking error, This indicates that the height tracking error is calculated using proportional-integral-differential operations.

4. The underwater vehicle altitude-holding navigation control method based on horizontal rudder and moving weight according to claim 1, characterized in that, The cooperative control mode described in step d) includes a fast cooperative control mode, which is triggered when the attitude deviation exceeds a preset deviation threshold and the seabed topographic slope angle... When the slope exceeds the preset threshold; In the rapid coordinated control mode, the horizontal rudder and the moving weight simultaneously adjust according to the target pitch angle. Perform the action to provide a rapid pitching torque.

5. The underwater vehicle altitude-holding navigation control method based on horizontal rudder and moving weight according to claim 4, characterized in that, In the rapid coordinated control mode, based on the physical response characteristics of the horizontal rudder and the moving weight, the total control torque is distributed to the rudder surface adjustment system and the center of gravity adjustment system through preset allocation weights.

6. The underwater vehicle altitude-holding navigation control method based on horizontal rudder and moving weight according to claim 1, characterized in that, The cooperative control mode described in step d) includes a smooth substitution transition mode, which is triggered when the attitude deviation is less than a preset deviation threshold. In the smooth replacement transition mode, the static attitude torque provided by the moving weight is gradually increased, while the deflection angle of the horizontal rudder is decreased, so that the moving weight can replace the horizontal rudder in bearing the steady-state torque demand caused by seabed topographic changes.

7. The underwater vehicle altitude-holding navigation control method based on horizontal rudder and moving weight according to claim 1, characterized in that, The collaborative control mode described in step d) includes an emergency safety control mode, the triggering condition of which is: when the target pitch angle is detected. When the kinematic limits of the underwater vehicle are exceeded, or when the distance to an obstacle is detected to be less than a safety threshold; In the emergency safety control mode, the horizontal rudder, the moving weight, and the buoyancy adjustment system work together to perform obstacle avoidance or safety protection actions.

8. An underwater vehicle altitude-holding navigation control system, wherein the system is used to execute the underwater vehicle altitude-holding navigation control method based on horizontal rudder and moving weight as described in any one of claims 1-7, characterized in that, include: The sensing module is used to obtain the vertical distance to the bottom of the underwater vehicle at its current position. and oblique distance from the bottom ; The processing module is used to determine the vertical distance to the bottom. , oblique distance from bottom And the geometric configuration parameters of the sensing module are used to estimate the seabed topographic slope angle. And calculate the target pitch angle by combining the altitude tracking error. ; The control module is used to determine the target pitch angle. Attitude deviation from the current pitch angle and the seabed topographic slope angle Output control commands; The actuators, including a rudder adjustment system and a center of gravity adjustment system, are used to drive the horizontal rudder to deflect and the moving weight to shift, respectively, in response to the control commands.

9. The underwater vehicle altitude-holding navigation control system according to claim 8, characterized in that, The actuator also includes a buoyancy adjustment system; When an emergency is detected, the control module coordinates and schedules the rudder adjustment system, the center of gravity adjustment system, and the buoyancy adjustment system.

10. An underwater vehicle, characterized in that, Includes the underwater vehicle altitude hold navigation control system as described in claim 8 or 9.

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