AUV (Autonomous Underwater Vehicle) motion control method and system for asymmetric head and tail X rudders

Abstract

The invention discloses a motion control method and system for an AUV (Autonomous Underwater Vehicle) with asymmetric head and tail X rudders. The method comprises the following steps: acquiring the current depth, pitch angle, horizontal position and course angle of the AUV; based on the target value and the current value of each degree of freedom, respectively calculating depth, pitching, horizontal position and course control quantity through independent control channels; mapping and distributing the control quantity to X-shaped control surfaces at the head part and the tail part of the AUV through a preset rudder angle distribution strategy, and generating a corresponding rudder angle instruction; and finally, a control surface executing mechanism is driven, so that the cooperative accurate control of the AUV on the depth, the horizontal position, the pitching and the course is realized. Through independent control channels and decoupled rudder angle distribution, the AUV equipped with the asymmetric head and tail X rudders can realize independent and cooperative control of multiple degrees of freedom in a wide speed domain range, especially under medium and high speed working conditions, and the maneuverability and task adaptability are effectively improved.

Description

Technical Field

[0001] This invention belongs to the technical field of autonomous underwater vehicle (AUV) control, specifically relating to an asymmetric bow-and-tail X-rudder AUV motion control method and system. Background Technology

[0002] Autonomous underwater vehicles (AUVs) are important tools for marine exploration, scientific research, engineering operations, and military applications. When performing underwater missions, AUVs need to achieve precise motion control, including depth control, horizontal position control, pitch attitude control, and heading control. This requires them to have the ability to manipulate multiple degrees of freedom, such as heave, sway, pitch, and yaw.

[0003] Currently, to achieve the above motion control, the common actuator configurations and control methods for AUVs mainly include the following categories: Main thruster plus rudder configuration: This is the most conventional configuration. The main thruster provides forward propulsion (puff control), and the rudder surfaces at the tail (usually a cruciform or X-rudder) generate turning and pitch moments, thus achieving coarse control of heading and pitch. However, this configuration is a typical underactuated system. Its fundamental drawback is that it cannot independently and simultaneously control all degrees of freedom. For example, when performing depth control, it is difficult to stabilize the pitch angle at any desired value; when performing horizontal position tracking, it is also impossible to simultaneously and independently adjust the heading angle to any angle. The control is highly coupled, resulting in a severe lack of flexibility.

[0004] Main thruster plus auxiliary thruster (vertical thruster / side thruster) configuration: To overcome underactuation issues, some AUVs are equipped with auxiliary thrusters, such as vertical thrusters (VSTs) and side thrusters (SSTs). This configuration provides good direct force control at low speeds or when hovering, thus enabling independent control of heave, yaw, and yaw. However, this approach has two significant drawbacks: First, the propulsion efficiency of the auxiliary thrusters decreases sharply as the AUV's forward speed increases, leading to a significant deterioration or even failure of maneuverability at medium and high speeds; second, the channels created to install the auxiliary thrusters disrupt the smooth, streamlined shape of the hull, increasing drag and severely impacting the AUV's endurance.

[0005] Bow leveling rudder (or bow rudder): To improve depth and pitch control, some AUVs are equipped with a leveling rudder in the bow. This enhances control over heave and pitch degrees of freedom. However, this configuration still cannot provide direct control over sway degree of freedom. Further adding a vertical rudder to the bow to attempt to gain sway or heading control could lead to mechanical interference with related equipment during bottom docking, deployment, and recovery operations, resulting in operational risks and design complexity.

[0006] In summary, existing AUV actuator configurations all have limitations. They either fail to meet the requirements for independent and coordinated control of multiple degrees of freedom, or have inherent defects in efficiency, drag, or structural interference. Therefore, there is an urgent need for a new control method and corresponding actuator configuration that can enable AUVs to achieve efficient and decoupled coordinated and precise control of depth, horizontal position, pitch, and heading over a wide speed range (especially in medium- and high-speed conditions) without significantly sacrificing hydrodynamic performance. Summary of the Invention

[0007] In view of this, the present invention proposes an asymmetric bow and stern X-rudder AUV motion control method and system, which configures the asymmetric bow and stern X-rudder to enable the AUV to simultaneously possess the maneuverability of degrees of freedom such as heave, sway, pitch, and bow roll, and designs a control strategy to achieve depth, horizontal position, pitch, and heading control.

[0008] The technical solution for implementing the present invention is as follows: An asymmetric bow-and-stern X-rudder AUV motion control method includes the following steps: Acquire the current motion status information of the AUV, which includes at least depth, pitch angle, horizontal position, and heading angle; Based on the preset target values ​​of each degree of freedom and the corresponding current motion state information, the independent control quantities of each degree of freedom are calculated through mutually independent control channels. The independent control quantities include at least depth control quantity, pitch control quantity, horizontal position control quantity and heading control quantity. The calculated independent control quantities are mapped and allocated to each control surface of the X-shaped rudder arranged at the front and rear of the AUV through a preset rudder angle allocation strategy, thereby generating corresponding front X-rudder rudder angle commands and rear X-rudder rudder angle commands. The head X-rudder angle command and tail X-rudder angle command drive the corresponding control surface actuators to achieve coordinated control of the AUV's depth, horizontal position, pitch and heading.

[0009] Furthermore, the independent control channels include a depth control channel, a pitch control channel, a horizontal position control channel, and a heading control channel.

[0010] Furthermore, the preset rudder angle allocation strategy includes: The depth control and horizontal position control are used as inputs to the virtual bow cross rudder, and converted into linkage rudder angle commands for the actual bow X-shaped rudder through the first rudder angle allocation matrix. The pitch control and heading control values ​​are used as inputs to the virtual tail cross rudder, and are converted into linked rudder angle commands for the actual tail X-shaped rudder through the second rudder angle allocation matrix.

[0011] Furthermore, the first rudder angle allocation matrix and the second rudder angle allocation matrix have the same structure, both being transformation matrices that convert the two orthogonal rudder angle control quantities of the virtual cross rudder into a pair of diagonally linked X rudder angle control quantities.

[0012] Furthermore, the rudder angle allocation matrix is ​​specifically as follows:

[0013] The matrix input consists of two orthogonal rudder angle control values ​​for the virtual cross rudder, and the output consists of a pair of diagonally linked X-rudder rudder angle commands.

[0014] Furthermore, the horizontal rudder angle control of the virtual bow cruciform is determined by the depth control, and its vertical rudder angle control is determined by the horizontal position control; the horizontal rudder angle control of the virtual tail cruciform is determined by the pitch control, and its vertical rudder angle control is determined by the heading control.

[0015] Furthermore, in each control channel, the independent control quantity is calculated using a PID control algorithm based on the deviation between the target value and the current value of the corresponding degree of freedom.

[0016] An asymmetric bow-and-stern X-rudder AUV motion control system includes: The sensor unit is used to acquire the current motion status information of the AUV; The controller is configured to execute the control method as described in any one of claims 1 to 7, generating rudder angle commands; The actuators, including the main thruster, the bow X-shaped rudder, and the tail X-shaped rudder, are used to respond to the rudder angle command to maneuver the AUV.

[0017] Beneficial effects: 1. By designing independent control channels for the four key degrees of freedom—depth, horizontal position, pitch, and yaw—and employing a rudder angle allocation strategy based on a virtual cross rudder, this invention achieves decoupled control of each degree of freedom. This enables the AUV to simultaneously and independently adjust its depth, horizontal position, pitch attitude, and yaw angle, solving the fundamental problem that traditional main thruster plus rudder underactuated configurations cannot simultaneously meet the requirements of multi-degree-of-freedom control.

[0018] 2. Compared with schemes that rely on auxiliary propulsion units (vertical thrusters / side thrusters), this invention relies entirely on the hydrodynamics generated by the main thrusters and the bow and stern X-shaped control surfaces for control. The control efficiency increases with speed, so this scheme can maintain efficient and strong maneuverability at medium and high speeds, overcoming the defect of auxiliary thrusters whose efficiency drops sharply with increasing speed, leading to a deterioration in maneuverability.

[0019] 3. By adopting an X-shaped rudder arrangement instead of the traditional bow cross rudder (especially the bow vertical rudder), this invention not only gives the AUV bow direct heave and sway control force, but also effectively avoids the problem of mechanical interference between the bow vertical rudder and related devices in specific operational scenarios such as bottom docking, deployment and recovery, thereby improving the practicality and safety of the system.

[0020] 4. This invention takes the classic PID control algorithm as an example and combines four-channel independent calculation with a diagonally linked rudder angle allocation matrix to construct a complete control logic. This strategy has a clear structure and well-defined steps, decomposing the complex multi-degree-of-freedom cooperative control problem into independent controller design and deterministic mathematical transformations. This facilitates engineering implementation, parameter tuning, and subsequent optimization, and has strong practical value. Attached Figure Description

[0021] Figure 1 This is a flowchart of the method of the present invention.

[0022] Figure 2 This is a schematic diagram of the X-rudder arrangement at the tail.

[0023] Figure 3 This is a schematic diagram of the arrangement of the X-rudder at the front.

[0024] Figure 4 This is a schematic diagram of the algorithm of the present invention. Detailed Implementation

[0025] This invention proposes an asymmetric bow-and-stern X-rudder AUV motion control method and system. The asymmetric bow-and-stern X-rudder AUV has a rotating hull and is equipped with a navigation system and a depth sensor. The navigation system outputs horizontal position, pitch angle, and heading angle, while the depth sensor outputs the navigation depth value. The motion actuators include a main thruster, a bow X-rudder, and a stern X-rudder, with the AUV's stern facing the bow. The specific arrangement is as follows: Figure 2 and Figure 3 As shown.

[0026] Based on the propulsion system providing pitch thrust to generate speed, depth, horizontal position, pitch, and heading are controlled via bow and stern X-rudders. Each channel independently calculates control parameters, which are then converted into individual rudder angle values ​​through rudder angle allocation, such as... Figure 1 and Figure 4 As shown.

[0027] Each channel uses a PID control algorithm to calculate the control quantity based on the target value and the current value, as shown in the following formula.

[0028]

[0029] In the formula, For depth control quantity, , , These are depth control parameters; For pitch control, , , These are pitch control parameters; This is a horizontal position control quantity. , , These are the horizontal position control parameters; For heading control, , , For heading control parameters; For depth deviation, For pitch deviation, To control the deviation in horizontal position, The heading control deviation is calculated using the following formula.

[0030]

[0031] In the formula, For the depth target value, This is the current depth value; For pitch target value, This is the current pitch value; For the target value, This is the current value of the horizontal position; The target heading value, This is the current heading value.

[0032] Assuming the AUV has virtual bow and stern cross rudders, and neglecting differential rudders, the bow and stern horizontal rudder angles are: and Looking from the stern towards the bow, the following is considered positive, with the bow and stern horizontal rudder angles being [value missing]. and Looking from the tail towards the head, the right side is considered the correct direction.

[0033] The X-shaped rudder has four rudders at the bow and four at the stern, using a diagonal linkage. That is, the upper right rudder is linked to the lower left rudder (numbered 1), with turning to the lower right being positive; the upper left rudder is linked to the lower right rudder (numbered 2), with turning to the lower left being positive. Therefore, the bow rudder is... and The tail rudder is and .

[0034] The method for calculating the bow and stern X-shaped rudders from the virtual bow and stern cross rudders is as follows.

[0035]

[0036] The bow rudder is used as the active rudder to control depth and horizontal position, and the stern rudder is used as the passive rudder to control pitch and heading. The virtual bow and stern cross rudder is as follows.

[0037]

[0038] The rudder angle distribution for the bow and stern X-shaped configuration is as follows.

[0039]

[0040] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An asymmetric bow-and-stern X-rudder AUV motion control method, characterized in that, Includes the following steps: Acquire the current motion status information of the AUV, which includes at least depth, pitch angle, horizontal position, and heading angle; Based on the preset target values ​​of each degree of freedom and the corresponding current motion state information, the independent control quantities of each degree of freedom are calculated through mutually independent control channels. The independent control quantities include at least depth control quantity, pitch control quantity, horizontal position control quantity and heading control quantity. The calculated independent control quantities are mapped and allocated to each control surface of the X-shaped rudder arranged at the front and rear of the AUV through a preset rudder angle allocation strategy, thereby generating corresponding front X-rudder rudder angle commands and rear X-rudder rudder angle commands. The head X-rudder angle command and tail X-rudder angle command drive the corresponding control surface actuators to achieve coordinated control of the AUV's depth, horizontal position, pitch and heading.

2. The asymmetric bow-and-stern X-rudder AUV motion control method according to claim 1, characterized in that, The independent control channels include a depth control channel, a pitch control channel, a horizontal position control channel, and a heading control channel.

3. The asymmetric bow-and-stern X-rudder AUV motion control method according to claim 1 or 2, characterized in that, The preset rudder angle allocation strategy includes: The depth control and horizontal position control are used as inputs to the virtual bow cross rudder, and converted into linkage rudder angle commands for the actual bow X-shaped rudder through the first rudder angle allocation matrix. The pitch control and heading control values ​​are used as inputs to the virtual tail cross rudder, and are converted into linked rudder angle commands for the actual tail X-shaped rudder through the second rudder angle allocation matrix.

4. The asymmetric bow-and-stern X-rudder AUV motion control method according to claim 3, characterized in that, The first rudder angle allocation matrix and the second rudder angle allocation matrix have the same structure. Both are transformation matrices that convert the two orthogonal rudder angle control quantities of the virtual cross rudder into a pair of diagonally linked X rudder angle control quantities.

5. The asymmetric bow-and-stern X-rudder AUV motion control method according to claim 4, characterized in that, The rudder angle allocation matrix is ​​specifically as follows: The matrix input consists of two orthogonal rudder angle control values ​​for the virtual cross rudder, and the output consists of a pair of diagonally linked X-rudder rudder angle commands.

6. The asymmetric bow-and-stern X-rudder AUV motion control method according to claim 3, characterized in that, The horizontal rudder angle control of the virtual bow cruciform is determined by the depth control, and its vertical rudder angle control is determined by the horizontal position control; the horizontal rudder angle control of the virtual tail cruciform is determined by the pitch control, and its vertical rudder angle control is determined by the heading control.

7. The asymmetric bow-and-stern X-rudder AUV motion control method according to claim 1 or 2, characterized in that, In each control channel, the independent control quantity is calculated using a PID control algorithm based on the deviation between the target value and the current value of the corresponding degree of freedom.

8. An asymmetric bow-and-stern X-rudder AUV motion control system, characterized in that, include: The sensor unit is used to acquire the current motion status information of the AUV; The controller is configured to execute the control method as described in any one of claims 1 to 7, generating rudder angle commands; The actuators, including the main thruster, the bow X-shaped rudder, and the tail X-shaped rudder, are used to respond to the rudder angle command to maneuver the AUV.

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