Building method for six-degree-of-freedom ROV operation simulation platform

Abstract

Disclosed in the present invention is a building method for a six-degree-of-freedom ROV operation simulation platform. The platform comprises a comprehensive control platform, a trainer control system, a marine environment simulation system, a simulation platform solution system, an ROV manipulation system, a display system, and a database storage system. The building method comprises: step (1), calculating a hydrodynamic coefficient and a delay function of a mother ship according to a mother ship profile; step (2), using a beam model to establish a finite difference model for an umbilical cable and a mooring line, and calculating the morphology and tension at two ends of each of the umbilical cable and the mooring line; step (3), establishing boundary conditions of the umbilical cable and the mooring line in a coupling model; step (4), modeling a mooring line management system by using a bar element model; step (5), a nonlinear ROV maneuverability equation; and step (6), establishing a mechanical arm dynamics model considering an ROV pose. The present invention improves the ROV operation efficiency, reduces the risk of device damage, and solves the problem of a poor training effect due to inconsistency between a simulator and an actual situation of a real ROV underwater operation.

Description

A method for building a six-degree-of-freedom ROV operation simulation platform Technical Field

[0001] The invention relates to a method for building a six-degree-of-freedom ROV operation simulation platform, and belongs to the field of ships. Background Art

[0002] Since the ocean is an important reserve base for modern oil and gas resources, the reserves of offshore oil and gas resources have increased by more than 2 times from shallow water, deep water to ultra-deep water, and the development of deepwater and ultra-deepwater oil and gas resources has gradually become a global focus, thus placing higher requirements on the installation of offshore structures and the use of oil production and storage equipment. Remotely controlled underwater tethered robots (ROVs) play an important role in the installation and use of offshore structures and equipment. During the installation phase of structures and equipment, ROVs are responsible for observing the installation status, inspecting the installation area, releasing and recovering moorings, and other operations. During the production process, they are responsible for monitoring underwater equipment and operating deepwater underwater equipment. Due to the complex underwater environment, safely and efficiently operating ROVs and completing operational tasks has become a major problem. In order to improve operational efficiency and reduce the risk of equipment damage, this patent invents a simulation platform for a six-degree-of-freedom ROV operating system.

[0003] The existing ROV simulation and operation simulation systems have the following deficiencies:

[0004] 1. Limitations of operating scenarios: The simulation modules of existing systems simulate and control ROVs based on the ROV and the local operating environment. The operating scenarios are limited to the ROV and its surrounding waters. However, actual ROV operations involve a variety of structures in both surface and underwater scenarios.

[0005] 2. Lack of factors affecting ROV operations: In existing ROV simulation and operation simulation systems, the factors affecting ROV operations only include cables, robotic arms and ocean currents. However, in actual operations, the ROV operation system also includes the mother ship, umbilical cable, tether management system (TMS) and tether. Environmental factors also include the waves and sea winds encountered by the mother ship and the ocean currents encountered by the repeater.

[0006] 3. ROV motion response is unrealistic: Since the existing ROV simulation and operation simulation systems lack factors such as surface scenes, mother ships and TMS, they are unable to simulate the impact of the mother ship's movement in wind and waves on the underwater TMS and ROV.

[0007] 4. The hydrodynamic coefficients during ROV deployment operations depend on the structural form of the ROV and TMS. Existing research rarely considers the dynamics of complex structures. The hydrodynamic parameters used in simulations cannot take into account the mutual interference of the hydrodynamic forces of local components of complex structures. As a result, there is a lack of effective time-domain modeling and estimation methods for extreme sea conditions that consider the complex morphology of the structure.

[0008] Summary of the Invention

[0009] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a method for constructing a six-degree-of-freedom ROV operation simulation platform. In addition to being able to realistically reflect the six-degree-of-freedom motion of the ROV, it also realistically simulates the impact of the surface mother ship, umbilical cable and robotic arm on the ROV operation system composed of them.

[0010] Technical Solution: To solve the above technical problems, the present invention provides a method for building a six-degree-of-freedom ROV operation simulation platform. The simulation platform comprises four parts: an HLA distributed integrated development framework, a system input module, a real-time simulation module, and a system output module. The system input module includes an integrated control platform and an instructor control system. The real-time simulation module includes an ocean environment simulation system, a simulation platform solution system, and an ROV manipulation system. The system output module includes a display system and a database storage system. Each system provides various services described in the interface specification through a runtime support system (RTI). The RTI is responsible for communication between systems to achieve interoperability.

[0011] The integrated control platform activates the instructor control system, marine environment simulation system, simulation platform solution system, ROV control system, and display system through the network. The instructor control system issues training subjects, intervenes in simulation platform equipment and operating system parameters during training, and can set faults and emergency situations to train operators' response capabilities, and arrange the positions and initial states of artificial underwater oil trees, manifolds, underwater blowout preventers, sea pipes, and templates.

[0012] The ocean environment simulation system releases ocean current, wave and sea wind environment, and can set ocean environment conditions to train operators' adaptability, and input the display system to perform three-dimensional display of the ocean environment;

[0013] The simulation platform solution system receives data from the instructor control system and the marine environment simulation system, simulates the motion of the mother ship and A-frame at sea, and solves the three-dimensional motion of the umbilical cable; receives data from the ROV control system, calculates the ROV's six-degree-of-freedom motion and the manipulator's motion; and calculates the motion or shape of underwater targets. The simulation platform solution system inputs the display system to display the third-person perspective of the operation system and the ROV's visual field.

[0014] The ROV control system is connected to the simulation platform solution system through a network communication, so as to collect the operator's operations and instructions and display the ROV posture and monitor view;

[0015] The display system receives simulation platform solution system data and is used to display the third perspective of the mother ship, umbilical cable, ROV, manipulator operation status and marine environment. The display system can change the perspective position to follow the movement of the mother ship and ROV.

[0016] The database storage system includes database storage and real-time drawing of mother ship, cable, TMS and ROV simulation status data, network transmission, track curve, speed curve, including the following steps:

[0017] Step 1: Calculate the hydrodynamic coefficient and time delay function of the mother ship based on the mother ship's line, and establish the time domain motion equation based on the mother ship's layout and A-frame position.

[0018] Where: M0 is the sum of the mother ship mass and the additional mass; C RB0 and C A0 are the centripetal force and Coriolis force matrices of the rigid body and fluid respectively; D0 is the damping matrix; K0(t-τ) is the time delay function, where t is the simulation time and γ is the integral variable; U is the longitudinal speed of the mother ship; e1 is the longitudinal unit vector; G0 is the stiffness matrix of the mother ship; τ wind0 is the wind load; τ wave0 is the wave load; v r0 is the relative speed of the mother ship and the ocean current in the body coordinate system, τ cable0 is the tension of the umbilical cable, which is expressed in the seakeeping coordinate system as: τ cable0 =[F x0 ,F y0 ,F z0 ,F z0 y f0 -F y z f0 ,F0z f0 -F z0 x f0 ,F y0 x f0 -F x0 y f0 ] T (15)

[0019] Among them F x0 ,F y0 ,F z0 is the tension at the top of the umbilical cable in the direction of the seakeeping coordinate system, calculated by the umbilical cable simulation module based on the beam model, (x f0 ,y f0 ,z f0 ) is the coordinate of the top of the A-frame relative to the center of gravity of the mother ship in the direction of the seakeeping coordinate system, and the linear velocity of the top of the A-frame in the seakeeping coordinate system is

[0020] Where U0, V0, W0 are the longitudinal, transverse and vertical velocities of the top of the A-frame in the seakeeping coordinate system, r is the radius vector of the top of the A-frame, and are the linear velocity and angular velocity of the mother ship in the body coordinate system respectively.

[0021] Step 2: Use the beam model to build a finite difference model of the umbilical cable and mooring cable to calculate the shape and tension at both ends:

[0022] Create a beam model of the umbilical and mooring cables:

[0023] Where: Y is the axial strain ε of the umbilical cable, normal stress S n , tangential stress S b , axial velocity u, normal velocity v, tangential velocity w, axial and normal rotation angles φ and θ of the microelement, torsion rate Ω1, normal curvature Ω2, tangential curvature Ω3; s is the length of the microelement of the umbilical cable; t is the simulation time; H is the coefficient matrix related to the mass, additional mass, diameter, axial and normal rotation angles, velocity and axial strain of the microelement of the umbilical cable; P is the coefficient matrix related to mass, velocity and stiffness; Q is the coefficient matrix related to S n 、S b , Ω1, Ω2, Ω3, vectors related to the axial and normal rotation angles, velocity, flow rate, resistance coefficient, and stiffness of the infinitesimal element;

[0024] Step 3: Establish boundary conditions for the umbilical and mooring cables in the coupled model

[0025] 1) Mechanical boundary: The umbilical cable and mooring cable are connected to the mother ship, TMS and ROV. In the direction of the seakeeping coordinate system, the tension on the top of the umbilical cable or mooring cable on the mother ship, TMS and ROV is:

[0026] Among them F x(0,n) ,F y(0,n) ,F z(0,n) are the longitudinal, transverse and vertical tensions in the seakeeping coordinate system, respectively; E is the Young's modulus of the umbilical cable; A is the cross-sectional area of ​​the umbilical cable; the subscript (0, n) represents the bottom or top parameter, 0 represents the top parameter, and n represents the bottom parameter;

[0027] 2) Motion boundary: The speeds of the two ends of the umbilical cable are consistent with the speeds of the A-frame top and the TMS connection. The speeds of the two ends of the mooring cable are consistent with the speeds of the ROV and TMS. The speeds of the two ends of the umbilical cable or mooring cable in the seakeeping coordinate system are:

[0028] Among them U t(0,n) ,V t(0,n) ,W t(0,n) are the longitudinal, transverse and vertical velocities of the seakeeping coordinate system, respectively. The boundary conditions of the mooring cable and the umbilical cable are calculated in a similar way. The top and end of the mooring cable are TMS and ROV, respectively.

[0029] 3) Establish a finite difference model of the mooring cable and umbilical cable:

[0030] Where: α h and α p is the difference coefficient; H i and H i-1 is the coefficient matrix related to the front and rear microelement and the umbilical cable microelement and mass, additional mass, diameter, axial and normal rotation angles of the microelement, velocity and axial strain; P i and P i-1 is the coefficient matrix related to mass, velocity and stiffness of front and rear microelements and umbilical cable microelements; Q i and Q i-1 The front and back infinitesimals and S n 、S b , Ω1, Ω2, Ω3, the axial and normal rotation angles of the infinitesimal element, velocity, flow rate, resistance coefficient, and stiffness vector; Y i and Y i-1 is the vector Y of the previous and next infinitesimal elements; △t is the time step; △s is the length of the infinitesimal element;

[0031] Step 4: Use the rod element model to model the mooring management system, considering the tension effect of the mooring cable and umbilical cable:

[0032] Where: M1 is the sum of TMS mass and additional mass; C1 is the centripetal force and Coriolis force matrix of TMS; D 11 and D 21 are the first-order and second-order hydrodynamic coefficients; K1(x) is the stiffness matrix of TMS; q 1r is the flow load on TMS; q 1cable and q 1tether are the tensions at the bottom end of the umbilical cable and the top end of the mooring cable, respectively. The calculation method is consistent with formula (7); x is the displacement of the TMS; is the speed of TMS; is the acceleration of the TMS; t is the simulation time; the hydrodynamic coefficient of the rod element is determined according to the form and shielding relationship of the discrete structure (cylinder or plate, etc.), taking into account the hydrodynamic characteristics that depend on depth changes; compared with the time-domain simulation method with fixed hydrodynamic coefficients, this model considers the mutual influence between the TMS and ROV structures and the influence of immersion depth, and more accurately calculates the hydrodynamic forces of the TMS and ROV during the process of passing through the free liquid surface.

[0033] Step 5: Nonlinear ROV maneuverability equation, considering the effects of tether tension and manipulator arm:

[0034] Where: M RB2 is the mass matrix of ROV; C RB2ROV's centripetal and Coriolis force matrices; M A2 is the additional mass matrix of ROV, including 36 main diagonal and off-diagonal additional masses and additional moments of inertia; N2 is the drag coefficient matrix; g2 is the restoring force matrix; τ 2thrust is the thrust of the propeller; τ 2tether is the mooring tension, and the calculation method is consistent with formula (7); τ2manipulator is the force exerted by the manipulator base on the ROV; v2 is the ROV speed; is the acceleration; v r2 The speed of the ROV relative to the ocean current; is the relative acceleration;

[0035] The N2 is expressed as an asymmetric hydrodynamic force, specifically:

[0036] Where F vv and F v|v| The second-order symmetric and asymmetric hydrodynamic coefficients, respectively;

[0037] Step 6: Establish a dynamic model of the robotic arm considering the ROV posture:

[0038] The forward kinematics of the robot simulation module involves finding the roll angle of the robot arm given a linear motion. The Denavit-Hartenbert notation is used to establish the generalized coordinates of the kinematic model and the calculation is performed using the Newton iteration method. The inverse kinematics involves finding the linear motion of the end given the roll angle of the link. The nonlinear dynamic model of the robot arm link is:

[0039] Where M i is the additional mass matrix of connecting rod i; C i is the fluid centripetal force and Coriolis force matrix of connecting rod i; G i (q i ) is the restoring force matrix of connecting rod i; τ Di is the damping of connecting rod i; τ i It is the driving force of the robotic arm; q i are the angular acceleration, angular velocity, and rotation angle of the connecting rod i, respectively. The boundary condition of the manipulator is that the base and the ROV end have equal velocity. The force on the ROV from the manipulator base n is:

[0040] The meanings of the characters in the formula are the same as those in formula (13), and the subscripts j and k represent the j-th and k-th connecting rods, respectively.

[0041] Preferably, the simulation platform solution system includes a main control module, a mother ship simulation module, an umbilical cable simulation module, an ROV simulation module, and a robotic arm simulation module, wherein:

[0042] The mother ship simulation module receives data from the ocean environment simulation system and the umbilical cable simulation module, and calculates the motion and position of the mother ship and the A-frame based on the time-domain ship seakeeping equation;

[0043] The umbilical cable simulation module receives data from the ocean current module, the mother ship simulation module and the ROV simulation module, calculates the shape and tension of the umbilical cable and the mooring cable based on the beam model and the finite difference method, and calculates the position and posture of the repeater TMS based on the rod element model;

[0044] The ROV simulation module receives data from the ocean current module, the umbilical cable simulation module, and the robotic arm simulation module, and calculates and controls the ROV's posture based on a six-degree-of-freedom nonlinear asymmetric maneuverability model;

[0045] The manipulator simulation module receives data from the ROV simulation module and calculates joint velocity, acceleration and force based on a dynamic model established based on the Newton-Euler method.

[0046] Preferably, the ROV maneuvering system includes an ROV control module, an ROV cable management system control module, and an ROV vision module, wherein:

[0047] The ROV control module includes an ROV body control module and a manipulator control module to control the movement of the ROV and the manipulator respectively;

[0048] The ROV cable management system control module includes an umbilical cable retraction and deployment system and a mooring cable retraction and deployment control, which respectively control the retraction and deployment activities of the A-frame and TMS;

[0049] The ROV control system converts digital input and output signals and analog input signals into corresponding engineering quantities through the system processor, realizing interactive simulation between humans and equipment.

[0050] In view of the shortcomings of the prior art, the overall solution of the present invention is implemented as follows:

[0051] 1. Establish an ocean environment simulation system including sea breeze module, ocean wave module, and ocean current module to simulate water surface scenes, including average wind speed, significant wave height, characteristic period, and current velocity distribution. This provides parameters for calculating wind, wave, and current loads on various structures on the surface and underwater.

[0052] 2. Establish a mathematical model of the mothership, a finite-difference model of the mooring cable and umbilical cable based on a beam model, and a dynamic model of the mooring management system based on a rod element model. These mathematical models can calculate the wind, wave, and current loads on various structures. Establish a simulation platform solution system to calculate the motion and forces of the mothership, TMS, and cables.

[0053] 3. The umbilical cable and mooring cable are coupled with the mother ship and ROV through kinematic and dynamic boundary conditions to simulate the impact of ship and TMS motion on ROV navigation and operation, thereby improving the realism of ROV operation simulation.

[0054] The technical problem further solved by the present invention is that the marine environment simulation system includes a sea breeze module, a wave module, a current module, and a display module. The sea breeze module calculates the sea breeze distribution in the operating sea area based on the sea condition information released by the instructor control system, and provides the wind speed and wind direction of the mother ship position to the simulation platform solution system. The wave module calculates the wave distribution in the operating sea area based on the sea condition information released by the instructor control system, and provides the wave surface time history and direction of the mother ship position to the simulation platform solution system. The current module calculates the distribution of ocean current along the depth in the operating sea area based on the sea condition information released by the instructor control system, and provides the ocean current speed and direction of the mother ship, ROV and umbilical cable position to the simulation platform solution system. The display module includes a wind and wave spectrum, a current speed profile, and a wind, wave and current time history display window. The signal output ends of the other three are connected to the signal input end of the display module for displaying instrument data.

[0055] The technical problem further solved by the present invention is that the simulation platform solution system includes a main control module, a mother ship simulation module, an umbilical cable simulation module, an ROV simulation module, and a manipulator simulation module. The main control module receives data from the ocean environment simulation system, the mother ship simulation module, the umbilical cable simulation module, the ROV simulation module, and the manipulator simulation module, and is used for operation scheduling and data management of the operation simulation platform. The mother ship simulation module receives data from the ocean environment simulation system and the umbilical cable simulation module, and calculates the movement and position of the mother ship and the A-frame based on the time-domain ship wavekeeping equation. The umbilical cable simulation module receives data from the ocean current module, the mother ship simulation module, and the ROV simulation module, calculates the shape and tension of the umbilical cable and the mooring cable based on the beam model, and calculates the repeater posture based on the rod element model. The ROV simulation module receives data from the ocean current module, the umbilical cable simulation module, and the manipulator simulation module, and calculates and controls the posture of the ROV based on a six-degree-of-freedom nonlinear maneuverability model. The manipulator simulation module receives data from the ROV simulation module, and calculates the joint velocity, acceleration, and force based on the dynamic model established by the Newton-Euler method.

[0056] The technical problem further solved by the present invention is that the ROV control system includes an ROV control module, an ROV cable management system control module, and an ROV vision module. The ROV control module is used for interaction between the ROV operator and the ROV, and its components include an ROV control stick, a navigator control screen, a five (seven) function manipulator control handle, a power control panel, and a camera adjustment handle. The components respectively control the ROV attitude, monitor the attitude sonar compass, control the five (seven) function manipulator arms, monitor the thruster status, and adjust the ROV camera viewing angle. The ROV cable management system (TMS) control module controls the umbilical and mooring cable of the A-frame and TMS, and its components include a winch control panel, a winch control stick, a TMS control slider, and a navigator control screen. The components respectively modify the winch speed, control the mooring cable retraction and extension, control the TMS retraction and extension, and monitor the mooring umbilical and TMS status. The ROV vision module receives data from the simulation platform solution system and the camera adjustment handle to display the ROV first-person perspective.

[0057] The present invention further solves a technical problem in that the display system includes a model simulation module and an environmental simulation module. The model simulation module dynamically renders the operation scene in real time based on the six-degree-of-freedom motion information of the mother ship, TMS, and ROV, as well as the shape and motion information of the mooring cable and umbilical cable, input from the simulation platform solution system. The environmental simulation module creates ocean and atmospheric effects based on the sea condition information input from the marine environment simulation system.

[0058] The instructor control system of the present invention publishes training subjects, adjusts simulation platform equipment and operating system parameters during training, and can set fault and emergency situations to train operators' response capabilities. It also arranges the positions and initial states of artificial underwater structures such as underwater Christmas trees, manifolds, underwater blowout preventers, sea pipes, and templates. The ocean environment simulation system publishes ocean currents, waves, and wind conditions and can set special ocean environmental conditions to train operators' response capabilities. The input display system displays the ocean environment in three dimensions. The simulation platform solution system receives data from the instructor control system and the ocean environment simulation system, simulates the motion of the offshore mother ship and A-frame, and solves the three-dimensional motion of the umbilical cable. It receives data from the ROV control system, calculates the ROV's six-degree-of-freedom motion and the manipulator's motion, and calculates the motion or shape of underwater targets. The simulation platform solution system inputs the display system to display the operating system's third-person perspective and the ROV's visual field. The ROV control system and the simulation platform solution system establish a network communication link to collect operator operations and instructions and display the ROV's position and monitor visual field. The display system receives data from the simulation platform's solution system and is used to display a third-person perspective of the mother ship, umbilical cable, ROV, manipulator operating status, and the marine environment. The display system can change its viewing angle to follow the movements of the mother ship and ROV. This invention can be applied to training ROV operators on operating procedures and underwater operation skills. It can also simulate, rehearse, and evaluate the ROV, repeater, mother ship, umbilical cable, and mooring cable, improving ROV operational efficiency and reducing the risk of equipment damage. It also addresses the issue of poor training effectiveness caused by the simulator not matching the actual ROV underwater operation conditions.

[0059] Beneficial effects: The advantages of the present invention compared with the prior art are:

[0060] 1. The six-degree-of-freedom ROV operation simulation platform of the present invention includes an integrated control platform, an instructor control system, a marine environment simulation system, a simulation platform solution system, an ROV control system, and a display system, forming a complete ROV operation simulation system that can meet the needs of teaching, coupled system research, ROV simulation experiments, and ROV operation training.

[0061] 2. The ocean environment simulation system of the present invention includes a sea breeze module, a wave module, and an ocean current module, which can realize the simulation of a real, complex and random ocean environment, restore the multi-body motion coupling during ROV underwater operations, and be close to the actual situation of real ROV underwater operations, thus solving the problem of poor training effect.

[0062] 3. The simulation platform solution system of the present invention includes a main control module, a mother ship simulation module, an umbilical cable simulation module, an ROV simulation module, and a robotic arm simulation module to realize the simulation of multiple mutually coupled objects in ROV operations.

[0063] 4. The ROV simulation module in the simulation platform solution system of the present invention calculates the six-degree-of-freedom motion of the ROV based on a maneuverability model that includes nonlinear asymmetric hydrodynamics, more accurately reflecting the impact of the ROV's asymmetric geometric shape on its hydrodynamic characteristics, and improving the accuracy of ROV motion simulation.

[0064] 5. The complex TMS and ROV were discretized using rod elements of the same size, and the deployment and recovery processes were simulated. Each rod element possessed the hydrodynamic coefficients of the discretized structure, including the drag coefficient and the inertia coefficient. Considering how these structural coefficients vary with immersion depth and motion frequency, the Morrison equation was used to calculate the rod element's hydrodynamic forces, including wave forces, drag, and slamming forces. A time-domain dynamic model was then used to calculate the structure's motion. This method accounts for the impact of immersion depth and the structure's effect on local and global hydrodynamic forces, allowing for more accurate calculation of the time-frequency dynamic response of the TMS and ROV during their gradual entry into the water. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 is a structural diagram of a six-degree-of-freedom ROV operation simulation platform;

[0066] Figure 2 is a diagram of the instructor control system structure;

[0067] Figure 3 is a structural diagram of the marine environment simulation system;

[0068] Figure 4 is a diagram showing the structure of the settlement system on the simulation platform;

[0069] Figure 5 is a coupled dynamics model of the simulation platform;

[0070] Figure 6 is a structural diagram of the ROV control system. DETAILED DESCRIPTION

[0071] The present invention will be further described below with reference to the accompanying drawings.

[0072] As shown in Figures 1 to 6, a six-degree-of-freedom ROV operation simulation platform consists of four parts: the HLA distributed integrated development framework, a system input module, a real-time simulation module, and a system output module. The system input module includes an integrated control platform and an instructor control system. The real-time simulation module includes an ocean environment simulation system, a simulation platform solution system, and an ROV manipulation system. The system output module includes a display system and a database storage system. Each system provides the services described in the interface specification through the runtime support system (RTI). RTI is responsible for communication between systems to achieve interoperability, including:

[0073] The integrated control platform activates the instructor control system, marine environment simulation system, simulation platform solution system, ROV control system, and display system through the network. The instructor control system issues training subjects, intervenes in simulation platform equipment and operating system parameters during training, and can set faults and emergency situations to train operators' response capabilities, and arrange the positions and initial states of artificial underwater oil trees, manifolds, underwater blowout preventers, sea pipes, and templates.

[0074] The ocean environment simulation system releases ocean current, wave and sea wind environment, and can set ocean environment conditions to train operators' adaptability, and input the display system to perform three-dimensional display of the ocean environment;

[0075] The simulation platform solution system receives data from the instructor control system and the marine environment simulation system, simulates the motion of the mother ship and A-frame at sea, and solves the three-dimensional motion of the umbilical cable; receives data from the ROV control system, calculates the ROV's six-degree-of-freedom motion and the manipulator's motion; and calculates the motion or shape of underwater targets. The simulation platform solution system inputs the display system to display the third-person perspective of the operation system and the ROV's visual field.

[0076] The ROV control system is connected to the simulation platform solution system through a network communication, so as to collect the operator's operations and instructions and display the ROV posture and monitor view;

[0077] The display system receives simulation platform solution system data and is used to display the third perspective of the mother ship, umbilical cable, ROV, manipulator operation status and marine environment. The display system can change the perspective position to follow the movement of the mother ship and ROV.

[0078] A method for building a six-degree-of-freedom ROV operation simulation platform includes the following steps: Step 1: The integrated control platform activates the instructor control system, ocean environment simulation system, simulation platform solution system, ROV operation system, and display system via the network. During operation, the operation simulation platform monitors the hardware status to ensure safe and stable operation of the hardware equipment during the ROV operation simulation.

[0079] Step 2: According to the instructor's instructions, as shown in Figure 2, the instructor control system includes the following steps:

[0080] The instructor control system announces the training subjects: The training area and environment are determined, including the reference altitude, the one-hour average wind speed and frequency at the reference altitude; significant wave height, characteristic period, directional spread function; water depth, and tidal velocity. The initial positions and attitudes of the mother ship, ROV, and TMS are announced. The training tasks are assigned, including parameter settings for the training scenario, underwater man-made structures, and training time.

[0081] 2. Monitor the training process. When the ROV operation simulation platform is running, the instructor can operate and control the start, pause, continue, and end of the training to complete a complete ROV operation simulation training.

[0082] 3. Set up emergency situations, including: sudden changes in ocean and atmospheric environment, and equipment failure of ROV operation system.

[0083] 4. Evaluation and reproduction, including recording the training process, conducting comprehensive evaluation of the driver's operation based on the recorded data of the ROV operation simulation process, and loading the recorded training process;

[0084] Step 3: The ocean environment simulation system includes a sea breeze module, a wave module, a current module, and a display module, as shown in Figure 3. The steps involved are as follows:

[0085] 1. The sea breeze module generates a wind spectrum and calculates the wind speed distribution history based on the reference height, one-hour average wind speed at the reference height, and frequency released by the instructor control system.

[0086] 2. The wave module generates wave spectrum and directional spectrum according to the significant wave height, characteristic period and directional expansion function issued by the teacher control system, and calculates the wave height time history.

[0087] 3. The ocean current module calculates the wind-induced velocity component based on the wind speed, and calculates the velocity distribution history based on the water depth and tidal velocity released by the instructor control system.

[0088] 4. The display module creates weather effects such as sunny, rainy, and foggy days based on the atmospheric and sea condition data transmitted by the instructor control system, and simulates the effects of the sun, moon, sky, light, and horizon. Based on the data from the wave module, it creates ocean effects, including wave surface undulations and the color of the ocean under sunlight / moonlight.

[0089] Step 4: The simulation platform solution system includes the main control module, mother ship simulation module, umbilical cable simulation module, ROV simulation module, and robotic arm simulation module. The steps involved are as follows:

[0090] The main control module is used for operation scheduling and data management of the ROV operation simulation platform, as shown in Figure 5. The signal output terminals of the mother ship simulation module, umbilical cable simulation module, ROV simulation module, and manipulator simulation module are connected to the signal input terminals of the main control module to simulate the posture and operation of the mother ship, TMS, and ROV. The mother ship simulation module receives data from the marine environment simulation system and the umbilical cable simulation module, and calculates the motion and position of the mother ship and A-frame based on the time-domain ship seakeeping equation. The umbilical cable simulation module receives data from the ocean current module, mother ship simulation module, and ROV simulation module, calculates the shape and tension of the umbilical cable and mooring cable based on the beam model, and calculates the repeater posture based on the rod element model. The ROV simulation module receives data from the ocean current module, umbilical cable simulation module, and manipulator simulation module, and calculates and controls the ROV posture based on a six-degree-of-freedom nonlinear asymmetric maneuverability model. The manipulator simulation module receives data from the ROV simulation module and calculates joint velocity, acceleration, and force based on a dynamic model established using the Newton-Euler method.

[0091] 2 Establish a mathematical model of the mother ship:

[0092] The mother ship simulation module calculates the mother ship motion based on the time domain seakeeping equation. The mother ship velocity is transformed from the body coordinate system to the seakeeping coordinate system:

[0093] Where: and η are the velocity and displacement of the mother ship in the seakeeping coordinate system, and are linear velocity and angular velocity respectively; J Θ (η) is the transformation matrix between the mother ship's seakeeping coordinate system and the body coordinate system; v0 is the mother ship's velocity in the body coordinate system.

[0094] Establish the six-degree-of-freedom dynamic model of the mother ship in the body coordinate system:

[0095] Where: M0 is the sum of the mother ship mass and the additional mass; C RB0 and C A0 are the centripetal force and Coriolis force matrices of the rigid body and fluid respectively; D0 is the damping matrix; K0(t-τ) is the time delay function, where t is the simulation time and γ is the integral variable; U is the longitudinal speed of the mother ship; e1 is the longitudinal unit vector; G0 is the stiffness matrix of the mother ship; τ wind0 is the wind load; τ wave0 is the wave load; v r0 is the relative speed of the mother ship and the ocean current in the body coordinate system; τ cable0 is the tension of the umbilical cable, expressed in the seakeeping coordinate system as: τ cable0 =[F x0 ,Fy0 ,F z0 ,F z0 y f0 -F y z f0 ,F0z f0 -F z0 x f0 ,F y0 x f0 -F x0 y f0 ] T (29)

[0096] Among them F x0 ,F y0 ,F z0 is the tension at the top of the umbilical cable in the direction of the seakeeping coordinate system, calculated by the umbilical cable simulation module based on the beam model, (x f0 ,y f0 ,z f0 ) is the coordinate of the top of the A-frame relative to the center of gravity of the mother ship in the direction of the seakeeping coordinate system. The linear velocity of the top of the A-frame in the seakeeping coordinate system is:

[0097] Where U0, V0, W0 are the longitudinal, transverse and vertical velocities of the top of the A-frame in the seakeeping coordinate system, r is the radius vector of the top of the A-frame, and are the linear velocity and angular velocity of the mother ship in the body coordinate system respectively.

[0098] 3. The umbilical cable simulation module is based on the beam model and uses the finite difference method to calculate the shape of the umbilical cable and the mooring cable, the tension at both ends of the TMS and the tension τ at the A-frame end. cable0 .

[0099] 1) Establish beam models for umbilical cables and mooring cables:

[0100] Where: Y is the axial strain ε of the umbilical cable, normal stress S n , tangential stress S b , axial velocity u, normal velocity v, tangential velocity w, axial and normal rotation angles φ and θ of the microelement, torsion rate Ω1, normal curvature Ω2, tangential curvature Ω3; s is the length of the microelement of the umbilical cable; t is the simulation time; H is the coefficient matrix related to the mass, additional mass, diameter, axial and normal rotation angles, velocity and axial strain of the microelement of the umbilical cable; P is the coefficient matrix related to mass, velocity and stiffness; Q is the coefficient matrix related to S n 、S b , Ω1, Ω2, Ω3, vectors related to the axial and normal rotation angles, velocity, flow rate, resistance coefficient, stiffness, etc. of the infinitesimal element.

[0101] 2) Establish boundary conditions for umbilical cables and mooring cables

[0102] The top of the umbilical cable is the mother ship, and the bottom is the TMS. The tension at the top and bottom in the seakeeping coordinate system is:

[0103] Among them F x(0,n) ,F y(0,n) ,F z(0,n) are the longitudinal, transverse and vertical tensions in the seakeeping coordinate system, E is the Young's modulus of the umbilical cable, A is the cross-sectional area of ​​the umbilical cable, and the subscript (0, n) represents the bottom or top parameter, 0 represents the top parameter, and n represents the bottom parameter.

[0104] The speeds of both ends of the umbilical cable at the connection points with the top of the A-frame and the TMS are consistent. The speeds of both ends of the umbilical cable in the direction of the seakeeping coordinate system are:

[0105] Among them U t(0,n) ,V t(0,n) ,W t(0,n) are the longitudinal, transverse and vertical velocities in the seakeeping coordinate system, respectively. The boundary conditions of the mooring cable and the umbilical cable are calculated in a similar way, with the top and end of the mooring cable being the TMS and the ROV, respectively.

[0106] 3) Establish a finite difference model of the mooring cable and umbilical cable:

[0107] Where: α h and α p is the difference coefficient; H i and H i-1 is the coefficient matrix related to the front and rear microelement and the umbilical cable microelement and mass, additional mass, diameter, axial and normal rotation angles of the microelement, velocity and axial strain; P i and P i-1 is the coefficient matrix related to mass, velocity and stiffness of front and rear microelements and umbilical cable microelements; Q i and Q i-1 The front and back infinitesimals and S n 、S b , Ω1, Ω2, Ω3, vectors related to the axial and normal rotation angles, velocity, flow rate, resistance coefficient, stiffness, etc. of the infinitesimal element; Y i and Y i-1 is the vector Y of the previous and next infinitesimal elements; △t is the time step; △s is the length of the infinitesimal element.

[0108] 4) Calculate the hydrodynamics of TMS and ROV deployment based on the rod element model. The dynamic model of the rod element:

[0109] Where: M1 is the sum of TMS mass and additional mass; C1 is the centripetal force and Coriolis force matrix of TMS; D 11 and D 21 are the first-order and second-order hydrodynamic coefficients; K1(x) is the stiffness matrix of TMS; q 1r is the flow load on TMS; q 1cable and q 1tether are the tensions at the bottom end of the umbilical cable and the top end of the mooring cable, respectively. The calculation method is consistent with formula (7); x is the displacement; for speed; acceleration; t is the simulation time. The hydrodynamic coefficients of the rod elements are determined based on the discrete structure form and shielding relationship (cylinder or plate, etc.), accounting for depth-dependent hydrodynamic characteristics. Compared to time-domain simulation methods with fixed hydrodynamic coefficients, this model considers the interaction between the TMS and ROV structures and the influence of immersion depth, allowing for more accurate calculation of the hydrodynamic forces of the TMS and ROV as they pass through the free surface.

[0110] The ROV simulation module calculates the motion of the ROV based on nonlinear asymmetric maneuverability equations and the ROV six-degree-of-freedom dynamic model:

[0111] Where: M RB2 is the mass matrix of ROV; C RB2 ROV's centripetal and Coriolis force matrices; M A2 is the additional mass matrix of ROV, including 36 main diagonal and off-diagonal additional masses and additional moments of inertia; N2 is the drag coefficient matrix; g2 is the restoring force matrix; τ 2thrust is the thrust of the propeller; τ 2tether is the mooring tension, and the calculation method is consistent with formula (7); τ2manipulator is the force exerted by the manipulator base on the ROV; v2 is the ROV speed; is the acceleration; v r2 The speed of the ROV relative to the ocean current; is the relative acceleration.

[0112] The N2 is expressed as an asymmetric hydrodynamic force, specifically:

[0113] Where F vv and F v|v| are the second-order symmetric and asymmetric hydrodynamic coefficients, respectively.

[0114] The forward kinematics of the 5-axis robot simulation module involves finding the roll angle of the robot arm given a linear motion. Denavit-Hartenbert notation can be used to establish the generalized coordinates of the kinematic model, which can be calculated using the Newton iteration method. Inverse kinematics involves finding the linear motion of the end point given the roll angle of the link. The nonlinear dynamic model of the robot arm link is:

[0115] Where M i is the additional mass matrix of connecting rod i; C i is the fluid centripetal force and Coriolis force matrix of connecting rod i; G i (q i ) is the restoring force matrix of connecting rod i; τ Di is the damping of connecting rod i; τ i It is the driving force of the robotic arm; q i are the angular acceleration, angular velocity and rotation angle of the connecting rod i respectively. The boundary condition of the manipulator is that the speed of the base and the ROV end are equal. The force on the ROV from the manipulator base n is:

[0116] The meanings of the characters in the formula are the same as those in formula (13), and the subscripts j and k represent the j-th and k-th connecting rods, respectively.

[0117] Step 5: The ROV control system, as shown in Figure 6, includes an ROV control module, an ROV cable management system control module, and an ROV vision module. The ROV control module includes an ROV body control module and a manipulator control module, which control the movement of the ROV and manipulator, respectively. The ROV cable management system control module includes an umbilical cable retraction and deployment system and a tether retraction and deployment control system, which respectively control the retraction and deployment of the A-frame and TMS. The ROV control system converts digital input and output signals and analog input signals into corresponding engineering quantities through the system processor, realizing interactive simulation between humans and equipment.

[0118] In order to verify the effectiveness and effect of the method of the present invention, an example is given for illustration, which includes the following steps:

[0119] 1. Manually start the integrated control platform, and remotely start the instructor control system, marine environment simulation system, simulation platform solution system, ROV control system, display system, etc. through the network, check whether the software and hardware of each system are running stably, and continue to detect the operation process of the simulation platform.

[0120] 2. After the system is started, the instructor operates the instructor control system to input the atmospheric and oceanic conditions of the ROV operating area. The instructor determines the initial positions and attitudes of the mother ship, ROV, and TMS, and arranges the operational tasks, including setting parameters for the training scene, underwater man-made structures, and training time. The ROV operation simulation platform then begins running, monitoring the ROV simulation training process through the display system. During the ROV operation simulation, the instructor can pause, resume, or end the simulation as needed, and can also configure emergency situations such as sudden changes in the oceanic and atmospheric conditions and ROV operation system equipment failures.

[0121] Based on the instructor's instructions, the Sea Breeze Module uses the Wave Module, Ocean Wave Module, and Ocean Current Module to establish the wind field, waves, and currents in the ROV's operating area. This generates a time history of wind speed distribution, wave elevation, and current distribution, and transmits this data to the response module in the simulation platform's solution system. The Display Module uses atmospheric and ocean data input from the instructor's control system to create weather effects such as sunny, rainy, and foggy days, simulating the sun, moon, sky, lighting, and horizon. Data from the Wave Module is used to create ocean effects, including wave undulations and ocean colors under sunlight and moonlight.

[0122] Within the simulation platform's solution system, the mothership simulation module, umbilical cable simulation module, ROV simulation module, and robotic arm simulation module receive initial simulation information from the instructor. Combined with environmental data calculated by the sea breeze module, they calculate the mothership's motion using the time-domain seakeeping equation; the umbilical cable and mooring cable's shape, tension, and TMS motion using beam and rod element models; the ROV's motion using nonlinear asymmetric maneuverability equations; and the robotic arm's motion using a dynamic model based on the Newton-Euler method. The main control module schedules the execution of other modules and manages data transfer between them.

[0123] After the instructor issues the start command for the simulation, the pilot uses the ROV control system and the umbilical cable retraction and deployment system to control the A-frame to release the umbilical cable. Once the ROV and TMS reach the predetermined depth for the mission, the pilot uses the ROV control module and the tether retraction and deployment control module to control the ROV's movement and the tether release from the TMS. Once the ROV reaches the vicinity of the underwater target, the pilot uses the manipulator control module to control the manipulator's movement and complete the underwater mission. Once the mission is complete, the pilot uses the ROV control system to retract the tether, ROV, and TMS. During the simulation, the pilot uses the ROV visual module to observe the ROV's surroundings.

[0124] 6 The instructor finishes the operation simulation and uses the operation process recorded by the instructor control system to conduct a comprehensive evaluation of the driver's operation, or loads the recorded training process and other operations.

[0125] 7 After the training and evaluation are completed, the integrated control platform shuts down all systems and the entire simulation platform ends.

[0126] The present invention can arbitrarily match various operation tasks under different environments and operation objects according to the ROV underwater operation training requirements, and restore the actual operation effects of ROV, TMS, mother ship, mooring cable and umbilical cable in underwater operation as much as possible, so that the driver can get a better sense of driving immersion.

[0127] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for building a six - degree - of - freedom ROV operation simulation platform. The simulation platform includes four major parts: HLA distributed integrated development framework, system input module, real - time simulation module, and system output module. The system input module includes an integrated control platform and an instructor control system. The real - time simulation module includes an ocean environment simulation system, a simulation platform solution system, and an ROV control system. The system output module includes a display system and a database storage system. Each system provides various services described in the interface specification through the Run - Time Infrastructure (RTI). The RTI is responsible for communication between systems to achieve interoperability, where: The integrated control platform turns on the instructor control system, ocean environment simulation system, simulation platform solution system, ROV control system, and display system through the network. The instructor control system issues training subjects, intervenes in the parameters of the simulation platform equipment and operation system during training, and can set faults and emergencies, and arrange the positions and initial states of artificial underwater Christmas trees, manifolds, subsea blowout preventers, submarine pipelines, and templates. The ocean environment simulation system publishes sea current, sea wave, and sea wind environments, and can set ocean environment conditions, and inputs them to the display system for three - dimensional display of the ocean environment. The simulation platform solution system receives data from the instructor control system and the ocean environment simulation system, simulates the movement of the offshore mother ship and A - frame, and solves the three - dimensional movement of the umbilical cable. It receives data from the ROV control system, calculates the six - degree - of - freedom movement of the ROV and the movement of the manipulator. The simulation platform solution system inputs to the display system for third - perspective display of the operation system and ROV vision display respectively. The ROV control system establishes a network communication link with the simulation platform solution system, which is used to collect the operations and instructions of the operator, and display the ROV pose and monitor vision. The display system receives data from the simulation platform solution system, which is used to display the third - perspective of the mother ship, umbilical cable, ROV, manipulator operation status, and ocean environment. The database storage system includes database storage and real - time drawing of the simulation states of the mother ship, cable, TMS, and ROV, network transmission, track curves, and speed curves. It is characterized by the following steps: Step 1: Calculate the hydrodynamic coefficients and time delay function of the mother ship according to the mother ship hull lines, and establish the time-domain motion equation based on the layout of the mother ship and the position of the A-frame. Where: M0 is the sum of the mother ship mass and the added mass; C RB0 and C A0 are the centripetal force and Coriolis force matrices of the rigid body and the fluid respectively; D0 is the damping matrix; K0(t - τ) is the time-delay function, where t is the simulation time and γ is the integration variable; U is the longitudinal speed of the mother ship; e1 is the longitudinal unit vector; G0 is the stiffness matrix of the mother ship; τ wind0 is the wind load; τ wave0 is the wave load; v r0 is for the mother ship in the co-moving The relative velocity with respect to the ocean current in the coordinate system, τ cable0 is the tension of the umbilical cable, which is labeled in the seakeeping coordinate system directions as: τ cable0 = [F x0 , F y0 , F z0 , F z0 y f0 -F y z f0 , F0z f0 -F z0 x f0 , F y0 x f0 -F x0 y f0 T (2)​ Among which F x0 , F y0 , F z0 is the tension of the top of the umbilical cable in the seakeeping coordinate system direction, calculated by the umbilical cable simulation module based on the beam model, (x f0 , y f0 , z f0 ) is the coordinate of the top of the A-frame relative to the center of gravity of the mother ship in the seakeeping coordinate system direction, and the linear velocity of the top of the A-frame in the seakeeping coordinate system is Where U0, V0, and W0 are the longitudinal, lateral, and vertical velocities at the top of the A-frame in the seakeeping coordinate system, respectively, and r is the radius vector at the top of the A-frame. and They are the linear velocity and angular velocity in the body - fixed coordinate system of the mother ship respectively. Step 2: The umbilical cable and mooring cable adopt a beam model to establish a finite - difference model to calculate the shape and tensions at both ends: Establish the beam models of the umbilical cable and the mooring cable: Where: Y is a vector composed of the axial strain ε of the umbilical cable, the normal stress S n , the tangential stress S b , the axial velocity u, the normal velocity v, the tangential velocity w, the axial and normal rotation angles φ and θ of the infinitesimal element, the torsional rate Ω1, the normal curvature Ω2, and the tangential curvature Ω3; s is the length of the umbilical cable infinitesimal element; t is the simulation time; H is a coefficient matrix related to the mass of the umbilical cable infinitesimal element, the added mass, the diameter, the axial and normal rotation angles, the velocity, and the axial strain of the infinitesimal element; P is a coefficient matrix related to the mass, velocity, and stiffness; Q is a vector related to S n , S b , Ω1, Ω2, Ω3, the axial and normal rotation angles, the velocity, the flow velocity, the drag coefficient, and the stiffness of the infinitesimal element; Step 3: Establish the boundary conditions of the umbilical cable and mooring cable in the coupling model: 1) Mechanical boundary: The umbilical cable and mooring line are connected to the mother ship, TMS, and ROV. In the direction of the seakeeping coordinate system, the tension at the top of the umbilical cable or mooring line acting on the mother ship, TMS, and ROV is as follows: where F x(0,n) , F y(0,n) , F z(0,n) are the longitudinal, lateral and vertical tensions in the seakeeping coordinate system respectively, E is the Young's modulus of the umbilical cable, and A is The cross - sectional area of the umbilical cable. The subscript (0,n) represents the parameters at the bottom or top. 0 represents the top parameter, and n represents the bottom parameter. 2) Motion boundary: The velocities at both ends of the umbilical cable are the same as those at the top of the A-frame and the connection to the TMS. The velocities at both ends of the mooring cable are the same as those of the ROV and the TMS. The velocities at both ends of the umbilical cable or the mooring cable in the direction of the seakeeping coordinate system are as follows: where U t(0,n) , V t(0,n) , W t(0,n) are respectively the longitudinal, lateral and vertical velocities in the seakeeping coordinate system. The calculation methods of the boundary conditions for the mooring line and the umbilical cable are similar. The top and bottom ends of the mooring line are the TMS and the ROV respectively; 3) Establish a finite difference model for the mooring line and umbilical cord: Where: α h and α p are differential coefficients; H i and H i-1 are coefficient matrices related to the mass, added mass, diameter, axial and normal rotation angles, velocity, and axial strain of the front and rear infinitesimals and the umbilical cable infinitesimal; P i and P i-1 are coefficient matrices related to the mass, velocity, and stiffness of the front and rear infinitesimals and the umbilical cable infinitesimal; Q i and Q i-1 are vectors of the front and rear infinitesimals related to S n 、S b 、Ω1, Ω2, Ω3, the axial and normal rotation angles, velocity, flow velocity, drag coefficient, and stiffness of the infinitesimal; Y i and Y i-1 are vectors Y of the front and rear infinitesimals; △t is the time step; △s is the infinitesimal length; Step 4: Model the mooring management system using a rod element model considering the tension effects of the mooring lines and umbilicals: Where: M1 is the sum of the TMS mass and the added mass; C1 is the centripetal force and Coriolis force matrix of the TMS; D 11 and D 21 are the first-order and second-order hydrodynamic coefficients; K1(x) is the stiffness matrix of the TMS; q 1r is the flow load on the TMS; q 1cable and q 1tether are the tensions at the bottom of the umbilical cable and the top of the mooring cable respectively, and the calculation method is the same as formula (7); x is the displacement of the TMS; is the speed of the TMS; is the acceleration of the TMS; t is the simulation time; the hydrodynamic coefficient of the rod element is determined according to the form and shielding relationship of the discrete structure, taking into account the depth - dependent hydrodynamic characteristics. Step 5: Nonlinear ROV maneuverability equation, considering the influence of mooring line tension and manipulator: where: M RB2 is the mass matrix of the ROV; C RB2 is the centripetal force and Coriolis force matrix of the ROV; M A2 is the added mass matrix of the ROV, including 36 added masses and added moments of inertia on the main diagonal and off-diagonal; N2 is the drag coefficient matrix; g2 is the restoring force matrix; τ 2thrust is the thruster thrust; τ 2tether is the tether tension, and the calculation method is the same as formula (7); τ2manipulator is the force on the ROV by the manipulator base; v2 is the ROV velocity; is the acceleration; v r2 the velocity of the ROV relative to the ocean current; is the relative acceleration; The described N2 expression is asymmetric hydrodynamic force, specifically: where F vv and F v|v| are the second-order symmetric and asymmetric hydrodynamic coefficients, respectively; Step 6: Establish a manipulator dynamics model considering the ROV pose: The forward kinematics of the robotic arm simulation module involves finding the roll angle of the robotic arm given a linear motion, establishing the generalized coordinates of the kinematic model using Denavit-Hartenbert notation, and calculating through the Newton iteration method; the inverse kinematics involves finding the linear motion of the end given the roll angles of the links; the non-linear dynamic model of the robotic arm links is: where M i is the additional mass matrix of link i; C i is the fluid centripetal force and Coriolis force matrix of link i; G i (q i ) is the restoring force matrix of link i; τ Di is the damping force on link i; τ i is the driving force of the robotic arm; q i They are respectively the angular acceleration, angular velocity and rotation angle of the connecting rod i. The boundary condition of the robotic arm is that the velocities of the base and the end of the ROV are equal. The force exerted on the ROV by the base n of the robotic arm is: The meanings of the characters in the formula are the same as those in formula (13). The subscripts j and k represent the j - th and k - th links respectively.

2. The method for building a six-degree-of-freedom ROV operation simulation platform according to claim 1, wherein: The simulation platform solution system includes a main control module, a mother ship simulation module, an umbilical cable simulation module, an ROV simulation module, and a manipulator simulation module, where: The described mother ship simulation module receives data from the ocean environment simulation system and the umbilical cable simulation module, and calculates the motions and positions of the mother ship and the A-frame based on the time-domain seakeeping equation of the ship. The described umbilical cable simulation module receives data from the ocean current module, the mother ship simulation module, and the ROV simulation module, and calculates the shape and tension of the umbilical cable and the mooring cable based on the beam model and the finite difference method, and calculates the pose of the repeater TMS based on the rod element model. The described ROV simulation module receives data from the ocean current module, the umbilical cable simulation module, and the manipulator simulation module, and calculates and controls the pose of the ROV based on the six-degree-of-freedom nonlinear asymmetric maneuverability model. The described manipulator simulation module receives data from the ROV simulation module, and calculates the joint velocities, accelerations, and forces based on the dynamic model established by the Newton-Euler method.

3. The method for building a six-degree-of-freedom ROV operation simulation platform according to claim 1, characterized in that: The described ROV control system includes an ROV control module, an ROV cable management system control module, and an ROV vision module, where: The described ROV control module includes an ROV body control module and a manipulator control module to control the motions of the ROV and the manipulator respectively. The described ROV cable management system control module includes an umbilical cable retracting and deploying system and a mooring cable retracting and deploying control to respectively control the retracting and deploying activities of the A-frame and the TMS. The ROV control system resolves the digital input / output signals and the analog input signals into corresponding engineering quantities through the system processor to achieve the interactive simulation between humans and equipment.

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