| CPC G06F 30/23 (2020.01) [G05B 17/02 (2013.01); G06F 30/15 (2020.01)] | 3 Claims |
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1. A method for constructing a six-degree-of-freedom ROV (Remoted operated vehicle) operation simulation platform, wherein 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 comprises an integrated control platform and an instructor control system, the real-time simulation module comprises a marine environment simulation system, a simulation platform calculation system and an ROV control system, and the system output module comprises a display system; and each system provides various services described in an interface specification through a run-time infrastructure (RTI) responsible for communication between the systems to achieve interoperability, wherein:
the integrated control platform starts the instructor control system, the marine environment simulation system, the simulation platform calculation system, the ROV control system and the display system through a network; the instructor control system issues training subjects, intervenes in parameters of a simulation platform device and an operating system during training, sets faults and emergencies, and arranges positions;
the marine environment simulation system releases a sea current, sea wave and sea wind environment, and sets marine environment conditions which are capable of being input to the display system;
the simulation platform calculation system receives data of the instructor control system and the marine environment simulation system, simulates motions of the mother ship and an A-shape frame at sea, and solves shapes and tensions of the umbilical cables;
receiving data of the ROV control system and calculating the ROV six-degree-of-freedom motion and manipulator motion; the simulation platform calculation system is input into the display system to carry out third perspective display and ROV visual display of the operating system respectively;
the ROV control system is in network communication with the simulation platform calculation system, and is used for collecting operations and instructions of operators, and displaying the pose of the ROV and monitor visual scene; and
the display system receives data of the simulation platform calculation system, and is used for displaying third perspective of the mother ship, the umbilical cables, the ROV, manipulator operation status and marine environment;
wherein the method comprises the following steps of:
step 1: calculating a hydrodynamic coefficient and a time delay function of a mother ship according to a profile of the mother ship, and establishing a time domain motion equation according to a layout of the mother ship and a position of the A-shape frame,
 wherein, in the formula: M0 is a sum of a mass of the mother ship and an additional mass; CRB0 and CA0 are centripetal force and Coriolis force matrixes of a rigid body and a fluid respectively; D0 is a damping matrix; and K0(t−τ) is the time delay function, wherein t is a simulation time, γ is an integration variable; U is a longitudinal velocity of the mother ship; e1 is a longitudinal unit vector; G0 is a stiffness matrix of the mother ship; τwind0 is a wind load; τwave0 is a wave load; vr0 is a relative velocity of the mother ship with a sea current in a body-fixed coordinate system, and τcable0 is a tension of the umbilical cables, which is marked in a direction of a seakeeping coordinate system as:
τcable0=[Fx0,Fy0,Fz0,Fz0yf0−Fyzf0,F0zf0−Fz0xf0,Fy0xf0−Fx0yf0]T (2)
wherein Fx0, Fy0, Fz0 are tensions of top ends of the umbilical cables in the direction of the seakeeping coordinate system, calculated by an umbilical cable simulation module based on a beam model, (xf0, yf0, zf0) are coordinates of a top end of the A-shape frame relative to a center of gravity of the mother ship in the direction of the seakeeping coordinate system, and a linear velocity of the top end of the A-shape frame in the seakeeping coordinate system is:
(U0,V0,W0)T=ξ0+ω0×r (3)
wherein U0, V0, W0 are respectively longitudinal, transverse and vertical velocities of the top end of the A-shape frame in the seakeeping coordinate system, r is a vector radius of the top end of the A-shape frame, and ξ0 and ω0 are respectively linear and angular velocities of the mother ship in the body-fixed coordinate system;
step 2: establishing a finite difference model of the umbilical cables and the tethers by adopting the beam model, and calculating a shape and tensions at both ends:
creating the beam model of the umbilical cables and the tethers:
 wherein, in the formula: Y is a vector consisting of a umbilical axial strain ε, a normal stress Sn, a tangential stress Sb, an axial velocity u, a normal velocity v, a tangential velocity w, axial and normal rotation angles ϕ and θ of an element, a torsion rate Ω1, a normal curvature Ω2 and a tangential curvature Ω3; s is an umbilical element length; t is a simulation time; H is a coefficient matrix related to a mass, an additional mass, a diameter, axial and normal rotation angles, a velocity and an axial strain of an umbilical element; P is a coefficient matrix related to mass, velocity and stiffness; Q is a vector related to Sn, Sb, Ω0, Ω2, Ω3, axial and normal rotation angles, a velocity, a current velocity, a resistance coefficient and a stiffness of an element;
step 3: establishing boundary conditions of the umbilical cables and the tethers in a coupling model:
1) the umbilical cables and the tethers are connected with the mother ship, a TMS (tether management systems) and the ROV, and in the direction of the seakeeping coordinate system, the tensions on the top ends of the umbilical cables or the tethers on the mother ship, the TMS and the ROV are:
 wherein Fx(0,n), Fy(0,n), Fz(0,n) are longitudinal, transverse and vertical tensions of the seakeeping coordinate system respectively, E is a Young's modulus of the umbilical cables, A is a cross-sectional area of the umbilical cables, and the subscript (0, n) represents parameters of a bottom end or the top end, 0 represents the parameters of the top end and n represents the parameters of the bottom end;
2) the velocities at a junction of both ends of umbilical cables and the top end of the A-shape frame and the TMS are consistent, and the velocities at both ends of the tethers are consistent with that of the ROV and the TMS, and the velocities at both ends of the umbilical cables or the tethers in the direction of seakeeping coordinate system are:
 wherein Ut(0,n), Vt(0,n), Wt(0,n) are respectively longitudinal, transverse and vertical velocities in the seakeeping coordinate system, and the boundary conditions of the tethers and umbilical cables are calculated in a similar way, with the TMS and the ROV at the top end and a tail end of the tethers respectively;
3) Establishing the finite difference model of the tethers and the umbilical cables:
(1−αh)2HiYiΔt+αh(1−αh)[HiYi-1+Hi-1Yi]Δt+αh2Hi-1Yi-1Δt+(1−αp)2PiYiΔs+αp(1−αp)[PiYi-1+Pi-1Yi]Δs+αp2Pi-1Yi-1Δs+(1−αp)QiΔsΔt+αpQi-1ΔsΔt=0 (8)
wherein, in the formula: αh and αp are difference coefficients; Hi and Hi-1 are coefficient matrices related to a mass, an additional mass, a diameter, axial and normal rotation angles, a velocity and an axial strain of front and rear elements and umbilical elements; Pi and Pi-1 are coefficient matrices of the front and rear elements and the umbilical elements related to mass, velocity and stiffness; Qi and Qi-1 are vectors of the front and rear elements and Sn, Sb, Ω1, Ω2, Ω3 and the axial and normal rotation angles, velocity, current velocity, drag coefficient and stiffness of the elements; Yi and Yi-1 are vector Y of the front and rear elements; Δt is a time step; and Δs is a length of the elements;
step 4: calculating a hydrodynamic force of a TMS and ROV deployment based on an element model, and a dynamic model of the element model:
M1x+C1x+D11x+D21f(x)+K1(x)x=q1r+q1cable+q1tether (9)
wherein, in the formula: M1 is a sum of a TMS mass and an additional mass; C1 is a centripetal force and Coriolis force matrix of the TMS; D11 and D21 are first-order and second-order hydrodynamic coefficients; K1(x) is a stiffness matrix of the TMS; q1r is a current load on the TMS; q1cable and q1tether are respectively tensions at the bottom end of the umbilical cables and the top end of the tethers, and the calculation method is consistent with formula (7); x is a displacement of the TMS; x is a velocity of the TMS; x is an acceleration of the TMS; t is a simulation time; a hydrodynamic coefficient of a bar element is determined according to a form of a structure and a shielding relationship, taking into account hydrodynamic characteristics dependent on a depth change;
step 5: establishing a nonlinear ROV maneuverability equation, considering influence of the tether tension and the manipulator:
MRB2v2+CRB2(v2)v2+MA2vr2+N2(vr2)+g2=τ2thrust+τ2tether+τ2manipulator (10)
wherein, in the formula: MRB2 is a mass matrix of the ROV; CRB2 is a centripetal force and Coriolis force matrix of the ROV; MA2 is an additional mass matrix of the ROV, comprising main diagonal and off-diagonal additional mass and additional moment of inertia, a total of 36; N2 is a drag coefficient matrix; g2 is a restoring force matrix; τ2thrust is a thrust of a thruster; τ2tether is a tension of the tethers, and the calculation method is consistent with formula (7); v2 is a velocity of the ROV; v2 is an acceleration; vr2 is a velocity of the ROV relative to the sea current; and vr2 is a relative acceleration; expression of N2 is an asymmetrical hydrodynamic force, specifically:
N2=Fvvvr22+Fv|v|vr2|vr2| (11)
wherein Fvv and Fv|v| are respectively second-order symmetric and asymmetric hydrodynamic coefficients; and
step 6: establishing a dynamic model of the manipulator considering the pose of the ROV:
wherein, forward kinematics of the manipulator simulation module comprises finding a roll angle of the manipulator in the case of a given linear motion, using a Denavit-Hartenberg symbol to establish generalized coordinates of the kinematic model, and calculating through a Newton iterative method; the inverse kinematics comprises giving a rolling angle of a connecting rod to find a linear motion of a tail end; and a nonlinear dynamic model of the connecting rod of the manipulator is:
Miqi+Ciqi+Gi(qi)+τDi=τi (12)
wherein, in the formula: Mi is an additional mass matrix of the connecting rod i; Ci is a fluid centripetal force and Coriolis force matrix of the connecting rod i; Gi(qi) is a restoring force matrix of the connecting rod i; τDi is a damping of the connecting rod i; τi is a driving force of the manipulator; qi, qi, qi are an angular acceleration, an angular velocity and a rotation angle of the connecting rod i respectively, the boundary conditions of the manipulator are that velocities of a base and the end of the ROV are equal, and a force on the ROV by the base n of the manipulator is:
 wherein, characters in the formula have the same meanings as those in formula (13), and the subscripts j and k respectively represent j-th and k-th connecting rods.
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