Using Adams/View to Develop a Real-Time ROV Simulator

Transcription

1 Using Adams/View to Develop a Real-Time ROV Simulator Marcelo Prado Gerson Brand Álvaro Costa Neto Multicorpos Engenharia John Hough MSC.Software Brazil Ricardo Capplonch Petrobrás

2 Summary Introduction Objectives ROV Modeling Hydrodynamics forces and torques Manipulator model Tether discretized model Human Interface Conclusions 2

3 Introduction The use of Remotely Operated Vehicle (ROV) for inspections, maintennance, building structures and surveillance in deep water offshore platforms is very intensive today. These missions are performed in risky environments where human beings cannot reach. ROV pilot needs to have great skill and experience in order to control the ROV. The cost of these missions is very expensive! Alternative to reduce cost and time: a real time simulator where the pilot can simulate the tasks in a predetermined mission 3

4 Introduction In this work we developed a real-time ROV simulator using Adams/View and Matlab/Simulink software. With the increased microprocessor power available today, there is a viable alternative. MSC Adams is a versatile tool for building complex mechanical models and it opens a new perspective in the human-in-the-loop environment. 4

5 Objectives Develop a real-time ROV simulator for training ROV pilots using Adams/View and MATLAB/Simulink. With this simulator the duration of the missions can be decreased and the likelihood of accidents minimized. Develop an open and powerful environment where the development team can implement new types of ROV in a short time. 5

6 ROV Modeling The multibody model of the ROV was developed using the Adams/View software. We can divide the model into three parts: ROV model a rigid body with 6 DOF Manipulator model 5 bodies, 5 DOF Tether model discretized model with 20 DOF (it is possible to increase the number of lumped masses in order to refine the model) In a sub sea environment hydrodynamics and drag forces and moments play a major role on the dynamics of the ROV. These forces are included into the model via Adams general forces applied on the ROV model 6

7 ROV Model Hydrodynamics Forces & Moments Hydrodynamics Forces & Moments The hydrodynamics forces and moments on the ROV can be linearly superposed. Considering the three components (Fossen, 1994): added mass due to inertia of the surrounding fluid damping force due to vortex shedding (Morrison s equation) restoring forces (weight and buoyancy) 7

8 ROV Model Added Masses Added Masses The added masses are additional inertia terms introduced into the ROV model in order to account for the effective mass of surrounding fluid that must be accelerated with the ROV. We assumed constant coefficients for the added masses. M A = diag { X, Y, Z, K, M N } u & v & w & p & q &, r & 8

9 ROV Model Damping Forces Viscous Damping In a system with a viscous fluid, frictional forces that are present are not conservative. The viscous damping forces acting on the ROV were modeled using Morrison s equation: F d 1 = C 2 d ρ AU U + C w r r m ρ AU& w Where Cd is the damping coefficient, ρw is the density of the sea water; A is the projected area of the ROV, U and U& are the relative velocities and accelerations between the ROV and the fluid. 9

10 ROV Model Restoring Forces Restoring Forces The restoring forces are the gravitational and the buoyancy forces. The buoyancy force is equal to the weight of fluid displaced by the ROV and is given by: F = ρ w gv B Where V is the volume of fluid displaced by the ROV and g is the acceleration of gravity. 10

11 ROV Model Applied Hydro Forces Hydrodynamics forces & moments on ROV model The hydrodynamics forces & torques were modeled using GFORCE and VFORCE into the Adams/View model GFORCEs VFORCEs 11

12 ROV Model Thruster Model Thruster Model The thruster force is given by the following equation: T = ρ D K 4 w T 0 ( J ) n n Where D is the diameter of the propeller, n is the propeller revolution, KT is the thruster coefficient and J 0 the advance number which can be rewritten: J Va / 0 = ( nd) Where V a is the speed of water going into the propeller (advance speed) 12

13 ROV Model - Thruster Model Applied thruster VFORCEs into ROV s model VFORCEs 13

14 ROV Modeling - Manipulator Manipulator The manipulator is composed of five bodies: two arms, the wrist and the gripper (two bodies) All the parts are connected using revolute joints (one rotational degree of freedom). 14

15 ROV Model Tether Cable Model The tether cable was modeled using the lumped parameter approach, which means dividing it into small pieces and connecting these pieces by means of a beam element. For each piece of the tether cable we can apply the hydrodynamics forces due to maritime sea current. GFORCE Hydrodynamic effects BEAM Element 15

16 Human Interface The interface between the MSC Adams ROV simulator and the human was implemented via two joysticks (one for the manipulator control and the other for the thrusters control) Using the joysticks the pilot can control the ROV s attitude, the manipulator and the gripper This interface was implemented using the Virtual Toolbox available in the MATLAB/Simulink software The task s mission can be performed in a very similar environment that the pilot will see in the real mission. It is possible to import the geometry in a standard CAD format (IGES, STEP, PARASOLID) 16

17 Human Interface Matlab/Simulink & Adams/View co-simulation Joystick for manipulator control Joystick for thrusters control ROV & Environment Models 17

18 Conclusions This work demonstrates the feasibility of using Adams/View as a tool for human-in-the loop environment for training ROV s pilot Adams is an open environment in which you can alter the model, including new types of manipulators, ROVs and the thrusters. Also it s possible to model the current using actual data in order to study the ROV s behavior under extreme conditions It s possible to create a very complex environment importing the offshore structures With the increasing power of computers, Adams will be used in more and more real-time applications in the future 18