Trajectory Tracking Of Remotely Operated Vehicle Based On Machine Vision

In general,remotely operated vehicle(ROV)docks into the garage-style Tether Management System(TMS)in motion by manual control,which heavily depend on the experience of operator.So it's valuable to develop a low cost underwater automatic docking technology,and the key is tracking the trajectory of TMS based on its position data.A method was proposed as follows: estimate the relative position and attitude(P&A)by monocular vision,and track the trajectory by a sliding mode controller,including image processing,control law designing and simulation model building.The main contents are listed as follows:Kinematics and kinetics equations of ROV,as a time-varying nonlinear system,were build according to rigid body theory.Then we took the external force into account and transformed the equation to system state equation in matrix representation.Simplified the equation based on the hydrodynamic force coefficient of 11000 m “Long Huang” ROV.Its model was built in robot simulator V-REP,and the communication API to simulate with external program synchronously was coded.In terms of estimating the relative position and attitude between ROV and TMS,a console application was developed consists of two modules,one is a feature point recognition module including threshold processing,morphological operation and contour finding,a method was proposed to determine whether contour was circle-like or not.The other is a P&A estimation module comprised Zhang Zhengyou method to calibrate the camera and PnP solver.The experiment results show that the console application was able to recognize the feature points in underwater environment,and estimated P&A in high-precision.As for the trajectory tracking,a robust sliding mode controller was designed for surging,swaying and heaving of ROV,and its performance was analysed by Lyapunov stability method.Sliding controller of Yawing was developed with a discrete disturbance observer.Then pole placement method was adopt to determine the control parameters.The simulation results show that ROV track the trajectory precisely in disturbing environment with the controllers.Finally,synchronous simulation was conduct between the console application and V-REP simulator on the basis of the designed architecture.The results proved that the application could control ROV tracking the trajectory of TMS based on monocular vision.