Modelling And Coordinated Motion Control Of Underwater Vehicle-manipulator Systems

The underwater vehicle-manipulator system(UVMS)is one of the important operation equipment for marine development and exploration,which has been applied widely for various underwater interventions,such as opening and closing of valves,sampling analysis of marine organisms,inspection of submarine pipelines,etc.Due to the kinematic coupling and dynamic coupling of the the UVMS,the coordinated motion control between the vehicle and manipulator is one of the key technologies to achieve its fully autonomous underwater intervention.And having a clear understanding of the UVMS model characteristic is the basis for achieving coordinated motion control.This thesis focuses on the UVMS modeling and coordinated motion control techniques,including modeling,motion planning,joint-space trajectory tracking control and task-space coordinated motion control.The aim is to achieve high-precision end-effector trajectory tracking and to provide theory for improving the autonomous intervention capability of the UVMSs.The research is concentrated on hydrodynamic calculation and UVMS coupling analysis during modeling,coordinated motion planning based on optimizing energy consumption and satisfying state constraints,joint-space trajectory tracking conrol based on fuzzy decoupling,and finally from the perspective of whether to allow the use of self-motion,the task-space coordinated motion control strategy is discussed,which is based on the motion planning and control research.The main research contents are as follows:(1)Considering that UVMS has the characteristics of uncertain hydrodynamics and strong coupling,the UVMS modeling problems are studied,including hydrodynamic calculation and coupling analysis.Generally,as the accuracy of numerical calculation of hydrodynamic coefficients is not high,pool expreiments are needed to verify the calculated values of hydrodynamic coefficients.Limited by experiment conditions,in this thesis,in view of dynamically similarity,the numerical calculated coefficients are verifed and adjusted based on comparisons with the experimental data of the REMUS AUV.Based on this,a simulation model of UVMS has been established.Simulation results verify the reliability of the simulation model,and the UVMS coupling effects are analyzed in detail,which establishs the foundation for the subsequent research.(2)In view of the UVMS kinematic coupling,self-carrying energy,state constraints and different response characteristics of each subsystem,the problem of the UVMS motion planning is researched.Although the traditional motion planning method can realize the optimization of the motion disturbution of the vehicle and manipulator,UVMS state constraints,energy consumption,etc.,its objective fuction is based on model.And the partial derivative calculation of the objective function is complicated.To solve this issue,this thesis proposes a new UVMS coordinated motion planning algorithm.With the research basis of coupling analysis,the proposed method introduces non-diagonal elements in the weighted matrix.Moreover,a new secondary task with nonlinear coefficients is designed to reduce energy consumption and satisfy state constraints.Simulation results show that the proposed motion planning method is simple and easy to implement,and its performance is significantly better than traditional motion planning method in terms of energy consumption optimization and state constraint satisfaction.(3)In view of the UVMS dynamic coupling,the issue of UVMS joint-space trajectory tracking control is studied.The traditional joint-space control method is based on feedback linearization to reduce the influence of the dynamic coupling on the system through decoupling the underwater vehicle and the manipulator,however,the influence of the underwater vehicle coupling and the manipulator coupling on the system is ignored.To solve this issue,a joint-space trajectory tracking control method based on fuzzy decoupling is proposed.Based on the UVMS coupling analysis,the proposed method introduces non-diagonal elements into the control gain matrix,designs fuzzy rules and adopts fuzzy algorithm to adjust the gain adaptively for reducing the influence of the dynamic coupling on the system.In addition,a decoupled AUV desired trajectory is designed to reduce energy consumption.Simulation results show that the proposed method is not depended on system model,and its performance is better than traditional control methods in terms of tracking errors and energy consumption.(4)In view of the UVMS kinemacic coupling and dynamic coupling,considering model uncertainty and external distrubances,the issue of the UVMS task-space coordinated motion control is researched from the perspective of not allowing to use self-motion.The traditional UVMS coordinated control algorithm is usually designed based on the joint-space variables,which does not include the manipulator end-effector tracking errors.For this reason,this mehtod may not be suitable for high-precision end-effector trajectory tracking tasks.To solve this issue,a task-space coordinated motion control method based on EKF-IDC-FC is proposed.The effect of large lumped uncertainty is eliminated and the task-space tracking error is minimized,by combining the task-space tracking errors and joint-space tracking errors,and by designing non-model-based inertial disturbance control(IDC)and fuzzy compensator(FC).In addition,the extended Kalman filter(EKF)is designed to estimate UVMS states for resisting the influence of sensory noise.Simulation results show that the proposed control method is simple and easy to implement,and its performance based on motin planning mehod with consumption energy optimization is better than traditional coordinated control method in terms of tracking errors,energy consumption and robustness.(5)In view of the above UVMS characteristics,considering the above factors,from the perspective of allowing to use system self-motion,the issue of UVMS task-space coordinated motion control is researched.The traditional coordinated control method can not guarantee the controllability of the time history of the UVMS self-motion,and can not satisfy the attitude tracking accuracy and state constraints.To solve these issues,a coordinated motion control method for the UVMS based on constrained self-motion is proposed,which uses self-motion to improve system performance while ensuring that self-motion is controllable and within state constraints.The proposed mehtod combines a coordinated control method that does not require inverse kinematics and a new joint-space trajectory tracking control.And on the research basis of motion planning and motion control,the joint-space control is desigend,which includs joint-space velocity tracking error and joint-space position tracking error with fractional power,and fuzzy algorithm adaptly tuning control gains.In addition,a disturbance observer and inertial disturbance compensator are designed to compensate the influence of the lumped uncertainties and disturbances.Simulation results show that the performance of the proposed method is better than traditional coordianted method in terms of tracking errors,energy consumption,state constraints and robustness.