Variable Target Control Allocation And Motion Control For Observation Class ROV

The over-actuated thrusters system can generate forces and torques of 6-DOF。 Therefore the motion of ROV whose thruster system is over-actuated is flexible.At the same time,the relationship between the thrust of eight thrusters and the force and torque of 6 degrees of freedom can not be expressed by simple mapping,which needs to be solved by control allocation system according to the optimization objective.In order to give full play to its flexible characteristics,the control allocation system needs to consider both the real-time and accuracy while considering the constraints of the thruster.ROV has a wide range of applications in underwater operation,and the underwater operation environment is complex while ROV is mostly open frame structure,it is difficult to obtain accurate hydrodynamic coefficient.These two points will bring challenges to the antidisturbance ability of ROV control system,so the control system of ROV needs strong antidisturbance ability.The constraint of the thruster will make the performance of the control system worse,so it is necessary to analyze the anti-disturbance ability of the ROV control system under the constraint of the thruster.Firstly,the control allocation system of an observation class ROV with eight thrust vectorsconfiguration is discussed with real-time performance and accuracy under constraints as the core.A variable target control allocation method combining minimizing energy consumption and minimizing error is proposed,and the singularity of thruster configure-matrix is eliminated by using Hessian correction,so that Newton method can be used to solve the quadratic programming problem which cost function is minimizing the error of thrust.The simulation results show that the control allocation error of the proposed method is better than that of the pseudo inverse method,and the solution speed is lower than that of the pseudo inverse method,but it can meet the control requirements.The thrust allocation method can give consideration to both accuracy and real-time performance under considering thruster constraints.Then,the theory of active disturbance rejection control technology is introduced,and the controller is designed.The anti-disturbance ability of the controller is verified by the simulation of the positioning of ROV vertical plane and horizontal plane under the disturbance of unknown current.The control system and control allcoation system are combined to simulate the positioning of ROV vertical plane and horizontal plane in the presence of thruster thrust change rate constraint,thrust saturation constraint and unknown disturbance to discuss the performance of the control system in the presence of thruster constraint and unknown mismatched disturbance.The simulation results show that the controller can resist a certain degree of mismatched uncertainties and complete the target positioning under the constraints of thrust change rate and thrust saturation.Finally,by combining the control system with the thrust allocation system,the flow angle and thrust variation constraints are taken as independent variables to analyze the danger angle to resist flow of ROV,and the relationship between the rate constraints and the disturbance resistance ability of ROV is quantitatively analyzed.The simulation results show that the rate constraints of ROV can weaken the disturbance rejection ability of ROV,and the disturbance rejection ability of ROV in horizontal positioning is weaker than that in vertical positioning,and it is more vulnerable to the influence of thrust change rate.