Research On An Active Heave Compensation System Based On The Secondary Control Unit

With the deepening of the Marine resources development, marine work is becoming more and more frequent. When one vessel is supplying cargoes to the other on the sea, the vessel may appear heave motions due to waves.The heave motions of vessels may have great influence on the replenishment operations, even cause failures.Consequently, it is necessary to study heave compensation technology to enhance safety and stability of the replenishment operations.An active heave compensation control system in vertical direction on the background of replenishment operations between vessels at sea is studied and a compensation system based on the secondary control unit is proposed. The system not only has the advantages of common active heave compensation systems, like strong anti-interference ability, good adaptability, high compensation accuracy and stable compensation performance. But also, the system structure is simpler and the compensation costs are lower by recycling and reusing the potential energy of the load.Firstly, the speed compensation principle of the active heave compensation system is described. Then, according to the system requirements of the active heave compensation system based on the secondary control unit under the condition of level 3 sea condition, the secondary unit and the hydraulic accumulator are selected. On this basis, combined with the specific parameters of system components, the overall mathematical model of active heave compensation system based on the secondary control unit is established and the transfer function model is given. The control algorithm in the inner swash plate angle loop is designed and the variable structure PID control is employed to control the speed of the secondary control unit in the outer loop. The parameters of the variable structure PID controller are adaptively adjusted based on the load feedbacks observed by model reference adaptive identification. Simulation results verify the effective of the double closed-loop control method of variable structure PID algorithm. The effect of the wave compensation of the replenishment system in two kinds of working conditions is simulated. The simulation results show that the system can successfully implement the heave compensation method for supply operation with both efficiency and security.Finally, the experiment platform of the active heave compensation system based on the secondary control unit is set up. The monitoring and testing application software and the control software are also developed by WIN-PED 6.6. After system debugging in the real test platform, the system has realized the data acquisition of functional modules and RS232 communication.