Study On Design And Control Of Active Heave Compensation System Of Deepsea Mining Based On Dynamic Vibration Absorber (DVA-AHCS)

As the important interface facilities between the mining ship, lifting system and its deployment system, heave compensation system of deepsea mining is essential to isolate the vibration of the underwater devices from deepsea mining ship’ motion induced by the wave excitation for the safety of deepsea mining operations. It is important for marine works to develop an active heave compensation system with small footprint, low energy consumption and easy installation.According to the characteristics of large underwater load, excessive heave amplitude of ocean wave, wide frequency bandwidth and so on, the design theory and its active control strategy of a novel active heave compensation system of deepsea mining based on dynamic vibration absorber in the light of1000m China’s deepsea poly-metallic nodule pilot mining system was studied in this paper. The P-M wave spectrum of China’s mining area was chosedn and the response of the deepsea mining ship under random and regular wave excitation was analyzed in time domain. The hydraulic actuator for dynamic vibration absorber and heave compensation system was then designed for the proposed system. And the mathematical model of the proposed active heave compensation system of deepsea mining based on dynamic vibration absorber with hydraulic actuator dynamics was built. Therefore the parameter design theory of the proposed active heave compensation system and its active control strategy was simulated and experimentally studied in order to form the system design theory and norms, as well as highly efficient and reliable control strategy of the active heave compensation system. The main results and conclusions are as follows:1. The active heave compensation system of deep-sea mining based on dynamic vibration absorber was proposed for the first time in view of the heave compensation performance requirements of1000m poly-metallic nodules pilot deepsea mining system. That is to say, the vetical movement of the heave compensation platform and its lifting pipeline was depressed by changing the energy distribution and motion transmission characteristic of the main heave compensation system by utilization of active control of dynamic vibration absorber (DVA).2. The P-M random wave spectrum suitable for China’s deepsea mining area was chosen and simulated in time domain. The equivalent hydrodynamic coefficients of the deepsea mining ship was designed and the response of the deepsea mining ship under regular wave excitation of sea condition four with nominal amplitude of2.5m and periods of10s and sea condition six with nominal amplitude of6m and periods of8.8s was simulated in time domain, thus the response of deepsea mining ship in irregular/sinusoidal wave excitation was obtained, which lay the foundation for the design of the active heave compensation system of deepsea mining.3. The proposed active heave compensation system of deep-sea mining based on dynamic vibration absorber is to combine the active control strategy for changing the energy distribution and transmission characteristics of the main system to achieve vibration control of the main vibration system with less energy consumption instead of controlling on the massive main vibration system directly as well as the flexibility of dynamic vibration absorber, that is to say, the dynamic vibration absorber (DVA) absorber the heave movement of active heave compensation system (AHCS) in the opposite direction induced by the wave excitation meanwhile the DVA move with safe and reasonable amplitude. And the system parameter and mathematics model of the proposed active heave compensation system with hydraulic actuator was designed for the subsequent study of the active controller design as well as the heave compensation performance analysis.4. An optimal controller was designed for the proposed active heave compensation system by using Linear-quadratic optimization technique to improve the system performance and system stability regarding the system response and the control input. The performance of the active heave compensation system of deepsea mining based on dynamic vibration absorber was simulated and analyzed in time domain and frequency domain. The simulation results show that the designed controller can achieve more than80%of heave compensation ratio and the dynamic vibration absorber move in safe and reasonable amplitude with reasonable energy consumption, which is beneficial to isolate the lift pipe and its support platform from the significant vibration of the mining ship motion induced by the sinusoidal wave as required by the1000m China’s deepsea poly-metallic nodule pilot mining system. 5. A Hoo Robust controller was designed for the proposed active heave compensation system by applying robust loop shaping control according to the heave compensation system control performance requirements of wave energy concentrated frequency domain of China’s deepsea mining field. The performance of Hoo robust controller and its robustness stability of the system are simulated and analyzed in frequency domain. The results show that the performance of the system in wave energy concentrated frequency domain of China’s deepsea mining field was improved by the concentrated weighting of output feedback and the control energy. And it also shows that the designed Hoo controller is perfect in system robustness stability against some parameter fluctuations of the system model.6. The test bench of semi-active vibration control system based on dynamic vibration absorber with magnetorheological damper was established. The parameter of the semi-active vibraton control system and the optimal designer was designed therefore the semi-active vibration control performance of the structure vibration control system based on dynamic vibration absorber was simulated by MATLAB, co-simulation of MATLAB AND Lab VIEW and experimentally studied based on the previous design theory. The results show that the vibration of the main mass with optimum dynamic vibration absorber and optimal controller was reduced by more than80%against that of without control. Therefore, the correctness of the proposed active heave compensation system based on dynamic vibration absorber and the effectiveness of active control strategy is verified.The study of design theory of the proposed active heave compensation system based on dynamic vibration absorber and its active control strategy in this paper can provide a new way for developing the heave compensation system for deepsea resources exploitation system with high efficiency and low power consumption as well as lay a foundation for the direct application of the proposed active heave compensation system.