The Modelling Research And Simulation Analysis On The Single-Rigid-Body Of Tracked Miner Moving On The Seafloor

With the gradual shortage of land mineral resources, the marine extremely rich mineral resources are becoming the competition focus of the world's main economies. The exploitation of deep-ocean mineral resources is becoming a great subject relating to the long-tern development of China, one of the world's emerging economies.According to the engineering background of the deep ocean poly-metallic nodule mining and the technical scheme of China's ocean mining system, a single-rigid-body fast simulation model of the self-propelled seafloor tracked miner is proposed and developed. Considering the motion and constraint relations of the total mining system, the single-rigid-body model of the miner is integrated with the discrete element model of the pipeline to form the fast simulation model of the total deep ocean mining system. The fast simulation researches of the total mining system during operations are achieved, which lay a basis for control researches of the total system, and further can provide theoretical analysis and technical reference for the actual mining operations and sea trials.The main research achievements are as follows:1. The laboratory experiment researches on the interaction mechanics between the miner's track and the seafloor sediment are performed. The bentonite-water mixture is selected as the substitute of the seafloor sediment according to the in-situ measurement data of the seafloor sediment in China's ocean poly-metallic mining contract area. With certain proportion of the bentonite and water, the seafloor sediment can be simulated. The pressure-sinkage experiments and shear stress-shear displacement experiments are performed with different dimensions of penetration plates and shear plates. The pressure-sinkage relationship based on Bekker's formula and shear stress-shear displacement relationship based on Wong's formula are respectively obtained to describe the mechanics characteristics of the seafloor sediment, which can provide doundary loading conditions for simulation analysis of the miner moving on the seafloor. 2. Using the obtained relationships depicting the mechanics characteristics of the seafloor sediment, and taking into account the principal design parameters of the miner for the 1000m sea trial, the relationship between the miner's total traction and miner's slip is derived. From the relationship, the optimum slip and permissible slip for the miner moving on the seafloor are proposed, which can provide important references for the miner's motion control.3. A new single-rigid-body model of the tracked vehicle is proposed and developed. Compared with the traditional multi-rigid-body model of the tracked vehicle, the single-rigid-body model only has 6 degrees of freedom, which can realize the fast simulation analysis of the tracked vehicle. Considering the distribution characteristic between the track-terrain interactions, a mechanics model based on mesh elements is proposed and established to describe the track-terrain interactions. A set of ordinary differential equations are yielded to describe the continuous variation of longitudinal and lateral shear displacements of mesh element points. The single-rigid-body model of the tracked vehicle is developed using dynamic modeling and simulation commercial program ADAMS. Compared to the specific and limited soil mechanics models provided in commercial programs for multi-rigid-body modeling and simulation of the tracked vehicle, various soil mechanics models can be applied to the single-rigid-body model of the tracked vehicle. Through comparative studies with multi-rigid-body models of tracked vehicles built by typical commercial program, it can be seen that the computation results of these two models match very well with each other, and meanwhile the computation speed of the single-rigid-body model is much higher than that of the multi-rigid-body, which verify the reasonableness and efficiency of the single-rigid-body model of the tracked vehicle.4. The experiment researches of a small-scale tracked vehicle moving on the soft soil are carried out. The experiment results match well with the simulation results, which further verify the reasonableness of the single-rigid-body modeling method for the tracked vehicle.5. The single-rigid-body fast simulation model of the tracked miner is established, and subsequently dynamic analyses are performed under various conditions for the miner moving on the seafloor. Two collecting paths are proposed to meet the demands of safety, efficiency and environmental protection for the miner working on the seafloor. The two collecting paths are analyzed and computed. Through controlling the motion state of the single-rigid-body model of the miner, the two paths can be simulated.6. The single-rigid-body model of the miner is integrated with the discrete element model of the pipeline to form the fast simulation model of the total deep ocean mining system. Two feasible operation modes for the total system are proposed and simulated. The integrated motion characteristics of the total system under the different paths of the miner are discussed. During the operations, the motion states of all the subsystems are stable. The simulation results indicate that the two newly proposed collecting paths for the miner are feasible, and the two integrated motion modes are reasonable.The researches of the paper provide a new modeling method for realizing the fast simulation analysis of the tracked vehicle. Based on the single-rigid-body model of the tracked miner moving on the seafloor, the fast simulation analysis of the miner and the total mining system can be realized. The paper provides a new idea for modeling the large-scale complex system.