Scholar - SciOpen

This study aims to develop a dynamic model of the longitudinal profile motion of wave gliders by modeling the umbilical cable as multiple hinged rigid rods, and to investigate the effects of environmental and umbilical cable parameters on the longitudinal motion characteristics.

Method

Based on reasonable assumptions and simplifications, the umbilical cable was modeled as a series of homogeneous, multi-segment rigid rods connected by hinges. The Lagrangian method was employed to construct a multi-rigid-body dynamic model of the wave glider in the longitudinal profile. Incorporating calculation methods for wave force, fluid resistance, and hydrofoil external forces, a simulation program was developed on the MATLAB/Simulink platform to solve the model. The model's validity was verified by comparing its results with those of existing studies. Finally, a sensitivity analysis was conducted to examine the influence of environmental and umbilical cable parameters on the system response.

Results

The results indicate that the longitudinal motion response increases with wave height; specifically, when the wave height rises from 0.2 m to 0.4 m, the longitudinal response increases by 78.20%. Under a current disturbance of 0.07 m/s, the longitudinal displacement within 60 s in the downstream condition increases from 1.53 m to 9.11 m compared with the upstream condition. Shorter umbilical cables amplify the longitudinal motion response; when the umbilical cable length decreases from 5 m to 2 m, the longitudinal response increases by 31.97%. Conversely, excessively small wave periods reduce the longitudinal response due to rigid impacts between the multi-segment hinged rigid rods. Changes in umbilical cable density, however, exert only a minor influence on the longitudinal motion response.

Conclusion

The findings of this study provide theoretical support for the structural optimization and motion control strategies of wave gliders.

Issue

Excavation Trajectory Planning with Optimal Energy Consumption for Mining Electric Shovel

Wei WANG, Yuan ZHANG, Shaoyu SHI, Gang SHEN, Wenqing YANG

Journal of South China University of Technology (Natural Science Edition) 2024, 52(12): 52-64

Published: 25 December 2024

Abstract

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The mining and loading operations are the central link in the open-pit coal mining process, and its energy consumption accounts more than half of the total energy consumption of open-pit coal mining and loading, which determines the mining efficiency and equipment energy consumption. Traditional open-pit coal mining and loading operations are completed by manually operating mining electric shovels, and the process is of low excavation full-bucket rate and high energy consumption. To further reduce the energy consumption and meet the requirements of unmanned and intelligent electric shovels, this paper deals with the optimal excavation trajectory of mining electric shovels. In the research, firstly, a kinematic analysis was conducted on the working device, and the relationship between the pose space and joint space of the working device was revealed through kinematic forward and inverse solutions. Secondly, a dynamic analysis was conducted on the working device of the mining electric shovel.Based on the static analysis of the working device during the excavation process, as well as the analysis of dynamic excavation resistance and material gravity, the Lagrange dynamic equation of the working device was constructed. Then, based on the particle swarm optimization algorithm and the optimization design model of trajectory planning, the optimal excavation trajectory for excavation energy consumption per unit material volume was obtained. Moreover, the effects of material pile surface characteristics, operating parameters and fitting functions on the energy consumption and operation stability of the working device were analyzed, and an excavation trajectory planning strategy that balances energy conservation and stability was proposed. Finally, an experimental study was conducted on the optimal excavation trajectory planning. The results show that the proposed excavation trajectory planning method based on the optimal energy consumption per unit material volume can ensure the efficiency and energy-saving requirement during the excavation with mining electric shovel.

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