Collision response and obstacle avoidance of the tethered-space net robot system with non-target objects

Purpose This paper aims to study the encounter issues of the Tethered-Space Net Robot System (TSNRS) with non-target objects on orbit during the maneuver, including the collision issues with small space debris and the obstacle avoidance from large obstacles. Design/methodology/approach For the collision of TSNRS with small debris, the available collision model of the tethered net and its limitation is discussed, and the collision detection method is improved. Then the dynamic response of TSNRS is studied and a closed-loop controller is designed. For the obstacle avoidance, the variable enveloping circle of the TSNRS has coupled with the artificial potential field (APF) method. In addition, the APF is improved with a local trajectory correction method to avoid the overbending segment of the trajectory. Findings The collision model coupled with the improved collision detection method solves the detection failure and speeds up calculation efficiency by 12 times. Collisions of TSNRS with small debris make the local thread stretch and deforms finally making the net a mess. The boundary of the disturbance is obtained by a series of collision tests, and the designed controller not only achieved the tracking control of the TSNRS but also suppressed the disturbance of the net. Practical implications This paper fills the gap in the research on the collision of the tethered net with small debris and makes the collision model more general and efficient by improving the collision detection method. And the coupled obstacle avoidance method makes the process of obstacle avoidance safer and smoother. Originality/value The work in this paper provides a reference for the on-orbit application of TSNRS in the active space debris removal mission.

STUDY ON THE ASSESSMENT OF IMPACT FORCE BETWEEN SHIP AND BRIDGE PIER

The bridge crossing water way is in the risk of impact by vessel, and thus it is very important to estimate the collision force for the safety of bridge. The impact force between bridge pier and vessel is investigated by numerical simulation and various empirical formulae. The collision response between a 5000t DWT bulk carrier with bulb bow and rigid bridge pier is simulated in the explicit finite element code of ANSYS LS-DYNA. The difference of the impact force between the empirical formulae and FE analysis are discussed. Based on the comparison of the results, the coefficient in the formulae is suggested for obtaining more accurate assessment of impact force.

A Local-Global Analysis Method for Arctic Drilling Riser Suffering from Ice Load

As world energy consumption intensifies, the oil and gas exploitation technology in the polar region are drawing more and more attention. However, due to the harsh environment, the oil and gas exploitation operation in the polar region are faced with enormous challenges, such as low temperature and sea ice collision, etc. This paper mainly focuses on the structural strength and integrity study of the arctic drilling riser suffering from the floe collision loading. First, the discrete element software IceDEM is employed to develop a local drilling riser - sea ice interaction model subjected to the floe collision loading in the splash zone, and the corresponding dynamic collision response between the drilling riser and the floe ice could be calculated and acquired. Then, a global drilling riser model is built within the framework of general finite element analysis software ABAQUS to investigate the dynamic behavior of the arctic drilling riser in the polar environment, and the dynamic collision loading derived from IceDEM simulation is also introduced in this global model. Finally, the dynamic responses of the arctic drilling riser based on the finite element simulation are investigated to research the riser’s security and integrity, which can provide reference for the design and application of the drilling riser in the polar region.

Emergency evacuation simulation of commercial aircraft

In order to receive certification approval for new products, aircraft manufacturers have to comply with the specifications regarding cabin evacuation. In case of real evacuation trials, agent-based simulation can be deployed, as they are a less cost-intensive mean of analysing passenger behaviour during the evacuation of commercial aircraft. This paper aims at examining the suitability of agent-based simulation software to reproduce passenger behaviour during evacuation processes. For this purpose, the algorithms and methods of the software PATHFINDER are introduced. Besides, the cabin of a single aisle aircraft is reconstructed in a high-density configuration using software-specific tools. A representative passenger distribution is implemented according to EASA regulations. Evacuation simulations for a single-aisle aircraft are conducted taking EASA standards into account. The effect of vital parameters such as walking speed, body dimension, conflict behaviour, collision response, acceleration time and exit allocation on evacuation times are examined. Results are discussed and examined for plausibility in order to determine whether evacuation simulations of commercial aircraft are possible using agent-based simulation software.

Study on the Assessment of Impact Force Between Ship and Bridge Pier

The bridge crossing water way is in the risk of impact by vessel, and thus it is very important to estimate the collision force for the safety of bridge. The impact force between bridge pier and vessel is investigated by numerical simulation and various empirical formulae. The collision response between a 5000t DWT bulk carrier with bulb bow and rigid bridge pier is simulated in the explicit finite element code of ANSYS LS-DYNA. The difference of the impact force between the empirical formulae and FE analysis are discussed. Based on the comparison of the results, the coefficient in the formulae is suggested for obtaining more accurate assessment of impact force.