Abstract
The valve-controlled hydraulic cylinder system (VCHCS) is commonly used for actuators such as manipulators in deep-sea equipment, whose working performance is crucial to subsea tasks. Affected by the ambient pressure introduced by the pressure compensator, the viscosity of the hydraulic oil increases significantly. On this basis, the viscosity changes further when flowing in the slender pipeline, making the pipeline pressure loss substantially increase and subsequently affecting the working performance of the deep-sea VCHCS. Aiming at this issue, a detailed nonlinear mathematical model of the deep-sea VCHCS is established, in which the viscosity-pressure characteristics of the hydraulic oil is considered to take the viscosity changes in the pipeline into account. Besides, the hydrodynamic effects are also included in the model. Then the corresponding numerical simulation model of the deep-sea VCHCS is established, and its working performance at different depths is simulated and analyzed. When the depth is 11km, the extension and retraction movements are delayed by 52.50% and 43.12% respectively. The root cause of the delay is then analyzed and discussed. Finally, the parameters that affect the working performance are studied, and suggestions to reduce or eliminate the delay phenomenon are given. The results can provide theoretical support for the performance optimization of the deep-sea VCHCS.
Highlights
Tian et al [27] proposed a detailed nonlinear model of a deep-sea hydraulic manipulator, in which the viscosity change of the hydraulic oil caused by the ambient pressure in the deep sea is considered
The results showed that the movement of the deep-sea valve-controlled hydraulic cylinder system (VCHCS) is significantly delayed when working at a depth of 11 km in the sea
The work of Tian et al [27] indicated that the output movement delay of the deepsea VCHCS is caused by the increase in pipeline pressure loss relating to the viscosity change of hydraulic oil
Summary
For deep-sea scientific investigations, resource development, or engineering applications, the manipulator, or robot arm, is the most important and suitable tool [1]. Tian et al [27] proposed a detailed nonlinear model of a deep-sea hydraulic manipulator, in which the viscosity change of the hydraulic oil caused by the ambient pressure in the deep sea is considered. The work of Tian et al [27] indicated that the output movement delay of the deepsea VCHCS is caused by the increase in pipeline pressure loss relating to the viscosity change of hydraulic oil. Only the increase in viscosity of hydraulic oil caused by the deep-sea ambient pressure is considered, while the viscosity change during the flowing process in the pipeline is ignored. A detailed nonlinear mathematical model of the deep-sea VCHCS is described, in which the pressure-dependent characteristics of hydraulic oil is considered to take the viscosity changes in the pipeline into account. The research results of this paper reveal the impact of the deep-sea environment on the performance of deep-sea VCHCS and the root cause for the movement delay of the deep-sea VCHCS, which can provide theoretical support for the performance optimization of the deep-sea VCHCS
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