  The performance of underwater crawling and adjustment of the body posture for
underwater manipulating of the deep-sea crawling and swimming robot (DCSR) is
directly influenced by the dynamic performance of the underwater mechanical
legs (UWML), as it serves as the executive mechanism of the DCSR. Compared with
the mechanical legs of legged robots working on land, the UWML of the DCSR not
only possesses the characteristics of the land used mechanical legs, but is
also affected by the influence of the deep-sea underwater working environment
(i.e., the hydrodynamic force, viscous resistance and dynamic seal resistance).
To reduce these influence, firstly, the hydrodynamic force of the UWML were
researched based on theory and experiment, and the hydrodynamic model was
established with the fitted hydrodynamic parameters. Secondly, the oil viscous
resistance and the dynamic seal resistance were studied experimentally, and the
change laws of both with respect to the joint speed and the ambient pressure
(depth of operation) were obtained. The results provide a basis for the
subsequent research on the structure optimization and high performance control
of the UWML and DCSR.
