Dynamic Analysis of a Manipulator in a Fluid Environment

The computation of the generalized forces produced by a fluid acting on the links of manipulators is considered here. The evaluation of these forces is necessary for the controller of an underwater manipulator (partially or totally immersed). This article presents an approximate method for the computation of buoyancy in local coordinates. The drag forces are computed by numerical integration of the local drag force. Numerical integration is necessary here to achieve a good precision. A new local reference frame is also added on each link to allow an easy description of the geometry of the links. When those computations are included in the dynamic model, a compromise must be made between computation time and precision, because this inclusion may result in doubling or tripling the number of operations to be performed in comparison with a standard dynamic algorithm.