Longitudinal Motion Planning and Control of a Swimming Machine

We propose a practical maneuvering control strategy for an aquatic vehicle (AV) that uses an oscillating foil as a propulsor. The challenge of this problem lies in the need to consider the hydrodynamic interaction as well as the underactuated and non-minimum phase natures of the AV system. The control task is decomposed into the off-line step of motion planning and the online step of feedback tracking. Optimal control techniques are used to compute a repertoire of time scalable and concatenable motion primitives. The complete motion plan is obtained by concatenating time-scaled copies of the primitives. The computed optimal motion plans are regulated by a controller that consists of a cascade of linear quadratic regulator, input-output feedback linearization and sliding mode control. Time varying LQ controllers can also be time scaled and concatenated. Therefore, they can be computed before hand. The proposed strategy has been experimentally validated for longitudinal maneuvers.