Abstract
Incorporation of parallel mechanisms inside propulsion systems in biomimetic autonomous underwater vehicles (BAUVs) is a novel approach for motion generation. The vehicle to which the studied propulsion system is implemented presents thunniform locomotion, and its thrust depends mainly on the oscillation from its caudal fin. This paper describes the kinematic and dynamic modeling of a 3-DOF spherical 3UCU-1S parallel robotic system to which the caudal fin of a BAUV is attached. Lagrange formalism was employed for inverse dynamic modeling, and its derivation is detailed throughout this paper. Additionally, the implementation of control strategies to compute forces required to actuate limbs to change platform’s flapping frequencies was developed. Four controllers: classic PD, a feedforward plus feedback PD, an adaptive Fuzzy-PD, and a feedforward plus Fuzzy-PD were compared in different simulations. Results showed that augmenting oscillating frequencies (from 0.5 to 5 Hz) increased the complexity of the path tracking task, where the classic control strategy (i.e., PD) was not sufficient, reaching percentage errors above 9%. Control strategies using feedforward terms combined with adaptive feedback techniques reduced tracking error below 2% even during the presence of external disturbances.
Highlights
Unmanned underwater vehicles, intelligent enough to follow specific objectives and tasks, have been largely developed in recent years
Just as fish propel their bodies by only using their fins, biomimetic autonomous underwater vehicles (BAUVs) can swim when they are properly equipped by mechanisms that correctly imitate natural propellants
The limbs presented a 3 UPU configuration, very similar to the novel design presented by Aparicio et al [10] for the propulsion system inside a BAUV
Summary
Intelligent enough to follow specific objectives and tasks, have been largely developed in recent years. Hraiech et al [23] developed the reduced inverse dynamic model of a 3 DOF translational platform using the Lagrange formalism From the latter investigation, the limbs presented a 3 UPU (universal-prismatic-universal) configuration, very similar to the novel design presented by Aparicio et al [10] for the propulsion system inside a BAUV. The BAUV’s propeller consists of a 3 DOF parallel mechanism coupled to an artificial caudal fin to produce a vectored thruster The limbs linking both platforms have a 3UCU-1S (3 universal-cylindrical-universal and 1 spherical joint) configuration that allows for the imitation of flapping thunniform locomotion, where more than 90% of the propulsive force comes from the caudal fin oscillation and larger and more efficient thrust is generated compared to other locomotion fashions [12]. Incorporating the dynamical model as a previous step for forecasting the system’s behavior complemented by an adaptive feedback stage was the best control strategy when following desired trajectories at preestablished speeds
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