Dynamic Control of 6-DOF AUVs
Control of UVMSs require full-DOF control of the vehicle, cruise vehicles with rudder and stern are not suitable to hold a manipulator arm for their incapacity to counteract the interaction forces with the arm itself. For this reason the following chapter
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Dynamic Control of 6-DOF AUVs
3.1 Introduction Control of UVMSs require full-DOF control of the vehicle, cruise vehicles with rudder and stern are not suitable to hold a manipulator arm for their incapacity to counteract the interaction forces with the arm itself. For this reason the following chapter restricts the discussion to the problem of controlling an underwater vehicle in 6-DOFs. To effectively compensate the hydrodynamic effects several adaptive (integral) control laws have been proposed in the literature (see, e.g., [1–5]). In [6], a number of adaptive control actions are proposed, where the presence of an external disturbance is taken into account and its counteraction is obtained by means of a switching term; simulation on the simplified three-DOF horizontal model of NEROV are given. In [7], a body-fixed-frame based adaptive control law is developed. In [8], an adaptive control law based on Euler angle representation of the orientation has been proposed for the control of an AUV; planar simulations are provided to show the effectiveness of the proposed approach. Reference [9] proposes a self-adaptive neuro-fuzzy inference system that makes use of a 5-layer-structured neural network to improve the function approximation. In [10] a fuzzy membership function based-neural network is proposed; the control’s membership functions derivation is achieved by a back propagation network. Six-DOF experimental results are not common in the literature [11]. References [6, 12–14] describe 6-DOF control laws in which the orientation is described by the use of quaternions. The papers [12, 13, 15–17] report 6-DOF experimental results on the underwater vehicle ODIN (Omni-Directional Intelligent Navigator). An experimental work is given in [18, 19] by the use of the Johns Hopkins University ROV on a single DOF. Different simple control laws are tested on the vehicle in presence of model mismatching and thruster saturation and their performance is evaluated. The work [20] gives an interesting 6-DOF experimental comparison among PID, model-based with and without exact linearization in a G. Antonelli, Underwater Robots, Springer Tracts in Advanced Robotics 96, DOI: 10.1007/978-3-319-02877-4_3, © Springer International Publishing Switzerland 2014
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3 Dynamic Control of 6-DOF AUVs
variety of operative conditions, by varying the control gains, implementing adaptive versions, by intentionally wrongly compensating for the terms, etc. The conclusions represent an important witness for control practitioners. In [21] an experimental comparison for 6-DOF control of the Johns Hopkins University ROV under model and non-model based approaches is performed to evaluate how it is important to compensate for the dynamics especially in the coupled maneuvers. Among the other hydrodynamic effects acting on a rigid body moving in a fluid, the restoring generalized forces (gravity plus buoyancy) and the ocean current are of major concern in designing a motion control law for underwater vehicles, since they are responsible of steady-state
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