Comparison of two second-order sliding mode control algorithms for an articulated intervention AUV: Theory and experimental results

Ida-Louise G Borlaug,Kristin Y Pettersen,Jan Tommy Gravdahl

doi:10.1016/j.oceaneng.2020.108480

Ida-Louise G Borlaug, Kristin Y Pettersen + Show 1 more

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https://doi.org/10.1016/j.oceaneng.2020.108480

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Abstract

An articulated intervention autonomous underwater vehicle (AIAUV) is a slender, multi-articulated underwater robot. Accurate trajectory tracking is essential for AIAUV operations. Furthermore, due to hydrodynamic and hydrostatic parameter uncertainties, uncertain thruster characteristics, unknown disturbances, and unmodelled dynamic effects, robustness is crucial. In this paper, we present a super-twisting algorithm (STA) with adaptive gains and a generalized super-twisting algorithm (GSTA) for trajectory tracking of the position and orientation of AIAUVs. A higher-order sliding mode observer (HOSMO) for estimating the linear and angular velocities when velocity measurements are unavailable is also presented. The tracking errors for the resulting system are proven to converge asymptotically to zero. Finally, we demonstrate the applicability of the presented control laws with comprehensive simulation and experimental results and perform a comparison study, with two tests (C-shape and C-shape with a moving head), between the two algorithms and also a benchmark PID controller. The STA with adaptive gains exhibits the best overall tracking performance, with average position root mean square error (RMSE) 0.0121 m and average orientation RMSE 0.0335 rad. The GSTA also presented good results with average position RMSE 0.0267 m and average orientation RMSE 0.0292 rad. The PID controller gave average position RMSE 0.0371 m and average orientation RMSE 0.0491 rad.

Highlights

An articulated intervention autonomous underwater vehicle (AIAUV) is an underwater swimming manipulator
The gains for the super-twisting algorithm (STA) with adaptive gains and the higher-order sliding mode observer (HOSMO) are presented in Table 2; for the generalized super-twisting algorithm (GSTA) and the HOSMO, the gains are presented in Table 3; and for the
If we compare the results obtained with the control laws from Sec. 3.1.1, Sec. 3.2.1 and Sec. 3.3.1, i.e., without the HOSMO, and the results obtained with the control laws from Sec. 3.1.2, Sec. 3.2.2 and Sec. 3.3.2, i.e., when the HOSMO is used, by comparing Table 5 with Table 7, Table 6 and Table 8, we find that when the HOSMO is used, we obtain better tracking results for the orientation for all the algorithms, as well as better tracking for position when the PID controller is used

Summary

Introduction

An articulated intervention autonomous underwater vehicle (AIAUV) is an underwater swimming manipulator. The thrusters enable the AIAUV to move for ward without using an undulating gait pattern and provides it with the ability to hover. This property is especially important for stationkeeping and trajectory tracking in narrow and confined spaces. These capabilities enable the AIAUV to operate as a floating base manipulator. Since it can use its slender body to access narrow spaces, use its thrusters to keep itself stationary and use its joints to perform intervention tasks, the AIAUV can exploit the full potential of the inherent kinematic redundancy, which has been addressed in detail in (Sverdrup-Thygeson et al, 2016), (Sverdrup-Thygeson et al, 2018)

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