Trajectory Tracking for Underwater Swimming Manipulators using a Super Twisting Algorithm

Abstract

The underwater swimming manipulator (USM) is a snake-like, multi-articulated, underwater robot that is equipped with thrusters. One of the main purposes of the USM is to act like an underwater floating base manipulator. As such, it is essential to achieve good station-keeping and trajectory tracking performance for the USM by using the thrusters and by using the joints to attain the desired position and orientation of the head and tail of the USM. In this 'paper, we propose a sliding mode control (SMC) law, specifically the super-twisting algorithm with adaptive gains, for the trajectory tracking of the USM's centre of mass. A higher-order sliding mode observer is proposed for state estimation. Furthermore, we show the ultimate boundedness of the tracking errors. We demonstrate the applicability of the proposed control law and show that it leads to better performance than a linear PD-controller.

Tracking control of an articulated intervention AUV in 6DOF using the generalized super-twisting algorithm

“…We want to compare the GSTA with an algorithm that has previously been used and proved more efficient than a PD controller for the AIAUV; the STA with adaptive gains, [20]. In this section for completeness, we briefly present the equations describing the STA with adaptive gains, previously presented in [20] and [21]. The difference between [20], [21] and the algorithm presented here, is that the sliding surface σ is chosen differently.…”

“…In this section for completeness, we briefly present the equations describing the STA with adaptive gains, previously presented in [20] and [21]. The difference between [20], [21] and the algorithm presented here, is that the sliding surface σ is chosen differently. The STA with adaptive gains proposed in [19] can be written by the update law…”

“…In recent years, SMC has been developed into higher-order SMC schemes, that removes the chattering problem. The super-twisting algorithm (STA) with adaptive gains [19] has been tested for the AIAUV in 2DOF and in 6DOF in [20] and [21], respectively, because it is the most powerful secondorder continuous SMC algorithm. STA attenuates chattering, and no conservative upper bound on the disturbance gradient has to be considered to maintain sliding because of the adaptive gains.…”

“…In [20] tracking control of the centre of mass of the AIAUV in 2D was considered by using STA with adaptive gains [19] and a higher-order sliding mode observer (HOSMO) [22]. It was proven that the tracking errors were ultimately bounded, and the simulation results demonstrated that the proposed control method provided excellent tracking capabilities.…”

“…In [21], the position, orientation and joint angles were considered for the tracking problem, and equally good results were obtained in theory and in simulations. In [20] and [21], a HOSMO had to be used because velocity measurements were unavailable. When using a HOSMO, Euler angles have to be used to represent the system since the observer does not work with a different number of states in position versus velocity.…”