Integral Sliding Mode Control for a Marine Growth Removing ROV with Water Jet Disturbance

Abstract

Oil & gas operators spend tens of million USD every year on removing marine growth, using manually operated remotely operated vehicles (ROV) with water jets. This study investigates the benefits of automating the ROV used for cleaning by demonstrating a sliding mode control (SMC) algorithm on a reconfigured BlueROV2 with an attached water jet. A nonlinear SMC was designed for the cleaning task. SMC was able to stabilize the orientation of the ROV while following a trajectory in depth. Regular SMC could not stabilize the ROV in front of the member, with the water jet activated. To accommodate for the delay, integral action was added to the SMC (IxSMC) in the surge direction, which stabilized the ROV. From the research presented in this paper, it can be concluded that automation of a marine growth removing ROV can be achieved by applying IxSMC.

On Marine Growth Removal on Offshore Structures

“…ROVs are cheaper than divers, however, relatively inefficient in harsh offshore environments due to underwater streams, waves and the effect from the attach tether. In most cases, a high-pressure water jet is used as cleaning actuator, which also is an acting force on the ROV [7]. Autonomous underwater vehicles (AUVs) are rarely used due to the need for robust and reliable solutions [8], although AUVs do not have any tether attached like ROVs, limiting the amount of disturbances.…”

A Quantitative Parametric Study on Output Time Delays for Autonomous Underwater Cleaning Operations

“…The modeling is based on Fossen's representation for underwater vehicles [21], and the parameters have been determined through a combination of experiments done in [15]. The details on the parameters can be found in the paper by Benzon et al [15] where the same platform has been used.…”

“…The external forces τ = [τ 1 , τ 2 , τ 3 , τ 4 , τ 5 , τ 6 ] T is the input given in force and torque. The rest of the variables in Equation ( 1) and ( 2) can be seen in Tables 3 and 4, which is also given in [15]. In Figure 5 both the North-East-Down (NED) (referred to as world frame as seen in Figure 5) and body-fixed frame definitions are shown.…”

“…The results are based on the min-max sensitivity peak, which evaluates the best closed-loop performance potential. In this study a linear quadratic regulator with integral action (LQRI) from a previous study [15] is used as inner-loop controller. The closed-loop system is modeled as multiple Single-Input, Single-Output (SISO) systems, which becomes unstable when the delay becomes sufficiently large.…”

“…The range of time delays investigated is based on commonly used sensor technologies. The ROV used in this paper is the same being used in [15], which has been modified to perform cleaning operations using high-pressure water jetting. The modified ROV can be seen in Figure 1.…”