Integral Line-of-Sight Guidance for Path Following Control of Underwater Snake Robots: Theory and Experiments

Abstract

Abstract-This paper proposes and experimentally validates a straight line path following controller for underwater snake robots in the presence of constant irrotational currents of unknown direction and magnitude. An integral line-of-sight (LOS) guidance law is presented, which is combined with a sinusoidal gait pattern and a directional controller that steers the robot towards and along the desired path. The stability of the proposed control scheme in the presence of ocean currents is investigated by using Poincaré map analysis. Simulation results are presented to illustrate the performance of the proposed path following controller for both lateral undulation and eellike motion. In addition, the performance of the path following controller is investigated through experiments with a physical underwater snake robot. The experimental results show that the proposed control strategy successfully steers the robot towards and along the desired path in the presence of an unknown constant irrotational current in the inertial frame.Index Terms-Underwater snake robots, modeling of swimming robots, path following controller, integral LOS.

Waypoint guidance control for underwater snake robots exposed to ocean currents

“…In [17], a path following controller was proposed based on a control-oriented, simplified model, and a general formal stability proof was presented for the closed-loop system. This paper extends the previous work by the authors on ILOS path following along straight lines presented in [17], [18] and [19], proposing an operator-friendly framework for waypoint guidance control of USRs under the influence of ocean current effects. Simulation results are presented for both lateral undulation and eel-like motion patterns illustrating the performance of the proposed waypoint guidance strategy.…”

“…However, extensive simulation results and experimental results presented in [18] and [19], respectively, show that the robot is able to compensate for the ocean current effects and follow the path by using the heading controller given in (20). In this paper, the waypoint guidance proposed in Section V will be implemented considering both (19) and (20) for the directional control of USRs.…”

“…The radius of acceptance for each waypoint was set to r accept = 0.8 m and the ILOS path following controller was implemented according to (16) - (19). The gains for the control system were chosen as follows: k p = 20, k d = 5 and k θ = 0.5.…”

“…Hence, this paper extends the waypoint guidance presented in [15] by considering the current effects and thus the control approach presented in [15] falls out as a special case where the current effects are neglected. In addition, the proposed guidance strategy in this paper can be combined with two different straight line path following control approaches previously proposed by the authors in [17], [18] and [19]. An integral line-of-sight (ILOS) path following controller derived based on the model proposed in [4] for USRs for which the stability analysis was studied using a Poincaré map was presented and experimentally validated in [18] and [19].…”

“…In addition, the proposed guidance strategy in this paper can be combined with two different straight line path following control approaches previously proposed by the authors in [17], [18] and [19]. An integral line-of-sight (ILOS) path following controller derived based on the model proposed in [4] for USRs for which the stability analysis was studied using a Poincaré map was presented and experimentally validated in [18] and [19]. In [17], a path following controller was proposed based on a control-oriented, simplified model, and a general formal stability proof was presented for the closed-loop system.…”