Region tracking based control of an autonomous underwater vehicle with input delay

• The controller maintains the AUV within a specific bounded region while tracking.
• The proposed auxiliary signal leads to development of a novel controller with compensation for known constant actuator delay.
• A suitable Lyapunov functional is proposed to prove the UUB stability of the closed loop system.
• Computation of input torque is reported which encourages the implementation of the proposed delay compensation scheme .

In this paper, a tracking controller is proposed to navigate the autonomous underwater vehicle (AUV) within a specific region with known constant input delay. The unit quaternion representation is used for attitude control to avoid singularity problem encountered with Euler Angles. However, compensation of actuator delay is a challenging problem to handle with the nonlinear dynamics of an AUV. A predictor based term is thus considered to cancel the input delay term in the open loop dynamics. Nevertheless for some application of an AUV like pipeline inspection or survey it is more practical to define a region as desired position than a specific point. Thus the proposed region tracking controller guarantees an AUV to move within a region for the mission duration. A Lyapunov based stability analysis using Lyapunov–Krasovskii functional is provided to prove uniformly ultimately bounded stability of the closed loop system. Numerical simulations considering a six DOF model of an AUV validate the proposed controller.