Tracking Control of an Underwater Vehicle Using Adaptive Back-Stepping With Tuning Function

In this article the design and simulation of a velocity and position control for an underwater Remotely Operated Vehicle (ROV) is addressed. The system has a nonlinear dynamic with parametric uncertainties making it a reasonable test-bed for investigating the effectiveness of robust nonlinear control algorithms. The studied ROV can be actively controlled along the 3 Cartesian coordinate directions and rotated about the vertical axis using 4 thrusters positioned on the ROV. The dynamics of the actuator system, consisting of thrusters, is assumed to be a first order linear system with an unknown parameter. To control this system adaptive back-stepping, as a robust adaptive nonlinear control method, is proposed. To increase the effectiveness of the control system, tuning function method is adopted to develop the control and adaptation laws. Noting that the presence of the thruster dynamics necessitates the use of thrusters’ angular velocity feedback to measure thruster forces, the controller design is addressed both with and without thruster dynamics. Based on the simulation results, in the velocity control mode, both controllers show good performance during step response operation. But for position tracking, inclusion of the thruster dynamics results in a better performance. Exclusion of the thruster dynamics during position control, results in a limit cycle. But using thruster force feedback one achieves better performance in the same cases.