Motion control of underwater robots with consideration of input saturations

In controlling underwater robots, accurate tracking, convergence rate, and stability are very important. The simultaneous adjustment of these features in a control algorithm will be possible by setting the appropriate control gains. Also, due to the direct effect of control gains on the control inputs, it is impossible to choose appropriate gains without considering the limitations of the robot’s actuators. In a situation where the control input is higher than the saturation limit of the actuator, this can lead to the instability of the control algorithm. On the other hand, simultaneously considering the saturation limit of an actuator and the stability of the control algorithm is a challenging problem. In this research, a control algorithm including kinematic and dynamic control based on the Lyapunov approach is presented. In the design of the kinematic control, the speed saturation limits and in the dynamic control design, the force saturation limits of the actuators have been considered. The advantage of the proposed method is that the saturation limit of the actuators is predetermined in the design of the control algorithm. To evaluate the performance of the proposed control algorithm, various analyses were performed. The obtained results showed that the control algorithm while following the reference trajectories, has fully met the requirements of the saturation limits of the actuators.