Nonlinear depth control in under-actuated AUV

In underwater vehicles controlled by thrusters and fins, effect of the AUV depth control could be seriously affected because of dead zone nonlinearity in steering gear transmission system. This paper takes a certain AUV as an example. In this paper, a nonlinear pid controller is desired in considering of the actuator being saturated; response speed of the actuator is improved through tracking differentiator; dynamic performance is improved in using of nonlinear combination. Also, a nonlinear PID depth controller with adaptive compensation is given. The controller is programmed in consider of dead zone nonlinearity in steering gear transmission system; under-actuated motion character with external bounded interference and model parameter uncertainty. The controller is designed according to adaptive concept and the model. Finally, simulation experiment show that the controller performed well.