Adaptive robust control design for underwater multi-DoF hydraulic manipulator

Owing to the increasing demand on exploration of subsea resources and the accumulating development of hydraulic technology, underwater hydraulic manipulator is widely used in various underwater operations. However, the complexity of underwater tasks is increasing at this stage, which leads to the increasing requirements for precision operation of underwater hydraulic manipulator. Nevertheless, the complexity of hydraulic system model together with severe external disturbance from subsea can make it more difficult to realize the precise motion control of underwater hydraulic manipulator. In order to realize the precise motion control of underwater hydraulic manipulator and make it suitable for underwater precision operations, an adaptive robust controller combined with backstepping strategy is proposed in this paper. To be specific, the backstepping method is used to simplify the manipulator model analysis for setting off the impact of higher-order model, and the influence from underwater external disturbance and the hydraulic dynamic model error could be handled well by the robust controller. Moreover, the parameter adaptive approach is introduced into the controller to cope with the model parameter uncertainties. Then, comparative simulation and experiment result are shown to illustrate the stability and effectiveness of the controller designed.