Subsea Inspection and Intervention with Underwater Swimming Manipulators
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This thesis examines dynamic motion control approaches and interaction control approaches for underwater swimming manipulators (USMs). USMs are innovative underwater vehicles with potential to increase efficiency and reduce costs of subsea inspection, maintenance and repair. Dynamic motion control of USMs can be used for USM inspection tasks, while interaction control must be considered for USM interaction with the environment. To illustrate the performance of the different controllers, a USM simulator is implemented with a complete control framework. An important aspect when designing dynamic control approaches for USMs is uncertainty in model knowledge. This is taken into account by the presented dynamic motion control approaches. For dynamic motion control, three control strategies are presented: adaptive inverse dynamics control, the super-twisting algorithm with adaptive gains and non-regressor-based adaptive control. The dynamic motion controllers are implemented with the USM simulator. The stability properties of the controllers are analyzed and their expected behaviour is compared to how they behave in simulations. The simulations show that all the dynamic motion control approaches result in behaviour that is in line with the theoretical analysis. The interaction control approaches presented in the thesis are an impedance controller and a PI force controller with impedance control. The simulator is extended to include interaction forces for the task of turning a valve and the interaction controllers are implemented with the simulator. The simulation results with the different interaction controllers are presented and the control strategies are compared. Both interaction controllers perform well in the simulations.