Robust control of Cassette Multi-functional Mover for ITER remote handling tasks

The Cassette Multi-functional Mover (CMM) is designed for performing safety-critical divertor cassettes movements in ITER. Therefore, special attention should be paid to the design and analysis of its feedback controllers. Firstly, the design of the multivariable tracking controller possesses many challenges. The hydraulic manipulator dynamics are highly nonlinear; moreover, the loaded mass spans a wide range. Secondly, a number of test runs (even a large number) do not necessarily reveal the controller sensitivity to all the system uncertainties. Thus, some theoretical tools are needed to assess the robustness of the controller. H∞-based approach is a reasonable choice since it provides a set of metrics to evaluate the controller robustness which can be validated in tests. In this paper, the dynamic model of CMM is first derived, characterizing the nominal system model and the model uncertainties. Then, a multivariable H∞ loop-shaping controller is synthesized which ensures both the robust stability and robust performance. Finally, the designed controller is validated by simulation results.