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Because of the light weight and less wear and tear on components, the flexible beam/arm has been and will continue to be an appealing option for civil and military applications, such as space-based flexible manipulators. However, flexibility brings with it unwanted oscillations and severe chattering which may even lead to an unstable system. To tackle these challenges, a two-time scale controller is presented to track a desired tip point signal and at the same time mitigate the tip point vibration using direct vision feedback. In particular, an linear quadratic regulator (LQR) controller in the fast mode stabilizes the oscillations of the beam, and a boundary layer augmented sliding mode controller is proposed to track the desired position. To obtain more precise information of the tip point location and facilitate the easy extension to multiple-flexible-link problems, a camera is used to provide vision feedback in which the delayed vision signal is compensated by the state estimator and predictor. The vision data, which provides a direct measurement of the tip point, proves to be a better substitute for the more traditional strain gauge, which can only provide indirect measurements based on the mathematically derived mode shapes of the beam. The controller is experimentally verified, and shown to exceed the performance of other tested controllers.
Date of Publication: Sept. 2009