End-point vibration sensing of planar flexible manipulators through visual servoing

A visual servoing approach to the control of planar flexible robotic manipulators is adopted in this paper, based on the composite control theory, where the camera sensor is used together with the strain gauge measurements, to estimate the tip deformation. A fast Kalman filter, built on an integral manifold approximation of the manipulator model, can be used to fuse in the most effective way the measurements coming from different sensors, each one perturbed by its own noise. As a consequence, the signal to noise ratio of the deformation measurements can be effectively improved. A difficulty however arises in deriving a linear relation between the camera output and the state variables: the specific contribution of this paper is the derivation of such a linear relation in the fast time scale. Simulation results based on a two link planar flexible manipulator show the potential of the proposed approach to gain a more effective suppression of the tip vibrations, while an experimental example demonstrates its practical feasibility.