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This study presents a method for global estimation of joint velocities in robotic manipulators. The authors consider a non-minimal model of a robotic manipulator and design an adaptive observer capable of handling uncertainties in robot dynamics. Smoothness of the dynamics of the proposed observer allows its easy implementation in comparison with non-smooth observers. Dimension of the proposed observer is shown to be at least 3n where n stands for the manipulator's degrees of freedom. This number is less than the dimension of most existing globally convergent adaptive observers. Global asymptotic convergence of state estimates to their true values is achieved under no persistency of excitation condition. Furthermore, under noisy position and force measurements, the proposed observer guarantees ultimate boundedness of estimation errors. Simulation results illustrate low noise sensitivity of the proposed observer in comparison with non-smooth observers.
Date of Publication: December 2010