Online algebraic identification of the payload changes in a single-link flexible manipulator moving under gravity

This paper presents a method for the on-line identification of the payload carried by a single-link flexible manipulator whose movement is constrained to the vertical plane. The vertical movement of the robot makes the effect of gravity not negligible, and determines therefore, the non-linear behaviour of the analysed system. The proposed estimator is based on the algebraic derivative approach in the frequency domain. The short period of time it takes for the algorithm to make an estimate, and its low computational burden make it suitable for real-time and adaptive control applications. The proposed estimator is experimentally tested in several situations carefully chosen to reproduce routine operations of the flexible manipulator.