Comment on "Precise Control for vibration of rigid-flexible mechanical arm"

The results presented in a paper by Zichen et al. [1] has some flaws. The idea in [1] is to combine assumed modes method using an integration method with optimal control adaptive law for a spatial rigid-flexible mechanical arm as an underactuated mechanical systems (UMS). The nonlinear dynamic equation formulation from reference [6] is incorrectly used in [1]. Furthermore, the control law approach in [1] was to achieve a similar result for a UMS rigid manipulator as the one published by Spong [2] and a proper citation must have been credited. (C) 2014 Elsevier Ltd. All rights reserved.