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In this brief, we propose a nonlinear tracking control method of 3-D overhead crane systems which works well even in the presence of the initial swing angle and the variation of payload weight. Besides the practical importance of the overhead cranes, this study is also theoretically interesting because four variables (trolley and girder positions, two swing angles) should be controlled using two control inputs (trolley and girder forces). To control such an underactuated system as cranes, a simple proportional-derivative (PD) controller has been normally used. Unlike the conventional regulation control, the newly proposed nonlinear tracking control law further improves the performance and robustness, which is based on the feedback linearizing control by using the swing angular rate as well as the swing angle. The proposed nonlinear tracking control law eliminates the nonlinear characteristics of the system and achieves the satisfactory position control and swing suppression, even when the initial swing angle and the variation of payload weight exist. We present the stability analysis and simulation results to demonstrate the practical application of our scheme.
Date of Publication: July 2009