Approximate nonlinear control for a two degree of freedom overhead crane: theory and experimentation

In this paper, we develop nonlinear algorithms for accurately controlling the payload position for a two-degree of freedom overhead crane system. Since this model does not lend itself to nonlinear control design in a straightforward manner, we develop an approximate model of the system which facilitates the construction of error systems suitable for the development of back-stepping type controllers. A Lyapunov-like argument is then applied to the approximate model under the proposed control to elucidate payload positioning performance. Experimental results are used to validate the performance of the control approach. A discussion of cable flexibility and actuator dynamics is also presented.