| Summary: | This paper describes an innovative design based on the spectral approach of a novel shaper that eliminates frequency components that induce unwanted residual oscillations in various flexible mechanical systems, such as tower cranes or chain carousels, which are vital to many manufacturing and material-handling processes. However, their physical structure leads to flexible effects that limit their usefulness. Apart from the circular motion problem, control is provided by a single actuator, which makes it a so-called underactuated system. The input signal needs to be modified so that the spectral components from several interconnected degrees of freedom are considered together during shaper design, which increases the complexity of this task since one of its components induces nonlinear behavior. This means that traditional shaping techniques, based on linear theory, fail to provide good performance over the whole input range. The underdamped dynamics of the model and the effect of nonlinearities on the spectrum of the final signal are examined; the proposed method for application as a command shaping control technique is applied; and its effectiveness is analyzed by simulation and real-time implementation. The theoretical results verified on an experimental crane system confirm the expected oscillation phenomenon and show that the designed nonlinear shaper can reduce the payload swing significantly.
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