Negative Input Shaping: Eliminating Overcurrenting and Maximizing the Command Space

Input shaping is a filtering method used for reducing oscillation in flexible systems. A class of these filters, called negative input shapers, has been developed to improve system rise-time beyond what is achievable using conventional input-shaping filters. However, negative input shapers can cause overcurrenting and subsequent system oscillation, when used with certain reference commands. This class of reference commands is examined in the context of the command space. The command space represents the space of all possible signals that may be issued to a system. It provides insight into how overcurrenting occurs, how overcurrenting can be mitigated, and the influence that mitigation strategies have on system performance. Two overcurrenting mitigation strategies are presented. The operational effects of overcurrenting and overcurrenting mitigation are evaluated using a three-dimensional simulation of a bridge crane, and experimental results from a $10ton$ industrial bridge crane.