Experimental verification of stability analysis of closed-loop signal shaping controllers

Input shaping is a vibration control technique that operates by filtering reference commands so that the modified (or shaped) command does not excite the system's natural frequencies. Usually, input shaping is implemented as a filtering operation outside of any feedback loops. However, this prevents input shaping from effecting some vital control issues including disturbance rejection, initial condition response, etc. Therefore, some research has studied the use of input shapers within feedback loops. This paper will present some investigations toward the fundamental understanding of how input shapers utilized within feedback loops affect closed-loop stability. Experimental results on a large bridge crane illustrate the key results.