Using approximate multi-crane frequencies for input shaper design

Cranes are the primary heavy lifter used in a wide array of industries. For the transport of large payloads, multiple cranes are often employed in a cooperative manner. One factor limiting the efficiency of all cranes is payload oscillation. For multi-crane lifts, the payload oscillation is a function of an array of crane and payload parameters, many of which are difficult to measure in real-time. This paper investigates the use of the estimates of the multi-crane natural frequencies in input shaper design. Two methods to design input shapers that rely only on the suspension cable lengths involved in the lift are presented. The accuracy of these estimations and the resulting effectiveness of input-shaping control are studied via simulation and experimental testing with a two-crane system.