Flexibility is often an unavoidable limitation when large-workspace high-speed manipulation is required. This flexibility can be mitigated in some circumstances through feedback control methods. However, these methods only correct for vibration after it has been measured. Therefore, if low-vibration reference commands can be generated, then the utility of these systems can be greatly improved. However, there are instances where system nonlinearities limit the effectiveness of many command-shaping techniques. This paper proposes a method for the generation of fast vibration-limiting trajectories for flexible systems based on the differential-flatness property of nonlinear systems. This approach is applied to a tower crane for simulation and experimental validation. The results are compared to those from standard command-shaping techniques. Practical implementation issues for real world systems are discussed.

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