This paper proposes a novel input shaping method for under-damped systems. The most important advantage of this method is that only the signals of system outputs are required for the filter design. As the model information on the target system is not needed, the problem of parameter uncertainty is avoided. The designed filter can minimize the difference between the outputs of the actual system and the reference model. Simulation and experimental results showed that the resulting filters were not only able to effectively eliminate the vibrations in the system outputs, but also achieve the desired system response time. The robustness of the resulting filters against the parameters variation was also verified by simulation and experimental results.