We study the occurrence of the synchronous rotation of a set of four uncoupled nonidentical double pendula arranged into a cross structure mounted on a vertically excited platform. Under the excitation, the pendula can rotate in different directions (counter-clockwise or clockwise). It has been shown that after a transient, many different types of synchronous configurations with the constant phase difference between pendula can be observed. The experimental results qualitatively agree with the numerical simulations.
Strzalko, J., Grabski, J., Wojewoda, J., Wiercigroch, M., & Kapitaniak, T. (2012). Synchronous rotation of the set of double pendula: Experimental observations. Chaos, 22(4), . https://doi.org/10.1063/1.4740460