“…In the case of the single pendulum, controllers have been designed to swing the pendulum up and/or stabilize it in the inverted position [11] , [46] , [47] , [47] , [48] , [49] , [50] , [51] , [52] , [53] , [54] , [55] , [56] , [57] , [58] , [59] . Similar control methods have been developed to swing up the arms of the double and triple pendulums [25] , [28] , [58] , [60] , [61] , [62] , [63] , [64] , [65] , [66] , [67] , [68] , [69] , [70] , [71] , [72] , stabilize their arms in various unstable vertical positions [58] , [60] , [73] , [74] , [75] , and perform time-periodic motion [26] , [27] , [31] , [76] , [77] , [78] . Due to the chaotic nature of multi-armed pendulums, the sensitivity increases as more arms are added to the pendulum, thus making it an increasingly difficult control benchmark.…”