Study On Control Methods Of Rotary Inverted Pendulum System

As a complicated, high speed, non-linear, multivariable, strongly coupled,naturally unstable non-minimum phase system, inverted pendulum represents theunder-driven control family. In the study of many control methods researchersalways lack proper controlled objects, thus lose the opportunity to further theresearch work and lead to the waste of valuable research resources. Invertedpendulum is a kind of ideal controlled object platform with its simple structure andrelatively low cost. In the family of inverted pendulum, rotary inverted pendulum(RIP) stands out as an effective testing equipment in the experiment and research ofcontrol strategies. Under the help of it, various abstract control concepts such asstability, controllability, convergence speed and noise resistance can be displayedconspicuously.This paper analytically investigates the structure of rotary inverted pendulumand the latest relative research productions at home and abroad. On this basis, thenon-linear mathematical model of the utilized RIP system is formulated by Lagrangemethod and the corresponding control methods are studied. After analyzing thenon-linear characteristics of the system, in the vicinity of the equilibrium point of it,the RIP model is linearized and its naturally unstable characteristic andcontrollability are verified. In addition, linear quadratic regulator LQR) and poleallocation method are designed and implemented on the RIP system in simulationand field experiment. In order to surpass the limitation of linearization of moderncontrol methods, a direct fuzzy controller is designed and implemented to balancethe RIP system, however, some oscillation occurs in the region near the origin.In order to increase the resolution of the fuzzy controller and thus to improvethe performance of the control system, an "auto-tuned fuzzy control" strategy isproposed. Based on linear controller parameters, it automatically tunes its parameterson-line to adapt to changing process dynamics. Experimental results are presented toshow the stable and robust responses of the control system. These results alsoindicate that the utilized synthesis controller effectively expand the region ofoperation of the controller beyond the linear region.