Design and Implementation of Pole-placement Control Strategy for Experimental Double Inverted Pendulum

Systems having degrees of freedom more than the number of control inputs, are called under-actuated systems. Due to small size of actuators, their cost and energy utilization are decreased and they can be implemented in a more simple way. Inverted pendulum system which is an unstable, nonlinear, non-minimum phase and uncertain system, is one of the most applicable and fundamental cases of under-actuated systems. In this paper, an inverted pendulum is modelled as a two degrees of freedom model. Then, a linear multivariable feedback controller is designed to stabilize the experimental set-up. The experimental inverted pendulum is constituted of two links; while one actuator is installed on the first link joint. According to the simulation results, a DC servo motor with specifications of 12 v and 1.2 W nominal power, is selected as the actuator. Experimental results show that the designed controller can appropriately control and stabilize the experimental system around its unstable up-equilibrium point up to6o.