Structural Proposition for a Triple Inverted Pendulum and Implementation of Swing-up Control Using an LW-RCP02

In this paper, we propose a new structure for a triple inverted pendulum with easy construction properties. We also implement a swing-up control for the proposed triple inverted pendulum using a lab-built rapid control prototyping environment known as light-weight rapid control prototyping 02 (LW-RCP02). The swing-up control of a triple inverted pendulum has a two-degree-of-freedom structure and requires a very accurate mathematical model. The proposed triple inverted pendulum adopts the same method that was developed for a double inverted pendulum by the authors’ laboratory to achieve excellent matching properties with the model. For free rotation of three pendulums, a hollow shaft revolute joint that can be used with a slip ring is newly proposed. Swing-up control of a triple inverted pendulum is implemented using Simulink and LW-RCP02. Moreover, a two-degree-of-freedom control structure combining feedforward and feedback is adopted for swing-up control of a triple inverted pendulum. We implement the parameter estimation method for the triple inverted pendulum and calculate the trajectory for feedforward control using estimated parameters and the direct transcription method. The uncertainty of feedforward control is compensated by adding a time-varying LQ feedback controller. As the sampling frequency of the implemented controller is 1KHz, real-time control is achievable using a standard PC.