Design and comparison of two linear controllers with precompensation gain for the Quadruple inverted pendulum

TL;DR

This paper compares two linear control methods, LQR and pole placement, with precompensation gain for stabilizing a quadruple inverted pendulum on a cart, focusing on eliminating steady-state error and analyzing performance.

Contribution

It introduces a workflow for designing and comparing LQR and pole placement controllers with precompensation gain for the quadruple inverted pendulum system.

Findings

Both controllers successfully stabilize the system.

Controllers achieve desired cart position setpoints.

Performance differences are discussed.

Abstract

In this work we present a workflow for designing two linear control techniques applied to the dynamic system quadruple inverted pendulum mounted on a cart (QIP) where the steady state error on cart position is eliminated through a precompensation gain. The first control law designed was based on LQR, technique that stabilizes the system states based on a minimization of the total energy of the system states and the second control technique was pole placement by 2nd order system approximation, this method allowed to define a settling time and overshoot of the desired response of the plant, for this control the system was considered SISO, being the only output of the plant the horizontal position of the cart. To eliminate the steady-state error generated by both linear controllers, an analysis of the stationary response of the system under control in the Laplace Domain was performed. The simulation environment used to validate the results presented in this paper was Simscape of Matlab, it is a simulation environment that allowed to simulate the dynamic of nonlinear mechanical systems. The results obtained indicate that both controllers are able to stabilize the plant and move the cart position to the desired setpoint. Finally, we discuss about the performances of both linear control techniques.