Active Force Control of An Inverted Pendulum: Simulation and Experimental Implementation

Abstract

The paper describes the simulation and practical implementation of active force control
(AFC) with proportional-integral-derivative (PID) control strategy to an inverted
pendulum system. The resulting two-degree of freedom (2-DOF) control system essentially
comprises two main feedback control loops to facilitate the control needs with reference to
the outer and inner loops. The outer control loop employs two PID controllers for the
computation of the desired force that use the cart position and pendulum angle errors as
the inputs to the respective controller. The inner loop of the control system implements an
AFC loop that is cascaded in series with each of the PID controller for the compensation
of the disturbances. An experimental rig was designed and developed, in which the
validation of the proposed AFC-based control method was subsequently carried out in realtime
incorporating the MATLAB/Simulink computing platform plus the use of Arduino
MEGA microcontroller. The performance of the proposed PID+AFC control scheme was
evaluated and benchmarked against the conventional PID controller to examine the
robustness of the proposed control method. It was found that the experimental results
demonstrate the superiority of the PID+AFC controller over the conventional PID
counterpart. The overshoot of the system response was reduced and the response of the
proposed controller was more stable, thereby implying that the stabilization of the inverted
pendulum is improved via the proposed control scheme; the inverted pendulum was able to
maintain an upright position when the controllers were activated.