Abstract

In this investigation, the nonlinear swing-up problem associated with the cart-pole system modeled as a multibody dynamical system is solved by developing a deep Reinforcement Learning (RL) controller. Furthermore, the sensitivity analysis of the deep RL controller applied to the cart-pole swing-up problem is carried out. To this end, the influence of modifying the physical properties of the system and the presence of dry friction forces are analyzed employing the cumulative reward during the task. Extreme limits for the modifications of the parameters are determined to prove that the neural network architecture employed in this work features enough learning capability to handle the task under modifications as high as 90% on the pendulum mass, as well as a 100% increment on the cart mass. As expected, the presence of dry friction greatly affects the performance of the controller. However, a post-training of the agent in the modified environment takes only thirty-nine episodes to find the optimal control policy, resulting in a promising path for further developments of robust controllers.

Highlights

  • This section provides some necessary background material and emphasizes the significance of the present research

  • This dynamic model is sufficiently complex to exhibit an interesting nonlinear behavior during the swing-up task and, at the same time, sufficiently simple to be used for a parametric study of the robustness and/or sensitivity of a nonlinear control law devised by using a deep Reinforcement Learning (RL) method

  • Learning (RL) controller applied to the cart-pole swing-up problem is performed

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Summary

Introduction

We provide some necessary background material and emphasizes the significance of the present research. The control of articulated mechanical systems relies on a high level of system understanding [1], expressed mainly through multibody dynamics models [2,3,4]. Considering model-based control algorithms, such as the linear-quadratic regulator (LQR) and back-stepping (BS) techniques, the use of differential-algebraic equations of motion typical of the multibody approach is challenging. These heavily rely on model accuracy, which hinders their application to real platforms [7].

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