Sim-to-Real Transfer Learning using Robustified Controllers in Robotic Tasks involving Complex Dynamics

TL;DR

This paper introduces a method for learning robust controllers in simulation that generalize better to real robots, significantly reducing fine-tuning time for complex dynamic tasks like maze navigation.

Contribution

The paper proposes a robustification technique in simulation by varying parameters, which decreases real-world fine-tuning and simplifies physics modeling for complex robotic tasks.

Findings

Robustified controllers require less fine-tuning in transfer learning.

The approach effectively handles complex dynamics like static friction.

Demonstrated on a maze navigation task with real robot experiments.

Abstract

Learning robot tasks or controllers using deep reinforcement learning has been proven effective in simulations. Learning in simulation has several advantages. For example, one can fully control the simulated environment, including halting motions while performing computations. Another advantage when robots are involved, is that the amount of time a robot is occupied learning a task---rather than being productive---can be reduced by transferring the learned task to the real robot. Transfer learning requires some amount of fine-tuning on the real robot. For tasks which involve complex (non-linear) dynamics, the fine-tuning itself may take a substantial amount of time. In order to reduce the amount of fine-tuning we propose to learn robustified controllers in simulation. Robustified controllers are learned by exploiting the ability to change simulation parameters (both appearance and dynamics) for successive training episodes. An additional benefit for this approach is that it alleviates the precise determination of physics parameters for the simulator, which is a non-trivial task. We demonstrate our proposed approach on a real setup in which a robot aims to solve a maze game, which involves complex dynamics due to static friction and potentially large accelerations. We show that the amount of fine-tuning in transfer learning for a robustified controller is substantially reduced compared to a non-robustified controller.