Reinforcement Learning for High-dimensional Continuous Control in Biomechanics: An Intro to ArtiSynth-RL

Abstract

Neural control is an exciting mystery which we instinctively master. Yet, researchers have a hard time explaining the motor control trajectories. Physiologically accurate biomechanical simulations can, to some extent, mimic live subjects and help us form evidence-based hypotheses. In these simulated environments, muscle excitations are typically calculated through inverse dynamic optimizations which do not possess a closed-form solution. Thus, computationally expensive, and occasionally unstable, iterative numerical solvers are the only widely utilized solution. In this work, we introduce ArtiSynth, a 3D modeling platform that supports the combined simulation of multi-body and finite element models, and extended to support reinforcement learning (RL) training. we further use ArtiSynth to investigate whether a deep RL policy can be trained to drive the motor control of a physiologically accurate biomechanical model in a large continuous action space. We run a comprehensive evaluation of its performance and compare the results with the forward dynamics assisted tracking with a quadratic objective function. We assess the two approaches in terms of correctness, stability, energy-efficiency, and temporal consistency.