Contacts from Motion: Learning Discrete Features for Automatic Contact Detection and Estimation from Human Movements *

This paper presents a novel method for detecting and estimating contact forces only from human motions using machine learning techniques. Knowing the location of the contacts with the environment and the magnitude of the exerted force is critical for dynamic human motion analysis. However, their annotation is usually made manually from captured motion data especially in case of multiple contacts even if the data includes force measurement. Moreover, most existing human motion datasets do not include contact force. To overcome these bottlenecks, we introduce a network that leverages vector-quantized variational autoencoder (VQ-VAE) and self-attention that learns a small set of discrete feature values representing various contact states. These feature values, called contact codes, allow human motions to be converted to contact states and resulting forces. By applying an optimization for contact estimation with a reduced set of manual annotations, the existence of contacts can be automatically determined, which is essential information for dynamic analysis. We validated the effectiveness and potential usefulness of the proposed method with a human walking gait dataset, by converting the human motions into contact sequences and forces and applying the estimated contacts to dynamic motion analysis.