Touch-Based Manipulation with Multi-Fingered Robot using Off-policy RL and Temporal Contrastive Learning

Tactile information holds promise for enhancing the manipulation capabilities of multi-fingered robots. In tasks such as in-hand manipulation, where robots frequently switch between contact and non-contact states, it is important to address the partial observability of tactile sensors and to properly consider the history of observations and actions. Previous studies have shown that Recurrent Neural Network (RNN) can be used to learn latent representations for handling observation and action histories. However, this approach is usually combined with on-policy reinforcement learning (RL) and suffers from low sample efficiency. Integrating RNN with off-policy RL could enhance sample efficiency, but this often compromises stability and robustness, especially as the dimensions of observation and action increase. This paper presents a time-contrastive learning approach tailored for off-policy RL. Our method incorporates a temporal contrastive model and introduces a surrogate loss to extract task-related latent representations, enhancing the pursuit of the optimal policy. Simulations and real robot experiments demonstrate that our proposed method outperforms RNN-based approaches.