From Simple to Complex Skills:
The Case of In-Hand Object Reorientation

Abstract

Learning policies in simulation and transferring them to the real world has become a promising approach in dexterous manipulation. However, bridging the sim-to-real gap for each new task requires substantial human effort, such as careful reward engineering, hyperparameter tuning, and system identification. In this work, we present a system that leverages low-level skills to address these challenges for more complex tasks. Specifically, we introduce a hierarchical policy for in-hand object reorientation based on previously acquired rotation skills. This hierarchical policy learns to select which low-level skill to execute based on feedback from both the environment and the low-level skill policies themselves. Compared to learning from scratch, the hierarchical policy is more robust to out-of-distribution changes and transfers easily from simulation to real-world environments. Additionally, we propose a generalizable object pose estimator that uses proprioceptive information, low-level skill predictions, and control errors as inputs to estimate the object's pose over time. We demonstrate that our system can reorient objects, including symmetrical and textureless ones, to a desired pose.

Main Results

We first choose the rotation targets that can be achieved by a single rotation axis.
To test if pose predictor is accurate.

Goal: Rotate -90° over z-axis
Goal: Rotate -90° over x-axis
Goal: Rotate -90° over z-axis
Goal: Rotate 135° over y-axis
Goal: Rotate -135° over z-axis
Goal: Rotate -90° over x-axis

We then choose the rotation targets that needs to select two policies.

Goal: Rotate -90° over z-axis then 90° over y-axis.

Pose Prediction in Simulation.

Training Objects.
Novel Objects.