# Factored Pose Estimation of Articulated Objects using Efficient Nonparametric Belief Propagation

## TL;DR

This paper introduces an efficient nonparametric belief propagation method for estimating the continuous, multi-modal poses of articulated objects in cluttered environments, enabling robots to perceive and manipulate complex jointed objects.

## Contribution

It presents a novel factored approach using a pairwise Markov Random Field and the PMPNBP algorithm for accurate articulated pose estimation from RGBD data.

## Key findings

- The method effectively estimates object-part poses in high-dimensional spaces.
- It demonstrates convergence over complex articulated scenes.
- The approach outperforms existing techniques in pose accuracy.

## Abstract

Robots working in human environments often encounter a wide range of articulated objects, such as tools, cabinets, and other jointed objects. Such articulated objects can take an infinite number of possible poses, as a point in a potentially high-dimensional continuous space. A robot must perceive this continuous pose to manipulate the object to a desired pose. This problem of perception and manipulation of articulated objects remains a challenge due to its high dimensionality and multi-modal uncertainty. In this paper, we propose a factored approach to estimate the poses of articulated objects using an efficient nonparametric belief propagation algorithm. We consider inputs as geometrical models with articulation constraints, and observed RGBD sensor data. The proposed framework produces object-part pose beliefs iteratively. The problem is formulated as a pairwise Markov Random Field (MRF) where each hidden node (continuous pose variable) is an observed object-part's pose and the edges denote the articulation constraints between the parts. We propose articulated pose estimation by Pull Message Passing algorithm for Nonparametric Belief Propagation (PMPNBP) and evaluate its convergence properties over scenes with articulated objects.