3D Mean-Shift Tracking of Human Body Parts and Recognition of Working Actions in an Industrial Environment

Abstract

In this study we describe a method for 3D trajectory based recognition of and discrimination between different working actions in an industrial environment. A motion-attributed 3D point cloud represents the scene based on images of a small-baseline trinocular camera system. A two-stage mean-shift algorithm is used for detection and 3D tracking of all moving objects in the scene. A sequence of working actions is recognised with a particle filter based matching of a non-stationary Hidden Markov Model, relying on spatial context and a classification of the observed 3D trajectories. The system is able to extract an object performing a known action out of a multitude of tracked objects. The 3D tracking stage is evaluated with respect to its metric accuracy based on nine real-world test image sequences for which ground truth data were determined. An experimental evaluation of the action recognition stage is conducted using 20 real-world test sequences acquired from different viewpoints in an industrial working environment. We show that our system is able to perform 3D tracking of human body parts and a subsequent recognition of working actions under difficult, realistic conditions. It detects interruptions of the sequence of working actions by entering a safety mode and returns to the regular mode as soon as the working actions continue.