Structure estimation of an articulated object by motion image analysis based on factorization method

A method for obtaining the structure of a target object from a motion image sequence observed from the motions of an articulated object or a multiple number of objects is proposed. By this technique, the motion and structure of each rigid body part are estimated and the restricting relationships between rigid bodies are estimated in two stages when estimating the structure of an object with a large number of degrees of freedom such as an articulated object. In the first stage, the structure and motion of each rigid body are estimated based on observed information obtained by grouping observed feature points for each rigid body, by using a factorization method having robustness against observation noise. In the second stage, the restricting relationships between rigid bodies are estimated by using the motion parameters of each rigid body. In this paper, the presence and absence of joints and the order numbers of the restricting relationships between rigid bodies are classified in terms of the ranks of the coefficient matrices by considering rotating joints and expressing the restricting relationships as linear simultaneous equations. The proposed method is applied to simulations and observations of the motions of the hand and the back of the hand and its effectiveness is verified. © 2001 Scripta Technica, Syst. Comp. Jpn.