Extending FABRIK with model constraints

Forward and Backward Reaching Inverse Kinematics (FABRIK) is a recent iterative inverse kinematics solver that became very popular because of its simplicity, convergence speed and control performance, especially in models with multiple end effectors. In this paper, we extend and/or adjust FABRIK to be used in problems with leaf joints and closed-loop chains and to control a fixed inter-joint distance in a kinetic chain with unsteady data. In addition, we provide optimisation solutions when the target is unreachable and a proof of convergence when a solution is available. We also present various techniques for constraining anthropometric and robotic joint models using FABRIK and provide clarifications and solutions to many questions raised since the first publication of FABRIK. Finally, a human-like model that has been structured hierarchically and sequentially using FABRIK is presented, utilising most of the suggested joint models; it can efficiently trace targets in real time, without oscillations or discontinuities, verifying the effectiveness of FABRIK. Copyright (c) 2015 John Wiley & Sons, Ltd.