Featherstone, Roy2015-12-101741-3176http://hdl.handle.net/1885/58551This paper presents a new method for calculating operational-space inertia matrices, and other related quantities, for branched kinematic trees. It is based on the exploitation of branch-induced sparsity in the joint-space inertia matrix and the task Jacobian. Detailed cost figures are given for the new method, and its efficacy is demonstrated by means of a realistic example based on the ASIMO Next-Generation humanoid robot. In this example, the new method is shown to be 6.7 times faster than the basic matrix method, and 1.6 times faster than the efficient low-order algorithm of Rodriguez et al. Furthermore, cost savings of more than 50,000 arithmetic operations are obtained in the calculation of the inertia-weighted pseudoinverse of the task Jacobian and its null-space projection matrix. Additional examples are considered briefly, in order to further compare the new method with the algorithm of Rodriguez et al.Keywords: Arithmetic operations; Basic matrices; Cost saving; Example based; Humanoid robot; humanoids; Inertia matrix; Intertia; Jacobians; Kinematic tree; Projection matrix; Pseudo-inverses; robot dynamics; Space dynamics; Anthropomorphic robots; Jacobian matrice brain-induced sparsity; humanoids; operational-space intertia; robot dynamicsExploiting Sparsity in Operational-space Dynamics201010.1177/02783649093576442016-02-24