This paper proposes an approach to evaluate the performance of robot manipulator from the view of energy analysis. Based on the dynamics analysis of the manipulator, the Energy Distribution Index (EDI) is defined to depict the energy increment contribution of its subsystem to the whole manipulator. EDI is applied to the evaluation of the buffering capability of the manipulator working under unpredictable and heavy external loads. A series of buffering indices, the Static Buffering Index (SBI), Kineto-Static Buffering Index (KBI), Dynamic Buffering Index (DBI), and Global Buffering Index (GBI) are proposed to evaluate the buffering capability under different conditions. In order to acquire higher calculation accuracy, the general stiffness mapping of manipulators considering the actuator stiffness, inertia of the manipulator, damping, as well as elasticity of linkages is developed. Three different robot manipulators are studied as evaluation cases, in which the buffering structures are mechanism with variable topology, linear springs, and the elasticity of linkages respectively. The case studies show that the indices based on energy analysis have the advantage of coordinate free and are effective for buffering capability evaluation. robot manipulator, performance evaluation, energy analysis, stiffness mapping Citation:Wang H, Zhao K, Chen G L, et al. Energy Distribution Index for robot manipulators and its application to buffering capability evaluation.