Control of Poly-Articular Chain Trajectory Using Temporal Sequence of Its Joints Displacements

This paper discusses on the role of joint temporal sequence while moving a two-dimensional arm from an initial position to targets into the fingertip workspace in humans. For this purpose, we proposed a general monotonic model of joint asymmetric displacement. Optimization consisted in minimizing least square displacement of either fingertip or arm centre of mass from arm initial position to four targets located into fingertip workspace, i.e. contralaterally and ipsilaterally. Except for 60° ipsilateral target, results of the simulation presented in all cases temporal sequences of the shoulder, the elbow and the wrist. We concluded that primary function of proximal-to-distal or distal-to-proximal joint sequence is to flatten the trajectory of the fingertip or body centre of mass.