Inverse dynamics and servomotor parameter estimation of a 2-DOF spherical parallel mechanism

Abstract

A novel reconfigurable 5-DOF hybrid manipulator-TriVariant-B is composed of a 2-DOF spherical parallel mechanism which is serially connected with a 3-DOF open-loop kinematic chain undergoing one translation and two rotations by a prismatic joint. The merit of this design is that a relatively large workspace/limbstroke ratio can be achieved thanks to the decomposition of the fixed point rotation and the relative translation. In this paper, on the basis of inverse dynamic formulation of the 2-DOF spherical parallel mechanism, an approach is proposed for estimating the servomotor parameters including moment of inertia, rated speed and the maximum torque in a quick manner. The approach has been employed for the development of a prototype for frame cutting process.parallel kinematic machine, inverse dynamics, servomotor parameters From numerous parallel kinematic machines (PKM), a family of PKM with fewer than 6 degrees of freedom (DOF) can be classified which is basically composed of a properly constrained active/passive limb and several identical unconstrained active limbs with 6-DOFs [1] , such as the SKM [2] and CGT machine [3] . If the properly constrained limb undergoes a fixed point rotation about two orthogonal axes and a translation along its axial axis, this family of PKM can be further divided into a sub-family named spherical coordinate parallel mechanism (SCPM) [4] . Tricept [5][6][7][8] , Gorge V [9] and TriVariant [10][11][12] are typical examples in this sub-family. The most significant feature of the SCPM is the large workspace/footprint ratio. Thus, by attaching a 2-or 3-DOF rotating head to the platform, a plug-and-play hybrid module can be formed, which can be used to configure different machines for various applications. Nevertheless, for the in-parallel SCPM, to achieve a relative large workspace requires the unconstrained limbs to have relative

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