Kinematic Analysis of a Novel Parallel 2SPRR+1U Ankle Mechanism in Humanoid Robot

Abstract

Parallel mechanisms are increasingly being used as modular subsystems in various robots and man-machine interfaces for their good stiffness, payload to weight ratio and dynamic properties. This paper presents the kinematic analysis of a novel parallel mechanism of type 2SPRR+1U for application as a humanoid ankle joint with two degrees of freedom. Tools from computational algebraic geometry are used to provide solutions to the forward and inverse kinematics problems. These are further used to characterize the workspace of this mechanism and provide description of its singularity curves. The kinematic analysis demonstrates that the chosen design can provide human ankle like workspace and good torque transmission capability without suffering from any singularities which makes it an ideal candidate for ankle joint module in humanoid robots.