Dynamic analysis of a 7-DOF redundant and hybrid mechanical arm

A novel 7-DOF redundant and serial-parallel hybrid humanoid arm mechanism was proposed, inspired by the motion characteristics of human arm joints, and the dynamic modeling method of the hybrid mechanism was proposed taking the mechanism as an example. The velocity and acceleration of each component are derived by the vector method in respective joint coordinate system, according to the motion transmissibility characteristics. The equilibrium equations of the redundant hybrid mechanical arm are established by the Newton-Euler method in respective joint coordinate system. The number of the unknown variables of the required solutions are 27, since the shoulder joint is an over-constrain mechanism. The number of dynamic equations based on Newton's Euler method is 24. Three deformation coordination equations are derived by utilizing the micro-deformation and superposition principle, by adding the relation between the deformation of the member caused by the redundant constrained force (torque) and the position error of the moving platform as a complementary condition. The complete dynamics model of the manipulator is obtained by simultaneous equations. The correctness of dynamics model is verified by simulation results of the linear, parabolic and circular trajectories. The correctness of the modeling lays the foundation for further research and application of the mechanism. Copyright ©2018 Journal of Zhejiang University (Engineering Science). All rights reserved.