Coupling analysis of a 5-degree-of-freedom hybrid manipulator based on a global index

Abstract

Parallel kinematic machines have been applied in aerospace and automotive manufacturing due to their potentials in high speed and high accuracy. However, there exists coupling in parallel kinematic machines, which makes dynamic analysis, rigidity enhancement, and control very complicated. In this article, coupling characteristics of a 5-degree-of-freedom (5-dof) hybrid manipulator are analyzed based on a local index and a global index. First, velocity analysis as well as acceleration analysis of the robot is conducted to provide essential information for dynamic modeling. Then the dynamic model is built based on the principle of virtual work. Whereas the mass matrix is off-diagonal, a local coupling index as well as a global index is defined, based on which coupling characteristics of the robot are analyzed. Results show that distributions of coupling indices are symmetric due to its structural features. And dimensional parameters, structural parameters, as well as mass parameters have a large influence on the system’s coupling characteristics. Research conducted in the article is of great help in optimal design and control. Meanwhile, the method proposed in the article can be applied to other types of parallel kinematic machines or hybrid manipulators.

A new hierarchical approach for the optimal design of a 5-dof hybrid serial-parallel kinematic machine

“…Taking the Trimule with parameters in [30,31] as an example, distributions of the condition number over a working plane are depicted in Fig. 4.…”

“…Based on mass parameters in [30], distributions of the maximum driving force among the three actuators , max 1~3 max a k k τ = over a working plane are calculated and shown in Fig. 5.…”

“…Based on the optimal design variables in this paper and parameters in [30,31], performance comparison of the two Trimule robots is listed in Table 4. To make it reasonable, performance comparison is conducted in their whole task workspace.…”

“…To make it reasonable, performance comparison is conducted in their whole task workspace. As shown in Table 4, the Trimule robot in [30,31] presents better kinematic performance throughout its whole task workspace. On the contrary, the optimal one in this paper has better dynamic behaviors and stiffness throughout the whole task workspace even though its kinematic performance is not good as the one in [30,31].…”

“…As shown in Table 4, the Trimule robot in [30,31] presents better kinematic performance throughout its whole task workspace. On the contrary, the optimal one in this paper has better dynamic behaviors and stiffness throughout the whole task workspace even though its kinematic performance is not good as the one in [30,31]. Especially, there is a relatively large difference in the dynamic index (acceleration ability) F 2 and stiffness index F 4 , which demonstrates that the optimal Trimule in this paper can achieve better working efficiency and rigidity.…”