Parameter optimization of heavy-load parallel manipulator by introducing stiffness distribution evaluation index

Abstract

：Aiming at the heavy-load parallel robotic manipulators, other than classic sequential 'topology-dimension-structure' parameter design methodology, this paper proposes a new way to optimize dimension and structure parameters 2 simultaneously. To deal with the low-speed but heavy load working environment, a new type of stiffness performance evaluation index is introduced based on kineto-elastic statics (KES) analysis. This stiffness distribution index, mainly focuses on the stiffness distribution among all parts in the manipulator, along with two other dynamic performance indices and some dimensional constraints, formulate a multi-objective optimization model.Then the particle swarm optimization (PSO) algorithm is introduced to search for the optimum parameters. This method is applied on a widely used TRICEPT parallel manipulator, the dynamic performances before and after optimization are compared to verify this effectiveness of this method.

A New Stiffness Performance Index: Volumetric Isotropy Index

“…where γ is the energy index [5,7,11,52]. Unfortunately, all the above indices are computed numerically.…”

“…Production quality during milling and drilling operations depends on the stiffness performance of the robot. Thus, many academic studies are devoted to the stiffness analysis and evaluation of industrial robots [1][2][3][4][5][6][7].…”

“…Another reason is to optimally design the manipulator parameters by considering the stiffness performance [5][6][7]13,[15][16][17]. The optimal design process of a manipulator requires objective functions that include the stiffness performance indices.…”

Stiffness modeling and analysis of a novel 5-DOF hybrid robot

“…Stiffness is one of the most important performances of the above-mentioned hybrid robots when they are applied for high-speed machining, where high rigidity and high accuracy are crucially required. Motivated by these requirements, the last two decades have seen tremendous efforts towards this topic [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] by taking the Tricept robot as the most widely studied subject [5][6][7][8][9][10][11][12][13][14][15]. For instance, Joshi and Tsai [5] compared the stiffness characteristics of the 3-DOF parallel mechanism within the Tricept robot with that of a 3-DOF manipulator having three supporting legs by merely considering the actuation compliances.…”

“…Wang et al [12] employed the overall Jacobian to formulate the stiffness model by taking into account the compatibility conditions of the passive limb. More recently, Wang et al [15] proposed a stiffness performance index for kineto-elastic statics analysis of parallel mechanism by which the structural optimization issue of the Tricept robot under heavy-load working conditions was investigated. As for the Exechon robot, it seems that Li et al [16] were first to present an analytical stiffness model using screw theory and the principle of virtual work.…”