Stiffness Modeling and Analysis of a Parallel Manipulator With Multi-Motion Modes

Abstract

Abstract. Parallel manipulators (PMs) have demonstrated significant potential in facility agriculture due to high-speed, high-accuracy, and high-dynamic response. Stiffness is a crucial indicator for PMs applied in precision operations in facility agriculture. To address this, a unified semianalytical stiffness model of a PM with multi-motion modes is proposed, based on which the stiffness performance is analyzed. First, unified inverse kinematic model is built, based on which, and considering relevant constraint conditions, the reachable workspace in different motion modes is analyzed. Second, considering the compliance of joints and limbs, a unified stiffness model is established by the substructure synthesis method, which is validated by finite element analysis (FEA) with good accuracy. Finally, stiffness indices demonstrating the uniformity of the system's linear and angular stiffness are proposed, and a parametric analysis is conducted. Results show that the moving platform's radius, the limb's length, and the limb's diameter have different impacts on the system's stiffness performance. Furthermore, the moving platform's radius demonstrates the most important influence on the system's linear and angular stiffness. This research can provide a basis for the optimal design of this PM with multi-motion modes.