Abstract: The singularity of parallel mechanisms is an inherent characteristic of most parallel mechanisms. In order to prevent the mechanism from approaching singular configurations during application, it is particularly important to grasp the singularity variation laws of the mechanism. For the 3-RRS parallel mechanism, a corresponding mathematical model was established to identify the obtained singular surfaces, obtaining a portion of parabolic, conical, and wavy surfaces. Then, the single variable method was used to study the influence of mechanism parameters on the singular surfaces of the mechanism. When the radius R of the fixed platform and the length l1 of the driving rod increase, the z value of the corresponding spatial singular point of the mechanism will correspondingly increase; When the radius r of the moving platform and the length l2 of the driven rod increase, the height of the singular point will decrease; The research also compared it with the 3-RPS parallel mechanism to explore the impact of changes in the mechanism itself on singular surfaces. In addition, this research calculates its degree of freedom based on the improved G-K method, traverses its workspace based on the inverse kinematics equation, establishes the constraint relationship in the motion branch plane, and gives the inverse kinematics equation of the corresponding mechanism. Then, according to the screw theory, the branch motion screw system, constraint screw and drive screw are established, and the full Jacobian matrix of the mechanism is constructed. The singularity discriminant is obtained by using the properties of the mechanism in the singular configuration, and the singular distribution surface is given. Finally, by building a prototype model of the mechanism and collecting pose data of the moving platform for experiments, the correctness of the theoretical research was verified.

Key words: 3-RRS parallel mechanism, singular surface, property identification, singular space