Research On Low-frequency Parallel Vibration Isolation Platform Based On Quasi Zero Stiffness

The research of multi-dimensional low-frequency vibration isolation platform has always been a difficult point in the field of low-frequency vibration isolation.Parallel mechanisms are often used to design multidimensional vibration isolation platforms due to their advantages such as multi branch chains,multi-dimensional motion,and compact structure.The commonly used design method is to install a nonlinear vibration isolator as a driving element onto each branch chain of a parallel mechanism to achieve multidimensional vibration isolation.However,due to the high stiffness characteristics of parallel mechanisms,their inherent frequencies are relatively high,and their performance is good when applied to high-frequency vibration isolation,but it is difficult to achieve lowfrequency vibration isolation.Considering the characteristics of parallel mechanisms with quasi zero stiffness in the singular direction when they are in certain singular configurations,this paper proposes a design concept of a multi-dimensional low-frequency vibration isolation platform with low dynamic stiffness and high bearing capacity based on the singular configuration of parallel mechanisms to achieve low-frequency vibration isolation.Based on the above concept,this paper takes parallel vibration isolation mechanisms as the research object,exploring the internal relationships among mechanism singularity,quasi zero stiffness,and low frequency vibration isolation from single degree of freedom to multi-dimensional low frequency vibration isolation.A singular classification method for vibration isolation mechanisms based on variational method is proposed to optimize the configuration of parallel vibration isolation mechanisms;The complete stiffness formula suitable for parallel vibration isolation mechanisms is derived based on large deformation spring driven elastic elements;Explore a quasi-zero stiffness workspace,establish a singular approximation mathematical model for natural frequencies and jump frequencies,and comprehensively evaluate the performance of vibration isolation mechanisms.Based on the above theoretical methods for vibration isolation mechanism design,a typical planar single degree of freedom parallel mechanism singularity configuration is applied to design a low frequency vibration isolation mechanism with single degree of freedom vertical and torsional vibration isolation.A novel planar four bar vertical vibration isolation mechanism and a planar 3-RRR torsional vibration isolation mechanism are proposed,and their stiffness characteristics are analyzed;Based on the design method of using a planar five-bar mechanism as a negative stiffness component of a low-frequency vibration isolation mechanism,a new type of symmetrical double five-bar vertical vibration isolation mechanism is proposed,and its stiffness and vibration isolation performance are analyzed.Finally,aiming at the problem that rotary polishing and polishing equipment often suffers from axial and circumferential low-frequency disturbances during operation,a multidimensional low-frequency vibration isolation platform is designed based on the singular configuration of a planar 2-RRR mechanism,and a novel C/2-(2-RRR)RR two-degree of freedom translation-rotation low-frequency vibration isolation platform is proposed.Establish a three-dimensional model,conduct static,stiffness,and dynamic analysis,and verify the effectiveness of low-frequency vibration isolation based on simulation and prototype experiments.