对称单自由度螺旋运动并联机构型综合

Type Synthesis of Structural Symmetry One Degree-of-freedom of Helical Motion Parallel Mechanisms

针对馈能减振器对运动转换机构的功能需求,提出基于并联机构的设计方案。采用约束螺旋理论提出一种结构对称单自由度螺旋运动(1H)并联机构型综合方法。运用螺旋理论,给出将力螺旋分解为空间多个力线矢的方法。在此基础上,将1H并联机构动平台约束螺旋系中的约束力螺旋,分解成与机构分支数相等的线性无关力线矢,用分解得到的力线矢替代该约束力螺旋,与动平台约束螺旋系中其它约束力和约束力偶形成新的机构约束螺旋系。通过反螺旋理论和空间几何理论确定分支约束螺旋系,进而求得分支运动螺旋系。通过线性组合和等效代换综合出全部合适的分支运动链,将结构相同的分支运动链沿动平台和定平台对称布置,得到一系列满足要求的1H并联机构。最后以3-UU机构为例,对综合得到机构进行自由度分析,分析结果验证了构型综合方法的正确性。

The design scheme based on the parallel mechanism is proposed in view of the function demand of regenerative shock absorber motion transfer mechanisms.Based on the constraint screw theory,a type of synthesis approach for structure symmetrical one degree of freedom helical motion(1 H)parallel mechanism is proposed.By using the screw theory,the method of decomposing the wrench into multiple forces in space is given.Based on that,the constraint wrench in the constraint screw system of the moving platform is decomposed into linearly independent constraint forces,and the number of these forces is equal to that of the limbs.Replacing the constraint wrench by these forces and constructing a new constraint screw system of the mechanism,after that the constraint screw system of the limbs is determined by using the screw theory and the spatial geometric theory,and the kinematic screw system of the limbs is obtained.Type synthesis of all the right limbs is accomplished by means of linear combination and equivalent substitution.Symmetrical arrangements limbs with the same structure along the moving platform and the fixed platform obtains a series of expected mechanisms.The degree of freedom analysis of a novel 3-UU parallel mechanism is performed and the result shows that the method of type synthesis for structural symmetry 1 H parallel mechanisms proposed here is correct.