The Kinematic Analysis And Graph Synthesis Of A Kind Of Dynamic Junction Mechanism

The dynamic junction over-constrained parallel-parallel mechanisms originate fromequivalent mechanism in helicopter automatic tilting device. Its performance is importantbecause it directly detemines the helicopter’s safety, reliability, maneuvering, flexibilityand the length of life. Deep research on it not only provides the necessary parameters foroptimal design, but also provides theoretical guarantee to improve the overall performanceof the helicopter rotor system. To synthesize it automatically can not only find new typeautomatic, but also provide many original models for selective preference.Firstly, two kinds of dynamic junction over-constrained parallel-parallel mechanisms3-SPS+RRS+PS+4-SPS+RRS are introduced. Then some analyses are made in the view ofkinematics, including the analyses of the degree of freedom(DOF), inverse displacementsolution, velocity and acceleration inverse solution and workspace’s boundary search. Theanalysis of the degree of freedom is made by the simplified method. According to thescrews and recrprocal screws’ geometry relationship which makes their reciprocal plotzero, the recrprocal screws can be determined, and it is easy to judge whether the DOF isinstantaneous. The inverse displacement solution theory analysis is done by the coordinatetransformation method, and the initiative input displacement curve is drawn byprogramming matlab code. In oder to make it easy to be calculated by computer, a directderivatives method is used to get velocity and acceleration. Meanwhile a algorithm ofHessian Matrix calculation is given which is suitable for all the mechanism that hascontinuously differentiable inverse solution of equation. The workspace of mechanism isanalyzed by boundary search method to calculate the any point’s workspace in movementcoordinates of mechanism.Secondly, in order to verify the correctness of the theory, a testing machine which is3-SPS+RRS+PS+4-SPS+RRS is designed. In the control design, there are upper computerand lower machine. The upper computer’s duties are intensive numerical calculation andsend the movement instructions to lower machine by serial interface. The responsibility oflower machine is decoding the movement instructions and controlling the devicemovement. Within a certain error rangement, the movement of mechanism fully meets performance expectation, the correctness of the theory is verified.Finally, in older to provide a large number of original models, this paper proposes agraph method to synthesize. This method can not only overcome the disadvantage oftraditional method that can not be used in spatial mechanism, but also can be programmedand run in computer. Many new kinds of dynamic junction over-constrainedparallel-parallel mechanisms are synthesized in this way.