Research On The Conceptual Design And Kinematic Synthesis Of A Eight-bar And Ten-pair Mechanism

This dissertation focused on the innovative design of a new feasible extensible mechanism in a heavy machinery. According to the analysis of a existent extensible mechanism and sufficient study on synthesis theory and method, the regenerated motion chain method based on graph theory was adopted to create new mechanisms firstly, then unified model of adaptive saddle-fitting optimization synthesis method of the new mechanisms was built to obtain the dimensions, the final analysis showed the feasibility of this solution procedure.Firstly, the background and the movement requirements of the researched extensible mechanism were presented, this excellent existent design was analyzed and the kinematical model was created by 3D simulation software so that the locus, velocity and acceleration was obtained.Secondly, for the purpose of conceptual innovative design, the synthesis of this metamorphic mechanism was converted to a problem of the synthesis of a normal closed chain mechanism, the regenerated kinematic chain method was used to create new mechanisms. At first, the original mechanism was generalized to a kinematic chain with 8 bars and 10 kinematic pairs, then sixteen isomerous motion chains were attained by number synthesis method, through the specializing of these motion chains, six regenerated motion chains were abtained. At last, the kinematic chains were specified to mechanisms, so six new mechanisms were synthesized.Finally, through the locus of the main arm's head, the position features of the controlling swing arm were extracted, the synthesis of planar eight-bar mechanism was translated to a synthesis of second grade assur group, and path synthesis of the main arm's head was turned to the location synthesis of the swing arm. Based on the approach of adaptive saddle-fitting, the circle point on the moving plane of the swing arm and the centre points on different moving planes corresponding to diverse mechanisms are searched for by optimization method. Taking some requirements such as the avoiding of limit position of the second grade assur group and the interfere of the roller and the main arm into consideration, the constraint conditions were established by mathematical modeling. So the kinematic synthesis of the new mechanisms was achieved.The optimized result of a new designed mechanism was given and its motion model was established by 3D simulation software. The effectiveness and feasibility of this approach were proved by the contrast of the moving requirements.