Research On Impact Dynamics And Parameter Optimization Of Constrained Metamorphic Mechanism

Metamorphic mechanism has been widely used in various engineering fields with the development of its basic theory.Such applications are mainly task oriented constrained metamorphic mechanisms.In the process of movement,the impact caused by configuration transformation will reduce the kinematic accuracy of the mechanism,and aggravate the dynamic output oscillation,which will affect the stability of the whole system and even may not be able to complete the metamorphic process.Therefore,it is of great value and significance to study the dynamic characteristics and parameter optimization of the constrained metamorphic mechanism considering the impact effect in both theoretical development and engineering application.This dissertation mainly studies the impact dynamic characteristics and parameter optimization of constrained metamorphic mechanism.Firstly,in order to effectively reflect the change of the constraint types of the kinematic pair in the augmented Assur groups during the metamorphic process,the equivalent resistance coefficient is introduced.The equivalent resistance coefficient of the metamorphic joint under typical constraint is analyzed,and the motion characteristics of metamorphic joint under the corresponding equivalent resistance coefficient are obtained.On this basis,metamorphic configuration of the augmented Assur groups is divided into three types,and its modular dynamic models are established,and then the modular dynamic model of constrained metamorphic mechanism under working configuration is obtained.The simulation research is carried out,and the impact motion of mechanism during configuration transformation is proposed.Secondly,according to the configuration transformation form,the impact motion of constrained metamorphic mechanism is divided into Type ? impact motion and Type? impact motion.Based on the dynamic theory of multi-rigid-body system,Type ? and Type ? impact dynamic models of the system are established respectively,and the corresponding impulse solving models are deduced combining the classical collision theory with the coefficient of restitution equation.The simulation analysis of Type ? and Type ? impact motion examples is carried out,and the impact dynamics test system is built to carry out experimental research.The theoretical results are in good agreement with the experimental results,which verifies the correctness and effectiveness of the established model.Thirdly,the equivalent analysis of Type ? and Type ? impact dynamic model is carried out,and the impulse solving model of metamorphic joint is established.Under the dual action of Type ? impulse and Type ? impulse and metamorphic joint impulse,the impulse solving model of non-metamorphic joint of constrained metamorphic mechanism is derived by using Newton-Euler equation.The internal joint impact problems of Type ? and Type ? impact motion are studied by simulation.Fourthly,the impact performance of constrained metamorphic mechanism with configuration transformation is studied.The influence factors of Type ? impulse and Type ? impulse,metamorphic joint impulse and non-metamorphic joint impulse are analyzed.The global/local condition number performance index and velocity performance index of the mechanism are established.The mapping matrix between the sudden change of velocity and Type ? impulse and Type ? impulse is extracted to construct the global/local impact performance index of the mechanism.The impact dynamic performance equation of the mechanism is established,and the global/local dynamic condition number index of the mechanism is proposed.The influence degree of mechanism parameters on impact performance index is quantitatively evaluated,which provides theoretical basis for parameter optimization and impact performance improvement of constrained metamorphic mechanism.Fifthly,based on the impact performance index,the multi performance index is transformed into the comprehensive performance index by using the weight coefficient method,so as to establish the mechanism parameter optimization design model.Taking Type ? and Type ? impact motion as research objects,the mechanism parameter optimization design models are established and its feasibility is verified.