Dynamic Reliability Study On A Novel Controllable Metamorphic Palletizing Robot

Metamorphic mechanism is a new type of mechanism that can realize multiple configurations.It can overcome the limitations of traditional linkage mechanism.Since it was proposed,it has become the frontier and hotspot of modern mechanisms.It has a wide application prospect in sugar industry,especially in the process of sugar mechanization.The reliability study of metamorphic mechanisms is an important premise to promote its application in engineering practice,and it is the basic guarantee for the normal and safe operation of mechanism system in practical application.In view of this,taking the stacking application in the sugar industry as the engineering background,in this paper,the dynamic reliability of controllable metamorphic mechanisms for stacking task is studied.The main work is as follows:Firstly,a controllable metamorphic palletizing robot is designed by taking the stacking task of sugar industry as the background.The configuration of the robot mechanism is designed based on the working task.After the kinematic,singularity and workspace analyses of this mechanism,a dimensional optimization method based on workspace discretization is proposed.Combined with its working performance,a suitable workspace is obtained.Then,the optimal maximum suitable workspace and corresponding optimal dimensional parameters of the robot mechanism are obtained by this method.The robot prototype is designed by using these parameters.Based on this,the robot is taken as the study object,and the dynamic reliability study is carried out.Secondly,aiming at a variety of uncertain variables(probabilistic random and non-probabilistic interval variables),the methods for multiple failure modes kinematic reliability analysis and optimization of metamorphic mechanisms is proposed.The analysis method generates the state space containing probability information according to the uncertain variables.Combining the failure function and the variables correlation function of the mechanisms,the safety space function in the variable state space is generated by the failure function.The reliability is obtained by solving this function.On this basis,a method to optimize the reliability model is developed.In case study,the kinematic reliability of the controllable metamorphic palletizing robot is analyzed and optimized by using these proposed methods,and the calculation results are compared with those gained by Monte-Carlo method and genetic algorithm,thus demonstrating the accuracy of these proposed methods.Moreover,the reliability analysis method for the configuration transformation of metamorphic mechanisms based on dynamic response interval is proposed.Based on the kinematic reliability analysis,considering the influence of the load force and the internal impact force of the configuration transformation of the robot in working progress,the nonlinear dynamic model of the robot is established by using the finite element method,and uncertain variables are introduced into the dynamic model.Combined with the variable state space,the dynamic response interval of the configuration transformation failure function is generated,and the reliability of its configuration transformation failure mode is obtained on this basis.A case is analyzed by using the proposed method.The calculation results are compared with those gained by the neural network-based Monte-Carlo method,thus validating the accuracy of this proposed method.In addition,the methods for dynamic reliability analysis and optimization of multiple failure modes of metamorphic mechanisms are proposed.In this analysis method,based on the introduction of uncertain variables into the robot dynamic model,the reliability is obtained by taking the dynamic response of the model as a new uncertain variable and the variable state space.On this basis,a reliability optimization method of the robot considering sensitivity is developed.Based on this,the method of dynamic reliability analysis of robot with multiple failure modes considering resonance is derived.In case study,the stiffness,strength and fatigue failure reliability of the robot are obtained by using this analysis method.The variable range of the robot in which the reliability meets the requirements is obtained using this optimization method.The calculation results are compared with those gained by the neural network-based Monte-Carlo method and genetic algorithm,thus demonstrating the accuracy of these proposed methods.Finally,the dynamic reliability of the prototype of the controllable metamorphic palletizing robot is experimentally studied.Taking uncertain variables as factors,the grouping test scheme is determined by orthogonal design method,and the strain data of each test group are measured.The neural network fitting model of the test data is established by using the neural network method.On this basis,the reliability of the model is calculated by using the Monte-Carlo method,and the calculation results are compared with those gained by the theoretical analysis methods in Chapters four and five respectively,The correctness of these analytical methods is verified by experiments.The research work of this paper provides a theoretical reference for the popularization and application of metamorphic mechanisms in sugar industry,and offers a practical theoretical foundation for the reliability design,manufacturing,operation and control of metamorphic mechanisms in engineering application.