Structural Design And Optimization Research Of Mechanical Arm Of Mobile Service Robot

With the rapid development of science and the progress of society, service robots have awider range of applications in assisting the elderly and the disabled and in guiding and caringfor people. They have more and more contact with the human. People benefit a lot from them.The main purpose of this paper is to design a mechanical arm for mobile service robot, andthrough topology optimization and size optimization based on performance index method tooptimize its structure, making it has the characteristics of high stiffness, lightweight, flexibleand stable movement.Firstly, the design criteria according to the requirements and index of design combinedwith the ergonomics theory were determined, and various configurations of mechanical armwere analyzed. With the global relative manipulability as the index, find out the optimalconfiguration of mechanical arm. According to the theory of anthropometry, determine thesize of the mechanical arm and joint angle range, to make it has the similar flexibility ofpeople. Based on this, the drive mode was determined and the driving force was obtained bysimulation and calculation, which provide the basis for selection of driver module. The wiringway was determined, and the structure design of links such as big arm and small arm wascompleted, which realizes the big arm and the whole mechanical arm of lightweight bytopological lightweight and materials lightweight. The construction of the virtual prototype ofmodular mechanical arm was completed, providing it the characteristics of high stiffness,lightweight and flexible.Secondly, analyze the action types of mobile service robot mechanical arm, and simplifythe mechanical arm model combined with the particularity of mechanical arm structure. Theparameters model of the simplified mechanical arm was build by D-H parameters method,and the forward kinematics was analyzed. The Jacobi matrix was solved, which laid a solidfoundation for the performance indicators that based on the Jacobi matrix. The workspace ofthe mechanical arm was calculated, which made an criteria for evaluation the effect of sizeoptimization.Then, according to the applications and function characteristics of mobile service robot,put forward the maximum working space distance indicators, the static stiffness performanceindex and the whole domain of velocity fluctuation performance index to evaluation of theperformance of mechanical arm.The coupling relationship between the optimization goals aredetermined through the analysis of the coupling optimization goal, and thus determine themaximum working space distance performance index and the whole domain of velocityfluctuation performance index as the optimize target. The sensitive degree of the optimizationgoal of the optimization variables were determined through sensitivity analysis. Theconstraint was determined based on the requirements of design index and the actualconditions, and the size optimization mathematical function model was established on the basis of all above that. the multi-objective and multi-constraint characteristics of the sizeoptimization function model, provides conditions for the selection of optimization algorithm.Finally, According to the multi-objective and multi-constraint characteristics ofoptimization function model, decide to take Multi Objective Particle Swarm Optimization(MOPSO) algorithm as the optimize method, which chooses the optimal solution based onPareto dominant principle. Aiming at the shortage of particle swarm optimization (PSO)algorithm in solving multi-objective problem, the algorithm was improved. Meanwhile theflying time factor is introduced, and the Improved Multiple Objectives with Particle SwarmOptimization (IMOPSO) algorithm was put forward. This improved algorithm was verified bytwo standard test functions, which shows that the accuracy was improved. Use the IMOPSOalgorithm to solve the optimize function model, and analyze the obtained results, whichtheoretically proved that using size optimization to reduce the velocity fluctuation in theprocess of mechanical arm movement is effective. The correctness and validity of theoptimization results used in practical application was verified by simulation experiments. Allshows that through the combination of topology optimization and size optimization, canprovide the mechanical arm which we designed with the characteristics of high stiffness, lightquality, flexible and stable movement.