Research On Structure System Dynamics And Characteristics Of Engineering Mechanical Arm

With the rapid development of computer technology and digital design technology, high speed, high precision, lightweight and impact resistant, low noise,and long life have become the development trend of mechanical products performance. The dynamic characteristic research more and more becomes the key of the mechanical products design, is becoming hot topics in the study of domestic and foreign experts. Engineering mechnical arm is the critical and important parts of various engineering machinery and equipment, it is a kind of multi-functional efficient mechanical parts.the performance play of machine is determined by the engineering arm. Working condition of engineering mechanical tending to be bad,and load of engineering mechanical arm being very complicated, it is necessary to conduct kinetic analysis, to ensure the safety and reliability of its work,and to improve construction quality and operational efficiency.The engineering mechanical arm generally is a mufti-body system with redundant freedom, strong nonlinear, coupled with rigid and flexible characters.The system is related to multi-body dynamics, control theory, structural dynamics and kinematic reverse problem, etc.Under the current condition, the Research on the engineering arm dynamics is in the exploration stage such as in the product modeling, simulation and numerical calculation, etc,but the user’s requirements for the performance of the engineering mechanical product is increasing. So it is of greattheoretic value and real engineering significance to study the engineering mechanical arm dynamics.In this article, the engineering arm system is considered as the study object. The application of mufti-body dynamics, especially the flexible mufti-body dynamics theory in the modeling and simulation is mainly studied, and focus on the theoretic analysis. Much research has been done on the dynamics modeling,simulation,numerical calculation, and motion control, structures dynamic optimization,etc.and the study is conducted Combined with the examples of hydraulic excavators and large marine excavator, and the main content is summarized as follows:1).The modeling method of multi-body dynamics equations and flexible multi-body dynamics equations of the engineering mechanical arm was researched,the equivalent finite element method and Lagrange theorems was mainly discussed,and the relevant theory has been studied, especially focusing on the multi-body dynamics.theoretical basis of the flexible beam.2).The modal functions are adopted to describe elastic deformation of the mechanical arm,Lagrange theorem and the principle of virtual work is used to establish rigid-flexible coupling nonlinear dynamic equations of arm frame system.And the established dynamic equation are analyzed through the numerical solution, dynamic simulation method.The dynamic equations are numerically solved byMATLAB, the rigid-flexible coupling model of hydraulic excavator’s mechanical arm is established and simulated by the simulation software ADAMS and NASTRAN, it is showed that the modeling method of dynamic equations adopted in this paper is correct by contrasting the both results. The modal and dynamic response is calculated by applying the numerical solution method,the sensitivity of the first natural frequency for the Geometric parameters related is solved, the main modal parameters are analyzed which influence dynamic characteristics of mechanical arm.3).Considering axial deformation of large marine excavator engineering arm, its flexible engineering mechanical arm dynamic equations by using Lagrange theorems, the method of numerical solution is adopting, institutional dynamics equations were decoupled by using complex state vector method in the complex modal analysis, and the relationship between the vibration natural frequencies in the vicinity of nominal movement and a wide range of rotation angular velocity is gotten.The virtual prototype model of marine excavator including a flexible boom, flexible grab hoisting rope,flexible luffing rope,rigid frame,rigid rotating platform is established by using soft such as UG,NASTRAN,ADAMS,etc. the load is applied and dynamic analysis is conducted according to structure and work conditions of marine excavator mechanical arm system,the dynamic performance of the system is gotten by post-processing module such as the displacement, velocity, acceleration, etc.4).The manipulator trajectory planning and motion control of hydraulic excavator’s mechanical arm are researched.the theoretical foundation of control strategy for the engineering mechanical arm is analyzed, based on control theory and manipulator bucket trajectory tracking control expression,the PID control model and PID control model based on RBF neural network of working device’s mechanical arm,the controlling model simulation is conducted by using matlab and related software, dynamic response and steady state error of system are analyzed, the conclusion which PID control based on RBF neural network is superior to conventional PID control is drawn,intelligent control of the hydraulic excavator’s working device trace Can be achieved.5).Modal analysis and harmonic response analysis is used to determine the modal frequency of the biggest influence on the system’s dynamic performance,based on this dynamic optimization objective function is built.and the sensitivity analysis is used to reduce design variables in order to improve the efficiency of dynamic optimization.The structure system dynamic structure optimization design for hydraulic excavator working device’s mechanical arm was conducted using finite element analysis software optimization module,Constrained dynamic optimization problem of hydraulic excavator working device structure is changed into unconstrained dynamic optimization problem by using the Lagrange multiplier method.Get the minimum point of Lagrange function and the Lagrange function extremum points gradually close to the constraint optimal point of the original objective function, the optimal solution can be approximated based on the convergence criterion.Based on finite element analysis,the orthogonal test method combined with BP neural network, the neural network model of the nonlinear mapping relationship between working device design variables and the dynamic characteristics is set up. The optimal solution is gotten by using genetic algorithm to optimize neural network model.