Research On Dynamic Characterstics And Accuracy Of A Type Of Controllable Welding Robot With Joint Clearances

The working efficiency and fatigue life of industrial robots will be reduced because of the vibration caused in operating and it is of great significance to improve the dynamic characteristic of robot by damping vibration.Two improvement methods are introduced as follows: one is to optimize the material parameters of links,the other is to reduce the quality of moving parts.The former will increase the manufacturing cost while the latter is a technical problem at this stage.In that case,the concept of “multi-degree of freedom controllable mechanism” is introduced into the field of robot,the equivalent mass and the moment of inertia are reduced by moving the drives and reducers to the framework.In this paper,the influence of the joint clearances on the dynamic characteristics and accuracy are researched based on the controllable welding robot,which provides the theory for prototype optimization,clearance compensation and vibration attenuation.The contents of this paper include the following aspects:The working principle and process are analyzed based on the welding robot industrially and the design requirements are proposed accordingly.Thestructural forms of links are analyzed based on the constraint synthesis method and the proper configuration is selected from all existing possibilities.Furthermore,the configuration is improved on the basis of structural analysis and the degree of freedom is verified by the screw theory.Kinematics of this controllable welding robot is analyzed.The forward and inverse position and posture are calculated by the Euler angle transformation method.The velocity,acceleration and the Jacobian matrix are obtained by deriving the forward solution of position and posture.The workspace is drawn by Monte Carlo method.The joints that influence the position and posture seriously are selected to establish the model with joint clearances,the displacement error curves are obtained by iterative solution and improved PSO algorithm is proposed to reduce it.Moreover,a GUI interface is established to research the influence of different clearances size,driving speed and optimization coefficients on the position and posture error and compensation.Dynamic of this controllable welding robot is analyzed.The dynamic models of ideal mechanism and mechanism with clearances are established based on the first Lagrange method.It provides the theoretical basis for the subsequent dynamic characteristic research by analyzing the constraint equation and clearance force.Dynamic characteristics of the controllable welding robot is analyzed.the ideal model and model with clearances are established in ADAMS software.The influence of clearances' size,position,number and driving speed on the dynamic performance are researched by setting the clearance evaluation index.A system named dynamic analysis of controllable welding robot with clearances is established by secondary development of ADAMS software.The dynamic performance of the mechanism with multiple clearances number,size and different driving speeds will be simulated based on this systems quickly,which provides references for the optimization of the clearances effect.Accuracy and reliability of the controllable welding robot is analyzed.The effects of the clearances size,position and number on the accuracy and reliability are calculated based on the Monte Carlo method,which provides the theoretical basis on predicting and extending the life of the equipment.