Research On Dynamic Characteristics And Structural Optimization Design Of Tandem Robot

Industrial robots are an important cornerstone and key supporting equipment for intelligent manufacturing.With the improvement of product quality and production efficiency,higher requirements have been placed on the motion stability and precision of industrial robots.In response to the demands of industrial production on the performance of robots,it becomes very important to grasp the dynamic characteristics of robots.The emergence of lightweight,high-speed,and high-precision robots puts forward higher requirements on the rigidity of robot links and joints.Therefore,the research on the dynamic performance of industrial robots is of great significance for mastering the stiffness performance of robots,improving the mechanical performance of the whole machine and optimizing the structure design,and providing reference.This article took six degrees of freedom tandem industrial robot as the research object.First,the D-H parameter method was used to model the kinematics of the industrial robot,the kinematics equations of the robot were derived,and the theoretical formula was verified with the MATLAB Robotic Toolbox.The linear Spong model was used to simulate joint flexibility,the hypothetical modal method was used to establish the link flexibility model,and the rigid-flexible coupling dynamic model considering the joint flexibility and the boom link flexibility was established based on the Kane method,and a virtual prototype model was established in ADAMS for dynamic simulation verification.At the same time,in order to grasp the stiffness characteristics of the robot,this article performed a stiffness conversion on the joint transmission parts of the robot,and then obtained the converted joint stiffness.To verify the correctness of the analysis method,a joint stiffness identification experiment was designed andconducted.On the one hand,it reflects the contribution of each transmission part to the flexibility of the joint,on the other hand,it provides stiffness parameters for the subsequent dynamic analysis and simulation.Secondly,in order to fully understand the dynamic characteristics of the robot,the joint stiffness value obtained from the identification experiment was applied to the dynamic analysis,and the influence of the robot's posture changes on the natural frequency was analyzed.Based on this,the robot's posture for modal analysis was selected.With the help of AN SYS,the industrial robot was simulated and analyzed in three different poses to obtain its natural frequency and modal formation.Due to the finite element simulation has certain limitations,the results needs to be proven by experiments.This article determined the modal experiment plan based on the theoretical analysis results,designed and built the test bench.The experimental test was carried out by the method of fixed acceleration sensor and moving hammer,and the data collection and analysis were carried out with the help of DASP data collection and signal processing system.The nine poses of the robot were taken for experimental testing and analysis,and the influence law of poses on the modals was obtained.Comparing the simulation and experimental modal results,we can get the influence law of pose on the modal,determine the position of the robot's weak link and the most dangerous pose.This is instructive for industrial robots to avoid dangerous working postures,avoid resonance during application,and optimize structures.In order to fully grasp the dynamic characteristics of the robot,the acceleration signal of the robot during the horizontal sweep motion was collected,and a self-spectrum analysis on the acceleration signal was performed to obtain the frequency component of the robot in the motion state.The frequency component was analyzed to find that the excitation frequency of the harmonic reducer is close to the low-order natural frequency of the robot,which is the main reason for the low-frequency vibration of the robot.Finally,based on the results of dynamic analysis,the optimization design of the boom structure was carried out.For the purpose of improving mechanical properties and weight reduction,the first-order natural frequency and mass of the boom were used as optimization goals.Through the sensitivity analysis of multiple optimization variables,the final optimization variable was selected,and the maximum deformation of the boom was selected.With the maximum equivalent stress as the constraint condition,a multi-objective optimization model was established.Through optimization,under the premise of ensuring that the maximum deformation and the maximum equivalent stress are far below the allowable limit,the overall mass of the boom is reduced by 10.87%,and the first-order natural frequency of the boom is increased by 108.8 Hz,which shows that the optimization has achieved light weight and improved Boom stiffness requirements.