Research On Rigid-Flexible Coupling Dynamics And Dynamic Characteristics Of Welding Robot For Coal Mines

As the modern mine mining equipment to the large-scale,automation development,welding robots become coal mine machinery equipment manufacturing"unmanned factory"new"workers",at the same time of welding robot in coal mine puts forward the high efficiency,high precision,quick adaptability,high compatibility and long life product performance requirements.Hydraulic support as a typical mine equipment in the welding plate parts assembled into the complex shape box structure,its characteristic is the internal weld intensive,with short distance and vertical cross weld is given priority to,3 d linear and a small amount of arc.Traditional manual welding because of frequent arc,arc,especially when it is difficult to reach small space,it is very easy to cause the virtual welding and leakage welding.In order to ensure that the welding robot has higher accuracy in complex working conditions,it is necessary to analyze the dynamic characteristics and dynamic characteristics of the robot.Welding robots are usually multi-body systems with multiple degrees of freedom,strong nonlinear and flexible coupling.Dynamic performance of the structure to guarantee the high quality the key to accomplish complex box structure welding function,welding robot dynamics research is also related to the inverse kinematics,dynamic characteristics,structural strength and flexible multi-body dynamics and control problems,become the hot topics in the study of many scholars both at home and abroad.Taking SR165 general welding robot as the research object,and to analyze factors affecting the precision of welding robot welding for the purpose,by reading the related literature and summarize recent years,the current status of industrial robots,welding robot by means of the existing virtual simulation,mathematical modeling and computer numerical simulation technology,related to carry out movement characteristics and dynamic characteristics research,product performance to improve the welding robot has the theoretical and engineering significance.The main research work is as follows:Based on kinematics theory,the pose error model is established,and the source of motion error of welding robot is analyzed.The inverse kinematics mathematical model of SR165 industrial robot was established by D-H parameter method,and a robot pose error model was built on this basis.Based on SR165 welding robot six degrees of freedom series joint and wrist Pieper structure,the inverse kinematics mathematical model was chosen to solve the inverse kinematics model and obtain the jacobian matrix.Using the MATLAB toolbox to restore is the inverse kinematics,the virtual simulation of the control panel to verify the correctness of the inverse kinematics mathematical description,and combining with the characteristics of hydraulic support welding manipulator welding task planning welding path,and simulate the 40 s from the space point B?1.985,0.780,1.985?to the point of C?1.985,0.769,1.985??unit/m?of linear welding process,obtain mechanical arm movement characteristic,describes the straight weld simulation in the process of each joint Angle displacement,angular velocity and angular acceleration,and the changes of the joint torque.Based on the kinematics model,a small displacement perturbation method is used to establish the structural parameter pose error model.On the basis of the static error study of the position,the static analysis of the large arm is analyzed,and the deformation error of the large arm is obtained when the SR165manipulator is in the limit equilibrium position.The large arm is the key part of carrying and carrying forward force.The disadvantage of the vertical six-dof series structure is that the deformation error will be passed to the end welding gun,which will affect the welding accuracy.The critical boundary conditions were obtained by the static equilibrium analysis of SR165 mechanical arm with horizontal position as the limit position.According to the real working conditions of the large arm,the addition of constraint conditions can be divided into two kinds:pre-tightening force and ideal fixed boundary.First add pre-tightening force constraints,obtain maximum deformation displacement of 0.217mm,the upper arm arm b end point A maximum deformation and displacement of 0.1686mm,welding robot welding torch at the end of the biggest deformation and displacement of 0.5536mm,the maximum equivalent stress in the upper arm arm and side b round hole,11.06MPa.Ideal constraints,A fixed maximum deformation displacement of 0.4612mm,the upper arm b end point A maximum deformation and displacement of 0.3817mm,welding robot welding torch at the end of1.2535mm maximum deformation displacement,the maximum equivalent stress41.114MPa in the upper arm arm can end A round hole.Therefore,the static error of the SR165 mechanical arm is within the permissible range when the pretension force is in the limit position.The yield strength of ductile iron is 365MPa and the corresponding allowable stress is 121MPa.The maximum equivalent stress of the large arm is41.114MPa,which can completely satisfy the static structural strength.According to the static characteristic analysis of the large arm according to different starting inertia force,the static strength of the large arm can be determined.Comparison and analysis,the natural frequency of the big arm under the effect of prestressed known prestressed will have little impact on the big arm stiffness matrix,finite element modal analysis,through the big arm for connecting rod after the flexible characteristics of the coupled system research.Besides static error,the influence of dynamic characteristics on dynamic error cannot be ignored.Based on the theory of structural dynamics and multi-body flexible dynamics,the dynamic analysis of two rigid and flexible coupling systems of the SR165 mechanical arm is made from the flexible Angle of the joint and the connecting rod.In this paper,the dynamic equations of the flexible joint system of the three-link joint are derived.Using euler-bernoulli beam as the equivalent model,the dynamics of flexible beam was studied.According to the elastic theory and continuum theory,a physical description of the small deformation of the flexible beam is carried out.In this paper,the nonlinear coupling terms of longitudinal deformation compression are calculated by assuming the transverse deformation and longitudinal deformation of the rotating beam.The dynamic equations are derived by using the hybrid coordinate method and the second Lagrange formula.In the planar rotating flexible beam system dynamics research,on the basis of the derived center rigid body-dynamic equations of flexible beam system and considering the end mass moment of inertia,and its contribution to the system dynamics model,further center rigid body-flexible beam was deduced,the dynamic equation of quality system.The equation contains three forms,the structural dynamics model of the rotating flexible beam system?no large displacement?;A rigid flexible coupling dynamics model of the system?large displacement movement?;And the approximate rigid coupling dynamics model of the system?large displacement movement?.The theoretical description of welding robot structure and the establishment of dynamic mathematical model have laid a theoretical foundation for the deep dynamic response analysis and error analysis of virtual simulation.On the basis of the coupled dynamics research of flexible joints-rigid connecting rod and rigid joints-flexible arm two system dynamics simulation,respectively by the coupled dynamics and structural dynamics analysis of dynamic response of the dynamic response,further verify the flexibility of the mechanical arm SR165 mechanical arm,the influence of the dynamic error.The first part,through the ADAMS platform for flexible joints-rigid link the coupled system,the simulation of three flexible joints alone gives different stiffness coefficient curve simulation,waist joint,shoulder joint and the stability of the elbow joint stiffness coefficient were 1.0e06N/mm,4.5e06 N/mm and 4.5e06N/mm,corresponding to the joints of the maximum error of the vibration of 0.41°and 1.36°and4°.On this basis,the end of the applied load different level?500N,1000N,1500N and2000N?get the joint angular velocity and torque curve,little impact load the dynamic characteristics of a flexible waist joints,and the shoulder joint and elbow under different loads,underlines the influence of the dynamic characteristics of flexible joint,and with the increase of load,vibration,the more obvious,the greater the dynamic error value.In combination with the practical condition of welding,curve and broken line simulation welding robot welding path under the dynamic response of the whole machine,triangle line simulation waist joint,shoulder joint and elbow in the vibration amplitude of 1°,2°and 6°,X,Y,and Z direction at the end of the vibration error is 40mm,50mm and 120mm.Dynamic vibration error analysis shows the vibration of the X and Y direction mainly comes from the waist joint and shoulder joint,Z direction error of main source of elbow,and error analysis for vibration,through welding path line is greater than the impact of the error curve.The second part,build the virtual prototype model of rigid joints and flexible connecting rod,according to the actual working condition,separately set curve and broken line two paths and give different load end of the mechanical arm,and then watch the end of the dynamic response,and force of the big arm.Simulation triangle line path,get the change law of dynamic error of mechanical arm SR165 in X,Y,and Z direction of the three largest displacement error for a 30mm,77mm and 90mm,and all appear in the intermediate position of the welding line?7.5s?simulation.Through dynamic simulation curve path,X,Y,and Z direction of the dynamic error,maximum error value of 1.19mm,2.2mm and 0.74mm,and the conclusion,and the different paths to arm the coupled system is different,the influence of the dynamic response of a linear displacement amplitude deviation curve is 10² times of the order of magnitude.Then,the maximum dynamic error of the end is observed with the increase of load?500N,1000N,1500N and 2000N?,and the maximum vibration error is increased from 18mm to 84mm.At the same time,the speed increases with the increase of load,and the mutation occurs at 7.5s.According to the dynamic response study under different loads,the vibration 3d curves of acceleration and vibration frequency are observed,and the resonant frequency of the large arms is about 5Hz in the transverse and longitudinal direction.Observe the stress curve under different load at the same time,the statistical arm of the top 10 biggest stress node,node number 260 is the biggest stress in the roots of the upper arm joints?and the risk of big arm position?,at about 7.5s stress value a spate of 10060N/mm².On the basis of the above theoretical study and virtual simulation,in order to further verify the SR165 real movement and the dynamic characteristics of mechanical arm,on line measurement precision and mechanical arm joint zero experiment and data analysis.First,measure the hydraulic support SR165 straight welding precision welding robot,along the X,Y,and Z direction of three straight trajectory scatter gathering space,through the space line fitting and the theory of straight track compared to get straight trajectory deviation distance?35?D of 0.5 mm in Z direction,in the X,Y,and Z direction Angle is0.42°and 0.27°and 0.57°,straight trajectory and three directions of repeated positioning accuracy to 0.053mm,0.018mm,0.12mm,provides the precision of welding robot welding line of evaluation criteria.Second,with the help of laser measuring instrument,six joints individually rotating mechanical arm measurements,to obtain the same joint on the shaft of two Spaces round,fitting out of the circle and joint axial vector X,compare the Z axis calculation six joints connecting rod coordinate system zero Angle error,?35??₁of 0,?35??₂ of-0.0209,?35??₃ of-0.2368,?35??₄ of-0.2142,?35??₅ of-0.0598,?35??₆ of 0,mechanical arm for SR165 initial state error compensation.The experimental measurement provides data reference and comparison verification for the theoretical and simulation research of the SR165 mechanical arm in static error and dynamic error.