Design Theory And Experimental Study Of CBR Reducer For Robot

With the continuous development of industry 4.0,high-quality manufacturing and intelligent manufacturing have been widely valued by various countries.Robot is a pearl in the palm of high-quality manufacturing and plays a key role in the development of industry 4.0.Joint reducer is one of the core components of robot.There are few kinds of mature reducer available for robot in the current market,and it is facing serious capacity shortage,which can not meet the rapid development of the robotic industry.Robot reducer has strict requirements on volume,transmission accuracy,payload capacity,sealing and impact resistance capacity,so it has certain requirements on the transmission type and structure of reducer.The reducer designed by cycloid-pin wheel transmission has the advantages of small size,light weight,compact structure,large payload capacity,strong impact resistance capacity,stable operation and large transmission ratio.This transmission type is more and more widely used in the field of precision transmission,and is very suitable for the requirements of robot reducer.Aiming at the application requirement of robot reducer,this paper study the theory and experiments of a designed precise cycloid-pin wheel reducer named CBR reducer.In order to ensure the transmission accuracy and service life of CBR reducer,it is necessary to deeply analyze the theory of cycloid drive and the loaded tooth contact characteristics.Manufacturing cost is also a special consideration of CBR reducer.Focusing only on transmission accuracy and ignoring the complexity,difficulty in processing and good product rate of manufacturing process will result in high processing cost and hinder the improvement of production capacity.Therefore,this paper synthetically uses the method of theoretical derivation,numerical analysis,simulation and experimental verification to study the factors affecting the transmission accuracy of CBR reducer and the reasonable tolerance allocation of processing cost.The generation and modification of cycloidal tooth profile,loaded tooth contact analysis,tolerance design and allocation,dynamic characteristics and testing are mainly studied.The main research contents are as follows:1.The tooth profile generation of cycloid gear is analyzed.The standard equation of cycloid gear is deduced by using the inverted gear train coordinate systems and the coordinate transformation rule.According to the basic parameters of standard equation of cycloid gear,the basic modification methods of cycloid gear and the influence of modification amount on the tooth shape are analyzed.Three available methods of compound modification of isometric and offset are given and applied to the cycloid gear of CBR25 reducer to compare the tooth shapes.At the same time,the geometric transformation analysis of the initial gap caused by the compound modification method is carried out,and the formula of the initial gap of modified cycloid gear is deduced intuitively.To reduce the transmission error,the parabolic modification method is applied to the modification of cycloid gear,and the tooth equation of parabolic modification is derived.The effects of second-order parabolic modification and fourth-order parabolic modification on tooth profile of CBR25 reducer were compared.It lays a foundation for the research of tooth contact analysis of CBR reducer.The structure and transmission principle of CBR reducer are introduced and compared with harmonic drive reducer and RV reducer.The 3D model of CBR reducer is built in SolidWorks software to prepare for multi-body dynamics simulation.2.According to the meshing principle of gears and the transformation of coordinate system,the unloaded tooth contact analysis equations are deduced.Given the input angle of crankshaft,the output angle of cycloid gear can be obtained by solving the tooth contact equations,thus the unloaded transmission error and backlash can be obtained.Based on unloaded tooth contact analysis,the force balance equations and deformation compatibility equations of cycloid-pin wheel are established.The deformation of cycloidal teeth and the change of output angle of cycloid gear are solved with the help of force balance equations and deformation compatibility equations,so that the loaded transmission error can be calculated.A new loaded contact analysis method based on discrete points of tooth profile is proposed,in which cycloid gear is regarded as the active component.According to the distance between the discrete profile of cycloid gear and the center of the corresponding pin teeth,the points are inspected to detect which point is the first contact point.Then the input angle of crankshaft is inversely calculated,and the transmission error is obtained.The efficiency of the conventional TCA and new TCA is compared under the same computing environment.3.The error sources that may occur in the grinding process of cycloid gear are analyed,and the main error sources that affect the accuracy of cycloid gear are found out: tooth profile error and tooth pitch error.The coordinates of cycloid gear are measured by three-coordinate measuring machine,and the equations of normal error and pitch error of tooth profile are established by using the idea of reverse seeking.Then the errors of tooth profile and tooth pitch are separated.The influence of six factors on transmission error and contact force of CBR25 reducer is analyzed,including tooth profile error,pitch error in tooth profile,radius error of pin,pin position error and eccentricity error of crank shaft.Then the causes of the lost motion of CBR reducer are analyzed,and the calculation formula for every cause is derived.The lost motion of CBR25 reducer is calculated with the formula.Based on the concept of design for manufacturing(DFM),the influence of tolerance on the manufacturing cost of CBR reducer is considered in the design stage.The Sequential Quadratic Programming(SQP)optimization algorithm is used to solve the optimal tolerance allocation of CBR25 reducer.4.The dynamic model and dynamic equation of CBR reducer are established.Then it is simplified to a Four-Degree-of-Freedom pure torsion dynamic model and the natural frequencies and modes are solved.Finally,the multi-body dynamics simulation software Recurdyn is used to simulate the multi-body dynamics.The displacement,velocity,acceleration and force of each component are analyzed,and the influence of clearance and modification method on the number of simultaneous meshing teeth and meshing force is analyzed.5.The processing technique and assembly technique of the protype of CBR reducer are introduced.The grinding equipment for controlling the final manufacturing accuracy of each part is also introduced.The testing devices of efficiency and transmission accuracy of CBR reducer are designed,and the corresponding testing methods are introduced.