| With the rapid development and profound changes of the world’s science and technology industry,intelligent manufacturing has become the main direction of our country’s future science and technology,and the product morphology and its geometric characteristics in industrial intelligence manufacturing have proposed online high-precision automatic measurement requirements.As a non-Carter space coordinate measuring device,the articulated arm coordinate measuring machine(AACMM)has the characteristics of simple structure,light weight,high measurement efficiency,strong environmental adaptability,and is widely used in aerospace,automotive,ship,biomedical and other important projects field.The existing manual articulated arm coordinate measuring machine adopts artificial traction measurement mode,which can realize the flexible measurement of complex surface geometric features.However,some unexpected characteristics make it difficult to meet the online automatic measurement needs of industrial intelligent manufacturing and development,such as the random measurement posture,the uncontrollabe measurement force,the poor measurement stability,and the low positioning and measurement accuracy,To this end,a new self-driven articulated arm coordinate measuring machine(referred to as a measuring machine)is proposed,and the integrated joint module is introduced into the rotary joint to achieve self-driven control and automatic measurement of the measuring machine.In order to improve the automatic positioning and measurement accuracy of the self-driven AACMM,the above new type of measuring machine is taken as the research object.The research mainly focuses on joint module angle error modeling,structural parameters error modeling,dynamic characteristics,and dynamic comprehensive error modeling due to joint driving control and automatic measurement system of the self-driven AACMM.The specific research work are as follows:(1)Based on the working principle and structural design of the new self-driven AACMM,the ideal measurement model of the measuring machine is established by the classic DH parameter method,and the theoretical measurement spatial range of the measuring machine is solved.The source of automatic positioning and measurement accuracy of the measuring machine system is analyzed.The overall structure static simulation and the optimization design of key part of the self-driven AACMM are conducted.The results show that the theoretical spatial range in X,Y,Z direction of the measuring machine is respectively [-818.2mm,824.4 mm],[-834.2mm,812.8mm],[-549.3mm,1015mm],ensuring the actual measurement spatial range 800 mm of the measuring machine The self-driven AACMM end probe static offset maximum reduced0.204 mm after the key part structural optimization,which improves the static positioning accuracy of the measuring machine.(2)For the joint angle error due to the introduction of joint module to the rotary joint of measuring machine,the error source and its generating mechanism are analysed based on the internal structure of the joint module.Individual models of joint module,containing the joint torsional deformation angle error,the harmonic reducer angle error,the magnetic encoder angle error,and servo motor angle error,are established.Accodingly,the joint angle error model of the self-driven articulated arm coordinate measuring machine is obtained.The numerical simulation and calibration experiment of joint module angle error were carried out.Studies have shown that the joint module angle simulation and calibration error are periodically changed in the range of 0°～360°,and the high-order harmonic error in the harmonic reducer and magnetic encoder is the main factors of joint module angle errors.The correctness of the joint module angle error model is verified,providing a theoretical basis for the measurement mechanical joint angle error compensation.(3)In order to accurately compensate the dynamic error of the measurement machine in the automatic positioning and measurement process,the dynamics simulation and dynamic characteristics experiment under different motion parameters have been carried out.The research found that the dynamic positioning error of the measuring machine is related to the joint rotation velocity,acceleration and the probe moving speed.And the opimal motion parameters of joint rotation velocity and acceleration are respectively 120 RPM and 100RPM/s,and the probe moving speed is6.6mm/s,which make the dynamic positioning error of the measuring machine minimize.The structural parameter error model of the measuring machine are established,generated by components manufacturing installation errors,connecting rod dynamic bending deformation errors,and joint dynamic torsion deformation errors.On this basis,the dynamic comprehensive measurement error model of the self-driven AACMM is established.The theoretical calculation and experiments of dynamic comprehensive error under specific conditions were carried out.The experimental results show that the measurement error after the compensation of the dynamic comprehensive error model is reduced by 0.0708 mm,and the online automatic measurement accuracy of the self-driven AACMM is improved.(4)According to the spherical coordinate principle,the spherical measurement space of the self-driven AACMM is divided.Based on the four-dimensional spherical linear interpolation algorithm,the different measurement posture of the measurement machine spatial point is solved.The positioning error distribution discipline of sampling points in the upper hemisphere measurement space is analyzed by the simulation software.In the measurement radius of 380mm～790mm,the rotation angle of 0°～180°,and the pitch angle 5°～80° range,the object-oriented optimal measurement area experiment is designed and conducted.The experimental results show that,when the standard block/standard ball placing in the measuring radius of532.2249mm～659.6279 mm,the rotation angle of 130°～180°,and the pitch angle of20.1028°～48.9367° range,their geometric characteristical measurement errors with a certain measurement posture are all smaller,and the average measurement error maximum are-1.3166 mm,-0.3324 mm,respectively.The above area is the optimal measurement area of the self-driven AACMM for different objects.The workpiece is placed in the measurement area,which can further improve the automatic measurement accuracy and measurement efficiency of the self-driven AACMM.Figure [87] Table [32] Reference [149]... |
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