On Machine Measurement Methods For Geometric Quantities Based On Laser Triangulation

As a unique measurement method,laser triangulation is widely used in modern industrial measurement because of its non-contact,anti-interference,simple structure,fast measurement speed and high measurement accuracy.However,the major measurement object of laser triangulation is the measurement of one-dimensional displacement.It is necessary to cooperate with certain measuring instruments and measuring methods to complete the measurement tasks of complex geometric quantities.In this paper,a series of high precision,non-contact,easy-to-automate geometrical on-machine measurement methods for some typical measurement requirements in the industrial field are proposed based on the existing laser triangulation measurement technique.The first part of the paper is for angle measurements.Firstly,an on-machine measurement method of dihedral angle based on rotating ray and machine coordinate system is proposed.The dihedral angle measurement task is accomplished by using the rotating ray measurement model to extract the plane information of the dihedral angle and fusing the sensor data with the machine coordinates.Compared with the relative truth value given by CMM,and the measurement error does not exceed 14 ".Secondly,a method of establishing of polar coordinate system is proposed by using the rotating ray measurement model and the angular coordinates.Using the polar angle of the characteristic points which are extracted from the change of the pole distance under the polar coordinate system,the dihedral angle measurement is finished.At the expense of sacrificing of accuracy,the method above release the dependence of machine coordinate system,simplify the measurement model and increase the measurement scope.Through the experimental verification,the measurement error does not exceed 20 ".The second part of the paper is for inner diameter measurements.According to the three-sensor internal diameter measurement method,an internal diameter measurement device is designed and realized,which can get rid of the dependence on the rotary spindle by using three one-dimensional distance measuring sensors which are fixed so that the measurement is completed once the measurement device is in place.Through the experimental verification,measurement error does not exceed ± 25?m.The third part of the paper is a new calibration method.For the three-sensor inner diameter measuring device and measurement method,a calibration method of measuring the attitude of the ray is put forward.Through the posture calibration,the mathematical model is reconstructed to improve the measuring accuracy of the three-sensor inner diameter measuring method.The experimental error is reduced to ± 20?m.This paper mainly includes two methods of dihedral angle measurement,an aperture measurement method and a plane attitude determination method.The feasibility and effectiveness of the methods are validated,which presents several available on-machine,automated measurement methods for industrial sites.