Study Of On-machine Measurement And Reconstruction Methodologies Without Reference Errors For Parallel Profiles Of Large-scale Workpieces

Regard parallel rails or parallel plates as a pair of parallel profiles,the basis for the evaluations of geometric parameters of them such as straightness and parallelism is to realize parallel profile reconstruction.Therefore,the accuracy of reconstruction results is very important.When reconstructing a pair of parallel profiles,it is usually a method to measure the measured profiles by scanning.At this time,the errors of the measurement reference will affect the measurement and reconstruction results.Especially for the geometric measurement of large workpieces,there are many applications of on-machine measurement.And the trajectory of the machine tool spindle is usually used as the measurement reference,whose accuracy is often at the same level as the accuracy of the measured profiles,and the influence of measurement reference errors is more serious.Therefore,reconstruction without reference errors is of great significance to the high-precision measurement of large workpieces.The key technologies in the parallel profile reconstruction methods without reference errors are researched.And three multi-sensor reconstruction methods suitable for different measurement requirements are studied to eliminate several types of errors that have great impacts on the results during the scanning measurement.The new methods can get rid of the dependence of reconstruction accuracy on the measurement reference,and achieve reconstruction without reference errors.The major contributions and innovations of this dissertation are as follows:1.Analyze and demonstrate the characteristics of several types of errors as well as the influence of these errors,which have major impacts on the reconstruction of parallel profiles.At present,the reconstruction methods based on the two-point method and the three-point method both have the problem of the existence of data processing error when meeting high lateral resolution.And the main factor that limits the practical applications of the reconstruction methods based on the three-point method is that they are affected seriously by the zero-adjustment error.2.A high lateral resolution reconstruction method of virtual shear which is based on the two-point method is proposed.Under the premise that the yaw error can be ignored or compensated,the method can meet the parallel profile reconstruction needs of high lateral resolution and no reference errors.The data processing algorithm is designed,which uses the virtual shear equal to the actual step spacing of the measuring device,and the data processing process is equivalent to the sequential two-point method.Simulation and experimental results confirm that the new method can eliminate the influence of the straightness error on the accuracy of the reconstruction result,and the data processing error is removed while ensuring a high lateral resolution at the same time.3.A zero-calibration-free reconstruction method with two scannings which is based on the three-point method is proposed.When the yaw error cannot be ignored,the parallel profile reconstruction without reference errors is realized.The virtual sensor method is proposed and the zero-adjustment error of sensors is offset during the data processing process.Simulation and experimental results confirm that the reconstruction result which is not affected by the straightness error,the yaw error,and the zero-adjustment error can be obtained.Besides,the calibration of the zero points of sensors is spared,which can solve the biggest obstacle in the practical applications of the methods based on the three-point method.4.A two scanning reconstruction method with two shears which is based on the three-point method is proposed.The exact reconstruction without reference errors is realized.Using the virtual sensor method to calculate the differentials of measured profiles,the straightness error,the yaw error,and the zero-adjustment error can be eliminated.Through an integral process,several primary reconstruction profiles that are not affected by data processing error can be obtained.Adjusting the poses of these primary reconstruction profiles,they can construct the final reconstruction result of the measured profiles.Simulation and experimental results confirm that the new method can eliminate several major errors that affect the reconstruction results in the scanning measurement of parallel profiles.The exact reconstruction can be obtained,and the random error can be suppressed due to the average effect.For the on-machine measurement of parallel profiles of large workpieces,three profile reconstruction methods,which can realize the reconstruction without reference errors under different measurement requirements,are proposed in the dissertation.The advantages and feasibility of these methods are verified by theoretical analysis,simulation,and experiments.The new reconstruction methods without reference errors theoretically solve the influence of the reference errors on the reconstruction accuracy in the on-machine measurement,and can also be used as general methods for the reconstruction of parallel profiles under other conditions.