Research on the Key Technique of Flexible Articulated Arm Coordinate Measuring System
|School||Huazhong University of Science and Technology|
|Course||Materials Processing Engineering|
|Keywords||Reverse Engineering Multi-joint coordinate measuring arm Screw Theory Kinematic Calibration Intelligent optimization algorithms|
With the rapid development of advanced manufacturing technology, reverse engineering as a quick means of advanced technology for three-dimensional model of the object, and has been widely used in large-scale field to zero, the geometry of the detection of parts, quality control, and virtual reality, and many other areas. The traditional reverse measurement equipment is the Cartesian coordinate measuring machine, it is entitled to its mature technology and excellent performance measurement center \industrial production in a variety of on-site measurement requirements. As a new type of multi-degree-of-freedom non-Cartesian coordinate measuring machines, multi-joint coordinate measuring arm came into being. Angle measurement basis instead of the length of the measurement reference of the coordinate measuring machine has the advantages of portability, small size, light weight, flexible movement, convenient on-site measurements, cheaper, and has broad prospects for development. The main contents include the mechanical structure of the multi-joint coordinate measuring arm, data acquisition systems, the kinematic model, error analysis of kinematic parameters, system calibration method key issues papers on these issues from the two levels of theory and technology systematic and in-depth exploration. Features for multi-joint coordinate measuring arm, the design of the mechanical structure and data acquisition system. Joint rotation mechanism using a high-precision rolling bearings in order to ensure measurement accuracy and compact structure of the entire measurement device, and to reduce the blurring of the rotation mechanism as much as possible; unlimited rotation in order to achieve the purpose of selection of the slip ring structure, thus avoiding the signal line in the measurement arm internal Jiaoduan. The data acquisition system uses state-of-the-art embedded systems and fieldbus technology, reducing the number of signal transmission lines, reducing the mechanical complexity of the structure, and improve the stability and reliability of the data acquisition system. According to literature studies have shown that 95% of the measuring arm positioning error is caused by the kinematic model inaccurate. Thus, the kinematic model of the measurement accuracy of the measuring arm is extremely important. At present, most of the domestic and foreign institutions or scholars still use the traditional DH model as a measuring arm kinematic model, its shortcomings is that it is 4 degrees of freedom parameter model, the lack of completeness. The status quo of this study, we propose the establishment of the principle of the best reference pose, easy the POE formula and the Local POE formulas to create the kinematic model of the measuring arm. These two models are 6-DOF parameter model, can overcome the defects of the conventional DH model. Kinematics on the basis of the establishment of the proposed key lever long design principles, in order to avoid \From three kinematic model, analyze the causes of the sources of error of the measuring arm kinematic correction model and each kinematic parameter errors on the measurement accuracy, and provides a theoretical basis for the design and manufacture of the measuring arm. In order to improve the measurement accuracy of the measuring arm, two novel method of calibration of the measuring arm. The characteristics of these two calibration method algorithm is easy to implement, simple calibration procedure. Them to overcome the complex calibration method used in the optimization algorithm, matrix morbid initial value selected is too harsh, iterative calculations in the derivation and inverse calculation errors will be introduced to a larger calculated result is very likely to fall into local optimal solution and not the global optimal solution and many other issues. The calibration experiment results show that, after calibration, the measurement accuracy to meet the accuracy requirements of the measuring arm. The above research work constitutes a set of multi-joint coordinate measuring arm of the key technologies needed to measure the R \u0026 D arm has laid a good theoretical basis and technical support. The basis of the related art described above, but also in a number of key technologies in the non-contact laser scanning probe were analyzed and summarized, and some exploratory research, integration of laser scanning probe for measuring arm made a forward-looking technical reserves .