Study On The Calibration Technology Of Articulated Arm Flexible CMMs

The articulated arm CMM is a new type of non-orthogonal system.Its configuration is just like the knuckle of the people,in which several poles and a probe are connected in series.In this system the benchmark is the angle, instead of the length.It possesses the advantages of simplicity in structure,large measuring range and small volume,moreover it is convenient to setup on site in production line.But there are few own research articulated arm CMM producted in China.In order to develop the new types of flexible CMM,the main work of this dissertation is just focused on the calibration techniques, which is the key techniques of this system.The content of this dissertation comes from the product development project"the Research and Development of the articulated arm CMM",and the project will be completed by both Tianjin University and Beijing Aviation Precision Machinery Institute .The following work has being done in this dissertation:The ideal mathematical model of the articualted arm CMM is established.All possible errors are analyzed and classified carefully ,and the mathematical model for the CMM with errors is established.The error mathematical model is practical and convenient for error compensation,because it includes all kinds of error factors.Based on analyzing some general views related to the calibration techniques of articulated arm CMM both home and abroad,a suitable calibration method is presented in a creative way.In this method, errors of all other parameters and rotational angles cause little error in the determined parameter.It has important significance in improving the accuracy of the calibration.In order to calibrate in the method mentioned above,a new calibration device is designed.The device is a kind of fixture,but not a measuring machine.The calibration device is designed to ensure the high-precision of the calibration and meet a variety of mission requirements.The measurement and control system is developed. At the core, a single chip system and visual instrument LabVIEW are used to control the equipment, and successfully accomplish the communication between the computer and the PCB board.Finally, experiments on movement accuracy of calibration device are carried on, experiments show that the equipment can meet the needs of calibration. Experiments are carried out for the ball bar,and the lengths are measured using the new calibration method. The correctness and feasibility of the programme are proven,and the accuracy of the calibration method is analyzed.