| In machining products, especially in the products for high precision, the shape error of the parts is an important symbol to evaluate the machining accuracy. It is also an important factor to affect the performance of the products and the quality in assembly process. It needs reasonable measurement and control.Therefore, it has great significance to evaluate the shape error of the parts accurately in machining testing.In this paper, a systematic shape error evaluation of typical parts is studied, and the current research status of shape error measurement is analyzed. Taking the coordinate measuring with the method of getting points information,building the mathematical model of the shape error based on the principle of least squares, a PSD laser tracking measurement system is designed.The system has the function of acquiring coordinates and evaluating shape error.Firstly, the hardware platform of the PSD laser tracker measuring system is built.The upper system is made up of computer and motion control card PCI-8134. The lower system is composed of ARM processor, PSD sensor, gyroscope module, RF module and other components. All of the modules including the upper part and the lower part form a whole measurement system, and the hardware platform of the system is built for software design.Secondly, the system software of graphics user interface is designed with VC to achieve motion control, data display, shape error evaluation and other functions. Motion control function includes relative motion control and absolute motion control.Data display function makes datas showed in real time.Shape error evaluation function collectes coordinates of all points to obtain error value by assessing algorithm.Thirdly, the lower system software is designed in MDK environment to driver each module peripheral. In order to improve the real-time and stability of the control system, the entire project uses modular programming and transplantes the embedded real-time operating system μC/OS-II. To ensure the reliability of the information,data transmission between the upper and lower system is completed by using the self-defined communication protocol.Finally, a calibration experiment is made about the system by using laser tracker device, and the shape error measurement experiments are carried out. The results show that the measurement system can meet the requirements of large size shape error measurement. |
