Research On Base On-line Measurement Error Separation Technology

The flatness of bases is one of the important factors that affect the ship construction quality. To ensure the construction quality, it is vital to measure the surface form error of the bases. In current production, the measurement of surface form error of bases is usually take place after processing. This way is of long surveying cycle and low production efficiency. If the measurement can be integrated into the processing, it will not only shorten the processing time but also result in a timely manner according to online measurement correction parameters, and ensure the accuracy of the base processing greatly improved under the premise of production efficiency.Because of the complex working field and changing environment, there is no current base-line separation and measurement instrument available. In this paper, an on-line measurement error separation system which based on multi-sensors was built according to practical needs while taking the error separation technique as the theoretical basis. Least-square serial two-point method was used to complete the online form error measurement plane on normal condition, for the bases with special shape or part of the narrow area which does not allow simultaneous measurement by all sensors two-point method in time domain was used to measurement base straightness error. Measurements simultaneously with multiple eddy current sensors coordinate information gathering marked points, and displacement information is converted to analog voltage signal. TMS320VC5509A DSP chip design to data acquisition subsystem at the core as well as the FPGA chip EP1C12Q240C8 for error separation subsystems. High-precision A/D is responsible for collecting the sensor analog voltage and transfers it into digital voltage. DSP timer interrupt controls A/D sampling frequency to match the machine's forward speed, this combination ensure that the sampling points are located in each grid which has been set accordingly. FPGA receives the data DSP sends and separate the shape of the real surface of the tested base error according to the number of the error measurement grids. Finally the results were sent through the RS-232 serial port to PC for real-time display and storage.Finally, the measurement system on-site installation and testing, test results were given. Repeatability of the measurement system was analyzed and the results of the online measurement of laser alignment and measurement of scanning results were compared. The result of experiments shows that the measuring accuracy of system meets the field requirement which means this system achieves the desired goal.