Research On Non-contact Measuring Of Big Diameter Based On Chord Length And Bow Altitude

To the measurement of big circle diameter, the paper puts into effect non-contact measurement of big circle diameter based on the measurement principle of bow altitude and chord length and selecting high precision laser-displacement sensors.Standardization formulas of relative positions of all the laser-displacement sensors are obtained by inferences. By analyzing the relations between relative positions of sensors and the bow altitude and chord length, the calculation formulas of the bow altitude and the chord length are o derived also. So the measurement formulas of great circle diameters are obtained.By analyzing standardizations and measurement errors, the paper disclosures the producing reasons of measurement errors and how measurement errors affect measurement precisions. Two methods of symmetric layouts of sensors and equalizing processing of measurement data are put forward to reduce system error. Corrections of system error are obtained by multiple measurements of the standardization circle, so the system error is reduces fourthly. Adopting means of multiple measurements as the measurement results weakens the effects of random errors.The big diameter and non-contact measurement instrument and the software system are designed. To improving measurement precisions, analyze the diameter of the standardization circle and the value of the chord length using in measurements, so the selecting methods of appropriate dimension of the standardization circle and value of the chord length are gained. The on-line measurement software system is developed based on LabVIEW, which has the functions of collecting, saving and calculating measurement data etc.Guiding by the theories mentioned above, the experimental equipment is constituted, and the experiments of relative position standardizations of sensors and diameter measurements are carried on. Diameter error of the measurement circle is reduced to the range of±30μm, so the measurement methods are correct and effective. The research findings not only improve greatly measurement precisions of big diameter revolving works, but also provide theoretical supports for the developments of measurement instruments of big diameter and non-contact measurement instrument.