Research On Profilometer With Digital Servo Focus Control System For Surface Measurement

It's easy to do damage on workpiece surface and wear the probe because the force exists during the contact measurement process. The field of using the contact measurement is limited because of this disadvantage. There is no force between the measured workpiece and the non-contact instrument during the measurement process. So the scratch won't be made on the workpiece surface. The non-contact instruments have been developed quickly. Among all surface measuring instruments based on various detection principles, the focus detection apparatus are most prominent on engineering surface measurement, because it have large vertical and horizontal measurement ranges, and high dynamic ratios of range to resolution.In our country, there are a lot of need on non-contact measurement instruments for surface topography characterization in the field of manufacturing industry and scientific research. But the mature products of non-contact measurement have not been developed and the foreign products are very expensive. In order to solve this problem, it's very necessary to develop the non-contact instrument.The main research contents and creative points in the thesis are as follows:The optical system of the non-contact profilometer is based on an improved Foucault focus detection method. Through the theoretic analysis of mathematical model of focus detecting optical path, it discloses essentially the imaging law of the instrument.Data acquisition circuit board and signal conditioning circuit board are designed for the fulfillment of instrument function. The data flow between the computer and outside equipments is introduced in detail. The signal processing circuit related with measurement is presented also.A new way which use the tentative and dichotomy method to detect the focus position has been designed in the software. It ensures computer do digital servo control on the volume motor for detecting the focus position. Compared with traditional analog servo method, it enhances the stability of the servo system and shortens the focus detection time. The profilometer work efficiently and precisely.A precise platform, which uses X-Y coplanar technology, is designed to satisfy the requirement of locating the position quickly and precisely. The structure of a volume coil motor, the servo mechanism of optical stylus profilometer, is designed to own superior static and dynamic characteristic and capability of focus tracing by whole line cutting.Virtual instrument technology is applied in this apparatus. Based on C++ builder, a complete-function program with virtual panel is programmed for the user. Friendly software Panel, standard parameter setting environment and various data processing functions ensure the user do intelligent operation. Some standard workpieces have been measured by the non-contact profilometer. The experimental results show that the profilometer satisfy the design requirement.