Research On Coaxiality Calibration Technology Based On LD/PSD

In the process of assemblage and maintenance of mechanical equipment, precise coaxial measurement and calibration is an important step, which can guarantee normal operation of the equipment, can reduce vibration and abrasion, can save energy consumption, and can prolong the useful life. According to the research of Royal institution, up to 50% of all breakdowns in rotating machinery are caused by misalignment.The shaft laser alignment is an optimal automatic alignment instrument presently. There are many high precision foreign products, such as ROTALIGN from German, FXITURLASER from Sweden. Because of the business secret, the principle is unknown. In the condition that there is no such instrument in inland, and such instrument is urgent need, this project researches a new alignment measuring technology and finishes the model machine's manufacture.The core components of shaft laser alignment are laser diode (LD) and position sensitive detector (PSD) with high resolution. A portable personal computer will process the main arithmetic and computer-human interaction. In this thesis, a new alignment instrument structure with single beam of laser and duel position sensitive detectors is designed. Two mathematic models and formulas are established based on two PSD and single PSD, which can respectively fulfill measurement with 90° rotating angle and discretionary angle each time. In practice, when coordinates of light spots in two positions are measured, people can obtain the offset, the angular deviation and adjust value. The hardware system includes LD, PSD, inclinometer, signal magnified circuit, data collection-handling system and LCD module. The software is programmed with C language, including data collection module, data processing module, and friendly computer-human interaction interface that can display the result of measurement as figures and words for user. To the question of nonlinearity of PSD, two methods of linearization are put forward, both linear interpolation and neural networks. After simulation of neural net, the output of PSD has well linearity. Through the analysis of theory and experiment, the author discusses the influence of testing condition on detection precision of PSD and brings anti-interference means forward. In combination with optics filtering, the software compensation method can basically eliminate the influence of background light. Finally, it proves the correctness of mathematic model and the repeatability of instrument by analyzing the experiment result.