Research On Magnetic Grid Rail Splicing And Fault Detection Key Technologies And Engineering Realization

In modern machinery industry, especially in the field of extreme manufacturing, the length of rails used in large equipment is increasingly longer, such as the fairing riveting equipment in a heavy launch vehicle, with a journey up to 70 to 80 meters. Magnetic grid linear rail is widely used in the field of high-end machine position measurement, owing to its small thermal deformation and high measurement accuracy characteristics. However, the magnetic grid rail is produced and sold at 3 or 5 meters per rail at home and abroad. Hence currently the multiple magnetic grid rails are spliced together for large and heavy machine tools. If the rails are spliced mechanically only, it would cause signal distortion and even signal loss, which severely reduces measurement accuracy when magnetic grid measuring system going over the butt joint. Additionally, after finishing splicing work, it is very common that the butt joint is offset and rail is distorted due to the loss of magnetic grid, ground subsidence, temperature change, etc. It is really a severe challenge for regular maintenance and stable work without a magnetic grid rail fault detector. Therefore, it is pretty meaningful to study a novel magnetic grid rail “seamless” spicing and fault detection technology and put it into practice.Firstly, this paper studies the principal and key technology of the magnetic grid rail “seamless” splicing. The principal is that it converts the rail “seamless” splicing problem into phase difference detection problem. Its key technology lies in seeking an effective phase difference detection algorithm, which not only doesn't need to give the exact signal frequency beforehand and sample periodically, but also has a strong noise rejection capability. Based on these principles mentioned above, this paper proposes a phase difference detection algorithm based on Nuttall window and related simulations on MATLAB. The results show that the method based on the N-DFT algorithm could detect the phase difference in real-time accurately whenever reading heads go over butt joints with any speed or acceleration, compared with traditional detection methods based on HDFT algorithm and K-DFT algorithm.Then the principle and key technology of the magnetic grid rail fault detection are investigated. The corresponding fault detection algorithm is designed by introducing the unique fault modes of the magnetic grid rail. Its key technology is the signal quality detection technology(Distortion Detection Technology(THD and THD + N), Lissajous graphics technology) and digital phase subdivision technology. With the simulation on MATLAB, it could be concluded that the signal distortion can be detected more accurately with THD + N method and the degree of signal distortion and noise interference could be described more vividly with Lissajous graphics technology.Finally, the project implementation method of the magnetic grid rail splicing technology and fault detection technology are presented, especially the overall design scheme of the magnetic grid rail splicing and fault detection. The hardware circuit design and software design and implementation are also shown in the thesis. Finally the experimental verification is performed in both the lab and the industrial field. The results show that it can realize the expected function.