Moire Fringe Subdivision Theory And Its Application In Grinder Measure And Control System

The Moire fringe signal subdivision technology is the core of the grating measurement technology. To obtain the displacement variation less than one grating distance with advaced Moire fringe signal subdivision method is a key in enhancing the resolution of grating measurement system. However, the commonly used subdivision methods exhibit some disadvantages in practical application. Obviously, it is of very important significance to perform the research on the Moire fringe signal subdivision method and to search the optimal subdivision scheme. In the present investigation, new Moire fringe signal subdivision theory and its application in both grating displacement measure system and grinder measure and control system have been discussed.Based on the digital integrated design idea, new phase-locking displacement grating Moire fringe signal subdivision theory was proposed. And both feasibility and validity of the proposed theory in subdivision and direction seeking were demonstrated with the mathematical method. In the present method, the phase modulation for the output signal of the grating sensor is conducted, and then the modulated signal is subdivided in phase-locking frequency multiplier after band-pass filtrating. The spatial displacement signal outputted by grating sensor is transferred into the directly proportional time signal through phase modulation. Thus, the original measurement for the spatial displacement is transformed into the measurement for the phase angle of time signal. Farthermore, the significant decrease of displacement tracing velocity with subdivision number as well as the serious influence of the variation in temperature, power and component parameters on the subdivision number can be avoided. Through introducing a constant frequency, a phase mass and a subdivision reference signal, three key problems get solved. And thus, the proposed method can synchronously finish both subdivision and direction seeking, avoid the uncoordination from individual counting in most subdivision methods, and is available for both complete period measurement and incomplete period measurement. In addition, the proposed method has such advantages as high subdivision number and convenient adjustment, and can be used for conducting the static and dynamic measurement. At the same time, the design idea that the original grating signal is modified with the frequency multiplication technology in order to reduce the requirement in the orthogonality and equal-amplitude as well as enhance further the practicality of the present subdivision method has been proposed.On the basis of new phase-locking Moire fringe signal subdivision theory, the grating displacement measuring system was developed. The original system design scheme adopting the discrete digital logic circuit was replaced, and the integrated design idea was proposed. Because the subdivision module and digital logic circuit are integrated in one programmable logic device, the integration degree of the system is considerably enhanced. It has been experimentally proved that the present system has such characteristics as high resolution, rapid tracing ability, good reliability and strong disturbance resistance.Through investigating the Moire fringe signal subdivision based on neural network, the method to combine the complete period hardware counting and direction seeking with the period inside neural network softeware subdivision was proposed. Two measures to enhance the subdivision precision were presented. With allowing neural network to learn a few learning samples and by the generalization of neural network for discretional input value, very precise output can be attained. Because the sine-cosine signal ratio of grating output is taken as the input of network during training, the influence of the amplitude fluctuation on the subdivision precision gets eliminated. The proposed subdivision method has such advantages as the simple hardware circuit as well as the higher resolution and reliability, and is of some practical application value.By analyzing the present status and development tendence of grinder measure and control system, the design idea to replace inductance coil with special mini grating sensor and to measure the dimensional variation in grinding process was proposed. The traditional inductance measuring method used for 30 years in our country is changed, and the nonlinear error from inductance coil as well as the serious influence of environmental temperature and humidity on measure and control precision get effectively avoided. Based on the proposed digital phase-locking subdivision theory and with utilizing the programable technology, the full digital integrated design was carried out for grinder measure and control system. With the parallel processing mode combining micro processor and field programable gate array, the FPGA was taken as a embedded chip of microcontroller and specially applied in the subdivision, direction seeking and count processing of grating Moire fringe signal as well as the integrated design of digital logic circuit. Thus, the processing speed of the system gets increased, and the real-time measure and control of the system for the grinding quantity of processed parts can be ensured.The partial serial FIR filter based on FPGA was adoped in the design of the system. Compared with the complete serial structure, the partial serial structure can considerably increase the operation velocity and reduce the operation delay. On the other hand, the partial serial structure can decrease the consumption of logic uint, compared with the complete parallel structure. In addition, a digital phase-locking frequency multiplication method based on FPGA was proposed, where the decimal frequency-division was realized using the integral frequency-division assemble. The simulation analysis proves that the proposed method has such advantages as high subdivision precision and large phase-locking velocity.The software design idea of intelligent grinder measure and control system as well as the realization method of partial functions were introduced. Such functions as on-line compensation, rapid drive and self-check were added, which can ensure the excellent performance of the system. The grinding tests prove that the system exhibits good repeatability and can meet the requirement of national standard. In addition, it has been demonstrated that the system has such characteristics as high measure and control precision, integrated function, easy operation and obvious practicability, which settles good foundation for home manufacturing of top-end products in Chinese grinding machine industry.