Studies On The Key Technology Of Signal Processing In Vibration Detecting System With Grating

The vibration detecting system with grating is a complex system for signal real-time analysis, immediate processing, based on the principle of moire fringe. The processing capability of moire fringe signals, which is the core of the grating detection system, decides such index as measure precision, measure speed and capability of anti-jamming of the whole grating detection system. How to deal with the problems of traditional direction distinguishting and subdivision technique to get the real-time, exact, high precision seismic wave signal, and convert it into analog singal which can be received by seismograph, have become the main tasks.Through the deeply reaserch on characteristic of vibration signal, the quality of current grating vibration signal processing methods is compared.Combined with the special advantages of CPLD and DSP in control and calculate function.respectively, the deeply studied on the real-time system of grating vibration signal processing based on the coprocessor CPLD and the processor DSP has been made.The main achievements in scientific research of this paper are as follows:1. The current methods of grating vibration signal detecting and processing are Summarized, the research on theory of grating sensor principle and signal direction distinguishting, subdivision technique is accomplished.2. According to the Concurrent Execution characteristic of hardware description language VHDL, designed two state machine processes in CPLD , synchronous data acquisition of two analog-to-digital converter is achieved. The limitation of traditional data acquisition method which use single sampling holder resulted in the asynchronism of data acquisition is eliminated.3. The vibration signal high expansion subdivision algorithm based on amplitude subdiivision principle by DSP is designed. The subdivision value calculation in separate quadrant by use of library function in C language is realized, the instruction time are saved, the algorithm is optimized, the speed and stability of the system.are improved.4. A new method to get the amplitude information of the vibaration is put forward in this paper. According to the working principle of the grating digital measuring device, the subdivision value of the not-full moire fringe wave is acquired and added to the full moire fringe number. Then the function which reflects the relationship of the amplitude of seismic wave and time will be acquired.The point where movement direction changed can be ignored in this method and direction distinguishing signal is only used to control the up-down counter.In this way, the error result from the delay direction distinguishing signal by hardware can be highly reduced .