The Research Of Grating Digital Signal Acquisition Technology

Photoelectric rotary encoder is a fine sensor which based on the metrological radial grating can change angular displacement and angular velocity into electrical signal. Photoelectric rotary encoder generally can be divided into acquisition and data processing. The part of signal acquisition is composed by the light source, measurement grating and optical receiver components. In order to achieving the purpose the accurate measurement, photoelectric rotary encoder relies mainly on measuring grating as detection tool, then change the object displacement or the rotation angle value into the analog or digital signal when through the photoelectric conversion. For the advantages of photoelectric rotary encoder, the simple structure, small size, light weight, high resolution and so on, it is used to be widely required on radar, theodolite, automatic, remote sensing applications.The high frequency jitter is generated when the output signal of grating encoder is subdivided more times, which will affect the correct count of the electrical pulses and further affect the accurate measurement of angular displacement when the object rotating. To solve these problems, the acquisition system of quadrate encoder signal is designed. FPGA was used as the main chip. The acquisition system is mainly divided into four parts, filter, frequency phase, counter and UART communications. Filter circuit will filter out the high frequency shaking; frequency phase circuit can identify the signal's direction when rotating, at the sometimes, it also can divide the signal into four times; counting circuit can count the pulses, then get the location information; finally UART interface will send location information to the host computer which will achieves position feedback.Firstly, the article introduces a brief background and significance of the topic, and then summarizes the status of current projects, it analyses the problem about the quadrate signals generated by encoder and designs a set of feasible acquisition circuit. At last, it introduces how to design by the hardware and discusses the software structure and each module.At present, the acquisition circuit has been completed in hardware, software and debugger.