Research Of Coding Image Acquisition System Of Precise Absolute Linear Encoder With Combination Of Macro And Micro

Linear encoder is important instrument for measurement of precision displacement and angle, and have been widely used in radar, photo-electric theodolite, robot, CNC machine and so on. Absolute optical encoder is not only one of precise displacement measurement, but also is our country science and technology research and development of key areas. There are lots of factors that decides accuracy of measurement, Main depends on the performance of its key part. Performance of acquisition system of positional information is key component that can ensure directly that accuracy of decoding and measurement of absolute optical encoder. Acquisition system of precise absolute linear encoder with combination of macro and micro can effectively solve the problem that maximum allowable speed of traditional optical encoder is inversely proportional with its resolution and the zero reset operation. In order to assuring design request of High speed, high efficiency, high real-time performance, high reliability of acquisition system of absolute optical encoder that is the combination of macro and micro, it is used that combination of high speed performance of collecting of incremental encoding and low speed performance and high definition of acquisition of absolute encoding with CMOS in this papers, this way not only solve the problem that low speed performance of acquisition of absolute encoding, but also can achieve acquisition of absolute encoding at high speed. Based on acquisition system of precise absolute linear encoder with combination of macro and micro as an object, the following several aspects of research work have been carried out:Based on the study of the FPGA technology, acquisition technology of the CMOS image sensor and the working principle of displacement information acquisition of optical encoder, According to the practical need of acquisition of absolute coding image and its coding decoding, It is completed that function of acquisition of absolute coding image whose design of the hardware circuit and software. At the same time, through the simulation of experiments, verify the logic function of hardware circuit, acquisition coding accurately.According to the measuring requirements of absolute linear encoder whose instantaneity of decoding, and combined with what the back-end DSP spend on decoding, and that it is used that window scanning of CMOS image sensor for improving speed of scanning, and the process of the image gray level and so on, it is completed that collecting image coding of CMOS image sensor code matching with speed of DSP decoding.Study what speed performance of position information acquisition of absolute linear encoder, it is used that differential circuit is designed for removing direct current component and that sine and cosine signal is converted into square signal for the analog signal is converted into digital signals what the FPGA need, Combined with that speed judgment and switchover is designed in the FPGA, it is realized that increment position information is collected at high speed, it is reasonable to switch to acquisition of absolute coding at low speed, thereby, it can collect position information accurately at fairly high speed that Design and research of coding image acquisition system of precise absolute linear encoder with combination of macro and micro.Based on the above design of acquisition system, further experimental verification and analysis is completed, absolute code acquisition real-time performance can meet the demand of the back-end DSP decoding, it is used the new-style model of switchover of the high-speed and low-velocity acquisition to have implemented that the fastest velocity of comprehensive measurement can be up to 2m/s. Collected encoding image is applied to the absolute optical measurement system back-end DSP decoding whose accuracy can be up to ±0.6μm It provide a new approach to developing high-velocity and high-precision measurement of absolute optical encoder.