The Research Of Automatic Detection System For Incremental Encoder Based On FPGA

Photoelectric encoder is a kind of angular displacement sensor based on moiré fringe signal characteristics,by photoelectric transformation technology,converting angular position information into digital code.It is widely used in the field of industrial control,automation and high-accuracy measurement.Photoelectric encoder can be classified into incremental encoder and absolute encoder according to the type of grating disk.The incremental encoder is widely used in the measurement field of velocity for high resolution and simple structure.With the widespread usage of incremental encoder,accuracy detecting is very necessary for ensuring the stability of the photoelectric encoder.Traditional detecting devices can only be used on the accuracy detecting of absolute encoder,but are not capable of implementing the accuracy detecting of the incremental encoder.Therefore,it is significant and practical to research high-precision and high-efficiency measurement device.On the basis of reference related literature at home and abroad,the working principle and detecting method of the incremental photoelectric encoder are studied.The merits and demerits of the incremental encoder's error detecting method are analyzed.An error detecting method of the incremental encoder based on angle is proposed and an automatic detecting system based on FPGA is established.The subdividing circuit of the high accuracy reference encoder is designed,and it realizes the moiré fringe photoelectric signal's 512 times subdivision.The data collecting and processing circuit,serial communication circuit and LCD display circuit are designed,using FPGA chip XC3S400 of Spartan-III series from Xilinx Company as its core component,which realize automatic collection and error calculation of the output signals of the benchmark encoder and the detected incremental encoder.The detection results can be displayed on the LCD screen,and be transmitted to the computer simultaneously for the further analyzing and processing.Replacing recording and calculating errors manually,with the programs of data collecting,LCD displaying,serial communication and error calculating are compiled by VHDL programming language,are realized the auto-detecting of uniformity and orthogonality error of the incremental encoder.Using the incremental encoder automatic detection system in this paper,uniformity and orthogonality's auto-detecting of the incremental encoder with 32400 output pulse's cycles and 10? resolution is realized,and the detecting time of an encoder is reduced from the original 2 to 3 minutes to 30 seconds.The experimental results show that the detection system can realize the automatic detecting of the uniformity and orthogonality error of the incremental encoder and avoid the error caused by the non-uniformity of the spindle speed of the encoder,which effectively improves the detecting efficiency and accuracy.