Research On The High-precision Position Detection Technology Based On Incremental Optical Encoder

Along with the continuous development of numerical control technology in the direction of highspeed and high precision, it has put forward more and more high demand for the performance ofoptical encoder. As making thinner ruled grating on coded disk to improve the position detectionaccuracy of the optical encoder has been close to physical limits, there is an urgent need to explorenew methods to improve the position measurement accuracy of optical encoder. Therefore, based onthe analysis of the structure, working principle and subdivision technology of the optical encoder athome and abroad, two segmentation methods were put forward to improve position detectionprecision of optical encoder: analog-digital conversion method and time-space conversion method.Meanwhile, the following researches were launched.(1)By adopting DSP and FPGA of high performance as the signal processing core, the hardwarecircuit of optical encoder used in high-precision position detection was built. It was also completed inthe design and debugging of several circuit modules such as A/D and D/A transformation of highresolution, differential signal receiving, optoelectronic isolation and data transmission interface ofhigh-speed as well.(2)Time-to-digit conversion(TDC) method was explored based on the phase shifting coding ofphase-locked loop(PLL) and the combination of coarse and fine timing. Then, by programmingthrough Verilog HDL language and simulation, the high-precision time detection in nanosecond wasrealized based on FPGA, which can provide support to improve position detection accuracy withtime-space conversion method.(3)Through the software programming, it completed the alignment, unitization and identifieddirection pretreatment of the original signal. Based on this, on the one hand, the subdivision of analogsignals of optical encoder can be achieved by constructing approximate triangular function; on theother hand, due to the characteristics that the objects in athletic process has inertia and the speed issteady, the pulse signal subdivision of optical encoder can be realized by high-precision timedetection, current speed detection and kalman filter estimation.(4)At last, the visual testing interface and the USB data transmission channel between DSP andPC ware established, and analog-digital conversion method and time-space conversion method wereused respectively on the position detection experiments and error analysis to verify that the proposedmethod can improve the position detection accuracy of optical encoder effectively.