Research On Coding And Decoding Theory Of Virtual Absolute Encoder

Optical encoder is a kind of angle displacement photoelectrical sensors. It is also called photoelectrical shaft encoder. It is digital angle measurement device in which optics, mechanics and electricity are integrated. As an important sensor it is used in many areas. However, in recent years, with the development of the technology, urgent demands to micro-sensors are increasing in military, aerospace, auto control and etc. The trend requires that optical encoder satisfies the high-precision and high-resolution characteristic. There are lots of shortcomings for traditional optical encoder to overcome and to meet developing needs. So New type of encoder——virtual absolute optical encoders are advanced.At first, the principle of virtual absolute encoder is introduced. A practical coding algorithm is designed according to the characters of the index code tracks. The code design of indexing track highest to 17 bits comes true with computer aided design (CAD). A method to decode is also developed, which can convert the binary cyclic code into binary natural code. The problems of subdivision and identification direction are analyzed, and a novel method is proposed.Then using EDA tools, signal processing circuit is simulated, and the signal processing circuit test system with the core of FPGA (Filed Programmable Gate Array) is accomplished. Combined with the incremental optical encoder using in the project, a series of experiments is designed for the model which can simulate the working process of the virtual absolute encoder. Experimental results show that virtual absolute optical encoder for high-precision measurement of the angle is feasible, and the circuit system as signal processing circuit of the virtual absolute optical encoder is reliable.Finally, the main factors impacting on the performance of virtual optical encoders are analyzed; the program is improved for the design defects. The experience obtained from this project is beneficial for the realization of the virtual absolute encoders.