The Study Of Super Miniaturization Matrix Encoder

Optical encoder is a kind of device used to measure the angular displacement; it converted the optical signal into electric pulse or digital quantity to achieve the angle output quantificationally. The encoder offered significant advantages over small cubage, high precision and reliable operation. Due to the requirement of light-duty encoder in manned space flight, the trend requires that encoder satisfies high-precision, super mini cubage and intelligentizing characteristic. However, the super mini cubage and high-precision is a pair of irreconcilable conflict under traditional reticle craftwork and encoding method. Therefore, current super miniaturization encoder was achieved by reducing the precision of encoder. To solve this problem, a new-style absolute matrix encoder was presented in the paper.First of all, the encoding principle of absolute optical encoder was analyzed, and the Gray code was adopted for encoding. A new-style matrix encoder was presented which carried out 12-bit matrix encoding by reticling two circles, so the cubage is super-small and it can reachΦ30mm×15mm. The decoding method was achieved by increasing the number of photodiode and improving the utilization factor of optical signal.Secondly, the issues about correction method of precise code,subdivision method and direction identification were analyzed, and a feasible scheme was produced, eventually it was validated in the simulation circuit.Then the digital decoding system based on FPGA was designed, the signal processing system was constructed by selecting the chip and designing the exterior circuit. The inner module of PFGA actualized digital decode, first input first output, serial port output and etc.Eventually, the measuring error of encoder was analyzed, the experiment showed that the resolution can reach 22-bit, and measuring precision can reach 0.8", the experiment data accords with theoretical calculation, it can satisfy the design requirement. The encoder breaks through the limitations of traditional gray code, and accomplishes the super miniaturization and high-precision, so it can satisfy the demands of manned space flight,military and nano technology to super miniaturization encoder.