光栅衍射型绝对式轴角编码方法和系统的研究

Absolute angle encoder is the sensor extensively applied in the fields of modern national defense, aerospace, industrial CNC, precision measurement, and so on. However, the traditional encoder is unable to have both high resolution and small size because insufficient light and diffraction become more apparent with the thinner lines, which disturbs its normal work. So this project is to investigate a new type absolute angular encoder based on diffractive gratings. The disc pattern is consisted of the diffractive gratings with various directions and various periods, which are arranged on a single ring. The positions of combined diffractive spots, which are used for angular coding, are probed by array detector. Electronic subdivision or extra diffractive subdivision code are introduced to improve the angular resolution. It can be seen that it is a more flexible non-binary coding technique. Since line width of its disc pattern is not limited in theory, it is good for minimizing the encoder. In this project, the diffractive absolute code is firstly designed and investigated. Then, the optical illumination module and signal detection module are set up in the coding theory. At last, the angular coding system is integrated and its working performance are tested.

绝对式轴角编码器是一种广泛应用于现代国防、航空航天、工业数控、精密测.量等领域的传感器，传统的光度型绝对式轴角编码器由于在码盘刻线过细的情况下会导致光.通量不足和光衍射现象进而影响编码器的正常工作，所以不能兼顾高分辨率和小尺寸。为此，.本项目拟探索一种新颖的光栅衍射型绝对式轴角编码技术，其码盘图案由不同方向和不同周期的衍射光栅排列在单圈上组成，利用阵列探测器检测多个衍射光斑的空间位置，这些空间位置构成角度编码，可使用电子细分或额外的衍射细分码提高测角分辨率。由此可见，这是一种更为灵活的非二进制编码技术，由于其码盘图案的线宽在理论上不受限制，所以有利于码盘的小型化。本项目将首先设计衍射绝对码，然后在编码理论的指导下构建编码系统的光学照明模块和信号探测模块，最后对编码系统进行集成并测试其工作性能。

现有的绝对式光电轴角编码器均基于透光/不透光原理，所以码盘的最小刻线宽度将限制其分辨率大小，为此本课题提出并实现了一种基于光栅衍射原理的新型绝对式轴角编码技术。课题的主要研究和解决了如下问题：①基于衍射光栅的衍射绝对码的设计和实现；②衍射信号的收集和检测，包括光学系统、探测器及光机结构；③衍射信号处理系统，包括粗码解码和信号细分。取得的主要成果是：提出了一套完整的衍射型绝对式轴角编码器的实现方案，包括衍射绝对码、衍射信号检测、解码及细分；建立了基于该原理的理论模型，为具体码盘参数的确定提供了一种仿真方法，从而可为实际编码器设计提供指导；搭建了一个衍射型绝对式轴角编码原理样机，码盘直径为40mm，分辨率约为20.63’’，测角精度为78.00’’。课题的研究结果表明：基于光栅衍射原理的绝对式轴角编码技术完全可行，采用合适的信号细分技术可以在满足小尺寸的基础上达到较高分辨率。本课题的研究为绝对式轴角编码器的设计提供了一种新的思路。