| The photoelectric encoder, which combines the digital and computer technology, has been widely applied into practice with the development of manufacture and automatization technology. But the development of encoder is limited by many aspects such as the complexity of coding method, the high precision of manufacture and alignment in recent years. Aiming at some defects which contains that the output value of incremental encoder is relative quantity, the multi-turn absolute encoder is not easy to realize miniaturization and the encoding method of single track absolute encoder is complex, the paper studies absolute angular position sensor based on machine vision. This sensor can measure the absolute angular position by detecting an absolute tag provided on the tag plate.Firstly, a new type of absolute angular position sensor is put forward and its working principle is introduced in detail. Absolute tag centroid fitting, absolute tag trajectory fitting, image processing and some other algorithms are studied. The absolute tag setting scheme is researched, two schemes, active absolute tag and passive absolute tag, are proposed. The better setting scheme is chose by analyzing experiment results of the two schemes.Secondly, based on the analysis of new sensor hardware, the circuits of image acquisition module, image processing module, power supply and other modules are designed. Parameters of every component are determined and the hardware circuit of the sensor is completed, which lay down the foundation of production in the future.Finally, based on the analysis of image processing algorithms and absolute tag fitting method, the overall design scheme of FPGA implementation is put forward and the components of software system are identified. The hardware design of algorithms is accomplished by using the ISE development platform and Verilog HDL programming language. The measuring accuracy is raised by analyzing experiment errors and improving experiment parameters. |
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