| Photoelectric rotary angular encoder is a precise displacement sensor, converting the angular position or angular displacement to the electric signals, which are widely used in precise measurement, automatic control and so on. The conventional absolute encoder is based on the binarized encoded disc, which is to obtain the angular information from the situations of light transmission along the radial direction of disc. So if the disc size is fixed, higher the resolution is, more the reticles in one circumference are and thinner the reticles become, which may cause the insufficiency of illuminance and light diffraction. Then the measurement accuracy should be decreased, which may influence it's normally operation.To solve the contradiction between the size and resolution, a new subdivision technique based on array detector is proposed for absolute angular encoder with a binary coded disc in the present study. The proposed technique can well improve the angular resolution without changing the coded disc and is convenient for installing and adjusting. The coded disk is firstly lighted by LED and then magnified by the image lens. The magnified image of coded disc is firstly received by the detector. Then the binary code is obtained and the minimum code unit is subdivided by the detector's pixels, respectively, which are both contributed to the angular position.The decoding process was completed by the circuit based on FPGA, the image of the disk was processed by several modules and finally output through UART module, thus achieves real-time processing.When the system has been built, working conditions, the linearity were analyzed .During the analysis, the influence of the focusing and illumination were mainly studied. Another measurement system has been introduced into the system and the measured results were compared. The angel resolution can be improved from 13 bit to 16 bit in the experiment, the absolute error of the raw code and the subdivision code are 0.0270°and 0.0031°. |
PDF Full Text Request