Research on the position control of double-pass schlieren component based on visual feedback

The traditional mechanical method of debugging the double-pass schlieren system exhibits the problems that the fine positioning of the working position of the spherical mirror mechanism cannot be ensured, and the optical paths cannot be completely coincided after passing through the flow field twice in the experimental application in the hypersonic low density wind tunnel. Here, a novel double-pass schlieren system based on visual feedback was developed. The system via absolute encoder instruction control the AC servo motor to adjust the position of the spherical mirror mechanism. Moreover, the pitch and left-right deflection of the spherical mirror can be adjusted by the schlieren image quality evaluation results provided by the machine vision system（visual information feedback）. The position control system of double-pass schlieren parts based on visual feedback realizes the automatic positioning closed-loop control of the double-pass schlieren spherical mirror mechanism, and ensures that the light paths overlap as much as possible after passing through the flow field twice to eliminate ghosting during imaging of the model flow field（the definition of the flow field image is improved by 2.2 times compared with that obtained by the traditional method）.