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| In field of precise positioning of piezoelectric platform, the accuracy is affected by hysteresis and creep characteristics of piezoelectric actuators, mechanical system error and other factors. To compensate these errors, a control method based on visual sensing was proposed in this paper. Visual sensing has the advantages of high precision, non-contact and intuitive. The application of visual servo in piezoelectric control can eliminate all these error factors. Most of the existing micro displacement control systems based on visual sensing are one or two-dimensional motion control system, and have the disadvantages of slow image processing speed, low positioning accuracy and short stroke. Therefore, a measurement and motion control system based on micro visual sensing was designed by our research group for a three dimensional piezoelectric platform. A high speed camera was used to aquire the defocused image of the microspheres under the microscope at 1000 fps. The position of the platform can be obtained in real time by image processing. Transfer it to the motion control system, the output was calculated through the incremental PID algorithm. Then an accurate, fast and stable closed loop control of the piezoelectric platform was realized. The experimental results showed that the positioning accuracy reach to 15nm in the 100um stroke. |
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| Keywords:Measurement technology and instruments; Piezoelectric platform; Micro visual sensing; PID control; Nano positioning |
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