Research On Ultra - Precision Positioning And Control Technology

The technology of precision positioning plays an essential and important role in modern precision manufacturing fields. It is widely pursued by industries of ultra-precision manufacture, semiconductor manufacturing, micro manufacturing technology and nanometer technology etc. Precision positioning is also a combined cycle control system involving physical optics, electronics, mechanical, and intelligent control, which has broad application prospects. The details include the following three aspects:1. By applying theories of physics optics, the principle of grating displacement detection were analyzed, the mathematical model between displacement of double diffracting gratings and the intensity of Moire signal was established, and simulate with MATLAB simulation software. The simulation results showed that the intensity of Moire signals varied periodically within the Fresnel zone when relative displacement of the gratings changed, and the cyclic variation is a constant of grating. At the condition of G=nP2/λ that maximum intensity of Moire signals was obtained. The effect of raster pitch, the features of Moire signal were also simulated by computer. And the experimental results are consistent with theoretical calculations. The grating displacement detector can be used in ultra-precision positioning system.2. A compound double drive for precision positioning was proposed, in which combined coarse alignment with fine alignment. By analyzing Moire signals, the industry control computer sent out the driven pulses. And the stepper motor drives the ball guide screw for coarse alignment. Then the industry control computer sent out the driven voltage, which were generated by Moire signals diffracted by fine grating to create corresponding deformation of piezoelectric ceramic brake. And then move the flexure hinge into the expected position. The final accuracy of the system could be±20nm.3. Piezoelectric ceramics is an important part of the micro-positioning system, research on the input and output characteristic of piezoelectric micro-displacement actuator is important. The load installment was designed to carry on the demarcation experiment with the output characteristic of piezoelectric under the different load. In view of existing nonlinearity and hysteresis of the piezoelectric, the mathematical models of piezoelectric based on input and output characteristic are established by the artificial neural network. The simulation results show that the model can stimulate the piezoelectric preferably. And then an adaptive neural network controller was designed to improve the positioning precision of piezoelectric stage according to the research of the model. The experimental result showed that adaptive neural network control could perform excellent control effect, such as, faster response, better stability. It could effectively improve positioning speed with high accuracy.