Research On Contol Technology Of Alignment Error Of Large-aperture Tiled-gratings

Under the need for inertial confinement fusion fast ignition and high energydensity physics research, it is the goal pursued by numerous researchers to improveoutput-energy and peak-power of the single short-pulse laser.It is possible to improvepeak-power of the single short-pulse laser for chirped pulse amplification technologyapplication.In the terminal of short-pulse laser device that is using chirped pulseamplification technology, the diffraction grating is used to compress the laser pulse.Caliber and damage threshold of compression gratings limit the output capacity ofshort-pulse device.As far as current technology is concerned, single piece of largediameter grating is not only difficulty in making technique, but also costly. Gratingtiling is considered to be the most economical and effective access to get large-diametergrating.Large-diameter grating obtained by grating tiling, which in theory has been provedto be feasible.But it is very difficult in the actual construction of the project.Thedifficulty lies in the grating tiling error precision control and stability keeping.According to extremely high requirements of grating tiling stability.The paper mainlyresearches grating tiling stability control technology.The paper used high-precision closed-loop control to control the grating tilingstability, used capacitance sensors as detection means of the grating tiling errors andused piezoelectric actuators as compensation measures. First, according to theadjustment requirements of grating tiling closed-loop control, the paper optimized thelocations of the capacitive sensors and piezoelectric actuators, in order to improverigidity of the overall structure and convenience of control systems. Δ-shaped andL-shaped are two common arrangements. From the optimization results, the L-shapedlayout avoided multi-degree of freedom linkage, and reduced the control difficulty.Second, according to the theory of piezoelectric and mechanical vibration, the device issimplified, and three degrees of freedom electromechanical dynamics system model isestablished. The transfer relationship of the MIMO system is proposed, and thesimulation for the piezoelectric actuator using the PID and fuzzy control algorithm isperformed by MATLB software. Simulation results show that fuzzy control algorithmhas better control performance than the PID control algorithm. Finally, control softwaredeveloped by Visual C++6.0is used by the control system with a computer, PI control box, grating splicing device and other components.Optimized combination of PIDparameters is Kp=0.2, Ki=0.035Kd=0.02.The control experiments are compared,with sensors data analyzed. The results show that the fuzzy control algorithm has highprecision, fast benefits. From the experimental results of the grating tiling, using fuzzycontrol algorithm can improve the stability of the grating, and splicing errors can becontrolled in the±30nm，and can remain stable for a long time. Experiment shows thatthis method can effectively improve the stability of the grating tiling, and can beenapplied in the actual construction of the project.