Precision Control Of Piezoelectric Deformable Mirror Using Charge Method

The adaptive optics system(AO)based on the principle of phase conjugate compensation can correct the wavefront aberration in real-time and make the system obtain the resolution close to diffraction limit.Therefore,it has been widely used in astronomy,living retinal imaging laser beam correction,biological microscope and other fields.With the increasing demand of AO technology,researcher have done a lot of work on deformable mirrors(DM),which are the key components of adaptive optics system(wavefront corrector).Various types of DM,such as piezoelectric DM,electrostatic DM,electromagnetic DM and liquid crystal spatial light modulator(LCS)have been developed.Among them,piezoelectric DM driven by piezoelectric material is one of the most widely used with the advantages of high frequency response,large deformation and good stability.However,the precise control the piezoelectric DM is difficult due to the large hysteresis of piezoelectric materials under voltage-driven mode.At the same time,the piezoelectric DM is a multi-actuator system,which limits its application range.In order to reduce the hysteresis effect of the piezoelectric DM and achieve precise control of the piezoelectric DM,a charge-driven method is proposed.In this thesis,the piezoelectric DM based on charge-driven is studied in the following aspects:1)The control principle of charge-driven the piezoelectric DM was studied and the driving power supply of charge was developed.The output displacement of piezoelectric material is proportional to the charge number at two ends of itself under the charge driving.A driving power supply of charge for piezoelectric DM with 19 actuators was designed.The working principle of charge drive unit was introduced and the control system of piezoelectric DM based on wavefront measurement was designed.Two methods of charge control for piezoelectric DM were put forward: serial control and parallel control.The influence of high voltage operational amplifier,high speed controllable analog switch and other key components on the circuit was analyzed in detail.An adaptive optics test platform based on the Shack-Hartman wavefront senor was built to verify the performance of the driving power supply.The experimental results show that the RMS error of the mirror deformation for the piezoelectric DM is 1.1 nm under the control of the charge driving power supply.It can satisfy the requirements of precise control of the piezoelectric DM in the field of AO.2)The charge control method was design of piezoelectric DM.The Zernike polynomial was used to fit the wavefront aberration.The influence function matrix(IFM)method of piezoelectric DM was introduced.The open-loop control and closed-loop control based on IFM were established.The control program was compiled according to the control flow chart.3)The contrast experiments of charge and voltage driving for piezoelectric DM.A series of open-loop control experiments for piezoelectric DM were carried out bade on charge and voltage driving.The experimental results show that the charge driving power supply can effectively reduce the hysteresis effect of piezoelectric DM.The overall hysteresis is about 1%.For the reconstruction experiments of different shapes,the reconfiguration accuracy under charge-driven mode is improved about 70%.The closed-loop control experimental show that the precise control of piezoelectric DM for long time can be got.In addition,there is a leakage phenomenon in the charge driven model,but it does not affect the application of the piezoelectric DM in the field of AO.