Opticl Interference Detection And Composite Control Of Piezoelectric

With the development of precision measurement technology,nanometer displacement detection needs higher system positioning accuracy and resolution.It is required higher precision,higher stability to realize the displacement measurement in industrial and scientific research.Piezoelectric ceramic with small volume,high sensitivity,light weight and low power consumption,is commonly used as nanoscale drive.Due to the nonlinear characteristics of hysteresis and creep,piezoelectric ceramic need a method which combined the higher precision detection with a control system for precise move.For all the above reasons,this paper designs a composite controller,which combines feedback with feed-forward,to control the displacement of the piezoelectric ceramic.This optical interference device can improve detection accuracy of real-time displacement.The research content is as follows:(1)We designed a micro displacement amplification device based on the traditional Michelson interference principle.This amplification device contains a multiple reflection device.One of the mirrors was driven by the piezoelectric ceramics.This device can improve the resolution of the Michelson interferometer.Numerical calculation of the device is found that tuning the light incident angle or the angle of two mirrors can change the amplification times(10 to 500 times)under a certain condition.In theory,this device can raise the precision of Michelson interferometer to the nanometer.The theoretical calculation results were validated by optical simulation software.We analyze and calculate the displacement of piezoelectric ceramics and the response time of the photoelectric detector.And we consider the displacement magnifying multiple effects on measurement system accuracy.The experimental optical bench which combined the photoelectric detector with high speed data acquisition system,was built based on displacement amplification of optical interferometry(2)Based on the hysteresis characteristics of piezoelectric ceramic,feed-forward controller is designed with mathematical modeling through the elliptical polar coordinates.The displacement of piezoelectric ceramic driving by offset voltage was measured in the experiment based on open-loop control.And this displacement contrasts with the measure result of higher precision by inductance sensor.It is found that when the driving voltage in the range of 0V ~ 10 V,this device error less than 22.6nm.It means that this device can meet the accuracy requirement of micron displacement.When in the range of 10 V ~ 110 V,this device error is larger,and the mean-square deviation is 46.6nm.(3)Compound control method,combining the open-loop control with the feedback,improves the response speed and stability of the control system of piezoelectric ceramic.This system set parameters of PID controller through the genetic algorithm.The adjustment time of the system is down to 1.8 ms,and the steady-state error is only 0.23 percent of the nominal displacement when Kp=36,Ki=0.14 and Kd=0.029.In theory,this device can realize accurate displacement with the error of 6.2nm after the setting of the composite control system.This system can be realized nanoscale accurate displacement of piezoelectric ceramic in low cost than inductance sensor.