Robust Control Of High-Precision Piezoelectric Nanopositioning System

The piezo-driven nano-positioning stage is the core component of a precision positioning system.It is capable of achieving nano-level precision positioning due to its fast response time,high positioning accuracy as well as high driving force,good stability,no noise and no heat generation.Widely used in semiconductor processing,ultra-precision imaging,biomedicine,nano-detection and data storage and many other cutting-edge technology fields.However,the inherent weakly damped vibration characteristics,hysteresis non-linearity and creep characteristics of the platform,as well as widespread model uncertainties and external disturbances,all affect the high-speed and high-precision positioning and platform stability of the platform.Research into the control technology of piezoelectrically driven nanopositioning platforms has therefore become a key means of achieving nanoscale positioning accuracy and is a pressing technical challenge to be addressed.This dissertation focuses on a piezoelectric-driven nanopositioning platform and investigates robust control methods that can achieve high speed and high accuracy motion positioning of the platform,aiming to improve the performance of the platform in terms of response speed,positioning accuracy,stability and robustness.The details of the research are as follows:Firstly,a comprehensive dynamics model of the piezoelectric-driven nano-positioning platform is developed from the multi-coupling characteristics of circuit,mechanical,piezoelectric and hysteresis effects,and the frequency characteristics of the system are analysed and control objectives are given.Secondly,positive position feedback control and integral damping control based on negative imaginary number theory are applied to the piezoelectric-driven nanopositioning platform.The parameter rectification process of the two control methods is given,and the advantages and limitations of these two control methods are analysed.Then,the performance limitations of the positive position feedback control method and the robustness of the integral damping control that is not considered in the parameter rectification process are addressed.A comprehensive H_∞ control design method is adopted.By analyzing the system characteristics,a suitable weighting function is selected and the H_∞ controller is solved to meet the multiple performance requirements.The comprehensive performance of the proposed controller is verified through experimental simulations.Finally,the structured H_∞ control strategy with multiple parameter decoupling and multiple control synergies is proposed considering the problems of high order of H_∞ controller,multiple performance coupling interlocking with each other and difficulty of implementation.Based on the integral damping control architecture while retaining the advantages of comprehensive H_∞ control design,the controller structure is pre-designed to meet the multiple performance requirements of the system with a low-complexity structured H_∞ controller.The proposed structured H_∞ controller is verified to be superior in terms of performance and structure through experimental simulation comparisons,and achieves high speed and high accuracy motion positioning.