Study On The High Bandwidth Control Of Flexure Nano-positioning Stage

With the development of nanotechnology,higher requirements have been put forward in terms of the speed and accuracy for flexure nanopositoning system.However,many studies have concluded that it is difficult for conventional control methods to achieve high nanopositioning bandwidth due to the hysteretic nonlinearity and resonance vibration characteristics.Although there are many existing control methods proposed to improve the nanopositioning bandwidth,the improvement of the performance is relatively limite d.Therefore,it is of great significance to design more effective high nanopositioning bandwidth control methods.In order to develop a more effective high nanopositioning bandwidth control method,the flexure nanopositioning stage is adopted as the resea rch object in this study.And the in-depth research is conducted from the perspective of the performance index acting on control design.And it is summarized as follows:(1)The limitation of existing methods is analyzed in term of the performance index.And then,according to the analysis results,the new performance index is explored and designed.It indicates that the existing performance indices of nanopositioning control methods are difficult to evaluate the motion speed and tracking accuracy simultaneously.Among them,the tracking error in the time domain focus es on evaluating tracking accuracy,while the bandwidth in the frequency domain concentrates on evaluating tracking speed.With the idea of combination of advantages,this paper proposes an errortolerant bandwidth performance index,which can simultaneously evaluate tracking accuracy and speed,and is more suitable for guiding the design of high nanopositioning bandwidth control methods.In addition,based on the error tolerance bandwidth,this paper also proposes the performance index of bandwidth approximation rate.It can more rationally evaluate the degree of contribution of the control method in the entire system to achieve high nanopositioning bandwidth performance.(2)A new high nanopositioning bandwidth control method is designed based on the error tolerance bandwidth.First,the simplest compound control(SCC-??)based on the error tolerance bandwidth is designed with the simplest compound control structure,and the theoretical analysis and simulation verification of its control quantity characteristics and stability were carried out.The results show that the nanopositioning bandwidth of SCC-?? can approach the limit of the second-order linear system 100%.Then,in view of the shortcomings of SCC-?? being unstable,the idea of virtual closed loop is adopted to improve the performance,and the virtual SCC-??(VSCC-??)is developed.Finally,aiming at the weak robustness of SCC-??,a variable step size MIT rule is introduced as a closed-loop strategy to improve the performance of the extreme control in terms of the robustness and implement.(3)In order to further improve the performance of high nanopositioning bandwidth of extreme controller,the trajectory shaping and model identification are adopted in this paper.For the trajectory shaping,a new triangle wave trajectory shaping method is proposed.And its transition trajectory is replaced by sine wave signal.The modified triangle wave trajectory can not only effectively suppress the tr acking vibration,but also directly control the triangle wave component of the modified trajectory.For the model identification,in order to obtain the model parameters efficiently,the direct parametr ic acquisition method is proposed in this paper.This method is developed by the analytical solution of the frequency-domain function for the second-order linear system.And only four characteristic parameters of the actual tracking process are required so that the effective parameters of the model can be obtained directly.(4)A series of experiments were carried out based on a typical lightly damping flexure nanopositioning stage.First,the prototype system was set up and the flexure nanopositioning stage involved were characterized via the frequency domain.Then the system identification was carried out.Then,based on the identification results,sine wave trajectory tracking test and triangle wave trajectory tracking test were carried out.Finally,when the reference trajectory frequency was close to the system resonance frequency,static load disturbance test and dynamic load disturbance test were carried out.Experimental results indicate that the extreme control can effectively achieve the high nanopositioning bandwidth performance,which is superi or to several existing methods and has strong robustness.