Design And Experimental Investigation Of Bionic Piezoelectric Inchworm Actuator

The rapid development of ultra-precision machining and measurement,precision optical engineering,biological engineering and modern medicine,micro-machining and assembly,aerospace and other advanced fields have put forward the characteristics of micro-nano positioning system,such as high positioning accuracy,fast frequency response,low energy consumption,light weight and small volume.However,the traditional mechanical driver is unable to meet the needs of high precision nanopositioning,the cross-scale nanoscale positioning technology with nanoscale positioning accuracy and millimeter motion stroke has become an indispensable key technology for nanoscale operation.The piezoelectric inchworm actuator based on biomimetic technology has the characteristics of large stroke and high resolution,which can meet the requirements of many micro-nano engineering fields for high resolution,large loading capacity and large stroke.However,the existing piezoelectric inchworm actuators have the problems of structural design and complex circuit sequences,which introduce a series of challenges to the miniaturization of the structure and the improvement of the drive speed.In addition,the theoretical research on the inchworm driver is still limited to the design and optimization of the flexible mechanism,the modeling of its main output performance,such as loading capacity and step length,remains to be improved.To address these questions and challenges,this dissertation proposes the complementary-type inchworm actuator based on the traditional flexible mechanism,and carries out the structure design and simulation,theoretical modeling and analysis,performance testing and exploration.The main research contents and achievements are listed as follows.In order to simplify the structure design and voltage sequences of the actuator,a two-channel signal driven complementary-type inchworm actuator is designed,which reduces the assembly difficulty.In order to realize the design of the new inchworm actuator driven by two piezostacks(PZTs),the output displacement and parasitic displacement are taken as the driving and clamping,respectively.Considering the influence of the mechanical characteristics of the flexible mechanism on the step length and loading capacity of the actuator,the finite element simulation analysis of the amplification ratio,stiffness and stress of the flexible mechanism is carried out with ANSYS software.To meet the demands of large stroke and high resolution.Based on the flexibility matrix method,the pseudo-rigid body model of the flexible amplifying mechanism is established,the simulation analysis and verification are carried out by finite element method.With this,the mathematical model of preload displacement and amplification ratio of flexible mechanism is further established.Considering the influence of preload mechanism on the loading capacity of the actuator,the relationship between preload displacement and clamping force is analyzed.In addition,the mathematical model of step length,motion direction and sub-step length is established to predict the step length.Considering the application of large clamping force and variable speed drive in high loading capacity and fast positioning system,a voltage sequence based variable step and variable loading capacity control strategy based on the characteristics of the proposed complementary-type inchworm actuator is proposed.The mathematical model of the step length and voltage sequence is established,realizing controllable bidirectional variable step motion.At the same time,the mathematical model of clamping force and voltage sequences is established to avoid the loading capacity loss caused by different voltage signals,which provides a new approach to optimize the performance of the actuator.Finally,on the basis of the driving principle,simulation results and theoretical analysis,the prototype of the bionic piezoelectric inchworm driver is fabricated,a whole set of experimental test system is set up to systematically test and explore its output performance,including the performance test of its basic output characteristics and the performance test of voltage sequences based variable step motion and variable loading capacity.The experimental results show that the designed inchworm actuator has good motion resolution,loading capacity and motion stability,which is instructive for the design of double-piezoelectric driven inchworm actuator with variable speed and large loading capacity.