Modeling And Control Technology For A Piezoelectricity-Stack Actuated Micromanipulator

In the fields of microassembly,micromanipulation,and micro-electro-mechanical systems,micro-nano manipulation technology is prevailing with the miniaturization development of research objects in the human society and the science technology.As the core components to connect the macroscopic system and the microscopic system,the multi-DOF micromanipulator including the piezoelectric microgripper and the microstage plays vital role in micro-nano manipulation applications.However,with performance requirements for multi scale,flexible nature,compact size,high precision and ease of control,existing micromanipulators and control technologies face a number of challenges.Firstly,the manipulated object is usually multiscale and irregular,the microgripper needs to possess merits containing large workspace,high resolution,parallel grasping manner,integrated sensors and ease of control.Meanwhile,the microstage needs to have advantages including the large workspace,high precision,multi-degree of freedom and decoupling output displacements.Secondly,the output displacement of the piezoelectric stack actuator has a severe nonlinear hysteresis loop,which leads to a compensation for the hysteresis and results in a precision control for the output displacement of the microstage,the output displacement of the microgripper and the gripping force of the microgripper.Thirdly,for typical manipulation tasks which need to achieve the large-scale and the high precision motion simultaneously,a macro-micro gripping system formed by mounting the compliant microgripper onto a macro stage is essential.It is important to investigate the dynamic characteristics of the macro-micro gripping system,and reduce the vibration(shift)of the compliant microgripper excited by the large-scale macro motion.To solve these above questions,a multi-DOF micromanipulator including a dual-driven microgripper and a XY microstage was designed,and a macro-micro gripping system including a compliant microgripper and a servo-driven macro stage was presented.In particular,the static and dynamic modeling for the microgripper and the microstage is performed,the hysteresis model for the piezoelectric stack actuator(PSA)is established.Moreover,precision trajectory control for the micromanipulator is conducted.In addition,the dynamic modeling and trajectory planning for the macro-micro gripping system is carried out.By means of simulations and experimental validations,the effectiveness of established models and control methods is verified.The thesis can be divided into seven chapters.Chapter 1 presents the research background of the thesis.The main four aspects concerned with the system structure of the piezoelectric micromanipulator,static and dynamic modeling,nonlinear hysteresis modeling theory,micro-nano precision positioning control technology and vibration suppression of compliant mechanisms with large-scale macro motion were elaborated.In chapter 2,a multi-DOF microgripper including a dual-driven piezoelectric microstage and a XY microstage is designed.Based on the right-circular flexure hinges,the dual-driven microgripper including the bridge-type amplification mechanism,the parallelogram mechanism,the PSA and the position/force sensors is proposed.Using the right circular and the leaf-type flexure hinges,the XY stage including the double-rocker mechanism,the parallelogram mechanism,the PSA and the laser sensor is presented.Then,the static and dynamic models were separately established using the pseudorigid-body-model(PBM)approach.Through a series of finite-element analysis(FEA)simulations,system static and dynamic models were verified.Finally,experimental systems were established and open-loop performances of the microgripper and the microstage were tested and analyzed.In chapter 3,a position/force synchronization control strategy suitable use for precision micromanipulation tasks was proposed on the basis of the chapter 2.Through the decomposition in the structure of the microgripper,the original single-input and dual-output(SIDO)control problem was transformed into a dual-input and dual-output(DIDO)issue.Accordingly,the output displacement of the left arm of the microgripper was controlled by the nonlinear fuzzy logic(NFL)controller,and the gripping force of the right arm was regulated using the PI controller.Therefore,the simultaneous control of the output displacement and the gripping force was realized.In addition,four typical trajectories(the square wave,the sinusoidal signal,the amplitude-attenuated signal and the multi-frequency sinusoidal signal)tracking experiments was preformed to verify the feasibility and effectiveness of the proposed synchronization control strategy.In chapter 4,the Bouc-Wen model was used to precisely describe the nonsymmetrical hysteresis nonlinear phenomenon arose from the inherit properties of the piezoelectric stack actuator(PSA).Moreover,an improved genetic algorithm was used to identify the model parameters of the nonsymmetrical Bouc-Wen hysteresis model.In addition,model predication experiments for the attenuated signal and the arbitrary signal were carried out.Besides,the effectiveness of the established Bouc-Wen model and parameter identification method was experimentally validated.In chapter 5,a feedforward controller was designed on the basis of the Bouc-Wen model derived from chapter 4.Moreover,a hybrid controller employing the feedforward controller and a PI controller was used to precisely regulate the output displacement trajectory of the piezoelectric microstage.Afterwards,the dual-driven microgripper was mounted onto the XY stage,and the cooperative control for the micromanipulator was performed.In particular,the position/gripping force of the piezoelectric microgripper was synchronously controlled by the NFL/PI controllers in a phased manner.Meanwhile,the output displacement trajectory of the piezoactuated microstage was precisely tracked using the hybrid controller.Experimental results verified the feasibility and effectiveness of the cooperative control strategy.In chapter 6,the dynamic modeling and trajectory planning of the macro-micro gripping system was conducted.A macro-micro gripping system with large-scale and high precision motion simulanteously was performed by mounting a compliant microgripper designed in chapter 2 onto a servo-driven macro stage.Typically,the servo-driven macro stage only have one degree of fredom.Then,the whole dynamic model for the macro-micro gripping system was derived by means of the pseudorigid-body-model approach,the assumed mode method and the Lagrange equation.After that,the elastic vibration(shift)of the compliant microgripper excited by the large-scale macro motion was reduced using the trajectory planning approach.Finally,to verify the efficiency of the dynamic model and the trajectory planning strategy,an experimental system was set up and several trajectory planning tests were carried out.Experimental results validate the correctness and effectiveness of the dynamic model and the trajectory planning strategy.Chapter 7 concludes the thesis,and the prospect for the micro-nano manipulation technology driven by the PSA was outlined.